Study of Cs-Promoted, α-Alumina-Supported Silver, Ethylene Epoxidation Catalysts

Minahan, David M.; Hoflund, Gar B.; Epling, William S.; Schoenfeld, D.

doi:10.1006/jcat.1997.1626

Cited by 50 publications

(25 citation statements)

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“…The results of XPS [24] over Ag-MoO 3 catalyst showed that the valence of Mo and Ag were 6Àd and d + , respectively, which indicated that the electron transferred from silver to MoO 3 to make the Mo oxyanion. It was also reported that the presence of Cs and Cl would cause the appearance of 10 cationic species of silver on the surface of Ag/a-Al 2 O 3 catalysts, and thus the selectivity to ethylene oxide was increased greatly [25][26][27]. Two peaks in Figure 8 could be assigned to higher oxidation states of Ag, and indicated the presence of the subsurface layer of electropositive Ag atoms, which was a prerequisite to produce active sites where electrophilic oxygen atoms could be absorbed and played an important role in the epoxidation of propylene.…”

Section: Effect Of Ag Loadingmentioning

confidence: 96%

Epoxidation of Propylene by Molecular Oxygen Over the Ag–Y2O3–K2O/α-Al2O3 Catalyst

et al. 2007

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The Ag/a-Al 2 O 3 catalyst modified with rare earth metal oxide (Y 2 O 3 ) and alkali metal oxide (K 2 O) for the epoxidation of propylene by molecular oxygen were prepared and characterized by TG-DTA, XRD and XPS. The results show that a small quantity of Y 2 O 3 added plays a role of electron and structure-type promoters, and can change the binding energies of Ag3d and restrain the sintering of Ag crystallites during catalyst preparation. The effects of promoters loading, Ag loading, reaction temperature, and calcination atmosphere on the performance of Ag catalyst were investigated. The results show that the loadings of K 2 O, Y 2 O 3 and Ag, and reaction temperature affect obviously the catalytic performance of Ag-Y 2 O 3 -K 2 O/a-Al 2 O 3 for the epoxidation of propylene to propylene oxide. Under the reaction conditions of 0.1 MPa, 245°C, GHSV of 2000 h À1 and the feed gas of 20%C 3 H 6 /8%O 2 / N 2 , the conversion of propylene of 4% and the selectivity to propylene oxide of 46.8% were achieved over the 20%Ag-0.1%Y 2 O 3 -0.1%K 2 O/a-Al 2 O 3 catalyst.

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Section: Effect Of Ag Loadingmentioning

confidence: 96%

Epoxidation of Propylene by Molecular Oxygen Over the Ag–Y2O3–K2O/α-Al2O3 Catalyst

et al. 2007

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“…3. Cs as a promoter facilitates Ag distribution on the α-Al 2 O 3 surface based on the high coverage and lack of crystallites with large contact angles [12]. The presence of Cs in the catalyst improves the distribution of Ag over the support and the Ag/Al interfacial area.…”

Section: Edx Mappingmentioning

confidence: 99%

Catalyst Characterization with FESEM/EDX by the Example of Silver-Catalyzed Epoxidation of 1,3-Butadiene

Otto¹,

Habicht²,

Dinjus³

et al. 2012

Scanning Electron Microscopy

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“…In addition to this, it has also been suggested that cesium plays a role in binding and dispersing the silver crystals on the catalyst support, as well as increasing the adsorption probability of oxygen on silver [15][16][17][18][19]. According to Minahan and co-workers [20], Cs acts as a binder between the Al 2 O 3 surface and the Ag crystallites to give a more uniform and higher coverage of the Ag component. Thus, the Cs serves to ''wet'' the Al 2 O 3 toward Ag deposition on the support.…”

Section: Introductionmentioning

confidence: 96%

Nano‐sized silver crystals and their dispersion over α‐alumina for ethylene epoxidation

Hassani¹,

Ghasemi²,

Rashidzadeh³

et al. 2009

Cryst. Res. Technol.

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Ethylene oxide catalyst is a high metal loading catalyst, in which silver crystals is impregnated on α-Al 2 O 3 support. In this type of catalyst, metal dispersion plays an important role on catalyst selectivity for desired products. In this work, silver nitrate and silver oxide together with oxalic and lactic acid as the raw materials were used with different impregnation techniques to make catalysts with high silver content and dispersion. It is also known that the use of promoters affect the metal dispersion on the catalyst support and for that cesium was used as the promoter to improve the silver crystal dispersion. Physical and chemical characteristics of the prepared catalysts, i.e., surface area, pore volume, silver content, nano-sized silver crystals and their dispersion were measured using BET method, Atomic Absorption Spectroscopy, X-ray diffraction and TEM.

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Study of Cs-Promoted, α-Alumina-Supported Silver, Ethylene Epoxidation Catalysts

Cited by 50 publications

References 0 publications

Epoxidation of Propylene by Molecular Oxygen Over the Ag–Y2O3–K2O/α-Al2O3 Catalyst

Epoxidation of Propylene by Molecular Oxygen Over the Ag–Y2O3–K2O/α-Al2O3 Catalyst

Catalyst Characterization with FESEM/EDX by the Example of Silver-Catalyzed Epoxidation of 1,3-Butadiene

Nano‐sized silver crystals and their dispersion over α‐alumina for ethylene epoxidation

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