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Alkylation of isobutane with 2-butene using 1-butyl-3-methylimidazolium chloride-aluminum chloride molten salts as catalysts

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Abstract

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.

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... The UV− vis spectra was recorded on a CARY 500 spectrometer to measure the acid strength of the SFILs. 4 ], were synthesized according to the previous literatures, respectively, with the optimized molecular structures as shown in Figure 1. 25−27 The detailed synthesis processes of SO 3 H-functionalized ILs and the acid strength represented by Hammett acidity function (H 0 ) as well as the measured process were included in the Supporting Information. ...
... It can be seen that the maximum absorbance peak is observed at the wavelength of 373 nm, and the peak intensity increases with the prolonged alkyl chain length, but corresponds to a decreased acid strength. Furthermore, the value of H 0 was determined by different absorbance at 373 nm and listed in Table 1 4 ], indicating that the SFILs with longer alkyl chain present a lower acid strength. However, the acid strength of SFILs is much lower than the optimal H 0 range for the isobutane alkylation (−8.1 to −12.7). ...
... 3 4 ] exceeds 10 wt %, the quality of alkylate begins to deteriorate. For the SFILs with longer chains, the addition amounts follow the similar trend as the shorter one. ...
Article
In this work, the SO3H-functionalized ionic liquids (SFILs) ([CnPSIm][HSO4], n=1, 2, 4, 6, and 8) were investigated as co-catalyst mixed with the concentrated H2SO4 for the isobutane alkylation. The SFILs with longer alkyl chain show a better catalytic performance with the C8 selectivity up to 75.73 and RON up to 95.66, respectively. The better catalytic performance can be attributed to the better dispersion of isobutane in the SFIL/H2SO4 system led by the SFILs with longer alkyl chain, which is further correlated with the nanostructured-aggregation feature of the longer alkyl chain confirmed by MD simulation. In addition, the reusability of SFIL/H2SO4 mixture can reach up to 22 runs, outclassing the pure H2SO4. The MD simulation, quantum chemistry calculations and 1H-NMR spectra revealed that cationic clusters are formed by the strong hydrogen bonds between the sulfonic acid group and the H2SO4, which is beneficial to the longer lifetime of the SFIL/H2SO4 mixtures. Hopefully, the useful information in this work will provide valuable insights into the screening and design of novel SFILs for the H2SO4 alkylation.
... Thus, it becomes one of the most valuable variables in maximizing alkylate quality. ILs derived from organometallic compounds represents one promising alternative to conventional acids due to their adaptation suitability to Lewis and Brønsted acidity [6]. It is known that HCl dissolved in an organochloroaluminate-IL is a Brønsted superacid, comparable to 100% H 2 SO 4 [7,8]. ...
... Several works related to LAC with chloroaluminate ILs can be assembled by the molar ratio of AlCl 3 to ILs or by the type of applied cations. For example, the relative amounts 55 and 67 mol% produced highly acidic Lewis chloroaluminate species, such as Al 2 Cl 4 − , or Al 2 Cl 7 − or Al 3 Cl 10 − and as a result, better butene conversion and higher RON [6,58,[66][67][68] were obtained due to the following mechanism (Fig. 8). ...
... Ionikilatyion™ process technology started from research reported in 1994 on the design of catalytic materials based on aluminum chloride and ILs [6]. In 2003, a pilot plant was built to produce 20 tons per year (TPY). ...
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.
... Up to now, there are only a few publications about ionic liquids as catalysts for the alkylation. But similar results regarding the effects of the acidity on the yield and product quality are reported [24,29]. ...
... The change of the alkylate distribution with stirring time in this case (Fig. 42 It is said that ILs have a potential for recycling [24,29]. However, an investigation about the reusability of ILs has up to now not been reported. ...
Thesis
Full-text available
During the last decades motor gasoline formulation has been forced by legislative requirements to make this still important transportation fuel more environmentally friendly. The effects of gasoline combustion on the environment are directly related to its properties and composition. Above all, the emissions of carbon monoxide, hydrocarbons, SOx, and NOx have to be reduced in the exhausts of vehicles. The clean air regulation in the E.U. and the U.S.A., concerning the contents of alkenes, sulfur, nitrogen and aromatics, especially of benzene, in the gasoline will become increasingly strict 1. Hence, the different blending compounds for gasoline must be reevaluated from an environmental point a view. The FCC gasoline (mainly aromatic and unsaturated HCs) and the catalytic reformate (mainly aromatic HCs) are still the most important blending components for petrol. Nevertheless, FCC gasoline is a major contributor of sulfur and olefins whereas reformate is the main source of benzene and aromatics. Substitutes, namely MTBE or other ethers, which were established in order to make the gasoline more environmentally benign, have been found to contaminate drinking water and will be removed at least in North America 1. Alcohols (e.g. ethanol) proposed as alternative oxygenates exhibit a very high blending vapour pressure when mixed into gasoline. Hence, this enhancement of vapour pressure reduces their broad usage in gasoline. In contrast to FCC gasoline and reformate, alkylate shows considerable advantages as a blending component. Alkylate offers a high octane number, a low Reid vapour pressure (RVP) and low octane sensitivity (difference of research octane number (RON) and motor octane number (MON)). It contains no aromatics and alkenes and nearly no sulfur. So it is an ideal blending component for gasoline [3, 4]. The world-wide installed alkylation production capacity is approx. 102 million tons/year. This amount of alkylate only fulfills about 10 % of the total amount of gasoline required all over the world. Although the products from alkylation are of high quality, the catalysts used up to now in the technical processes are not ideal. Currently, the catalysts industrially employed are mainly sulfuric acid or anhydrous hydrofluoric acid. Therefore, the wide application of the alkylation process is restricted because of the high toxicity and corrosiveness of both acids [5, 6]. Numerous alternative catalysts, most of which are solid acids (e.g. zeolites, sulfate-promoted metal oxides) have been investigated [7 -13]. However, they have not yet achieved technical application as alkylation catalysts because of rapid catalyst decay by coking [14 - 16]. Therefore, an extensive research was carried out during the past decades in the industry and in academic research laboratories to overcome this problem. An important requirement for a new alkylation catalyst is a very strong acidity and thus so-called ionic liquids could be an attractive option. During the last decades ionic liquids (ILs) were introduced as a new class of liquid material [17 - 20]. ILs are defined as salts melting below 100 °C. They have in general no (or a practically not measurable) vapour pressure and thus a loss by evaporisation is impossible. Besides of a lot of other very unique and valuable properties, ILs can be prepared to have a high acidity. Therefore, they are intensively discussed as environmentally friendly and less hazardous solvents or catalysts in industry [21 - 24]. Therefore, some acidic ionic liquids ([BMIM]Cl/AlCl3, [CnMIM]X/AlCl3, and Et3NHCl/AlCl3) were already investigated as a new source for environmentally friendly catalysts for the alkylation of iso-butane with butenes [25 - 28]. Furthermore, the acidity can be tuned in the range from low acidic to superacidic systems 29. The published results showed that alkylation catalysed by highly acidic ILs can be performed successfully but with a lower selectivity and alkylate quality compared to the up to now industrially used catalysts (HF, H2SO4). The results indicate that ionic liquids possessing a high acidity would be suitable as alkylation catalysts. During the final preparation of this work, an industrial plant for alkylation based on superacidic ILs was started in 2006 in China which does show the high potential of ILs for this process 30. Therefore, it was the subject of this work to study acidic ionic liquids as alternative catalysts in the alkylation reaction. The focus of the thesis was directed to the tuning of the required acidity concerning the product quality and the stability of the catalytic systems. In the ideal case only highly branched hydrocarbons with a boiling point in the gasoline range and thus with a high octane number should be formed.
