FR2470105A1 - Isobutylene sepn. from hydrocarbon fractions - by countercurrent hydration followed by dehydration of tert.-butanol - Google Patents

Abstract

Sepn. of isobutylene (I) from 4C hydrocarbon fractions is carried out by (a) contacting the feed with H2O at 70-110 degrees C and 16-23 atm. in the presence of a shaped ion-exchanger catalyst, and (b) dehydrating the resulting t-butanol (II) at 80-110 degrees C and =3 atm. in the presence of the same catalyst. The improvement is characterised in that the feed and H2O are contacted in countercurrent in step (a), with an H2O supply rate of 5-30 m/sec. and a 4C feed flow rate through the catalyst bed of 0.001-0.020 m/sec. Countercurrent contacting increases the reaction rate and allows (I) to be recovered in yields of up to 99.98%.

Description

 The present invention relates to a process for separating olefins from hydrocarbon fractions and more specifically relates to a process for separating isobutylene from C4 hydrocarbon fractions.

 Isobutylene has wide applications in the synthetic rubber industry as a base monomer for butyl rubber synthesis, in the petroleum refining industry and in the petrochemical industry for the production of polyisobutylene, additives stabilizers for lubricating oils, fuels and other products; in the organic synthesis it serves for the preparation of metallyl and other products.

 the claimed process can also be used for the refining of C4 hydrocarbon fractions (isobutane - isobutylene, butylene - butane, butylene and other moieties) to remove isobutylene.

 Thus, the butylene fraction liberated from 1-sobutylene can be used as a mercageable product in the dehydrogenation processes for obtaining butadiene.

 The tertiary butyl alcohol prepared in the process in question as an intermediate product can be used as a marketable product in organic synthesis processes for the production of t-butyl peroxides and hydroperoxides, pyrocatechol and other products.

 A catalytic process for separating concentrated isobutylene from a C4 hydrocarbon fraction is presently known.

This process consists in the fact that most of the isobutylene is extracted from the hydrocarbon mixture in a multistage unit by 40 ~ 55apo sulfuric acid at a temperature of 30 to 40OC. The C4 hydrocarbon fraction containing up to 5.8 isobutylene is then treated with 40-55% sulfuric acid to isolate the tertiary butyl alcohol. The isobutylene residue is then converted into oligomers in the presence of 60 to 70% sulfuric acid at a temperature of 10 to 25.degree.
The C 4 hydrocarbon fraction contains at most 0.2% by weight of isobutylene; the conversion rate of isobutylene is 99.6% (German Patent No. 2,362,115).

the known method has several serious drawbacks, namely
1. Complexity of the technological scheme of the process and the multiplicity of its stages;
2. Presence of corrosive environments which requires the construction of facilities made of special materials;
3. Difficulty separating the catalyst from the reaction mass;
4. Considerable losses of isobutylene due to its pligenation;
5. Need to separate tertiary butyl alcohol from hydrocarbon fraction before treating with 60-70% sulfuric acid;
6. Relatively low purity of separated isobutylene.

 A process is known for separating isobutylene from the C4 hydrocarbon fraction which comprises separating the isobutylene by treating said fraction with water (hydration) at a temperature of 70 to 100 ° C under a pressure from 16 to 23 atmospheres in the presence of a polar solvent taken from 10 to 70 <0 of the mass of water, an emulsifier taken at a rate of 0.2 to 3.0% of the body of water and in the presence of a shaped (extruded) ion exchange catalyst. As the emulsifier, hydroxyethyl higher fatty alcohols, hydroxyethylated alkylphenols and n-dodecylpyridine chloride are used.

As the catalyst is used a shaped ion exchange catalyst (extruded) which is constituted by
a sulfonated styrene-divinylbenzene copolymer composition in powder or styrene-diisopropenylbenzene sulphonated powder and a thermoplastic material taken in proportions of 4/1 to 1/1 by weight obtained by extruding the initial mixture in a extruder at the melting temperature of the thermoplastic;
a sulfonated composition of styrene-divinylbenzene or diisopropenylbenzene copolymer and a thermoplastic material taken in proportions of 4/1 to 1/2 by weight and obtained by extrusion of a mixture of a styrene-divinylbenzene copolymer or disopropenylbenzene and a thermoplastic material with subsequent treatment of the extruded product with an energetic sulfonating agent.

 the catalyst is in granules 5 mm in diameter and 10 mm in length and has an exchange capacity of 2.9 to 4.3 milli equivalents per gram of dry catalyst.

