Fig xA XRD patterns of spent

Based on our previous work, we also examined the effect of different mesoporous supports on CH3OH synthesis activity over Pd–Cu bimetallic catalysts, as summarized in Table 1. The Pd and Cu loadings were fixed at 5.7 wt% and 10 wt%, respectively, in order to compare with Ca-promoted Pd catalysts in our previous work [40]. The formation rate of CH3OH over supported Pd–Cu catalysts decreased in the following order: amorphous silica > SBA-15 ∼ MCM-41 > MSU-F. The amorphous Daunorubicin HCl supported Pd–Cu catalyst showed the highest CH3OH selectivity (31 mol%) among the bimetallic catalysts. It is also worth mentioning segregation the formation rates of CH3OH over Pd–Cu catalysts supported on SBA-15, MCM-41 and MSU-F are greater than the sum of those over corresponding monometallic catalysts. Thus, bimetallic promotion on CH3OH formation is observed for these supported Pd–Cu catalysts as well. XRD patterns (Fig. 5 and Fig. 6) confirm the alloy formation over bimetallic catalysts supported on these uniform mesoporous silicas, which is responsible for such significant synergistic effect on methanol promotion.