... 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. ...
... It is wellknown that when the ratio of AlCl 3 to the [Bmim]Cl is above 50%, with the increase of the AlCl 3 content in the [Bmim]Cl, the anion [AlCl 4 ] will decrease and the anion [Al 2 Cl 7 ] will increase. Therefore, it can be inferred that taking the effect of both the acidity and the diffusion into account, there should be an optimal content of AlCl 3 to produce the best result of the C 4 alkylation catalyzed by chloroaluminate-based ionic liquids, which has been confirmed by Chauvin et al. (1994). ...
... Huang et al. [19] and Wang et al. [20] studied the isomerization of dicyclopentadienes by [Hpy]Cl-AlCl3. In particular, the alkylation reaction of isobutane and butenes catalyzed by chloroaluminate ionic liquids, such as [C4mim]Cl-AlCl3 [21], [(C2H5)3NH]Cl-AlCl3 [22], and amide-AlCl3-based IL [23], have been studied intensively for years [15]. Compared with chloroaluminate ILs, the chlorometallate systems that only contain Fe-, Cu-, Zn-, In-, or Sn-based anions usually present lower Lewis acidity [24]. ...
Article
Full-text available
Mixed chlorometallate ionic liquids (ILs) have been regarded as potential solvents, catalysts, and reagents for many organic processes. The acidity and basicity of these ILs were correlated with theoretically estimated parameters such as electrostatic surface potential maxima and minima, average local surface ionization energy, and Fukui and dual descriptor functions. The introduction of metal chloride into the anions would influence the acidity/basicity of ILs by withdrawing the electron density from the cationic counterpart. For the [C4mim]-based ILs with the mixed-metal anions, the acidity tends to attenuate while the basicity becomes stronger, as compared to the corresponding chloroaluminate ILs. However, the acidity of [(C2H5)3NH]-based ILs with the mixed-metal anions are greater than that of the net chloroaluminate ILs. The Fukui function values showed that most of the mixed chlorometallate ILs belong to bifunctional distribution. The mixed chlorometallate ILs both have electrophilic and nucleophilic sites, which would be beneficial for their applications.
... The liquid product should be distilled in a Claisen flask to remove the excess isobutane, and then the alkylate was analyzed in the gas chromatograph (Hewlett-Packard, 6890) equipped with a Supelco Petrocol DH capillary column (50 m × 0.1 mm × 0.1 mm). The research octane number (RON) of alkylates was calculated according to the Chauvin's methods [40]. The batch reactor could be easily converted to a continuously stirred tank reactor (CSTR) for studying the C 4 alkylation reaction. ...
... Aliquots of the hydrocarbon phase were withdrawn and then injected into a gas chromatograph (Hewlett-Packard, 6890) for analysis. In this study, the RON of the alkylate was calculated according to a previously described method (Chauvin et al., 1994). The C 8 content of the alkylate was defined as the total weight of isooctane (trimethylpentane + dimethylhexane + methylheptane). ...
... In recent years, ionic liquids (ILs) have attracted numerous attentions as an alternative and promising solvent or catalyst for the https://doi.org/10.1016/j.cej.2018.08.130 isobutane alkylation due to their considerable advantages, such as strong Brønsted and Lewis acidity, negligible-vapor pressure, highchemical stability, designable structures, and good solubility for a large amount of organic and inorganic compounds [10,11]. A large amount of research work has been done using the chloroaluminate-based ILs (CILs) with the Lewis acidity as the catalyst for the alkylation over the past decade in term of catalytic performances [12][13][14][15][16][17][18][19][20], as well as interfacial properties [21][22][23]. However, the CILs possess the nature of the high cost and extremely easy formation of HCl with traces of H 2 O, which limits their extensive applications [24]. ...
Article
The interfacial microenvironments between catalysts and C4 hydrocarbons for the isobutane alkylation is of vital importance to producing high-quality alkylate. In the present work, the interfacial properties between Brønsted acidic ionic liquids (BILs)/H2SO4 and C4 mixtures, as well as between the cationic and anionic surfactants/H2SO4 and C4 mixtures were investigated using molecular dynamic (MD) simulations, in which BILs share different alkyl chain length on cations with or without a sulfonic acid group. It indicated both BILs and surfactants can enhance the H2SO4/C4 reactants interfacial properties and facilitate C4 reactants dissolution, contributing to a better catalytic performance. The enhancement of the interfacial properties can be ascribed into the stronger density enrichment and perpendicular behaviors of the longer alkyl chains at the interface. Compared to non-SFILs, sulfonic-acid-functionalized Brønsted acidic ionic liquids (SFILs) can facilitate a higher dissolution of isobutane in both bulk and interfacial regions, but result in a lower interfacial diffusion. In addition, the much stronger interfacial enrichment of surfactants without mixing with H2SO4 leads to a worse catalytic performance than BILs. However, the better mixing between BILs and H2SO4 leading to better catalytic performance suggests the important role of the BILs acting as phase transfer catalyst for the H2SO4-catalyzed alkylation.
... As a promising solvent or catalyst for the C4 alkylation, ionic liquids (ILs) have attracted numerous attentions because of their considerable advantages, including the strong Brønsted and Lewis acidity, negligiblevapor pressure, high-chemical stability, and designable structures [11,12]. A series of studies on the catalytic performances and interfacial properties of the chloroaluminate-based ILs (CILs) with the Lewis acidity used in the alkylation process have been done over the past decade [13][14][15][16][17][18][19][20]. However, the extensive applications of the CILs were limited due to the nature of the high cost and extremely easy formation of HCl with traces of H 2 O [21]. ...
