What diseases can benzene cause? Is it fatal?

Sorry, the other materials I quoted are a little long, so I'll just say it briefly.

It is generally believed that benzene poisoning is caused by metabolites, which means that benzene must be metabolized before it can cause harm to life. Benzene can be metabolized in liver and bone marrow, and bone marrow is the place where red blood cells, white blood cells and platelets are formed, so benzene can enter the body and form metabolites with blood toxicity in hematopoietic tissue itself. Long-term exposure to benzene can cause bone marrow and genetic damage, and hemogram examination can find leukopenia, thrombocytopenia, pancytopenia, aplastic anemia and even leukemia. Someone has investigated the health status of workers exposed to low concentrations of benzene. The results showed that the number of white blood cells in peripheral blood was within the normal range, but it was significantly lower than that in the control group. The distribution of lymphocyte micronucleus rate in benzene exposed workers was higher than that in non-benzene exposed workers, and there was significant difference between the observation group and the control group. With the increase of benzene concentration in the working environment, the number of white blood cells tends to decrease and the micronucleus rate of lymphocytes tends to increase. All these prove that low concentration of benzene is harmful to workers' health, especially to human genetic material. Inhalation of benzene above 4000ppm for a short time not only stimulates mucosa and lungs, but also inhibits the central nervous system, accompanied by headache, nausea, gait instability, coma, convulsions and arrhythmia. Inhalation of benzene above 14000ppm will lead to immediate death.

Here are the details!

Because benzene is volatile, it spreads easily when it comes into contact with air. Inhalation or skin contact of large amounts of benzene by humans and animals can cause acute and chronic benzene poisoning. Some research reports show that benzene poisoning is partly caused by benzene producing phenol in the body.

Benzene can paralyze the central nervous system and lead to acute poisoning. In severe cases, there will be headache, nausea, vomiting, confusion, loss of consciousness, coma, convulsions and so on. In severe cases, people will die because of paralysis of the central system. A small amount of benzene can also cause drowsiness, dizziness, increased heart rate, headache, trembling, confusion and unconsciousness. Intake of foods containing too much benzene can lead to vomiting, stomachache, dizziness, insomnia, convulsions, increased heart rate and even death. Inhalation of 20000ppm benzene vapor for 5- 10 minutes will be fatal.

Long-term exposure to benzene will do great harm to blood and cause chronic poisoning. Cause neurasthenia syndrome. Benzene can damage bone marrow, reduce the number of red blood cells, white blood cells and platelets, and distort chromosomes, thus leading to leukemia and even aplastic anemia. Benzene can cause a lot of bleeding, thus inhibiting the function of the immune system and allowing diseases to take advantage of it. It is reported that the incubation period of benzene in the body can be as long as 12- 15 years.

After inhaling too much benzene, women will have irregular menstruation and ovarian atrophy for several months. The effects on fetal development and male fertility are still unknown. Inhalation of benzene in pregnant animals will lead to underweight, delayed bone development and bone marrow damage in larvae.

It can irritate skin and mucous membrane. The International Centre for Research on Cancer (IARC) has been identified as a carcinogen.

Exposure limit:

* The maximum allowable usage in China is 40 mg/m3.

* American ACGIH 10ppm, 32mg/m3 TWA: OSHA 1ppm, 3.2mg/m3.

Toxicity:

* LD50: rat 3306 mg/kg (oral); 48 mg/kg (transdermal absorption in mice)

* LC50: 10000 ppm for 7 hours (inhaled by rats)

Of course, because everyone's health and contact conditions are different, their sensitivity to benzene is also different. When you smell benzene, its concentration is about 1.5ppm. Pay attention to the danger of poisoning. During the examination, it is easy to find out the degree of benzene poisoning through urine and blood examination.

benzene

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benzene

Chinese naming of IUPAC

benzene

routine

Molecular formula C6H6

Smile C 1=CC=CC=C 1

The molecular weight is 78. 1 1 g/mol.

