Propylene comparison

Figure 6.15. (a) Thermal fragmentation of C3 hydrocarbons, propadiene, methylacetylene, propylene. Comparison with ethylene [34], (b) Thermal fragmentation pathways for/ -xyIene and o-xylene 135). 

All of the propylene glycols display a low acute oral toxicity in laboratory rats as shown in Table 7 (30). Information for sucrose is shown for comparison. 

Direct Oxidation of Propylene to Propylene Oxide. Comparison of ethylene (qv) and propylene gas-phase oxidation on supported silver and silver—gold catalysts shows propylene oxide formation to be 17 times slower than ethylene oxide (qv) formation and the CO2 formation in the propylene system to be six times faster, accounting for the lower selectivity to propylene oxide than for ethylene oxide. Increasing gold content in the catalyst results in increasing acrolein selectivity (198). In propylene oxidation a polymer forms on the catalyst surface that is oxidized to CO2 (199—201). Studies of propylene oxide oxidation to CO2 on a silver catalyst showed a rate oscillation, presumably owing to polymerization on the catalyst surface upon subsequent oxidation (202). 

Styrene manufacture by dehydrogenation of ethylbenzene is simple ia concept and has the virtue of beiag a siagle-product technology, an important consideration for a product of such enormous volume. This route is used for nearly 90% of the worldwide styrene production. The rest is obtained from the coproduction of propylene oxide (PO) and styrene (SM). The PO—SM route is complex and capital-iatensive ia comparison to dehydrogenation of ethylbenzene, but it stiU can be very attractive. However, its use is limited by the mismatch between the demands for styrene and propylene oxides (qv). 

A Comparison of Ethylene Glycol with Propylene Glycol, Union Carbide Chemicals and Plastics Co., Inc., Danbury, Conn., 1989. 

The economic importance of copolymers can be cleady illustrated by a comparison of U.S. production of various homopolymer and copolymer elastomers and resins (102). Figure 5 shows the relative contribution of elastomeric copolymers (SBR, ethylene—propylene, nitrile mbber) and elastomeric homopolymers (polybutadiene, polyisoprene) to the total production of synthetic elastomers. Clearly, SBR, a random copolymer, constitutes the bulk of the entire U.S. production. Copolymers of ethylene and propylene, and nitrile mbber (a random copolymer of butadiene and acrylonitrile) are manufactured in smaller quantities. Nevertheless, the latter copolymers approach the volume of elastomeric butadiene homopolymers. 

The following information was used in olefin plant case studies to determine if the ethylene/propylene cascaded refrigeration systems had enough horsepower for various plant operations. The propylene was condensed against cooling water at 110°F and the ethylene was condensed against propylene at -20°F. For comparison, the horsepower requirements for each refrigerant alone are also shown. 

The current chemical demand for propylene is a little over one half that for ethylene. This is somewhat surprising because the added complexity of the propylene molecule (due to presence of a methyl group) should permit a wider spectrum of end products and markets. However, such a difference can lead to the production of undesirable by-products, and it frequently does. This may explain the relatively limited use of propylene in comparison to ethylene. Nevertheless, many important chemicals are produced from propylene. 

Note that the flux and the area A are based on unit reactor volume. This permits direct comparison between resistances during the course of a reaction because it remains constant. Propylene concentration is expressed in gmol per liter of gas, a number which is kinetically significant. The activity of the propylene contacting the catalyst surface is assumed to be proportional to its concentration at the surface, Cg. 

Table II summarizes the yields obtained from the CONGAS computer output variable study of the gas phase polymerization of propylene. The reactor is assumed to be a perfect backmix type. The base case for this comparison corresponds to the most active BASF TiC 3 operated at almost the same conditions used by Wisseroth, 80 C and 400 psig. Agitation speed is assumed to have no effect on yield provided there is sufficient mixing. The variable study is divided into two parts for discussion catalyst parameters and reactor conditions. The catalyst is characterized by kg , X, and d7. Percent solubles is not considered because there is presently so little kinetic data to describe this. The reactor conditions chosen for study are those that have some significant effect on the kinetics temperature, pressure, and gas composition.

