Ministry of General Education of the Russian Federation

KAZAN STATE TECHNOLOGICAL

UNIVERSITY

NIZHNEKAMSK CHEMICAL AND TECHNOLOGICAL

INSTITUTE

Department of Chemical technology

Group

course project

Topic: Obtaining ethylbenzene by the method of alkylation of benzene with ethylene

Student:

Supervisor (_________)

Student ka (_________)

Nizhnekamsk

INTRODUCTION

The topic of this course project is the production of ethylbenzene by the method of alkylation of benzene with ethylene.

The most common process of petrochemical synthesis is the catalytic alkylation of benzene with olefins, which is determined by the high demand for alkylaromatic hydrocarbons - raw materials in the production of synthetic rubbers, plastics, synthetic fibers, etc.

Alkylation is the process of introducing alkyl groups into mo- molecules of organic and some inorganic substances. These reactions are of great practical value for the synthesis of alkylaromatic compounds, iso-alkanes, amines, mercaptans and sulfides, etc.

The reaction of benzene alkylation with alkyl chlorides in the presence of anhydrous aluminum chloride was first carried out in 1877 by S. Friedel and J. Crafts. In 1878, Friedel's student Balson obtained ethylbenzene by alkylation of benzene with ethylene in the presence of ALCL3.

Since the discovery of the alkylation reaction, many different methods have been developed to replace the hydrogen atoms of benzene and other aromatic hydrocarbons with alkyl radicals. Various alkylating agents and catalysts have been used for this 48,49.

The rate of alkylation of aromatic hydrocarbons is several hundred times higher than that of paraffins; therefore, the alkyl group is almost always directed not to the side chain, but to the core.

For the alkylation of aromatic hydrocarbons with olefins, numerous catalysts are used, which have the character strong acids, in particular sulphuric acid(85-95%), phosphoric and pyrophosphoric acids, anhydrous hydrogen fluoride, synthetic and natural

aluminosilicates, ion exchangers, heteropolyacids. Acids in liquid form exhibit catalytic activity in alkylation reactions at low temperatures (5-100°C); acids on solid carriers, for example phosphoric acid on diatomaceous earth, act at 200-300°C; aluminosilicates are active at 300-400 and 500°C and a pressure of 20-40 kgf/cm² (1.96-3.92 MN/m²).

The relevance of this topic is that in the future styrene is obtained from ethylbenzene by the dehydrogenation of ethylbenzene.

1. THEORETICAL PART

2.1 Theoretical foundations of the adopted method of production.

Alkylation of benzene with ethylene. Industrial processes for the alkylation of benzene with ethylene vary depending on the catalyst used. A number of catalysts have been tested on a pilot scale.

In 1943, Copers carried out the alkylation of benzene with ethylene on an aluminosilicate catalyst in the liquid phase at 310°C and 63 kgf/cm2 (6.17 MN/m2) at an ethylene:benzene molar ratio of 1:4.

The process of alkylation of benzene with ethylene on aluminum chloride at atmospheric or slightly elevated pressure and a temperature of 80-100 ° C has become widespread.

Alkylation on a solid phosphoric acid catalyst competes with this method, but only isopropylbenzene can be obtained on this catalyst. Alkylation of benzene with ethylene is practically not carried out on it.

A large group of alkylation catalysts are aprotic acids (Lewis acids) - halides of some metals. They usually exhibit catalytic activity in the presence of promoters with which they form products having the character of strong protonic acids. Of the catalysts of this type, aluminum chloride, aluminum bromide, iron trichloride, zinc chloride, titanium trichloride and tetrachloride can be used. Industrial use is only aluminum chloride.

About the mechanism of reactions of alkylation of benzene and its homologues with olefins adhere to the following general ideas.

Alkylation in the presence of aluminum chloride is interpreted according to the mechanism

mu acid catalysis. In this case, the system must have

promoter, the role of which is played by hydrogen chloride. The latter may

formed in the presence of water:

CH3 CH=CH2 + H – CL ∙ ALCL3 ↔ CH3 – CH – CH3 ∙ CL ∙ ALCL3

Further attachment to the aromatic nucleus proceeds according to a mechanism similar to that discussed above:

HCL(CH3)2 ∙CL∙ALCL3 +CH3 –CH–CH3 ∙CL∙ALCL3 →HCH(CH3)2 + CH(CH3)2 + CL ∙ALCL3 + HCL + ALCL3

In the presence of aluminum chloride, dealkylation easily proceeds, which indicates the reversibility of the alkylation reaction. Dealkylation reactions are used to convert polyalkylbenzenes to monoalkyl-

Thermodynamics of the alkylation reaction. Based on physicochemical

constants of hydrocarbons and their thermodynamic functions - enthalpies ΔН and

entropy ΔS, you can find the equilibrium constants and calculate the equilibrium

yields of alkyl derivatives during the alkylation of benzene with olefins depending on

bridges on temperature and pressure.

The equilibrium yield of ethylbenzene increases with increasing molar

excess benzene and with increasing pressure at a given temperature.

C6 H6 + C2 H4 ↔ C6 H5 C2 H5

When benzene is alkylated with ethylene at temperatures below 250-300°C

almost complete conversion of benzene to ethylbenzene is achieved. At 450

-500°C to increase the depth of transformation requires an increase in pressure to 10-20 kgf/cm2 (0.98-1.96 MN/m2).

The alkylation reaction of benzene with ethylene is a first-order sequential reversible reaction. With the deepening of the process, along with monoalkylbenzene, polyalkylbenzenes are also formed.

C6 H6 + Cn H2n ↔ C6 H5 Cn H2n+1

C6 H5 Cn H2n+1 + Cn H2n ↔ C6 H4 (Cn H2n+1)2 which are unwanted by-products. Therefore, the composition of the reaction mixture of alkylates is more often determined by kinetic factors than by thermodynamic equilibrium.

Thus, dealkylation is thermodynamically possible with great depth at 50-100°C. Indeed, in the presence of aluminum chloride, it proceeds well, since with this catalyst the alkylation process is reversible. However, at the same temperatures in the presence of acids, dealkylation does not occur at all. M.A. Dalin experimentally studied the composition of the products of benzene alkylation with ethylene in the presence of aluminum chloride.

The composition of the reaction mixture is determined by the ratio of benzene and ethylene and does not depend on how the alkylate is obtained: by direct alkylation or dealkylation of polyalkylbenzene. However, this conclusion is valid only when aluminum chloride is used as a catalyst.

The alkylation process is carried out in an alkylator - a reaction column lined or lined with graphite tiles to protect against corrosion. Three sections of the column have jackets for cooling, but the main amount of heat is removed by evaporation of some of the benzene. Alkylation is carried out in the presence of a liquid catalyst complex consisting of aluminum chloride (10-12%), benzene (50-60%) and polyalkylbenzenes (25-30%). For the formation of hydrogen chloride, which is the promoter of the reaction, 2% of water from

masses of aluminum chloride, as well as dichloroethane or ethyl chloride, the splitting of which produces hydrogen chloride.

To isolate ethylbenzene from the alkylate, benzene is distilled off at atmospheric pressure (traces of water are removed simultaneously with benzene). A wide fraction, a mixture of ethylbenzene and polyalkylbenzenes, is distilled off from the bottom liquid at reduced pressure (200 mm Hg, 0.026 MN/m²). In the next column at a residual pressure of 50 mm Hg. (0.0065 MN/m²) polyalkylbenzenes are separated from resins. The broad fraction is dispersed in a vacuum column at a residual pressure of 420-450 mm Hg. (0.054-0.058 MN/m²). Commodity ethylbenzene is distilled in the range of 135.5-136.2°C.

To obtain ethylbenzene, ethane is used - the ethylene fraction of pyrolysis containing 60-70% ethylene.

Benzene for alkylation should contain no more than 0.003-0.006% water, while commercial benzene contains 0.06-0.08% water. Dehydration of benzene is carried out by azeotropic distillation. The sulfur content in benzene should not exceed 0.1%. The increased sulfur content causes an increase in the consumption of aluminum chloride and degrades the quality of the finished product.

1.2. Characteristics of raw materials and the resulting product.

Name of raw materials, materials, reagents, catalysts. semi-finished products manufactured products.	State number venous or branch standard, technical standard enterprises.	Quality indicators to be verified.	Norma (according to OST, stan- dartu enterprise	Appointment, application area.
1.ETHYLBENZENE	colorless transparent liquid. The main indicators of the properties of ethylbenzene: Molecular weight=106.17 Density, g / cm³ \u003d 0.86705 Temperature, ° C Boiling \u003d 176.1 Melting = -25.4 Flashes = 20 Self-ignition = 431. Heat, kJ/mol melting point=9.95 Evaporation \u003d 33.85 Heat capacity, J / mol ∙ K \u003d 106.4 Heat of combustion, kcal/mol=1089.4 Solubility in water, g/100ml=0.014	In industry, it is mainly used as a raw material for the synthesis of styrene, as an additive to motor fuel, as a diluent and solvent. C6 H5 C2 H5 Most of the ethylbenzene is obtained by alkylation of benzene with ethylene, and a much smaller amount is isolated by ultra-clear distillation from straight-run gasoline reforming products. The main indicators of the properties of ethylbenzene: Ethylbenzene irritates the skin, has convulsive action. MPC in the atmospheric air is 0.02 mg/m³; domestic use - 0.01 mg / l. CPV 0.9-3.9% by volume. The volume of the world production of about 17 million tons per year (1987). Production volume in Russia 0.8 million tons per year (1990).