Article
As a dual solvent-catalyst, sulfonic-acid-functionalized ionic liquids (SFILs) are promising catalysts for the C4 alkylation. In the present work, the effect of the SFILs with different ratios to the H2SO4 on the catalytic performance and interfacial properties for the H2SO4-catalyzed alkylation was investigated by the combination of experiments and MD simulation. Experimental results indicated that compared to pure H2SO4, the introduction of the SFILs can contribute to a higher selectivity of C8-alkylates as well as Research Octane Number (RON), suggesting a higher quality of alkylate. Moreover, the catalytic performance of the SFIL/H2SO4 catalyst is improved with the increased addition ratio of the SFIL into the H2SO4 within the range of 10 wt%. MD simulation results revealed that the obvious density enrichment of the cations of the SFILs at the interface results in a larger interface width, and higher interface number and better dispersion of C4 hydrocarbons at the interface, which can be ascribed to the location of the alkyl chains close to the C4 hydrocarbon phase with the extended and perpendicular behaviors. The improvement of interfacial properties due to the addition of the SFILs is favorable to the enhancement of the quality of alkylate, which is in excellent agreement with experimental results. Hopefully, the useful information in this work can provide a reference to the design of the SFILs and the optimization of the C4 alkylation process.
... However, chloroaluminate ILs are usually sensitive to moisture and hydrolyze easily to form HCl, which results in the irreversible deactivation of the catalyst system. 27 The effect of I/O molar ratio on the reaction results is also given in Table 3 (Entries 2, 11 and 12). With increasing I/O molar ratio, the 2-butene conversion and TMP selectivity increased, and the C 9 + selectivity decreased. ...
Article
Full-text available
The alkylation reaction of isobutane with 2-butene to yield C8-alkylates was performed using Brønsted–Lewis acidic ionic liquids (ILs) comprising various metal chlorides (ZnCl2, FeCl2, FeCl3, CuCl2, CuCl, and AlCl3) on the anion. IL 1-(3-sulfonic acid)-propyl-3-methylimidazolium chlorozincinate [HO3S-(CH2)3-mim]Cl-ZnCl2 (x=0.67) exhibited outstanding catalytic performance, which is attributed to the appropriate acidity, the synergistic effect originating from its double acidic sites and the promoting effect of water on the formation and transfer of protons. The Lewis acidic strength of IL played an important role in improving IL catalytic performance. A 100% conversion of 2-butene with 85.8% selectivity for C8-alkylate was obtained under mild reaction conditions. The IL reusability was good because its alkyl sulfonic acid group being tethered covalently, its anion [Zn2Cl5]⁻ inertia to the active hydrogen, and its insolubility in the product. IL [HO3S-(CH2)3-mim]Cl-ZnCl2 had potential applicability in the benzene alkylation reaction with olefins and halohydrocarbons.
... 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). ...
... 氯铝酸离子液体是碳四烷基化研究中备受关注的 一类离子液体 [11] , 在其合成时AlCl 3 摩尔分数大于0.5时 具有较强的Lewis酸性, 且酸性可依据AlCl 3 摩尔分数 不同进行适当调节; 而当氯铝酸离子液体同时存在 HCl时, 离子液体具有超强的Brønsted酸性. 法国石油 研究院(IFP)的Chauvin等 [12] 国外的研究单位包括美国辛辛那提大学(Univer-sity of Cincinnati) [13] 、德国亚琛大学(University of Aachen) [14] 、美国堪萨斯大学(University of Kansas) [15] 、 德国拜罗伊特大学(University of Bayreuth) [16,17] 、越南 河内矿业地质大学(Hanoi University of Mining and Geology) [16] 、雪佛龙公司(Chevron Corporation) [18,19] 、 壳牌石油公司(Shell Global Solution International B. ...
Article
Full-text available
Alkylate from isobutane alkylation is an ideal blending component of motor gasoline. In China its blending ratio in gasoline is continuously increased with upgrading the gasoline quality standards. A series of studies on ionic liquid catalyzed isobutane alkylation were carried out around a new industrial process of alkylate production. The composition, structure and catalytic performance of chloroaluminate ionic liquids were studied, and a composite ionic liquid (CIL) with high catalytic activity and high selectivity was designed and synthesized. The deactivation mechanism of CIL during isobutane alkylation was studied and a feasible regeneration scheme was developed, including a Lewis acid activity monitoring method of chloroaluminate ionic liquids. A long period (2 months) operation test was carried out in a pilot plant, and then the initial process development of CIL catalyzed isobutane alkylation technology (CILA) was completed. A new type static mixing reactor and a hydrocyclone were developed. The first industrial plant of CILA was designed and constructed. The plant includes feed pretreatment, alkylation reaction, catalyst regeneration, product separation and clean-up systems. The industrial operation results were excellent. Butene conversion reached 100%, research octane number of alkylate maintained stably at above 95 and could reached up to above 98 at optimal operating conditions, end boiling point of alkylate was below 198 °C, and Cl content in alkylate was below 5 mg/L. CILA can produce clean alkylate with clean process, having a good application prospect and promotion value. http://engine.scichina.com/doi/10.1360/N032017-00168
... In recent years they are being regarded as promising alkylation catalysts, improving the reactivity and selectivity of the classical catalysts used until today. In particular, when using acidic choloroaluminate IL catalysts, a high quality alkylate was obtained, presumably because of the adjustable and suitable Lewis and Brønsted acidity [23][24][25][26]. 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. ...
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.
... 3,[16][17][18][19][20][21][22] Due to the excellent Lewis acidic properties, the chloroaluminatebased ILs have been the most frequently investigated substitutes to catalyze the alkylation with better catalytic performances. 3,20,[23][24][25][26][27][28] For instance, the selectivity of trimethylpentanes (TMPs) of alkylate using chloroaluminate-based ILs as catalysts reported by Liu et al. 27 was up to 87.5 wt % and the corresponding RON reached 100.5. 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. ...
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.
Article
Group IIIA halometallate ionic liquids (ILs) present fascinating properties for the field of catalysis, particular through the ability to tune their Lewis acidity solely by changing the metal complex speciation. In this review, we present a critical perspective on the use of Group IIIA halide-derived ILs in catalysis, focusing on the effect of speciation of the metal-containing ions on various acid-catalyzed reactions, some of which are applied industrially. We summarize all applications of Group IIIA halometallates in catalysis (where they are notably well-represented in reactions of importance in petroleum refining and processing), compare the authors’ investigations or assumptions with regard to chemical speciation, and present examples of how the tunability of these materials is used to overcome their initially perceived drawbacks. Further, advances in the field of halometallate ILs such as the role of the cations in the IL, IL analogues, and heterogenization strategies are discussed. High selectivity, reactivity, and stability are the corner stones of ideal catalyst, and the journey of catalysis research towards ideal catalyst will be possible only with rational catalyst design and innovative thinking.
