Characterization of NO_x Release during Combustion Synthesis and Cyclic Reaction Performance of Cu-Based Oxygen Carriers Prepared with Citric Acid

Chemical looping combustion technology has received attention as a novel combustion technology. In this paper, anhydrous citric acid was selected as the complexing agent and copper-based oxygen carriers (OCs) were prepared by the combustion synthesis method. The characteristics of NOx release during the combustion synthesis of copper-based OCs were investigated by citric acid addition. The NO release decreased significantly as the molar ratio of citric acid and Cu(NO3)(2)3H(2)O (R) increased. The peak NO concentration decreased from 100 to almost 0 ppm. The peak NO2 concentration was maintained in the range 0-4 ppm. When R was less than 1.00, the products of copper-based OC precursor combustion were mainly NO, with very little generation of NO2. When R reached 1.25, only a very small amount of NO2 was produced, and NO was negligible. The redox properties of the prepared copper-based OCs during 10 cycles were explored. The copper-based OCs all had stable redox properties in cycles. In each reduction, the peak CO2 concentration was 3% and above. The CH4 conversion rate and CO2 yield were maintained at about 80% during the 10 cycles. The CO2 selectivity was maintained at 95% and above. Among them, OC5 (R: 1.25) had the best redox capacity.