Method of producing concentrate of aromatic hydrocarbons from liquid hydrocarbon fractions and installation for implementing same

The invention relates to the field of petrochemistry and oil refining, and more particularly to methods and devices for producing an aromatic hydrocarbon concentrate (KAU) from liquid hydrocarbon fractions, in which initial components are fed to the mixer, heated, fed to a reactor in which the heated components are converted in the presence of a catalyst in aromatic hydrocarbons, separated into liquid and gaseous phases, the gaseous phase is fed into the mixer, and the liquid phase into a distillation column from which KAU is taken and can be used in oil refining and petrochemistry to obtain KAU for use as a component with increased detonation resistance of gasolines for internal combustion engines, as well as for further processing into marketable aromatic hydrocarbons.

By marketable aromatic hydrocarbons are meant individual hydrocarbons and their fractions (benzene, toluene, p-xylene, o-xylene, etc.) that correspond to the trade specifications usually described in GOST or TU for the product.

The liquid hydrocarbon fractions that serve as the feedstock are by-products of petrochemical industries, such as light aliphatic and alicyclic hydrocarbon fractions, gas topping products and hydrocarbon stabilization products, pyrocondensates, benzene and benzene toluene fractions of various origin.

By methanol as used herein is meant methanol or crude methanol.

In the processing of hydrocarbon raw materials, the task often arises of utilizing various hydrocarbon fractions, which are by-products of various processes. In particular, such fractions include broad fractions of light aliphatic hydrocarbons of various origins, for example, catalytic cracking gases, stabilization of hydrocarbons from various processes, etc., benzene or benzene-toluene-containing fractions, for example, such as liquid pyrolysis products, benzene fractions, for example, separable from reforming gasolines in order to reduce the benzene content of gasolines.

There is the task of diversifying the raw materials for the production of gasolines, marketable aromatic hydrocarbons and other products into more affordable gas processing products, such as a wide fraction of light hydrocarbons, liquefied petroleum gases, methanol.

The above products can be processed into the target component of gasolines, consisting mainly of aromatic hydrocarbons.₇-FROM₉. The share of aromatic hydrocarbons in gasolines, according to the technical regulations for the production of fifth and fourth grade gasolines (according to the classification of the EurAsEC Technical Regulation, Safety requirements for motor gasoline, diesel fuel and fuel oil) should not exceed 35% or ~ 40% by weight.

As experience shows, it is difficult to produce gasolines with OCHI = 95/98 (the octane number according to the research method according to GOST appears in the gasoline brand after the letter And, for example AI-98) with an aromatic hydrocarbon content of less than 40 wt.%. To compensate for the shortage of aromatic hydrocarbons, refineries are forced to operate reformers in a more stringent mode, associated with increased gas generation.

The invention is aimed at solving the problem of balancing a gasoline pool (component base for compounding gasolines) for aromatic hydrocarbons₇₊ by using for production of aromatic hydrocarbons by-products from other industries and cheaper and more affordable products of processing gas raw materials (a wide fraction of light hydrocarbons, methanol), as well as using the above-mentioned by-products of petrochemical plants for the production of KAU, used as raw materials for the production of commercial aromatic hydrocarbons (e.g. toluene, xylenes).

The prior art method

By its first side, the present invention relates to methods for producing KAU from liquid hydrocarbon fractions, in which the starting components are fed into the mixer, the mixed components are heated, and fed to the reactor, in which the heated components are converted in the presence of a zeolite-containing catalyst into aromatic hydrocarbons, and the resulting product is divided into the liquid and gaseous phases, the obtained gaseous phase is fed to the mixer, the liquid phase is fed to the distillation column, from which KAU is selected.

This method is described in US patent No. 6635792B2, published October 21, 2003. This method is the closest in technical essence and is selected for the prototype of the invention as a method.

