Production of carbon-negative syngas through CO2-driven thermochemical conversion of acacia sawdust

Abstract

This paper proposes a strategic approach for producing carbon-negative syngas through the thermochemical conversion of biomass using acacia sawdust as a model compound. CO2 was employed as the reactive medium during the pyrolysis of acacia sawdust to increase the conversion of carbon in biocrude into syngas. In the single- stage pyrolysis, more production of CO under CO2 than N2 condition was observed above 580 & ring;C. This observation demonstrated that the reaction in gaseous medium between the CO2 and volatile matter released from the thermolysis of acacia sawdust did occur. However, the kinetics of the reaction in gaseous medium driven by CO2 were slow. As such, a Ni-based catalyst was introduced to promote the kinetics of reaction in gaseous medium driven by CO2. Introducing CO2 in the catalytic pyrolysis further increased the yield of syngas, reaching 22.8 mmol gsample-1 , which was higher than that under N2 conditions (18.6 mmol gsample-1). The proposed process (CO2- driven catalytic pyrolysis of acacia sawdust) achieved a net CO2 emission of-151.0 mg gsample-1 . All the experimental findings show that the CO2-drvien catalytic pyrolysis system may serve as an effective strategy for carbon-negative syngas production, contributing to greenhouse gas (CO2) mitigation.