Propylene oxide

Chemical properties

Propylene oxide （PO） is a clear colorless volatile liquid with an ethereal odor. The industrial products are the racemic mixture for two optical isomers. It can be partially miscible with water [the solubility at 20 °C in water is 40.5% by weight; water solubility in propylene oxide is 12.8% by weight]. It can be miscible with ethanol and ethyl ether and form a binary azeotrope with dichloromethane, pentane, pentene, cyclopentane and cyclopentene.
Propylene oxide molecule contains an asymmetrical carbon atom, being able to carry out many chemical reactions. It has slightly lower chemical activity than ethylene oxide with reaction with active hydrogen (such as water, alcohols, acids, amines) containing material, with ring-opening to form diol, alcohol ether and alcohol amine. Hydrolysis reaction can generate propylene glycol with etherification reaction leading to the formation of alcohol ether. Under the action of catalyst, it can produce polyether polyol. Reaction with glycerol can generate polyether triol. It can react with carboxylic acid to generate ester. It can react with ammonia, leading to the formation of alcohol amine. It can react with hydrogen halide to generate halogenated alcohol. It can react with hydrogen sulfide to generate mercaptan formation. It can react with thiophenol to generate hydroxypropyl benzene sulfide. Under the catalysis of the trimethylamine, it can react with carbon disulfide, leading to the formation of allyl trithiocarbonate. Under the action of catalyst, it can be isomerized to generate propionaldehyde. Propylene oxide is toxic with irritating effect on skin and eyes, even at a concentration of 1%. Its vapor can cause stimulation of respiratory organs and eyes with inhaled causing the inhibition on the central nervous system. Rat oral LD50:930mg/kg. The maximum allowable concentration of the workplace is 20 × 10-6.

Figure 1 the three-dimensional structure of propylene oxide.

Uses

Propylene oxide is an excellent low-boiling solvent and raw material of organic synthesis, being able to be used for the preparation of propylene glycol, glycerol, propylene glycol, polyester resin, foam and surfactants. It can also be used as the solvent of cellulose acetate, nitrocellulose and resin solvents. Propylene oxide can react with ammonia to produce isopropanolamine (monoisopropanolamine, diisopropanolamine and triisopropanolamine). Isopropanolamine is alkaline, being able to absorb acidic gas, widely used in gas purification such as the desulfurization of synthetic ammonia industry and decarbonation.

1. Propylene oxide is mainly used in the production of propylene glycol, polyether polyols, polypropylene glycol, propylene glycol ether and synthetic glycerin, also used in the manufacture of isopropanolamine, propylene carbonate;
2. It can be used for the manufacturing of organic synthesis and plastics, also used as solvents, chromatography standards;
3. Epoxypropane is an intermediate of metolachlor and is also an important chemical industrial raw material for the organic synthesis. It can be used for the production of propylene glycol, propylene alcohol, propionaldehyde, isopropylamine, synthetic glycerol, organic acid, etc., and can also used for preparing nonionic surfactant, wetting agents, emulsifiers, detergents and the like.
4. Propylene oxide is an important organic chemical raw material. It is the third largest product of propylene system. The largest use is to produce poly (polyether), which is used in the distribution of US and Western Europe. The application in the aspect accounts respectively for 60% and 70% or more. Propylene oxide can be used for the manufacturing of propylene Glycol, organic Acids, Synthetic Resins, Foam Plasticizers, Plasticizers, Emulsifiers, Wetting Agents, Detergents, Bactericides, fumigants and the like. Propylene oxide-derived fine chemicals are used in virtually all industrial sectors and in everyday life.
5. It can be used as disinfectant.
6. It is important petrochemical raw materials for the production of polyether, propylene glycol, surfactants, foaming agent, demulsifier and mineral processing agent.
7. The usage amount of propylene oxide for various kinds of applications: polyether polyol (raw materials of polyurethane plastic): Propylene glycol: (raw material of unsaturated polyester resin) 60%; 8% to 10%; reinforced plastics and non-toxic solvents: 20%~25%; surfactant: 5% to 10%.

Identification test

Solubility: 1g can be dissolved in 1.7ml water; miscible in ethanol and ether (OT-42).

