No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Alkylation of isobutane/isobutene using Brønsted–Lewis acidic ionic liquids as catalysts
Abstract
Abstract The alkylation of isobutane/isobutene to produce alkylate was investigated in the presence of Brønsted-Lewis acidic ionic liquids (ILs). The results show that the IL (3-sulfonic acid)-propyltriethylammonium chlorozincinate [HO3SC3NEt3]Cl-ZnCl2 (molar fraction of ZnCl2, x = 0.83) was an efficient catalyst for the alkylation reaction. The conversion of isobutene was about 100% and the selectivity for the C8-alkylate reached 91.7%, in which the mass ratio of trimethylpentane to dimethylhexane was more than 75. The IL reusability was good and its catalytic performance did not significantly decrease after ten reaction cycles. It was also found that a synergetic effect of Brønsted and Lewis acid sites enhanced the catalytic performance of ILs.
... [3] Although these two catalysts show high catalytic activity and selectivity in the reaction, the processes have plenty of drawbacks, including equipment corrosion and high post-processing cost. [4,5] HF is highly toxic and can form aerosol clouds containing deadly hydrogen fluoride, which is very harmfull to health. Hence, HF should be replaced urgently as an alkylation catalyst. ...
... [29] Furthermore, Liu et al. synthesized Brønsted-Lewis acidic ILs (possessing Brønsted and Lewis dual acids) which had good catalytic performance in the conversion and selectivity with strong cycle performance owing to the synergetic effect of Brønsted and Lewis acidic sites. [5] In fact, simultaneously increasing the conductivity and the selectivity of alkylation is impossible for industrial production. However, as is well known, few studies have been reported on long-chain alkene alkylation and high cyclic performance concurrently. ...
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.
... One of the observed results was that the dual Brønsted-Lewis ILs were inert in air and moisture and, as a consequence, had better catalytic performance than a traditional catalytic system. Also, Liu et al. [92] investigated the alkylation of isobutane/butene using dual ILs derived from [HO 3 SC 3 NEt 3 ]Cl in combination with metal salts (ZnCl 2 , CuCl 2 , CuCl FeCl 3, and AlCl 3 ). The best result showed 100% of isobutane conversion and the selectivity to alkylated C8 reached 97.1% with a TMP/DMH ratio of 75%. ...
... In another investigation, Liu et al. [93] reported on the use of dual ILs derived from 1-(3-sulfonic acid)-propyl-3-methylimidazolium chloride ILs [HO 3 SC 3 MIM]Cl in combinations with metal chlorides (ZnCl 2 , FeCl 2 , FeCl 3 , CuCl 2 , CuCl, and AlCl 3 ), under the following conditions: feed = 11.3 g, iso-butane/iso-butene molar ratio = 10:1, catalyst mass = 3.0 g, X (Lewis acidic metal chloride) = 0.67, H 2 O = 1.3 g, T = 80 • C and t = 4 h. A similar effect was observed in their previous work [92]. That is, a synergistic effect by the presence of Brønsted and Lewis acidic sites resulted in a conversion close to 100% and TMP selectivity of 80.5% (Table 2, entry 6), which were much higher than the respective ILs containing only Brønsted or Lewis acidic sites, obtaining conversions of 51.3 and 66%, and TMP selectivities of 64.7 and 64.1%, respectively (Table 2, entries 7 and 8). ...
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.
... However, the rapid deactivation by coking limits their widespread industrial use (Feller et al., 2004;Hamzehlouyan et al., 2010;Sarsani and Subramaniam, 2009;Xu et al., 2006). As a green solvent or catalyst, ionic liquids (ILs) have attracted numerous attentions for considerable applications in alkylation (Liu et al., 2015a), transesterification (Ishak et al., 2017;Yang et al., 2015), isomerization (Kim et al., 2014;Zhang et al., 2008), oligomerization (Behr et al., 2017;Yang et al., 2008), and desulfurization (Jiang et al., 2016), due to their excellence advantages, such as negligible vapor pressure, strong chemical stability, adjustable Brønsted and Lewis acidity, easy separation from the products, and good dissolving capacity to a wide range of organic and inorganic compounds (Welton, 1999). For the alkylation of isobutane with C 4 olefins, the chloroaluminate-based ILs have been widely investigated. ...
The alkylation kinetics of isobutane with 2-butene catalyzed by composite ionic liquid (CIL) was investigated with batch experiments. The optimized reaction time of CIL-catalyzed alkylation was found to be less than 30 s, much shorter than the traditional H2SO4-catalyzed one. Based on the carbonium ion mechanism, the kinetic model was further established, in which the concentration profiles of three groups of key components in alkylates with time can be well predicted, i.e. trimethylpentane (TMPs), dimethylhexanes (DMHs) and heavy ends (HEs). The rate constant related to the formation of TMPs in the CIL alkylation is more than two orders of magnitude larger than that in the H2SO4 alkylation. The enhancement of the rate constants for the CIL alkylation at the macroscopic scale can be ascribed into the higher solvation and diffusion of isobutane in the CIL at the microscopic scale, which is confirmed by the solvation free energy and diffusion coefficient calculation using molecular dynamics simulation. Hopefully, the multi-scale information in this work can bring novel insights into the understanding of CIL-catalyzed alkylation and further the design and optimization of this process.
... 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 . ...
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.
... Bronsted acidic ILs are used for isobutene alkylation either alone or in combination with acids, like sulfuric acid or trifluoromethanesulfonic acid. Examples are N,N-dimethyl-N-ethanolammonium hydrogen sulfate, N-methyl-N,N-diethanolammonium hydrogen sulfate, N,N-diethyl-Nethanolammonium triflate, 2-hydroxy-N,N-dimethylpropan-1-ammonium triflate, etc. [139] Resins like Dowex 50 in combination with Bronsted acidic ionic liquids containing sulfonic groups are also suitable species for catalyzing alkylation of alkenes and isoalkanes [51,[140][141][142]. ...
