The rising temperature of the earth's atmosphere is a major environmental issue that is only getting worse because of the carbon dioxide levels in the atmosphere. The combustion of our finite fossil fuel supplies results in a strong anthropogenic CO2 release, which exceeds nature's CO2 recycling ability, causing significant environmental harm. Due to this, it is imperative to develop efficient methods to employ CO2 as an abundant C1 building block to produce materials and fuels. One of the most sought-after avenues to achieve this is through the development of novel catalysts that can effectively reduce CO2 to value-added products. This study investigates how the ion exchange of transition metals into ZSM-5 and alkali metal promotion of ZSM-5 impacts the Fe-based catalyst active phase as well as the zeolite's performance in the conversion of CO2 to value-added products (fuels). A series of metal-modified ZSM-5 catalysts were prepared by an ion-exchange method, resulting in Fe-ZSM-5, Co-Fe-ZSM5, Mn/Co-Fe-ZSM5 and K-Mn /Co-Fe-ZSM-5 each synthesized at Si/Al ratios of 50. To investigate the structure and crystallinity of the exchanged zeolites, XRD and FTIR analysis was done. The results proved that after the ion exchange method the structure of ZSM-5 was not damaged. The material retained its crystallinity, and this was observed at 2θ below 10° which is characteristic of highly crystalline material. Strong acid sites were well preserved after metal modification, and this was confirmed using pyridine FTIR. Surface area changes and pore size/volume changes were studied using Brunauer Emmet Teller (BET). With each metal modification, the BET surface area increased. Si/Al ratio and metal ion percentage were confirmed using XRF and morphological properties of the catalysts were studied using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). These findings will further advance techniques for exchanging well-characterized and selective CO2 hydrogenation catalysts.

Preparation and characterization of Co and Fe exchanged ZSM-5 catalysts promoted with K and Mn for hydrogenation of CO2 to value-added products

ACS Spring 2022

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