Ethane is an organic compound with the structural formula CHthreeCHthree, a colorless and odorless gas, insoluble in water, is the second member of the alkane series and the simplest hydrocarbon containing carbon carbon single bond.The content of ethane in some natural gas is 5%~10%, second only to methane;It exists in petroleum in dissolved state.Ethane is often used as outdoor fuel and refrigerant.[2][5]
1834Michael Faraday First use electrolysisPotassium acetateEthane was produced by the method of.He mistakenly thought that the product of this reaction was methane, so he did not continue his research.
In 1847 and 1849, Adolf William Herman Colby and Edward Frankland used metal potassium to reducePropionitrileandIodoethaneAnd producing ethane by electrolysis of acetate.But they mistakenly thought that the product of these reactions was methyl radical, not methyl dimer ethane.
1864Carl SholemaCorrected this error, he proved that the product of all these reactions was ethane.[2]
Physical and chemical properties
Announce
edit
physical property
1. Character: colorless and odorless.
2. Melting point (℃): - 183 (101.325 kpa)[5]
3. Boiling point (℃): - 88.6 (101.325 kpa)
4. Relative density (water=1): 0.45 (0 ℃)
5. Relative vapor density (air=1): 1.05
6. Saturated vapor pressure (kPa): 3850 (20 ℃)
7. Combustion heat (kJ/mol): -1558.3
8. Critical temperature (℃): 32.2
9. Critical pressure (MPa): 4.87
10. Octanol/water partition coefficient: 1.81
11. Flash point (℃): - 135
12. Ignition temperature (℃): 472
13. Upper explosive limit (%): 12.5
14. Lower explosive limit (%): 3.0
15. Solubility: insoluble in water, soluble in ethanol, ether, acetone and benzene.
16. Critical density (g · cm-3）：0.0266
17. Critical volume (cmthree·mol-1）：145.5
18. Critical compressibility factor: 0.279
19. Eccentricity factor: 0.099
20. Lennard Jones parameter (A): 4.4080
21. Lennard Jones parameter (K): 226.55
22. Solubility parameter (J · cm-3)zero point five：12.375
23. van der Waals area (cmtwo·mol-1）：4.240×10nine
24. van der Waals volume (cmthree·mol-1）：27.340
25. Gas phase standard combustion heat (enthalpy) (kJ · mol-1)：-1560.67
26. Gas phase standard claimed heat (enthalpy) (kJ · mol-1)：-783.85
27. Gas phase standard entropy (J · mol-1·K-1) ：229.23
28. Gas phase standard free energy of formation (kJ · mol-1)：-31.9
29. Gas phase standard hot melt (J · mol-1·K-1)：52.47[3]
conformation
Cross conformation of ethane
The C-C single bond of ethane can rotate freely. If one of the C atoms in ethane does not move and the other rotates freely around the C-C single bond, the three H's on one C atom can have countless spatial arrangements relative to the three H's on the other C atom.The different arrangements of atoms or groups in the molecule due to the rotation of single bond in space are calledconformationEach conformation is called aConformational isomerDue to the free rotation of the C-C single bond, ethane can have numerous conformationsDominant conformationIt is cross type.At this time, the distance between H on the two C atoms is the farthest, and the mutual repulsion force is the smallest, soIntramolecular energyThe lowest and most stable.The highest internal energy is the overlapping type. At this time, the two H pairs on the two Cs are opposite, and the mutual repulsion force is the largest. The internal energy is the highest and the most unstable. The other conformational internal energies are between the two.In the process of rotation, because the relative positions of the hydrogen atoms on the two methyl groups are constantly changing, many different spatial arrangements are formed.One is that the hydrogen atom of one methyl is just on the centerline between the two hydrogen atoms of the other methyl.This arrangement is called cross conformation.The other is that each hydrogen atom on the two carbon atoms is in the opposite position to each other.This arrangement is called overlapping conformation.Crossed and overlapping are the two extremes of ethane's countless conformations.
The included angle between C and H is 111.17, not 109.5
The rotation of ethane single bond is not completely free.This energy barrier can be regarded as the energy needed to overcome the repulsion force of hydrogen atoms, and probably also the repulsion force between the carbon hydrogen bond electron clouds.The overlap formula has the highest energy due to the closest distance between the two hydrogen atoms and the largest repulsive force of the eight electron cloud between the hydrocarbon bonds. In the cross formula, C-H has the farthest distance, the smallest repulsive force, and the lowest energy, which is the most favorable conformation of ethane.
