3.2 Catalytic performance of methanol dehydrogenation in CMNR
The conversion efficiencies of methanol dehydrogenation under the
reaction temperature 340 ℃, the gas flux 8
m3·m-2·h-1 through
the membrane, and only one sheet of membrane of thickness 1 mm, are
shown in Figure 8. It can be seen that Ti membrane substrate is almost
inactive for methanol dehydrogenation. There is a slight increase of
conversion efficiency of methanol after the reactant gas permeating
through the Cu/Ti membrane and ZnO/Ti membrane. On the contrary, the
conversion efficiency of methanol can be increased significantly after
the reactant gas permeating through the Cu/ZnO/Ti CMNR, with its value
being one order of magnitude higher than the Cu/Ti membrane. The higher
conversion efficiency of methanol in the Cu/ZnO/Ti CMNR can be
attributed to several factors. Higher Cu immobilization in Cu/ZnO/Ti
CMNR could increase contact probability between the catalyst and
reactant. Besides, ZnO as Cu carrier can improve the utilization of Cu
atom, promote the dispersion of Cu nanoparticles and more catalysis
active site can be exposed during the process of methanol crack.
Furthermore, Cu and ZnO nanoparticles could synergistic methanol
dehydrogenation34. It has been reported that the
presence of Lewis acid sites on the surface of metal oxides can improve
the first step of methanol dehydrogenation-the formation of
methoxy35. Besides, ZnO also can enhance the spillover
of H atoms, which is attributed to the interaction between methanol and
O anions of ZnO36.