1-Propylene oxide

Propylene oxide is similar in its structure to ethylene oxide, but due to the presence of an additional methyl group, it has different physical and chemical properties. It is a liquid that boils at 33.9°C, and it is only slightly soluble in water. (Ethylene oxide, a gas, is very soluble in water). 

The main method to obtain propylene oxide is chlorohydrination followed by epoxidation. This older method still holds a dominant role in propylene oxide production. Chlorohydrination is the reaction between an olefin and hypochlorous acid. When propylene is the reactant, propylene chlorohydrin is produced. The reaction occurs at approximately 35°C and normal pressure without any catalyst  

Approximately 87-90% yield could be achieved. The main by-product is propylene dichloride (6-9%). The next step is the dehydrochlorination of the chlorohydrin with a 5% Ca(OH)2 solution  

The second important process for propylene oxide is epoxidation with peroxides. Many hydroperoxides have been used as oxygen carriers for this reaction. Examples are t-butylhydroperoxide, ethylbenzene hydroperoxide, and peracetic acid. An important advantage of the process is that the coproducts from epoxidation have appreciable economic values. 

Epoxidation of propylene with ethylbenzene hydroperoxide is carried out at approximately 130°C and 35 atmospheres in presence of molybdenum catalyst. A conversion of 98% on the hydroperoxide has been reported  

Propylene oxide [75-56-9] (methyloxirane, 1,2-epoxypropane) is a significant organic chemical used primarily as a reaction intermediate for production of polyether polyols, propylene glycol, alkanolamines (qv), glycol ethers, and many other useful products (see Glycols). Propylene oxide was first prepared in 1861 by Oser and first polymerized by Levene and Walti in 1927 (1). Propylene oxide is manufactured by two basic processes the traditional chlorohydrin process (see Chlorohydrins) and the hydroperoxide process, where either / fZ-butanol (see Butyl alcohols) or styrene (qv) is a co-product. Research continues in an effort to develop a direct oxidation process to be used commercially. 

Propylene oxide is a colorless, low hoiling (34.2°C) liquid. Table 1 lists general physical properties Table 2 provides equations for temperature variation on some thermodynamic functions. Vapor—liquid equilibrium data for binary mixtures of propylene oxide and other chemicals of commercial importance ate available. References for binary mixtures include 1,2-propanediol (14), water (7,8,15), 1,2-dichloropropane [78-87-5] (16), 2-propanol [67-63-0] (17), 2-methyl-2-pentene [625-27-4] (18), methyl formate [107-31-3] (19), acetaldehyde [75-07-0] (17), methanol [67-56-1] (20), ptopanal [123-38-6] (16), 1-phenylethanol [60-12-8] (21), and / /f-butanol [75-65-0] (22,23). 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 133 

Polymerization to Polyether Polyols. The addition polymerization of propylene oxide to form polyether polyols is very important commercially. Polyols are made by addition of epoxides to initiators, ie, compounds that contain an active hydrogen, such as alcohols or amines. The polymerization occurs with either anionic (base) or cationic (acidic) catalysis. The base catalysis is preferred commercially (25,27). 

Some of the simplest polyols are produced from reaction of propylene oxide and propylene glycol and glycerol initiators. Polyether diols and polyether triols are produced, respectively (27) (see Glycols). 

Propylene Oxide. Unlike ethylene, propylene cannot be selectively transformed to propylene oxide by silver-catalyzed oxidation. Instead, indirect oxidations (the peracid and the hydroperoxide routes) are employed.912-915 

In the peracid process (Bayer-Degussa technology916) propionic acid is oxidized by hydrogen peroxide in the presence of H2S04 to yield perpropionic acid, which, in turn, is used to oxidize propylene to propylene oxide. The peracetic acid process (Daicel technology ) employs a mixture of acetaldehyde, ethyl acetate, and 

About 50% of the current worldwide propylene oxide capacity is based on a newer process called hydroperoxide (coproduct or oxirene) route (Halcon-Arco technology919,920). According to this process, hydroperoxides synthesized by the oxidation of certain hydrocarbons, such as ethylbenzene or isobutane, are used for epoxidation of propylene in the presence of a transition-metal catalyst  

The additional advantage of this process is the possibility of the utilization of the alcohol products. fcrf-BuOH (and MTBE, its methyl ether) is used as a gasoline additive. It can be dehydrated to yield isobutylene, which is used to produce high-octane alkylates (see Section 5.5.1). 1-Phenylethanol is dehydrated to styrene over Ti02 on alumina.919 

In the C4 coproduct route isobutane is oxidized with oxygen at 130-160°C and under pressure to tert-BuOOH, which is then used in epoxidation. In the styrene coproduct process ethylbenzene hydroperoxide is produced at 100-130°C and at lower pressure (a few atmospheres) and is then applied in isobutane oxidation. Epoxidations are carried out in high excess of propylene at about 100°C under high pressure (20-70 atm) in the presence of molybdenum naphthenate catalyst. About 95% epoxide selectivity can be achieved at near complete hydroperoxide and 10-15% propylene conversions. Shell developed an alternative, heterogeneous catalytic system (T1O2 on SiOi), which is employed in a styrene coproduct process.913 914 

Propylene oxide, 1,2-epoxy-propane, PO, is a very reactive substance and one of the most important chemical intermediates.The worldwide propylene oxide capacity was estimated to 4.9 million t/y in 1996, the increase is ca. 4%/y. After the PVC production, the chlorination of propylene is the second largest single chlorine consumer. 

