Catalytic pyrolysis of pine bark over Ni/SiO2 in a CO2 atmosphere

Abstract

Syngas was produced by catalytic pyrolysis of pine bark (PB) using CO2 as a raw feedstock as part of an effort to realize the sustainable utilization of biomass carbon. An examination of both liquid and gaseous pyrolysates from pyrolysis revealed that CO2 expedited gas-phase reactions (GPRs) with volatile pyrolysates (VPs) evolved from thermolysis of PB. The GPRs between CO2 and VPs led to the generation of CO at ≥ 600 °C regardless of Boudouard reactions. Two-step pyrolysis was conducted with an additional heating source, and the synergetic use of Ni/SiO2 and CO2 stimulated syngas formation at ≤ 600 °C. Evolution of H2 and CO from catalytic pyrolysis at 700 °C in CO2 atmosphere was greater by factors of 10 and 5, respectively, compared with those from two-step pyrolysis. The conditions for catalytic deactivation between virgin and used catalysts were compared using temperature-programmed oxidation. An apparent reduction of organic species on the surface of used catalysts by CO2 indicates that the addition of CO2 suppressed the formation of coke for deposition. Accordingly, combinational use of CO2 and Ni/SiO2 in catalytic pyrolysis can be recommended as an advanced technical option for production of syngas under favorably retarded conditions for catalyst deactivation.