Catalytic Activity Of Ionic Liquids Research Articles

Structure–reactivity relationships in the ionic-liquid-catalyzed oxidation of cumene: Cation effects

Cumene oxidation is a key step in the industrial synthesis of phenol via cumyl hydroperoxide (CHP) formation. Ionic liquids (ILs) are attractive as green, metal-free alternatives catalysts for this reaction, but few studies have explored their potential. The study of the relationship between the structure and catalytic performance of ILs is crucial for the development of ionic liquids with excellent performance. In this study, we aimed to establish a theoretical protocol to evaluate the catalytic activity of ILs for cumene oxidation, as well as the structure–activity relationship, using density functional theory calculations. The calculations showed that the catalytic activity of the studied ILs decreased as follows: 1-n-butyl-3-methylimidazolium bromide > 1-butyl-1-methylpyrrolidinium bromide > N-n-butylpyridinium bromide > triethylammonium bromide > 1-n-butyl-2-methylpyrrolinium bromide. Moreover, the polarity, solubility, and maximum electrostatic potential of the ILs were linearly correlated with their catalytic activity. The theoretical predictions were verified by experiment. Additionally, DFT calculation and EPR analysis demonstrated that the catalytic activity of ionic liquids originates from the formation of hydrogen-abstracting radicals. Furthermore, using 1-butyl-1-methylpyrrolidinium bromide as a representative catalyst, we optimized the reaction conditions, a cumene conversion of 24.2 % and a CHP selectivity of > 90 % were obtained. Compared with the aqueous NaOH as a stabilizing agent, the reaction time is reduced by 8 h. This study provides new insights for designing efficient, low-cost, and environmentally friendly catalysts for cumene oxidation.

Immobilization of Ionic Liquid on a Covalent Organic Framework for Effectively Catalyzing Cycloaddition of CO2 to Epoxides.

Transforming CO2 into value-added chemicals has been an important subject in recent years. The development of a novel heterogeneous catalyst for highly effective CO2 conversion still remains a great challenge. As an emerging class of porous organic polymers, covalent organic frameworks (COFs) have exhibited superior potential as catalysts for various chemical reactions, due to their unique structure and properties. In this study, a layered two-dimensional (2D) COF, IM4F-Py-COF, was prepared through a three-component condensation reaction. Benzimidazole moiety, as an ionic liquid precursor, was integrated onto the skeleton of the COF using a benzimidazole-containing building unit. Ionization of the benzimidazole framework was then achieved through quaternization with 1-bromobutane to produce an ionic liquid-immobilized COF, i.e., BMIM4F-Py-COF. The resulting ionic COF shows excellent catalytic activity in promoting the chemical fixation of CO2 via reaction with epoxides under solvent-free and co-catalyst-free conditions. High porosity, the one-dimensional (1D) open-channel structure of the COF and the high catalytic activity of ionic liquid may contribute to the excellent catalytic performance. Moreover, the COF catalyst could be reused at least five times without significant loss of its catalytic activity.

Microwave synthesized ionic liquids as green catalysts for the synthesis of benzimidazoles: Spectral and computational studies for potential anticancer activity

• Innovative, green chemical processes for solvent free, quicker, efficient reaction times & products i.e., MW & ILs. • Modifying conventional organic transformations with green catalysts (ILs) e. g. Benzimidazoles. • Identifying the possibility to develop benzimidazole derivatives as promising anti-breast cancer drugs. • As breast cancer mutant, oxidoreductase enzyme (3hb5) was used as a molecular docking target in this investigation. • Further, Ligand's and/or protein's surface proved to be a useful tool for lead optimization. Imidazolium based ionic liquid (IL) [bmim] Br or 1-butyl-3-methyl imidazolium bromide synthesized from 1-methyl imidazole and butyl bromide by microwave (MW) method and is used for efficient synthesis of benzimidazoles from o-phenylene diamine and aldehydes at room temperature (RT). Our attention has been drawn to the development of cost-effective and environmentally friendly catalytic systems for chemical synthesis because of the increasing need for greener and more sustainable technologies. This procedure has various benefits, including excellent yields (≈100%) of synthesized benzimidazole derivatives in 3 h and product recovery with minimal experimental work-up. The catalytic activity of ionic liquid can be recovered and reused up to four times without losing its activity. The 17 beta-hydroxysteroid dehydrogenase (PDB ID: 3hb5) was used as a target in a molecular docking study of these benzimidazole derivatives using Flare V5GUI software. They have the greatest LF dG score, ranging from −8.03 to −6.3 kcal/mol, indicating that these benzimidazole derivatives could be developed as promising anti-breast cancer drug candidates. Further, the electrostatic complementarity approach outlined here is a useful and versatile technique for drug development. The ability to observe EC values over the surface of a ligand or protein has a huge advantage when considered optimization.

