KR20060136427A - Method for the separation of pentenenitrile isomers - Google Patents

Abstract

The present invention relates to a process for separating pentenenitrile isomer mixtures, wherein at least one isomer in the mixture is enriched, and the separation of mixtures of pentenenitrile mixtures is carried out by distillation under reduced pressure.

Pentennitrile Isomer Mixtures

Description

Separation Method of Pentenenitrile Isomers {METHOD FOR THE SEPARATION OF PENTENENITRILE ISOMERS}

The present invention relates to a process for the preparation of pentenenitrile isomer mixtures.

Adipononitrile, an important intermediate in nylon production, is prepared by two-stage hydrocyanation of 1,3-butadiene. In the first hydrocyanation step, 1,3-butadiene is reacted with hydrogen cyanide in the presence of nickel (0) stabilized with a phosphorus ligand to give 3-pentenenitrile. The second component of the first hydrocyanation is substantially 2-methyl-3-butenenitrile, 2-pentenenitrile, 2-methyl-2-butennitrile, C ₉ nitrile, methylglutaronitrile and 4-vinylcyclohexene . In the second hydrocyanation, 3-pentenenitrile is subsequently reacted with hydrogen cyanide on nickel catalyst as well but with addition of Lewis acid to give adiponitrile. The second hydrocyanation also gives a mixture of reactant and product nitrile and also the second component mentioned above.

Complex mixtures generated in the two reactions must be separated from one another in order to economically perform the adiponitrile manufacturing process. In the conventional process for preparing adiponitrile by hydrocyanation of 1,3-butadiene and subsequent reaction of 3-pentenenitrile resulting therefrom with additional hydrogen cyanide molecules, a method for separating complex compounds, in particular for separating pentenenitrile isomers Is unknown.

As described in DE 100 49 265, the relative volatilities α of the pentenenitrile isomers at atmospheric pressure are in the range of 1.0 to 2.0, and in the case of a series of isomeric pairs, in the range of 1.0 to 1.5, the pentenenitrile isomers by distillation Separation presents a significant problem. Relative volatility α is the ratio of the vapor pressures of the two substances, where the vapor pressure of the substance with the higher vapor pressure becomes the molecule of the ratio.

Pentenenitrile Isomer Pairs Relative volatility at atmospheric pressure 2-methyl-3-butenenitrile / trans-3-pentenenitrile 1.72 Cis-2-pentenenitrile / trans-3-pentenenitrile 1.55 (E) -2-methyl-2-butenenitrile / trans-3-pentenenitrile 1.19 2-methyl-3-butenenitrile / (Z) -2-methyl-2-butenenitrile 1.12

Separation by distillation of the mentioned chemical species can be realized, but since the relative volatility at atmospheric pressure exceeds 1.0, it actually causes considerable technical complexity and energy consumption.

In order to avoid the situation of separating trans-3-pentenenitrile and trans 2-pentenenitrile, for example, US Pat. No. 3,526,654, US Pat. No. 3,564,040, US Pat. No. 3,852,325 and US Pat. It has been proposed to switch to something that can be easily removed by.

The disadvantage is that catalytic isomerization leads to the loss of valuable products due to the formation of undesirable isomers or oligomers.

 In order to avoid the situation of separating (Z) -2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile, and also trans-2-pentenyltrile and trans-3-pentennitrile, US 3,865,865 is a nitrile. The mixture is treated with aqueous sulfite solution to in each case an aqueous phase comprising certain bisulfite adducts of conjugated nitrile (Z) -2-methyl-2-butenenitrile or trans-2-pentenitrile, and the organic phase with reduced nitrile Suggested to get. The disadvantage of this method is that water must be completely removed before further use of the resulting organic phase in hydrocyanation using a nickel (0) catalyst with phosphorus (III) ligand, otherwise the phosphorus (III) ) Ligands are irreversibly hydrolyzed and inactivated. A further disadvantage of this process is that, as described in US Pat. No. 3,865,865, the resulting bisulfite adduct can be separated only for further use of conjugated nitriles only in reduced yield under strong conditions.

To improve the resolution, DE 100 49 265 proposes an increase in the removal capacity by extractive distillation by adding a liquid diluent. This process also has the disadvantage of first completely removing the liquid diluent, in particular water, from the nitrile stream produced in the further process.

It is therefore an object of the present invention to provide a process which enables the separation by distillation of pentenenitrile isomers having a relative volatility α in the range of 1.0 to 2.0 at atmospheric pressure in a technically simple and economically practical manner.

According to the invention, this object is achieved by a method of separating a mixture of pentenenitrile isomers which removes one or more isomers from the mixture.

In the process according to the invention, the separation of the pentennitrile isomer mixture is by distillation under reduced pressure.

In the process according to the invention, it is preferred to separate two or more different isomers.

The method according to the invention preferentially

A mixture comprising 2-methyl-3-butenenitrile and 3-pentenenitrile,

A mixture comprising 2-methyl-3-butenenitrile and (Z) -2-methyl-2-butenenitrile,

A mixture comprising cis-2-pentenenitrile and 3-pentenenitrile, and

A mixture comprising (E) -2-methyl-2-butennitrile and 3-pentenenitrile

Suitable for mixtures selected from the group consisting of:

In the context of the present invention, the term 3-pentenenitrile means a mixture of trans-3-pentenenitrile or trans-3-pentenenitrile with or without cis-3-pentenenitrile and 4-pentenenitrile. do.

Hydrocyanation of butadiene to 3-pentenenitrile and mixtures of these and 2-methyl-3-butenenitrile is carried out in the presence of a nickel (0) catalyst.

Ni (O) catalysts are complexes containing free phosphorus ligands and / or phosphorus ligands, preferably homogeneously dissolved nickel (O) complexes.

The phosphorus ligand and free phosphorus ligand of the nickel (O) complex are preferably selected from single or bidentate phosphine, phosphite, phosphinite and phosphonite.

These phosphorus ligands preferably have the following formula (I).

P (X ¹ R ¹ ) (X ² R ² ) (X ³ R ³ )

In the context of the present invention, compound I is a single compound or a mixture of different compounds having the above-mentioned formula.

According to the invention, X ¹ , X ² , X ³ are each independently oxygen or a single bond. When all of the X ¹ , X ² and X ³ groups are single bonds, compound I is a phosphine of formula P (R ¹ R ² R ³ ), wherein the definitions of R ¹ , R ² and R ³ are specified herein Is).

When two of the X ¹ , X ² and X ³ groups are single bonds and one is oxygen, compound I is of the formula P (OR ¹ ) (R ² ) (R ³ ) or P (R ¹ ) (OR ² ) (R ³ ) or phosphinite of P (R ¹ ) (R ² ) (OR ³ ), wherein the definitions of R ¹ , R ² and R ³ are specified herein.

When one of the X ¹ , X ² and X ³ groups is a single bond and two are oxygen, Compound I is of the formula P (OR ¹ ) (OR ² ) (R ³ ) or P (R ¹ ) (OR ² ) (OR ³ ) or phosphonite of P (OR ¹ ) (R ² ) (OR ³ ), wherein the definitions of R ¹ , R ² and R ³ are specified herein.

