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Ionic liquid enhanced alkylation of iso-butane and 1-butene

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Abstract

The alkylation of iso-butane with 1-butene was catalyzed by triflic acid (TFOH) coupled with a series of protic ammonium-based ionic liquids (AMILs), and the addition of the AMILs dramatically enhanced the efficiency of TFOH for the alkylation reaction. Up to 85.1% trimethylpentanes (TMP) selectivity and 98 research octane number (RON) were achieved with the optimized TFOH/AMIL catalyst (75 vol.% triflic acid and 25 vol.% triethylammonium hydrogen sulfate), which were much better than that with the commercial H2SO4 catalyst (65% TMP selectivity, 97 RON) and pure triflic acid. The addition of AMILs increased the I/O ratio dissolved in the catalyst system and adjusted the acidity of the TFOH/AMILs catalyst system, which were highly beneficial to the alkylation reaction and resulted in high TMP selectivity and high RON.

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... As a promising solvent and catalyst, ILs have been extensively used in a large amount of chemical processes, such as transesterification (Wang et al., 2015), desulfurization (Domań ska and Wlazło, 2014;Jiang et al., 2014), and isomerization (Kim et al., 2014). In recent years, the ILs with Lewis or Brønsted acidity have been extensively investigated for the isobutane alkylation (Chauvin et al., 1994;Cui et al., 2013;Huang et al., 2004;Huang et al., 2015;Liu et al., 2015Liu et al., , 2016Liu et al., , 2014cSchilder et al., 2013;Tang et al., 2009;Xing et al., 2012;Yoo et al., 2004). For example, the Lewis acidic ILs to catalyze the isobutane alkylation could achieve a better catalytic performance with the trimethylpentanes (TMPs) selectivity and the research octane number (RON) up to 87.5 wt% and 100.5, respectively (Liu et al., 2015). ...
... For example, the Lewis acidic ILs to catalyze the isobutane alkylation could achieve a better catalytic performance with the trimethylpentanes (TMPs) selectivity and the research octane number (RON) up to 87.5 wt% and 100.5, respectively (Liu et al., 2015). The Brønsted acidic ILs were also used as the co-catalyst for the isobutane alkylation to improve the catalytic activity and stability of the conventional strong acid catalyst (Cui et al., 2013;Huang et al., 2015;Tang et al., 2009;Xing et al., 2012). For both cases, the use of the ILs for the alkylation is more favorable for a higher catalytic activity, better catalyst reusability, higher selectivity of TMPs, and higher RON. ...
... For instance, the most important properties of C 4 alkylation may be the acid strength and the solubility of isobutane in the acid [13]. But for ILs, these properties can be readily tuned by using different organic cations or inorganic anions [14][15][16][17]. Additionally, many ILs can maintain high catalytic activity during the whole alkylation reaction without carbon deposition problems as compared to solid acid alkylation. ...
... The most plausible explanation for these data involves rapid oligomerization of the non-deuterated 2-butene followed by cracking and hydrogen transfer reactions that produce trimethylpentanes with less deuterium. A mechanistic scheme for this is presented in Reactions (13) (14) i-C 4 D 10 ...
Article
The ionic liquid catalyzed alkylation of 2-butene with deuterated isobutane was studied in a continuous flow equipment. Product analyses with time and deuterated distribution determinations were obtained. It is found that the induction period of ionic liquid alkylation is much shorter than that of sulfuric acid. A considerable difference in isobutane solubility between ionic liquid and sulfuric acid was observed with ionic liquid having a greater tendency to dissolve isobutane at the start-up of alkylation. Deuterated product distributions indicate that trimethylpentane fractions stemmed primarily from the self-alkylation of isobutane, the direct alkylation reaction of C4 hydrocarbons, and the scission of C12+ intermediates. Most dimethylhexanes should come from the direct addition of sec-butyl carbonium ions to 2-butenes.
... The C 8 selectivity and the alkylate RON were 85.5% and 98.5 in the 16th cycles. However, the catalytic performance of several ionic liquids catalysts in the literatures began to decrease significantly when it was reused for 4-6 times [27,51]. In summary, [OMIm][OTf]/H 2 SO 4 composite catalyst has excellent reutilization performance. ...
Article
The products of isobutane/butene alkylation are ideal high-octane blending components of gasoline pool. Binary mixtures of acidic imidazolium ionic liquids [CnMIm][OTf] (n = 4, 6, 8) and H2SO4 were used to catalyze isobutane/butane alkylation in a microreactor integrated with staggered herringbone grooves. The mixing behaviors of acid and hydrocarbons were simulated in the microchannel configured with micromixing elements by computational fluid dynamics (CFD) simulation. [CnMIm][OTf]/H2SO4 showed better catalytic performance than H2SO4 solely. Especially the [OMIm][OTf]/H2SO4 showed excellent performance. In the designed microreactor, the alkylate with research octane number (RON) of 99.5 was obtained at 10.0°C and reaction time of 81 s with [OMIm][OTf]/H2SO4 as catalyst. The results are better than currently available research works implemented in batch reactors. The catalyst [OMIm][OTf]/H2SO4 was recycled 14 times without reducing the catalytic activity. It indicates that the composite catalysts possess excellent reutilization performance.
... However, the industrial application of solid catalysts is difficult because of their intrinsic defects, easy deactivation and difficult regeneration. In addition, ionic liquids are considered to be promising catalysts for alkylation [11][12][13][14][15][16][17] . The selectivity of trimethylpentane (TMP) can be as high as 85% when using ionic liquids as catalysts 18 . ...
Article
H2SO4 alkylation of isobutane and butene is one of the primary commercial processes used to produce alkylates. This work presents a technology for the intensification of sulfuric acid alkylation with the addition of trifluoroacetic acid (TFA). The addition of TFA increased the solubility of isobutane in H2SO4, decreased its viscosity, and adjusted the acidity of H2SO4. With the addition of TFA, the selectivity of C8 was dramatically improved from 36.8% to 95.7%. The TFA content, stirring speed, reaction temperature, volume ratio of acid to hydrocarbon (H/C), molar ratio of isobutane to 2‐butene (I/O), reaction time, and reuse of H2SO4/TFA were also investigated in this work. Compared with the conventional process, the new technology provided a considerably higher quality alkylation with considerably lower energy consumption. This article is protected by copyright. All rights reserved.
... Adding water in an acidic molten salt can play a similar role to HCl [11]. For nonchloroaluminate based IL, a dramatic enhancement of the catalytic effect was observed when the IL containing the SbF 6 − anion [12,13]. ...
Article
Ionic liquid catalyzed isobutane/2-butene alkylation modified with metal compounds was studied. The effect of catalyst composition on the alkylation selectivity was investigated. 27Al NMR, ESI-MS, and FTIR spectra reveal that the catalytic selectivity of the modified ionic liquid is probably determined by the catalyst composition rather than by the acid strength. The complexation of transition metal with 2-butene can increase the internal isobutane-to-olefin ratio of feed during the alkylation reaction, which results in the better selectivity of the modified ionic liquid. The best ionic liquid catalysts were those containing CuAlCl4 complexes, giving the alkylate with 87.5 wt% trimethylpentanes and a calculated research octane number (RON) of 100.5.
... On the one hand, they have general characteristics like other ILs such as low volatility, wide liquid range, good solubility with other solvents and are function adjustable according to different combinations of cations and anions. On the other hand, they also have many special properties, including low cost, high electrical conductivity, and ease of preparation through direct neutralization between corresponding acid and base, which can endow them excellent performance in many fields such as alkylation reactions [1], absorption of SO 2 [2] and CO 2 [3], extraction of soluble dyes [4], stability of proteins [5,6], dissolution of cellulose [7], electrochemistry [8] and wastewater treatments [9]. Obviously, knowledge of interactions between ammonium based ILs and molecular solvents is essential for their applications in chemical and industrial processes. ...
Article
Full-text available
In order to uncover the micro-structural heterogeneities in solutions of ammonium based ionic liquids, triethylamine nitrate (N222NO3) has been synthesized using acid–base neutralization and the 1H NMR spectra of two binary mixtures, namely N222NO3/dimethyl sulfoxide (DMSO) and N222NO3/acetone at different concentrations, have been measured at 298.15 K. The internal reference method was adopted to obtain the concentration-dependent chemical shifts of –CH3 in N222NO3, which have been correlated using the 1H NMR local composition (LC) model to obtain the local mole fractions. It has been revealed that within N222NO3 rich region, self-association of the ionic liquid was predominant instead of N222NO3–solvent interactions. However, in the solvent rich region, N222NO3 mainly interacts with solvent molecules, indicating that the self-association network of N222NO3 has been greatly destroyed by solvents. In addition, the different influences of DMSO and acetone have been detected. DMSO molecules more effectively destroy the original network of the ionic liquid, due to its higher dielectric constant. Also, LC behavior in N222NO3/DMSO systems is more significant than in N222NO3/acetone, indicating that DMSO can induce more obvious heterogeneities in DMSO/N222NO3 mixtures, which is consistent with physicochemical properties and cellulose solubility of solutions.
... Compared with solid acid catalysts, IL catalysts have more tunable properties. The organic cation and inorganic anion in ILs can have very different physical and chemical properties [246][247][248]. Chloroaluminated ILs and protic ammonium-based ILs have been extensively investigated for alkylation [247,249]. ...
Chapter
Full-text available
Over the last few decades, researchers have extensively studied the conversion of fossil resources into fuels and chemicals. Nearly all transportation fuels are produced by a series of catalytic processes. For example, about 70?80?wt% of the motor gasoline in China is produced through fluid catalytic cracking (FCC) by zeolitic catalysts. Petroleum chemical reactions contain complicated reaction networks and complicated reaction pathways. Under certain conditions, the types and directions of chemical reactions could be determined by the characteristics of the feedstock and the properties of the catalysts used. Therefore, novel catalysts with high activities and selectivities are required for special production aims. Molecular modeling is a useful tool for catalyst design and provides insights into the catalytic reaction processes at the atomic or molecular level. Modeling helps us fully understand the microscopic mechanisms and identify the key factors that affect the structure?activity relationships. Moreover, with the rapid development of computer techniques and theoretical methods, bigger systems and more complicated reaction processes, such as the adsorption and diffusion behaviors of adsorbates in the zeolite pore system by molecular simulation or the catalytic reaction mechanism by quantum chemical calculations, can be revealed at the molecular level. This work reviews some applications of molecular modeling methods and attempts to design novel catalysts for petroleum refining.
