Co-thermal in-situ reduction of inorganic carbonates to reduce carbon-dioxide emission

April 21st, 2023

Hydrogenation of CaCO3 to produce CO and CaO is achieved via co-thermal in-situ reduction coupled with green hydrogen system. The strategy of co-thermal in-situ reduction not only reduces energy consumption, but also significantly inhibits the carbon emissions. The products of CO and CaO have great applications in industry. Credit: ©Science China Press

This study is led by Prof. Mingfei Shao and Prof. Xue Duan (College of Chemistry, Beijing University of Chemical Technology). Interestingly, the beginning decomposition temperature of CaCO₃ in hydrogen atmosphere is clearly reduced (as low as 600 °C) and the emission of CO₂ was largely inhibited. Instead, gaseous CO was produced with a high selectivity of 95.8% and the reaction rate could be up to 0.756 mmol min⁻¹.

Meanwhile, the high-purity and porous solid CaO was produced, which has the great application potentials. This study demonstrated that the CO results from the selective cleavage of Ca–O bonds at the surface of CaCO₃via the direct hydrogenation mechanism at relatively low temperature. However, it undergoes the reverse water-gas shift (RWGS) reaction path at high temperature, i.e., CO being produced by the reduction of CO₂ released by the decomposition of carbonates.

"The hydrogenation of metal carbonates gives a potential chance to change the carbon transfer pathway in order to inhibit CO₂ emission and obtain high value-added gaseous products (such as CO). Co-thermal via residual heats generated by carbonate decomposition, coupling the thermal decomposition of carbonate and reduction process will make a huge breakthrough. we are surprised that in-situ hydrogenation of carbonates coupled with a green hydrogen system not only makes full use of energy, but also solves the storage, transport, and safety problems of hydrogen." Shao says.

A few implications thus emerge for designing the system for Co-thermal in-situ reduction of inorganic carbonates: 1) Hydrogenation mechanism and carbon transfer path are of great significance for emission reduction and efficiency enhancement; 2) Through the design and development of the co-thermal in-situ reduction process toward high value-added products will produce huge social and environmental benefits.

More information:
Zhen Xue et al, Co-thermal in-situ reduction of inorganic carbonates to reduce carbon-dioxide emission, Science China Chemistry (2023). DOI: 10.1007/s11426-022-1537-6

Provided by Science China Press