RU2385856C2 - Method of producing high-octane component of motor petrol - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing a high-octane component of motor petrol through alkylation of the isobutane fraction of butylene-containing material in the presence of concentrated sulphuric acid successively in two reaction devices while stirring, subsequent separation of acid and hydrocarbons, purification of the reaction products from acidic impurities. The method is characterised by that alkylation is carried out in two reaction devices having a common loop for circulating sulphuric acid and separate loops for the hydrocarbon phase. The mixture of reaction products and acid from the first reaction device is cooled in a settling zone to 4-6°C and separated with subsequent return of the balance portion of sulphuric acid to the first reaction device. The reaction products and the other portion of sulphuric acid are directed in parallel streams to the second reaction device where butylene-containing material is fed in amount of 1-3 m³/h (in equivalent of 100% butylene) per 1 m³ sulphuric acic inside the reactor. Temperature at the outlet of the reaction device is kept at 15°C or below without additional supply of isobutene. Further, the mixture of reaction products, excess isobutene and acid from the second reaction device is separated in a hydrocyclone into a hydrocarbon phase and sulphuric acid, which is returned to the settling zone of the first reaction device, while the hydrocarbon phase is directed to the settling tank of the second reaction device for thorough separation of acid and then to a purification unit. Optimum concentration of sulphuric acid (90-93%) in the combined loop for circulating acid is maintained through constant supply of fresh 98-99% sulphuric acid.

EFFECT: use of the method improves quality of reaction products, reduces consumption of sulphuric acid, improves temperature conditions in the second reaction device, reduces acidity of the hydrocarbon phase, reduces energy consumption, stabilises operation fo the reactor block, increases the load on unsaturated material in the reaction device, reduces rate of corrosion of equipment and pipes.

1 cl, 3 ex

Description

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

The alkylation of isoparaffins with olefins takes place in the presence of catalysts. One of the main catalysts used in industry is concentrated sulfuric acid. The most commonly used starting components are isobutane and C3-C4 olefins, as well as fractions of these hydrocarbons.

Known methods for the alkylation of isoparaffins with olefins by carrying out the reaction in a horizontal reactor with internal cooling. Raw materials - isobutane and olefins - and circulating sulfuric acid enter a reactor equipped with mixers [Dorogochinsky A.Z. and others. "Sulfuric acid alkylation of isoparaffins with olefins." M., Chemistry, 1970, 216 p .; "Refinery Handbook." Ed. G.A. Lastovkina et al. L., Chemistry, 1986, p. 167-171; Navalikhin P.G. and others. "Chemistry and technology of fuels and oils", 1996, No. 7-8, p.30-32; “Alkylation. Research and industrial design process. " Ed. L. Albright and A. Goldsby. M., Chemistry, 1982]. Most often, isobutane from HFC plants and the butane-butylene fraction from catalytic cracking units are used as raw materials for this process.

According to known methods, alkylbenzene with an octane number (OC) is obtained by the research method of 92 points or more, a boiling point above 205 ° C, followed by isolation by distillation of an alkylbenzene having a boiling point below 205 ° C. The yield of alkylate is 170-200% of the amount of olefinic hydrocarbons processed.

The disadvantages of the known methods are: the yield of alkylbenzene is below the optimum possible for a particular raw material, the octane number of alkylbenzene does not reach the optimum value for a particular raw material, the low quality of alkylbenzene, and the insufficient productivity of unsaturated raw materials.

Known [A. USSR No. 585655 (class C07C 9/16), 1099834 (class B01F 19/00), 1346219 (class B01F 19/00), 1713641 (class B01F 19/00), 1832475 (class C07C 2/62 ), RF patent No. 2092475 (class C07C 2/62)] methods for producing alkylbenzene by alkylating isoparaffins with olefins using sulfuric acid as a catalyst and using reactors of various designs (vertical, horizontal tubular, etc.).

A disadvantage of the known methods is the use of existing industrial reactors having a number of disadvantages that do not allow to obtain alkylbenzene with a maximum content of trimethylpentanes and a correspondingly high octane number. In addition, in these types of reactors, the reactants are fed simultaneously to one point. This leads to the occurrence of side reactions, such as sulfonation, polymerization, etc., prior to the formation of the emulsion, leading to an unfavorable change in the ratio of reaction products of the alkylation process. In addition, the use of mechanical mixing devices necessitates their audit and repair, including unplanned ones.

