JPH0717542B2 - Separation method of 2,6-dimethylnaphthalene - Google Patents

Description

The present invention relates to a method for separating 2,6-dimethylnaphthalene from a feedstock containing a mixture of dimethylnaphthalene isomers. More specifically, the present invention uses a specific solid adsorbent and a specific desorbent that selectively adsorbs and desorbs 2,6-dimethylnaphthalene, and 2,6-dimethylnaphthalene and at least one other The present invention relates to a method for separating 2,6-dimethylnaphthalene from a feedstock feed stream containing the dimethylnaphthalene isomer and / or a hydrocarbon having a boiling range of 220 to 270 ° C. and / or a derivative thereof.

[Prior Art] It is also known in the prior art that a specific dimethylnaphthalene can be separated from a mixture in which an X-type or Y-type zeolite containing a certain cation at an exchangeable cation site contains a dimethylnaphthalene isomer. It recognized. For example, U.S. Pat.No. 3,133,126 and U.S. Pat.
Point out that the X-type zeolite containing sodium or calcium at the exchangeable cation site is useful as a selective adsorbent between dimethylnaphthalene isomers.

In Japanese Examined Patent Publication No. 52-945, Y type zeolite is used, and benzene, toluene and orthoxylene are used as desorbing agents.
Selectively from a 6 / 2,7-dimethylnaphthalene eutectic mixture,
It is stated that 2,7-dimethylnaphthalene can be separated.

JP-B-49-27578 describes that Y-type zeolite can be used to separate 2,6-dimethylnaphthalene.
Furthermore, Dutch Patent 7307794, US Patent 3,772,299, US Patent 3,840,610, US Patent 3,895,080, US Patent 4,014,949.
In each of the above, it is described that Y-type zeolite is useful as an adsorbent in the separation of cyclic hydrocarbons.

[Problems to be Solved by the Invention] However, US Patent 3,133,126 and US Patent 3,11
4,782, when observing the adsorption selectivity between dimethylnaphthalene isomers, the adsorption selectivity was determined by the stationary batch method for a dilute solution of a dimethylnaphthalene isomer mixture in the presence of paraffin, which does not actually participate strongly in adsorption. However, there is no description about the involvement of the desorbing agent, which is indispensable when actually operating industrially, for example, when performing continuous separation using a simulated moving bed or the like.

Regarding the industrially essential releasing agent, there is no description that the above-mentioned Japanese Patent Publication No. 49-27578, U.S. Patent 3,772,399, U.S. Patent 3,895,080, U.S. Patent 4,014,949, Dutch Patent 730779.
The same applies to 4.

Generally, in an adsorption separation operation, an excellent adsorption separation system is
First of all, regarding the adsorbent, the separation coefficient and adsorption capacity when reaching the equilibrium state are large, no alteration of the substance to be separated is observed, and further the rate of adsorption and desorption of the substance to be separated is fast. Regarding the desorbing agent, the desorbing agent has an adsorbing power that is intermediate between the weakest adsorbing power and the strongest adsorbing power among the substances to be separated.
Among the substances to be separated, a substance that promotes adsorption and desorption of the target substance is particularly required. If such requirements are not satisfied, problems such as increased tailing of the substance to be separated occur and the target substance cannot be efficiently separated.

Further, when a single adsorbent is used in the adsorption tower, for example, the separability between the target substance 2,6-dimethylnaphthalene and other components shows a good tailing tendency or no tailing tendency. Causes a difficulty in separation operation such as lack of separation ability. Further, for example, a boiling range of 220 to 270 derived from a coal tar fraction or a petroleum fraction, or the alkylation reaction product of naphthalene or methylnaphthalene.
Impurities such as biphenyl, ethylnaphthalene, etc. are present in the feedstock oil containing hydrocarbons and / or dielectrics thereof at 0 ° C. There has been a problem that the product flows out at the same time as 2,6-dimethylnaphthalene, resulting in a decrease in the purity of the product 2,6-dimethylnaphthalene, or an operational problem such as tailing.

