RU2147019C1 - Method of isolation of tert-c4-c5. alkenes - Google Patents

Abstract

FIELD: petrochemistry. SUBSTANCE: hydrocarbon mixture is made to contact with mixture containing predominantly non- tertiary alcohol(s) having at least 2 carbon atoms and water at concentration from 0.5 to 90 wt % in the presence of highly acidic cationic catalyst. Unreacted hydrocarbons are distilled off, catalytic decomposition of the resulting compounds is carried out in the presence of highly acidic cationic catalyst, and tert-C₄-C₅. alkenes are distilled off. EFFECT: higher yield of the desired product and longer catalyst service life. 8 cl, 2 dwg, 2 tbl

Description

 The invention relates to the field of separation of tert-alkenes from hydrocarbon mixtures.

More specifically, the invention relates to the field of extraction of C ₄ -C ₅ tert-alkenes from hydrocarbon mixtures by combining them with hydroxyl-containing substances, separating the resulting substances from unreacted hydrocarbons and their subsequent separation with distillation of tert-alkenes.

 Known methods for the separation of tert-alkenes from hydrocarbon mixtures by reacting with water or non-tertiary alcohols in the presence of acidic catalysts, followed by continuous or simultaneous distillation of unreacted hydrocarbons and further decomposition of the resulting tertiary alcohol or ether in the presence of acidic catalysts and distillation of tert-alkene (s). Contacting with water is carried out in liquid-phase (contacting two liquid phases) devices with direct-flow or counter-flow of reacting substances / S.Yu. Pavlov. Isolation and purification of monomers for synthetic rubber, L .: Chemistry, 1987, p. 128 - 142 /.

 The disadvantage of the method based on interaction with water is the low reaction rate (s) due to the very slight mutual solubility of hydrocarbons and water.

 To overcome this drawback, it was proposed to maintain 2 to 20 wt.% Of the resulting tertiary alcohol in water. This, however, leads to a significant limitation of the conversion of tert-alkenes due to the introduction of the product under conditions of equilibrium reaction / RU 2076091, 03/27/97 /.

A known method for the extraction of tert-alkenes from hydrocarbon mixtures by contacting with aliphatic alcohols C ₁ -C ₄ in the presence of an ion-exchange molded catalyst in a reaction-distillation apparatus followed by decomposition of the alkyl-tert-alkyl ether (s) forming them (s) in the second reactive distillation apparatus, also containing a molded sulfoionite catalyst / RU 20057710, 01/15/94 /.

 The specified method is the closest to what we offer.

 The disadvantage of this method is the significant formation of dimers and oligomers from tert-alkenes, which leads to the loss of tert-alkenes, a decrease in the life of the catalyst, as well as to the accumulation of dimers and oligomers in aliphatic alcohol during its repeated use (recycling) for contact with a shared hydrocarbon mixture.

We propose a method for the isolation of C ₄ -C ₅ tert-alkenes from hydrocarbon mixtures, including at least their catalytic contacting with hydroxyl-containing compounds in the presence of a highly acidic cation exchange catalyst, distillation of unreacted hydrocarbons, catalytic decomposition of the compounds formed in the presence of a high-acid cation exchange catalyst, and distillation of a stream containing mainly tert-alkene (s), wherein the hydrocarbon mixture is contacted with a mixture containing essentially non-tertiary (e) alcohol (s) with a number of carbon atoms of at least 2 and water in a concentration of from 0.5 to 90 wt.%.

 As one of the options, a method is proposed that the catalytic contacting and distillation of unreacted hydrocarbons is carried out in a reaction-distillation type system including an exhaustive reaction zone, a reaction zone with a catalyst connected in series with counter flows of liquids and steam, and possibly strengthening the distillation zone, moreover, the shared hydrocarbon mixture is served in the lower part of the reaction zone and / or the upper part of the exhaustive zone, and in the upper part of the reaction th zone and / or the lower part of the reinforcing zone serves alcohol-containing mixture in which a water concentration of 0.5 to 5.0 wt.% is maintained.

 Alternatively, a method is proposed that consists in contacting in a liquid-phase (s) once-through (s) and / or counter-current (s) apparatus (s) and / or once-through apparatus with partial evaporation of the reaction mass and maintain a concentration of 5 in the feed mixture 92% of water relative to its total weight with alcohol (s).

