RU2411078C1 - Method of producing gas-fluid reactions in sub- and supercritical fluid - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to continuous gas-fluid reactions in high-pressure tubular reactor. Proposed method comprises feeding, at least, one fluid reagent by gas reagent flow feeder 2, and, not obligatorily, by feeder 3. Note here that, at least, one initial flow is fed at supercritical pressure. It comprises also heating, at least, one said flow by heater 4 connected with feeder and combining said flows in jet mixer 5. Obtained gas-fluid mix reacts in direct-flow tubular reactor in, in fact, adiabatic conditions. Reaction mix flow is throttle via reducing device 7 into evaporating separator 8 at lower pressure with stripping gas flow comprising, mainly, low-boiling components from top part of evaporating separator 8, and liquid flow comprising, mainly, high-boiling components from bottom part of said evaporating separator 8. Note here that said flows are heated to temperature that allows interaction reaction in supercritical fluid. Aforesaid flows are combined in jet mixer 5 with gas-fluid mix rate of 10-350 m/s. Note here that time whereat combination occurs makes less than 1 second. Obtained gas-fluid mix interacts in direct-flow tubular reactor 6 that drastically reduces liner rate of said gas-fluid mix to 0.01-10 m/s. Note also that time whereat said interaction occurs makes less than 600 seconds.

EFFECT: higher reaction rate and target product yield.

25 cl, 3 ex, 1 dwg

Description

Technical field

The invention relates to a method for carrying out gas-liquid reactions in a once-through high-pressure tubular reactor in a sub- and supercritical fluid, in particular for carrying out hydrogenation, oxidation, amination, nitration, chlorination, fluorination, carbonization processes and can be used in chemical, petrochemical, food, perfumery - cosmetic, pharmaceutical and other industries.

State of the art

There is a method of mass transfer and reaction processes in liquid-liquid and liquid-gas systems, which consists in feeding the initial mixture into channels parallel to each other, made with a periodically changing cross section, while the continuous medium is fed continuously and the dispersed medium is periodically repetitive pulses (RU 2342990). The disadvantage of this reactor design is the low degree of dispersion of the gas in the liquid.

A known method of chemical reactions in supercritical fluids (options) and a method of creating local regular seals (RU 2182037). The disadvantage of this method is the periodic introduction of organic compounds into the volume of supercritical fluid and the withdrawal of reaction products.

Known gas-liquid reactor containing a vertical cylindrical body with two nozzles for introducing liquid reagents and a nozzle for introducing a gaseous reagent located in the lower part of the reactor, a nozzle for withdrawing reaction products located in the upper part of the reactor, and a cap mixing device located above the nozzle for introducing reagents (SU 1088779 ) The disadvantage of this reactor design is the low intensity of mixing of the reagents due to poor turbulence of the stream at the outlet of the mixer.

A gas-liquid reactor is known, comprising a vertical cylindrical body with nozzles for introducing liquid and gaseous reagents, a nozzle for withdrawing reaction products and a nozzle for discharging exhaust gases and a distribution device for supplying a gaseous reactant located in the lower part of the reactor (SU 1648544). The disadvantage of this reactor design is the uneven distribution of the reactants in the liquid volume and the insufficient degree of dispersion of the gas in the reactor due to the separate input of the reactants.

Known gas-liquid reactor containing a vertical cylindrical body, inside which a dividing wall is mounted with a device for condensing heavy hydrocarbons from oxidation exhaust gases mounted on it, a cavitation-vortex apparatus made in the form of a mixing and foam chambers interconnected by a narrowing nozzle, technological pipes : pipe for introducing raw materials into the cavitation-vortex apparatus in the form of a nozzle with a cavitation ring located along the axis of the mixing chamber, tained tangentially inlet for air supply pipe for the finished output oxidized product disposed side reactor (RU 2381155). The disadvantage of this apparatus design is the uneven distribution of gas in the liquid volume and over the cross section of the monolithic catalyst.

