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Effect on the structure and morphology of vanadium phosphates of the addition of alkanes during the alcoholreduction of VOPO4·2H2O

Sithamparappillai, Umacaran, Nuno, Jesus Luque, Dummer, Nicholas, Weng, Weihao, Kiely, Christopher John, Bartley, Jonathan Keith and Hutchings, Graham John 2010. Effect on the structure and morphology of vanadium phosphates of the addition of alkanes during the alcoholreduction of VOPO4·2H2O. Journal of Materials Chemistry 20 (25) , pp. 5310-5318. 10.1039/c0jm00403k

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Abstract

Vanadium phosphatecatalysts were prepared by the reduction of VOPO4·2H2O with an alcohol and characterised using a combination of powder XRD, BET surface area measurement, scanning electron microscopy and transmission electron microscopy. The effect of the addition of an alkane co-solvent during the reflux stage of the preparation was investigated. The addition of C4–C16n-alkanes was observed to affect the structure of the vanadium phosphate products significantly. Without the alkane the product is VOHPO4·0.5H2O which is the precursor to the industrial catalyst. Addition of the alkane leads to the formation of VO(H2PO4)2, with its characteristic block-shaped crystallites, and the alkane/alcohol liquid phase solubilises the excess vanadium. The amount of alkane required to induce these changes decreased with increasing carbon number of the n-alkane. The effect of the addition of the alkane co-solvent is thought to effect the rate of reduction of V5+ to V4+ which then reacts with phosphoric acid to give either VOHPO4·0.5H2O or VO(H2PO4)2. If the reduction step is fast then the local P : V4+ ratio is approximately 1 and VOHPO4·0.5H2O is the major product. However, if the reduction step is slow then the local P : V4+ ratio is much higher and VO(H2PO4)2 is preferentially formed.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Subjects: Q Science > QD Chemistry
Publisher: Royal Society of Chemistry
ISSN: 0959-9428
Last Modified: 02 Jun 2019 22:39
URI: http://orca.cf.ac.uk/id/eprint/6853

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