Study of Impregnated Chromia on Alumina Catalysts with an Electron Probe Microanalyzer

Chen, Hong-Chiu; Anderson, R. B.

doi:10.1021/i360046a005

Cited by 33 publications

(6 citation statements)

References 13 publications

(16 reference statements)

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“…The addition of coadsorbents may have a harmful effect on the catalytic activity [3]. Egg-shell catalysts with transition metals can also be prepared using adsorption techniques [7][8][9]. However, the reduction of transition metal ions, which are chemisorbed onto support material, can be difficult [10].…”

Section: Introductionmentioning

confidence: 99%

Novel synthesis route for egg-shell, egg-white and egg-yolk type of cobalt on silica catalysts

Zhuang

Claeys

Steen

2006

Applied Catalysis A: General

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Section: Introductionmentioning

confidence: 99%

Novel synthesis route for egg-shell, egg-white and egg-yolk type of cobalt on silica catalysts

Zhuang

Claeys

Steen

2006

Applied Catalysis A: General

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“…By this method, the loss of cobalt during the preparing process can be entirely prevented. 56,57 The mixture was uniformly poured into 1 g of KIT-6 and then placed at room temperature for 5 h. The product was dried at 100 °C for 1 h in a drying oven and then calcinated in a muffle furnace at 550 °C for another 5 h.…”

Section: Methodsmentioning

confidence: 99%

Suppressing Ammonia Re-Emission with the Aid of the Co₃O₄-NPs@KIT-6 Catalyst in Ammonia-Based Desulfurization

Wang

et al. 2019

Environ. Sci. Technol.

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The re-emission of NH3 and SO2 caused by the decomposition of (NH4)2SO3 is a crucial concern in ammonia-based desulfurization. In this study, a novel Co3O4-NPs@KIT-6 catalyst with a three-dimensional two-helix structure is proposed for converting (NH4)2SO3 into (NH4)2SO4. The oxidation rate of (NH4)2SO3 with the catalyst was 7.5 times that without any catalyst, and this improvement was attributed to appropriately dispersed Co3O4 nanoparticles with a size of 4–10 nm that interacted with the KIT-6 support. Therefore, the number of active sites with substitution and hole defects was substantially increased, which is advantageous for high catalytic activities. Consequently, the amount of NH3 and SO2 re-emission during (NH4)2SO3 oxidation was reduced by 43.9%, which considerably reduced potential environmental risks. The results of this study serve to advance ammonia desulfurization by improving the desulfurization efficiency, downsizing the oxidation tank, and generating considerable profit from efficient reclaiming of (NH4)2SO4 as a fertilizer.

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“…A Buchi Rotavapor RE/A rotary vacuum evaporator, used in early attempts to achieve even batch impregnation, was found to give nonuniform product. A tuba1 apparatus similar to that used by Chen and Anderson (1973) also proved unsuccessful in providing uniform shell thicknesses. A beaker with constant agitation by a magnetic stirrer was finally chosen.…”

Section: Catalyst Preparationmentioning

confidence: 99%

“…The ZAF correction package was based on that used by Chen and Anderson (1973). The program structure was modified by introduction of a hyperbolic iteration function proposed by Criss and Birks (1966).…”

Section: Development and Behavior Of The Sem-edax Pib-zaf Analysismentioning

confidence: 99%

“…Conversion of the SEM-EDAX data to quantitative Mo distributions is difficult. Chen and Anderson (1973), in their pioneering study of chromia-alumina catalysts by electron probe microanalysis (EPMA), deduced chromia profiles in cut pellets that had undergone metallurgical polishing. The EPMA data showed considerable scatter in spite of the polishing, and the smoothed concentration profiles contained oscillations.…”

Section: Introductionmentioning

confidence: 99%

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Thermal behavior of shell molybdena‐alumina catalysts

