Natural sources of hydrocarbons. Natural gas: composition, use as a fuel. Natural sources of hydrocarbons, their processing Natural sources of hydrocarbons message
Origin of fossil fuels.
In addition to the fact that all living organisms consist of organic substances, the main source of organic compounds are: oil, coal, natural and associated petroleum gases.
Oil, coal and natural gas are sources of hydrocarbons.
These natural resources are used:
· As a fuel (source of energy and heat) - this is conventional combustion;
In the form of raw materials for further processing - this is organic synthesis.
Theories of the origin of organic substances:
1- Theory of organic origin.
According to this theory, deposits were formed from the remains of extinct plant and animal organisms, which turned into a mixture of hydrocarbons in the thickness of the earth's crust under the action of bacteria, high pressure and temperature.
2- Theory of mineral (volcanic) origin of oil.
According to this theory, oil, coal and natural gas were formed at the initial stage of the formation of the planet Earth. In this case, the metals combined with carbon, forming carbides. As a result of the reaction of carbides with water vapor, gaseous hydrocarbons were formed in the depths of the planet, in particular methane and acetylene. And under the influence of heating, radiation and catalysts, other compounds contained in oil were formed from them. In the upper layers of the lithosphere, liquid oil components evaporated, the liquid thickened, turned into asphalt and then into coal.
This theory was first expressed by D.I. Mendeleev, and then in the 20th century, the French scientist P. Sabatier simulated the described process in the laboratory and obtained a mixture of hydrocarbons similar to oil.
main component natural gas is methane. It also contains ethane, propane, butane. The higher the molecular weight of the hydrocarbon, the less it is contained in natural gas.
Application: When natural gas is burned, a lot of heat is released, so it serves as an energy efficient and cheap fuel in industry. Natural gas is also a source of raw materials for the chemical industry: the production of acetylene, ethylene, hydrogen, soot, various plastics, acetic acid, dyes, medicines and other products.
Associated petroleum gases found naturally above oil or dissolved in it under pressure. Previously, associated petroleum gases were not used, they were burned. Currently, they are captured and used as fuel and valuable chemical raw materials. Associated gases contain less methane than natural gas, but they contain much more of its homologues. Associated petroleum gases are separated to a narrower composition.
For example: gas gasoline - a mixture of pentane, hexane and other hydrocarbons is added to gasoline to improve engine starting; propane-butane fraction in the form of liquefied gas is used as fuel; dry gas - similar in composition to natural gas - is used to produce acetylene, hydrogen, and also as fuel. Sometimes associated petroleum gases are subjected to a more thorough separation and individual hydrocarbons are extracted from them, from which unsaturated hydrocarbons are then obtained.
Coal remains one of the most common fuels and raw materials for organic synthesis. What types of coal are there, where does the coal come from and what products are used to obtain it - these are the main questions that we will consider today in the lesson. As a source of chemicals, coal was used earlier than oil and natural gas.
Coal is not an individual substance. It consists of: free carbon (up to 10%), organic substances containing, in addition to carbon and hydrogen, oxygen, sulfur, nitrogen, minerals that remain in the form of slag when coal is burned.
Coal is a solid fossil fuel of organic origin. According to the biogenic hypothesis, it was formed from dead plants as a result of the vital activity of microorganisms in the Carboniferous period of the Paleozoic era (about 300 million years ago). Coal is cheaper than oil, it is more evenly distributed in the earth's crust, its natural reserves far exceed those of oil and, according to scientists, will not be exhausted for another century.
The formation of coal from plant residues (coalification) occurs in several stages: peat - brown coal - hard coal - anthracite.
The process of coalification consists in a gradual increase in the relative content of carbon in organic matter due to its depletion in oxygen and hydrogen. The formation of peat and brown coal occurs as a result of the biochemical decomposition of plant residues without oxygen. The transition of brown coal into - stone occurs under the influence of elevated temperatures and pressures associated with mountain-forming and volcanic processes.
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 chains, straight and branched, then rings, then 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 when burning coal, it emits a loud crack.
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.”
During the lesson, you will be able to study the topic “Natural sources of hydrocarbons. Oil refining". More than 90% of all energy currently consumed by mankind is extracted from fossil natural organic compounds. You will learn about natural resources (natural gas, oil, coal), what happens to oil after it is extracted.
Topic: Limit hydrocarbons
Lesson: Natural Sources of Hydrocarbons
About 90% of the energy consumed by modern civilization is generated by burning natural fossil fuels - natural gas, oil and coal.
