JPH0418894B2 - - Google Patents

Description

[Detailed description of the invention]

B. Field of Industrial Application of the Invention The present invention relates to a method for producing an adsorbent for separating _C8 aromatic hydrocarbon isomers. Conventional technology As an adsorbent for separating _C8 aromatic hydrocarbon isomers, Japanese Patent Publication No. 17654/1988 describes the use of faujasite-type zeolite with K, Cd, Li, Zn, Fe,
Although it has been described that the selectivity of para-xylene is improved by ion exchange in combination with one of Ni and Co, the selectivity does not necessarily improve (see Comparative Example 5 described later). Japanese Unexamined Patent Publication No. 49-80026 describes an ion exchanger mainly composed of K of faujasite type zeolite, which contains divalent and trivalent cations in a certain proportion. All of these attempt to improve selectivity through ion exchange. USP3698157 specifies the general formula Here, R is an organic radical, R ₁ is an organic radical, H or a halogen, and at least one of R ₁ is a halogen. The organic radical-substituted silane is dissolved in a solvent and contacted with the crystalline zeolite at 75 to 200°C. After that, filter and wash, 75~125
A method has been described in which selectivity is improved by drying at ℃ and bonding organic radicals to zeolite, but the adsorption capacity is small. In addition, regarding silane-modified zeolite,
JP-A-59-173137, JP-A-60-7943, JP-A-Sho
No. 56-136652, etc., but all of them are used as catalysts and do not relate to adsorbents that separate _C8 aromatic hydrocarbon isomers. (b) Means for Solving the Constituent Problems of the Invention The method for producing an adsorbent for separating paraxylene from a mixture containing _C8 aromatic hydrocarbons according to the present invention is based on the following formula: Here, R ₁ to _{R 4} are alkoxysilanes represented by alkyl groups having 2 to 4 carbon atoms under anhydrous conditions.
The zeolite is silanized by contacting in liquid form at a temperature of 10-250°C, then after washing, filtering and drying,
This is done by firing at a temperature of 300 to 600°C. The present invention will be explained in detail below. Examples of the faujasite type zeolite include natural faujasite, X-type zeolite, and Y-type zeolite, and in addition to proton bodies, it may also be an ion exchanger of alkali metals or alkaline earth metals. Typical alkoxysilanes represented by the above general formula are ethyl orthosilicate and butyl orthosilicate. Methyl orthosilicate, in which R ₁ to _{R 4} have one carbon number, is not suitable because it enters the pores of the faujasite-type zeolite and significantly reduces the adsorption capacity. Alkoxysilane may be used alone, or may be diluted with an oxygen-containing organic substance such as paraffin, aromatic hydrocarbon, or alcohol. The concentration of alkoxysilane when brought into contact with zeolite is 0.1% to 100% (vol), preferably 1% to
Set to 100% (vol). The contact conditions may be such that the alkoxysilane is in a liquid state. The temperature is 10 to 250°C, preferably 50 to 200°C, and at a temperature higher than the boiling point of the silanizing agent (alkoxysilane) and diluent at normal pressure, pressure is applied to effect contact in liquid form. If the temperature is too low, the degree of improvement in p-xylene selectivity will be small. Furthermore, if the temperature is too high, the adsorption capacity will be significantly lowered, which is undesirable. The contact time should be approximately 10 minutes or more. Since the selectivity of p-xylene does not improve much even if the heating time is too long, a time of 10 minutes to 100 hours, preferably about 10 minutes to 15 hours is sufficient. The amount of silanizing agent used is preferably such that the alkoxysilane is 0.05 mol or more per 100 g of zeolite. Contacting the silanizing agent with the zeolite is carried out under anhydrous conditions. After the reaction is completed, the zeolite is washed with alcohol or a low boiling point hydrocarbon to remove unreacted alkoxysilane. It is then filtered, dried, and then fired. Firing temperature is 300℃~600℃, preferably 300~530℃
℃. During firing, the temperature is gradually raised. The temperature increasing speed is preferably 0.1°C/min to 50°C/min, more preferably 1°C/min to 10°C/min. Rapid temperature rise causes oxidation, carbonization, etc. of the silanizing agent, which adversely affects adsorption performance. Firing may be performed in any atmosphere of inert gas, reducing gas, oxygen gas, or oxygen-containing gas. It is necessary to sufficiently remove unreacted alkoxysilane and diluent remaining on the zeolite surface.
For this purpose, sufficient cleaning is required. In addition, if washing is insufficient, it is sufficient to remove it sufficiently during the drying process, or to sufficiently remove unreacted alkoxysilane and diluent by keeping it at a relatively low temperature during firing, and then to remove it sufficiently at a high temperature. It may also be baked. By this treatment, a SiO ₂ layer is suitably formed at the pore entrance and outer surface of the zeolite,
