| Studies of the hydrogenation of acetic acid to produce bio-fuel and chemicals such as ethanol and ethyl acetate are increasingly popular in recent years. Many studies have showed that noble metal catalysts are efficient for acetic acid hydrogenation, but fewer non-noble metal catalysts were studied.In this paper, a series of non-noble metal catalysts were prepared with incipient-wetness impregnation method using Cu(NO3)2·3H2O, Zn(NO3)2·6H2O and Fe(NO3)2-9H2O as metal precursors and SiO2 as support for the acetic acid hydrogenation reaction. Cu-Fe/SiO2 bimetallic catalyst exhibited the best hydrogenation performance among all the prepared catalysts in acetic acid hydrogenation reaction. Based on this result, the effects of Fe/Cu mass ratio and metal loading of Cu-Fe/SiO2 bimetallic catalysts on acetic acid hydrogenation were investigated, and the 15%Cu-15%Fe/SiO2 catalyst showed the best catalytic performance. The effects of reaction temperature, reaction pressure, H2/acid molar ratio and acetic acid liquid hourly space velocity on catalytic performance of the Cu-Fe bimetallic catalysts were further studied, showing that high reaction temperature, reaction pressure, H2/acid molar ratio and low acetic acid liquid hourly space velocity facilitated the hydrogenation performance. Besides, the study on the support indicated that SiO2 is a better choice as the support of Cu-Fe bimetallic catalyst. The 15% Cu-15%Fe/SiO2 catalyst showed the excellent stability for acetic acid hydrogenation through 42 hours continuous reaction test.Catalysts under different conditions were characterized by XRD, TEM, H2-TPR and XPS. The reaction mechanism of acetic acid hydrogenation over the Cu-Fe/SiO2 catalyst was proposed combined with the characterization and reaction results:the oxygen vacancies of iron oxides provide the active sites for acetic acid adsorption and reaction, while Cu0 activates the hydrogen and supplies H atoms to the active sites through the hydrogen spillover. |
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