JPS5813527B2 - Improved xylenol separation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for separating xylenol from a mixture of xylenol and cresol by an adsorption separation method.

Industries using phenol, cresol, xylenol, etc. have been rapidly growing in recent years, and they are widely used in synthetic resins, plasticizers, disinfectants, agricultural chemicals, raw materials for medicines, etc.

On the other hand, phenol, cresol isomers, xylenol, etc. are obtained as a mixture during synthesis and have similar boiling points, making them difficult to obtain as single products.

In addition to distillation, methods for separating these cresols include:
Although crystal separation methods and the like have been carried out, separation by adsorption separation method has not been industrially successful.

The present inventors have investigated various methods for effectively separating xylenol and cresol by adsorption separation, and have found that the selection of adsorbent is most important.

That is, in the present invention, when xylenol is separated from a mixture of cresol and xylenol by an adsorption separation method, the adsorbent has an opening diameter of 5.5 Å or more and a silicon to aluminum ratio of 4.5 or less (Si/Al≦4. 5) is obtained by ion-exchanging the zeolite with one or more ions selected from lithium, potassium, nickel and ammonium, and the total content of cations is 20% by weight or more based on the total cations contained. This is a xylenol separation method characterized by using a certain zeolite.

By the method of the present invention, it has become possible to stably and efficiently adsorb and separate xylenol and cresol, which have a phenolic hydroxyl group and have a relatively similar structure.

The adsorbent used in the present invention has an opening diameter of 5.5 Å or more,
It is a zeolite having a composition in which the ratio of silicon to aluminum is 4.5 times or less.

In the case of a zeolite with an opening diameter of 5.5 Å, the adsorption amount of cresols is extremely small, which is industrially disadvantageous.

Also, the ratio of silicon to aluminum is large, 4.5
Zeolites exceeding 100% are reactive with cresols.

Therefore, the conditions under which such zeolites can be used are limited, and it is necessary to use extremely thin cresols or to develop them at low temperatures, for example, about 40°C or less.
Not industrially advantageous.

On the other hand, although it is not essential, if this ratio is less than 1.0, the strength tends to be weak.

Through investigation, the present inventors have clarified the interaction between cresols and zeolite.

In other words, the interaction sufficient to cause the adsorption phenomenon on zeolite is a unique effect of cresols having an OH group and an aromatic ring, and the interaction is irreversible. The surprising result was that no reaction occurred.

Furthermore, it has been discovered based on these findings that zeolites with Si/Al>4.5 are subject to various limitations on usage conditions.

From the above, the effective adsorbent for the separation of cresols is zeolite, which is an omega type (Na6.8, TMA11.6
[(Al2O)8(S i02)28]・21H2O)
, natural faujasite, type X (Na86 [(AlO2
)86-(SiO2)106]・264H2O, ), Y
Type (Na56 [(Al02)56(SiO2)136]
・250H2O, ), L type (K9 [(AlO2)9(S
102)27].22H2O), and X-type and Y-type are particularly preferred.

Although these zeolites can be collected from nature, their synthesis methods are well known, and they are described in Japanese Patent Publications No. 32-6712, No. 35-18267, No. 36
-1639, Japanese Patent Publication No. 38-124, etc., for details.

As a result of examining zeolites with even better separation characteristics among these zeolites, it was found that zeolites ion-exchanged with specific ions gave even better results.

The ions to be exchanged are one or more selected from lithium, potassium, nickel, and ammonium.

The total content of these ions is 20% by weight or more based on the total cation content.

A typical adsorbent of the present invention can be produced by using faujasite type zeolite among zeolites as a starting material and subjecting it to ion exchange.

The faujasite-type zeolite used as a starting material belongs to the 4th group of crystalline alumina silicates, which are generally called zeolites, and is called a "double hexacyclic ring" due to its crystal structure.

The fourth group includes zeolites called faujasite, chabasite, gmelinite, and ZK-5.L, of which faujasite is a type of polyhedral cage and is characterized by β,26-bedron.

In addition to natural faujasite, typical faujasites include oxides Na2O, Al2O3, 25Si02
・6H20, unit cell constant display Na86 [(AlO2)
86(SiO2)106]・264H2O density: 1.9
3g/cc, unit cell constant: 25.02 ~ 24.
86Å void volume: 0.5cc/cc, opening diameter: 12 rings-
There is an X-type synthetic zeolite characterized by a diameter of 7.4 Å, 6 rings - 2.2 Å, and a velocity aperture of 8.1 Å.

Also, oxidation display: Na2OAl203-4.8Si02・
8.9H20, unit cell constant display: Na56 [(AlO
2) 56(Si02)136]・250・H20, density: 1.92g/cc, unit cell constant: 24.85-
24.61Å void volume: 0.48cc/cc, opening diameter:
12 rings 7.4 Å, 6 rings 2.2 Å, velocity aperture diameter: 8.1 Å
There is a Y-type synthetic zeolite characterized by

Among the oxidation elements, Na is used mainly due to synthetic requirements during zeolite synthesis, and can be replaced with cations such as alkali metal ions after crystal formation.

For substitution of cations, a soluble metal salt may be dissolved in water and brought into contact with the starting material.

As the metal salt, chlorides, nitrate compounds, sulfuric compounds, carbonate compounds, etc. are usually used, and the absolute amount of cations is set to be 0.8 times or more the equivalent amount in the faujasite-type zeolite to be exchanged. is desirable.

