Oxygen occupies 21% of atmospheric air. Most of it is found in the earth's crust, fresh water and living microorganisms. It is used in many industries and is used for household and medical needs. The demand for a substance is due to chemical and physical characteristics.

How is oxygen produced in industry. 3 methods

The production of oxygen in industry is carried out by dividing atmospheric air. The following methods are used for this:

The production of oxygen on an industrial scale is of great importance. Increased attention should be paid to the choice of technology and appropriate equipment. The mistakes made can negatively affect the technological process and lead to an increase in costs after the slaughter.

Technical features of equipment for oxygen production in industry

Generators of the industrial type "OXIMAT" help to establish the process of obtaining oxygen in a gaseous state. Their technical characteristics and design features are aimed at obtaining this substance in the industry of the required purity and the required quantity throughout the day (without interruption). It should be noted that the equipment can operate in any mode, with or without stops. The unit operates under pressure. At the inlet, there must be dried air in a compressed state, free from moisture. Models of small, average and big productivity are provided.

Plan:

Discovery history

Origin of name

Being in nature

Receipt

Physical Properties

Chemical properties

Application

10. Isotopes

Oxygen

Oxygen- an element of the 16th group (according to the outdated classification - the main subgroup of group VI), the second period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 8. It is designated by the symbol O (lat. Oxygenium). Oxygen is a reactive non-metal and is the lightest element of the chalcogen group. simple substance oxygen(CAS number: 7782-44-7) under normal conditions - a gas without color, taste and smell, the molecule of which consists of two oxygen atoms (formula O 2), and therefore it is also called dioxygen. Liquid oxygen has a light blue, and the solid is light blue crystals.

There are other allotropic forms of oxygen, for example, ozone (CAS number: 10028-15-6) - under normal conditions, a blue gas with a specific odor, the molecule of which consists of three oxygen atoms (formula O 3).

Discovery history

It is officially believed that oxygen was discovered by the English chemist Joseph Priestley on August 1, 1774 by decomposing mercury oxide in a hermetically sealed vessel (Priestley directed the sun's rays at this compound using a powerful lens).

However, Priestley did not initially realize that he had discovered a new simple substance, he believed that he isolated one of the constituent parts of air (and called this gas "dephlogisticated air"). Priestley reported his discovery to the outstanding French chemist Antoine Lavoisier. In 1775, A. Lavoisier established that oxygen is an integral part of air, acids and is found in many substances.

A few years earlier (in 1771), the Swedish chemist Carl Scheele had obtained oxygen. He calcined saltpeter with sulfuric acid and then decomposed the resulting nitric oxide. Scheele called this gas "fiery air" and described his discovery in a book published in 1777 (precisely because the book was published later than Priestley announced his discovery, the latter is considered the discoverer of oxygen). Scheele also reported his experience to Lavoisier.

An important stage that contributed to the discovery of oxygen was the work of the French chemist Pierre Bayen, who published work on the oxidation of mercury and the subsequent decomposition of its oxide.

Finally, A. Lavoisier finally figured out the nature of the resulting gas, using information from Priestley and Scheele. His work was of great importance, because thanks to it, the phlogiston theory that dominated at that time and hindered the development of chemistry was overthrown. Lavoisier conducted an experiment on the combustion of various substances and refuted the theory of phlogiston by publishing the results on the weight of the burned elements. The weight of the ash exceeded the initial weight of the element, which gave Lavoisier the right to assert that during combustion a chemical reaction (oxidation) of the substance occurs, in connection with this, the mass of the original substance increases, which refutes the theory of phlogiston.

Thus, the credit for the discovery of oxygen is actually shared by Priestley, Scheele, and Lavoisier.

Origin of name

The word oxygen (at the beginning of the 19th century it was still called "acid"), its appearance in the Russian language is to some extent due to M.V. Lomonosov, who introduced, along with other neologisms, the word "acid"; thus the word "oxygen", in turn, was a tracing-paper of the term "oxygen" (French oxygène), proposed by A. Lavoisier (from other Greek ὀξύς - "sour" and γεννάω - "I give birth"), which translates as “generating acid”, which is associated with its original meaning - “acid”, which previously meant substances called oxides according to modern international nomenclature.

