Silica-supported aminopyridinium halides for catalytic transformations of epoxides to cyclic carbonates under atmospheric pressure of carbon dioxide

Abstract

Silica-supported 4-pyrrolidinopyridinium iodide was prepared by quaternization of 4-pyrrolidinopyridine with silica-supported alkyl iodide. The pyrrolidinopyridinium structure on the silica surface was confirmed by solid-state 13 C CP MAS NMR. The silica-supported 4-pyrrolidinopyridinium iodide showed excellent catalytic performances for transformations of various epoxides to cyclic carbonates under atmospheric pressure of carbon dioxide (CO 2 ). The reactions took place without any solvents or additives other than the catalyst. The catalyst was reusable with retention of activity and selectivity. 1-n-Hexyl-4-pyrrolidinopyridinium as a homogeneous catalyst showed a lower catalytic performance than the supported catalyst. Bifunctional catalysis involving acidic surface silanol and the basic 4-pyrrolidinopyridinium iodide was proposed.

Ionic Liquids in Green Carbonate Synthesis

“…The surprising enhancement of the activity by supporting on silica was ascribed to the co-operational activation of the epoxide by the acidic surface silanol groups and the halide anion of the immobilized phosphonium IL (Scheme 11). The enhancement of the activity by the immobilization was also observed with other ILs [44,46]. Thus, the activity of an inorganic solid-immobilized IL catalyst would be determined not only by its IL content, but also by the amount of surface hydroxyl group.…”

Cyclic Carbonates Based on Vegetable Oils

“…Heterogeneous catalytic system (silica-supported 4-pyrrolidinopyridinium iodide on SiO 2 (SiO 2 -I) [13] which has well proved in the process of propylene oxides and styrole carbonation [16], has appeared not so successful for CCVO synthesis. The generalized data on researches of epoxidized vegetable oils carbonation process presented in Table 1.…”

Highly efficient synthesis of cyclic carbonate with CO2catalyzed by ionic liquid in a microreactor

“…In addition, the TOF values are varied in the range of 860-4700 h −1 for 140°C and 1600-5900 h −1 for 160°C, respectively, which are also much larger than the results of the conventional stirred reactor. 16 Moreover, the residence time can be decreased from several hours to about 10 s. 6,13,16,37 Effect of the pressure To study the effect of pressure on the yield and STY, experiments were carried out in the range of 1.0-4.0 MPa at 11.09 mol% and 4.47 mol% HETBAB in PO. The residence time is maintained at 14 s. The molar ratio of CO 2 and PO is kept constant by varying the gas and liquid flow rates at the same time.…”

“…Based on this mechanism, Motokura et al 13 proposed acidbase bifunctional catalyst involving acidic surface silanol and the basic 4-pyrrolidinopyridinium iodide. Zhang's group [14][15][16][17][18] synthesized a series of hydroxyl-functionalized ionic liquids and systematically investigated the catalytic performance of CO 2 cycloaddition, which have both acidic and basic characteristics, and found that the hydroxyl group had a synergetic effect with the halide anion to promote the reaction.…”