Ethylene, chemical formula CtwoHfour, with a molecular weight of 28.054, is an organic compound composed of two carbon atoms and four hydrogen atoms.Between two carbon atomsCarbon carbon double bondconnect.Ethylene is found in some tissues and organs of plantsmethionineIt is converted under sufficient oxygen supply.
Ethylene is one of the largest chemical products in the world. Ethylene industry is the core of petrochemical industry. Ethylene products account for more than 75% of petrochemical products and play an important role in the national economy.The world has taken ethylene production as one of the important indicators to measure the development level of a country's petrochemical industry.
Physiological functions are: triple reaction, promoting fruit maturity, promoting leaf senescence, inducing adventitious roots and root hairs, breaking the dormancy of plant seeds and buds, inhibiting the flowering of many plants (but it can induce and promote the flowering of pineapple and other plants of the same genus), and changing the direction of flower sex differentiation at the early stage of flower development in monoecious plants.
On October 27, 2017, the list of carcinogens published by the International Agency for Research on Cancer of the World Health Organization (WHO) was preliminarily sorted out for reference, and ethylene was included in the list of category 3 carcinogens.
In the first half of 2023, the output of 331 of 620 products will increase year on year.Among them, 15.43 million tons of ethylene, up 3.8%.[3]
In ancient China, it was found that putting fruit in the house burning incense candles can promote the ripening of fruit picking.In the 19th century, Germans found that the leaves near the leaking gas pipe were easy to fall off.Kazens was the first to find that plant materials can produce a gas, which can affect neighboring plants. He found that the gas produced by oranges can ripen bananas mixed with them.It was not until 1934 that Gane first proved that plant tissue could indeed produce ethylene.With the application of gas chromatography technology, many achievements have been made in the biochemical and physiological research of ethylene, and it has been proved that ethylene can be produced in all parts of higher plants. In 1966, ethylene was officially identified as a plant hormone.
Development status
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With the rapid development of China's economy, the living standard of the middle class has been greatly improved, and China's demand for end products in the ethylene derivatives market is growing rapidly;India's market demand is also growing synchronously, but the base is relatively small.In 2010, Northeast Asia will become the region with the largest ethylene demand in the world, accounting for 35% of the global ethylene market demand from 21% in 2000;It is estimated that China's ethylene demand will account for 36% of the world's total demand in 2014.
Data shows that although China's ethylene industry is developing rapidly and occupies a pivotal position in the world ethylene market, there are still some unavoidable risks.
First, market competition risks.Ethylene enterprises in the Middle East mainly use ethane as raw material to produce ethylene. The cost of ethane in this region is very low. Even with freight, the cost is much lower than that in the United States, Western Europe and other regions of the world, including China, and the region is quite competitive.Cheap downstream products of Middle East ethylenepolyethylene、glycolSuch massive influx into the Asia Pacific and Chinese markets will certainly pose a serious threat to the relevant products in China's market.
Secondly, environmental protection risks.There is a certain degree of environmental pollution in the production process of ethylene industry, but under the current environmental protection technology, ethylene production will cause a certain degree of pollution to the atmosphere and water bodies.With the continuous operation of new projects and the introduction of more stringent environmental protection standards by the Chinese government in the future, higher requirements will be put forward for the environmental protection work of ethylene enterprises. There is a risk that the operating costs of enterprises will rise due to the increase of environmental protection treatment costs.
In addition, there are risks of oil import.The massive construction of ethylene plants has also increased the demand for chemical oil.As China is facing the constraints of oil shortage, the domestic development of petrochemical industry is also facing the contradiction of resource constraints. The domestic crude oil output has been around 200 million tons, far below the growth rate of oil demand.With the development of ethylene industry in the future, the contradiction of chemical oil shortage will become increasingly prominent.
molecular structure
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Molecular formula: CtwoHfour
Structural formula:: CHtwo=CHtwo
Ethylene molecular proportion model
Ethylene is bound by four hydrogen atoms, and carbon atoms are connected by double bonds.All six atoms of ethylene are coplanar.H-C-C angle is 121.3 °;H-C-H angle is 117.4 °, close to 120 °, which is ideal sptwoMixed track domain.This molecule is also relatively rigid: rotating the C=C bond is a highly endothermic process, which needs to break the π bond while retainingσCarbon atoms between bonds.VSEPR model is a plane rectangle, and the three-dimensional structure is also a plane rectangle.Double bond is an area with high electron cloud density, so most reactions take place in this location.
