(708d) Partial Oxidation of Methane to Methanol over the Small-Pore Zeolite Cu-SSZ-39

The direct conversion of methane to methanol using molecular oxidant is a grand challenge in the chemical sciences. Many catalytic materials have been investigated for this reaction.¹ Copper-containing zeolites have emerged as one promising class of materials.² Here we describe our efforts in using Cu-SSZ-39 for this chemistry and show that it is very promising material for this reaction and much more active in our hands than the small-pore zeolite Cu-SSZ-13³ under similar conditions.

Initial testing at 225°C showed that copper-containing zeolite SSZ-39 showed superior activity to the current zeolite literature benchmark catalyst for methane partial oxidation, Cu-SSZ-13. We have focused on 1) mapping out the catalytic behavior of this material over a range of operating conditions and metal loadings, and 2) understanding whether there are multiple types of active sites in this material. Figure 1 shows one such suite of data – the site time yield of the Cu-SSZ-39 as a function of copper content in the zeolite. A clear maximum in methanol productivity, both in terms of a mass catalyst basis and copper basis is observed at a Cu/Al ~ 0.2. We should note that this site time yield significantly exceeds our prior work with Cu-SSZ-13³. We have also mapped out the reactivity and catalyst selectivity as a function of reaction temperature. This, and results of experiments in the absence of O₂ analogous to prior work with SSZ-13 will also be reported.

References

1. Gesser, H. D.; Hunter, N. R.; Prakash, C. B., Chem. Rev. 1985, 85 (4), 235-244.
2. Tomkins, P.; Ranocchiari, M.; van Bokhoven, J. A., Accounts of Chemical Research 2017, 50 (2), 418-425.
3. Koishybay, A.; Shantz, D. F., J. Am. Chem. Soc. 2020, 142 (28), 11962-11966.