A known apparatus for conducting gas-liquid catalytic reactions, comprising a long-form housing with a monolithic catalyst installed in it, arranged in the form of several successively installed tiers, nozzles for introducing gas and liquid into the housing, a device for the primary dispersion and distribution of gas over the apparatus cross-section with those installed in the housing between the tiers of a monolithic catalyst, devices for additional dispersion and distribution of gas over the cross section of the apparatus, made in the form of one sludge and several series-connected Venturi tubes or in the form of an impeller (RU 2348451). The disadvantage of this apparatus design is the insufficiently efficient mass transfer of gas with liquid.

Closest to the technical nature of the proposed method is a method for continuously conducting a heterogeneous chemical process in an adiabatic tube reactor at supercritical pressure (application 2006134901). The disadvantages of this method are the low degree of dispersion of the gas in the liquid and the inability to use a solid catalyst.

SUMMARY OF THE INVENTION

An object of the invention is the development and description of a method for the continuous implementation of gas-liquid reactions in sub- and supercritical fluid. The technical result achieved by the invention is to increase the efficiency of mass transfer and reaction processes, which is expressed in a significant increase in the reaction rate, yield of the target product, decrease in the formation of side compounds and increase the specific productivity of the installation. The proposed method for the continuous implementation of gas-liquid reactions provides a high level of stability and controllability of all given process parameters.

The above technical result is achieved in that in a method for continuously carrying out gas-liquid reactions in a sub- and supercritical fluid, comprising supplying at least one source stream of a liquid reactant by means of its supply, at least one source stream of a gaseous reactant by means of its supply and, optionally, an initial solvent stream by means of its supply, wherein at least one initial stream is supplied with supercritical pressure; heating at least one of the specified stream means for heating it, connected by a line with means for feeding it; combining these streams in a jet mixer; the reaction of the resulting reaction mixture in a straight-through tube reactor, essentially under adiabatic conditions; throttling the flow of the reaction mixture through a reducing device into a lower-pressure evaporator separator, stripping off the gas stream containing predominantly low boiling components from the upper part of the evaporator separator and a liquid stream containing predominantly high boiling components from the lower part of the evaporator separator; flow below the supercritical fluid pressure to form a gas phase and conduct e rapid reaction of the interaction of the obtained gas-liquid mixture occurs, at least during the phase transition of the gas phase into a supercritical fluid with the formation of reaction products.

It is known that in addition to the three aggregate states of a substance (solid, liquid and gaseous), there is another state - supercritical fluids, in which the substance has unique properties, such as low viscosity and solubility, are an order of magnitude greater than traditional solvents.

The high compressibility of supercritical media in comparison with an ideal gas provides a strong change in the density of the medium at small pressure changes, which in turn allows one to well regulate the solvation ability. In the supercritical state, the diffusion coefficients are very large, and the resistance to mass transfer is practically absent, so that all conditions for the rapid occurrence of gas-liquid reactions are ensured. Subcritical (subcritical) fluid is formed at a temperature below the critical point by 10-15 ° C, and supercritical fluid is formed in a state in which the pressure and temperature exceed the critical parameters. Lowering the temperature below the critical point removes the substance from the supercritical state to the liquid state, and lowering the pressure below the critical point removes the substance from the supercritical state to the gaseous state.

Most gas-liquid reactions are poorly controlled and produce a wide range of products. The poor solubility of gaseous reagents, such as hydrogen, fluorine, chlorine, ammonia, in most organic compounds leads to a low rate of their attachment to multiple bonds under the conditions of a heterogeneous reaction in a gas-liquid system.

In supercritical fluid, gaseous reagents dissolve perfectly, for example, for hydrogen and nitrogen, soluble in such media, it is possible to achieve concentrations 10-20 times higher than in conventional solvents. As a supercritical fluid (reaction medium, supercritical solvent) for the implementation of gas-liquid reactions, carbon dioxide is used predominantly, possibly nitric oxide, ethylene, ethane, ammonia, water or other suitable substances. Most commonly used supercritical media form a non-oxidizing and non-destructive atmosphere for thermally unstable compounds due to their inertness and low reaction temperature.