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A series of adamantane-based ionic liquids (ADM-ILs) with [MFn]⁻ anions were synthesized as co-catalyst for the alkylation of isobutane and butene. By systematically tuning the structure of cation and anion and their combination, the optimized ionic liquids―ADM-C12-SbF6 exhibit significant enhancement on the C8 selectivities ( especially trimethylpentanes(TMPs)), the research octane number (RON) of the alkylate products and the lifetime of sulfuric acid. The selectivity of TMPs was improved from 81.9% to 84.5% and the alkylate RON from 96.6 to 98.6 with the addition of ADM-ILs. In addition, the lifetime of ADM-ILs/H2SO4 system was increased twice that of using H2SO4 alone. Based on experimental measurements and DFT calculation, all these enhancements were attributed to the multifunctions cooperatively integrated into the task-specific ADM-ILs, such as surfactant action-improving interfacial properties of acid/hydrocarbon biphases, buffer action-stabilizing the acidity change during the reaction process, and hydride donor action-accelerating the H⁻ transfer rate which promoted the production of TMPs. This study is beneficial to improve the isobutane alkylation process catalyzed by concentrated sulfuric acid.
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Two solids of differing Lewis acidities, triethylammonium tetrachlorozincate ([HN222]2[ZnCl4]) and AlCl3, have been combined across 0.1 to 0.9 mole fractions (with respect to [HN222]2[ZnCl4]), and homogeneous solid double salts or mixed metal [HN222]2x[(1-x)AlCl3+xZnCl4] double salt ionic liquids (DSIL) were obtained at x = 0.33, 0.4, and 0.5 with varying Lewis acidity. Characterization of the prepared DSILs (melting point, color, homogeneity, 1H, 13C, and 27Al nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), Single Crystal X-ray Diffraction (SCXRD), and matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) mass spectrometry suggest that [HN222]2[ZnCl4] transfers Cl- from [ZnCl4]2- to the stronger Lewis acid AlCl3, forming intermediate acidic DSILs with [AlCl4]- and [Al2Cl7]- anions and mixed anionic Zn species. Qualitative Lewis acidity measurements using acetonitrile as an IR-active probe showed that the acidity of the DSILs decreased as the amount of [ZnCl4]- increased. In a Beckman rearrangement reaction of acetophenone oxime, significant catalytic activity was observed for DSIL x = 0.33, where the activity of the DSIL was found to be even higher than [HN222][Al2Cl7], AlCl3, [HN222]2[ZnCl4], or ZnCl2 despite its lower Lewis acidity, apparently due to the synergistic effect of AlCl3 and [ZnCl4]- as Cl- donors for the formation of catalytically active species. The findings illustrate a DSIL-based approach for modifying the catalytic activity of a known complex without changing its inner coordination sphere.
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A series of carbon-based materials were illustrated to be efficient additives to improve the product distribution of isobutane/butene alkylation catalyzed by H2SO4. Among the tested materials, graphene oxide (GO) was shown to be the most efficient additive. With the presence of trace amounts (e.g., 0.1 wt%) of GO sheet, weight percentage of C8 in the product could increase by ~11% and research octane number (RON) of the alkylate was enhanced by ~2. The presence of GO in H2SO4 led to no obvious change of the acidity. The improved product distribution could be attributed to the enhanced emulsification and better dispersion of the reactants in the acid. The lifetime of the catalytic system was extended to 140 times, as the formation of acid soluble oil was inhibited when the additive was present. This efficient and environmentally benign emulsifier could be a particularly promising additive for current alkylation process catalyzed by H2SO4.
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Liquid-liquid separations based on countercurrent chromatography, in which at least one phase contains an ionic liquid, represent a new empirical approach for the separation of organic, inorganic, or bio-based materials. A custom-designed instrument has been developed and constructed specifically to perform separations (including transition metal salts, arenes, alkenes, alkanes, and sugars) with ionic liquids, and has been demonstrated for use on the 0.1 to 10g scale.
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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
A series of Organic-inorganic heteropoly acid ionic liquids was synthesized and used for catalyzing oxidative desulfurization of simulated gasoline under ultrasound. With the help of ultrasonic wave, the reaction time was largely reduced, and the desulfurization efficiency was also raised. The results showed that Zr0.25[BMIM]HPW12O40 exhibits the best catalytic activity. The effects of ultrasonic power, ultrasonic/clearance time, the amount of catalyst, reaction temperature, reaction time, and the amount of H2O2 on the desulfurization rate were fully investigated. The selected optimal conditions were as follows: n(Cat.)=0.008 mmol, V(H2O2)=40 μL, V(simulated oil)=10 mL, V(acetonitrile)=1 mL, reaction temperature 25℃, reaction time 10 min, the ultrasonic power 300 W, the ultrasonic time 2 s, and the ultrasonic off-time 1.5 s. Under the optimal conditions, the sulfur removal of DBT could reach 97.8%. The solid catalyst Zr0.25[BMIM]HPW12O40 could be directly separated out after the reaction, and could be reused after the vacuum drying. The results showed that Zr0.25[BMIM]HPW12O40 also exhibited good recyclability. After 5 recycles, the desulfurization rate still could reach 81.9%. By using Zr0.25[BMIM]HPW12O40 as catalyst, the reaction activity decreased in the order of DBT>4,6-DMDBT>ethyl thioether>phenyl thioether>n-butyl mercaptan>methyl phenyl thioether>BT>thiophene.
Article
Alkylate is an ideal blending component for motor gasoline. The alkylation of isobutane with 2-butene to produce high-quality alkylate was catalyzed by several amide-AlCl3-based ionic liquid (IL) analogues with different structures and CuCl modification. The influences of the amide structure, amide/AlCl3 molar ratio, and CuCl modification on the catalytic performance were investigated in an autoclave operated in semicontinuous mode. Results showed that the N-methylacetamide-AlCl3-based IL analogue (molar ratio of N-methylacetamide to AlCl3 was 0.75, marked as 0.75NMA-1.0AlCl3) with bidentate coordination and low viscosity was an efficient catalyst for isobutane alkylation. Furthermore, CuCl modification further enhanced the catalytic performance of 0.75NMA-1.0AlCl3. The selectivity of C8 increased from 76.18 wt% to 94.65 wt%, in which the molar ratio of trimethylpentanes to dimethylhexanes (TMPs/DMHs ratio) and the research octane number (RON) of alkylate reached up to 14.98 and 98.40, respectively. The effects of reaction conditions on the alkylation performance were investigated in an autoclave operated in batch mode. The results indicated that the alkylation of isobutane with 2-butene catalyzed by CuCl-modified 0.75NMA-1.0AlCl3 was a short-time and fast reaction. The optimal reaction temperature, reaction time, stirrer speed, and isobutane/2-butene molar ratio were 15 °C, 30 s, 1500 r/min, and 100:1, respectively. Under these optimal reaction conditions, the selectivity of C8, TMPs/DMHs ratio, and RON were 84.10 wt%, 14.86, and 96.54, respectively.
Chapter
This chapter summarises the current state of the art with regard to the chemical engineering of ionic liquid processes, key to their industrialisation. It initially focusses on homogeneous catalytic processes, with particular emphasis on Lewis acidic chloroaluminate(III) systems, and then graduates to heterogeneous systems, with a focus on immobilised catalysts (both SILP and SCILL). Finally, it summarises the various industrial-scale approaches to product separation.
