JPS593970B2 - Conversion method for xylenes including ethylbenzene - Google Patents

Description

Detailed Description of the Invention The present invention involves contacting xylenes containing ethylbenzene with a specific catalyst in the gas phase in the presence of hydrogen to isomerize the xylenes and convert ethylbenzene into other aromatic carbons. It is related to converting it into hydrogen.

Among the xylene mixtures, those currently of industrial importance are para-xylene and ortho-xylene.

Paraxylene is used as a crude raw material for synthetic fiber polyester.
Until now, the demand has increased significantly. It is expected that this trend will remain unchanged even after 5 years. Ortho-xylene is used as a crude raw material for phthalate ester, a plasticizer for polyvinyl chloride. However, the current demand for ortho-xylene is lower than that for para-xylene. On the other hand, there are currently almost no industrial uses for metaxylene. For this reason, it is industrially important to convert meta-xylene and ortho-xylene to para-xylene. Since the boiling points of xylene mixtures are close to each other, especially since the boiling points of para-xylene and meta-xylene are very close, it is economically disadvantageous to separate para-xylene by distillation. However, until now, industrial separation of paraxylene has been carried out by cryogenic separation that takes advantage of the difference in melting points. In the case of cryogenic separation, there is a limit to the recovery rate of paraxylene fluoride per bath due to the eutectic point, which is at most (60%)/(1 bath). As a result, the concentration of paraxylene in the roughinate fluid after paraxylene recovery is quite high. On the other hand, recently, the
49-28181, 50-10547, 50-■511
343, 51-46093, adsorption separation method was developed as a new separation technique. In this adsorption separation method, paraxylene is theoretically 100% per bath.
It becomes possible to collect it. That is, the concentration of paraxylene in the raffinate fluid after adsorption and separation is extremely low and theoretically becomes zero. Ortho-xylene is generally separated by precision distillation. The remaining roughinate fluid from which para-xylene and ortho-xylene have been separated in this way is sent to an isomerization step, and meta-xylene and/or ortho-xylene are isomerized to a para-xylene concentration close to the thermodynamic equilibrium composition. It is then mixed with fresh feedstock and sent to a separation step where the cycle (7-) is repeated.

When such a combination is used in a process, when the remaining ruffinate fluid from which paraxylene has been separated by cryogenic separation is supplied to the isomerization step, the concentration of paraxylene in the roughinate fluid is relatively high, as described above. In the case of a roughinate fluid after paraxylene has been separated by an adsorption separation method, the concentration of paraxylene is extremely low.

Therefore, the reaction in the isomerization step is required to be more severe in the latter case. Generally, the xylene raw materials used industrially are reformed oil xylene obtained by reforming naphtha and subsequent aromatic extraction and fractional distillation, or aromatic It is classified as a cracked oil-based xylene obtained by extraction and fractional distillation.

A particularly characteristic feature of cracked oil-based xylene is that the concentration of ethylbenzene is more than twice as high as that of reformed oil-based xylene. An example of its typical composition is shown in Table 1. Thus, a considerable amount of ethylbenzene is generally present in a xylene mixture, but unless ethylbenzene is removed by some means, it will accumulate as it is recycled through the separation and isomerization steps. , an undesirable situation arises in which the concentration increases.

For these reasons, it is currently preferable to use modified oil-based xylene with a low ethylbenzene concentration as a fresh feedstock, but in any case, it is necessary to reduce the ethylbenzene concentration, and several Methods are practiced industrially and several methods have also been proposed. The methods can be broadly classified into two: one is to separate ethylbenzene as it is, and the other is to convert it into other useful compounds through reaction.
Distillation is a method for separating ethylbenzene.

In this method, since the boiling point difference between xylenes and xylenes is small, it is necessary to use ultra-precision distillation, which requires a huge industrial investment in equipment and also has high operating costs, making it an economically disadvantageous method. Furthermore, recently, there have been proposals to separate ethylbenzene by adsorption separation, as shown in Japanese Patent Application Laid-Open No. 52-10223, etc., but the separation performance thereof is not fully satisfactory.

Another method for removing ethylbenzene is to convert it into other useful components.

The most typical method is 49-46606, 49
147733, 51-15044, 51-36253,
This is a method of converting ethylbenzene into xylene, as disclosed in JP-A-54-16390. However, in this method, it is essential that the catalyst contains platinum, which is an extremely expensive noble metal. Furthermore, in order to convert ethylbenzene into xylene, the reaction mechanism requires the intervention of non-aromatic components such as naphthene and paraffin, and the concentration of these components in the product ranges from several percent to several tens of percent. It's reaching. Furthermore, the conversion rate of ethylbenzene is limited by the thermodynamic equilibrium (Table 2), which is a disadvantage. A method for converting ethylbenzene into other components other than xylene has recently been published in Japanese Patent Publication No. 53-4165.
7, proposed in Japanese Patent Application Laid-Open No. 52-148028.