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.
... Hence, the separation of N-compounds from fuels is vital important for atmospheric protection because the N-compounds in fuels not only can alter to polluting nitrogen oxides after burning, but also can deter the hydrodesulphurization process of fuels and enhance the sulfur oxides emission. (Garcia et al. 2015b, Li et al. 2015c) Among different methods, (Bovkun et al. 2007, Cocchetto et al. 1976, Ishihara et al. 2005, Kamo 1993, Liu et al. 2008a, Thompson et al. 1962, Yuan et al. 2006) liquid-liquid extraction is an attractive method for fuels denitrogenation, because it can be easily applied for large sample output along with small quantities of solvents, simple equipment and easiness to scale up. In previous studies, the extraction efficiency of N-compounds from fuels into a series of conventional toxic molecular solvents has been used. ...
... The conversion of 1,3-butadiene to various C 4 -olefins has an industrial importance, especially for the refining processes. Likewise, separation of these C 4hydrocarbons is also very important for various industrial applications, such as for rubber industry [14] and for petroleum industry, especially in isomerization [15], alkylation [16], and oligomerization [17] reactions. ILs can also offer solutions in this respect as well. ...
Solubilities of C 4 -hydrocarbons, 1,3-butadiene (13BD), trans/cis-2-butene (T2B and C2B), 1-butene (1B), isobutene (i-But), isobutane (i-B), and butane (B), in 3267 different imidazolium-type ionic liquids (ILs) in a temperature range from 273.15 to 373.15 K were estimated by means of the COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS) calculations. Simple temperature-dependent mathematical expressions were developed to predict the solubility of 13BD, C2B, T2B, 1B, i-But, i-B, and B at any temperature in a range from 273 to 373 K. The COSMO-RS results for each hydrocarbon considered were then analyzed using machine learning tools, including association rule mining and decision tree classification, using semi-empirically derived molecular descriptors of ILs. It was found that the polarizabilities of both cation and anion, together with the anion's CPK (space filling model) area, are the most important descriptors for determining the affinity of ILs towards C 4 -hydrocarbons. Results also present the selection rules for imidazolium ILs, offering opportunities for the rational design of new ILs by using these simply-determined structural descriptors to meet the desired solubility (or selectivity) requirements for each C 4 -hydrocarbon considered.
... We have found that the selectivity of trimethylpentanes (TMP) was greater than 85% and the alkylates with 98-101 research octane numbers (RON) could be obtained when the C 4 alkylation was catalyzed by chloroaluminate ILs [22][23][24]. The studies of other groups also showed that it is feasible to use ILs to catalyze the C 4 alkylation [25][26][27][28][29][30]. Under similar reaction conditions, the quality of IL alkylates was usually better than that of the H 2 SO 4 alkylates. ...
... The special properties of ionic liquids (ILs) have gained considerable attention in various fields owing to the low vapor pressure, non-flammability, appropriate viscosity, and tunable solubility and acidity [1][2][3]. Advances in using ILs as catalyst, solvent, or additive to accelerate chemical reactions hold considerable promise for many applications, such as isomerization, esterification and alkylation process [4][5][6]. Among these catalytic processes, using ILs as the additives to construct new multiple complex ILs/acid systems have attracted more consideration due to their great potential in industrial-scale catalysis [7]. ...
Ionic liquid coupled with strong acid systems presents considerable promise in some catalytic fields. In the present work, the multiple complex systems composed by 98 wt% concentrated sulfuric acid and [Bmim][SbF6] were investigated in the terms of stability, acidity and interaction properties. It was found that acidolysis of [Bmim][SbF6] occurred in the 98 wt% concentrated sulfuric acid accompanied by HF releasing and SbF6⁻degrading to [SbF6−y(HSO4)y]⁻. The species after acidolysis in the multiple complex systems were checked and confirmed by electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared spectroscopy (FT-IR), ¹H NMR and ¹⁹F NMR. Acidity increased slightly with less than 1 wt% [Bmim][SbF6] addition, while decreased with more proportion, which was determined based on the Hammett acidity functions H0, using ¹³C NMR. The strong hydrogen bond S–O–H···F of interaction among the multiple complex systems was confirmed by molecular dynamic simulation. © 2017 Science China Press and Springer-Verlag Berlin Heidelberg
... Generally, all these technologies could allow for the lack of fluid catalytic cracking downstream when reinforced olefins production was obtained by new FCC catalysts. Moreover, Liu et al. 32,33 investigated the production of alkylate from the alkylation process in the existence of Bronsted−Lewis acidic ionic liquids. The results showed that the ionic liquid (3sulfonicacid)-propyl triethylammonium chlorozincinate [HO 3 SC 3 NEt 3 ] Cl-ZnCl 2 (molar fraction of ZnCl 2 , x = 0.83) has been an efficient catalyst for the alkylation reaction. ...
Currently, one of the most important problems in Russian refineries is the lack of production of high-octane gasoline that meets current and future environmental requirements. One solution for this problem is blending oxygenates into gasoline for example, tertiary amyl methyl ether (TAME) and methyl tertiary butyl ether (MTBE). Each of these substances has its advantages and disadvantages. Prospects for obtaining other high-octane components alternative to MTBE and TAME may have good prospects. One choice is dimerization of isobutylene to produce di-isobutylene and the product consists mainly of isooctene isomers. Physico-chemical characteristics of isooctene sample as component of motor gasoline in comparison with MTBE and TAME are investigated. The results have been shown that the introduction of isooctene, which has low volatility, leads to a decrease in Reid vapor pressure (RVP) of base gasoline at the level of TAME. Furthermore, the antiknock properties of isooctene in various gasoline bases are established. The values of the isooctene blend octane numbers calculated in the ranges 108-150 by the research methods and 92-136 by the motor methods are calculated according to the obtained results, isooctene has high antiknock detonation efficiency at the MTBE level. Finally, the use of isooctene as gasoline additives gives good prospects to refining companies in light of decreasing the overhead, enhancing the grade of product and great effect on the environment.