The chlorohydrin process is carried out in two steps the synthesis of propylene chlorohydrin, PCH, and subsequent dehydrochlorination of PCH to PO. In the first step, propene and chlorine are reacted in aqueous solution to give a mixture of 90 % l-chloro-2-propanol and 10 % 2-chloro-l-propanol 

In the second step, this mixture is dehydrochlorinated with a base, either lime (Ca(OH)2) or caustic soda to form crude PO and a dilute salt stream of CaCl2 or NaCl. 

The PO is removed rapidly by steam in order to prevent hydrolysis and is subsequently condensed and purified by distillation. Half of the alkali is used for the conversion of PCH to PO, the other half is required to neutralize the hydrogen chloride produced in the chlorohydrination step. Ca. 1.4 tonnes of CaCl2 per tonne of PO are formed as waste water. 

Byproducts are dichlorodiisopropylether, which is incinerated, and dichloropropane, which is used as a solvent. 

About 60% of the propylene oxide made is polymerized to polypropylene glycol and other polyethers for use in polyurethane foams and adhesives. Propylene glycol is also widely used in polyester resins based on maleic anhydride. 

Most automobile and furniture seating, foam mattresses, carpet underlay-ment, and other similar products are made from polyurethanes based on polypropylene glycol (PPG). PPG is the preferred raw material for these type of polymers because of the wide variation of possible properties of the end product and the relatively low cost. 

Almost all of the isopropylbenzene produced is used for making phenol and acetone. The largest use of acetone is as a chemical intermediate to methyl methacrylate and along with phenol to make bisphenol A for preparation of polymers. Acetone is also used widely as a solvent. 

Suppliers Shell, Sunoco Chemical, Aristech Chemical, Georgia Gulf, Dow Phenolchemie, Union Carbide, and others. 

About a billion pounds per year of methyl methacrylate is made from acetone, hydrogen cyanide, and methanol. 

World annual production of propylene oxide is about 4 billion pounds (1.8 million metric tons) (1982). About 42 percent of this production is in the United States, about 44 percent is in Western Europe, and about 10 percent is in Japan. The principal uses for propylene oxide in the United States are listed in Table 4. 

The second largest use of propylene oxide is for propylene glycol. Propylene glycol, 

There are two major processes used to produce propylene oxide the chlorohydrin process and peroxidation of propylene. More than half of world production is by the chlorohydrin route. In this process, the first step is reaction of propylene with hypochlorous acid to obtain propylene chlorohydrin. 

Propylene chlorohydrin is then treated with caustic or calcium hydroxide to obtain propylene oxide. 

While the chlorohydrin process is efficient, it consumes caustic and chlorine and produces by-product salt. It is difficult to operate this process unless production is associated with a sizable chlor-alkali business. In the United States, about half of the production capacity for propylene oxide uses the chlorohydrin process. 

There are two important methods for the manufacture of propylene oxide. The older method involves chlorohydrin formation from the reaction of propylene with chlorine water (Fig. 1). 

The dilute cholorohydrin solution is mixed with a 10% slurry of lime to form the oxide, which is purified by distillation, boiling point 34°C. The yield is 90 percent. 

A new variation of the chlorohydrin process uses /-butyl hypochlorite as the chlorinating agent. The waste brine solution can be converted back to chlorine and caustic by a special electrolytic cell to avoid the waste of chlorine. 

The second manufacturing method for propylene oxide is via peroxidation of propylene (Halcon process). Oxygen is first used to oxidize Ao-butane to /-butyl hydroperoxide (BHP) over a molybdenum naphthenate catalyst at 90°C and 450 psi (Fig. 2). 

4CH3CH(CH3)CH3 + 302 - 2CH3C(CH3)2OOH + 2(CH3)3COH The /-butyl hydroperoxide is then used to oxidize propylene to the oxide. 

Highly flammable flash point (closed cup) —17°C (0°F) vapor pressure 1095 torr at 20°C (68°F) vapor density 1.5 (air=l) the vapor can travel a considerable distance to a source of ignition and flash back ignition temperature in air 429°C (804°F), ignition temperature in the absence of air (100% ethylene oxide) 570°C (1058°F) fireextinguishing agent use a water spray from an explosion-resistant location to fight fire use water to flush the spill and to keep containers cool. 

