RU2132838C1 - Method of preparing concentrate and high-octane components - Google Patents

Abstract

FIELD: chemical industry, more particularly preparation of 1,3-butadiene and high-octane products. SUBSTANCE: method of preparing butadiene concentrate and high-octane components from hydrocarbon mixtures containing at least 1,3-butadiene, isobutene straight- chain butenes and other C₄, hydrocarbons comprises separating hydrocarbons by extractive rectification in the presence of polar extracting agent, subsequently contacting the resulting isobutene-containing distillate with acid catalyst in the presence of non-tertiary alcohol(s) and distilling at least unreacted C₄, hydrocarbons. Extractive rectification is used to withdraw hydrocarbon distillate stream containing from 0.5 to 15% of 1,3-butadiene. After being purified, the latter is made to contact with acid catalyst in the presence of alcohol(s), and desorbate stream containing from 70 of 95% of 1,3-butadiene and not more than 5%, preferably not more than 2% of butenes, is used for manufacturing synthetic rubber. EFFECT: simplified process. 6 cl, 3 dwg, 6 ex, 3 tbl

Description

 The method relates to the field of producing monomers for synthetic rubbers and high-octane gasoline components.

More specifically, the method relates to the field of separation of 1,3-butadiene and the production of high-octane products from mixtures of hydrocarbons containing at least 1,3-butadiene, isobutene, n-butenes and other C ₄ hydrocarbons.

A known method for the isolation of 1,3-butadiene, suitable for polymerization in rubbers, from mixtures of C ₄ hydrocarbons by extractive distillation with polar solvents, for example acetonitrile and dimethylformamide [1], according to which concentrated concentrate is isolated in one extractive distillation zone (followed by desorption from the extractant) 1,3-butadiene containing not more than 1-2% butenes and butanes, and in another extractive distillation zone (followed by distillation of 1,3-butadiene as desorbate), it is purified from acetylenes C ₄ , last what are the impurities of propine and heavy hydrocarbons separated in it in two columns of conventional rectification (Pavlov S.Yu. Synthetic rubber. L .: Chemistry, 1976, p. 164-180) [1].

The main disadvantages of this method is the necessity of using extractive distillation columns with a large number of plates and high energy consumption due to the inversion of the relative volatility of 2-butenes (relative to 1,3-butadiene), because 2-butenes have boiling points higher than 1,3-butadiene (at atmospheric pressure - cis-2-butene + 3.7 ^o , trans-2-butene + 0.9 ^o and 1,3-butadiene 4.4 ^o ), while during extractive distillation according to the method [1], 2-butenes are removed in the composition of the upper product along with butanes, 1-butene and isobutene, and 1,3-butadiene in the lower stream (saturated extractant), and then as a desorbate, practically free of buds.

 Due to the difficulty of separating 2-butenes and 1,3-butadiene in this method, very large reflux numbers are required even when using the most selective, nitrogen-containing extractants (3.5-6) and a large supply of extractant relative to the mixture to be separated. Moreover, due to the high concentration of 1,3-butadiene, its significant thermopolymerization and clogging of equipment by polymer deposits takes place. The use of less selective solvents (for example, alcohols) is practically impossible.

A known method [2] for the production of alkyl tert-alkyl esters, in particular methyl tert-butyl ether, by contacting mixtures of C ₄ hydrocarbons containing isobutene and 1,3-butadiene by contacting the hydrocarbon mixture and alcohol (s) with acid catalysts, in particular sulfocathionites, followed by the isolation of alkyl tert-butyl ether (s) by distillation (US Pat. No. 4,039,590, 08/02/77) [2].

 The disadvantage of this method is that under the conditions of synthesis of alkyl tert-butyl ether (s), partial oligomerization and polymerization of 1,3-butadiene and acetylenes occurs and the active sites of the catalyst are deactivated by deposits of oligomers and polymers.

Closest to our proposed method is [3], according to which 1,3-butadiene suitable for polymerization into rubber is first isolated from a mixture of C ₄ hydrocarbons, and then the remaining mixture of C ₄ hydrocarbons is contacted in the presence of alcohol (s) with heterogeneous acid a catalyst.

 The disadvantage of this method is the need for extractive distillation columns with a large number of plates and high energy consumption due to high reflux numbers and the supply of a large amount of extractant, as indicated in the criticism of the method [1].