H2C=CH2. A colorless gas with a slight odor. Ethylene dissolves in water 0.256 cm³ / cm³ (at 0 ° C), dissolves in alcohols and ethers. Ethylene has the properties of phytohormones - it slows down growth, accelerates cell aging, ripening and falling of fruits. It is explosive, CPV 3-34% (by volume), MPC in the atmospheric air 3 mg / m³, in the air of the working area 100 mg / m³. World production 50 million tons per year (1988).

Large quantities (20%) are found in refinery gases; included in coke oven gas. One of the main products of the petrochemical industry: it is used for the synthesis of vinyl chloride, ethylene oxide, ethyl alcohol, polyethylene, etc. Ethylene is obtained during the processing of oil and natural gas. Vyde- The ethylene fraction contains 90-95% ethylene with an admixture of propylene, methane, and ethane. It is used as a raw material in the production of polyethylene, ethylene oxide, ethyl alcohol, ethanolamine, polyvinyl chloride, in surgery - for anesthesia.

C6 H6. Colorless liquid with a peculiar pungent odor hom. Forms explosive mixtures with air, mixes well with ethers, gasoline and other organic solvents. Solubility in water 1.79 g/l (at 25°C). Toxic, hazardous to the environment, flammable. Benzene is an aromatic hydrocarbon. The main indicators of the properties of benzene: Molecular weight=78.12 Density, g/cm³=0.879 Temperature, °С: Boiling=80.1 melting point=5.4 Flashes=-11 Self-ignition=562 Heat, kJ/mol: melting point=9.95 Evaporation=33.85 Heat capacity, J / mol ∙ K \u003d 81.6 Benzene is miscible in all respects with non-polar solvents: hydrocarbons, turpentine, ethers, dissolves fats, rubber, resins (tar). It gives an azeotropic mixture with water with a boiling point of 69.25 ° C, forms double and triple azeotropic mixtures with many compounds.

Found in some oils, motor fuels, gasolines. It is widely used in industry, is the raw material for the production of medicines, various plastics, synthetic rubber, dyes. Benzene is a component of crude oil, but on an industrial scale, for the most part, it is synthesized from its other components. It is also used to obtain ethylbenzene, phenol, nitrobenzene, chlorobenzene, as a solvent. Depending on the production technology, various grades of benzene are obtained. Petroleum benzene is obtained in the process of catalytic reforming of gasoline fractions, catalytic hydrodealkylation of toluene and xylene, as well as during the pyrolysis of petroleum feedstock.

2.3. Description of the technological scheme.

Appendix A shows the process flow diagram for the production of ethylbenzene. The process of alkylation of benzene with ethylene is carried out in the alkylator pos. P-1 in an ethyl chloride medium at a temperature of 125-135C and a pressure of 0.26-0.4 MPa. The following are fed into the alkylator: dried benzene mixture, catalytic complex, polyalkylbenzene fraction, ethylene, recirculating catalytic complex, return benzene.

The alkylation reaction proceeds with the release of heat, the excess of which is removed by the recirculating catalytic complex and evaporating benzene. Benzene from the upper part of the alkylator, mixed with off-gas, is sent to the condenser pos. T-1, cooled by water. Uncondensed gases from the condenser pos. T-1 are sent to the condenser pos. Т-2, cooled by chilled water t=0°C. Blowers after the condenser pos. T-2 are sent for further benzene vapor recovery. Benzene condensate from condensers pos. T-1 and T-2 merges by gravity into the bottom of the alkylator pos. R-1. From the alkylator pos. R-1 reaction mass through the heat exchanger pos. T-3, where it is cooled with water to 40-60 ° C, is sent to the sump pos. E-1 to separate from the circulating catalyst complex. The settled catalytic complex from the bottom of the sump pos. E-1 is taken by the pump pos. H-1 and returns to the alkylator pos. R-1. To maintain catalyst activity, ethyl chloride is fed into the recycle complex line. In the event of a decrease in the activity of the catalyst, the output of the spent catalytic complex for decomposition is provided. The reaction mass from the sump pos. E-1 is collected in a container pos. E-2, from where, due to the pressure in the alkylation system, it enters the mixer pos. E-3 for mixing with acidic water circulating in the decomposition system:

sump pos. E-4-pump, pos. H-2-mixer, pos. E-3. The ratio of the circulating water supplied to the mixer and the reaction mass is l/2: 1. Yes, the decomposition system is supplied from the collection of pos. E-5 pump pos. H-3. The reaction mass is settled from water in the sump pos. E-4; lower water layer pump pos. H-2 is sent to the mixer; and the top layer - the reaction mass - flows by gravity into the washing column pos. K-1 for secondary flushing with water supplied by the pump pos. H-4 from the washing column pos. K-2. From the wash column pos. K-1 reaction mass by gravity enters the collection pos. E-6, from where the pump pos. H-5 is pumped out for neutralization into the mixer pos. E-7.

The lower aqueous layer from the wash column pos. K-1 drains by gravity into the container pos. E-5 and pump pos. H-3 is fed into the mixer pos. E-3. Neutralization of the reaction mass in the mixer pos. E-7 is carried out with a 2-10% sodium hydroxide solution. The ratio of the reaction mass and the circulating sodium hydroxide solution is 1:1. The separation of the reaction mass from the alkali solution occurs in the sump pos. E-8, from where the reaction mass flows by gravity into the column pos. K-2 for cleaning from alkali with water condensate. The bottom layer - chemically contaminated water - is drained from the column into a container pos. E-9 and pump pos. H-4 is pumped out for washing the reaction mass in the column pos. K-1. The reaction mass from the top of the column flows by gravity into the sump pos. E-10, then collected in an intermediate container pos. E-11 and is pumped out by the pump pos. H-7 to the warehouse.

Technological scheme for the alkylation of benzene with ethylene on aluminum chloride, which is also suitable for the alkylation of benzene with propylene.

The alkylation process is carried out in an alkylator - a reaction column lined with enamelled or lined with graphite tiles to protect against corrosion. Three sections of the column have jackets for cooling, but the main amount of heat is removed by evaporation of some of the benzene. Alkylation is carried out in the presence of a liquid catalyst complex consisting of aluminum chloride (10–12%), benzene (50–60%) and

polyalkylbenzenes (25 - 30%). For the formation of hydrogen chloride, which is the promoter of the reaction, 2% of water by weight of aluminum chloride, as well as dichloroethane or ethyl chloride, are added to the catalytic complex, during the splitting of which hydrogen chloride is formed.

1.5. Description of devices and principle of operation of the main apparatus.

Alkylation is carried out in a column-type reactor without mechanical agitation at a pressure close to atmospheric (Appendix B). The reactor consists of four tsargs, enameled or lined with ceramic or graphite tiles. For better contact, there is a nozzle inside the reactor. The height of the reactor is 12 m, the diameter is 1.4 m. Each drawer is equipped with a jacket for heat removal during the normal operation of the reactor (it is also used for heating when starting the reactor). The reactor is filled to the top with a mixture of benzene and catalyst. Dried benzene, catalytic complex and gaseous ethylene are continuously fed into the lower part of the reactor. Liquid products of the alkylation reaction are continuously withdrawn at a height of about 8 m from the base of the reactor, and a vapor-gas mixture consisting of unreacted gases and benzene vapor is discharged from the top of the reactor. The temperature in the lower part of the reactor is 100°C, in the upper part it is 90 - 95°C. The catalyst complex is prepared in an apparatus from which the catalyst suspension is continuously fed into the alkylation reactor.

Alkilator for the production of ethylbenzene in the liquid phase is a steel column lined inside with an acid-resistant lining pos. 4 or covered with acid-resistant enamel to protect the walls from the corrosive action of hydrochloric acid. The device has four tsargi pos. 1, connected by flanges pos. 2. Three kings are equipped with shirts pos. 3 for cooling with water (for heat removal during the alkylation reaction). The reactor during operation is filled with a reaction liquid whose column height is 10 m . Two coils are sometimes placed above the liquid level, in which water circulates, for additional cooling.

The operation of the alkylator is continuous: benzene, ethylene and a catalytic complex are constantly fed into its lower part; the mixture of reactants and catalyst rises into upper part apparatus and from here flows into the sump. The vapors leaving the top of the alkylator (consisting mainly of benzene) condense and return to the alkylator again as a liquid.

In one pass, ethylene reacts almost completely, and benzene only 50-55%; therefore, the yield of ethylbenzene per pass is about 50% of theoretical; the rest of the ethylene is lost to the formation of di- and polyethylbenzene.

The pressure in the alkylator during operation is 0.5 at(excess), temperature 95-100°C.

Alkylation of benzene with ethylene can also be carried out in the gas phase, over a solid catalyst, but this method is still little used in industry.

The yield of ethylbenzene is 90 - 95% in terms of benzene and 93% in terms of ethylene. Consumption per 1 ton of ethylbenzene is: ethylene 0.297 tons,

benzene 0.770 tons, aluminum chloride 12 - 15 kg.