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The acceptor properties of mixed chlorometallate ionic liquids for isobutane-butene alkylation (C4 alkylation) reaction were studied. These ionic liquids were prepared by mixing metal chlorides with either triethylamine hydrochloride or 1-butyl-3-methylimidazolium chloride in various molar ratios. Using triethylphosphine oxide as a probe, Gutmann Acceptor Numbers (AN) of the catalysts were determined, and the Lewis acidity of mixed chlorometallate ionic liquids was quantitatively measured. Additionally, AN value was developed to determine the relationship between Lewis acidity and catalytic selectivity. The favorite AN value for the C4 alkylation reaction should be around 93.0. The [(C2H5)3NH]Cl–AlCl3−CuCl appears to be more Lewis acidity than that of [(C2H5)3NH]Cl–AlCl3. The correlation of the acceptor numbers to speciation of the mixed chlorometallate ionic liquids has also been investigated. [AlCl4]−, [Al2Cl7]−, and [MAlCl5]− (M = Cu, Ag) are the main anionic species of the mixed chlorometallate ILs. While the presence of [(C2H5)3N·M]+ cation always decreases the acidity of the [(C2H5)3NH]Cl−AlCl3−MCl ionic liquids.
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Catalysts based on different halo‐alkanes structures with durable catalytic performance were synthesized and applied to the Friedel–Crafts alkylation of long‐chain alkenes (mixed C16–24 olefins) with toluene. Surprisingly, compared with the usual industrial catalysts (~10 runs), the cyclic times of the ionic liquid (IL) catalysts reached up to 24 runs, which greatly promotes the industrialization process. Then, Lewis acids of catalysts with different precursor/AlCl3 molar ratios were investigated and a close relation was discovered between the Lewis acid and catalytic activity. In addition, a comparison of the different halo‐alkanes structures about those catalysts was made. The results showed that the [C6Et3N]Cl–AlCl3 had the strongest Lewis acid, corresponding to the highest catalytic performance. Also, the structures of precursors and the specific gravity and active site species of catalysts were investigated by Fourier transform infrared and Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR). Meanwhile, the various parameters (catalyst dosage, toluene/olefin molar ratio, reaction temperature and reaction time) of long‐chain alkenes alkylation with toluene were studied. Finally, under the optimized reaction conditions, the conversion and selectivity of long‐chain alkenes alkylation reached 99.92 and 32.99%, respectively.
Article
DFT calculations combined with MD simulations have been used to investigate the complicated reaction mechanism of isobutane-isobutylene alkylation catalyzed by the neat chloroaluminate ionic liquid (NIL) and the Cu-containing chloroaluminate ionic liquid (CIL). Transition states of three key elementary reactions were obtained to address the selectivity of the alkylate formation versus the by-product formation in different ionic liquids. The DFT calculations indicate that the Cu species would significantly inhibit the polymerization of C4= olefins and C8⁺ carbenium ions. Compared to the competitive H-transfer reaction, the reaction rate of polymerization in the NIL was very fast resulting in poor product selectivity. The Mayer bond order (MBO) and electron localization function (ELF) maps reveal that H-transfer from isobutane to C8⁺ carbenium ion occurs via a concerted H-Cu bond formation between a C8⁺ and an isobutane to generate the desired isooctane. The Cu complex did engage in the H-transfer of isobutane/C8⁺, but it did not weaken the catalytic activity in comparison to the neat chloroaluminate anions. The MD simulations show that a combination of high isobutane concentration and low isobutylene concentration at the CIL-hydrocarbon interface can be attributed to the effects of Cu complex, which also leads to the improvement of the alkylation selectivity. An essential role of Cu species in the CIL alkylation is to impede the formation of C12⁺ carbenium ions and promote the H-transfer between isobutane and C8⁺ carbenium ion.
Chapter
There is absolutely no doubt that green chemistry has brought about medical revolution (e.g., synthesis of drugs etc.). The world’s food supply has increased many folds due to the discovery of hybrid varieties, improved methods of farming, better seeds and use of agro chemicals, like fertilizers, insecticides, herbicides and so on. Also, the quality of life has improved due to the discovery of dyes, plastics, cosmetics and other materials. All these developments increased the average life expectancy from 47 years in 1900 to about 80 years in 2010. However, the ill-effects of all the development became pronounced. The most important effect is the release of hazardous by-products of chemical industries and the release of agro chemicals in the atmosphere, land and water bodies; all these are responsible for polluting the environment, including atmosphere, land and water bodies. Owing to all these, green chemistry assumed special importance.
Article
Butene oligomerization followed by hydrogenation is regarded as a promising way to produce alkylate oil, and the challenge of this process is the oriented conversion of butene to octene, which closely relates to the alkylate quality. Ionic liquids (ILs) are a kind of promising catalyst for olefin oligomerization. In this study, a series of functional metal-free acidic ILs (11 in total) were synthesized, characterized, and used for the oligomerization of isobutene. It was found that among the tested neat ILs, sulfobutyltriethylammonium triflate ([TENBs][CF3SO3]) exhibited the best performance. This IL catalyst could be reused for 25 times, without obvious loss in catalytic activity. To improve catalytic activity of the neat IL, composite ILs formed by mixing [TENBs][CF3SO3] with a second functional IL were developed. In the best composite system with tunable acidity, isobutene conversion could increase by ~88% compared with the neat IL, and meantime the dimer selectivity could increase to 79%. The conversion could increase from 25% to over 80% in the best composite system with enhanced mass transfer capability. Spectroscopic characterization and Gaussian simulation revealed the different catalytic behaviors of these ILs, which demonstrated that ILs with lower bond dissociation enthalpy (< 521 KJ·mol⁻¹) and proper binding energy with isobutene (−27 to −20 KJ·mol⁻¹) could efficiently catalyze isobutene oligomerization, the acidic active sites were from the sulfonic acid group in the cation and the acidic anion, and that deactivation of the IL catalyst after being used for 29 times could be attributed to the loss of the acid sites in both the cation and anion.
Article
Chloroaluminate ionic liquids (CIL) mixed with a small amount of aromatics are highly selective catalysts for the alkylation of isobutane and 2-butene. The effects of aromatics on the alkylation reaction were investigated by experimental methods and theoretical calculations. Through NMR, in situ IR, and Raman characterizations, it is found that the aromatics interacted with ions and formed aromatic-AlCl4⁻, aromatic-Al2Cl7⁻, and [aromatic-H]⁺ species. These new species buffer the acidity at a lower level and modify the activity of CIL. Theoretical calculations show that only the aromatic enriched at the acid-hydrocarbon interface and with appropriate charge transfer can effectively affect the CIL alkylation. The aromatic−ion interaction inhibited the polymerization side-reactions and promoted the hydride transfer from isobutane to C8⁺. These new insights have improved our understanding of the effects of ions on the CIL alkylation reaction.
