Influence of Rare-Earth and Bimetallic Promoters on Various VPO Catalysts for Partial Oxidation of n-Butane

Abstract

Vanadium phosphorous oxide (VPO) catalyst was prepared using dihydrate method and tested for the potential use in selective oxidation of n-butane to maleic anhydride. The catalysts were doped by La, Ce and combined components Ce + Co and Ce + Bi through impregnation. The effect of promoters on catalyst morphology and the development of acid and redox sites were studied through XRD, BET, SEM, H₂-TPR and TPRn reaction of n-butane/He. Addition of rare-earth element to VPO formulation and drying of catalyst precursor by microwave irradiation increased the fall width at half maximum (FWHM) and reduced the crystallite size of the Vanadyl hydrogen phosphate hemihydrate (VOHPO₄ · 1/2 H₂O, VHP) precursor phase and thus led to the production of final catalysts with larger surface area. The Ce doped VPO catalyst which, assisted by the microwave heating method, exhibited the highest surface area. Moreover, the addition of promoters significantly increased catalyst activity and selectivity as compared to undoped VPO catalyst in the oxidation reaction of n-butane. The H₂-TPR and TPRn reaction profiles showed that the highest amount of active oxygen species, i.e., the V4+-O- pair, was removed from the bimetallic (Ce + Bi) promoted catalyst. This pair is responsible for n-butane activation. Furthermore, based on catalytic test results, it was demonstrated that the catalyst promoted with Ce and Bi (VPOD1) was the most active and selective catalyst among the produced catalysts with 52% reaction yield. This suggests that the rare earth metal promoted vanadium phosphate catalyst is a promising method to improve the catalytic properties of VPO for the partial oxidation of n-butane to maleic anhydride.

Department(s)

Chemical and Biochemical Engineering

Keywords and Phrases

Active Oxygen Species; Bimetallic Promoter; Catalyst Morphology; Catalyst Precursors; Catalytic Properties; Catalytic Tests; Dihydrate; Effect of Promoters; n-Butane; n-Butane Oxidation; Oxidation Reactions; Partial Oxidations; Precursor Phase; Promoted Catalysts; Rare Earth Metals; Rare-Earth Dopant; Reaction Profile; Reaction Yields; Redox Sites; Selective Catalysts; Selective Oxidation of n-Butane; SEM; Surface Area; Temperature Programmed Reaction; Vanadium Phosphate Catalysts; Vanadium Phosphorous Oxide; Vanadyl Hydrogen Phosphate Hemihydrate; VPO Catalyst; XRD; Butane; Catalysis; Catalyst Activity; Catalytic Oxidation; Cerium; Cerium Compounds; Crystallite Size; Doping (Additives); Hydrogen; Ionization of Gases; Irradiation; Liquefied Petroleum Gas; Maleic Anhydride; Microwave Irradiation; Oxidation; Oxygen; Phosphorus; Rare Earths; Reaction Kinetics; Vanadium; Vanadium Alloys; Vanadium Compounds; Catalyst Selectivity

International Standard Serial Number (ISSN)

1011-372X; 1572-879X

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2009 Springer Verlag, All rights reserved.

Publication Date

01 Jul 2009

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