Thermal Decomposition of Carbonates Coupled with Dry Reforming of Methane to Synthesize High-Value Products: A Perspective

Traditional industries, such as the production of cement, steel, refractory materials, and calcium carbide, involve the thermal decomposition of carbonates. Large amounts of carbon dioxide (CO2) emitted by these processes comprise more than 50% of the total industrial carbon emissions in China. Furthermore, to ensure the complete decomposition of carbonates, the input of excess heat is required, leading to the generation of residual heat. Notably, the reduction in CO2 emissions and complete utilization of the produced residual heat in the above processes are considerable challenges. However, co-thermal coupling of carbonate decomposition with H2, CH4, and other gases containing hydrogen molecules enables the production of high-value-added products such as syngas. Furthermore, this approach is environmentally friendly and economical, with potential for realization in the near future. This paper summarizes recent advances in the coupling of the thermal decomposition of carbonates with dry reforming of methane, dry reforming of alcohols, and CO2 capture. Combining CO2-emitting thermal decomposition of carbonates with the CO2-consuming methane reforming reaction allows the simultaneous reduction of CO2 emissions and syngas production. Although many experimental studies have been conducted on the coupling of the thermal decomposition of carbonates with dry reforming of methane, few reports have revealed the mechanism theoretically. At present, the theoretical research is limited to the adsorption of methane on carbonate surfaces without a clearly understood mechanism; this paper briefly introduces recent research progress in the thermal decomposition of carbonates coupled with H2 reduction and dry reforming of methane. Notably, alcohols are promising hydrogen donors for coupling with the thermal decomposition of carbonates because they can be produced by fermentation of biomass or renewable raw materials, including energy plants, waste materials from agro-industry or forestry residue materials, and organic municipal solid waste. In addition, CO2 can also be captured and converted using metal oxides (e.g., CaO, MgO); these are typical CO2 solid sorbents, which can capture CO2 by calcium looping and be regenerated in CH4. Our group has also recently made progress in the co-thermal coupling of the decomposition of carbonates with dry reforming of methane. By regulating the concentration of CH4, adding O2 to the CH4 atmosphere, and using catalysts, CO2 emissions can be decreased with the evolution of syngas. In this perspective, we summarize the latest results on the coupling of the thermal decomposition of carbonates with dry reforming of methane, including the results obtained by our research group, which allows efficient utilization of CO2 and emissions reduction.