... 440,441 In one example, Cui and co-workers studied the alkylation of isobutane with 1-butene catalyzed by triflic acid (TFOH) coupled with a series of protic ammonium-based ionic liquids (AMILs), and they found that addition of the AMILs can dramatically enhance the efficiency of TFOH for the alkylation reaction. 442 The alkylate compositions produced by the optimized TFOH/IL with HSO 4 − anions are shown in As described earlier there are numerous applications of acidic ionic liquids in alkylation reactions and some selected examples and their references are shown in Table 13. ...
Article
Ionic liquid with acidic properties is an important branch in the wide ionic liquid field and the aim of this article is to cover all aspects of these acidic ionic liquids, especially focusing on the developments in the last four years. The structural diversity and synthesis of acidic ionic liquids are discussed in the introduction sections of this review. In addition, an unambiguous classification system for various types of acidic ionic liquids is presented in the introduction. The physical properties including acidity, thermo-physical properties, ionic conductivity, spectroscopy, and computational studies on acidic ionic liquids are covered in the next sections. The final section provides a comprehensive review on applications of acidic ionic liquids in a wide array of fields including catalysis, CO2 fixation, ionogel, electrolyte, fuel-cell, membrane, biomass processing, biodiesel synthesis, desulfurization of gasoline/diesel, metal processing, and metal electrodeposition.
... 440,441 In one example, Cui and co-workers studied the alkylation of isobutane with 1-butene catalyzed by triflic acid (TFOH) coupled with a series of protic ammonium-based ionic liquids (AMILs), and they found that addition of the AMILs can dramatically enhance the efficiency of TFOH for the alkylation reaction. 442 The alkylate compositions produced by the optimized TFOH/IL with HSO 4 − anions are shown in As described earlier there are numerous applications of acidic ionic liquids in alkylation reactions and some selected examples and their references are shown in Table 13. ...
Article
Ionic liquid with acidic properties is an important branch in the wide ionic liquid field and the aim of this article is to cover all aspects of these acidic ionic liquids, especially focusing on the developments in the last four years. The structural diversity and synthesis of acidic ionic liquids are discussed in the introduction sections of this review. In addition, an unambiguous classification system for various types of acidic ionic liquids is presented in the introduction. The physical properties including acidity, thermo-physical properties, ionic conductivity, spectroscopy and computational studies on acidic ionic liquids are covered in the next sections. The final section provides a comprehensive review on applications of acidic ionic liquids in a wide array of fields including: catalysis, CO2 fixation, ionogel, electrolyte, fuel-cell, membrane, biomass processing, biodiesel synthesis, desulfurization of gasoline/diesel, metal processing and metal electrodeposition.
... This is by far the largest commercial usage of ILs reported to date. (Xing et al. 2012, Cui et al. 2013. As seen, the presence of ILs promotes the catalytic performance of the conventional strong acid significantly; however, the safety and environmental concerns during the storage, transport, and use of concentrated liquid acids as well as the disposal of acid soluble oil are still there more or less as same with the conventional mineral strong acid catalyst alone. ...
Article
Full-text available
Ionic liquids (ILs) and supercritical CO2 (scCO2) are two promising types of reaction media for green chemical processes due to their unique properties. They can be integrated into chemical reactions as catalysts and solvents to develop green and environment-friendly processes. This review presents current research trends aiming to solve the major chemical engineering issues in light of a fundamental understanding of these media. Applications of these media in the petrochemical industry, biochemical engineering, and fine chemical production are reviewed, suggesting the challenges and directions of utilizing them for green processes prospectively. These recent explorations and successful examples of applications demonstrate that ILs and scCO2 offer huge potential for novel and green chemical engineering processes.
... Numerous ILs have been developed as new reaction medias or catalysts in organic synthesis and catalytic reactions with excellent selectivity and outstanding recyclability (Fehér et al., 2012;Taheri et al., 2015;Yang et al., 2015;Zhang et al., 2008). Among these applications, acidic ionic liquids, including Lewis acidic ILs (Chauvin et al., 1994;Cui et al., 2014;Huang et al., 2004;Liu et al., 2014;Yoo et al., 2004), Brønsted acidic ILs (Cui et al., 2013;Huang et al., 2015;Tang et al., 2009;Wang et al., 2016;Xing et al., 2012), and Brønsted-Lewis acidic ILs (Liu et al., 2015a), have been extensively used to catalyze the isobutane alkylation. For example, Lewis acidic ILs reported by Liu (Liu et al., 2015b) have been studied to catalyze the isobutane alkylation with the selectivity of trimethylpentanes (TMP) and research octane number (RON) up to 87.5 wt.% and 100.5, respectively. ...
... The catalytic capacity of these compounds was evaluated by identifying and confirming that the optimal ILs contents in the catalytic system were 15, 25, or 40 vol.% depending on the ILs structure [36]; in general, these chemical species mixed with CF 3 SO 3 H had good selectivity to C8 (between 87 and 92%) and high RON (96)(97)(98) with reaction temperature of 10 • C for 10 min. The authors considered that the good results were due to the excellent solubility of CF 3 SO 3 H in the ammonium ILs, minimizing the polymerization of 2-butene, and the alkylation results were better with CF 3 SO 3 than with HSO 4 , highlighting that the [Et 3 NH][CF 3 SO 3 ]/CF 3 SO 3 H system almost kept a constant acidity, changing the surface tension, viscosity, and density of TfOH, in addition, to be reused up to 36 times. ...
Article
The isobutane/butene alkylation reaction is one of the most crucial refining processes since it gives rise to high octane and high purity gasoline, one of the main contributors to the gasoline pool. Conventionally, the alkylation reaction is carried out industrially using hydrofluoric and sulfuric acids, which have significant safety, corrosivity, recyclability, and sustainability concerns, making the development of efficient, environmentally friendly, and sustainable catalysts for this reaction an active research topic. Due to their attractive physicochemical properties, ionic liquids seem to be the most promising alternative to replace the catalysts commonly used at the industrial level. The present compendium reviews research works to develop ionic liquids as catalysts of the isobutane/butane reaction to obtain a more efficient, sustainable, and environmentally friendly process. These compounds can mitigate the environmental problems associated with inorganic acids that have been used for many years as catalysts of this reaction on an industrial scale. The most recent articles and patents dealing with the advances in the alkylation reaction employing commercial technologies to obtain alkylated gasoline based on ionic-liquid catalysts, which have not been featured in previous reviews, are emphasized and discussed here.
... Alternatively, the Brønsted acidic ILs have been proved to be a promising cocatalyst for the alkylation, which can enhance the activity and stability of the strong acid. 18,19,21,22,29 Compared to the H 2 SO 4 , the binary mixtures of Brønsted acidic ILs/strong acids reported by Tang et al. 21 showed an outstanding catalytic performance with the optimized selectivity of C 8 -alkylates up to 75.8 wt%. ...
Article
The interfacial properties between the hydrocarbon phase including isobutane and 2-butene and the catalyst phase including H2SO4 or ionic liquids (ILs) with various alkyl chain length on their imidazolium cations have been investigated using molecular dynamics (MD) simulations. Compared to H2SO4, ILs could obviously improve the interfacial width, solubility and diffusion of reactants at the interface. The ILs with longer chains on cations exhibit a significant density enrichment of alkyl chains at the interface and tend to orient themselves with alkyl chains perpendicular to the interface and protruding into the reactants phase, which is in good agreement with the van der Waals energy between the reactants and cations of the ILs. The longer chains on cations could promote the interfacial width and facilitate the dissolution of isobutane in catalyst phase, and thus exhibits a better catalytic performance, which agrees well with alkylation experiments in this work. This article is protected by copyright. All rights reserved.
... On the other hand, this catalyst suffers from extreme oxophilicity and ease of losing hydrogen chloride, which results in its deactivation and reduction of halide content. Thus, more attention has been devoted to the addition of ILs to strong acids, such as H 2 SO 4 and CF 3 SO 3 H, to enhance their catalytic performance [27]. Olah et al. used amine-poly(HF) ILs as additives in the HF alkylation process, obtaining a good yield of alkylate and a research octane number (RON) up to 94 [28]. ...
Article
In this work, the alkylation of isobutane and butene, catalyzed by sulfuric acid in the presence of the fluoride–containing ionic liquids [Bmim][PF6] and [Bmim][SbF6], was investigated. The use of the binary mixture catalysts brought to a higher C8 selectivity and longer catalyst lifetime, compared with the results obtained when working with sulfuric acid only. This was attributed to the formation of new species when [Bmim][PF6] or [Bmim][SbF6] are added to sulfuric acid. The acidolysis of [Bmim][PF6] and [Bmim][SbF6] was accompanied by the release of hydrogen fluoride (HF) and the decomposition of anions to [PF6−x−2y(HSO4)x(SO4)y]⁻ and [SbF6−x−2y(HSO4)x(SO4)y]⁻, respectively. The presence of these new species after acidolysis was measured and confirmed by ion chromatography, ¹H–Nuclear Magnetic Resonance (NMR), ¹⁹F–NMR and ³¹P–NMR. The production of HF and the complexation of anions and carbenium ions both play an important role in stabilizing the carbenium ion and improving the catalytic performance.
... Yet, acid catalyzed alkylation suffers from disadvantages for example, high acid consumption and toxicity. Though viewed as an alternative to H 2 SO 4 and HF [1], however, ionic liquid catalyzed alkylation is still under development, mainly on improving selectivity [2,3]. Researchers have also been advocating solid catalyst alkylation (SCA) process that would eliminate the safety and corrosion issues associated with liquid acid catalyst. ...
Article
The isobutane/2-butene alkylation process using fixed bed arrays as reactors and β-zeolite as the catalyst is simulated and analyzed. By employing the Lagrange's method, numerical problems that originate from nonlinear reactions and Eulerian girds are neutralized. Sensitivity of operating parameters on process performance are discussed, such as paraffin/olefine ratio, alkylate reflux ratio and liquid velocity. It is found that larger paraffin/olefine is required for greater olefine to alkylate selectiviy. And alkylate reflux is also necessary to save energy cost in the distillation operations. Alternative configurations such as multiple inlet points and radical bed are discussed. To determine the optimal operating parameters, a techno-economical model is established and optimized. In the final analysis, guidelines for the further design of solid acid catalyzed alkylation process are presented.
