Doped Keggin heteropolyacids as catalysts in sulfide oxidation

Abstract

In this research, we report the preparation of doped PMo Keggin heteropolyacids where Mo is partially replaced by V, Bi, and Bi-V. These catalysts were characterized by means of ICP-AES analysis, 31 P-NMR, UV-visible spectra, FT-IR spectra, thermal analysis, and textural properties. In addition, the activities of the synthesized catalysts were evaluated in the selective oxidation of sulfides to sulfoxides/sulfones. The incorporation of V, Bi and Bi-V into the structure of H 3 PMo 12 O 40 increases the catalytic activity. The two most active catalysts, those with V and V-Bi were supported on aminopropyl-functionalized silica (SiO 2 NH 2 ) and they were found to be and efficient heterogeneous catalysts for the selective oxidation of diphenylsulfide to the corresponding sulfoxide/sulfone.

Doped Keggin Heteropolyacids as Catalyst in the Solvent-free, Multicomponent Synthesis of Substituted 3,4-dihydropyrimidin-2-(1H)-ones

“…The results obtained by 31 P-MAS-NMR and FT-IR are coincident with the ones reported in the literature [14]. N 2 adsorption tests were used to make a textural characterization.…”

“…These catalysts were well characterized by means of 31 P-NMR, FT-IR spectra, textural properties and potentiometric titration. Mo, V and Bi amounts were estimated by ICP-AES analysis, and their properties are coincident with the ones previously reported by us [14].…”

“…They were prepared by the hydrothermal synthesis method [14]. The following heteropolyacids HPA synthesis procedure was used: a stoichiometric mixture of MoO 3 , the corresponding metal oxide and H 3 PO 4 (85% (w/v)) was suspended in 120 mL of distilled water.…”

“…In order to interpret the results, it is suggested that the initial electrode potential (E) indicates the maximum acid strength of the surface sites, and the values (meq/g solid) where the plateau is reached indicate the total number of acid sites. The acid strength of surface sites can be assigned according to the following ranges: very strong site, E > 100 mV; strong site, 0 < E < 100 mV; weak site, 100 < E < 0 mV, and very weak site, E < 100 mV [14].…”

“…Vanadium incorporated molybdophosphoric acid (PMoV) shows unique catalytic features for oxidations due to its bifunctional character, which arises because of the redox nature of vanadium and the oxidation/acidic character of the molybdophosphoric acid catalysts by replacing Mo atoms with the corresponding V atoms [14]. Several reactions have been studied including hydroxylation of benzene, oxidation of toluene, and norbornene using aqueous hydrogen peroxide [15], oxidation of benzoins to benzyls [16], and liquid-phase oxidation of methane with hydrogen peroxide [17].…”