Direct and highly selective conversion of captured CO2 into methane through integrated carbon capture and utilization over dual functional materials

Excessive atmospheric CO2 emission is regarded as one of the main factors causing global climate change. Thus, there is an urgent need to explore the possibility of CO2 capture and converting the captured CO2 to fuels or value-added products. Recently, an integrated carbon capture and utilization (ICCU) process performed in a single reactor under isothermal conditions draws intensive attentions due to the reduction of energy requirement for sorbent regeneration. However, from literature, normally a low loading of sorbent in dual functional materials (DFMs) was applied resulting in a very low CO2 capture capacity and consequent low CH4 yield in the ICCU process. Herein, we demonstrate the intermediate-temperature DFMs using inexpensive high-capacity MgO sorbent. The synthesized DFMs are a physical mixture of sorbent and Ru/CeO2 catalyst by the mass ratio of 2:1 allowing simultaneous regeneration of sorbent and conversion of CO2 in a single reactor at 300 °C. During the 1st cycle of ICCU process, 10Ru/CeO2-MgO exhibits the best ICCU performance with the highest CH4 yield of 7.07 mmol g−1 and CO2 conversion of 89 %. However, after 10 cycles of ICCU process, 5Ru/CeO2-MgO exhibits the highest CH4 yield (3.36 mmol g−1) and CO2 conversion (79 %), which are much higher than that of 2.5Ru/CeO2-MgO (1.13 mmol g−1 and 39 %) and 10Ru/CeO2-MgO (2.31 mmol g−1 and 69 %). It is mainly attributed to that more oxygen vacancies are remained in 5Ru/CeO2-MgO resulted from the metal-support interaction.