DE1618666C - Process for separating mixtures of hydrocarbons with various degrees of unsaturation - Google Patents

Description

3 4

Initiated distillation column 10, namely in the cent isobutene, 11.0 mol percent 1-butene, 3.2 Molpromeisten Cases in the vapor phase. Introduced by the above cent η-butane and 2.7 mole percent isobutane, Line 12 arranged in line 11 is used. For this purpose, a solvent mixture of 94.9 according to the invention was added Solvent from alkoxynitrile and weight percent 3-methoxypropionitrile and 5.1 GeWasser usually in the liquid phase in the column 5 weight percent water in such an amount initiated. The solvent flows downward due to that weight ratio of solvent the column 10 and thereby comes into contact with a hydrocarbon mixture of about 4: 1. The the upwardly flowing vapors of the feedstock mixture of solvents obtained in this way mix. The contact between the solvent and hydrocarbons was reduced to about 54 ° C and medium and the hydrocarbon feed, the io is brought to a pressure of 4.15 atmospheres and below this more unsaturated hydrocarbons prefer reflux conditions for about 2 hours absorbed. Which is not absorbed by the solvent. At the end of the 2 hours, samples of the bated part of the feed mixture flows in the extra gas and liquid phase taken and analyzed Distillation column 10 upwards and occurs Siert. The vapor phase contained about 28.5 percent by weight the line 13 in the condenser 14, 15 cent butadiene, 4.8% cis-butene-2, 7.1 weight percent in which the unabsorbed vapors are condensed trans-butene-2, a total of 50.1 percent by weight of butene-1 the. Part of the condensate is via line 15 and isobutene, 4.9 percent by weight η-butane and 4.6 as reflux into the extracting distillation column weight percent isobutane. It turned out that the Lö-10 returned. The remainder of the condensate is solvent from the hydrocarbon mixture 39.9 the condenser 14 via the line 16 uses 20 percent by weight butadiene, 5.3 percent by weight cisdung fed. The solvent enriched with absorbed hydrocarbons-butene-2,6.7% trans-butene-2, a total of 43.2 weight percent, flows downwards percent butene-1 and isobutene, 2.9 weight percent absorbed by the extractive distillation column 10 and η-butane and 2.0 weight percent isobutane is circulated through the reheater 17. In this had. The carbon absorbed by the solvent becomes the solvent heated so that part of the amount of hydrogen as was 18.7 percent by weight, what absorbed hydrocarbons from the solution with a load of 23.1 kg hydrocarbons per tel is stripped and evaporated. These hydrocarbons corresponded to 100 kg of solvent, Substances then flow up the column 10. The . . Solvent and the absorbed hydrocarbons example are from the extracting distillation column 10 30 To demonstrate the benefits of extracting over the line 18 withdrawn and columned to a stripping distillation process and solvents 19, in which the absorbed charcoal measurements of the invention can be achieved, was the Hydrogen stripped from the solvent and extracted as a mixed solution according to Example 1 Steam via line 20 of its use is passed through distillation with a solvent system of 95 will. After stripping, the solution becomes 35 weight percent furfural and 5 weight percent water subjected to medium from the stripping column 19 via a line 21, under the same conditions either led to line 12 and thus again as in Example 1, with the difference that the pressure introduced into the column 10, or processed further 4.57 atmospheres and the ratio of solvent to carbon or fed to another location. hydrogen was 4.1: 1. After 2 hours were If, within the scope of the invention, the alkoxynitrile is taken from 40 vapor and liquid samples. the along with water and another sample of solvent and steam, consisted of 26.9 percent by weight butatel is used, a correction may occasionally be used, 5.0 percent by weight of cis-butene-2, 7.3 percent by weight of the Concentration of the constituents by removal percent trans-butene-2, total 48.7 percent by weight or addition of the water or other concomitantly used 1-butene and isobutene, 6.4 percent by weight of n-Bu solvents or the alkoxynitrile may be required. 45 tan and 5.7 percent by weight isobutane. That of that Such a correction is in the area of expert solvent shears consisting of furfural and water Measures and will in most cases consist of hydrocarbon mixture absorbed in the system Relation to the function of the stripping column of 35.8 percent by weight butadiene, 6.0 percent by weight on which, via line 21, the stripping percentage of cis-butene-2, 8.0 percent by weight of trans-butene-2, lonne 19 withdrawn solvent made. There 50 a total of 43.0 percent by weight of 1-butene and isobutene, It may also be necessary to use more than a scraper, 4.5 percent by weight η-butane and 2.7 percent by weight lonne to use so the more unsaturated, isobutane. The amount absorbed by the solvent Hydrocarbons in sufficient quantity system-absorbed hydrocarbons fraudulent by S.O. removed from the solvent. The determination percentage, corresponding to a loading of the solution the number and efficiency of the stripping agent with 25.0 kg of hydrocarbons per columns that are sufficient to remove the stronger 100 kg of solvents.