A substance in a supercritical state can act not only as a supercritical solvent, but also as a reagent or catalyst. The combination of supercritical carbon dioxide and a nanosized catalyst, mounted on a solid support, brings significant advantages to the implementation of the catalytic process, which will allow you to do without the use of organic solvents.

Carbon dioxide turns into a supercritical fluid at a pressure of more than 7.3 MPa and a temperature of more than 31 ° C. The attractiveness of supercritical carbon dioxide for chemical technology is determined by its low cost and environmental safety for chemical reactions.

As the liquid reagent, any organic compound is used. As the gaseous reagent, hydrogen, ammonia, oxygen, fluorine and other suitable substances used for carrying out chemical reaction reactions are used.

To enable reactions in a supercritical fluid, it is necessary that, after a sharp decrease in the velocity of the gas-liquid mixture in the tubular reactor, at least one initial reagent is in a supercritical state, for which at least one initial reagent is fed with supercritical pressure and heated to supercritical temperature.

In the proposed invention, a fast stage of combining the starting reagents using a jet mixer is separated under conditions of a significant level of turbulence and a relatively slow stage of direct interaction of the gas-liquid mixture in a direct-flow tubular reactor of ideal displacement in a supercritical fluid of low density. Together, this will increase the degree of dispersion of the gas and significantly intensify the mixing of the starting reagents. Combining the flows of liquid and gaseous reagents is carried out in a jet mixer with an axisymmetric turbulent mode of motion under conditions of high molecular dispersion of the reagents, as a result of the combined action of molecular diffusion, which provides instant interaction of the gas-liquid mixture without a significant induction reaction period. The intensification of mixing of the flow of reagents and increasing the degree of dispersion of the gas is achieved by ensuring their movement in the jet mixer with high speed, due to which there is a partial conversion of the potential pressure energy into the kinetic energy of the translational motion of the gas-liquid mixture. As a result of the occurrence of sufficiently large accelerations of the flow, as well as a powerful shear field, a rapid and effective dispersion of gas occurs. The high axial mixing rate of the gas-liquid mixture and, accordingly, the decrease in the flow pressure in the jet mixer creates the conditions for the evaporation of the supercritical fluid and the formation of a finely dispersed structure of gas bubbles with a size of about 0.5-10 microns. The droplet size control is provided by the nozzle design and the gas-liquid mixture flow rate. Thus, at least a partial phase transition of the fluid from the supercritical state to the gas phase takes place in the jet mixer, while the diffusion resistance, which prevents the transfer of reagents through the contact surface of the phases, is significantly reduced. As a result of the direct-flow movement of the flow at high speed, a stable gas-liquid flow with a finely dispersed structure is formed at the outlet of the jet mixer, which uniformly fills the entire cross section of the tubular reactor. An increase in the interfacial contact surface simultaneously leads to an exponential increase in the rate constant and the overall reaction rate due to the replacement of slow molecular diffusion by turbulent (convective).

The reactor is an apparatus made in the form of a vertical pipe, at the entrance to which the specified jet mixer is located. The use of a straight-through cylindrical reactor instead of a capacitive one will make it possible to accept ultra-high working pressures, which will significantly increase the reaction rate and, accordingly, reduce the residence time of the reaction mixture. The maximum working pressure of the tubular reactor is essentially limited only by the technical characteristics of the feed means for the initial reagents.

A sharp decrease in the speed of the gas-liquid mixture in the tubular reactor creates the conditions for condensation of the gas phase, as a result of which the gas bubbles instantly collapse. This process, called cavitation, leads to the formation of local zones in a supercritical fluid with high temperature and pressure, under the influence of which the molecules become excited and the chemical bonds of the molecules are broken, forming atoms and radicals. The high pressure of the gas-liquid reaction contributes to a more frequent collision of dispersed particles and a decrease in activation energy, depending on the type and nature of the process. Thus, in a tubular reactor, essentially a homogeneous reaction mixture is formed, in which, under a continuous mode of motion, the reactants react chemically in a supercritical fluid.

