Effect of chain length on catalytic activity in quaternary ammonium halides catalyzed cycloaddition of CO2 to propylene Oxide

A series of organic quaternary ammonium bromide with varying carbon chain length in alkyl group were investigated as the catalyst for CO2/PO cycloaddition. When the length of the single-chain in alkyl tributyl ammonium bromide increased from 2 to 16 progressively, the catalytic activity first increased and then decreased slightly. When four alkyl groups on the nitrogen atom of ammonium bromide changed from methyl, ethyl to butyl, the catalytic activity increased sharply. By changing the solvent effect of organic ammonium bromide in PO and the electrostatic interaction between cations and anions, the change of chain length might influence the concentration of “free” anions, and therefore influence the catalytic activity.