Syngas production via chemical looping reforming biomass pyrolysis oil using NiO/dolomite as oxygen carrier, catalyst or sorbent

Chemical looping reforming (CLR) with biomass pyrolysis oil (BPO) for syngas production was investigated using NiO/dolomite as the bed material which was prepared by the wet impregnation method. The NiO/dolomite was used as catalyst and oxygen carrier in the whole temperature range, while it was also acted as in-situ CO₂ sorbent at 600 °C and 700 °C. The syngas production was dominated by the sorption enhanced and catalytic reforming of BPO, due to the formation of NiO–MgO solid solution, which had a lower reducibility at low temperatures. Although, the low level CGE at low temperature could be improved by elevating the oxygen coefficient at the certain extent, poor cyclic performance of NiO/dolomite at 700 °C was observed, owning to the sintering and agglomeration during the repeated carbonation/calcination reactions. High temperatures inhibited the carbonation reaction and facilitated the reduction of NiO–MgO solid solution to provide more lattice oxygen and catalytic active sites. The syngas production was governed by the synergistic effect of lattice oxygen and catalysis at high temperatures. The optimum operating condition for syngas production in CLR was obtained by the analysis showed as follows: the temperature at 900 °C with ϕ = 0.4 in fuel reactor. The corresponding values of cold gas efficiency (CGE), syngas yield (Y_syn) and syngas purity (P_syn) were 80.76%, 1.318 Nm³/kg and 92.06%, respectively. Besides that, the NiO/dolomite exhibited a good cycle performance under this condition. The CGE and Y_syn decreased slightly to 76.26% and 1.265 Nm³/kg after 10 cycles, respectively. Overall, NiO/dolomite is a promising multifunctional material in the CLR process with BPO for syngas production. More attention should be paid to improve the mechanical strength of NiO/dolomite in the future.