In a preferred embodiment, all X ¹ , X ² and X ³ groups must be oxygen, thus compound I is advantageously a phosphite of the formula P (OR ¹ ) (OR ² ) (OR ³ ) wherein R ¹ , The definitions of R ² and R ³ are specified below).

According to the invention, R ¹ , R ² , R ³ are each independently the same or different organic radicals. R ¹ , R ² and R ³ are each independently, preferably an alkyl radical having 1 to 10 carbon atoms (eg methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s -Butyl, t-butyl), an aryl group (e.g. phenyl, o-tolyl, m-tolyl, p-tolyl, 1-naphthyl, 2-naphthyl) or hydro having preferably 1 to 20 carbon atoms Carbyl (eg 1,1′-biphenol, 1,1′-binaftol). The R ¹ , R ² and R ³ groups may be directly bonded together, ie not solely through the central phosphorus atom. It is preferred that the R ¹ , R ² and R ³ groups are not directly bonded together.

In a preferred embodiment, the R ¹ , R ² and R ³ groups are radicals selected from the group consisting of phenyl, o-tolyl, m-tolyl and p-tolyl. In a particularly preferred embodiment, at most two of the R ¹ , R ² and R ³ groups should be phenyl groups.

In another preferred embodiment, at most two of the R ¹ , R ² and R ³ groups should be o-tolyl groups.

Particularly preferred compounds I which can be used are those having the general formula (Ia).

(o-tolyl-O-) _w (m-tolyl-O-) _x (p-tolyl-O-) _y (phenyl-O-) _z P

(Wherein w, x, y and z are each natural numbers and the following conditions apply: w + x + y + z = 3 and w, z ≤ 2)

The compound Ia is, for example, (p-tolyl-O-) (phenyl-0-) ₂ P, (m-tolyl-O-) (phenyl-O-) ₂ P, (o-tolyl-O-) (Phenyl-O-) ₂ P, (p-tolyl-O-) ₂ (phenyl-0-) P, (m-tolyl-O-) ₂ (phenyl-O-) P, (o-tolyl-O- ) ₂ (phenyl-0-) P, (m-tolyl-O-) (p-tolyl-O-) (phenyl-O-) P, (o-tolyl-O-) (p-tolyl-0-) (Phenyl-0-) P, (o-tolyl-O-) (m-tolyl-O-) (phenyl-0-) P, (p-tolyl-O-) ₃ P, (m-tolyl-O- ) (p-tolyl-O-) ₂ P, (o-tolyl-O-) (p-tolyl-O-) ₂ P, (m-tolyl-O-) ₂ (p-tolyl-O-) P, (o-tolyl-O-) ₂ (p-tolyl-O-) P, (o-tolyl-O-) (m-tolyl-O-) (p-tolyl-O-) P, (m-tolyl- O-) ₃ P, (o-tolyl-O-) (m-tolyl-O-) ₂ P, (o-tolyl-O-) ₂ (m-tolyl-O-) P or mixtures of the above compounds.

For example, by reacting a mixture comprising m-cresol and p-cresol in a molar ratio of 2: 1, in particular as obtained by working up by distillation of the crude oil, a phosphorus trihalide such as phosphorus trichloride (m -Tolyl-O-) ₃ P, (m-tolyl-O-) ₂ (p-tolyl-O-) P, (m-tolyl-O-) (p-tolyl-O-) ₂ P and (p- A mixture comprising tolyl-O-) ₃ P can be obtained.

In another likewise preferred embodiment, the phosphorus ligand is a phosphite of formula Ib, which is described in detail in DE-A 199 53 058:

P (OR ¹ ) _x (OR ² ) _y (OR ³ ) _z (OR ⁴ ) _p

(In the meal,

R ¹ : has a C ₁ -C ₁₈ -alkyl substituent at the o-position to the oxygen atom linking the phosphorus atom to the aromatic system or an aromatic substituent at the o-position to an oxygen atom linking the phosphorus atom to the aromatic system Or an aromatic radical having an aromatic system fused at the o-position to an oxygen atom linking the phosphorus atom to the aromatic system,

R ² : has a C ₁ -C ₁₈ -alkyl substituent at the m-position to the oxygen atom linking the phosphorus atom to the aromatic system or an aromatic substituent at the m-position to the oxygen atom linking the phosphorus atom to the aromatic system Aromatic radicals having an aromatic system fused at the m-position to the oxygen atom linking the phosphorus atom to the aromatic system and having a hydrogen atom at the o-position to the oxygen atom linking the phosphorus atom to the aromatic system ,

R ³ : has a C ₁ -C ₁₈ -alkyl substituent at the p-position to the oxygen atom linking the phosphorus atom to the aromatic system or an aromatic substituent at the p-position to an oxygen atom linking the phosphorus atom to the aromatic system An aromatic radical having a hydrogen atom at the o-position to an oxygen atom linking the phosphorus atom to the aromatic system,

R ⁴ : has substituents other than those defined for R ¹ , R ² and R ³ at the o-, m- and p-positions to the oxygen atom linking the phosphorus atom to the aromatic system, and the phosphorus atom to the aromatic system Aromatic radicals having a hydrogen atom in the o-position to the oxygen atom to which they are attached,

x: 1 or 2,

y, z, p: each independently 0, 1 or 2, but x + y + z + p = 3)

Preferred phosphites of formula Ib can be taken from DE-A 199 53 058. The R ¹ radical is advantageously o-tolyl, o-ethylphenyl, on-propylphenyl, o-isopropylphenyl, on-butylphenyl, o-sec-butylphenyl, o-tert-butylphenyl, (o-phenyl ) Phenyl or 1-naphthyl group.

Preferred R ² radicals are m-tolyl, m-ethylphenyl, mn-propylphenyl, m-isopropylphenyl, mn-butylphenyl, m-sec-butylphenyl, m-tert-butylphenyl, (m-phenyl) phenyl Or 2-naphthyl group.

Advantageous R ³ radicals are p-tolyl, p-ethylphenyl, pn-propylphenyl, p-isopropylphenyl, pn-butylphenyl, p-sec-butylphenyl, p-tert-butylphenyl or (p-phenyl) phenyl Qi.

The R ⁴ radical is preferably phenyl. p is preferably 0. For the indices x, y, z and p in compound Ib are possible:

Preferred phosphites of formula (Ib) are those in which p is 0, R ¹ , R ² and R ³ are each independently selected from o-isopropylphenyl, m-tolyl and p-tolyl, and R ⁴ is phenyl.

Particularly preferred phosphites of formula (Ib) are those in which R ¹ is an o-isopropylphenyl radical, R ² is an m-tolyl radical, R ³ is a p-tolyl radical and has the indices specified in the table above; In addition, R ¹ is an o-tolyl radical, R ² is an m-tolyl radical, R ³ is a p-tolyl radical, and has the indices specified in the table above; Additionally, R ¹ is a 1-naphthyl radical, R ² is an m-tolyl radical, R ³ is a p-tolyl radical and has the indices specified in the table above; In addition, R ¹ is an o-tolyl radical, R ² is a 2-naphthyl radical, R ³ is a p-tolyl radical, and has the indices specified in the table above; And finally R ¹ is an o-isopropylphenyl radical, R ² is a 2-naphthyl radical, R ³ is a p-tolyl radical and has the indices specified in the table above; And mixtures of these phosphites.

