JPH0538431A - Method for baking zeolite adsorbent - Google Patents

Abstract

(57) [Summary] [Structure] When calcination of a zeolite adsorbent containing a halogenated hydrocarbon, calcination is performed after the halogenated hydrocarbon contained in the zeolite adsorbent is removed. Method of baking agent. [Effect] The calcination can be performed without degrading the zeolite adsorbent containing the halogenated hydrocarbon.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for calcination of a zeolite adsorbent containing a halogenated hydrocarbon.

[0002]

2. Description of the Related Art Separation of aromatic isomers is generally carried out by boiling point difference,
Since the difference in freezing point is small, it is often difficult to apply the conventional general distillation separation method.

On the other hand, in recent years, a method of adsorbing and separating a dialkylbenzene isomer mixture with a zeolite adsorbent has been developed, and it has become possible to obtain the desired isomer in a considerably high purity.

In these methods, when the adsorption / separation performance deteriorates due to the accumulation of carbon in the zeolite adsorbent or the adsorption of water, polar compounds, etc., an operation of removing these adhering components and recovering the adsorption / separation performance is performed. is necessary.

For this operation, a method in which a heated gas is brought into contact with zeolite and the above components are removed by combustion or evaporation is generally used (for example, JP-A-50-124893). By operation, the zeolite can be used repeatedly.

[0006]

However, when a zeolite adsorbent containing a halogenated hydrocarbon, such as a zeolite adsorbent used for adsorption separation in the coexistence of a halogenated hydrocarbon, is calcined, the amount of adhered substances contained Although the components are removed, the adsorptive separation performance deteriorates, making it impossible to reuse.

[0007]

Means and Actions for Solving the Problems As a result of intensive studies made by the present inventors to establish a method for preventing the deterioration of the zeolite adsorbent during firing, as a result, the cause of deterioration is the halogen remaining in the adsorbent. It was found that they are in hydrocarbons, and the present invention was reached.

That is, the present invention is characterized in that, when a zeolite adsorbent containing a halogenated hydrocarbon is calcined, the halogenated hydrocarbon contained in the zeolite adsorbent is removed and then calcined. A method for firing the agent is provided.

In the present invention, the halogenated hydrocarbon is a hydrocarbon containing one or more halogen atoms, and 2
When one or more halogen atoms are included, the halogen atoms may be the same or different. The halogen atom is, specifically, a chlorine atom, a bromine atom, an iodine atom or the like, preferably a chlorine atom.

Specific examples of the halogenated hydrocarbon include trichlene, tetrachloroethane, trichloropropane,
Examples thereof include dichlorobenzene, chlorotoluene, dichlorotoluene, trichlorobenzene, dibromobenzene, dibromotoluene and the like. Of these, dichlorobenzene, chlorotoluene, and dichlorotoluene can be preferably used. These halogenated hydrocarbons may be contained in the adsorption separation raw material or may be contained in the desorbing agent.

The zeolite adsorbent used in the present invention is not particularly limited, but specific examples include X-type and Y-type faujasite type zeolites,
The effect of the present invention is remarkable when a pentasil-type zeolite such as ZSM-5, a mordenite-type zeolite, an L-type zeolite, a beta-type zeolite, an A-type zeolite or the like is used.

Examples of the method for removing the halogenated hydrocarbon contained in the zeolite adsorbent in the present invention include vacuum drying, aeration drying, water washing, and washing with a non-halogen organic solvent. Washing with a solvent is preferred.

The non-halogenated organic solvent has an effect of dissolving the halogenated hydrocarbon and replacing the halogenated hydrocarbon adsorbed on the zeolite adsorbent. Therefore, those having a large solubility of halogenated hydrocarbons and those having a large adsorptive power to the zeolite adsorbent are preferable. Specific examples of the non-halogen organic solvent include methanol, ethanol, acetone, and alkylbenzene such as benzene, toluene, and xylene. These may be a mixture of two or more kinds of organic solvents.

The washing is carried out until the content of halogenated hydrocarbon contained in the zeolite adsorbent becomes substantially negligible. Usually, it is carried out until the content of halogenated hydrocarbon contained in the zeolite adsorbent becomes 0.5% or less.

The washing method may be a fixed bed, a moving bed or a fluidized bed, and may be a flow type or a batch type. It is effective to stir, but excessive stirring is not preferable because the adsorbent is abraded.