Alternatively, a method is proposed that after separation of the reaction mass, at least a portion of the aqueous layer is returned, preferably after cooling, to the entrance to the catalytic contact zone, and C ₃ -C ₄ hydrocarbons are distilled off from the organic layer and the residue is fed to the decomposition zone of the resulting (s) ester (s) and tertiary alcohol.

 Alternatively, a method is proposed in which the catalytic decomposition of the resulting ester (s) and tertiary alcohol is carried out with continuous distillation of the tert-alkene (s) and the bottom residue is preferably returned to the catalytic contact zone (s) with the tert-alkene-containing mixture.

 Alternatively, a method is proposed that consists in the fact that in the zones of catalytic contact and catalytic decomposition, a sulfocationite (e) catalyst (s) with a particle size of 2 to 40 mm and / or fine-grained sulfonic ionite with a particle size of 0.3 to 2 mm are used, loaded into apparatus (s) in the form of microcontainers with a mesh or permeable shell so that the proportion of free cross-section in the apparatus (s) is at least 30%.

 Alternatively, a method is proposed, namely, that finely grained catalyst with a particle size of 0.3 - 2 mm is poured into the liquid-phase (e) contacting apparatus (s), and the catalyst according to claim 6 is used in other reactors.

 Alternatively, a method is proposed that consists in the fact that during the distillation of tert-alkene (s) from the catalytic decomposition zone, partial condensation of the distilled stream is carried out and the condensed part is returned as reflux, and the rest is subjected to distillation and bottoms containing mainly alcohol (s) and / or ether (s) are returned to the catalytic decomposition zone and / or the catalytic contact zone with the tert-alkene-containing mixture.

 The term liquid-phase (e) apparatus (s) in the claims and description of the invention is understood as apparatus (s) in which substances are almost completely in a condensed state.

 Various design options for reactors and heat removal methods in a contacting and heat supply apparatus in a decomposition reactor can be used.

 When contacting in the once-through (s) reactor (s), the supply of reagents can be carried out both from top to bottom and from bottom to top.

 In the presence of two liquid phases, the hydrocarbon phase can serve as the continuous phase, and the water-alcohol phase as the distributed phase, or the water-alcohol continuous phase, and the hydrocarbon phase as the distributed phase. The settling zone can be located both inside the contact apparatus and outside it in a separate settler.

 The implementation of the invention is illustrated in FIG. 1 to 2 and examples 1 to 4.

 These drawings and examples do not exclude possible embodiments of the invention and other technical solutions are possible while observing the essence of the invention set forth in the claims.

 According to FIG. 1, a shared hydrocarbon mixture F (stream 1) enters under the layer or between the layers of the cation exchange catalyst into the PP-1 reactive distillation apparatus. Above the catalyst bed is stream 2 containing alcohol (s) and water (collectively referred to as “R” reagents).

At the top of PP-1, stream 3 containing predominantly unreacted hydrocarbons is discharged as distillate D ₁ .

 Bottom PP-1 discharges stream 4, containing predominantly formed ether (s) and tertiary alcohol, as well as possibly incompletely reacting non-tertiary (e) alcohol and water.

 Stream 4 is fed to the PP-2 apparatus above the layer and / or between the layers and / or below the cation exchange catalyst layer.

 On top of PP-2, stream 5, containing predominantly tert-alkene (s), is withdrawn, and below, stream 6, containing predominantly non-tertiary (e) alcohol (s) and water.

 Stream 6 is preferably returned to the PP-1 apparatus, possibly after purification from accumulating impurities (purification zone “0” is indicated by a dotted line).

 According to FIG. 2, the hydrocarbon mixture F to be separated and mixture R, containing predominantly non-tertiary alcohol (s) and water, are fed into the reactor P-1 by flows 1 and 2, respectively. Upon leaving the contact zone, the mixture (if there is heterogeneity) is subjected to delamination.

 A mixture containing predominantly unreacted hydrocarbons, ester (s) and tert-alcohol formed, and possibly unreacted (e) non-tertiary alcohol and water, is sent by stream 3 to a K-1 distillation column. The water-alcohol layer can be recycled (preferably through a refrigerator) to the inlet of the reactor P-1 (stream 4) or / and removed from the system by stream 4a.

 A stream 5 containing predominantly unreacted hydrocarbons is discharged at the top of the K-1 column, and a stream 6 containing predominantly formed ether (s) and tert-alcohol, and possibly non-tertiary alcohol and water, are discharged.