Phosphites of Formula (Ib)

a) reacting the phosphorus trihalide with an alcohol selected from the group consisting of R ¹ OH, R ² 0H, R ³ 0H and R ⁴ 0H or mixtures thereof to obtain a dihaloin monoester,

b) reacting the dihaloin monoesters mentioned with an alcohol selected from the group consisting of R ¹ OH, R ² 0H, R ³ 0H and R ⁴ 0H or mixtures thereof to obtain a monohalodiene diester, and

c) reacting the mentioned monohalodiene diester with an alcohol selected from the group consisting of R ¹ OH, R ² 0H, R ³ 0H and R ⁴ 0H or mixtures thereof to obtain phosphites of formula Ib

Can be obtained by

The reaction can be carried out in three separate steps. Equivalently two of the three stages can be combined, i.e. a) and b) or b) and c). Alternatively, all of steps a), b) and c) can be combined together.

Suitable parameters and amounts of alcohols selected from the group consisting of R ¹ OH, R ² 0H, R ³ 0H and R ⁴ 0H or mixtures thereof can be readily determined by a few simple preliminary experiments.

Useful phosphorus trihalides are in principle all phosphorus trihalides, preferably the halides used are Cl, Br, I, in particular Cl, and mixtures thereof. It is also possible to use a mixture of various identical or differently halogen-substituted phosphines as the phosphorus trihalide. PCl ₃ is particularly preferred. Further details on reaction conditions and workup in the preparation of phosphite Ib can be taken from DE-A 199 53 058.

Phosphite Ib can also be used in the form of a mixture of different phosphite Ib as ligands. Such mixtures can be obtained for example in the preparation of phosphite Ib.

However, it is preferred that the phosphorus ligand is multidentate, especially bidentate. The ligand used therefore preferably has the formula (II).

(In the meal,

X ¹¹ , X ¹² , X ¹³ , X ²¹ , X ²² , X ²³ are each independently oxygen or a single bond,

R ¹¹ , R ¹² are each independently the same or different, separate or bridged organic radicals,

R ²¹ , R ²² are each independently the same or different, separate or bridged organic radicals,

Y is the combined legs

In the context of the present invention, compound II is a single compound or a mixture of different compounds having the above-mentioned formula.

In a preferred embodiment, X ¹¹ , X ¹² , X ¹³ , X ²¹ , X ²² , X ²³ may each be oxygen. In this case, the bridging group Y is bonded to the phosphite group.

In another preferred embodiment, X ¹¹ and X ¹² are each oxygen and X ¹³ is a single bond, or X ¹¹ and X ¹³ are each oxygen and X ¹² can be a single bond, such that X ¹¹ , X ¹² and X ¹³ The phosphorus atom surrounded by is the central atom of the phosphonite. In this case, X ²¹ , X ²² and X ²³ are each oxygen, or X ²¹ and X ²² are each oxygen and X ²³ is a single bond, or X ²¹ and X ²³ are each oxygen and X ²² is a single bond, Or X ²³ is oxygen and X ²¹ and X ²² are each a single bond, or X ²¹ is oxygen and X ²² and X ²³ are each a single bond, or X ²¹ , X ²² and X ²³ are each a single bond, The phosphorus atom surrounded by X ²¹ , X ²² and X ²³ may be the central atom of phosphite, phosphonite, phosphinite or phosphine, preferably phosphonite.

In another preferred embodiment, X ¹³ is oxygen and X ¹¹ and X ¹² are each a single bond, or X ¹¹ is oxygen and X ¹² and X ¹³ can each be a single bond, such that X ¹¹ , X ¹² and X ¹³ The phosphorus atom surrounded by is the central atom of the phosphonite. In this case, X ²¹ , X ²² and X ²³ are each oxygen, or X ²³ is oxygen and X ²¹ and X ²² are each single bond, or X ²¹ is oxygen and X ²² and X ²³ are each single bond, or Or X ²¹ , X ²² and X ²³ may each be a single bond such that the phosphorus valence surrounded by X ²¹ , X ²² and X ²³ is a central atom of phosphite, phosphinite or phosphine, preferably phosphinite Can be.

In another preferred embodiment, X ¹¹ , X ¹² and X ¹³ can each be a single bond such that the phosphorus valence surrounded by X ¹¹ , X ¹² and X ¹³ is the central atom of the phosphine. In this case, X ²¹ , X ²² and X ²³ may each be oxygen, or X ²¹ , X ²² and X ²³ may each be a single bond such that the phosphorus valence phosphite surrounded by X ²¹ , X ²² and X ²³ , Or phosphine, preferably a central atom of phosphine.

The bridging group Y is advantageously aryl unsubstituted or substituted by, for example, C ₁ -C ₄ -alkyl, halogen such as fluorine, chlorine, bromine, halogenated alkyl such as trifluoromethyl, aryl such as phenyl Groups, preferably groups having 6 to 20 carbon atoms in the aromatic system, in particular pyrocatechol, bis (phenol) or bis (naphthol).

The R ¹¹ and R ¹² radicals may each independently be the same or different organic radicals. Advantageous R ¹¹ and R ¹² radicals are aryl radicals, preferably unsubstituted or especially C ₁ -C ₄ -alkyl, halogen, for example fluorine, chlorine, bromine, halogenated alkyl, for example trifluoromethyl, aryl One having 6 to 10 carbon atoms, which may be mono- or polysubstituted by, for example, phenyl or an unsubstituted aryl group.

The R ²¹ and R ²² radicals may each independently be the same or different organic radicals. Advantageous R ²¹ and R ²² radicals are aryl radicals, preferably unsubstituted or in particular C ₁ -C ₄ -alkyl, halogen such as fluorine, chlorine, bromine, halogenated alkyl such as trifluoromethyl, aryl such as phenyl, Or having from 6 to 10 carbon atoms, which may be mono- or polysubstituted by an unsubstituted aryl group.

The R ¹¹ and R ¹² radicals may each be separate or bridged. The R ²¹ and R ²² radicals may also be separate or bridged, respectively. The R ¹¹ , R ¹² , R ²¹ and R ²² radicals may each be separate, two may be bridged and two may be separate, or all four may be bridged in the manner described.

In particularly preferred embodiments, useful compounds are those having the formulas I, II, III, IV and V as specified in US Pat. No. 5,723,641. In particularly preferred embodiments, useful compounds are those having the formulas (I), (II), (III), (IV), (V), (VI) and (VII) specified in US Pat. No. 5,512,696, in particular the compounds used in Examples 1 to 31. In particularly preferred embodiments, the useful compounds are those having the formulas I, II, III, IV, V, VI, VIII, VIII, VIII, X, XI, XII, XIII, XIV and XV, in particular in the practice described in US Pat. No. 5,821,378. The compound used in Examples 1-73.