... Gasoline from isobutane/butene alkylation has a high octane number, a low vapor pressure and free of aromatics, sulfur and olefins [1,2]. Much attention has been devoted to the alkylation of isobutane with butene in recent years [3][4][5]. ...
... 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. ...
... [2] Traditionally, various homogeneous catalysts have been used in this reaction, for instance, H 2 SO 4 , HF, and AlCl 3 , but their environmental nonfriendliness, troublesome product recovery and purification, and impossibility of catalyst recycling make them unsuitable for the purpose. [3][4][5] Therefore, many efforts have been made to exploit the environmentally friendly catalytic technology for the target reaction. Some types of solid acid catalysts such as modified zeolite and immobilized heteropolyacids or superacids have been investigated as substitutes to eliminate the aforementioned drawbacks associated with the conventional liquid acids. ...
The influence of anhydrous ferric chloride on the catalytic properties of chloroaluminate ionic liquids catalyst for Friedel–Crafts alkylation was investigated. The catalysts were characterized by Fourier‐transform infrared (FT‐IR) (acetonitrile molecule as probe), specific gravity, and 27Al NMR. Besides, the effect of the mass ratio of FeCl3 to AlCl3, catalysts dosage, toluene/olefin molar ratio, reaction temperature, and reaction time on long‐chain alkenes alkylation were investigated thoroughly. And bromine value and high‐performance liquid chromatography (HPLC) were employed as the evaluation method for alkylation products. It was observed that the addition of anhydrous ferric chloride results in improvement in terms of Lewis acid and its catalytic recyclability. Among these catalysts studied, the catalyst modified with 1.0 wt.% anhydrous FeCl3 showed the best catalytic performance in terms of yield and stability, which can be attributed to the formation of new stronger acidic ions [Al2FeCll0]− when the added ferric chloride reacts with acidic ions [Al2Cl7]−. The influence of FeCl3 on the catalytic properties of chloroaluminate ionic liquids catalyst for long‐chain alkenes alkylation was investigated. The addition of FeCl3 results in improvement in terms of Lewis acid and its catalytic recyclability. Among these catalysts studied, the catalyst modified with 1.0 wt.% anhydrous FeCl3 had the best catalytic performance in terms of yield and stability.
... The evaluation of Lewis acid ILs containing halometalates such as chlorogalates, 126 chlorozincate, 127 and chloroferrate as anions 128 have also been used. However, definitely, haloaluminate-based ILs 32,124,128−, 130 and their composites have been the most studied catalysts for isobutane/butene alkylation. ...
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.
... On the other hand, imidazolium-based IL catalyst were active for longer time-on-stream suggesting that imidazolium based ILs were better catalysts than phosphonium based ILs. Liu et al. [105] studied the effect of adding cuprous (I) chloride (CuCl) to triethylamine hydrochloride-aluminum chloride [(C 2 H 5 ) 3 NH]Cl-AlCl 3 . The composite IL catalyst successfully minimized side reactions occurring due to high acidity of [(C 2 H 5 ) 3 NH]Cl-AlCl 3 and displayed higher TMP selectivity than sulfuric acid catalyst proving its suitability for commercial use. ...
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.
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.
To explore sustainable catalysts with innovative mechanisms, the alkylation mechanism of o-xylene with styrene was studied using DFT method in AlCl3-ionic liquid catalytic system. The reaction pathway was consisted of C-C coupling and a hydrogen shift, in which two transition states were found and further discussed. The reactive energy catalyzed by superelectrophilic AlCl2⁺ (12.6 kcal/mol) was distinctly lower than AlCl3 (43.0 kcal/mol), which was determined as the rate-determining step. Mulliken charge along IRC gave a comprehensive understanding of charge distribution and electron transfer in dynamic progress. Bond orders and AIM theory were used to study the nature of chemical bonds and the driving forces in different reaction stages.
A practical and highly efficient silylation of alcohol and phenol derivatives with hexamethyldisilazane (HMDS) using acidic ionic liquids under mild reaction conditions is described. A series of Brønsted as well as Brønsted–Lewis acidic ionic liquids were prepared and their performance investigated for the silylation of a wide variety of alcohols and phenols with HMDS. Imidazole- as well as N-methyl-2-pyrrolidone-based acidic ionic liquids have a higher catalytic activity for the protection of sensitive, hindered alcohols and phenols, thus providing an environmentally begin and versatile alternative to current acid catalysts. In addition, the acidic ionic liquids are reusable, being recovered easily and reused several times without significant deterioration in catalytic activity.
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.
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.
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.
An imidazolium based Brønsted–Lewis acidic ionic liquid has been shown to be an excellent catalyst and reaction medium for the tetrahydropyranylation of various alcohols in good to excellent yields with short reaction times. Selective protection of benzyl alcohol in the presence of phenol was achieved. The novel ionic liquid was prepared from readily available starting materials and could be easily recovered and reused several times without significant deterioration in catalytic activity.
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.
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.
Lignocellulosic biomass is the most abundant organic carbon source and has received a great deal of interest as renewable and sustainable feedstock for the production of potential biofuels and value-added chemicals with a wide range of designed catalytic systems. However, those natural polymeric materials are composed of short-chain monomers (typically C6 and C5 sugars) and complex lignin molecules containing plenty of oxygen, resulting in products during the downstream processing having low-grade fuel properties or limited applications in organic syntheses. Accordingly, approaches to increase the carbon-chain length or carbon atom number have been developed as crucial catalytic routes for upgrading biomass into energy-intensive fuels and chemicals. The primary focus of this review is to systematically describe the recent examples on the selective synthesis of long-chain oxygenates via different C-C coupling catalytic processes, such as Aldol condensation, hydroalkylation/alkylation, oligomerization, ketonization, Diels-Alder, Guerbet and acylation reactions. Other integrated reaction steps including e.g., hydrolysis, dehydration, oxidation, partial hydrogenation and hydrodeoxygenation (HDO) to derive corresponding key intermediates or final products are also reviewed. The effects of catalyst structure/type and reaction parameters on the catalytic performance along with relevant reaction mechanisms are in detail discussed. Apart from this, the formation of other useful compounds containing C-X bonds (X = O, N and S) derived from biomass-based substrates for producing fuel additives and valuable chemicals is also briefly reviewed.
