Resolving Interparticle Heterogeneities in Composition and Hydrogenation Performance between Individual Supported Silver on Silica Catalysts

Plessers, Eva; Stassen, Ivo; Sree, Sreeprasanth Pulinthanathu; Janssen, Kris P. F.; Yuan, Haifeng; Martens, Johan A.; Hofkens, Johan; Vos, Dirk De; Roeffaers, Maarten B. J.

doi:10.1021/acscatal.5b02119

Cited by 24 publications

(41 citation statements)

References 26 publications

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“…Frequently inhomogeneous egg‐shell or egg‐yolk metal distributions are obtained, depending on the chemical nature of metal ions and the support, and thus on the rate of adsorption and rate of diffusion of metal ions through the catalyst body . Likewise, heterogeneities were observed between micrometer‐sized granules when these were used as catalyst support . It was shown that the drying procedure had a large influence on metal distribution.…”

Section: Introductionmentioning

confidence: 99%

The Origin of Metal Loading Heterogeneities in Pt/Zeolite Y Bifunctional Catalysts

2019

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Preparing catalysts with highly dispersed metal nanoparticles and narrow particle size distribution has been in the focus of numerous studies. Besides size and size distribution, the location of metal nanoparticles within and local metal loading of the support can have significant impact on catalytic performance. This study revealed that great variations in Pt loading between individual Pt/zeolite Y crystals occurred irrespective of the metal deposition method, namely ion‐exchange (IE) or incipient wetness impregnation (IWI). The variation in Pt loading was found to be directly related to different Si/Al ratios of individual zeolite crystals. Results indicate that this Si/Al variation was likely induced by post‐synthesis treatments, commonly performed to introduce mesoporosity. In view of the great importance of zeolite‐based catalysts for oil refining, understanding the origin of such metal loading heterogeneities may lead to further improvement of zeolite‐based catalytic performance.

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Section: Introductionmentioning

confidence: 99%

The Origin of Metal Loading Heterogeneities in Pt/Zeolite Y Bifunctional Catalysts

2019

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“…The dry powder was impregnated with 1.24 g dry silver oxalate dissolved in 2.0 mL of 0.73 g/g milliQ ethylene diamine(en)/water (1:4:16 mol ratio Ag 2 C 2 O 4: en: H 2 O) mixture and subsequently dried in static air at 60°C [12,53,54]. To favor a homogeneous distribution of silver over the support, the powder was mixed during drying [55]. After drying for 5, 10 and 30 min the powder was mixed manually before leaving the powder overnight to dry.…”

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confidence: 99%

Preparation and particle size effects of Ag/α-Al2O3 catalysts for ethylene epoxidation

Reijen

Kanungo

Welling

et al. 2017

Journal of Catalysis

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a-AluminaCatalyst design Ethylene oxide Particle size effect a b s t r a c t Currently, for the industrial ethylene epoxidation a-alumina supported silver catalysts are the only catalyst of choice. We demonstrate a novel method to produce these catalysts with different silver particle sizes, but without changing other key parameters that may affect the catalytic performance such as support specific surface area or metal precursor. a-Alumina was impregnated with a silver oxalate solution, and was subsequently dried and treated in different gas atmospheres and at different temperatures to tune the silver particle sizes in the range of 20-500 nm. Particles of 20 nm exhibited a lower turnover frequency than particles of 70 nm and larger, which exhibit a constant turnover frequency, in accordance with results in literature. However, the selectivity, when measured at constant conversion, was particle size independent. This is the first time that the effect of the particle size on the selectivity of ethylene epoxidation is reported at constant conversion. This was made possible by a new method of producing supported silver catalysts, which we expect that is also applicable for silver catalysts with other supports and for the preparation of other supported metal catalysts.

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“…The use of electron tomography, for example, revealed that typical impregnation and drying results in a non‐uniform metal distribution and nanoparticle size, whereas optimization of drying and calcination resulted in a more homogeneous loading . However, to the best of our knowledge, studies on interparticle heterogeneities at the support granule level have only been reported twice: (1) advanced electron tomography on Pt‐loaded submicron USY zeolites and (2) a correlative approach by using optical microscopy on Ag‐loaded mesoporous silica granules . In both cases, at least a 10‐fold variation in metal loading between different support particles was found.…”

Section: Introductionmentioning

confidence: 88%

“…These metal nanoparticle catalysts are also used commonly in catalyst discovery research on a laboratory scale and are often prepared by incipient wetness impregnation (IWI). Generally, the preparation method influences the final catalytic performance significantly as the metal nanoparticle size and distribution inside the support depend on the preparation method . This was the driving force for the development and application of various characterization techniques.…”

Section: Introductionmentioning

confidence: 99%

“…In both cases, at least a 10‐fold variation in metal loading between different support particles was found. Furthermore, these differences in the metal loading were shown to affect the catalytic performance severely if the same granule scale was measured . In contrast to millimeter‐sized support bodies, in which the transport of the metal precursor by the impregnation solution during drying is responsible for the heterogeneous metal loading, the origin of the heterogeneity during the preparation of supported nanoparticles at micrometer‐sized granules has not yet been investigated.…”

Section: Introductionmentioning

confidence: 99%

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Origin and Abatement of Heterogeneity at the Support Granule Scale of Silver on Silica Catalysts

et al. 2017

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Incipient wetness impregnation is used commonly to form supported metal nanoparticle catalysts. Recently, it has been revealed that this approach may induce severe heterogeneity between catalyst granules of the same batch. At least a 10‐fold variation in metal loading was observed, which affect the catalytic performance of individual catalyst granules severely. However, the origin of this heterogeneity is still unclear. Here we show that every elementary step in the preparation procedure of a Ag on silica catalyst has an effect on the resulting interparticle heterogeneity, but the influence of the drying step is the most important. This is because drying by capillary force results in a heterogeneous sample. Specifically, the position of a granule in the stagnant drying bed influences the resulting color and, thus, Ag loading significantly. This is further demonstrated by varying the drying conditions: freeze‐drying and fluidized‐bed drying led to a more homogeneous Ag loading. An investigation of the fluidized‐bed‐dried sample by using optical microscopy revealed a large fraction of transparent granules (94 %), which indicates that almost all the Ag nanoparticles in this sample are confined within the 6 nm pores. The optimized supported Ag on silica catalyst shows a good catalytic performance. This adaptation of the drying step can be implemented easily on a laboratory scale, is scalable, and does not require the use of expensive solvents or metal precursors.

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Resolving Interparticle Heterogeneities in Composition and Hydrogenation Performance between Individual Supported Silver on Silica Catalysts

Cited by 24 publications

References 26 publications

The Origin of Metal Loading Heterogeneities in Pt/Zeolite Y Bifunctional Catalysts

The Origin of Metal Loading Heterogeneities in Pt/Zeolite Y Bifunctional Catalysts

Preparation and particle size effects of Ag/α-Al2O3 catalysts for ethylene epoxidation

Origin and Abatement of Heterogeneity at the Support Granule Scale of Silver on Silica Catalysts

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