Methane Conversion to Methanol on Copper Containing Small Pore Zeolites

Meeting Program – February 2015

Bahar Ipek
Department of Chemical and Biomolecular Engineering
University of Delaware

Bahar Ipek
Abstract
Methanotrophic bacteria containing particular methane monooxygenase (pMMO), a Cu-containing enzyme, or soluble methane monooxygenase (sMMO), an iron-metalloenzyme can oxidize methane to methanol selectively at ambient conditions 1. The zeolite Cu-ZSM-5 was reported to activate the methane C-H bond—with a homolytic bond dissociation energy of 104 kcal/mol— at temperatures as low as 120 °C 2 after pretreatment in O2 3. The reactive copper species are believed to contain extra-lattice oxygen, and in the case of Cu-ZSM-5, to be a mono-μ-oxo-dicopper complex ([Cu—O—Cu]2+) 4. Although a correlation was found between the concentration of mono-μ-oxo-dicopper species and the amount of methanol produced by Cu-ZSM-5 5, no such correlation was found for other zeolites that produce methanol such as Cu-mordenite and Cu-ferrierite 2. We have recently showed methanol production on copper (II) exchanged small pore zeolites including SSZ-13 (CHA), SSZ-16 (AFX) and SSZ-39 (AEI) with yields as high as 39 μmol CH3OH/g and CH3OH/Cu ratios up to 0.09 (the largest reported to date).6 Here, copper species in these small pore zeolites were investigated with UV–vis and Raman spectroscopy after O2-treatment at a temperature of 450 °C. No evidence of mono-μ-oxo-dicopper species was found in the spectra of Cu-SSZ-13,Cu-SSZ-16 and Cu-SSZ-39 6, however Cu—Oextralattice vibrations at 574 cm-1 were detected in Raman spectra of Cu-SSZ-13 and Cu-SSZ-39 zeolites which is indicative of a different CuxOy active species responsible for methanol production in small pore zeolites.

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