 The initial mixing liquid composed of a C 4 hydrocarbon fraction, water, a polar solvent and an emulsifier in the proportions indicated above is admitted by sending it directly to a reactor at a rate of 2 At 3 hours 1. In the reactor at a temperature of 70 to 110 ° C and at a pressure of 16 to 23 atmospheres there is an interaction of isobutylene and water with formation of tertiary butyl alcohol. The C4 hydrocarbon fraction which has not reacted by evaporation is separated from the reaction mixture while the tertiary butyl alcohol solution containing the solvent, the emulsifier and -products resulting from the interaction of isobutylene with the solvent.The concentrated aqueous solution of tertiary butyl alcohol obtained in isobutylene is dehydrated at a temperature. 80OC to 1109C and under a pressure up to 3 atmospheres in the presence of the aforesaid catalyst.

 Under these conditions, when the isobutylene is separated from the fraction which contains 30 to 45% by weight of isobutylene, the residual isobutylene content of the C 4 fraction is 5 to 7% by weight for a conversion rate of 1 to 4% by weight. isobutylene 92 to 97 at the hydration stage (US Pat. No. 4,012,456, class 260-677A, 1977).

 The disadvantage of the aforementioned process is that, to ensure the contact of the reactants with the catalyst are introduced into the initial mixture of the C4 hydrocarbon fraction and water that does not dissolve virtually one in the other, a homogenising additive such as a polar solvent and an emulsifier.

 the polar solvent under the reaction conditions forms by-products while the emulsifying additives impede the separation of the reaction mixture into hydrocarbon and aqueous phases which complicates the separation scheme in a total manner, entails additional charges for auxiliary materials and 'utility. In addition, the total extraction of isobutylene from the C 4 hydrocarbon fraction is not achieved leading to considerable losses of isobutylene.

 The object of the present invention is to eliminate the aforesaid drawbacks.

It has therefore been proposed to improve the process for separating ispbutylene from the C4 hydrocarbon fraction by its hydration with water, which simplifies the process technology and increases the extraction rate. isobutylene from said fractions up to 99.9 and to obtain a hydrocarbon fraction in
C4 freed from isobutylene so that its residual content does not exceed 0.5% by weight.

 The solution to the problem thus posed is that in the claimed process for separating isobutylene from the C4 hydrocarbon fraction comprising the stage of treatment of the C4 hydrocarbon fraction with water at a temperature of 70.degree. at 110 ° C and at a pressure of 16 to 23 atm at the presence of an extruded ion exchange catalyst and a stage of dehydration of tertiary butyl alcohol which is formed at isobutylene at a temperature of 80 to 11000 and at a temperature of 80.degree. pressure of up to 3 atmospheres in the presence of said catalyst, according to the invention the treatment of the C 4 hydrocarbon fraction with water under conditions of their countercurrent contact at a feed rate of water of 5 to 30 m 2, and a flow rate of the C 4 hydrocarbon fraction in a catalyst bed of 0.001 to 0.020 m / s.

 The use of the principle of countercurrent flow of the reagents through the catalyst bed makes it possible to conduct the process in extraction mode. This leads to an increase in the speed of the hydration reaction, ie the interaction of isobutylene with the water which ensures the increase of the isobutylene extraction rate of the d-fraction. C4 hydrocarbons and simplification of the process technology.

 It is advantageous to increase the productivity of the process at the water treatment stage to remove the C 4 hydrocarbon fraction containing from 5 to 50% by weight tertiary butyl alcohol from the reaction zone, to separate it. of said alcohol and return it to the reaction zone.

The claimed process is carried out in a reactor which is an extraction-reaction column packed with an extruded ion exchange catalyst according to US Pat.
No. 4,012,456 in the form of bodies of varied geometry, particularly in the form of cylinders of 5 × 10 mm used simultaneously as a packing body. In the reactor, overhead at a rate of 10 to 20 m / h is used in the reactor which serves as a continuous phase.

