Ethylene oxide, decomposition

Antwerp, Belgium (Ref. 16) 0 An ethylene oxide decomposition led to an overpressure and rupture of a process column. There was extensive damage to the unit and blast damage (glass breakage) as far away as 6.2 mi (10 km) from the facility. 

Greater than equilibrium concentrations of intermediate species have been observed in the combustion products of several reactant systems. Examples are the concentrations of ammonia in the products of the decomposition of hydrazine (32), the concentration of CH4 in ethylene oxide decomposition (33), nitric oxide and ammonia in the products of the reaction of hydrazine and nitrogen tetroxide (34), and chlorine monofluoride in the products of the reaction of hydrazine and chlorine pentafluorlde (35). 

Similarly reactions leading to condensed phase products are also very slow. Thus, as mentioned in section U.B.4., equilibrium concentrations of carbon are not found in ethylene oxide decomposition, and it is not likely equilibrium concentrations of carbon would be found in other rocket systems, particularly low temperature ones. The slow condensed phase reaction may be the reason for some of the efficiency pro-... 

The oxidation of ethylene oxide on silver yields carbon dioxide and water, but the amounts of these are not equivalent to C2H40 consumption. Twigg believes that this is accounted for by an adsorbed organic residue formed on the catalyst surface. Ethylene also detected in oxidation products was thought to be formed by ethylene oxide decomposition to ethylene and adsorbed oxygen. 

The reaction is carried out over a supported metallic silver catalyst at 250—300°C and 1—2 MPa (10—20 bar). A few parts per million (ppm) of 1,2-dichloroethane are added to the ethylene to inhibit further oxidation to carbon dioxide and water. This results ia chlorine generation, which deactivates the surface of the catalyst. Chem Systems of the United States has developed a process that produces ethylene glycol monoacetate as an iatermediate, which on thermal decomposition yields ethylene oxide [75-21-8]. 

Ethylene oxide storage tanks ate pressurized with inert gas to keep the vapor space in a nonexplosive region and prevent the potential for decomposition of the ethylene oxide vapor. The total pressure that should be maintained in a storage tank increases with Hquid temperature, since the partial pressure of ethylene oxide will also increase. Figure 5 shows the recommended minimum storage pressures for Hquid ethylene oxide under nitrogen or methane blanketing gas. 

Liquid Hazards. Pure liquid ethylene oxide will deflagrate given sufficient initiating energy either at or below the surface, and a propagating flame may be produced (266,267). This requites certain minimum temperatures and pressures sensitive to the mode of initiation and system geometry. Under fire exposure conditions, an ethylene oxide pipeline may undergo internal decomposition either by direct initiation of the Hquid, or by formation and subsequent decomposition of a vapor pocket (190). 

While the deflagration pressure ratio for ethylene oxide vapor is about 11 or less, Hquid mist decomposition can give much greater pressures and very fast rates of pressure rise (190). 

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. 

Explosion prevention can be practiced by mixing decomposable gases with inert diluents. For example, acetylene can oe made nonexplosive at a pressure of 100 atm (10.1 MPa) by including 14.5 percent water vapor and 8 percent butane (Bodurtha, 1980). One way to prevent the decomposition reaction of ethylene oxide vapor is to use methane gas to blanket the ethylene oxide hquid. 

An explosive decomposition in an ethylene oxide (EO) distillation column, similar in its results to that described in Section 7.3.2, may have been set off by polymerization of EO in a dead-end spot in the column base where rust, a polymerization catalyst, had accumulated. Such deadends should be avoided. However, it is more likely that a flange leaked the leaking gas ignited and heated an area of the column above the temperature at which spontaneous decomposition occurs. The source of ignition of the leak may have been reaction with the insulation, as described... 

Storage tanks containing ethylene oxide are usually inerted with nitrogen. One plant used nitrogen made by cracking ammonia. The nitrogen contained traces of ammonia, which catalyzed an explosive decomposition of the ethylene oxide. Similar decompositions have been set off by traces of other bases, chlorides, and rust. 