The closest solution in technical essence and the achieved results is a method for producing alkylbenzene by sulfuric acid alkylation of isobutane with olefins [RF patent No. 2229470], according to which the high-octane component of gasolines is obtained by alkylation of the isobutane fraction with an olefin-containing raw material in the presence of concentrated sulfuric acid in series in two reaction devices with autonomous circuits of sulfuric acid, which is separated from the reaction products in a common sump after e withdrawing the reaction mixture from each reaction device. In the first reaction device, butylene-containing feed is introduced into the emulsion of isobutane with sulfuric acid, a propylene-containing fraction (PPF) in a volume ratio of propylene to isobutane from 1: 4 to 1: 6 is added to the gas product mixture withdrawn from the first reaction device to the second reaction device, and alkylation of isobutane with propylene is carried out when applying a PPF of 0.7-1.5 m ³ / h (in terms of 100% propylene) per 1 m ^{3 of} sulfuric acid in the reactor volume.

The disadvantage of the method adopted for the prototype is the high contamination of the reaction products with acidic impurities, adverse temperature conditions in the second reaction device, increased consumption of sulfuric acid, increased energy consumption, a narrow range of consumption of unsaturated raw materials in the second reactor, increased corrosion rate of equipment and pipelines, reduced octane the number of alkylbenzene by increasing the content of the C ₇ fraction therein as a result of the alkylation reaction of isobutane with propylene.

The aim of the invention is to improve the quality of the reaction products, reduce the consumption of sulfuric acid, improve the temperature in the second reaction device, reduce the acidity of the hydrocarbon phase, reduce energy consumption, stabilize the operation of the reactor unit, increase the load on unsaturated raw materials in the second reaction device, reduce the corrosion rate of equipment and pipelines.

This goal is achieved by the method according to which the high-octane component of gasoline is obtained by alkylation of the isobutane fraction with a butylene-containing feed in the presence of concentrated sulfuric acid in series in two reaction devices equipped with a common sulfuric acid circulation circuit and separate circuits for the hydrocarbon phase. The mixture of reaction products and sulfuric acid from the first reaction device is separated in the settling zone of this reaction device and further cooled to a temperature of 4-6 ° C due to the evaporation of part of isobutane. Next, the balance part of sulfuric acid is returned to the first reaction device, and the reaction products and the other part of sulfuric acid are fed in parallel flows to the second reaction device, which also contains butylene-containing raw materials in an amount of 1-3 m ³ / h (in terms of 100% butylene) per 1 m ³ sulfuric acid in the reactor volume. Maintaining the required temperature in the second reaction device - not higher than 15 ° C at the outlet of the reactor, is carried out due to the cooled sulfuric acid and reaction products coming from the settling zone of the first reaction device, without additional supply of isobutane. At the outlet of the second reaction device, a mixture consisting of reaction products, an excess of isobutane and sulfuric acid, is separated in a hydrocyclone. Sulfuric acid is returned to the sump of the first reaction device. The hydrocarbon phase is sent to the sump of the second reaction device for a more thorough separation of the acid, and then to the purification unit. The optimal concentration of acid (90-93%) is maintained due to the constant supply of fresh 98-99% sulfuric acid to the combined circulation circuit.

The method for producing a high-octane component of gasolines according to the proposed technical solution allows to increase the productivity of the alkylation unit, improve the quality of the obtained alkylbenzene, reduce the consumption of sulfuric acid, reduce energy costs for the process and increase the efficiency of the equipment.

An essential distinguishing feature of the proposed method for producing a high-octane component of gasoline in comparison with the method adopted for the prototype is the alkylation process in series in two reaction devices equipped with a common sulfuric acid circuit and separate circuits for the hydrocarbon phase, while the mixture of reaction products and sulfuric acid from the first reaction device is cooled in the settling zone to 4-6 ° C and separated with the subsequent return of the balance part of sulfuric acid s in the first reaction device, and the reaction products and the other part of sulfuric acid in parallel streams are sent to the second reaction device, which also serves butylene-containing raw materials in an amount of 1-3 m ³ / h (in terms of 100% butylene) per 1 m ^{3 of} sulfuric acid in the reactor volume, while the temperature at the outlet of the second reaction device is maintained no higher than 15 ° C without additional supply of isobutane, then the mixture of reaction products, excess isobutane and acid from the second reaction device is separated in a hydrocyclone. Sulfuric acid is returned to the settling zone of the first reaction device, and the hydrocarbon phase is sent to the settling tank of the second reaction device for more thorough separation of the acid, and then to the purification unit. The optimal concentration of sulfuric acid (90-93%) is maintained due to the constant supply of fresh 98-99% sulfuric acid to the general circulation circuit of sulfuric acid.

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

Analysis of the known technical solutions for the alkylation of isoparaffins with olefins 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 an inventive step.