... Extensive previous studies have reported that a binary mixture of mineral acid and ionic liquid as a catalyst in the isobutane/butene alkylation can substantially improve the product yield and catalyst life [31][32][33][34]. The ILs are believed to change the interfacial properties and the solubility of hydrocarbon in the catalyst system, which are favorable for the alkylation reaction. ...
Article
The adsorption ratio of isobutane/1-butene on the catalyst surface is one of the most important factors for the C4 alkylation process. Regulation of isobutane/1-butene adsorption ratio on the zeolite-supported acid catalyst is a big challenge for catalyst preparation. To regulate the isobutane/1-butene adsorption ratio, four types of ionic liquid (i.e., IL) with different alkyl chain lengths and different acid group numbers were synthesized and were subsequently immobilized onto the MCM-22 zeolite. The as-synthesized IL-immobilized MCM-22 (i.e., MCM-22-IL) were characterized by FTIR, TGA, BET, XPS and XRD, and their adsorption capacities and adsorption molar ratios of isobutane to 1-butene (I/O) were investigated to correlate with surface features of MCM-22-IL. Results showed that the immobilization of ILs led to a decrease of specific surface area and pore volume. But the surface density of acid groups was increased and the adsorption molar ratio of isobutane/1-butene (I/O) was significantly improved by the immobilization of ionic liquids. The adsorption molar ratio of I/O is substantially improved from 0.75 to above 0.9 at 300 kPa upon immobilizing ILs. Although the alkyl chain length of ILs were found to have little effect on the adsorption molar ratio of I/O, the increase of acid group numbers led to a dramatic decrease in the adsorption I/O ratio. The results illustrated that immobilizing ionic liquids is an effective way to modify the textural, chemical and morphological properties of MCM-22. Accordingly, the immobilization of ionic liquids provides a novel and a feasible way to regulate the adsorption I/O ratio on an adsorbent or a solid catalyst.
... Actually, the emulsification between reactants (methylcyclopentane and cyclopentanol) and H 2 SO 4 is not sufficient, as a result, cyclopentanol directly contacts with H 2 SO 4 to occur intensive dehydration and polymerization. It has been reported that adding surfactants to H 2 SO 4 -catalytic system can enhance emulsification between reactants and H 2 SO 4 to increase the dispersion of reactants, which greatly restrains the formation of coke in isobutane alkylation [31][32][33]. Graphene oxide (GO) is a benign emulsifier that can stabilize the oil-in-water emulsions due to its amphiphilic property [34]. For example, Meng et al. used GO to enhance the emulsification of isobutane/butene in H 2 SO 4 and to improve alkylation of isobutane and butene [35]. ...
... Furthermore, multi-scale modeling of isobutane alkylation with 2-butene using composite ionic liquids as catalyst were developed and investigated on an industrial scale basis by Zheng et al. [107]. Cui et al. [108] examined ammonium- based ionic liquids coupled with triflic acid. The ionic liquid/triflic acid combination displayed 85.1% TMP selectivity and 98 RON in comparison to sulfuric acid/triflic acid combination which had only showed 65% TMP selectivity and 97 RON. ...
Article
Petroleum refining has been one of the key technologies driving global economic development and technological advancement for well over a century. Although much of the technology used in refineries is considered mature, the industry is always seeking ways to make process improvements, reduce environmental impact, enhance safety, and achieve cost reductions. In particular, much focus has been placed on improving the existing technology for desulfurization, denitrogenation and alkylation. Due to their unique physical and chemical properties and environmental advantages over traditionally used solvents or catalysts, interest in ionic liquids for such refinery processes has been increasing exponentially in recent years. This review outlines the existing technology used in refineries, such as desulfurization, denitrogenation and alkylation, critically examines recent research into the use of ionic liquid-based alternatives, and discusses the major challenges that must be overcome to facilitate the widespread implementation of ionic liquid-based refinery technology on an industrial scale.
... It is difficult to control the acidity of chloroaluminated ionic liquids. Presence of SbF 6 − anion drastically enhances the catalytic effect of non-chloroaluminate based ionic liquids [132,133]. Composite ionic liquids contain anions in the form of ligands with two or more metallic centres, such as [AlCuCl 5 ] − [101,130,134]. Under appropriate reaction conditions, composite ionic liquids are able to result in alkylation with around 92% trimethyl pentanes (TMPs) selectively [39,49,135]. ...
Article
Alkylation of isoalkane and alkene owns a note-worthy position among octane improving chemical conversions. Widely adopted catalysts (H 2 SO 4 and HF)for alkylation at industrial level suffer severe drawbacks associated with environmental concerns, recycling, reactor corrosion, etc. Solid acid catalysts are good, but represent deactivation issues. Compared to this, ionic liquids are considered green catalysts for obtaining alkylate as an efficient blending component for clean oil. This review article presents various ionic liquids effective for alkylation reaction. Their structures, properties, and catalytic activities are briefed in this analysis. Impact of additives on various ionic liquids and their efficiencies has also been discussed. The article will help the researchers to gain a deep insight and understanding about the reaction conditions suitable for alkylation and its chemistry in detail.
... Actually, the emulsification between reactants (methylcyclopentane and cyclopentanol) and H 2 SO 4 is not sufficient, as a result, cyclopentanol directly contacts with H 2 SO 4 to occur intensive dehydration and polymerization. It has been reported that adding surfactants to H 2 SO 4 -catalytic system can enhance emulsification between reactants and H 2 SO 4 to increase the dispersion of reactants, which greatly restrains the formation of coke in isobutane alkylation [31][32][33]. Graphene oxide (GO) is a benign emulsifier that can stabilize the oil-in-water emulsions due to its amphiphilic property [34]. For example, Meng et al. used GO to enhance the emulsification of isobutane/butene in H 2 SO 4 and to improve alkylation of isobutane and butene [35]. ...
Article
Synthesis of jet fuel with high density, good low-temperature property and high thermal stability is significant to aerospace industry. Here, a great-performance jet fuel blending including bi- and tri-cyclic hydrocarbons (C10 ~ C16) is synthesized with high yield through reduced graphene oxide (rGO) assisted H2SO4 catalytic one-pot reaction of cyclopentanol and methylcyclopentane. The reaction occurs through a consecutive way of dehydration, alkylation, rearrangement and hydrogen transfer. Carbon-based materials especially rGO are used as additive to increase the carbon yield by promoting the emulsification of reactants in sulfuric acid. Promoted emulsification improves the alkylation of cyclopentanol with methylcyclopentane and makes the hydrogen transfer easier, which highly increases the conversion of methylcyclopentane (54.9%), the carbon yield (83.2%) and the selectivity (97.3%) of products. Finally, a jet-fuel-ranged blending with overall yield of 71.8% is obtained by distillation, which shows high density of 0.90 g/mL, low freezing point of <-72 °C and a high oxidation onset temperature of 195.0 °C. This work provides a simple, efficient and low-cost way to synthesize high performance jet fuel from biomass.
Article
Two oxopyrrolidinium-based ionic liquids (ILs) with different functional groups namely, epoxypropane and dihydroxy propane in cation, were synthesized in this work. Propanoic acid and butanoic acid were mixed with the synthesized ILs to create a series of binary liquid mixtures with various mole fractions. The physicochemical properties of density (ρ) and speed of sound (u) of the binary systems were measured in the range of 0.1–1.0 mol fraction at temperatures from 293.15 to 313.15 K at a 5 K interval under atmospheric pressure (p = 101 kPa). Based on these experimental data, the excess molar volume, (VmE), isentropic compressibility, (ks), deviation in isentropic compressibility (∆ks) and intermolecular free length (Lf) were then calculated. Furthermore, the interactions such as H-bond, ionic interaction, dipole-dipole interactions and weak van der Waals interactions among the IL and carboxylic acid were inferred through the experimental and derived data. These interactions appear to play a major role in determining the potential usefulness of these IL-acid binary systems. The negative values of VmE and ∆ks may be indicative of strong interactions between IL and acid. A long carbon chain of acid appears to enhance the interaction strength that could be attributed to the increase in viscosity of systems due to the longer alkyl chain and big size of acid. The derived thermodynamic properties, including VmE, ∆ks and Lf were fitted in Redlich-Kister polynomial equation and standard deviation.
Article
Trace amounts of ionic liquids have been mixed in sulfuric acid to enhance the catalytic performance for the alkylation of isobutane with butene. The experimental results from batch reactors indicated that the reaction efficiency was significantly improved. The effective catalytic lifetime of concentrated H2SO4 mixed with [Bmim][SbF6] was twice compared with pure H2SO4. Under the optimal conditions, the alkylate research octane (RON) reached 98, and the selectivity of C8 was 90%. The ionic liquids with SbF6 anion worked similar to buffer agents, which were in favor of keeping the acid strength of catalytic system, slowing the growth of acid soluble oil, and reducing acid consumption. In conclusion, the new catalytic system of acid and trace amounts of ionic liquids is very promising to substitute the old catalytic system of concentrated H2SO4 alone for the alkylation.
Article
Ionic liquids (ILs) are emerging as a new family of environmentally benign solvents alternative to the conventional solvents for most catalytic reactions due to their nonvolatility. In such applications, thermal stability and solubility are vital for the selection of a suitable IL solvent for a particular reaction. In this work, the thermal stability of three commonly used imidazolium ILs (bmim[BF4], bmim[PF6], bmim[Tf2N]) was studied with both nonisothermal and isothermal thermogravimetric analysis (TGA). The decomposition kinetics indicated the relative anion stability for imidazolium based ILs was Tf2N > PF6 > BF4. In addition, the solubility data of three organic compounds (methanol, ethyl acetate, and benzene) in ILs were specified by the binary vapor-liquid equilibrium (VLE) at elevated temperatures. The results indicated bmim[Tf2N] was the best solvent for the organics investigated. For the same IL, the solute with a higher polarity tends to possess a lower activity coefficient. The activity coefficients of the organic compounds agreed well with the nonrandom two-liquid (NRTL) model.