Content analysis

Same as the content analysis in "07115, ethylene oxide", but the formula can be changed to:
Propylene oxide (%) = NaOH solution volume (ml) x 0.0581/sample mass x 100%

Toxicity

LD50:580mg/kg (mice, oral) direct inhalation of its vapor can cause vomiting, diarrhea, coma.
Propylene oxide is less toxic than ethylene oxide with stimulating effect of the major role, together with mild anesthetic and original pulp toxicity. Direct contact can stimulate the skin with severe cases causing skin necrosis. The olfactory threshold was 360 mg/m3. At a few minutes after inhalation of high concentrations can cause poisoning, eye and upper respiratory tract irritation symptoms, difficulty in breathing, head pain, dizziness, weakness, calf muscle spasms, gait instability, nausea, vomiting and diarrhea, restlessness, delirium and coma. During the disease course, it can be seen of elevated blood pressure, arrhythmia, myocardial damage, gastrointestinal bleeding, toxic intestinal paralysis and liver and kidney damage.
Because of its poisoning symptoms may be related to increased levels of histamine and other biologically active substances, it can be treated with anti-histamine drugs and sodium thiosulfate.
The threshold for epoxypropane in the air at workplace is tentatively set at 240 mg/m3 (TLV-TWA, US, 1980), with a maximum allowable concentration of 1 mg/m3 (Sue, 1972).

Usage limit

The maximum allowable concentration in the place of disinfection is 1mg/m3.

Production method

There are mainly chlorohydrin method and indirect oxidation. 1. Chlorohydrin method; apply propylene, chlorine and water for being acidified by hypochlorous at 60 °C under normal pressure to generate chloropropanol, followed by saponification, condensation and distillation to derive. 2. Indirect oxidation: it is derived from the oxidation of ethylbenzene (or isobutane, cumene, etc.) to form hydrogen peroxide ethylbenzene (or tert-butyl hydroperoxide, cumene hydroperoxide, etc.), which further has epoxidation with propylene in the catalysis of naphthenic acid molybdenum. (3) Electrochemical Chlorohydrin Method: this method is based on the principle that the aqueous solution of sodium chloride (or potassium chloride, sodium bromide, sodium iodide) for electrolysis to generate chlorine and sodium hydroxide. Send the propylene in the anode area to generate chlorine alcohol, which further reacts with sodium hydroxide to generate propylene oxide in the cathode area.
The preparation method is as follows.
(1) Chlorohydrin method
Take propylene as raw materials, followed by hypochlorous acidification, saponification, and then enrichment and distillation to derive the products.
The reaction of propylene with hypochlorous acid is carried out in an aqueous solution, and the chlorine gas is mixed with hypochlorous acid and hydrochloric acid in water. The reaction temperature is 30-50 DEG C, and the produced aqueous chloropropanol and 10% lime milk are saponified in a saponification reactor for saponification; the saponification kettle is sent into the water vapor, steaming out the propylene oxide, and then subject to condensed distillation derived products.
CH3CH = CH2 + HOCl →CH3CHOHCH2Cl + CH3CHClCH2OH
This method requires a low purity of propylene, and the yield is high, but it consuming large amounts of chlorine and lime milk, equipment with serious corrosion on the device, resulting in environmental pollution problems. It is mainly adopted in China to produce propylene oxide.
 (2) Peroxide method
The main process is the manufacture of organic hydrogen peroxide. Apply peroxide for oxidation of propylene. This reaction is always liquid phase reaction either in the production of organic hydrogen peroxide or in the presence of a catalyst for the transfer of oxygen from the peroxide to the propylene molecule. In addition to produce the propylene oxide as the main product, there are also co-products.
Current ways that has realized industrialization include ethyl benzene Haakon method and isobutane Haakon method.
Ethylbenzene Haakon mainly adopts ethylbenzene as raw material for production of ethylbenzene hydroperoxide by oxidation. Under the catalyst of copper naphthenate, it is subject to propylene epoxidation reaction, generating propylene oxide as well as alpha-phenylethanol simultaneously, followed by dehydration to give the styrene.
The reaction temperature of ethylbenzene oxidation is 130-150 ℃, the pressure is 0.07-0.14 MPa, the selectivity of generating ethylbenzene hydroperoxide is 90%; the temperature of epoxidation is 50-120 ℃; The pressure is between atmospheric pressure to 0.864 MPa. For example, a mixture of 14% of ethylbenzene hydroperoxide, 35% of propylene, 50% of ethylbenzene and 1% of α-phenylethanol is added to 0.4% of naphthenic acid manganese naphthenate (nMo/nNa = 2 , Molar ratio) to be as the catalyst for reaction at 1.5 h at 100 ℃, resulting conversion rate of ethylbenzene hydroperoxide, 99% and selectivity of propylene oxide as 78%. The reaction product can be obtained by distillation of propylene oxide to obtain the finished product. The α-phenylethanol, in the dehydration reactor, is subject to dehydration at 250-280 ℃ using TiO3-Al2O3 as catalyst, resulting a conversion rate to styrene of 100% with a selectivity of 92%.
The features of the method: low cost, being economic and reasonable, less waste, with co-production of styrene.
Isobutane Haakon method uses isobutane as raw material, via oxidant tert-butyl hydroperoxide, further being reacted with propylene to generate propylene oxide and tert-butyl alcohol. The whole process is similar to ethylbenzene Haakon method. Manufacturing of tert-butyl hydroperoxide was carried out at 100~110 °C without catalyst, usually using tert-butyl hydroperoxide as initiator. Epoxidation of propylene was carried out under the conditions of reaction temperature 121 °C and pressure of 4.1 MPa to be carried out in the presence of molybdenum catalyst. The reaction time is 0.5 h with the yield of propylene oxide 88% (peroxides), selectivity of 81%. (CH3) 2CHCH3 + O2 → (CH3) 3COOH + (CH3) 3COH (CH3) 3COOH

