Ethylene temperature

Circulating this stream faster or slower through the refrigeration unit keeps the liquid ethylene temperature in balance with the change in temperature outside the tank. 

Toluene alkylation by ethylene temperature inside catalyst bed... 

The experiments under examination are carried out at temperatures higher than the critical ethylene temperature. The observed effects cannot possibly result from any ethylene liquefaction (capillary condensation) within the solid pores. 

Temperature Effect. The experiments concerning temperature effects are carried out between — 80°C. and -b60°C. in the presence of a 5 A. LMS. Comparison of various experiments with constant ethylene and solid quantity submitted to equal amounts of gamma energy, at temperatures beyond 9°C. which is the critical ethylene temperature, shows the polymerization rate to decrease with increasing temperature. Below 9°C. down to — 80°C., the polymerization rate varies slowly and seems to be slightly affected by temperature. 

The effect of that Cs loading was studied by O2 TPD and by ethylene temperature-programmed reaction [3]. The O2 desorption spectrum obtained by Atkins and co-workers for the Cs/Ag/v-AhOa catalyst is shown in Fig. 7.9, lower curve. The upper curve with two peak maxima at 523 K (250 °C) and 573 K (300 °C) is that shown previously for O2 desorption from a fresh, unpromoted Ag/a-Al2O3 catalyst (Fig. 7.1). 

The ethylene temperature-programmed reaction spectrum of an oxygen-covered Cs/Ag/a-Al203 catalyst produced a peak for the co-evolution of EO and CO2 at 373 K (100 °C) with a selectivity to EO of 44%. The Cs had had no effect on the kinetics of desorption of oxygen from Ag(lll) nor on the amount of oxygen desorbing from that surface, nor on its selectivity in its oxidising ethylene to EO (Eig. 7.10). 

F. 43. Plot of quantity F,)/(F — 1 ) against the logarithm (rf time for the crystallization rf a linear poly(ethylene). Temperature of crystallization is indicated for each isotherm. [Ref. (246fl... 

The first section of the reactor is used as preheater. The ethylene temperature must be sufficiently high to start the reaction. While only organic peroxides are used as an initiator for the autoclave reactor, oxygen (air) is also used to generate the free radicals needed to initiate the polymerization reaction in the tubular reactor. 

Some technological problems involved in building large LDPE production units are process operation, size of compressors, reactor structure, high-pressure valves, and safety problems [7]. Due to high exothermicity of the polymerization reaction, the removal of reaction heat is a critical design problem. Factors that affect the heat removal include reactor surface/volume ratio, reaction mixture and feed ethylene temperature difference, thickness of the polyethylene layer at the inner wall of the reactor, reaction mixture flow rate, and reactor material heat conductance. It should be noted that the thickness of the laminar layer at the reactor wall is affected by the reaction mixture flow rate. 

A fiowsheet for this part of the vinyl chloride process is shown in Fig. 10.5. The reactants, ethylene and chlorine, dissolve in circulating liquid dichloroethane and react in solution to form more dichloroethane. Temperature is maintained between 45 and 65°C, and a small amount of ferric chloride is present to catalyze the reaction. The reaction generates considerable heat. 

Under certain conditions of temperature and pressure, and in the presence of free water, hydrocarbon gases can form hydrates, which are a solid formed by the combination of water molecules and the methane, ethane, propane or butane. Hydrates look like compacted snow, and can form blockages in pipelines and other vessels. Process engineers use correlation techniques and process simulation to predict the possibility of hydrate formation, and prevent its formation by either drying the gas or adding a chemical (such as tri-ethylene glycol), or a combination of both. This is further discussed in SectionlO.1. 

Studies to determine the nature of intermediate species have been made on a variety of transition metals, and especially on Pt, with emphasis on the Pt(lll) surface. Techniques such as TPD (temperature-programmed desorption), SIMS, NEXAFS (see Table VIII-1) and RAIRS (reflection absorption infrared spectroscopy) have been used, as well as all kinds of isotopic labeling (see Refs. 286 and 289). On Pt(III) the surface is covered with C2H3, ethylidyne, tightly bound to a three-fold hollow site, see Fig. XVIII-25, and Ref. 290. A current mechanism is that of the figure, in which ethylidyne acts as a kind of surface catalyst, allowing surface H atoms to add to a second, perhaps physically adsorbed layer of ethylene this is, in effect, a kind of Eley-Rideal mechanism. 

