Synthesis of 4,4′-MDC in the Presence of Sulfonic Acid-functionalized Ionic Liquids

Abstract The synthesis of methylene diphenyl dimethylcarbamate (4,4′-MDC) from methyl N -phenyl carbonate (MPC) and formaldehyde (HCHO) was conducted in the presence of sulfonic acid-functionalized ionic liquids (ILs) as dual solvent-catalyst. The influences of the kind of anion in the ionic liquids, reaction conditions and the recycle of the ionic liquid on 4,4′-MDC synthesis reaction were investigated. In addition, the acid strength of ILs was determined by the Hammett method with UV-visible spectroscopy, and the acid strength-catalytic activity relationship was correlated. The activity estimation results showed that [HSO 3 -bmim]CF 3 SO 3 was the optimal dual solvent-catalyst. Under the suitable reaction conditions of 70°C, 40 min, molar ratio of n MPC / n HCHO 10/1 and mass ratio of W ILs / W MPC 4.5/1, the yield of 4,4′-MDC based on HCHO was 89.9 % and the selectivity of 4,4′-MDC with respect to MPC was 74.9%. Besides, [HSO 3 -bmim]CF 3 SO 3 was reused four times after being purified and no significant loss in the catalytic activity was observed.