Low-Temperature Decomposition of CaCO3 in NiO/CaCO3 and CuO/CaCO3 Powder Under H2 at Industrial Waste Heat Temperatures

Calcium looping (CaL) is a CO2 capture technology based on the reversible carbonation of calcium salts. Calcium-based materials are highly reactive with CO2 and are generated as by-products or waste across a wide range of industries—such as cement, steel, and fisheries—leading to expectations that the calcium looping (CaL) process can be implemented at a low cost. However, a key challenge remains in the regeneration step: releasing CO2 from CaCO3, the carbonated form of the sorbent, and returning it to a reusable state conventionally requires calcination at around 700 °C, which imposes a substantial energy penalty. This study investigates the decomposition of solid-phase calcium carbonate (CaCO3) using Ni-supported composites under a hydrogen atmosphere at industrial waste heat temperatures. TPD-MS confirmed CO2 release below 250 °C, far lower than 700 °C, the typical decomposition temperature of CaCO3. The XRD and XPS results showed that CaCO3 was partially converted to Ca(OH)2 in the surface region. In situ DRIFTS measurements revealed a decrease in the CO32− signal upon heating metal oxide/CaCO3 composites under a hydrogen atmosphere. The magnitude of decrease in the CO32− signal was significant in Ni-loaded CaCO3 compared to Cu-loaded CaCO3, suggesting a difference in hydrogen dissociation ability of loaded metals.