Organic synthesis
The organic synthesis industry increases the production and range of chemical products every year. Among them are a variety of monomers and synthetic resins based on them, rubbers, fibers, plastics, adhesives, dyes and a large number of various paints and lubricants, solvents, surfactants, pesticides, flotation agents, antifreeze and anti-knock agents, explosives and medicines, photoreagents, fragrant compounds, etc.
RAW MATERIALS OF ORGANIC SYNTHESIS
Currently, almost all organic synthesis is based on fossil organic raw materials: oil and natural gases, coal, shale. In the processes of physicochemical transformations of these substances (reforming, conversion, cracking, pyrolysis, coking, distillation and rectification, absorption-desorption methods) five groups of starting substances are obtained that are used for the synthesis of many thousands of other compounds (Fig. 1):
1) paraffin hydrocarbons (from CH 4 to mixtures of C 15 -C 40);
2) olefins (mainly C 2 H 4, C 3 H 6, C 4 H 8);
3) acetylene;
4) carbon monoxide and synthesis gas;
5) aromatic compounds (benzene, toluene, naphthalene, etc.).
In addition, in organic technology in large quantities
Inorganic compounds are also used: acids, alkalis, soda, chlorine, etc., without which many processes are impossible.
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In its development, the organic synthesis industry was divided into a number of specific industries, among which the industry of basic organic and petrochemical synthesis occupies an important place. Like basic inorganic chemistry and technology, the term "basic" organic synthesis covers the production of large-scale organic matter, serving as the basis for all other organic technology.
The main object of basic organic synthesis is the primary processing of five types of starting substances into other products (various hydrocarbons, chlorine derivatives, alcohols and ethers, aldehydes and ketones, carboxylic acids and their derivatives, phenols, nitro compounds, organosulfur compounds, i.e. substances on which based on the production of all other organic products). According to their practical purpose, the products of basic organic synthesis are divided into intermediate products (intermediates) for the synthesis of other substances and products for their intended purpose.
The connection between the raw materials and the finished product can be represented by the following diagram:
Raw materials ® Intermediates ® ... ® Finished product
Let's look at this with the following example. A product of the petrochemical and coke-benzene industries, benzene serves as a good solvent for fats, resins, rubber, sulfur and other compounds. At the same time, it represents the feedstock for the production of phenol, styrene, nitrobenzene, aniline, maleic anhydride, monosulfonic acid and other chemical products and intermediates used for the production of synthetic rubber, plastics, varnishes, explosives, pharmaceuticals, etc.
Topic: Current state of petrochemical synthesis. Main products and technologies
Introduction
1. Alternative fuels, raw materials
1.1 Dimethyl ether
1.2 Synthetic gasoline
1.3 Alcohol fuels
1.4 Biomass fuel
2. Technologies
2.1 Synthesis of DME from natural gas (via methanol)
2.2 One-step synthesis of DME from synthesis gas and synthesis of gasoline (via DME)
2.3 Unconventional processes and technologies for producing motor fuels
2.3.1 BIMT technology
2.3.2 BIMT-2 technology
2.3.3 BICYCLAR process
Conclusion
Literature
Introduction
The development of the fuel industry is determined by a number of factors. Increasing costs for searching, production and delivery to places of mass consumption of petroleum raw materials ultimately led to an increase in the cost of fuel obtained from oil. Increasing demands from environmentalists for the quality of produced motor fuel also causes an increase in the cost of processing initial oil fractions.
Another important factor determining the trajectory of changes in the fuel sector of the energy sector is due to the need to reduce emissions of carbon dioxide into the atmosphere, which is the main greenhouse gas. From an environmentalist's point of view, none of the currently existing types of fuel can be considered acceptable. All that is used in transport to produce energy is carbon compounds. When they burn in a car engine or in the furnace of a power plant (factory or power plant), it forms (in optimal option) carbon dioxide entering the atmosphere. The future of road transport and large energy installations is usually associated with the use of electrical energy and hydrogen, produced from renewable energy sources using methods that, as it now seems, will not harm the environment. The implementation of these ambitious projects involves many technical problems, the solution of which will take quite a lot of time even with the mobilization of global scientific and technical potential.
