Effect of direct ultrasound synthesis via a sesquihydrate route on bismuth‐promoted vanadyl pyrophosphate catalysts

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 wellcrystallized (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. K E Y W O R D Sbismuth, butane oxidation, direct ultrasound synthesis, selective oxidation, sesquihydrate, vanadyl pyrophosphate catalyst

Mono-, Bi-, and Tri-Metallic DES Are Prepared from Nb, Zr, and Mo for n-Butane Selective Oxidation via VPO Catalyst

“…In addition to these physiochemical properties, the electronic characteristics also affect the catalytic performance. Various synthesis techniques such as ultrasound [13], microwave [14], ball milling [15], hydrothermal [16], electrospinning [17], and barothermal [18] have been introduced to explore the physiochemical properties of efficient VPO catalysts. The purely crystalline catalysts and precursors prepared via the above-mentioned process found in literature usually adopt a smooth lamellar structure.…”