In particularly preferred embodiments, useful compounds are those having the formulas I, II, III, IV, V and VI as specified in US Pat. No. 5,512,695, in particular the compounds used in Examples 1-6. In particularly preferred embodiments, useful compounds are those having the formulas (I), (II), (III), (IV), (V), (VI), (VII), (VII), (X), (XI), (XII), (XIII) and (XIV), in particular Examples 1 to Compound used at 66.

In particularly preferred embodiments, useful compounds are those specified in US Pat. No. 6,127,567 and the compounds used in Examples 1-29. In particularly preferred embodiments, useful compounds are those having the formulas (I), (II), (III), (IV), (V), (VI), (VII), (X) and (X) as specified in US Pat. No. 6,020,516, in particular the compounds used in Examples 1 to 33. In particularly preferred embodiments, useful compounds are those specified in US Pat. No. 5,959,135, in particular the compounds used in Examples 1-13.

In particularly preferred embodiments, useful compounds are those having the formulas (I), (II) and (III) as specified in US Pat. No. 5,847,191. In particularly preferred embodiments, useful compounds are those specified in US Pat. No. 5,523,453, in particular in formulas 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 , 18, 19, 20 and 21. In a particularly preferred embodiment, useful compounds are those specified in WO 01/14392, preferably of the formulas V, VI, X, X, X, X, XI, XII, XIII, XIV, XV, XVI, XVII, XXI, XXII , Compounds exemplified in XXIII.

In a particularly preferred embodiment, useful compounds are those specified in WO 98/27054. In a particularly preferred embodiment, useful compounds are those specified in WO 99/13983. In a particularly preferred embodiment, useful compounds are those specified in WO 99/64155.

In a particularly preferred embodiment, useful compounds are those specified in German patent application DE 100 380 37. In a particularly preferred embodiment, useful compounds are those specified in German patent application DE 100 460 25. In a particularly preferred embodiment, useful compounds are those specified in German patent application DE 101 502 85.

In a particularly preferred embodiment, useful compounds are those specified in German patent application DE 101 502 86. In a particularly preferred embodiment, useful compounds are those specified in German patent application DE 102 071 65. In a further particularly preferred embodiment of the invention, the useful phosphorus chelating ligands are those specified in US 2003/0100442 A1.

In a further particularly preferred embodiment of the invention, the useful phosphorus chelating ligands are assigned to the German patent application reference number DE 103 50 999.2 of October 30, 2003, which has a faster priority date but is not published on the priority date of the present application. Are specified.

The compounds I, Ia, Ib and II described, and their preparation, are known. The phosphorus ligand used may also be a mixture comprising two or more of compounds I, Ia, Ib and II.

In a particularly preferred embodiment of the method according to the invention, the phosphorus ligand and / or free phosphorus ligand of the nickel (O) complex is selected from tritolyl phosphite, bidentate phosphorus chelating ligand and phosphite of formula (Ib) and mixtures thereof do.

<Formula Ib>

P (OR ¹ ) _x (OR ² ) _y (OR ³ ) _z (OR ⁴ ) _p

Wherein R ¹ , R ² and R ³ are each independently selected from o-isopropylphenyl, m-tolyl and p-tolyl, R ⁴ is phenyl; x is 1 or 2, and y, z , p are each independently 0, 1 or 2, except that x + y + z + p = 3)

The desired products of hydrocyanation that can be used for adiponitrile preparation are trans-3-pentenenitrile, cis-3-pentennitrile and 4-pentenenitrile, which are referred to as 3-pentenenitriles in the context of the present invention. However, depending on the catalyst system, the 2-methyl-3-butenenitrile generated in the hydrocyanation in a percentage of at least two digits based on the sum of all pentenenitrile isomers formed must be removed before further treatment of the hydrocyanation effluent. Reduction of 2-methyl-3-butenenitrile in 3-pentenenitrile because methylglutaronitrile (MGN), an undesirable byproduct of adiponitrile preparation, is formed from 2-methyl-3-butenenitrile in subsequent hydrocyanation The standards are strict and should be followed. However, the complex equipment and energy needs for substantially complete removal of 2-methyl-3-butennitrile from 3-pentenenitrile are very high, 416.8 K and 2-methyl-3-butennitrile for trans-3-pentennitrile. Is determined by the relative volatility, defined as the ratio of the vapor pressures of these two materials to about 1.7 at atmospheric pressure, derived from a known standard boiling point of 396.1 K. In accordance with the present invention, it has been found that the relative volatilities of 2-methyl-3-butenenitrile and 3-pentenenitrile increase at pressures below atmospheric pressure.

Thus, the process according to the invention is to separate the mixture comprising 2-methyl-3-butennitrile and 3-pentennitrile in embodiment I. The mixture is preferably obtained in the reaction of 1,3-butadiene with hydrogen cyanide on a hydrocyanation catalyst, the hydrocyanide effluent being typically 1, unconverted during hydrocyanation, which can be at least partially removed by a suitable method. It is possible to remove the catalyst component present in the product stream, which comprises a portion of 3-butadiene, in a suitable manner. Methods of this type are described, for example, in DE-A-102 004 004 720 and DE-A-102 004 004 724. However, it is not necessary to remove unconverted 1,3-butadiene and the catalyst component.

The mixture comprising 2-methyl-3-butenenitrile and 3-pentenenitrile is preferably in each case 0.1 to 99.9% by weight, more preferably 1 to 99% by weight, based on the sum of the pentenenitrile isomers in the mixture In particular 10 to 90% by weight of the mixture. The fraction of 3-pentenenitrile in the mixture is in each case preferably 0.1 to 99.9% by weight, more preferably 1 to 99% by weight, in particular 10 to 90% by weight, based on the sum of the pentenenitrile isomers in the mixture.

Separation of the mixture comprising 2-methyl-3-butenenitrile and 3-pentenenitrile can be carried out in any suitable apparatus known to those skilled in the art. Suitable apparatus for distillation are described, for example, in Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed., Vol. 8, John Wiley & Sons, New York, 1996, page 334-348, for example described as sieve towers, bubble-cap tray columns, towers with organized filling or irregular filling, and also divided It can also work as a wall tower. In each case the distillation apparatus is equipped with a device suitable for evaporation, such as a falling film evaporator, a thin film evaporator, a multiphase spiral tube evaporator, a natural circulation evaporator or a forced circulation flash evaporator, and also a device for condensing the vapor stream. Distillation can be carried out in a plurality, for example two or three apparatuses, preferably in a single apparatus. In the case of partial evaporation of the feed stream, distillation can additionally be carried out in one step.

The number of theoretical stages in the distillation column is preferably 0 to 100, more preferably 1 to 60, in particular 10 to 40. The reflux ratio, m (column extraction) / m (reflux to the tower) is preferably 0.01 to 100, more preferably 0.1 to 10, especially 0.2 to 5. The feed to the distillation column can be liquid or gaseous. The feed to the rectifying tower can enter the bottom or top of the tower. The feed is in each case up to the height of the tower corresponding to preferably 1 to 99%, more preferably 5 to 90%, in particular 10 to 80%, of the total number of tower stages, counted upwardly from the bottom.

