Cycloaddition of Carbon Dioxide to Epoxides for the Synthesis of Cyclic Carbonates with a Mixed Catalyst of Layered Double Hydroxide and Tetrabutylammonium Bromide at Ambient Temperature

A series of nickel-aluminium, cobalt-aluminium and zinc-aluminum layered double hydroxides were synthesized by urea hydrolysis (UH) and reverse micelle (RM) methods and then applied for the cycloaddition of carbon dioxide to propylene oxide (PO) under solvent-free and ambient conditions. The most efficient catalyst was zinc-aluminum layered double hydroxide prepared by RM (denoted as ZnAl-RM) and it showed, in the presence of a co-catalyst of tetrabutylammonium bromide, 96% propylene carbonate (PC) yield in 12 h at 25 degrees C and 1 MPa carbon dioxide. It is noteworthy for the same catalyst system that 74% PC yield was achieved in 24 h at room temperature (about 25 degrees C) and atmospheric carbon dioxide pressure. The high catalytic performance of the ZnAl-RM and tetrabutylammonium bromide system should result from cooperative effects between zinc ion and bromine ion. Moreover, the ZnAl-RM and tetrabutylammonium bromide system showed excellent versatility, which was also an active catalyst to the transformation of carbon dioxide and other epoxides into corresponding cyclic carbonates under mild temperature and pressure conditions.