unsaturated, absorbed hydrocarbons. For comparison of the selectivity required in Examples 1 is within the range of expert measures and 2 solvent systems were used. the relative volatility values of trans-butene-2 The invention is explained below with reference to Aus 60 and the butadiene in the feed mixture according to supplementary examples. game 1 and in the presence of the solvent systems. ·,., ^{Calculated according} to Examples 1 and 2. The relative volatility of Example 1 is calculated according to the following equation: In a distillation unit with a soil flow

degree of efficiency of about 1 (theoretical soils to 65 relative volatility = dene soils) was a hydrocarbon mixture of

about 37.0 mole percent butadiene, 7.6 mole percent cis- in which A, in mole percent, is the proportion of trans-butene-2

Butene-2, 6.5 mol percent trans-butene-2, 32.0 molpro- in the vapor phase, B the proportion of trans-butene-2 in

of the liquid phase, C is the proportion of butadiene in the vapor phase and D is the proportion of butadiene in the liquid phase. The relative volatility of trans-butene-2 in the above hydrocarbon mixture in the absence of a solvent was 0.843. In the presence of the solvent system according to Example 1 it was 1.489 and in the presence of the customary furfural-water system (Example 2) it was 1.200.

B e i s ρ i e 1 3

To demonstrate the superiority of the extractive distillation process and solvent system in accordance with the invention, three extractive distillation attempts were made at lower temperatures and higher pressures. There were furfural, acetonitrile and 3-methoxypropionitrile, respectively with 5 weight percent water. The taking of the samples from the steam and the liquid phase took place as in Examples 1 and 2. It was the loading of the solvent and the relative volatility of trans-butene-2 and of butadiene when using each of the solvent systems mentioned definitely. The following table shows the conditions for the extractive distillation and the results achieved with it.

Furfural-H ₂ O

Acetonitrile-H ₂ O

3-methoxy

propionitrile

H ₂ O

Temperature, ⁰ C

Pressure, atü

Solvent to hydrocarbon weight ratio

Loading of the solvent kg / 100 kg solvent Relative volatility '.;.

From the above, it can be seen that the solvent system of the present invention is an essential one has higher selectivity than the two common solvents. Furthermore, the solvent according to the invention has under the conditions of these extractive distillation attempts a higher dissolving power than the usual solvent system furfural - water.

B e i s ρ i e 1 4

The hydrocarbon mixture according to Example 1, the extractive distillation with 3-methoxypropionitrile at a ratio of 3: 1 between solvent and used, a temperature of 6O ⁰ C and a pressure of 4.92 atm in a DestiUationseinheit with a tray efficiency of about 1 ( theoretical soils per existing soil). For this extractive distillation experiment, the amount of hydrocarbons absorbed by the solvent in percent by weight, the loading of the solvent and the relative volatility according to the. defined above. The amount of hydrocarbons absorbed by the solvent was 26.5 percent by weight, corresponding to a loading of the solvent with 27.8 kg of hydrocarbons per 100 kg of the solvent. The relative volatility of trans-butene-2 and of butadiene was found to be 1.325.

B e i s ρ i e 1 5

A mixture of C ^ hydrocarbons, the butane, Containing butenes, 1,2-butadiene, 1,3-butadiene, vinylacetylene and ethyiacetylene, was an extractive Distillation using a mixture of, 93.8 percent by weight 3-methoxypropionitrile and Subjected to 6.2 percent by weight of water as a solvent. The feed mixture contained 3500 ppm vinyl acetylene and 1800 ppm ethyiacetylene.

The mixture of C ₄ hydrocarbons is introduced in the lower part, the solvent mixture in the upper part of the column; the column contained 145 trays. The ratio of solvent to input 71.1
5.69

5.8: 1
15.0
1.247

71.1
5.80

3.3: 1
28.7

1.329

71.1 5.84

4.5: 1 20.6 1.453

was 1.5: 1. The reheater was with a temperature operated at 171.7 ° C. The top product from the column contained practically all of the butanes, Butenes and much of the 1,3-butadiene that was present in the feed, but only 13 ppm vinyl acetylene and only 11 ppm ethyiacetylene. The solvent phase was significantly richer in vinyl acetylene and ethyiacetylene as the feed mixture.

