JPH0336811B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a selective solvent for extractive distillation used in separating monocyclic hydrocarbons by extractive distillation. Unsaturated monocyclic hydrocarbons are compounds useful as intermediates for various industrial chemical raw materials. For example, cyclohexene is a substance useful as a raw material and solvent for industrial chemicals such as adipic acid, lysine, cyclohexanol, and cyclohexanone. Cyclopentene is also useful as a raw material for industrial chemicals such as cyclopentanol, cyclopentanone, and sebacic acid. <Prior Art> It is already known that unsaturated monocyclic hydrocarbons can be obtained by partial hydrogenation reaction of aromatic monocyclic hydrocarbons or partial dehydrogenation reaction of saturated monocyclic hydrocarbons. As a method for obtaining unsaturated monocyclic hydrocarbons by partial hydrogenation reaction of aromatic monocyclic hydrocarbons,
60-21126, JP 57-130926, JP 56-22850, etc., it has been shown that cyclohexene can be obtained by partial hydrogenation reaction of benzene, and cyclohexane is produced as a by-product. ing. It is also known that cyclopentene is obtained by a partial hydrogenation reaction of cyclopentadiene, which is a by-product that accounts for 4 to 5% by weight of ethylene production, and that cyclopentane is produced as a by-product. As a method for obtaining unsaturated monocyclic hydrocarbons by partial dehydrogenation of saturated monocyclic hydrocarbons, the Industrial Chemistry Journal Vol. 74, No. 11, 2401P-2402P (1971) and JP-A Sho
Publication No. 60-100530 etc. disclose that cyclohexene is obtained by partial dehydrogenation of cyclohexane, and benzene is produced as a by-product.
Furthermore, U.S. Patent No. 4187156, Japanese Patent Publication No. 49-41192, and Japanese Patent Publication No. 48-35063 show that cyclohexene can be obtained by electrolytic reduction of benzene, and cyclohexadiene is produced as a by-product. ing. It is already known that cyclohexadiene can be converted into cyclohexane and cyclohexene through a partial hydrogenation reaction. Journal of the Japan Petroleum Institute VOL.25, No.3, 142P-149P (1982
2003) and Japanese Patent Application Laid-Open No. 1983-62253, it is shown that cyclohexene is obtained by catalytic decomposition of cyclohexylbenzene, and benzene is produced as a by-product. The products obtained by each of these reactions are obtained as a mixture of saturated monocyclic hydrocarbons, unsaturated monocyclic hydrocarbons, and aromatic monocyclic hydrocarbons, and these mixtures can be used for the following purposes. Or,
In order to subject the unreacted raw materials to the reaction again, it is necessary to separate each raw material. However, when these mixtures are separated by distillation, aromatic monocyclic hydrocarbons, saturated monocyclic hydrocarbons,
The boiling points of unsaturated monocyclic hydrocarbons are too close together. For example, the boiling points of benzene, cyclohexane, and cyclohexene are 80.1℃, 80.8℃, and 83.3℃, respectively.
℃, and the boiling points of cyclopentadiene, cyclopentene, and cyclopentane are 41℃ and 44℃, respectively.