Being in nature

Oxygen is the most common element on Earth, its share (as part of various compounds, mainly silicates) accounts for about 47.4% of the mass of the solid earth's crust. Sea and fresh waters contain a huge amount of bound oxygen - 88.8% (by mass), in the atmosphere the content of free oxygen is 20.95% by volume and 23.12% by mass. More than 1500 compounds of the earth's crust contain oxygen in their composition.

Oxygen is a constituent of many organic substances and is present in all living cells. In terms of the number of atoms in living cells, it is about 25%, in terms of mass fraction - about 65%.

Receipt

At present, in industry, oxygen is obtained from the air. The main industrial method for obtaining oxygen is cryogenic distillation. Oxygen plants based on membrane technology are also well known and successfully used in industry.

In laboratories, industrial oxygen is used, supplied in steel cylinders under a pressure of about 15 MPa.

Small amounts of oxygen can be obtained by heating potassium permanganate KMnO 4:

The reaction of the catalytic decomposition of hydrogen peroxide H 2 O 2 in the presence of manganese (IV) oxide is also used:

Oxygen can be obtained by catalytic decomposition of potassium chlorate (bertolet salt) KClO 3:

Laboratory methods for producing oxygen include the method of electrolysis of aqueous solutions of alkalis, as well as the decomposition of mercury (II) oxide (at t = 100 ° C):

On submarines, it is usually obtained by the reaction of sodium peroxide and carbon dioxide exhaled by a person:

Physical Properties

In the oceans, the content of dissolved O 2 is greater in cold water, and less in warm water.

Under normal conditions, oxygen is a colorless, tasteless and odorless gas.

1 liter of it has a mass of 1.429 g. It is slightly heavier than air. Slightly soluble in water (4.9 ml/100 g at 0°C, 2.09 ml/100 g at 50°C) and alcohol (2.78 ml/100 g at 25°C). It dissolves well in molten silver (22 volumes of O 2 in 1 volume of Ag at 961 ° C). Interatomic distance - 0.12074 nm. It is paramagnetic.

When gaseous oxygen is heated, its reversible dissociation into atoms occurs: at 2000 °C - 0.03%, at 2600 °C - 1%, 4000 °C - 59%, 6000 °C - 99.5%.

Liquid oxygen (boiling point −182.98 °C) is a pale blue liquid.

O 2 phase diagram

Solid oxygen (melting point −218.35°C) - blue crystals. Six crystalline phases are known, of which three exist at a pressure of 1 atm.:

α-O 2 - exists at temperatures below 23.65 K; bright blue crystals belong to the monoclinic system, cell parameters a=5.403 Å, b=3.429 Å, c=5.086 Å; β=132.53°.

β-O 2 - exists in the temperature range from 23.65 to 43.65 K; pale blue crystals (with increasing pressure, the color turns into pink) have a rhombohedral lattice, cell parameters a=4.21 Å, α=46.25°.

γ-O 2 - exists at temperatures from 43.65 to 54.21 K; pale blue crystals have cubic symmetry, lattice period a=6.83 Å.

Three more phases are formed at high pressures:

δ-O 2 temperature range 20-240 K and pressure 6-8 GPa, orange crystals;

ε-O 4 pressure from 10 to 96 GPa, crystal color from dark red to black, monoclinic system;

ζ-O n pressure more than 96 GPa, metallic state with a characteristic metallic luster, at low temperatures passes into a superconducting state.

