propylene

[bǐng xī]

Organic compound

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This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Propylene is an organic compound with molecular formula C three H six , colorless, odorless, slightly sweet gas, flammable, will produce bright flame when burning, and the explosion limit in the air is 2% ～ 11.1%^{[6-7 ]} ； Insoluble in water, soluble in ethanol and ether.

Propylene is one of the basic raw materials of the three major synthetic materials, and the largest amount of propylene is used to produce polypropylene. In addition. Propylene can be used to prepare acrylonitrile, propylene oxide, isopropanol, phenol, acetone, butanol, octanol, acrylic acid and its esters, propylene glycol, epichlorohydrin and synthetic glycerol.^[1]

On October 27, 2017, the list of carcinogens released by the International Agency for Research on Cancer of the World Health Organization (WHO) was preliminarily collated and referred to. Propylene was included in the list of three types of carcinogens.^[4]

Chinese name: propylene
Foreign name: propylene
chemical formula: C three H six
molecular weight: forty-two point zero seven nine seven
CAS login number: 115-07-1
EINECS login number: 204-062-1
Melting point: -185 ℃
Boiling point: -47.7 ℃

Water solubility: Insoluble
Density: 1.914 kg/m³
Appearance: Colorless, odorless, slightly sweet gas
Flash point: -108 ℃
Application: Production of polypropylene, preparation of acrylonitrile, propylene oxide, etc
Security description: S9；S16；S33
Hazard symbol: F+
Hazard description: R12

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nine Operation, disposal, storage and transportation
ten security information
▪ Safety terminology
▪ Risk terminology

essential information

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Chemical formula: C three H six

Molecular weight: 42.0797

CAS No.: 115-07-1

EINECS No. 204-062-1

Physical and chemical properties

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physical property

Density: 1.914kg/m three

Melting point: - 185 ℃

Boiling point: - 47.7 ℃

Flash point: - 108 ℃

Refractive index: 1.3567

Saturated vapor pressure: 1158kPa (25 ℃)

Critical temperature: 91.9 ℃

Critical pressure: 4.62MPa

Ignition temperature: 460 ℃

Upper explosive limit（ V/V ）：11.1%^{[7 ]}

Lower explosive limit（ V/V ）：2%^{[7 ]}

Appearance: colorless gas

Solubility: slightly soluble in water, easy to ethanol and ether^[5]

chemical property

polymerization

The chemical properties of propylene are determined by its double bond and the hydrogen atom on the allyl group. In the molecular structure of propylene, it is the smallest stable unsaturated hydrocarbon because the projection on the main plane only shows low symmetry. This asymmetry is also shown in that the dipole moment of propylene is only 0.35D, which is prone to various types of chemical reactions. The carbon atoms at position 1 and position 2 have the same structure as the ethylene molecule. On the same triangle plane, they cannot rotate freely due to the existence of double bonds, while the carbon atoms at position 3 are located in the tetrahedron like methane and can rotate freely. The hydrogen atom on the allyl group is attracted by the carbon atom. The hydrogen atom on the allyl group is the main reason why its chemical properties are different from those of ethylene.^[3]

Propylene molecule can carry out self addition reaction. When phosphoric acid, boron fluoride or sulfuric acid is used as catalyst on the solid, the reaction is carried out according to the positive carbon ion mechanism. At low temperature, the main product of propylene dimerization is 4-Methyl-2-pentene 。^[3]

For example, alkyl alkali metals and some alkali metal compounds are used as catalysts to conduct dimerization of propylene Negative carbonion The product is mainly 4-Methyl-1-pentene 。 Due to the asymmetry of propylene molecule and simultaneous double bond displacement and cis trans structure conversion, the product composition may include various hexene isomers and C six More than olefins. C six Olefins can be used as raw materials for polymer synthesis, gasoline admixtures, etc^[3] 。

Formation of propylene after oligomerization on acid catalyst Nonene and Dodecene , when propylene is mixed with Butene When the mixture is co oligomerized, its polymer contains a large amount of Heptene 。

with Alkyl aluminium and Titanium trichloride As catalyst or Metallocene and Methylaluminoxane As a catalyst, propylene polymerization is carried out by bulk, emulsion or gas phase method at a certain temperature and pressure to obtain polypropylene^[3] 。