Colorless and transparent volatile liquid.

The smell has a strong aromatic smell. The smell of paint thinner can be detected at the concentration of 12ppm.

Si Nuo. 7 1-43-2

RTECS number CY 1400000

IMDG rule page 3 185

Un number 1 1 14

nature

The density at STP is 0.8786 g/cm3.

Solubility 0.18g/100 ml of water.

Melting point: 278.65 K (5.5℃)

Boiling point: 353.25 K (80. 1℃)

stage

The triple point is 278.5±0.6k

Critical point 289.5℃

4.92 MPa

Fusion, heat

(δfusH)9.84 kJ/mol

heat of vapourization

(δvapH)44.3 kJ/mol

The combustion heat is 3264.4 kJ/mol.

danger

Flash point-10. 1 1℃ (closed cup)

The spontaneous combustion temperature is 562.22℃

Explosion limit 1.2-8.0%

Eating by mistake can cause acute poisoning and paralysis of the central nervous system, so you need to rinse your mouth, drink water and lavage your stomach as soon as possible.

Inhalation can cause difficulty breathing. Severe cases may lead to respiratory and cardiac arrest.

The skin becomes dry, peeling and chapped, and some may have allergic eczema.

Eyes are very exciting. Rinse with plenty of water.

Processing mode

* Danger:

O easy to burn and explode when exposed to heat and open flame.

* Personal protection:

O protective gloves, protective clothing, gas masks must be equipped when the concentration is too high.

* stability:

O can react strongly with oxidant. Cannot be stored with diborane.

* storage:

Cool and airy. Stay away from fire and heat sources. Avoid direct sunlight. Sealed storage. Prevent static electricity

Liquid property

Standard enthalpy of formation

(δδfH0 solution) 48.95 0.54kj/mol

standard entropy

(S0 solution) 173.26 Joule/mol k

heat capacity

(Cp) 135.69 joules/molar kelvin (298. 15 kelvin)

Unless otherwise specified, all data conform to the international system of units and come from standard temperature and pressure conditions. Reference and exemption clauses

Benzene (C6H6) is a colorless, sweet and transparent liquid with a strong aromatic smell at room temperature. Benzene is flammable, toxic and a carcinogen.

Chemically, benzene is a hydrocarbon and the simplest aromatic hydrocarbon. It is insoluble in water, soluble in organic solvents, and can also be used as organic solvents. Benzene is the basic raw material of petrochemical industry. The output and technical level of benzene production is one of the symbols of a country's petrochemical development level. Benzene has a ring system called benzene ring, which is the simplest aromatic ring The structure of benzene molecule after removing one hydrogen is called phenyl, which is expressed by pH, so benzene can also be expressed as PhH.

catalogue

[hide]

* 1 discovery

* 2 Structure

* 3 Physical properties

* 4 chemical properties

O 4. 1 substitution reaction

+4. 1. 1 halogenation reaction

+4. 1.2 nitration reaction

+4. 1.3 sulfonation reaction

+4. 1.4 alkylation reaction

O 4.2 addition reaction

O 4.3 oxidation reaction

O 4.4 Other reactions

* 5 preparation

O 5. 1 Extraction from coal tar

O 5.2 petroleum extraction

+5.2. 1 catalytic reforming

Steam cracking

O 5.3 aromatics separation

O 5.4 dealkylation of toluene

+5.4. Catalytic hydrodealkylation of1toluene

+5.4.2 Thermal dealkylation of toluene

O 5.5 toluene disproportionation and transalkylation

O 5.6 other methods

* 6 Analysis and test methods

* 7 Security

O 7. 1 toxicity

O 7.2 Flammability

* 8 industrial use

* 9 benzene isomers

* 10 benzene derivatives

O 10. 1 substituted benzene

O 10.2 polycyclic aromatic hydrocarbons

1 1 see synonyms at.

