Ethylene oxide Operating conditions

Process Safety Considerations. Unit optimization studies combined with dynamic simulations of the process may identify operating conditions that are unsafe regarding fire safety, equipment damage potential, and operating sensitivity. Several instances of fires and deflagrations in ethylene oxide production units have been reported in the past (160). These incidents have occurred in both the reaction cycle and ethylene oxide refining areas. Therefore, ethylene oxide units should always be designed to prevent the formation of explosive gas mixtures. 

Ethylene is currently converted to ethylene oxide with a selectivity of more than 80% under commercial conditions. Typical operating conditions are temperatures in the range 470 to 600 K with total pressures of 1 to 3 Mpa. In order to attain high selectivity to ethylene oxide (>80%), alkali promoters (e.g Rb or Cs) are added to the silver catalyst and ppm levels of chlorinated hydrocarbons (moderators) are added to the gas phase. Recently the addition of Re to the metal and of ppm levels of NOx to the gas phase has been found to further enhance the selectivity to ethylene oxide. 

GP 2] [R 2] New microstructured silver platelets have no initial activity for ethylene oxide formation [26, 40]. After treatment with the OAOR process, a small increase in activity was observed. After 1000 h of operation under oxygen conditions, larger amounts of ethylene oxide were produced. 

Another study drew a comparison between the polymerisation of ethylene oxides and propylene oxides in similar operating conditions and in the presence of 10% of sodium hydroxide. When the polymerisation reached its maximum speed, the temperature reached 439°C for the former and 451 °C for the latter the pressures obtained are 44.6 and 26.6 bar respectively. 

Fig. 4 gives the results for experiments in which all of the water used contained surfactant at a concentration of 0.02% (w/v). Under these operating conditions, maximal extraction occurred with surfactant containing 15—20 mol% ethylene oxide. This corresponds to an HLB of 7.6—8.0. The maximum value obtained was 22% of the total bitumen in the surface fraction (Makon 20). Fig. 5 gives the results for experiements in which"all the surfactant was added in a small volume of water at the beginning of the process, resulting in a much higher initial... 

There is also an apparent trend in manufacturing operations toward simplification by direct processing. Examples of this include the oxidation of ethylene for direct manufacture of ethylene oxide the direct hydration of ethylene to produce ethyl alcohol production of chlorinated derivatives by direct halogenation in place of round-about syntheses and the manufacture of acrolein by olefin oxidation. The evolution of alternate sources, varying process routes, and competing end products has given the United States aliphatic chemical industry much of its vitality and ability to adjust to varying market conditions. 

The Carbowax column is very sensitive to oxidation when the stationary phase is exposed to traces of water or air especially at temperatures above about 160°C. A new type of cross-linking has been reported to impart resistance to oxidative degradation of the stationary phase [5-7]. Two other phases which show promise are an oligo-(ethylene oxide)-substituted polysiloxane (glyme) and an 18-crown-6-substituted polysilox-ane [8]. The glyme column offers a polar phase with good operational conditions to a low of a least 20°C with the same selectivity of Carbowax. The crown polysiloxane selectivity is based on the interaction of the solute molecule with the cavity of the crown ether. 

The nature of ethylene oxide and, to a lesser degree, the higher alkylene oxides, because of their high reactivity, flammability and explosion hazards mean that plants handling these reactants must be designed to eliminate all possible ignition sources. Reactions must be operated in inert conditions and have explosion pressure rated plant design [ 1-4]. 

Description Ammonia solution, recycled amines and ethylene oxide are fed continuously to a reaction system (1) that operates under mild conditions and simultaneously produces MEA, DEA and TEA. Product ratios can be varied to maximize MEA, DEA or TEA production. The correct selection of the NH3/EO ratio and recycling of amines produces the desired product mix. The reactor products are sent to a separation system where ammonia (2) and water are separated and recycled to the reaction system. Vacuum distillation (4,5,6,7) is used to produce pure MEA, DEA and TEA. A saleable heavies tar byproduct is also produced. Technical grade TEA (85 wt%) can also be produced if required. 

The liquid phase processes resembled Wacker-Hoechst s acetaldehyde process, i.e., acetic acid solutions of PdCl2 and CuCl2 are used as catalysts. The water produced from the oxidation of Cu(I) to Cu(II) (Figure 27) forms acetaldehyde in a secondary reaction with ethylene. The ratio of acetaldehyde to vinyl acetate can be regulated by changing the operating conditions. The reaction takes place at 110-130°C and 30-40 bar. The vinyl acetate selectivity reaches 93% (based on acetic acid). The net selectivity to acetaldehyde and vinyl acetate is about 83% (based on ethylene), the by-products being CO2, formic acid, oxalic acid, butene and chlorinated compounds. The reaction solution is very corrosive, so that titanium must be used for many plant components. After a few years of operation, in 1969-1970 both ICI and Celanese shut down their plants due to corrosion and economic problems. 

Occupational exposure of sterilizing staff to ethylene oxide in hospitals, tissue banks, and research facilities can result during any of the following operations and conditions (1) ... 

Figure P3.31 is the flow diagram for the process. The catalytic reactor operates at 300 C and 1.2 atm. At these conditions, single-pass measurements on the reactor show that 50% of the ethylene entering the reactor is consumed per pass, and of this, 70% is converted to ethylene oxide. The remainder of the ethylene consumed decomposes to form CO2 and water.

This section describes in detail three topics in heterogeneous catalysis to which DFT calculations have recently been applied with great effect, the prediction of CO oxidation rates over RuO2(110), the prediction of ammonia synthesis rates by supported nanoparticles of Ru, and the DFT-based design of new selective catalysts for ethylene epoxidation. All three examples involve the careful application of DFT calculations and other appropriate theoretical methods to make quantitative predictions about the performance of heterogeneous catalysts under realistic operating conditions. 

All these reactions and especially the latter two. which correspond to the complete combustion of ethylene and of its oxide, are highly exothermic and complete. in the operating conditions of ethylene oxide synthesis. To guide the transformation in the direction of the first reaction, the operations require the presence of a metallic catalyst. The catalyst is generally considered to act according to the foliowring reaction mechanism ... 

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