A Microwave-Assisted Boudouard Reaction: A Highly Effective Reduction of the Greenhouse Gas CO(2) to Useful CO Feedstock with Semi-Coke

The conversion of CO(2) into more synthetically flexible CO is an effective and potential method for CO(2) remediation, utilization and carbon emission reduction. In this paper, the reaction of carbon-carbon dioxide (the Boudouard reaction) was performed in a microwave fixed bed reactor using semi-coke (SC) as both the microwave absorber and reactant and was systematically compared with that heated in a conventional thermal field. The effects of the heating source, SC particle size, CO(2) flow rate and additives on CO(2) conversion and CO output were investigated. By microwave heating (MWH), CO(2) conversion reached more than 99% while by conventional heating (CH), the maximum conversion of CO(2) was approximately 29% at 900 °C. Meanwhile, for the reaction with 5 wt% barium carbonate added as a promoter, the reaction temperature was significantly reduced to 750 °C with an almost quantitative conversion of CO(2). Further kinetic calculations showed that the apparent activation energy of the reaction under microwave heating was 46.3 kJ/mol, which was only one-third of that observed under conventional heating. The microwave-assisted Boudouard reaction with catalytic barium carbonate is a promising method for carbon dioxide utilization.