Article
The solubility of isobutane in three ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]), and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([BMIm][Tf2N]) at temperatures ranging from 288.2 K to 313.2 K and pressures up to near atmospheric pressure were determined by a saturation technique. The solubility values were correlated using the Peng-Robinson equation of state with van der Waals 2-parameter mixing rules. In general, the model and the experimental data were in good agreement. Henry’s constants were calculated on the basis of the solubility data at different temperatures and fitted to the Benson-Krause (BK) equation well. The results showed that the solubilities of isobutane in these three ionic liquids increased with increasing pressure and decreased with increasing temperature and were in the sequence: [BMIm][Tf2N] > [BMIm][PF6] > [BMIm][BF4]. The solubility parameters (δ) of these three ILs were calculated and were used to qualitatively explain the difference of the solubility of isobutane in different ILs. Partial molar thermodynamic functions of solvation such as standard Gibbs free energy, enthalpy, and entropy were calculated from the solubility results.
Article
The past decade has witnessed an explosive growth in the applications of ionic liquids in homogeneous catalysis and the emphasis is no longer solely based on their use as green alternatives to volatile organic solvents but on understanding their physiochemical properties and their effect on reactivity such as enhancements in activity, selectivity, catalyst stability/longevity, improving catalyst separation/recovery protocols as well as recycling and engineering new processes. Other recent developments include the introduction of task specific functionality such as Bronsted acidic groups and heteroatom donors to target specific properties which will undoubtedly present opportunities to engineer new and/or improved processes and strategies. This chapter attempts to provide a practical and working overview that will enable a researcher inexperienced in the use of ionic liquids to make an informed decision about the possible benefits of applying ionic liquids to their research. An overview covers up-to-date synthesis, details about the non-innocent character of ionic liquids, ionic liquid effects on selectivity and activity, strategies in ionic liquid-based catalysis such as homogeneous and liquid–liquid biphasic catalysis and catalyst immobilisation, thermoregulated reversible ionic liquid biphasic systems, ionic liquid–scCO2 biphasic catalysis and supported ionic liquid phase catalysis, as well as a discussion of the use of polymer immobilised ionic liquids in catalysis. The survey is not exhaustive and has been limited to selected key and evolving areas including carbonylation-based transformations and cross-couplings, oxidations and hydrogenations, Lewis and Bronsted acid catalysis, organocatalysis, metathesis, ring opening polymerisation and dimerisation/oligomerisation, biomass transformations and concluding with catalysis by transition metal nanoparticles; a number of these overviews complement coverage provided by other chapters. For ease of navigation the chapter has been divided into five main sections “Carbonylation, Hydroformylation and Cross-Coupling”, “Oxidation and Hydrogenation”, “Lewis and Bronsted Acid Catalysis”, “Organocatalysis, Metathesis, Ring Opening Polymerisation and Dimerisation/Oligomerisation”, “Biomass Transformations and Catalysis with Transition Metal Nanoparticles”.
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A series of acidic ether functionalized chloroaluminate ionic liquids were synthesized and studied. The catalyst with the highest acidity was screened out by FT-IR spectra using acetonitrile as infrared probe and used to catalyze the alkylation of isobutane with 2-butene. It was proved that the acidity of 1-methoxyethyl-3-methylimidazolium bromide aluminium chloride ([MOEMIM]Br/AlCl3) was the highest when the molar ratio of AlCl3 was 0.75. The high quality alkylate with a C8 selectivity of 66.6%(mass) was obtained at 35℃ with the isoparaffin/olefin molar ratio (I/O) of 10, which was much better than that with non-ether functionalized chloroaluminate ionic liquids. The catalysts could be reused several times without obvious loss of activity.
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A convenient protocol for the synthesis of natural isoprenoid-derived carboxylic esters via reaction of allylic terpenols with triethyl orthoacetate (propionate) in the presence of 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6] (10 mol%), has been developed. The desired terpene derivatives were prepared in moderate to high yield. The ionic liquid (IL) can be easily separated from the products and repeatedly used up to ten times without reduction in the product yield. Experimental data evidence that HF, generated in situ from the IL, most likely acts as a true catalyst in the Johnson-Claisen rearrangement.
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Although research in renewables is growing at a tremendous rate, the world will still be greatly dependent on fossil fuels for at least the first half of this century. In the quest for more efficient and clean fuels, oil refining companies have turned their attention to processes such as reforming and alkylation technologies; in the latter process, isobutane is reacted with butenes and/or propylenes to produce, among others, branched isooctane, which is the main high-octane component of the gasoline pool. The main benefit of this process is the possibility to produce sulfur-free high-octane fuels, so important economic and environmental advantages are foreseen if investments in this area are realized. This Review analyzes and discusses the most recent progress on catalyst technologies, starting from the traditional sulfuric acid process and proceeding to newly emerging catalyst technologies such as solid acid and ionic liquid-based catalysts. We start with basic mechanistic analyses and conclude this Review with the new non-liquid acid-based commercial and emerging technologies for isobutane alkylation. Emphasis is given to the structure-activity relationships and the advantages and disadvantages present in every discussed catalyst material.
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Friedel–Crafts alkylation of benzene with 1-dodecene, which is an important reaction of synthetic detergent, was studied via ionic liquid [bmim][TFSI]/AlCl3 (1-butyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide/AlCl3) immobilized on SBA-15 catalysts. XRD, BET, TEM, TG, ammonia TPD investigations were used to search insight into catalyst characteristic. The immobilized catalysts preserved ordered structure and presented high specific surface areas. The utilization of active sites was significantly improved by immobilization. Based on ammonia TPD, immobilized catalysts exhibited higher Lewis acidity than aluminum chloride grafted SBA-15. TG indicated that thermal stability of ionic liquid has been improved by immobilization. The influences of various reaction conditions including reaction time, benzene/1-dodecene ratio were studied. Immobilized ionic liquids have better performance of no matter 1-dodecene conversion or 2-linear alkyl benzene (2-LAB) selectivity, than bulk ionic liquid catalysts or aluminum chloride grafted mesoporous materials. 2-LAB selectivity can be increased from about 35% with bulk ionic liquid to more than 60% with immobilized catalysts. Under optimal condition, 2-LAB selectivity reached as high as 80%. The immobilized catalysts could be reused. And at 3th cycle of catalysts, 1-dodecene conversion could still reach more than 50%. The role of deactivation was proposed based on TEM, BET and TG investigations. By-products as oligomer, produced by oligomerization of olefin, blocked or covered the pores, led to deactivation of catalysts.
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The complicated reaction mechanism and the character of competitive reactions leads to a stringent requirements for the catalyst of C4 alkylation process. Due to their unique properties, ionic liquids (ILs) are thought to be new potential acid catalysts for C4 alkylation. An analysis of the regular and modified chloroaluminate ILs, novel BrØnsted ILs and composite ILs used in isobutane/butene alkylation shows that the use of either ILs or ILs coupled with mineral acid as homogeneous catalysts can help greatly adjust the acid strength. By modifying the structural parameters of the cations and anions of the ILs, the solubility of the reactants could also be adjusted, which in turn displays a positive effect on improving the activity of ILs. Immobilization of ILs is an effective way to modulate the surface adsorption/desorption properties and acid strength distribution of the solid acid catalysts. Such a process has a tremendous potential to reduce the deactivation of catalyst and enhance the activity of the solid acid catalyst. The development of novel acid catalysts for C4 alkylation is a comprehensive consideration of acid strength and its distribution, interfacial properties and transport characteristics.
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Conventional strong liquid acids such as H2SO4 and HF are used for the majority of current commercial isobutane alkylation process to produce motor fuel alkylates, but these acids can have significant safety and sustainability concerns. Ionic liquid (IL) catalyst technologies offer potential advantages over current processes due to the negligible vapor pressure, and molecularly tunable properties that can optimize both the chemistry and engineering for alkylate production. In this review, IL-based catalysts used in isobutane alkylation are reviewed. ILs are categorized and discussed by the type: (1) metal-based Lewis acidic ILs, (2) metal-based Brönsted-Lewis acidic ILs, (3) non-metal based Brönsted acidic ILs, and (4) immobilized/supported ILs. A critical perspective on the use of these ILs in alkylation is presented, focusing on the effect of speciation and physicochemical properties on chemical reaction. Further, a summary of IL speciation is provided and examples of how the tunability of ILs can be used to overcome current limitations in alkylation chemistry. The reaction conditions and performance (conversion, C8 selectivity, trimenthylpentane:dimethylhexane ratio, etc.) of literature reports are summarized. A comparison of IL-based catalysts with the incumbent H2SO4 process and the new ISOALKYTM Chevron process are also discussed. Gaps in the literature (e.g. mass transfer rates, material compatibilities, phase equilibrium, etc.) associated with IL-based alkylation technology and our perspectives on solving the relevant issues in this field are summarized.
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The alkylation of isobutane with 2-butene catalyzed by ionic liquid/solid acid was studied in this work. In order to improve the product quality, the rotating packed bed (RPB) reactor was used to enhance the mass transfer of alkylation process. Residence time, reaction temperature, isobutane-to-olefins ratio, and acid-to-hydrocarbon ratio all markedly affect the quality of alkylates. Under the optimal conditions, the research octane number could reach 99.8, and the amount of trimethylpentanes was 87.1 wt%. Because of the high efficiencies of mass transfer and micro-mixing, RPB reactor can greatly improve the reaction efficiency of isobutane alkylation. By observing the droplets in RPB, the relationship between the average droplet diameter and the interfacial area was investigated. The droplet diameter and interfacial area were highly dependent on the physical parameters, such as acid-to-hydrocarbon ratio, rotational speed, and the interface tension of acid-hydrocarbon. Moreover, a correlation model was proposed to calculate the interfacial area of the RPB reactor. Smaller droplet diameter and larger interfacial area are beneficial to the production of high quality alkylates. RPB is one of promising industrial reactors for the ionic liquid/solid acid alkylation.
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A new background to organize diverse synthetic and natural resources to fabricate functional materials in a safe environment by using RoomTemperature Ionic Liquids (RTILs) is highly stressed. A newapproach to classify various RTILs on the basis of induced structural moieties is explored. RTILs are reviewed as reactionmedia to process functional materials, green composites, cellulose dissolution, energy production, additives, cleaner, chromatography, hetero/biocatalysis, bio/electrochemical sensors and interaction with bio-membranes to attract current academic and industrial development. RTILs are expected to substitute conventional solvents as RTILs have challenged both our experimental and intellectual abilities to explore further.