℃, 49℃. Also, azeotropic mixtures may be formed, such as benzene and cyclohexane, or benzene and cyclohexene. In order to solve the above problems, attempts have been made to establish a method for separating and refining the above-mentioned mixtures of unsaturated monocyclic hydrocarbons, saturated monocyclic hydrocarbons, and aromatic monocyclic hydrocarbons by extractive distillation. For example, Tokukai Akira
No. 57-149234 proposes pentenenitrile as a solvent. Also, JP-A-51-127043, JP-A-52-5733, JP-A-52-144649, JP-A-52-144650, JP-A-58-
164524, JP 58-164525, and JP 58-172323 each use sulfone compounds such as dimethyl sulfoxide, N-methylpyrrolidone, dimethylformamide, γ-butyrolactone, dimethylacetamide, and sulfolane as solvents; Aliphatic dinitrile compounds such as adiponitrile have been proposed. Additionally, as a solvent for separating monocyclic hydrocarbon mixtures containing aromatic monocyclic hydrocarbons by extractive distillation, JP-A-49-86331 discloses N-alkyl-ε-caprolactam, γ- Valerolactone and ε-caprolactone have been proposed. <Problems to be solved by the invention> When monocyclic hydrocarbon mixtures are industrially separated by extractive distillation, conventional solvents have poor separation efficiency, so it is necessary to use a large amount of solvent and increase the reflux ratio. There is. As a result, it has disadvantages such as increased equipment size and high energy cost for separation. In particular, conventional solvents have poor separation efficiency between unsaturated monocyclic hydrocarbons and saturated monocyclic hydrocarbons, such as cyclohexene and cyclohexane, and in industrial implementation, solvents with even better separation efficiency are required. Regarding selectivity and solubility as evaluation indicators of separation efficiency, conventional solvents generally have good selectivity but have poor solubility, and solvents with good solubility have poor selectivity. The present invention overcomes the drawbacks of these conventional methods and extractively distills a mixture of saturated monocyclic hydrocarbons, unsaturated monocyclic hydrocarbons, and aromatic monocyclic hydrocarbons using a solvent with superior selectivity and solubility. The purpose is to separate and purify it using a method. <Means for Solving the Problems> As a result of intensive research into the separation and purification of monocyclic hydrocarbon mixtures by extractive distillation, the present inventors have found that phthalic acid diester has superior separation efficiency compared to conventional solvents. This discovery led to the completion of the present invention. That is, the present invention provides for producing saturated monocyclic hydrocarbons or unsaturated monocyclic hydrocarbons by extractive distillation from a mixture of at least two types of monocyclic hydrocarbons selected from saturated monocyclic hydrocarbons, unsaturated monocyclic hydrocarbons, and aromatic monocyclic hydrocarbons. The present invention relates to a method for separating saturated monocyclic hydrocarbons, characterized in that a phthalic acid diester is used as an extraction solvent. Examples of aromatic monocyclic hydrocarbons used in the present invention include benzene, toluene, O-xylene, m-xylene, P-xylene, ethylbenzene, diethylbenzene, isopropylbenzene, and trimethylbenzene. Examples of saturated monocyclic hydrocarbons include cyclopentane,
Cyclohexane, methylcyclohexane, 1,2
-Dimethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, cyclooctane, cyclodecane, cyclododecane, methylcyclopentane, ethylcyclohexane, diethylcyclohexane, ethylcyclopentane, etc., and unsaturated monocyclic hydrocarbons Examples include cyclopentene, cyclohexene, methylcyclohexene, dimethylcyclohexene, cyclooctene, cyclodecene, cyclododecene, ethylcyclohexene, methylcyclopentene, ethylcyclopentene, cyclopentadiene, cyclohexadiene, methylcyclohexadiene, cycloheptadiene, cyclooctadiene, cyclodecadiene. , cyclododecadiene, etc. The saturated monocyclic hydrocarbons and unsaturated monocyclic hydrocarbons used in the present invention are produced by partial hydrogenation reaction and electrolytic reduction reaction of aromatic monocyclic hydrocarbons, and the aromatic monocyclic hydrocarbons and unsaturated monocyclic hydrocarbons are saturated. Although they are produced by partial dehydrogenation of monocyclic hydrocarbons, the method of producing these monocyclic hydrocarbons is not limited in any way when applying the method of the present invention. The method of the present invention may be applied to mixtures containing aromatic monocyclic hydrocarbons, saturated monocyclic hydrocarbons, and unsaturated monocyclic hydrocarbons obtained by the various reaction methods described above, while being removed from the reactor. In some cases, after separating the catalyst, high-boiling point components, and low-boiling point components that can be easily separated by other known separation operations such as distillation, extraction, liquid separation, crystallization, and filtration, the present invention The method described above may be applied. In some cases, the method of the present invention may be applied after separating a part of the saturated monocyclic hydrocarbons or aromatic monocyclic hydrocarbons by liquid-liquid extraction using the solvents shown in the present invention. The presence or absence of these pre-treatments and the pre-treatment method are not particularly limited. In carrying out the method of the present invention, there are no particular limitations on the combination of mixtures consisting of aromatic monocyclic hydrocarbons, saturated monocyclic hydrocarbons, and unsaturated monocyclic hydrocarbons. Generally, if the boiling point difference and specific volatility are large and there is no azeotropic relationship, separation can be easily performed by a normal distillation method without using the solvent shown in the present invention.
