Influences of the Size and Stability of Cu Crystallite on Hydrogenation of Ethyl Acetate for Preparation of Ethanol

Hydrogenation of ethyl acetate (EA) is a promising route for the synthesis of ethanol (EtOH), but the involved catalysts have a series of problems, such as low hydrogenation activity, easy sintering at high temperature, and poor stability. Therefore, it’s necessary to develop catalysts with high catalytic efficiency and stability for the hydrogenation of EA to prepare EtOH. Rare earth elements have abundant energy level structure and unique 4f orbital, and their oxides modified catalysts generally have high adsorption selectivity, excellent thermal stability and other advantages. In this paper, the Cu/SiO₂ catalysts modified by different rare earth elements (Y, La, Ce and Pr) were prepared by co-precipitation method, and characterized by XRD, TEM, BET, H₂-TPR, NH₃-TPD and XPS. The effects of the modifications on Cu/SiO₂ with different rare earth elements (Y, La, Ce and Pr) on the catalytic performances for hydrogenation of EA were investigated in a fixed bed reactor. The experimental results show that the modifications with rare earth elements (Y, La, Ce and Pr) can reduce the crystallite size of copper in the catalyst, thereby accelerating the dispersion of copper active components and increasing the pore size of the catalyst, by which the catalyst is easier to be reduced, and its surface acidity is tunable. As a result, the catalytic activity of the Cu/SiO₂ catalyst for the hydrogenation is significantly increased. Furthermore, Y-modified Cu/SiO₂ catalyst showed the highest hydrogenation activity due to the smallest copper crystallite size, the highest copper dispersion, the largest pore diameter, and the suitable surface acidity and n (Cu⁰)/n (Cu⁰+Cu⁺). Under the reaction conditions of 250 ℃, 2.0 MPa, weight hourly space velocity (WHSV) of 5.0 h⁻¹ and the molar ratio of H₂ to EA of 5.0, the conversion of EA could reach 96.3% with a selectivity of EtOH of 99.1%. Also, Y-modified Cu/SiO₂ catalyst showed excellent stability and resistance to sintering.