Yuchao LI1,2, Jiru GUO1, Yansong ZHAO2
1Institute of Clean Chemical Technology, School of Chemistry and Chemical Engineering, Shandong University of Technology, ZiBo, China
2Department of Safety, Chemistry and Biomedical Laboratory Sciences, Faculty of Engineering and Science, Western Norway University of Applied Sciences (HVL), Bergen, Norway
4,4'-Dichlorodiphenyl sulfoxide is the main raw material for producing polysulfone, polyether sulfone and other engineering plastics. In addition, 4,4'-dichlorodiphenyl sulfoxide is intermediate of medicine, dye and pesticide. 4,4'-Dichlorodiphenyl sulfoxide has been widely utilized in engineering plastics, fine chemicals and other fields. Ionic liquid has obvious "green" environmental protection properties, can be used to replace the traditional catalyst, to provide the possibility of green chemical reaction process. The functional ionic liquid can change and modify the anions appropriately according to the reaction and catalytic process itself, so that it can meet the reaction requirements as a new catalytic material with some specific functions. Although the traditional acidic ionic liquid has strong acidity, it has obvious advantages in improving the selectivity of the reaction and increasing the reaction rate in the catalytic process, but its relatively poor thermal stability makes the recycling of ionic liquid become a problem. In the field of ionic liquid research, melting point divergence tends to increase after the functionalization of cations, while the opposite trend occurs after the functionalization of anions. However, the functionalization of anions in ionic liquid requires multiple steps and strict organic synthesis techniques, leading to the lag in the research of functionalization. The imidazolum-based acidic ionic liquids synthesized by us have the advantages of simple synthesis, easy degradation and good biocompatibility, and can be used as catalysts or "green" alternatives to traditional organic solvents in alkylation catalytic reactions[1-3].
In this work, metal-based methylimidazolium ionic liquids were synthesized, which were found to be efficient catalysts for alkylation reactions. Acidic ionic liquids were used in the alkylation of chlorobenzene with thionyl chloride. Synergistic effects of various metal chlorine/1-butyl-3-methylimidazoline-chloride molar ratios and various metal chlorine additives on Lewis and Brønsted acid center catalysis were investigated. The fissionable species of AlCl3 in ionic liquid will enhance the acidity of ionic liquid and thus promote catalytic performance of ionic liquid. Under the optimized reaction conditions, the conversion rate of excess chlorobenzene was 45.3%, and the selectivity for 4,4'-dichlorodiphenyl sulfoxide was 31.9%. In addition, a series of acidic ionic liquids have been prepared by changing anions of imidazole, showing good catalytic performance for alkylation.
References
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[2] Sheng X, Gao H, Zhou Y, et al. Stable poly (ionic liquids) with unique cross?linked mesoporous?macroporous structure as efficient catalyst for alkylation of o?xylene and styrene[J]. Applied Organometallic Chemistry, 2019, 33(8): e4979.
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