Pyrolysis of sawdust with various Fe-based catalysts: Influence of support characteristics on hydrogen-rich gas production

Abstract

In the present study, we studied the hydrogen-rich gas production from catalytic pyrolysis of sawdust using various Fe-based catalysts derived from layered double hydroxide (LDH) precursor in a two-stage fixed-bed reactor. Specifically, we investigated the effect of support characteristics (Fe–Mg, Fe–Ca and Fe–Al) on the physicochemical properties and catalytic performances in relation to hydrogen production and coke formation. Various characterization techniques, such as XRD, SEM, BET, H2-TPR and TG-DTG temperature-programmed oxidation (TPO), were employed to thoroughly characterize the fresh and reacted Fe-based catalysts. It revealed that the support characteristics played an important role in determining the iron species form, textural properties and catalytic abilities of the resulting catalysts. The Al-supported Fe-based catalyst was found to be the most effective catalyst for hydrogen-rich gas production with the highest gaseous efficiency of 61.4 wt.%, gas yield of 598 mL/g biomass, H2 yield of 217 mL/g biomass, and H2/CO molar ratio of 2.5 at 700 °C. Based on the results of structural characteristics, this might be attributed to its fine particle, enhanced reducibility, high surface area and generation of surface acidity by introduction of Al form, which could provide efficient active sites for pyrolysis volatiles to crack and reform through a series of catalytic reactions. According to GC–MS experiment results, the Fe–Al catalyst was capable of selectively producing aromatic compounds, with the maximum yield as high as almost 100%. Therefore, the Fe–Al catalyst developed in this work could provide a promising route for hydrogen-rich gas production from catalytic pyrolysis of biomass.