Preparation of Fe-based catalysts from waste biomass as a carbon carrier and its catalytic performance in CO2 hydrogenation

Abstract

Biomass, the only renewable source of organic carbon, has been widely used and developed as a functional carbon material owing to its low cost and easy accessibility. In this study, a simple and green strategy to prepare an iron catalyst based on waste biomass (litchi shell, LC) as a catalyst carrier is proposed. The Fe/LC composite catalyst was prepared by the one-step carbonization of LC impregnated with iron nitrate to improve its dispersion. During CO₂ hydrogenation, the biomass-based carbon material effectively inhibited the oxidation of water on the catalyst. Thus, the stability of the catalyst improved and the formation of olefins was significantly promoted, resulting in excellent catalytic performance. The optimized Fe/LC catalyst exhibited good catalytic performance for CO₂ hydrogenation, and its selectivity for light olefins (C⁼_2–4) was 47 wt% (olefin/alkane molar ratio = 3.1). The characterization results revealed the formation of a graphitic-carbon-anchored Fe₃O₄ structure during high-temperature carbonization. This structure played a coordinated role with the natural K minerals in LC, effectively improving the CO₂-hydrogenation activity of the catalyst and increasing its selectivity for C⁼_2–4 products. The direct use of waste biomass without any chemical pretreatment, purification, or addition of promoters provides a simple design method and synthesis strategy for the low-cost, large-scale preparation of high-performance carbon-based catalysts.