Optimization of a two-step process comprising lipase catalysis and thermal cyclizationimproves the efficiency of synthesis of six-membered cyclic carbonate from trimethylolpropane and dimethylcarbonate.
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Six-membered cyclic carbonates are potential monomers for phosgene and/or isocyanate free polycarbonates and polyurethanes via ring-opening polymerization. A two-step process for their synthesis comprising lipase-catalyzed transesterificationofa polyol, trimethylolpropane(TMP) with dimethylcarbonate(DMC)in a solvent-free system followed by thermal cyclization was optimized to improve process efficiency and selectivity. Using full factorial designed experiments and partial least squares (PLS) modeling for thereaction catalyzed by Novozym®435 (N435; immobilized Candida antarctica lipase B), the optimum conditions for obtaining either high proportion of mono-carbonated TMP and TMP-cyclic-carbonate (3 and 4), or di-carbonated TMP and monocarbonated TMP-cyclic-carbonate (5 and 6) were found. The PLS model predicted that the reactions using 15-20% (w/w) N435 at DMC:TMP molar ratio of 10-30 can reach about 65% total yield of 3 and 4 within 10 h, and 65-70% total yield of 5 and 6 within 32-37 h, respectively. High consistency between the predictedresults and empirical data was shown with 66.1% yield of 3 and 4 at 7 h and 67.4% yield of 5 and 6 at 35 h, using 18% (w/w) biocatalyst and DMC:TMPmolar ratio of20. Thermal cyclization of the product from 7 h reaction, at 110 °C in the presence of acetonitrile increased the overall yield of cyclic carbonate 4 from about 2% to more than 75%within 24 h.N435 was reused for 5 consecutive batches, 10 h each, to give 3+4 with a yield of about 65% in each run. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012.
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Ämnesklassifikation (UKÄ) – OBLIGATORISK
|Status||Published - 2013|
|Peer review utförd||Ja|