Currently, against the backdrop of rising prices for oil and its processing methods, growing motorization and the growing need of civilization for high-quality fuel, chemists are turning their attention to non-oil sources for the production of new compositions of hydrocarbon fuels that have become familiar to the motorist consumer.
Currently, the only economically acceptable way to improve the environmental friendliness of vehicles is to switch them to alternative fuels that reduce harmful emissions in environment car engines to a level that meets stringent European standards. The European Commission plans to develop a large-scale program for the introduction of alternative types of motor fuels. By 2020, over 1/5 of oil-based fuels should be replaced by alternative products such as biofuels, natural gas and hydrogen.
1. Alternative fuels, raw materials
1.1 Dimethyl ether
The synthesis of dimethyl ether (DME) and gasoline through dimethyl ether is one of the new directions in the field of processing natural gas and other carbon sources (coal, wood residues, etc.). The main routes for processing methane into motor fuels are shown in Scheme 1. As can be seen from the diagram, the synthesis of DME fits into the scheme of natural gas processing as an alternative route to the synthesis of methanol.
Motor fuels
Hema 1 Main ways of processing natural gas into motor fuels
1.2 Synthetic gasoline
The raw materials for the production of synthetic non-petroleum gasoline can be coal, natural and associated petroleum gases, biomass, shale, etc. The most promising source for the production of alternative motor fuels is natural gas, as well as the synthesis gas obtained from it (a mixture of CO and H2 in various proportions). Where natural gas is easily recovered, it can be used in compressed and liquefied states as a motor fuel for internal combustion engines. Liquefaction of natural gas, compared to compression, has the advantage of reducing the volume of its storage system by almost three times.
The use of alternative fuels obtained from natural gas ensures a reduction in the content of toxic components in vehicle exhaust gases.
1.3 Alcohol fuels
A significant disadvantage of this type of fuel remains its high cost - depending on the production technology, alcohol fuels are 1.8-3.7 times more expensive than oil ones. Among various alcohols and their mixtures, methanol and ethanol are most widely used as motor fuels. Synthesis gas is currently used to produce methanol, but natural gas is the preferred feedstock for large-scale processes. From an energy point of view, the advantage of alcohols lies mainly in their high detonation resistance, which determines the predominant use of alcohols in spark-ignition internal combustion engines. Their main disadvantages are low heat of combustion, high heat of evaporation and low vapor pressure.
Ethanol is generally better in performance than methanol. The cost of ethanol is on average much higher than the cost of gasoline. Currently, methanol as a motor fuel is used in limited quantities. It is mainly used to produce synthetic liquid fuels, as a high-octane fuel additive and as a raw material for the production of an anti-knock additive - methyl tert-butyl ether.
One of the most serious problems hampering the use of methanol additives is the low stability of gasoline-methanol mixtures and their sensitivity to the presence of water. The difference in the densities of gasoline and methanol and the high solubility of the latter in water lead to the fact that the entry of even small amounts of water into the mixture causes its immediate separation, and the tendency to separation increases with decreasing temperature, increasing water concentration and decreasing the content of aromatic compounds in gasoline. To stabilize gasoline-methanol mixtures, additives are used - propanol, isopropanol, isobutanol and other alcohols.
1.4 Biomass fuel
Biomass is a very promising renewable raw material. It can be used to produce ethanol as an alternative fuel. It is estimated that so much biomass is grown and grown in the wild each year that it can produce eight times more energy than all fossil fuels currently provide. Research aimed at creating the production of liquid fuels from renewable raw materials of plant origin has been expanding in recent years.
Bioethanol and biobutanol are produced by fermentation. A wide range of carbohydrate materials can be used as raw materials for fermentation: sugars, starch, cellulose, etc. The basis for the production of bioethanol from starch is two stages: hydrolysis of starch to glucose under the action of enzymes and fermentation of glucose to ethanol. A significant drawback of this technology is due to the fact that when the concentration of ethanol in the reaction mixture increases above a certain level, it begins to have an inhibitory effect on the fermentation process. In addition, fermentation usually results in the formation of a number of metabolites, which at elevated concentrations also reduce the efficiency of the process.
