The effect of CO2 and a promoter over a Ni-based catalyst on the gas production of toluene as a model tar compound

Catalytic cracking of biomass tar can increase the gas production of biomass gasification and reduce tar content. Taking tar model compound (toluene) as the research object, HZSM-5 as the catalyst carrier, the influence of different Ni loadings, promoters, and CO2 atmosphere on the gas production trend of toluene catalytic cracking was studied. The crystal structure, specific surface area, microstructure and carbon deposition of the catalyst were investigated. When the Ni/HZSM-5 load was 8 wt%, the H2 instantaneous gas production reached highest value. When the load was increased to 10 wt%, catalyst deactivation was delayed, leading to an increase in gas production. With the addition of Ca, Mn and Fe as promoters, Ca decreased the catalytic activity of Ni/HZSM-5, leading to a decrease in H2 instantaneous gas production; however, both Mn and Fe promoted the catalytic activity of Ni/HZSM-5, with Fe resulting in the highest H2 instantaneous gas production. When 20% CO2 was introduced, Ni-Mn/HZSM-5 had the highest catalytic activity and produced the highest H2 content. The characterization of the catalysts showed the addition of CO2 effectively inhibited the formation of carbon deposits, which was beneficial to prolong the catalytic effect and increase gas production.