(581f) Controlling the Performance of Cu/SiO2 Catalysts for Methyl Acetate Hydrogenation By the Introduction of Dilute Quantities of Pt

The production of ethanol has received a lot of attention in recent years due to its application as a fuel. Hydrogenation of methyl acetate is potentially a more sustainable route for ethanol production compared to the common corn-to-ethanol pathway. Copper based catalysts have been utilized to selectively produce ethanol and methanol from methyl acetate, but these catalysts are limited by low activity. An approach that has been used to improve the activity of metals with low activity but high selectivity like copper is the introduction of active metals like platinum in dilute quantities. Here, Pt is expected to increase activity by accelerating dissociative adsorption of H₂. In this study, we introduced dilute quantities of platinum (0.3 – 0.6wt%) to a Cu/SiO₂ catalyst using the galvanic replacement method. This method involves the introduction of the Pt precursor to the reduced Cu/SiO₂ in solution leading to a redox process in which Pt atoms are reduced to the surface and Cu atoms are oxidized into solution. The Pt-Cu/SiO₂ catalysts led to improved activity for the methyl acetate hydrogenation reaction while still maintaining good selectivity to the ethanol product as compared to the native Cu/SiO₂ catalyst. Hydrogen-temperature programmed reduction results show that introducing platinum improved the reducibility of the Cu/SiO₂ catalysts. This improved reducibility as seen from lower reduction temperatures suggests that even at very low quantities, Pt can improve hydrogen dissociation and spillover leading to improved activity. However, introducing dilute quantities of Pt to smaller supported Cu nanoparticles prepared by the ammonia evaporation method led to a decline in activity. Thus, the effect of Pt on activity is sensitive to particle size suggesting that the role of Pt may be more complex for small Cu nanoparticles, and that small Cu nanoparticles possess sites with unique reactivity.