The main natural sources of saturated hydrocarbons. Production of aromatic hydrocarbons. natural sources. Coke production and the problem of obtaining liquid fuel

Dry distillation of coal.

Aromatic hydrocarbons are obtained mainly from the dry distillation of coal. When coal is heated in retorts or coking ovens without air at 1000–1300 °C, the organic matter of coal decomposes to form solid, liquid, and gaseous products.

The solid product of dry distillation - coke - is a porous mass consisting of carbon with an admixture of ash. Coke is produced in huge quantities and consumed mainly by the metallurgical industry as a reducing agent in the production of metals (primarily iron) from ores.

The liquid products of dry distillation are black viscous tar (coal tar), and the aqueous layer containing ammonia is ammonia water. Coal tar is obtained on average 3% of the mass of the original coal. Ammonia water is one of the important sources of ammonia production. Gaseous products of dry distillation of coal are called coke gas. Coke oven gas has a different composition depending on the grade of coal, coking mode, etc. Coke gas produced in coke oven batteries is passed through a series of absorbers that trap tar, ammonia and light oil vapors. Light oil obtained by condensation from coke oven gas contains 60% benzene, toluene and other hydrocarbons. Most of the benzene (up to 90%) is obtained in this way and only a little - by fractionation of coal tar.

Processing of coal tar. Coal tar has the appearance of a black resinous mass with a characteristic odor. Currently, more than 120 different products have been isolated from coal tar. Among them are aromatic hydrocarbons, as well as aromatic oxygen-containing substances of an acidic nature (phenols), nitrogen-containing substances of a basic nature (pyridine, quinoline), substances containing sulfur (thiophene), etc.

Coal tar is subjected to fractional distillation, as a result of which several fractions are obtained.

Light oil contains benzene, toluene, xylenes and some other hydrocarbons. Medium, or carbolic, oil contains a number of phenols.

Heavy, or creosote, oil: Of the hydrocarbons in heavy oil, naphthalene is contained.

Getting hydrocarbons from oil Oil is one of the main sources of aromatic hydrocarbons. Most species

oil contains only a very small amount of aromatic hydrocarbons. From domestic oil rich in aromatic hydrocarbons is the oil of the Ural (Perm) field. The oil of the "Second Baku" contains up to 60% aromatic hydrocarbons.

Due to the scarcity of aromatic hydrocarbons, “oil flavoring” is now used: oil products are heated at a temperature of about 700 ° C, as a result of which 15–18% of aromatic hydrocarbons can be obtained from the decomposition products of oil.

32. Synthesis, physical and chemical properties of aromatic hydrocarbons

1. Synthesis from aromatic hydrocarbons and fatty halo derivatives in the presence of catalysts (Friedel-Crafts synthesis).

2. Synthesis from salts of aromatic acids.

When dry salts of aromatic acids are heated with soda lime, the salts decompose to form hydrocarbons. This method is similar to the production of fatty hydrocarbons.

3. Synthesis from acetylene. This reaction is of interest as an example of the synthesis of benzene from fatty hydrocarbons.

When acetylene is passed through a heated catalyst (at 500 °C), the triple bonds of acetylene are broken and three of its molecules polymerize into one benzene molecule.

Physical properties Aromatic hydrocarbons are liquids or solids with

characteristic odour. Hydrocarbons with no more than one benzene ring in their molecules are lighter than water. Aromatic hydrocarbons are slightly soluble in water.

The IR spectra of aromatic hydrocarbons are primarily characterized by three regions:

1) about 3000 cm-1, due to C-H stretching vibrations;

2) the 1600–1500 cm-1 region associated with skeletal vibrations of aromatic carbon-carbon bonds and significantly varying in peak positions depending on the structure;

3) the area below 900 cm-1 related to the bending vibrations of C-H of the aromatic ring.

Chemical properties The most important general chemical properties of aromatic hydrocarbons are

their tendency to substitution reactions and the high strength of the benzene nucleus.

Benzene homologues have a benzene core and a side chain in their molecule, for example, in the hydrocarbon C 6 H5 -C2 H5, the C6 H5 group is the benzene core, and C2 H5 is the side chain. Properties

benzene ring in the molecules of benzene homologues approach the properties of benzene itself. The properties of the side chains, which are residues of fatty hydrocarbons, approach the properties of fatty hydrocarbons.

The reactions of benzene hydrocarbons can be divided into four groups.

33. Orientation rules in the benzene nucleus

When studying substitution reactions in the benzene nucleus, it was found that if the benzene nucleus already contains any substituent group, then the second group enters a certain position depending on the nature of the first substituent. Thus, each substituent in the benzene nucleus has a certain directing, or orienting, action.

