Catalytic synthesis of methylene diphenyl dicarbamate from methyl phenyl carbamate and trioxane over sulfuric acid catalyst

Methylene diphenyl dicarbamate (MDC) was synthesized from methyl phenyl carbamate (MPC) and trioxane using sulfuric acid (H₂SO₄) as catalyst. The effects of reaction temperature, reaction time, molar ratio of reactants and the content of catalyst have been studied in details. The results showed that H₂SO₄ exhibited high catalytic activity with the merits of moderate reaction velocity. Under the conditions of n(MPC)/n(trioxane) = 3:1, reaction temperature of 95°C, reaction time of 3.5 h and 30% H₂SO₄, the conversion of MPC reached 99.0% with the selectivity of MDC 81.6%. Moreover, the H₂SO₄ catalyst was reused five times without obviously activity decrease. Based on the identification of byproducts, a possible reaction mechanism was proposed.