Hazards & Safety Information

Category : Flammable liquids
Toxicity classification:  highly toxic
Acute toxicity:  Oral-Rat LD50: 380 mg/kg; Oral-mouse LD50: 440 mg/kg
Stimulation Data:  Skin-Rabbit 415 mg Moderate; Eyes-Rabbit 20 mg Severe
Explosive and hazardous properties:  Being explosive in case of ammonia, chlorosulfonic acid, hydrochloric acid, hydrogen fluoride, nitric acid, sulfuric acid and fuming sulfuric acid.
Flammability and hazard characteristics:  it is combustible in case of fire, high temperature and oxidant with combustion generating irritant smoke
Storage and transportation characteristics  Treasury: ventilated, low-temperature and dry; store it separately from oxidants and acids
Extinguishing agent:  dry powder, dry sand, carbon dioxide, foam, 1211 extinguishing agent
Occupational Standard:  TWA PPM 100

Description

Propylene oxide is an allergic and irritant agent, used as a solvent and raw material in the chemical industry as starting material and intermediate for a broad spectrum of polymers.

Chemical Properties

Propylene oxide is soluble in water and miscible with most organic solvents. It is found to be an excellent low-boiling solvent for cellulose acetate, nitrocellulose, adhesive compositions and vinyl chloride-acetate resins. It is also a solvent for hydrocarbons, gums and shellac. Some of its uses are as a solvent and stabilizer in DDT aerosol-type insecticides, and as a fumigant and food preservative. Since it is an acid acceptor, it is also used as a stabilizer for vinyl chloride resins and other chlorinated systems.

Physical properties

Propylene oxide is a colorless liquid with an agreeable, ether-like odor. Experimentally determined detection and recognition odor threshold concentrations were 24 mg/m³ (10 ppm_v) and 84 μg/m³ (35 ppm_v), respectively (Hellman and Small, 1974).

Uses

Chemical intermediate in preparation of polyethers to form polyurethanes; in preparation of urethane polyols and propylene and dipropylene glycols; in preparation of lubricants, surfactants, oil demulsifiers. As solvent; fumigant; soil sterilant.

Uses

It can be used as a dehydrating agent for the preparation of slides in electron microscopy. Occupational dermatitis was also reported while using a skin disinfectant swab.

Uses

Propylene oxide is used as a fumigant forfoodstuffs; as a stabilizer for fuels, heat-ing oils, and chlorinated hydrocarbons; asa fuel–air explosive in munitions; and toenhance the decay resistance of wood andparticleboard (Mallari et al. 1989). Recentstudies indicate that the fumigant potentialof propylene oxide enhances at a low pres-sure of 100 mm Hg which could render it asan alternative to methyl bromide for rapiddisinfection of commodities (Isikber et al.2004).

Production Methods

Propylene oxide is synthesized commercially from propylene through the intermediate propylene chlorohydrin. It also can be made by peroxidation of propylene using alkylhydroperoxides, but this method produces coproducts as well, often styrene or cumene. Propylene oxide is also synthesized via oxidation of propylene with hydrogen peroxide, which produceswater as the only coproduct.

