Behavior of Molybdenum–Vanadium Mixed Oxides in Selective Oxidation and Disproportionation of Toluene

Abstract

This study deals with the behavior of molybdenum–vanadium (Mo/V) mixed oxides catalysts in both disproportionation and selective oxidation of toluene. Samples containing different Mo/V ratios were prepared by a modified method using tetradecyltrimethylammonium bromide and acetic acid. The catalysts were characterized using several techniques: nitrogen adsorption–desorption isotherms, X-Ray diffraction (XRD), ammonia temperature-programmed desorption (TPD-NH3), temperature-programmed reduction by hydrogen (H2-TPR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier-transform infrared-spectroscopy (FTIR) and ultraviolet-visible spectroscopies (UV–VIS). The XRD results evidenced the presence of orthorhombic α-MoO3 and V2O5 phases, as well as monoclinic β-MoO3 and V2MoO8 phases, their abundance depending on the Mo to V ratio, while the TPD-NH3 emphasized that, the total amount of the acid sites diminished with the increase of the Mo loading. The TPR investigations indicated that the samples with higher Mo/V ratio possess a higher reducibility. The main findings of this study led to the conclusion that the presence of strong acid sites afforded a high conversion in toluene disproportionation (Mo/V = 1), while a higher reducibility is a prerequisite to accomplishing high conversion in toluene oxidation (Mo/V = 2). The catalyst with Mo/V = 1 acquires the best yield to xylenes from the toluene disproportionation reaction, while the catalyst with Mo/V = 0.33 presents the highest yield to benzaldehyde.

Electrophoretic Codeposition of MoOx/MoS2 Thin Film for Platinum-Free Counter Electrode in Quantum Dot Solar Cells

“…The molybdenum oxide appeared to be a mixture of MoO 2 and MoO 3 . As observed in the XRD spectrum, besides the peaks of FTO, there are some other peaks which may belong to MoO 2 as the reduction-decomposition product of the heptamolybdate salt [68] and MoO 3 as the calcination products at 350 °C [69,70]. More specifically, the peaks at 2θ = 9:0, Next, the surface morphology and composition of MoO x /MoS 2 thin film deposited at 25 V in 10 minutes were analyzed by field emission scanning electron microscope with Oxford Energy-dispersive X-ray Spectrometer (FE-SEM/EDS).…”

Increased Photoelectrochemical Performance of Vanadium Oxide Thin Film by Helium Plasma Treatment with Auxiliary Molybdenum Deposition

“…One of the strategies taken to improve the performance of vanadium oxides is a mixture with other semiconductors including bismuth vanadate () [ 49,50 ] and molybdenum trioxide (). [ 51–53 ] Arunachalam et al showed that the incident photon to current efficiency improved more than 50% at the wavelength of 425 nm by forming a heterostructure of , [ 49 ] and Chuai et al showed that composite exhibited enhanced visible‐light photocatalytic activity because of the formation of heterostructures at the interface between and . [ 51 ]…”

Preparation of a Nanorod-like Mo-VOx Catalyst for Gas Phase Selective Oxidation of Methyl Lactate with Air

“…Multicomponent interaction , and morphology regulation , are practiced as effective manipulations to elevate the surface active site density and, in turn, the activation capability. Molybdenum has been widely selected as the active component in the oxidation reaction, − and the higher performance at lower temperature is expected as promising with higher selectivity of the product. In a recent study of catalyst screening for EL to EP, Huchede et al reported that among selected V- or Mo-containing catalysts, MoO 3 exhibited the best yield of EP, which was 63% at 300 °C with 78% EL conversion.…”

“…As is generally accepted, the constitution and distribution of active components are crucial to the catalytic performance of oxide-based catalysts. 31,32,36 Notably, the MoV 2 O 8 phase has been reported as a remarkably active phase (approximately 3.5 times than the separate V 2 O 5 or MoO 3 ) in glycerol ODH reaction resulting from the valance state cycling of contained V active species and related dynamic formation of oxygen vacancies. 35 Temperature-Programmed Analysis.…”