Stefan Lundmark

Cyclic carbonates as monomers for phosgene- and isocyanate-free polyurethanes and polycarbonates

Polyurethanes and polycarbonates are widely used in a variety of applications including engineering, optical devices, and high-performance adhesives and coatings, etc., and are expected to find use also in the biomedical field owing to their biocompatibility and low toxicity. However, these polymers are currently produced using hazardous phosgene and isocyanates, which are derived from the reaction between an amine and phosgene. Extensive safety procedures are required to prevent exposure to phosgene and isocyanate because of its high toxicity. Therefore, the demand for the production of isocyanate-free polymers has now emerged. Among the alternative greener routes that have been proposed, a popular way is the ring-opening polymerization (ROP) of cyclic carbonate in bulk or solution, usually using metallic catalyst, metal-free initiator, or biocatalyst. This review presents the recent developments in the preparation and application of cyclic carbonates as monomers for ROP, with emphasis on phosgene- and isocyanate-free polymerization to produce aliphatic polycarbonates and polyurethanes and their copolymers.

An economical biorefinery process for propionic acid production from glycerol and potato juice using high cell density fermentation.

An economically sustainable process was developed for propionic acid production by fermentation of glycerol using Propionibacterium acidipropionici and potato juice, a by-product of starch processing, as a nitrogen/vitamin source. The fermentation was done as high-cell-density sequential batches with cell recycle. Propionic acid production and glycerol consumption rates were dependent on initial biomass concentration, and reached a maximum of 1.42 and 2.30 g L(-1) h(-1), respectively, from 50 g L(-1) glycerol at initial cell density of 23.7 gCDW L(-1). Halving the concentration of nitrogen/vitamin source resulted in reduction of acetic and succinic acids yields by ~39% each. At glycerol concentrations of 85 and 120 g L(-1), respectively, 43.8 and 50.8 g L(-1) propionic acid were obtained at a rate of 0.88 and 0.29 g L(-1) h(-1) and yield of 84 and 78 mol%. Succinic acid was 13 g% of propionic acid and could represent a potential co-product covering the cost of nitrogen/vitamin source.

A new route for the synthesis of methacrylic acid from 2-methyl-1,3-propanediol by integrating biotransformation and catalytic dehydration

Methacrylic acid was produced in high yield by an integrated process involving bioconversion of 2-methyl-1,3-propanediol (2M1,3PD) to 3-hydroxy-2-methylpropionic acid (3H2MPA) via 3-hydroxy-2-methylpropanal (3H2MPAL), and catalytic dehydration of the resulting acid. Whole cells of Gluconobacter oxydans grown on glycerol-based culture medium were used as the catalyst for oxidative biotransformation that involved alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) enzymes in the organism. The effect of several reaction parameters on bioconversion in a batch system was investigated to obtain 95–100% conversion of 2M1,3PD with over 95% selectivity to 3H2MPA. The optimum conditions for bioconversion were pH 6–7.5, 25–30 °C, 5–10 g substrate and 2.6 g cell (dry weight) per liter. Higher substrate concentrations led to enzyme inhibition and incomplete conversion. Loss of catalytic activity was noted during recycling of the cells. The cells were active for a longer period when used for biotransformation of 20 g per L of substrate in a continuous reactor with cell retention. The product of the bio-oxidation, 3H2MPA, was converted using titanium dioxide at 210 °C to give methacrylic acid (MA) with a yield of over 85%. The integrated process provides a new environmentally benign route for production of methacrylic acid from 2-methyl-1,3-propanediol, an industrial by-product, compared with the conventional acetone-cyanohydrin (ACH) process.

Optimization of a two-step process comprising lipase catalysis and thermal cyclization improves the efficiency of synthesis of six-membered cyclic carbonate from trimethylolpropane and dimethylcarbonate.

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 transesterification of a 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 the reaction catalyzed by Novozym®435 (N435; immobilized Candida antarctica lipase B), the optimum conditions for obtaining either high proportion of monocarbonated TMP and TMP‐cyclic‐carbonate (3 and 4), or dicarbonated 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 predicted results 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:TMP molar ratio of 20. 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 five consecutive batches, 10 h each, to give 3+4 with a yield of about 65% in each run.