Low Levels of Zinc Exchanged into Cu-SSZ-13 Increase Methanol Production in the Partial Oxidation of Methane to Methanol.

Cu-SSZ-13 is currently used industrially for the selective catalytic reduction of nitric oxides and has shown potential for the direct oxidation of methane to methanol. Here, how exchanging a small amount of zinc into Cu-SSZ-13 impacts the methane to methanol activity is reported. Samples containing only zinc are catalytically inactive. By contrast, small levels of zinc (Zn/Al = 0.06 or less) lead to a marked increase in methanol production. In the best case, Cu,Zn-SSZ-13 (Cu/Al = 0.21, Zn/Al = 0.06) has a site time yield (STY) of 26.4 ± 0.42 mmol mol-Cu-h^-1 and specific activity (SA) of 11.5 ± 0.18 μmol g-h^-1. This is over an 80% increase in both STY and SA over Cu-SSZ-13 samples with comparable copper loadings (Cu/Al = 0.2-0.26). A similar, but slightly less significant improvement, is observed for Cu,Zn samples at a copper loading of ≈0.12, where 50% increase in methanol production over just copper samples is observed. Infrared spectroscopy results suggest that the presence of zinc makes the copper more electron-deficient, providing one possible explanation for the increased activity.