This report will review the technological development in ionic liquids particularly as it relates to the chemical industry. The production costs for different types of ionic liquid based on high production volumes are discussed. The process economics for two case studies involving chemical syntheses using ionic liquids are analyzed. The processes evaluated were an alkylation process using a chloroaluminate ionic liquid as a catalyst to produce ethylbenzene and a hydroformylation process using an ionic liquid as a solvent to produce isononal. The isononal is subsequently hydrogenated to produce isononyl alcohol. The resulting process economics are compared to those of the conventional processes. This report will be of interest to manufacturers and consumers of industrial solvents and individuals interested in alternative "green" processes. Because of potential improvement in chemical synthesis, this report will be of general interest to the chemical industry.
The overview of the published data on a new class of polyelectrolytes—the so-called polymeric ionic liquids or poly(ionic liquid)s—is presented. The peculiarities of their synthesis and the factors affecting their molar masses, solubility, ionic conductivity, electrochemical stability, and thermal properties are discussed. The mainstreams in the application of poly(ionic liquid)s and materials formed on their basis are illustrated by specific examples.
Ionic liquids, due to their strong dissolving capacity, negligible vapor pressure, high thermal and chemical stability, have attracted much attention. The emergence of functionalized ionic liquids extends the application fields of ionic liquids. Acidic ionic liquids are a kind of functionalized ionic liquids, and recently have attracted more interests due to their advantages of both solid acid and liquid acid.
In this work, two novel Brønsted-Lewis acidic ionic liquids with both Brønsted and Lewis acidic sites in the cation were prepared first, and then their structures and acidity were characterized.
Two novel Brønsted-Lewis acidic ionic liquids, 1-carboxyethylene-3-(4-zinc acetate sulfobutyl) imidazolium chloride ([CH3COO-Zn-O3S-bim-CH2CH2COOH]ClBLILs-1) and 1-(1,2-dicarboxy) ethylene-3-(4-zinc acetate sulfobutyl) imidazolium chloride ([CH3COO-Zn-O3Sbim-C4H5O4]Cl, BLILs-2), were synthesized and characterized in this work.
The synthesis approach of BLILs-1 consisted of four-step reactions (Scheme 1). 1-ethoxycarbonylethylene imidazole (Intermediate Product-1, IP-1) was obtained through an addition reaction of imidazole and ethyl acrylate first. Then IP-1 reacted with 1, 4-butane sultone to yield 1- ethoxycarbonylethylene-3-(4-sulfobutyl) imidazole (IP-2). The third step was the generation of 1-carboxye-thylene-3-(4-sulfobutyl) imidazolium chloride (IP-3). The Brønsted-Lewis acidic ionic liquid BLILs-1 was synthe sized lastly by the reaction of IP-3 and zinc acetate, and the yield of the target product was 89.6%. In order to improve the acid strength and acid amount, diethyl maleate was used as a substitute for ethyl acrylate to introduce Bronsted acid site in the first step and other steps were similar to that for the synthesis of BLILs-1. Thus another Brønsted-Lewis acidic ionic liquid BLILs-2 was obtained (91.3% yield). The synthetic route was shown in Scheme 2.
The structures of the intermediates (IP-2 and IP-3) were determined by means of FT-IR while the structures of intermediates (IP-4, IP-5 and IP-6) were determined by means of 1H NMR analysis. The structures of BLILs-1 and BLILs-2 were characterized by IR, 1H NMR and Elemental analysis, and the results indicated that the structures of the Brønsted-Lewis acidic ionic liquids synthesized in this work were corresponding to those of the target products.
The acid strength values (H0) of the ionic liquids were determined by the UV-visible spectroscopy combined with Hammett indicator method at room temperature . From it can be seen that H0 values of the BLILs- 1 and BLILs-2 were 5.6 and 4.2, respectively, indicating that the acid strength of BLILs-2 is higher than that of BLILs-1. The acid amount of the two Brønsted-Lewis acidic ionic liquids determined by acid-base titration was 2.0 mol NaOH/mol BLILs-1 and 3.0 mol NaOH/mol BLILs-2, respectively. The number of moles of -COOH in BLILs-2 (2.0 mol) were more than that in BLILs-1 (1.0 mol), which may be responsible for the higher acid strength and acid amount of BLILs-2.
The melting points of BLILs-1 and BLILs-2 were 80˚C - 81˚C and 85˚C - 86˚C, respectively, so the Brønsted-Lewis acidic ionic liquids with lower melting point
are expected to be synthesized by changing the structures of anions or cations in the future, which are more beneficial for the applications of Brønsted-Lewis acidic ionic liquids in catalysis.
The preparation of ionic liquids, even in largequantities, presents no significant difficulties. Provided they are ofsufficient purity, most ionic liquids can be stored withoutdecomposition for extended periods, although some are relatively .
The Fourier transform infrared (FT-IR) spectra of the ionic liquids were recorded on a Bruker Vector 22 infrared spectroscopy (liquid film or KBr pellet) between 400 and 4000 cm−1 and collected at a resolution of 4 cm−1. 1H NMR spectra were recorded on a Bruker Avance 400 instrument in D2O with TMS as the external standard. Elemental analysis of the ionic liquids was performed with a Vairo EL elemental analysis instrument. The acid strength of ionic liquids was determined by the UV-visible spectroscopy combined with Hammett indicator method, which was recorded on a Cary 300 UV-visible spectroscope at room temperature.
Imidazole (0.5 mol), ethyl acrylate (0.55 mol) and solvent toluene were charged into a 250 mL three-necked flask equipped with a mechanical stirrer. Then the mixture was heated to 100˚C for 24 h under vigorous stirring. After that, toluene and remaining ethyl acrylate were distilled off from the reaction mixture under vacuum at 100˚C and a brown liquid IP-1 was obtained.