Molecular structure data
1. Molar refractive index: 11.31
2. Molar volume (cmthree/mol）：61.5
3. Isotonic specific volume (90.2K): 111.7
4. Surface tension (dyne/cm): 10.8
5. Polarization rate (10-24cm3): 4.48[3]
chemical property
Ethane is one of the lower alkanes, which can produce many typical reactions.
Halogenation reactionEthane can also react with chlorine, bromine, iodine and other halogens under certain conditionsChloroethane、BromoethaneorIodoethaneHowever, the activation energy required for reaction with iodine is high.For example, under the action of ultraviolet light or heat (250~400 ℃), ethane andchlorineReaction to chloroethane:[2]
Similar to methane, methyl chloride can also be further reacted with chlorine to formDichloroethane、TrichloroethaneEtc.
Nitrification: andnitric acidorNitrogen tetroxide（NtwoOfour）Conduct gas phase (400~450 ℃) reaction to generateNitro compound（RNOtwo）。 The reaction that directly generates nitro compounds is callednitrificationIt is a very important reaction in industry.It is important because nitroalkanes can be converted into many other types of compounds, such asamine、hydroxylamine、nitrile、alcohol、aldehyde、ketoneandcarboxylic acidEtc.In addition, nitroalkanes can undergo a variety of reactions, and the gas phase nitration method has great limitations in the laboratory. Therefore, nitroalkanes are mainly prepared by indirect methods in the laboratory.Nitroalkanes are prepared by gas phase nitration, and the mixture of various nitro compounds is often obtained.[2]
Sulfonation of ethaneEthane reacts with sulfuric acid at high temperature, which is similar to that of nitric acidEthyl sulfonic acid, this reaction is calledsulfonation。[2]
Oxidation and reduction reaction: Ethane can burn, that is, violent oxidation reaction occurs.When completely burned, the reactants are all destroyed, generating carbon dioxide and water, and releasing a lot of heat at the same time.[6]
Ethane can also be oxidized by oxygen under the action of catalyst to generate acetic acid.[8]
Ethane can also be oxidized to acetaldehyde under catalysis.[10]
Cracking of ethane: Ethane can be cracked under the action of high temperature and catalystethyleneAnd hydrogen, which is often used in industry to prepare ethylene.[6]
Preparation method
Announce
edit
Source: This product is separated from petroleum gas, natural gas, coke oven gas and petroleum pyrolysis gas.
one
Apart from methane, oil field gas or natural gas separated from oil field gas also contains a small amount of ethane, propane or other hydrocarbons with more carbon atoms. The content in natural gas is about 5-10%, second only to methane. Ethane can be obtained through separation.The liquidus obtained from cryogenic separation of natural gas is composed of ethanepropane。Light weight with butane as the main componentHydrocarbonsThe composition of the mixture is related to the source of natural gas, separation and processing temperature and pressure conditions. Typical composition (P) is 37.6% ethane, 35.9% propane, 11.6% butane, 3.9% isobutaneN-pentane3.1%, others 7.9%.
two
The petroleum processing gas separated from refinery gas contains ethane, propane, C4 and C5 hydrocarbons in addition to methane. Ethane can be obtained through separation.[7]
three
Ethane can be separated from pyrolysis gas by cryogenic method.[3]
four
Commonly used in laboratoriespropionic acidDeacidification reaction occurs under catalysis to prepare a small amount of ethane.[9]
The carbon dioxide in the reaction gas mixture can be removed by passing it into the sodium hydroxide solution to produce pure ethane.
