Enhanced hydrogen production from biomass gasification by in-situ CO₂ capture with Ni/Ca-based catalysts

Biomass is the important renewable clean energy. Compared to conventional technologies, biomass gasification experiences the problems of low hydrogen purity, low yield and high tar by-products. Coupling CO₂ capture with biomass gasification for hydrogen production can promote the steam reforming and water-gas shift reaction to improve hydrogen production regarding both purity and yield. In addition, energy consumption of the reforming process can be reduced as well due to the heat release from CO₂ adsorption. The application of Ni-based catalysts and CaO-based adsorbents faces problems such as poor resistance to sintering and easy deactivation. Here, biomass gasification experiments were conducted in a two-stage fixed-bed using pine sawdust as biomass raw materials. A range of Ni–Ce/CaO catalysts with different Ni loadings were synthesized using a sol-gel method. Characterization of these catalysts was carried out using techniques such as N₂ adsorption-desorption, X-ray diffraction, and field-emission scanning electron microscopy. Subsequently, a comprehensive investigation was conducted to assess the CO₂ capture performance, catalytic activity and stability of the prepared catalyst. Results show that the Ni–Ce/CaO catalyst has the best performance at reaction temperature of 600 °C, Ni/Ce ratio of 2:1, and the steam flow rate of 5 mL/h. The optimum condition produced the lowest CO₂ yield and the highest H₂ yield, which are 2.31 mmol/g and 12.8 mmol/g, respectively. The stability test of the Ni–Ce/CaO catalyst was also conducted, showing fluctration in gas concentrations initially during the first 5 h, then stablized for the remaining stability test.