The Synthesis And Study Of Catalyst For Carbon Dioxide And Epoxide

As a member of catalytic system for the copolymerization of carbon dioxide and epoxides, the SalenMX-based catalytic system has been of significant interest due to their high activity, the stability of the metal species against moisture and air, unprecedented opportunities for controlling the region- and stereochemistry of copolymerization, and high selectivity of polycarbonate with narrow molecular weight distribution.In this paper, a series of salen ligands were synthesized and employed to prepare the metal salen complexes (SalenMIIIX, M = Co or Cr; X = Cl, NO3, Br, N3, CF3COO and BF4, diamine=1, 2-diphenylethyleneamine for M=Co; X = Cl, NO3 and N3, diamine = o-cyclohexanediamine for M=Co; X = Cl, diamine=1, 2-diphenylethyleneamine, o-cyclohexanediamine and o-phenylene -diamine for M=Cr). Most of the complexes were characterized using 1H-NMR, 13C-NMR, IR, UV-Vis, cyclic voltammetry, MS and elemental analysis. All of the metal salen complexes were probed their catalytic behavior in the process of the PO/CO2copolymerization. The effects of backbone of salen ligand, axial anion of metal complexes, polymerization reaction conditions, and the molar ratio of catalyst with monomer on the copolymerization were systemally investigated. Some conclusions were made as follows:1. The catalysts we synthesized have good activity and polycarbonate/cyclic carbonate selectivity in the copolymerization of carbon dioxide and propylene oxide and the catalyst Co-L13 has the best catalytic effect. Under the suited conditions, in 24 hours the turnover frequency for PPC mol PO consumed per mole of catalyst per hour could be reached 59.18h-1 and the total conversion of propylene oxide ratio reached 73.2%; in 30 hours the polycarbon -ate/cyclic carbonate selectivity is in more than 99.0% and the head-to-tail structure in the polycarbonate reached 81.1%.2. For the SalenCoIIIX catalytic system, when the diamine is cyclohexanediamine, the complexes show higher catalytic activity than those of corresponding phenylethylenediamine. In relation to metal center, complexes with Co center display higher catalytic activity and better selectivity for PPC than the corresponding Cr center for the copolymerization of catbon dioxide and propylene oxide.