Modified Ceria for 'Low-Temperature' CO_2 Utilization: A Chemical Looping Route to Exploit Industrial Waste Heat

摘要

Efficient CO2 utilization is key to limit global climate change. Carbon monoxide, which is a crucial feedstock for chemical synthesis, can be produced by splitting CO2. However, existing thermochemical routes are energy intensive requiring high operating temperatures. A hybrid redox process (HRP) involving CO2-to-CO conversion using a lattice oxygen-deprived redox catalyst at relatively low temperatures (<700 degrees C) is reported. The lattice oxygen of the redox catalyst, restored during CO2-splitting, is subsequently used to convert methane to syngas. Operated at temperatures significantly lower than a number of industrial waste heat sources, this cyclic redox process allows for efficient waste heat-utilization to convert CO2. To enable the low temperature operation, lanthanum modified ceria (1:1 Ce:La) promoted by rhodium (0.5 wt%) is reported as an effective redox catalyst. Near-complete CO2 conversion with a syngas yield of up to 83% at low temperatures is achieved using Rh-promoted LaCeO4-x. While La improves low-temperature bulk redox properties of ceria, Rh considerably enhances the surface catalytic properties for methane activation. Density functional theory calculations further illustrate the underlying functions of La-substitution. The highly effective redox catalyst and HRP scheme provide a potentially attractive route for chemical production using CO2, industrial waste heat, and methane, with appreciably lowered CO2 emissions.