New Evidence for the Key Role of Hydrogen Bonding Between N‐Hydroxyphthalimide and Halide Ionic Liquids in Hydrocarbons Oxidation

AbstractThis paper demonstrates the catalytic activity of ionic liquids with an 1‐alkyl‐3‐methylimidazolium cation ([Rmim][X]) in the oxidation of ethylbenzene as a model hydrocarbon. The interaction between ionic liquids and N‐hydroxyphthalimide (NHPI) were examinated with or without Co(II). The activity of the studied ionic liquids and selected tetraalkylammonium salts ([R4N][X]) is compared. The influence of the structure of the alkyl substituents [R] and anions (in which [X]=[Cl], [Br], or [I]) on the reaction course was determined. The interaction between NHPI and the selected ionic liquids was proven using 1H NMR. It was shown that the formation of hydrogen bonds between the hydrogen atom in the −NOH group in NHPI and the anion [X] in [Rmim][X] influenced the rate of the oxidation reaction by accelerating the formation of the N‐oxyl radical responsible for the NHPI activity.

Fabrication of a metal free catalyst for chemical reactions through decoration of chitosan with ionic liquid terminated dendritic moiety

In attempt to develop a biocompatible metal-free catalyst, a dendritic moiety was grown on chitosan through successive reactions with 2,4,6-trichloro-1,3,5-triazine and ethylenediamine. Subsequently, the terminal functional groups of the dendron were decorated with 1-methylimidazolium chloride. The catalyst was characterized with SEM, EDS, TGA, FTIR, XRD and mapping analysis. Then, the catalytic activity of the resultant composite was scrutinized for catalyzing Knoevenagel condensation and synthesis of xanthene derivatives in aqueous media under mild reaction condition. The results confirmed high activity of the catalyst, superior to ionic liquid free counterpart and bare chitosan. This observation was ascribed to the instinct catalytic activity of ionic liquid. Moreover, using control catalysts, it was confirmed that the presence of the dendritic moiety that could increase the content of ionic liquid on the backbone of the catalyst enhanced the catalytic activity.

Ionization of a covalent organic framework for catalyzing the cycloaddition reaction between epoxides and carbon dioxide

Covalent organic frameworks (COFs), with two dimensional (2D-) or three dimensional (3D-) structures, have accessible open channels or nanopores, with uniform sizes ranging from angstroms to nanometers and have emerged as an excellent and promising platform for designing catalysts or catalyst carriers. Herein, a 2D-COF grafted with a 1-alkyl-3-methylimidazolium-based ionic liquid (AMIMBr@H2P-DHPh COF) on the channel walls was synthesized and utilized as a highly efficient heterogeneous catalyst for the chemical fixation of CO2 via a reaction with epoxides under solvent-free and co-catalyst-free conditions. The as-synthesized AMIMBr@H2P-DHPh COF shows excellent catalytic activity in promoting the cycloaddition reactions between epoxide and CO2; the excellent catalytic activity was maintained for up to five cycles. Advantages like high porosity, functional versatility, easy modification of COFs, and high catalytic activity of ionic liquids, have been realized in a single material.

Synergistic cooperation of bi-active hydrogen atoms in protic carboxyl imidazolium ionic liquids to push cycloaddition of CO2 under benign conditions

Nine protic carboxyl imidazolium ionic liquids are synthesized. Then, they are employed to catalyze the chemical fixation of carbon dioxide (CO2) and propylene oxide leading to propylene carbonate in the absence of co-catalyst and organic solvent. HCPImBr presents the best catalytic activity with the product yield of 92% under reaction temperature 120 °C, CO2 initial pressure 1.5 MPa, catalyst amount 0.5 mol%, and reaction time 2.0 h. Even if the reaction temperature and CO2 initial pressure are decreased to 80 °C and 1.0 MPa, respectively, the 85% of product yield would be kept with the 1.0% catalyst dosage along with 12.0 h. With the exception of the most optimal reaction conditions, generality, and recyclability of HCPImBr are also investigated. More importantly, the reaction mechanism is investigated by the density functional theory, which is the first time to report the mechanism for protic carboxyl imidazolium ionic liquids. The catalytic activity of ionic liquids would be further improved with the reasonable combination of cation and anion.

