RU2637922C2 - Method of alkylating isobutane in three-phase reactor with fixed layer of catalyst - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: butylenes are fed to each catalyst bed, and isobutane taken in excess to the top of the reactor, an alkylation reaction is carried out, the unreacted isobutane is separated and recycled, and the resulting alkyl benzene is recovered. The temperature and pressure are chosen so that the isobutane vapour is in a saturated state, and additional evaporation of the liquid in the reactor under the action of the reaction heat provides isothermal conditions for the alkylation process. The liquid flows freely without bubbling under the action of gravity at a space velocity of not more than W_max, equal to W_max=0.787D²[ε(1-ε_g)]{[ρ_f+ε_g/(1-ε_g)ρ_g]U_max}/ρ_f, and not less than W_min, equal to W_min=0.787D²[ε(1-ε_g)]{[ρ_f+ε_g/(1-ε_g)ρ_g]U_min}/ρ_f, where D is the cross section of the catalyst bed, m, ε - porosity of the catalyst bed, ε_g - the vapour content in the reactor under the reaction conditions, ρ_f - the liquid density at the reactor inlet, kg/m³, ρ_g - the vapour density in the reactor under the reaction conditions, kg/m³, - is the maximum linear velocity of the freely flowing fluid U_max, m/s, calculated from the system of equations

,

, where H is the height of the catalyst bed, m, g is the acceleration due to the gravity, m/s², Δp_lost - the lost pressure, Pa, d_p - the average particle diameter of the catalyst, m, μ - the fluid viscosity, Pa/s. The minimum linear velocity of the freely flowing fluid U_min, m/s is equal to

, where Ga is Galileo's criterion defined by the formula:

, μ - the dynamic viscosity of the liquid, Pa/s, ρ_f - the density, g/m³; d_p - the average particle diameter of the catalyst, m.

EFFECT: increasing the process stability while maintaining high catalyst activity for a long time.

1 dwg, 1 tbl, 7 dwg

Description

The invention relates to the field of catalytic chemistry and can be used in the alkylation of isobutane with olefins, in particular butylenes.

The use of three-phase catalytic reactors in a variety of chemical processes, including the petrochemical industry, is known. Three-phase reactors, in which the liquid phase is fed from top to bottom, can operate in various modes.

The irrigation mode or the jet mode, when the liquid flows downward in the form of thin films, is usually set at low rates of fluid supply and at the same time, relatively low speeds of gas directed continuously from top to bottom. With an increase in the gas supply rate and while maintaining a relatively low liquid supply rate, a drip mode is obtained. If the gas flow rate is kept relatively low and the fluid flow rate is significantly increased, then the apparatus is in the bubble (bubble) mode. With a simultaneous increase in the feed rates of both phases, a pulsating mode is obtained. These modes are characterized by very different hydrodynamic parameters, which, in particular, affect the processes of mass transfer, determine the degree of conversion and selectivity of reactions that occur in three-phase reactors (see Ullmann’s Encyclopedia of Industrial Chemistry, T. B4, pp. 309-320).

Most often, during the operation of three-phase reactors, gas is bubbled through the liquid stream, which leads to overheating and shortened catalyst life, and also does not allow to achieve high selectivity of the process.

A known method of conducting heterogeneous reactions, mainly hydrogenation and oxidation, in a gas-liquid system in a three-phase reactor with a fixed catalyst bed, where the liquid is drained by a film and eliminated overheating due to the fact that the heterogeneous catalyst particles are placed on a structured packing of plates or layers metal in such a way that they form gaps in which the ratio of the hydraulic diameter for the fluid flow through the nozzle to the equivalent diameter of the catalyst particles is in exceeded 2-20, and the catalyst particles introduced into these gaps are freely distributed in them, dropping under the action of gravity (see US 2003/106837 Al, СС 5/02, 06/12/2003).

The disadvantages of this method are that it requires special manufacture and installation in the reactor of metal nozzles of a certain shape, and therefore it is time-consuming, metal-intensive and uneconomical.

There is also known a method for carrying out chemical reactions, namely the alkylation of aromatic hydrocarbons with C ₂ -C ₄ olefins, in a three-phase reactor with a fixed catalyst bed, where the liquid falls into the space between the catalyst particles in the jet mode without sparging, which is ensured by the conditions defined by the formulas:

where ρl, ρg, ρair, ρwater are the densities of liquid aromatic hydrocarbons, olefins, air and water, kg / m ³ ;

σ, σwater - surface tension of aromatic hydrocarbons and water, N / m;

ul, ug — reduced flow rates of aromatic hydrocarbons and olefins, m / s, respectively (see EP 0776876 A, C07C 15/02, 06/04/1997).