This method attempts to isomerize xylene and at the same time convert ethylbenzene into benzene and diethylbenzene through a disproportionation reaction, and separate the benzene and diethylbenzene by taking advantage of the large boiling point difference between them. Benzene obtained in this way is in great demand as a raw material for synthetic fiber nylon, but there is little demand for diethylbenzene, which is economically disadvantageous because it needs to be converted into other useful compounds. Furthermore, the disproportionation reaction of ethylbenzene is controlled by thermodynamic equilibrium, and there is a limit to the conversion rate of ethylbenzene. Under these circumstances, there is currently a strong desire to be able to convert ethylbenzene into useful compounds without being subject to constraints such as thermodynamic equilibrium.

Furthermore, as is clear from what has been said so far, it is possible to sufficiently use xylene containing a high concentration of ethylbenzene, such as cracked oil, and in the isomerization of xylene, for example, it is possible to use the ruffinate fluid after adsorption and separation of para-xylene. There is a need for a catalyst system that has the property of being able to sufficiently isomerize the

In view of this current situation, the present inventor carried out hydrogenation dealkylation to benzene and ethane as a method for removing ethylbenzene, with almost no thermodynamic constraints, and at the same time,
As a result of considering catalyst systems that can isomerize xylene,
We thought that this reaction could be carried out by combining a solid acid component and a hydrogenation component, and conducted extensive studies on various catalysts. As a result, they discovered that this reaction can proceed efficiently by combining mordenite-type zeolite as the solid acid component and rhenium component as the hydrogenation component, and have arrived at the present invention. That is, when a xylene mixture containing ethylbenzene is brought into contact with a mordenite-type zeolite catalyst containing rhenium in the presence of hydrogen, it is possible to isomerize xylene and convert ethylbenzene to other compounds, mainly dealkylation to benzene. Make it familiar. The mordenite-type zeolite that can be used in the present invention may be a synthetic product,
Natural products can be used, and of course, mixtures thereof may also be used.

Mordenite-type zeolite belongs to the crystalline aluminosilicate composed of silica and alumina, and the aluminosilicate basically has a three-dimensional framework structure in which SiO4 and AlO4 tetrahedra are cross-bonded by sharing oxygen atoms. It's summery.

Tetrahedrons containing aluminum have a negative electron valence and are kept electrically neutralized by containing alkali metal, alkaline earth metal ions, or other cations.
Such cations can be exchanged for other cations by known ion exchange techniques. ; Generally,
Synthetic products mainly contain sodium ions, and natural products mainly contain various alkali metal ions and/or alkaline earth metal ions.

When used in the present invention, it is particularly preferable to impart acidity to these mordenite-type zeolites.

In order to impart acidity, a partial dealkalization treatment is performed. The dealkalization treatment here refers to a type of ion exchange treatment in which zeolite is treated with a solution containing an acid and/or an ammonium salt compound, and hydrogen ions and/or ammonium ions, which are hydrogen ion precursors, are introduced into the zeolite. be. Dealkalization treatment is generally carried out in an aqueous solution.

Acids that can be used are inorganic acids or organic acids. Examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, carbonic acid, etc., but of course other acids may be used as long as they contain hydrogen ions. Examples of organic acids include formic acid, acetic acid, propionic acid, oxalic acid, citric acid, and tartaric acid. When using an inorganic acid, it is not preferable to treat with a solution of too high a concentration because the mordenite structure will be destroyed. The concentration of the acid preferably used varies greatly depending on the type of acid, so it is difficult to define it unambiguously, and when using it, it is necessary to be careful not to destroy the mordenite structure. As ammonium salt compounds, inorganic ammonium salts such as ammonium nitrate, ammonium chloride, ammonium sulfate, ammonium carbonate, aqueous ammonia, etc., or ammonium salts of organic acids such as ammonium formate, ammonium acetate, ammonium citrate, etc. can be used as well. More preferred are inorganic ammonium salts.

The concentration of ammonium salt used is preferably about 0.0
A 5 to 4 normal solution is used, more preferably about 0
, 1 to 2 provisions. As a method for dealkalizing mordenite type zeolite with an acid and/or ammonium salt solution, either a batch method or a flow method is preferably used.