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.
Production of high-quality fuels and petrochemicals are both energy and emission intensive with traditional methods. Thermal activation of reactions by catalysts or high temperature and pressure or both are very...
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...
Friedel-Crafts alkylation of long-chain alkenes (mixed C16~24 olefins) with toluene catalyzed by chloroaluminate ionic liquids was investigated systematically in this work. The catalysts were characterized by FT-IR(acetonitrile molecule as probe), specific gravity and 27Al NMR. Besides, the effect of chloroaluminate ionic liquids catalysts, catalysts dosage, toluene/olefins molar ratio, reaction temperature, reaction time and C16~24 olefins (long-chain alkenes) on alkylation were investigated thoroughly. And Bromine value and High Performance Liquid Chromatography (HPLC) were employed as the evaluation method for alkylation products. The experiment results indicate that excellent conversion(99.85%) and good selectivity(32.99%) of C18 olefins alkylation have been reached up under the optimal reaction conditions (T/O molar ratio=10:1, catalyst/olefins=0.3:1, 50 °C, 20 minutes). Moreover, the catalytic recyclability of [HMIM]Cl-2AlCl3 was proved after ten reuses. The study shows that [HMIM]Cl-2AlCl3 not only has catalytic performance on long-chain alkenes alkylation but also exhibits excellent recyclability, possessing a possibility of industrial continuous production.
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.
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.
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.
Various particle size Al2O3 binders were used to formulate zeolites Y based catalyst, and the acidity of catalysts increases with the decreasing Al2O3 particle size. Characterization results showed that the amount and location of Al immigration are related to the Al2O3 particle size, thus influence the catalysts’ acidity and activity. An Al2O3-zeolites interaction scheme is proposed, the contact area increase with the decreasing Al2O3 particle size, which would increase Al immigration possibility. Comparing with microscale Al2O3, nanoscale Al2O3 particle is more likely to immigrate into zeolites due to its great diffusivity into zeolite. Catalysts formulated by nanoscale Al2O3 have better alkylation performance than that formulated by microscale Al2O3 because of its higher acidity. The research on zeolites-binder interaction would give inspirations to zeolites-based catalysts design and industrial application.
Brӧnsted-Lewis acidic ionic liquids (BLAILs)[3-methyl-1-(3-sulfonic acid) imidazolium zinc sulfate ([MIMPS]+(1/2Zn²⁺)SO4²⁻)] with Brӧnsted acid ionic liquid [MIMPS]+HSO4- and ZnO were synthesized, and their acidities were determined by infrared pyridine probe. Ti doped SBA-15 mesoporous molecular sieves (Ti-SBA-15) were synthesized by co-condensation method. Ionic liquid [MIMPS]+(1/2Zn²⁺)SO4²⁻ and Ti-SBA-15 are compounded at different mass ratios by impregnation method. FT-IR, TG, XRD, N2 physical adsorption, elemental analysis, mass spectroscopy, TEM, and XPS were used to characterize the composition and structure of the catalysts. The catalytic activities of catalysts were investigated via esterification of acetic acid with benzyl alcohol (BnOH). When the reaction temperature is 90 ℃, reaction time is 3 h, nbenzyl alcohol/nacetic acid =1.8, and the amount of catalyst was 0.4 g, the conversion of acetic acid was as high as 93.8 %. After 5 cycles, the conversion of acetic acid decreased only 5%, suggesting that the resulting catalyst had good stability.
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.
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.
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.
A class of Brønsted–Lewis acid bifunctionalized ionic liquids based heteropolyacid hybrid (BLA-ILs-HPA) solid acids were developed by combining the double sulfonic groups grafted, ionic liquids based heteropolyacid hybrid with Lewis acidic centers (M = Zn, Co, Fe, Ni, Cu). The prepared BLA-ILs-HPA show both Brønsted and Lewis acidic sites with extremely-high acid strength and enhanced stabilities, as determined by FT-IR, Py-IR, TG, XPS and ³¹P solid state NMR results. BLA-ILs-HPA were successfully applied in esterification camphene with acetic acid to produce isobornyl acetate, and dehydration of glucose to produce 5-hydrozymethylfural. BLA-ILs-HPA show enhanced catalytic activities in comparison with various acid catalysts. The effects of reaction temperatures, initial reactant molar ratio, catalyst dosage, and reaction time were studied in detail. The optimal reaction conditions were obtained, and the experimental data was successfully correlated by a pseudohomogeneous (PH) reaction kinetic model in the temperature range of 313.15–333.15 K. The calculated values obtained by the reaction kinetic model were in good agreement with the experimental data. Moreover, as a heterogeneous reaction catalyst, BLA-ILs-HPA can be recovered by simple treatment. After six times cycling, the decreasing in the catalytic activity of BLA-ILs-HPA could not be observed significantly, suggesting their good reusability.