Russia is a country rich in natural fossil fuels. There are large reserves of oil and natural gas in Western Siberia and the Urals. Hard coal is mined in the Kuznetsk, South Yakutsk basins and other regions.
Natural gas consists on average of 95% by volume of methane.
In addition to methane, natural gas from various fields contains nitrogen, carbon dioxide, helium, hydrogen sulfide, and other light alkanes - ethane, propane and butanes.
Natural gas is extracted from underground deposits, where it is under high pressure. Methane and other hydrocarbons are formed from organic substances of plant and animal origin during their decomposition without air access. Methane is produced constantly and currently as a result of the activity of microorganisms.
Methane is found on the planets of the solar system and their satellites.
Pure methane is odorless. However, the gas used in everyday life has a characteristic unpleasant odor. This is the smell of special additives - mercaptans. The smell of mercaptans allows you to detect a leak of domestic gas in time. Mixtures of methane with air are explosive in a wide range of ratios - from 5 to 15% of gas by volume. Therefore, if you smell gas in the room, you can not only light a fire, but also use electrical switches. The smallest spark can cause an explosion.
Rice. 1. Oil from different fields
Oil- a thick liquid like oil. Its color is from light yellow to brown and black.
Rice. 2. Oil fields
Oil from different fields varies greatly in composition. Rice. 1. The main part of oil is hydrocarbons containing 5 or more carbon atoms. Basically, these hydrocarbons are saturated, i.e. alkanes. Rice. 2.
The composition of oil also includes organic compounds containing sulfur, oxygen, nitrogen. Oil contains water and inorganic impurities.
Gases are dissolved in oil, which are released during its extraction - associated petroleum gases. These are methane, ethane, propane, butanes with impurities of nitrogen, carbon dioxide and hydrogen sulfide.
Coal, like oil, is a complex mixture. The share of carbon in it accounts for 80-90%. The rest is hydrogen, oxygen, sulfur, nitrogen and some other elements. In brown coal the proportion of carbon and organic matter is lower than in stone. Even less organic oil shale.
In industry, coal is heated to 900-1100 0 C without air. This process is called coking. The result is coke with a high carbon content, coke gas and coal tar, necessary for metallurgy. A lot of organic substances are released from the gas and tar. Rice. 3.
Rice. 3. The device of the coke oven
Natural gas and oil are the most important sources of raw materials for the chemical industry. Oil as it is produced, or "crude oil", is difficult to use even as a fuel. Therefore, crude oil is divided into fractions (from the English "fraction" - "part"), using differences in the boiling points of its constituent substances.
The method of separating oil, based on the different boiling points of its constituent hydrocarbons, is called distillation or distillation. Rice. 4.
Rice. 4. Products of oil refining
The fraction that is distilled from about 50 to 180 0 C is called gasoline.
Kerosene boils at temperatures of 180-300 0 С.
A thick black residue that does not contain volatile substances is called fuel oil.
There are also a number of intermediate fractions boiling in narrower ranges - petroleum ethers (40-70 0 C and 70-100 0 C), white spirit (149-204 ° C), and gas oil (200-500 0 C). They are used as solvents. Fuel oil can be distilled under reduced pressure, in this way lubricating oils and paraffin are obtained from it. Solid residue from the distillation of fuel oil - asphalt. It is used for the production of road surfaces.
Processing of associated petroleum gases is a separate industry and makes it possible to obtain a number of valuable products.
Summing up the lesson
During the lesson, you studied the topic “Natural sources of hydrocarbons. Oil refining". More than 90% of all energy currently consumed by mankind is extracted from fossil natural organic compounds. You learned about natural resources (natural gas, oil, coal), about what happens to oil after it is extracted.
Bibliography
1. Rudzitis G.E. Chemistry. Fundamentals of General Chemistry. Grade 10: textbook for educational institutions: basic level / G. E. Rudzitis, F.G. Feldman. - 14th edition. - M.: Education, 2012.
2. Chemistry. Grade 10. Profile level: textbook. for general education institutions / V.V. Eremin, N.E. Kuzmenko, V.V. Lunin and others - M.: Drofa, 2008. - 463 p.
3. Chemistry. Grade 11. Profile level: textbook. for general education institutions / V.V. Eremin, N.E. Kuzmenko, V.V. Lunin and others - M.: Drofa, 2010. - 462 p.
4. Khomchenko G.P., Khomchenko I.G. Collection of problems in chemistry for those entering the universities. - 4th ed. - M.: RIA "New Wave": Publisher Umerenkov, 2012. - 278 p.
