Safe and efficient synthesis of diphenylmethane dicarbamate and kinetic study of the reaction in a microreactor

• Acid‑resistant microreactor enables safer 120°C operation with reduced holdup. • Continuous MDC synthesis achieved 68.91% yield via intensified mass transfer. • Kinetic modeling identifies the second condensation as rate‑determining step. As Diphenylmethane dicarbamate (MDC) is a critical precursor for methylene diphenyl diisocyanate (MDI) and thus polyurethane production, the safe and efficient synthesis of MDC holds significant industrial importance. Conventional batch processes employ formaldehyde and strong acids with safety hazards and efficiency limitations. This study overcame these challenges by developing an acid-resistant pressurized microreactor-batch aging system. By enhancing mass transfer and optimizing parameters, continuous MDC synthesis was achieved within 40 min at 120°C. Subsequent aging at 60°C within 40 min significantly boosted product selectivity, yielding 68.91% MDC. This represents an improvement over the conventional batch process, which requires 4 h and achieves only 53.57% yield. The first kinetic model established for this process identifies the condensation step as rate-determining ( Ea 2 = 75.23 kJ/mol > Ea 1 = 65.27 kJ/mol). This study pioneers the application of microreactor technology to methyl phenyl carbamate condensation reactions and offers new insights into the reaction mechanism.