Closest to the proposed invention is a method of alkylation of isobutane with olefins, including butylenes, in a three-phase catalytic reactor at a temperature of 40-100 ° C and elevated pressure, in which isobutane is fed to the upper section of the reactor and sequentially passed through all sections with a catalyst, and the olefin-containing the feed is fed into the catalyst sections in parallel streams, each of which is mixed with a stream of alkylating agent (isobutane: olefins ratio 1: (10-200)). The hydrocarbon stream containing unreacted isobutane and the reaction products are divided into two streams: steam, obtained by evaporation of isobutane due to the heat of reaction or supply of heat from the outside, and liquid, which is the reaction products. The steam stream is then condensed and recycled. Thanks to this technique, the process takes place in an equilibrium vapor-liquid system, which ensures approximately the same temperature over the entire height of the reactor (isothermal conditions). The pressure corresponds to the saturated vapor pressure of the reacting mixture, including taken in excess of isobutane, at the reaction temperature (USSR Author's Certificate No. 1076423 A1, class C07C 9/00, 02.28.1984).

The disadvantage of the proposed method is that in the reactor gas is bubbled through the liquid stream, which leads to instability of the flow and, consequently, an accelerated decrease in the activity of the catalyst, as well as the instability of the process as a whole.

The objective of the invention is to maintain stable activity of the catalyst during the reaction cycle and increase the stability of the process of alkylation of isobutane with butylenes.

To solve this problem, in the method of isobutane alkylation in a three-phase reactor with a fixed catalyst bed, butylene is fed to each catalyst bed and isobutane taken in excess with respect to butylene to the upper part of the reactor, the alkylation reaction is carried out at temperature and pressure, which are chosen so that isobutane vapors were in a state of saturation, and additional evaporation of the liquid in the reactor under the action of the heat of reaction provided isothermal conditions for the alkylation process, separation and return on the recycling of unreacted isobutane and the withdrawal of the obtained alkylbenzene, the liquid flows freely without sparging under the action of gravity at a space velocity of

no more than the value of W _max equal to

,

,

and not less than the value of W _min equal to

,

,

where W _max - the maximum space velocity of the flowing liquid, m ³ / s,

where W _min - the minimum space velocity of the flowing liquid, m ³ / s,

D is the inner diameter of the reactor, m,

ε is the porosity of the catalyst layer,

ε _g - vapor content in the reactor under the reaction conditions,

ρ _W - the density of the liquid at the inlet to the reactor, kg / m ³ ,

ρ _g - vapor density in the reactor under the conditions of the reaction, kg / m ³ ,

U _max - the maximum linear velocity of the freely flowing liquid, m / s, calculated on the basis of the system of equations:

,

,

,

,

where N is the height of the catalyst layer, m,

g is the acceleration of gravity, m / s ² ,

Δр _sweat - lost pressure, Pa,

d _p is the average particle diameter of the catalyst, m,

μ is the dynamic viscosity of the liquid, Pa / s,

U _min - the minimum linear velocity of a freely flowing liquid, m / s, equal to

,

,

where Ga is the Galileo criterion, determined by the formula:

,

,

(see El-Hisnavi A.A., Dudukovic M.P., Mills P.L. / ASC Symp. Series, 1982, v. 196, p. 431).

The reaction should proceed under isothermal conditions, which is achieved not only by evaporation of the liquid, but also by the fact that the vapors of the component taken in excess transfer thermal energy to the external heat carrier or air during condensation on the inner wall of the reactor.

In order to prevent bubbling, the volumetric velocity of the liquid should not be greater than the volumetric velocity of the beginning of flooding Volumetric velocity of the beginning of flooding, which is taken as the maximum volumetric velocity of the flowing liquid, W _max is such a value that is equal to the product of the linear velocity of free runoff and the total free volume in a fixed catalyst bed.