The distillation of the mixture comprising 2-methyl-3-butenenitrile and 3-pentenenitrile is preferably carried out at a pressure of 0.001 to 1 bar, more preferably 0.01 to 0.5 bar, in particular 0.05 to 0.2 bar. The distillation is carried out in such a way that the temperature at the bottom of the column is preferably 20 to 200 ° C, more preferably 30 to 150 ° C, in particular 50 to 100 ° C. Distillation is carried out in such a way that the temperature at the top of the column is preferably -15 to 200 ° C, more preferably 0 to 100 ° C, in particular 20 to 50 ° C. In a particularly preferred embodiment of the process according to the invention, the abovementioned temperature range is achieved at both the bottom and the top of the distillation apparatus.

In the top of the distillation apparatus, a mixture rich in 2-methyl-3-butenenitrile is obtained as compared to the feed stream. Through the bottom of the distillation apparatus, a mixture rich in 3-pentenenitrile is obtained as compared to the feed stream.

In embodiment II, the process according to the invention relates to the separation of a mixture comprising 2-methyl-3-butennitrile and (Z) -2-methyl-2-butennitrile.

As already mentioned above, in the hydrocyanation process for adiponitrile preparation, the 1,3-butadiene is first hydrocyanated with 3-pentenenitrile. The byproduct obtained is 2-methyl-3-butenenitrile. As described in embodiment I of the present invention, the by-products are preferably removed from the reaction stream before the second hydrocyanation step. The 2-methyl-3-butenenitrile removed can be isomerized to 3-pentenenitrile, a valuable product in an integrated process for hydrocyanation of 1,3-butadiene during further process steps. (Z) -2-methyl-2-butenenitrile is formed as a byproduct during isomerization, and during post-treatment of the isomerization effluent to prevent in-process accumulation during recycling of 2-methyl-3-butenenitrile during the isomerization step Must be removed from methyl-3-butenenitrile.

Because of the substantially same boiling point, it is not possible to separate (Z) -2-methyl-2-butennitrile from 2-methyl-3-butennitrile at atmospheric pressure by distillation at an economically acceptable level of complexity and cost. Complex device and energy needs for the reduction of (Z) -2-methyl-2-butenenitrile from mixtures containing 2-methyl-3-butenenitrile are very high, and (Z) -2-methyl-2-butennitrile Is determined by the relative volatility, defined as the ratio of the vapor pressures of these two materials at about 1.1 at atmospheric pressure, derived from known standard boiling points of 392.1 K for and 396.1 K for 2-methyl-3-butenenitrile. According to the invention, the relative volatilities of (Z) -2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile increase at pressures below atmospheric pressure, and thus include 2-methyl-3-butenenitrile. It has been found that the removal of (Z) -2-methyl-2-butenenitrile from the mixture is possible at an economically acceptable level of complexity and cost under reduced pressure.

Thus, the process according to the invention also preferentially comprises 2-methyl-3-butennitrile and (Z) -2-methyl-2-butennitrile, for example isomerization of 2-methyl-3-butennitrile It is suitable for separating the mixture derived from.

Isomerization is preferably

a) nickel (0),

b) trivalent phosphorus-containing compounds complexing nickel (0) as ligands, and

c) Lewis acid

It is carried out in the presence of a system comprising a.

Nickel (0) -containing catalyst systems can be prepared by known methods.

The ligand used in the isomerization catalyst may be the same phosphorus ligand as in the case of hydrocyanation described above.

In addition, the system may comprise Lewis acids.

In the context of the present invention, Lewis acid means a single Lewis acid or a mixture of a plurality, such as two, three or four Lewis acids.

Useful Lewis acids are inorganic or organometallic compounds, where the cation consists of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, copper, zinc, boron, aluminum, yttrium, zirconium, niobium, molybdenum, cadmium, rhenium and tin Selected from the group. Examples include ZnBr ₂ , ZnI ₂ , ZnCl ₂ , ZnSO ₄ , CuCl ₂ , CuCl, Cu (O ₃ SCF ₃ ) ₂ , CoCl ₂ , CoI ₂ , FeI as described, for example, in US 6,127,567, US 6,171,996 and US 6,380,421. ₂ , FeCl ₃ , FeCl ₂ , FeCl ₂ (THF) ₂ , TiCl ₄ (THF) ₂ , TiCl ₄ , TiCl ₃ , ClTi (Oi-propyl) ₃ , MnCl ₂ , ScCl ₃ , AlCl ₃ , (C ₈ H ₁₇ ) AlCl ₂ , (C ₈ H ₁₇ ) ₂ AlCl, (iC ₄ H ₉ ) ₂ AlCl, (C ₆ H ₅ ) ₂ AlCl, (C ₆ H ₅ ) AlCl ₂ , ReCl ₅ , ZrCl ₄ , NbCl ₅ , VCl ₃ , CrCl ₂ , MoCl ₅ , YCl ₃ , CdCl ₂ , LaCl ₃ , Er (O ₃ SCF ₃ ) ₃ , Yb (O ₂ CCF ₃ ) ₃ , SmCl ₃ , B (C ₆ H ₅ ) ₃ , TaCl ₅ Included. Metal salts such as ZnCl ₂ , CoI ₂ and SnCl ₂ , and organometallic compounds such as RAlCl ₂ , R ₂ AlCl, RSnO ₃ SCF ₃ and R ₃ B, as also described, for example, in US 3,496,217, US 3,496,218 and US 4,774,353 Is useful, wherein R is an alkyl or aryl group. According to US 3,773,809, the accelerators used are also zinc, cadmium, beryllium, aluminum, gallium, indium, thallium, titanium, zirconium, hafnium, erbium, germanium, tin, vanadium, niobium, scandium, chromium, molybdenum, tungsten, manganese, Rhenium, palladium, thorium, iron and cobalt, preferably metals in cation form selected from the group consisting of zinc, cadmium, titanium, tin, chromium, iron and cobalt, the anionic moiety of the compound being a halide such as fluoride, ^a-chloride, bromide and iodide anion, HPO ₃ ² of the carbon atoms of 2 to lower fatty acids having 7 ^-, H ₃ PO ^{2 -,} CF ₃ COO ^-, C ₇ H ₁₅ OSO ₂ ^- or SO ₄ ² It may be selected from the group consisting of. Further suitable promoters disclosed in US Pat. No. 3,773,809 are borohydrides, organoborohydrides and boric esters of formula R ₃ B and B (OR) ₃ , wherein R is hydrogen, an aryl radical having 6 to 18 carbon atoms, Aryl radicals substituted by alkyl groups having 1 to 7 carbon atoms, and aryl radicals substituted by cyano-substituted alkyl groups having 1 to 7 carbon atoms, advantageously triphenylboron. In addition, as described in US Pat. No. 4,874,884, it is possible to use synergistically active combinations of Lewis acids to increase the activity of the catalyst system. Suitable promoters can be selected, for example, from the group consisting of CdCl ₂ , FeCl ₂ , ZnCl ₂ , B (C ₆ H ₅ ) ₃ and (C ₆ H ₅ ) ₃ SnX, where X is CF ₃ SO ₃ , CH ₃ C ₆ H ₄ SO ₃ or (C ₆ H ₅ ) ₃ BCN, and the preferred ratio of promoter to nickel specified is about 1:16 to about 50: 1.

