Performance Comparison of Spray-Dried Oxygen Carriers: The Effect of NiO and Pseudoboehmite Content in Raw Materials

The effect of NiO and pseudoboehmite content in raw materials on the performances of spray-dried oxygen carriers was investigated. Oxygen carriers were prepared by the spray-drying method using 60, 70, and 80 wt % NiO and gamma-Al2O3. For 70 wt % NiO, gamma-Al2O3 mixed with 0, 5, and 10 wt % pseudoboehmite was used as raw support materials. The prepared oxygen carriers showed excellent physical properties suitable for fluidized-bed process applications. Oxygen carriers prepared using 70 wt % NiO showed higher attrition resistance than that of other oxygen carriers and a commercial fluid catalytic cracking catalyst. Especially, the calcination temperature to obtain sufficient mechanical strength was lowered to 1000 degrees C. for the oxygen carrier prepared using 70 wt % NiO and 30 wt % gamma-Al2O3. The oxygen carriers prepared using 70 and 80 wt % NiO and calcined at 1100 degrees C showed high oxygen transfer capacities and oxygen utilization above 13.3 wt 'V. and 88.7%, respectively. However, the oxygen utilization of the oxygen carriers prepared using 60 wt % NiO significantly decreased below 51%. With the increase of the pseudoboehmite content, the mechanical strength slightly decreased and the oxygen transfer capacity slightly increased. The oxygen transfer rate was much higher at the higher NiO content and at a lower calcination temperature, and there were little differences by pscudoboehmite content change. The higher oxygen utilization and the higher oxygen transfer rate at the higher NiO content could be ascribed to the fact that the interaction between NiO and support was lowered by the higher NiO content as well as by the reduced calcination temperature resulting from the use of gamma-Al2O3 and pseudoboehmite. This was verified by temperature-programmed reduction analysis.