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The reaction mechanism of isobutane/1-butene alkylation is very complicated. Many parallel and competitive reactions exist in the reaction system. Stringent mass and heat transfer is a key to achieve satisfied selectivity and yield for this exothermic and mass transfer controlling reaction process. A microreactor configured with staggered herringbone grooves was adopted for intensifying the mass and heat transfer of this process. The hydrodynamic and mixing behaviors of reactants phase and catalyst phase in the microreactor with different channel size were simulated through Computational Fluid Dynamics. The simulation shows that smaller channel depth results in the relatively better mixing performance. The performance of isobutane/1-butene in the designed microreactor were studied systematically. Comparing with the stirring batch reactor, the designed microreactor provides constant reaction temperature and the reaction time can be shortened significantly to 29 s with 1-butene conversion of 91.4%. Under the optimal reaction conditions, the 1-butene conversion was 94.9%, the selectivity of C8 was 91.08%, and the alkylate research octane number was 99.7. The designed microreactor configured with staggered herringbone grooves is much better than the conventional reactors for isobutane/1-butene alkylation due to its excellent mass and heat transfer performance.
Article
Catalyst acidity is among the crucial parameters affecting the direction and degree of acid-catalyzed reactions. The Hammett acidity functions (H0) of binary mixtures of triflic acid (TfOH) and ionic liquids (ILs), namely, [BMim][HSO4], [BMim][TfO], and [BMim][TFA], were measured by the 13C NMR method using mesityl oxide as a probe. The results show that the H0 values of the mixtures can be effectively controlled by tailoring the structure of the IL or tuning the amount of IL added to the system. The -H0 values of the binary mixtures decrease with increasing amount of IL. Mixtures of [BMim][HSO4]/TfOH and [BMim][TfO]/TfOH show minimal changes in acidity (-H0 > 13.00) when the IL mole fraction is less than 0.05, a sharp decline in acidity (-H0 = 13.00 → 8.00) at an IL mole fraction of 0.05 to 0.20, and a relatively stable acidity (-H0 = 8.00 → 5.40) at an IL mole fraction of 0.20 to 0.50. These mixtures share nearly the same H0 value when the IL mole fraction is less than 0.20. The addition of [BMim][TFA] can alter the Hammett acidities of the binary systems more easily than [BMim][HSO4] or [BMim][TfO] at the same concentration. Models to predict the H0 values of the three IL/TfOH binary systems as a function of acid concentration are also proposed.
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Isobutane alkylation is a typical carbocation chain growth reaction that requires proper acidity with less acidity change for its enhanced lifetime and activity of the catalyst. In this work, a family of protic ionic liquid/triflic acid as synergistic catalysts has been developed for isobutane alkylation, with special emphasis on its reusability. The slowest acidity change was found with varied concentrations of triflic acid for the protic ionic liquids which is probably buffered by binding and releasing the solubilized acid in the formed anionic cluster [N222H][CF3SO3(CF3SO3H)x] as indicated by FT-IR and ¹H NMR spectroscopy. As a promising isobutane alkylation catalyst, the protic ionic liquids have shown a maximum selectivity toward C8 up to 86.23%, research octane number (RON) up to 97.3, and reusability up to 36 runs, outclassing the sulfuric acid or triflic acid catalysts under the same reaction conditions. Apart from the excellent catalytic performance, the new catalytic system showed better impurities compatibility and significantly less corrosion rate to carbon steel and stainless steel than sulfuric acid and pure triflic acid.
Article
Searching for new additives to enhance alkylation of isobutane and butene in H2SO4 has attracted interests of academic as well as industrial since the process was introduced to produce high quality oil product in large scale. This research focused on alkylation of isobutane and butene with additive of caprolactam (CPL) in H2SO4. With the new additive of caprolactam, selectivity of C8 was obviously improved due to the improved solubility of isobutane in H2SO4 and the decreased acidity. Different additive amounts of caprolactam were test, showing that 1.0 wt% is optimal and selectivity of alkane C8 can be improved from nearly 80% to 88%. And the effects of stirring speed, reaction temperature, acid to hydrocarbon volume ratio (H/C), isobutane to butene molar ratio (I/O), reaction time and variety of olefin were also studied carefully and respectively. Extended duration runs were practiced which has demonstrated that the system was stable. This new additive is potential to be applied in large scale industrial processes to improve the quality of alkylation.
Article
The alkylation of isobutane with butene is an important refining process for the production of a complex mixture of branched alkanes, which is an ideal blending component for gasoline. The current catalysts used in industrial processes are concentrated H2SO4 and HF, which have problems including serious environmental pollution, equipment corrosion, potential safety hazard, high energy consumption in waste acid recycling, etc. Solid catalysts are another type of catalyst for this alkylation; however, they suffer from problems related to rapid deactivation. Ionic liquids (ILs) can be considered as catalysts of the third generation to replace traditional catalysts in isobutane/butene alkylation to produce clean oil. In this review, alkylation catalyzed by various kinds of acidic ILs, including Lewis acidic ILs (such as chloroaluminate ones) and ILs containing Bronsted acidic functional groups (e.g., -SO3H ,[HSO4](-)), is reviewed. The currently reported ILs used in the catalysis of isobutane alkylation and their corresponding catalytic activity are summarized and compared. This will help the readers to know what kinds of ILs are effective for the alkylation of isobutane with butene and to understand which factors affect the catalytic performance. The advantages of the catalysis of isobutane/butene alkylation by ILs include tunable acidity of the catalyst by varying the ion structure, limited solubility of the products in the IL phase and therefore easy separation of the alkylate from the catalyst, environmental friendliness, less corrosion of equipment, etc., thus making catalysis by ILs greener. The mechanism and kinetics of the alkylation catalyzed by ILs are discussed. Finally, perspectives and challenges of the isobutane/butene alkylation catalyzed by ILs are given.
Article
The deuterated 2-butene was used to determine the alkylation reaction of isobutane and 2-butene in the composite ionic liquid ([BMIM]Cl-AlCl3-CuCl, CIL). The alkylation reaction was investigated in a batch stirred reactor. The self-alkylation and the oligomerization of 2-butene are more likely to occur in the CIL. The key components of the alkylates, such as trimethylpentane (TMP), dimethylhexane (DMH), light ends (LE), and heavy ends (HE), were investigated at different reaction temperatures. The kinetics model with the primary and secondary reactions was established to predict the alkylation reaction. In order to test the reliability of the kinetics model, the solubility and diffusivity of isobutane in the CIL were measured. The isobutane alkylation under the industrial reaction conditions was also studied in a static mixer. Whether in the traditional batch reactor or the static mixer, the predicted data from the kinetics model are in good agreement with the experimental values. The obtained model is much more reliable to describe the alkylation reaction catalyzed by ionic liquids. By using deuterated 2-butene and on-line rapid analysis technology, the relationship between the isobutane-to-olefins ratio and the kinetic parameters was determined.
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A liquid-liquid cyclone reactor was proposed for iso-butane alkylation catalyzed by ionic liquids. The reaction and separation were happened simultaneously in the reactor. RSM model combined with Eulerian multiphase and Transport models were used to simulate residence time distribution (RTD) of light-phase liquids in the reactor. The effects of flow rate ratio of heavy/light phases and total inlet flow rates on RTD were also investigated. The results show that the experimental values of mean residence time (MRT) are closed to the simulated values. The RTD curves show one single peak without a long tail, which indicates that there is no obvious back-mixing in the liquid-liquid cyclone reactor. MRT decreases as the inlet flow increases. Finally, the relationship between the mean residence time and the inlet flow are established, and proper operation conditions can be predicted base on the reaction time of iso-butane alkylation. © 2017, Editorial Board of “Journal of Chemical Engineering of Chinese Universities”. All right reserved.
Article
A series of novel polyether-based Brønsted acidic ionic liquids (ILs) have been synthesized, which contain both a polyoxyethylene (POE) chain and a sulfonic group (SO3H). The prepared ILs can well dissolve trifluoromethanesulfonic acid (TfOH), and IL/TfOH mixture has good intermiscibility with the reactants of isobutane and isobutene. Then, a new IL/TfOH catalytic system for the preparation of alkylate gasoline has been developed. The advantages of the new catalytic system are high selectivity for C8-alkylate product and the recyclability of TfOH catalyst. Under the optimal catalytic conditions (using the IL with the polymerization degree n = 75, IL/TfOH(v/v) = 5, reaction temperature 60 °C, reaction time 30 min, and stirring rate 800 rpm), the C8-selectivity can reach 80%, and above 95% of C8-alkylate product is trimethylpentane (TMP). Therefore, the new IL/TfOH catalytic system can afford high-quality alkylate gasoline. In addition, the conversion of isobutene and C8-selectivity both have gradually a little drop during 6 recycles, which should attribute to a little loss of TfOH in every recycle.
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Purpose The purpose of this paper is to synthesize amines/phenolic antioxidants by a new method and to characterize the influence of antioxidants on thermo-oxidative degradation in trimethylolpropane trioleate (TMPTO) base oil. Design/methodology/approach The molecule structures of antioxidants and lubricants were confirmed using Fourier transform infrared spectroscopy (FTIR). The oxidative stability of antioxidants and lubricants was evaluated by pressurized differential scanning calorimetry (PDSC). Findings These findings suggested that butyl-octyl-diphenylamine has obvious advantage on kinematic viscosity inhibition, and amine-phenol combination antioxidant has a slightly better suppression of total acid in TMPTO under thermal oxidation at 200°C for 96 h. The FTIR characterizations showed that all antioxidants could protect the basic structure of TMPTO in the early stage of thermal degradation. Originality/value Under the action of butyl-octyl-diphenylamine, the dehydrogenation of TMPTO is easily met with the alkenyl hydrogen = C–H bond in the unsaturated C = C. Meanwhile, as octadecyl 3-(3, 5-di-tert-butyl-4-hydroxyphenyl)propionate protects TMPTO, the unsaturated C = C bond in the base oil molecule easily breaks down during transition.
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Conventional acidic catalysts for isobutane and isobutene alkylation exhibit low alkylate selectivity. Herein, we employed a acidic deep eutectic solvent, consisting of trifluoromethanesulfonic acid and taurine, in polyethylene glycol as...
