Chemical looping reforming of toluene as bio-oil model compound via NiFe₂O₄@SBA-15 for hydrogen-rich syngas production

Hydrogen-rich syngas was a clean energy and an important industrial material. Based on the decoupling strategy of biomass chemical looping gasification process, this paper proposed a strategy of metal oxides embedded into molecular sieves to prepare highly dispersed and nanosized oxygen carriers for producing hydrogen-rich syngas. NiO@SBA-15, Fe₂O₃@SBA-15, and NiFe₂O₄@SBA-15 were prepared by the impregnation method, and the reaction conditions on the chemical looping reforming of toluene were investigated. The results showed that NiFe₂O₄@SBA-15 had the highest toluene conversion rate of 93.4% and a relatively high CO selectivity rate of 80.7%. It was confirmed that the embedding strategy can effectively enhance the nanocrystallization and dispersion of metal oxides in oxygen carriers, which could effectively reduce sintering. The inverse spinel structure of NiFe₂O₄ made the oxygen carrier have more metal adsorption sites and a closer reaction distance, which were beneficial to the adsorption and reaction of the fuel. After testing, the optimum reaction temperature was 750 °C, and the optimum weight hourly space velocity was 1.168 h⁻¹. In the 10 cycles of testing of 20 NiFe₂O₄@SBA-15, the average conversion rate of toluene was 95.34%, the moderate selectivity of CO in the gaseous product was 94.83%, the average H/C ratio was 1.97, which indicated that the cycle stability is good. It provided a reference for developing and designing future oxygen carriers of biomass chemical looping reforming.