Investigation on deactivation progress of biochar supported Ni catalyst during biomass catalytic cracking process

Abstract

Herein, the biochar-supported Ni catalysts was synthesized by carbothermal reduction and its catalytic activity for biomass-derived heavy components was investigated in a pyrolysis-catalysis two stage reactor at the catalytic cracking temperature of 700 °C. The change in catalytic activity of biochar-supported Ni catalyst was divided into three stages according to conversion efficiency of heavy components: rapid reduction stage (from 95.30% to 85.58%), stabilization stage (from 84.65% to 82.98%), and slow reduction stage of activity (from 81.21% to 76.98%), corresponding to rapid decreasing stage (from 88.95% to 63.53%), stable stage (from 62.1% to 57.55%), and slow increasing stage (57.66% to 60.17%) of the mass retention percentage of catalyst. The characterizations of catalyst after different cycles showed that the initial deactivation mainly caused by the sintering of Ni active sites. With the severe sintering of Ni nanoparticles, coke deposition became the main reason of later catalyst deactivation. Particularly, the carbon elimination reaction promoted by highly dispersed Ni particle was observed which contributed to enrich the mesoporous structure and retarded the deactivation of the catalyst. The research marks a further understanding of the interaction and deactivation mechanisms between biochar support and Ni active sites during catalytic cracking of biomass-derived heavy components.