SYNTHESIS OF METHYLENE DIPHENYL DICARBAMATE IN COMPOUND-SOLVENT SYSTEM OVER LIQUID ACID

摘要

Methylene diphenyl diisocyanate (MDI) is one of the most important isocyanates, which are the major raw materials for synthesizing polyurethane, pesticides and herbicides. At present, the commercial method for producing MDI is via the phosgene route. The toxicity and corrosiveness of the feedstock and the resulting byproduct (HCl) make this synthesis process harmful to the environmental. Many efforts have continuously been devoted to the non-phosgene routes. One route using dimethyl carbonate (DMC) as reactant to synthesis the isocyanate is seen to be much attractive. Since DMC has been commercially synthesized indirectly from greenhouse gas CO2, therefore, synthesis of MDI from DMC will promote synthesis of important chemicals based on CO2, and greatly reduce CO2 emission as well. In this route, the methylene diphenyl dicarbamate (MDC) is a key intermediate in synthesis of MDI.