The position of the newly introduced substituent is also influenced by the nature of the substituent itself, i.e., the electrophilic or nucleophilic nature of the active reagent. The vast majority of the most important substitution reactions in the benzene ring are electrophilic substitution reactions (replacement of a hydrogen atom split off in the form of a proton by a positively charged particle) - halogenation, sulfonation, nitration reactions, etc.

All substitutes are divided into two groups according to the nature of their guiding action.

1. Substituents of the first kind in reactions electrophilic substitution direct subsequent introduced groups to the ortho- and para-positions.

Substituents of this kind include, for example, the following groups, arranged in descending order of their directing power: -NH2, -OH, -CH3.

2. Substituents of the second kind in reactions electrophilic substitution direct subsequent introduced groups to the meta position.

Substituents of this kind include the following groups, arranged in descending order of their directing force: -NO2, -C≡N, -SO3 H.

Substituents of the first kind contain single bonds; substituents of the second kind are characterized by the presence of double or triple bonds.

Substituents of the first kind in the overwhelming majority of cases facilitate substitution reactions. For example, to nitrate benzene, you need to heat it with a mixture of concentrated nitric and sulfuric acids, while phenol C6 H5 OH can be successfully

nitrate with dilute nitric acid at room temperature to form ortho- and paranitrophenol.

Substituents of the second kind generally hinder substitution reactions altogether. Particularly difficult is the substitution in the ortho- and para-positions, and the substitution in the meta-position is relatively easier.

Currently, the influence of substituents is explained by the fact that substituents of the first kind are electron-donating (donating electrons), i.e., their electron clouds are shifted towards the benzene nucleus, which increases the reactivity of hydrogen atoms.

An increase in the reactivity of hydrogen atoms in the ring facilitates the course of electrophilic substitution reactions. So, for example, in the presence of hydroxyl, the free electrons of the oxygen atom are shifted towards the ring, which increases the electron density in the ring, and the electron density of carbon atoms in the ortho and para positions to the substituent especially increases.

34. Substitution rules in the benzene ring

The rules of substitution in the benzene ring are of great practical importance, since they make it possible to predict the course of the reaction and choose the correct path for the synthesis of one or another desired substance.

The mechanism of electrophilic substitution reactions in the aromatic series. Modern research methods have made it possible to largely elucidate the mechanism of substitution in the aromatic series. Interestingly, in many respects, especially at the first stages, the mechanism of electrophilic substitution in the aromatic series turned out to be similar to the mechanism of electrophilic addition in the fatty series.

The first step in electrophilic substitution is (as in electrophilic addition) the formation of a p-complex. The electrophilic particle Xd+ binds to all six p-electrons of the benzene ring.

The second stage is the formation of the p-complex. In this case, the electrophilic particle "pulls out" two electrons from six p-electrons to form an ordinary covalent bond. The resulting p-complex no longer has an aromatic structure: it is an unstable carbocation in which four p-electrons in a delocalized state are distributed between five carbon atoms, while the sixth carbon atom passes into a saturated state. The introduced substituent X and the hydrogen atom are in a plane perpendicular to the plane of the six-membered ring. The S-complex is an intermediate whose formation and structure have been proven by a number of methods, in particular by spectroscopy.

The third stage of electrophilic substitution is the stabilization of the S-complex, which is achieved by the elimination of a hydrogen atom in the form of a proton. The two electrons involved in the formation of the C-H bond, after the removal of a proton, together with four delocalized electrons of five carbon atoms, give the usual stable aromatic structure of substituted benzene. The role of the catalyst (usually A 1 Cl3) in this case

The process consists in strengthening the polarization of haloalkyl with the formation of a positively charged particle, which enters into an electrophilic substitution reaction.

Addition Reactions Benzene hydrocarbons react with great difficulty

decolorize with bromine water and KMnO4 solution. However, under special reaction conditions

connections are still possible. 1. Addition of halogens.

Oxygen in this reaction plays the role of a negative catalyst: in its presence, the reaction does not proceed. Hydrogen addition in the presence of a catalyst:

C6 H6 + 3H2 → C6 H12

2. Oxidation of aromatic hydrocarbons.

Benzene itself is exceptionally resistant to oxidation - more resistant than paraffins. Under the action of energetic oxidizing agents (KMnO4 in an acidic medium, etc.) on benzene homologues, the benzene core is not oxidized, while the side chains undergo oxidation with the formation of aromatic acids.

NATURAL SOURCES OF HYDROCARBONS

Hydrocarbons are all so different -
Liquid, solid, and gaseous.
Why are there so many of them in nature?
It's insatiable carbon.