Article
When a small amount of benzene was introduced into the chloroaluminate ionic liquid (IL), the IL − alkylation can produce premium alkylation gasoline. In order to deepen our understanding of IL − alkylation in general, the electronic properties of [BMIm][AlCl4]/benzene/reactant system were analyzed by the ADCH charge analysis, DOS analysis, frontier molecular orbital analysis, non − covalent interactions (NCI), and energy decomposition analysis (EDA). ADCH analysis reveals that benzene could markedly affect the charge transfer of alkanes and chloroaluminate anions, which weakened the super−acidity of the IL. Frontier molecular orbital analysis shows that the IL system has a significant decrease of H − Lgap, and it increases the sensitivity of the reactants. The anchoring effect of [BMIm]⁺ cation was observed in the DOS spectra, which enhanced stabilization of the IL structure. NCI analysis shows that π − H bonds could be formed between benzene and the IL. It is believed that better alkylation performance of IL/benzene system is due to these weak interactions.
Article
The adsorption and diffusion behaviors of isobutane, 2-butene, and trimethylpentane (TMP) on the silica surface with various surface groups were investigated using molecular dynamics (MD) simulations in this work. A significant concentration gradient and density enhancement of isobutane and butene were observed on the silica surface due to their strong interaction with surface groups. The hydrophobic modification of the silica surface can improve the adsorption ratio of isoparaffin to olefins (I/O), further inhibiting the catalyst deactivation. However, the hydrophilic modification will increase the surface polarity and the interaction between propanesulfonic acid groups and butene, which is not beneficial for the alkylation reaction. The diffusion rate of molecules is affected by their size and follows the order of 2-butene > isobutane > TMP, while the difference between isobutane and 2-butene is the smallest in the hydrophobically modified system. Both surface modification and the presence of the C8 product will inhibit the diffusion and update rate of C4 hydrocarbons, while the increase in temperature will promote their diffusion. Hopefully, this work would bring deep insights into the countermeasures of solid acid deactivation.
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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.
Article
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.
Article
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.
Article
The isobutane/butene alkylation catalyzed by H2SO4 is a liquid/liquid reaction, and the limited solubility of the hydrocarbon in the catalyst inhibits mass transfer, leading to occurrence of side reactions. Amphiphilic surfactant could enhance mass transfer in multiphasic systems. In this study, a series of quaternary ammonium and phosphonium surfactants were used as the additive to enhance the catalytic performance of H2SO4 for isobutane/butene alkylation. Ammonium surfactants showed much better activity to improve product distribution than the phosphonium one. The enhanced product distribution and alkylate quality were attributed to the well dispersion of the hydrocarbon in the acid and increased hydrocarbon solubility in the catalytic system, i.e., enhanced mass transfer in the reaction system. The reaction parameters were optimized, and under these conditions, weight percentage of C8 in the product was 87.5%, and research octane number (RON) of the alkylate could reach 97.8. Lifetime of the surfactant/H2SO4 system was 130 times compared with 51 times for the system with no additive due to inhibition of the formation of acid soluble oil (i.e., products of side reactions). This proposed catalytic system with the ammonium surfactant as the additive is promising to be employed in industrial C4 alkylation process.
Article
Alkylation of isobutane and butenes in ionic liquids (ILs) is an important industrially applied and environmentally friendly process for the production of high quality gasoline. In a scale-up reactor, we found that the ILs with a small amount of aromatics would exhibit excellent performances for the alkylation reaction. The behaviors of aromatics on the liquid-liquid interface and the alkylation performance of IL/benzene have been investigated by molecular dynamics simulations and experimental studies. Based on density profile, segment orientation, and self-diffusion coefficient, the main reason that benzene affects the IL alkylation performance was discussed. Although the amount of benzene was small, benzene would accumulate in the acid-hydrocarbon interfacial layer during the alkylation process. A little benzene was enough to buffer the strong acidity of chloroaluminate anions at the interface. The presence of benzene also provided a transport channel for reactants, increasing the concentration of isobutane at the interface. At the interface, the proper acidity and higher isobutane-to-olefin ratio significantly improved the IL alkylation performance. Effects of other aromatics on the C4 alkylation have also been studied, which further confirmed our findings in the IL/benzene alkylation reaction. Hopefully, these studies can provide useful information to the design of the ionic liquid catalysts and the optimization of the C4 alkylation process.
Article
The two most common commercial catalysts for the acylation of isobutylbenzene to produce the major ibuprofen intermediate 4-isobutylacetophenone are HF and AlCl3, however, both of these catalysts suffer from significant drawbacks including the stringent safety issues associated with using volatile/toxic HF and the requirement for additional processing for de-acidification of AlCl3. Here, two chloroaluminate-based catalysts, the ionic liquid (IL) [HN222][Al2Cl7] ([HN222] = triethylammonium) and the liquid coordination complex (LCC, here an IL analog) AlCl3/O-NMP χAlCl3 0.6 (O-NMP = N-methyl-2-pyrrolidone) were investigated and found to be efficient in the acylation of isobutylbenzene. Of the tested catalysts, the LCC, which along with neutral species has both a Lewis acidic cation ([AlCl2(O-NMP)2]+) and anion ([Al2Cl7]-, had the best catalytic performance (99% conversion with 96% selectivity).
Article
The alkylation process of isobutane with butene is important in the petroleum industry. Ionic liquids (ILs) are considered as attractive alternative catalysts for isobutane alkylation besides strong liquid acids (H2SO4 or HF) and solid superacids. In this study, ILs based on amides-aluminum chloride (AlCl3) were synthesized and characterized, which exhibited both Lewis and Brønsted acidities. These deep eutectic ILs were found to be efficient catalysts for isobutane alkylation. The influences of the amide substrate, AlCl3/amide molar ratio, and metal additive on Lewis and Brønsted acidities were observed together with the synergetic effect of Lewis and Brønsted acid sites in the catalytic process. CuCl modified Urea-1.6AlCl3 showed the best catalytic performance. The butene conversion was about 99.9% and C8 selectivity reached 57.6% under optimized reaction conditions (temperature of 15 °C, stirring rate of 1500 rpm, hydrocarbon feeding rate of 300 mL/h, isobutane/olefin molar ratio of 15:1, and reaction time of 15 min). In addition, Urea-1.6AlCl3-0.13CuCl could be recycled and reused for at least 20 times without obvious loss in catalytic activity.
