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Influence of the reaction conditions on the synthesis of vanadium phosphate catalyst for butane oxidation to maleic anhydride

Sithamparappillai, Umacaran 2008. Influence of the reaction conditions on the synthesis of vanadium phosphate catalyst for butane oxidation to maleic anhydride. PhD Thesis, Cardiff University.

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Abstract

Vanadium phosphate catalysts prepared by the reduction of VOPO4.2H2O with 1-butanol are described and discussed. In particular, the effect of the addition of an alkane during the reflux stage of the preparation has been investigated. The materials were characterised using a combination of powder XRD, BET surface area measurement, laser Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The addition of C(, - Ci 6 w-alkanes was studied and has been observed to significantly affect both the morphology and the structure of the vanadium phosphates. In the absence of an alkane VOPO42H2O is reduced to VOHPO4O 5H2O with rosette morphology. Addition of low amounts of alkanes leads to a change in the crystallite morphology and platelet crystallites are preferentially formed. Decreasing the alcohol concentration further leads to the formation of VO(H2PC4)2, with its characteristic block-shaped crystallites. The amount of alkane required to induce these changes decreased with increasing carbon number of the n-alkane. Furthermore, the different concentration of the alcohol results in a different reduction rate of V5+ to V4+ which changes the V: P ratio of the prepared materials. Therefore, different materials were obtained with respect to V: P ratio. Evaluation of the materials as catalysts for the oxidation of butane to maleic anhydride shows that the materials exhibit their characteristic activities and selectivities for this reaction. A new synthesis route has been developed to prepare (VO)2P2C7 directly from VOPO42H2O using a reducing environment. Hydrogen (5% H2/Argon 50 ml // min) was used for this transformation for 72 hours at temperature 550 C. The specific activity of these materials is higher than the conventional catalysts due to the low surface area.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
ISBN: 9781303183171
Date of First Compliant Deposit: 30 March 2016
Last Modified: 12 Feb 2016 23:14
URI: http://orca.cf.ac.uk/id/eprint/55746

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