ChemInform Abstract: A STUDY OF THE VAPOR-PHASE EPOXIDATION OF PROPYLENE AND ETHYLENE ON SILVER AND SILVER-GOLD ALLOY CATALYSTS

GEENEN, P. V.; BOSS, H. J.; Pott, G. T.

doi:10.1002/chin.198308089

Cited by 7 publications

(14 citation statements)

References 1 publication

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“…As a result, the addition of gold simply creates new adsorption sites for molecular oxygen, which is also responsible for the ethylene epoxidation reaction [10]. The reason why the Au-Ag/(HSA)c-Al 2 O 3 showed the highest selectivity for carbon dioxide is that the O 2-species are separated from each other, and the adsorbed ethylene complex can consequently react with atomic oxygen to form carbon dioxide and water [34]. Obviously, the Ag/(HSA)c-Al 2 O 3 catalyst was shown to be more active for the total oxidation reaction than the Ag/(LSA)a-Al 2 O 3 and the sole plasma system.…”

Section: Effect Of Type Of Catalystmentioning

confidence: 97%

“…This is due to the fact that oxygen forms strong chemisorption bonds with silver, while it does not chemically adsorb, to any appreciable extent, on gold. It is well known that the component that forms the strongest chemisorption bonds tends to segregate at the surface of the alloy particles [34], resulting in less oxygen chemisorption and consequent lower oxygen conversion in the case of the Au-Ag/(HSA)c-Al 2 O 3 . Interestingly, the oxygen conversion in the sole plasma system was higher than that in the case of the combined catalytic and plasma systems.…”

Section: Effect Of Type Of Catalystmentioning

confidence: 99%

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Ethylene Epoxidation over Alumina-Supported Silver Catalysts in Low-Temperature AC Corona Discharge

Chavadej

Tansuwan

Sreethawong

2008

Plasma Chem Plasma Process

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In this paper, the epoxidation of ethylene over different catalysts-namely Ag/(low-surface-area, LSA)a-Al 2 O 3 , Ag/(high-surface-area, HSA)c-Al 2 O 3 , and Au-Ag/ (HSA)c-Al 2 O 3 -in a low-temperature corona discharge system was investigated. In a comparison among the studied catalysts, the Ag/(LSA)a-Al 2 O 3 catalyst was found to offer the highest selectivity for ethylene oxide, as well as the lowest selectivity for carbon dioxide and carbon monoxide. The selectivity for ethylene oxide increased with increasing applied voltage, while the selectivity for ethylene oxide remained unchanged when the frequency was varied in the range of 300-500 Hz. Nevertheless, the selectivity for ethylene oxide decreased with increasing frequency beyond 500 Hz. The optimum Ag loading on (LSA)a-Al 2 O 3 was found to be 12.5 wt.%, at which a maximum ethylene oxide selectivity of 12.9% was obtained at the optimum applied voltage and input frequency of 15 kV and 500 Hz, respectively. Under these optimum conditions, the power consumption was found to be 12.6 9 10 -16 W s/molecule of ethylene oxide produced. In addition, a low oxygen-to-ethylene molar ratio and a low feed flow rate were also experimentally found to be beneficial for the ethylene epoxidation.

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Section: Effect Of Type Of Catalystmentioning

confidence: 97%

Section: Effect Of Type Of Catalystmentioning

confidence: 99%

Ethylene Epoxidation over Alumina-Supported Silver Catalysts in Low-Temperature AC Corona Discharge

Chavadej

Tansuwan

Sreethawong

2008

Plasma Chem Plasma Process

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“…As shown in the aforementioned results, there were several reactions occurring in the plasma reaction zone so it is not possible to easily carry out the kinetic consideration of the ethylene epoxidation reaction. Future works will then be focused on the combination of the low-temperature DBD system with various reported catalytically active catalysts used in the conventional catalytic process, especially Ag/Al 2 O 3 -based catalysts [5][6][7][8][9][10][11][12][13][14][15]20], aiming to enhance the EO yield. The comparative study of ethylene epoxidation under different kinds of lowtemperature plasma discharges, such as corona discharge system with pin and plate electrodes, is also of our strong interest.…”

Section: Effect Of Electrode Gap Distancementioning

confidence: 99%

“…Since 1940, almost all EO produced industrially has been made using this method [4]. To date, silver catalysts supported on alpha-alumina (Ag/a-Al 2 O 3 ) with alkali and transition metal promoters [5][6][7][8][9][10][11][12][13][14][15], such as Cs, Cu, Re, and Au, or with addition of chlorine-containing moderators into gaseous reactants [16][17][18][19][20], such as dichloroethane (C 2 H 4 Cl 2 ) and vinyl chloride (C 2 H 3 Cl), provide high selectivity for EO. However, the conventional catalytic process normally requires high temperatures, i.e.…”

Section: Introductionmentioning

confidence: 99%

Ethylene Epoxidation in Low-Temperature AC Dielectric Barrier Discharge: Effects of Oxygen-to-Ethylene Feed Molar Ratio and Operating Parameters

Sreethawong

Suwannabart

Chavadej

2008

Plasma Chem Plasma Process

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Ethylene oxide (EO), a valuable chemical feedstock in producing many industrial chemicals, which is industrially produced by the partial oxidation of ethylene, so-called ethylene epoxidation, has been of great interest in many global research studies. In this work, the epoxidation of ethylene under a low-temperature dielectric barrier discharge (DBD) was feasibly investigated to find the best operating conditions. It was experimentally found that the EO yield decreased with increasing O 2 /C 2 H 4 feed molar ratio, feed flow rate, input frequency, and electrode gap distance, while it increased with increasing applied voltage up to 19 kV. The highest EO yield of 5.6% was obtained when an input frequency of 500 Hz and an applied voltage of 19 kV were used, with an O 2 /C 2 H 4 feed molar ratio of 1:1, a feed flow rate of 50 cm 3 /min, and an electrode gap distance of 10 mm. Under these best conditions, the power consumption was found to be as low as 6.07 9 10 -16 Ws/molecule of EO produced.

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“…However, the selectivity to PO was less than 15% with the conversion of propylene less than 15% [2]. Previous studies suggested that the low selectivity to PO was due to the more easily connecting of allylic hydrogen with the adsorbed oxygen species to form the resonance-stabilized allyl radical or anion that can be easily further oxidized to CO 2 and H 2 O [3][4][5][6][7]. However, Kitson and Lambert [8] and Grant and Lambert [9] presumed that the valence charge state of the adsorbed atomic oxygen (O ad ) determined the reaction selectivity.…”

Section: Introductionmentioning

confidence: 98%

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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ChemInform Abstract: A STUDY OF THE VAPOR-PHASE EPOXIDATION OF PROPYLENE AND ETHYLENE ON SILVER AND SILVER-GOLD ALLOY CATALYSTS

Cited by 7 publications

References 1 publication

Ethylene Epoxidation over Alumina-Supported Silver Catalysts in Low-Temperature AC Corona Discharge

Ethylene Epoxidation over Alumina-Supported Silver Catalysts in Low-Temperature AC Corona Discharge

Ethylene Epoxidation in Low-Temperature AC Dielectric Barrier Discharge: Effects of Oxygen-to-Ethylene Feed Molar Ratio and Operating Parameters

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

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