 The C4 hydrocarbon fraction is sent as a dispersed phase into the lower part of the reactor through a distributor device. The rate of rise of the dispersed phase in the catalyst bed is a function of the difference in the densities of the reagents and the bulk density of the catalyst and is 0.001 to 0.020 m / s. Isobutylene reacts with water on the extruded ion-exchange catalyst to form tertiary butyl alcohol, it being understood that at the same time an extraction of the tertiary butyl alcohol formed from one of the phases takes place. (Aqueous or hydrocarbon) .The reactor is maintained at a temperature of 70 to 110.degree. C., a pressure of 16 to 23 atmospheres sufficient for carrying out the reaction in the liquid phase, and a hydrocarbon fraction / water volume ratio of at least 5. / 1. The isobutylene content of the C4 hydrocarbon fraction may be arbitrary.

The extraction rate of isobutylene reaches 99.98%. In the water treatment stage of the C 4 hydrocarbon fraction, it is possible to carry out: the removal of the reaction zone from the C 4 hydrocarbon fraction containing 5 to 50% by weight of tertiary butyl alcohol, separating said alcohol and recycling it to the reaction zone. The C 4 hydrocarbon fraction of tertiary butyl alcohol is separated by well known methods, such as by rectification or washing with water.

 The purified C4 hydrocarbon fraction of isobutylene is collected in the upper portion of the reactor and is admitted to the rectification column where it is separated from tertiary butyl alcohol. The residual content of tertiary butyl alcohol of the C4 hydrocarbon fraction does not exceed 0.4% by weight, the residual isobutylene content is less than 0.5% by weight.

The tertiary butyl alcohol aqueous solution taken from the bottom of the reactor is admitted to the rectification where said alcohol is isolated in the form of an azeotropic mixture having a concentration of 88%. The dehydration of tertiary butyl alcohol to isobutylene is carried out in a two-part column-type reactor: lower rectification portion and higher reaction part charged with extruded ion-exchange catalyst at a temperature of 80 to 110 ° C, under a temperature range of 80 to 110 ° C. pressure up to 3 atmospheres, at an initial alcohol feed rate of 0.1 to 1.0 hours at a linear velocity of C-, 1 to 0.4 m / s. tertiary butyl alcohol is 98 to 100
The resulting isobutylene has a concentration of 99.9552 by weight and above.

By comparison with the nearest prior art, the claimed method makes it possible to obtain the following
1. Increase the rate of extraction of isobutylene from the C4 hydrocarbon fraction up to 99S980XS without the use of homogenizing additives, through the use of the countercurrent principle through the bed catalyst.

 2. To lower the electrical energy consumption by excluding from the hydration process scheme the evaporation subset of C4 hydrocarbons not entered in the reaction from the aqueous solution of alcohol and the subset of condensation.

 3. Simplify the separation scheme of the products of the reaction by exclusion of the hydration process of the homogenizing additives due to the absence of interaction by-products of the polar solvents with the olefins.

 4. Use the purified C4 fraction purified of isobutylene to a residual isobutylene content not exceeding 0.5% by weight, without further purification as a marketable product.

5. With the removal of the C4 hydrocarbon fraction containing from 5 to 50% by weight of tertiary butyl alcohol, at the water treatment stage of the C4 hydrocarbon fraction it became possible to perform the following:
a) reduce the catalyst consumption by 10 to 15%;
b) reduce the capacity of the equipment, which leads to a reduction in energy costs and fixed assets.

 Other features and advantages of the invention will be better understood on reading the following description of embodiments of the claimed method.

 EXEDSLE 1.

 110 liters of extruded ion catalyst (composition according to US Pat. No. 4,012,456) are placed in a column reactor.

 From the top of the reactor, water is admitted at a rate of 184 l / h (linear velocity 10.8 m / h) and from below an iso-butane-isobutylene fraction containing 42.6% by weight of isobutylene at a rate of 27.5 l / h (flow rate of the C 4 hydrocarbon fraction in the bed of said catalyst: 0.010 m / s).