Hydrolysis of rapeseed oil to fatty acids using pyrrolidonium ionic liquids as catalysts

ABSTRACTThis study aimed to evaluate the hydrolysis of rapeseed oil using pyrrolidonium ionic liquids as catalysts under atmospheric pressure. The process parameters were optimized using a sequence of experimental protocols to evaluate the effects of ionic liquid loading, dosage of emulsifier, weight ratios of substrates, temperature and time. The results demonstrated that the ranking of catalytic activity of ionic liquids is N-methyl-2-pyrrolidonium hydrogen sulfate salt ([HNMP]HSO4)>1-(3-sulfonic acid) propyl-2-pyrrolidonium hydrogen sulfate salt ([C3SO3Hnhp]HSO4)>2-pyrrolidonium hydrogen sulfate salt ([Hnhp]HSO4). In a batch reactor, the hydrolysis reaction conditions in the presence of [HNMP]HSO4 were investigated and optimized as follows: catalyst loading of 20% (based on the weight of oil), oil/water weight ratio of 1:2, emulsifier loading dosage of 4 wt % (based on the weight of oil), hydrolysis temperature of 100°C, and hydrolysis time of 30 h. The catalytic performance of this ionic liquid remained excellent even after reuse five times.

Continuous Conversion of Carbon Dioxide to Propylene Carbonate with Supported Ionic Liquids

We present the use of silica-supported ionic liquids as catalysts for the continuous production of propylene carbonate from propylene oxide using supercritical carbon dioxide as solvent and reagent. Considerable differences in the catalytic activity of ionic liquids in homogeneous catalysis in batch mode and in continuous-flow using supported species processes were found, suggesting that a synergistic effect between ionic liquid and silica support material takes place. While supported ionic liquids prepared via physisorption of [C2mim]Br showed the highest catalytic activity, studies on long-term stability showed a rapid loss in yield due to the formation of undesired polypropylene carbonate that agglomerated in the ionic liquid layer. Improved long-term stability was found for ionic liquids covalently bound to the silica support materials, suggesting that a compromise between activity and stability is the best solution for the continuous production of propylene carbonate.

WITHDRAWN: Novel polysulfone membrane covalent bearing functionalized ionic liquids and its catalytic performance for biomass inulin hydrolysis

Abstract Polysulfone powders covalently linked with acidic ionic liquids (ILs) as catalyst (PSF-ILs) were synthesized. It was prepared into casting solution to fabricate membrane via non-solvent induced phase separation method. Chemical structure of the PSF-ILs was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The microstructure of PSF-ILs membranes was characterized by the scanning electron microscopy, pore size, porosity and contact angle measurements. The effects of the covalently incorporated ILs on the water flux, bovine serum albumin rejection and especially catalytic performance were investigated systematically to elucidate the microstructure-performance relationships. The structure of the membrane was regulated subtly by varying solvent or polymer concentration. Compared with the finger-like membrane, the resultant sponge-like membrane exhibited better catalytic performance for inulin hydrolysis due to higher porosity and specific surface area. Moreover, the effects of membrane thickness, porosity, reaction temperature and flux on catalytic performance of membrane that was constructed as a reactor were investigated. Interestingly, the turnover number of PSF-ILs membrane, i.e. the number of products generated by each active site of catalyst in unit time, was higher than the homogeneous ILs and PEK-C-ILs powders. Furthermore, the extended trial of the membrane demonstrated its reusability with only a little loss of catalytic activity. This novel catalytic membrane was first designed and prepared, not only subtly avoided the recycling of homogeneous ILs catalyst, but also effectively strengthened the mass transfer of substrates between the bulk of the feed and active sites on the pore wall, consequentially, improved the catalytic activity of ILs.

Ionic Liquid-Attached Colloidal Silica Nanoparticles as a New Class of Silica Nanoparticles for the Preparation of Propargylamines

We reported a novel class of organic–inorganic hybrid material based on the ionic liquid bis(1(3-trimethoxysilylpropyl)-3-methyl-imidazolium) nickel tetrachloride tethered to colloidal silica nanoparticles and characterized by 1H NMR spectroscopy, scanning electron microscope, energy dispersive spectroscopy, thermogravimetric analysis, and dynamic light scattering. Meanwhile, we compared the catalytic activity of ionic liquid immobilized colloidal nano-silica with ionic liquid immobilized nano-SiO2 produced by sol–gel route. A proper, atom-economical, straightforward one-pot multicomponent synthetic route for the synthesis of propargylamines in good yields has been devised using ionic liquid tethered to colloidal silica nanoparticles.

