CO2 hydrogenation to methyl formate in the presence of methanol under high pressure.
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Ag/ZrO2 catalyst shows the highest activity known to date.
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Operando transient IR study highlights the critical roles of the perimeter sites.
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Formates spill over from Ag to the acidic support serving as a formate reservoir.
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Methanol adsorption and surface diffusion play decisive roles in defining the reaction rate.
Abstract
Silica-supported silver nanoparticles exhibit outstanding efficiency in the CO2 hydrogenation to methyl formate in the presence of methanol under high pressure. Here, we show that ZrO2 and Al2O3 supports significantly increase the catalyst activity, in line with their higher Lewis acidity. The weight time yield of methyl formate over Ag/ZrO2 is up to 16.2 gMF gAg h−1 without detectable side-products, 25 times higher compared to Ag/SiO2 at the same temperature. Transient in situ and operando DRIFTS studies uncover spillover processes of formate species from Ag onto the acidic support materials and show that the surface formates can further react with adsorbed methanol at the sites near the perimeter between Ag and the support to yield methyl formate.