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Chemical reaction process intensification for clean fuel is becoming a hot topic for sustainable development. This work presents a new intensification technology of sulfuric acid alkylation of isobutane and butene using a microstructured chemical system. A microstructured chemical system has been designed and constructed. The reaction performance was determined, and the effect of acid concentration, phase ratio, reaction temperature, reaction time, and ratio of isobutane to butene (I/O) were investigated carefully. The results show that the microsturctured chemical system could obviously improve the quality of alkylates with much smaller size reactor and much shorter reaction time for high transfer performances. The conversion of olefin could be as high as 100% within 30 s. The selectivity of C8 was 71% with a research octane number (RON) 94.4 under the 94 wt% H2SO4. No obvious changes of H2SO4 concentration was observed after several cycles, indicating that the acid consumption could be effectively reduced in the microreaction process.
Article
The densities and surface tensions of [Bmim][TFO]/H2SO4, [Hmim][TFO]/H2SO4 and [Omim][TFO]/H2SO4 binary mixtures were measured by pycnometer and Wilhelmy plate method respectively. The results show that densities and surface tensions of the mixtures decreased monotonously with increasing temperatures and increasing ionic liquid (IL) molar fraction. IL with longer alkyl side-chain length brings a lower density and a smaller surface tension to the ILs/H2SO4 binary mixtures. The densities and surface tensions of the mixtures are fitted well by Jouyban-Acree (JAM) model and LWW model respectively. Redlich − Kister (R-K) equation and modified Redlich − Kister (R-K) equation describe the excess molar volumes and excess surface tensions of the mixtures well respectively. Adding a small amount of ILs (xIL < 0.1) into sulfuric acid brings an obvious decrease to the density and the surface tension. The results imply that the densities and surface tensions of ILs/H2SO4 binary mixtures can be modulated by changing the ILs dosage or tailoring the ILs structure.
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In China, the rapid development greatly promotes the national economic power and living standard but also inevitably brings a series of environmental problems. In order to resolve these problems fundamentally, Chinese scientists have been undertaking research in the area of green chemical engineering (GCE) for many years and achieved great progresses. In this paper, we reviewed the research progresses related to GCE in China and screened four typical topics related to the Chinese resources characteristics and environmental requirements, i.e. ionic liquids and their applications, biomass utilization and bio-based materials/products, green solvent-mediated extraction technologies, and cold plasmas for coal conversion. Afterwards, the perspectives and development tendencies of GCE were proposed, and the challenges which will be faced while developing available industrial technologies in China were mentioned.
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Alkylation of isobutane with 2-butene was performed in a batch reactor using the ionic liquid 1-n-octyl-3-methylimidazolium bromide aluminium chloride ([OMIM]Br-AlCl3) pure, and in a mixture with compounds containing SO3H-groups. The acidity of the ionic liquid (IL) was modified by the addition of acid cation exchange resins (dry or with a small amount of water), or by the addition of a second IL ([(HO3SBu)MIM]HSO4). A high content of the desired trimethylpentanes (up to 64%) and thus a high research octane number (RON up to 96) of the alkylate was obtained. The reusability of the IL systems was studied and compared with a catalyst commercially used at present (H2SO4).
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Extraction of S- and N-compounds from gasoline and diesel oil by ionic liquids (ILs) indicates that such a process could be an alternative to common hydrodesulfurization (HDS) for deep desulfurization down to values of 10 ppm S or even lower. The results show the selective extraction properties of ILs, especially with regard to those S-compounds which are hard to remove by HDS, e.g. dibenzothiophene derivatives present in middle distillates like diesel oil. The application of mild process conditions (ambient pressure and temperature) and the fact that no hydrogen is needed, are additional advantages compared to HDS. Very promising ILs are [BMIM][OcSO4] and [EMIM][EtSO4], as they are halogen-free and available from relatively cheap starting materials. Extraction with ILs is not limited to diesel oil, but probably even more attractive for FCC-gasoline. Although HDS of S-species present in this gasoline constituent – mainly thiophenes – is relatively straightforward, a major drawback is the loss in octane number by olefin saturation, which favours extraction with ILs.
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Ionic liquids are generally regarded as solvents, but these modular, tunable compounds have far greater technological potential. With a coat of silver, they become ideal materials for the liquid mirror of a space telescope.
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An easy experimental method to measure the solubility of isobutane/alkenes in sulfuric acid is established. By addition of minor amounts of anionic, cationic or ampholytic surfactants, the solubility value of isobutane/alkenes changes; that also influences the yield pattern of sulfuric-acid catalyzed alkylation reaction. According to solubility parameters, some additives are evaluated to enhance the solubility ratios of isobutane/alkenes. This gives rise to an improvement of the higher selectivity to trimethylpentanes; the research octane number is between 100 and I 10 and the material is an excellent component of gasoline. These additives are applied to isopentane/alkenes alkylation reaction simultaneously. It was found that the quality of alkylate gets better, due to the obvious decrease of the yield of heavy end materials (C(10+)). These facts reveal the industrially practical of solubility parameter and additives. Meanwhile, the yield of trimethylpentane is related linearly with the solubility ratio of isobutane/alkenes.
Article
The isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) to exo-THDCPD (Jet Propellant-10) and adamantane was investigated using ionic liquid (IL) as acid catalyst to explore an alternative greener than widely applied AlCl3-based operation. ILs composed of various 1-alkyl-3-methylimidazolium chlorides ([RMIM]Cl) and metal chlorides were checked, and [BMIM]Cl/AlCl3 was the best. The effects of acidity and dosage of IL, reaction temperature and time were studied for endo- to exo-isomerization of THDCPD. The reaction occurs quickly under mild conditions with both conversion and selectivity beyond 98%. Purifying the reactant can suppress deactivation of IL; and the used IL can be recycled four times by heating under vacuum after each run. By adjusting the reaction to severe conditions, i.e. higher IL dosage, higher temperature and longer time, exo-THDCPD is further isomerized to adamantane. But both the conversion and selectivity are much lower than those of endo- to exo- isomerization. The highest yield of adamantane is 50.9%, which can be further improved by some additives like 1-bromoadamantane. Compared with other methods, IL catalysis has many advantages from energy and environmental perspectives.
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A biphasic ionic liquid (IL) and compressed carbon dioxide system has a number of advantages for efficient homogeneous catalysis. The hydroformylation of 1-octene to nonanal catalyzed by a rhodium−triphenylphosphine complex was used as a model reaction to illustrate the effects of carbon dioxide in a biphasic ionic liquid/CO2 system using the model ionic liquid, 1-hexyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide ([HMIm][Tf2N]). Detailed phase equilibrium studies were conducted to determine volume expansion of the IL phase and the multiphase equilibria and mixture critical points between the reactant, product, and IL with CO2 and syngas (CO/H2). These data ultimately affect the concentration of the reactant and, thus, the apparent reaction rate. The viscosity of the IL with CO2 pressure was measured and demonstrates the dramatic decrease with increasing CO2 pressure. The self-diffusion coefficient of the ionic liquid and 1-octene were measured and indicate a large increase with CO2 pressure (solubility). With an understanding of the kinetics, phase behavior, and mass transport, biphasic IL/CO2 reaction systems may be properly understood and designed.
Article
Heteropolyacid (HPA) catalysts and their cesium salts were synthesized, characterized and evaluated for the alkylation of isobutane with 1-butene. Steady butene conversion and C8 alkylates production were demonstrated for over 50 h in dense CO2-enhanced reaction media in both a fixed bed reactor and a CSTR operated at 368 K, 80 bar, and molar feed isobutane/olefin ratio of 5 with 70 mol % CO2. The C8 alkylates selectivity is highest (25%) on HPA/SiO2, observed in a CSTR operated at an olefin space velocity of 0.05 h-1. This value is comparable to that obtained at similar operating conditions with Nafion/SiO2 (SAC-25), an ion-exchange resin. The cesium salts of HPA (either supported or unsupported) show high selectivity toward dimerization (>60%). The estimated effective alkylation rate constant is highest for SAC-25 closely followed by 70% HPA/SiO2. On all the catalysts tested, effective alkylation rate constants are 2 to 3 orders of magnitude lower than the dimerization rate constant. Hence, the design of solid acid catalysts that provide stable, industrially attractive C8 alkylates selectivity (70+%) remains a challenge.
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We will describe the use of superacids, in particular 1,1,2,2-tetrafluoroethanesulfonic acid (TFESA) and 1,1,2,3,3,3-hexafluoropropanesulfonic acid (HFPSA) in the presence of ionic liquids for improved chemical processing for a range of industrially important chemical reactions. In a number of cases the reaction mixture starts as a single phase, allowing for high reactivity, then separates into two phases upon completion of the reaction. This allows for ease of product separation P. T. Anastas and T. C. Williamson, Green Chemistry: Frontiers in Benign Chemical Syntheses and Processes, Oxford University Press, 1998.1
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The alkylation of isobutane with 1-butene was investigated on microporous (β-zeolite) and mesoporous (silica supported heteropolyacids) catalysts in a slurry reactor. The reaction was investigated in the range of 25–100 bar and 15–95 °C in liquid phase and in near critical reaction media with either dense CO2 or dense ethane as diluent, partially replacing the excess isobutane. At 75 °C, the selectivity towards trimethylpentanes (TMP) in the liquid phase is 70%+ initially, but decreases with time on all the catalysts investigated. While near-critical reaction mixtures were employed in order to enhance pore diffusion rates, the conversion and selectivity profiles obtained with such mixtures are comparable to those obtained with liquid phase reaction mixtures in both microporous and mesoporous catalysts. This implies that pore diffusion effects play a limited role at higher temperatures (75–95 °C). In contrast, the liquid phase results at sub-ambient temperatures indicate that the catalyst is deactivated before the TMPs diffuse out of the pores, indicating that pore diffusion effects play an important role in the deactivation process at low temperatures. Our results suggest that novel approaches that enhance the pore-diffusion rates of the TMPs at lower temperatures must be pursued.
Article
Various ionic liquids have been examined along with some traditional phase-transfer catalysts, such as Aliquat reagents, in a standard liquid−liquid phase-transfer catalysis (LLPTC) reaction. A standard O-alkylation LLPTC reaction was chosen because of its relatively high yields and low incident of reaction side products. As expected, quaternary tetraalkyl ammonium catalysts all resulted in high conversion to product. Aliquat HTA-1, a high temperature phase-transfer catalyst normally used in nonaqueous reactions, resulted in yields only slightly higher than the noncatalyzed reaction. Substituted pyrrolidinium salts had relatively good catalytic activity, while substituted pyridinium and imidazolium catalysts showed either very little or no catalytic activity. Catalysts with fixed cationic charges resulted in high conversion for the etherification reactions; however, compounds with an aromatic π-bonding system were not suitable as phase-transfer catalysts.
