Synthesis, characterization and catalytic properties of mesoporous HPMo/SiO₂ composite

Abstract

A novel mesoporous HPMo/SiO₂ composite was synthesized by the sol-gel method with triblock copolymer EO₂₀PO₇₀EO₂₀ as template. The properties of the product were characterized by X-ray diffraction, transmission electron microscopy, N₂ adsorption-desorption isotherms, Fourier transform infrared spectrometer and inductively-coupled plasma analysis. The experimental results show that the product has a very ordered hexagonal mesostructure, and the HPMo is immobilized into the framework of silica. The final mesoporous composite shows excellent stability in polar solvents. Results of catalytic tests indicate that the composite is an effective catalyst for oxidation of dibenzothiophen, and there are few activity losses even after the third cycle of uses. The high catalytic activity and good insolubility make it a promising catalyst in oxidative desulfurization process.

Keywords

mesoporous composite / phosphomolybdic acid / catalyst / oxidative desulfurization

References

[1] Okuhara T., Mizuno N., Misono M. Catalytic Chemistry of Heteropoly Compounds[J]. Adv. Catal., 1996, 41: 113-252.

[2] Choi S., Wang Y., Nie Z., . Cs-substituted Tungstophosphoric Acid salt Supported on Mesoporous Silica[J]. Catal. Today, 2000, 55(1): 117-124.

[3] Misono M. Unique Acid Catalysis of Heteropoly Compounds (Heteropolyoxometalates) in the Solid State[J]. Chem. Commun., 2001, 13: 1141-1142.

[4] Cavani F. Heteropolycompound-based Catalysts: A Blend of Acid and Oxidizing Properties[J]. Catal. Today, 1998, 41(1–3): 73-86.

[5] Ding Y., Gao Q., Li G. X., . Selective Expoxidation of Cyclohexene to Cyclohexene Oxide Catalyzed by Keggin-type Heterpoly Compounds Using Anhydrous Urea-hydrogen Peroxide as Oxidizing Reagent and Acetonitrile as the Solvent[J]. J. Mol. Catal. A, 2004, 218(2): 161-170.

[6] Yazu K., Furuya T., Miki K. Immobilized Tungstophosphoric Acid-catalyzed Oxidative Desulfurization Od Diesel Oil with Hydrogen Peroxide[J]. J. Japan Petro. Inst., 2003, 46(6): 379-382.

[7] Kukovecz A., Balogi Z., Konya Z., . Synthesis, Characterisation and Catalytic Applications of Sol-gel Derived Silica-phosphotungstic Acid Composites[J]. Appl. Catal. A., 2002, 228(1–2): 83-94.

[8] Lapkin A., Bozkaya B., Mays T., . Preparation and Characterisation of Chemisorbents Based on Heteropolyacids Supported on Synthetic Mesoporous Carbons and Silica [J]. Catal. Today, 2003, 81(4): 611-621.

[9] Hodjati S., Vaezzadeh K., Petit C., . The Mechanism of the Selective NO_x Sorption on H₃PW₁₂O₄₀ Center dot 6H₂O (HPW) [J]. Topic. Catal., 2001, 16(1–4): 151-155.

[10] Kaleta W., Nowi’nska K. Immobilisation of Heteropoly Anions in Si-MCM-41 Channels by means of Chemical Bonding to Aminosilane Groups [J]. Chem. Commun., 2001, 6: 535-536.

[11] Yan X. M., Lei J. H., Liu D., . Synthesis and Catalytic Properties of Mesoporous Phosphotungstic Acid/SiO₂ in a Self-generated Acidic Environment by Evaporation-induced Self-assembly[J]. Mater. Res. Bull., 2007, 42(11): 1905-1913.

[12] Rao P. M., Wolfson A., Kababya S., . Immobilization of Molecular H₃PW₁₂O₄₀ Heteropolyacid Catalyst in Alumina-grafted Silica-gel and Mesostructured SBA-15 Silica Matrices[J]. J. Catal., 2005, 232(1): 210-225.

[13] Yan X. M., Lei J. H., Liu D., . Oxidation Reactivities of Organic Sulfur Compound in Fuel Oil Using Immobilized Heteropoly Acid as Catalyst[J]. J. Wuhan University of Technology-Mater. Sci. Ed., 2007, 22(2): 320-324.

[14] Yun H. S., Kuwabara M., Zhou H. S., . One-step Synthesis of Mesoporous PWA/SiO₂ Composite Materials Using Triblock Copolymer templates[J]. J. Mater. Sci., 2004, 39(7): 2341-2347.

[15] Shi C. F., Wang R. W., Zhu G. S., . In Situ Synthesis, Characterization of SiPMo-X, and Different Catalytic Properties of SiPMo-X and SiPW-X[J]. Eur. J. Inorg. Chem., 2006, 15: 3054-3060.

[16] Damyanova S., Dimitrov L., Mariscal R., . Immobilization of 12-molybdophosphoric and 12-tungstophosphoric Acids on Metal-substituted Hexagonal Mesoporous Silica[J]. Appl.Catal. A: Gen., 2003, 256(1–2): 183-197.

[17] Huang D., Wang Y. J., Yang L. M., . Chemical Oxidation of Dibenzothiophene with a Directly Combined Amphiphilic Catalyst for Deep Desulfurization [J]. Ind. Eng. Chem. Res., 2006, 45(6): 1880-1885.

[18] Te M., Fairbridge C., Ring Z. Oxidation Reactivities of Dibenzothiophenes in Polyoxometalate/H₂O₂ and Formic Acid/H₂O₂ Systems[J]. Appl. Catal. A: Gen., 2001, 219(1–2): 267-280.

[19] Li C., Gao J. B., Jiang Z. X., . Selective oxidations on Recoverable Catalysts Assembled in Emulsions[J]. Topics in Catal., 2005, 35(1–2): 169-175.

[20] Yang L. N., Li J., Yuan X. D., . One Step non-hydrodesulfurization of Fuel Oil: Catalyzed Oxidation Adsorption Desulfurization Over HPWA-SBA-15[J]. J. Mole. Catal. A: Chem., 2007, 262(1–2): 114-118.