Control of the crystal morphology of VOHPO4·0.5H2O precursors prepared via light alcohols-assisted solvothermal synthesis and influence on the selective oxidation of n-butane

• Published in: Journal of catalysis 2019-09, Vol.377, p.638-651
• Main Authors: Nguyen Dinh, M.T., Nguyen, T.L., Phan, M.D., Nguyen Dinh, L., Truong, Q.D., Bordes-Richard, E.
• Format: Article
• Language: English
• Subjects: Intercalation; Maleic anhydride; n-butane oxidation; Solvothermal method; Vanadyl alkyl-phosphate; VOHPO4·0.5H2O; VPO catalysts
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2019.08.004

[Display omitted] •Solvothermal preparation of {001} facets of VOHPO4.0.5H2O in C2-C4 alkanoic alcohols.•Metastable intercalated alkyl-phosphate was only formed when using linear alcohols.•The metastable phase was converted to platy VOHPO4·0.5H2O crystallites at 330 °C.•Pseudomorphic {2 0 0} facets of (VO)2P2O7 obtained via annealing or in situ activation.•Good ethanol-derived VPO catalyst with larger V5+ amount and thinner crystallites. The catalytic performance of vanadyl pyrophosphate (VPP) catalysts in the oxidation of n-butane to maleic anhydride (MA) depends strongly on the display of the active and selective {0 0 1} faces, that may be controlled during the preparation of VOHPO4·0.5H2O precursor by solvothermal technique using C2 to C4 alkanoic alcohols. Intercalated metastable vanadyl-alkyl-phosphates were formed when linear alcohols (ethanol, n-butanol) were used, at variance with iso-alcohols. {0 0 1} platelets of VOHPO4·0.5H2O yielded {2 0 0} platelets to (VO)2P2O7 in nitrogen or in situ in the reactor, as revealed by structural analyses. The catalysts prepared in ethanol or n-butanol in situ activated at 440 °C were more active and selective to MA than in iso-alcohols, but if the equilibration was performed at 380 °C the influence of alcohol was mitigated. The highest MA yield was obtained with the ethanol-derived catalyst, which exhibited the smallest platy crystallites of (VO)2P2O7, as well as surface V5+ species as seen by XPS.