RU2147568C1 - Method of preparing alkylgasoline - Google Patents

Abstract

FIELD: petroleum processing and petrochemical industries. SUBSTANCE: isobutane is alkylated with olefins in the presence of sulfuric acid. Mixture of alkylgasoline and unreacted isobutane is fed to the top of deisobutanization column, and stable C₄ isomerizate is fed to bottom of said column in amount of 10-25 vol % of amount of reaction mixture. Stable isomerizate containing, vol %: isobutane, 25-55; n-butane, 45-75 at pressure of 7-8 MPa and temperature at top, 50-55 C and 85-90 C at bottom, and there occurs separation of isobutane recycled into alkylation reactor. Fraction containing alkylgasoline and n-butane is withdrawn from deisobutanization column bottom and this mixture is fed into debutanization column to separate n-butane fraction from alkylgasoline which is together with n-butane fraction is heated in furnace to temperature of 200-430 C and is isomerized in the presence of catalyst comprising 0.40-0.55 wt % of platinum, 3-7 wt % of halogen on aluminium oxide carried at pressure of 2.0-3.5 MPa, volumetric stock rate of 1-2 h^-1. After separation of hydrogen-containing gas from unstable C₄ isomerizate, the latter is directed to stabilization column in which becomes stable and is recycled to deicobutanization column and then into alkylation reactor. EFFECT: increased yield of alkyl gasoline. 3 ex, 1 tbl

Description

 The invention relates to chemical technology, in particular to methods for producing alkylbenzene by alkylation of isoparaffins with olefins and can be used in the refining and petrochemical industries.

 One of the main processes aimed at obtaining high-octane gasoline components is the process of sulfuric acid alkylation of isoparaffins with olefins.

A known method of alkylation of isoparaffins with olefins by carrying out the reaction in a horizontal reactor with internal cooling. Most often, isobutane from gas fractionation units (HFCs) and a butane-butylene fraction from catalytic cracking units, which together with circulating sulfuric acid enter the reactor, are used as the raw material of this process. In the entire reactor volume, isobutane and other hydrocarbons are in a liquid state and, with the help of stirrers, circulate intensively in the apparatus, as a result of which a large active contact surface of reacting hydrocarbons with the catalytic complex is formed. Reaction conditions: temperature 2-7 ^o C, the ratio of isobutane: olefins in the stream entering the reactor is not less than 5 1, the acid concentration in the reactor is more than 85 wt.% (Refinery Handbook. Edited by G.A. Lastovkin et al., L., Chemistry, 1986, c. 167-171.)
The disadvantage of this method is that the yield of alkylbenzene is lower than possible due to the reduced ratio of isobutane to butylenes in the reaction zone.

The closest solution in technical essence and the achieved results is a method for producing alkylbenzene by alkylating isoparaffins with olefins in the presence of sulfuric acid using isobutane and butane-butylene fraction (BBP) as a raw material. Fresh and recycle isobutane, together with BBP and sulfuric acid, enter a horizontal reactor, in the entire volume of which hydrocarbons are in a liquid state and intensively circulate with the help of stirrers in the apparatus. Reaction conditions: temperature 2-7 ^o C, the ratio of isobutane: olefins in the inlet stream of at least 5: 1, the acid concentration in the reactor is more than 90 wt.%. The reaction mixture, consisting of acid, unreacted isobutane and alkylbenzene, after settling the spent acid, acid and alkaline cleaning, is sent to separation in a deisobutanization column to separate isobutane, which is then mixed with the isobutane fraction with HFC and after cooling is sent to the alkylation reactor. (Dorogochinsky A.3. Et al. Sulfuric acid alkylation of isoparaffins with olefins. M., Chemistry, 1970, p.216.)
The disadvantage of the method adopted for the prototype is the insufficiently high yield of alkylbenzene, which is most often caused by the insufficient amount of isobutane in the reaction mixture due to the limited resources at the plants in the form of the isobutane fraction of the HFC unit and the butane-butylene fraction (BBF) of the catalytic cracking unit.

 The aim of the invention is to increase the yield of alkylbenzene.