The influence of ionic liquids on curing rheokinetics and properties of strengthening composition based on polyesterurethane rubber with epoxyurethane groups

A study of the influence of ionic liquids on the curing and properties of a strengthening composition based on polyesterurethane rubber with epoxyurethane end groups has been carried out. The catalytic activity of ionic liquids has been found to be dependent on the anion chemical structure and to increase as the anion size decreases. It has been shown that introduction of methylbenzylamine and ionic liquid (1-ethyl-3-methyl-imidazolyl dicyanamide) results in strengthening compositions with close mechanical properties, lifetime, swelling in transformer oil, and glass transition temperature.

One-pot synthesis of levulinic acid from cellulose in ionic liquids

A simple and effective route for the production of levulinic acid (LA) from cellulose has been developed in SO3H-functionalized ionic liquids. The effects of ionic liquid structures, reaction conditions and combination of metal chlorides with ILs on the yield of LA were investigated, where the highest yield of 39.4% was obtained for 120min in the presence of 1-(4-sulfonic acid) butyl-3-methylimidazolium hydrogen sulphate ([BSMim]HSO4) with addition of H2O. The catalytic activities of ionic liquids depended on the anions and decreased in the order: CF3SO3−>HSO4−>OAc−, which was in good agreement with their acidity order. The ILs play a dual solvent-acid role for the cellulose conversion into LA and exhibited favorable catalytic activity over four repeated runs.

Study of the Catalytic Activity of Acidic Ionic Liquid in the Synthesis of Methyl Oleate

Four kinds of Brønsted-acidic ionic liquids were synthesized with netrogen-contained chemical groups and different anions,and were characterized by nuclear magnetic resonance (NMR) and infrared spectrum (IR). On this basic, when the mole ratio of catalyst quantity to oleic acid was 0.019, that of alcohol to acid was 2, the reaction temperature was 150°C and the reaction time was 5 hours,the esterification of oleic and methanol were studied and the catalytic activities of ionic liquids for the esterification were investigated. The results showed their catalytic activities were associated with the structures of nitrogen-contained chemical groups, anionic acid strength and acid volume. Under the coaction of anions and cations, ionic liquids ([MPy]HSO4) had the best catalysis activity. Meanwhile the conversion rate of oleic acid could reach 88.21% .

Hydrolysis of Vegetable Oils to Fatty Acids Using Brønsted Acidic Ionic Liquids as Catalysts

This work reports the hydrolysis of vegetable oils catalyzed by SO3H-functional Brønsted acidic ionic liquids at moderate hydrolysis temperature and reaction time. The results demonstrated that the catalytic activity of ionic liquids is in the sequence 1-(4-sulfonic group) butylcaprolactamium hydrogen sulfate ([HSO3-bCPL][HSO4]) > 1-(4-sulfonic group) butylpyridinium hydrogen sulfate ([HSO3-bPy][HSO4]) > 1-(4-sulfonic group) butyl-3-methylimidazolium hydrogen sulfate ([HSO3-bMIM][HSO4]) > 1-(4-sulfonic group) butyltriethylaminium hydrogen sulfate ([HSO3-bTEA][HSO4]). In the batch reactor, the reaction conditions of the hydrolysis in the presence of [HSO3-bCPL][HSO4] were investigated and optimized. The yield of fatty acids was greater than 95 wt % at [HSO3-bCPL][HSO4] dosage of 8 wt % (based on the weight of oil), water/oil molar ratio of 10:1, hydrolysis temperature of 180 °C, and hydrolysis time of 6 h. The catalytic performance of this ionic liquid remained excellent even after reuse six times.

Efficient and selective alcoholysis of furfuryl alcohol to alkyl levulinates catalyzed by double SO3H-functionalized ionic liquids

The production of alkyl levulinates from furfuryl alcohol (FAL) in alcohol media was investigated at moderate temperature in the presence of Bronsted acidic ionic liquids. The reaction was examined and optimized under batch conditions, where it was found that furfuryl alcohol was rapidly and almost quantitatively converted into intermediate products including 2-alkoxymethylfuran and 4,5,5-trialkoxypentan-2-one, and high alkyl levulinates yield of 95% can be achieved after reaching a steady state in 2 h. An advantage of this catalyst system is that undesired dialkyl ether (DEE) formed by a side reaction of the dehydration of alcohol is negligible. The Hammett method was used to determine the acidities of these ionic liquids, which indicated that the acidity and the molecular structure have strong effects on the catalytic activity of ionic liquids. Based on the experimental results, a possible mechanism for the alcoholysis of FAL is proposed.