Chemical properties

A strong oxidizing agent, interacts with almost all elements, forming oxides. The oxidation state is −2. As a rule, the oxidation reaction proceeds with the release of heat and accelerates with increasing temperature (see Combustion). An example of reactions occurring at room temperature:

Oxidizes compounds that contain elements with a non-maximum oxidation state:

Oxidizes most organic compounds:

Under certain conditions, it is possible to carry out a mild oxidation of an organic compound:

Oxygen reacts directly (under normal conditions, when heated and/or in the presence of catalysts) with all simple substances, except for Au and inert gases (He, Ne, Ar, Kr, Xe, Rn); reactions with halogens occur under the influence of an electric discharge or ultraviolet radiation. Oxides of gold and heavy inert gases (Xe, Rn) were obtained indirectly. In all two-element compounds of oxygen with other elements, oxygen plays the role of an oxidizing agent, except for compounds with fluorine

Oxygen forms peroxides with the oxidation state of the oxygen atom formally equal to −1.

For example, peroxides are obtained by burning alkali metals in oxygen:

Some oxides absorb oxygen:

According to the combustion theory developed by A. N. Bach and K. O. Engler, oxidation occurs in two stages with the formation of an intermediate peroxide compound. This intermediate compound can be isolated, for example, when a flame of burning hydrogen is cooled with ice, along with water, hydrogen peroxide is formed:

In superoxides, oxygen formally has an oxidation state of −½, that is, one electron per two oxygen atoms (the O − 2 ion). Obtained by the interaction of peroxides with oxygen at elevated pressure and temperature:

Potassium K, rubidium Rb and cesium Cs react with oxygen to form superoxides:

In the dioxygenyl ion O 2 +, oxygen formally has an oxidation state of +½. Get by reaction:

Oxygen fluorides

Oxygen difluoride, OF 2 oxygen oxidation state +2, is obtained by passing fluorine through an alkali solution:

Oxygen monofluoride (Dioxydifluoride), O 2 F 2 , is unstable, oxygen oxidation state is +1. Obtained from a mixture of fluorine and oxygen in a glow discharge at a temperature of −196 ° C:

Passing a glow discharge through a mixture of fluorine with oxygen at a certain pressure and temperature, mixtures of higher oxygen fluorides O 3 F 2, O 4 F 2, O 5 F 2 and O 6 F 2 are obtained.

Quantum mechanical calculations predict the stable existence of the OF 3 + trifluorohydroxonium ion. If this ion really exists, then the oxidation state of oxygen in it will be +4.

Oxygen supports the processes of respiration, combustion, and decay.

In its free form, the element exists in two allotropic modifications: O 2 and O 3 (ozone). As established in 1899 by Pierre Curie and Maria Sklodowska-Curie, under the influence of ionizing radiation, O 2 turns into O 3.

Application

The widespread industrial use of oxygen began in the middle of the 20th century, after the invention of turboexpanders - devices for liquefying and separating liquid air.

ATmetallurgy

The converter method of steel production or matte processing is associated with the use of oxygen. In many metallurgical units, for more efficient combustion of fuel, an oxygen-air mixture is used in burners instead of air.

Welding and cutting of metals

Oxygen in blue cylinders is widely used for flame cutting and welding of metals.

Rocket fuel

Liquid oxygen, hydrogen peroxide, nitric acid and other oxygen-rich compounds are used as an oxidizing agent for rocket fuel. A mixture of liquid oxygen and liquid ozone is one of the most powerful rocket fuel oxidizers (the specific impulse of a hydrogen-ozone mixture exceeds the specific impulse for a hydrogen-fluorine and hydrogen-oxygen fluoride pair).