Another disadvantage of the method is that after the transportation of 1,3-butadiene that meets the requirements of polymerization at the consumer enterprise carrying out the polymerization, it becomes necessary to clean it of impurities that accumulate during transportation, in particular from oxygen-containing compounds and a polymerization inhibitor, i.e. . purification of 1,3-butadiene has to be carried out twice (Pavlov S. Yu. et al. Complex processing of C ₄ fractions _of thermal and thermocatalytic conversion of hydrocarbons. Chemical industry prom. 4, 1989, N 11, pp. 39 - 46) [3].

 When concentrated butadiene is isolated, the problem arises of inhibiting the spontaneous polymerization of butadiene and other unsaturated hydrocarbons. With an increase in the concentration of butadiene, the task of inhibiting thermopolymerization becomes more difficult, which is also a serious disadvantage of the known method.

We propose a method for producing butadiene concentrate and high-octane components from hydrocarbon mixtures containing at least 1,3-butadiene, isobutene, n-butenes and other C ₄ hydrocarbons by separation of hydrocarbons by extractive distillation in the presence of a polar extractant, subsequent contacting of the obtained distillate containing isobutene, with an acidic catalyst in the presence of non-tertiary alcohol (s) and distillation of at least unreacted C ₄ hydrocarbons from a stream of high-octane components, cat The second one is that, during extractive rectification, a stream of hydrocarbon distillate containing from 0.5 to 15% 1,3-butadiene is removed, which is sent directly or after preliminary purification from the entrained extractant and its hydrolysis products to contact with an acid catalyst in the presence of alcohol (s), and a desorbate stream containing from 70 to 95% 1,3-butadiene and not more than 5%, preferably not more than 2% 1-butenes, which directly or after further purification is sent to the production of synthetic rubber.

 It is also proposed that methanol, acetonitrile, methoxypropionitrile, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, or mixtures of these substances, or mixtures thereof with water and extractive rectification, are used as extractant. in a column having an efficiency of 30-60 theoretical plates, with a mass ratio of extractant: hydrocarbon mixture flows from 1.5 to 15 and a reflux ratio of 1.5 to 5.

A variant is also proposed which consists in the preliminary catalytic hydrogenation of α-acetylenes in the initial hydrocarbon mixture, and a mixture with a concentration of α-acetylenes C ₄ not exceeding the concentration allowed in 1,3-butadiene for polymerization multiplied by mass fraction of 1,3-butadiene in the starting mixture, preferably not more than 0.002%.

 This option does not limit the use of other methods for purifying butadiene from acetylene hydrocarbons. In particular, the option of purifying butadiene by extractive distillation, catalytic hydrogenation, etc. is possible. When purifying by catalytic hydrogenation of butadiene diluted to 70% with butylenes, the problem of inhibiting spontaneous thermopolymerization of butadiene is greatly simplified and the catalyst service life is increased.

 A variant is proposed which consists in the use of sulfocationionite as an acid catalyst.

 In addition, it is proposed that the distillate stream is subjected to purification from nitrogen-containing impurities by distillation and / or contacting with an acid and / or acidic sorbent solution and / or water before being fed into contact with an acidic catalyst.

 A variant is also proposed which consists in directing a distillate stream containing from 2 to 25% methanol and, optionally, a stream of methanol recovered by water washing the butadiene-containing desorbate and stripping from water, and / or an additional stream, for contacting with the acid catalyst. methanol and / or other non-tertiary alcohols.

 The distillation of methanol from the aqueous solution obtained by washing the butadiene-containing desorbate can be carried out separately or together with the distillation from the aqueous solution obtained by washing the hydrocarbon stream distilled from the high-octane components after the stage of contacting with the acid catalyst.

 The proposed method is illustrated by the following figures and examples. These figures and examples do not exclude other possible technological variations in the implementation of the method, subject to the essence of the invention set forth in the claims.

According to FIG. 1, a hydrocarbon mixture containing 1,3-butadiene, isobutene and other C ₄ hydrocarbons (stream F) is fed through line 1 to the middle of extractive distillation column 1. At the top of column 1, an extractant stream “E” is fed through line 2. A stream D ₁ separated from most of the 1,3-butadiene is discharged from the top of column 1 through line 3, and a saturated extractant (stream W ₁ ) containing mainly 1,3-butadiene and cis-2-butene is discharged from the bottom of column 1 through line 4 .

The stream of saturated extractant is sent to the desorption column 2, from which the butadiene concentrate stream (stream D ₂ ) is withdrawn from above along line 5. The latter can be subjected to additional water washing (not shown). Bottom of the column along line 6 is a stream of desorbed extractant, which is returned to line 1 through line 2.