Homework
1. Nos. 3, 6 (p. 74) Rudzitis G.E., Feldman F.G. Chemistry: Organic Chemistry. Grade 10: textbook for educational institutions: basic level / G. E. Rudzitis, F.G. Feldman. - 14th edition. - M.: Education, 2012.
2. What is the difference between associated petroleum gas and natural gas?
3. How is oil refining carried out?
Natural source of hydrocarbons | Its main features |
Oil | Multi-component mixture consisting mainly of hydrocarbons. Hydrocarbons are mainly represented by alkanes, cycloalkanes and arenes. |
Associated petroleum gas | A mixture consisting almost exclusively of alkanes with a long carbon chain from 1 to 6 carbon atoms, is formed along with the extraction of oil, hence the origin of the name. There is a trend: the lower the molecular weight of the alkane, the higher its percentage in associated petroleum gas. |
Natural gas | A mixture consisting predominantly of low molecular weight alkanes. The main component of natural gas is methane. Its percentage, depending on the gas field, can be from 75 to 99%. In second place in terms of concentration by a wide margin is ethane, propane is even less contained, etc. The fundamental difference between natural gas and associated petroleum gas is that the proportion of propane and isomeric butanes in associated petroleum gas is much higher. |
Coal | Multicomponent mixture of various compounds of carbon, hydrogen, oxygen, nitrogen and sulfur. Also, the composition of coal includes a significant amount of inorganic substances, the proportion of which is significantly higher than in oil. |
Oil refining
Oil is a multicomponent mixture of various substances, mainly hydrocarbons. These components differ from each other in boiling points. In this regard, if oil is heated, then the lightest-boiling components will first evaporate from it, then compounds with a higher boiling point, etc. Based on this phenomenon primary oil refining , consisting in distillation (rectification) oil. This process is called primary, since it is assumed that during its course chemical transformations of substances do not occur, and oil is only separated into fractions with different boiling points. Below is a schematic diagram of a distillation column with a brief description of the distillation process itself:
Before the rectification process, oil is prepared in a special way, namely, it is removed from impurity water with salts dissolved in it and from solid mechanical impurities. The oil prepared in this way enters the tubular furnace, where it is heated to a high temperature (320-350 o C). After being heated in a tubular furnace, high-temperature oil enters the lower part of the distillation column, where individual fractions evaporate and their vapors rise up the distillation column. The higher the section of the distillation column is, the lower its temperature. Thus, the following fractions are taken at different heights:
1) distillation gases (taken from the very top of the column, and therefore their boiling point does not exceed 40 ° C);
2) gasoline fraction (boiling point from 35 to 200 o C);
3) naphtha fraction (boiling points from 150 to 250 o C);
4) kerosene fraction (boiling points from 190 to 300 o C);
5) diesel fraction (boiling point from 200 to 300 o C);
6) fuel oil (boiling point over 350 o C).
It should be noted that the average fractions isolated during the rectification of oil do not meet the standards for fuel quality. In addition, as a result of oil distillation, a considerable amount of fuel oil is formed - far from being the most demanded product. In this regard, after the primary processing of oil, the task is to increase the yield of more expensive, in particular, gasoline fractions, as well as to improve the quality of these fractions. These tasks are solved using various processes. oil refining , such as cracking andreforming .
It should be noted that the number of processes used in the secondary processing of oil is much larger, and we touch on only some of the main ones. Let's now understand what is the meaning of these processes.
Cracking (thermal or catalytic)
This process is designed to increase the yield of the gasoline fraction. For this purpose, heavy fractions, such as fuel oil, are subjected to strong heating, most often in the presence of a catalyst. As a result of this action, long-chain molecules that are part of the heavy fractions are torn and hydrocarbons with a lower molecular weight are formed. In fact, this leads to an additional yield of a more valuable gasoline fraction than the original fuel oil. The chemical essence of this process is reflected by the equation:
Reforming
This process performs the task of improving the quality of the gasoline fraction, in particular, increasing its knock resistance (octane number). It is this characteristic of gasolines that is indicated at gas stations (92nd, 95th, 98th gasoline, etc.).
As a result of the reforming process, the proportion of aromatic hydrocarbons in the gasoline fraction increases, which among other hydrocarbons has one of the highest octane numbers. Such an increase in the proportion of aromatic hydrocarbons is achieved mainly as a result of the dehydrocyclization reactions occurring during the reforming process. For example, when heated sufficiently n-hexane in the presence of a platinum catalyst, it turns into benzene, and n-heptane in a similar way - into toluene:
Coal processing
The main method of coal processing is coking . Coal coking called the process in which coal is heated without access to air. At the same time, as a result of such heating, four main products are isolated from coal:
1) coke
A solid substance that is almost pure carbon.
