The effect of Cu loading on the formation of methyl formate and C2-oxygenates from CH3OH and CO over K- or Cs-promoted Cu-MgO catalysts

The reaction of CH3OH in the presence of CO at 101 kPa over K- or Cs-promoted Cu-MgO is reported. The selectivity to methyl formate was >92 C-atom% whereas selectivity to CO2 and C-2 species (ethanol and acetic acid) was <8 C-atom% at 498 and 523 K over the promoted 5 wt% Cu-MgO catalyst. The activity increased as the Cu loading was increased from 5 wt% to 40 wt%, whereas at the same conversion, the product distribution was almost the same over both the 0.5 wt% Cs-5 wt% Cu-MgO and the 0.5 wt% Cs-40 wt% Cu-MgO catalysts. At approximately constant specific basicity, an increase in Cu-0 surface area of the promoted Cu-MgO catalysts correlated with an increased methyl formate yield, whereas no correlation between Cu2+ surface area and methyl formate yield was observed. The results suggest that methyl formate is formed on Cu-0 sites as opposed to Cu2+ sites. The mechanism of methyl formate formation from CH3OH over the promoted Cu-MgO catalysts is discussed in view of these results. (C) 2011 Elsevier B.V. All rights reserved.