 Temperature in column 81OC, pressure 20 atm. The isobutylene concentration of the purified C4 hydrocarbon fraction is 0.16% by weight. The conversion rate of isobutylene is 99.7%. the isobutylene-freed C4 hydrocarbon fraction is removed from the top of the reactor. The tertiary butyl alcohol aqueous solution is removed from the bottom of the reactor and an azeotropic mixture containing 88% by weight of tertiary butyl alcohol is isolated therefrom.

 The dehydration of tertiary butyl alcohol is carried out in a two-part lower column rectification column reactor and a top reaction part filled with the same catalyst as in the above-mentioned process, in a proportion of 70 liters.

 Temperature in column 87oC, pressure 0.7 atm. The solution of tertiary butyl alcohol is admitted at a speed of 80 l / h.

 the conversion rate of tertiary butyl alcohol under these conditions is 99%. - The separated isobutylene, after drying and rectification at a concentration of 99.95%.

 EXAMPLE 2.

 93 liters of extruded ion-exchange catalyst according to Example 1 are placed in a column-type reactor. The water at a speed of 240 liters / hour is admitted from above in the column (linear velocity 14.1 m). / h) and from below - a pyrolysis fraction having isobutylene content of 62.4% by weight at a rate of 30 I / h (flow rate of the C 4 hydrocarbon fraction in the catalyst bed of the catalyst). 0.009 m / s).

 80 ° C to 92 ° C, 20 atm pressure. the isobutylene concentration of the purified C4 hydrocarbon fraction is 0.03 gr, by weight, the isobutylene conversion of 99.98%.

 the separation and dehydration of the tertiary butyl alcohol is as described in Example 1. Isobutylene isolated after drying and rectification at a concentration of 99.98.

 EXES: RLE 3.

A column-type reactor 110 1 of an extruded ion-exchange catalyst is placed in accordance with example 1. The water is admitted from above in the column at a speed of 240 l / h (linear velocity 14, 1 m / h) and from below a butane-butylene fraction containing 28.8% by weight of isobutylene at a rate of 40 l / h (flow rate of the C 4 hydrocarbon fraction in the catalyst bed
C, 009m / s). Temperature from 100 to 110 ° C, pressure 23 atm. The isobutylene concentration of the purified C4 hydrocarbon fraction is 0.25 by weight. The conversion rate of isobutylene is 98.51%.

 The tertiary butyl alcohol is separated and dehydrated as in Example 1. The concentration of isolated isobutylene after drying and rectification is 99.95%.

 EXAMPLE 4

 The procedure is as in Example 1. The water admission speed is 240 l / h (linear speed 14.1 m / h). A C 4 hydrocarbon fraction having an isobutylene content of 15% by weight from below is allowed at a rate of 40 l / h (flow rate of the C 4 hydrocarbon fraction in the catalyst bed of 0.009). m / s). The temperature in the column is 70oC, the pressure is 16 atm. The isobutylene concentration of the purified fraction is 0.2% by weight. the conversion rate of isobutylene is 98.86%.

 The separation and dehydration of the tertiary butyl alcohol is carried out as in Example 1. Isobutylene isolated after drying and rectification at a concentration of 99.95.

 EXAMPLE 5

 The procedure is analogous to that of Example 1. Water admission speed 34 G l / h (linear velocity 20 m / h). A pyrolysis fraction having an isobutylene content of 62.4% by weight from below is allowed at a rate of 40 l / h (flow rate of the C 4 hydrocarbon fraction in the catalyst bed 0.005 m / h). s). Temperature 85oC, pressure 20 atm. The isobutylene concentration of the purified fraction is 0.01 by weight. The conversion rate of isobutylene is 99.99%.

 Tertiary butyl alcohol is isolated and dried as in Example 1. Isolated isobutylene concentration after drying and rectification 99.97%.

 EXSMPLE 6.

The process is carried out in a manner analogous to that of Example 1. Water is admitted into the column from above at a speed of 85 l / h (linear velocity 5 m / h), an isobutane-isobutylene fraction is allowed. from below at a rate of 12 l / h (rate of flow of the hydrocarbon fraction in
C4 in the catalyst bed 0.020m / sec). The temperature of the reaction is 90oC, the pressure of 20 atm. The isobutylene concentration of the purified fraction is 0.3% by weight.