Chemical interaction occurs when the reaction mixture moves in a downward or upward piston flow in the diffusion region inside each particle, each of which is essentially a separate thermodynamically stable system.

When the reaction mixture interacts in the reaction zone of the tubular reactor, a thermal explosion occurs, i.e. due to the thermal effect of the autothermal reaction, the temperature of the reaction mixture rises sharply. The necessary degree of conversion of the gas-liquid reaction is completely completed essentially in a time of less than 10 minutes.

After the reaction, the reaction mixture is sharply discharged through a reducing device into an evaporation separator with a lower pressure, where due to a sharp decrease in the density of the reaction mixture and the heat of vaporization of supercritical fluid, the reaction mixture is instantly cooled. Rapid cooling of the reaction mixture in an evaporation separator due to the evaporation of volatile gases will also eliminate undesirable interactions of reaction products. When throttling under the influence of initial perturbations and aerodynamic drag forces, the jet decomposes into small droplets, which intensifies the rapid evaporation of low-boiling reaction components.

To achieve the required temperature, a solvent can be supplied in front of the reducing device. The solvent also allows you to effectively free the reaction products from impurities and unreacted reagents.

A gas stream containing predominantly low boiling components, as well as a solvent (when supplied), which is recycled, is taken from the upper part of the evaporative separator. A liquid stream is selected from the bottom of the evaporator separator, which contains predominantly high boiling components, which are isolated in a known manner. Further purification of the desired reaction products in a distillation column is possible.

To ensure the required temperature in the evaporator separator, additional cooling of the evaporator separator or cooling of the gas stream at the outlet of the evaporator separator is possible.

Carrying out the reactions of interaction of organic compounds in sub- and supercritical carbon dioxide will significantly reduce the temperature of the process, which will maximize the selectivity of the process. Lowering the temperature in such systems suppresses side processes, usually characterized by a higher activation energy. When using a solid catalyst, periodic regeneration of the catalyst by a supercritical solvent, for example carbon dioxide, is possible.

The main feature of gas-liquid reactions occurring in a sub- and supercritical fluid is that the energy for initiating the process is drawn from the system itself, and not supplied from an additional source, as is typical for initiated reactions. The adiabatic regime allows the efficient use of the heat of the reactions themselves, both to maintain the temperature process and to compensate for the energy costs of heating the starting reagents.

The proposed method for the continuous implementation of gas-liquid reactions in a once-through tubular reactor has several distinctive essential features (design features):

- first carry out the separate supply of at least one source stream of a liquid reagent feed means (1), at least one source stream of a gaseous reactant feed means (2) and, optionally, the initial solvent stream feed means (3), moreover, at least one feed stream is supplied with supercritical pressure;

- then carry out heating of at least one of the specified stream, for example, the flow of a liquid reagent by means of heating (4), connected by a line with a means of supply, to a temperature that ensures, when these flows are combined, an interaction reaction proceeds in a supercritical fluid, and heating of the starting reagents produced using external heat exchange, exposure to electric or electromagnetic fields;

- then combine the specified stream of liquid reagent, the specified stream of gaseous reagent and, optionally, the specified stream of solvent in the jet mixer (5), with a linear velocity of the gas-liquid mixture equal to 10-350 m / s, preferably 14-100 m / s, providing pressure joint turbulent outflow below the supercritical pressure of the fluid during which at least a partial transition of the supercritical fluid into the gas phase occurs, and the period of time during which the specified combination is essentially y is less than 1 second, preferably less than 0.1 seconds;

