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
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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