Selective Autooxidation of Ethanol over Titania‐Supported Molybdenum Oxide Catalysts: Structure and Reactivity

Abstract

We study the selective catalytic oxidation of ethanol with air as a sustainable alternative route to acetaldehyde. The reaction is catalysed by molybdenum oxide supported on titania, in a flow reactor under ambient pressure. High selectivity to acetaldehyde (70%–89%, depending on the Mo loading) is obtained at 150 °C. Subsequently, we investigate the structure/performance relationship for various molybdenum oxide species using a combination of techniques including diffuse reflectance UV-visible, infrared, X-ray photoelectron spectroscopies, X-ray diffraction and temperature programmed reduction. As their surface density increases, the monomeric molybdenum oxide species undergo two-dimensional and three-dimensional oligomerisation. This results in polymolybdates and molybdenum oxide crystallites. Importantly, the ethanol oxidation rate depends not only on the overall molybdenum loading and dispersion, but also on the type of molybdenum oxide species prevalent at each surface density and on the domain size. As the molybdenum oxide oligomerisation increases, electron delocalisation becomes easier. This lowers the absorption edge energy and increases the reaction rate.

A simple synthesis of symmetric phthalocyanines and their respective perfluoro and transition‐metal complexes

“…As part of our ongoing research into selective oxidation with molecular oxygen, we tried building synthetic porphyrin analogues that could serve as good single‐atom catalysts in vitro . For this, we turned to phthalocyanines (Pcs), which are highly stable two‐dimensional macrocycles with a structure analogous to that of porphyrins (Scheme ).…”

Highly Selective Copper Catalyst Supported on Mesoporous Carbon for the Dehydrogenation of Ethanol to Acetaldehyde

“…6–12 In particular, acetaldehyde, a significant bulk chemical, is valuable for the production of peracetic acid, pentaerythritol, pyridine bases, butanediol, and trichloroacetic aldehyde, with a worldwide production over 10 6 tons per year 13. 14…”

Investigation of a molybdenum-containing silica catalyst synthesized by the sol–gel process in heterogeneous catalytic esterification reactions using methanol and ethanol

“…Molybdenum oxides were immobilized on different supports like benzimidazole-functionalized dendrons [14], alumina [15,16], titania [17], zirconia [18], and silica [19,20], for use as catalyst in different process; e.g., catalytic oxidation of ethanol with air, esterification of acetic acid with n-butanol and ethanol, transesterification of sunflower oil with methanol, and transesterification of dimethyl oxalate (DMO) with phenol.…”