A series of Brønsted–Lewis acids bifunctionalized heteropolyacid based ionic liquids hybrid solid acid catalysts (BLA-HPA-ILs) were synthesized by combining the Brønsted acidic ionic liquid [Bis–Bs–BDMAEE]HPW12O40 with metallic oxide in different composition ratios and applied in the esterification of cyclohexene to cyclohexyl acetate. Among the synthesized catalysts, the ¹/2Cu[Bis–Bs–BDMAEE]HPW12O40 catalyst with Brønsted and Lewis acidities shown the most excellent catalytic performance for the esterification of cyclohexene with acetic acid. The BLA-HPA-ILs catalysts were characterized by elemental analysis, FT-IR, Py-IR, TG, ¹H NMR, SEM and EDX. The effects of reaction temperature, catalyst dosage, and initial reactant molar ratio has been investigated in detail. A pseudohomogeneous (PH) kinetic model was used to correlate the kinetic data in the temperature range of 333.15–363.15 K, and the kinetic parameters were estimated, indicating the results calculated by the kinetic model are well coincidence with the experimental results. Moreover, as a heterogeneous reaction catalyst, ¹/2Cu[Bis–Bs–BDMAEE]HPW12O40 could be easily recovered by a simple treatment and reused six times without any obvious decrease in catalytic activity, displaying good reusability.
Graphic Abstract
A novel IL/Zr-SBA-15 (n(Si)/n(Zr)=2,10,40) catalysts were synthesized, and characterized by XRD, FTIR, SEM, TEM, N2 adsorption–desorption measurement and DSC/TG. The results showed that ionic liquid (IL) has been successfully immobilized on the surface of Zr-SBA-15, and the ordered mesoporous structure can also be well preserved, even after chemical grafting reaction. Using water as a solvent, Raney Ni and IL/Zr-SBA-15 composite catalysts were investigated by hydrodeoxygenation (HDO) of phenol. The synergy of acid and metal catalysts can effectively catalyze phenol as a model compound for pyrolysis oil by tandem reactions. Under optimum reaction condition, the mean selectivity and yield of cyclohexane was 81.08% and 76.26%, respectively. The catalyst still provided satisfactory results after 5 runs. With reference to the study of phenol, HDO was carried out on the coconut clothes pyrolysis oil. The process conditions were optimized by response surface methodology. In addition, it is concluded that reaction conditions affect the order of naphthenes component content as reaction temperature>reaction time>hydrogen pressure. As a result, the content of naphthenes components in the bio-fuel reaches 34.43% and the HHV of 37.58 MJ/kg, indicating that this catalyst also has a good effect on HDO of the pyrolysis oil.
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.
This review is the first attempt to collect papers about possible use of ionic liquids for the chemical processing of oleochemical raw materials. The main focus is put on the processes based on vegetable oils, due to the fact that the majority of published reports in this area were dedicated to the synthesis of fatty acid methyl esters (FAME, biodiesel), which are originated mainly from vegetable oils. A significant amount of reports, including several review papers, were dedicated to the use of ionic liquids in the synthesis of biodiesel, but also other processes such as the synthesis of fatty acid esters or reactions with the use of unsaturated bonds still remain underrated. However, it is important enough to justify their collection in one paper in order to adequately appreciate the potential use of ionic liquids and benefits resulting from the chemistry of vegetable raw materials.
In the present work, aluminium chloride based ionic liquids (ILs) were used as catalysts for alkylation of iso-butane with butene-2. Some additives such as, transition metal salts, water and acidic cation exchange resins were used to improve the selectivity of the main products and the yield of reaction. A high content of the desired trimethylpentanes (TMPs) (up to 72.3%) and thus a high research octane number (RON up to 98) of the alkylate were received on using CuCl modified triethylamine hydrochloride aluminium chloride ([Et3NH]Cl/AlCl3) (molar fraction of AlCl3 is 0.6) at − 5 °C over a period of 15 min.The effectiveness of additives is assumed to explain by the formation of Brønsted acid or complexes which exhibit the Brønsted acidity or superacidity. The acidity of investigated catalytic systems was evaluated by FT-IR and confirmed that. The Brønsted and Lewis acidic sites were detected by FT-IR. The Lewis acidity can be adjusted mainly by mol fraction of AlCl3 while the Brønsted acidity can be increased by using the suitable amounts of additives. This is a valuable guide to explain the mechanism and to select the catalysts for alkylation.
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).
The effect of different promoters on activity and selectivity of Lewis-acidic chloroaluminate ionic liquid catalysts was studied for isobutane/2-butene alkylation. When tert-butyl halides are used as promoters, the active species of the alkylation reaction, which is the tert-butyl cation, is directly generated whereas upon catalysis with Brønsted-acid supported ionic liquids, this species is indirectly provided through a hydride shift between protonated 2-butene and isobutane. Experimental results both from batch and continuously operated liquid phase alkylation reactors indicate, that tert-butyl halides are able to speed up the reaction rate significantly and shift the C8-selectivity towards the desired high-octane trimethylpentanes (TMPs). However, secondary reactions like oligomerization and cracking could not be suppressed by the use of this additives and high deactivation rates in continuous opperation were observed. Suggestions are made, how the product composition is effected by the additive and how the promoted IL-catalyst system is deactivated with time on stream.
Graphical Abstract
The alkylation of naphthalene with 1,2,4,5-tetramethylbenzene was studied using various catalysts and solvents. Among many alkyl halide solvents and Lewis acid catalysts screened, aluminum chloride and dichloromethane were found the most effective catalyst and solvent, respectively. The alkylation activity was enhanced and product distributions were also favorably changed by introducing a small amount of benzylchloride to the base solvent of dichloromethane.
The synthesis of monoalkyldiphenyl oxide via the alkylation of diphenyl oxide with dodecene catalyzed by 1-butyl-3-methylimidazolium chloroaluminate (III) ([bmim]Cl/AlCl3) was studied. The catalytic activity of [bmim]Cl/AlCl3 was much higher than that of the AlCl3 catalyst. A low amount of [bmim]Cl/AlCl3 significantly improved the monoalkyldiphenyl oxide yield. A high yield of monoalkyldiphenyl oxide of about 90% could be obtained at 80°C reaction temperature, and a diphenyl oxide/dodecene molar ratio of 7. The process catalyzed by the ionic liquids simplified the product isolation evidently and could be regarded as an environmentally benign system.