The bond length of C=C double bond in ethylene molecule is 1.33 × 10-10m. Two carbon atoms and four hydrogen atoms in ethylene molecule are in the same plane.The bond angle between them is about 120 °.The bond energy of ethylene double bond is 615kJ/mol, and the experimental measurement shows that the bond length of ethane C-C single bond is 1.54 × 10-10m. The bond energy is 348kJ/mol.This shows that the bond energy of C=C double bond is not twice as much as that of C-C single bond, but slightly less than twice.So, it takes less energy to break one of the double bonds.This is the reason why ethylene is active and prone to addition reaction.
In the process of forming ethylene molecule, each carbon atom hybridizes with one 2s orbital and two 2p orbitals to form three equivalent sptwoHybrid orbitals.The three sptwoThe hybrid orbits are in the same plane and form an included angle of 120 ° with each other.Therefore, 5σBond, four of which are C-H bonds and one is C-C bonds. The two carbon atoms are left with two parallel p orbitals that do not participate in hybridization, which overlap on the side to form another chemical bond: π bond, andσThe plane of the key is vertical.For example, the C=C double bond in ethylene molecule is composed of aσBond and a pi bond.The degree of overlap between the two bond orbits is different.πThe bond is formed by the overlap of p orbitals from the side, and the degree of overlap is greater thanσThe overlap of keys from the front is smaller, soπKey is inferior toσThe key is firm, easy to break, and requires less energy to break.
Physical and chemical properties
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physical property
density
1.178kg/mthree
melting point
-169.4℃
boiling point
-103.7℃
flash point
-125.1℃
Refractive index
one point three six three
Saturated vapor pressure
4083.40kPa（0℃）
critical temperature
9.6℃
critical pressure
5.07MPa
Pilot temperature
450℃
Upper explosive limit（V/V）
36%
Lower explosive limit（V/V）
2.7%
appearance
Colourless gas
Solubility
Insoluble in water, slightly soluble in ethanol, soluble in ether, acetone, benzene
chemical property
1. It is easily oxidized by oxidants at room temperature.If ethylene is introduced into acid KMnOfourThe purple color of the solution fades, and ethylene is oxidized to carbon dioxide, thus ethylene can be identified.
2. It is easy to burn and emits heat. When burning, the flame is bright and produces black smoke.
CHtwo═CHtwo+3Otwo→2COtwo+2HtwoO
3. Olefin ozonation:
4. Addition reaction
CHtwo═CHtwo+Brtwo→CHtwoBr—CHtwoBr
(Preparation of chloroethane)
(alcohol production)
CHtwo═CHtwo+Cltwo→CHtwoCl—CHtwoCl
Addition reaction: the reaction in which the carbon atoms at both ends of the double bond (or triple bond) in the organic molecule directly combine with other atoms or atomic clusters to form new compounds.
5. Addition polymerization
nCHtwo═CHtwo→-[CHtwo—CHtwo]-n(made of polyethylene)
Under certain conditions, one of the unsaturated C \\\\\\\\\\\\\\\\\\\\\\\\\\.
This reaction is called polymerization, in which compounds (monomers) with relatively small molecular weight combine with each other to form compounds with relatively large molecular weight.This polymerization is a reaction in which one or more unsaturated compounds (monomers) are added to each other through unsaturated bonds to form polymer compounds, so it is also an addition reaction, which is called addition polymerization for short.
Molecular structure data
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Molar refractive index
ten point seven zero
Molar volume (cmthree/mol）
fifty-eight point one
Isotonic specific volume (90.2K)
one hundred and two point five
Surface tension (dyne/cm)
nine point six
Polarization (10-24cmthree）
four point two four[1]
toxicology data
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1. Acute toxicity
LCfifty: 95ppm (inhalation to mice, 2h)
2. Subacute and chronic toxicity
Rats inhaled 11.5g/mthree, 1a, there were differences in growth and development between the control group and the control group.[1]
Ecological data
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Biodegradability
Non biodegradable
Other harmful effects
Aerobic biodegradability
24~672h
Photooxidation half-life in air (h)
6.2~56h
This substance is harmful to the environment, so special attention should be paid to fish.Special attention should also be paid to the pollution of surface water, soil, atmosphere and drinking water.[1]
Anaerobic biodegradability
96~2688h
application area
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Industrial field
1. One of the most basic raw materials for petrochemical industry.In terms of synthetic materials, it is widely used in the production of polyethylene, vinyl chloride and polyvinyl chloride, ethylbenzene, styrene, polystyrene and ethylene propylene rubber;In organic synthesis, it is widely used to synthesize ethanol, ethylene oxide, ethylene glycol, acetaldehyde, acetic acid, propionaldehyde, propionic acid and its derivatives and other basic organic synthetic materials;After halogenation, chloroethylene, chloroethane and bromoethane can be produced;Can be prepared by oligomerizationα-Olefins, and then produce higher alcohols, alkylbenzene, etc;