Definition

ChEBI: An epoxide that is oxirane substituted by a methyl group at position 2.

General Description

A clear colorless volatile liquid with an ethereal odor. Flash point -35°F. Boiling point 95°F. Density 6.9 lb./gal. Flammable over a wide range of vapor-air concentrations. If contaminated, may polymerize with evolution of heat and possible rupture of container. Vapors irritate eyes, skin, and respiratory system. Prolonged contact with skin may result in delayed burns. Vapors heavier than air. Used as a fumigant, in making detergents and lubricants, and to make other chemicals.

Air & Water Reactions

Highly flammable. Soluble in water.

Reactivity Profile

1,3-Propylene oxide react with oxidizing agents and strong acids . Reacts with Grignard reagents and organolithium compounds. An explosion occurred when Propylene oxide was added to an epoxy resin. Propylene oxide was concluded that polymerization was catalyzed by an amine accelerator in the resin [Bretherick, 5th Ed., 1995]. Underwent polymerization when mixed with sodium hydroxide causing ignition and explosion of a drum of the crude product. [Combust Sci. Technol., 1983].

Hazard

Highly flammable, dangerous fire risk, explosive limits in air 2–22%. An irritant. TLV: 20 ppm; animal carcinogen.

Health Hazard

Exposure to propylene oxide vapors cancause moderate to severe irritation of the eyes, mucous membranes, and skin. Inhala-tion can also produce weakness and drowsi-ness. Symptoms of acute exposure in testanimals were lachrymation, salivation, gasp-ing, and labored breathing and dischargefrom nose. Harris et al. (1989) in a studyon Fischer-344 female rats found no adverseeffect below a 300-ppm exposure level.However, at the chronic inhalation levelof 500 ppm the gain in the maternal bodyweight and food consumption were reducedsignificantly. In a similar chronic inhalationstudy on Wistar rats, Kuper et al. (1988)observed a decrease in the body weight anddegenerative and hyperplastic change in thenasal mucosa when rats were exposed to300 ppm of propylene oxide. The investiga-tors have reported an increase in the inci-dence of malignant tumors in the mammaryglands and other sites in female rats.
Contact with its dilute aqueous solutionscan produce edema, blistering, and burns onthe skin. It is mutagenic in the Ames test anda suspected animal carcinogen. Its carcino-genicity in humans is not established. Omuraet al. (1994) reported dose-dependent testicu-lar toxicity of this compound in rats inducedfrom repeated intraperitoneal injections. Itsodor threshold is 200 ppm.

Fire Hazard

Vapor is heavier than air and may travel considerable distance to source of ignition and flash back. Vapors form explosive mixture with air. If polymerization takes place in container, there may be a violent rupture of container. Explosion hazard is severe when exposed to flame. Violently reacts with acetylide- forming metals such as copper or copper alloys, ammonium hydroxide; chlorosulfonic acid; hydrochloric acid; hydrofluoric acid; nitric acid; oleum and sulfuric acid. Hazardous polymerization may occur. Avoid active catalytic surfaces such as anhydrous chlorides of iron, tin, and aluminum; peroxides of iron and aluminum; and alkali metal hydroxides, high temperatures; alkalies; aqueous acids; amines and acidic alcohols.

Chemical Reactivity

Reactivity with Water No reaction; Reactivity with Common Materials: No reactions; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Not pertinent; Polymerization: Polymerization can occur when this product is exposed to high temperatures or is contaminated with alkalies, aqueous acids, amines, and acidic alcohols; Inhibitor of Polymerization: Not pertinent.

Industrial uses

Propylene oxide finds its largest use as chemical intermediates. It reacts readily with dilute amounts of mineral acids (e.g., hydrochloric acid) to form the chlorohydrin addition product. This reactivity with acid makes this epoxy solvent valuable acid acceptor-type stabilizers for several chlorinated solvents. Trace amounts of hydrogen chloride from chlorinated solvent degradation are immediately neutralized by reaction with the propylene oxide stabilizer. Reaction of propylene oxide with an alcohol or phenol in the presence of an acid catalyst yields the monoether of propylene glycol.

Contact allergens

Propylene oxide is an allergic and irritant agent, used as a solvent and raw material in the chemical industry, as the starting material and intermediate for a broad spectrum of polymers. It can be used as a dehydrating agent for the preparation of slides in electron microscopy. Occupational dermatitis was also reported following the use of a skin disinfectant swab.