ATmedicine

Medical oxygen is stored in blue high-pressure metal gas cylinders (for compressed or liquefied gases) of various capacities from 1.2 to 10.0 liters under pressure up to 15 MPa (150 atm) and is used to enrich respiratory gas mixtures in anesthesia equipment, with respiratory failure, to stop an attack of bronchial asthma, eliminate hypoxia of any origin, with decompression sickness, for the treatment of pathology of the gastrointestinal tract in the form of oxygen cocktails. For individual use, medical oxygen from cylinders is filled with special rubberized containers - oxygen pillows. To supply oxygen or an oxygen-air mixture simultaneously to one or two victims in the field or in a hospital, oxygen inhalers of various models and modifications are used. The advantage of an oxygen inhaler is the presence of a condenser-humidifier of the gas mixture, which uses the moisture of the exhaled air. To calculate the amount of oxygen remaining in the cylinder in liters, the pressure in the cylinder in atmospheres (according to the pressure gauge of the reducer) is usually multiplied by the cylinder capacity in liters. For example, in a cylinder with a capacity of 2 liters, the pressure gauge shows an oxygen pressure of 100 atm. The volume of oxygen in this case is 100 × 2 = 200 liters.

ATFood Industry

In the food industry, oxygen is registered as food additive E948, as a propellant and packaging gas.

ATchemical industry

In the chemical industry, oxygen is used as an oxidizing agent in numerous syntheses, for example, the oxidation of hydrocarbons to oxygen-containing compounds (alcohols, aldehydes, acids), ammonia to nitrogen oxides in the production of nitric acid. Due to the high temperatures developed during oxidation, the latter are often carried out in the combustion mode.

ATagriculture

In greenhouses, for the manufacture of oxygen cocktails, for weight gain in animals, for enriching the aquatic environment with oxygen in fish farming.

The biological role of oxygen

Emergency supply of oxygen in a bomb shelter

Most living things (aerobes) breathe oxygen from the air. Oxygen is widely used in medicine. In cardiovascular diseases, to improve metabolic processes, oxygen foam (“oxygen cocktail”) is introduced into the stomach. Subcutaneous oxygen administration is used for trophic ulcers, elephantiasis, gangrene and other serious diseases. Artificial enrichment with ozone is used to disinfect and deodorize the air and purify drinking water. The radioactive isotope of oxygen 15 O is used to study the rate of blood flow, pulmonary ventilation.

Toxic oxygen derivatives

Some oxygen derivatives (so-called reactive oxygen species), such as singlet oxygen, hydrogen peroxide, superoxide, ozone, and the hydroxyl radical, are highly toxic products. They are formed in the process of activation or partial reduction of oxygen. Superoxide (superoxide radical), hydrogen peroxide and hydroxyl radical can be formed in the cells and tissues of the human and animal body and cause oxidative stress.

isotopes

Oxygen has three stable isotopes: 16 O, 17 O and 18 O, the average content of which is respectively 99.759%, 0.037% and 0.204% of the total number of oxygen atoms on Earth. The sharp predominance of the lightest of them, 16 O, in the mixture of isotopes is due to the fact that the nucleus of the 16 O atom consists of 8 protons and 8 neutrons (double magic nucleus with filled neutron and proton shells). And such nuclei, as follows from the theory of the structure of the atomic nucleus, have a special stability.

Radioactive oxygen isotopes with mass numbers from 12 O to 24 O are also known. All radioactive oxygen isotopes have a short half-life, the longest-lived of them is 15 O with a half-life of ~120 s. The shortest-lived 12 O isotope has a half-life of 5.8·10 −22 s.

PROPERTIES OF OXYGEN AND METHODS FOR ITS PRODUCTION

Oxygen O 2 is the most abundant element on earth. It is found in large quantities in the form of chemical compounds with various substances in the earth's crust (up to 50% wt.), in combination with hydrogen in water (about 86% wt.) and in a free state in atmospheric air, mixed mainly with nitrogen in the amount of 20.93% vol. (23.15% by weight).

Oxygen is of great importance in the national economy. It is widely used in metallurgy; chemical industry; for flame treatment of metals, fire drilling of hard rocks, underground coal gasification; in medicine and various breathing apparatus, for example, for high-altitude flights, and in other areas.

Under normal conditions, oxygen is a colorless, odorless and tasteless gas, non-flammable, but actively supports combustion. At very low temperatures, oxygen turns into a liquid and even a solid.