* 12 reference

* 13 external link

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find

Kekule's Swing Double Bond

strengthen

Kekule's Swing Double Bond

Benzene was first synthesized at the beginning of18th century, when gas was used as lighting gas. 1803-1819g.t. accum produced many products by the same method, and some samples were detected with a small amount of benzene by modern analytical methods. But it is generally believed that benzene was discovered by michael faraday in 1825. He separated high-purity benzene from the pyrolysis products of fish oil and other similar substances, which was called "double carburet of hydrogen". Some physical properties and chemical composition of benzene were determined, and the hydrocarbon ratio of benzene molecule was expounded.

1833, Milscherlich determined the empirical formula (C6H6) of six carbons and six hydrogen atoms in benzene molecule. 1865, Friedrich Kekule proposed the structure of alternating single and double bonds of benzene ring and infinite * * * yoke, which is now called Kekule type. This structure also explains that the position of the double bond in the ring is not fixed and can move quickly, so six carbons are equivalent. By studying the types of monochlorobenzene and dichlorobenzene, he found that benzene is a cyclic structure, and each carbon is connected with a hydrogen. Others put forward other ideas:

James dewar summarized different structures; Dewar benzene named after it has been proved to be another substance different from benzene, which can be obtained from benzene by illumination.

1845, German chemist Hoffman discovered benzene from the light fraction of coal tar, and his student C Mansfield subsequently processed and purified it. Later, he invented crystallization to refine benzene. He also conducted industrial application research, which opened a way for the processing and utilization of benzene. The industrial production of benzene started from 1865. It was originally recovered from coal tar. With the expansion of applications, the output is rising, and 1930 has become one of the top ten tonnage products in the world.

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structure

Benzene has special aromaticity because of its benzene ring structure. Benzene ring is the simplest aromatic ring, which consists of six carbon atoms, and each carbon atom has a group behind it. All six groups of benzene are hydrogen atoms.

Six p orbitals form an electron cloud with large delocalization bonds.

strengthen

Six p orbitals form an electron cloud with large delocalization bonds.

Cycloolefins with a carbon number of 4n+2(n is a natural number) and alternating single and double bonds are called annulenes, and benzene is [6]- annulenes.

Benzene is a plane molecule, with 12 atoms on the same plane, 6 carbons and 6 hydrogens are equal, and the bond length of C-H is 1.08? C-C bond length is 1.40? This value is between the length of single bond and double bond. All bond angles in the molecule are 120, indicating that all carbon atoms are sp2 hybridized. In this way, each carbon atom still has a p orbit perpendicular to the molecular plane, and each orbit has an electron. So the six orbitals overlap to form delocalized large ∏ bond, which is now considered to be the reason why the benzene ring is very stable and directly leads to the aromaticity of the benzene ring.

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physical features

The boiling point of benzene is 80. 1℃ and the melting point is 5.5℃. At room temperature, it is a colorless, fragrant and transparent liquid, which is volatile. The density of benzene is lower than that of water, with a density of 0.88g/ml, but its molecular weight is heavier than that of water. Benzene is insoluble in water, and 1.7g benzene can be dissolved in 1 liter of water at most; However, benzene is a good organic solvent, and it has strong solubility for organic molecules and some nonpolar inorganic molecules.

Benzene can react with water to form azeotrope with boiling point of 69.25℃ and benzene content of 9 1.2%. Therefore, benzene distillation is often added in the reaction of generating water to take it out.

The saturated vapor pressure between 10- 1500mmHg can be calculated according to antoine equation:

\ LG P = A-{ B \ divided by C+t}

Where: the unit of P is mmHg, the unit of T is℃, a = 6.9 12 10, b = 12 14.645, and c = 22 1.205.

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chemical property

There are three kinds of chemical reactions in which benzene participates: one is the substitution reaction between other groups and hydrogen atoms on benzene ring; One is the addition reaction on the carbon-carbon double bond; One is the break of benzene ring.

