Chemical Looping Conversion of Gaseous and Liquid Fuels for Chemical Production: A Review

Chemical looping technology enables achievement of the simultaneous feedstock conversion and product separation without additional processes via circulating solid intermediates (so-called oxygen/nitrogen carriers) in a redox process, which contributes to the improvement of product selectivity and energy conservation. In general, methane, CO2, N-2, ethane, propane, ethanol, and glycerol are typical gaseous and liquid fuels for producing syngas, pure H-2, pure CO, NH3, ethylene, and propylene via the chemical looping process. Central to this technology is the solid intermediates that act as reservoirs for storing and releasing O or N in multiple sub-reactions to close the loop. This work comprehensively describes the chemical looping conversion of gaseous or liquid fuels for chemical production, covering chemical looping reforming of methane, chemical looping oxidative coupling of methane, chemical looping reforming of liquid fuels, chemical looping oxidative dehydrogenation, and chemical looping ammonia synthesis technologies. Specifically, this review mainly focuses on the development of oxygen/nitrogen carrier materials, especially the related research in China. The effects of composition, structure, and morphology on the performance and related reaction mechanisms are discussed.