Formaldehyde and methanol formation from reaction of carbon monoxide and hydrogen on neutral Fe2S2 clusters in the gas phase

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Reaction of CO with H2on neutral FemSnclusters in a fast flow reactor is investigated both experimentally and theoretically. Single photon ionization at 118 nm is used to detect neutral cluster distributions through time of flight mass spectrometry. FemSnclusters are generated through laser ablation of a mixed iron–sulfur target in the presence of a pure helium carrier gas. A strong size dependent reactivity of (FeS)mclusters toward CO is characterized. The reaction FeS + CO → Fe + OCS is found for the FeS cluster, and the association product Fe2S2CO is observed for the Fe2S2cluster. Products Fe2S213COH2and Fe2S213COH4are identified for reactions of13CO and H2on Fe2S2clusters: this suggests that the Fe2S2cluster has a high catalytic activity for hydrogenation reactions of CO to form formaldehyde and methanol. Density functional theory (DFT) calculations are performed to explore the potential energy surfaces for the two reactions: Fe2S2+ CO + 2H2→ Fe2S2+ CH3OH; and Fe2S2+ CO + H2→ Fe2S2+ CH2O. A barrierless, thermodynamically favorable pathway is obtained for both catalytic processes. Catalytic cycles for formaldehyde and methanol formation from CO and H2on a Fe2S2cluster are proposed based on our experimental and theoretical investigations. The various reaction mechanisms explored by DFT are in good agreement with the experimental results. Condensed phase iron sulfide, which contains exposed Fe2S2units on its surface, is suggested to be a good catalyst for low temperature formaldehyde/methanol synthesis.

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IRON-SULFUR CLUSTERS SUPPORTED COPPER CATALYST METAL-CLUSTERS PHOTOELECTRON-SPECTROSCOPY ELECTRONIC-STRUCTURE MOLYBDATE CATALYSTS SELECTIVE OXIDATION SURFACE-REACTIONS NIOBIUM CLUSTERS DIMETHYL ETHER