Efficient Hydrogen-Rich Syngas Production via Synergistic Tar Cracking and Sorption-Enhanced Steam Gasification of Woody Waste over Ni/CaO Catalysts

Steam gasification of woody waste represents a sustainable pathway for addressing environmental issues with energy recovery. However, challenges such as low hydrogen content and high tar yield severely limit the gasification efficiency and hinder its large-scale application. In this study, a composite Ni/CaO catalyst was developed to enhance the yield of H2-rich syngas in woody waste gasification, with Ni loading serving as the active site for catalytic cracking and CaO support as the CO2 sorbent for sorption-enhancement. Ni nanoparticles ranging from 18 to 28 nm in diameter are uniformly distributed on the CaO support. At 700 °C, Ni/CaO with 10 wt.% Ni loading enables the 455.4 mL/g H2 yield with an H2/CO ratio of 1.93, representing increases of 137% and 230%, respectively, compared to non-catalytic conditions. Meanwhile, the tar yield was 12.1 wt.% with an aromatics selectivity of 37%, corresponding to reductions of 50.2% and 54%, respectively. Characterizations confirmed that Ni particles were uniformly distributed on the support in the form of metallic Ni. The Ni active sites promote syngas production by facilitating the cleavage of C-C and C-H bonds in volatiles, while the CaO support enhances H2 generation by shifting the water–gas shift reaction equilibrium forward. This study provides a promising strategy for enhancing hydrogen-rich syngas production from woody waste gasification.