The disadvantage of this method is the low efficiency of obtaining KAU, a low content of alkylbenzenes, in particular xylenes. Indeed, in this method, non-aromatic hydrocarbons are cracked to form C hydrocarbons₁-FROM₄, and aromatic hydrocarbons are partially dealkylated, that is, there is no increase in aromatic hydrocarbons. In this method, the percentage of aromatic hydrocarbons in the output is only 82-83% of the mass of aromatic hydrocarbons in the feedstock (according to examples of the prototype, the content of aromatic hydrocarbons in the feedstock

- 1,032,256 genera of 65 wt.%, And the content of aromatic hydrocarbons in the conversion products is 55-60 wt.%) At the same time, the high content of undesirable benzene and insignificant aromatic hydrocarbons C are recorded in the resulting KAU₇-FROM₈.

Disclosure of the invention as a method

The present invention mainly aims to propose a method for producing KAU from liquid hydrocarbon fractions, which allows to increase the efficiency of obtaining KAU and increase the content of alkylbenzenes, in particular xylenes.

To solve the technical problem, methanol is additionally fed into the mixer, the mixed components are heated to a gas phase state when they are fully homogenized, the hydrocarbon components remaining in the distillation column after selection are fed at least partially to the mixer of the starting components, the liquid phase is additionally separated into liquid hydrocarbons and water, liquid hydrocarbons are fed to the distillation column, and water is removed, measure the composition of liquid aromatic hydrocarbons that are fed to the distillation column, and according to the results of measurements of the composition of liquid aromatic hydrocarbons, regulate the ratio between the initial components supplied to the mixer and / or the temperature of the distillation column cube.

Thanks to these advantageous characteristics, it becomes possible to increase the efficiency of obtaining KAU and increase the content of alkylbenzenes, in particular xylenes.

Indeed, even a crude pyrocondensate that has not undergone the liquid phase hydrogenation of dienes and styrenes in a mixture with methanol does not form deposits on the walls of the heat exchangers when the mixture is heated, and the presence of methanol inhibits the radical oligomerization of dienes and aromatic olefins present in the feedstock when it is heated. Also, in the joint conversion of hydrocarbons and methanol on zeolite catalysts, coke deposition on the catalyst surface is less intense, which is also associated with the presence of water vapor (which is noted, for example, in KI patent 2030376) formed during the conversion of methanol, as well as with a high process temperature, which is higher than the temperature at which the rate of radical oligomerization of dienes is lower than the rate of their depolymerization.

The presence of benzene and toluene in the converted mixture leads to their alkylation with the formation of higher alkylbenzenes. In this case, methanol acts as an alkylating agent. The presence of m-xylene in a convertible mixture leads to the disproportionation of m-xylene with the formation of a xylene mixture, the composition of which is close to equilibrium.

The hydrocarbon fraction removed from the bottom of the column during the joint conversion of hydrocarbons with methanol actually consists mainly of alkylbenzenes, including and xylenes.

Light aliphatic hydrocarbons, benzene, toluene, withdrawn from the top of the column during recycling to the beginning of the process (mixing the feedstock with methanol) are also partially converted to higher aromatic hydrocarbons. This allows the use of recycling of these fractions to increase the yield of alkylbenzenes. Aromatic hydrocarbons contained in the recycling also participate in disproportionation and alkylation reactions, which leads to the formation of higher aromatic hydrocarbons.

The xylene composition in the conversion product is close to equilibrium with the predominance of m-xylene. At the same time, disproportionation reactions occur on the catalyst, which allows not only benzene and toluene mixed with aliphatic hydrocarbons to be recycled to the process head, but also, for example, methaxylene for its conversion to a xylene mixture containing ortho and paraxylene.

Due to such an advantageous characteristic as measuring the composition of liquid aromatic hydrocarbons that are fed to the distillation column and, based on the measurement results, adjusting the ratio between the initial components supplied to the mixer and / or the temperature of the distillation column, it becomes possible to precisely adjust the process parameters to the maximum yield of the desired product.

There is a variant of the invention in which methanol is fed into the mixer to form a mixture in which the mass fraction of methanol is 20-70%.

Due to this advantageous characteristic, it becomes possible to increase the concentration of aromatic hydrocarbons and the content of alkylbenzenes, in particular xylenes.

There is a variant of the invention in which, when measuring the composition of liquid aromatic hydrocarbons that are fed to the distillation column, the concentration of benzene and the concentration of the sum of aromatic hydrocarbons, consisting mainly of methylbenzenes, are determined when the ratio of the concentration of benzene to the concentration of the sum of aromatic hydrocarbons is exceeded or decreased, the initial components supplied to the mixer, and / or the temperature of the distillation column so that the mass content of benzene in the mixture fed to the column, relative to the mass content of the sum of aromatic hydrocarbons in the mixture fed to the column, is in the range of 8-30%.