2. CONCLUSIONS ON THE PROJECT.

The cheapest ethylbenzene is obtained by separating it from the xylene fraction of reforming or pyrolysis products, where it is contained in an amount of 10-15%. But the main method for obtaining ethylbenzene remains the method of catalytic alkylation of benzene.

Despite the presence of large-scale production of alkylbenzenes, there are a number of unresolved problems that reduce the efficiency and technical and economic performance of alkylation processes. The following disadvantages can be noted:

Lack of stable, highly active catalysts for the alkylation of benzene with olefins; Catalysts that have found widespread use - aluminum chloride, sulfuric acid, etc. cause equipment corrosion and are not regenerated;

The occurrence of secondary reactions that reduce the selectivity of the production of alkylbenzenes, which requires additional costs for the purification of the resulting products;

Formation of a large amount of wastewater and industrial wastes with existing technological schemes of alkylation;

Insufficient unit production capacity.

Thus, due to the high value of ethylbenzene, at present the demand for it is very high, while its cost is relatively low. The raw material base for the production of ethylbenzene is also wide: benzene and ethylene are obtained in large quantities during the cracking and pyrolysis of petroleum fractions.

3. STANDARDIZATION

The following GOSTs were applied in the course project:

GOST 2.105 - 95 General requirements for text documents.

GOST 7.32 - 81 General requirements and rules for the design of coursework and theses.

GOST 2.109 - 73 Basic drawing requirements.

GOST 2.104 - 68 Main inscriptions on the drawings.

GOST 2.108 - 68 Specifications.

GOST 2.701 - 84 Schemes, types, types, general requirements.

GOST 2.702 - 75 Rules for the implementation of schemes various kinds.

GOST 2.721 - 74 Conditional and graphic designations in diagrams.

GOST 21.108 - 78 Conditional and graphic representation in the drawings.

GOST 7.1 - 84 Rules for the design of the list of references.

4. LIST OF USED LITERATURE.

1. Traven V.F. Organic chemistry: in 2 volumes: textbook for universities / V.F. Traven. - M.: NCC Akademkniga, 2005. - 727 p.: ill. – Bibliography: p. 704 - 708.

2. Epstein D.A. General chemical technology: textbook for vocational schools / D.A. Epstein. - M.: Chemistry, - 1979. - 312 p.: ill.

3. Litvin O.B. Fundamentals of rubber synthesis technology. / ABOUT. Litvin. - M.: Chemistry, 1972. - 528 p.: ill.

4. Akhmetov N.S. General and inorganic chemistry: textbook for universities - 4th ed., corrected. / N.S. Akhmetov. – M.: high school, ed. center Academy, 2001. - 743 p.: ill.

5. Yukelson I.I. Technology of basic organic synthesis. / I.I. Yukelson. - M .: Chemistry, -1968. - 820 p.: ill.

6. Paushkin Ya.M., Adelson S.V., Vishnyakova T.P. Technology of petrochemical synthesis: part 1: Hydrocarbon feedstock and products of its oxidation. / Ya.M. Paushkin, S.V. Adelson, T.P. Vishnyakova. - M .: Chemistry, -1973. - 448 p.: ill.

7. Lebedev N.N. Chemistry and technology of basic organic and petrochemical synthesis: textbook for universities - 4th ed., revised. and additional / N.N. Lebedev. - M .: Chemistry, -1988. - 592 p.: ill.

8. Plate N.A., Slivinsky E.V. Fundamentals of chemistry and technology of monomers: textbook. / N.A. Plate, E.V. Slivinsky. – M.: MAIK Nauka / Interperiodika, -2002. - 696 p.: ill.

Introduction……………………………………………………………………………3

2.Technological part……………………………………………………….

2.1. Theoretical foundations of the accepted method of production………….5

2.2. Characteristics of raw materials and the resulting product…………………..9

2.3. Description of the technological scheme………………………………………………12

2.4. Material calculation of production……………………………….15

2.5. Description of the device and the principle of operation of the main apparatus ... .20

3. Conclusions on the project…………………………………………………………….22

4. Standardization………………………………………………………..........24

5. List of literature used……………………………………………25

6. Specification…………………………………………………………………26

7. Appendix A………………………………………………………………………………………………………………………………………………………………………27

8. Annex B…………………………………………………………………28

Ethylbenzene and toluene are two substances similar in their properties, belonging to the class "hydrocarbons". They are extremely toxic to humans and adversely affect the body.

Toluene is a colorless liquid, also known as methylbenzene. The substance has a characteristic sharp and caustic "aroma". Toluene occurs naturally in crude oils and is also found quite often in tolu balsam. Methylbenzene is obtained in the process of catalytic reforming of gasoline fractions of oil. Other methods for obtaining this toxic substance are also known. For example, toluene is released during the distillation of wood resin.

Methylbenzene is a necessary element in the manufacture of benzene. Thus, toluene is a very important raw material used in the chemical industry. The substance has excellent solvent properties, therefore it is ideal for most polymers and paints and varnishes.

Ethylbenzene is also a colorless liquid with a characteristic "gasoline" smell. The substance of organic origin is found in coal tar and oil. Ethylbenzene is obtained in the process of processing benzene into ethylene or as a result of reforming. The substance is used in the production of styrene, which later becomes one of the components for plastics. Among other things, ethylbenzene is actively used in the manufacture of high-octane gasoline, rubber and rubber glue. Like toluene, this liquid is used as a strong solvent.

Both substances are almost insoluble in water, but they are easily mixed with substances such as benzene, alcohol and ether.

A person can identify ethylbenzene and toluene by smell if the concentration of substances in the air is 8ppm (for toluene) and 2.3ppm (for ethylbenzene). To taste, both liquids appear much earlier. At elevated concentrations, toluene and ethylbenzene can cause severe harm to any living organism, so all precautions should be observed when working with them.

Ethylbenzene and toluene: environmental impact

In the process of evaporation, both liquids easily interact with air and enter the atmosphere. In the event of an accidental spill of such chemical components or oil products, toxic substances penetrate into groundwater and reservoirs. Gasoline leaks are fraught with soil contamination with toluene and benzene. Pollution of this kind is most often found in areas of industrial landfills and industrial waste disposal sites.

It is worth noting that, despite their toxic properties, toluene and ethylbenzene evaporate very quickly in water. Also, they do not remain in the soil, as they are processed by numerous microorganisms. The situation changes radically if liquids enter groundwater or open air. The fact is that in these places there is no necessary number of microorganisms, so the substances simply do not have time to be processed naturally. In this case, a person can easily get poisoned. Liquid substances easily penetrate the skin and quickly enter the bloodstream. If a person inhaled harmful fumes, then toluene and ethylbenzene enter the body through the respiratory tract, and then into the blood.

In daily life, we are constantly confronted with the results chemical production containing ethylbenzene and toluene. It can be gasoline, kerosene, heating oil, dyes, solvents, cleaners and even cosmetics. Some toluene has been found in regular cigarette smoke. Thus, the average smoker smokes more than 1000 micrograms of a toxic substance per day. An employee of a plant that uses various petroleum products receives an even higher dose of fumes, which is 1000 milligrams.

How toluene affects the human body

For a long time, scientists have been studying the effect of toluene on the human brain. Unfortunately, the research results are not encouraging. When a toxic substance enters the body, a person begins to experience severe headaches and suffer from insomnia. Toluene disrupts the normal activity of the human brain, as a result of which the mental abilities of the victim decrease. In the case of prolonged poisoning with a substance, symptoms such as constant fatigue, memory loss, and a sharp decrease in appetite are observed. At some point, a person simply loses control over his muscle and brain activity.

After prolonged interaction with toluene, a person experiences problems with hearing and vision. With chronic poisoning, it becomes very difficult to distinguish colors. That is why every time you work with glue for a long time, you start to get confused in your thoughts, you feel sleepy. It is worth paying attention to such symptoms, since a person can not only lose consciousness, but also die with such poisoning.

Among other things, toluene affects the work of the kidneys. If you inhale the toxin and consume alcoholic drinks, then intoxication will be many times stronger.

The toxin has a negative effect on female body causing miscarriages and premature births. If during the entire pregnancy a woman constantly inhaled toluene vapors, then its effect on the child will also affect after childbirth, if the mother feeds him with breast milk.

How ethylbenzene can affect the human body

A person who inhales ethylbenzene vapor begins to experience the following symptoms: severe fatigue, constant drowsiness, acute headache. There is also a strange itching sensation in the mouth, nose and abdomen. Eyes begin to water, and breathing becomes heavy. Ethylbenzene also adversely affects muscle function and leads to impaired coordination.

With longer exposure, the toxin can lead to serious liver and blood diseases.

To date, scientists have conducted a number of studies, on the basis of which it was possible to establish that the evaporation of toluene and ethylbenzene can cause malignant tumors.

In order to determine the content of toluene and ethylbenzene in your apartment, it is recommended to invite experts who will conduct a quick and high-quality air analysis.

Usage: petrochemistry. Essence: alkylation of benzene with ethylene is carried out by supplying a dried benzene mixture, a catalytic complex based on aluminum chloride, ethylene, a recirculating catalytic complex and return benzene to the alkylation reactor, separating the resulting reaction mass from the catalytic complex, neutralizing the reaction mass with alkali and washing with water from alkali, followed by separation of the reaction mass by distillation. In this case, before being fed into the alkylation reactor, the dried benzene mixture, the catalytic complex, ethylene, the recirculating catalytic complex and the return benzene are mixed in a turbulent mode and fed into the alkylation reactor also under turbulent conditions. EFFECT: increased conversion of the ethylbenzene production process.

