Preparation and performance of Cu-based bimetallic oxygen carriers in chemical looping combustion with gaseous and solid fuels

Abstract

Chemical looping with oxygen uncoupling (CLOU) is promising for carbon capture in fossil fuel combustion. Oxygen carriers (OC) are the key aspect for the development of CLOU technology. Four Cu-based bimetallic OC (80Cu20Mn, 40Cu60Fe, 60Cu40Co and 60Cu40Ni) were prepared by sol-gel method in this work. The oxygen release and adsorption behavior of the OC were examined in alternating Ar and air. Chemical looping combustion (CLC) with both gaseous and char were conducted to investigate the performance of the OC. The oxygen transport capacity remained stable in 20 cycles for 80Cu20Mn, 40Cu60Fe and 60Cu40Ni, but a remarkable decrease was observed for 60Cu40Co. For the CLC tests with gaseous fuel, only 80Cu20Mn exhibited stable CO conversion (XCO), while the other three OC showed reducing XCO in the redox cycles. Both 60Cu40Co and 60Cu40Ni were sintered, and insufficient oxidation was confirmed after CLC with 11.3%CO/N2. In CLC with coal char, all the OC significantly enhanced carbon conversion (XCO), reaction rate(γC) as well as CO2 selectivity (YCO2). However, γC decreased prominently in cycling tests indicating reduced reactivity. Agglomeration, sintering and transformation of active components into composite salts such as CuFe2O4 and CuMnO2 were responsible for the deteriorated performance of the Cu-based bimetallic OC.