Indeed, this element, like no other, is “insatiable”: it strives to form either chains, straight and branched, or rings, or grids from a multitude of its atoms. Hence the many compounds of carbon and hydrogen atoms.

Hydrocarbons are both natural gas - methane, and another household combustible gas, which is filled with cylinders - propane C 3 H 8. Hydrocarbons are oil, gasoline, and kerosene. And also - an organic solvent C 6 H 6, paraffin, from which New Year's candles are made, petroleum jelly from a pharmacy, and even a plastic bag for food packaging ...

The most important natural sources of hydrocarbons are minerals - coal, oil, gas.

COAL

More known around the world 36 thousand coal basins and deposits, which together occupy 15% territories of the globe. Coal fields can stretch for thousands of kilometers. In total, the general geological reserves of coal on the globe are 5 trillion 500 billion tons, including explored deposits - 1 trillion 750 billion tons.

There are three main types of fossil coals. When burning brown coal, anthracite, the flame is invisible, the combustion is smokeless, and coal makes a loud crack when burning.

Anthraciteis the oldest fossil coal. Differs in the big density and gloss. Contains up to 95% carbon.

Coal- contains up to 99% carbon. Of all fossil coals, it is the most widely used.

Brown coal- contains up to 72% carbon. Has a brown color. As the youngest fossil coal, it often retains traces of the structure of the tree from which it was formed. Differs in high hygroscopicity and high ash content ( from 7% to 38%), therefore, it is used only as a local fuel and as a raw material for chemical processing. In particular, valuable types of liquid fuels are obtained by hydrogenation: gasoline and kerosene.

Carbon is the main constituent of coal 99% ), brown coal ( up to 72%). The origin of the name carbon, i.e., “bearing coal”. Similarly, the Latin name "carboneum" at the base contains the root carbo-coal.

Like oil, coal contains a large amount of organic matter. In addition to organic substances, it also includes inorganic substances, such as water, ammonia, hydrogen sulfide and, of course, carbon itself - coal. One of the main ways of coal processing is coking - calcination without air access. As a result of coking, which is carried out at a temperature of 1000 0 C, the following is formed:

coke oven gas- it consists of hydrogen, methane, carbon monoxide and carbon dioxide, impurities of ammonia, nitrogen and other gases.

Coal tar - contains several hundred different organic substances, including benzene and its homologues, phenol and aromatic alcohols, naphthalene and various heterocyclic compounds.

Top-tar or ammonia water - containing, as the name implies, dissolved ammonia, as well as phenol, hydrogen sulfide and other substances.

Coke– solid coking residue, practically pure carbon.

Coke is used in the production of iron and steel, ammonia is used in the production of nitrogen and combined fertilizers, and the importance of organic coking products cannot be overestimated. What is the geography of distribution of this mineral?

The main part of coal resources falls on the northern hemisphere - Asia, North America, Eurasia. What countries stand out in terms of reserves and coal production?

China, USA, India, Australia, Russia.

Countries are the main exporters of coal.

USA, Australia, Russia, South Africa.

main import centers.

Japan, Overseas Europe.

It is a very environmentally dirty fuel. Explosions and fires of methane occur during coal mining, and certain environmental problems arise.

Environmental pollution - this is any undesirable change in the state of this environment as a result of human activities. This also happens in mining. Imagine a situation in a coal mining area. Together with coal, a huge amount of waste rock rises to the surface, which, as unnecessary, is simply sent to dumps. Gradually formed waste heaps- huge, tens of meters high, cone-shaped mountains of waste rock, which distort the appearance of the natural landscape. And will all the coal raised to the surface be necessarily exported to the consumer? Of course not. After all, the process is not hermetic. A huge amount of coal dust settles on the surface of the earth. As a result, the composition of soils and groundwater changes, which will inevitably affect the flora and fauna of the region.

Coal contains radioactive carbon - C, but after the fuel is burned, the hazardous substance, along with smoke, enters the air, water, soil, and is baked into slag or ash, which is used to produce building materials. As a result, in residential buildings, walls and ceilings “glow” and pose a threat to human health.

OIL

Oil has been known to mankind since ancient times. On the banks of the Euphrates, it was mined

6-7 thousand years BC uh . It was used to illuminate dwellings, to prepare mortars, as medicines and ointments, and for embalming. Oil in the ancient world was a formidable weapon: fiery rivers poured on the heads of those who stormed the fortress walls, burning arrows dipped in oil flew to the besieged cities. Oil was an integral part of the incendiary agent that went down in history under the name "Greek fire" In the Middle Ages, it was mainly used for street lighting.

More than 600 oil and gas basins have been explored, 450 are being developed , and the total number of oil fields reaches 50 thousand.

