NSF/EPA: Biocatalytic Polymer Synthesis in and from Carbon Dioxide for Pollution Prevention

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9613166 Russell The proposed research has two thrusts; one involves using carbon dioxide (CO2) as either a reactant, solvent or both, and the other uses enzymes as heterogeneous catalysts in CO2 to promote required reactions selectively at low temperatures. CO2 will be used as the solvent during the enzymatic polymerization of diols and diesters to form polyester polyols (hydroxy-capped polyesters). Polyester polyols are important constituents of polyurethane elastomers. Presently, they are generated via the high temperature reaction of diols with diacids. Constant removal of water is used to drive the reaction to completion. Pollution prevention will be accomplished through energy savings related to low temperature operation, as well as elimination of cyclic byproducts through use of the enzyme, lipase. The enzyme may enable the generation of dihydroxy capped material without resorting to high stoichiometric imbalances, thus reducing waste. In addition, the use of enzymes in concert with a pressure- tunable solvent such as CO2 enables the production of polyesters with narrow molecular weight distributions. Such materials are presently unavailable using conventional condensation polyester synthetic techniques. The proposed research also will investigate the details of the polymerization process in an attempt to rationally design a continuous method for synthesis of polyol polyester intermediates for the urethane industry. CO2 will be used as a raw material, in concert with enzymatic catalysis, in the synthesis of diphenyl carbamate, the monomer for bisphenol A polycarbonate (BAPC), a widely used thermoplastic. Current processes for production of diphenyl carbonate require phosgene as a raw material, generating large quantities of waste salt and organic solvent. A two-step reaction, where CO2 is used in the first step to generate a dialkyl carbonate, followed by an enzymatically catalyzed transesterification, will be used to produce diphenyl c arbonate. If successful, the research will use reactants and processes that save energy, minimize waste and use an environmentally benign solvent.