The most important physical constants of oxygen are as follows:

Molecular weight	32
Weight 1 m 3 at 0 ° C and 760 mm Hg. Art. in kg	1,43
The same at 20 ° C and 760 mm Hg. Art. in kg	1,33
Critical temperature in °C	-118
Critical pressure in kgf / m 3	51,35
Boiling point at 760 mm Hg. Art. in °С	-182,97
Weight of 1 liter of liquid oxygen at -182, 97 °C and 760 mm Hg. Art. in kg.	1,13
The amount of gaseous oxygen obtained from 1 liter of liquid at 20 ° C and 760 mm Hg. Art. in l	850
Solidification temperature at 760 mm Hg. Art. in °C	-218,4

Oxygen has a high chemical activity and forms compounds with all chemical elements, except for rare gases. Reactions of oxygen with organic substances have a pronounced exothermic character. So, when compressed oxygen interacts with fatty or finely dispersed solid combustible substances, they are instantly oxidized and the heat released contributes to spontaneous combustion of these substances, which can cause a fire or explosion. This property must be especially taken into account when handling oxygen equipment.

One of the important properties of oxygen is its ability to form widely explosive mixtures with combustible gases and vapors of liquid combustibles, which can also lead to explosions in the presence of an open flame or even a spark. Explosives are also mixtures of air with gaseous or vaporous combustibles.

Oxygen can be obtained: 1) by chemical means; 2) water electrolysis; 3) by physical means from the air.

Chemical methods, which consist in obtaining oxygen from various substances, are inefficient and currently have only laboratory significance.

The electrolysis of water, i.e., its decomposition into components - hydrogen and oxygen, is carried out in apparatuses called electrolyzers. A direct current is passed through water, into which caustic soda NaOH is added to increase the electrical conductivity; oxygen is collected at the anode and hydrogen is collected at the cathode. The disadvantage of this method is the high power consumption: 12-15 kW is consumed per 1 m 3 0 2 (in addition, 2 m 3 H 2 is obtained). h. This method is rational in the presence of cheap electricity, as well as in the production of electrolytic hydrogen, when oxygen is a waste product.

The physical method consists in the separation of air into components by deep cooling. This method makes it possible to obtain oxygen in practically unlimited quantities and is of major industrial importance. Electricity consumption per 1 m 3 O 2 is 0.4-1.6 kW. h, depending on the type of installation.

OBTAINING OXYGEN FROM AIR

Atmospheric air is basically a mechanical mixture of three gases with the following volume content: nitrogen - 78.09%, oxygen - 20.93%, argon - 0.93%. In addition, it contains about 0.03% carbon dioxide and small amounts of rare gases, hydrogen, nitrous oxide, etc.

The main task in obtaining oxygen from air is to separate the air into oxygen and nitrogen. Along the way, argon is separated, the use of which in special welding methods is constantly increasing, as well as rare gases, which play an important role in a number of industries. Nitrogen has some uses in welding as a shielding gas, in medicine and other fields.

The essence of the method lies in the deep cooling of air with its conversion to a liquid state, which at normal atmospheric pressure can be achieved in the temperature range from -191.8 ° C (the beginning of liquefaction) to -193.7 ° C (the end of liquefaction).

The separation of liquid into oxygen and nitrogen is carried out by using the difference in their boiling points, namely: T kip. o2 \u003d -182.97 ° C; Boiling point N2 = -195.8 ° C (at 760 mm Hg).

With the gradual evaporation of the liquid, nitrogen, which has a lower boiling point, will first pass into the gaseous phase, and as it is released, the liquid will be enriched with oxygen. Repeating this process many times makes it possible to obtain oxygen and nitrogen of the required purity. This method of separating liquids into their component parts is called rectification.

For the production of oxygen from the air, there are specialized enterprises equipped with high-performance plants. In addition, large metalworking enterprises have their own oxygen stations.

The low temperatures required to liquefy the air are obtained by means of so-called refrigeration cycles. The main refrigeration cycles used in modern installations are briefly discussed below.