Article
The use of Ionic Liquids (ILs) as both catalysts and solvents in a wide range of chemical reactions has received considerable attention over the last years due to its positive effects in enhancing reaction rates and selectivities. In this work hybrid Quantum Mechanics/Molecular Mechanics (QM/MM) Molecular Dynamic Simulations were carried in conjunction with Umbrella-Sampling techniques to study the Bimolecular Nucleophilic Substitution (SN2) fluorination reaction between propyl-mesylate and potassium fluoride using as solvents five ILs, specifically: 1-Butyl-3-methylimidazolium Mesylate ([C4mim][OMs]), 1-Butyl-3-methylimidazolium Tetrafluoroborate ([C4mim][BF4]), 1-Butyl-3-methylimidazolium Trifluoroacetate ([C4mim][CF3COO]), 1-Butyl-3-methylimidazolium Bromide ([C4mim][Br]), and 1-Butyl-3-methylimidazolium Chloride ([C4mim][Cl]) at 373.15 K. The QM region (reactive part) in all QM/MM systems was simulated using the Parametric Method 6 (PM6) semiempirical methods and for the MM region (ILs solvent) classical Force Fields (FF) were employed, FF developed within the group. The calculated activation free energy barriers (∆G^‡) for the SN2 reaction in the presence of [C4mim][OMs] and [C4mim][BF4] ILs were in agreement with the experimental values reported in the literature. On the other hand, only predicted values were obtained for the activation energies for the [C4mim][CF3COO], [C4mim][Br], and [C4mim][Cl] ILs. These activation energies indicated that the SN2 reaction would be more facile to proceed using the [C4mim][Cl] and [C4mim][OMs] ILs, in contrast with the use of [C4mim][Br] IL, which presented the highest activation energy. Energy Pair Distributions (EPDs), Radial Distribution Functions (RDFs), and Non-Covalent Interactions (NCI) were also calculated in order to elucidate the molecular interactions between the reactive QM region and the solvents or reaction media. From these calculations, it was found that not only the reactivity can be enhanced by selecting a specific anion to increase the K-F separation, but also the cation plays a relevant role, producing a synergetic effect by forming hydrogen bonds with the fluorine atom from KF and with the oxygen atoms within the mesylate leaving group. Three interactions are significant for the IL catalytic behavior: F_QM-HX, K_QM-anion, and O_QM-HX interactions, where the F_QM and K_QM labels correspond to fluorine and potassium atoms from the KF salt; O_QMcorresponds to oxygen atoms within the mesylate leaving group (reactant), and HX refer to hydrogen atoms within the IL cation. The NCI analysis revealed that K_QM-anion interactions are of a weak-type, indicating the importance of hydrogen bond interactions from the cation such as F_QM-HX and O_QM-HX for the catalytic behavior of ILs.
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Lewis acid/base catalysts of AlCl3/N-methyl-2-pyrrolidone (O-NMP) and AlCl3/1-methylimidazole (N-Mim) were prepared and found to have higher catalytic activity in the Friedel–Crafts alkylation of benzene than the known super acidic ionic...
Chapter
Biomass, particularly lignocellulosic biomass, is a promising platform for the production of renewable fuels and chemicals. This chapter explores the different C—C bond forming reactions that can be utilized to optimize the upgrading process and maximize the yield in the desirable molecular weight range for the specific production of gasoline, diesel, or chemicals. Some of these C—C coupling reactions include base‐catalyzed aldol condensation, alkylation, hydroxyalkylation, acylation, and ketonization. The chapter critically evaluates the different ideas presented in the literature concerning the reaction mechanisms for each of these reactions – structure/function relationships being analyzed – with a focus on the topological and chemical requirements of the active sites (acid, base, acid–base pairs, both of Bronsted and Lewis types) – along with some of the specific materials (magnesium oxide, zeolites) that are particularly effective for each task.
Article
Brøsted acidic pyridinium-based ILs of [NS][CF3SO3] and [NS][HSO4] have been synthesized for oligomerization of isobutene with the excellent conversion of 92.8% and the good selective dimerization at the temperature of below 100 °C. Hydroxyl-containing materials, especially ethanol, could facilitate catalytic activities to excellent conversions of isobutene and 84.2% selectivity of diisobutene. [NS][CF3SO3] could be recovered by a simple liquid-to-liquid separation and reused more than ten times without obvious loss of catalytic activities. The formation process of oligomers has been examined by in-situ NMR spectroscopy, and a step-by-step generation process of carbonium ions varying from C4⁺, C8⁺ to C12⁺ was proposed. The work behaves the significance of constructing a better catalysis system for highly selective dimerization of isobutene, and potential being scaled-up for industrialization.
Article
The Friedel-Crafts acylation of 2-methoxynaphthalene (2-MN) with acetic anhydride (AA) was carried out in the ionic liquid (IL) butylpyridinium tetrafluoroborate ([BPy]BF4) using phosphotungstic acid (H3PW12O40) as the catalyst. The [BPy]BF4-mediated 2-MN acylation displays good conversion and selectivity towards 1-acyl-2-methoxynaphthalene (1-AC-2-MN), with 70.4% conversion of 2-MN and 96.4% selectivity to 1-AC-2-MN obtained under the optimal conditions. Owing to the rearrangement of 1-AC-2-MN, 6-acyl-2-methoxynaphthalene (6-AC-2-MN) can be detected after 1 h of reaction time, with the highest 6-AC-2-MN yield of 11.3% obtained under the examined reaction conditions. The system can be recycled and reused at least 6 times without significant loss of activity, indicating the good stability of the H3PW12O40/[BPy]BF4 catalytic system.
Article
Alkylation of short-chain olefins with isobutane catalyzed by sulfuric acid is a common process for reformulated fuel. Here, pilot-plant and commercial C3 and C4alkylates were examined for sulfur content, acid content, and emulsion formation. Even though the thermodynamic solubility of sulfuric acid in alkylate is negligible at process conditions, the C4 alkylate samples contained ~20 ppm sulfur mostly from very dilute emulsions with ~3 µm droplets of sulfuric acid and alkyl sulfates that were stable even after 6 months. The sulfur content and droplet size increased for propylene alkylation. However, no detectable emulsion or sulfur content could be generated synthetically by intense mixing with either 2,2,4-trimethylpentane (a model alkylate) or a treated pilot-plant alkylate with concentrated or spent sulfuric acid over the course of several hours. Thus, the alkylate sulfur content is most probably created during the acid-catalyzed chemical reaction steps and not from high-shear mixing.
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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
We have found that acidic molten salts based on aluminum-trichloride and 3-butyl-1-methyl-imidazolium chloride (BMIC) can be used either as an acidic catalyst for isobutane alkylation or as a solvent for the cationic nickel catalysis for propene dimerization. In principle, these two reactions, the operating conditions of which are fairly similar, might be performed successively in the same reactor, thus providing a convenient way of producing high octane-number hydrocarbons, the importance of which is currently enhanced by new specifications for reformulated gasoline. Isobutane alkylation with ethylene is catalyzed only with acidic AlCl3/BMIC based melts in whicy the Al molar fraction is higher than 0.57. The activity is then all the higher as N increases, but for N>0.67 the salt is no longer liquid at room temperature. The dissolution, at -15°C, of a cationic nickel complex containing a metal carbon bond, such as (π-ally NiL) +PF6-, in an acidic AlCl3/BMIC molten salt provides a very active catalyst for the dimerization of propene.