The invention relates to the field of petrochemistry, specifically to the process of obtaining ethylbenzene by alkylation of benzene with ethylene in the presence of a catalytic complex based on aluminum chloride.

A known method for producing ethylbenzene, including alkylation of benzene with ethylene in the presence of aluminum chloride, separation of the target product by distillation from unreacted benzene and hydrocarbon impurities, azeotropic drying of a mixture of initial benzene with unreacted benzene and hydrocarbon impurities with the release of dried benzene, recycled for alkylation, and a fraction containing water , hydrocarbon impurities and benzene, which is subjected to condensation to obtain hydrocarbon and aqueous layers (AS USSR No. 825466, IPC C 07 C 2/58, 15/02, publ. 30.04.81).

The disadvantage of the described method is the increased consumption of aluminum chloride and benzene.

A known method for producing ethylbenzene by alkylation of benzene with ethylene in the presence of a catalytic complex based on aluminum chloride (TV Bashkatov, YL Zhigalin. "Technology of synthetic rubber", M., "Chemistry", 1980, pp. 108-112). The catalytic complex obtained from aluminum chloride, ethyl chloride, diethylbenzene and benzene is continuously fed into the lower part of the alkylation reactor, where dried fresh and recycled benzene, as well as ethylene, diethylbenzene saturated with benzene, and recycled catalytic complex are continuously supplied. Liquid products of benzene alkylation from the upper part of the reactor enter the settling tank, where they are separated into two layers. The lower layer - the catalytic complex - is returned to the reactor, the upper layer - alkylate - is mixed with water to destroy the residues of the catalytic complex, neutralized with an aqueous solution of alkali and washed from alkali. Further, the alkylate undergoes a three-stage rectification with the separation of unreacted benzene in the first column and its return to the alkylation reactor, with the separation of the target product - ethylbenzene - in the second column and diethylbenzene, which is returned to the reactor for dealkylation, and polyalkylbenzenes sent to the warehouse in the third column.

The disadvantage of this method for producing ethylbenzene is the insufficiently high conversion of the process - 90-95% for benzene and about 93% for ethylene.

A known method for producing ethylbenzene, including the alkylation of benzene with ethylene in the presence of a catalytic complex based on aluminum chloride and rectification of the reaction mass (P.A. L., "Chemistry", 1986, pp. 94-97). The dried benzene mixture, fresh and recycled catalytic complex, polyalkylbenzene fraction and ethyl chloride are supplied to the lower part of the alkylation reactor through a collector; ethylene is fed directly to the lower part of the reactor. From the alkylator, the reaction mass is sent to a settling tank for separation from the circulating catalytic complex and then to water washing, neutralization with an alkali solution, and water washing from alkali. The washed reaction mass is fed to separation by distillation with the release of unreacted benzene in the first column, rectified ethylbenzene in the second column and the polyalkylbenzene fraction in the third distillation column.

The disadvantage of this method is the poor mixing of the components supplied to the alkylation reactor, and, as a consequence, the low conversion of the process.

The objective of the invention is to increase the conversion of the process for producing ethylbenzene.

The problem is solved by developing a method for producing ethylbenzene, including the alkylation of benzene with ethylene by supplying a dried benzene charge, a catalytic complex based on aluminum chloride, ethylene, a recirculating catalytic complex and recycled benzene to the alkylation reactor, separating the resulting reaction mass from the catalytic complex, neutralizing the reaction mass with alkali and washing with water from alkali, followed by separation of the reaction mass by rectification, while before being fed into the alkylation reactor, the dried benzene charge, the catalytic complex, ethylene, the recirculating catalytic complex and the return benzene are mixed in a turbulent mode and fed into the alkylation reactor also under turbulence conditions.

The difference between the proposed method and the known ones is that, before being fed into the alkylation reactor, the dried benzene charge, the catalytic complex, ethylene, the recirculating catalytic complex and the return benzene are mixed under turbulent conditions and they are also fed into the alkylation reactor under turbulence conditions.

As a device with which you can achieve turbulent mixing of flows and give them turbulent motion, you can use, for example, a volumeless mixer equipped with confuser-diffuser sections, or Raschig rings loaded into the pipe, or any other known means made from chemically resistant materials or with a protective chemical-resistant coating.

According to the proposed method, ethylbenzene is obtained as follows.

The process of alkylation of benzene with ethylene is carried out in a column-type alkylation reactor at a temperature of 125-140°C and a top pressure of 0.12-0.25 MPa. The dried benzene charge, the aluminum chloride-based catalytic complex, ethylene, the recirculating catalytic complex and the recycled benzene are continuously supplied to the lower part of the alkylation reactor by means of a turbulizing device. All components are mixed in turbulent mode and enter the reactor under conditions of turbulent flow. From the alkylation reactor, the reaction mass is fed into a settling tank for settling the circulating catalytic complex. The settled recycled catalyst complex is removed from the bottom of the settler and returned to the alkylation reactor. To maintain the activity of the catalytic complex, ethyl chloride is supplied to the line of the recycled catalytic complex. Next, the reaction mass enters the mixer, where it is mixed with acidic water in a water:reaction mass ratio of at least 1:1. The sediment of the reaction mass from water occurs in the settler, from where the upper layer - the reaction mass - enters the washing column for washing with water and then for neutralization with a 2-10% alkali solution. The neutralized reaction mass enters the column for washing with water from alkali. Washing the reaction mass from alkali can be done with water or steam condensate. The washed reaction mass is fed to the separation in the first distillation column, where unreacted benzene is separated by distillate, which is fed to drying. VAT product of the first column enters the second distillation column. The target product, ethylbenzene, is isolated from the column distillate, and the bottom product is fed to the third distillation column, where diethylbenzene and polyalkylbenzene fractions are isolated as distillate.

The implementation of the method is illustrated by the following examples.

Dry benzene charge, aluminum chloride-based catalytic complex, ethylene, recirculating catalytic complex and return benzene are continuously fed into the lower part of the alkylation reactor through a volumeless mixer equipped with diffuser-confuser sections. All components are mixed in turbulent mode and enter the reactor under conditions of turbulent flow. The process of alkylation of benzene with ethylene is carried out in a column-type alkylation reactor at a temperature of 130°C and a top pressure of 0.20 MPa. From the alkylation reactor, the reaction mass enters the settling tank for settling the circulating catalytic complex. The settled recycled catalyst complex is removed from the bottom of the settler and returned to the alkylation reactor. Next, the reaction mass enters the mixer, where it is mixed with acidic water in a water:reaction mass ratio of at least 1:1. The sediment of the reaction mass from water occurs in the settler, from where the upper layer - the reaction mass - enters the washing column for washing with water and then for neutralization with a 2-10% alkali solution. The volume ratio of the alkali solution to the reaction mass is kept equal to 1:1. The neutralized reaction mass enters the column for washing with water from alkali. The washed reaction mass is fed to the separation in the first distillation column, where unreacted benzene is separated by distillate, which is fed to drying. VAT product of the first column enters the second distillation column. The distillate of the column allocate the target product - ethylbenzene containing 99.8% wt. ethylbenzene, and the bottom product is fed into the third distillation column, where fractions of diethylbenzene and polyalkylbenzenes are isolated as a distillate. The process conversion for benzene is 97%, for ethylene - 95%.

Ethylbenzene is obtained in the same way as described in example 1, but the mixing of the dried benzene mixture, catalytic complex, ethylene, recycle catalytic complex and recycled benzene before being fed into the alkylation reactor is carried out in a pipe filled with Raschig rings.

The process conversion for benzene is 98%, for ethylene - 95.5%.

As can be seen from the above examples, the pre-mixing of the dried benzene charge, the catalytic complex, ethylene, the recirculating catalytic complex and the return benzene under turbulent conditions before being fed into the alkylation reactor and the supply of all components for alkylation under turbulent conditions makes it possible to achieve high conversion rates in the production of ethylbenzene.

A method for producing ethylbenzene, including alkylation of benzene with ethylene by supplying a dried benzene charge, a catalytic complex based on aluminum chloride, ethylene, a recirculating catalytic complex and recycled benzene to the alkylation reactor, separating the resulting reaction mass from the catalytic complex, neutralizing the reaction mass with alkali and washing with water from alkali followed by separation of the reaction mass by distillation, characterized in that before being fed into the alkylation reactor, the dried benzene charge, the catalytic complex, ethylene, the recirculating catalytic complex and the return benzene are mixed in a turbulent mode and fed into the alkylation reactor also under turbulence conditions.

COURSE WORK

in the discipline "Fundamentals of technology for the production of organic substances"

on the topic "Technology for the production of styrene by dehydrogenation of ethylbenzene"

• Table of contents
• Introduction
• 1. Styrene. Properties
• 2. Obtaining styrene
• 3. Styrene production
• 5. Dehydrogenation of ethylbenzene
• Conclusion

Introduction

Styrene is one of the main monomers for the production of polymeric materials, without which no industry can currently do, both in Russia and abroad. Styrene is used to produce polystyrene, thermoplastic elastomers, and various paint and varnish compositions. The main method for obtaining styrene is the process of dehydrogenation of ethylbenzene. This determined the choice as the topic of the course work.