Modern research to improve existing processes for the production of bioethanol is carried out mainly in two directions: the development of fermentation systems operating in a continuous mode, and increasing the productivity of ethanol extraction and purification methods in order to reduce energy costs for the production of fuel alcohol.
2. Technologies
2.1 Synthesis of dimethyl ether from natural gas (via methanol)
Natural gas is the simplest and most accessible raw material for the synthesis of dimethyl ether and, accordingly, the process of producing DME based on natural gas has the best economic indicators. Currently, industrial production of DME (aerosol filler) is approx. 150 thousand tons per year and is based on methanol processing. A simplified scheme for the production of DME based on natural gas through the synthesis and subsequent dehydration of methanol can be represented as Scheme 2.
Scheme 2 Scheme for the synthesis of DME from natural gas through the stages of synthesis and dehydration of methanol
Let us consider the individual stages of this synthesis.
Methane conversion.
Conversion of methane (reforming) into synthesis gas is a high-temperature process that can be carried out using various reactions (involving various reagents). Among them:
steam reforming CH4+H3O=CO+3H3 (1)
carbon dioxide conversion CH4+CO2+2CO+2H3 (2)
incomplete oxidation CH4+1/2O2=CO+2H3 (3)
Reactions (1) and (2) are highly endothermic, so autothermal reforming—steam reforming in the presence of oxygen—has become widespread. To the reactions (1) and (3) occurring under autothermal reforming conditions are added highly exothermic reactions of complete oxidation:
CH4+2O2=CO2+2H3O (4)
H3+1/2O2=H3O (5)
CO+1/2O2=CO2 (6)
These processes provide compensation for heat losses in reaction (1), but lead to additional costs of raw materials.
Synthesis gas is a mixture of CO and hydrogen with a small amount of CO2, which may also contain nitrogen. The most important characteristic of synthesis gas is the H2:CO concentration ratio. To synthesize methanol, this ratio must be greater than two, which makes the use of steam reforming inevitable (reaction 1).
Reforming conditions are the result of a compromise between the requirements of thermodynamics (increasing temperature and decreasing pressure to increase equilibrium methane conversion), economics and materials science. At high temperatures (800-900 ºС) and not too high pressure (1-3 MPa), the thermodynamics of the process are favorable, which allows the reaction to be brought to a transformation close to complete. The compromise achieved leads to the fact that in the process of methanol synthesis, the reforming stage requires approximately 2/3 of capital investments and more than half of operating costs. This circumstance led to the search for new ways to convert natural gas into synthesis gas.
Direct gas-phase selective oxidation of methane into CO and H2, i.e. into synthesis gas (reaction 3), would be the simplest of the alternative methods, but the selectivity of this process under practical conditions is low (at 50%). High selectivity can be achieved at high temperatures (approx. 1500 K), when the equilibrium is favorable specifically for the formation of synthesis gas. However, carrying out the process at such temperatures is associated with a number of difficulties due to very stringent requirements for the reactor material in contact with a corrosive environment at high temperatures, and the complexity of controlling the process, since the laws of combustion of “rich” mixtures have been relatively little studied.
The question also arises of what to use as an oxidizing agent. If you oxidize methane with pure oxygen, the capital investment and cost of synthesis gas increase, and if you use air, you get “poor” low-quality synthesis gas with a high nitrogen content (at least 50-60% vol.).
LECTURE COURSE ON ALTERNATIVE SOURCES OF HYDROCARBONS
CONTROL
The basic organic synthesis industry is one of the most important sectors of both chemical and petrochemical production. Basic organic synthesis includes the production of monomers for the production of artificial fibers, plastics, synthetic rubbers, surfactants, synthetic fertilizers, solvents and many other products necessary for the normal functioning and development of the economy of any country. In addition to chemical products, to maintain economic activity Enterprises, housing and transport all over the world consume huge amounts of hydrocarbon raw materials for the functioning of the fuel and energy complex. Therefore, raw materials are one of the main elements of production and largely determine the scale, technology and economics of industry. In this regard, the Department of Chemical and Technical Technologies is already training specialists in the field of technology of organic substances and fuels (including alternative ones).