The expression for the volume velocity of the onset of flooding W _max (1) takes into account the fact that, firstly, the free cross section through which the liquid passes decreases by a relative value ε _g (it is assumed that the variation in the volume flow rate by ε _{g is} negligible or so that ε _{g is} kept constant), secondly, the formula does not include the total volumetric flow rate of the liquid, and W is the flow rate of that liquid that remains after vaporization in the reactor space, which can be determined through the material ball ns threads

,

,

W _w - overall flow rate, ^m3 / s.

The vapor density can be determined by the law of an ideal gas. Formula (1) can also be used when the vapor content is 0. The same dependence can be expressed in terms of the minimum diameter of the reactor

where U is the linear velocity of the freely flowing liquid, m / s.

The dependences of the diameter of the reactor on the flooding rate for isobutane at different diameters of the catalyst particles are shown in FIG. one.

The proposed technical solution is illustrated by the following examples.

Example 1

An alkylated component (isobutane) is fed into the upper part of the six-section reactor with a fixed granular catalyst bed, which is zeolite Y cylinders in REZEN-form, 5 mm high and 5 mm in diameter. Butylenes (olefins) are supplied in six parallel streams to each catalyst bed through devices that provide good mixing of the hydrocarbon stream (products of the alkylation reaction together with unevaporated isobutane) leaving the previous layer and the butylene stream. The temperature in the reaction zone is kept at 90 ° C, a pressure of 1.6 MPa, which corresponds to the equilibrium state of the vapor-liquid hydrocarbon mixture. Isobutane vapors are saturated in this case.

The quantitative ratio of the flows is established in such a way that, in the whole reactor, the calculated ratio of isobutane: butylenes is 6: 1, i.e., isobutane is taken in excess. The released heat of reaction is removed due to the evaporation of excess isobutane in each section, which ensures isothermal process conditions.

The volumetric velocity of the flowing liquid is chosen so that it is not less than W _min and not more than W _max .

The values of W _min and W _{max are} preliminarily calculated by the formulas (1) ÷ (6). In this and the following experiments, the values of W _min and W _max were calculated using these formulas using a computer program in the Microsoft Excel editor.

The liquid flows freely under the action of gravity. While maintaining the fluid velocity in the calculated sparging interval is not observed.

The hydrocarbon stream at the outlet of the reactor containing unreacted isobutane and reaction products is divided into two streams: steam, obtained by evaporation of isobutane, which is then condensed and sent for recycling, and liquid, which is the reaction products - alkylbenzene, which is removed from the reaction system.

The condensed isobutane in the form of recirculate (irrigation) is mixed with a fresh stream of isobutane and fed into the reaction zone, namely the catalyst bed. This increases the multiplicity of circulation of isobutane, and the actual ratio of isobutane: butenes at the entrance to each catalyst bed is (70-75): 1 with a total ratio of 6: 1 in the reactor.

The reaction is carried out within 24 hours

The yield of alkylbenzene to the missing butylenes is 195% of the mass.

The octane number by the motor method in its pure form is 93.6 points.

The process indicators are shown in table 1.

Example 2

An alkylated component (isobutane) is fed to the upper part of the six-section reactor with a fixed granular catalyst bed, which is zeolite X cylinders in REZEN-form, 5 mm high and 5 mm in diameter. Butylenes (olefins) are supplied in six parallel streams to each catalyst bed through devices that provide good mixing of the hydrocarbon stream (products of the alkylation reaction together with non-evaporated isobutane) leaving the previous layer and the butene-1 stream. The temperature in the reaction zone is kept at 80 ° C, pressure (1.32 MPa), which corresponds to the equilibrium state of the vapor-liquid hydrocarbon mixture. Isobutane vapors are saturated in this case. The quantitative ratio of the flows is established in such a way that, in the whole reactor, the calculated ratio of isobutane: butylenes is 6: 1, i.e., isobutane is taken in excess. The released heat of reaction is removed due to the evaporation of excess isobutane in each section, which ensures isothermal process conditions.

The volumetric velocity of the flowing liquid is chosen so that it is not less than W _min and not more than W _max .

The values of W _min and W _{max are} preliminarily calculated by the formulas (1) ÷ (6). The liquid flows freely under the action of gravity. While maintaining the fluid velocity in the calculated sparging interval is not observed.