- then carry out the interaction of the obtained gas-liquid mixture in a straight-through tubular reactor (6), in which the linear velocity of the gas-liquid mixture is sharply reduced to 0.01-10 m / s, preferably to 0.02-0.5 m / s, providing at least a partial transition of the gas phase into a supercritical fluid, with the formation of a homogeneous reaction mixture, the period of time during which this interaction is carried out with the formation of reaction products, essentially less than 600 seconds, preferably less than 300 ekund, particularly preferably less than 120 seconds;

- then throttle the specified stream of the reaction mixture through a reducing device (7) into an evaporation separator (8) with a lower pressure, and at the same time, the supercritical fluid pressure in the reaction zone of the tubular reactor (6) is maintained by the degree of opening of the reducing device (7), after which the gas stream is diverted containing predominantly low boiling components from the upper part of the evaporator separator (8) and a liquid stream containing mainly high boiling components from the lower part of the evaporative separator (8);

- the jet mixer (5) is made essentially in the form of a cylindrical pipe with a length of at least three equivalent diameters, having at least one inlet for the flow of liquid reagent, connected by a corresponding line to the supply means through the heating means (4), at least , one inlet for the flow of the gaseous reactant connected by a suitable line to the supply means (2), optionally, through the heating means, at least optionally, one inlet for the flow of solvent is connected a corresponding line with the supply means (3), optionally, through the heating means and one outlet for the gas-liquid mixture, connected to the internal cavity of the tubular reactor (6);

- the tubular reactor (6) is made essentially in the form of a hollow cylindrical high-pressure housing, the distance between the cylindrical surfaces of which does not exceed 150 mm, optionally filled with a fixed catalyst layer, closed at one end by a lid through which the cylindrical pipe of the jet mixer (5) is passed for the gas-liquid mixture flow, and at the other end closed by the bottom, having at least one outlet for the reaction mixture flow, while the tubular reactor (6) contains at least one measuring means for controlling the temperature and at least one measuring means for controlling the pressure and at least one means for regulating the reducing device (7) operably connected with said measuring means for controlling the pressure and the reducing device (7);

- the reducing device (7) contains a control valve or control nozzle connected by a line to the outlet of the tubular reactor (6) and to the evaporation separator (8) so that the cone angle of the reducing device (7) is made in the range from about 30 to 180 ° preferably from 90 to 140 °;

- the evaporation separator (8) is connected to the reducing device (7) so that the cone of the jet of the reducing device (7) is in the evaporation separator (8) and having at least one first gas flow outlet in the upper part containing predominantly low-boiling components, and in the lower part, at least one second outlet for liquid flow, containing mainly high-boiling components, moreover, an evaporator separator (8) or a gas stream at the outlet of the evaporative separator torus (8) is further cooled;

- in order to reduce the temperature in front of the reducing device (7), a stream of solvent, possibly carbon dioxide, optionally in a supercritical state, is added to the stream of the reaction mixture, the temperature in the evaporation separator (8) being controlled depending on the flow of the specified solvent stream to the stream of the reaction mixture wherein said solvent stream is recycled.

Brief Description of the Drawings

The invention is disclosed in a flow chart for the continuous implementation of gas-liquid reactions in a sub- and supercritical fluid, including means for supplying (1) a stream of liquid reagent, means for supplying (2) a stream of gaseous reagent, means for supplying (3) a stream of solvent, heating means (4) a stream of liquid reagent, a jet mixer (5), a tubular reactor (6), a reducing device (7) and an evaporative separator (8).

The main structural element is a tubular reactor (6), having the form of a cylindrical hollow high-pressure casing, closed at one end with a cap through which the cylindrical pipe of the jet mixer (5) is passed, and closed at the other end with a bottom having an outlet for the flow of the reaction mixture. The jet mixer (5) has three inlet openings connected by respective lines to the supply means (1) of the liquid reagent stream through the heating means (4), to the supply means (2) of the gaseous reagent stream, to the supply means (3) of the solvent stream and one outlet an opening for a gas-liquid mixture connected to the internal cavity of the tubular reactor (6). The tubular reactor (6) also contains measuring means for monitoring temperature and pressure.

