Kinetic study of the methoxycarbonylation of 1,5-pentanediamine with dimethyl carbonate using sodium methoxide catalyst

Pentamethylene-1,5-diisocyanate (PDI) is a novel raw material for producing high-performance polyurethane. The current industrial production method, the phosgene process, poses significant safety hazards and environmental pollution risks. Consequently, the non-phosgene methods for synthesizing isocyanates from amines and dimethyl carbonate have garnered attention. In this study, catalyst sodium methoxide was used for the efficient and green synthesis of pentamethylene-1,5-dicarbamate (PDC) via the methoxycarbonylation of 1,5-pentanediamine (PDA) and dimethyl carbonate (DMC). The effects of reaction conditions on the synthesis of PDC were investigated. Under conditions of a PDA:DMC molar ratio of 1:3.5, 7wt.% sodium methoxide catalyst (based on the mass of PDA), a reaction temperature of 70°C, and a reaction time of 3 hours, the conversion of PDA and yield of PDC both reached 100%. A kinetic model for the synthesis of PDC was established, yielding activation energies of 30.3 kJ/mol and 42.2 kJ/mol for the first and second reaction steps, respectively. The kinetic model demonstrated excellent agreement with experimental data, providing a theoretical basis for subsequent applications of PDC.