In the context of the present invention, the term Lewis acid also includes the promoters specified in US 3,496,217, US 3,496,218, US 4,774,353, US 4,874,884, US 6,127,567, US 6,171,996 and US 6,380,421.

Particularly preferred Lewis acids among those mentioned above are in particular metal salts, more preferably metal halides such as fluoride, chloride, bromide, iodide, in particular chloride, zinc chloride, iron (II) chloride and iron (III) chloride in particular desirable.

Isomerization is carried out with liquid diluents, for example hydrocarbons (eg hexane, heptane, octane, cyclohexane, methylcyclohexane, benzene), ethers (eg diethyl ether, tetrahydrofuran, dioxane, glycol dimethyl ether, anisole ), Esters (eg ethyl acetate, methyl benzoate) or nitriles (eg acetonitrile, benzonitrile), or mixtures of such diluents. In a particularly preferred embodiment, useful isomerization is carried out in the absence of such liquid diluents.

In addition, it has been found to be advantageous if the isomerization is carried out under a non-oxidizing atmosphere, for example a protective gas atmosphere consisting of nitrogen or a Group 0 gas such as argon.

Separation of the mixture comprising (Z) -2-methyl-2-butennitrile and 2-methyl-3-butennitrile can be carried out in any suitable apparatus known to those skilled in the art. Suitable apparatus for distillation are described, for example, in Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed., Vol. 8, John Wiley & Sons, New York, 1996, page 334-348, for example, may be performed in a sieve tower, a seed tower, a tower with systemized filling or irregular filling, and may be operated as a split wall tower. . In each case, the distillation apparatus is equipped with a device suitable for evaporation, such as a falling film evaporator, a thin film evaporator, a multiphase spiral tube evaporator, a natural circulation evaporator or a forced circulation flash evaporator, and also a device for condensing the vapor stream. Distillation can be carried out in a plurality, for example two or three apparatuses, preferably in a single apparatus. In the case of partial evaporation of the feed stream, distillation can additionally be carried out in one step.

The number of theoretical stages in the distillation column is preferably 0 to 100, more preferably 1 to 60, in particular 10 to 40. The reflux ratio, m (column extraction) / m (reflux to the tower), is preferably 1 to 500, more preferably 1 to 200, especially 10 to 100. The feed to the distillation column can be liquid or gaseous. The feed may exceed the total height of the tower, the feed being in each case up to the height of the tower corresponding to preferably 0 to 90%, in particular 0 to 50% of the total number of tower stages, counted upwardly from the bottom. .

The mixture used in the process of the invention according to embodiment II is preferably from 0.1 to 99% by weight, more preferably from 1 to 99% by weight, based in each case on the sum of the pentenenitrile isomers in the mixture, In particular 10 to 90% by weight of the mixture. The fraction of (Z) -2-methyl-2-butenenitrile in the mixture is preferably 0.1 to 99% by weight, more preferably 1 to 90% by weight, in each case based on the sum of the pentennitrile isomers in the mixture , In particular, from 2 to 70% by weight.

According to embodiment II the process according to the invention is preferably carried out at a pressure of 0.001 to 1.0 bar, more preferably 0.01 to 0.5 bar, in particular 0.05 to 0.2 bar. The distillation is carried out in such a way that the temperature at the bottom of the column is preferably 20 to 200 ° C, more preferably 30 to 150 ° C, in particular 50 to 100 ° C. Distillation is carried out in such a way that the temperature at the top of the column is preferably -15 to 200 ° C, more preferably 0 to 100 ° C, in particular 20 to 50 ° C. In a particularly preferred embodiment of the process according to the invention, the abovementioned temperature range is maintained at both the bottom and the top of the distillation apparatus.

The top of the distillation apparatus gives a mixture with reduced 2-methyl-3-butenenitrile compared to the feed stream. Through the bottom of the distillation apparatus, a mixture with reduced (Z) -2-methyl-2-butenenitrile is obtained as compared to the feed stream.

In embodiment III, the process according to the invention relates to the separation of a mixture comprising cis-2-pentenenitrile and 3-pentenenitrile.

In the hydrocyanation reaction of 3-pentenenitrile to obtain adiponitrile, cis-2-pentenenitrile can form and accumulate in the 3-pentenenitrile circulating stream, thus preferably removing it from the circulation system.

The removed cis-2-pentenenitrile can be isomerized thermally or under catalysis to the valuable 3-pentenenitrile product. A mixture with substantially trans-2-pentennitrile, trans-3-pentennitrile and unconverted cis-2-pentennitrile is obtained. A prerequisite for inserting the isomerization step as an integrated process for adiponitrile preparation is that the removal of cis-2-pentenenitrile from the mixture is economically feasible.

According to embodiment III, the invention relates to a process for separating pentenenitrile isomeric mixtures, wherein the separation is carried out by distillation under reduced pressure, the mixture comprising cis-2-pentenenitrile and 3-pentenenitrile. These mixtures are for example derived from the reaction of 3-pentenenitrile with hydrogen cyanide over a hydrocyanation catalyst. In addition, these mixtures may be derived from thermal or catalytic isomerization of cis-2-pentenenitrile.

The device requirements and energy requirements for the reduction of cis-2-pentenenitrile from 3-pentenenitrile are high, with known standard boiling points of 400.1 K for cis-2-pentenenitrile and 416.8 K for trans-3-pentennitrile. The relative volatility, α, is defined as the ratio of the vapor pressure of these two materials, which is about 1.55 at atmospheric pressure, derived from. In accordance with the present invention, it has been found that the relative volatilities of cis-2-pentenenitrile and trans-3-pentennitrile increase at pressures below atmospheric pressure.

The proportion of cis-2-pentenenitrile in these mixtures in each case is preferably 0.1 to 99.9% by weight, more preferably 1 to 99% by weight, in particular 1 to 90% by weight, based on the sum of the pentenenitrile isomers in the mixture in each case %to be. The fraction of 3-pentenenitrile in the mixture is in each case preferably 0.1 to 99.9% by weight, more preferably 1 to 99% by weight, in particular 2 to 90% by weight, based on the sum of the pentenenitrile isomers in the mixture.

