Ethylene decomposition temperature

The LDPE reactor is sometimes termed heat transfer limited in conversion. While this is true, the molecular weight (or melt index)—conversion relationship is not since this work shows that a selected initiator can allow conversion improvements to be made under adiabatic conditions for a specified molecular weight. The actual limitation to conversion is the decomposition temperature of the ethylene and given that temperature as a maximum limitation, an initiator (not necessarily commercial or even known with present initiator technology) can be found which will allow any product to be made at the rate dictated by this temperature. Conceptually, this is a constant (maximum) conversion reactor, runnirg at constant operating conditions where the product produced dictates the initiator to be used. 

Develop any necessary rate data from these values. You are given that the adiabatic decomposition temperature of gaseous ethylene oxide is 1300 K. The heat of formation of gaseous ethylene oxide at 300K is 50kJ/mol. The overall reaction is... 

These catalysts require temperatures above 100° and usually 150-200° for reasonable rates. Alkylsodium compounds at their decomposition temperatures (50-90°) have also been used by Pines and Haag (9). Lithium reacted with ethylene diamine has also been reported by Reggel et al. (4) as a catalyst for this reaction. The homogeneous system thus formed seems to lower the temperature requirement to 100° (4), whereas the use of potassium amide in liquid ammonia requires 120° (S). Sodium reacted with ethylene diamine has been reported to be an ineffective catalyst (4)- The most active catalyst systems reported so far are high-surface alkali metals and activated-alumina supports. They are very effective at or near room temperature (10-12). 

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°. 

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... 

For ADMET polymerizations in general, the condensation product, ethylene, is observed immediately followed by a rapid increase in viscosity (ca. 30 min). Polymerization reactions are heated to a maximum of 60 °C (generally considered to be catalyst decomposition temperature) and continued for several hours with evacuation of ethylene until stirring is no longer possible owing to formation of the solid state. The ADMET condensation of dienes is an exceptionally clean polymerization reaction and produces a polymer containing only one type of repeat unit and condensate. 

Table 4 shows polymerization conditions and properties of crystalline polymers of cyclobutene, cyclopentene, norbomene, and tetracyclododecene produced by zirconocenes. The activities for the polymerization of cycloalkenes are significantly lower than for ethylene. The melting points are surprisingly high they were found to be 395 °C for polycyclopentene and over 400 °C for the others the decomposition temperatures lie in the same range. 

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. 

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