Prepare a Grignard reagent from 24 -5 g. of magnesium turnings, 179 g. (157 ml.) of n-heptyl bromide (Section 111,37), and 300 ml. of di-n-butyl ether (1). Cool the solution to 0° and, with vigorous stirring, add an excess of ethylene oxide. Maintain the temperature at 0° for 1 hour after the ethylene oxide has been introduced, then allow the temperature to rise to 40° and maintain the mixture at this temperature for 1 hour. Finally heat the mixture on a water bath for 2 hours. Decompose the addition product and isolate the alcohol according to the procedure for n-hexyl alcohol (Section 111,18) the addition of benzene is unnecessary. Collect the n-nonyl alcohol at 95-100°/12 mm. The yield is 95 g. 

If the temperature is allowed to rise to 170°, much of the ethyl hydrogen sulphate decomposes into ethylene ... 

The number of ethylenic linkages In a given compound can be established with accuracy by quantitative titration with perbenzoic acid. A solution of the substance ajid excess of perbenzoic acid in chloroform is allowed to stand for several hours at a low temperature and the amount of unreacted perbenzoic acid in solution is determined a blank experiment is run simultaneously. 

Ethylene. Under the influence of pressure and a catalyst, ethylene yields a white, tough but flexible waxy sohd, known as Polythene. Polyethylene possesses excellent electric insulation properties and high water resistance it has a low specific gravity and a low softening point (about 110°). The chemical inertness oi Polythene has found application in the manufacture of many items of apparatus for the laboratory. It is a useful lubricant for ground glass connexions, particularly at relatively high temperatures. 

The salt gradually dissolved. After an additional 30 min (at -60°C) the solution was cooled to -75°C and 19 ml of dry, pure HMPT and 0.4 mol (large excess) of ethylene oxide (cooled below 0°C) were added successively in 1-2 min. The temperature of the mixture was held at -60°C for 2 h, and was then allowed to rise gradually in 2 h to 0°C. Ice-water (200 ml) was added (with stirring) and, after Separation of the layers, five extractions with diethyl ether were carried out. 

A solution of a-lithiomethoxyallene was prepared from nethoxyal lene and 0.20 mol of ethyllithiurn (note 1) in about 200 ml of diethyl ether (see Chapter II, Exp. 15). The solution was cooled to -50°C and 0.20 mol of ethylene oxide was added immediately. The cooling bath was removed temporarily and the temperature was allowed to rise to -15 c and was kept at this level for 2.5 h. The mixture was then poured into 200 ml of saturated ammonium chloride solution, to which a few millilitres of aqueous ammonia had been added (note 2). After shaking the layers were separated. The aqueous layer was extracted six times with small portions of diethyl ether. The combined ethereal solutions were dried over sodium sulfate and subsequently concentrated in a water-pump vacuum. Distillation of the... 

A suspension of di1ithiohexyne in diethyl ether was made from 0.20 mol of 1-hexyne and 0.5 mol ethyllithium in 400 ml of diethyl ether in the same way as described for 1-heptyne (see this chapter, Exp. 27). The suspension was cooled to -40°C and at this temperature a solution of 0.20 mol of ethylene oxide in 50 ril of diethyl ether was added in 15 min, the brown colour changing into yellow. Subsequently the temperature was allowed to rise graduallyduring 1 h to +5°C. 

Athene formation requires that X and Y be substituents on adjacent carbon atoms By mak mg X the reference atom and identifying the carbon attached to it as the a carbon we see that atom Y is a substituent on the p carbon Carbons succeedmgly more remote from the reference atom are designated 7 8 and so on Only p elimination reactions will be dis cussed m this chapter [Beta (p) elimination reactions are also known as i 2 eliminations ] You are already familiar with one type of p elimination having seen m Section 5 1 that ethylene and propene are prepared on an industrial scale by the high temperature dehydrogenation of ethane and propane Both reactions involve (3 elimination of H2... 