The hydrocarbon stream through line 3 and the stream of alcohol (s) through line 7 is fed to the node 3 synthesis of high-octane components (FOC). The reaction mixture through line 8 is fed to a distillation column 4, on top of which a stream D ₄ is withdrawn from line 9, containing mainly hydrocarbons freed from most of the isobutene.

If necessary, the stream D _{4 is} sent to the recovery unit of the alcohol (s) (not shown). Further in the tables, the composition and amount of the stream D ₄ are indicated net of alcohol (after recovery).

Bottom of column 4 along line 10, a stream W _{4 is} obtained, containing predominantly high-octane components.

 According to FIG. 2 processing is carried out similarly to that shown in FIG. 1, with the difference that the initial hydrocarbon mixture F is subjected to selective catalytic hydrogenation in unit “G”, as a result of which most of the α-acetylene hydrocarbons are converted to the corresponding alkenes and alkadiene. The resulting hydrocarbon mixture F 'through line 1A is sent to column 1.

According to FIG. 3, in contrast to FIG. 1, the hydrocarbon stream D ₁ , discharged from above the column 1, is fed through line 3 for purification from impurities that poison the heterogeneous acid catalyst, in particular from a nitrogen-containing compound.

 The purification is carried out by distillation in column 3 or in the unit for contacting with an acid or acidic sorbent (unit 3A) and possibly then in the unit for water washing (unit 3B), or directly in the unit for water washing 3B. Purified from these impurities, the stream is sent to the reaction-distillation apparatus 4, which contains at least in the middle zone an acidic heterogeneous catalyst.

On top of the apparatus 4, a stream D ₄ , containing predominantly unreacted hydrocarbons, is withdrawn via line 9. From the bottom of the apparatus 4, a stream W ₄ , containing predominantly high-octane components,
Example 1

 The mixture is subjected to processing containing 2% isobutane, 5% n-butane, 27% isobutene, 13.5% 1-butene, 5% trans-2-butene, 4.5% cis-2-butene, 42% 1.3 -butadiene, 0.2% 1-butine, 0.05% 2-butine, 0.8% butenine.

Processing is carried out according to FIG. 1. Aqueous N-methylpyrrolidone (5% by weight of water) is used as extractant in column 1, fine-grained, coarse-grained, large-pore Amberlist-35 sulphocationite, as a catalyst in node 3, and methanol in node 3. Preferably, methyl tert-butyl ether is obtained in the composition of stream W ₄ .

 The compositions of the main products and process indicators are given in table. 1.

 Example 2

 The mixture is subjected to processing containing 2% isobutane, 5% n-butane, 27% isobutene, 13.5% 1-butene, 5% trans-2-butene, 4.5% cis-2-butene, 42% butadiene, 0 , 2% 1-butine, 0.05% 2-butine, 0.7% butenine and 0.1% propine. Processing is carried out according to FIG. 2. In contrast to Example 1, α-acetylenes are selectively hydrogenated in unit “G” on a “palladium on alumina” catalyst. Β-methoxypropionitrile is used as extractant in column 1, fine-grained coarse-grained catalyst KU-23 is used as a catalyst in node 3, methanol is fed as alcohol to node 3.

Hydrogenation is carried out at a temperature of 15-20 ^o C with a supply of hydrocarbons of 9 l / l of catalyst per hour and a supply of hydrogen in the ratio to the sum of α-acetylene hydrocarbons 11: 1 (mol.).

 The compositions of the main products and process indicators are given in table. 1.

 Example 3

Processing is carried out according to FIG. 3. The processed C ₄ mixture has a composition similar to that described in Example 1. In contrast to Example 1, acetonitrile is used as extractant in column 1. Stream D ₁ , containing 2.5% acetonitrile and 0.001% ammonia, is subjected to water washing in the node "3B" to a residual acetonitrile content of 0.0001-0.0003% and ammonia <0.0001%.

 A molded sulfoionite catalyst KIF containing polyethylene is used as a catalyst in a reactive distillation apparatus, and ethanol is used as an alcohol.

 The compositions of the main products and process indicators are given in table. 2.

 Example 4

 Processing is carried out according to FIG. 3. The composition of the initial hydrocarbon mixture is similar to example 1.

Unlike the previous examples, N, N-dimethylformamide (DMF) was used as extractant in column 1. Stream D ₁ containing 0.005% N, N-dimethylformamide and 0.004% dimethylamine is rectified from N, N-dimethylformamide impurities in column 3, and then purified from dimethylamine and traces of N, N-dimethylformamide by contacting with an aqueous solution containing phosphoric acid (0.5%) in node 3A.

