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 27A1NMR, 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. C) 2013 Elsevier B.V. All rights reserved.