Article
A new process for 1-butene/isobutane alkylation to yield C8-alkylates is described using binary mixtures of certain acidic imidazolium ionic liquids (ILs) and strong acids such as sulfuric or trifluoromethanesulfonic (triflic) acid. Equivalent or better conversion (>95%), C8-alkylates selectivity (>70%) and trimethylpentane/dimethylhexane selectivity (TMP/DMH>7) were achieved with the IL/acid mixtures over the pure acids themselves. Six types of substituted 3-methyl-imidazolium ionic liquids were investigated, wherein acidity is imparted via either the cation with sulfonic acid groups or the anion (hydrogen sulfate) or both. Long-term studies up to 30+ recycles indicate that the catalyst stability was increased by sometimes greater than 30+% with the IL/acid mixtures over the pure acid. The ionic liquid is believed to tune the acidity, solubility, and interfacial properties, resulting in these enhanced results. In addition, this concept could also be applicable to Friedel–Crafts alkylation, acylation chemistries, or other acid-catalyzed reactions.
Article
Like our previous work with imidazolium- and phosphonium-based ionic liquids, we report diffusivities over a range of viscosities (71–532cP) and develop a predictive diffusivity correlation. Reported are the permeability, solubility, and diffusivity data for nine gases in nine ammonium RTILs liquids at 30°C, as determined with a lag-time technique. The gas solubilities and diffusivities of the ammonium RTILs are of the same magnitude as those for the phosphonium and imidazolium RTILs. The ammonium RTILs used, in this study, included cations with both N-alkyl groups and branched alkyl groups. We also report on ammonium-based RTILs derived from quaternary ammonium surfactants. These surfactants-derived ammonium-based RTILs offer a relatively inexpensive alternative to imidazolium-based RTILs. We compare and contrast the thermodynamic (solubility) and transport (diffusivities) phenomena in the ammonium-based RTILs with both the imidazolium and the phosphonium RTILs in the context of being working fluids in a chemical process. From this comparison came certain “universal” trends for diffusivity in RTILs. Specifically, diffusivity scales roughly with the inverse of the square-root of viscosity and inversely with solute molar volume to the power of 1–1.3. This means that diffusivity, in RTILs, is less dependent on viscosity, and more dependent on solute size than predicted by the conventional Stokes–Einstein model. The gases tested were carbon dioxide, nitrogen, oxygen, methane, ethylene, propylene, 1-butene, butane, and 1,3-butadiene.
Article
The isobutane alkylation with butenes is a reaction in which the substitution of mineral acids, such as sulphuric and hydrofluoric acids, by solid acid catalysts is highly desirable. Solid catalysts with good activity and selectivity for this reaction have been previously reported. However, bad stability is a major drawback in most cases. In this work, catalysts based on beta zeolite, exchanged with lanthanum were studied. It was found that these catalysts have lower activity than the Y zeolite both, in the protonic form, or with lanthanum in replacement of protons. EDX analyses showed that lanthanum is practically fully removed from the zeolite structure during an exchange with ammonium nitrate, even though the catalyst was precalcined. The total acidity as measured by pyridine temperature-programmed desorption is similar in the beta and the Y zeolites. However, the former zeolite has stronger acid sites, and because of this, the deactivation process occurs faster. Pulses of 1-butene at different temperatures can be used as a technique to predict the catalytic behavior of acid catalysts in the alkylation reaction. Using this technique, it was possible to determine that the beta zeolite is deactivated during the alkylation reaction by pore mouth plugging. The addition of platinum to the beta zeolite is useful in order to regenerate the catalyst using hydrogen at 80°C, although long times are needed to accomplish this regeneration.
Article
Hydrophobicity modification of the intrinsic polarity of the surface of SBA-15 mesoporous by ethoxytrimethylsilane was used in this work to make hybrid organic–inorganic mesoporous matrix. This matrix was functionalized with perfluorosulfonic acidic Nafion resin by a post-synthetic impregnation method. Characterized by N2-physisorption, XRD, and transmission electron micrographs (TEM), all the materials synthesized were highly ordered. Elemental analysis, 29Si MAS NMR, thermal gravimetric analysis (TGA), energy-dispersive X-ray (EDX) and potentiometric titration showed that trimethylsilane is grafted on the surface by capping the OHs and the Nafion resin was incorporated, revealing a strong solid acid with hydrophobic surface. The alkylation of isobutane/1-butene was thereafter evaluated on each material under specified conditions. Compared with the polar surface of conventional SBA-15 and commercial Nafion silica nanocomposite SAC-13, methyl-modified surface of SBA-15 material (denoted as Me-SBA-15) is a much better solid acid catalyst for isobutane/1-butene alkylation.
Article
Density functional theory method was employed to determine the alkylation reaction course of 2-butene and isobutane. A carbonium ion mechanism is supported through this theoretical simulation. The first step is the formation of sec-C4H9+ from the protonation of 2-butene. The carbonium ion reacts with isobutane to form tert-butyl carbonium ion via hydride transfer. This carbonium ion reacts with 2-butene quickly to produce trimethylpentane carbonium ion (TMP+), which is finally converted to TMP at a high reaction rate via hydride transfer from isobutane. Their transition states are obtained by QST2 method and the transition states are verified by frequency analysis. The calculation results indicate that the energy barrier of each reaction is below zero, suggesting that each reaction step is fast because of the characteristics of carbonium ions. However, the additive reaction is considered to be the rate-limiting step.
Article
Mesoporous SBA-15 silica materials have been functionalized with perfluorosulfonic acidic Nafion resin using a post-synthetic impregnation method. The remarkable physicochemical properties of hexagonally ordered SBA-15 silicas (high surface area, large and narrow pore size distribution and thermal stability) make them particularly attractive for the immobilization of strongly acidic perfluorosulfonic sites. The loading of Nafion resin was varied between 10wt.% and 20wt.%. The synthesized Nafion/SBA-15 hybrid materials were evaluated in the Friedel-Crafts acylation of anisole. The optimum catalytic performance of Nafion/SBA-15 hybrid material with a resin loading around 13wt.% was compared with other perfluorosulfonic acid-based catalysts either commercially available or prepared following recipes reported in the literature. The influence of several variables on the acylation of anisole, such as the reaction temperature and the anisole/acylating agent ratio, has also been assessed by means of a factorial design of experiments. The catalytic activity of Nafion-modified SBA-15 materials is strongly affected by the reaction temperature, whereas a lesser effect was evidenced for the reaction mixture composition in the range under study. The optimal operation conditions in terms of anisole conversion were achieved at 150°C and equimolar anisole/acetic anhydride mixture. The deposition of poly-acetylated by-products on the catalytic acid sites is mainly responsible for the catalyst deactivation, whereas the leaching of sulfonic groups and their contribution in the anisole acylation via homogeneous catalysis has been ruled out. Finally, the recovery of the catalytic activity by regeneration of the spent catalyst by refluxing in nitric acid solution was demonstrated. The characterization of the regenerated catalyst indicates that the regained activity is likely related to the displacement of the deactivating by-products out of the perflurorosulfonic acid sites during the nitric acid regeneration.
Article
Ionic liquids (ILs) and immobilized ionic liquids were used as acid catalysts for the liquid phase alkylation of raffinate II and isobutane. The influences of reactant concentration (molar ratio of iC4/C4), time, temperature and acid strength of the ionic liquids were studied. Using a step-up design under batch conditions with a very dilute mixture of isobutane and alkene, the conversion for a variety of ionic liquids was found to follow a pattern based on acid strength of the catalyst. Imidazolium based ILs were found to be superior to phosphonium based ILs. Novel Lewis-Acid Catalysts II (NLAC II, immobilization by grafting on siliceous MCM 41 or on silica FK 700) are better than other solid acid catalysts tested, such as SAC 13, zeolite H-Beta (Si/Al=14) and NLAC I (impregnation of ILs on silica FK 700). Possible leaching of the ionic liquid from the catalyst surface was followed by ICP measurements of the catalyst after reaction and of the reaction mixture.
Article
In the isobutane alkylation, alkylated gasoline is obtained which is a valuable blending component for the gasoline pool. Thereby the C3–C4 cut from the FCC units can be extensively used. Established technologies and recent developments will be reviewed and future perspectives will be given.
Article
The alkylation of isobutane with C4 olefins is studied, using heteropolyacids (HPA) with Wells–Dawson (WD) structure supported on silica (WD/SiO2). The catalytic performance of these catalysts is compared with a lanthanum-exchanged Y-zeolite catalyst. The loading of the HPA on silica was varied between 9 and 28wt.%. These catalysts have activity for trimethylpentanes (TMP) production. The selectivity towards these products is not as high as in the case of the lanthanum containing Y-zeolite. The acidity of WD/SiO2 catalysts increases as the loading increases, as seen by 1H MAS-NMR. Correspondingly, a better TMP production is observed. The increase both in acidity and in the TMP production as a function of the WD content is more noticeable at low loading. The coke formed during the reaction requires high temperatures, 550°C approximately, in order to be fully removed with an oxygen containing carrier gas. The temperature-programmed oxidation (TPO) profile of this coke displays two peaks, the first one between 80 and 300°C associated with hydrocarbons that are released upon heating, and the second between 300 and 550°C, associated with coke that changed its structure during the heating. A regeneration at intermediate temperatures, e.g. 300°C, removes the coke that corresponds to the first peak, but does not restore the initial activity. If the regeneration is carried out at higher temperatures, e.g. 500°C, most of the coke is removed, but this treatment leads to changes in the structure of the HPA, as indicated by FTIR and MAS-NMR analysis. Regeneration with O3 at low temperature (125°C) is effective both for coke removal and to recover the catalytic activity.
Article
An easy experimental method to measure the solubility of isobutane/alkenes in sulfuric acid is established. By addition of minor amounts of anionic, cationic or ampholytic surfactants, the solubility value of isobutane/alkenes changes; that also influences the yield pattern of sulfuric-acid catalyzed alkylation reaction. According to solubility parameters, some additives are evaluated to enhance the solubility ratios of isobutane/alkenes. This gives rise to an improvement of the higher selectivity to trimethylpentanes; the research octane number is between 100 and 110 and the material is an excellent component of gasoline. These additives are applied to isopentane/alkenes alkylation reaction simultaneously. It was found that the quality of alkylate gets better, due to the obvious decrease of the yield of heavy end materials (C10+). These facts reveal the industrially practical of solubility parameter and additives. Meanwhile, the yield of trimethylpentane is related linearly with the solubility ratio of isobutane/alkenes.
