Ethylene absorption

Figure I. Vinyl chloride/poly ethylene absorption isotherms at 68°C...

Fig. 18. Effect of the ethylene absorption on the v(OH) and i>(ZnH) modes, parts (a) and (b), respectively. Spectra A and B report the regions before and after ethylene adsorption, respectively. (Unpublished results).

Ethylene. The ethylene absorption spectrum has three continua140 with bands superposed. Figure 23 presents the absorption coefficients. The continuum from 1375 to 2000 A. whose maximum lies at about 1620 A. corresponds to the V(Biu) — NQAi,) transition. While the CH2 groups in the ground-state molecule are coplanar, the upper state... 

Henry s Law constant is equal to the ratio of the vapor pressure of a species over the operating system pressure. If the number of stages required in a separation decreases with increasing Henry s Law constant, how can the Henry s Law constant be increased (i.e., of what thermodynamic variable is vapor pressure a function) Laboratory experiments were performed to assess the feasibility of separating ethylene from ethane. It was determined that the equilibrium solubilities of ethylene and ethane in an acidic copper(I) aqueous solution were similar. The rates of uptake of the two gases into the aqueous solution were measured independently and it was found that the rate of ethylene absorption is several times greater than that of ethane. Is this an example of an equilibrium- or a rate-controlled separation and why ... 

The submitters report that substitution of an ethanolie solution of sodium tetrachloroplatinate(II) reduces the time necessary for ethylene absorption to 1 day. 

A T7 —> 77 transition in excitation of ethylene. Absorption of ultraviolet radiation causes a transition of an electron from a T7-bonding MO in the ground state to a ir-antibonding MO in the excited state.There is no change in electron spin. 

We evaluated the activity profiles of some of our catalyst systems, and a representative example is shown in Figure 7.5a. In this experiment, the precatalyst 14 had been activated with MAO 10 min before the polymerization run. The solvent (toluene) was presaturated with ethylene at room temperature and the activated catalyst solution was introduced. The ethylene absorption maximum was... 

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. 

Figure Bl.22.10. Carbon K-edge near-edge x-ray absorption (NEXAFS) speetra as a fiinotion of photon ineidenee angle from a submonolayer of vinyl moieties adsorbed on Ni(lOO) (prepared by dosing 0.2 1 of ethylene on that surfaee at 180 K). Several eleetronie transitions are identified in these speetra, to both the pi (284 and 286 eV) and the sigma (>292 eV) imoeeupied levels of the moleeule. The relative variations in the intensities of those peaks with ineidenee angle ean be easily eonverted into adsorption geometry data the vinyl plane was found in this ease to be at a tilt angle of about 65° from the surfaee [71], Similar geometrieal detenninations using NEXAFS have been earried out for a number of simple adsorbate systems over the past few deeades.

Zaera F, Fischer D A, Carr R G and Gland J L 1988 Determination of chemisorption geometries for complex molecules by using near-edge X-ray absorption fine structure ethylene on Ni(IOO) J. Chem. Rhys. 89 5335-41... 

In an ambitious study, the AIMS method was used to calculate the absorption and resonance Raman spectra of ethylene [221]. In this, sets starting with 10 functions were calculated. To cope with the huge resources required for these calculations the code was parallelized. The spectra, obtained from the autocorrelation function, compare well with the experimental ones. It was also found that the non-adiabatic processes described above do not influence the spectra, as their profiles are formed in the time before the packet reaches the intersection, that is, the observed dynamic is dominated by the torsional motion. Calculations using the Condon approximation were also compared to calculations implicitly including the transition dipole, and little difference was seen. 

Bromine. Slip slightly to one side the glass plate covering one jar of ethylene, add 2-3 ml. of bromine water (preparation, p. 525), restore the glass plate in position, and then shake the jar vigorously. The colour of the bromine rapidly disappears as 1,2-dibromoethanc is formed. Note that owing to the absorption... 

