The catalytic pyrolysis of plant biomass was investigated in a dual-particle powder fluidized-bed (PPFB), where the primary decompositions and secondary reactions occurred simultaneously under ambient pressure. The yields and distributions of the pyrolysis products were studied under various operating conditions. In the absence of catalyst, the amount of volatile released from woody biomass depended on the pyrolysis temperature, and only 13.8 g H(2)/kg biomass (def: dry ash-free basis) was produced at 1173 K. NiMo/Al(2)O(3) catalyst promoted the decomposition of tar and light aromatic hydrocarbon compounds from the primary decomposition reaction, and significantly reduced the temperature required for the secondary phase reaction. With NiMo/Al(2)O(3) catalyst at 723 K, clean combustion gas accounted for 91.25 vol% of the total gas products, which was composed of 49.73 vol% of H(2), 34.50 vol% of CO, and 7.03 vol% of low molecular weight hydrocarbon gases. The contents of H(2) and CO were 33.6 g H(2)/kg biomass (def) and 326.3 g CO/kg biomass (def), respectively. Therefore, it is critical to control the secondary phase reaction conditions during the catalytic pyrolysis in order to produce hydrogen-rich gas. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.