- 2 032256

Thanks to this advantageous characteristic, it becomes possible to fine-tune process parameters to the maximum yield of the desired product. Indeed, there is a dependence of the composition of the equilibrium mixture of methylbenzenes on the ratio of the number of methyl groups to the number of phenyl groups. With an increase in the ratio of the sum of methyl groups to the sum of phenyl groups above 1.7, the molar content of xylenes practically does not change, but the content of trimethylbenzenes, tetramethylbenzenes, etc. increases. up to hexamethylbenzenes. These are heavy aromatic hydrocarbons and their use is limited. Although the composition of methylbenzenes in the conversion product is not equilibrium, the rule of increasing the number of methyl groups to the number of phenyl groups in the aromatic fraction with an increase in the supply of methanol with respect to hydrocarbons is maintained. If the target product of the process is toluene, which is a valuable component of gasolines, it is best to reduce the methanol / hydrocarbon ratio to a minimum.

There is a variant of the invention in which the flow rate of the starting components supplied to the mixer is controlled by changing the flow rate of methanol.

Thanks to this advantageous characteristic, it becomes possible to control the process by controlling precisely the methanol consumption.

There is a variant of the invention in which the flow rate of the starting components supplied to the mixer is controlled by changing the flow rate of hydrocarbon fractions.

Thanks to this advantageous characteristic, it becomes possible to control the process by precisely regulating the flow of hydrocarbon fractions.

There is a variant of the invention in which, after heating the mixed components to a temperature at which the predominant evaporation of hydrocarbons with boiling points under normal conditions up to 250 ° C occurs, the resins (products of the radical oligomerization of dienes and aromatic olefins present in the feed) are separated using centrifugal resin separator.

Due to this advantageous characteristic, it becomes possible to separate and remove unwanted products.

There is a variant of the invention in which the measurement of the composition of liquid aromatic hydrocarbons is carried out using a flow chromatograph.

Due to this advantageous characteristic, it becomes possible to measure the composition of liquid aromatic hydrocarbons using an accurate and proven method.

The set of essential features of the present invention is unknown from the prior art for methods of similar purpose, which allows us to conclude that the novelty criterion for the invention as a method meets.

Prior art installation

The other side of the present invention relates to a plant for the production of KAU from liquid hydrocarbon fractions, including a mixer of the initial components, the output of which is connected to the input of the unit for heating the mixed components, the output of which is connected to the input of the reactor, in which the conversion of heated components in the presence of a catalyst to aromatic hydrocarbons, the outlet of which is connected to the input of the unit for separating the obtained product into liquid and gaseous phases, the first outlet of the gaseous phase of which is connected to the first inlet of the mixer of the starting components, and the second outlet of the liquid phase of which is connected to the inlet of the distillation column, from the first outlet of which the aromatic hydrocarbon concentrate is taken.

Such an installation is described in US patent No. 6635792B2, published October 21, 2003. This installation is the closest in technical essence and is selected as a prototype of the invention as a device.

The disadvantage of the prototype invention is the low efficiency of obtaining KAU, a low content of alkylbenzenes, in particular xylenes. Indeed, in this setup, non-aromatic hydrocarbons are cracked to form C₁-FROM₄, and aromatic hydrocarbons are partially dealkylated, i.e. there is no increase in aromatic hydrocarbons. In this installation, the percentage of aromatic hydrocarbons at the outlet is only 82-83% of the content in the feedstock, however, the proportion of non-aromatic hydrocarbons in fraction C₅₊ the conversion product is only 1-1.8 wt.%. Moreover, in the conversion products a high content of undesirable benzene and an insufficient content of alkylbenzenes C₇-FROM₉.

SUMMARY OF THE INVENTION

The present invention also aims to propose a plant for the production of KAU from liquid hydrocarbon fractions, which allows at least to alleviate the above drawback, namely, to increase the efficiency of obtaining KAU and increase the content of alkylbenzenes, in particular xylenes.

