R. Marr

Enzymatic catalysis in supercritical carbon dioxide: Effect of water activity*

Publisher Summary This chapter discusses the enzymatic catalysis in supercritical carbon dioxide (scCO 2 ). scCO 2 offers some advantages over organic solvents. It is not flammable, non toxic, and relatively cheap and offers the possibility of an integrated separation process. To take advantage of the stereoselectivity of enzymatic catalysis, this chapter describes the use of transesterification of menthol as model system. Esterase EP10 from Pseudomonas marginata proved to be a suitable catalyst for the production of enantiomerically pure menthyl acetate. The water content of the reaction medium is an important factor governing the reaction rate of the transesterification. Various groups have investigated the role of water content on reaction velocity. The chapter describes the use of aluminum oxide humidity sensor to measure inline, the water vapor pressure. The partitioning of water between scCO 2 and the enzyme preparation is examined and the influence of water activity on the initial reaction velocity is determined in the chapter.

Solubilities and phase equilibria for the system furfural — CH3COOH — H2O and supercritical CO2

Publisher Summary Furfural is produced by hydrolyzing the pentoses of several natural products. The recovery of furfural and acetic acid from aqueous effluents of a paper mill has successfully been achieved on an industrial scale by a process based on the extraction of furfural and acetic acid with the solvent tri-octylphosphinoxide (TOPO). This chapter discusses the recovery and purification of furfural with supercritical carbondioxide. The chapter reviews the high-pressure extraction of furfural from aqueous effluents, considering the multi-component system furfural–acetic acid and water. The solubility of furfural in supercritical CO 2 is measured at different temperatures and pressures. For the solubility measurements of furfural in compressed CO 2 , a high-pressure equilibrium cell with a total volume of 300 ml is used. The solubility of furfural in supercritical CO 2 is determined in the equilibrium cell at temperatures of 298, 313, and 333 K within a pressure range of 80 to 340 bar.