However, in cases where the boiling point difference is extremely small and the specific volatility is close to 1, separation is extremely difficult and is uneconomical and industrially undesirable or impossible using normal distillation methods, such as aromatic monocyclic hydrocarbons. ,
Saturated monocyclic hydrocarbons, unsaturated monocyclic hydrocarbons such as benzene, cyclohexane, cyclohexene or toluene, methylcyclohexane, methylcyclohexene or cyclopentanecyclopentene,
When attempting to separate a mixture containing cyclopentadiene, etc., the phthalic acid diester shown in the present invention has an excellent separation effect. The phthalic acid diesters used in the present invention include dimethyl phthalate, diethyl phthalate,
Examples include di-n-butyl phthalate, di-isobutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, and dimethyl phthalate is particularly preferred. A sufficient effect can be obtained even if the phthalic acid diester is used alone as a solvent, but a mixture of two or more phthalic acid diesters may be used. Furthermore, there is no problem in using phthalic acid diester in a mixture with other polar solvents;
In combination with other polar solvents, solvents that have high selectivity for the separation of saturated monocyclic hydrocarbons but have insufficient solubility, such as sulfone compounds such as sulfolane, aliphatic dinitrile compounds such as adiponitrile, etc. When used in combination, they exhibit excellent separation effects. If the amount of solvent used in the present invention is small, the separation efficiency of the target monocyclic hydrocarbon will be poor, and if the amount of solvent used is too large, the equipment will be too large to improve the separation efficiency. Become,
Furthermore, the cost of recovering the solvent increases, which is not desirable from an industrial perspective. The amount of solvent used is usually about 0.5 to 10 times, preferably about 1 to 5 times, the molar ratio of the monocyclic hydrocarbon mixture to be separated. The extractive distillation operation method may be either a commonly used batch method or a continuous method, and the apparatus for carrying out the distillation does not need to be a special one. In addition, the operating pressure when performing extractive distillation is normal pressure, pressurized,
Either depressurization may be used, and if a multiple effect system is used to effectively utilize energy, it is desirable to combine depressurization systems. <Examples> The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited in any way by these Examples. Here, the specific volatility α _AB of hydrocarbon A with respect to hydrocarbon B is as follows. α _AB = Y(A)/X(A)/Y(B)/X(B) However, Y(A) and Y(B) are hydrocarbon A and hydrocarbon B in the gas phase at the time of vapor-liquid equilibrium. represents the molar fraction of hydrocarbon A and hydrocarbon B relative to the sum of
(A) and X(B) represent the molar fractions of hydrocarbon A and hydrocarbon B relative to the total of hydrocarbon A and hydrocarbon B in the liquid phase at the time of vapor-liquid equilibrium. Note that the percentages in the examples are by weight. The analysis was also carried out by gas chromatography. Examples 1 to 7 To confirm the excellent selectivity of the solvent of the present invention,
Two types of monocyclic hydrocarbon mixtures and a solvent were placed in a gas-liquid equilibrium measurement test device with stirring, and the ratio of the number of moles of the solvent to the total number of moles of the monocyclic hydrocarbon mixture (number of moles of solvent/
The total number of moles of each monocyclic hydrocarbon was charged to be 1.8, and after the gas and liquid were sufficiently equilibrated, the compositions of the gas and liquid phases were analyzed. The specific volatility α _AB between the two types of monocyclic hydrocarbon mixtures was determined from the analytical values and is shown in Table 1. Comparative Examples 1 to 3 Two types of monocyclic hydrocarbon mixtures and a solvent were placed in a gas-liquid equilibrium measurement test device with stirring, and the ratio of the number of moles of the solvent to the total number of moles of the monocyclic hydrocarbon mixture (number of moles of solvent/
The total number of moles of each single hydrocarbon was prepared to be 1.8, or without adding any solvent, and after the gas and liquid were sufficiently equilibrated, the composition of the gas and liquid phases was analyzed. . The specific volatility α _AB between the two types of monocyclic hydrocarbon mixtures was determined from the analytical values and is shown in Table 1. Example 8 The first distillation column with a length of 4.5 m was packed with stainless steel Dickson packing for a total length of 2.7 m.
