Facile solid-state synthesis of Cu–Zn–O catalysts for novel ethanol synthesis from dimethyl ether (DME) and syngas (CO + H2)

The Cux–Zny–O (Cu:Zn = x:y) mixed oxide catalysts with different Cu:Zn atomic ratio were prepared through a new solid-state reaction method. The physicochemical properties of these catalysts were characterized by thermal analysis (TG-DTA), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), N2 adsorption and H2 temperature programmed reduction (H2-TPR). The results showed that with the increase of the molar ratio of Cu:Zn, the crystallite sizes decreased at first and then increased. The smallest crystallite size was realized when the molar ratio of Cu:Zn was 4:6. At the same time, the largest surface area was also obtained at this molar ratio. The catalytic performances of Cux–Zny–O mixed oxide to hydrogenation of methyl acetate were tested using flow-type fixed bed reactor. The conversion of the Cu0.4–Zn0.6–O catalyst to methyl acetate was 72.6%, higher than those of Cux–Zny–O catalysts with other molar ratios. The highest catalytic activity of the Cu0.4–Zn0.6–O catalyst was due to its smaller crystallite size, larger surface area and higher particles dispersion compared with the other samples. Furthermore, Cu0.4–Zn0.6–O catalyst was tested in dual-catalyst-bed reactor to synthesize ethanol from dimethyl ether (DME) and syngas (CO + H2) with the coexisting zeolite catalyst. For comparison, the Cu–Zn–O catalyst prepared by the conventional co-precipitation method was also tested as a reference catalyst. The reaction results showed that the conversion of Cu0.4–Zn0.6–O catalyst to DME was higher than that of Cu–Zn–O catalyst. All in all, both the preparation method and the molar ratio of Cu–Zn are responsible for the catalytic activity of the prepared catalysts.