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displacement reaction

Under certain conditions, the hydrogen atom on the benzene ring can be substituted by halogen, nitro, sulfonic acid group, hydrocarbon group and so on. , and can generate the corresponding derivative. Because of different substituents, the position and number of hydrogen atoms are different, and isomers with different numbers and structures can be generated.

The electron cloud density of benzene ring is relatively high, so the substitution reaction on benzene ring is mostly electrophilic substitution. Electrophilic substitution is a typical reaction of aromatic rings. When benzene substituents are electrophilic, the position of the second substituent is related to the original substituent.

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halogenation

The general formula of benzene halogenation reaction can be written as:

PhH+X _ 2 \ to PhX+HX

During the reaction, halogen molecules are heterozygous under the action of benzene and catalyst, X+ attacks benzene ring, and X- combines with catalyst.

Take bromine as an example: iron powder needs to be added to the reaction, and iron is converted into ferric tribromide under the action of bromine.

Br^- to febr _ 4-

Phh+br++Febr _ 4-\ to PhBr+FeBr_3+HBr.

In industry, the substitution of chlorine and bromine in halogenated benzene is the most important.

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nitrify

Benzene and nitric acid can produce nitrobenzene under the catalysis of concentrated sulfuric acid;

PhH+HONO _ 2 \ to PhNO _ 2+H2O

Nitrification is a strong exothermic reaction, which is easy to produce substitutes, but the further reaction speed is slow.

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Sulfonation reaction

Benzene can be sulfonated into benzene sulfonic acid with concentrated sulfuric acid or fuming sulfuric acid at higher temperature.

H2so 4+PhH \ into PhSO 3H+H2O.

After sulfonic acid group is introduced into benzene ring, the reaction ability decreases and it is not easy to be further sulfonated. The introduction of the second and third sulfonic acid groups requires a higher temperature. This shows that nitro and sulfonic groups are passivation groups, that is, groups that hinder electrophilic substitution again.

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Alkylation reaction

Under the catalysis of AlCl3, the hydrogen atom on benzene ring can be replaced by alkyl (olefin) to produce alkylbenzene, which is called alkylation reaction, also known as Friedel-Crafts alkylation reaction. For example, ethylbenzene is produced by alkylation of ethylene:

PhH+C _ 2H _ 4 \ to Ph\! -\! 2H 5

During the reaction, the R group may be rearranged: for example, 1- chloropropane reacts with benzene to produce cumene, because free radicals always tend to a stable configuration.

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addition reaction

Although the benzene ring is very stable, the addition reaction of double bonds can also occur under certain conditions. Usually by catalytic hydrogenation, using nickel as catalyst, benzene can produce cyclohexane.

C _ 6H _ 6+3H _ 2 \ to C_6H_{ 12}

In addition, the reaction of producing hexachlorocyclohexane (HCH) from benzene can be obtained by the addition of benzene and chlorine under ultraviolet irradiation.

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oxidizing reaction

Like other hydrocarbons, benzene can burn. When oxygen is sufficient, the products are carbon dioxide and water.

2C _ 6H _ 6+ 15O _ 2 \ to 12CO _ 2+6h2o

But under normal circumstances, benzene cannot be oxidized by strong oxidants. However, in the presence of catalysts such as molybdenum oxide, benzene can be selectively oxidized to maleic anhydride by reacting with oxygen in the air. This is one of the few reactions that can destroy the six-membered carbocyclic system of benzene. (Maleic anhydride is a five-membered heterocyclic ring. )

2C _ 6H _ 6+9O _ 2 \ to 2C_4H_2O_3+4CO_2+4H_2O

This is a strongly exothermic reaction.

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Other reactions

Using iron, copper and nickel as catalysts, benzene can be condensed to biphenyl at high temperature. Chlorotoluene can be produced from formaldehyde and hypochlorous acid in the presence of zinc chloride. And alkyl metalates such as sodium ethyl can react to form phenyl metalates. In tetrahydrofuran, chlorobenzene or bromobenzene reacts with magnesium to produce phenylglycine reagent.

