Abstract: Methylene diphenyl dicarbamate (MDC), an intermediate for the production of methylene diphenyl diisocyanate, was directly synthesized from dimethyl carbonate (DMC), aniline, and formaldehyde solution over the bifunctional H4SiW12O40-ZrO2/SiO2 catalyst. The effects of reaction time, reaction temperature, and H4SiW12O40loading were studied. Suitable reaction conditions are as follows: DMC/aniline/formaldehyde molar ratio is 20/1/0.05, H4SiW12O40loading is 10%, and reaction temperature is controlled by stages (i.e., reaction at 443 K for7 hand then at 373 K for 4.5 h). Under these conditions, the yield of MDC is 24.9%.

Key words: silicotungstic acid, zirconia, bifunctional catalyst, methylene diphenyl dicarbamate, direct synthesis, dimethyl carbonate, aniline, formaldehyde solution