To achieve this, the feed component mixer has a second methanol feed inlet adapted for connection to a methanol feed unit. The distillation column has a second output of components remaining after the selection of KAU, connected to the third input of the mixer

- 3 032256 running components. The unit for separating the obtained product into liquid and gaseous phases additionally has a module for separating the liquid phase into liquid hydrocarbons and water, connected to the inlet of the distillation column and having an outlet for outputting water.

The installation further includes a unit for measuring the composition of liquid aromatic hydrocarbons that are supplied to the distillation column, and a unit for controlling the flow rate of the initial components supplied to the mixer and / or temperature control of the distillation column connected to it.

Thanks to these advantageous characteristics, it becomes possible to increase the efficiency of obtaining KAU and increase the content of alkylbenzenes, in particular xylenes. Indeed, the ability to measure the composition of liquid aromatic hydrocarbons and process control - all this is aimed at increasing the useful product at the output.

There is an embodiment of the invention in which the installation further includes a unit for separating undesired oligomerization products of dienes and aromatic olefins (resins) located in the heating unit after the raw material evaporator with boiling points under normal conditions up to 250 ° C and before the mixture is overheated to the mixture a reactor, the first input of which is connected to the output of the mixture heater, the first output of which is connected to the mixture superheater, and the second outlet is a resin outlet.

Due to this advantageous characteristic, it becomes possible to separate and remove unwanted resins.

There is a variant of the invention in which the unit for measuring the composition of liquid aromatic hydrocarbons is made in the form of a flow chromatograph.

Thanks to this advantageous characteristic, it becomes possible to measure the composition of liquid aromatic hydrocarbons using an accurate and proven device.

The set of essential features of the invention is unknown from the prior art for devices of a similar purpose, which allows us to conclude that the novelty criterion for the invention as an installation is met.

A brief description of the drawings.

Other features and advantages of the invention clearly follow from the description below for illustration and not being restrictive, with reference to the accompanying figures, in which FIG. 1 schematically depicts a plant for the production of KAU from liquid hydrocarbon fractions according to the invention;

FIG. 2 schematically depicts the steps of a method for producing an aromatic hydrocarbon concentrate from liquid hydrocarbon fractions according to the invention;

FIG. 3 is a table showing the Change in sulfur content in the products of hydrogenation and processing of pyrolysis gasoline according to the invention;

FIG. 4 presents a table Comparison of the composition parameters of hydrocarbons and conversion products in the prototype and according to the invention.

According to FIG. 1 installation for the production of KAU from liquid hydrocarbon fractions includes a mixer 1 of the initial components, the output 10 of which is connected to the input 21 of the block 2 for heating the mixed components, the output 22 of which is connected to the input 31 of the reactor 3, in which the heated components are converted into aromatic hydrocarbons. Reactor 3 provides a near-isothermal hydrocarbon conversion mode. The output 32 of the reactor 3 through the heat recovery and recovery unit 10 (heat is used to evaporate the mixture, heat the cube of the column, heat the refrigerant used to condense liquid hydrocarbons in the conversion product) is connected to the input 40 of the unit 4 for separating the obtained product into liquid and gaseous phases. The first exit 41 of the gaseous phase of block 4 is connected to the first input 11 of the mixer 1 of the source components. The second output 42 of the liquid phase of which is connected to the input 50 of the distillation column 5, from the first output 51 of which KAU is selected.

The mixer 1 of the source components has a second input 12 for supplying methanol, adapted for connection with the block 6 for supplying methanol. Block 6 is not included in the installation.

The mixer 1 of the source components has a third input 14 for supplying the hydrocarbon feed, adapted for connection with the block 9 of the feed hydrocarbon feed. Block 9 is not part of the installation.

The distillation column 5 has a second output of 52 components remaining after the selection of KAU, connected to the third input 13 of the mixer 1 of the original components. The selection of components at the exit 52 can be carried out both in the gaseous and in the liquid and gaseous phases.

The unit 4 for separating the obtained product into liquid and gaseous phases additionally has a module 43 for separating the liquid phase into liquid hydrocarbons and water, connected to the inlet 50 of the distillation column 5 and having an outlet 44 for water output.