The method is as follows. The raw material of the proposed method is a butylene-containing fraction, which uses a butane-butylene fraction, which is removed from the catalytic cracking unit and further processed to recover isobutylene in a plant for the production of methyl tert-butyl ether (MTBE), and this butane-butylene fraction can have the following basic component composition: the minimum content of isobutane and the amount of butylenes is 35.9 wt.% and 39.5 wt.%, respectively, and the maximum content of the main components is isobu ana amount and butylenes can be:. 43.5 wt% and 52.5 wt% respectively.. This butylene-containing fraction is sent to the first reaction unit of the sulfuric acid alkylation unit. An isobutane fraction is also fed there, which is removed from a gas fractionation unit (HFC) with a content of 94.5 wt.% - 99.9 wt.%, Respectively, of the minimum and maximum amount of the main component - isobutane. At the same time, concentrated sulfuric acid is supplied to the same reaction device. With vigorous stirring with stirrers, an emulsion forms and an alkylation reaction proceeds. As the raw material mixture arrives, the reaction mass, representing the emulsion from the reaction products and sulfuric acid, flows from the reactor to the sump, where it is cooled to 4-6 ° C due to the evaporation of part of the isobutane and separation of the emulsion into acidic and hydrocarbon phases. Next, the balance part of sulfuric acid from the sump together with an additional amount of concentrated 98-99% sulfuric acid supplied to the combined circulation circuit of sulfuric acid in order to maintain the optimal concentration of sulfuric acid in the system (90-93%) is returned to the first reaction device. The other part of sulfuric acid and the hydrocarbon phase (in full) from the sump of the first reaction device are sent in parallel streams to the second reaction device. It is also fed there in an amount of 1-3 m ³ / h (in terms of 100% butylene) per 1 m ^{3 of} sulfuric acid in the reactor volume butylene-containing raw materials. The required temperature is maintained - not higher than 15 ° C at the outlet of the second reaction device due to the sulfuric acid and hydrocarbon phase cooled to 4-6 ° C entering the second reaction device from the settling zone of the first reaction device, and without additional supply of isobutane to this reactor . Next, the reaction mixture, the excess of isobutane and sulfuric acid at the outlet of the second reactor are separated in a hydrocyclone. The acid is sent to the sump of the first reaction device for cooling, and the hydrocarbon phase to the sump of the second reaction device to separate the remaining acidic impurities from it. Next, the acid phase from this sump is also returned to the sump of the first reaction device, and the hydrocarbon phase is sent to the purification unit.

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

Example 1

At the 25/7 sulfuric acid alkylation unit at OAO Slavneft-YANOS, the butane-butylene fraction from the catalytic cracking unit after isobutylene extraction at the MTBE unit and the isobutane fraction from the HFC unit are used as raw materials. The butane-butylene fraction contains 40-50% butylene and about 40 wt.% Isobutane, as well as a small amount of isobutylene, n-butane, propane. The 95 wt% isobutane fraction consists of isobutane.

The butane-butylene fraction and isobutane pre-cooled to 4-8 ° C are mixed in a ratio of 1: 1-1: 2 and sent to the first reaction device (horizontal cascade type reactor), where in the presence of sulfuric acid with a concentration of 90-93 wt.% at a temperature of 5 ° C under conditions of vigorous stirring with propeller stirrers, an alkylation reaction proceeds. In addition, an additional amount of isobutane pre-cooled to 4-8 ° C in proportion to the butane-butylene fraction as 10: 1, respectively, is also fed into the reactor.

The temperature in the reactor is maintained due to the evaporation of part of the isobutane using a compressor at a pressure of 0.6-0.7 kgf / cm ² . Compressed isobutane after purification is returned to the reactor.

The reaction mass, which is an emulsion of alkylbenzene, an excess of isobutane and sulfuric acid, flows from the reactor to the sump, where, under the influence of gravity, it separates into acid and hydrocarbon phases. In the sump, their cooling also occurs due to the evaporation of part of isobutane. Part of the acid phase is returned to the cascade reactor. To maintain the optimum acid concentration (90-93%), about 0.6 m ³ / h of fresh 98-99% sulfuric acid is fed into the acid return line from the sump to the cascade reactor. And a part of the acid phase in an amount of 140 m ³ / h and the entire volume (100-140 m ³ / h) of the hydrocarbon phase from the sump in separate streams enter the second reaction device (adiabatic jet reactor). An emulsion is created from acid and hydrocarbons in a jet reactor. A butylene-containing fraction of 15 m ³ / h is introduced into the emulsion obtained. The reaction mass as it moves along the length of the reactor is heated by the heat of the alkylation reaction and reaches a maximum value at the outlet of the reactor. The temperature in the jet reactor is maintained by the flows of sulfuric acid and reaction products cooled in the cascade reactor sump to a temperature of 4-6 ° C and, therefore, does not exceed 15 ° C at the outlet of the jet reactor.

