Propylene oxide, base chemical

The following describes some of the important chemicals based on propylene oxide. 

Polyetheramines. Polyetheramines are produced by reacting polyols derived from ethylene oxide or propylene oxide with amines. The more commercially successful adducts are based on propylene oxide and are available in different MWs (JEFFAMINE from Huntsman). The longer chain backbone provides improved flexibility but slower cure rate. Chemical and thermal resistance properties are also reduced. Polyetheramines are often used in combination with other amines in flooring, and adhesive and electrical potting applications. 

Propylene requirements for acrylates remain small compared to other chemical uses (polypropylene, acrylonitrile, propylene oxide, 2-propanol, and cumene for acetone and phenol). Hence, cost and availabihty are expected to remain attractive and new acrylate capacity should continue to be propylene-based until after the turn of the century. 

Dehydrochlorination to Epoxides. The most useful chemical reaction of chlorohydrins is dehydrochlotination to form epoxides (oxkanes). This reaction was first described by Wurtz in 1859 (12) in which ethylene chlorohydria and propylene chlorohydria were treated with aqueous potassium hydroxide [1310-58-3] to form ethylene oxide and propylene oxide, respectively. For many years both of these epoxides were produced industrially by the dehydrochlotination reaction. In the past 40 years, the ethylene oxide process based on chlorohydria has been replaced by the dkect oxidation of ethylene over silver catalysts. However, such epoxides as propylene oxide (qv) and epichl orohydrin are stiU manufactured by processes that involve chlorohydria intermediates. 

The most important chemical reaction of chi orohydrin s is dehydrochloriaation to produce epoxides. In the case of propylene oxide. The Dow Chemical Company is the only manufacturer ia the United States that still uses the chlorohydrin technology. In 1990 the U.S. propylene oxide production capacity was hsted as 1.43 x 10 t/yr, shared almost equally by Dow and Arco Chemical Co., which uses a process based on hydroperoxide iatermediates (69,70). More recentiy, Dow Europe SA, aimounced a decision to expand its propylene oxide capacity by 160,000 metric tons per year at the Stade, Germany site. This represents about a 40% iacrease over the current capacity (71). 

Statistical and block copolymers based on ethylene oxide (EO) and propylene oxide (PO) are important precursors of polyurethanes. Their detailed chemical structure, that is, the chemical composition, block length, and molar mass of the individual blocks may be decisive for the properties of the final product. For triblock copolymers HO (EO) (PO)m(EO) OH, the detailed analysis relates to the determination of the total molar mass and the degrees of polymerization of the inner PPO block (m) and the outer PEO blocks (n). 

The most recent entrant-to the. club of commodity chemicals is 1,4-butanediol (BDO), a petrochemical used in some of the more specialized applications such as chemical intermediates for the production of tetrahydro-furane and gama-butyrolactone, polybutylene terephthalate, and the more familiar polyurethanes. Traditionally, the Reppe process was the primary route to BDO, based bn acetylene and formaldehyde feeds. More recently, the share of BDO from butane and propylene oxide based production has grown rapidly. 

Chlorine (from the Greek chloros for yellow-green ) is the most abundant halogen (0.19 w% of the earth s crust) and plays a key role in chemical processes. The chlor-alkali industry has been in operation since the 1890s and improvements in the technology are still important and noticeable, for example, the transition from the mercury-based technology to membrane cells [60]. Most chlorine produced today is used for the manufacture of polyvinyl chloride, chloroprene, chlorinated hydrocarbons, propylene oxide, in the pulp and paper industry, in water treatment, and in disinfection processes [61]. A summary of typical redox states of chlorine, standard potentials for acidic aqueous media, and applications is given in Scheme 2. 

Building on earlier work in these laboratories (8) we have overcome the typical mass transfer limitations of phase transfer catalysis for propylene oxidation by the use of 3-component liquid phases based on CO2 expanded liquids (CXLs). For the application to oxidations by aqueous H2O2, the organic component of the CXL is chosen because it is miscible with both dense CO2 and water. In this way, homogeneous systems are produced which decrease mass-transfer limitations and intensify chemical reactions. Previous reports using CXL systems have shown that they enhance the oxidation of the substrate and improve the selectivity at moderate reaction temperatures and pressures (3, 8, 9). 