This paper describes the properties of styrene, its application, the main methods of obtaining and technological processes.

The aim of the work is to consider the technology of obtaining styrene by dehydrogenation of ethylbenzene as the main method for obtaining the monomer in question.

1. Styrene. Properties

Styrene C8H8 (phenylethylene, vinylbenzene) is a colorless liquid with a specific odor. Styrene is practically insoluble in water, readily soluble in organic solvents, a good solvent for polymers. Styrene belongs to the second hazard class.

Physical properties

Molar mass 104.15 g/mol

Density 0.909 g/cm

Thermal Properties

Melting point -30 °C

Boiling point 145 °C

Properties

Styrene is easily oxidized, attaches halogens, polymerizes (forming a solid glassy mass - polystyrene) and copolymerizes with various monomers. Polymerization occurs already at room temperature (sometimes with an explosion), therefore, during storage, styrene is stabilized with antioxidants (for example, tert-butylpyrocatechol, hydroquinone). Halogenation, for example, in the reaction with bromine, unlike aniline, does not proceed along the benzene ring, but along the vinyl group with the formation of 1,2-dibromoethylphenyl.

1. Oxidation: C6H5-CH=Cp+O2>C6H5-Cp-COOH

2. Halogenation: C6H5-CH=CH2 +Br2> C6H5-CHBr=CHBr2

3. Polymerization: n Cp=CH-C6H5>(-Cp-CH-) n - C6H5

4. Copolymerization: Cp=CH+Cp=CH-CH=Cp>-Cp-CH-Cp-CH=CH-Cp- C6H5 -C6H5

Toxicity

Styrene is a poison of general toxic action, it has an irritating, mutagenic and carcinogenic effect and has a very unpleasant odor (smell threshold - 0.07 mg/m3). In chronic intoxication, workers are affected by the central and peripheral nervous system, the hematopoietic system, the digestive tract, nitrogen-protein, cholesterol and lipid metabolism is disturbed, and reproductive function is disturbed in women. Styrene enters the body mainly by inhalation. In case of contact with the mucous membranes of the nose, eyes and pharynx, vapors and aerosols styrene causes their irritation. The content of benzene metabolites in urine - mandelic, phenylglyoxin, ginuric and benzoic acid- used as an exposure test.

The average lethal dose is about 500-5000 mg/m3 (for rats). Styrene belongs to the second hazard class.

Maximum Permissible Concentrations (MPC) of styrene:

MPKr.z. = 30 mg/mі

MPC.s. = 10 mg/mі

MPCm.r. = 0.04 mg/mі

MPCs.s. = 0.002 mg/mі

MPCv. = 0.02 mg/l

Application

Styrene is used almost exclusively for the production of polymers. Numerous types of styrene-based polymers include polystyrene, styrofoam (expanded polystyrene), styrene-modified polyesters, ABS (acrylonitrile-butadiene-styrene) and SAN (styrene-acrylonitrile) plastics. Styrene is also part of napalm.

2. Obtaining styrene

Most of the styrene (about 85%) in the industry is obtained by dehydrogenation of ethylbenzene at a temperature of 600--650 ° C, atmospheric pressure and diluted with superheated water vapor by 3-10 times. Oxide iron-chromium catalysts with the addition of potassium carbonate are used.

Another industrial method, by which the remaining 15% is obtained, is the dehydration of methylphenylcarbinol, which is formed in the process of obtaining propylene oxide from ethylbenzene hydroperoxide. Ethylbenzene hydroperoxide is obtained from ethylbenzene by non-catalytic air oxidation.

Alternative methods for producing styrene are being developed. Catalytic cyclodimerization of butadiene to vinylcyclohexene followed by its dehydrogenation. Oxidative coupling of toluene to form stilbene; stilbene metathesis with ethylene leads to styrene. Styrene can also be obtained by reacting toluene with methanol. In addition, methods for isolating styrene from liquid pyrolysis products have been actively developed. To date, none of these processes is economically viable and has not been implemented on an industrial scale.

In laboratory conditions, it can be obtained by heating polystyrene to 320 ° C with its instant removal.

1) Thermal decarboxylation of cinnamic acid is carried out at a temperature of 120-130°C and atmospheric pressure. Styrene yield is about 40%

2) Dehydration of phenylethyl alcohol. The reaction can be implemented both in gas and liquid phases. Liquid-phase dehydration of phenylethyl alcohol is carried out in the presence of phosphoric acid or potassium bisulfite. Dehydration in the vapor phase is carried out over catalysts: oxides of aluminum, thorium or tungsten. When using alumina, the yield of styrene is up to 90% of theory.

3) Synthesis from acetophenone. Styrene can be obtained by the reaction of acetophenone with ethyl alcohol over silica gel:

The yield is about 30%.

4) Obtaining styrene from haloethylbenzene:

5) Obtaining styrene by dehydrogenation of ethylbenzene.

6) Production method from ethylbenzene through ethylbenzene hydroperoxide with simultaneous production of propylene oxide (chalcone process):

7) Obtaining styrene by metathesis of ethylene with stilbene obtained by oxidation of toluene:

8) Obtaining styrene by catalytic cyclodimerization of butadiene:

All the above methods for obtaining styrene (with the exception of dehydrogenation) are multi-stage, use high pressure and high temperature, which leads to the complexity and cost of production. For some methods, not very accessible raw materials are used. Small exits.

The main method of industrial production of styrene is the catalytic dehydrogenation of ethylbenzene. More than 90% of the world production of ethylbenzene is obtained by this method. Complex compositions based on zinc or iron oxides are used as dehydrogenation catalysts. Previously, the most common catalyst was styrene-contact based on ZnO. Recently, mainly iron oxide catalysts containing 55-80% Fe2O3 have been used; 2-28% Cr2O3; 15-35% K2CO3 and some oxide additives. In particular, the NIIMSK K-24 catalyst with the composition Fe2O3 - 66-70% is widely used; K2CO3 - 19-20%; Cr2O3 - 7-8%; ZnO2 - 2.4-3.0%; K2SiO3 - 2.0-2.6%. A significant content of K2CO3 in the catalyst is due to the fact that it contributes to additional self-regeneration of the catalyst due to the conversion of carbon deposits with water vapor. The catalyst operates continuously for 2 months, after which it is regenerated by burning the coke with air. The total service life of the catalyst is 2 years. [6]

The reaction unit for the dehydrogenation of ethylbenzene can be performed different ways. One option is a flue gas heated tubular reactor of the type shown in Figure 1.

Rice. 1 Reaction unit for dehydrogenation of alcohols: 1 - evaporators-superheaters; 2 - tubular reactor; 3 - tseda; blower

Its advantage is a temperature profile close to isothermal, which makes it possible to obtain an increased degree of conversion with good selectivity. However, the high metal consumption and capital costs for such a reactor led to the creation of other devices - with a continuous catalyst layer, which do not have heat exchange surfaces (Fig. 2a).

They work under adiabatic conditions, and the reaction mixture is gradually cooled, and water vapor also plays the role of a heat accumulator here, preventing the mixture from cooling excessively. In the production of styrene in a single adiabatic reactor, the usual degree of conversion of ethylbenzene is about 40%. The disadvantages of such a single reactor are the significant cooling of the mixture, the simultaneous shift of the equilibrium in an undesirable direction and the resulting decrease in speed and selectivity. The degree of conversion cannot be brought to an acceptable value, because this increases the specific steam consumption.

Rice. 2 a - a single reactor of the adiabatic type; b - a unit of two reactors with intermediate heating of the mixture; c - reactor with several layers of catalyst and sectioned supply of superheated steam.

Other settings (Fig. 2B) bring the process closer to isothermal and better take into account the features of the equilibrium of the reaction. In such an installation, there are 2 reactors (or two catalyst beds). The mixture cooled in the first reactor is heated with superheated steam before being fed into the second reactor. The reactor in Figure B has two to three annular beds of catalyst, with the first bed receiving all of the ethylbenzene but only a portion of the water vapor.

An additional amount of superheated steam is fed into the space between the catalyst layers. With its help, the temperature of the mixture rises and a stepwise dilution of the mixture occurs with its removal from the equilibrium state, which contributes to an increase in the rate and selectivity of the reaction.

3. Styrene production

Technology of joint production of styrene and propylene oxide

The general technological scheme for the joint production of styrene and propylene oxide is shown in fig. 3. In this technology, the oxidation of ethylbenzene is carried out in a tray column 1. In this case, both heated ethylbenzene and air are fed to the bottom of the column. The column is equipped with coils located on the plates. Heat is removed by water supplied to these coils. If a catalyst is used to intensify the process, then the process must be carried out in a series of bubbling reactors connected in series, into which ethylbenzene charge (a mixture of fresh and return ethylbenzene with a catalyst solution) is fed countercurrently to air. In this case, the oxidation products pass sequentially through the reactors, each of which is supplied with air.