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prepare

Benzene can be obtained by incomplete combustion of substances with high carbon content. In nature, both volcanic eruptions and forest fires produce benzene. Benzene also exists in cigarette smoke.

Until World War II, benzene was a by-product in the coking process of iron and steel industry. This method can only extract 1 kg benzene from 1 ton coal. After 1950' s, with the increasing demand for benzene in industry, especially in the developing plastic industry, the process of making benzene from petroleum came into being. At present, most of the benzene in the world comes from petrochemical industry. The three most important methods to produce benzene in industry are catalytic reforming, hydrodealkylation of toluene and steam cracking.

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Coal tar extract

Light tar produced in the process of coal coking contains a lot of benzene. This is the original method of producing benzene. The generated coal tar and coal gas pass through washing and absorption equipment together, and high-boiling coal tar is used as washing and absorbent to recover coal tar in coal gas, and crude benzene and other high-boiling fractions are obtained after distillation. Crude benzene can be refined to obtain industrial grade benzene. The benzene obtained by this method has low purity, serious environmental pollution and backward technology.

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Extract from petroleum

Crude oil contains a small amount of benzene, and extracting benzene from petroleum products is the most widely used preparation method.

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catforming

Reforming here refers to the process of cyclodehydrogenation of aliphatic hydrocarbons to form aromatic hydrocarbons. This is a process developed during the Second World War.

At 500-525℃ and 8-50 atmospheric pressure, various aliphatic hydrocarbons with boiling point between 60-200℃ are converted into benzene and other aromatic hydrocarbons by dehydrogenation and cyclization with platinum-rhenium catalyst. After extracting aromatic products from the mixture, benzene can be separated by distillation. These fractions can also be used as high octane gasoline.

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Steam cracking

Steam cracking is a process of producing olefins from low molecular alkanes such as ethane, propane or butane and petroleum components such as naphtha and heavy diesel oil. Cracked gasoline, one of its by-products, is rich in benzene, which can be fractionated into benzene and other components. Cracked gasoline can also be mixed with other hydrocarbons as gasoline additives.

The content of benzene in pyrolysis gasoline is about 40-60%, and it also contains other unsaturated components such as diene and styrene. These impurities are easy to further react to form polymer colloid during storage. Therefore, it is necessary to remove these impurities and sulfides from cracked gasoline by hydrotreating first, and then carry out appropriate separation to obtain benzene products.

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Aromatic hydrocarbon separation

The components of benzene-containing fractions obtained by different methods are very complicated, and it is difficult to get effective separation by ordinary separation methods. Generally, aromatic hydrocarbons are separated by solvent liquid-liquid extraction or extractive distillation, and then benzene, toluene and xylene are separated by common separation methods. There are many separation methods according to different solvents and technologies used.

* Udex method: jointly developed by National Highway Chemical Company and UOP Company in 1950. At first, diethylene glycol ether was used as solvent, and later it was improved to triethylene glycol ether and tetraethylene glycol ether as solvent. In this process, a multi-stage multouocomer extractor is used. The yield of benzene is 100%.

* Suifolane method: developed by Dutch Shell Company and patented by UOP Company. The solvent is sulfolane, which is extracted by rotary extraction tower, and the product needs to be treated with clay. The yield of benzene is 99.9%.

* Arosolvan method: developed by Lurgi Company of the Federal Republic of Germany in 1962. The solvent is N- methylpyrrolidone (NMP). In order to improve the yield, 10-20% glycol ether is sometimes added. With a specially designed mechanical extractor, the yield of benzene is 99.9%.

* IFP method: 1967 developed by French Institute of Petroleum Chemistry. Using anhydrous dimethyl sulfoxide (DMSO) as solvent and butane as stripping agent, stripping was carried out in a rotary table tower. The yield of benzene is 99.9%.

* Formex method: developed by Italian SNAM Company and LRSR Petroleum Processing Department on 197 1. Morpholine or N- formylmorpholine is used as solvent, and a turntable tower is adopted. The total yield of aromatics is 98.8%, in which the yield of benzene is 100%.

