Nickel cerium olivine catalyst for catalytic gasification of biomass

Abstract

A nickel cerium modified olivine was used as a fluidized bed material in a biomass gasifier and the impact of the modification on biomass conversion, product gas composition, and tar speciation at different temperatures of oak gasification was measured. The experiments were conducted in the pyrolysis mode, without additional input of steam or oxygen (e.g., from air) into the system. In both plain and modified olivine, carbon- and hydrogen-based yields in light gases produced increased as temperature increased from 600 to 800°C. Using modified olivine resulted in significant improvement in carbon- and hydrogen-based yields and substantial reduction in tars and methane. With modified olivine, the biochar produced at 800°C was 40% less than that with plain olivine. Characterization of the fresh and post-reaction catalyst showed that a fraction of the NiO was reduced in situ in the gasifier by the syngas. In addition, the catalyst was also contributing oxygen to the environment inside the gasifier in a chemical-looping like mode, resulting in less char and coke formation than that of gasification of biomass without an additional oxygen source. Statistical analysis of molecular beam mass spectrometry data provided detailed tar speciation information under different gasification conditions. At both 650 and 800°C, the modified olivine was effective in producing more syngas either through conversion of hydrocarbon rich tars into syngas or blocking the pathway for hydrocarbon rich tar formation. However, the impact of the modified olivine in converting oxygenates (that are primarily derived from deconstruction of biomass) into deoxygenated compounds was probably minimal.