Chemical looping reforming of toluene via Fe2O3@SBA-15 based on controlling reaction microenvironments

Macromolecular volatiles are one of the important components of biomass pyrolysis products. Chemical looping reforming can efficiently convert macromolecular components into hydrogen-rich syngas. Oxygen carriers with good partial oxidation performance and excellent recycling performance are the key factor. In this work, the embeddedness strategy was proposed to regulate the micro-reaction environment of oxygen carriers and thus improve the recycling and partial oxidation performance. The characteristics of toluene chemical looping reforming via Fe2O3 embedded in SBA-15 (Fe2O3@SBA-15) were studied in fixed-bed reactor. The performances of Fe2O3 and Fe2O3@SBA-15 were compared. The effect of pure Fe2O3 particle size, Fe2O3 loading amount, and reaction temperature were investigated. Thermodynamic analysis results showed that the reaction could proceed spontaneously when the temperature was higher than 600 degrees C. The experimental results showed that chemical looping reforming process could be divided into two stages, including partial oxidation and catalytic cracking. The main product in the first stage was syngas, while the main product in the latter stage was H2 and coke. The Fe2O3 particle size decreased from 5um to 30 nm, and the CO selectivity increased from 25.87% to 33.15%. This indicated that the nanocrystallization of Fe2O3 would improve the partial oxidation performance. Compared with pure Fe2O3, the CO selectivity of Fe2O3@SBA-15 rose from 25.9% to 96.2%. The utilization rate of lattice oxygen and the conversion rate of toluene increased significantly. At 900 degrees C, toluene was nearly completely converted, and the utilization rate of lattice oxygen reached 92.7%. The toluene conversion increased with the elevation of Fe2O3 loading, and the CO selectivity always remained above 87.9%. With the elevation of reaction temperature from 700 degrees C-900 degrees C, toluene conversion increased from 30.5% to 95.6%, while CO selectivity decreased slightly. More importantly, the stability test results showed that after 10 cycles, toluene conversion rate only dropped by 1.9%, and the average concentration of gas products remained stable. The above results showed that the embeddedness of Fe2O3 in SBA-15 could effectively improve CO selectivity, enhance the transmission and release of lattice oxygen, and elevate the catalytic performance and cycle stability of oxygen carriers.

Automated summary

This study successfully regulated the micro-reaction environment of oxygen carriers through the embeddedness strategy, improving the recycling and partial oxidation performance. The results showed that Fe2O3@SBA-15 has higher CO selectivity and catalytic performance, along with good cycle stability.