The successful development of a Bronsted acid catalyzed Friedel-Crafts alkylation reaction between trifluoromethyl-alpha,beta-ynones and indoles has been described. The reaction is catalyzed by benzoic acid (5 mol%), with the indoles adding to the carbonyl carbon of the trifluoromethyl-alpha,beta-ynones producing the corresponding 1,2-addition products as trifluoromethyl propargyl alcohols in high yields. Furthermore, treatment of the product with indoles in the presence of trifluoroacetic acid (10 mol%) afforded trifluoromethyl-functionalized unsymmetrical bis(indolyl)propynes in high yields.
The reaction kinetics and chemical equilibrium of the transesterification of methyl acetate and isoamyl alcohol catalyzed by 1-sulfobutyl-3-methylimidazolium hydrogen sulfate ([HSO3bmim][HSO4]) were investigated. The effects of reaction temperature, initial reactant molar ratio, and catalyst concentration on the kinetics were studied. Two kinetic models, the ideal homogeneous (IH) model and the nonideal homogeneous (NIH) model, were used to correlate the kinetic data. The NIH model was more reliable to describe the reaction rate. The residue curve maps of the reaction system at different mole fractions of IL catalyst were computed, and according to the analysis of residue curve maps, a reactive distillation process was proposed. Effects of operational and structural parameters of reactive distillation column were investigated. An experiment of the reactive distillation in a lab-scale column was then conducted to validate the simulation results.
Desulfurization of diesel fuel with ionic liquids (ILs), as alternative to traditional hydrodesulfurization (HDS), has been studied intensively for the latest years. Most works, however, were focused on the investigation of model diesel fuel. In this work, two acidic ILs ([(CH2)4SO3HMIm][Tos] and [(CH2)4SO3HMIm][ZnCl3]) were synthesized and studied their desulfurization performance for real diesel fuel in a coupled oxidative–extractive way, where 30 wt% H2O2 acted as oxidant and ILs served as both extractants and catalysts with adding no acidic catalysts that were usually used in traditional oxidative desulfurization. The influences, on desulfurization, of temperature, time, mass ratio of ILs/oil, molar ratio of O/S, multiple desulfurization and ILs recycle were investigated. It was observed that sulfur content (S-content) in the real diesel fuel was reduced to <10 ppm from original 225 ppm in a coupled oxidative–extractive way ([(CH2)4SO3HMIm][Tos]; mass ratio of ILs/oil 1/2; 3 h, 348.15 K and molar ratio of O/S 40/1 in oxidative step; 30 min and 333.15 K in extractive step). These results are more competitive than other previous results. After 5 cycles of oxidative desulfurization with used ILs, the loss of efficiency is less than 1% at a mild temperature. Distribution of S-compounds in diesel fuel before and after desulfurization were determined by gas chromatograph with sulfur chemiluminescence detector. This work shows that such acidic ILs are capable of removing S-compounds effectively from real diesel fuel with a coupled oxidative–extractive operation.
In the absence of external reductant, C3-cycloalkylated indole could be synthesized through reductive alkylation of indole with cyclic ketone by using a sulfonyl-functionalized Brønsted acid ionic liquid as catalyst. The reaction proceeded most likely in a radical way. Water was involved as a key component of the reaction.
In isobutane/2-butene alkylation, chloroaluminate ionic liquid catalysts (CAIL) deactivate fast with time on stream with respect to activity and selectivity. Hence, the effect of anhydrous hydrogen chloride (HCl), which shows co-catalytic behavior, was studied in a batch reactor and its effect on both parameters was investigated. The co-catalyst leads to an increased reaction rate and improves the yield of trimethylpentanes, the primarily desired high-octane compounds of alkylation. Moreover, already deactivated CAIL catalysts are reactivated by gaseous HCl. In addition saturation of the ionic liquid with HCl prior to the reaction effectively suppresses the deactivation of the CAIL catalyst. Thus, the solubility of hydrochloric acid is reported for both the CAIL (IL: [BMIM]Cl/AlCl3, x=0.64) and organic phase to gain a deeper understanding of the reaction system. Finally conjunct polymers dissolved in the ionic liquid were extracted to study their influence on deactivation.
Alkylate is an important clean blending component of gasoline due to the increased statutory reduction of the content of aromatics and olefins in commercial gasoline. The alkylation of isobutane with 2‐butene catalyzed by a composite ionic liquid was investigated. The composite ionic liquid showed efficient catalytic performance at a short contact time (10–60 s). The optimal conditions were: reaction temperature 15°C, contact time 20 s, ionic liquid to hydrocarbon volume ratio 1:1, and isobutane to olefin mole ratio 54:1. Under these optimal reaction conditions, the butene conversion was 100%, the yields of C8 and trimethylpentanes were 88.9 and 82.0%, respectively, the ratio of trimethylpentane to dimethylhexane was 11.9, and the alkylate research octane number (RON) was 97.3. A correlation model is developed to predict the product yields and the alkylate RON. The correlation model shows a low calculation error. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2244–2253, 2014
A library of di- and triaryl (and heteroaryl) methanes was prepared in good yields and regioselectivity via a simple and efficient alkylation of aromatic compounds through direct SN1-type alcohol nucleophilic substitution in the presence of o-benzenedisulfonimide under neat conditions.
The dimerization of fatty acid methyl ester was investigated using Brönsted–Lewis acidic ionic liquids (ILs) as catalysts. It is found that IL (3-sulfonic acid)-propyl-triethylammonium chlorozincinate [HO3S–(CH2)3–NEt3]Cl–ZnCl2 (x=0.64, x: molar fraction of ZnCl2, x=moles of ZnCl2/(moles of ZnCl2+moles of ammonium salt) was of good catalytic performance. Under the optimum conditions m(biodiesel):m(IL) 15:1, biodiesel 15g, reaction temperature 240°C, and reaction time 5h, the yield of product dimeric acid methyl ester was 96.8%. The reusability of IL was good and after it was used five times, the dimeric acid methyl ester yield was still more than 94%. Otherwise, a synergetic effect of Brönsted and Lewis acid sites enhanced the catalytic performance of the IL.