 As a catalyst in apparatus 4, mixtures of (1: 1 wt) sulfonated ionized catalyst KU-2FPP containing polypropylene and a phosphoric acid on silica gel catalyst are used. Propanol is used as alcohol.

 The compositions of the main products and process indicators are given in table. 2.

 Example 5

 Processing is carried out according to FIG. 1.

In contrast to Example 1, methanol is used as the extractant in the extractive distillation column. As a hydrocarbon feed, a C ₄ fraction containing (wt%) is used: isobutane 3.83, n-butane 7.16, isobutene 27.02, 1-butene 14.55, trans-2-butene 0.78, cis-2-butene 1.50, butadiene 45.1 and butenine 0.05. Stream D ₁ , containing 20% methanol, is sent without separation of the extractant to node 3 for the synthesis of methyl tert-butyl ether. The rest of the methanol is fed through line 7. From the bottom of column 4, a stream containing methyl tert-butyl ether is withdrawn.

Stream D ₂ containing 3% methanol is directed to water washing from methanol. After washing the butadiene, the water-methanol mixture is sent to a methanol distillation column from water (not shown).

 The compositions of the main products and process indicators are given in table. 3.

 Example 6

Processing is carried out according to the scheme shown in FIG. 2. Use the original C ₄ mixture similar to that described in Example 2. A mixture of N-methylpyrrolidone and methanol in a ratio of 3: 1 (wt.) Is used as the extractant. A hydrocarbon mixture containing 3.5% methanol is withdrawn from the top of column 1, which is sent to a wok synthesis unit (unit 3) containing an acidic heterogeneous catalyst. The stream discharged from the top of the stripper containing 3% methanol is subjected to water washing (not placed).

 The stream withdrawn from the top of column 4 containing 0.1% methanol is also subjected to water washing. Aqueous methanol solutions from both washing columns are combined and methanol is distilled off from water, which is returned to unit 3.

 From the cube of column 4, a mixture of high octane components (FOC) is removed, containing mainly isobutene dimers and methyl tert-butyl ether.

 The compositions of the main products and process indicators are given in table. 3.

Claims (6)

1. A method of producing butadiene concentrate and high-octane components from hydrocarbon mixtures containing at least 1,3-butadiene, isobutene, normal butenes and other C ₄ hydrocarbons, by separation of the hydrocarbon by extractive distillation in the presence of a polar extractant, subsequent contacting of the obtained distillate containing isobutene, with an acidic catalyst in the presence of non-tertiary alcohol (s) and distillation of at least unreacted C ₄ hydrocarbons from a stream of high-octane components, distinguishing The fact is that, during extractive distillation, a stream of hydrocarbon distillate containing 0.5-15% 1,3-butadiene is removed, which, directly or after preliminary purification from the entrained extractant and its hydrolysis products, is directed to contact with an acidic catalyst in the presence of alcohol (s) and a desorbate stream containing 70 to 95% of 1,3-butadiene and not more than 5%, preferably not more than 2%, 1-butenes, which, directly or after further purification, is sent to the production of synthetic rubber.  2. The method according to claim 1, characterized in that methanol, acetonitrile, methoxypropionitrile, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone or mixtures of these substances, or mixtures thereof with water and extractive rectification are used as extractant carried out in a column having an efficiency of 30-60 theoretical plates, with a mass ratio of the flows of the extractant: hydrocarbon mixture from 1.5 to 15 and the reflux ratio of 1.5 to 5. 3. The method according to PP. 1 and 2, characterized in that the preliminary catalytic hydrogenation of α-acetylenes in the initial hydrocarbon mixture is carried out and a mixture with a concentration of α-acetylenes C ₄ not exceeding the concentration allowed in 1,3-butadiene for polymerization multiplied by mass fraction is fed to extractive rectification 1,3-butadiene in the starting mixture, preferably not more than 0.002%.  4. The method according to claims 1 to 3, characterized in that sulfonic cation exchange resin is used as the acidic catalyst.  5. The method according to claims 1 to 4, characterized in that the distillate stream is subjected to purification from nitrogen-containing impurities by rectification and / or contacting with an acid and / or acidic sorbent solution and / or water with possible recovery of extractant.  6. The method according to claims 1 to 5, characterized in that a distillate stream containing 2 to 25% methanol is sent to contact with the acidic catalyst, and a stream of methanol recovered by water washing of the butadiene-containing desorbate and stripping from water, and / or additional a stream of methanol and / or other non-tertiary alcohols.

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