Influence of Synthesized Method on the Cycle Stability of NiO/NiAl2O4 during Chemical Looping Combustion of Biomass Pyrolysis Gas

The industrial application of NiO/NiAl2O4 oxygen carrier is always restricted by its poor cycle stability. The cycle stability of NiO/NiAl2O4 synthesized by different methods was compared based on the change of activity, structure, and composition of oxygen carrier after several cycles. The results showed that the oxygen carrier obtained by the coprecipitation method exhibits better cycle stability, and the average CH4 conversion and CO2 selectivity of coprecipitated NiO/NiAl2O4 could reach 99% and 75%, respectively. The results of X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller investigations proved that the phase separation of NiAl2O4 and the agglomeration of NiO were the main reasons for the decrease of cycle stability. The oxygen carrier synthesized by the coprecipitation method possessed high stability and activity after 10 cycles of chemical looping combustion, for it displayed a more proper distribution of NiAl2O4 and NiO. The research supplied a better choice for a synthesized highly the mechanism of the cycle stability decrease.