Boosting Carbonate Hydrogenation through In Situ Formation of the CaO/CaCO <sub>3</sub> Interface
Bin Shao, Yongjun Jiang, Su Li, Zhicheng Xie, Zhi-Qiang Wang, Sheng Dai, Honglai Liu, Feng Qian, Jun Hu
Abstract
High-temperature calcination of carbonate minerals in energy-intensive industrial sectors is one of the greatest contributors to global carbon dioxide (CO 2 ) emissions. The hydrogenation of the most abundant carbonate minerals could potentially mitigate unavoidable CO 2 emissions by converting them into value-added products, but progress has been hindered by a limited understanding of this process. Here, we aim to elucidate the underlying mechanism of self-induced direct hydrogenation of carbonates (DHC) to produce metal oxides and syngas at relatively lower temperature without using any catalysts. Various in situ technologies corroboratively illustrate H 2 molecules can penetrate into CaCO 3 to form multiple CaO/CaCO 3 interfaces, resulting in porous CaO. The density functional theory calculations reveal the neighboring O and C sites at the active CaO/CaCO 3 interface are responsible for the heterolytic dissociation of H 2, leading to the progressively self-induced DHC. An intrinsic microkinetic analysis by tracing the formation rate of the intermediate further verifies its self-induced catalytic characteristics. This subverts the consensus regarding the infeasible self-catalysis of stable ionic crystals. By lowering the temperature to 650 °C, 100% CaCO 3 conversion is achieved with a CO selectivity of 91.8% in a packed bed reactor. Inspired by extensive applications of DHC to various carbonates, this innovative idea of treating carbonates as a White Carbon resource may pave a breakthrough pathway toward Carbon Neutrality in the industry.