Distinguish between light and heavy oil. Light oil is extracted from the subsoil by pumps or by the fountain method. Mostly gasoline and kerosene are made from such oil. Heavy grades of oil are sometimes extracted even by the mine method (in the Komi Republic), and bitumen, fuel oil, and various oils are prepared from it.

Oil is the most versatile fuel, high-calorie. Its extraction is relatively simple and cheap, because when extracting oil, there is no need to lower people underground. Transporting oil through pipelines is not a big problem. The main disadvantage of this type of fuel is the low availability of resources (about 50 years ) . General geological reserves are equal to 500 billion tons, including explored 140 billion tons .

AT 2007 Russian scientists proved to the world community that the underwater ridges of Lomonosov and Mendeleev, which are located in the Arctic Ocean, are a shelf zone of the mainland, and therefore belong to the Russian Federation. The chemistry teacher will tell about the composition of oil, its properties.

Oil is a "bundle of energy". With only 1 ml of it, you can heat a whole bucket of water by one degree, and in order to boil a bucket samovar, you need less than half a glass of oil. In terms of energy concentration per unit volume, oil ranks first among natural substances. Even radioactive ores cannot compete with it in this regard, since the content of radioactive substances in them is so small that 1mg can be extracted. nuclear fuel must be processed tons of rocks.

Oil is not only the basis of the fuel and energy complex of any state.

Here, the famous words of D. I. Mendeleev are in place “burning oil is the same as heating a furnace banknotes". Each drop of oil contains more than 900 various chemical compounds, more than half of the chemical elements of the Periodic Table. This is truly a miracle of nature, the basis of the petrochemical industry. Approximately 90% of all oil produced is used as fuel. In spite of “ own 10%” , petrochemical synthesis provides many thousands of organic compounds that satisfy the urgent needs of modern society. No wonder people respectfully call oil “black gold”, “the blood of the Earth”.

Oil is an oily dark brown liquid with a reddish or greenish tint, sometimes black, red, blue or light and even transparent with a characteristic pungent odor. Sometimes oil is white or colorless, like water (for example, in the Surukhanskoye field in Azerbaijan, in some fields in Algeria).

The composition of oil is not the same. But all of them usually contain three types of hydrocarbons - alkanes (mainly normal structure), cycloalkanes and aromatic hydrocarbons. The ratio of these hydrocarbons in the oil of different fields is different: for example, Mangyshlak oil is rich in alkanes, and oil in the Baku region is rich in cycloalkanes.

The main oil reserves are in the northern hemisphere. Total 75 countries of the world produce oil, but 90% of its production falls on the share of only 10 countries. Near ? world oil reserves are in developing countries. (The teacher calls and shows on the map).

Main producing countries:

Saudi Arabia, USA, Russia, Iran, Mexico.

At the same time more 4/5 oil consumption falls on the share of economically developed countries, which are the main importing countries:

Japan, Overseas Europe, USA.

Oil in its raw form is not used anywhere, but refined products are used.

Oil refining

A modern plant consists of an oil heating furnace and a distillation column where the oil is separated into factions - individual mixtures of hydrocarbons according to their boiling points: gasoline, naphtha, kerosene. The furnace has a long tube coiled into a coil. The furnace is heated by the combustion products of fuel oil or gas. Oil is continuously supplied to the coil: there it is heated to 320 - 350 0 C in the form of a mixture of liquid and vapor and enters the distillation column. The distillation column is a steel cylindrical apparatus with a height of about 40m. It has inside several dozen horizontal partitions with holes - the so-called plates. Oil vapors, entering the column, rise up and pass through the holes in the plates. As they gradually cool as they move upwards, they partially liquefy. Less volatile hydrocarbons are liquefied already on the first plates, forming a gas oil fraction; more volatile hydrocarbons are collected above and form a kerosene fraction; even higher - naphtha fraction. The most volatile hydrocarbons leave the column as vapors and, after condensation, form gasoline. Part of the gasoline is fed back to the column for "irrigation", which contributes to a better mode of operation. (Entry in a notebook). Gasoline - contains hydrocarbons C5 - C11, boiling in the range from 40 0 C to 200 0 C; naphtha - contains hydrocarbons C8 - C14 with a boiling point of 120 0 C to 240 0 C; kerosene - contains hydrocarbons C12 - C18, boiling at a temperature of 180 0 C to 300 0 C; gas oil - contains hydrocarbons C13 - C15, distilled off at a temperature of 230 0 C to 360 0 C; lubricating oils - C16 - C28, boil at a temperature of 350 0 C and above.