Ethylene oxide forms an explosive mixture with air the LEL and UEL values are 3% and 100% by volume, respectively. It explodes when heated in a closed vessel. It polymerizes violently when in contact with active catalyst surfaces. Rearrangement or polymerization occurs exothermically in the presence of concentrated acids and bases, alkali metals, oxides of iron and aluminum, and their anhydrous chlorides (Hess and Tilton 1950). It may explode when combined with alcohols and mercaptans or with ammonia under high pressure (NEPA 1986). 

Ethylene oxide is stored in an outside cool area below 30°C (86°E), provided with a water-spray system, and isolated from combustible materials such as acids, bases, chlorides, oxides, and metallic potassium. Protect against physical damage. Avoid inside storage. Shipping should be done in steel cylinders, drums, and insulated tank cars. 

Ethylene oxide can be analyzed by a gas chromatograph equipped with ECD or PID. Ambient air drawn directly into a syringe is injected into a Carbopack column in a GC 

DOT Label Flammable Liquid, UN 1280 Formula C3H7O MW 58.08 CAS [75-56-9] Structure and functional group  

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An example of this t3T)e of reaction which does not produce a byproduct is the production of allyl alcohol from propylene oxide ... 

Alkanolamines with at least one NCH2CHOHCH,i grouping. Important materials include monoisopropanolamine NHX H CHOHCH, b.p. 159 C di-iso-propanolamine NH(CH CHOHCH b.p. 248 C triisopropanolamine NtCH -CHOHCHi). , b.p. 300 C. Manufactured from ammonia and propylene oxide. U ed, is weedkillers, as stabilizers for plastics, in detergents, alkanolaniine soaps for sweetening natural gas and in synthesis. 

Styrene is manufactured by alkylating benzene with ethene followed by dehydrogenation, or from petroleum reformate coproduction with propylene oxide. Styrene is used almost exclusively for the manufacture of polymers, of which the most important are polystyrene, ABS plastics and styrene-butadiene rubber. U.S. production 1980 3 megatonnes. 

DIblook oopolymers of ethylene oxide and propylene oxide... 

Alexandridis P and Hatton T A 1995 Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) blook oopolymer surfaotants in aqueous solutions and at interfaoes thermodynamios, struoture, dynamios, modeling Colloids Surf. A 96 1-46... 

Bloor D M, Wan-Yunis W M Z, Wan-Badhi W A, Li Y, Hoizwarth J F and Wyn-Jones E 1995 Equilibrium and kinetio studies assooiated with the binding of sodium dodeoyl sulfate to the polymers poly(propylene oxide) and ethyl-(hydroxyethyl)oellulose Langmuir 3395-400... 

Fig. 6. Snapshot from a dynamic density functional simulation of the self-organisation of the block copolymer PL64 (containing 30 propylene oxide rmd 26 ethylene oxide units (EO)i3(PO)3o(EO)i3) in 70% aqueous solution. The simulation was carried out during 6250 time steps on a 64 x 64 x 64 grid (courtesy of B.A.C. van Vlimmeren and J.G.E.M. Praaije, Groningen).

Three membered rings that contain oxygen are called epoxides At one time epox ides were named as oxides of alkenes Ethylene oxide and propylene oxide for exam pie are the common names of two industrially important epoxides... 

Substitutive lUPAC nomenclature names epoxides as epoxy derivatives of alkanes According to this system ethylene oxide becomes epoxyethane and propylene oxide becomes 1 2 epoxypropane The prefix epoxy always immediately precedes the alkane ending it is not listed m alphabetical order like other substituents... 

PROPENE The major use of propene is in the produc tion of polypropylene Two other propene derived organic chemicals acrylonitrile and propylene oxide are also starting materials for polymer synthesis Acrylonitrile is used to make acrylic fibers (see Table 6 5) and propylene oxide is one component in the preparation of polyurethane polymers Cumene itself has no direct uses but rather serves as the starting material in a process that yields two valuable indus trial chemicals acetone and phenol... 

Hydrogen fluoride Acetic anhydride, 2-aminoethanol, ammonia, arsenic trioxide, chlorosulfonic acid, ethylenediamine, ethyleneimine, fluorine, HgO, oleum, phosphorus trioxide, propylene oxide, sodium, sulfuric acid, vinyl acetate... 

Figure 4.12 Spherulites of poly( 1-propylene oxide) observed through crossed Polaroid filters by optical microscopy. See text for significance of Maltese cross and banding in these images. [From J. H. MaGill, Treatise on Materials Science and Technology, Vol. lOA, J. M. Schultz (Ed.), Academic, New York, 1977, with permission.]...

This situation can be generalized. If the ratios do not become constant until the ratio of pentads to tetrads is considered, then the unit before the next to last-called the antepenultimate unit-plays a role in the addition. This situation has been observed for propylene oxide-maleic anhydride copolymers. 

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