2) Coal tar
Contains a large number of various predominantly aromatic compounds, such as benzene, its homologues, phenols, aromatic alcohols, naphthalene, naphthalene homologues, etc.;
3) Ammonia water
Despite its name, this fraction, in addition to ammonia and water, also contains phenol, hydrogen sulfide and some other compounds.
4) coke oven gas
The main components of coke oven gas are hydrogen, methane, carbon dioxide, nitrogen, ethylene, etc.
The most important sources of hydrocarbons are natural and associated petroleum gases, oil, and coal.
By reserves natural gas the first place in the world belongs to our country. Natural gas contains low molecular weight hydrocarbons. It has the following approximate composition (by volume): 80-98% methane, 2-3% of its closest homologues - ethane, propane, butane and a small amount of impurities - hydrogen sulfide H 2 S, nitrogen N 2 , noble gases, carbon monoxide (IV ) CO 2 and water vapor H 2 O . The composition of the gas is specific to each field. There is the following pattern: the higher the relative molecular weight of hydrocarbon, the less it is contained in natural gas.
Natural gas is widely used as a cheap fuel with high calorific value (combustion of 1m 3 releases up to 54,400 kJ). It is one of the best types of fuel for domestic and industrial needs. In addition, natural gas is a valuable raw material for the chemical industry: the production of acetylene, ethylene, hydrogen, soot, various plastics, acetic acid, dyes, medicines and other products.
Associated petroleum gases are in deposits together with oil: they are dissolved in it and are located above the oil, forming a gas “cap”. When extracting oil to the surface, gases are separated from it due to a sharp drop in pressure. Previously, associated gases were not used and were flared during oil production. Currently, they are captured and used as fuel and valuable chemical raw materials. Associated gases contain less methane than natural gas, but more ethane, propane, butane and higher hydrocarbons. In addition, they contain basically the same impurities as in natural gas: H 2 S, N 2, noble gases, H 2 O vapor, CO 2 . Individual hydrocarbons (ethane, propane, butane, etc.) are extracted from associated gases, their processing makes it possible to obtain unsaturated hydrocarbons by dehydrogenation - propylene, butylene, butadiene, from which rubbers and plastics are then synthesized. A mixture of propane and butane (liquefied gas) is used as a household fuel. Natural gasoline (a mixture of pentane and hexane) is used as an additive to gasoline for better ignition of the fuel when starting the engine. Oxidation of hydrocarbons produces organic acids, alcohols and other products.
Oil- oily flammable liquid of dark brown or almost black color with a characteristic odor. It is lighter than water (= 0.73–0.97 g / cm 3), practically insoluble in water. By composition, oil is a complex mixture of hydrocarbons of various molecular weights, so it does not have a specific boiling point.
Oil consists mainly of liquid hydrocarbons (solid and gaseous hydrocarbons are dissolved in them). Usually these are alkanes (mainly of a normal structure), cycloalkanes and arenes, the ratio of which in oils from various fields varies widely. Ural oil contains more arenes. In addition to hydrocarbons, oil contains oxygen, sulfur and nitrogenous organic compounds.
Crude oil is not normally used. To obtain technically valuable products from oil, it is subjected to processing.
Primary processing oil consists in its distillation. Distillation is carried out at refineries after the separation of associated gases. During the distillation of oil, light oil products are obtained:
gasoline ( t kip \u003d 40–200 ° С) contains hydrocarbons С 5 -С 11,
naphtha ( t kip \u003d 150–250 ° С) contains hydrocarbons С 8 -С 14,
kerosene ( t kip \u003d 180–300 ° С) contains hydrocarbons С 12 -С 18,
gas oil ( t kip > 275 °C),
and in the remainder - a viscous black liquid - fuel oil.
Oil is subjected to further processing. It is distilled under reduced pressure (to prevent decomposition) and lubricating oils are isolated: spindle, engine, cylinder, etc. Petroleum jelly and paraffin are isolated from fuel oil of some grades of oil. The residue of fuel oil after distillation - tar - after partial oxidation is used to produce asphalt. The main disadvantage of oil refining is the low yield of gasoline (no more than 20%).
Oil distillation products have various uses.
