Morphological changes of vanadyl pyrophosphate due to thermal excursions

Badehbakhsh, Sepideh; Saadatkhah, Nooshin; Mahboub, Mohammad Jaber Darabi; Guerrero‐Pérez, M. Olga; Patience, Gregory S.

doi:10.1016/j.cattod.2021.12.008

Cited by 6 publications

(1 citation statement)

References 103 publications

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“…It becomes a dark brownish colour after years in a circulating fluidized bed reactor (Figure 13). [ 59 ] Conventional thinking attributed the colour change to smaller particles that turned black due to thermal excursions at oxygen spargers and combustion downstream of the stripper and cyclone. The image shows that the equilibrated catalyst becomes shiny, so shiny that the circle of dots of light illuminating the catalyst from above is evident.…”

Section: Optical Microscopy Versus Semmentioning

confidence: 99%

Experimental methods in chemical engineering: Scanning electron microscopy andX‐ray ultra‐microscopy—SEMandXuM

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Bessette

et al. 2022

Can J Chem Eng

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Scanning electron microscopy (SEM) produces images at 500 000 times magnification and better than 1 nm resolution to characterize inorganic and organic solid morphology, surface topography, and crystallography. An electron beam interacts with the material and generates secondary electrons (SE) and backscattered electrons (BSE) that detectors capture. Coupled with X-ray energydispersive spectroscopy (X-EDS), SEM-EDS identifies elemental composition. X-ray ultra-microscopy (XuM) traverses particles to identify phase changes and areas of high density and voids without slicing through the solids by microtome. Although SEM instrument capability continuously evolves with higher magnification and better resolution, desktop SEMs are becoming standard in laboratories that require frequent imaging and lower magnification. Hand-held cameras (800-1500Â) have the advantage of low cost, ease of use, and better colours. SEM depth of field is better than visible light microscopy, but image stacking software has narrowed the gap between the two. Modern user interfaces mean that today's SEM instruments are easier to operate and data acquisition is faster, but operators must be able to select the right technique for the application (e.g., SE vs. BSE). Furthermore, they must understand how operating parameters like probe current, accelerating voltage, spot-diameter, convergence angle, and working distance compromise sample integrity. The number of articles the Web of Science indexes that mention SEM has grown from 1000 in 1990 to over 40 000 in 2021. A bibliometric map identified four clusters of research: mechanical properties and microstructure; nanoparticles, composites, and graphene; antibacterial and green synthesis; and adsorption and wastewater.

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Section: Optical Microscopy Versus Semmentioning

confidence: 99%

Experimental methods in chemical engineering: Scanning electron microscopy andX‐ray ultra‐microscopy—SEMandXuM

Davies

Bessette

et al. 2022

Can J Chem Eng

Self Cite

View full text Add to dashboard Cite

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Combined Operando XANES and NMR and ESR Spectroscopies for the Determination of VPO Dynamic States

et al. 2023

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Nanoscaled-VPO (vanadium phosphate oxide) catalysts have been prepared on an alumina support with the objective of obtaining crystallites of the active phase with a high surface-to-volume ratio. Since the catalysed reaction occurs at the surface, these nanoscaled catalysts allows studying surface species transformations with a minimized signal from the bulk dominion. The chemical environment and oxidation state of these species has been determined by a combination of NMR, ESR and XANES spectroscopies. The results have allowed to optimize V + P coverage and V/P molar ratio to minimize the concentration of isolated vanadium oxide species and maximize V4+ concentration. The distribution of phosphorus islands ordered and significantly distorted of tetra- and penta-coordinated aluminium sites of the catalytic support, thus shaping the catalytic material to an optimal structure for the desired partial oxidation reaction.

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