Alkali and Alkaline Earth Metals (K, Ca, Sr) Promoted Cu/SiO₂ Catalyst for Hydrogenation of Methyl Acetate to Ethanol

The advancing effects of various alkali and alkaline earth metals (inclusive of K, Ca, and Sr) modified Cu/SiO₂ catalysts, prepared with a modified precipitation-gel method, were investigated for the production of ethanol via hydrogenation of methyl acetate. Our results showed that Sr-doped catalysts exhibited the best and most consistent results during catalytic tests. A series of techniques, including X-ray diffraction technique, Raman spectroscopy, N₂ adsorption/desorption, N₂O titration method, FTIR spectroscopy, and H₂ temperature, programmed desorption and reduction (TPD and TPR), and X-ray Photoelectron Spectroscopy, which was used to check the detailed characterization of Sr modification in the catalyst and its structural impacts on the properties of the catalyst. These results demonstrated that the addition of 5%Sr could strengthen the intrinsic stability of the catalyst by formulating the appropriate ratio of Cu⁺/(Cu⁰ + Cu⁺) to facilitate catalytic outcome improvement. The addition of 5%Sr-30%Cu/SiO₂ under the most favorable conditions, resulting in the peak conversion of MA (95%) and ethanol selectivity (96%), indicates its magnificent catalytic stabilizing effects. Furthermore, the best performing catalyst was compared and tested under various conditions (LHSV and temperatures) and a 300 h long life run.