High-Visible-Light Photoactivity of Plasma-Promoted Vanadium Clusters on Nanozeolites for Partial Photooxidation of Methanol

Abstract

Cold VCl-plasma is employed for the preparation of highly dispersed vanadium oxide clusters on nanosized zeolite. Different types of zeolites, such as EMT, FAU (z.X), and Beta, are used. The activity of the prepared catalysts is studied in the selective photooxidation of methanol under polychromatic visible and UV irradiations. The physicochemical properties and catalytic performance of plasma-treated zeolite Beta (P-VO@Beta) catalyst is compared with zeolite Beta (VO@Beta) and amorphous silica (VO@SiO) impregnated vanadium oxide catalysts. Pure VO is used as a reference material. The set of catalytic data shows that plasma-prepared zeolite Beta based catalyst displays the highest activity. Complementary characterization techniques including XRD, N-sorption, FTIR, ionic exchange, pyridine adsorption, Raman, NMR, TPR, and EDX-TEM are used to study the impact of the preparation approach on the physicochemical properties and catalytic performance of photocatalysts.

Photocatalytic Methanol Oxidation by Supported Vanadium Oxide Species: Influence of Support and Degree of Oligomerization

“…In any case, it is interesting to note that the high selectivity to formaldehyde is lost when extended vanadia structures such as V 2 O 5 nanoparticles are additionally present. This is in line with the observation of different products in the work of El‐Roz et al Since the exact state of hydration is not known under reaction conditions, we cannot unambiguously comment on a potential activity of hydrated monomers and dimers. Wavelengths longer than 320 nm are still sufficiently energetic to excite charge carriers in those species (absorption at about 410 to 440 nm).…”

“…The V 2 O 5 NPs, however, were inactive in the photocatalytic reaction, in spite of their ability to function as catalysts in the conventional process at elevated temperature. This is in line with the observation by El‐Roz et al that amorphous VO x clusters are beneficial for the methanol oxidation reaction . In both previous studies, the support was always silica‐based (bulk SiO 2 , mesoporous SiO 2 , or zeolites).…”

“…In two publications,, it was demonstrated that supported vanadium oxide species on silica, dehydrated before the measurement, are also able to photocatalytically convert methanol to formaldehyde and other products, such as dimethoxymethane or dimethyl ether. It was found that the isolated surface VO 4 species catalyze the selective formation of formaldehyde both thermally and light‐induced, but formaldehyde desorption was rate‐limiting in the photocatalytic process .…”

Proof of Equivalent Catalytic Functionality upon Photon‐Induced and Thermal Activation of Supported Isolated Vanadia Species in Methanol Oxidation

“…Previously, El‐Roz et al . showed that photocatalytic methanol oxidation was in principle feasible with vanadium oxide moieties supported on silica and on zeolites.…”

Ag-Based Catalysts in Heterogeneous Selective Oxidation of Alcohols: A Review

“…Other recently mentioned substrates are methanol, being selectively photooxidized on Au/WO 3 [176], Au-and/or Ag-modified TiO 2 [177], Ag-modified TiO 2 and SiO 2 [178], vanadia systems [179], 2-propanol, with a study featuring Au/TiO 2 [180]. A few other works discuss the same process for carbohydrates like glucose in the presence of Fe 3+ ions on TiO 2 [181] or undoped sol-gel TiO 2 [182].…”