Heterogeneous Catalysts SILP with Phosphotungstic Acid for Oxidative Desulfurization: Effect of Ionic Liquid
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rogeneous Catalysts SILP with Phosphotungstic Acid for Oxidative Desulfurization: Effect of Ionic Liquid A. A. Bryzhina, A. K. Buryakb, M. G. Gantmanc, V. M. Zelikmana, M. I. Shilinaa, and I. G. Tarkhanovaa, * aDepartment
of Chemistry, Moscow State University, Moscow, 119991 Russia Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, 119071 Russia cHelmholtz Institut Erlangen-Nürnberg for Renewable Energy, Erlangen, 91058 Germany *e-mail: [email protected]
b
Received November 7, 2019; revised January 28, 2020; accepted March 6, 2020
Abstract—SILP (supporting ionic liquid phase) catalysts for peroxide thiophene oxidation were obtained on silica gel, they included imidazole cations with sulfonic acid group and phosphotungstate anions. The composition of the active phase and the surface structure of the catalysts are characterized by a set of modern physicochemical methods, including mass spectrometry using the SALDI technique. It was found that the organic cation structure affects the stability of heteropolyanions, decomposition processes in the SILP and the catalytic properties of the samples. SILP catalysts are effective in desulfurization of the diesel fraction and provide fuel with an S content of less than 10 ppm. Keywords: thiophene oxidation, hydrogen peroxide, phosphotungstic heteropolyacid, SILP catalysts, diesel desulfurization DOI: 10.1134/S0023158420050018
INTRODUCTION Heteropolyacids (HPAs) and polyoxometallate compounds based on them are widely used in combination with ionic liquids (ILs) to create catalytically active hybrid materials. Due to their high acidity, oxidation potential, and compatibility with green oxidants, such as oxygen and hydrogen peroxide, these kinds of compositions are effectively used in a number of oxidative processes [1], including the desulfurization of petroleum [2–4]. Desulfurization is an important process in the oil refining industry, which is aimed at obtaining fuel that meets modern environmental standards (total sulfur content of less than 10 ppm) [5]. The problem of petroleum processing is directly related to the removal of heteroatomic compounds that have a negative impact on the environment, corrode equipment, and etch expensive catalysts. The traditional method of Abbreviations: HPA, heteropolyacid; IL, ionic liquid; ODS, oxidative desulfurization; ZI, Zwitterionic compound; PTA, phosphotungstic heteropolyacid; SALDI, surface-assisted laser desorption/ionization; NMR, nuclear magnetic resonance; TPD NH3, temperature programmed desorption of ammonia; SEM, scanning electron microscopy; SEI, secondary electron imaging; GLC, gas–liquid chromatography; DMF, dimethylformamide; BJH, Barrett–Joyner–Halenda method; BET, Brunauer–Emmett–Teller method.
fuel purification from sulfur-containing compounds, i.e., hydrodesulfurization (HDS), requires high temperature, pressure, and high hydrogen consumption [6]. The HDS process is effective for removal of thiols, sulfides, and thiophene, but to remove heterocyclic compounds, for examp
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