The catalytic synthesis of methylene diphenyl-4,4'-diisocyanate (MDI) consists of three steps. Starting from the catalytic reaction of aniline and dimethyl carbonate (DMC), methyl phenyl carbamate (MPC) is formed. Then MPC condenses with formaldehyde to produce dimethyl methylene diphenyl-4,4'-dicarbamate (MDC). Last, MDC is decomposed to MDI. For the first step, the properties of supported zinc acetate catalysts on different supports have been examined. Supported zinc acetate catalyst on activated carbon (AC) or alpha-Al2O3 shows good catalytic properties. Over Zn(OAc)(2)/AC catalyst, MPC yield reaches 78% and the selectivity is 98%. For the second step, when zinc chloride is used as a catalyst and nitrobenzene as a solvent, MDC yield can reach 87.4%. The catalytic activity of AC-supported ZnCl2 catalyst, which is calculated based. on 1 mol of ZnCl2, is much higher than that of homogeneous ZnCl2. For the third step, zinc powder and its organic salts show higher catalytic activity; MDI yield is 87.3% over zinc powder catalyst.