JPH0112734B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to dichlorobenzene (hereinafter abbreviated as DCB)
It is concerned with the separation method of isomers, especially
The present invention relates to a method for separating and recovering m-DCB from a DCB isomer mixture. DCB is important as an intermediate raw material for concentrated medicines, but
The boiling points of DCB isomers are similar (o:
180.4, m: 173.0, p: 174.1°C), it is extremely difficult to separate these alone. this house,
The o-isomer has a slightly higher boiling point than the m- and p-isomers, so it can be recovered by distillation, but when attempting to separate and recover the m-isomer, it is extremely difficult to separate it from the p-isomer. becomes difficult. As a method for recovering only m-DCB from a DCB isomer mixture containing o-, m-, and p-DCB, for example, o-DCB is separated by distillation, followed by a sulfonation step, and then m-DCB is separated by crystallization. 4-
There is a method of recovering m-DCB as sulfonic acid. The present inventors have demonstrated that m-DCB can be directly separated from a DCB isomer mixture containing o-, m-, and p-DCB by an adsorption separation method using a zeolite adsorbent without going through the complicated process described above. As a result of intensive research to develop a method to collect DCB alone, we found that the following points are important. In other words, the adsorption separation method in the present invention refers to a chromatographic preparative method in which a mixture of substances to be separated is developed on an adsorbent using a developing agent and chromatographically separated and recovered, or a continuous adsorption separation method using a simulated moving bed. (In this case, the developing agent is referred to as a desorbing agent.) However, the separation performance of the adsorbent in the presence of these desorbing agents or developing agents is an important matter. In the above-mentioned adsorption separation technology, since the adsorption operation of DCB is carried out in the presence of a desorbent, both are adsorbed onto the zeolite-based adsorbent in the form of competitive adsorption. At this time,
This means that the adsorbed desorbent should not impair the DCB separation performance of the adsorbent. In view of this point, the present inventor has conducted intensive research and has found that the DCB separation performance of a specific zeolite adsorbent is rather improved in the presence of a desorbent, and has arrived at the present invention. That is, the present invention uses a Y-type zeolite containing potassium and silver ions as essential components as an adsorbent when adsorbing a dichlorobenzene isomer mixture containing o-, m-, and p-dichlorobenzene. The present invention provides a method for separating dichlorobenzene isomers, which is characterized by separating and recovering m-dichlorobenzene from. In the method of the present invention, m-DCB is separated and recovered as a substance that is least adsorbable among DCB isomers. Y used as adsorbent in the method of the present invention
Type zeolite is a crystalline aluminosilicate that belongs to the faujasite type zeolite,
It can be expressed by the following molar ratio of oxides. (See USP-3130007). 0.9±0.2M _2/o O: Al ₂ O ₃ : 3 to 6 SiO ₂ : yH ₂ O M: cation, n: valence of M, y: varies depending on degree of hydration. Although M can be any cation, Y-type zeolites are usually obtained in which M is sodium. In the case of the adsorbent of the invention, it is necessary to ion-exchange it with potassium and silver. Any known ion exchange method may be used as appropriate, but ions are usually exchanged with potassium and silver nitrate aqueous solutions either individually or simultaneously. It is also preferable to use other water-soluble salts such as chlorides in place of nitrates. The ratio of potassium and silver among the cations in Y-type zeolite is 10 to 95 for potassium,
Preferably, the silver content is 5 to 80 mol%. Especially 50-90 mol%
of potassium and 10-50 mol% of silver cations give good results. The Y-type zeolite of the present invention may of course contain other cation components in addition to potassium and silver ions, such as A group other than sodium, A
It may also contain metals of group A, group A, group A metals, protons, and the like. The adsorption separation technology for adsorbing and separating the DCB isomer mixture using the adsorbent of the present invention may be the so-called chromatographic separation method as mentioned above, or a pseudo moving bed that is a continuous method of this method. An adsorption separation method may also be used. Continuous adsorption separation technology using a simulated moving bed is basically carried out by continuously cycling the following adsorption operation, concentration operation, and desorption operation. (1) Adsorption operation: A feedstock containing a mixture of DCB isomers is contacted with the adsorbent of the present invention to obtain p- and o-
DCB is selectively adsorbed. remaining m-DCB
is recovered as roughinate along with a desorption agent, which will be described later. (2) Concentration operation: The adsorbent that has selectively adsorbed o- and p-DCB is brought into contact with a part of the extract, which will be described later, to drive out m-DCB that has been adsorbed subordinately on the adsorbent. o- and p-
DCB components are concentrated. (3) Desorption operation: concentrated o- and p-DCB
is expelled from the adsorbent by the desorbent and recovered together with the desorbent as an extract. The desorbent concentration in the adsorbent bed in the above operation is approximately 10
Since the amount is nearly 100% by weight, the separation performance of the adsorbent in the presence of the desorbent is important. The desorbent used in the above adsorption separation method is preferably an alkyl-substituted aromatic hydrocarbon or a chloro-substituted aromatic hydrocarbon, particularly preferably toluene, xylene, chlorobenzene, dichlorotoluene, chloroxylene, or the like. The operating conditions for the adsorption separation method include a temperature ranging from room temperature to 350°C, preferably 50 to 250°C, and a pressure ranging from atmospheric pressure to 40 Kg/cm ² G, preferably from atmospheric pressure to 30 Kg/cm ² G. It is. Although the adsorption separation process of the present invention can be carried out in the gas or liquid phase, it is preferably carried out in the liquid phase to lower operating temperatures and reduce undesirable side reactions of the feedstock or desorbent. Next, the method of the present invention will be explained by giving examples.
In the examples, the adsorption characteristics of the adsorbent are expressed by the adsorption selectivity (α) of the following formula. α(o or p/m) = (weight fraction of o or p/weight fraction of m) _A / (weight fraction of o or p/weight fraction of m) _U (1) where, o, m and p are o-DCB and m, respectively.
-DCB, p-DCB, A indicates the adsorbed phase, and U indicates the liquid phase in equilibrium with the adsorbed phase. The larger the α value in the above equation is, the more difficult it is for m-DCB to be adsorbed compared to o- and p-DCB. That is, an adsorbent suitable for separating and recovering m-DCB preferably has α _p/n and α _p/n both greater than 1 or less than 1. The present invention relates to the former. Example 1 10 wt% of alumina sol (calculated as Al ₂ O ₃ ) was added as a binder to Na-Y type zeolite powder (manufactured by Union Carbide Co., Ltd., SK-40), and a granulated product of 24 to 32 meshes was obtained by extrusion molding. This granulated product was dried at 100℃, then baked at 500℃ for 1 hour,
A Na-Y type adsorbent was prepared. Next, the adsorbent was treated with an aqueous potassium nitrate solution to ion-exchange 90% or more of the sodium ions to prepare a K-Y type adsorbent. Next, the K-Y type and Na-Y type zeolites were treated with a silver nitrate aqueous solution containing silver ions corresponding to 30 mol% of the K and Na cations in the K-Y type and Na-Y type zeolites.
-Y-type zeolite is treated at 60℃, Ag-K-Y
type and Ag-Na-Y type adsorbent were prepared. In order to measure the adsorption selectivity between DCB isomers of the four types of adsorbents mentioned above, 2 g of the above adsorbent calcined at 500°C for 1 hour was filled into an autoclave with an internal volume of 5 ml, and the mixture was stirred occasionally at 110°C for 1 hour. I left it there while doing so. The composition of the charged liquid phase mixture is n-nonane:p-DCB:m-DCB:o-DCB=1:
The ratio is 1:3:3 (weight ratio). N-nonane was added as an internal standard substance in gas chromatography analysis, and is a substance that is substantially inactive with respect to adsorption under the above experimental conditions. The composition of the liquid phase mixture after contact with the adsorbent was analyzed by gas chromatography, and the adsorption selectivity between DCB isomers was determined using equation (1). The results are shown in Table 1.

