Facile one-step synthesis of hierarchical porous carbon monoliths as superior supports of Fe-based catalysts for CO2 hydrogenation

Abstract

A versatile strategy involving one-step desilication of coke-deposited spent zeolite catalyst was successfully developed to prepare hierarchical porous carbon monoliths (HPCMs). Such a strategy avoids the use of hard or soft templates and carbon sources, eliminates high temperature carbonization, simultaneously minimizing the emissions from processing spent catalysts. The resulting carbon exhibits a controlled morphology such as three-dimensional networks, hollow spheres or nanosheets, a high degree of graphitization and a multi-level porous structure. Its mesopore (2–50 nm) surface area can reach 522 m² g⁻¹ and both mesopore and macropore (50–350 nm) volumes are more than 1.0 cm³ g⁻¹. Such hierarchical porous carbon was found to be a superior support for minimizing the nanoparticle size and enhancing the synergism of the Fe–K catalyst for promoting CO₂ hydrogenation. Using such a catalyst results in increased conversion of carbon dioxide and enhanced selectivity of high value olefins (C_2–4) and long-chain hydrocarbons (C₅⁺).