Propylene production comparison

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. 

Comparison of Propylene Production of Different Zeolite Combination... 

This table, points out the low production of propylene in comparison with the steam cracking of naphtha, the high coproduction of acetylene ranging up to nearly 150 kg t ofethyiene instead of the 15 kg/t observed in naphtha steam cracking, and the substantial formation of fuel oil and tars. 

The basis of the economic evaluation is the comparison of operating and investment costs for a membrane reactor with those for a conventional dehydrogenation plant. The return on investment (ROI) and the propylene production costs of the different processes have been calculated. The results are summarised in Table 14.6. Details of the calculations are reported in Ref. [33]. In the calculations a propane price of 130 /tonne and a propylene price of 330 /tonne has been assumed [33]. 

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). 

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. 

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. 

Dunkelberg H Carcinogenic activity of ethylene oxide and its reaction products 2-chloroethanol, 2-bromoethanol, ethylene glycol and diethylene glycol. I. Carcinogenicity of ethylene oxide in comparison with 1,2-propylene oxide after subcutaneous administration in mice. 7M Bakt Hyg I Abt OrigB 174 383-404, 1981... 

Hydrocarbon oxidation on base metal catalysts is also susceptible to lead poisoning, especially if the catalysts are exposed to relatively high temperatures, for at least part of their service time. It was noted above that lead retention, especially on base metal catalysts, also increases with temperature up to a certain point. This behavior is shown by the results of Yao and Kummer (81) in Fig. 18. One should note that the hydrocarbon used for testing catalyst activity, namely propylene, was quite reactive. With a less reactive test hydrocarbon one could expect a still sharper effect. The comparison with a reference production noble metal catalyst, given in Fig. 18, is quite instructive. 

The calculated thermodynamic equilibrium conversions and product compositions for propylene disproportionation at 200 to 400 C were reported by Heckelsberg, Banks, and Bailey16). Atlar, Pis man, and Bakhshi-Zade 8S) made similar calculations for the 50 - 300 °C range. They noted that the equilibrium constants were independent of pressure. Banks and Regier 57) showed thermodynamic equilibrium conversions as a function of temperature for the various reactions involved in the synthesis of isoamylene via disproportionation (Fig. 3). A comparison of calculated equilibrium composition for... 

Table II. Comparison between the pore size of catalysts and the product distributions of meta-diisopropylbenzene alkylation with propylene at...

Figure 2. A comparison of product TPD spectra obtained after exposure of 1.6 L propanal, 2.3 L 1-propanol, or 2.1 L propylene oxide to the clean Rh(l 11) surface at ca. 91 K.

The e.s.r. spectrum of a deposit formed by the deposition of hydrogen atoms on propylene in a matrix of adamantane is shown in Fig. 18. Comparison with the spectra of the two possible product radicals, n-propyl and isoprop3d, shows clearly that addition has occurred almost exclusively to the terminal CH2-group to form the isopropyl radical. The possibility that a small amount of n-propyl radical is present cannot be ruled out, but from an analysis of the e.s.r. spectrum it is conservatively 3... 

The comparison is made not in relative percentages, but in terms of the relative Quantities of each of the products (including the feedstock), for a given production of ethylene and consequently propylene. 

Further evidence for heterolytic decomposition is obtained from the effect of olefin structure on product distribution. Table II shows the ratio of carbonyl to glycol product for three olefins. Listed for comparison is the carbonyl/glycol ratio for the chlorohydrin, which corresponds to the structure of the oxythallation adduct from ethylene and propylene. The effect of structure on the ratio is qualitatively the same for the thallic ion oxidation and the hydrolysis of the corresponding chlorohydrin. Since the product distributions for both are inconsistent with neighboring hydroxyl participation (Reaction 33) the carbonyl/glycol ratio is a measure of the competition between hydride shift vs. water attack in... 

---