Catalytic performance of ion-exchanged montmorillonite with quaternary ammonium salts for the glycerolysis of urea
•Quaternary ammonium salt (QX) ionic liquids were immobilized onto montmorillonite clay.•It showed enhanced catalytic performance in the glycerolysis of urea.•Effects of the ionic liquid structure and reaction parameters were discussed.•The catalyst could be reused in up to three consecutive runs.
Various quaternary ammonium salt (QX) ionic liquids immobilized onto montmorillonite clay (Q-MMT) were prepared by ion-exchange reaction between the tetra-alkyl ammonium salts and ions in the clay interlayer. The Q-MMTs were characterized by elemental analyses, nitrogen adsorption–desorption, XRD, 13C and 27Al NMR, TGA, FT-IR, and HRTEM. The d-spacing of the Q-MMTs increased with increasing alkyl chain lengths, however, the surface areas decreased by immobilizing QX onto MMTs. The Q-MMTs showed good catalytic activity for the synthesis of glycerol carbonate from glycerol and urea. The effects of the ionic liquid cation structure, and reaction parameters, such as temperature and degree of vacuum, on the performance of Q-MMTs were also discussed. The catalyst could be reused in up to four consecutive runs without any considerable loss of activity.
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Journal: Catalysis Today - Volume 232, 1 September 2014, Pages 127–133