[Table] Example 2 The adsorption selectivity of DCB isomers of the four types of adsorbents prepared in Example 1 in the presence of a desorbent was measured. As a desorbent, 3,4-dichlorotoluene (DCT
) and chlorobenzene (abbreviated as CB). The composition of the feed solution in contact with the adsorbent is n-nonane:p-DCB:m-DCB:o-DCB:desorbent=
The weight ratio is 1:1:3:3:7. Other conditions are the same as in Example 1. The measurement results are shown in Table 2.

[Table] As is clear from the above examples, Ag of the present invention
For adsorbents other than the -K-Y type adsorbent, the adsorption selectivity in the absence of a desorbent shows a value that allows m-DCB to be recovered from a DCB isomer mixture;
In the presence of desorbent, which is the actual adsorption condition, α _p/n
Alternatively, the α _p/n value approaches 1, and m-DCB is
It becomes very difficult to separate from DCB isomers.
On the other hand, the Ag-K-Y type adsorbent shows no decrease in adsorption selectivity even in the presence of a desorbent, making it a highly preferred adsorbent for industrially separating and recovering m-DCB. Recognize. Example 3 o-DCB:m-DCB:p-DCB=54:28:
A DCB isomer mixture consisting of 18 wt% was adsorbed and separated using a simulated moving bed apparatus schematically shown in FIG. The Ag-K-Y type adsorbent prepared in Example 1 was filled into adsorption chambers 1 to 12 each having an internal volume of about 13 ml. 284.8 chlorbenzene, a desorbent, is supplied from line 13.
ml/hr, and the above isomer mixture was fed from line 15 at 11.2 ml/hr. An extract stream was withdrawn from line 14 at 61.0 ml/hr, a roughinate stream was withdrawn from line 16 at 27.1 ml/hr, and the remaining fluid was withdrawn from line 17. Further, the flow of fluid between the adsorption chambers 1 and 12 is controlled by a valve 18.
is closed. At this time, adsorption chamber 1 was moved simultaneously to 12, 11 to 10, 8 to 7, and 5 to 4 at intervals of about 150 seconds (the other adsorption chambers were also moved upward by one adsorption chamber at the same time). ). The adsorption temperature was 130°C. The purity of m-DCB in the DCB isomer mixture contained in the raffinate stream obtained in the above experiment was 99.5.
%, and the recovery rate of m-DCB was over 80%.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing an adsorption separation operation using a simulated moving bed, which is an embodiment of the present invention. 1 to 12...Adsorption chamber, 13...Desorbent supply line, 14...Extract extraction line, 1
5... Isomer mixture supply line, 16... Roughinate extraction line, 17... Desorbent recovery line, 18... Valve.

Claims (1)

[Claims] 1 When adsorbing a dichlorobenzene isomer mixture containing o-, m-, and p-dichlorobenzene, m- A method for separating dichlorobenzene isomers, the method comprising separating and recovering dichlorobenzene.