The gas-vapor mixture from the upper part of the reactor enters condenser 2, in which the entrained ethylbenzene, as well as impurities of benzoic and formic acids, are mainly condensed. After separating the condensate from the cans, it is sent to the scrubber 4 x / i neutralization of acids with alkali. After neutralization, ethylbenzene is returned to reactor C 1. Ethylbenzene is also fed there from column 10. Gases are removed from the system. The oxidate from the bottom of column 1, containing about 10% hydroperoxide, is sent to distillation column 3 for concentration. The hydroperoxide concentration is carried out under high vacuum. Despite the high energy costs, this process is best carried out on a double distillation unit. At the same time, part of the ethylbenzene is distilled off in the first column at a lower vacuum, and the rest of the ethylbenzene with impurities is distilled off in the second column at a deeper vacuum. The distillate of this column is returned to the first column, and concentrated (up to 90%) hydroperoxide is obtained in the cube, which is sent for epoxidation. The oxidate is preliminarily cooled in the heat exchanger 5 by the initial ethylbenzene.

Rice. 4. Technological scheme for the joint production of styrene and propylene oxide; 1 - oxidation column; 2 - capacitor; 3.7-10.18 - distillation columns; 4 - alkaline scrubber; 5,12,14 - heat exchangers; 6 - epoxidation column; 11 - mixing evaporator; 13.15 - dehydration reactors; 16 - refrigerator; 17 - Florentine vessel; I - air; II - ethylbenzene; III - propylene; IV - alkali solution; V - gases; VI - catalyst solution; VII - propylene oxide; VIII - resins; IX - water layer; X - styrene; XI - for dehydrogenation; XII-steam

In column 3, ethylbenzene with acid impurities is distilled off, so the upper product is also sent to scrubber 4. From the bottom of column 3, concentrated hydroperoxide enters epoxidation column 6. (Epoxidation can also be carried out in a cascade of reactors.) A catalyst solution from cube of column 9. Fresh catalyst is also fed there. Fresh and return (from column 7) propylene is also fed to the bottom of the column. The reaction products, together with the catalyst solution, are withdrawn from the top of the column and sent to distillation column 7 for distillation of propylene. The gases are removed from the top of the column and from the system for disposal or incineration. The bottom product of column 7 enters the distillation column 8 to isolate product propylene oxide as a distillate. The bottom liquid of column # enters column 9 to separate the synthesis products from the catalyst solution.

The catalyst solution from the bottom of the column is returned to the epoxidation column 6, and the top product enters the Yull distillation column for separating ethylbenzene from methylphenylcarbinol and acetophenone. A mixture of methylphenylcarbinol (MPC) and acetophenone is fed into evaporator 11, in which methylphenylcarbinol and acetophenone are evaporated and separated from the resins using superheated steam. The vapor mixture, overheated to 300°C, enters reactor 13 for dehydration of methylphenylcarbinol. This reactor is partially dehydrated. Since the dehydration reaction is endothermic, before the dehydration products enter the other reactor (reactor 15), the dehydration products are superheated in the heat exchanger 14.

The conversion of methylphenylcarbinol after two reactors reaches 90%. The dehydration products are cooled with water in the refrigerator 76 and enter the Florentine vessel 17, in which the organic layer is separated from the water. The upper hydrocarbon layer enters the distillation column 18 to separate styrene from acetophenone. Acetophenone is then hydrogenated in a separate unit to methylphenylcarbinol, which is fed to the dehydration section.

The selectivity of the process for propylene oxide is 95–97%, and the yield of styrene reaches 90% for ethylbenzene. In this case, 2.6-2.7 tons of styrene is obtained from 1 ton of propylene oxide.

Thus, the considered technology is a complex system that includes many recycles for ethylbenzene, propylene, and a catalyst. These recycles lead, on the one hand, to an increase in energy costs, and on the other hand, they allow the process to be carried out under safe conditions (at a low concentration of hydroperoxide - 10--13%) and achieve complete conversion of the reagents: ethylbenzene and propylene.

Therefore, this process needs to be optimized. The proposed technological scheme makes full use of the heat of reactions and flows. However, instead of the refrigerator 16, it is better to use a waste heat boiler, in which low-pressure steam can be produced. To do this, it is necessary to supply water condensate to the waste heat boiler, from which steam will be obtained. In addition, it is necessary to provide for a more complete use of exhaust gases and tar, an alkaline salt solution from scrubber 4, as well as additional purification of the water layer of the Florentine vessel. The most significant improvement in the technological scheme can be the replacement of dehydration reactors with a column in which a combined reaction-rectification process can be organized. This process takes place on an ion-exchange catalyst in the vapor-liquid version, i.e., at the boiling temperature of the mixtures passing through the column, and can be represented by a diagram (Fig. 5).

Rice. five. circuit diagram registration of the combined process

In this version of the process, the conversion and selectivity can reach 100%, since the process proceeds at low temperatures and a short residence time of the synthesis products in the reactor. heteroazeotrope with water (boiling point below 100 °C), which makes it possible to exclude its thermopolymerization.

4. Principles in the technology of joint production of styrene and propylene oxide

The production technology for styrene and propylene oxide uses available, high-volume ethylbenzene and propylene as raw materials. This process cannot be classified as a low-stage process, since it includes several chemical reactions: the oxidation of ethylbenzene to hydroperoxide, the epoxidation of propylene, the dehydration of methylphenylcarbinol, and the hydrogenation of acetophenone. Nevertheless, even such a multi-stage structure of the technology makes it possible to obtain target products with a propylene oxide selectivity of 95–97% and a styrene yield of ethylbenzene up to 90%. Thus, the production under consideration can be classified as highly efficient. Moreover, this technology is a vivid example of "coupled" production, providing the simultaneous production of several target products, allows the production of styrene with a higher quality than dehydrogenation (from the point of view of polymerization processes) and replaces the environmentally dirty production of propylene oxide by the chlorohydrin method. In connection with the multi-stage nature of the technology, it is necessary to distinguish in it the nodes that provide high conversions in one pass - epoxidation, dehydration, hydrogenation, and those that do not have such a character - the production of ethylbenzene hydroperoxide.

In this case, restrictions on the conversion of ethylbenzene are associated with the sequential nature of side reactions and the explosive nature of hydroperoxide at high concentrations under the temperature conditions (140–160 °C) of the reaction. Accordingly, recirculation streams aimed at the full use of the feedstock have large volumes at the oxidation stage and smaller volumes for the remaining stages (recycle over the catalyst solution of the epoxidation stage; recycle over return ethylbenzene.

Due to the multi-stage nature of this technology, it is necessary to fully implement the principle of complete separation of products from the reaction mass, since it is the pure compounds entering each of the stages of the chemical transformation that provide high rates of the process as a whole. The exothermic nature of the oxidation and epoxidation processes makes it possible to use the energy resources (steam) obtained at these stages for separation processes and, thereby, ensure the implementation of the principle of complete use of the system energy. In general, the technological solution developed and implemented in our country is highly effective.

5. Dehydrogenation of ethylbenzene

The dehydrogenation of ethylbenzene to styrene proceeds according to the reaction:

C6H5CpCp > C6H5CH=Cp + p

The reaction is endothermic and proceeds with an increase in volume. Accordingly, with an increase in temperature and a decrease in the partial pressure of hydrocarbon, the degree of conversion of ethylbenzene to styrene increases. At a pressure of 0.1 MPa, this dependence looks like this:

Dehydrogenation temperature, K 700 800 900 1000

Equilibrium degree of conversion 0.055 0.21 0.53 0.83

To increase the depth of transformation, the raw material is diluted with water vapor, which is equivalent to reducing the pressure of the reacting mixture. So, at 900K, the equilibrium degree of dehydrogenation of ethylbenzene to styrene, depending on dilution with water vapor, increases as follows:

Molar ratio pO: C6H5CH=Cp 0 5 10 20

Equilibrium degree of dehydrogenation 0.53 0.77 0.85 0.9

During the dehydrogenation of ethylbenzene, along with styrene, a number of by-products are formed. In particular, in accordance with the scheme of chemical transformations given below, benzene and toluene are obtained in the largest quantities:

C6H5C2H5 > C6H5CH=Cp + p (styrene)

C6H5C2H5 > C6H6 + C2H4 (benzene)

C6H5C2H5 > C6H5Cp + CH4 (toluene)

C6H5C2H5 > C6H6 + C2H6 (benzene)

C6H5C2H5 > 7C + CH4 + 3p

Therefore, in addition to hydrogen, the resulting gas contains methane, ethylene, ethane, and carbon oxides (due to coke conversion).

In industry, dilution with water vapor is used in the ratio of steam: gas = (15-20): 1 and the reaction is carried out at a temperature of 830-900 K. Catalysts are prepared on the basis of iron oxide with K and Cr additives. Side transformations also occur on them, so the dehydrogenation reaction can be represented by the following scheme:

The selectivity for styrene is about 98%. In addition to the decomposition reaction, carbon deposits are formed on the catalyst. Water vapor supplied for dilution not only shifts the equilibrium, but also gasifies carbon deposits on the catalyst surface. There is a continuous regeneration of the catalyst, and its service life is 1.5-2 years.

The reversible endothermic reaction is carried out adiabatically in a fixed catalyst bed. The process in a two-layer reactor with steam distribution between the layers makes it possible to increase the degree of conversion. The use of a reactor with radial catalyst beds significantly reduces its hydraulic resistance. The reaction mixture after the reactor enters the separation. The heat of the reaction mixture is recovered.