RAW MATERIAL SOURCES OF KHTOV INDUSTRY
There are mineral (non-renewable) and renewable hydrocarbon raw materials. To mineral include: coals, shale, tar sands, peat, oil and natural gas - once formed from products of organic origin. These also include acetylene based on mineral sources of non-organic origin. Data on reserves of mineral springs are quite contradictory, since they are difficult to assess. However, it is known for sure that the reserves of solid fossil fuels significantly exceed the reserves of oil and gas. Calculations by geochemists show that the ratio of various fossil fuels in the earth’s crust is (in%):
Coals, shale and tar sands - 81-95.8; Peat - 3.4-5; Oil - 0.7-9.8 (90% as fuel); Natural gas - 0.1-4.4 (50-52% converted into electricity)
In addition to mineral - exhaustible sources of energy (fuel >90%) and chemical (5-8%) raw materials, the reserves of renewable sources are limitless - this is biomass. It reproduces spontaneously, regardless of human activity, in just one year in quantities of about 200 billion tons with a total energy potential 3 . 10 21 J, which is ~ 10 times the volume of global fossil fuel production. From the total amount of biomass, ~ 40 billion tons are formed in the form of wood, ~ 30 billion tons in the form of living organisms (~ 10 billion tons of adipose tissue) and ~ 2-3 billion tons in the form of oil-containing components in oil-producing plants (for comparison, according to some data, world oil reserves are currently estimated at approximately 90 billion tons). This exceeds all proven reserves of mineral raw materials, but their collection is difficult, and processing technologies are at the stage of experimental or pilot-industrial research. In this regard, today the most acceptable and cheapest sources for meeting the fuel, energy and chemical needs of the country are: oil, natural and associated gases, as well as oil refining gases. However, it should be noted that in the future the trend will change due to the depletion of reserves of the above mineral springs.
Modern development in most countries, in recent years it has been taking place under conditions of a general economic crisis, in particular the energy and raw materials crisis. Although currently the share of oil and gas in the fuel balance of the main capitalist countries is significant, forecast estimates reveal a general trend aimed at reducing their consumption and a slight increase in the share of coal and other renewable hydrocarbon sources.
World oil consumption in 1970 reached ~3 billion tons, in 1990 this value reached ~4 - 4.5 billion tons per year. in 2000, ~5 billion tons were already processed, in 2020 it is planned to process ~6 billion tons or more. At this level (and it will steadily increase), the service life of these reserves will be about 90/5 = 16 years. ????? This, of course, does not mean that during this time all the oil on earth will be exhausted, but it shows that the current, still prosperous state of oil on the world market is apparent. (This is clearly visible in the interruptions in oil supply in our country, and in particular at the Nyan Refinery Plant, the production of which by the Slav-Neft company in 2015 amounted to 20 million tons per year, and refining at the Nyan Refinery Plant in the most successful year of 2015 in the last 10 years amounted to 13-14 million tons per year, with a plant capacity of 15-16 million tons per year) For comparison, expected oil production and processing in Russia in 2020 will be no more than 500 million tons, which is less than 1980 - 610 million tons.
The Russian gas industry is a relatively young branch of the fuel and energy industry, which has been developing at a rapid pace, and already in 1990. natural gas production amounted to 850 billion m3. In 2015, due to the fuel and energy crisis, production will remain at the same level (or slightly less). By the end of 2015, the deficit of gas resources amounted to 20 billion m3, and by the end of 2016-2017 it will increase to 45-50 billion m3. Today's price (as of January 1, 2016) of gas is ~ 280-320 dollars. for 1 thousand m 3. (for now it is 2-3 times cheaper than fuel oil and coal, but the upward trend in prices is obvious). This is due to the fact that the development of new gas fields takes 7 to 10 years, and the cost of exploration, production and transportation is rising.
