Influence of Vanadium Location in Titania Supported Vanadomolybdophosphoric Acid Catalysts and Its Effect on the Oxidation and Ammoxidation Functionalities
نویسندگان
چکیده
Titania supported vanadomolybdophosphoric acid (VMPA) catalysts with vanadium in different positions, incorporated into the molybdophosphoric acid structure by substituting for molybdenum and cation exchanged on the molybdophosphoric acid surface, were synthesized. The catalysts were characterized by XRD, FT-IR, Raman spectroscopy, TPR, XPS, and ESR techniques. The FT-IR and Raman spectral analyses confirm that the molybdophosphoric acid is present with the Keggin ion structure during modifications. The incorporation of vanadium into the primary or secondary structures of the Keggin heteropoly acid was confirmed by ESR, Raman, and XPS analysis. These catalysts were investigated for the vapor phase ammoxidation of 2-methyl pyrazine and methanol oxidation. The specific location of vanadium in the 12-molybdophosphoric acid was found to affect the catalytic redox performance. The catalyst with vanadium present in the primary structure of the Keggin ion possesses enhanced catalytic redox activity and selectivity compared to when vanadium is present on the Keggin surface for both the ammoxidation and oxidation reactions.
منابع مشابه
Vanadium Oxide Supported on Al-modified Titania Nanotubes for Oxidative Dehydrogenation of Propane
In this study, characterization of vanadia supported on Al-modified titania nanotubes (TiNTs) synthesized by the alkaline hydrothermal treatment of TiO2 powders has been reported. A promising catalyst for oxidative dehydrogenation (ODH) of propane was prepared via the incipient wetness impregnation method. The morphology and crystalline structure of TiNTs were characterized by transmission elec...
متن کاملSelective Liquid Phase Ammoxidation of Aromatic Aldehydes to Aromatic Nitriles with VPO Titania Heterogeneous Catalysts in Air
Preparation of 2-Chlorobenzonitrile, and benzonitrile are reported here from the corresponding 2-Chlorobenzaldehyde and benzaldehyde by the reaction of ammonium hydroxide/VPO titania, VPO bulk (...
متن کاملCatalytic Oxidation of 4-Methylpyridine on Modified Vanadium Oxide Catalysts
The reaction of gas-phase oxidation of 4-methylpyridine on individual V2O5, binary and ternary vanadium-oxide catalysts was studied. These catalysts were modified by additives of SnO2 and TiO2. It was found that modifying V2O5 leads to increase the activity of binary contacts. Upon transition from binary V2O5<...
متن کاملThe Selective Catalytic Reduction of NOx with NH3 over Titania Supported Rhenium Oxide Catalysts
Titania supported vanadium oxide catalysts have been demonstrated to be very efficient catalysts for the selective reduction of NOx with NH3 and have found widespread industrial application for the control of NOx emissions from stationary sources (1). Characterization studies have demonstrated that supported vanadium oxide catalysts consist of a two-dimensional metal oxide overlayer on the oxid...
متن کاملDirect oxidation of benzene to phenol in liquid phase by H2O2 over vanadium catalyst supported on highly ordered nanoporous silica
Vanadium supported on highly ordered nanoporous silica (VOx-LUS-1) was synthesized and characterized by XRD, Nitrogen adsorption‑desorption isotherms and UV-visible spectrophotometer. Direct oxidation of benzene to phenol in liquid phase by H2O2 peroxide were examined by using various solvents (methanol, acetone, acetic acid, acetonitryl). The maximum yield (25%) and selectivity (73%) of the ph...
متن کامل