Safety Profile

Confirmed carcinogen with experimental carcinogenic, neoplastigenic, and tumorigenic data. Poison by intraperitoneal route. Moderately toxic by ingestion, inhalation, and skin contact. An experimental teratogen. Experimental reproductive effects. Human mutation data reported. A severe skin and eye irritant. Flammable liquid. A very dangerous fire and explosion hazard when exposed to heat or flame. Explosive reaction with epoxy resin and sodium hydroxide. Forms explosive mixtures with oxygen. Reacts with ethylene oxide + polyhydric alcohol to form the thermally unstable polyether alcohol. Incompatible with NH4OH, chlorosulfonic acid, HCl, HF, HNO3, oleum, H2SO4. Dangerous; can react vigorously with oxidizing materials. Keep away from heat and open flame. To fight fire, use alcohol foam, CO2, dry chemical. When heated to decomposition it emits acrid smoke and fumes.

Potential Exposure

Propylene oxide is used as an interme- diate in the production of polyether polyols and propylene glycol; as a fumigant; in the production of adducts as ure- thane foam ingredients; in detergent manufacture; as a component in brake fluids.

Carcinogenicity

Propylene oxide is reasonably anticipated to be a human carcinogenbased on sufficient evidence of carcinogenicity from studies in experimental animals.

Environmental Fate

Biological. Bridié et al. (1979) reported BOD and COD values of 0.17 and 1.77 g/g using filtered effluent from a biological sanitary waste treatment plant. These values were determined using a standard dilution method at 20 °C for a 5 d period. When a sewage seed was used in a separate screening test, a BOD value of 0.20 g/g was obtained. The ThOD for propylene oxide is 2.21 g/g.
Photolytic. Anticipated products from the reaction of propylene oxide with ozone or OH radicals in the atmosphere are formaldehyde, pyruvic acid, CH3C(O)OCHO, and HC(O)OCHO (Cupitt, 1980). An experimentally determined reaction rate constant of 5.2 x 10^-13 cm³/molecule?sec was reported for the gas phase reaction of propylene oxide with OH radicals (Güsten et al., 1981).
Chemical/Physical. The reported hydrolysis half-life for the conversion of propylene oxide to 1,2-propanediol in water at 25 °C and pH 7 is 14.6 d (Mabey and Mill, 1978). The second-order hydrolysis rate constant of propylene oxide in 3.98 mM perchloric acid and 36.3 °C is 0.124/M?sec (Kirkovsky et al., 1998).
May polymerize at high temperatures or on contact with alkalies, aqueous acids, amines, and acid alcohols (NIOSH, 1997).
At an influent concentration of 1.0 g/L, treatment with GAC resulted in an effluent concentration of 739 mg/L. The adsorbability of the GAC used was 52 mg/g carbon (Guisti et al., 1974).

storage

Propylene oxide is stored in a flammableliquid cabinet isolated from combustible andoxidizable materials. It is shipped in glassbottles and metal containers under a nitrogenatmosphere.

Shipping

UN1280 Propylene oxide, Hazard Class: 3; Labels: 3-Flammable liquid

Purification Methods

Dry the oxide with Na2SO4 or CaH2 and fractionally distil it through a packed column (glass helices), after refluxing with Na, CaH2, or KOH pellets. [Beilstein 17 I 4, 17 II 131, 17 III/IV 17, 17/1 V 17.] The R(+)enantiomer [15448-47-2] and the S(-)enantiomer [16088-62-3] have b 33-34o/atm and [] 20 ±14.6o (neat). [Beilstein 17/1 V 17.]

Toxicity evaluation

The toxic effects of propylene oxide are related to its ability to react directly, without metabolic activation, with cellular macromolecules, nucleophilic sites, and nonprotein sulfhydryls. Therefore, it reacts with various components of cells, including DNA, RNA, and proteins.

Incompatibilities

Vapors may form explosive mixture with air. Reacts with strong oxidizers, anhydrous metal chlor- ides; chlorine, iron, strong acids; caustics and peroxides. Polymerization may occur due to high temperatures or con- tamination with alkalis, aqueous acids; amines, metal chlor- ides; and acidic alcohols. Attacks some plastics, coatings and rubber.

Waste Disposal

Concentrated waste contain- ing no peroxides-discharge liquid at a controlled rate near a pilot flame. Concentrated waste containing peroxides- perforation of a container of the waste from a safe distance followed by open burning