MODERN TRENDS IN THE DEVELOPMENT OF THE PETROCHEMICAL SYNTHESIS INDUSTRY AND THE EFFECTIVENESS OF USING ALTERNATIVE SOURCES OF HYDROCARBON RAW MATERIALS
Limited oil and gas reserves have raised new important challenges for the oil refining and petrochemical industries:
deepening oil refining processes with maximum selection of light oil products;
expanding the use of oil as a feedstock for petrochemicals, and to a lesser extent as a fuel (including power plants and heating plants);
widespread use of coal as boiler fuel (in replacement of gas and oil, since its reserves are large);
rational use of fuel and electrical energy in modern processes oil refining and petrochemicals;
use of nuclear energy in oil refining and petrochemistry;
development (coal-based) processes for the production of synthetic liquid fuels and natural gas substitutes;
transferring the production of a number of petrochemical products to coal raw materials.
Currently, processes for the production of alternative fuels are also being widely developed. These include:
liquefied and compressed natural gas (as fuel for cars and other types of transport);
liquefied gases (fuels for vehicles);
methanol based on synthesis gas (today it is successfully used directly as fuel or as an additive to gasoline, increasing their octane number, and is also processed into (MTBE) methyl tert-butyl ether, a high-octane additive, into high-octane gasoline, etc.) ;
a substitute for natural gas produced by coal gasification;
ethyl alcohol (as an additive to gasoline, etc.);
acetylene based on calcium carbide and methane pyrolysis (chemical products based on it are varied, since acetylene has 3 double bonds and is very reactive).
Catalysis in petrochemistry
General information about catalytic methods for refining oil and petroleum hydrocarbons. Main types of heterogeneous catalysts in petrochemical processes.Specific features of different areas of catalysis: homogeneous, heterogeneous and microheterogeneous. Active centers. Characteristics of catalysts - activity, selectivity. Energy aspects in catalysis. Electronic factors in heterogeneous catalysis. Promoters and poisons. Stages of adsorption and diffusion in heterogeneous catalysis. Macrokinetic factors in catalysis. Acid-base catalysis. Homogeneous catalysis, metal complex catalysis. Coordination and ligand exchange. Catalytic cycles. Key reactions in homogeneous catalysis. Oxidative addition and reductive elimination. Implementation reactions. Catalysis by ions and complexes. Enzyme catalysis.
New approaches to catalyst immobilization. Two-phase catalysis (SHOP - alpha-olefin production process). Water-soluble metal complex catalysts (process of hydroformylation of propene and butene-1 from Rhone-Poulenc/Ruchrchemie). Fluorine catalysis. Metal complex catalysis in supercritical carbon dioxide. Catalysis in ionic liquids.
Use of synthetic receptors in catalysis. Supramolecular catalysts. Molecular recognition ability and substrate selectivity
Problems of deactivation and regeneration of catalysts.
Kinetic methods for studying reactions and catalysts. Process modeling. Process optimization methods.
Obtaining primary petrochemical products based on secondary oil refining processes
The pyrolysis process is a source of petrochemical products: ethylene, propylene, butylenes, divinyl, isoprene, allene, aromatic hydrocarbons. Raw materials for pyrolysis.
Catalytic cracking, raw materials for cracking. Cracking catalysts – amorphous aluminosilicates, zeolites, etc., their stability. Poisoning of catalysts by metals contained in heavy oil fractions and residues. Passivation of the catalytic action of metals, passivators. Mechanism of catalytic cracking. Behavior of hydrocarbons of various classes under catalytic cracking conditions.
Main products of catalytic cracking. Hydrocracking. The role of hydrogen in the process. Hydrotreating.
Aromatic hydrocarbon resources. Release of aromatic hydrocarbons. Benzene and ways of its use. Ways to increase benzene resources. Xylenes, resources, separation of isomers. Ways to increase p-xylene resources. Cumene, synthesis and oxidation.
Chemistry of oxygen- and sulfur-containing components of oil and coal processing products
Phenols. Sources of phenols, methods of isolation and separation. Methods for producing one-, two- and polyhydric phenols. Hindered phenols. Tautomerism of phenols. Electrophilic substitution reactions in a series of hindered phenols. Bisphenols. Antioxidant properties of phenols. Phenols are additives for fuels, oils and polymeric materials.
