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

Abstract

• The embedding strategy for oxygen carriers proposed Fe 2 O 3 nano-sized and dispersed. • The embedding strategy improved the recycling and reforming performance of OCs. • The utilization efficiency of lattice oxygen was dincreased for embedding strategy. • The nanocrystallization of Fe 2 O 3 reduces the potential barrier to forming CO. 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 Fe 2 O 3 embedded in SBA-15 (Fe 2 O 3 @SBA-15) were studied in fixed-bed reactor. The performances of Fe 2 O 3 and Fe 2 O 3 @SBA-15 were compared. The effect of pure Fe 2 O 3 particle size, Fe 2 O 3 loading amount, and reaction temperature were investigated. Thermodynamic analysis results showed that the reaction could proceed spontaneously when the temperature was higher than 600℃. 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 H 2 and coke. The Fe 2 O 3 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 Fe 2 O 3 would improve the partial oxidation performance. Compared with pure Fe 2 O 3 , the CO selectivity of Fe 2 O 3 @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℃, toluene was nearly completely converted, and the utilization rate of lattice oxygen reached 92.7%. The toluene conversion increased with the elevation of Fe 2 O 3 loading, and the CO selectivity always remained above 87.9%. With the elevation of reaction temperature from 700℃-900℃, 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 Fe 2 O 3 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.