Isobutane was alkylated with 1-butene in the presence of sulfuric acid in a small (24 ml.) stirred autoclave at various rates of agitation, 10° to 40°C., isobutane-1-butene ratios of 2.5 to 1 and 5 to 1, average residence time in the reactor of 15 to 60 seconds, and volumetric acid-hydrocarbon ratios of 0.5:1 to 2:1. The sulfuric acid used as feed varied from 88 to 99% acid containing 1 to 2% water and the remainder organic materials formed in the alkylation reaction. The hydrocarbon product was analyzed using a gas chromatographic procedure for all major compounds through the C9 range. Several C10 and higher peaks were noted but not identified. Numerous runs were made to determine quantitatively the effect of operating variables on the product quality, yields, and drop in acid strength. In all runs, the 1-butene reacted completely by polymerization, esterification, or alkylation reactions. Reasons for certain phenomena are postulated.
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.
Well-characterized examples of the large-pore zeolites X and Y in their acidic form were explored as catalysts for isobutane/butene alkylation in order to understand the principal requirements for successful solid acid catalysts. The materials were tested in a continuously operated stirred tank reactor under industrially relevant conditions. A high ratio of Brønsted to Lewis acid sites and a high concentration of strong Brønsted acid sites are seen to cause high hydride transfer activity and are mandatory for long catalyst life. Isobutane “self-alkylation” activity is higher in catalysts with a high hydride transfer activity. The catalyst lifetime is very sensitive with respect to the reaction temperature reaching the optimum between 70 and 80°C concurrent with a maximum in self-alkylation activity. The lifetimes were found to be correlated linearly with the reciprocal of the olefin space velocity, while it hardly influenced the total productivity of the catalysts. The selectivities on the other hand strongly depended on the butene feed rate per active site.
Lanthanum exchanged X and Y type zeolites were prepared by ion exchange and investigated as catalysts for isobutane/2-butene alkylation. With the reactions performed in a continuously operated stirred tank reactor under industrially relevant conditions (T=348K, p=20bar, paraffin/olefin molar ratio=10, olefin weight hourly space velocity=0.2h−1) the catalyst lifetime of LaX was nearly twice as long as that of LaY. Moreover, a much higher yield of octane isomers was observed with LaX. The product distributions showed that LaX had a high activity for hydride transfer and “self-alkylation” as well as a higher concentration of strong Brønsted acid sites. These differences are related to a higher residual concentration of sodium cations in LaY leading not only to less, but also weaker strong Brønsted acid sites in LaY than in LaX. The replacement of the residual sodium cations by lanthanum cations is less favorable in LaY due to the lower concentration of appropriate sites to accommodate multivalent cations.
A detailed study of the alkylation of isobutane with 2-butene in ionic liquid media has been conducted using 1-alkyl-3-methylimidazolium halides–aluminum chloride encompassing various alkyl groups (butyl-, hexyl-, and octyl-) and halides (Cl, Br and I) on its cations and anions, respectively. The emphasis has been to delineate the role of both cations and anions in this reaction. The ionic liquids bearing a larger alkyl
group on their cation ([C8mim]) displayed relatively higher activity than a smaller one ([C6 or C4mim]) with the same anionic composition, due to the high solubility of reactants in the former. Among the ionic liquids with different halide groups, bromides ([C8mim]Br–AlCl3) showed outstanding activity, because of the higher inherent acidity relative to others. From the 27Al NMR study, a major peak at ∼ 99.5 ppm corresponding to [AlCl3Br]− (∼ 99.5 ppm) was observed. Moreover, the anion showed a strong acidity based on FT-IR characterization; the largest peak related to acidity (1570 cm−1) was detected. Under various composition conditions, catalytic activity and amount of TMPs increased with concentration of anion. This is mainly attributed to a higher amount of strong acid ions [Al2Cl6Br]− which can react with hydrogen atoms at the 2-position of an imidazolium ion to form Brønsted acid. However, the ionic liquid with strong acidity (X = 0.58) deactivated rapidly due to a higher sensitivity to moisture, causing decomposition. Under various reaction temperature conditions, optimum catalytic activity was observed at 80 ◦C. The result is also attributed to the effect of anion composition. The strong acidic anion increased with temperature. However, at higher reaction temperatures (120 ◦C), the ionic liquid showed a lower activity and TMP selectivity, since the solubility and Brønsted acid sites were reduced by decomposition of imidazolium ions. The selected ionic liquid sample ([C8mim]Br–AlCl3) was compared with one of the standard commercial catalysts, sulfuric acid. Under optimum experimental conditions, it was observed that both catalysts showed comparable catalytic behavior. However, ionic liquid showed higher activity, and lower TMP selectivity due to a more acidic nature and a lower amount of Brønsted acid sites, respectively.
Isomerization oil becomes an important motor gasoline blending component due to increased statutory reduction of aromatics and olefins (high octane number components) contents in motor gasoline. The ionic liquid Et3NHCl−AlCl3 (mole fraction of AlCl3 is 0.67) shows good catalytic performance for the isomerization of n-pentane. The conversion of n-pentane increases with the enhancement of reaction temperature, reaction time, and catalyst/oil volume ratio (C/O ratio), while the yield of isomerization oil and the selectivity of isoparaffins decrease. The optimal reaction temperature, reaction time, and C/O ratio are 30 °C, 3 h, and 1:1, respectively. Under the optimal reaction conditions, the conversion of n-pentane, the yield of isomerization oil, and the selectivity of isoparaffins are 44.61 wt %, 96.07 wt %, and 90.52%, respectively. High conversion of n-pentane favors the octane number improvement of isomerization oil without the circulation of n-pentane, while low conversion of n-pentane is preferential with the circulation of n-pentane.