Polypropylene produced by propylene polymerization

Propylene can also be copolymerized with ethylene in the solution of soluble vanadium aluminum catalytic system to synthesize ethylene propylene rubber^[3] 。

Hydrogenation

Like other olefins containing a double bond, propylene emits the same heat per mole in the hydrogenation reaction, about 12.56kJ/mol. However, propylene hydrogenation has no industrial value^[3] 。

hydration

Propylene can be indirectly hydrated under the action of acid. In the presence of solid catalyst, it can be directly hydrated to isopropanol. When sulfuric acid is used as the catalyst for hydration, propylene first reacts with sulfuric acid to generate sulfuric acid ester, which is hydrolyzed to isopropanol. The reaction equation is as follows:

CH three -CH=CH two +H two SO four →(CH three ) two CH-O-SO three H

CH three -CH=CH two +(CH three ) two CH-O-SO three H→(CH three ) two CH-O-SO two -O-CH(CH three ) two

(CH three ) two CH-O-SO three H+H two O→CH three -CH(OH)-CH three +H two SO four

The yield of isopropanol in the above reaction can reach 95%^[3] 。

Isopropanol can also be obtained by direct hydration, and the reaction equation is:

CH three CHCH two +H two O→(CH three ) two CHOH

catalytic oxidation

Catalytic oxidation of propylene to acrolein.

Using bismuth molybdate or molybdophosphate as catalyst in Sohio process is a new economic breakthrough in acrolein production. Many companies have also developed high selectivity Multicomponent catalyst System, selectivity can reach 75~84% based on propylene^[3] 。

Palladium chloride as catalyst Propylene oxide Acetone is obtained with a yield of 92%. The reaction equation is as follows:

CH three CH=CH two +PbCl two +H two O→CH three COCH three +Pb+2HCI

Reaction with halogen

Propylene and halogen can undergo two addition reactions under different conditions^[3] 。

Propylene reacts with halogen at room temperature or under the action of gas phase light or with catalyst^[3] 。

X two +CH three CH=CH two →CH three CHXCH two X (1,2-dihalopropane)

Reaction in water:

CH three CH=CH two +CI two +H two O→CH three CH (OH) CHCI+HCI or CH three CHClCH two OH+HCl

Reaction with hydrogen bromide

The addition of asymmetric alkenes to hydrogen halides follows the law of asymmetric addition. However, hydrogen bromide is different from hydrogen chloride and hydrogen iodide in the presence of peroxide during reaction. Generated is 1-Bromopropane instead of 2-bromopropane ^[3] 。

CH three CH=CH two +HBr→CH three CH two CH two Br (peroxide as catalyst)

CH three CH=CH two +HBr→CH three CH two BrCH three^[3]

Epoxidation reaction

The co oxidation method uses Organic peroxide Produce oxygen free radicals, and transfer the oxygen in the peroxide part to propylene under the action of catalyst to generate Epoxide In this way, the hydroperoxide can be converted into alcohol or ketone, and the peracid can be converted into acid. The reaction equation is as follows^[3] ：

Co oxidation method

Molecular structure data

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Molar refractive index: 15.67

Molar volume (cm three /mol）：73.1

Isotonic specific volume (90.2K): 140.5

Surface tension (dyne/cm): 13.6

Polarization (10 -24 cm three ）：6.21^[5]

Calculate chemical data

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Reference value for drainage parameter calculation (XlogP): 1.4

Number of hydrogen bond donors: 0

Number of hydrogen bond receptors: 0

Number of rotatable chemical bonds: 0

Number of tautomers: 0

Topological molecular polar surface area: 0

Number of heavy atoms: 3

Surface charge: 0

Complexity: 7.5

Number of isotope atoms: 0

Determine the number of atomic structure centers: 0

Number of uncertain atomic structure centers: 0

Determine the number of chemical bond structure centers: 0

Number of uncertain chemical bond structure centers: 0

Number of covalent bond units: 1^[5]

toxicology data

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1. Acute toxicity

LC fifty : 65800mg/m3 (inhaled by rats, 4h)

2. Subacute and chronic toxicity

Mice inhaled 35% of the product for 20 times, causing slight fatty infiltration in the liver.

