Simultaneous Coproduction of Hydrogen and Ethanol in Anaerobic Packed-Bed Reactors

This study evaluated the use of an anaerobic packed-bed reactor for hydrogen production at different hydraulic retention times (HRT) (1–8 h). Two reactors filled with expanded clay and fed with glucose (3136–3875 mg L(−1)) were operated at different total upflow velocities: 0.30 cm s(−1) (R030) and 0.60 cm s(−1) (R060). The effluent pH of the reactors was maintained between 4 and 5 by adding NaHCO(3) and HCl solutions. It was observed a maximum hydrogen production rate of 0.92 L H(2) h(−1) L(−1) in R030 at HRT of 1 h. Furthermore, the highest hydrogen yield of 2.39 mol H(2) mol(−1) glucose was obtained in R060. No clear trend was observed by doubling the upflow velocities at this experiment. High ethanol production was also observed, indicating that the ethanol-pathway prevailed throughout the experiment.