The refrigeration cycle with air throttling is based on the Joule-Thomson effect, i.e., a sharp decrease in the temperature of the gas during its free expansion. The cycle diagram is shown in fig. 2.

The air is compressed in a multi-stage compressor 1 to 200 kgf/cm 2 and then passes through the cooler 2 with running water. Deep air cooling takes place in the heat exchanger 3 by a reverse flow of cold gas from the liquid collector (liquefier) ​​4. As a result of air expansion in the throttle valve 5, it is additionally cooled and partially liquefied.

The pressure in the collection 4 is regulated within 1-2 kgf/cm 2 . The liquid is periodically drained from the collector into special containers through valve 6. The non-liquefied part of the air is removed through the heat exchanger, cooling new portions of the incoming air.

Air is cooled down to the liquefaction temperature gradually; when the unit is turned on, there is a start-up period during which no air liquefaction is observed, but only the unit cools down. This period takes several hours.

The advantage of the cycle is its simplicity, and the disadvantage is the relatively high power consumption - up to 4.1 kW. h per 1 kg of liquefied air at a compressor pressure of 200 kgf/cm 2 ; at lower pressure, the specific power consumption increases sharply. This cycle is used in installations of small and medium capacity to produce gaseous oxygen.

Somewhat more complex is the throttling cycle with ammonia pre-cooling.

The medium-pressure refrigeration cycle with expansion in an expander is based on lowering the gas temperature during expansion with the return of external work. In addition, the Joule-Thomson effect is also used. The cycle diagram is shown in fig. 3.

The air is compressed in the compressor 1 to 20-40 kgf / cm 2, passes through the refrigerator 2 and then through the heat exchangers 3 and 4. After the heat exchanger 3, most of the air (70-80%) is sent to the piston expansion machine-expander 6, and the smaller part air (20-30%) goes to free expansion into the throttle valve 5 and then the collector 7, which has a valve 8 for draining the liquid. In expander 6

the air, already cooled in the first heat exchanger, does work - it pushes the piston of the machine, its pressure drops to 1 kgf / cm 2, due to which the temperature drops sharply. From the expander, cold air, having a temperature of about -100 ° C, is discharged outside through heat exchangers 4 and 3, cooling the incoming air. Thus, the expander provides a very efficient cooling of the plant at a relatively low pressure in the compressor. The work of the expander is used usefully and this partially compensates for the energy spent on compressing the air in the compressor.

The advantages of the cycle are: a relatively low compression pressure, which simplifies the design of the compressor and increased cooling capacity (thanks to the expander), which ensures stable operation of the unit when oxygen is taken in liquid form.

Low-pressure refrigeration cycle with expansion in a turbo-expander, developed by Acad. P. L. Kapitsa, is based on the use of low-pressure air with cold production only due to the expansion of this air in an air turbine (turbo expander) with the production of external work. The cycle diagram is shown in fig. 4.

The air is compressed by the turbocharger 1 to 6-7 kgf/cm 2 , cooled with water in the cooler 2 and enters the regenerators 3 (heat exchangers), where it is cooled by a reverse flow of cold air. Up to 95% of the air after the regenerators is sent to the turbo expander 4, expands to an absolute pressure of 1 kgf / cm 2 with the performance of external work and is rapidly cooled, after which it is fed into the tube space of the condenser 5 and condenses the rest of the compressed air (5%), entering the annulus. From the condenser 5, the main air flow is directed to the regenerators and cools the incoming air, and the liquid air is passed through the throttle valve 6 to the collector 7, from which it drains through the valve 8. The diagram shows one regenerator, but in reality they are installed several and switched on in turn.

The advantages of a low-pressure cycle with a turbo-expander are: higher efficiency of turbomachines compared to piston-type machines, simplification of the technological scheme, and increased reliability and explosion safety of the installation. The cycle is used in installations of high productivity.

