Thermal plasma-sprayed nickel catalysts in the clean-up of biomass gasification gas

Plasma spraying is a potential catalyst preparation method for hot gas clean-up which requires very durable catalytic coatings. In this work, the multi-layer composite coating powders consisted of a gibbsite or boehmite core together with a hydrotalcite coating. We used the coating powders in the preparation of the powder form Ni catalysts, which were characterized by XRD, BET, XPS, and XRF. The coating powders were also used in the preparation of plasma sprayed metal substrate supported Ni catalysts. Selected plasma-sprayed nickel containing catalysts were characterized by XRD and SEM. In addition, for comparative purposes we prepared and used a ceramic monolithic Ni catalyst on modified ZrO₂. The performance of all catalysts were studied in the clean-up of synthetic gasification gas, i.e. the decomposition of tar, ammonia, and methane, at 700 and 900 °C, without and with the addition of H₂S. Catalysts with a gibbsite-core showed higher activity and better sulfur resistance than those with a boehmite-core. The high activity of the gibbsite-core Ni catalyst with a sulfur-containing gas together with the promising mechanical and thermal strength makes the plasma spraying method an interesting alternative for gas clean-up catalysts in biomass gasification processes.