After distillation of light products from oil, a viscous black liquid remains - fuel oil. It is a valuable mixture of hydrocarbons. Lubricating oils are obtained from fuel oil by additional distillation. The non-distilling part of fuel oil is called tar, which is used in construction and when paving roads. (Demonstration of a video fragment). The most valuable fraction of direct distillation of oil is gasoline. However, the yield of this fraction does not exceed 17-20% by weight of crude oil. The problem arises: how to meet the ever-increasing needs of society in automotive and aviation fuel? The solution was found at the end of the 19th century by a Russian engineer Vladimir Grigorievich Shukhov. AT 1891 year, he first carried out an industrial cracking kerosene fraction of oil, which made it possible to increase the yield of gasoline to 65-70% (calculated as crude oil). Only for the development of the process of thermal cracking of petroleum products, grateful humanity inscribed the name of this unique person in the history of civilization with golden letters.

The products obtained as a result of oil rectification are subjected to chemical processing, which includes a number of complex processes, one of them is the cracking of petroleum products (from the English "Cracking" - splitting). There are several types of cracking: thermal, catalytic, high pressure cracking, reduction. Thermal cracking consists in the splitting of hydrocarbon molecules with a long chain into shorter ones under the influence of high temperature (470-550 0 C). In the process of this splitting, along with alkanes, alkenes are formed:

Currently, catalytic cracking is the most common. It is carried out at a temperature of 450-500 0 C, but at a higher speed and allows you to get higher quality gasoline. Under the conditions of catalytic cracking, along with cleavage reactions, isomerization reactions take place, that is, the transformation of hydrocarbons of a normal structure into branched hydrocarbons.

Isomerization affects the quality of gasoline, since the presence of branched hydrocarbons greatly increases its octane number. Cracking is referred to the so-called secondary processes of oil refining. A number of other catalytic processes, such as reforming, are also classified as secondary. Reforming- this is the aromatization of gasolines by heating them in the presence of a catalyst, for example, platinum. Under these conditions, alkanes and cycloalkanes are converted into aromatic hydrocarbons, as a result of which the octane number of gasoline also increases significantly.

Ecology and oilfield

For petrochemical production, the problem of the environment is especially relevant. Oil production is associated with energy costs and environmental pollution. A dangerous source of pollution of the oceans is offshore oil production, and the oceans are also polluted during the transportation of oil. Each of us has seen on TV the consequences of oil tanker accidents. Black, oil-covered shores, black surf, choking dolphins, Birds whose wings are covered in viscous oil, people in protective suits collecting oil with shovels and buckets. I would like to cite the data of a serious environmental disaster that occurred in the Kerch Strait in November 2007. 2,000 tons of oil products and about 7,000 tons of sulfur got into the water. The Tuzla Spit, which is located at the junction of the Black and Azov Seas, and the Chushka Spit suffered the most because of the disaster. After the accident, fuel oil settled to the bottom, which killed a small shell-heart-shaped, the main food of the inhabitants of the sea. It will take 10 years to restore the ecosystem. More than 15 thousand birds died. A liter of oil, having fallen into the water, spreads over its surface in spots of 100 sq.m. The oil film, although very thin, forms an insurmountable barrier to the path of oxygen from the atmosphere to the water column. As a result, the oxygen regime and the ocean are disturbed. "suffocate". Plankton, which is the backbone of the ocean food chain, is dying. Currently, about 20% of the area of the World Ocean is covered with oil spills, and the area affected by oil pollution is growing. In addition to the fact that the World Ocean is covered with an oil film, we can also observe it on land. For example, in the oil fields of Western Siberia, more oil is spilled per year than a tanker can hold - up to 20 million tons. About half of this oil ends up on the ground as a result of accidents, the rest is “planned” fountains and leaks during well startups, exploratory drilling, and pipeline repairs. The largest area of oil-contaminated land, according to the Committee for the Environment of the Yamalo-Nenets Autonomous Okrug, falls on the Purovsky District.

NATURAL AND ASSOCIATED PETROLEUM GAS

Natural gas contains hydrocarbons with a low molecular weight, the main components are methane. Its content in the gas of various fields ranges from 80% to 97%. In addition to methane - ethane, propane, butane. Inorganic: nitrogen - 2%; CO2; H2O; H2S, noble gases. When natural gas is burned, a lot of heat is released.

In terms of its properties, natural gas as a fuel surpasses even oil, it is more caloric. This is the youngest branch of the fuel industry. Gas is even easier to extract and transport. It is the most economical of all fuels. True, there are also disadvantages: the complex intercontinental transportation of gas. Tankers - methane manure, transporting gas in a liquefied state, are extremely complex and expensive structures.

It is used as: effective fuel, raw material in the chemical industry, in the production of acetylene, ethylene, hydrogen, soot, plastics, acetic acid, dyes, medicines, etc. production. Petroleum gas contains less methane, but more propane, butane and other higher hydrocarbons. Where is the gas produced?

