Effect of oxomolybdate species dispersion on direct methanol oxidation to dimethoxymethane over MoO_x/TiO₂ catalysts

Abstract

The one-step selective oxidation of methanol to dimethoxymethane (DMM) was demonstrated over titania-supported molybdenum oxide catalysts, containing different amounts of molybdenum and prepared using two different impregnation techniques, namely wet impregnation and incipient wetness impregnation. The corresponding catalysts exhibited both acidic and redox properties, which are necessary for the oxidation of methanol to formaldehyde with subsequent condensation of the latter with excess methanol to finally yield DMM. The formation of well-dispersed polyoxomolybdate species on the catalyst surface was evidenced using IR-Raman, X-ray diffraction, and nitrogen physisorption. Varying the amount of these polyoxomolydate species was associated with a modulation of the acidic and redox properties, as shown by NH 3 -TPD and H 2 -TPR. With respect to the catalytic performances, the best balance between acid and redox properties was observed over the samples containing 8 wt.% Mo, which corresponds to a theoretical MoO x species coverage close to a monolayer.

Ultradispersed Mo/TiO2catalysts for CO2hydrogenation to methanol

“…42 Non-precious catalysts containing Mo-based species supported on TiO 2 (MoO x /TiO 2 , MoS 2 /TiO 2 , etc.) are well-known for photocatalysis, 43 as well as thermocatalytic oxidation 44,45 and hydrodesulfurization [46][47][48] reactions. When CO and CO 2 hydrogenation reactions were carried out over Mo/TiO 2 , [49][50][51] this system was found inefficient.…”

Photocatalytic Production of Methyl Formate by Methanol Self-Coupling: From Oxidative Dehydrogenation to Direct Dehydrogenation

“…However, traditional downstream demand, mainly of formaldehyde, dimethyl ether, and methyl tert -butyl ether (MTBE), is sluggish, and urgent requirements have been put forward for the conversion of methanol into higher value-added oils and chemicals. Conversion methods include methanol to light olefins (MTO), methanol carbonylation to produce acetic acid, MF, and dimethyl carbonate, , methanol oxidation to produce methylal , and MF, − etc. Of these, MF is a chemical intermediate of great application value, which can be used to produce formic acid, formamide, ethylene glycol, etc.…”

Biomass-derived Platform Molecules Upgrading through Catalytic Processes: Yielding Chemicals and Fuels

“…Note that, over MoOx/TiO2 model systems, we highlighted the beneficial effect of an adequate balance between redox and acid properties of the catalysts on activity, and showed that it was realized for a MoOx species quasi-monolayer 20) . This reaction has driven much attention in the recent years, and a variety of heterogeneous catalytic systems were applied, such as molybdenum-based catalysts 21) 24) heteropolyacids (HPAs) 25), 26) , vanadium-based catalysts 27) 31) , oxides of ruthenium 32) and of rhenium 33) 37) .…”