Synergistic effects of CO2 on ex situ catalytic pyrolysis of lignocellulosic biomass over a Ni/SiO2 catalyst

Abstract

This work laid emphasis on catalytic pyrolysis of Styrax japonicus to construct a biomass-to-energy conversion platform. CO2 was particularly chosen to enhance the catalytic pyrolysis of the biomass waste, in reference to N2-purged pyrolysis. The specific roles of CO2 on pyrolysis of S. japonicus in line with synergistic effect of Ni-based catalysts was investigated. It was shown that CO2 played as an oxidant for CO formation via homogeneous gas phase reaction of CO2 with volatile organic carbons (VOCs) liberated from the thermolysis of S. japonicus. Ni/SiO2 catalyst expedited dehydrogenation (DH) of the VOCs, resulting in significant H2 generation and alteration of aromaticity in VOCs. Each CO2 and Ni catalyst independently enhanced CO and H2 formation, respectively, and their synergistic effects were shown at ≥ 600 °C. Coke deposition on the Ni/SiO2 catalyst was confirmed after catalytic pyrolysis, while the suppression of coke formation on the catalyst surface was achieved under the CO2 environment.