 Stream 6 is sent to the decomposition apparatus (apparatus P-2). A stream 7 containing mainly tert-alkene (s) is withdrawn from the top of the P-2 apparatus, and a stream 8, which contains mainly non-tertiary alcohol (s) and water, which is returned to the P-1 reactor and / or removed from the system, is led out from below.

 Stream 7 can be directed to an additional unit for the separation of entrained alcohols and / or esters, for example, by rectification (in Fig. 2 in column K-2) or by water washing.

Examples of recovering isobutene from isobutene-containing C ₄ hydrocarbon mixtures and extracting tert-pentenes (2-methyl-2-butene and 2-methyl-1-butene) from isopentene-containing C ₅ hydrocarbon mixtures are given as examples.

 The main indicators are given in table. 1 and 2. The catalysts indicated in the examples are: “sulfocationite with polyethylene” and “sulfocationite with polypropylene” - sulfonated catalysts molded with polyethylene and polypropylene containing styrene divinylbenzene copolymer as a sulfonated matrix (particle size of the catalysts is 4-10 mm).

Catalysts KU-23 and Amberlist-15 are fine-grained coarse-grained industrial sulfocationic catalysts with a particle size of 0.3 - 1 mm. All catalysts were used in the H ⁺ form.

 In all experiments, the formation of dimers and oligomers of tert-alkenes was almost completely absent and there was no decrease in the activity of catalysts during the many-hour experiment.

Claims (7)

1. A method of separating C ₄ -C ₅ tert-alkenes from hydrocarbon mixtures, including at least catalytically contacting them with hydroxyl-containing compounds in the presence of a high acid cation exchange catalyst, distilling off unreacted hydrocarbons, catalytic decomposition of the compounds formed in the presence of a high acid cation exchange catalyst, and distilling a stream containing mainly tert-alkene (s), characterized in that the hydrocarbon mixture is contacted with a mixture containing predominantly non-tertiary first (e), the alcohol (s) with a carbon number not less than 2, and water in a concentration of 0.5 - 90 wt.%.  2. The method according to claim 1, characterized in that the catalytic contacting and distillation of unreacted hydrocarbons is carried out in a reaction-distillation type system comprising an exhaustive reaction zone, a reaction zone with a catalyst connected in series with counter flows of liquids and steam, and possibly strengthening the distillation zone, moreover, the shared hydrocarbon mixture is fed into the lower part of the reaction zone and / or the upper part of the exhaustive zone, and the top part of the reaction zone and / or lower part is strengthened yayuschey zone serves alcohol-containing mixture, which is maintained at a water concentration of 0.5 - 5.0 wt.%.  3. The method according to claim 1, characterized in that the catalytic contacting is carried out in a liquid phase (s) once-through (s) and / or counter-current (s) apparatus (s) and / or once-through apparatus with partial evaporation of the reaction mass and in the feed mixture support a concentration of 5 - 92% of water relative to its total mass with alcohol (s). 4 The method according to claims 1 to 3, characterized in that after separation of the reaction mass, at least part of the aqueous layer is returned, preferably after cooling, to the entrance to the catalytic contact zone, and C ₃ -C ₄ hydrocarbons are distilled off from the organic layer and the residue is fed to the decomposition zone of the ester (s) and tertiary alcohol formed (them).  5. The method according to claims 1 to 4, characterized in that the catalytic decomposition of the resulting ester (s) and tertiary alcohol is carried out with continuous distillation of tert-alkene (s) and the bottom residue is preferably returned to the catalytic contact zone (s) with tert-alkene-containing a mixture.  6. The method according to claims 1 to 5, characterized in that in the zones of catalytic contacting and catalytic decomposition using sulfocationite (e) catalyst (s) with a particle size of 2 to 40 mm and / or fine-grained sulfonate with a particle size of 0.3 to 2 mm, loaded into the apparatus (s) in the form of microcontainers with a mesh or permeable shell so that the fraction of free section in the apparatus (s) is at least 30%.  7. The method according to claims 1 to 6, characterized in that a fine-grained catalyst with a particle size of 0.3 - 2 mm is poured into the liquid-phase (e) contacting apparatus (s), and the catalyst according to paragraph 1 is used in the remaining reactors. 6.  8. The method according to claims 1 to 7, characterized in that during the distillation of tert-alkene (s) from the catalytic decomposition zone, partial condensation of the distilled stream is carried out and the condensed part is returned as reflux, and the remainder is subjected to rectification and still bottoms, containing mainly alcohol (s) and / or ether (s) are returned to the catalytic decomposition zone and / or the catalytic contact zone with the tert-alkene-containing mixture.

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