A number of other gases can undergo reactions that produce decomposition flames—for instance, ethylene, ethylene oxide, methyl nitrate, ethyl nitrate, and hydrazine (CCPS 1993). 

Recklinghausen, K. 1978. Method and Devise for Protecting Ethylene Oxide Producing and Processing Plants Against the Decomposition of Ethylene Oxide. German Patent Submission No. P28.50254.7 (November 20, 1978). 

Decomposition Flames Flames that are produced hy exothermic decomposition of certain gases in the absence of any oxidant, provided that they are above minimum conditions of pressure, temperature, and pipe diameter. Common examples include acetylene, ethylene oxide, and ethylene. 

Specific Volume of Gases Formed on Explosion. 723ml/g (NG 712ml) (Ref 46) Stabilization. Chromatographically pure Mannitol Hexanitrate was mixed with varying percentages of 22 stabilizers and the mixts tested for stability in the 100° heat test best results were obtained with a mixt of 96% MHN, 2% Amm oxalate, and 2% dicyandiamide (4.07% wt loss after 48 hours, 5.74% after 96 hours) (Ref 56). The use of ethylene oxide as a stabilizer is reported in Ref 27 Thermal Decomposition. Slow heating causes decompn at 150° with evolution of red fumes (Ref 20, p 249)... 

DMC and EG were main products of the transesterification reaction. No by-product such as dimethyl ether and glycol monoethyl ether was observed in the resulting products. Only small peaks of ethylene oxide from the decomposition of EC could be detected at longer reaction time and at high temperature. 

The effects of reaction temperature, pressure and catalyst amount on the catalytic activity were also studied with TBAC. The results are summarized in Table 2. The conversion of EC increased with the increase of reaction temperature and the amount of catalyst. The conversion of EC and the selectivity of DMC increased as the pressure increased finm 250 psig to 350 psig. But, at the pressure over 350 psig, the EC conversion decreased. Although CO2 is not required for this reaction, its presence alters the reaction profile. It is reported that high pressure of CO2 can inhibit the decomposition of EC to ethylene oxide and C02[12]. 

When analysing the previous table, it shows the ambiguity of NFPA reactivity codes vis-a-vis instability. It is not so much an instability code but rather, like its name indicates, a code related to dangerous chemical reactions. Degrees 3 and 4 are the only ones that are more or less usable for defining an instability level, with the exception of ethylene oxide. So, even ethylene oxide s main hazard is not its explosive decomposition but its very violent polymerization caused by catalytic impurities (see chapter 6). 

The formation of peroxides and formaldehyde in the high-purity polyoxyethylene surfactants in toiletries has been shown to lead to contact dermatitis [31], Peroxides in hydrogenated castor oil can cause autoxidation of miconazole [32], Oxidative decomposition of the polyoxyethylene chains occurs at elevated temperature, leading to the formation of ethylene glycol, which may then be oxidized to formaldehyde. When polyethylene glycol and poloxamer were used to prepare solid dispersions of bendroflumethiazide, a potent, lipophilic diuretic drug, the drug reacted with the formaldehyde to produce hydroflumethiazide [33],... 

A polyether-alcohol, prepared by co-condensation of ethylene oxide and propylene oxide with a polyhydric alcohol, was stored at above 100°C and exposed to air via a vent line. After 10-15 h, violent decomposition occurred, rupturing the vessel. It was subsequently found that exothermic oxidation of the product occurred above 100°C, and that at 300°C a rapid exothermic reaction set in, accompanied by vigorous gas evolution. 

The rate of decomposition of gaseous ethylene oxide (QFUO), to CH4 and CO, has been studied by Mueller and Walters (1951) by determination of the fraction (/A) of oxide (A) reacted after a definite time interval (f) in a constant-volume batch reactor. In a series of experiments, the initial pressure of the oxide (P 0) was varied. Some of the results are as follows ... 

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