Hydrogen storage in amine boranes: Ionic liquid supported thermal dehydrogenation of ethylene diamine bisborane

A variety of ionic liquids has been tested for its catalytic effect on the dehydrogenation of ethylene diamine bisborane (EDB). The catalytic activity of ionic liquids, such as 1-butyl-2,3-dimethylimidazolium chloride ([BMMIM]Cl), 1-butyl-2,3-dimethylimidazolium acetate ([BMMIM][OAc]), 1-butyl-3-methylimidazolium acetate ([BMIM][OAc]) and 1-butyl-3-methylimidazolium methylsulfonate ([BMIM][OMs]) is compared and the mixture [BMMIM]Cl/EDB was investigated. This system is able to deliver about 6.5 wt% of hydrogen at 140 °C competing with conventional hydrogen storage pressure tanks. The correlation between polarity of the ILs and hydrogen yield was investigated and the suitability for hydrogen storage systems is evaluated and discussed.

Efficient synthesis of phytosteryl esters using the Lewis acidic ionic liquid

Phytosteryl esters are of significant importance due to their recent recognition and contribution as cholesterol-lowering agents in food and nutrition. The synthesis of phytosteryl esters from phytosterols and fatty acids in the presence of ionic liquids with high yield and purity was investigated. Six common ionic liquids, including [Bmim]BF4, [Bmim]CF3SO3, ChCl·2SnCl2, ChCl·2ZnCl2, ChCl·2.5SnCl2 and ChCl·2FeCl3, were evaluated to determine the satisfactory catalyst for the esterification, and the results showed that ChCl·2SnCl2 was the most suitable catalyst in this study. Moreover, it was found that the catalytic activity of ionic liquids for the esterification enhanced with the increase of their Lewis acidity, which was determined by pyridine as IR spectroscopic probe. The reaction conditions were further surveyed and the experimental esterification rate reached a greatly high level of 92.3% using ChCl·2SnCl2 as catalyst with the molar ratio 3:1 (lauric acid:plant sterols) at 150°C for 4h. FT-IR, MS, and NMR analyses were adopted to evaluate the synthesized phytosteryl laurate. And also the physiochemical property of phytosterols and phytosteryl laurate was compared, suggesting that phytosteryl ester favored its wide application in fatty based food.

SO3H-functionalized ionic liquids as efficient catalysts for the synthesis of bioadditives

Three kinds of SO3H-functionalized Brønsted-acidic ionic liquids with different acidities were applied to the etherification of glycerol with tert-butyl alcohol. High conversion and good selectivity were obtained under mild conditions. Among the ionic liquids investigated, those having a HSO4− anion afforded the highest glycerol conversion and those having a F3CSO3− anion afforded the largest head product selectivity for glycerol etherification. The minimum-energy geometries and experimental results show that acidities and catalytic activities of ionic liquids are not only related to their structures but also to their immiscibility.

Novel SO3H-Functionalized Ionic Liquids Based on Benzimidazolium Cation: Efficient and Recyclable Catalysts for One-Pot Synthesis of Biscoumarin Derivatives

In this article, a new group of SO3H-functionalized ionic liquids based on benzimidazolium cation was synthesized and used as environmentally benign catalysts for the one-pot synthesis of biscoumarin derivatives. The ionic liquids showed high catalytic activities and reusabilities with good to excellent yields of the desired products. H 0 (Hammett function) values and the minimum-energy geometries of SO3H-functionalized ionic liquids were determined and the results revealed that the acidities and catalytic activities of ionic liquids in the synthesis of biscoumarin derivatives were related to their structures. The simple, more efficient way for synthesis of biscoumarin derivatives has been developed. This new method abandon the traditional hazardous organic liquid and is carried out by using a one-pot reaction of 4-hydroxycoumarin with aromatic aldehydes in the presence of novel SO3H-functionalized ionic liquids based on benzimidazolium cation as catalysts. The ionic liquids showed high catalytic activities and reusabilities with good to excellent yields of the desired products. H 0 (Hammett function) values and the minimum-energy geometries of SO3H-functionalized ionic liquids were determined and the results revealed that the acidities and catalytic activities of ionic liquids in the synthesis of biscoumarin derivatives were influenced by their structures.