The conversion rate of isobutylene is 99.59%.

 The separation and dehydration of the tertiary butyl alcohol is carried out as in Example 1. Isobutylene isolated after drying and rectification at a concentration of 99.95%.

EXESSLE.7
1.2 liters of extruded ion-exchange catalyst according to Example 1 are placed in a column-type reactor. The column is admitted to the top of the water at a rate of 52 l / h (linear velocity 30 m). / h), from below an isobutane-isobutylene fraction containing 42.6C / w of isobutylene at a rate of 5, tri l / h (rate of flow of the C 4 hydrocarbon fraction in the catalyst bed 0.001 m / s).

 Temperature in column 80OC, pressure 20 atm. Isobutylene concentration of the C4 hydrocarbon fraction freed from 0.02% isobutylene, conversion rate of isobutylene 99, 98.

 The isolation and dehydration of the tertiary butyl alcohol is carried out as in Example 1. Isobutylene isolated after drying and rectification at a concentration of 99.97%.

 EXAMPLE 8.

 100 liters of extruded ion exchange catalyst according to Example 1 were placed in a column-type reactor.

 From above water is admitted at a linear velocity of 17 m / h at the rate of 290 l / h, at the bottom a pyrolysis fraction containing 5 by weight of isobutylene at a rate of 48 l / h (speed of flow of the C4 hydrocarbon fraction in the catalyst bed of 0.010 m / s). Temperature in the 8G reactor at 82oC, 20 atm pressure.

 The C4 hydrocarbon fraction containing 36% by weight of tertiary butyl alcohol was removed from the reaction zone and directed to a rectification.

 The C4 hydrocarbon fraction separated from the tertiary butyl alcohol is introduced to an alcohol content of 50% by weight in the reactor in the same reaction zone.

 The fraction of C4 hydrocarbons freed from isobutylene discharged at the top of the reactor contains 0.3% by weight of isobutylene. the conversion rate of isobutylene is 99.7.

 The aqueous solution of tertiary butyl alcohol after mixing with the tertiary butyl alcohol isolated from the C4 hydrocarbon fraction is subjected to concentration and dehydration.

 The dehydration of the tertiary butyl alcohol is carried out as in Example 1.

 The isobutylene isolated after drying and rectification has a concentration of 99.95%.

 EXAMPLE 9

100 liters of ion exchanger catalyst extruded according to Example 1 are placed in a column-type reactor. Up to 14 m / h of water at a rate of 240 ml is allowed from above. from below an isobutane-isobutylene fraction containing 40.5% isobutylene at a rate of 40 l / h (flow rate of the C 4 hydrocarbon fraction in the catalyst bed 0.009 m / s). Temperature in the reactor 81 C, pressure 20 atm. The C 4 hydrocarbon fraction containing 5% by weight of tertiary butyl alcohol is removed from the reaction zone, cooled to a temperature of 20 to 30 ° C and sent to the wash at room temperature. water in
a purifier. After washing, the tertiary butyl alcohol content of the C 4 hydrocarbon fraction is 0.4% by weight. The above fraction released from tertiary butyl alcohol is recycled to the reactor in the same reaction zone.

 The fraction of C4 hydrocarbons freed from isobutylene and discharged at the top of the reactor contains 0.2 g of isobutylene. The conversion rate of isobutylene is 99.75%.

 The aqueous solution of tertiary butyl alcohol from the reactor with the washings is admitted for the concentration, and an azeotropic mixture of a concentration of 88% by weight is obtained. The dehydration of the tertiary butyl alcohol is carried out as in Example 1.

 the isobutylene obtained after drying and rectification at a concentration of 99.95%.

 EXAMPLE 10.

 100 l of extruded ion exchange catalyst according to example 1 are placed in a column-type reactor.

 Water was fed from above at a rate of 17 m / h at the rate of 290 l / h, at the bottom a pyrolysis fraction containing 62.5% by weight of isobutylene at a rate of 48 l / h ( flow rate of the C4 hydrocarbon fraction in the catalyst bed of 0.010 m / s). Temperature in the reactor 80oC, pressure 20 atm.