In addition, the salt concentration of the solution for ion exchange is 0.01% by weight.
A saturated solution is used, preferably about 5 to 20% by weight.

On the other hand, the temperature during exchange is in the range of 2°C to 98°C, but a relatively high temperature is desirable in order to speed up the ion exchange time.

It is also desirable to make the desired product by converting it into an ammonium form, then firing it to make it into a hydrogen form, and then ion-exchanging it.

These ion exchange methods are disclosed in detail in Japanese Patent Publications No. 32-6713, No. 33-618, No. 33-5523, etc.

The cation of the starting material is usually in the sodium form, but the residual amount of sodium in ion exchange should be reduced to about 10% by weight or less.

Fouge Y-site type zeolite that has undergone ion exchange through such operations is usually vacuum dried, freeze-dried, hot-dried,
It is used after being dried to an appropriate amount of moisture through drying means such as electric oven drying.

Before use, an elemental analyzer is applied to confirm the constituent element ratio, cation composition ratio, substitution rate, etc., and an X-ray diffraction meter is used to confirm the crystal structure.

The adsorbent of the present invention can be used in a wide range of shapes, from a 2-micron single substance to a 1/8-inch pellet containing about 20% inorganic binder.
In order to increase the ion exchange rate and adsorption/desorption rate, it is desirable that the particle size is as small as possible, and from an operational technical point of view, in order to reduce pressure loss and facilitate operation, particles with a large particle size or It is preferable to use pellets.

The substance to be separated to which the present invention can be applied is a mixture of xylenol and cresol; examples of cresol include O-cresol, m-cresol, and p-cucresol, and examples of xylenol include 2,3-, 2,4- ,2,5-,2
, 6-, 3,1- and 3,5-xylenol.

When separating the above substances to be separated, there are no particular restrictions on the composition ratio of these raw materials.

Furthermore, the contamination of third substances other than xylenol and cresol is not an essential problem.

Various types of adsorption/desorption operations are known in the adsorption separation method, and the basic unit is an operation in which substances to be separated that use strong adsorption force are preferentially adsorbed to the adsorbent, and those with weaker adsorption force are taken out first. be.

As an example of adsorption/desorption operation to which the present invention is applied, first is a batch separation method, which is a simple method in which the above basic unit is one unit, and the separation is carried out on an adsorption bed filled with an adsorbent. Substances are fed and streams rich in weaker adsorbents are taken first, and those that are more strongly adsorbed are recovered thermally or using a desorbing agent.

The performance required of the desorbing agent, etc. at this time is wide and wide.The second method is a continuous separation method.One of these methods is to circulate the developer through the adsorption bed while overtaking the substance to be separated. In this method, separation is carried out by the action of the agent and adsorbent.Other methods are such that the displacing agent does not substantially overtake the substance to be separated, but instead moves the adsorption zone of the substance to be separated. This is a method of separation.

Although the above three methods and several methods combining them are based on the same adsorption/desorption principle, they differ in their technical content, separation principle, and factors governing separation efficiency.

Since this characteristic becomes apparent during the process of desorption, what is generally called a displacing agent is referred to as a desorbing agent, a developing agent, and a displacing agent in the above explanation for easier understanding.

Examples of the present invention are shown below, but the present invention is not limited thereto.

EXAMPLE A glass column for equilibrium experiments with a cylindrical jacket and having a diameter of 2 cm and a length of 50 m is maintained at 140°C.

A solution consisting of 80% 26-xylenol and 20% p-cresol was used as the equilibrium solution.

Typical examples of adsorbents include the aforementioned X type and Y type, including comparative examples.
Ion-exchange type zeolite and display it as an ion display.
1 was used.

In the operation, the above-mentioned adsorbent is packed into a column, and 10 liters of the equilibrium solution maintained at 140° C. is allowed to flow down each column over a period of 4 hours.

Subsequently, the non-adsorbed portion was removed with nitrogen gas, the adsorbed portion was desorbed with 2 liters of methyl alcohol, and this liquid was analyzed.

The adsorbent after desorption was dried and weighed to confirm that no adsorbed material remained.

The adsorption force was expressed by the following formula, where the first liquid of the above-mentioned equilibrium liquid composition is a, b the second liquid is b, and the selectivity coefficient Ka between a and b is Ka.

The selection coefficient results are shown in Table 1.

Separation efficiency is greatly influenced by the separation coefficient between substances to be separated.

In this sense, improving the separation factor can change the fundamental requirements of the recruitment process.

As clearly shown in the examples, the selectivity of the zeolite of the present invention is greatly improved.

It was unexpected that the selectivity between cresol and xylenol, which have essentially similar properties, would be improved in this way, and the degree of improvement greatly exceeds the usual improvement range of 10% to 20%. .

That is, the substitution effect of lithium, potassium, nickel, and ammonium ions is remarkable, and at the same time, the improvement in the sodium content is also remarkable.

Claims (1)

[Claims] 1. When xylenol is separated from a mixture of cresol and xylenol by an adsorption separation method, the adsorbent has an opening diameter of 5.5 Å or more and a silicon to aluminum ratio of 4.5.
Obtained by ion-exchanging zeolite with the following (Si/Al≦4.5) with one or more ions selected from thirium, potassium, nickel, and ammonium.
A method for separating xylenol, comprising using a zeolite in which the total content of cations is 20% by weight or more based on all the cations contained. 2. The xylenol separation method according to claim 1, wherein the ion-exchanged zeolite contains 10% or less of sodium ions.