Article
The acidity of HCl in Lewis acid mixtures of AlCl{sub 3} and 1-ethyl-3-methyl-1H-imidazolium chloride (EMIC) has been determined as a function of HCl pressure (P{sub HCl}) and melt composition at ambient temperatures. The equilibrium constant (K{prime}{sub b}) for the protonation of arene bases (B) according to the reaction HCl + B {r reversible} BH{sup +} + Cl{sup {minus}} was determined from the relation log K{prime}{sub B} = H{prime} + log ((BH{sup +})/(B)) with the protonation ratio measured spectrophotometrically and the acidity function, H{prime} = log ((Cl{sup {minus}})/P{sub HCl}), evaluated by using the thermodynamic model of Dymek et al. to calculate (Cl{sup {minus}}). Values of log K{prime}{sub B} were determined for chrysene, fluorene, 2-methylnaphthalene, and mesitylene over a range of HCl pressures and melt compositions, while estimates for benzene, toluene and naphthalene were obtained at a single pressure and composition (1 atm, 66.4 mol % AlCl{sub 3}). The correlation between log K{prime}{sub B} for these arenes in HCl/AlCl{sub 3}-EMIC and log K{sub B} for the same arenes in HF/BF{sub 3} suggests that H{prime} {minus} H{sub 0} {approx equal} 0.4, where H{sub 0} is the Hammett acidity function. According to this criterion H{sub 0} for 0.01 atm HCl in 51 mol %more » AlCl{sub 3} has a value of {minus}12.6 (a superacid comparable to 100% H{sub 2}SO{sub 4}). At 1 atm HCl, a melt saturated with AlCl{sub 3} at ambient temperatures ({approximately} 67 mol % AlCl{sub 3}) is a much stronger superacid with a value of H{sub 0} on the order of {minus}18.« less
Article
The system HCl (0.1-1 atm)/AlCl{sub 3}-EMIC (55.0 mol % AlCl{sub 3}) (EMIC = 1-ethyl-3-methyl-1H-imidazolium chloride) at 23{degree}C is a Broensted superacid capable of protonating arenes to a degree similar to that of liquid HF at 0{degree}C (H{sub 0} = {minus}15.1). Arenes used in this investigation were biphenyl (I), naphthalene (II), 9H-fluorene (III), chrysene (IV), 2-methylnaphthalene (V), mesitylene (VI), pentamethylbenzene (VII), hexamethylbenzene (VIII), anthracene (IX), and 9,10-dimethylanthracene (X). In both the chloroaluminate melt and HF I is a weak base while VIII-X are strong bases. In between these extremes the order of basicities in both media is II < III and IV < V < VI < VII < VIII. A study of the effect of HCl partial pressure showed, for example that V is 50% protonated at 0.3 atm HCl. The overall reaction is arene + HCl + Al{sub 2}Cl{sub 7}{sup {minus}} {r reversible} arene {times} H{sup +} + 2AlCl{sub 4}{sup {minus}} and is reversible. The degree of protonation was measured by optical absorption spectrophotometry. The arenes are stable in the liquid chloroaluminate for many hours, and their protonated forms (arenium ions) are stable for 1 h or more. A new procedure for the preparation of EMIC was developed that more » yields exceptionally clean AlCl{sub 3}-EMIC melts with very low concentrations of protic and oxidizing impurities. 17 refs., 6 figs., 2 tabs. « less
Article
Isobutane was alkylated either with a pure C5 olefin, with a mixture of a pure C5 olefin and mixed C4 olefins, with C4 olefins, or with propylene using sulfuric acid as the catalyst. Alkylates produced at operating conditions of commercial importance had research octane numbers of 90.7-91.7, 97.8, 93.2, and 89.0, respectively, when C5 olefins, n-butenes, isobutylene, and propylene were used as olefins. The compositions of the alkylates produced from n-pentenes, and especially 2-pentenes, were significantly different than those of alkylates produced from isopentenes. Cyclopentene which is present in C5 mixtures of refinery products produces very poor quality alkylates in low yields. For both n-pentenes and isopentenes, isopentane is produced by self-alkylation in appreciable amounts. The alkylation chemistry differs significantly for various C5 olefins, and reaction mechanisms are proposed and compared to those for C3 and C4 olefins.
Article
The donor-acceptor properties of room-temperature chloroaluminate ionic liquids composed of mixtures of AlCl3 with either N-(1-butyl)pyridinium chloride or 1-ethyl-3-methylimidazolium chloride were studied. Gutmann donor and acceptor numbers were determined by using the Eu(III) reduction potential and the 31P chemical shift of triethylphosphine oxide, respectively. Acidic melts are extremely poor donor and strong acceptor media. Basic melts are similar in basicity to DMF. No conclusions concerning the acceptor properties of the basic melt are drawn from this work since the strongly basic probe molecule, Et3P=O, is leveled by the solvent. Conditions under which these parameters are potentially useful are outlined.
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Etudes par voltammetrie cyclique et chronoamperometrie du comportement electrochimique de Fe(phen) 2 (CN) 2 , Cp 4 Fe 4 (CO) 4 et CpFe(CO) 2 (CN) avec phen=phenanthroline-1,10 et Cp=cyclopentadienyl. Donnees completes par des mesures de spectres UV visibles et IR
Article
Proton speciation in ambient-temperature chloroaluminate ionic liquids, composed of 1-ethyl-3-methylimidazolium chloride (ImCl) and aluminum chloride has been examined by 2H NMR and FT-IR spectroscopies. In oxide free basic melts (excess ImCl), two proton-containing species, HCl and HCl2-, exist which are in an equilibrium that strongly favors the formation of the dichloride ion. In oxide free acidic melts (excess AlCl3) HCl is the only proton-containing species. There is a single aluminum hydroxychloride species in acidic melts containing oxides, and there is at least one aluminum hydroxychloride species in basic melts containing oxides.
Article
Ethylene polymerization via Ziegler-Natta catalysis occurs in the ambient-temperature molten salt AlCl3·MEIC (MEIC = 1-ethyl-3-methylimidazolium chloride) employing Cp2TiCl2 as the catalyst and AlCl3-xRx (R = Me, Et) as a cocatalyst. Catalysis occurs only in melts with AlCl3:MEIC molar ratios > 1. Cp2ZrCl2 and Cp2HfCl2 with AlCl3-xRx cocatalysts are not catalytically active in acidic melts. 1H NMR studies indicate formation of a strong 1:1 complex between Cp2TiCl2 and AlCl3, while Zr and Hf form much weaker 1:1 complexes due to strong Zr-Cl and Hf-Cl bonding. This stronger M-Cl bonding for Zr and Hf is proposed to preclude the initiation reaction for ethylene polymerization in the molten salt.