Separation of the mixture comprising cis-2-pentenenitrile and 3-pentenenitrile can be carried out in any suitable apparatus known to those skilled in the art. Suitable apparatus for distillation are described, for example, in Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed., Vol. 8, John Wiley & Sons, New York, 1996, page 334-348, such as, for example, a sieve tower, a seed tower, a tower with systemized filling or irregular filling, and can also act as a split wall tower. . In each case the distillation apparatus is equipped with a device suitable for evaporation, such as a falling film evaporator, a thin film evaporator, a multiphase spiral tube evaporator, a natural circulation evaporator or a forced circulation flash evaporator, and also a device for condensing the vapor stream. Distillation can be carried out in a plurality, for example two or three apparatuses, preferably in a single apparatus. In the case of partial evaporation of the feed stream, distillation can additionally be carried out in one step.

The number of theoretical stages in the distillation column is preferably 0 to 100, more preferably 1 to 60, in particular 10 to 40. The reflux ratio, m (column extraction) / m (reflux to the tower) is preferably 0.1 to 500, more preferably 1 to 200, especially 10 to 50. The feed to the distillation column can be liquid or gaseous. The feed may exceed the total height of the tower, the feed being in each case up to the height of the tower corresponding to preferably 0 to 90%, in particular 0 to 50% of the total number of tower stages, counted upwardly from the bottom. .

The separation according to embodiment III is preferably carried out at a pressure of 0.001 to 1.0 bar, more preferably 0.01 to 0.5 bar, in particular 0.05 to 0.2 bar. Distillation is carried out in such a way that the temperature at the bottom of the column is preferably 20 to 200 ° C, more preferably 30 to 150 ° C, in particular 50 to 100 ° C. Distillation is maintained in such a way that the temperature at the top of the column is preferably -15 to 200 ° C, more preferably 0 to 100 ° C, in particular 20 to 50 ° C. In a particularly preferred embodiment of the process according to the invention, the above mentioned temperature range is achieved at both the bottom and the top of the tower.

In the top of the distillation unit, a mixture with reduced 3-pentenenitrile is obtained compared to the feed stream. Through the bottom of the distillation unit, a mixture with reduced cis-2-pentenenitrile is obtained as compared to the feed stream.

In embodiment VI, the process according to the invention relates to the separation of a mixture comprising 3-pentenenitrile and (E) -2-methyl-2-butenenitrile.

During the preparation of 3-pentenenitrile, in both hydrocyanation of 1,3-butadiene and isomerization of 2-methyl-3-butenenitrile, small amounts of (E) -2-methyl-2-butenenitrile are formed as by-products. In this case, the amount of (E) -2-methyl-2-butennitrile formed is generally found in the product stream together with 3-pentenenitrile. As described in DE-A-102 004 004 683, some of (E) -2-methyl-2-butenenitrile accumulates in the existing method for hydrocyanating 3-pentenenitrile to adiponitril, whereas in hydrocyanation ( E) A portion of 3-pentenenitrile unconverted with 2-methyl-2-butenenitrile is typically recycled to the reactant, and a portion of (E) -2-methyl-2-butennitrile is substantially inert during the reaction. Because it cannot be removed from the system unless additional means are provided for (E) -2-methyl-2-butenenitrile emissions.

The device requirements and energy requirements for the reduction of (E) -2-methyl-2-butenenitrile from 3-pentenenitrile are high, 410.1 K and trans-3 for (E) -2-methyl-2-butenenitrile. The relative volatility, α, is defined as the ratio of the vapor pressure of these two materials at about 1.19 at atmospheric pressure, derived from a known standard boiling point of 416.8 K for pentenenitrile. According to the present invention, it has been found that the relative volatilities of (E) -2-methyl-2-butenenitrile and 3-pentenenitrile increase at pressures below atmospheric pressure.

In the process of hydrocyanation from 3-pentenenitrile to adiponitrile, (E) -2-methyl-2-butenenitrile accumulates in the 3-pentenenitrile circulation stream in some cases. As a mixture of pentenenitriles, the circulating stream may consist of, for example, a portion of pentenenitrile, which is first removed immediately after the hydrocyanation reaction. It is then also possible to add to the circulation stream the remaining pentenitrile after removal of the catalyst component in the adipononitrile-containing product stream, as described in DE-A-102 004 004 683, filed on the same date as the present application. Likewise, it is removed from the stream for the purpose of recycling.

According to embodiment IV, the process according to the invention is preferably carried out from the reaction of 1,3-butadiene and hydrogen cyanide on a hydrocyanation catalyst or on the isomerization or hydrocyanation catalyst of 2-methyl-3-butenenitrile. It is aimed at a mixture derived from the reaction of pentenenitrile with hydrogen cyanide.

In these mixtures, the fraction of 3-pentenenitrile is in each case preferably 0.1 to 99.9% by weight, more preferably 1 to 99% by weight, in particular 10 to 90% by weight, based on the sum of the pentenenitrile isomers in the mixture to be. The fraction of (E) -2-methyl-2-butenenitrile in the mixture is preferably in each case 0.1 to 99.9% by weight, more preferably 0.5 to 99% by weight, based on the sum of the pentenenitrile isomers in the mixture, Especially 1 to 50% by weight.

Separation of the mixture comprising 3-pentenenitrile and (E) -2-methyl-2-butenenitrile can be carried out in any suitable apparatus known to those skilled in the art. Suitable apparatus for distillation are described, for example, in Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed., Vol. 8, John Wiley & Sons, New York, 1996, page 334-348, such as, for example, a sieve tower, a seed tower, a tower with systemized filling or irregular filling, and can also act as a split wall tower. . In each case, the distillation apparatus is equipped with a device suitable for evaporation, such as a falling film evaporator, a thin film evaporator, a multiphase spiral tube evaporator, a natural circulation evaporator or a forced circulation flash evaporator, and also a device for condensing the evaporation stream. Distillation can be carried out in a plurality, for example in two or three apparatuses, in particular in a single apparatus. In the case of partial evaporation of the feed stream, distillation can additionally be carried out in one step.

The number of theoretical stages in the distillation column is preferably 0 to 150, more preferably 1 to 120, in particular 10 to 60. The reflux ratio, m (column extraction) / m (reflux to the tower), is preferably 0.1 to 500, more preferably 1 to 200, particularly 10 to 100. The feed to the distillation column can be liquid or gaseous. The feed may be at any desired height between the total heights of the towers, which in each case preferably corresponds to 0 to 90%, in particular 0 to 50% of the total number of tower stages, counted upwardly from the bottom. To the height of the tower.

The top of the distillation unit yields a mixture with reduced 3-pentenenitrile compared to the feed stream. Through the bottom of the distillation unit a mixture with reduced (E) -2-methyl-2-butenenitrile is obtained as compared to the feed stream.

The present invention for separating pentenenitrile isomeric mixtures utilizes less separation steps and less energy to in each case 2-methyl-3-butennitrile or (E) -2-methyl-2-butennitrile in 3-pentenenitrile. Get the possibility of separation. Separation in the case of separation of 2-methyl-3-butenenitrile and (Z) -2-methyl-2-butennitrile, and also separation of (E) -2-methyl-2-butennitrile and 3-pentenenitrile Or to make the enhancements and reductions virtually feasible in an economical way with industrially feasible levels of complexity.

The invention will be described in detail with reference to the following examples.

The following abbreviations were used as follows.