At the outlet of the reactor containing unreacted isobutane and reaction products, additional heat is introduced into the hydrocarbon stream by supplying steam through the coil in such a way as to separate the reaction products into two streams: steam obtained by evaporation of isobutane, which is then condensed and sent for recycling and liquid, representing the reaction products - alkylbenzene, which is removed from the reaction system. This increases the multiplicity of circulation of isobutane, and the actual ratio of isobutane: butene-1 at the entrance to each catalyst bed is 1000: 1 with a total ratio of 6: 1 in the reactor. The reaction is carried out for 52 hours.

The yield of alkylbenzene to the missing butylenes is 204% of the mass.

The octane number by the motor method in its pure form is 95.2 points.

Product quality is shown in table 1.

Example 3

An alkylated component (isobutane) is fed into the upper part of the four-section reactor with a fixed granular catalyst bed, which is extrudates of an aluminum-zirconium catalyst with a diameter of 2.5 mm and a length of 3 mm. Butylenes (olefins) are supplied in four parallel streams to each catalyst bed through devices that provide good mixing of the hydrocarbon stream (products of the alkylation reaction together with non-evaporated isobutane) leaving the previous layer and the butene-1 stream. The temperature in the reaction zone is kept at 40 ° C, pressure (0.60 MPa), which corresponds to the equilibrium state of the vapor-liquid hydrocarbon mixture. Isobutane vapors are saturated in this case. The quantitative ratio of the flows is established in such a way that, in the whole reactor, the calculated ratio of isobutane: butylenes is 6: 1, i.e., isobutane is taken in excess. The released heat of reaction is removed due to the evaporation of excess isobutane in each section, which ensures isothermal process conditions.

The volumetric velocity of the flowing liquid is chosen so that it is not less than W _min and not more than W _max .

The values of W _min and W _{max are} preliminarily calculated by the formulas (1) ÷ (6). The liquid flows freely under the action of gravity. While maintaining the fluid velocity in the calculated sparging interval is not observed.

At the outlet of the reactor containing unreacted isobutane and reaction products, additional heat is introduced into the hydrocarbon stream by supplying steam through the coil in such a way as to separate the reaction products into two streams: steam obtained by evaporation of isobutane, which is then condensed and sent to and liquid, which is alkylbenzene, which is removed from the reaction system. This increases the multiplicity of circulation of isobutane, and the actual ratio of isobutane: butene-1 at the entrance to each catalyst bed is 200: 1 with a total ratio of 6: 1 in the reactor.

The reaction is carried out for 36 hours

The yield of alkylbenzene to the missed butylenes is 200% of the mass.

The octane number by the motor method in its pure form is 93.9 points.

Product quality is shown in table 1.

Example 4

An alkylated component (isobutane) is fed into the upper part of the eight-section reactor with a fixed granular catalyst bed, which is extrudates of zeolite Y in REZEN-form with a diameter of 1.2 mm and a length of 3 mm. Butylene (olefins) are supplied in eight parallel streams to each catalyst bed through devices that provide good mixing of the hydrocarbon stream (products of the alkylation reaction together with the non-evaporated isobutane) leaving the previous layer and the butene-1 stream. The temperature in the reaction zone is kept at 60 ° C, pressure (0.85 MPa), which corresponds to the equilibrium state of the vapor-liquid hydrocarbon mixture. Isobutane vapors are saturated in this case.

The quantitative ratio of the flows is established in such a way that, in the whole reactor, the calculated ratio of isobutane: butylenes is 6: 1, i.e., isobutane is taken in excess. The released heat of reaction is removed due to the evaporation of excess isobutane in each section, which ensures isothermal process conditions.

The volumetric velocity of the flowing liquid is chosen so that it is not less than W _min and not more than W _max .

The values of W _min and W _{max are} preliminarily calculated by the formulas (1) ÷ (6). The liquid flows freely under the action of gravity. While maintaining the fluid velocity in the calculated sparging interval is not observed.

At the outlet of the reactor containing unreacted isobutane and reaction products, additional heat is introduced into the hydrocarbon stream by supplying steam through the coil in such a way as to separate the reaction products into two streams: steam obtained by evaporation of isobutane, which is then condensed and sent for recycling and liquid, which is the reaction product - alkylbenzene, which is removed from the reaction system. This increases the multiplicity of circulation of isobutane, and the actual ratio of isobutane: butene-1 at the entrance to each catalyst bed is 250: 1 with a total ratio of 6: 1 in the reactor.

The reaction is carried out for 36 hours

The yield of alkylbenzene to the missed butylenes is 200% of the mass.