Duncombe

Weller

1985

AIChE Journal

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Heat treatment of "shell" molybdena-alumina catalyst pellets results in macroscopic redistribution of the molybdena. Redistribution is minimal at 625°C but extensive at 750°C. After 6 hours at 750", a sharp maximum is observed in the radial distribution. This is a result of opposing factors: radial diffusion inward from the initial shell, and preferential sintering of the alumina support in the shell region.Loss of molybdena by vaporization is not appreciable at 750°C but is serious at 875°C. A computer program has been developed to convert SEM-EDAX (scanning electron microscopy energydispersive analysis of x-ray) data for unpolished pellet sections to a quantitative, smooth profile of Mo concentration as a function of reduced radial position. Conventional preparation of these catalysts by impregnation of pelleted alumina with ammonium heptamolybdate is known to lead to a peripheral distribution of molybdena ("shell" catalysts). In contrast to supported metal catalysts, which sinter by growth of metal crystallites but without macroscopic redistribution of the metal, molybdena-alumina suffers gross change of the Mo distribution within the pellet and, ultimately, loss of molybdena by vaporization. Superimposed on these effects is a molybdena-catalyzed sintering of the alumina support.The changes in radial distribution of Mo in the pellet can be followed crudely by optical microscopy and more exactly by energydispersive analysis of x-rays (EDAX) with a scanning electron microscope (SEM). Previous work of this kind on other systems (especially chromia-alumina), with use of an electron probe microanalyzer (EPMA), has employed metallurgically polished sections of catalyst pellets; the radial concentration profiles deduced from the EPMA data have shown marked undulations, even after data smoothing procedures. Of interest in the present SEM-EDAX work are the questions: (1) Is it possible to achieve semiquantitative concentration profiles from SEM-EDAX data on rough (unpolished) surfaces of sectioned catalyst pellets? and (2) Do the correction procedures lead to plausible profiles without undulations? If so, it becomes possible to follow the time-temperature history of the Mo redistribution in molybdena-alumina catalysts with some degree of convenience and assurance. CONCLUSIONS AND SIGNIFICANCEThe changes in Mo distribution within a molybdena-alumina pelleted catalyst on heat treatment in air have been followed both by optical microscopy and, in much greater detail, by a scanning electron microscope equipped with an energydispersive x-ray analyzer (SEM-EDAX). Rough, unpolished surfaces of catalyst sections can be satisfactorily analyzed if the SEM-EDAX data are subjected to proper corrections; these include corrections for peak/background (to accommodate rough surfaces), and for x-ray backscattering and electron stopping by the matrix (a, x-ray absorption (A), and fluorescence by nonanalyte elements (F). A computer program has been developed which incorporates these corrections and includes a systematic procedure for ter...

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Study of Impregnated Chromia on Alumina Catalysts with an Electron Probe Microanalyzer

Cited by 33 publications

References 13 publications

Novel synthesis route for egg-shell, egg-white and egg-yolk type of cobalt on silica catalysts

Novel synthesis route for egg-shell, egg-white and egg-yolk type of cobalt on silica catalysts

Suppressing Ammonia Re-Emission with the Aid of the Co₃O₄-NPs@KIT-6 Catalyst in Ammonia-Based Desulfurization

Thermal behavior of shell molybdena‐alumina catalysts

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Study of Impregnated Chromia on Alumina Catalysts with an Electron Probe Microanalyzer

Cited by 33 publications

References 13 publications

Novel synthesis route for egg-shell, egg-white and egg-yolk type of cobalt on silica catalysts

Novel synthesis route for egg-shell, egg-white and egg-yolk type of cobalt on silica catalysts

Suppressing Ammonia Re-Emission with the Aid of the Co3O4-NPs@KIT-6 Catalyst in Ammonia-Based Desulfurization

Thermal behavior of shell molybdena‐alumina catalysts

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Product

Resources

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Suppressing Ammonia Re-Emission with the Aid of the Co₃O₄-NPs@KIT-6 Catalyst in Ammonia-Based Desulfurization