Catalytic gasification of cellulose and pinewood to H2 in supercritical water

In this work, supercritical water gasification (SCWG) of cellulose and pinewood was studied at different operating conditions without and with catalysts. The effects of two parameters including gasification temperature (400, 470, and 550 °C) and water to biomass weight ratio (3:1 and 7:1) for different catalysts (Ni/CeO2/Al2O3, KOH, calcined dolomite and calcined olivine), were studied on SCWG of cellulose and pinewood. For non-catalytic runs, with an increase in water to biomass ratio from 3 to 7, H2 yield of cellulose gasification increased by 44%, 11% and 22% at 400, 470 and 550 °C, respectively. For catalytic gasification of cellulose using KOH, H2 yield increased by 194% compared to that for non-catalytic run at 400 °C and water to biomass ratio of 3. At the same operating conditions, the presence of Ni/CeO2/Al2O3 contributed to a 30.7% increase in H2 yield followed by a 28.3% increase using dolomite compared to that for non-catalytic run. As a real biomass, pinewood was gasified in supercritical water at the optimum operating conditions (550 °C and water to biomass ratio of 7) obtained from set of experiments performed for cellulose, using three kinds of catalysts: Ni/CeO2/Al2O3, dolomite and KOH. At the same operating conditions, H2 yield for pinewood gasification was smaller than that for cellulose gasification in the range of 20.0-41.4% depending on the type of catalyst. The effects of catalyst on H2 production from SCW in the absence of biomass were also studied. The results showed that a trace amount of H2 was formed using Ni based catalyst or dolomite while small amount of CO2 was formed with Ni/AC.