[Means for Solving Problems] Then, the inventors of the present invention have made extensive studies to solve these problems, and as a result, by combining a specific Y-type zeolite and a specific X-type zeolite, The present invention has been achieved by finding that it is very effective in preventing the purity of 6-dimethylnaphthalene from decreasing. That is, the present invention provides a method for efficiently separating and obtaining 2,6-dimethylnaphthalene from a dimethylnaphthalene isomer mixture with high purity.

And this object, according to the present invention, in the method of separating 2,6-dimethylnaphthalene by treating the feedstock oil dimethylnaphthalene isomer mixture with an adsorbent, and then treating with a desorbent, as an adsorbent, A Y-type zeolite containing an alkali metal or zinc at its cation site and an X-type zeolite containing an alkali metal at its cation site are used, and an aromatic hydrocarbon having 7 to 10 carbon atoms is used as a desorbing agent. It is achieved by

Hereinafter, the present invention will be described in more detail.

Many types of zeolite are known to be naturally produced and artificially synthesized. However, not all of these zeolites are effective as the adsorbent for separating 2,6-dimethylnaphthalene by the method of the present invention, and Y-type zeolite and X-type zeolite are used in the present invention. Y-type zeolite, which belongs to faujasite-type zeolite, has 0.9 ± 0.2 Na ₂ O: Al ₂ O ₃ : 4.5 ± 1.5 SiO ₂ : YH ₂ O (where Y is zero or less than 0) As shown by the formula (1), it can be represented by the molarization of the oxide with respect to the sodium form. Similarly, the X-type zeolite, which belongs to the faujasite-type zeolite, has an oxide display of 0.9 ± 0.2 Na ₂ O: Al ₂ O ₃ : 2.5 ± 0.5 SiO ₂ : YH ₂ O (where Y is 0 or less than 8). It can be represented by the molar conversion of the oxide with respect to the sodium form.

As the adsorbent used in the present invention, a Y-type zeolite containing an alkali metal or zinc at its cation site and an X-type zeolite containing an alkali metal at its cation site are used.

Examples of the cation for the Y-type zeolite include alkali metal ions such as sodium, potassium and lithium, or zinc ions. On the other hand, examples of the cation for the X-type zeolite include the above-mentioned alkali metal ions.

In order to prepare these zeolites, the sodium form can be used without any particular preparation, but in the case of a cation other than sodium, the sodium form is a known method, for example, a salt solution of the cation to be exchanged. May be used to ion-exchange a part or almost all of the part with a desired cation.

In the present invention, the Y-type zeolite and the X-type zeolite thus prepared are used in combination, and various combinations are adopted. For example, a form in which one or more types of the above-mentioned Y-type zeolite and X-type zeolite are alternately laminated, specifically, one zeolite is sandwiched between the other zeolites, or one zeolite is placed upstream with the other zeolite. The form of filling so that it may become a downstream part, the form of mixing each zeolite physically, etc. are mentioned. In short, it is important to use each adsorbent in combination so that the characteristics of each adsorbent are utilized and the combination with excellent separation efficiency is achieved as a synergistic effect. And in the most preferred embodiment of the present invention, the above Y-type zeolite is filled upstream with respect to the feed stream of the dimethylnaphthalene isomer mixture, and then the above X-type zeolite is filled downstream thereof so that they are alternately laminated. Alternatively, a connected form is preferable. When each zeolite is used in a physically mixed state, it is used as a single bed, and when different zeolites are divided into two or more adsorption towers and used as a mixed bed, dimethylnaphthalene is used. A mixture of isomers or containing said mixture, for example with a boiling point of 22
Contact the feedstock at 0-270 ° C, and then on this bed for 2,6
-A continuous separation technique such as an elution-type chromatography method or a simulated moving bed method in which a desorbent substance that selectively desorbs dimethylnaphthalene is circulated can be used.

Zeolite as an adsorbent is not limited to powder form, may be formed into pellets, extruded products, granules, etc. In that case, silica, alumina, clay or the like is used as a binder, but any binder material is used. It can also be used. When packed in a column, the shape of the zeolite may be spherical, crushed, or the like, but when the average particle diameter of the zeolite is d and the inner diameter of the packed column is D, the ratio thereof is Those having a size such that D / b is 15 or more, preferably 20 or more are preferable.