Example 6

For separating a hydrocarbon mixture having essentially the same composition like the mixture given in Example 1, a fractionation column of 51 mm in diameter and about 145 floors used. The hydrocarbon mixture was fed into the column in an amount of 240 g / h at a point 72 plates from the bottom of the column. A solvent system 95 percent by weight of 3-methoxypropionitrile and 5 percent by weight of water was fed into the fractionating column introduced at a point which was 140 trays from the bottom of the column, and in in an amount such that the weight ratio of solvent to feed was 10: 1. The column was operated at a reflux ratio (weight ratio of reflux to feed) of 3.2. The distillate passing over was essentially free of butadiene. The mixture of solvent and butadiene was continuously withdrawn from the lower end of the column and subjected to distillation, wherein the butadiene is obtained in a concentration of about 91%. The rest essentially consists of cis-butene-2, which can then be fractionated from the butadiene.

In the context of the invention, alkoxynitriles with the formula are used as solvents

_O _R-R-C-N

used. R is an alkyl radical. These alkyl radicals in most cases contain no more than 5 carbon atoms, usually no more than 3 carbon atoms. The alkyl radicals can be straight-chain

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or be branched. In the context of the invention, the compounds, the degree of effectiveness and the

those alkoxynitriles are preferred in which R is an extraction distillation and the

straight chain alkyl radical with 1 to 3 carbon separator depending. Generally amounts to

atoms is. This preferred group includes both the weight ratio between solvent and

for example 3-methoxyacetonitrile, 3-ethoxyacetonitrile, 5 use about 0.5: 1 to about 20: 1

S-PropoxyacetonitriljS-Methoxypropionitril.S-Ethoxy- also work with a ratio that is below or

propionitrile, 3-propoxypropionitrile, 4-methoxybuty- is above this range. Preferably the ge

ronitrile, 4-ethoxybutyronitrile and 4-propoxybutyronitrile weight ratio between solvent and insert

nitrile. 3-Methoxypropio- between about 1: 1 and 10: 1 are particularly preferred.

nitrile and 3-ethoxypropionitrile. io The reflux ratio with which the column is operated

The solvent mixture according to the invention can be used, depends on the soil efficiency of the colon

alone or together with other solvents, the ratio of solvent to use, the

be turned. For the purposes of the invention, a composition of the feed mixture and the

Particularly well-suited solvent mixture contains the desired selectivity depending on. In general

85 to 95 percent by weight of alkoxynitrile and 5 to 15, a reflux ratio of 0.01: 1 to 20: 1 is sufficient.

15 weight percent water. The reflux ratio is preferably in the

The invention can be used with any conventional distillation range from 0.5: 1 to 5: 1.

direction can be carried out, both in batches The distillation process according to the invention can

Process (Example 1 and 2) as well as continuously under atmospheric pressure or under or

(Example 6). Any conventional fractionation pressure can be carried out. Generally working

direction use, for example a packing cor-

lonne or a column with perforated plates, see bell pressure and 14.1 atm. Preferably the

floor or a system of baffles. The number of pressures between atmospheric pressure and 2.8

the theoretical trays of the fractionation device up to 6.3 atmospheres.

The temperature at which the extracting distillation of the feed mixture, the amount of the solution is carried out according to the invention, depends on the means, the reflux ratio and other factors of the hydrocarbon mixture to be separated, which depends on the desired degree of separation, the composition Are known to those skilled in the art. The floor gig. In general, one works within the scope of the degree of efficiency (number of theoretical plates per finding with a temperature in the range from 0 to existing soil) can be 1, as in the case of 30 204 ⁰ C. When applying the invention to the games 1 and 2, or 150 or more. The object specified below is preferably used when a fractionation column is used in which a housing with temperatures in the range from 45 to stirring of vapor and liquid in countercurrent at 149.degree.

brought about and with reheating and reflux. The invention is primarily used for separating

is working. The soil efficiency is generally less than 35 strongly unsaturated hydrocarbons

common 25 to 150. more unsaturated hydrocarbons are used.

In the preferred embodiment of the invention. According to the invention, monoolefins of paraffins, is the feed mixture in the fractionating column of diolefins, triolefins, acetylenes, etc. or diol or just below the middle of the column and the spoon of paraffins, monoolefins, triolefins, acetysing agents are separated above the entry point of the insert 40 len, etc., the 3 to 5 carbons introduced. In most cases the supply will be atoms per molecule and various unsaturation of the Solvent in the column at a point that have grade. In a particularly preferred view At the top of the column or in the vicinity of the embodiment, the invention is based on the separation of same is located. Generally, the feed will be 3 to 5 mixed carbon diolefin hydrocarbons into the fractionation column preferably at a 45 atomic number of mono-olefin and paraffin-carbon sites initiated, the applied between half and three hydrogens with 3 to 5 carbon atoms-fifth the height of the column from whose lower det.

End measured, lies; the solvent is at a die of the solvent site according to the invention introduced, which absorbed by no more than a third of the composition, more unsaturated Height of the column from the top of the column 50 Hydrocarbons can refer to any known is. Way to be recovered from the solvent,

The fractionated used in the process according to the invention, for example by flash evaporation

te amount of solvent is to some extent from distillation, stripping with a gas or to others

desired selectivity, the usual way to be separated from each other.

