Biogas partial oxidation in a heat recirculation reactor for syngas production and CO2 utilization

Abstract

Carbon dioxide and methane are two most important gases causing global warming; they are also the most crucial constituents in biogas. To efficiently convert the two greenhouse gases from biogas into synthesis gas (or syngas), the catalytic partial oxidation of methane (CPOM) triggered by a rhodium-based (Rh-based) catalyst in a spiral Swiss-roll reactor is studied. Three different biogases, including landfill, sewage, and farm biogases, are taken into consideration and the O2-to-CH4 (O2/CH4) molar ratio is between 0.6 and 0.7. It suggests that the reactor with heat recovery can substantially enhance the CH4 conversion when compared with that without heat recirculation, and almost all CH4 in the three biogases is converted. On account of certain amount of CO2 contained in the biogases, the role played by dry reforming on CPOM is beyond those played by methane combustion and steam reforming. Within the investigated range of O2/CH4 ratio, the maximum CO2 conversion is 31.12%. The higher the CH4 concentration and the lower the CO2 one in a biogas, the better the H2 and CO selectivity. The highest syngas yield is 2.80 mol/(mol CH4), accounting for around 93% of theoretical result. Overall, the CH4 conversion, H2 yield, and H2/CO ratio in the product gas are higher than other studies, revealing that the excess enthalpy reactor is a promising device to simultaneously achieve syngas production and CO2 utilization from biogas in industry.