The reaction mass after the jet reactor enters the inertial separator of the emulsion - hydrocyclone, where due to the difference in the density of acid and hydrocarbons, there is a separation into acid and hydrocarbon phases. The acid is returned to the cascade reactor sump, and the hydrocarbon phase enters the jet reactor sump to remove acidic impurities. Further, the acid phase from this sump also returns to the cascade reactor sump, and the hydrocarbon phase is sent to the purification unit.

When using this scheme, the acidity of the hydrocarbon phase reaches 7 mg KOH / 100 cm ³ and the corrosion rate of equipment and pipelines reaches 0.1 mm / year.

The alkylation product is alkylbenzene having an octane number of 93 points, after neutralization, washing and isolation of circulating isobutane (which is then returned to the cascade reactor) in an amount of 360 tons per day, it is fed to compounding to prepare marketable gasolines. The specific consumption of sulfuric acid is 95 kg / t of alkylbenzene.

Example 2

At the 25/7 sulfuric acid alkylation unit at OAO Slavneft-YANOS, the butane-butylene fraction from the catalytic cracking unit after isobutylene extraction at the MTBE unit and the isobutane fraction from the HFC unit are used as raw materials. The butane-butylene fraction contains 40-50% butylene and about 40 wt.% Isobutane, as well as a small amount of isobutylene, n-butane, propane. The 95 wt% isobutane fraction consists of isobutane.

The butane-butylene fraction and isobutane pre-cooled to 4-8 ° C are mixed in a ratio of 1: 1-1: 2 and sent to the first reaction device (horizontal cascade type reactor), where in the presence of sulfuric acid with a concentration of 90-93 wt.% at a temperature of 10 ° C under conditions of vigorous stirring with propeller stirrers, an alkylation reaction proceeds. In addition, an additional amount of isobutane pre-cooled to 4-8 ° C in proportion to the butane-butylene fraction as 10: 1, respectively, is fed into the reactor.

The temperature in the reactor is maintained due to the evaporation of part of the isobutane using a compressor at a pressure of 0.6-0.7 kgf / cm ² . Compressed isobutane after purification is returned to the reactor.

The reaction mass, which is an emulsion of alkylbenzene, an excess of isobutane and sulfuric acid, flows from the reactor to the sump, where, under the influence of gravity, it separates into acid and hydrocarbon phases. In the sump, their cooling also occurs due to the evaporation of part of isobutane. Part of the acid phase is returned to the cascade reactor. To maintain the optimum acid concentration (90-93%), 0.5 m ³ / h of fresh 98% sulfuric acid is fed into the acid return line from the sump to the cascade reactor. And part of the acid phase in an amount of 300 m ³ / h and the entire volume (100-140 m ³ / h) of the hydrocarbon phase from the sump are fed in separate streams to the second reaction device (adiabatic jet reactor). An emulsion is created from acid and hydrocarbons in a jet reactor. An additional amount of a butylene-containing fraction is introduced into the emulsion obtained — about 10 m ³ / h. The reaction mass as it moves along the length of the reactor is heated by the heat of the alkylation reaction and reaches a maximum value at the outlet of the reactor. The temperature in the jet reactor is maintained by the flows of sulfuric acid and reaction products cooled in the cascade reactor sump to a temperature of 4-6 ° C and, therefore, does not exceed 15 ° C at the outlet of the jet reactor.

The reaction mass after the jet reactor enters the inertial separator of the emulsion - hydrocyclone, where due to the difference in the density of acid and hydrocarbons, there is a separation into acid and hydrocarbon phases. The acid is returned to the cascade reactor sump, and the hydrocarbon phase enters the jet reactor sump to remove acidic impurities. Further, the acid phase from this sump returns to the cascade reactor sump, and the hydrocarbon phase is sent to the purification unit.

When using this scheme, the acidity of the hydrocarbon phase reaches 5 mg KOH / 100 cm ³ and the corrosion rate of equipment and pipelines reaches 0.1 mm / year.

The alkylation product is alkylbenzene having an octane number of 93 points, after neutralization, washing and isolation of circulating isobutane (which is then returned to the cascade reactor) in an amount of 340 tons per day, it is fed to compounding to prepare marketable gasolines. The specific consumption of sulfuric acid is 90 kg / t of alkylbenzene.

