Premium
Effect of direct ultrasound synthesis via a sesquihydrate route on bismuth‐promoted vanadyl pyrophosphate catalysts
Author(s) -
Goo KangZhi,
Yap YeowHong,
Lin KuenSong,
Leong LoongKong
Publication year - 2020
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.201900075
Subject(s) - chemistry , catalysis , vanadium , maleic anhydride , inorganic chemistry , bismuth , vanadium oxide , butane , calcination , analytical chemistry (journal) , xanes , nuclear chemistry , spectral line , organic chemistry , copolymer , polymer , physics , astronomy
Abstract A series of 1, 3, and 5% Bi‐doped vanadium phosphate catalyst catalysts were prepared via sesquihydrate route using direct ultrasound method and were denoted as VPSB1, VPSB3, and VPSB5, respectively. These catalysts were synthesized solely using a direct ultrasound technique and calcined in a n ‐butane/air mixture. This study showed that catalyst synthesis time can be drastically reduced to only 2 hr compared to conventional 32–48 hr. All Bi‐doped catalysts exhibited a well‐crystallized (VO) 2 P 2 O 7 phase. In addition, two V 5+ phases, that is, β‐VOPO 4 and α II ‐VOPO 4 , were observed leading to an increase in the average oxidation state of vanadium. All catalysts showed V2p 3/2 at approx. 517 eV, giving the vanadium oxidation state at approx. 4.3–4.6. Field‐emission scanning electron microscopy micrographs showed the secondary structure consisting of thin and small plate‐like crystal clusters due to the cavitation effect of ultrasound waves. VPSB5 showed the highest amount of oxygen species removed associated with the V 5+ and V 4+ species in temperature‐programmed reduction in H 2 analyses. TheX‐ray absorption near edge structure (XANES) measurement showed the occurrence of vanadium oxide reductions in hydrogen gas flow, indicating the presence of V 4+ and V 5+ species. Higher average valence states of V 5+ , indicating more V 5+ phases, were present. The addition of bismuth has increased the activity and selectivity to maleic anhydride.