2. It is mainly used as standard gas for analytical instruments in petrochemical enterprises;
3. Ethylene is used as an environmentally friendly ripening gas for navel orange, tangerine, banana and other fruits;
4. Ethylene is used in pharmaceutical synthesis and high-tech material synthesis.
Ecological field
Triple response of ethylene: ① inhibit the elongation and growth of stems; ②Promote the thickening of stems and roots; ③Promote the lateral growth of stems.Treatment of etiolated seedling stems with ethylene can make the stems thicker and the petioles grow upward.
Since ethylene can promote the synthesis of RNA and protein, and increase the permeability of cell membrane in higher plants, accelerating respiration, when the ethylene content in fruits increases, the synthesized auxin can be decomposed by enzymes in plants or light from the outside, further promoting the transformation of organic substances and accelerating maturity.Soaking immature tomatoes, apples, pears, bananas, persimmons and other fruits with ethephon solution can significantly promote maturity.
Ethylene also has the effect of promoting organ abscission and aging.Ethylene plays an important role in the shedding of flowers, leaves and fruits.
Ethylene can also promote the flowering and female flower differentiation of some plants (such as melons), and promote the discharge of milk from rubber trees, sumac trees, etc.
Ethylene can also induce the formation of adventitious roots of cuttings, promote the growth and differentiation of roots, break the dormancy of seeds and buds, and induce the secretion of secondary substances.
Agriculture
Ethylene is an endogenous hormone of plants. All parts of higher plants, such as leaves, stems, roots, flowers, fruits, tubers, seeds and seedlings, can produce ethylene under certain conditions.It is the smallest molecule in plant hormones, and its physiological function is mainly to promote fruit and cell expansion.It can ripen grains, promote the shedding of leaves, flowers and fruits, induce flower bud differentiation, break dormancy, promote germination, inhibit flowering, organ shedding, dwarf plants and promote adventitious root formation.
Ethylene is a gas, which is difficult to be applied in the field. It was not until ethrel was developed that practical ethylene plant growth regulators were provided for agriculture.The main products are ethephon, vinyl silicon, glyoxime, metronidazole, delophosphine, cycloheximide (actinomycete), which can release ethylene, or plant growth regulators that promote plants to produce ethylene, so they are collectively called ethylene releasers.Ethephon is the most commonly used only at home and abroad, and is widely used to accelerate fruit ripening, defoliate cotton before harvesting, promote cotton boll cracking and boll opening, stimulate rubber latex secretion, dwarf rice, increase female flowers of melons, and promote pineapple flowering.
Some ethylene plant growth regulators can regulate plant growth by inhibiting ethylene synthesis in plants, which is called ethylene synthesis inhibitor.There is no such product in the domestic market, so it will not be introduced.
First aid measures
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Contact part
First aid measures
Skin contact
Do not rub or use hot water in case of frostbite.Use clean and dry dressings for dressing and seek medical treatment.
Eye contact
Immediately lift the eyelid, and thoroughly flush it with a large amount of flowing water or physiological saline for at least 30 minutes.Get medical attention.
inhalation
Quickly leave the site to fresh air.Keep the respiratory tract unobstructed.If breathing is difficult, give oxygen.If breathing stops, perform artificial respiration immediately.Get medical attention.
Ingestion
Drink enough warm water to induce vomiting.Get medical attention.
Fire fighting measures
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Hazard characteristics: flammable, can form explosive mixture when mixed with air.In case of open fire, high heat or contact with oxidant, there is a risk of combustion and explosion.Violent chemical reaction will occur in contact with fluorine, chlorine, etc.
Hazardous combustion product: carbon monoxide.
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.
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.Reasonable ventilation to accelerate diffusion.Dilute with spray water.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.
Handling and storage
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Precautions for operation: closed operation, full ventilation.Operators must be specially trained and strictly abide by the operating procedures.It is recommended that operators 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.
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 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.
security information
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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.
S46：If swallowed, seek medical advice immediately and show this container or label.
If ingested, seek medical advice immediately and show the container/label.