Extractive distillation was carried out in a continuous manner at normal pressure using a packed column. Benzene from a position 1.5m below the top of the filling
48.5%, cyclohexene 42.0%, cyclohexane
A 9.5% mixture was fed at 600 g/Hr, while 3200 g/Hr of dimethyl phthalate was fed as a solvent from a position 0.2 m below the top of the packing, and continuous operation was performed at a reflux ratio of 15. As a result, the purity was 97.8 from the top of the column. % of cyclohexane/Hr was obtained. The mixture obtained from the bottom of the first distillation column is
2nd distillation column (with the same stainless steel Dickson packing as the first distillation column as packing)
2500g/Hr of dimethyl phthalate was supplied as a solvent from a position 0.2m below the top of the filling, and continuous operation was performed at a reflux ratio of 8. As a result, 251 g/Hr of cyclohexene with a purity of 98.3% was obtained from the top of the column. Example 9 Extractive distillation was carried out using the same equipment as in Example 8, with the same liquid supply amount, overhead distillation amount, and reflux ratio as in Example 8, except that diethyl phthalate was used as the solvent. However, the purity of cyclohexane obtained from the top of the first distillation column is 97.0%, and the purity of cyclohexene obtained from the top of the second distillation column is 97.0%.
It was 97.5%. Example 10 Using the first distillation column shown in Example 8, methylcyclohexene was added from a position 1.5 m below the top of the packing.
Supplying 600g/Hr of a mixture of 60% and 40% toluene,
On the other hand, 2000 g/Hr of dimethyl phthalate was supplied as a solvent from a position 0.2 m below the top of the column, and continuous operation was performed at a reflux ratio of 10.
% methylcyclohexene/hr was obtained. The mixture obtained from the bottom of the first distillation column was supplied from a position 1.3 m below the top of the packing of the second distillation column shown in Example 8, and continuous operation was performed at a reflux ratio of 0.5. 95.4% toluene from 239
g/Hr was obtained. Comparative Example 4 Extractive distillation was carried out using the same equipment as in Example 8 and with the same liquid supply amount, overhead distillation amount, and reflux ratio as in Example 8, except that dimethyl sulfoxide was used as the solvent. The purity of cyclohexane obtained from the top of the first distillation column was 91.6%, and the purity of the cyclohexane obtained from the top of the first distillation column was 91.6%.
The purity of cyclohexene obtained from the top of the distillation column was 94.0%. <Effects of the Invention> According to the method of the present invention, unsaturated monocyclic hydrocarbons, saturated monocyclic hydrocarbons, and aromatic monocyclic hydrocarbon mixtures can be separated more easily than when conventionally known solvents are used. Unsaturated monocyclic hydrocarbons and saturated monocyclic hydrocarbons can be efficiently separated. 【table】

Claims (1)

[Scope of Claims] 1. Saturated monocyclic hydrocarbons are produced by extractive distillation from a mixture of at least two types of monocyclic hydrocarbons among saturated monocyclic hydrocarbons, unsaturated monocyclic hydrocarbons, and aromatic monocyclic hydrocarbons. A method for separating hydrogen or unsaturated monocyclic hydrocarbons, characterized in that a phthalic acid diester obtained by a reaction between phthalic acid and an aliphatic alcohol having 1 to 8 carbon atoms is used as an extraction solvent. Method for separating ring hydrocarbons. 2. The method for separating monocyclic hydrocarbons according to claim 1, wherein the phthalic acid diester is dimethyl phthalate.