The reaction is endothermic and the equilibrium favors ethylene at low temperatures but shifts to favor acetylene above 1150°C Indeed at very high temperatures most hydro carbons even methane are converted to acetylene Acetylene has value not only by itself but IS also the starting material from which higher alkynes are prepared... 

The simplest of all Diels-Alder reactions cycloaddition of ethylene to 1 3 butadi ene does not proceed readily It has a high activation energy and a low reaction rate Substituents such as C=0 or C=N however when directly attached to the double bond of the dienophile increase its reactivity and compounds of this type give high yields of Diels-Alder adducts at modest temperatures... 

When applied to the synthesis of ethers the reaction is effective only with primary alcohols Elimination to form alkenes predominates with secondary and tertiary alcohols Diethyl ether is prepared on an industrial scale by heating ethanol with sulfuric acid at 140°C At higher temperatures elimination predominates and ethylene is the major product A mechanism for the formation of diethyl ether is outlined m Figure 15 3 The individual steps of this mechanism are analogous to those seen earlier Nucleophilic attack on a protonated alcohol was encountered m the reaction of primary alcohols with hydrogen halides (Section 4 12) and the nucleophilic properties of alcohols were dis cussed m the context of solvolysis reactions (Section 8 7) Both the first and the last steps are proton transfer reactions between oxygens... 

It resembles polytetrafiuoroethylene and fiuorinated ethylene propylene in its chemical resistance, electrical properties, and coefficient of friction. Its strength, hardness, and wear resistance are about equal to the former plastic and superior to that of the latter at temperatures above 150°C. 

Next let us examine an experimental test of the Avrami equation and the assortment of predictions from its various forms as summarized in Table 4.3. Figure 4.9 is a plot of ln[ln(l - 0)" ] versus In t for poly (ethylene terephtha-late) at three different temperatures. According to Eq. (4.35), this type of... 

Figure 4.9 Log-log plot of ln(l - 6) versus time for poly(ethylene tereph-thalate) at three different temperatures. [Reprinted from L. B. Morgan, Philos. Trans. R. Soc. London 247A 13 (1954).]...

The crystallization of poly(ethylene terephthalate) at different temperatures after prior fusion at 294 C has been observed to follow the Avrami equation with the following parameters applying at the indicated temperatures ... 

Ester interchange reactions are valuable, since, say, methyl esters of di-carboxylic acids are often more soluble and easier to purify than the diacid itself. The methanol by-product is easily removed by evaporation. Poly (ethylene terephthalate) is an example of a polymer prepared by double application of reaction 4 in Table 5.3. The first stage of the reaction is conducted at temperatures below 200°C and involves the interchange of dimethyl terephthalate with ethylene glycol... 

The rate of this reaction is increased by using excess ethylene glycol, and removal of the methanol is assured by the elevated temperature. Polymer is produced in the second stage after the temperature is raised above the melting point of the polymer, about 260°C. 

Ben2onitri1e [100-47-0] C H CN, is a colorless Hquid with a characteristic almondlike odor. Its physical properties are Hsted in Table 10. It is miscible with acetone, ben2ene, chloroform, ethyl acetate, ethylene chloride, and other common organic solvents but is immiscible with water at ambient temperatures and soluble to ca 1 wt% at 100°C. It distills at atmospheric pressure without decomposition, but slowly discolors in the presence of light. 

Hydrolysis yielding terephthaHc acid and ethylene glycol is a third process (33). High temperatures and pressures are required for this currently noncommercial process. The purification of the terephthaHc acid is costly and is the reason the hydrolysis process is no longer commercial. 

Materials that typify thermoresponsive behavior are polyethylene—poly (ethylene glycol) copolymers that are used to functionalize the surfaces of polyethylene films (smart surfaces) (20). When the copolymer is immersed in water, the poly(ethylene glycol) functionaUties at the surfaces have solvation behavior similar to poly(ethylene glycol) itself. The abiUty to design a smart surface in these cases is based on the observed behavior of inverse temperature-dependent solubiUty of poly(alkene oxide)s in water. The behavior is used to produce surface-modified polymers that reversibly change their hydrophilicity and solvation with changes in temperatures. Similar behaviors have been observed as a function of changes in pH (21—24). 

Other examples of materials that respond smartly to changes in temperature are the poly(ethylene glycol)s-modifted cottons, polyesters, and... 

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