(188c) Atomically Dispersed Iron in Zeolite Y for Alkyne Semi-Hydrogenation

Ethylene produced from steam cracking has acetylene impurity of 0.5-3%, harming the downstream polymerisation. To achieve polymer-grade ethylene, acetylene is removed by chemoselectively hydrogenating it to ethylene without over-hydrogenation to ethane. However, current industrial catalysts are Pd-based (hence scarce and costly) and deploy large nanoparticles as active sites, showing poor selectivity and often requiring toxic CO injections. This has led the petrochemical industry to demand more effective, non-noble and non-precious catalysts. We hypothesised that deploying a well-dispersed and isolated active metal may offer a promising solution, simultaneously reducing costs and improving selectivity; the latter arising due to the preferential desorption of ethylene (Ï€-bonding) over its hydrogenation on isolated active sites. Zeolites are well regarded in the catalysis field for their distinctive abilities in molecular sieving and separation. Moreover, with the emergence of new, precisely-engineered catalysts, zeolites are potentially suitable candidates for anchoring isolated metal atoms due to their microporous structure, thermal stability, and high surface area. To date, however, zeolite-supported isolated metal atoms have received limited attention for this reaction in the literature. Our work seeks to address this gap. Additionally, to enhance the sustainability of this reaction, we have utilised a cheap, non-toxic, and earth-abundant metal, namely iron. To our knowledge, no data has been reported thus far on embedding isolated iron atoms in zeolites for alkyne semi-hydrogenation. We anchored iron atoms in Zeolite Y, Fe₁@Y, through an in-situ hydrothermal synthesis method. Characterisation techniques, including XRD, N₂-physisorption, XPS, ToF-SIMS, and H₂-TPD, verified attaining crystallinity with high surface area and absence of nanoparticles. TEM and XAS confirmed the presence of isolated metal atoms. For acetylene semi-hydrogenation, the catalyst demonstrated an excellent performance with selectivity towards ethylene >90% at full conversion of acetylene, with no oligomers formed.