| Abstract: | A hollow fiber module was used as a reactor for conversion of ethanol to acetaldehyde in the presence of horse liver alcohol dehydrogenase as catalyst. Mass transport rates for NAD+, the overall acetaldehyde generation rate, catalyst effectiveness factors, and the overall order of the reaction with respect to NAD+ concentration were measured. A coupled-substrate reactor with continuous in situ regeneration of cofactor was also examined. Two substrates of opposite redox state were added simultaneously to the feed stream. NADH and acetaldehyde concentrations were monitored in the effluent stream. The cofactor recycle number, or ratio of moles of product to moles of NADH produced, exceeded 10,000 under certain conditions. While decreasing the NAD+ concentration in the feed stream decreased reactor productivity somewhat, it greatly enhanced the ratio of product formed per mole of NAD+ fed to the reactor. It is suggested that high cofactor costs in dehydrogenase reactors may be overcome with efficient in situ regeneration and secondary recovery and recycling of cofactor from the process stream. |