On Fig. 6 shows the technological scheme for the dehydrogenation of ethylbenzene. The original ethylbenzene is mixed with recycle from the distillation unit and with water vapor and evaporates in heat exchanger 2. Vapors are superheated in heat exchanger 4 to 500 - 520°C. Evaporator 2 is heated by flue gases, and superheater 4 is heated by contact gas leaving reactor 3. Vapors of alkylbenzene and water are mixed in front of the reactor with superheated water vapor at a temperature of 700-730 °C. The superheated steam is generated in the superheating furnace 1, where fuel from the plant network and hydrogen-containing gas from the dehydrogenation section are burned.

The temperature of the mixture at the inlet to the catalyst bed is 600-640°C, at the outlet it decreases by 50-60°C due to the endothermic dehydrogenation reaction. The heat of the contact gases is sequentially recuperated in the heat exchanger 4 and the waste heat boiler 5. The saturated steam from the waste heat boiler is used to dilute the ethylbenzene. The contact gas enters the foam apparatus, where it is additionally cooled to 102°C and purified from catalyst dust. Cooling and condensation of water and hydrocarbons from the contact gas takes place in the air cooler 7 and then in the water and brine condensers (not shown in the diagram). In the separator 8, the gaseous reaction products are separated as combustible VER. Hydrocarbons are separated from water in a phase separator 9 and sent for rectification. The aqueous layer enters the froth apparatus 6 and, after being cleaned from dissolved hydrocarbons (not shown), is fed to the waste heat boiler 5 and then to the recycling. Excess water is directed to biological treatment.

Rice. 6. Scheme of dehydrogenation of ethylbenzene to styrene: 1 - superheating furnace; 2 - ethylbenzene evaporator; 3 - dehydrogenation reactor; 4 - ethylbenzene heater; 5 - water heater; b - foam apparatus; 7 - air cooler; 8- separator; 9 - phase separator. Flows: EB - ethylbenzene (fresh recycle); H2, CH4 - combustible gases into the fuel network; DG - flue gases; K - condensate; PD - products of dehydrogenation.

Hydrocarbon condensate contains the following reaction products:

Benzene (B) ~2 80.1

Toluene (T) ~2 110.6

Ethylbenzene (EB) 38 136.2

Styrene (St) 58 146.0

Here are the boiling points of the components. In accordance with the rules for the separation of a multicomponent mixture (a condensate separation scheme has been constructed. Ethylbenzene and styrene are low-boiling liquids, therefore, benzene and toluene are first separated from them. They are separated separately in a distillation column. Ethylbenzene is separated from styrene in a column and returned to dehydrogenation as a recycle. Styrene undergoes additional purification in the next distillation column.Since it easily dimerizes, purification is carried out under vacuum conditions at a temperature not exceeding 120 ° C and with the addition of an inhibitor - sulfur.Vat residues of styrene rectification can be regenerated.The efficiency of the thermal scheme of the ethylbenzene dehydrogenation unit can be evaluated with using thermal efficiency.

In industrial units for the dehydrogenation of ethylbenzene, the thermal efficiency, as a rule, does not exceed 28-33%. The analysis shows that main reason low thermal efficiency is associated with the lack of heat recovery of the low-temperature contact gas. Indeed, in traditional schemes, the heat of condensation of water and hydrocarbon vapors is not used and is lost in environment with air flow in air condensers and with circulating water. The heat flow diagram in the ethylbenzene dehydrogenation unit confirms that a significant proportion of the heat supplied with the fuel is lost to the environment during cooling and condensation of the contact gas in the cooler-condenser 7 and separator 8 (Fig. 4).

It is possible to significantly improve the use of the energy potential of the process in the energy technology system. An example of such a system in the production of styrene is interesting in that it results from a physicochemical analysis of the dehydrogenation reaction conditions. As noted above, the dilution of ethylbenzene with water vapor has two goals: to shift the reaction equilibrium to the right and to create conditions for the continuous regeneration of the catalyst. Water vapor itself does not participate in the reaction; it has to be obtained by evaporation of water and then separated from the reaction products by condensation. Despite the regeneration of heat flows, evaporation and heating, cooling and condensation are thermodynamically irreversible processes in production, and the energy potential is far from being fully used.

Another component, such as CO2, can have the same effect on the process as water vapor. It is inert in the reaction, that is, it can be a diluent, and promotes the regeneration of the catalyst by interacting with carbon deposits. Get CO2 by burning fuel gas. Combustion products are an energy carrier. This additional property of the diluent makes it possible to create an energy-technological scheme for the production of styrene.

Natural gas is burned in a furnace, and combustible gases generated in the process are burned in a catalytic reactor-oxidizer. The resulting mixture of gases with a temperature of 1050°C is sent to the gas turbine to drive the compressor and generate power. Next, gases with a temperature of 750°C are mixed with ethylbenzene and sent to the reaction unit, which consists of two reactors. The dilution of ethylbenzene is the same as in the traditional steam process. Intermediate heating of the reacting mixture is carried out in the heat exchanger 5 with hot gases. The resulting products are sent to the separation system. Its scheme is different from CTS with the use of water vapor, since the components of the mixture being separated are different. But in this case it doesn't matter. In the separation system, combustible gases are returned to the power unit of the system, and the hydrocarbon mixture is sent for rectification. There are a number of nodes in the energy technological scheme - for heating ethylbenzene, air, fuel gas, using the heat of heated streams. The latter are necessary to balance the heat fluxes of the entire CTS. This method Obtaining styral by dehydrogenation of ethylbenzene makes it possible to almost double the energy efficiency - up to 70%.

The technological scheme of rectification is shown in fig. 7. In distillation column 1, the main amount of ethylbenzene is separated along with benzene and toluene.

Further, in the distillation column 2, benzene and toluene are separated from ethylbenzene. In column 3, all ethylbenzene and part of styrene are distilled off as a distillate. This fraction is returned as feed to column 1. Thus, columns 1-3 work as a three-column complex. The final purification of styrene from resins is carried out in column 4 (often a distillation cube is used for this).

All columns in which styrene is present operate under high vacuum so that the bottom temperature does not exceed 100 °C.

Rice. Fig. 7. Typical industrial scheme for the separation of styrene: 1-4 - distillation columns; I - oven oil; II - ethylbenzene for recycling to the reactor subsystem; III - benzene-toluene fraction; IV - styrene; V -- resin

Let us consider some features of the above technological separation scheme. In such a production scheme, a variant is usually used in which the second predetermined separation is carried out in the first stage. Namely, benzene and toluene are distilled off together with ethylbenzene in the first column, and then volatile components are distilled off from ethylbenzene. In terms of energy costs, this option is less profitable. At the same time. given the reactivity of styrene (high activity and ability to thermopolymerize), this option is more preferable. Especially if we take into account the low content of benzene and toluene in the reaction mixture.

Considering the high reactivity of styrene, “double rectification” is usually used to separate the “ethylbenzene-styrene” pair, which makes it possible to reduce the hydraulic resistance of the distillation columns, and, consequently, the temperature in the stills, which should not be higher than 100 "C (with the necessary vacuum) It is at this temperature that the thermopolymerization of styrene begins.In the general case, any "double rectification" is unacceptable both in terms of energy and capital costs.The use of this option is a necessary measure.

In this case, two variants of "double rectification" are possible (Fig. 8, a, b). In the first variant, in the first column, along with the complete distillation of ethylbenzene (or a highly volatile component) for any other system), part of the styrene is distilled off. In this case, the ratio between ethylbenzene and styrene in the distillate of the first column is chosen so that the bottom liquid of column 2 in its composition approximately corresponds to the composition of the initial mixture of column 1.

Rice. 8 Technological design of "double" rectification: a - option I; b- option II; 1-2 - distillation columns; I - a mixture of ethylbenzene and styrene; II - styrene and polymers; III -- ethylbenzene

In the second variant, pure ethylbenzene is distilled off in column 1. In the cube of this column, such an amount of ethylbenzene remains that allows, under an acceptable vacuum, to maintain a temperature of no more than 100 "C. In column 2, the remaining ethylbenzene is distilled off as a distillate together with styrene, the amount of which is determined by the ratio of ethylbenzene and styrene in the initial mixture of the first column. In In the case of separation of ethylbenzene and styrene, preference can be given to the first option of “double rectification”, in which only part of the styrene is heated in column 2, while in the second option, all styrene is heated in the stills of both columns, and this even under vacuum leads to its losses. through thermopolymerization.

True, a large difference in energy costs can compensate for the loss of styrene, but this requires a more detailed comparison. To solve the problem of separating the pair "ethylbenzene - styrene", a variant with one column filled with packing with low hydraulic resistance can be proposed. In this case, given the large reflux flows, there will be different amounts of liquid and vapor flows along the height of the column. Therefore, for stable operation of the packed column, different diameters of the upper and lower parts of the column are required (Fig. 9.). Such a column makes it possible to separate this pair of components at a temperature in the cube of the column not higher than 100 °C.