An adsorbent with shape selectivity is obtained. By contacting the adsorbent obtained by the method of the present invention with a mixture containing _C8 aromatic hydrocarbons, _C8 aromatic hydrocarbon isomers can be separated favorably. In addition to p-xylene, the mixture containing C ₈ aromatic hydrocarbons may include a mixture consisting of at least one of m-xylene and o-xylene, or a mixture containing paraffins in addition to these C ₈ aromatic hydrocarbons. , olefins, benzene, toluene, and the like. Example 1 50 g of proton Y type (HY type) zeolite was brought into contact with 300 c.c. of ethyl orthosilicate at 100°C for 10 minutes to carry out a silanization reaction. After the reaction was completed, it was washed with ethanol, filtered, and dried. After the dried zeolite was held at a temperature (180°C) that could sufficiently remove unreacted ethyl orthosilicate for 6 hours, the temperature was further raised to 520°C at a rate of 1°C/min, and calcined at that temperature for 12 hours. I went there. Note that the firing was performed in air. The obtained modified zeolite was mixed with p-xylene, m-
A 1,3,5-triisopropylbenzene solution containing 2 vol% each of xylene and o-xylene.
Adsorption selectivity was tested by contacting at 250°C. Separately, the modified zeolite was brought into contact with gaseous n-hexane to measure its adsorption capacity. The results obtained are shown in Table 1. Furthermore, the selectivity of p-xylene to m-xylene (pX/mX) is pX/mX=Yp/Ym/Xp/Xm, and the selectivity of p-xylene to o-xylene (pX/oX) is pX/oX =Yp/Yo/Xp/Xo However, Yp: Volume % of p-xylene in the adsorption phase Ym: Volume % of m-xylene in the adsorption phase Yo: Volume % of o-xylene in the adsorption phase Xp: Liquid phase % by volume of p-xylene in the liquid phase Xm: % by volume of m-xylene in the liquid phase Xo: % by volume of o-xylene in the liquid phase. Examples 2 to 6 Silanization time was 15 hours, silanization temperature was 10
°C (Example 2), 50 °C (Example 3), 100 °C (Example 4), and 150 °C (Example 5), and the silanization time was 96 hours and the silanization temperature was 100 °C (Example 6). )
A modified zeolite was obtained by performing the same operation as in Example 1 except for the following. Table 1 shows the results of the same adsorption evaluation as in Example 1. Examples 7 to 9 20 g of proton Y type (H-Y type) zeolite and 40 c.c. of butyl orthosilicate are brought into contact at 120°C for 2 hours, then washed with butanol, filtered, dried, and calcined at 520°C to produce modified zeolite. was obtained (Example 7). Alternatively, butyl orthosilicate was used as a 10 vol% p-xylene solution at 40 c.c. (Example 8), and as a 40 vol% p-xylene solution at 40 c.c. (Example 9), and the silanization treatment temperature was 100 ° C. A modified zeolite was obtained in the same manner as in Example 7 except for this. Table 1 shows the results of adsorption evaluation conducted in the same manner as in Example 1. Examples 10-12 Add 300 c.c. of ethyl orthosilicate to 50 g of sodium Y-type zeolite at 100°C (Example 10) and 200°C (Example
11) or at 250°C (Example 12) for 15 hours to carry out a silanization reaction, washed with ethanol, filtered, dried, and calcined in air at 520°C to obtain a modified zeolite. Table 1 shows the results of an adsorption test conducted in the same manner as in Example 1. Comparative Examples 1 to 5 H-Y without silanization treatment according to the present invention
type (comparative example 1), Na-Y type (comparative example 2), K-Y
type (Comparative Example 3), Li-Y type (Comparative Example 4) and K,
Li-Y type (Comparative Example 5: According to the Japanese Patent Publication No. 58-17654)
An adsorption test was conducted on zeolite in the same manner as in Example 1, and the results are shown in Table 1.

[Table] As is clear from Table 1, the selectivity of p-xylene to m-xylene and o-xylene of the forujasite-type zeolite that has been silanized according to the present invention is the same as that of the untreated forujasite. This is a marked improvement over type zeolite. C. Effects of the invention An adsorbent that can separate paraxylene with good selectivity can be obtained.

Claims (1)

[Claims] 1. The forujasite type zeolite has the general formula Here, R ₁ to _{R 4} are alkoxysilanes represented by alkyl groups having 2 to 4 carbon atoms under anhydrous conditions.
The zeolite is silanized by contacting in liquid form at a temperature of 10-250°C, then after washing, filtering and drying,
A method for producing an adsorbent for the separation of para-xylene from a mixture containing _C8 aromatic hydrocarbons, comprising calcination at a temperature of 300-600°C. 2. The method for producing an adsorbent according to claim 1, wherein the temperature at which the alkoxysilane is brought into contact with the phasiasite-type zeolite is 50 to 200°C.