Petrol used in large quantities as aviation and automotive fuel. It usually consists of hydrocarbons containing an average of 5 to 9 C atoms in molecules. Naphtha It is used as a fuel for tractors, as well as a solvent in the paint and varnish industry. Large quantities are processed into gasoline. Kerosene It is used as a fuel for tractors, jet planes and rockets, as well as for domestic needs. solar oil - gas oil- used as a motor fuel, and lubricating oils- for lubricating mechanisms. Petrolatum used in medicine. It consists of a mixture of liquid and solid hydrocarbons. Paraffin used to obtain higher carboxylic acids, to impregnate wood in the production of matches and pencils, for the manufacture of candles, shoe polish, etc. It consists of a mixture of solid hydrocarbons. fuel oil in addition to processing into lubricating oils and gasoline, it is used as boiler liquid fuel.
At secondary processing methods oil is a change in the structure of the hydrocarbons that make up its composition. Among these methods, of great importance is the cracking of oil hydrocarbons, which is carried out in order to increase the yield of gasoline (up to 65–70%).
Cracking- the process of splitting hydrocarbons contained in oil, as a result of which hydrocarbons with a smaller number of C atoms in the molecule are formed. There are two main types of cracking: thermal and catalytic.
Thermal cracking is carried out by heating the feedstock (fuel oil, etc.) at a temperature of 470–550 °C and a pressure of 2–6 MPa. In this case, hydrocarbon molecules with a large number of C atoms are split into molecules with a smaller number of atoms of both saturated and unsaturated hydrocarbons. For example:
(radical mechanism),
In this way, mainly automobile gasoline is obtained. Its output from oil reaches 70%. Thermal cracking was discovered by Russian engineer V.G. Shukhov in 1891.
catalytic cracking is carried out in the presence of catalysts (usually aluminosilicates) at 450–500 °C and atmospheric pressure. In this way, aviation gasoline is obtained with a yield of up to 80%. This type of cracking is mainly subjected to kerosene and gas oil fractions of oil. In catalytic cracking, along with cleavage reactions, isomerization reactions occur. As a result of the latter, saturated hydrocarbons with a branched carbon skeleton of molecules are formed, which improves the quality of gasoline:
Catalytic cracked gasoline is of higher quality. The process of obtaining it proceeds much faster, with less consumption of thermal energy. In addition, relatively many branched-chain hydrocarbons (isocompounds) are formed during catalytic cracking, which are of great value for organic synthesis.
At t= 700 °C and above, pyrolysis occurs.
Pyrolysis- decomposition of organic substances without air access at high temperature. During oil pyrolysis, the main reaction products are unsaturated gaseous hydrocarbons (ethylene, acetylene) and aromatic hydrocarbons - benzene, toluene, etc. Since oil pyrolysis is one of the most important ways to obtain aromatic hydrocarbons, this process is often called oil aromatization.
Aromatization– transformation of alkanes and cycloalkanes into arenes. When heavy fractions of petroleum products are heated in the presence of a catalyst (Pt or Mo), hydrocarbons containing 6–8 C atoms per molecule are converted into aromatic hydrocarbons. These processes occur during reforming (upgrading of gasoline).
Reforming- this is the aromatization of gasolines, carried out as a result of heating them in the presence of a catalyst, for example, Pt. Under these conditions, alkanes and cycloalkanes are converted into aromatic hydrocarbons, as a result of which the octane number of gasoline also increases significantly. Aromatization is used to obtain individual aromatic hydrocarbons (benzene, toluene) from gasoline fractions of oil.
In recent years, petroleum hydrocarbons have been widely used as a source of chemical raw materials. Substances necessary for the production of plastics, synthetic textile fibers, synthetic rubber, alcohols, acids, synthetic detergents, explosives, pesticides, synthetic fats, etc. are obtained from them in various ways.
Coal just like natural gas and oil, it is a source of energy and a valuable chemical raw material.
The main method of coal processing is coking(dry distillation). During coking (heating up to 1000 °С - 1200 °С without air access), various products are obtained: coke, coal tar, tar water and coke oven gas (scheme).
Scheme
Coke is used as a reducing agent in the production of iron in metallurgical plants.
Coal tar serves as a source of aromatic hydrocarbons. It is subjected to rectification distillation and benzene, toluene, xylene, naphthalene, as well as phenols, nitrogen-containing compounds, etc. are obtained.
Ammonia, ammonium sulfate, phenol, etc. are obtained from tar water.
Coke oven gas is used to heat coke ovens (combustion of 1 m 3 releases about 18,000 kJ), but it is mainly subjected to chemical processing. So, hydrogen is extracted from it for the synthesis of ammonia, which is then used to produce nitrogen fertilizers, as well as methane, benzene, toluene, ammonium sulfate, and ethylene.