Bromine. Slip the glass cover of a jar momentarily aside, add 2-3 ml. of bromine water, replace the cover and shake the contents of the jar vigorously. Note that the bromine is absorbed only very slowly, in marked contrast to the rapid absorption by ethylene. This slow reaction with bromine water is also in marked contrast to the action of chlorine water, which unites with acetylene with explosive violence. (Therefore do not attempt this test with chlorine or chlorine water.)... 

These absorptions are ascribed to n-n transitions, that is, transitions of an electron from the highest occupied n molecular orbital (HOMO) to the lowest unoccupied n molecular orbital (LUMO). One can decide which orbitals are the HOMO and LUMO by filling electrons into the molecular energy level diagram from the bottom up, two electrons to each molecular orbital. The number of electrons is the number of sp carbon atoms contributing to the n system of a neuhal polyalkene, two for each double bond. In ethylene, there is only one occupied MO and one unoccupied MO. The occupied orbital in ethylene is p below the energy level represented by ot, and the unoccupied orbital is p above it. The separation between the only possibilities for the HOMO and LUMO is 2.00p. 

The windows of the absorption cell are made from polymer material such as polyethylene, poly(ethylene terephthalate Terylene ) or polystyrene. 

Polyimide. Polyimide is a biaxiaHy oriented high performance film that is tough, flexible, and temperature- and combustion-resistant. Its room temperature properties compare to poly(ethylene terephthalate), but it retains these good characteristics at temperatures above 400°C. Its electrical resistance is good and it is dimensionally stable. The principal detriment is fairly high moisture absorbance. The main uses are for electrical insulation, particularly where high temperatures are prevalent or ionizing radiation is a problem. The films may be coated to reduce water absorption and enhance... 

Acetylene Recovery Process. A process to recover coproduct acetylene developed by Linde AG (Fig. 11), and reduced to practice in 11 commercial plants, comprises three sections acetylene absorption, ethylene stripper, and acetylene stripper. 

Fig. 11. Linde AG acetylene recovery unit for acetylene absorption, ethylene stripping, and acetylene stripping. CW = cooling water.

Ethylene Stripping. The acetylene absorber bottom product is routed to the ethylene stripper, which operates at low pressure. In the bottom part of this tower the loaded solvent is stripped by heat input according to the purity specifications of the acetylene product. A lean DMF fraction is routed to the top of the upper part for selective absorption of acetylene. This feature reduces the acetylene content in the recycle gas to its minimum (typically 1%). The overhead gas fraction is recycled to the cracked gas compression of the olefin plant for the recovery of the ethylene. 

Most by-product acetylene from ethylene production is hydrogenated to ethylene in the course of separation and purification of ethylene. In this process, however, acetylene can be recovered economically by solvent absorption instead of hydrogenation. Commercial recovery processes based on acetone, dimetbylform amide, or /V-metby1pyrro1idinone have a long history of successfiil operation. The difficulty in using this relatively low cost acetylene is that each 450, 000 t/yr world-scale ethylene plant only produces from 7000 9000 t/yr of acetylene. This is a small volume for an economically scaled derivatives unit. 

Infrared Spectra of Ionomers. Infrared absorption data, first pubHshed in 1964 (11), show that partial neutralization of ethylene—methacryhc acid introduced new absorption bands at 1480 1670 cm for the ionized carboxylate group while the 1698 — cm band of the free acid carboxyl diminishes in size (21). In addition to providing information on stmctural features, the numerous absorption bands ate significant in apphcations technology, providing rapid warmup of film and sheet under infrared radiation. 

Diphenylamine can be alkylated exclusively in the ortho positions by reacting with an olefin in the presence of aluminum diphenylamide (7), which can be readily obtained by heating DPA with powdered aluminum, or more easily by treating sodium diphenylamide with AIQ. - Ethylene is more reactive than propylene, which in turn is more reactive than isobutylene. Eor a typical reaction, a small amount of the amide is generated in a DPA melt and ethylene is introduced under pressure (5 —30 MPa) at 200—400°C. The absorption of ethylene stops after about 30 min and 2,2 -diethyldiphenylamine is obtained in 95% yield. With propylene only a 25% yield of the 2,2 -diisopropyldiphenylamine is obtained. 

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