期刊
ACS CATALYSIS
卷 9, 期 1, 页码 365-375出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.8b04437
关键词
Cu-MOR; Methane activation; MAS NMR; De-/Realumination; Methanol
资金
- iCSI (industrial Catalysis Science and Innovation) Center for Research-based Innovation
- Research Council of Norway [237922]
Herein we investigated the activity of copper mordenites in the methane-to-methanol conversion and the material de- and realumination. From four parent materials, a library of copper mordenites was synthesized by liquid- and solid-state ion-exchange techniques. Two key properties govern the activity of these materials in the methane conversion: the parent counterion and the copper ion-exchange procedure. H-form parents result in more active materials. The optimum stoichiometry between silicon, aluminum, and copper leads to a methanol productivity of up to 169 mu mol/g. This equals a stoichiometry of up to 0.47 methanol molecules formed per copper atom. The methanol productivity is constant over up to three cycles. The stability of the mordenite framework was monitored by SEM, EDX, Al-27, and Si-29 MAS NMR spectroscopy. No detectable copper nanoparticles formed. However, a dealumination of the mordenite framework and the formation of extra-framework aluminum (EFAl) species in quantities of up to 12% were observed on H-form copper mordenites. The dealumination is weak or completely inhibited if counterions like Na+ or Cu2+ are present. These ions stabilize the framework aluminum during the reaction steps and upon heat treatments. Notably, the most active materials have significant EFAl contents present.
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