The conversion of carbon dioxide (CO2) into valuable hydrocarbons represents a crucial strategy for mitigating greenhouse gas emissions and advancing a sustainable, carbon-neutral economy. This study presents an investigation into the catalytic performance of iron-based ZSM-5 Zeolites for the direct hydrogenation of CO2, focusing on a series of strategic modifications to enhance both catalytic conversion and product selectivity. The prepared ZSM-5 support was first synthesized using various aluminum sources, including aluminum sulfate, aluminum nitrate, sodium aluminate, and aluminum hydroxide, with a key finding being that aluminum hydroxide yielded a catalyst with significantly improved physical properties, resulting in a remarkable hydrocarbon selectivity of up to 73%. Transmission electron microscopy (TEM) analysis reveals that iron impregnation is affected by the aluminum source, where Z-Al(NO3)3-W and Z-Al2(SO4)3-W display clean crystal surfaces and clear lattice fringes indicative of subnanometer, internally dispersed species. Pyr-Fourier-transform infrared (Pyr-FTIR) quantification showed that the Z-Al(OH)3-W sample has negligible Brønsted acid sites (0.002 mmol/g), reflecting the lack of interaction between the iron species and the internal zeolite framework. Building on this optimized zeolitic support, iron was incorporated using different solvent types, including aniline, ethanol, acetone, and water, revealing that water provided the most effective dispersion and catalytic performance. The optimized catalyst showed that hydrocarbon product distribution was the most favorable, with a majority of the products being methane (79.56%), a significant portion of valuable C2–C4 paraffins (19.25%), and minor amounts of light olefins and C5+ products. This suggests that the aluminum source and solvent source dictate the physical structure of the zeolite, which in turn influences reactant diffusion and access to active sites.
Sanhoob et al. (Thu,) studied this question.