Silver oxide, catalyst

Ethylene oxide, the simplest epoxide, is an intermediate in the manufacture of both ethylene glycol, used for automobile antifreeze, and polyester polymers. More than 4 million tons of ethylene oxide is produced each year in the United States by air oxidation of ethylene over a silver oxide catalyst at 300 °C. This process is not useful for other epoxides, however, and is of little value in the laboratory. Note that the name ethylene oxide is not a systematic one because the -ene ending implies the presence of a double bond in the molecule. The name is frequently used, however, because ethylene oxide is derived pom ethylene by addition of an oxygen atom. Other simple epoxides are named similarly. The systematic name for ethylene oxide is 1,2-epoxyethane. 

A reaction of immense industrial importance is the formation of oxacy-clopropane itself (most often called ethylene oxide) by oxidation of ethene with oxygen over a silver oxide catalyst at 300° ... 

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). 

The conventional route to ethylene oxide entails the direct vapor phase oxidation of ethylene. The reaction proceeds at 200-300°C and 10-30 atmospheres to produce ethylene oxide in 65-80 mole percent selectivity. The success of this technology is attributable to the development of fairly selective silver oxide catalysts which limit combustion of ethylene to CO, CO and water. The CO2 is present in the purge gas. Oxygen-based ethylene oxide plants produce approximately 60 MCF of CO2 per day. 

Ethylene is partially oxidized to ethylene oxide in the presence of a silver oxide catalyst. The selectivity of ethylene to ethylene oxide is 65 to 80%. The reaction is a vapor phase oxidation carried out at 220-300°C (430-570°F) and 10-30 kg/cm (145-435 psig) pressure. Either air or oxygen can be used as the oxidant [5]. 

A mixture of ethylene, high purity oxygen, and recycle gas is reacted in a vertical multitubular reactor filled with silver oxide catalyst. The exothermic heat of reaction is removed by the generation of steam in the reactor shell. The ethylene oxide product is absorbed from the reactor effluent gas with water. It is then recovered from the water stream by steam stripping, partial condensation, and adsorption to form a concentrated aqueous solution. The aqueous solution is further concentrated in a two-stage distillation system. The first-stage separates water and the second removes light ends. 

The oxidation of inexpensive olefins to maleic anhydride is of economic interest, since apparently it is competitive with the oxidation of benzene to maleic anhydride in some locations. As yet, however, oxidation of C4 hydrocarbons to maleic anhydride has given only about 50 % of the theoretically possible conversion to the desired product. Bretton, Wan, and Dodge 12) examined the oxidation of several C4 olefins over silver and silver oxide catalysts, but found only traces of products other than COg and HgO. With a vanadium catalyst prepared by decomposition of ammonium metavanadate on low-area alumina, substantial yields of intermediate products were found. Longfield and Dixon 57) and Matsumoto and co-workers 156) reported similar results a summary is given in Table XIV. These reactions were usually... 

Other interesting potential FTPAS kinetic studies that we have planned include measurement of the rate of leaching of copper ions from suspensions of highly colored copper sulfide ores in acidic ferric sulfate solutions and an infrared FTPAS study of the epoxidation of ethylene on a solid silver-silver oxide catalyst. 

Directly oxidizing ethylene feedstock by passing it over a silver oxide catalyst at higher temperature and pressure is by far the preferred way to make EO because this process gives better yields and is more reliable. 

Ethylene oxide is produced by direct oxidation of ethylene with atmospheric oxygen over silver oxide catalysts. 

---