Organosulfur compounds of oils in petrochemistry. Current state of the recycling problem organic compounds sulfur of oils, its chemical, environmental and economic aspects. Features of the chemical behavior of petroleum organosulfur compounds. Practical use of petroleum sulfur concentrates. Application of petroleum mercaptans, sulfides, thiophenes. Use of petroleum disulfides of secondary origin.
Economic effect of using petroleum organic sulfur compounds (using the example of petroleum sulfur extractants).
Production of organic sulfur derivatives based on petrochemical raw materials.
Catalytic synthesis of mercaptans. Methyl mercaptan, methionine, dodecyl mercaptans.
Production of dimethyl sulfide.
Production of sulfoxides and sulfones. Dimethyl sulfoxide. Sulfolane. Divinyl sulfoxide.
Production of thiophenes, benzothiophene. Areas of application of these compounds.
Promising ways to produce organic sulfur compounds.
Syntheses based on acetylene. High-temperature reactions of organic compounds with hydrogen sulfide, thiols, sulfides, disulfides, sulfoxides. New catalytic syntheses. Organic sulfur compounds containing other heteroatoms.
Alternative feedstocks for petrochemical synthesis
Coal is an alternative to oil and natural gas as raw materials for the petrochemical industry.Methods for processing coal into hydrocarbon raw materials (thermal dissolution, hydroliquefaction, destructive hydrogenation).
Gasification of coals. Semi-coking and coking. Coke tar is a source of aromatic raw materials.
Use of carbon oxide and dioxide in the production of fuels and petrochemical raw materials. Fischer-Tropsch process. Modern ideas about the mechanism.
Methanol is a fuel and raw material for petrochemical synthesis. Conversion of methanol into hydrocarbons. Methyl ethers are non-hydrocarbon fuel additives.
The use of carbon oxide and dioxide in the synthesis of organic substances of various classes.
Literature
1.L.Puckett. Fundamentals of modern chemistry of heterocyclic compounds. M.: Mir, 1971.
2. T. Gilchrist, R. Starr. Organic reactions and orbital symmetry. M.: Mir, 1986.
3. Karakhanov E.A., Maksimov A.L. Catalysis by soluble Macromolecular Metal Complexes. In. Editors Wohrle E.D., Pomogailo A.D. Metal Complexes and Metals in Macromolecules. Synthesis, Structure and properties. 2003, Wiley-VCH [email protected]. P.457-502.
4.N.K. Lyapina. Chemistry and physical chemistry of organosulfur compounds of petroleum distillates. M.: Nauka, 1984.
5.V.F.Kamyanov, V.S.Aksenov, V.I.Titov. Heteroatomic components of oils. Novisibirsk: Nauka, 1984.
6.N.S.Pechuro, D.V.Panin, O.Yu.Pesin. Chemistry and technology of synthetic fuel and gas. M.: Chemistry, 1986.
7. R. A. Sheldon. Chemical products based on synthesis gas. M.: Chemistry, 1987.
8. G. Henrizzi-Olivet, S. Olive. Chemistry of catalytic hydrogenation of CO. M.: Chemistry, 1987.
9. Catalysis in C1-chemistry (edited by Klaim L.) Leningrad: Chemistry, 1987.
10.V.S. Arutyunov, O.V. Krylov. Oxidative transformations of methane. M.: Nauka, 1998.
The main hydrocarbon raw materials for petrochemical syntheses are mixtures of gaseous, liquid and solid hydrocarbons.
Natural gases consist mainly of methane and other saturated hydrocarbons; they also contain inert gases (nitrogen, carbon dioxide) and rare gases (argon, xenon). Natural gases are produced during the development of gas and condensate fields.
Associated petroleum gases obtained as a by-product during oil production. These gases are dissolved in reservoir oil and are released during its production due to a decrease in pressure. Associated petroleum gas consists of saturated hydrocarbons ranging from methane to pentanes and usually contains some inert gases; Associated gases from some fields also contain free hydrogen sulfide. As a rule, associated petroleum gases contain significant amounts of hydrocarbon components - ethane, propane and butanes, which are valuable raw materials for petrochemicals.