Ethylene and Propylene Oxides. Ethylene oxide (26) and its derivatives are among the important aliphatic chemicals the 1950 production amounted to between 400,000,000 and 500,000,000 pounds. The chlorohydrin process was introduced in the early 1920 s and the direct oxidation process in the 1930 s, both based on ethylene. In the older process, the one most used today, the ethylene reacts in solution with hypo-chlorous acid at room temperature. 

The oxidation of propylene oxide on porous polycrystalline Ag films supported on stabilized zirconia was studied in a CSTR at temperatures between 240 and 400°C and atmospheric total pressure. The technique of solid electrolyte potentiometry (SEP) was used to monitor the chemical potential of oxygen adsorbed on the catalyst surface. The steady state kinetic and potentiometric results are consistent with a Langmuir-Hinshelwood mechanism. However over a wide range of temperature and gaseous composition both the reaction rate and the surface oxygen activity were found to exhibit self-sustained isothermal oscillations. The limit cycles can be understood assuming that adsorbed propylene oxide undergoes both oxidation to CO2 and H2O as well as conversion to an adsorbed polymeric residue. A dynamic model based on the above assumption explains qualitatively the experimental observations. 

Standard Oil of California added the petrochemicals of Gulf Oil, purchased in 1984, to its subsidiary Chevron Chemical. Other United States petrochemical producers took advantage of special circumstances. Amoco was served by a strong terephthalic (TPA) base and its good performance in polypropylene Arco, by its Lyondell subsidiary in Channelview, Texas, and by its development of the Oxirane process through which propylene oxide could be produced by direct oxidation with styrene as a coproduct. The process also led to MTBE (methyl tertiary-butyl ether), the antiknock agent used as a substitute for tetraethyl lead. 

Hiis method, initially intended for the more selective production of propylene oxide, is commercialized by ARCO Chemical (formerly Oxirane an Atlantic Richfield Co subsidiary, and by Sheli The first industrial plant was built in 1973 by Montoro, a Joint venture of Oxirane and Empecrol, at Alcudia, Spain. This plant can now manufacture 100.0CX) t/year of styrene and 40,000 t/year of propylene oxide. Two other facilities based on this technology are also in operadoo, one at Channelview, Texas, and the second in Japan, owned jointly by Sumitomo and Showa Denka (Nippon Oxirane), capable of producing 455,000 and 225,000 t year of styrene respectively, as well as about 180,000 and 90.0001/ year of propylene oxide. Shell has also built production capacities of 330,000 and 12SJXX) tf year of these two products at its Moerdijk complex in the Netherlands. 

Similar to the basic surface studies discussed above, promoters often show markedly different behaviors depending on the alkene species used. Lambert and co-workers (68) reported a study of ethene and propene epoxidation with different promoters that showed no real correlation based on the promoter used. In the case of NOx species as promoters, there was no effect for the formation of propylene oxide, which is interesting considering the high activity of NO in formation of ethylene oxide. Also, addition of potassium ions into the NO promoter feed decreased both activity and selectivity for propylene oxide formation, again completely opposite to the behavior seen for EO. As in the other surface studies, the authors postulate a chemical effect from the presence of allylic hydrogens. 

The key to the success of the oxidation examples cited above is the ability of the catalysts used to exert proper kinetic control on the possible side reactions. Without it, thermodynamically favorable but undesired products such as CO2 and H2O are made instead. Controlling oxidation kinetics to stop at the desired oxygenated products is quite difficult, and has yet to be solved for many other systems. For instance, although many attempts have been made to develop a commercial process for the oxidation of propylene to propylene oxide, both the activity and the selectivity of the systems proposed to date, mostly based on silver catalysts, are still too low to be of industrial interest " propylene oxide is presently manufactured by processes based on chlorohydrin or hydrogen peroxide instead. In spite of these difficulties, though, recent advances in selective liquid phase oxidation of fine chemicals on supported metal catalysts have shown some promise, offering high yields (close to 100%) under mild reaction conditions." ... 

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