The selection of a desorbing agent is important for efficient adsorption separation of 2,6-dimethylnaphthalene. That is, the desorbing agent is capable of selectively and easily desorbing 2,6-dimethylnaphthalene from zeolite separately and further from the raw material oil components, and further distilling or other methods to remove 2,6
-It must be easily removable from dimethylnaphthalene. For that purpose, a desorbing agent having an adsorbing power to the zeolite between the 2,6-dimethylnaphthalene present in the feedstock containing a mixture of dimethylnaphthalene isomers and the component having the strongest adsorbing power is preferable.

The desorbing agent used for desorbing 2,6-dimethylnaphthalene in the present invention is an aromatic hydrocarbon having 7 to 10 carbon atoms. Specifically, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, n-propylbenzene, isopropylbenzene, 4-ethyltoluene, 3
-Ethyltoluene, 2-ethyltoluene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, 1,2,3-
Trimethylbenzene, o-cymene, m-cymene, p-cymene, o-diethylbenzene, m-diethylbenzene,
p-diethylbenzene, o-propyltoluene, m-propyltoluene, p-propyltoluene, n-butylbenzene, sec-butylbenzene, tert-butylbenzene, 1,2,3,4-tetramethylbenzene, 1,2, Examples thereof include 3,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene, and tetralin, and two or more of these may be mixed and used. Among the above mixtures, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, n-propylbenzene, isopropylbenzene, 4-ethyltoluene, 1,2,4-trimethylbenzene, p-diethylbenzene, p-cymene. , Tetralin is preferred, and most preferred are toluene, o-xylene, p-xylene, ethylbenzene, isopropylbenzene, 4-ethyltoluene and tetralin.

Further, the above-mentioned elimination agent can be used as a mixture with an inert diluent, in which case the diluent has a saturated chain hydrocarbon which is liquid at the operating temperature, or an alkyl substituent. It is possible to use naphthenes which are saturated cyclic hydrocarbons having 6 to 20 carbon atoms.

In the method of the present invention, the raw material oil containing the raw material diethylnaphthalene isomer mixture, as the dimethylnaphthalene content, 2,6-dimethylnaphthalene, 2,7-dimethylnaphthalene, 2,3-dimethylnaphthalene, 1,2-dimethyl Of the naphthalene, 1,3-dimethylnaphthalene, 1,4-dimethylnaphthalene, 1,5-dimethylnaphthalene, 1,6-dimethylnaphthalene, 1,7-dimethylnaphthalene, 1,8-dimethylnaphthalene, 2,6- It contains one or more dimethylnaphthalene isomers of dimethylnaphthalene and other dimethylnaphthalene, and a hydrocarbon compound having a boiling point range of 220 to 270 ° C., for example, α-methylnaphthalene, β-methylnaphthalene, α- It mainly contains ethylnaphthalene, β-ethylnaphthalene, and biphenyl. Alkanes, alkenes, in which cycloalkenes may contain partially saturated polycyclic aromatic hydrocarbons.

The method of the present invention can be carried out in either the gas phase or the liquid phase, but the liquid phase is preferred. The operating conditions when the substance to be separated and the desorbent are brought into contact with the zeolite adsorbent, the physical properties of the substance to be separated and the desorbent, such as melting point, boiling point, viscosity, etc. must be appropriately selected in consideration of the liquid. In order to maintain the phase state, a temperature in the range of 0 to 300 ° C, approximately atmospheric pressure to 5
Pressures in the 0 atmosphere range are preferred. More preferably, 60-200
It is selected from the temperature range of ° C, a pressure in the range of approximately atmospheric pressure to 20 atm.

According to the method of the present invention, in a dimethylnaphthalene mixture,
It is clear that impurities other than 6-dimethylnaphthalene are separated from 2,6-dimethylnaphthalene, and the purity of 2,6-dimethylnaphthalene in the product is improved.

