Preparation, characterization, and catalytic performances of a pyrazine dicarboxylate-bridging rare-earth-containing polytungstoarsenate aggregate for selective oxidation of thiophenes and deep desulfurization of model fuels

Abstract

A new polytungstoarsenate, K₆LiH₆[Ce₄(H₂O)₁₄(pzdc)(H₂pzdc)As₃W₂₉O₁₀₃]·22H₂O (1) (H₂pzdc = 2,3-pyrazinedicarboxylic acid), was synthesized via a conventional aqueous solution method. In this synthetic approach, the organic ligand pyrazine dicarboxylate acid was introduced into the arsenotungstate system. The synthesized compound 1 was well characterized using elemental analysis, IR spectroscopy, UV-vis spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. The catalytic activity of compound 1 was tested in acetonitrile to oxidize organosulfur compounds (benzothiophene (BT) and dibenzothiophene (DBT)) with hydrogen peroxide as an oxidant at room temperature. Two substrates were oxidized to their corresponding sulfones with high conversion and selectivity. Taking advantage of this remarkable catalytic move, the 1/H₂O₂/CH₃CN system was further utilized in the oxidation of model fuels (MF) including a mixture of BT and DBT in octane. As a result, the organosulfur compounds in the model fuels were fully converted into their corresponding sulfones. Furthermore, the fluorescence properties of 1 were also investigated.