The separation of liquid air into components is carried out by means of a rectification process, the essence of which is that the vaporous mixture of nitrogen and oxygen formed during the evaporation of liquid air is passed through a liquid with a lower oxygen content. Since there is less oxygen in the liquid and more nitrogen, it has a lower temperature than the vapor passing through it, and this causes the condensation of oxygen from the vapor and the enrichment of the liquid with simultaneous evaporation of nitrogen from the liquid, i.e., the enrichment of the vapor above the liquid .

An idea of ​​the essence of the rectification process can be given by the one shown in Fig. 5 is a simplified diagram of the process of multiple evaporation and condensation of liquid air.

We assume that air consists only of nitrogen and oxygen. Imagine that there are several vessels connected to each other (I-V), in the upper one there is liquid air with a content of 21% oxygen. Due to the stepped arrangement of the vessels, the liquid will flow down and, at the same time, will gradually be enriched with oxygen, and its temperature will increase.

Let us assume that in vessel II there is a liquid containing 30% 0 2 , in vessel III - 40%, in vessel IV - 50%, and in vessel V - 60% oxygen.

To determine the oxygen content in the vapor phase, we use a special graph - fig. 6, whose curves indicate the oxygen content in liquid and vapor at various pressures.

Let's start to evaporate the liquid in the vessel V at an absolute pressure of 1 kgf/cm 2 . As can be seen from fig. 6, above the liquid in this vessel, consisting of 60% 0 2 and 40% N 2, there can be an equilibrium vapor in composition, containing 26.5% 0 2 and 73.5% N 2, having the same temperature as the liquid . We feed this vapor into vessel IV, where the liquid contains only 50% 0 2 and 50% N 2 and therefore will be colder. From fig. 6 it can be seen that above this liquid, the vapor can contain only 19% 0 2 and 81% N 2, and only in this case its temperature will be equal to the temperature of the liquid in this vessel.

Therefore, the steam supplied to vessel IV from vessel V, containing 26.5% O 2 , has a higher temperature than the liquid in vessel IV; therefore, the oxygen of the vapor condenses in the liquid of vessel IV, and part of the nitrogen from it will evaporate. As a result, the liquid in vessel IV will be enriched with oxygen, and the vapor above it with nitrogen.

Similarly, the process will take place in other vessels and, thus, when draining from the upper vessels into the lower ones, the liquid is enriched with oxygen, condensing it from the rising vapors and giving them its nitrogen.

Continuing the process up, you can get a vapor consisting of almost pure nitrogen, and in the lower part - pure liquid oxygen. In fact, the rectification process that occurs in the distillation columns of oxygen plants is much more complicated than described, but its fundamental content is the same.

Regardless of the technological scheme of the installation and the type of refrigeration cycle, the process of producing oxygen from air includes the following stages:

1) air purification from dust, water vapor and carbon dioxide. The binding of CO 2 is achieved by passing air through an aqueous solution of NaOH;

2) air compression in the compressor with subsequent cooling in refrigerators;

3) cooling of compressed air in heat exchangers;

4) expansion of compressed air in a throttle valve or expander for its cooling and liquefaction;

5) liquefaction and rectification of air to obtain oxygen and nitrogen;

6) discharge of liquid oxygen into stationary tanks and removal of gaseous oxygen into gas holders;

7) quality control of the resulting oxygen;

8) filling transport tanks with liquid oxygen and filling cylinders with gaseous oxygen.

The quality of gaseous and liquid oxygen is regulated by the relevant GOSTs.

According to GOST 5583-58, gaseous technical oxygen of three grades is produced: the highest - with a content of at least 99.5% O 2, the 1st - at least 99.2% O 2 and the 2nd - at least 98.5% O 2 , the rest is argon and nitrogen (0.5-1.5%). The moisture content should not exceed 0.07 g/l 3 . Oxygen obtained by electrolysis of water must not contain more than 0.7% hydrogen by volume.

