Novel Ni–Al nanosheet catalyst with homogeneously embedded nickel nanoparticles for hydrogen-rich syngas production from biomass pyrolysis

Abstract

In this work, an innovative porous Ni–Al nanosheet catalyst synthesized by a homogeneous precipitation method via urea hydrolysis is proposed for enhanced hydrogen-rich syngas production from catalytic pyrolysis of rice husk in a two-stage reactor system. The role of synthesis temperature in modulating the crystalline composition, particle size, metal dispersion as well as porous structure of resulting Ni–Al nanocomposite has been delineated. The results indicate that fine spherical NiO and metallic Ni0 nanoparticles are homogeneously embedded in amorphous Al2O3 matrix for all Ni–Al catalysts, which also have developed bimodal micro/mesoporous structure with high surface areas (513–948 m2/g). Catalytic tests show that these highly active catalysts exhibit almost ten times higher hydrogen production rate (7.74–17.39 mmol/g biomass) and H2/CO molar ratio (1.96–2.74) than that in the absence of catalyst (0.56–1.64 mmol/g, 0.11–0.24) by tuning catalytic temperatures. The Ni–Al catalysts that with the presence of metallic Ni0 and developed porous structure exhibit higher catalytic activity and suppression of coke deposition through providing more active sites for catalytic cracking and reforming reactions, and rapid diffusion of intermediate products.