Ethylene Oxide Process

Can the useful material lost in the purge streams be reduced by additional reaction If the purge stream contains significant quantities of reactants, then placing a reactor and additional separation on the purge can sometimes be justified. This technique is used in some designs of ethylene oxide processes. 

Dehydrochlorination to Epoxides. The most useful chemical reaction of chlorohydrins is dehydrochlotination to form epoxides (oxkanes). This reaction was first described by Wurtz in 1859 (12) in which ethylene chlorohydria and propylene chlorohydria were treated with aqueous potassium hydroxide [1310-58-3] to form ethylene oxide and propylene oxide, respectively. For many years both of these epoxides were produced industrially by the dehydrochlotination reaction. In the past 40 years, the ethylene oxide process based on chlorohydria has been replaced by the dkect oxidation of ethylene over silver catalysts. However, such epoxides as propylene oxide (qv) and epichl orohydrin are stiU manufactured by processes that involve chlorohydria intermediates. 

Air-Based Direct Oxidation Process. A schematic flow diagram of the air-based ethylene oxide process is shown in Figure 2. Pubhshed information on the detailed evolution of commercial ethylene oxide processes is very scanty, and Figure 2 does not necessarily correspond to the actual equipment or process employed in any modem ethylene oxide plant. Precise information regarding process technology is proprietary. However, Figure 2 does illustrate all the saUent concepts involved in the manufacturing process. The process can be conveniently divided into three primary sections reaction system, oxide recovery, and oxide purification. 

Process Technology Considerations. Innumerable complex and interacting factors ultimately determine the success or failure of a given ethylene oxide process. Those aspects of process technology that are common to both the air- and oxygen-based systems are reviewed below, along with some of the primary differences. 

For the same production capacity, the oxygen-based process requires fewer reactors, all of which operate in parallel and are exposed to reaction gas of the same composition. However, the use of purge reactors in series for an air-based process in conjunction with the associated energy recovery system increases the overall complexity of the unit. Given the same degree of automation, the operation of an oxygen-based unit is simpler and easier if the air-separation plant is outside the battery limits of the ethylene oxide process (97). 

Development of the first recycle reactor was one of the consequences of a challenging situation. The ethylene oxide process had reached a high level of sophistication and excellent performance after 25 years of continuous R D. To improve results achieved by so many excellent people over so many years was a formidable task. 

The RR developed by the author at UCC was the only one that had a high recycle rate with a reasonably known internal flow (Berty, 1969). This original reactor was named later after the author as the Berty Reactor . Over five hundred of these have been in use around the world over the last 30 years. The use of Berty reactors for ethylene oxide process improvement alone has resulted in 300 million pounds per year increase in production, without addition of new facilities (Mason, 1966). Similar improvements are possible with many other catalytic processes. In recent years a new blower design, a labyrinth seal between the blower and catalyst basket, and a better drive resulted in an even better reactor that has the registered trade name of ROTOBERTY . ... 

The ethylene oxidation process can be carried out in either a liquid or a vapour phase but the latter method is often preferred because it avoids corrosion problems and the use of solvents. 

Kirby (1999) reports two snccessful applications of deflagration flame arresters. In one incident, a deflagration flame arrester was installed near the junction of a collection header from an ethylene oxide process nnit with a flare stack. Although this type of flame arrester was really inappro-... 

Figure 7-3. The Scientific Design Co. Ethylene Oxide process (1) reactor, (2) scrubber, (3,4) C02 removal, (5) stripper, (6,7) fractionators.

A higher glycol yield (approximately 94%) than from the ethylene oxide process is anticipated. However, there are certain problems inherent in the Oxirane process such as corrosion caused hy acetic acid and the incomplete hydrolysis of the acetates. Also, the separation of the glycol from unhydrolyzed monoacetate is hard to accomplish. 

It has been shown, particularly for the latter reaction and for the ethylene oxide process, that micro reactors allow safe processing of otherwise hazardous oxidations [4, 26, 40, 42, 43, 84]. This is first due to the fact that the inner volume of micro reactors is small so that explosions also happen only on a micro scale . The... 

Scheme I. The two competing ethylene oxidation processes. The upper channel is the desired partial oxidation processes, whereas the lower channel leads to total oxidation (combustion).

The transducers of the telemetry implant are calibrated prior to implantation and the unit is sterilized using a low pressure ethylene oxide process. 

Scientific Design. Company, Inc Ethylene glycol Ethylene and oxygen or ethylene oxide Process features variable feed capabilities with high-quality product 55 1998... 

D-values have only a very limited value for comparing the resistance of various microorganisms and various ethylene oxide processes. This is because inactivation characteristics are subject to the influence of numerous other vari-... 

As mentioned above, alkali-metal salts are used as promoters for various surface reactions [22]. One way to explain the enhanced efficiency in the presence of a promoter ion in, say, the ethylene oxide process is to propose that the alkali-metal cations (or solvent-separated ion pairs) absorb to burning sites (sites that lead ultimately to conversion to CO2). As a result of their adsorption, the reactive site is deactivated. 

A simplified process flow diagram of the air-based ethylene oxidation process is shown in Figure 2 [3J. Only the reaction section is shown as the recovery section is identical for both the air- and oxygen-based processes. 

Comparative cost estimates are presented in Table 4 for ethylene oxide processes. The higher cost of ethylene feedstock for the air-based process is a reflection of lower overall yield. More ethylene is required to compensate for the quantity that is oxidized to carbon oxides. This cost advantage for the oxygen-based process is partially offset by the cost of the oxygen and the higher cost for methane ballast gas and other chemicals for the carbon dioxide removal system. 

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