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US 5,668,077 AGranted
Silver catalyst for the oxidation of ethylene oxide
AssigneeHuels Aktiengesellschaft
InventorsBurkhard Klopries, Harald Metz, Wilma Dibowski, Dietmar Kyewski, Jurgen Pospiech
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Abstract
The invention relates to a silver catalyst for the partial oxidation of ethylene with molecular oxygen in the gas phase to form ethylene oxide and a process for preparing ethylene oxide using this catalyst. The catalyst is superior to comparable catalysts of the prior art through an increased selectivity (at high activity) and/or a more favorable ageing behavior. The process for preparing ethylene oxide is distinguished by improved economics.
Claims19
A supported silver catalyst, comprising:
- (a) a macroporous, nonacidic, heat resistant ceramic support having a number-average pore volume of greater than about 0.35 cm.sup.3 /g as determined by mercury porosimetry at a pressure rising to 2,000 bar, and having a number-average pore volume upper limit such that the lateral fracture strength of the finished catalyst is not less than 20N and wherein said macroporous ceramic support has a surface area of macropores of greater than about 0.8 m.sup.2 /g as determined by mercury porosimetry at a pressure rising to 2,000 bar;
- (b) silver particles having number-average diameters as determined by scanning electron microscopy of from about 0.05 .mu.m to about 0.4 .mu.m,
- wherein the average diameter of said silver particles is less than about 0.4 of the number-average macropore diameter of said macroporous support, said macropore diameter determined by mercury porosimetry at a pressure rising to 2,000 bar and being greater than or equal to about 1 .mu.m;
- and
- wherein said silver particles in the outer surface of the finished catalyst form essentially no silver bridges, such that the catalyst behaves likes an insulator with high electrical resistance.
2 more elements
A supported silver catalyst, comprising:
- (a) a macroporous, nonacidic, heat resistant ceramic support having a pore volume of greater than about 0.35 cm.sup.3 /g as determined by mercury porosimetry at a pressure rising to 2000 bar, and having a pore volume upper limit such that the lateral fracture strength of the finished catalyst is not less than 20N;
- (b) silver particles having number-average diameters as determined by scanning electron microscopy of from about 0.05 .mu.m to about 0.4 .mu.m,
- wherein the average diameter of said silver particles is less than about 0.4 of the number-average macropore diameter of said macroporous support, said macropore diameter determined by mercury porosimetry at a pressure rising to 2000 bar and being greater than or equal to about 1 .mu.m;
- wherein said silver particles in the outer surface of the finished catalyst form essentially no silver bridges, such that the catalyst behaves like an insulator with high electrical resistance;
- wherein the average contact angle between silver particles and the support is greater than about 30.degree.;
- wherein said contact angle is adjusted by doping the metallic silver with a cationic component selected from the group consisting of the compounds of Li, Na, K, Cs, Mg, Ca, Ba, Ti, V, Cr, and Re;
- wherein the untreated macroporous support has a surface area of the macropores of greater than about 0.8 m.sup.2 /g and a BET pore volume of less than 0.03 cm.sup.3 /g;
- and
- wherein said untreated support comprises aluminum oxide in an amount greater than about 80 weight percent.
6 more elements
Dependencies are inferred from the claim text.