Oil refining gasesare formed in the processes of cracking, coking, reforming; they are also selected at oil stabilization and direct distillation plants. Depending on the nature of these processes, the composition of the resulting gases varies within wide limits. For example, catalytic reforming gases contain up to 60% hydrogen; the rest are saturated hydrocarbons. Cracking and coking gases consist of saturated and unsaturated hydrocarbons.
Oil stabilization gasesThey are characterized by a high content of propane, butane, pentane and isopentane, which makes them a valuable raw material for the production of butadiene and isoprene.
Gasoline gasolines boils away in the range of 30-120 0 C; they contain butane, pentane, isopentane, as well as C6 and C7 hydrocarbons of normal and isostructure.
Gas condensatesboils away in the range 40-360 0 C. They contain 15-30% aromatic hydrocarbons; 25-40% naphthenes and 20-60% paraffins (depending on the field).
Liquid distillates and petroleum products, formed during various processes oil refining are also used as feedstock in petrochemical processes, or more precisely as a source for isolating certain groups of hydrocarbons. Thus, aromatic hydrocarbons are isolated from the products of catalytic reforming, olefins from the products of thermal and catalytic cracking, and paraffins from the products of dewaxing of diesel fuel.
Hydrocarbons isolated from hydrocarbon raw materials are of great practical importance. For example, natural gas methane is used as fuel and raw material for the production of hydrogen, acetylene, ammonia and methanol. Ethane serves as a feedstock for pyrolysis processes to produce ethylene; gas condensates– raw materials for the production of butadiene, isoprene, aromatic hydrocarbons.
v Requirements for hydrocarbon raw materials
Hydrocarbon feedstocks for petrochemical processes are usually subject to much more stringent requirements than feedstocks for petroleum refining processes.
The reactions used in petrochemical synthesis are mostly catalytic or radical chain, and in order to obtain the required products, high selectivity of the catalyst is required, side reactions are completely unacceptable, etc. Therefore, a high degree of purity of raw materials is required. Thus, for the production of ethyl alcohol by direct hydration of ethylene, 97-98% ethylene, practically free of hydrogen sulfide (up to 0.002% H 2 S), is required. For the production of polyethylene high pressure requires 99.99% ethylene, completely free of acetylene.
Thorough purification of ethylene from hydrogen sulfide when producing ethyl alcohol is necessary because the rectification equipment for separating the resulting alcohol from the reaction mixture quickly corrodes and fails. For the same reason, ethylene should not contain acetylene.
When oxidizing liquid and solid paraffins to alcohols and acids, it is necessary that the feedstock contain a minimum amount (up to 0.5%) of naphthenic and aromatic hydrocarbons that inhibit oxidation. Equally important is the absence of phenols, nitrogen and sulfur compounds that interrupt the oxidation chain. In this regard, the requirements for the sulfur content in aromatic hydrocarbons are strict (no more than 0.02%) and its permissible content is constantly decreasing.
In some cases, it is necessary to purify hydrocarbon raw materials from isomers and homologues of the same chemical nature. Thus, if paraffins contain hydrocarbons of isostructure, the products of subsequent oxidation contain increased amount low molecular weight acids, as well as isoacids with an extremely unpleasant odor.
The admixture of dienes in olefins leads to the development of resin formation during isomerization and alkylation.
For hydrocarbon raw materials there must be restrictions on the content of carbon oxides, ammonia and humidity.
All of the above indicates the need for careful preparation of hydrocarbon feedstock.
v Meaning preliminary preparation hydrocarbon raw materials for processing
Hydrocarbon raw materials must meet high requirements determined by the specifics of further chemical transformations of hydrocarbons. One of the main requirements for hydrocarbon raw materials is the minimum content or complete absence of substances of a different chemical nature. Careful preparation of hydrocarbon raw materials for processing is necessary to prevent corrosion of process equipment; the service life of catalysts increased; clogging of pipelines and their throughput were excluded; the amount of by-products decreased, the yield of the target product increased and its quality increased.
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