The oligomerization of isobutene catalyzed by ionic liquids containing FeCl4− and Fe2Cl7− was conducted in an autoclave. The conversion of isobutene was above 83 wt%, and the selectivity of diisobutene plus triisobutene was above 75% when the mole ratio of FeCl3 to [(C2H5)3NH]Cl ranged from 1.2:1 to 2:1. The addition of cuprous chloride to the ionic liquid increased the conversion of isobutene and the selectivity of diisobutene plus triisobutene. The latter reached 90% at the mole ratio of CuCl to [(C2H5)3NH]Cl-1.5FeCl3 of 0.25:1. The reaction pathway of the oligomerization of isobutene catalyzed by iron(III) chloride ionic liquids was explained by the carbonium ion mechanism.
The acylation reaction of anthracene with oxalyl chloride was investigated in the presence of [bmim]Cl/AlCl3 ([bmin]+ = 1-butyl-3-methylimidazolium cation) ionic liquid. Pure 1,2-aceanthrylenedione was obtained by extraction and recrystallization of the reaction mixture. The structure of 1,2-aceanthrylenedione was identified by GC/MS, FTIR and 1H NMR spectra. The effects of various reaction parameters were investigated. The optimum synthesis conditions of the acylation reaction were given as follows: reacting at 45 °C for 6 h, the molar ratio of AlCl3 in [bmim]Cl/AlCl3 to [bmim]Cl/AlCl3 and [bmim]Cl/AlCl3 to anthracene equal to 0.67 and 2, respectively, and the molar ratio of oxalyl chloride to anthracene equals to 2. At the optimum conditions, the yield of 1,2-aceanthrylenedione is 88.2% and the selectivity is 98.2%. The reusing experiment shows that [bmim]Cl/AlCl3 can be used as both catalyst and solvent, and it is reusable and environmentally friendly for the preparation of 1,2-aceanthryenedione.
Alkylation of isobutane and butene was carried out in a continuous unit using triethylamine hydrochloride–aluminium(III)chloride ionic liquid as catalyst. The effects of additives of HCl and metal chlorides on the properties of ionic liquids for alkylation were investigated. Improvement of production distribution with high yields of C8 and selectivity of TMP under a mild reaction condition has been observed after addition of CuCl.
A composite ionic liquid was used as an acid catalyst for the liquid phase alkylation of isobutane and 2-butene. The main product obtained was trimethylpentane (>85 wt.%) and the research octane numbers of the alkylates was 98–101. In the ionic liquid sample, a composite anion [AlCl4CuCl]− was detected by means of ESI-MS. This new species was also confirmed by 27Al NMR and FT-IR characterizations. The effects of anion composition on the product distribution have been investigated. The composite anion plays important roles in improving alkylate quality.Graphical abstractA composite ionic liquid was used as an acid catalyst for the alkylation of isobutane and 2-butene. The research octane number of alkylate obtained was 98–101. The effects of anion composition on the product distribution have been investigated. The composite anion ([AlCl4CuCl]−) plays important roles in improving alkylate quality.
The catalytic activity of Brønsted acid sites in zeolites was studied by the monomolecular conversion of propane over zeolites with varying framework topologies and Si/Al ratios. The rates and apparent activation energies of cracking and dehydrogenation were determined. The activity of the Brønsted acid sites depends on the rate-limiting step of the reaction. In the cracking reaction, the protonation of the alkane is the rate-limiting step, and the heat of reactant adsorption dominates the differences in the observed activity. The similar intrinsic activities over the different zeolites show that the ability of zeolitic Brønsted acid sites to transfer a proton to an alkane does not vary significantly, suggesting that the acid sites that participate in the reaction have very similar strengths. In the dehydrogenation reaction, the rate-limiting step is the desorption of the alkoxide species. The rate is determined by the stability of the alkoxide species, which is influenced by the local geometric and electronic structure of the Brønsted acid site and is affected by zeolite structure and Si/Al ratio. Implications of these conclusions are related to other reactions, such as catalytic cracking and alkylation.
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.
The role of Lewis and Brönsted acidities in alkylation of resorcinol is demonstrated through the gallium-zeolite beta by varying the amount of Lewis and Brönsted acid sites. The synergism of Lewis and Brönsted acid sites takes place heterogeneously in Friedel-Crafts alkylation of resorcinol with methyl tert-butyl ether to produce 4-tert-butyl resorcinol and 4,6-di-tert-butyl resorcinol as the major and minor products, respectively.
C-H bond functionalization enables strategically new approaches to the synthesis of complex organic molecules including biologically active compounds, research probes and functional organic materials. To address the shortcomings of transition metal catalyzed processes, we have developed a new approach to direct coupling of sp(3) C-H bonds and alkenes based on Lewis acid-promoted hydride transfer. Activation of alpha,beta-unsaturated aldehydes and ketones with Lewis acid triggers intramolecular hydride transfer, leading to a zwitterionic intermediate, which in turn undergoes ionic cyclization to afford the cyclic alkylation product. The scope of this method is expanded by the generation of alkenyl-oxocarbenium species as highly activated alkene intermediates capable of abstracting a hydride from unreactive carbon centers, including benzyl-, allyl-, and crotyl-ethers, as well as primary alkyl ethers, at room temperature. The alkenyl acetal and ketal substrates show dramatically faster rates of cyclization, as well as improved chemical yield and diastereoselectivity, compared to the corresponding carbonyl compounds. Furthermore, the use of boron trifluoride etherate as the Lewis acid and ethylene glycol as the organocatalyst provides a highly active catalytic system, presumably via the in situ formation of alkenyl-oxocarbenium intermediates, which eliminates the need for expensive transition metal Lewis acids or the preparation of ketal substrates. This binary catalytic system greatly improves the efficiency of the hydride transfer-initiated alkylation reactions.