Rice. 9. Packed column with strengthening and exhausting parts of different diameters: I - a mixture of ethylbenzene and styrene; II - styrene and polymers; III -- ethylbenzene

A more preferred change in the separation technology of the reaction mixture is to feed it into the vapor phase. In this case, it is not necessary to condense the reaction vapors (both water and brine condensation are excluded). And this leads to a significant reduction in the energy consumed in the system as a whole. In addition, since the process of dehydrogenation of ethylbenzene is carried out in the presence of water vapor, and all hydrocarbons (benzene, toluene, ethylbenzene, styrene, etc.) form heteroazeotropes with water (Table 1). then even at atmospheric pressure the temperature in the columns will be below 100 °C, since the boiling point of heteroazeotropes of hydrocarbons with water is always less than 100 °C. Some vacuum must be maintained in the columns just to prevent the rise in temperature due to the flow resistance of the columns. In addition, styrene is heated in the presence of water, i.e., is in a dilute state, which reduces its reactivity.

Table 1

One of the variants of the technological system for separating the products of ethylbenzene dehydrogenation in the presence of water is shown in Fig. 7.6. The initial mixture at a temperature close to the condensation temperature is fed in the vapor phase to column 1. In this column, benzene and toluene are distilled off in the form of heteroazeotropes with water. The vapor stream exiting the top of the column is condensed and the condensate enters the Florentine vessel 7. The lower aqueous layer is returned to the column 1 and the upper hydrocarbon layer is fed to the top of the column 2.

Rice. Fig. 10. Technological scheme for the separation of products of dehydrogenation of ethylbenzene into styrene when the reaction products are supplied in the vapor phase: 1-6 - distillation columns; 7 -- liquid-liquid separator; I - benzene-toluene fraction; II - ethylbenzene; III - styrene; IV - resins; V -- fuse water

In this column, water is distilled off from benzene and toluene in the form of a heteroazeotrope. The vapor stream of column 2 is combined with the vapor stream of column 1. Dehydrated benzene and toluene are removed from the bottom of column 2. The bottom stream of column 1, also in the vapor phase, is sent to a two-column installation consisting of columns J and 4. In column 3, ethylbenzene is distilled off in the form of a heteroazeotrope with water. The vapors are condensed and the condensate enters the Florentine vessel 7. The lower aqueous layer is returned to column 3 and the upper hydrocarbon layer enters column 4. In this column, water is distilled off from ethylbenzene in the form of a heteroazeotrope. The vapor stream of this column is combined with the vapor stream of column 3. Anhydrous ethylbenzene is removed from the bottom of column 4. The bottom product of column 3 enters the Florentine vessel 7, the upper styrene layer enters the stripping column 5, in which water is distilled off in the form of a heteroazeotrope. The vapors are condensed, and the condensate enters the Florentine vessel 7, the upper styrene layer returns to the column 5, and the lower aqueous layer enters the stripping column 6. The lower layer from the Florentine vessel 7 also enters there, in which the bottom product of the distillation column 3 is stratified. 6 are combined with the vapors of column 5. Styrene can be removed in the vapor phase from the bottom of column 5, and a resin solution from the bottom. Fuselage water is discharged from the bottom of column 6. The upper layers of Florentine vessels are hydrocarbons containing water (0.01-0.02% wt.), and the lower layers are water containing hydrocarbons (0.01% wt.). Therefore, stripping columns 2 and 4 can be excluded from the technological scheme, since the solubility of water in hydrocarbons is low, and ethylbenzene is returned to dehydrogenation, which is carried out in the presence of water.

There is a patent for a method for producing styrene, which was issued to the Voronezh OJSC "Sintezkauchukproekt", for a period of 6 years from 11.28.2006 to 11.28. 2012, the essence of which is a method for producing styrene by catalytic dehydrogenation of ethylbenzene in multistage adiabatic reactors at elevated temperature in the presence of steam. The purpose of the invention is the optimal way to obtain styrene with minimal waste and emissions of harmful substances into the atmosphere.

This goal is achieved by the fact that in the known method for producing styrene, the heat recovery of the contact gas occurs first in waste heat boilers with water condensate purified from aromatic hydrocarbons, which is purified by distillation in a vacuum distillation column in the presence of a recirculating extractant of the benzene-toluene fraction, then cooled in a foam apparatus water condensate supplied from the settling and separation unit, where, due to contact gas cooling, hydrocarbons are stripped from water condensate before it is supplied for treatment, secondary water vapor generated in waste heat boilers is sent to a superheating furnace and then mixed with ethylbenzene charge, and the excess of water condensate is used to feed the circulating water supply, hydrocarbon condensate is separated in distillation columns with regular packing under vacuum, heavy hydrocarbons (KORS) are used to prepare KORS lacquer and as fuel for For a superheating furnace, cleaning of non-condensed gas and vents from pumps and tanks from aromatic hydrocarbons is carried out in a packed scrubber, irrigated with return ethylbenzene cooled to 5-6 ° C under excess pressure, which, after absorption, is sent to the line of return ethylbenzene or to the line of hydrocarbon condensate, off-gas is directly sent to a superheating furnace for combustion, the flue gases of which are used to produce hot water, which is sent to heat the bottom of the rectified styrene recovery column.

6. Principles in the technology of obtaining styrene by dehydrogenation of ethylbenzene

The technology for the production of styrene by dehydrogenation of ethylbenzene is one-stage chemical processes. Available ethylbenzene, obtained by alkylation of benzene with olefins, is used as a feedstock. Technological solutions used in industry with the introduction of steam between two or three catalyst layers, the use of heat exchangers built into the reactor, as well as an efficient catalytic system make it possible to achieve a conversion of ethylbenzene in one pass at a level of 60–75% at a sufficiently high selectivity of about 90% at a level of 60–75%. The benzene recirculation flow connecting the separation and reactor subsystems of the technology ensures complete conversion of the feedstock.

Reduction of energy consumption for the dehydrogenation process can be achieved not only due to efficient heat exchange between incoming and outgoing streams, but also due to the use of inert gas instead of water vapor (energy carrier and diluent). In this case, heat must be supplied between the catalyst beds using built-in heat exchangers. Replacing steam with an inert gas (nitrogen, CO2) makes it possible to avoid repeated evaporation and condensation of water, which has a high latent heat of evaporation. In this case, the cost of cleaning water condensate contaminated with aromatic compounds will also decrease, and, in general, the total consumption of water by production will decrease.

An important component of the technology is the separation subsystem. In this case, as noted earlier, a significant factor influencing the overall performance of the technology is the modes of distillation separation. They must provide conditions under which there is no thermopolymerization of styrene. It is most expedient energetically to use one packed column with low hydraulic resistance instead of double distillation, or a scheme of heteroazeotropic distillation complexes.

Finally, the heterogeneous catalytic nature of the process makes it quite easy to create apparatuses and technological lines of large unit capacity.

styrene ethylbenzene distillation

Conclusion

In this term paper the properties and main methods for producing styrene are outlined, as well as the most common and relevant scheme for producing styrene - the production of styrene by dehydrogenation of ethylbenzene - is specifically considered and described in detail. As it turned out, this method is more accessible, energy-intensive, economical and efficient of all methods for obtaining styrene. This is justified by the fact that the technology for the production of styrene by dehydrogenation of ethylbenzene refers to one-stage chemical processes. Available ethylbenzene is used as feedstock. Technological solutions used in industry with the introduction of steam between two or three catalyst layers, the use of heat exchange devices built into the reactor, as well as an efficient catalytic system make it possible to achieve complete conversion of the feedstock at a sufficiently high selectivity of about 90%.

The reduction of energy consumption for the dehydrogenation process can also be achieved by using an inert gas instead of water vapor (energy carrier and diluent). In this case, heat must be supplied between the catalyst beds using built-in heat exchangers. Replacing steam with an inert gas (nitrogen, CO2) makes it possible to avoid repeated evaporation and condensation of water, which has a high latent heat of evaporation. In this case, the cost of cleaning water condensate contaminated with aromatic compounds will also decrease, and, in general, the total consumption of water by production will decrease.

List of used literature

1. Hauptman Z., Grefe Yu., Remane H. Organic chemistry. Per. with him. / Ed. Potapova V.M. - M., Chemistry, 2009. - 832 p., ill.

2. Organic chemistry. B.N. Stepanenko.-6th ed.-M.: Medicine, 1980, 320 p., ill.

3. Organic chemistry; Textbook for technical schools. 4th ed., Perer. and additional - M .: Chemistry, 1989. - 448 pp.

4. Nesmeyanov A.N., Nesmeyanov N.A. Beginnings of organic chemistry. In two books. Book 2. Ed. 2nd, per.M., "Chemistry", 1974. 744 p. , 30 tab., 49 pic.

5. V.S. Timofeev, L.A. Serafimov Principles of technology of basic organic and petrochemical synthesis: Proc. allowance for universities /. - 2nd ed., revised. - M.: Higher school, 2012. - 536 p., ill.

6. A.M. Kutepov, T.I. Bondareva, M.G. Berengarten General chemical technology - M.; ICC "Akademkniga" 2004. -357p.

7. Lebedev N.N. Chemistry and technology of basic organic synthesis. - M.: Chemistry, 2008. - 582 p.

8. Lisitsyn V.N. Chemistry and technology of intermediate products: A textbook for universities. - M.: Chemistry, 2014. - 368 p.

9. Khananashvili L.M., Andriyanov K.A. Technology of organoelement monomers and polymers: Textbook for universities. - M.: Chemistry, 2010. - 413 p., ill.

10. Patent 2322432 (13) C1, Voronezh OAO Sintezkauchukproekt.

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