1 sheet of drawings

209 541/545

Claims (1)

Method known that an accurate prediction of the Claim: Conditions permitted under which a particular process for separating mixtures of solvents used for a particular purpose can be C - to Q-hydrocarbons with different. For this reason, it is only possible to establish very degrees of unsaturation in which the carbons are difficult to determine which of the possible solvents, hydrogen mixtures of an extracting distillery, are useful for a given separation process in the presence of a solvent from and under which conditions these solvents are subjected to carboxylic acid nitrile and water An object of the invention is to provide an improved extractable distillation process saturation level of hydrocarbons with a high concentration of hydrocarbons and a solvent fraction for separating mixtures of hydrocarbons with a high hydrocarbon content substances with different degrees of unsaturation. With a higher degree of unsaturation, the invention further aims to create a characterized in that, as an improved solvent system for separating extraction solvent, a mixture of 75 to 15 mixtures of hydrocarbons with various 99 percent by weight of an alkoxynitrile of the degrees of eye unsaturation by extracting distillamines formula R - O - R - CN, in which the tion. A further object of the invention consists in the alkyl radicals R having no more than 5 carbon atoms, creating an improved extracting distillase, and 1 to 25 percent by weight of water being used for separating mixtures. '' ²⁰ hydrocarbons with different degrees of unsaturation according to the degree of unsaturation of the hydrocarbons and of solvents for The invention relates to a method for separating use in this method. The task of the Ervon Hydrocarbons, in particular one method of discovery, consists in creating an extracting one for separating mixtures of hydrocarbons * 5 Distillation process for separating polyolefin with different degrees of unsaturation due to extra hydrocarbons from monoolefin and / or pan ends Distillation. In particular, the invention relates to refined hydrocarbons and acetylene-carbon separation of hydrocarbon mixtures by hydrogen of polyolefin, monoolefin and / or selective removal of the more unsaturated carbon-paraffin hydrocarbons. Hydrogen components by extracting distillation 3o The invention relates to a method for lation. Separation of mixtures of C ₃ - to C _s hydrocarbons - It has long been known that many hydrocarbons with various degrees of unsaturation, in mixtures of substances by ordinary distillation, which the hydrocarbon mixtures can practically not be separated in an extra process, resulting in distillation The presence of a solution either because the boiling points are too close together, by means of a carboxylic acid nitrile and water, or because azotropic mixtures are formed. Some those thrown, in which a distillate with considerable mixtures with hydrocarbons, the azeotropic form with higher contents of hydrocarbons with low mixtures or close together boiling higher unsaturation and solvent points, however, contain hydrocarbons fractions with a high content of hydrocarbons different degrees of unsaturation, for example 4 ° substances with a higher degree of unsaturation, butadiene and butylenes are obtained. In order to overcome the problem, a mixture of 75 to 99 parts by weight of these mixtures has been proposed as extraction disadvantages of the usual distillation in the separating solvent, the cent of an alkoxynitrile of the general formula volatility ratio of the mixture components by R - O - R - CN, in which the alkyl radicals R have the addition of a selectively acting solvent 45 no more than 5 carbon atoms, and 1 to 25 percent water is used for the more unsaturated hydrocarbon component, to change the components of the mixture. Several diene and butylenes can be used for the solvent and the extracting distillafurol alone or with water for separating butation processes according to the invention. Because of its important advantages. The solution-corrosive action and instability according to the invention has however proved to be average allow the use of larger amounts of furfural, alone or with water, not so well, of water as an auxiliary solvent, because the alkoxy as might otherwise be assumed. nitrile has a higher solubility in water. Furthermore, with dimethylformamide and acetonitrile, the solvents according to the invention have been achieved a certain success. Selectivity and a high solubility in the separation of hydrocarbons shown in place of furfural for the hydrocarbons, which are a large number of selectively soluble in the solutions according to their degree of unsaturation. They are not reactive towards the currently known chemical compounds, which are more unsaturated hydrocarbons, and their combinations are used and capable of being induced and have a high level of oxidation resistance and numerous compounds that are not yet synthetic heat resistance. Furthermore, they have been manufactured a lesser one. So far, however, no process has ⁶ ° corrosive effects as furfural. Further advantages of the prior art that can be used to predict the effectiveness of a given solvent and solvent process in a given separation process can be predicted from the description below. Furthermore, a solution to the subject matter of the invention can emerge, means under certain conditions, for example, a preferred embodiment with regard to the temperature, the pressure, the deformation of the invention is shown schematically in the drawing. According to the ratio of solvent to input, the accompanying drawing, an input mixture with coal-used solvents, etc., will be usable and under other conditions useless under hydrogen with various degrees of unsaturation. So far there is no own, via the line 11 in an extracting