The installation additionally includes a unit 7 for measuring the composition of liquid aromatic hydrocarbons, which are fed to the distillation column 5. With block 7 is connected to the unit 71 regulation

- 4 032256 flow rate of the initial components supplied to the mixer, and / or the temperature control unit (cube) of the distillation column 75.

The installation may further include a resin separation unit 8 located after the raw material evaporator 24 located in block 2 with boiling points under normal conditions up to 250 ° C and before the mixture superheater 33 located in the reactor 3 to the temperature of the mixture supply to the reactor 3. First inlet 81 unit 8 is connected to the mixture heater 24, and the first outlet 82 of the unit 8 is connected to the mixture superheater 33, and the second outlet 83 is the resin outlet.

Block 8 separation of the resin-separator can be made on the basis of a centrifugal separator.

The measuring unit 7 of the composition of liquid aromatic hydrocarbons can be made in the form of a flow chromatograph.

By the reaction zone of the reactor 3 here is meant the entire space of the reactor in which the conversion of hydrocarbons takes place, including that divided into separate segments. The reactor 3 may be shelf-mounted, for example, by mixing flows within the reactor. There may be several mixing and feeding zones. The reactor can also be tubular with the loading of the catalyst in the reaction tubes, etc.

In the process of converting hydrocarbons to KAU, fixed-bed reactors with periodic catalyst regeneration or a fluidized-bed reactor with continuous catalyst regeneration can be used.

In the proposed device and method for its implementation, a catalyst is mainly used that contains a zeolite of the pentasil type with a silicate module B10₂/ A1₂0₃= 40-50, pre-treated with an aqueous solution of alkali, modified with lanthanum oxide in an amount of 0.5-2.0 wt.%, As well as a binder in an amount of from 20 to 25 wt.% By weight of the catalyst. Alumina and / or silica are preferably used as the binder. In the case of using a mixture of oxides, the content in the mixture of silicon oxide may be from 0.1 to 99.9 wt.%. A distinctive feature of the method is that the aluminosilicate catalyst is simultaneously active in the aromatization and alkylation reactions of lower aromatic hydrocarbons (benzene, toluene, etc.) with olefins C₂-FROM₄formed (ίη cue) during the conversion of oxygenates.

By water is meant water, which may have a residual content of hydrocarbons and oxygenates.

The implementation of the invention

Obtaining KAU according to the invention is as follows.

Stage A1.

Convertible hydrocarbons, as well as recycling products, are fed into the mixer 1 of the starting components under a pressure of 1-4 MPa. There they are mixed with methanol, which is supplied from the methanol supply unit 6 in a ratio at which the mass fraction of methanol in the mixture is 20-70%.

Stage A2.

Next, the mixture is fed to block 2 for heating the mixed components, where the evaporation of methanol and hydrocarbons with boiling points under normal conditions up to 250 ° C. When heated, 100% homogenization of the mixture is achieved.

Stage A3.

Optionally, the mixture is fed to the resin separation unit 8, for which a centrifugal separator can be used. The resin is removed from the resin separation unit 8, and the gas-phase mixture is fed to the reactor 3 and then to the heat recovery unit 10, in which the conversion product is cooled with condensation of liquid hydrocarbons and water.

Stage A4.

The reaction product is fed to a unit 4 for separating the obtained product into liquid and gaseous phases, which also has a module 43 for separating the liquid phase into liquid hydrocarbons and water. Water is taken out. The gaseous phase is partially recycled to mixer 1 of the starting components.

Stage A5.

The remaining mixture of hydrocarbons is fed to distillation column 5. In it, the mixture is separated into fractions. The hydrocarbon components remaining after selection in the distillation column are at least partially fed into the mixer 1 of the initial components, and the KAU is discharged.

Stage A6.

The composition of liquid aromatic hydrocarbons is measured, which are fed to the distillation column 5, and according to the results of measurements of the composition of liquid aromatic hydrocarbons, the ratio between the initial components supplied to the mixer 1 using block 71 and / or the temperature of the distillation column 5 using block 75 are controlled. Block 7 measuring the concentration of liquid aromatic hydrocarbons compares information on the current and required mass ratio of benzene to total aromatic hydrocarbon content. When exceeding or decreasing the ratio of the concentration of benzene in relation to the concentration of the sum of aromatic hydrocarbons in the product, the block, on the basis of comparison, gives a control action on blocks 71 and 75.

