Commercial Production of Ethylene Oxide

EO was first mentioned in 1859 by the French chemist Charles Adolphe Wurtz (1817-1884), who prepared EO by the reaction of ethylene chlorohydrin with a potassium hydroxide solution. After its discovery, EO became increasingly attractive to the chemical industry (during the First World War as precursor for the coolant 

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A method of considerable industrial importance for the large-scale preparation of ethylene oxide is direct oxidation of ethylene at elevated temperatures over a suitably prepared metallic silver catalyst. Although the reaction may be written aa indicated in Eq. (09), in actual practice only about half the ethylene is converted into ethylene oxide, the remainder being oxidized further to carbon dioxide and water. In spite of this seeming disadvantage, catalytic oxidation appears at present to bo economically competitive with chlorohydrin formation aa a means for the commercial production of ethylene oxide.MM Unfortunately, other olefins, such as propylene and mo-butylene for example, apparently give only carbon dioxide and water under the usual oxidation conditions,1310 so that until now the patent hu balance ethylene oxide has been the only representative accessible by tins route. 

P3-8 There were 5430 milhon pounds of ethylene oxide produced in the United States in 1995. The flowsheet for the commercial production of ethylene oxide (EO) by oxidation of ethylene is shown below. We note that the process essentially consists cf two systems, a reaction system and a separation system. Describe how your answers to P3-7 c,)would change if air is used as a feed This reaction is studied further in Example 4-6. 

Biological. Several recent patents have claimed the production of ethylene oxide from a wide variety of raw materials using enzymatic catalysts (221—224). However, no commercial production routes based on biological mechanisms have been proposed. 

Ethanolamines became available commercially in the early 1930s they assumed steadily growing commercial importance as intermediates after 1945, because of the large-scale production of ethylene oxide. Since the mid-1970s, economical production of very pure, colourless ethanolamines has been possible. Ethanolamines are produced on an industrial scale exclusively by reaction of ethylene oxide (see lARC, 1994) with excess ammonia. This reaction takes place slowly but is accelerated by water. An... 

Methane-based commercial production of ethylene via oxidative coupling has been investigated, but to date the lower per pass conversions required for acceptable ethylene selectivities combined with purified oxygen costs make this process noncompetitive with thermal cracking of ethane from natural gas liquids. 

Table 12 gives the average commercial specifications of ethylene oxide. Its main uses in 1984 are listed in Table 73 for Western Europe, the United States and Japan. Production. capacities and consumption for these three geographic areas are also given. 

There is a great demand for ethylene as a consequence of wide applications of ethylene based products like polythene (HDPE and LDPE) poly vinyl chloride, styrene, ethylene oxide, ethylene glycol etc. The commercial production of ethylene is carried out by two different well known routes, viz. 

Commercial polyacetal copolymers contain 0.1 to 15 mole percent of a cyclic ether, commonly ethylene oxide or 1,3-dioxolane. Typical catalysts for this reaction are BF, or its ether complexes. In 1964, Weissermel and coworkers[5] showed that in the copolymerization of trioxane with ethylene oxide, the latter was almost completely consumed before any visible polymer was observed. During this stage of the polymerization, soluble prepolymers of ethylene oxide could be isolated [6], These prepolymers consisted primarily of oligomers with mono-, di-, and tri-ethylene oxide units. Celanese workers in 1980[7] verified also the presence of cyclic ethers, predominately 1,3-dioxolane and 1,3,5-tri-oxepane, as part of the reaction mixture. These are likely formed as reaction products of ethylene oxide and monomeric formaldehyde generated from the opening of the trioxane ring. 

Processes rendered obsolete by the propylene ammoxidation process (51) include the ethylene cyanohydrin process (52—54) practiced commercially by American Cyanamid and Union Carbide in the United States and by I. G. Farben in Germany. The process involved the production of ethylene cyanohydrin by the base-cataly2ed addition of HCN to ethylene oxide in the liquid phase at about 60°C. A typical base catalyst used in this step was diethylamine. This was followed by liquid-phase or vapor-phase dehydration of the cyanohydrin. The Hquid-phase dehydration was performed at about 200°C using alkah metal or alkaline earth metal salts of organic acids, primarily formates and magnesium carbonate. Vapor-phase dehydration was accomphshed over alumina at about 250°C. 

In 1937 the first commercial apphcation of the Lefort direct ethylene oxidation to ethylene oxide [73-21-8] followed by hydrolysis of ethylene oxide became, and remains in the 1990s, the main commercial source of ethylene glycol production (1) (see Ethylene oxide). Ethylene oxide hydrolysis proceeds with... 

Ethylene glycol can be produced by an electrohydrodimerization of formaldehyde (16). The process has a number of variables necessary for optimum current efficiency including pH, electrolyte, temperature, methanol concentration, electrode materials, and cell design. Other methods include production of valuable oxidized materials at the electrochemical cell s anode simultaneous with formation of glycol at the cathode (17). The compound formed at the anode maybe used for commercial value direcdy, or coupled as an oxidant in a separate process. 

