Enhanced degradation of VOCs from biomass gasification catalyzed by Ni/HZSM-5 series catalyst.

ABSTRACT

Volatile organic compounds (VOCs) evolved from biomass gasification plays a positive role in the formation of PM2.5 and odor pollution. In order to improve the removal rate of various VOCs produced by biomass gasification, a nickel-based supported HZSM-5 cataly st (Ni/HZSM-5 and Ni-Ca-Co/HZSM-5) was prepared by different auxiliary methods, Ni loadings, and pyrolysis temperatures. The catalytic cracking performance of Ni/HZSM-5 catalysts for different VOCs model compounds such as toluene, phenol, furan, acetic acid and cyclohexane were studied in a fixed-bed reactor. The catalysts were further characterized and analyzed by XRD, SEM, XPS and BET. The results showed that the Ni/HZSM--C-Co5 catalyst prepared by ultrasonic-assisted excess impregnation method with Ni loading of 8 wt%, Ca loading of 4 wt%, Co loading of 0.1 wt% had strong catalytic activity for VOCs degradation. With the increase of the cracking temperature, the conversion rate and gas yield of from model compound cracking improved significantly. At 800 °C, the conversion of each model compound was more than 90%, accompanied by the generation of cracking gases such as H2 and CH4. The selectivity of H2 and CH4 from toluene cracking reached 93%, and cyclohexane reached 98%. The models with higher oxygen content and lower bond energy were more likely to undergo reforming reaction to form small molecular gas. Model compounds with large molecular weight and high carbon content provided more carbon sources. Under the conversion degree towards the gas direction was high. This study provides a new idea on the removal of VOCs for the efficient utilization of biomass resources.