[Examples] Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 Granules of Y-type zeolite (particle size distribution 250 to 420 μm) in which about 70% of cation sites are lithium are in the upper layer, and granules of X-type zeolite in which cation sites are sodium (particle size distribution 250 to 420 μm). ) Is the lower layer, and the weight ratio is 4.
It was packed into a stainless steel column with an inner diameter of 8 mm and a length of 1 m with a jacket for heat insulation so that it became 4/1. The upper end of the column was used as an inlet, and a distributor for liquid dispersion was attached to the inlet of the column so that uneven flow did not occur. The column temperature was maintained at 100 ° C., paraxylene as a releasing agent was fed from one end of the column at a rate of 5 ml / min, and the column was filled with the releasing agent for conditioning. Then, using a dimethylnaphthalene isomer mixture containing 10 wt% of 2,6-dimethylnaphthalene as a raw material, a 3 ml pulse was sent to the top of the column, and then the desorbent flow was switched again to 0.4 ml / min.
The desorbent was fed in at a ratio of, and the raw material feed was developed in the column. The outlet flow is sampled at regular intervals with the time point when the development with the desorbent is started as 0, and the components contained in each fraction are quantified using a gas chromatograph,
The change in the concentration of the raw material components in the outlet flow with the elapse of the outflow time was measured.

As a result, the recovery rate of 95% pure 2,6-dimethylnaphthalene was 39.4%.

Example 2 Y-type zeolite granules (particle size distribution 250 to 420 μm) in which about 70% of cation sites are lithium are in the upper layer, and Y-type zeolite granules having cation sites are potassium (particle size distribution 250 to 420 μm). ) In the middle layer and granules of X-type zeolite with sodium as the cation site (particle size distribution 250-420 μm) in the lower layer, the inner diameter is 8 mm and the length is 1 m so that the weight ratio becomes 6.5 / 1/1. Example 1 was repeated except that the column was made of stainless steel with a jacket for heat retention.

As a result, the recovery rate of 95% pure 2,6-dimethylnaphthalene was 14.2%.

Example-3 Granules of Y-type zeolite having a cation site of about 70% zinc (particle size distribution 250 to 420 μm) in the upper layer, granules of x-type zeolite having a cation site of sodium (particle size distribution 250 to 420 μm) Was carried out in the same manner as in Example 1 except that the lower layer was packed in a stainless steel column with an inner diameter of 8 mm and a length of 1 m and a jacket for heat retention so that the weight ratio was halved.

As a result, the recovery rate of 95% pure 2,6-dimethylnaphthalene was 53.8%.

Comparative Example-1 A Y-type zeolite granular product (particle size distribution 250 to 420 μm) in which about 70% of cation sites are lithium (inner diameter 8 mm, length 1)
Example 1 was repeated except that the column was made of stainless steel with a jacket for heat insulation of m.

As a result, the recovery rate of 95% pure 2,6-dimethylnaphthalene was 3.0%.

Comparative Example-2 Y-type zeolite granules (particle size distribution 250 to 420 μm) in which about 70% of cation sites are potassium (inner diameter 8 mm, length 1)
Example 1 was repeated except that the column was made of stainless steel with a jacket for heat insulation of m.

As a result, the recovery rate of 95% pure 2,6-dimethylnaphthalene was 0.1%.

Comparative Example-3 Example except that Y-type zeolite granules (particle size distribution 250 to 420 μm) in which about 70% of cation sites are zinc (particle size distribution 250 to 420 μm) were packed in a stainless steel column with an inner diameter of 8 mm and a length of 1 m and a heat insulation jacket. The same procedure as for -1 was performed.

As a result, the recovery rate of 95% pure 2,6-dimethylnaphthalene was 11.7%.

[Effects of the Invention] According to the present invention, 2,6-dimethylnaphthalene can be efficiently and selectively separated from a stock oil containing a dimethylnaphthalene isomer mixture.

Claims (1)

[Claims] 1. A method for separating 2,6-dimethylnaphthalene by treating a feedstock oil containing a mixture of dimethylnaphthalene isomers with an adsorbent, and then treating it with a desorbing agent, which is used as an adsorbent at its cation site. A Y-type zeolite containing an alkali metal or zinc and an X-type zeolite containing an alkali metal at its cation site are used, and an aromatic hydrocarbon having 7 to 10 carbon atoms is used as a desorbing agent. A method for separating 2,6-dimethylnaphthalene.