Mechanistic Insight into the Formation of Acetic Acid from the Direct Conversion of Methane and Carbon Dioxide on Zinc-Modified H–ZSM-5 Zeolite

Abstract

Methane and carbon dioxide are known greenhouse gases, and the conversion of these two C1-building blocks into useful fuels and chemicals is a subject of great importance. By solid-state NMR spectroscopy, we found that methane and carbon dioxide can be co-converted on a zinc-modified H-ZSM-5 zeolite (denoted as Zn/H-ZSM-5) to form acetic acid at a low temperature range of 523-773 K. Solid-state (13)C and (1)H MAS NMR investigation indicates that the unique nature of the bifunctional Zn/H-ZSM-5 catalyst is responsible for this highly selective transformation. The zinc sites efficiently activate CH4 to form zinc methyl species (-Zn-CH3), the Zn-C bond of which is further subject to the CO2 insertion to produce surface acetate species (-Zn-OOCCH3). Moreover, the Brønsted acid sites play an important role for the final formation of acetic acid by the proton transfer to the surface acetate species. The results disclosed herein may offer the new possibility for the efficient activation and selective transformation of methane at low temperatures through the co-conversion strategy. Also, the mechanistic understanding of this process will help to the rational design of robust catalytic systems for the practical conversion of greenhouse gases into useful chemicals.

Enhanced Catalytic Performance of Zn‐containing HZSM‐5 upon Selective Desilication in Ethane Dehydroaromatization Process

“…Here a clear resonance is observed at a chemical shift of 1.25 ppm for C-ZSM-5-5 %Zn, which has previously been assigned to ZnÀ OH moieties. [48] The peak around 4.8 ppm is rehydrated water, which masks the observation of Brønsted acid sites, typically observed around a chemical shift of 4.2 ppm. The signals between 1.6 and 2.1 ppm can be assigned to silanol groups.…”

Perovskite nanocomposites as effective CO 2 -splitting agents in a cyclic redox scheme

“…Here, acetic acid production was investigated as an example. Direct conversion of methane and CO 2 to acetic acid is thermodynamically unfavorable, albeit being atom-economic ( 44 ). State-of-the-art approach is the syngas route: Coal is first gasified to produce syngas, and then the syngas is cleaned and conditioned to remove excess CO and CO 2 .…”

Across the Board: Gabriele Centi

“…[14] In the presence of carbon dioxide, the zinc methyl species is further transformed to produce surface acetate species (ÀZnÀOOCCH 3 ). Isolated zinc sites in ZSM-5 efficiently activate CH 4 to form zinc methyl species (ÀZnÀCH 3 ) at low temperatures (temperature range of 250-500 8C).…”