The new polymers are intermediate in composition and crystallinity between the essentially amorphous EPR and the semicrystalhne iPP. The presence of the complementary blocks of elastomers for both ethylene and propylene crystallinity should not indicate a similarity, beyond the levels of the crystallinity in the properties of the E-plastomers and the P-plastomers. The E-plastomers and the P-plastomers differ in their stmctural, rheological, as well as their thermal, mechanical, and elastic properties. In a comparison of the tensile strength and tensile recovery (tension set) from a 100% elongation for a range of P-plastomers and E-plastomers, the former have lower tension set than EPR and iPP. However, for comparative E-plastomers and P-plastomers at equivalent tensile strength, the latter have significantly better tension set. In summary, P-plastomers are tough polyolefins which are uniquely soft and elastic. 

Comparison of Properties of Sulfur- and Peroxide-Cured Ethylene-Propylene-Diene Rubber (EPDM)... 

DillingWL. 1977. Interphase transfer processes. 11. Evaporation rates of chloromethanes, ethanes, ethylenes, propanes, and propylenes from dilute aqueous solutions. Comparisons with theoretical predictions. Environmental Science and Technology 11 405-409. 

Allyl alcohol + NHs- The coadsorption experiments were made by first putting the catalyst into contact with NH3 at 200°C followed by removal of gaseous NH3 at r.t. and then putting the catalyst with the chemisorbed ammonia into contact with the allyl alcohol at r.t. Using procedures for the coadsorption tests like those used for propylene + NH3, less resolved spectra were obtained. The more remarkable differences in comparison with the analogous spectra for propylene + NH3 (Fig. 3) or acrylic acid + NH3 coadsorption (see below) are that (i) the band in-... 

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. 

Table 1 Comparison of degree of crystallinity for metallocene isotactic poly(propylenes) from wide-angle X-ray scattering analyzed by different methods...

Also included in Table IV are the metastable product yields for comparison to the ion beam and IR activation results. From these data it appears that the processes involving elimination of hydrogen and methane involve a competitive dissociation from a common intermediate as shown in Figure 16. However, a common intermediate may not be involved in the elimination of ethylene and propylene (the latter product appears to be formed in a faster process), and Scheme HI is overly simplistic. 

A comparison of Tables 9-12 indicates that naturally occurring species tend to produce stable membranes more abundantly. We believe this is due to the cyclic nature and rigidity of the backbone, as will be discussed in the following section of the paper. Several trends are immediately obvious. For example, the hydrophobicity of the polymer appears to be a critical parameter. While polyacrylic acid can form a stable membrane with virtually all polycations, poly-methacrylic acid is much less effective. Similarly, propylene glycol modified alginate is less effective than sodium alginate. Furthermore, when the poly-... 

Figure 4.79 displays the optimized structures of secondary-Cp (IIsec) and primary-Cp(IIPri) complexes, and Table 4.43 includes geometrical and charge parameters of these propylene complexes for comparison with those of the corresponding ethylene complex in Table 4.42. The IIsec complex can be seen to have smaller Ti—Cp metal-alkene separation (by 0.1 A) and other evidence of tighter metal-alkene binding than that in the IIpri complex, in accordance with the donor-acceptor stabilizations discussed above. 

The first comparison is based on the T values of gaseous, liquid and adsorbed molecules. Unfortunately, no measurements are available for butenes in the gas or liquid phase. Nevertheless a reasonable parallel can be drawn with propylene where the three different phases were investigated (35) at 295 K for the gas (1 atm) Tj of C2 is 0.095 s in the liquid state (2.6. M in CDCI3) 59.9, 58.7 and 65.2 s for Cj, C2 and C3 respectively adsorbed on NaY zeolite 0.81, 1.6 and 0.81 s. The shortest relaxation times characterize the gas phase where the spin-rotation mechanism (NOE factor n = 0) is very effective (30,35). In the liquid, dipole-dipole and spin-rotation mechanisms both play a role and the total relaxation rate is about three orders of magnitude lower than in the gas phase. The adsorbed molecules show therefore an intermediate behaviour between gas and liquid, as it was also suggested by chemical shift data. 

Absorption spectra, emission spectra and excitation polarization spectra were recorded in a propylene glycol-dioxane glass at 200 K. Comparison was made with the reference chromophore 2-ethylnaphthoate (NAEt). 

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