Heterogeneous Catalytic Methoxycarbonylation of 1,6-Hexanediamine by Dimethyl Carbonate to Dimethylhexane-1,6-dicarbamate

A nonphosgene route for synthesis of dimethylhexane-1,6-dicarbamate (HDC) by methoxycarbonylation of 1,6-hexanediamine (HDA) with dimethyl carbonate (DMC) using AlSBA-15 as a heterogeneous catalyst was proposed. Catalyst was characterized, and effects of catalyst concentration, DMC to HDA molar ratio, reaction temperature, and reaction time were investigated. Results showed that AlSBA-15 exhibited high catalytic activity because of its large surface area and average pore diameter as well as acidity because of impregnation with Al. Under the optimum conditions of 5% Al incorporation, 5% catalyst concentration, 6:1 DMC to HDA molar ratio, 70 °C reaction temperature, and 35 h reaction time, the HDC yield reached 84.2%. Catalyst was easily separated, and no obvious deactivation was found even after the catalyst was used four times. Interactions of AlSBA-15 with the substrates were also studied by quasi in situ Fourier transform infrared (FTIR), and a possible reaction mechanism was proposed.