According to GOST 6331-52, liquid oxygen of two grades is produced: grade A with a content of at least 99.2% O 2 and grade B with a content of at least 98.5% O 2. The content of acetylene in liquid oxygen should not exceed 0.3 cm 3 /l.

Used for the intensification of various processes at the enterprises of the metallurgical, chemical and other industries, technological oxygen contains 90-98% O 2 .

Quality control of gaseous, as well as liquid oxygen is carried out directly in the production process using special instruments.

Administration Overall rating of the article: Published: 2012.06.01

Question number 2 How is oxygen obtained in the laboratory and in industry? Write the equations for the corresponding reactions. How do these methods differ from each other?

Answer:

In the laboratory, oxygen can be obtained in the following ways:

1) Decomposition of hydrogen peroxide in the presence of a catalyst (manganese oxide

2) Decomposition of Berthollet salt (potassium chlorate):

3) Decomposition of potassium permanganate:

In industry, oxygen is obtained from air, which contains about 20% by volume. Air is liquefied under pressure and with strong cooling. Oxygen and nitrogen (the second main component of air) have different boiling points. Therefore, they can be separated by distillation: nitrogen has a lower boiling point than oxygen, so nitrogen evaporates before oxygen.

Differences between industrial and laboratory methods for producing oxygen:

1) All laboratory methods for obtaining oxygen are chemical, that is, in this case, some substances are converted into others. The process of obtaining oxygen from the air is a physical process, since the transformation of some substances into others does not occur.

2) Oxygen can be obtained from the air in much larger quantities.

This lesson is devoted to the study of modern methods of obtaining oxygen. You will learn by what methods and from what substances oxygen is obtained in the laboratory and industry.

Topic: Substances and their transformations

Lesson:Obtaining oxygen

For industrial purposes, oxygen must be obtained in large volumes and as cheaply as possible. This method of obtaining oxygen was proposed by the Nobel Prize winner Peter Leonidovich Kapitsa. He invented the air liquefaction plant. As you know, about 21% by volume of oxygen is in the air. Oxygen can be separated from liquid air by distillation, because All substances in air have different boiling points. The boiling point of oxygen is -183°C, and that of nitrogen is -196°C. This means that during the distillation of liquefied air, nitrogen will boil and evaporate first, and then oxygen.

In the laboratory, oxygen is not required in such large quantities as in industry. Usually it is brought in blue steel cylinders in which it is under pressure. In some cases, it is still required to obtain oxygen chemically. For this, decomposition reactions are used.

EXPERIMENT 1. Pour a solution of hydrogen peroxide into a Petri dish. At room temperature, hydrogen peroxide decomposes slowly (we do not see signs of a reaction), but this process can be accelerated by adding a few grains of manganese (IV) oxide to the solution. Around the grains of black oxide, gas bubbles immediately begin to stand out. This is oxygen. No matter how long the reaction takes, grains of manganese(IV) oxide do not dissolve in the solution. That is, manganese(IV) oxide participates in the reaction, accelerates it, but is not itself consumed in it.

Substances that speed up a reaction but are not consumed in the reaction are called catalysts.

Reactions accelerated by catalysts are called catalytic.

The acceleration of a reaction by a catalyst is called catalysis.

Thus, manganese (IV) oxide serves as a catalyst in the decomposition of hydrogen peroxide. In the reaction equation, the catalyst formula is written above the equal sign. Let's write down the equation of the carried out reaction. When hydrogen peroxide decomposes, oxygen is released and water is formed. The release of oxygen from the solution is shown by an arrow pointing up:

2. A single collection of digital educational resources ().

3. Electronic version of the journal "Chemistry and Life" ().

Homework

with. 66-67 №№ 2 - 5 from the Workbook in chemistry: 8th grade: to the textbook by P.A. Orzhekovsky and others. “Chemistry. Grade 8” / O.V. Ushakova, P.I. Bespalov, P.A. Orzhekovsky; under. ed. prof. P.A. Orzhekovsky - M.: AST: Astrel: Profizdat, 2006.