This goal is achieved by the method according to which a mixture of alkylbenzene and unreacted isobutane is fed to the top of the deisobutanization column, stable C ₄ isomerizate composition, vol.%: Isobutane 25-55 is supplied in the amount of the reaction mixture in the amount of 10-25% by volume of the reaction mixture. , n-butane 45-75, at a pressure of 7-8 MPa and temperature, ^o C: top 50-55, bottom 85-90, isobutane is separated off and returned to the alkylation reactor; from the bottom of the deisobutanization column, a fraction containing alkylbenzene and n-butane is withdrawn, which is fed to the debutanization column to separate the n-butane fraction, which, together with the n-butane fraction of HFCs, is then heated in an oven to a temperature of 200-430 ^° C and isomerized in the presence of a catalyst containing 0.40-0.55 wt.% platinum, 3-7 wt. % of halogen on an aluminum oxide carrier, at a pressure of 2.0 - 3.5 MPa, a volumetric feed rate of 1 - 2 h ^-1 , then, after separation of the hydrogen-containing gas from the unstable C ₄ isomerizate, the latter is sent to a stabilization column, where at a pressure of 7 - 8 MPa and temperature, ^o C: top 40-50, bottom 80-90 it is stabilized, followed by return to the deisobutanization column and then to the alkylation reactor.

 The method of producing alkylbenzene according to the proposed technical solution allows to increase the amount of isobutane supplied to the alkylation reactor and increase the yield of alkylbenzene.

A significant distinguishing feature of the proposed method compared to the method adopted for the prototype is the countercurrent contacting of a mixture of alkylbenzene and unreacted isobutane fed to the top of the deisobutanization column with stable C ₄ isomerizate fed to the lower part of this column in an amount of 10-25 vol.% Of the amount of the reaction mixture and the isomerization of n-butane separated on the debutanization column from alkylbenzene.

 Thus, the claimed method meets the criteria of the invention of "novelty."

The method is as follows. The high-octane component of gasoline (alkylbenzene) is obtained by alkylation of isobutane with olefins in the reactor block of a sulfuric acid alkylation unit (SCA) in the presence of sulfuric acid in a horizontal reactor with internal cooling. Reaction conditions: temperature 2-7 ^o C, the ratio of isobutane: olefins in the stream entering the reactor at least 5: 1. The reaction mixture, consisting of acid, unreacted and fresh isobutane and alkylbenzene, is sent after the spent acid has settled, acid and alkaline cleaning for separation at the top of the deisobutanization column. Stable C ₄ isomerizate _{of the} composition, vol.%: Isobutane 25-55, n-butane 45-75 obtained on the isomerization unit, in an amount of 10-25 vol.% Of the amount of the reaction mixture, is fed to the bottom of this column. As a result of countercurrent contacting of these flows at a pressure of 7-8 MPa and temperature, ^o C: top 50-55, bottom 85-90, a more distinct separation of isobutane occurs, which is discharged by the top of the deisobutanization column and, together with the isobutane fraction of HFCs, is sent to the reactor after cooling alkylation.

From the bottom of the deisobutanization column, a fraction containing alkylbenzene and n-butane is withdrawn, which is fed to the debutanization column to separate the n-butane fraction from the alkylbenzene at a pressure of 3.5-5 MPa and temperature, ^o C: top 35-45, bottom 120-130 . Alkylbenzene is removed from the cube of the debutanization column to the finished product park as a high-octane component for the preparation of marketable gasolines.

The n-butane fraction — the top of the debutanization column — is mixed with the n-butane fraction with HFCs, heated in an oven) to a temperature of 200-430 ^° C and isomerized in a reactor in the presence of a catalyst containing 0.40-0.55 wt.% Platinum , 3-7 wt.% Halogen and alumina - the rest is up to 100%, at a pressure of 2.0 - 3.5 MPa, a volumetric feed rate of 1 - 2 h ^-1 . The output of isobutane per passage is 20-55 wt.% On the missed raw materials.

A mixture of unstable isomerizate and hydrogen-containing gas (VGS) is sent to a separator to separate the circulating VGS and then to a stabilization column, where at a pressure of 7-8 MPa and temperature, ^o C: top 40-50, bottom 80-90, the unstable isomerizate is stabilized.

Stable C ₄ isomerizate with a composition of 20-55 wt.% Isobutane, 45 - 80 wt.% N-butane is sent to the deisobutanization column and then to the alkylation reactor.