3. Carcinogenicity

IARC carcinogenicity review: G3, insufficient evidence of carcinogenicity to humans and animals.^[5]

Ecological data

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1. Ecotoxicity

LC fifty : 8.4~9.6mg/L (96h) (fish); 1.8~13mg/L (96h) (invertebrate)

2. Biodegradability

Aerobic biodegradation: 168~672h

Anaerobic biodegradation: 672~2688h

3. Non biodegradable

Photooxidation half-life in water: 1070~43000h

Photooxidation half-life in air: 1.7~13.7h

Bioaccumulation or bioaccumulation: BCF: 13~31

4. Other harmful effects

This substance is harmful to the environment, so special attention should be paid to fish and water bodies. Special attention should also be paid to the pollution of surface water, soil, atmosphere and drinking water.^[5]

purpose

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Propylene can be polymerized to produce polypropylene, copolymerized with ethylene to produce ethylene propylene rubber, alkylated to produce cumene, hydrated to produce isopropanol, oxidized to produce propylene oxide, etc. As shown in^[2] ：

Main uses of propylene

Protective measures

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Respiratory system protection: Generally, no special protection is required, but it is recommended to wear a self-priming filter gas mask (half mask) under special circumstances.

Eye protection: Generally, no special protection is required, and chemical safety goggles can be worn in case of high concentration contact.

Body protection: Wear anti-static work clothes.

Hand protection: wear general operation protective gloves.

Other protection: smoking is strictly prohibited at the work site. Avoid long-term repeated contact. When entering tanks, confined spaces or other high concentration areas for operation, someone must supervise.

Leakage emergency treatment

Evacuate the personnel in the leakage contaminated area to the windward place quickly, isolate them, and strictly restrict access. Cut off the ignition source. It is recommended that emergency personnel wear self-contained positive pressure respirators and anti-static work clothes. Cut off the leakage source as much as possible. Cover the sewer and other places near the leakage point with industrial coating or adsorption/absorbent to prevent gas from entering. Reasonable ventilation to accelerate diffusion. Dilute and dissolve with spray water. Build a dike or dig a pit to collect a large amount of wastewater generated. If possible, use an exhaust fan to send the leaked gas to an open place or install an appropriate nozzle to burn it. Leaking containers shall be properly treated, repaired and inspected before reuse.

Operation, disposal, storage and transportation

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Precautions for operation: closed operation, full ventilation. Operators must be specially trained and strictly abide by the operating procedures. Keep away from kindling and heat sources, and smoking is strictly prohibited in the workplace. Use explosion-proof ventilation systems and equipment. Prevent gas leakage into the air of the workplace. Avoid contact with oxidants and acids. During transmission, the cylinder and container must be grounded and bridged to prevent static electricity. The cylinder and accessories shall be handled with care to prevent damage. Fire fighting equipment and leakage emergency treatment equipment of corresponding types and quantities shall be provided.

Precautions for storage: store in a cool and ventilated warehouse. Keep away from kindling and heat sources. The warehouse temperature should not exceed 30 ℃. It shall be stored separately from oxidants and acids, and mixed storage is strictly prohibited. Explosion proof lighting and ventilation facilities shall be adopted. It is prohibited to use mechanical equipment and tools that are easy to generate sparks. The storage area shall be equipped with leakage emergency treatment equipment.

Precautions for transportation: the safety helmet on the cylinder must be worn when the cylinder is used for transportation. Cylinders are generally placed horizontally, and the mouth of the cylinder should be in the same direction, not crossed; The height shall not exceed the protective fence of the vehicle, and shall be firmly clamped with triangular wood pad to prevent rolling. The transport vehicles shall be equipped with corresponding types and quantities of fire-fighting equipment. The exhaust pipe of the vehicle transporting this article must be equipped with a fire retardant device. It is prohibited to use mechanical equipment and tools that are easy to generate sparks for loading and unloading. It is strictly prohibited to mix with oxidants, acids, etc. Transport in the morning and evening in summer to prevent sunlight exposure. Keep away from kindling and heat sources during stopover. Road transportation shall be carried out according to the specified route, and do not stay in residential areas and densely populated areas.