Article
Trifluoromethanesulfonic acid (TFSA) catalyzed isobutane-isobutylene alkylation modified with trifluoroacetic acid (TFA) or water, was studied over a wide range of acidity (Ho: −10.1 to −14.1). The effect of the acidity of these nonoxidizing strong mixed acid systems on the alkylation, is reported. For both systems, the best alkylation conditions were those at an acid strength of about Ho= −10.7, giving a calculated research octane number (RON) of 89.1 (TFSA/TFA) and 91.3 (TFSA/H2O).
Article
The deactivation of solid acid catalysts during the alkylation of isobutane with butene has significantly impeded replacement of the commonly used homogeneous catalysts. The relative rates of alkylation and hydride transfer control the rate of heavy hydrocarbon buildup, leading to blocking of catalyst pores and acid sites. Herein the mechanisms of hydride transfer and alkylation over phosphotungstic acid are examined using ab initio density functional theory methods. The transition state of hydride transfer is a carbenium ion, with shared-hydride carbonium ions representing lower energy intermediates. Although the transition state for the alkylation step is also a carbenium ion, it is stabilized by interaction with the alkene reactant. Therefore, the barrier for alkylation is intrinsically lower than that for hydride transfer, thus providing a favorable path to the buildup of heavy hydrocarbons on the acid surface. The implications of these findings on the design of effective catalysts for alkylation are discussed.
Article
12-Tungstophosphoric acid (HPW) has been supported on three different carriers: a commercial silica, a high surface area amorphous aluminosilicate (MSA), and an all-silica mesoporous MCM-41; and their catalytic properties have been determined for the alkylation of 2-butene with isobutane at 33°C and 2.5 MPa. A maximum in activity, selectivity to TMP and stability with time on stream was found for the HPW/SiO2 catalyst with 40 wt% acid loading, despite the higher acid dispersions achieved with the high surface area MCM-41 and MSA supports. The lower activity of the HPW/MSA samples is due to a stronger interaction of HPW with the surface sites of the aluminosilicate, which in turn decreased both the number and the average acid strength of the Brönsted acid sites of the heteropolyacid. When the HPW was supported on MCM-41 a continuous decrease of the catalytic activity with the HPW content was observed. This fact, together with the characterization results, suggests a partial blockage of the monodimensional pores of MCM-41, which decreased the accessibility of the reactants to the Brönsted acid sites of the heteropolyacid located inside the pores. We show that this pore blockage can be decreased, and the catalytic activity of HPW/MCM-41 catalysts increased, by using a MCM-41 sample with larger pore diameter.
Article
The chloroaluminate ionic liquid (CAIL) of the (CH3)3NHCl·nAlCl3 composition was studied by physico-chemical methods and catalytic activity measurements in heptane isomerization reaction. The data were also obtained on HCl solubility in CAIL depending on pressure and AlCl3 distribution between CAIL and heptanes depending on concentration. Based on obtained results CAIL is a homogeneous catalytic system containing an active component (HCl), co-catalyst (AlCl3) strengthening its catalytic activity, and solvent—so-called “neutral” ionic liquid. The CAIL main deactivation causes were studied including HCl loss and formation of acid soluble oil (ASO) poisoning the catalyst. The difference between CAIL and superacid catalysts poisoning by ASO was discussed.
Article
Reported are the solubility, diffusivity, and permeability data for various gases in five phosphonium-based ionic liquids at 30 °C, as determined with a lag-time technique. The ionic liquids have a viscosity range of 200−3000 cP. The gas solubilities and diffusivities of the phosphonium-based ionic liquids are of the same magnitude as the gas solubilities for the more familiar imidazolium-based liquids. The gas diffusivity appears to be inversely proportional to the viscosity with an average power of 0.35 for the phosphonium-based ionic liquids. This is in contrast to the power of 0.6 for the imidazolium-based ionic liquids, suggesting that the viscosity−diffusivity relationship varies for different classes of ionic liquids. Despite the generally higher viscosities of the phosphonium-based RTILs compared to the imidazolium-based RTILs, the similarity in thermodynamic and transport properties allows the consideration of the phosphonium-based RTILs as low-cost alternatives for reaction media or separation agents. The gases tested were carbon dioxide, ethylene, propylene, butene, and 1,3-butadiene. Also reported are the permeabilities of methane, nitrogen, and oxygen.
Article
The Friedel-Crafts acylations of representative aromatic compounds with acetic anhydride in pyridinium based ionic liquids (ILs) were investigated. The effect of factors such as reactant composition, catalyst-IL composition, catalyst dosage and reaction temperature were studied. The reactions were found to proceed under relatively mild conditions with excellent conversions; and a simple product isolation procedure was achieved. ILs could also be recycled and reused effectively, thus rendering green characteristic to this reaction.
Article
This report presents the systematic study on the solubilities of 1-alkyl-3-methylimidazolium hexafluorophosphate [e, or bmim][PF The data were correlated by means of the UNIQUAC and modified nonrandom two-liquid (NRTL) equations utilizing parameters derived from the solid–liquid equilibrium (SLE). The root-mean-square deviations of the solubility temperatures for all calculated data depend on the particular system and the equation used. The solubilities of [C
Article
Alkylation of isobutane and butene was carried out in a batch unit using 1-butyl-3-methylimidazolium chloride (BMIC)-aluminium (III) chloride (AlCl3) ionic liquid as catalyst. The effects of additives of butyl thioalcohol and ethyl thioether on the properties of ionic liquids for alkylation were investigated. Improvement of production distribution with high yields of isooctane and selectivity of TMP under a mild reaction condition was observed after addition of butyl thioalcohol. Moreover, the effects of operating variables were investigated and the mechanism was discussed.
Article
Liquid-phase processes with concentrated sulfuric acid or hydrogen fluoride as catalysts are currently being used in petroleum refining for the manufacture of alkylation gasoline from isobutane and butenes. While the product, i.e., alkylate, is a most valuable gasoline component, the existing processes for its manufacture are less satisfactory. Replacement of the liquid catalysts by a solid acid is an important target of modern research. In the past two decades, a large number of solid acids have been scrutinized, and at least four developments were driven till the pilot plant stage. In this paper, an attempt is made to rationalize, on a mechanistic basis, the selectivity loss almost always encountered with solid acids after relatively short times-on-stream. Suggestions are made concerning a more target-oriented research on isobutane/alkene alkylation in the future.
Article
Organically modified mesoporous silica materials have been prepared by direct co-condensation of styrylethyl-trimethoxysilane (STETMOS) and tetraethyl-orthosilicate (TEOS) in one-pot synthesis. The polymerizable nature of the styryl-containing precursor induces the formation of anchored polystyrene blocks on the silica surface, which are amenable to be functionalized with acid groups via sulfonation. The resultant organosulfonic-modified mesostructured silica materials exhibit hexagonal long-range mesoscopic arrangement with extended surface areas and narrow mean pore size distributions. Upon sulfonation a high number of sulfonic-acid sites have been introduced on the silica-anchored polystyrene-type organic moieties, thus providing strong acid sites embedded in a hydrophobic microenvironment. The catalytic performance of these strongly acidic hydrophobic materials has been assessed and compared with commercial catalysts in three different acid-catalyzed reactions. Two of them are acid strength-demanding reactions such as acylation of anisole with acetic anhydride and Fries rearrangement of phenyl acetate. The third one, based on the esterification of oleic acid with n-butanol, is a catalytic test wherein the hydrophobic nature of the catalyst surface plays an essential role. As result of these catalytic tests, the sulfonated polystyrene-modified hybrid materials have been shown as versatile and highly active acid heterogeneous catalysts, especially in hydrophobicity-demanding systems.
Article
Isobutane was alkylated with 2-butene, in batchwise conditions, using liquid 1-butyl-3-methylimidazolium chloride—aluminium chloride molten salts as the acidic catalyst. The effect of the operating variables on the product composition has been investigated. The control of the acidity of the catalyst has made possible the production of a high quality alkylate.
Article
The effect of adding aromatic compounds and varying the AlCl3 molar fraction on the catalytic performance of chloroaluminate ionic liquids in isobutane/2-butene alkylation was investigated. 27Al NMR results and comparison with alkylation catalyzed by solid AlCl3 reveal that the activity of the ionic liquids presumably comes from traces of AlCl3 or Al2Cl6. The addition of benzene increases the selectivity of C8 as well as the TMP:DMH ratio in the alkylate. The performance of the modified catalyst is optimized at high isobutane to 2-butene ratios and low temperatures. The used catalyst can be regenerated by replenishment of the aromatic additives.
Article
Supercritical alkylation and butene dimerization were investigated using sulfated zirconia (SZ) and iron–manganese promoted sulfated zirconia catalysts (SFMZ), as a function of iso-butane/olefin (I/O) ratio and at temperatures between 60 and 155°C. Detailed product analysis demonstrated that while C8 yields were as high as 80 wt.%, neither catalyst produced significant quantities of trimethyl pentanes, although both had high selectivities to dimethyl hexenes. A comparison of 1-butene versus 2-butene as the olefin feed charge showed that 1-butene first isomerizes to 2-butene, which then produces C8 products. In all cases, the products consisted primarily of C8 olefins, which in turn was dominated by dimethyl hexenes. The addition of water at a concentration as low as 1.4 mol% was found to increase dimethyl hexene selectivity (94 wt.%), and lowered the deactivation rate by 30%. The dimerization of a straight 2-butene charge produced a C5+ yield in excess of 90 wt.%, with a 73 wt.% selectivity to dimethyl hexenes. Subsequent regenerations of this catalyst resulted in about 10% conversion loss/generation, but with minimal change in dimethyl hexene selectivities.
Article
Ionic liquids are a new class of organic solvents with high polarity and a preorganized solvent structure. Very polar reactions can be carried out in these liquid in the absence of or with a controlled amount of water, and crystalline nanoparticles can be synthesized conveniently at ambient temperatures. The pronounced self-organization of the solvent is used in the synthesis of self-assembled, highly organized hybrid nanostructures with unparalleled quality. The extraordinary potential of ionic liquids in materials synthesis is described in this minireview and a physicochemical explanation is given.