 The C 4 hydrocarbon fraction containing 50% by weight of tertiary butyl alcohol is removed from the reaction zone and directed to rectification. The fraction purified of tertiary butyl alcohol, containing 0.5% by weight of tertiary butyl alcohol, which is returned to the same reaction zone, is recycled to the reactor. After hydration, the purified C4 hydrocarbon fraction of isobutylene contains 0.5% by weight of isobutylene. the conversion of isobutylene is 99.6%.

 The separation and dehydration of the tertiary butyl alcohol is carried out as in Example 1.

 isolated isobutylene after drying and rectification at a concentration of 99.95%.

 By way of comparison with the claimed process for the separation of isobutylene from a C4 hydrocarbon fraction, an exemplary embodiment of the known process can be cited (prior art: US Pat. America No. 4,012,456).

 EX SOLE 11.

 130 liters of an extruded ion exchange catalyst are placed in a column-type reactor. A mixture of a C 4 hydrocarbon fraction isolated from the gasoline pyrolysis products is continuously admitted into the reactor. containing 42.5% by weight of isobutylene and an aqueous solution of ethylcellosolve of a concentration of 50% by weight containing 1% by weight of water, of emulsifier which are hydroxyethyl higher fatty alcohols (C10-C18 fraction). The molar ratio of hydrocarbon / water fraction is 1/10, the admission speed of the mixture is 260 l / h (2.0 hour 1). The pressure in the reactor is maintained at 18 atm, the temperature at 85 to 100OC. The conversion rate of isobutylene to tertiary butyl alcohol is 93 ° C. The isobutylene concentration of the C4 hydrocarbon fraction is 4.9.

 The reaction mixture containing the tertiary butyl alcohol and water is sent to an intermediate capacity for removal by evaporation of the non-entrained hydrocarbons, after which it is sent to the rectification.

An aqueous solution of tertiary butyl alcohol containing volatile hydrocarbons in solution is isolated by rectification. These are removed by distillation. A tertiary butyl alcohol aqueous solution of 85% concentration is obtained which is sent to the dehydration of the aforesaid alcohol.

 The dehydration of tertiary butyl alcohol is carried out in a column type reactor. the reactor consists of two parts: the lower part functioning as a rectification column and the upper part which is the seat of the reaction. The lower part of the reactor is filled with a packing, the upper part is loaded with a catalyst at 200 1. The same catalyst is used as that used in the hydration stage. The reactor is equipped with a boiler and a partial condenser.

 The aqueous solution of tertiary butyl alcohol in the middle part of the reactor is continuously admitted under the catalyst bed at a rate of 1.0 hour 1. The temperature in this part is maintained between 85 and 87.degree. C., the pressure at 0.7.degree. ATM. The gaseous isobutylene which forms at the same time as the vapors of the tertiary butyl alcohol not entering the back reaction arrives in the partial condenser where the tertiary butyl alcohol condenses; said tertiary butyl alcohol is continuously returned to the catalyst. isobutylene is discharged continuously from the circuit, is condensed and purified by rectification.

 the conversion rate of tertiary butyl alcohol is 99%. The isobutylene concentration of the product obtained is 99.95%.

Claims (2)

- Claims  1 - A process for separating isobutylene from a C4 hydrocarbon fraction, comprising a stage of treatment of the C4 hydrocarbon fraction with water at a temperature of 70 to 11000 and a pressure of 16 to 23 atm in the presence of an extruded ion exchange catalyst and a dehydration stage of the tertiary butyl alcohol which is formed in isobutylene at a temperature of 80 to 11000 and at a pressure not exceeding 3 atm in the presence of the aforesaid catalyst, characterized in that the C 4 hydrocarbon fraction is treated with water by countercurrent contacting at a water inlet velocity of 5 to 30 m / h and at a rate of flow rate of the C4 hydrocarbon fraction in the catalyst bed from 0.001 to 0.020 m / s.  2 - Process according to claim 1, characterized in that, at the stage of treatment with water, the C4 hydrocarbon fraction containing 5 to 50% by weight of tertiary butyl alcohol is removed from the zone of the reaction, separates said alcohol and is recycled to the reaction zone.