 Analysis of the known technical solutions for the alkylation of isoparaffins with olefins and the production of alkylbenzenes allows us to conclude that they lack features similar to the essential distinguishing features of the claimed method, that is, the compliance of the proposed method with the requirements of the inventive step.

 The advantages of the proposed method are illustrated by the following examples.

Example 1
Alkylbenzene is obtained by alkylation of isobutane with olefins in the reactor block of a sulfuric acid alkylation unit in the presence of sulfuric acid in a horizontal reactor with internal cooling. The reaction mixture, consisting of acid, unreacted isobutane and alkylbenzene, after settling the spent acid, acid and alkaline purification is sent to the separation in the top of the deisobutanization column. In the lower part of this column, stable C ₄ isomerizate obtained from the isomerization unit is fed in an amount of 10 vol.% Of the amount of the reaction mixture. As a result of countercurrent contacting of these streams, isobutane is separated, which is discharged by the top of the deisobutanization column and, together with the isobutane fraction with HFCs, after cooling to 25 ^° C, is sent to the alkylation reactor.

 From the bottom of the deisobutanization column, a fraction containing alkylbenzene and n-butane is withdrawn, which is fed to the debutanization column to separate the n-butane fraction from the alkylbenzene, which is removed from the cube of the debutanization column to the finished product park as a high-octane component for the preparation of commercial gasolines.

The N-butane fraction — the top of the debutanization column — is mixed with the n-butane fraction of HFCs, heated to a temperature of 430 ^° C. and subjected to isomerization in a reactor in the presence of a catalyst containing 0.55 wt.% Platinum, 3 wt. % halogen and alumina - the rest is up to 100% at a pressure of 2.0 MPa, the volumetric feed rate of 1 h ^-1 .

A mixture of an unstable isomerizate and a hydrogen-containing gas (HSG) after cooling to a temperature of 35 ^o C and separation of the circulating HSG is sent to a stabilization column to stabilize the isomerizate.

Stable C ₄ isomerizate with a composition of 25 wt.% Isobutane, 75 vol.% N-butane is sent to a deisobutanization column and then to an alkylation reactor.

 The main technological indicators are given in the table.

Example 2
Alkylation of isobutane with olefins was carried out according to example 1. The main technological indicators are shown in the table.

Example 3
Alkylation of isobutane with olefins was carried out according to example 1, but without isomerization of circulating n-butane and without supply of stable C ₄ isomerizate to the bottom of the deisobutanization column. The main technological indicators are given in the table.

 Thus, the process according to the proposed method (examples 1-2) allows to increase the yield of alkylbenzene by 6.7-13.3 vol.% N

Claims (1)

The method of producing alkylbenzene by alkylating isobutane with olefins in the presence of sulfuric acid with the supply of fresh and recycle isobutane to a horizontal reactor, settling the reaction mixture consisting of acid, unreacted isobutane and alkylbenzene, acid and alkaline purification, separating the isobutane in the deisobutanization column, which is then returned alkylation, characterized in that the mixture of alkylbenzene and unreacted isobutane is fed to the top of the deisobutanization column, to the bottom of this column fed in an amount of 10 - 25 vol.% of the amount of the reaction mixture stable C ₄ isomerizate composition, vol.%: isobutane 25 - 55, n-butane 45 - 75, at a pressure of 7 - 8 MPa and temperature, ^o C: top 50 - 55, bottom 85 - 90, isobutane is returned to the alkylation reactor, a fraction containing alkylbenzene and n-butane is withdrawn from the bottom of the deisobutanization column, which is fed to the debutanization column to separate the n-butane fraction from the alkylbenzene, which is further combined with n-butane HFC fraction is heated in an oven to 200 - 430 ^o C and isomerized in the presence of the presence of a catalyst containing 0.40 - 0.55 wt.% platinum, 3 - 7 wt.% halogen on an aluminum oxide support, at a pressure of 2.0 - 3.5 MPa, a bulk feed rate of 1 - 2 h ^-1 , then after separation of the hydrogen-containing gas from the unstable C ₄ isomerizate, the latter is sent to a stabilization column, where at a pressure of 7-8 MPa and temperature, ^o С: top 40 - 50, bottom 80 - 90 it is stabilized, followed by return to the deisobutanization column and then to the alkylation reactor.

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