Acetylene ethylene oxide process

Diol Components. Ethylene glycol (ethane 1,2-diol) is made from ethylene by direct air oxidation to ethylene oxide and ring opening with water to give 1,2-diol (40) (see Glycols). Butane-1,4-diol is stiU made by the Reppe process acetylene reacts with formaldehyde in the presence of catalyst to give 2-butyne-l,4-diol which is hydrogenated to butanediol (see Acetylene-DERIVED chemicals). The ethynylation step depends on a special cuprous... 

Decomposition Flame Arresters Above certain minimum pipe diameters, temperatures, and pressures, some gases may propagate decomposition flames in the absence of oxidant. Special in-line arresters have been developed (Fig. 26-27). Both deflagration and detonation flames of acetylene have been arrested by hydrauhc valve arresters, packed beds (which can be additionally water-wetted), and arrays of parallel sintered metal elements. Information on hydraulic and packed-bed arresters can be found in the Compressed Gas Association Pamphlet G1.3, Acetylene Transmission for Chemical Synthesis. Special arresters have also been used for ethylene in 1000- to 1500-psi transmission lines and for ethylene oxide in process units. Since ethylene is not known to detonate in the absence of oxidant, these arresters were designed for in-line deflagration application. 

This displaced more complex, capital-and-energy-intensive processes based on acetylene or ethylene oxide ... 

Acrylonitrile was first produced in Germany and the United States on an industrial scale in the early 1940s. These processes were based on the catalytic dehydration of ethylene cyanohydrin. Ethylene cyanohydrin was produced from ethylene oxide and aqueous hydrocyanic acid at 60°C in the presence of a basic catalyst. The intermediate was then dehydrated in the liquid phase at 200°C in the presence of magnesium carbonate and alkaline or alkaline earth salts of fonnic acid. A second commercial route to acrylonitrile was the catalytic addition of hydrogen cyanide to acetylene. The last commercial plants using these process technologies were shut down in 1970 (Langvardt, 1985 Brazdil, 1991). 

Acrolein and condensable by-products, mainly acrylic acid plus some acetic acid and acetaldehyde, are separated from nitrogen and carbon oxides in a water absorber. However in most industrial plants the product is not isolated for sale, but instead the acrolein-rich effluent is transferred to a second-stage reactor for oxidation to acrylic acid. In fact the volume of acrylic acid production ca. 4.2 Mt/a worldwide) is an order of magnitude larger than that of commercial acrolein. The propylene oxidation has supplanted earlier acrylic acid processes based on other feedstocks, such as the Reppe synthesis from acetylene, the ketene process from acetic acid and formaldehyde, or the hydrolysis of acrylonitrile or of ethylene cyanohydrin (from ethylene oxide). In addition to the (preferred) stepwise process, via acrolein (Equation 30), a... 

The initial drive for acrylonitrile (AN) production (6.2 Mt/a in 2004 worldwide) was the discovery, in the late 1930s, of the synthetic rubber Buna N. Today nitrile rubbers represent only a minor outlet for AN which is utilized primarily for polymerization to give textile fibres (50%) and ABS resins (24%), and for dimerization to adiponitrile (10%). Early industrial processes depended on the addition of hydrogen cyanide to acetylene or to ethylene oxide, followed by the dehydration of intermediate ethylene cyanohydrin. Both processes are obsolete and are now supplanted by the ammoxidation of propylene (Equation 34) introduced in 1960 by Standard Oil of Indiana (Sohio). The reason for the success stems from the effectiveness of the catalyst and because propylene,... 

The vinoxy CH2CHO and 1-methylvinoxy (acetonyl) radicals are key intermediates in the mechanisms of many reactions of importance for atmospheric and combustion chemistry. The formation of vinoxy radicals has been observed in several chemical processes. They may be formed in reactions of OH radicals with ethylene oxide (C2H4O) and with acetylene (C2H2) in the presence of 02.8 They are also produced in reactions of 0(3P) atoms with alkenes and in the reactions of reactive atoms such as F or 0(3P) with acetaldehyde.164,165 The 1-methylvinoxy (acetonyl) radical CH2C(CH3)0 is considered an important intermediate in the atmospheric oxidation of acetone initiated by the OH radical.166171 Spectroscopic studies by Washida et al.164 and Williams et al.m allow estimation of the rate constant for the reaction of acetonyl with 02. 

Under suitable conditions methane forms higher liquid and solid hydrocarbons when heated.89 These conditions have been found to be short times of contact on the order of less than one second and at temperatures of 1000° to 1200° C. The products may consist of acetylene, ethylene, ethane, higher olefins, benzene and higher aromatic hydrocarbons, carbon, and hydrogen.40 However, as the temperature range in which these effects have been noted is much higher than is used in oxidation work an investigation of the process is not warranted here. 

By exploding mixtures of ethane and oxygen in borosilicate bulbs, carbon monoxide, hydrogen, methane, acetylene, and ethylene have been obtained.10 140 As the initial pressure is decreased the amount of unsaturated hydrocarbons and water in the products showed a tendency to increase. The fact that no carbon is produced in these experiments and that water and ethylene are formed lends support to Bone s hydroxylation theory since it is probable that the alcohol formed in the initial step is dehydrated immediately to yield unsaturated hydrocarbon and water. The presence of hydrogen and aldehyde, especially at lower initial pressures, is also indicative of alcohol dissociation. The failure of any ethanol to appear in the product does not preclude its formation and immediate decomposition. It is hardly to be expected that ethanol if formed would exist long enough to pass out of the reaction zone and appear in the product since it is known that at the temperature of the oxidation process ethanol is entirely unstable. 

From 1930 to 1950, there were essentially no major improvements in the manufacturing technology for vinyl chloride. Two processes were available, either the reaction of acetylene with hydrochloric acid to obtain vinyl chloride according to the German technology or thermal cracking of ethylene dichloride (EDC). Ethylene dichloride was available either as a by-product of the chlorohydrin process for ethylene oxide or made by the chlorination of ethylene. 

The ammoxidation process ( eq. 8 ) displaced the more expensive acetylene-HCN-based route in the early 1960 s (eq. 20). Other obsolete processes also involve more expensive reagents (e.g. ethylene oxide, eq. 19, and acetaldehyde, eq. 21) and oxidants (e.g. NO, eq. 22). The impact of the introduction of the ammoxidation process in 1960 was an immediate drastic reduction in acrylonitrile price and greatly increased production which made possible many of today s high-volume applications of acrylonitrile (Figure 6A). The production of acrylonitrile, which accounts for 17% of the total U. S. propylene consumption, is used extensively in fibers, plastics and resins (ARS/SA) and rubber industries, with a growing number of miscellaneous applications, including the electro-hydrodimerization process for adiponitrile production (Figure 6B). 

Even while he was busy with the manufacture of ethylene oxide, Walter Reppe was also involved with the development of Buna synthetic rubber. In 1926, the newly formed I.G. Farben decided to embark on the industrial synthesis of rubber, despite the poor quality of the methyl rubber made during World War I. This time, however, it was agreed that butadiene would be used. Several routes to butadiene were investigated, including decyclization of cyclohexene (a retro-Diels-Alder reaction), but the so-called four-step process (Vierstufen Verfahren) soon won out. This was partly because it used acetylene, and hence surplus carbide from cyanamide manufacture, but also because it drew on the steps - and hence the momentum - of the BASF butanol synthesis. As a member of the former butanol group, Reppe was a natural candidate for the four-step process project. 

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