More than 70 countries of the world have commercial gas reserves. Moreover, as in the case of oil, developing countries have very large reserves. But gas production is carried out mainly by developed countries. They have opportunities to use it or a way to sell gas to other countries that are on the same continent with them. International gas trade is less active than oil trade. About 15% of the world's produced gas enters the international market. Almost 2/3 of world gas production is provided by Russia and the USA. Undoubtedly, the leading gas production region not only in our country, but also in the world is the Yamalo-Nenets Autonomous Okrug, where this industry has been developing for 30 years. Our city Novy Urengoy is rightfully recognized as the gas capital. The largest deposits include Urengoyskoye, Yamburgskoye, Medvezhye, Zapolyarnoye. The Urengoy field is included in the Guinness Book of Records. The reserves and production of the deposit are unique. Explored reserves exceed 10 trillion. m 3 , 6 trln. m 3. In 2008 JSC "Gazprom" plans to produce 598 billion m 3 of "blue gold" at the Urengoy field.

Gas and ecology

The imperfection of the technology of oil and gas production, their transportation causes the constant burning of the volume of gas in the heat units of compressor stations and in flares. Compressor stations account for about 30% of these emissions. About 450,000 tons of natural and associated gas are burned annually at flare installations, while more than 60,000 tons of pollutants enter the atmosphere.

Oil, gas, coal are valuable raw materials for the chemical industry. In the near future, they will find a replacement in the fuel and energy complex of our country. Currently, scientists are looking for ways to use solar and wind energy, nuclear fuel in order to completely replace oil. Hydrogen is the most promising fuel of the future. Reducing the use of oil in thermal power engineering is the way not only to its more rational use, but also to the preservation of this raw material for future generations. Hydrocarbon raw materials should be used only in the processing industry to obtain a variety of products. Unfortunately, the situation is not changing yet, and up to 94% of the produced oil is used as fuel. D. I. Mendeleev wisely said: “Burning oil is the same as heating the furnace with banknotes.”

The most important natural sources of hydrocarbons are oil , natural gas and coal . They form rich deposits in various regions of the Earth.

Previously, extracted natural products were used exclusively as fuel. At present, methods for their processing have been developed and are widely used, which make it possible to isolate valuable hydrocarbons, which are used both as high-quality fuel and as raw materials for various organic synthesis. Processing of natural sources of raw materials petrochemical industry . Let us analyze the main methods of processing natural hydrocarbons.

The most valuable source of natural raw materials - oil . It is an oily liquid of dark brown or black color with a characteristic odor, practically insoluble in water. The density of oil is 0.73–0.97 g/cm3. Oil is a complex mixture of various liquid hydrocarbons in which gaseous and solid hydrocarbons are dissolved, and the composition of oil from different fields may differ. Alkanes, cycloalkanes, aromatic hydrocarbons, as well as oxygen-, sulfur- and nitrogen-containing organic compounds can be present in oil in various proportions.

Crude oil is practically not used, but is processed.

Distinguish primary oil refining (distillation ), i.e. separating it into fractions with different boiling points, and recycling (cracking ), during which the structure of hydrocarbons is changed

dov included in its composition.

Primary oil refining It is based on the fact that the boiling point of hydrocarbons is the greater, the greater their molar mass. Oil contains compounds with boiling points from 30 to 550°C. As a result of distillation, oil is separated into fractions boiling at different temperatures and containing mixtures of hydrocarbons with different molar masses. These fractions find a variety of uses (see table 10.2).

Table 10.2. Products of primary oil refining.

Fraction	Boiling point, °С	Compound	Application
Liquefied gas	<30	Hydrocarbons С 3 -С 4	Gaseous fuels, raw materials for the chemical industry
Petrol	40-200	Hydrocarbons C 5 - C 9	Aviation and automotive fuel, solvent
Naphtha	150-250	Hydrocarbons C 9 - C 12	Diesel engine fuel, solvent
Kerosene	180-300	Hydrocarbons С 9 -С 16	Diesel engine fuel, household fuel, lighting fuel
gas oil	250-360	Hydrocarbons С 12 -С 35	Diesel fuel, feedstock for catalytic cracking
fuel oil	> 360	Higher hydrocarbons, O-, N-, S-, Me-containing substances	Fuel for boiler plants and industrial furnaces, feedstock for further distillation

The share of fuel oil accounts for about half of the mass of oil. Therefore, it is also subjected to thermal processing. To prevent decomposition, the fuel oil is distilled under reduced pressure. In this case, several fractions are obtained: liquid hydrocarbons, which are used as lubricating oils ; mixture of liquid and solid hydrocarbons - petrolatum used in the preparation of ointments; a mixture of solid hydrocarbons - paraffin , going to the production of shoe polish, candles, matches and pencils, as well as for the impregnation of wood; non-volatile residue tar used to produce road, construction and roofing bitumen.