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Dealkylation of toluene

Dealkylation of toluene can be used to produce benzene by catalytic hydrogenation or thermal dealkylation without catalyst. The raw material can be toluene, its mixture with xylene or fractions containing benzene and other alkylaromatic and nonaromatic hydrocarbons.

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Catalytic hydrodealkylation of toluene

Using chromium, molybdenum or platinum oxides as catalysts, toluene can be mixed with hydrogen to produce benzene at 500-600℃ and 40-60 atmospheric pressure. This process is called hydrodealkylation. If the temperature is higher, the catalyst can be omitted. The reaction is carried out according to the following equation:

Ph\！ -CH _ 3+H _ 2 \ to Ph\! -Hydrogen+methane

Depending on the catalyst used and the process conditions, there are many processes:

* Hydeal method: by Ashi and&; Refing and UOP were developed in 196 1. Raw materials can be reformed oil, hydrocracking gasoline, toluene, C6-C8 mixed aromatic hydrocarbons, dealkylated coal tar, etc. The catalyst is alumina-chromium oxide, the reaction temperature is 600-650℃, the pressure is 3.43-3.92MPa, the theoretical yield of benzene is 98%, the purity can reach over 99.98%, and the quality is better than that of Udex method.

* Detol method: developed by Houdry Company. Using alumina and magnesia as catalysts, the reaction temperature is 540-650℃, the reaction pressure is 0.69-5.4MPa, and the raw materials are mainly C7-C9 aromatics. The theoretical yield of benzene is 97% and the purity can reach 99.97%.

Pyrotol method: developed by Air products and chemicals Company and Houdry Company. It is suitable for benzene production from ethylene by-product pyrolysis gasoline. The catalyst is alumina-chromium oxide, the reaction temperature is 600-650℃ and the pressure is 0.49-5.4MPa.

* Bextol method: developed by Shell.

* BASF method: developed by BASF company.

* Unidak method: developed by UOP company.

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Thermal dealkylation of toluene

Toluene can be dealkylated to benzene without catalyst under high temperature hydrogen flow. The reaction is exothermic, and various technological processes have been developed for different problems encountered.

* MHC hydrodealkylation process: developed by Mitsubishi Petrochemical Company and Chiyoda Construction Company in 1967. Raw materials can be pure alkylbenzene such as toluene, and aromatic fractions containing less than 30% non-aromatic hydrocarbons. The operating temperature is 500-800℃, the operating pressure is 0.98MPa and the hydrogen-hydrocarbon ratio is 1- 10. The process selectivity is 97-99% (mol), and the product purity is 99.99%.

* HDA hydrodealkylation process: developed by American Hydrocarbon Research Company and Atlantic Ridgefield Company on 1962. The raw materials are toluene, xylene, hydrocracking gasoline and reforming oil. The reaction temperature is controlled from different parts of the reactor, such as hydrogen, the reaction temperature is 600-760℃, the pressure is 3.43-6.85MPa, the hydrogen-hydrocarbon ratio is 1-5, and the residence time is 5-30 seconds. The selectivity was 95% and the yield was 96- 100%.

* Sun technology: developed by Sun Oil Company.

* THD process: developed by Gulf Research and Development Corporation.

* Monsanto process: developed by Monsanto.

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Toluene disproportionation and transalkylation

With the increase of xylene consumption, toluene disproportionation and transalkylation technologies were successively developed at the end of1960s, which can increase xylene production at the same time. The main reactions are as follows:

Toluene disproportionation and transalkylation reaction

This reaction is reversible, and there are different technological processes according to the catalyst used, process conditions and raw materials.

* LTD liquid phase toluene disproportionation process: developed by American Mobil Chemical Company 197 1, using nonmetallic zeolite or molecular sieve catalyst, the reaction temperature is 260-3 15℃, and the reactor adopts liquid phase adiabatic fixed bed with toluene as raw material, with a conversion rate of over 99%.