The sequence of steps is exemplary and allows you to rearrange , add or produce

- 5 032256 to perform certain operations simultaneously without losing the ability to provide KAU from liquid hydrocarbon fractions.

Industrial applicability.

The proposed installation for the production of aromatic hydrocarbon concentrate from liquid hydrocarbon fractions can be carried out in practice and, when implemented, ensures the implementation of the declared purpose, which allows us to conclude that the criterion of industrial applicability for the invention is met.

In accordance with the proposed invention, tests and calculations of obtaining a concentrate of aromatic hydrocarbons from liquid hydrocarbon fractions were carried out.

As a result of measurements and calculations, the following was discovered:

A high yield of aromatic hydrocarbons (in the prototype, the yield of aromatic hydrocarbons is 82-83% of its content in the feedstock) in the proposed method, 150-160 wt.% Of the sum of aromatic hydrocarbons in the feedstock. Accordingly, less light C hydrocarbons are formed.₁-FROM₄.

Indirectly, as a raw material, natural gas is involved through methanol, produced, as a rule, from natural gas.

As a feedstock in the conversion with methanol, it is possible to use, among other things, a feedstock containing dienes prone to gum formation and aromatic olefins. An example of such a raw material is low-sulfur crude (non-hydrogenated) pyrocondensate (liquid pyrolysis products).

The concentration of methanol in a convertible raw material mixture can be used to control the component composition of the resulting aromatic hydrocarbon concentrate.

With the same methanol / hydrocarbon volume ratio, the crude pyrolysis condensate process proceeds with higher yield of aromatic hydrocarbon concentrate to the initial pyrolysis condensate. So, with a volume ratio of methanol / hydrocarbon = 1, the yield of aromatic hydrocarbon concentrate was 120.7 wt.% Versus 116 wt.% When using selective olefin-hydrogenated pyrocondensate.

A significant increase in the content of the total amount of aromatic hydrocarbons per fraction of the onset of boiling (n. To.) And the end of boiling (to. To.) (From 70-75 to 88-90 wt.% Upon conversion of crude or selectively hydrogenated pyrocondensate was recorded. in the fraction of 150 ° C, the cc reaches 98%.

A significant decrease in the olefins of the liquid hydrocarbon fraction of the conversion product (residual content of ~ 0.5%) was recorded.

A significant decrease in the content of saturated hydrocarbons in the conversion products of both selectively hydrogenated and crude pyrocondensates was recorded. Thus, the content of cycloparaffins in the conversion product of selectively (for olefins) hydrogenated pyrocondensate decreased from 8.4 to 0.5%. The paraffin content in the conversion products in the pyrocondensate samples decreased from 15-17% to 7%, which allows us to make an assumption about the cracking and dehydrocyclization of saturated hydrocarbons.

An increase in the ratio of the sum of methyl groups to the sum of phenyl groups in the liquid conversion product to 1.5-1.7 was recorded, which allows us to state the expected increase in the yield of xylenes during subsequent processing of the liquid conversion product using transalkylation technologies.

A decrease in the content of sulfur compounds by a factor of 6 was recorded due to the conversion of sulfur compounds to hydrogen sulfide. A comparison of the sulfur content in the starting product and the conversion product is shown in the table in FIG. 3.

The off-gas of the process is a wide fraction of light hydrocarbons with a propane content in the region of 55-60% and olefins 12-15% and is a valuable chemical raw material, for example, for pyrolysis.

An increase in the efficiency of producing alkylbenzene concentrates when the ratio of the yield of aromatic hydrocarbon concentrate to the initial hydrocarbon fraction reaches 120%, but this occurs with significantly less gas generation, as well as a decrease in the cost of the catalyst due to the possibility of the absence of noble metals in it.

A comparison of the parameters of the composition of hydrocarbon feed and conversion products in the prototype and according to the invention is shown in the table in FIG. four.

Thus, in this invention the goal is achieved - increasing the efficiency of obtaining concentrates of aromatic hydrocarbons and increasing the content of alkylbenzenes, in particular xylenes.