The octane number by the motor method in its pure form is 94.0 points.

Product quality is shown in table 1.

Example 5

An alkylated component (isobutane) is fed into the upper part of a two-section reactor with a fixed granular catalyst bed, which is an extrudate of zeolite X in a Pd-RESEN form with a diameter of 2.0 mm and a length of 3 mm. Butylenes (olefins) are fed in two parallel streams to each catalyst bed through devices that provide good mixing of the hydrocarbon stream (products of the alkylation reaction together with non-evaporated isobutane) leaving the previous layer and the butene-1 stream. The temperature in the reaction zone is kept at 90 ° C, pressure (1.62 MPa), which corresponds to the equilibrium state of the vapor-liquid hydrocarbon mixture. Isobutane vapors are saturated in this case. The quantitative ratio of the flows is established in such a way that, in the whole reactor, the calculated ratio of isobutane: butylenes is 6: 1, i.e., isobutane is taken in excess. The released heat of reaction is removed due to the evaporation of excess isobutane in each section, which ensures isothermal process conditions.

The volumetric velocity of the flowing liquid is chosen so that it is not less than W _min and not more than W _max .

The values of W _min and W _{max are} preliminarily calculated by the formulas (1) ÷ (6). The liquid flows freely under the action of gravity. While maintaining the fluid velocity in the calculated sparging interval is not observed.

At the outlet of the reactor containing unreacted isobutane and reaction products, additional heat is introduced into the hydrocarbon stream by supplying steam through the coil in such a way as to separate the reaction products into two streams: steam obtained by evaporation of isobutane, which is then condensed and sent for recycling and liquid, representing the reaction products - alkylbenzene, which is removed from the reaction system. This increases the multiplicity of circulation of isobutane, and the actual ratio of isobutane: butene-1 at the entrance to each catalyst bed is 100: 1 with a total ratio of 6: 1 in the reactor.

The reaction is carried out for 28 hours.

The yield of alkylbenzene to the missing butylenes is 198% of the mass.

The octane number by the motor method in its pure form is 93.7 points.

Product quality is shown in table 1.

Example 6

An alkylated component (isobutane) is fed to the upper part of the ten-section reactor with a fixed granular catalyst bed, which is extrudates of zeolite X in a Ni-REZEN-form with a diameter of 2.5 mm and a length of 3 mm. Butylenes (olefins) are supplied in ten parallel streams to each catalyst bed through devices that provide good mixing of the hydrocarbon stream (products of the alkylation reaction together with unevaporated isobutane) leaving the previous layer and the butene-1 stream. The temperature in the reaction zone is kept at 100 ° C, pressure (1.70 MPa), which corresponds to the equilibrium state of the vapor-liquid hydrocarbon mixture. Isobutane vapors are saturated in this case. The quantitative ratio of the flows is established in such a way that, in the whole reactor, the calculated ratio of isobutane: butylenes is 6: 1, i.e., isobutane is taken in excess. The released heat of reaction is removed due to the evaporation of excess isobutane in each section, which ensures isothermal process conditions.

The volumetric velocity of the flowing liquid is chosen so that it is not less than W _min and not more than W _max .

The values of W _min and W _{max are} preliminarily calculated by the formulas (1) ÷ (6). The liquid flows freely under the action of gravity. While maintaining the fluid velocity in the calculated sparging interval is not observed.

The hydrocarbon stream, at the outlet of the reactor, containing unreacted isobutane and reaction products introduces additional heat by supplying steam through the coil in such a way as to separate the reaction products into two streams: steam obtained by evaporation of isobutane, which is then condensed and sent for recycling liquid, which is the reaction product - alkylbenzene, which is removed from the reaction system. This increases the multiplicity of circulation of isobutane, and the actual ratio of isobutane: butene-1 at the entrance to each catalyst bed is 500: 1 with a total ratio of 6: 1 in the reactor.

The reaction is carried out for 46 hours

The yield of alkylbenzene to the missing butylenes is 204% of the mass.

The octane number by the motor method in its pure form is 94.5 points.

Product quality is shown in table 1.