application area
Announce
edit
China's external dependence on ethane is constantly increasing. By 2017, China's external dependence on ethane has reached 11%. It is estimated that China will become the main global ethane market in the future.Based on the application characteristics and scope of ethane, the consumption of ethane products in China has become more and more vigorous in recent years, and the consumption of ethane has always been higher than the output of ethane, presenting a market situation of "supply exceeds demand".[7]
Cracking to ethylene
In the chemical industry, ethane is mainly produced by steam crackingethylene。When mixed with steam, heavy hydrocarbons are cracked into light hydrocarbons at high temperature of 900 ℃ or above.Compared with other heavier raw materials, ethane becomes ethylene in a large part during steam cracking, while heavier compounds will produce many mixtures, including many heavy olefins such aspropylene、butadieneas well asAromatic hydrocarbon。[3]
cryogen
Ethane can be used as a refrigerant in refrigeration facilities.In scientific research, liquid ethaneElectron microscopyIs used to make samples with high water content transparent.The thin water layer will freeze quickly when it is immersed in liquid ethane at - 150 ℃ or lower in the facility, and will not form crystals.Such rapid freezing will not destroy the structure of soft materials in liquid water as ice crystallizes.[7]
Used as fuel
Ethane is a common combustible gas, which is often stored in liquefied steel cylinders as gaseous fuel.Ethane is commonly used for household heating, cooking and industrial heating.Bottled gas "or" suburban propane "contains about 90% propane and 5% ethane.In addition, ethane can also be used for gas welding and cutting.[5]
Organic synthesis
Ethane can be used for organic synthesis, such as synthesis of acetic acid, ethanol, ethylene, chloroethaneNitroethaneAnd synthesis of polyvinyl acetate, ethyl celluloseethylene oxideAmong them, ethanol is the most common organic solvent and disinfectant, and acetic acid is an important food chemical raw material and organic solvent.It can also be used for intermediate synthesis of medicine. For example, the synthetic acetic anhydride can be used to produce drugs such as methaqualone, dibazol, caffeine, aspirin, and sulfa.[3][10]
Calculate chemical data
Announce
edit
1. Reference value for drainage parameter calculation (XlogP): 1.3
2. Number of hydrogen bond donors: 0
3. Number of hydrogen bond receptors: 0
4. Number of rotatable chemical bonds: 0
5. Number of tautomers: none
6. Topological molecular polar surface area 0
7. Number of heavy atoms: 2
8. Surface charge: 0
9. Complexity: 0
10. Number of isotope atoms: 0
11. Determine the number of atomic structure centers: 0
12. Number of uncertain atomic structure centers: 0
13. Determine the number of chemical bond structural centers: 0
14. Number of indeterminate chemical bond structure centers: 0
15. Number of covalent bond units: 1[5]
Safety measures
Announce
edit
Protective measures
Engineering control: the production process is closed and fully ventilated.
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.
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.
Inhalation: quickly leave the site to a place with fresh air.Keep the respiratory tract unobstructed.If breathing is difficult, give oxygen.If breathing stops, perform artificial respiration immediately.Get medical attention.[4]
Fire fighting measures
Combustion characteristics: flammable, can form explosive mixture when mixed with air, and may cause combustion and explosion when encountering heat source and open fire.Violent chemical reaction will occur in contact with fluorine, chlorine, etc.
Extinguishing method: cut off the gas source.If the air source cannot be cut off, it is not allowed to extinguish the flame at the leakage.Spray water to cool the container, and move the container from the fire site to an open place if possible.Extinguishing agent: spray water, foam, carbon dioxide, dry powder.[4]
Safety terminology
S9：Keep container in a well-ventilated place.
Keep the container in a well ventilated place.
S16：Keep away from sources of ignition - No smoking.
Keep away from ignition sources and no smoking.
S33：Take precautionary measures against static discharges.
Take precautions against static electricity.
R12：Extremely flammable.
Extremely flammable.[4]
Storage and transportation
Announce
edit
Transport method
steel cylinderClosed operation, full ventilation.Operators must be specially trained and strictly abide by the operating procedures.Operators shall wear anti-static work clothes.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 halogens.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.When steel cylinders are used for transportation, safety helmets on steel cylinders must be worn.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, halogens, 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.It is forbidden to slip during railway transportation.[4]
Storage method
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 halogens, 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.
Packing group: O52
Packaging method: steel gas cylinder[4]
Regulatory information
Announce
edit
Regulations on the Safety Management of Dangerous Chemicals (issued by the State Council on February 17, 1987), detailed rules for the implementation of the Regulations on the Safety Management of Dangerous Chemicals (HLF [1992] No. 677), regulations on the safe use of chemicals in the workplace (LBF [1996] No. 423) and other regulations have made corresponding provisions on the safe use, production, storage, transportation, loading and unloading of dangerous chemicals;The classification and signs of commonly used hazardous chemicals (GB 13690-92) classify the substance as Class 2.1 flammable gas.[1]