The technological process for the continuous implementation of gas-liquid reactions is as follows. The initial flows of the solvent, liquid and gaseous reagents are fed by means of supply (1, 2, 3), respectively, to the jet mixer (5), where these reagents are mixed. Before mixing, at least one source duct is heated to supercritical temperature.

In a tubular reactor (6), the linear velocity of the reaction medium is instantly reduced and the chemical reaction of the specified reaction mixture is carried out with the formation of reaction products. The supercritical fluid pressure in the reaction cavity of the tubular reactor (6) is supported by a reducing device (7), the degree of opening of which is determined by a measuring means for controlling the pressure of the tubular reactor (6). After the reducing device (7), the reaction mixture stream is throttled to the evaporation separator (8), where the reaction mixture is separated into a gas stream containing predominantly low boiling components, which is removed from the upper part of the evaporator separator (8), and a liquid stream containing mainly high boiling components which is withdrawn from the bottom of the evaporation separator (8).

The implementation of the invention

Example 1. Obtaining cyclopentene.

Cyclopentadiene, hydrogen and carbon dioxide are supplied separately by means of supply (1, 2, 3), providing pressure from 12 to 15 MPa. Cyclopentadiene and carbon dioxide are preheated by means of heating to 50 ° C. The combination of flows is carried out in a jet mixer (5), where a linear flow velocity of 35 m / s is provided. Hydrogenation is carried out in the reaction zone of the tubular reactor (6) at a pressure of from about 12 to 15 MPa, a temperature of not more than 60 ° C, a residence time of about 60 to 180 seconds, the molar ratio of hydrogen and CPD is from 1.2: 1 to 1.8 :one. After the reactor (6), the reaction mixture passes through a reducing device (7) to a separator (8), where the reaction mixture is cooled due to a sharp pressure drop due to an increase in gas volume. Evaporated carbon dioxide is recycled.

The yield of cyclopentene is approximately 90-95%.

Example 2. Obtaining aniline.

Nitrobenzene, hydrogen and carbon dioxide are supplied separately by means of supply (1, 2, 3), providing a pressure from 5 to 10 MPa. Nitrobenzene and carbon dioxide are preheated to 40-50 ° C. The combination of flows is carried out in a jet mixer (5), where a linear flow velocity of 50 m / s is provided. The oxidation is carried out at a pressure of 5 to 10 MPa, a residence time of 60 to 180 seconds. As a result of the reduction reaction in a slightly acidic medium at pH 3-4, the reaction product is aniline.

The yield of aniline is approximately 95-98%.

Example 3. Obtaining ethylene oxide.

Ethylene, oxygen and carbon dioxide are fed separately by means of supply (1, 2, 3), providing pressure from 5 to 10 MPa. Ethylene and carbon dioxide are preheated to 150-350 ° C. The combination of flows is carried out in a jet mixer (5), where a linear flow velocity of 80 m / s is ensured. The reaction is carried out at a pressure of from 5 to 10 MPa, a residence time of from 60 to 180 seconds.

The yield of ethylene oxide is approximately 75-85%.

These examples do not limit the use of this invention.

Claims (25)