Example 7

An alkylated component (isobutane) is fed into the upper part of a three-section reactor with a fixed granular catalyst bed, which is extrudates of zeolite Y in a Pt-REZEN-form with a diameter of 1.6 mm and a length of 3 mm. Butylenes (olefins) are fed in three parallel streams to each catalyst bed through devices that provide good mixing of the hydrocarbon stream (products of the alkylation reaction together with non-evaporated isobutane) leaving the previous layer and the butene-1 stream. The temperature in the reaction zone is kept at 80 ° C, pressure (1.32 MPa), which corresponds to the equilibrium state of the vapor-liquid hydrocarbon mixture. Isobutane vapors are saturated in this case. The quantitative ratio of the flows is established in such a way that, in the whole reactor, the calculated ratio of isobutane: butylenes is 6: 1, i.e., isobutane is taken in excess. The released heat of reaction is removed due to the evaporation of excess isobutane in each section, which ensures isothermal process conditions.

The volumetric velocity of the flowing liquid is chosen so that it is not less than W _min and not more than W _max .

The values of W _min and W _{max are} preliminarily calculated by the formulas (1) ÷ (6). The liquid flows freely under the action of gravity. While maintaining the fluid velocity in the calculated sparging interval is not observed.

At the outlet of the reactor containing unreacted isobutane and reaction products, additional heat is introduced into the hydrocarbon stream by supplying steam through the coil in such a way as to separate the reaction products into two streams: steam obtained by evaporation of isobutane, which is then condensed and sent for recycling and liquid, which is a reaction product - alkylbenzene - which is removed from the reaction system. This increases the multiplicity of circulation of isobutane, and the actual ratio of isobutane: butene-1 at the entrance to each catalyst bed is 800: 1 with a total ratio of 6: 1 in the reactor.

The reaction is carried out for 42 hours

The yield of alkylbenzene to the missing butylenes is 204% of the mass.

The pure octane number by the motor method is 95.1 points.

Product quality is shown in table 1.

Example 8 (comparative)

An alkylated component (isobutane) is fed into the upper part of the six-section reactor with a fixed granular catalyst bed, which is zeolite Y cylinders in REZEN-form, 5 mm high and 5 mm in diameter.

Butylenes (olefins) are supplied in six parallel streams to each catalyst bed through devices that provide good mixing of the hydrocarbon stream (products of the alkylation reaction together with unevaporated isobutane) leaving the previous layer and the butylene stream. The temperature in the reaction zone is kept at 80 ° C, pressure (1.32 MPa), which corresponds to the equilibrium state of the vapor-liquid hydrocarbon mixture. Isobutane vapors are saturated in this case. The quantitative ratio of the flows is established in such a way that, in the whole reactor, the calculated ratio of isobutane: butylenes is 6: 1, i.e., isobutane is taken in excess. The released heat of reaction is removed due to the evaporation of excess isobutane in each section, which ensures isothermal process conditions.

They calculate W _min and W _max according to formulas (1) ÷ (6), but do not maintain the fluid velocity in these limits. The value of real volumetric fluid velocity does not reach the value of W _min . The hydrocarbon stream at the outlet of the reactor containing unreacted isobutane and reaction products is divided into two streams: steam, obtained by evaporation of isobutane, which is then condensed and sent for recycling, and liquid, which is the reaction products - alkylbenzene, which is removed from the reaction system.

The condensed isobutane in the form of recirculate (irrigation) is mixed with a fresh stream of isobutane and fed into the reaction zone, namely the catalyst bed.

This increases the multiplicity of circulation of isobutane, and the actual ratio of isobutane: butenes at the entrance to each catalyst bed is (70-75): 1 with a total ratio of 6: 1 in the reactor.

The reaction is carried out for 12 hours

The yield of alkylbenzene to the missed butylenes is 190% of the mass.

The octane number by the motor method in its pure form is 92.0 points.

The results are shown in table 1.

Example 9 (comparative)

An alkylated component (isobutane) is fed into the upper part of the six-section reactor with a fixed granular catalyst bed, which is zeolite Y cylinders in REZEN-form, 5 mm high and 5 mm in diameter. Butylenes (olefins) are supplied in four parallel streams to each catalyst bed through devices that provide good mixing of the hydrocarbon stream (products of the alkylation reaction together with non-evaporated isobutane) leaving the previous layer and the butene-1 stream. The temperature in the reaction zone is kept at 80 ° C, pressure (1.32 MPa), which corresponds to the equilibrium state of the vapor-liquid hydrocarbon mixture. Isobutane vapors are saturated in this case. The quantitative ratio of the flows is established in such a way that, in the whole reactor, the calculated ratio of isobutane: butylenes is 6: 1, i.e., isobutane is taken in excess. The released heat of reaction is removed due to the evaporation of excess isobutane in each section, which ensures isothermal process conditions.