Example 3. (prototype)

The isobutane fraction (isobutane content is 83 wt.%) Is subjected to alkylation by the butane-butylene fraction obtained from the catalytic cracking unit (contains, wt.%: Isobutane - 38.3; n-butane - 9.9; the sum of butylenes - 50.1 ) in the presence of sulfuric acid (concentration of 91.6 wt.%).

Alkylation is carried out sequentially in two reaction devices having autonomous circuits of sulfuric acid, which is separated from the reaction products after they are removed from each reaction device.

In the reaction devices, the first (horizontal cascade type reactor) and the second (vertical jet type reactor) - butylene and a mixture of isobutane and acid are fed in parallel flows to each reaction section with the reaction mass flowing from the cascade to the cascade of the first reaction device and simultaneously removing the hydrocarbon emulsion with spent acid from each reaction device. Reaction conditions: temperature 7 ° C., isobutane: olefins ratio in a 10: 1 stream entering the first reaction device. The amount of processed butane-butylene fraction 270 tons / day.

In the lateral inlet of the second reaction device, a propylene-containing fraction is additionally supplied in an amount of 40 tons / day in a volume ratio of propylene to isobutane 1: 5. Alkylation of isobutane with propylene is carried out by applying a PPF of 0.7 m ³ / h (in terms of 100% propylene) per 1 m of sulfuric acid in the volume of the second reaction device.

The product mixture discharged from each reaction device and consisting of acid, unreacted isobutane and alkylbenzene is combined and settled in a settling tank to separate the acid, which is returned to the reactor.

Alkylbenzene is subjected to acid and alkaline purification, isobutane is separated from it in the deisobutanization column, which is then returned to the reaction devices.

When using this scheme, the acidity of the hydrocarbon phase reaches 12 mg KOH / 100 cm ³ and the corrosion rate of equipment and pipelines reaches 1 mm / year.

The alkylation product is alkylbenzene having an octane number (m) of 92.5 points, after neutralization, washing and isolation of circulating isobutane (which is then returned to the reaction devices) in an amount of 348 t / day, it is fed to compounding to prepare marketable gasolines. The specific consumption of sulfuric acid is 121 kg / t of alkylbenzene.

Thus, the process of alkylation of isobutane with butylene-containing raw materials according to the proposed method (example 1,2) allows to increase the octane number of alkylbenzene by 0.5 points, reduce the specific consumption of acid by more than 25 kg / ton of alkylbenzene, and equalize the temperatures at the outlet of the jet reactor and hydrocyclone (excluded the reaction in the pipe reactor between the jet and hydrocyclone), to stabilize the acidity of the hydrocarbon phase at a level of 5-7 mg KOH / 100 cm ^3, to reduce the load on the compressor unit is not due to a cart rata 100-140 m ³ / h of the warm reaction products in the settling zone of the reactor cascade, stabilize operation of the reactor unit by dividing the circulation circuit by a hydrocarbon phase using an additional settler, increase load on butilensoderzhaschemu feed on jet reactor to 1-3 ^m3 / h (based on 100% butylene) per 1 m ³ of sulfuric acid in the reactor volume, decrease the rate of corrosion of equipment and pipelines to 0.1 mm / year, to maintain a jet reactor by cooled gas-product acid and optimal mixture th temperature, allowing the jet to exit the reactor be no higher than 15 ° C.

Claims (1)

A method of producing a high-octane component of motor gasolines by alkylating an isobutane fraction with a butylene feed in the presence of concentrated sulfuric acid in series in two reaction devices with active stirring, subsequent separation of acid and hydrocarbons, purification of the reaction products from acidic impurities, characterized in that the alkylation is carried out in two reaction devices, equipped with a common circuit for the circulation of sulfuric acid and separate circuits for the hydrocarbon phase, at the mixture of reaction products and acid from the first reaction device is cooled in the settling zone to 4-6 ° C and separated, followed by the return of the balance part of sulfuric acid to the first reaction device, and the reaction products and other part of sulfuric acid are sent in parallel streams to the second reaction device, which also serves butilensoderzhaschee feedstock in an amount of 1-3 m ³ / h (calculated as 100% butylene) per 1 m ³ of sulfuric acid in the reactor volume, with the temperature at the outlet of the second reaction apparatus is maintained not you e 15 ° C without additional supply of isobutane, then the mixture of reaction products, the excess of isobutane and acid from the second reaction device is separated in a hydrocyclone into a hydrocarbon phase and sulfuric acid, which is returned to the settling zone of the first reaction device, and the hydrocarbon phase is sent to the settling tank of the second reaction device for a more thorough separation of the acid, and then to the purification unit, while the optimal concentration of sulfuric acid (90-93%) in the combined acid circuit is maintained by yannoy supply of fresh 98-99% sulfuric acid.