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Download fileSolid-State Ion-Exchanged Cu/Mordenite Catalysts for the Direct Conversion of Methane to Methanol
journal contribution
posted on 03.01.2017, 00:00 authored by Ha V. Le, Samira Parishan, Anton Sagaltchik, Caren Göbel, Christopher Schlesiger, Wolfgang Malzer, Annette Trunschke, Reinhard Schomäcker, Arne ThomasThe
selective oxidation of methane to methanol is a highly challenging
target, which is of considerable interest to gain value-added chemicals
directly from fuel gas. Copper-containing zeolites, such as Cu/mordenite,
have been currently reported to be the most efficient catalysts for
this reaction. In this work, it is shown that solid-state ion-exchanged
Cu/mordenites exhibit a significantly higher activity for the partial
oxidation of methane to methanol than comparable reference catalysts,
i.e., Cu/mordenites prepared by the conventional liquid-phase ion
exchange procedure. The efficiency of these Cu/mordenites remained
unchanged over several successive cycles. From temperature-programmed
reduction (TPR) measurements, it can be concluded that the solid-state
protocol accelerates Cu exchange at the small pores of mordenite:
those are positions where the most active Cu species are presumably
located. In situ ultraviolet–visible (UV-vis)
spectroscopy furthermore indicates that different active clusters
including dicopper- and tricopper-oxo complexes are formed in the
catalyst upon oxygen treatment. Notably after activation of methane,
different methoxy intermediates seem to be generated at the Cu sites
from which one is preferably transformed to methanol by reaction with
water. It is furthermore described that the applied reaction conditions
have considerable influence on the finally observed methanol production
from methane.