Another attractive commercial route to MEK is via direct oxidation of / -butenes (34—39) in a reaction analogous to the Wacker-Hoechst process for acetaldehyde production via ethylene oxidation. In the Wacker-Hoechst process the oxidation of olefins is conducted in an aqueous solution containing palladium and copper chlorides. However, unlike acetaldehyde production, / -butene oxidation has not proved commercially successflil because chlorinated butanones and butyraldehyde by-products form which both reduce yields and compHcate product purification, and also because titanium-lined equipment is required to withstand chloride corrosion. 

Ethoxylated andSulfatedAlkylphenols. Because these aLkylphenols degrade less readily than the sulfated alcohol ethoxylates, their anticipated expansion failed to materialize, although by 1965 they were widely used in retail detergent products. Sulfated alkylphenol ethoxylates are used in hospital cleaning products, textile processing, and emulsion polymerization. Sulfated alkyphenol ethoxylates are sold as colorless, odorless aqueous solutions at concentrations of >30%. The presence of ethylene oxide in the molecule increases resistance to hardness ions and reduces skin irritation. Representative commercial sulfated alkylphenol ethoxylates are given in Table 12. 

There are other commercial processes available for the production of butylenes. However, these are site or manufacturer specific, eg, the Oxirane process for the production of propylene oxide the disproportionation of higher olefins and the oligomerisation of ethylene. Any of these processes can become an important source in the future. More recentiy, the Coastal Isobutane process began commercialisation to produce isobutylene from butanes for meeting the expected demand for methyl-/ rZ-butyl ether (40). 

Equation 1 is referred to as the selective reaction, equation 2 is called the nonselective reaction, and equation 3 is termed the consecutive reaction and is considered to proceed via isomerization of ethylene oxide to acetaldehyde, which undergoes rapid total combustion under the conditions present in the reactor. Only silver has been found to effect the selective partial oxidation of ethylene to ethylene oxide. The maximum selectivity for this reaction is considered to be 85.7%, based on mechanistic considerations. The best catalysts used in ethylene oxide production achieve 80—84% selectivity at commercially useful ethylene—oxygen conversion levels (68,69). 

Ethylene oxide treatment can also be considered as an alternative to radiation sterilizahon in the commercial production of disposable medical devices (Chapter 21). These techniques do not, however, offer the same degree of sterility assuranee as heat methods and are generally reserved for temperature-sensihve items. 

Commercial mixtures of surfactants consist of several tens to hundreds of homologues oligomers and isomers. Their separation and quantification is complicated and a cumbersome task. Detection, identification and quantification of these compounds in aqueous solutions, even in the form of matrix-free standards, present the analyst with considerable problems. The low volatility and high polarity of some surfactants and their metabolites hamper the application of gas-chromatographic (GC) methods. GC is directly applicable only for surfactants with a low number of ethylene oxide groups and to some relatively volatile metabolic products, while the analysis of higher-molecular-mass oligomers is severely limited and requires adequate derivatisation. 

An industrial blend of ethylene oxide (EO) PEMS marketed as a personal care product was examined by positive ion FIA-APCI-MS and LC-APCI-MS-MS (Fig. 2.8.8) [41]. The FIA-APCI-MS spectrum without LC separation (Fig. 2.8.8(a)) is dominated by ions corresponding to unreacted PEG (m/z 520, 564, 608, 652,...), whilst the ions corresponding to the PEMS (m/z 516, 560, 604, 648,...) could only be clearly observed following LC separation (Fig. 2.8.8(b)). Comparison of the TIC chromatograms of PEMS and PEG (Fig. 2.8.8(c) and (h)) demonstrates the dominance of the PEG by-products in the commercial formulation. It is unclear whether the observed relative intensities are representative of the actual amounts or of the different ionisation efficiencies, due to the confidential nature of the product composition. However, the spectra indicate a trisiloxane surfactant structure of that shown in Fig. 2.8.2 (R = Ac) and FIA-MS analysis of another commercial formulation of this product showed good spectra dominated by the silicone surfactants [48], indicating that the PEG by-product composition can vary significantly in commercially available PEMS formulations. 

The chemical uses for ethylene prior to World War II were limited, for the most part, to ethylene glycol and ethyl alcohol. After the war, the demand for styrene and polyethylene took off, stimulating ethylene production and olefin plant construction. Todays list of chemical applications for ethylene reads like the WTiat s What of petrochemicals polyethylene, ethylbenzene (a precursor to styrene), ethylene dichloride, vinyl chloride, ethylene oxide, ethylene glycol, ethyl alcohol, vinyl acetate, alpha olefins, and linear alcohols are some of the more commercial derivatives of ethylene. The consumer products derived from these chemicals are found everywhere, from soap to construction materials to plastic products to synthetic motor oils. 

Most commercial products are mixtures because of the way they are manufactured. For instance many surfactant hydrophobes come from assorted products such as petroleiun alkylate cuts or triglyceride oils, with a molecular weight distribution that could be narrow or wide. Usually, a purification and separation of single isomeric species would be too costly and, in most cases, pointless. Moreover, the synthesis reactions involved in the surfactant manufacturing might be the intrinsic reason of the production of a mixture, such as in the case of polycondensation of ethylene oxide which results in an often wide spread ethylene oxide munber (EON) distribution. A residual content of some intermediates or by-products might also be a significant cause for mixture effects. 

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