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Questions And Answer

• 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;

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