The washed zeolite adsorbent is preferably dried and then calcined to remove excess organic solvent. In order to improve the efficiency of the drying process, it is also effective to wash it beforehand with water to remove the attached non-halogenated organic solvent. The method of drying is not particularly limited. Generally, it is carried out by a ventilation drying method or the like, preferably at 200 ° C. or lower until the organic solvent and water contained in the adsorbent become substantially negligible. This makes it possible to prevent deactivation of the adsorbent due to rapid combustion of the organic solvent and rapid evaporation of water during firing.

Firing in the present invention means an operation of removing carbon, organic matter, water and the like contained in the adsorbent by burning or evaporation at a temperature of 200 ° C. or higher. The firing method is not particularly limited. The firing temperature is preferably 400 to 600 ° C.

Thus, the calcined zeolite can be reused as an adsorbent without deteriorating the adsorption performance.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples. In the examples, the adsorption characteristic of the adsorbent is represented by the adsorption selectivity (α) of the following equation.

[0020]

[Equation 1]

Here, A and B represent any one of aromatic isomers or a desorbent, S represents an adsorption phase, and L represents a liquid phase in equilibrium with the adsorption phase.

When the adsorption selectivity α _{A / B} is greater than 1, the A component is selectively adsorbed, and when it is less than 1, the B component is selectively adsorbed. Also, the adsorption selectivity α _{A / B}
The adsorbent having a value of greater than 1 or an adsorbent having a value of less than 1 and closer to 0 facilitates adsorption separation of A and B.

Example 1 A zeolite adsorbent for separating metachlorotoluene (abbreviated as m-CT) was prepared by the method described in JP-A-58-131923. This zeolite adsorbent is a Y-type zeolite containing protons, potassium ions, and silver ions as cations.

The zeolite adsorbent was calcined at 500 ° C. for 2 hours and then adsorbed 3,4-dichlorotoluene.
After that, the excess 3,4-dichlorotoluene was removed by drying,
An adsorbent containing 3,4-dichlorotoluene was obtained. The following treatments were performed in order to calcine the obtained adsorbent. Methanol having a solid-liquid ratio of 5 was added to the obtained zeolite adsorbent, and the mixture was washed with stirring. This methanol washing was repeated 10 times. Dichlorotoluene contained in this zeolite adsorbent was 0.1%. Next, it was washed 10 times with water having a solid-liquid ratio of 5. After washing, it was dried at 120 ° C. for 5 hours and then fired at 500 ° C. for 2 hours using a muffle furnace.

M-CT and ortho-chlorotoluene (o-C
T) and parachlorotoluene (abbreviated as p-CT) to measure the adsorption selectivity between the adsorbent 2 g and the chlorotoluene isomer mixture 3 g in an autoclave having an internal volume of 5 ml, and at 130 ° C. It was left for 0.5 hours with occasional stirring. The composition of the charged chlorotoluene isomer mixture was o-CT: m-CT: p-CT = 1:
It is 1: 1 (weight ratio). Further, 5 wt% of n-nonane with respect to the chlorotoluene isomer mixture was simultaneously charged as a reference substance for gas chromatography analysis. n
Nonane is a substance which is practically inert under the above conditions with respect to the adsorption properties of zeolites.

The composition of the liquid phase mixture after being contacted with the adsorbent was analyzed by gas chromatography to determine the adsorption selectivity between the chlorotoluene isomers. Further, the adsorbent prepared by the above method was directly burned by the above method without adsorbing 3,4-dichlorotoluene, and the adsorption selectivity was measured to obtain a blank. The results are shown in Table 1.

Example 2 The firing and adsorption selectivity were measured in the same manner as in Example 1 except that o-xylene was used in place of methanol in Example 1 and direct drying was performed without washing with water. The results are shown in Table 1.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the dried adsorbent containing 3,4-dichlorotoluene was directly calcined without washing with methanol, and the adsorption was performed. The selectivity was measured. The results are shown in Table 1.

[0029]

[Table 1]

[0030]

According to the present invention, calcination can be carried out without degrading the zeolite adsorbent containing halogenated hydrocarbon.

Claims (2)

[Claims] 1. A method for calcination of a zeolite adsorbent, characterized in that when calcination of a zeolite adsorbent containing a halogenated hydrocarbon, the calcination is performed after removing the halogenated hydrocarbon contained in the zeolite adsorbent. .. 2. The method for calcination of a zeolite adsorbent according to claim 1, wherein the halogenated hydrocarbon is removed by washing with a non-halogen organic solvent.