International Journal of Hydrogen Energy, Vol.36, No.17, 10674-10682, 2011
Enhanced hydrogen production from biomass via the sulfur redox cycle under hydrothermal conditions
A new method of hydrogen production from biomass via a sulfur redox cycle at moderate temperatures has been proposed. This method, which can utilize excess sulfur from hydrocarbon refining processes and waste or geothermal heat, consists of two half cycles: (1) hydrogen production from an aqueous alkaline solution at subcritical conditions of water, where sulfide, HS(-) and S(2-), acts as a reducing agent of water, and (2) sulfide regeneration under much milder conditions, with an organic compound derived from biomass acting as a reducing agent of polysulfide, S(n)(2-), and sulfur oxyanion, S(x)O(y)(2-), formed in the first half cycle. During a 60-min reaction of an aqueous sodium sulfide solution, hydrogen production was observed at >= 280 degrees C and corresponding saturated vapor pressures. Addition of D-glucose, C(6)H(12)O(6), to the solution after hydrogen production at 300 degrees C resulted in sulfide regeneration at temperatures >60 degrees C in the present 10-min reaction. Moreover, hydrogen production from glucose via the sulfur redox cycle was demonstrated, where the hydrogen production and sulfide regeneration were conducted at 300 degrees C and 105 degrees C, respectively. Results indicated that hydrogen production from 1 mol glucose was greater than that by hydrothermal gasification of glucose at much higher temperatures up to 500 degrees C. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.