Production of hydrogen-rich gas from biomass by catalytic pyrolysis

Aimed at producing hydrogen-rich gas, pyrolysis of rice straw and sawdust was carried out in a fixed-bed reactor at different temperatures with catalyst (Cr_2O_3, MnO, FeO, Al_2O_3, CaO, CuO and Na_2CO_3). The results show that at current operating conditions, total gas yield and hydrogen-rich gas yield are low. However, it could be improved by using catalysts. The addition of Cr_2O_3 at 750?℃ leads to the increase of the total gas yield by 10% and the concentration of hydrogen-rich gas by 13%. High temperature favours the yield of total gas and the concentration of hydrogen-rich gas. When the temperature rises from 500?℃ to 850?℃, the yield of total gas and the concentration of hydrogen-rich gas, for rice straw pyrolysis, increase from 29.0% to 40.6%, and 41.2% to 48.2%, respectively; for sawdust pyrolysis from 35.0% to 46.5%, and 40.6% to 47.0%, respectively. The catalysts used exert positive effect on pyrolysis of rice straw and sawdust, however, Cr_2O_3 appears stronger catalytic role than other metal oxides. 30% catalysts (CaCO_3, Na_2CO_3) is recommended because higher amount of catalyst almost does not improve catalytic activity again. The addition of CaCO_3 or Na_2CO_3 increases the yields of total gas and also of hydrogen-rich gas. Catalytic performance of Na_2CO_3 shows a little bit better than that of CaCO_3 in the case of rice straw pyrolysis.