Oil refining includes chemical reactions that change the composition and chemical structure of hydrocarbons. Its variety

ty - thermal cracking, catalytic cracking, catalytic reforming.

Thermal cracking usually subjected to fuel oil and other heavy oil fractions. At a temperature of 450–550°C and a pressure of 2–7 MPa, the free radical mechanism splits hydrocarbon molecules into fragments with a smaller number of carbon atoms, and saturated and unsaturated compounds are formed:

C 16 N 34 ¾® C 8 N 18 + C 8 N 16

C 8 H 18 ¾®C 4 H 10 +C 4 H 8

In this way, automobile gasoline is obtained.

catalytic cracking carried out in the presence of catalysts (usually aluminosilicates) at atmospheric pressure and a temperature of 550 - 600°C. At the same time, aviation gasoline is obtained from kerosene and gas oil fractions of oil.

The splitting of hydrocarbons in the presence of aluminosilicates proceeds according to the ionic mechanism and is accompanied by isomerization, i.e. the formation of a mixture of saturated and unsaturated hydrocarbons with a branched carbon skeleton, for example:

CH 3 CH 3 CH 3 CH 3 CH 3

cat., t||

C 16 H 34 ¾¾® CH 3 -C -C-CH 3 + CH 3 -C \u003d C - CH-CH 3

catalytic reforming carried out at a temperature of 470-540°C and a pressure of 1-5 MPa using platinum or platinum-rhenium catalysts deposited on a base of Al 2 O 3 . Under these conditions, the transformation of paraffins and

petroleum cycloparaffins to aromatic hydrocarbons

cat., t, p

¾¾¾¾® + 3H 2

cat., t, p

C 6 H 14 ¾¾¾¾® + 4H 2

Catalytic processes make it possible to obtain gasoline of improved quality due to the high content of branched and aromatic hydrocarbons in it. The quality of gasoline is characterized by its octane rating. The more the mixture of fuel and air is compressed by the pistons, the greater the power of the engine. However, compression can only be carried out up to a certain limit, above which detonation (explosion) occurs.

gas mixture, causing overheating and premature engine wear. The lowest resistance to detonation in normal paraffins. With a decrease in the chain length, an increase in its branching and the number of double

ny connections, it increases; it is especially high in aromatic carbohydrates.

before giving birth. To assess the resistance to detonation of various grades of gasoline, they are compared with similar indicators for a mixture isooctane and n-heptane with different ratio of components; the octane number is equal to the percentage of isooctane in this mixture. The larger it is, the higher the quality of gasoline. The octane number can also be increased by adding special antiknock agents, for example, tetraethyl lead Pb(C 2 H 5) 4 , however, such gasoline and its combustion products are toxic.

In addition to liquid fuels, lower gaseous hydrocarbons are obtained in catalytic processes, which are then used as raw materials for organic synthesis.

Another important natural source of hydrocarbons, the importance of which is constantly increasing - natural gas. It contains up to 98% by volume of methane, 2–3% by volume. its closest homologues, as well as impurities of hydrogen sulfide, nitrogen, carbon dioxide, noble gases and water. Gases released during oil production ( passing ), contain less methane, but more of its homologues.

Natural gas is used as fuel. In addition, individual saturated hydrocarbons are isolated from it by distillation, as well as synthesis gas , consisting mainly of CO and hydrogen; they are used as raw materials for various organic syntheses.

Mined in large quantities coal - inhomogeneous solid material of black or gray-black color. It is a complex mixture of various macromolecular compounds.

Coal is used as a solid fuel, and is also subjected to coking – dry distillation without air access at 1000-1200°C. As a result of this process are formed: coke , which is a finely divided graphite and is used in metallurgy as a reducing agent; coal tar , which is subjected to distillation and aromatic hydrocarbons (benzene, toluene, xylene, phenol, etc.) are obtained and pitch , going to the preparation of roofing roofing; ammonia water and coke oven gas containing about 60% hydrogen and 25% methane.

Thus, natural sources of hydrocarbons provide

the chemical industry with diverse and relatively cheap raw materials for organic syntheses, which make it possible to obtain numerous organic compounds that are not found in nature, but are necessary for man.

The general scheme for the use of natural raw materials for the main organic and petrochemical synthesis can be represented as follows.

Arenas Syngas Acetylene AlkenesAlkanes

Basic organic and petrochemical synthesis

Control tasks.