T3PN trans-3-pentenenitrile

C3PN cis-3-pentenenitrile

4PN 4-pentenenitrile

2M3BN 2-methyl-3-butenenitrile

T2PN trans-2-pentenenitrile

C2PN cis-2-pentenenitrile

E2M2BN (E) -2-methyl-2-butenenitrile

Z2M2BN (Z) -2-methyl-2-butenenitrile

VAN valeronitrile

VCH 4-vinylcyclohexene

1. A mixture comprising 2-methyl-3-butenenitrile and 3-pentenenitrile.

Separation was carried out in a distillation tower with an evaporator, a total condenser and a reflux divider. The distillation tower contained 15 theoretical stages. The reflux ratio m (takeout) / m (reflux to the tower) was one. As shown below, the supply amount to the distillation column until step 10 was 10 kg / h, the extraction amount from the column top was 5 kg / h.

The mixture has the following composition.

Examples 1 to 6 show that at the same reflux ratio and the same removal rate, the lower the pressure of the column is set below 1.0 bar, the higher the efficiency, resulting in better separation of 2-methyl-3-butenenitrile and 3-pentenenitrile. The pressure indicates that the residual content of 2-methyl-3-butenenitrile at the bottom is reduced and the residual content of trans-3-pentenenitrile at the top is also reduced.

2. Mixtures comprising 2-methyl-3-butenenitrile and (Z) -2-methyl-2-butenenitrile

Separation was carried out in a distillation tower having an evaporator, a total condenser and a reflux distributor. The distillation column has 15 theoretical stages. The reflux ratio m (takeout) / m (reflux to the tower) was 50. The feed amount to the evaporator was 10 kg / h into the column bottom, and the extraction amount from the tower top was 0.05 kg / h.

In Examples 7 to 12, the lower the pressure of the column at the same reflux ratio and the same removal rate, the higher the efficiency, so that 2-methyl-3-butenenitrile and (Z) -2-methyl-2-butennitrile were easily separated. At low pressures, the residual content of 2-methyl-3-butenenitrile in the column tops decreases and the residual content of (Z) -2-methyl-2-butenenitrile in the column tops increases.

3. Mixtures Containing Cis-2-pentenenitrile and 3-pentenenitrile

Separation was carried out in a distillation tower having an evaporator, a total condenser and a reflux distributor. The distillation column has 15 theoretical stages. The reflux ratio m (takeout) / m (reflux to the tower) was 50. As shown below, the feed to the distillation column up to step 10 was 10 kg / h in the distillation column. The extraction amount in the column top was 0.05 kg / h.

In Examples 13 to 18, the lower the pressure of the column at the same reflux ratio and the same removal rate, the higher the efficiency, so that the separation of trans-3-pentenenitrile and cis-2-pentenitrile is better, and at lower pressure, It indicates that the residual content of trans-3-pentenenitrile in is decreased and the content of cis-2-pentenenitrile removed from the column is increased.

4. Mixtures Containing 3-Pentenenitrile and (E) -2-methyl-2-butenenitrile

Separation was carried out in a distillation tower having an evaporator, a total condenser and a reflux distributor. The distillation column has 40 theoretical stages. The reflux ratio m (takeout) / m (reflux to the tower) was 50. As shown below, the feed to the distillation column up to step 5 was 10 kg / h. The extraction amount in the column top was 1.5 kg / h.

In Examples 19 to 24, the lower the pressure of the column at the same reflux ratio and the same removal rate, the higher the efficiency, so that the separation of trans-3-pentenenitrile and (E) -2-methyl-2-butenenitrile is better. Low pressure indicates that the residual content of (E) -2-methyl-2-butenenitrile in the bottom draw stream decreases and increases in the top draw stream.

From Examples 1 to 24, when the distillation is carried out under reduced pressure, contrary to the commonly known dilution principle, consideration of the known standard boiling point for achieving the necessary details of the particular pentenenitrile isomer at the bottom and the top of the distillation column It can be understood from the understanding that less separation steps and / or less energy are required than expected.

Claims (11)

A process for separation of a pentenenitrile isomeric mixture, wherein at least one isomer is reduced from the mixture, comprising performing separation of the pentenenitrile isomeric mixture by distillation under reduced pressure. The method of claim 1, wherein the separation of two or more different isomers. The method of claim 1 or 2, wherein the mixture is A mixture comprising 2-methyl-3-butenenitrile and 3-pentenenitrile, A mixture comprising 2-methyl-3-butenenitrile and (Z) -2-methyl-2-butenenitrile, A mixture comprising cis-2-pentenenitrile and 3-pentenenitrile, and A mixture comprising (E) -2-methyl-2-butennitrile and 3-pentenenitrile The method is selected from the group consisting of. The process of claim 1, wherein the mixture comprises 2-methyl-3-butenenitrile and 3-pentenenitrile and is derived from the reaction of 1,3-butadiene with hydrogen cyanide on a hydrocyanation catalyst. Way. 5. The method of claim 4 wherein the fraction of 2-methyl-3-butenenitrile in the mixture is from 0.1 to 99.9% by weight based on the sum of all pentenenitrile isomers in the mixture and / or the fraction of 3-pentenenitrile in the mixture is 0.1 to 99.9 wt%, based on the sum of the pentene nitrile isomers. The process according to claim 1, wherein the mixture comprises 2-methyl-3-butenenitrile and (Z) -2-methyl-2-butennitrile, wherein Method derived from isomerization. The method of claim 6, wherein the fraction of 2-methyl-3-butenenitrile in the mixture is from 0.1 to 99% by weight based on the sum of the pentenenitrile isomers in the mixture and / or (Z) -2-methyl-2 in the mixture. The fraction of butenenitrile is from 0.1 to 99% by weight, based on the sum of the pentenenitrile isomers in the mixture. The process according to claim 1, wherein the mixture comprises cis-2-pentenenitrile and 3-pentenenitrile and is derived from the reaction of 3-pentenenitrile with hydrogen cyanide on a hydrocyanation catalyst. The fraction of cis-2-pentenenitrile in the mixture is from 0.1 to 99.9% by weight based on the sum of the pentenenitrile isomers in the mixture and / or the fraction of 3-pentenenitrile in the mixture is pentenenitrile in the mixture. 0.1 to 99.9% by weight, based on the sum of the isomers. The process according to any of claims 1 to 3, wherein the mixture comprises (E) -2-methyl-2-butennitrile and 3-pentenenitrile, wherein the mixture of 1,3-butadiene and hydrogen cyanide on a hydrocyanation catalyst Reaction, isomerization of 2-methyl-3-butenenitrile or a process derived from the reaction of 3-pentenenitrile with hydrogen cyanide over a hydrocyanation catalyst. The fraction of 3-pentenenitrile in the mixture according to claim 10, wherein the fraction of 3-pentenenitrile in the mixture is from 0.1 to 99.9% by weight based on the sum of pentenenitrile in the mixture and / or the fraction of (E) -2-methyl-2-butenenitrile in the mixture. 0.1 to 99.9% by weight, based on the sum of pentenenitrile isomers in this mixture.