One-Pot Synthesis of Dimethyl Hexane-1,6-diyldicarbamate from CO2, Methanol, and Diamine over CeO2 Catalysts: A Route to an Isocyanate-Free Feedstock for Polyurethanes

A new one-pot synthesis method of dimethyl hexane-1,6-diyldicarbamate (HDC), a potential intermediate compound in the synthesis of polyurethanes, from CO2, methanol, and 1,6-hexanediamine (HDA) is disclosed. The starting materials are renewable, stable, easily available, and cheap. The process was implemented in 1-methyl-2-pyrrolidinone (NMP) solvent over CeO2 catalysts. Three different CeO2 catalysts (commercial nanospheres, CeO2(c) obtained by direct calcination of (NH4)2Ce(NO3)6, and CeO2 nanorods) were tested in this reaction and their micromorphology and physical–chemical properties were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and N2 adsorption. CeO2 nanorods proved to be the most active catalytic material. The influence of different parameters on reaction outcome was studied. The yield of HDC was about 80% under optimized reaction conditions. Experiments for better understanding of reaction mechanism were also performed.