1222. What is the difference between primary oil refining and secondary refining?

1223. What compounds determine the high quality of gasoline?

1224. Suggest a method that allows, starting from oil, to obtain ethyl alcohol.

Dry distillation of coal.

Coal tar is subjected to fractional distillation, as a result of which several fractions are obtained.

Light oil contains benzene, toluene, xylenes and some other hydrocarbons.

Medium, or carbolic, oil contains a number of phenols.

Heavy, or creosote, oil: Of the hydrocarbons in heavy oil, naphthalene is contained.

Production of hydrocarbons from oil

Oil is one of the main sources of aromatic hydrocarbons. Most oils contain only very small amounts of aromatic hydrocarbons. From domestic oil rich in aromatic hydrocarbons is the oil of the Ural (Perm) field. The oil of the "Second Baku" contains up to 60% aromatic hydrocarbons.

Receipt aromatic hydrocarbons. Natural sources
Receipt hydrocarbons from oil. Oil is one of the main sources aromatic hydrocarbons.

Receipt aromatic hydrocarbons. Natural sources. Dry distillation of coal. aromatic hydrocarbons obtained mainly from Nomenclature and isomerism aromatic hydrocarbons.

Receipt aromatic hydrocarbons. Natural sources. Dry distillation of coal. aromatic hydrocarbons obtained mainly from

Receipt aromatic hydrocarbons. Natural sources.
1. Synthesis from aromatic hydrocarbons and halo-derivatives of the fatty series in the presence of catalysis ... more ».

To the group aromatic compounds included a number of substances, received from natural resins, balms and essential oils.
Rational names aromatic hydrocarbons usually produced from the name. aromatic hydrocarbons.

Natural sources marginal hydrocarbons. Gaseous, liquid and solid substances are widely distributed in nature. hydrocarbons, in most cases occurring not in the form of pure compounds, but in the form of various, sometimes very complex mixtures.

isomerism, natural sources and ways receiving olefins. The isomerism of olefins depends on the isomerism of the carbon chain, i.e., on whether the chain is n. Unsaturated (unsaturated) hydrocarbons.

hydrocarbons. Carbohydrates are widely distributed in nature and play a very important role in human life. They are part of the food, and usually a person's need for energy is covered when eating for the most part precisely at the expense of carbohydrates.

The H2C=CH- radical derived from ethylene is usually called vinyl; the H2C=CH-CH2- radical derived from propylene is called allyl. Natural sources and ways receiving olefins.

Natural sources marginal hydrocarbons there are also some products of the dry distillation of wood, peat, brown and black coal, oil shale. Synthetic ways receiving marginal hydrocarbons.

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– consists (mainly) of methane and (in smaller quantities) of its closest homologues - ethane, propane, butane, pentane, hexane, etc.; observed in associated petroleum gas, i.e., natural gas that is in nature above oil or dissolved in it under pressure.

Oil

- it is an oily combustible liquid, consisting of alkanes, cycloalkanes, arenes (predominate), as well as oxygen-, nitrogen- and sulfur-containing compounds.

Coal

- solid fuel mineral of organic origin. It contains little graphite a and many complex cyclic compounds, including the elements C, H, O, N and S. There are anthracite (almost anhydrous), coal (-4% moisture) and brown coal (50-60% moisture). By coking coal is converted into hydrocarbons (gaseous, liquid and solid) and coke (rather pure graphite).

Coal coking

Heating coal without air access to 900-1050 ° C leads to its thermal decomposition with the formation of volatile products (coal tar, ammonia water and coke oven gas) and a solid residue - coke.

Main products: coke - 96-98% carbon; coke oven gas - 60% hydrogen, 25% methane, 7% carbon monoxide (II), etc.

By-products: coal tar (benzene, toluene), ammonia (from coke oven gas), etc.

Oil refining by rectification method

The pre-purified oil is subjected to atmospheric (or vacuum) distillation into fractions with certain boiling point ranges in continuous distillation columns.

Main products: light and heavy gasoline, kerosene, gas oil, lubricating oils, fuel oil, tar.

Oil refining by catalytic cracking

Raw materials: high-boiling oil fractions (kerosene, gas oil, etc.)

Auxiliary materials: catalysts (modified aluminosilicates).

The main chemical process: at a temperature of 500-600 ° C and a pressure of 5 10 5 Pa, hydrocarbon molecules are split into smaller molecules, catalytic cracking is accompanied by aromatization, isomerization, alkylation reactions.

Products: mixture of low-boiling hydrocarbons (fuel, feedstock for petrochemicals).

C 16. H 34 → C 8 H 18 + C 8 H 16
C 8 H 18 → C 4 H 10 + C 4 H 8
C 4 H 10 → C 2 H 6 + C 2 H 4