Aerobic Oxidation of Formaldehyde Catalyzed by Polyvanadotungstates

Abstract

Three tetra-n-butylammonium (TBA) salts of polyvanadotungstates, [n-Bu4N]6[PW9V3O40] (PW 9 V 3 ), [n-Bu4N]5H2PW8V4O40 (PW 8 V 4 ), and [n-Bu4N]4H5PW6V6O40·20H2O (PW 6 V 6 ), have been synthesized and shown to be effective catalysts for the aerobic oxidation of formaldehyde to formic acid under ambient conditions. These complexes, characterized by elemental analysis, Fourier transform infrared spectroscopy, UV–vis spectroscopy, and thermogravimetric analysis, exhibit a catalytic activity for this reaction comparable to those of other polyoxometalates. Importantly, they are more effective in the presence of water than the metal oxide-supported Pt and/or Au nanoparticles traditionally used as catalysts for formaldehyde oxidation in the gas phase. The polyvanadotungstate-catalyzed oxidation reactions are first-order in formaldehyde, parabolic-order (slow, fast, and slow again) in catalyst, and zero-order in O2. Under optimized conditions, a turnover number of ∼57 has been obtained. These catalysts can be recycled and reused without a significant loss of catalytic activity.

Dioxygen in Polyoxometalate Mediated Reactions

“…Thus, C–H bond cleavage can be thermally initiated or metal catalyzed, leading to radical chain reactions and formation of the corresponding carboxylic acids. Such reactions have been carried out with a variety of polyoxometalates and in a variety of contexts, such as decontamination of air containing formaldehyde to industrial synthesis of methacrylic acid from methacrolein. − The easy oxidation of aldehydes and the possibility of “capturing” peroxo intermediates has led to the use of aldehyde/O 2 combinations for the epoxidation of alkenes. − Similarly the combination of cumene/O 2 can also be used for alkene epoxidation . Another strategy used to aerobically oxidize substrates with polyoxometalates is to reduce the polyoxometalate with a sacrificial donor that is not an aldehyde.…”

Effect of Support on the Activity of Ag-based Catalysts for Formaldehyde Oxidation

“…Formaldehyde (HCHO) is one of the major contaminants for the indoor air pollution and is detrimental to human’s health 1 . Long-term exposure to HCHO can cause irritation in eye, throat 2 , spatial memory deficits 3 , severe allergic reactions 4 and even cancer 5 . Due to the growing concern for this hazard, enormous efforts have been made to remove the indoor HCHO.…”

Diversity of Polyoxometalate‐Based Copper Compounds Obtained from the Same Reaction System

“…In the spectrum of 1 , the three bands at ν̃ ≈ 1060 cm –1 are related to the asymmetric P–O vibrations, and the symmetric and asymmetric M–O stretching bands are observed at ν̃ ≈ 1000–900 (M–O t ), 900–830 (M–O b –M bridges) and 830–715 cm –1 (M–O c –M bridges inside a M 3 O 13 set) …”