Crystal Imperfections of Industrial Vanadium Phosphorous Oxide Catalysts

This study presents information about crystal imperfections in the main phase of industrial vanadium phosphorous oxide catalysts that are used to catalyze the oxidation of <i>n</i>-butane to maleic anhydride, being an important intermediate in the chemical industry. The mechanism of this...

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Autores principales:	Isabella Kappel, Sebastian Böcklein, SoHyun Park, Michael Wharmby, Gerhard Mestl, Wolfgang W. Schmahl
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	VPO vanadyl pyrophosphate industrial catalyst real structure analysis X-ray diffraction <i>n</i>-butane oxidation Chemical technology TP1-1185 Chemistry QD1-999
Acceso en línea:	https://doaj.org/article/0609b91a68ad46af8fa22447608f17ea
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spelling	oai:doaj.org-article:0609b91a68ad46af8fa22447608f17ea2021-11-25T17:05:54ZCrystal Imperfections of Industrial Vanadium Phosphorous Oxide Catalysts10.3390/catal111113252073-4344https://doaj.org/article/0609b91a68ad46af8fa22447608f17ea2021-10-01T00:00:00Zhttps://www.mdpi.com/2073-4344/11/11/1325https://doaj.org/toc/2073-4344This study presents information about crystal imperfections in the main phase of industrial vanadium phosphorous oxide catalysts that are used to catalyze the oxidation of <i>n</i>-butane to maleic anhydride, being an important intermediate in the chemical industry. The mechanism of this reaction is still debated, and the catalytically active and selective surface centers have not yet been identified. The results presented are based on X-ray diffraction data obtained by both laboratory-scale and synchrotron powder diffraction experiments, as well as laboratory-scale single-crystal diffraction experiments. It has been proven that pronounced Bragg reflection broadening effects found in laboratory-scale powder diffraction patterns of industrial VPO catalysts are real and not due to an insufficient 2-θ resolution of the apparatus. In the framework of this work, a powder diffraction full profile fitting strategy was developed using the TOPAS software, which was applied to analyze the X-ray diffraction data of four differently activated industrial catalyst samples, originating from one batch after they had been catalytically tested. It was found that the reflection broadening is mainly caused by an anisotropic crystal size, which results in platelet-shaped crystallites of vanadyl pyrophosphate. A further contribution to the reflex broadening, especially for (111), was found to be a result of stacking faults perpendicular to the <b>a</b> direction in the crystal structure of vanadyl pyrophosphate. These results were used to elaborate on possible correlations between structural proxies and catalytic performance. A direct correlation between the extension of coherently scattering domains in the <b>z</b> direction and the catalyst’s selectivity could be proven, whereas the activity turned out to be dependent on the crystallite shape. Regarding the phase contents, it could be shown that sample catalysts containing a higher amount of β-VO(PO<sub>3</sub>)<sub>2</sub> showed increased catalytic activity.Isabella KappelSebastian BöckleinSoHyun ParkMichael WharmbyGerhard MestlWolfgang W. SchmahlMDPI AGarticleVPOvanadyl pyrophosphateindustrial catalystreal structure analysisX-ray diffraction<i>n</i>-butane oxidationChemical technologyTP1-1185ChemistryQD1-999ENCatalysts, Vol 11, Iss 1325, p 1325 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	VPO vanadyl pyrophosphate industrial catalyst real structure analysis X-ray diffraction <i>n</i>-butane oxidation Chemical technology TP1-1185 Chemistry QD1-999
spellingShingle	VPO vanadyl pyrophosphate industrial catalyst real structure analysis X-ray diffraction <i>n</i>-butane oxidation Chemical technology TP1-1185 Chemistry QD1-999 Isabella Kappel Sebastian Böcklein SoHyun Park Michael Wharmby Gerhard Mestl Wolfgang W. Schmahl Crystal Imperfections of Industrial Vanadium Phosphorous Oxide Catalysts
description	This study presents information about crystal imperfections in the main phase of industrial vanadium phosphorous oxide catalysts that are used to catalyze the oxidation of <i>n</i>-butane to maleic anhydride, being an important intermediate in the chemical industry. The mechanism of this reaction is still debated, and the catalytically active and selective surface centers have not yet been identified. The results presented are based on X-ray diffraction data obtained by both laboratory-scale and synchrotron powder diffraction experiments, as well as laboratory-scale single-crystal diffraction experiments. It has been proven that pronounced Bragg reflection broadening effects found in laboratory-scale powder diffraction patterns of industrial VPO catalysts are real and not due to an insufficient 2-θ resolution of the apparatus. In the framework of this work, a powder diffraction full profile fitting strategy was developed using the TOPAS software, which was applied to analyze the X-ray diffraction data of four differently activated industrial catalyst samples, originating from one batch after they had been catalytically tested. It was found that the reflection broadening is mainly caused by an anisotropic crystal size, which results in platelet-shaped crystallites of vanadyl pyrophosphate. A further contribution to the reflex broadening, especially for (111), was found to be a result of stacking faults perpendicular to the <b>a</b> direction in the crystal structure of vanadyl pyrophosphate. These results were used to elaborate on possible correlations between structural proxies and catalytic performance. A direct correlation between the extension of coherently scattering domains in the <b>z</b> direction and the catalyst’s selectivity could be proven, whereas the activity turned out to be dependent on the crystallite shape. Regarding the phase contents, it could be shown that sample catalysts containing a higher amount of β-VO(PO<sub>3</sub>)<sub>2</sub> showed increased catalytic activity.
format	article
author	Isabella Kappel Sebastian Böcklein SoHyun Park Michael Wharmby Gerhard Mestl Wolfgang W. Schmahl
author_facet	Isabella Kappel Sebastian Böcklein SoHyun Park Michael Wharmby Gerhard Mestl Wolfgang W. Schmahl
author_sort	Isabella Kappel
title	Crystal Imperfections of Industrial Vanadium Phosphorous Oxide Catalysts
title_short	Crystal Imperfections of Industrial Vanadium Phosphorous Oxide Catalysts
title_full	Crystal Imperfections of Industrial Vanadium Phosphorous Oxide Catalysts
title_fullStr	Crystal Imperfections of Industrial Vanadium Phosphorous Oxide Catalysts
title_full_unstemmed	Crystal Imperfections of Industrial Vanadium Phosphorous Oxide Catalysts
title_sort	crystal imperfections of industrial vanadium phosphorous oxide catalysts
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/0609b91a68ad46af8fa22447608f17ea
work_keys_str_mv	AT isabellakappel crystalimperfectionsofindustrialvanadiumphosphorousoxidecatalysts AT sebastianbocklein crystalimperfectionsofindustrialvanadiumphosphorousoxidecatalysts AT sohyunpark crystalimperfectionsofindustrialvanadiumphosphorousoxidecatalysts AT michaelwharmby crystalimperfectionsofindustrialvanadiumphosphorousoxidecatalysts AT gerhardmestl crystalimperfectionsofindustrialvanadiumphosphorousoxidecatalysts AT wolfgangwschmahl crystalimperfectionsofindustrialvanadiumphosphorousoxidecatalysts
_version_	1718412692506542080

Crystal Imperfections of Industrial Vanadium Phosphorous Oxide Catalysts

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