Ethylene decomposition

On the contrary, on oxygen-modified metal surfaces where secondary reactions between the adsorbed oxygen and ethylene decomposition products can easily occur, the effect of oxygen on the adsorptive capacity of the... 

Carbon dioxide can form as a result of combustion of ethylene, acetic acid, or vinyl acetate. The 1,2 C-ethylene experiments provided evidence on the role of Au and KOAc and its influence over the formation of carbon dioxide in the process. COj would be a characteristic of acetate decomposition, while COj would be characteristic of ethylene decomposition. 

Reduction of NO is promoted by N atoms and CH2 radicals formed by ethylene decomposition, but it is much less important as compared to oxidation. 

Tris(ethylene)platinum(0) is stable for several hours at 20° under 1 atm of ethylene and keeps for many weeks at -20°.6 In the absence of ethylene, decomposition to metallic platinum occurs in minutes at room temperature. The complex is quite volatile, with a vile smell, and sublimes slowly at 20° in an atmosphere of ethylene onto a cold finger at 0°. 

Loss prevention of polyethylene plants is outlined in Chapter 7.2. The major hazard that can occur is the runaway of the high-pressure reactor and decomposition of ethylene besides fire and disintegration of high-pressure separators, pipes, and compressors. The critical conditions for runaway and ethylene decomposition during homo- and copolymerization are revealed together with the influence of decomposition sensitizers. Relief devices and venting systems are described. 

Energy balance for a bursting polyethylene reactor during ethylene decomposition. Pressure 200 MPa volume 0.5 m3 [20] ... 

The major hazard that can occur in the high-pressure polyethylene process is a runaway of the reactor and decomposition of ethylene as well as fires, explosion, and disintegration of high-pressure parts. Although the last incidents are well understood, the reasons for runaway and ethylene decomposition have been evaluated only recently. Experience over twenty years has shown that decomposition mostly takes place in the reactor and in the high-pressure separator, but decompositions have also been reported from ethylene-feed and product lines. 

In a review of low level ethylene decomposition since its discovery in 1842, the main factors are recognised as pressure—temperature—ignition relationships, heat balance in... 

As discussed in Chapter 2 (sections 2.2 and 2.3), safety is a key consideration in high pressure processes. Handling organic peroxides presents potential hazards, but another serious concern is the possibility of ethylene decomposition within the reactor. High pressure processes must be designed to relieve pressure rapidly to prevent catastrophic explosions. Mirra of Polimeri Europa has described a reactor safety discharge system that quenches hot gases if an ethylene "decomp" takes place (4). 

Carter EA, Koel BE (1990) A method for estimating surface reaction energetics Application to the mechanism of ethylene decomposition on Pt(lll). Surf Sci 226 339... 

The relative importance of the electronic properties of the surface, the surface geometry of the crystal lattice, and the effect of imperfections cannot be resolved from this study of ethylene hydrogenation. In the case of high temperature ethylene decomposition, it is indicated that dislocations may have an important role. Although it is not posable at this time definitely to attribute the formation of carbon to dislocations, evidence in this direction has been found. Some aspects of this factor are discussed in the section on results. 

Fig. 7. The model of ethylene decomposition and hydrogenation over the cobalt foil catalyst...

In the high-pressure LDPE reactor, runaway reactions can occur with very fast increases in temperature (>500 °C) and pressure (maximum achievable pressure limited by safety devices) and this can lead to ethylene decomposition. Thermal decomposition of ethylene is a radical reaction leading to the formation of carbon, hydrogen, and methane. The decomposition reaction may occur at temperatures above 330 °C when the operating pressure is above 2500 barg. At lower pressures, higher temperatures are required to have spontaneous decomposition. Other factors such as impurities or the presence of iron oxides or other metal oxides can facilitate the initiation of this reaction. 

Ethylene decomposition is strongly exothermic (AHjecomp ethylene = 125kJ/mol) and its associated reaction heat causes simultaneous temperature and pressure increases inside the reactor vhthin a few seconds, further accelerating the decomposition reaction itself... 

One of the well-known phenomena in high-pressure polyethylene processes is a rapid ethylene decomposition reaction or thermal runaway, known as decomp. At 300°C, ethylene and even polyethylene decompose to carbon, methane, hydrogen, and other hydrocarbon by-products. When the decomposition reaction takes place, the reactor pressure builds up quickly and the reactor must be vented, shut down, and flushed for a long period of time before a new startup is initiated. The resulting economic loss will be quite... 

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