They calculate W _min and W _max according to formulas (1) ÷ (6), but do not maintain the fluid velocity in these limits. The value of the real volumetric fluid velocity exceeds the value of W _max .

At the outlet of the reactor containing unreacted isobutane and reaction products, additional heat is introduced into the hydrocarbon stream by supplying steam through the coil in such a way as to separate the reaction products into two streams: steam obtained by evaporation of isobutane, which is then condensed and sent for recycling and liquid, representing the reaction products - alkylbenzene, which is removed from the reaction system.

This increases the multiplicity of circulation of isobutane, and the actual ratio of isobutane: butene-1 at the entrance to each catalyst bed is 200: 1 with a total ratio of 6: 1 in the reactor.

The reaction is carried out within 24 hours

The yield of alkylbenzene to the missing butylenes is 195% of the mass.

The octane number by the motor method in its pure form is 93.0 points.

Product quality is shown in table 1.

As follows from the above examples, in order to obtain satisfactory results of the process of isobutane alkylation with butylenes, it is necessary to maintain the volumetric velocity of the flowing liquid at intermediate boundaries, its permissible ones, of minimum and maximum values.

A comparison of examples 1 and 9 shows that the same yield of alkylbenzene and the same service life of the catalyst, expressed in terms of the duration of the inter-regeneration run, in the example of the prototype is provided with the ratio of isobutane: butylene at the inlet to each layer 200: 1 (in the example according to the invention the ratio is 70: 1). Thus, the required product yield and catalyst life at too high a rate of liquid dripping can be achieved only by increasing the proportion of recycling, that is, reducing the productivity of the process. The octane number in the prototype method, despite this, remains lower.

From a comparison of examples 1 and 8, in which the isobutane alkylation process is carried out under the same conditions, including an equal multiplicity of circulation, it can be seen that at an insufficient fluid velocity the octane number, catalyst service life and alkylbenzene yield fall.

It can be seen that when alkylating isobutane with butylenes according to the prototype — without maintaining the fluid velocity within the required limits — the process will become unstable. The yield and octane of the product will be inconsistent, and the catalyst will require more frequent regeneration.

The alkylation of isobutane by the proposed method provides an increase in process stability while maintaining high catalyst activity for a long time.

Claims (24)

A method of alkylating isobutane in a three-phase reactor with a fixed catalyst bed, comprising supplying butylene to each catalyst bed and isobutane taken in excess with respect to butylene to the upper part of the reactor, carrying out an alkylation reaction at a temperature and pressure that is selected so that the isobutane vapors are in a state of saturation, and additional evaporation of the liquid in the reactor under the action of the heat of the reaction provided isothermal conditions for the alkylation process, separation and return to recycling react isobutane and outputting the resulting alkylbenzene, characterized in that the liquid flows freely without bubbling under gravity at a flow rate component no more than the value of W _max equal to W _max = 0.787D ² [ε (1-ε _g )] {[ρ _W + ε _g / (1-ε _g ) ρ _g ] U _max } / ρ _W , and not less than the value of W _min equal to W _min = 0.787D ² [ε (1-ε _g )] {[ρ _W + ε _g / (1-ε _g ) ρ _g ] U _min } / ρ _W , where W _max - the maximum space velocity of the flowing liquid, m ³ / s, where W _min - the minimum space velocity of the flowing liquid, m ³ / s, D is the inner diameter of the reactor, m, ε is the porosity of the catalyst layer, ε _g - vapor content in the reactor under the reaction conditions, ρ _W - the density of the liquid at the inlet to the reactor, kg / m ³ , ρ _g - vapor density in the reactor under the conditions of the reaction, kg / m ³ , U _max - the maximum linear velocity of a freely flowing liquid, m / s, calculated on the basis of the system of equations

where N is the height of the catalyst layer, m, g is the acceleration of gravity, m / s ² , Δр _sweat - lost pressure, Pa, d _p is the average particle diameter of the catalyst, m, μ is the dynamic viscosity of the liquid, Pa / s, U _min - the minimum linear velocity of a freely flowing liquid, m / s, equal to

where Ga is the Galileo criterion, determined by the formula

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