Abstract
Rare earth element (Ce, Y, and La) modified Cu/SiO2 catalysts via hydrolysis precipitation and impregnation method were fabricated for the vapor-phase hydrogenation of methyl acetate to ethanol. LaOx showed the most pronounced promotion in the catalytic tests. After detailed characterizations, via N2 adsorption–desorption, XRD, N2O chemisorption, FTIR, H2-TPR, H2-TPD, TEM, XPS, and TG/DTA, we found that the addition of promoter LaOx can decrease the particle size while in turn, it can increase the dispersion of copper species. The strong interactions between copper and lanthanum atoms alter the surface chemical states of the copper species. This results in the generation of more Cu+ species and high SCu+ values, which are responsible for the excellent activity and stability during hydrogenation. In addition, the content of additive LaOx and reaction conditions (reaction temperature and LHSV) were optimized. Then, the long-term stability performance was evaluated over the selected catalyst in contrast with Cu/SiO2.
Highlights
As a renewable and sustainable energy source, ethanol has been widely used as a solvent and disinfectant; it acts as an alternative fuel for vehicles
The 5% Ladoped Cu/SiO2 catalyst shows the maximum value of space time yield of ethanol (STY) (1.04 gEtOH gcatÀ1 hÀ1), further increasing the La content to 10%, which decreases to 0.96 gEtOH gcatÀ1 hÀ1 be due to partial covering of the active sites.[30]
The strong interaction between Cu and La might be derived from their close proximity, which would retard the transformation of Cu2+ to Cu0 to some extent.[36]
Summary
As a renewable and sustainable energy source, ethanol has been widely used as a solvent and disinfectant; it acts as an alternative fuel for vehicles. The Cu0 active sites are bene cial for activation of H2 molecules, while Cu+ species could adsorb and activate the C]O groups in MA The latter is believed to be the rate controlling step.[22,23] In previous studies, it has been shown that adding a second metal such as Zn, Ni, B, In, Ag, Mn, or Mg to the Cu/SiO2 catalyst could improve the catalytic activity.[17,24,25,26,27,28,29] The promotion is attributed to the enhancement in copper species dispersion and the appropriate Cu+/(Cu+ + Cu0) ratio on the surface of the catalyst. The structure– activity relationship of La-doped Cu/SiO2 catalyst and the deactivation analysis of Cu/SiO2 catalyst were investigated
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