Silver peroxide catalyst

Diols are prepared from alkenes by oxidation with reagents such as osmium tetroxide, potassium permanganate, or hydrogen peroxide (Section 11-7C). However, ethylene glycol is made on a commercial scale from oxacy-clopropane, which in turn is made by air oxidation of ethene at high temperatures over a silver oxide catalyst (Section 11-7D). 

Sazama, P. and Wichterlova, B. (2005) Selective catalytic reduction of NOx by hydrocarbons enhanced by hydrogen peroxide over silver/alumina catalysts. Chem. Commun, 38, 4810-4811. 

An important aspect of epoxidation is the source of the oxygen. The most desirable terminal source is molecular oxygen, which is a plentiful and economical reagent. However, aside from silver, other catalysts almost universally employ activated forms of oxygen, which involve the use of a sacrificial reductant for their production. Hydrogen peroxide has emerged as the most attractive oxidant at laboratory and commercial scales, and the reasons and implications of this will be discussed. 

Finally, titanium silicates have also been extensively investigated for the epoxida-tion of olefins. The reaction of ethylene over a silver-supported catalyst to ethylene oxide is one of the few large-scale industrial oxidation reactions with molecular oxygen as the oxidant. Numerous studies have shown TS-1 to be effective at selectively forming propylene oxide (PO) from propylene using hydrogen peroxide as the oxidant. This is a more environmentally friendly route to PO than the currently used chlorhydrin route, and it is likely that this process will see commercialization in the near future. 

Much research was and is focused on ODCs for chlor-alkali electrolysis which are based on carbon carrier materials [4]. However, until now the stability of such ODCs is insufficient. The most probable reason is the formation of hydrogen peroxide species which attack the carbon and destroy the connection between catalyst metal and carbon carrier. Using pure silver as catalyst, no peroxide formation has to be expected. 

Phenylchlorosilanes can be prepared by a direct process from silicon and chlorobenzene with copper or silver catalyst, but yields are not so good as those of methylchlorosilanes. Alternative routes are Grignard or phenylsodium arylation of SiQ4, and the reaction between benzene and either H2SiCl2 or HSiCla in the presence of platinum or peroxide catalysts. The required intermediates are made from silicon-copper (or-iron) and HQ ... 

Union Carbide abandoned the ketene—crotonaldehyde route in 1953 in favor of the oxidation of 2,4-hexadienal made by acetaldehyde condensation. A silver compound used as the catalyst prevented peroxidation of the ethylenic bonds (39,40). Thein plant operated until 1970. 

Hydrogen peroxide breaks down into water and oxygen. A liter of 3 percent hydrogen peroxide will generate 10 liters of oxygen when a catalyst is used to facilitate the breakdown. Catalysts can be metals such as iron, copper, or silver, or organics such as the blood enzyme... 

The preparation of Pans-1,2-cyclohexanediol by oxidation of cyclohexene with peroxyformic acid and subsequent hydrolysis of the diol monoformate has been described, and other methods for the preparation of both cis- and trans-l,2-cyclohexanediols were cited. Subsequently the trans diol has been prepared by oxidation of cyclohexene with various peroxy acids, with hydrogen peroxide and selenium dioxide, and with iodine and silver acetate by the Prevost reaction. Alternative methods for preparing the trans isomer are hydroboration of various enol derivatives of cyclohexanone and reduction of Pans-2-cyclohexen-l-ol epoxide with lithium aluminum hydride. cis-1,2-Cyclohexanediol has been prepared by cis hydroxylation of cyclohexene with various reagents or catalysts derived from osmium tetroxide, by solvolysis of Pans-2-halocyclohexanol esters in a manner similar to the Woodward-Prevost reaction, by reduction of cis-2-cyclohexen-l-ol epoxide with lithium aluminum hydride, and by oxymercuration of 2-cyclohexen-l-ol with mercury(II) trifluoro-acetate in the presence of ehloral and subsequent reduction. ... 

It was found that the value of F, is markedly increased by ions which are effective catalysts of oxidation reactions of peroxydisulphate. These are silver(I) copper(n), and iron(III). Cobalt(II) and nickel(II) ions, although they are good catalysts for the decomposition of hydrogen peroxide, exert their effect merely as inert electrolytes in the induced reaction. Therefore it can be concluded that, in this process, activation of the rather less reactive 8203 is more important than that of hydrogen peroxide . ... 

Hibernia A process for making formaldehyde by the partial oxidation of methane by ozonized oxygen. The catalyst is barium peroxide activated with silver oxide. Developed in Germany during World War II but not commercialized. 

Olefins - [FEEDSTOCKS - COALCHEMICALS] (Vol 10) - [FEEDSTOCKS-PETROCHEMICALS] (VollO) - [HYDROCARBONS - SURVEY] (Vol 13) -m automobile exhaust [EXHAUSTCONTROL, AUTOMOTIVE] (Vol 9) -catalyst for stereospeafic polymerization [TITANIUMCOMPOUNDS - INORGANIC] (Vol 24) -esters from [ESTERIFICATION] (Vol 9) -hydroxylation using H202 [HYDROGEN PEROXIDE] (Vol 13) -luminometer ratings [AVIATION AND OTHER GAS TURBINE FUELS] (Vol 3) -osmium oxidations of [PLATINUM-GROUP METALS, COMPOUNDS] (Vol 19) -polymerization [SULFONIC ACIDS] (Vol 23) -reaction with EDA [DIAMINES AND HIGHER AMINES ALIPHATIC] (Vol 8) -silver complexes of [SILVER COMPOUNDS] (Vol 22)... 

Trialkyl boron was first claimed as a new anionic initiator for the polymerization of vinyl compounds (264), although it was rather improbable in view of the low ionic character of the boron-carbon bond. The error was quickly corrected when it was shown that free radicals were involved (265, 266) and that oxygen, peroxides, silver salts and copper salts were co-catalysts (262, 267). Aluminum alkyls can also initiate radical polymerizations in the presence of oxygen (267,262) but, as in the case of zinc, cadmium or boron alkyls, the products were not stereoregular. Thus, complexing between catalyst and monomer probably does not occur. 

Although non-ZiEGLER catalysts are involved, there is excellent evidence for free radical polymerization of yr-complexed monomer. Bier et al (348) have shown that ethylene forms complexes with silver salts in neutral aqueous solution at 10—40° C. and 5—50 atmospheres ethylene. Initiation by peroxides produced high molecular weight, branched... 

---