A phosgene-free approach for the synthesis of phenyl isocyanate (PI) was developed, using the heterogeneous catalytic decomposition of methyl N-phenyl carbamate (MPC). Twenty oxide-catalysts were investigated and compared; the Bi 2 O 3 catalyst gave the better catalytic performance. From bismuth (III) nitrate pentahydrate, Bi 2 O 3 was prepared by different methods, which included the direct decomposition, mechano-chemical method, direct precipitation and indirect precipitation. The catalysts were characterized by N 2 adsorption/desorption, XRD, FTIR and TEM analyses. After optimization, the Bi 2 O 3 catalyst prepared by direct calcination of bismuth (III) nitrate pentahydrate at 723 K in air for 4 h gives the best activity. When the reaction was carried out at the boiling temperature of o-dichlorobenzene (ODCB) at normal pressure, the optimal reaction conditions over Bi 2 O 3 catalyst are as follows: the mass ratio of catalyst/MPC is 0.05, mass ratio of ODCB/ MPC is 15:1, reaction time of 60 min. The optimized conversion of MPC and the yield of PI are 86.2% and 78.5%, respectively. There was a good durability for the Bi 2 O 3 catalyst, and the species of Bi (III) ions of catalyst were partially oxidized to Bi (IV) ions during the reaction, supported by the results of XRD and XPS techniques.

A simple and efficient route for one-pot synthesis of high-molecular-weight aliphatic polycarbonates (APCs) by directly melt transesterification of diphenyl carbonate (DPC) with aliphatic diols at equimolar amounts was developed. Zn(OAc) 2 was found to be the best catalyst for this reaction among the screened transition metal acetates. The effects of reaction conditions on M w and yield of the poly(1,4-butylene carbonate) (PBC) were investigated, where the highest M w of 156200 g/mol with yield of 83 % was obtained under suitable reaction conditions. In addition, based on the results of thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscope (SEM) and fourier transform infrared spectroscopy (FT-IR), a plausible reaction mechanism over Zn(OAc) 2 was proposed for APCs synthesis.