* Tatoray process: developed by Toray Company and UOP Company in 1969. Toluene and mixed c9 aromatics were used as raw materials, mordenite was used as catalyst, the reaction temperature was 350-530℃, the pressure was 2.94MPa, and the ratio of hydrogen to hydrocarbon was 5- 12. An adiabatic fixed bed reactor was adopted. The one-way conversion rate is over 40% and the yield is 95%.

* Xylene plas process: developed by American Atlantic Richfield Company and Engelhard Company. Rare earth Y molecular sieve is used as catalyst, and the reactor is a gas-phase moving bed. The reaction temperature is 47 1-49 1℃ at atmospheric pressure.

* notification process: developed by Mitsubishi Gas Chemical Company of Japan 1968, hydrofluoric acid-boron fluoride catalyst, reaction temperature 60- 120℃, low pressure liquid phase. It is corrosive.

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Other methods

In addition, benzene can also be obtained by acetylene addition. The reaction equation is as follows:

\rm 3CH\！ \equiv\！ CH \ right arrow C_6H_6

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Analytical test method

Gas chromatography and liquid chromatography can detect the content of benzene in various products. Freezing point method is usually used to determine the purity of benzene.

Trace benzene in the air can be absorbed by volatile organic solvents such as methyl silicone oil or low molecular weight polymers, and then analyzed by chromatography. Or colorimetric analysis; You can also deeply freeze the air containing benzene, freeze benzene, then add ferric sulfate and hydrogen peroxide solution to obtain yellowish brown or black precipitate, then dissolve it with nitric acid, and then analyze it by colorimetry. Or directly use nitric acid to absorb benzene in the air, nitrate it into m-dinitrobenzene, and then titrate it with titanium dichloride solution, or use methyl ethyl ketone alkali solution prepared from m-xylene for colorimetric quantification.

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safe

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toxicity

See benzene poisoning

Because benzene is volatile, it spreads easily when it comes into contact with air. Inhalation or skin contact of large amounts of benzene by humans and animals can cause acute and chronic benzene poisoning. Some research reports show that benzene poisoning is partly caused by benzene producing phenol in the body.

Benzene can paralyze the central nervous system and lead to acute poisoning. In severe cases, there will be headache, nausea, vomiting, confusion, loss of consciousness, coma, convulsions and so on. In severe cases, people will die because of paralysis of the central system. A small amount of benzene can also cause drowsiness, dizziness, increased heart rate, headache, trembling, confusion and unconsciousness. Intake of foods containing too much benzene can lead to vomiting, stomachache, dizziness, insomnia, convulsions, increased heart rate and even death. Inhalation of 20000ppm benzene vapor for 5- 10 minutes will be fatal.

Long-term exposure to benzene will do great harm to blood and cause chronic poisoning. Cause neurasthenia syndrome. Benzene can damage bone marrow, reduce the number of red blood cells, white blood cells and platelets, and distort chromosomes, thus leading to leukemia and even aplastic anemia. Benzene can cause a lot of bleeding, thus inhibiting the function of the immune system and allowing diseases to take advantage of it. It is reported that the incubation period of benzene in the body can be as long as 12- 15 years.

After inhaling too much benzene, women will have irregular menstruation and ovarian atrophy for several months. The effects on fetal development and male fertility are still unknown. Inhalation of benzene in pregnant animals will lead to underweight, delayed bone development and bone marrow damage in larvae.

It can irritate skin and mucous membrane. The International Centre for Research on Cancer (IARC) has been identified as a carcinogen.

Exposure limit:

* The maximum allowable usage in China is 40 mg/m3.

* American ACGIH 10ppm, 32mg/m3 TWA: OSHA 1ppm, 3.2mg/m3.

