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Vanadium Phosphate Oxide Seeds and Their Influence on the Formation of Vanadium Phosphate Catalyst Precursors
Author(s) -
Al Otaibi Raja,
Weng Weihao,
Bartley Jonathan K.,
Dummer Nicholas F.,
Kiely Christopher J.,
Hutchings Graham J.
Publication year - 2010
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.200900274
Subject(s) - vanadium , catalysis , phosphate , chemistry , octanol , inorganic chemistry , solvent , vanadium oxide , yield (engineering) , nuclear chemistry , organic chemistry , materials science , metallurgy , partition coefficient
Vanadium phosphate materials, based on a VOHPO 4 ⋅0.5 H 2 O precursor and with (VO) 2 P 2 O 7 as an active high‐temperature phase, are used as catalysts for the oxidation of alkanes. VOHPO 4 ⋅0.5 H 2 O is prepared from VOPO 4 ⋅2 H 2 O using 1‐octanol, 3‐octanol, 2‐butanol, or 2‐methyl‐1‐propanol as both solvent and reducing agent. With 1‐octanol, the reaction temperature was found to be crucial in obtaining a high yield of the precursor phase. At temperatures of 160 °C or greater, a solution containing V 4+ ions formed in preference to VOHPO 4 ⋅0.5 H 2 O. However, VOHPO 4 ⋅0.5 H 2 O formation can be achieved above 160 °C by carrying out the reduction process in the presence of a small amount of vanadium phosphate material, which effectively acts as a templating seed. The use of this seeding concept is shown to have a dramatic effect on the morphology of the final activated catalyst. In contrast, when 3‐octanol is used, solely VO(H 2 PO 4 ) 2 is generated, except in the presence of a vanadium phosphate seed where significant amounts of VOHPO 4 ⋅0.5 H 2 O can also be formed. Furthermore, VO(H 2 PO 4 ) 2 can be transformed to VOHPO 4 ⋅0.5 H 2 O by heating at reflux with an alcohol in the presence of VOHPO 4 ⋅0.5 H 2 O precursor seeds. The findings reported herein show that both the phase composition and morphology of vanadium phosphates can be influenced by the use of seeds during the preparation process.