1. A method for continuously conducting gas-liquid reactions in a sub- and supercritical fluid, comprising supplying at least one feed stream of a liquid reactant with a feed (1), at least one feed stream of a gaseous reactant with a feed (2) and, optionally, an initial solvent stream by a supply means (3), wherein at least one initial stream is supplied with supercritical pressure; heating at least one of said streams with heating means (4) connected by a line to the supply means; combining these streams in a jet mixer (5); the reaction of the obtained gas-liquid mixture in a straight-through tubular reactor, essentially under adiabatic conditions; throttling the flow of the reaction mixture through a reducing device (7) into an evaporator separator (8) with lower pressure, with a gas stream containing mainly low boiling components distilled from the top of the evaporator separator (8) and a liquid stream containing mainly high boiling components , from the bottom of the evaporation separator (8), characterized in that
a) heating of these streams is carried out to a temperature which ensures that when these flows are combined, the reaction proceeds in a supercritical fluid;
b) combine the specified stream of liquid reagent, the specified stream of gaseous reagent and, optionally, the specified stream of solvent in the jet mixer (5), with a linear velocity of the gas-liquid mixture of 10-350 m / s, and the period of time during which the specified combination substantially less than 1 s;
c) the interaction of the obtained gas-liquid mixture is carried out in a straight-through tube reactor (6), in which the linear velocity of the specified gas-liquid mixture is sharply reduced to 0.01-10 m / s, and the period of time during which the specified interaction is carried out with the formation of reaction products substantially less than 600 s. 2. The method according to claim 1, characterized in that cyclopentadiene, nitrobenzene, ethylene are used as the liquid reagent. 3. The method according to claim 1, characterized in that hydrogen, ammonia, oxygen, fluorine are used as the gaseous reactant. 4. The method according to claim 1, characterized in that the solvent used is carbon dioxide, possibly nitric oxide, ethylene, ethane, ammonia, water. 5. The method according to claim 1, characterized in that the starting reagents are heated using external heat exchange, by the action of an electric or electromagnetic field. 6. The method according to claim 1, characterized in that the jet mixer (5) is made essentially in the form of a cylindrical pipe with a length of at least three equivalent diameters. 7. The method according to claim 1, characterized in that the linear velocity in the jet mixer (5) is preferably 14-100 m / s. 8. The method according to claim 1, characterized in that the time period for combining the flows in the jet mixer (5) is preferably less than 0.1 s. 9. The method according to claim 1, characterized in that the tubular reactor (6) is made in the form of a hollow cylindrical high-pressure housing. 10. The method according to claim 1, characterized in that the linear velocity in the tubular reactor is preferably 0.02-0.5 m / s. 11. The method according to claim 1, characterized in that the period of time for the formation of reaction products in the tubular reactor (6) is preferably less than 300 s, particularly preferably less than 120 s. 12. The method according to claim 9, characterized in that the distance between the cylindrical surfaces of the tubular reactor (6) does not exceed 150 mm 13. The method according to claim 9, characterized in that the tubular reactor (6) contains a fixed catalyst layer. 14. The method according to claim 9, characterized in that the tubular reactor (6) contains at least one measuring means for temperature control. 15. The method according to claim 9, characterized in that the tubular reactor (6) contains at least one measuring means for monitoring pressure and at least one means for regulating the reducing device (7), functionally associated with said measuring means and a reducing device (7). 16. The method according to claim 1, characterized in that the reducing device (7) contains a control valve connected by a line to the outlet of the tubular reactor (6). 17. The method according to claim 1, characterized in that the reducing device (7) contains a control nozzle connected by a line to the outlet of the tubular reactor (6). 18. The method according to claim 1, characterized in that the evaporation separator (8) is connected to the reducing device (7) so that the cone of the jet of the reducing device (7) is in the evaporation separator (8). 19. The method according to claim 1, characterized in that the reducing device (7) is made with a cone angle of the jet in the range from about 30 to 180 °, preferably from 90 to 140 °. 20. The method according to claim 1, characterized in that the degree of opening of the reducing device (7) maintains supercritical fluid pressure in the reaction zone of the tubular reactor (6). 21. The method according to claim 1, characterized in that a solvent stream is added to the stream of the reaction mixture before the reducing device (7). 22. The method according to claim 20, characterized in that the solvent stream is recycled. 23. The method according to claim 20, characterized in that the temperature in the evaporation separator (8) is controlled depending on the flow of the solvent stream to the stream of the reaction mixture. 24. The method according to claim 1, characterized in that the evaporator separator (8) or the gas stream at the outlet of the evaporator separator (8) is further cooled. 25. The method according to item 13, wherein the catalyst is regenerated by a supercritical solvent.