Toxicity:

* LD50: rat 3306 mg/kg (oral); 48 mg/kg (transdermal absorption in mice)

* LC50: 10000 ppm for 7 hours (inhaled by rats)

Of course, because everyone's health and contact conditions are different, their sensitivity to benzene is also different. When you smell benzene, its concentration is about 1.5ppm. Pay attention to the danger of poisoning. During the examination, it is easy to find out the degree of benzene poisoning through urine and blood examination.

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Flammability [thermal flammability]

Because benzene can burn in air, it is usually classified as a dangerous chemical. For example, in the List of Dangerous Goods in People's Republic of China (PRC) (GB 12268-90), benzene is a medium flash point liquid among the flammable liquids of the third category of dangerous goods. Moreover, due to its volatility, it may cause local accumulation of steam, so it is generally required to stay away from fire sources and heat sources during storage and transportation to prevent static electricity.

Because of the high freezing point of benzene, it will be difficult to transport it in cold weather, but heating and melting will bring danger.

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Industrial use

As early as 1920s, benzene has been a common solvent in industry, mainly used for metal degreasing. Because benzene is toxic, the human body can directly contact the solvent in the production process, and now benzene is not used as a solvent.

Benzene can be used as gasoline additive because it can reduce knock. Before tetraethyl lead was used in 1950 s, all antiknock agents were benzene. However, with the fading of leaded gasoline, benzene was used again. Because benzene has a bad influence on human body and pollutes groundwater quality, European and American countries limit the benzene content in gasoline to no more than 1%.

The most important use of benzene in industry is as a chemical raw material. Benzene can be synthesized into a series of benzene derivatives:

* Benzene reacts with ethylene to produce ethylbenzene, which can be used to produce styrene for plastics.

* Production of cumene from propylene can be used to produce acetone and phenol for resins and adhesives by cumene method.

* Cyclohexane for nylon production

* Synthesis of maleic anhydride

* Nitrobenzene is used to make aniline.

* Various chlorobenzenes mostly used as pesticides.

* Synthesis of various alkylbenzenes used in the production of detergents and additives.

In addition, it can also be used to synthesize hydroquinone, anthraquinone and other chemical products.

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Isomers of benzene

* Dewar bottles of benzene

* canned benzene

* Vaccinium benzene

* In Priscilla.

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Benzene derivative

The following are some representative benzene substitutes or substances with similar structures to benzene.

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Substituted benzene

Alkyl substitution

* Toluene

* Xylene

* Styrene

Oxygen-containing group substitution

* Phenol

* Benzoic acid

* acetophenone

* benzoquinone

halogenate

* chlorobenzene

* Bromobenzene

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polycyclic aromatic hydrocarbon

* Biphenyl

* Triphenyl

* Polycyclic aromatic hydrocarbons

O-naphthalene

O-anthracene

O fee

O-indene

O-fluorene

O-acenaphthene

O-sting

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involve

* Aromaticity

* BTX

* π bond

* Crude benzene

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refer to

1. China Petrochemical Beijing Research Institute of Chemical Industry, Safety Data Card of Common Hazardous Chemicals (internal data), 2004.

2. Wei Wende, editor-in-chief, Organic Chemical Raw Materials, Volume III, Chemical Industry Press, 1994, P358-38 1, ISBN 7-5025-0684-5.

3. (British) Hancock (Ru), editor-in-chief, Benzene and its Industrial Derivatives, Chemical Industry Press, 1982.438+0 1.

4. USA 38633 10 (1975).

5.FR 1549 188( 1972)。

6.JP 45-24933 ( 1970)。

7.GB 124 13 16( 1975)。

8. USA 3879602 (1983).

9.Wilson, L.D., "Health hazards of aromatic hydrocarbons", Des Plaines, III. , Global Petroleum Products Company, 1962

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benzene

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* benzene material safety data sheet

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* Diagnostic criteria for occupational benzene poisoning -GBZ 68-2002

* Chemical World Benzene Network-provides the market situation of benzene.

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Page classification: aromatic hydrocarbons | aromatic compounds | carcinogens