In the case of batch treatment, the solid-liquid ratio is preferably about 1 m1/F7 or more, which is an amount that allows the zeolite to come into sufficient contact with the liquid. A treatment time of about 0.1 to 72 hours is sufficient, preferably about 0.5 to 24 hours. The treatment temperature may be below the boiling point, but it is preferable to heat it to accelerate the dealkalization rate. One treatment is sufficient, but
The process may be repeated if necessary. Fixed bed systems, fluidized bed systems, etc. can be used when processing with a flow system, but in the case of a flow system, special measures must be taken to prevent uneven flow of the fluid or to ensure uniform ion exchange. .

In this way, exchangeable metal cations of the mordenite-type zeolite are removed and hydrogen ions are introduced using an acid, or ammonium ions, which are hydrogen ion precursors, are introduced using an ammonium salt. As the dealkalization treatment proceeds, the activity of the catalyst increases significantly, but side reactions occur along with this, so excessive dealkalization treatment is not preferred. The preferable dealkalization rate is 50% or less,
That is, the amount of hydrogen ions or ammonium ions that are hydrogen ion precursors is 0.5 equivalent or less per gram atom of aluminum in the mordenite-type zeolite. Moreover, it is preferable that it is 0.2 equivalent or more. In other words, it is desirable that the exchangeable metal cation is present in an amount of 0.5 equivalent or more per gram atom of ammonium. The mordenite-type zeolite thus dealkalized is then thoroughly washed with water. The water-washed zeolite is dried, if necessary, and further calcined. Drying is carried out at 50 to 250°C, preferably 100 to 200°C, for 0.1 hour or more, preferably 0.5 to 48 hours. Preferred firing conditions are 300 to 700°C for 0.1 hour or more, more preferably 400 to 600°C for 0.5 to 24 hours. Such a dealkalization treatment may be carried out before the rhenium component is supported on the mordenite or after the rhenium component is supported, but it is more preferably performed before the rhenium component is supported.

Rhenium as used herein is a compound such as an oxide, sulfide, selenide, or its elemental form. Preferred methods for supporting rhenium on mordenite-type zeolite include kneading method, impregnation method,
Examples include a method of physically mixing powders together, but the method is not necessarily limited to these methods.

However, the more uniformly the rhenium component is dispersed in the mordenite-type zeolite, the better the activity and selectivity. Therefore, the preferably used methods are the kneading method and the impregnation method, with the kneading method being particularly preferred. The kneading method is a method in which the mordenite component is powdered to a size of 100 mesh or less, and the rhenium component is sufficiently uniformly kneaded into this powder in the presence of water. In order to obtain sufficient uniformity, the kneading time is 10 minutes or more, preferably 30 minutes or more. In the case of the impregnation method, since the mordenite component is brought into contact with an aqueous solution containing the rhenium component, soluble perrhenic acid or ammonium perrhenate is preferably used as the rhenium. The amount of the rhenium compound supported is 0.01 to 3% by weight in elemental form based on the total weight, preferably 0.05 to 0.
．． It is 5% by weight. Among the rhenium components supported on mordenite-type zeolite, rhenium oxide (b) is easily dissolved as perrhenic acid when it comes into contact with water, so it may be brought into contact with hydrogen sulfide in a supported state to form insoluble rhenium sulfide. Although either a fixed bed or a fluidized bed can be used as the reactor, a fixed bed type is preferred because it is simpler and easier to operate.

In the case of a fixed bed system, the smaller the catalyst particle size is, the more preferable it is from the point of view of the catalyst effectiveness coefficient, but if the particle size becomes too small, pressure loss increases, which is not preferable. Therefore, there is a preferable range for the catalyst particle size. Preferably used particle size is 0
．． 05~10m7! L, more preferably 0.1
~2 fights. In order to obtain a catalyst having such a preferable range, it may be necessary to mold the catalyst in some cases. Molding methods include compression molding, extrusion molding, etc., and a binder is used to improve moldability or to impart strength to the catalyst. Of course, it goes without saying that there is no need to use a binder if it can be sufficiently molded without a binder. As a binder,
For example, clay materials such as bentonite and acid clay, silica gel, and alumina sol are preferably used. The amount added is 3 on an absolute dry weight basis.
It is 0% by weight or less, preferably 20% by weight or less. The molding may be performed before or after dealkalizing the mordenite zeolite, and further before or after supporting the rhenium component. Any method that is easy to carry out may be used, taking into account the shape of the mordenite-type zeolite used, the type of rhenium compound, and the method of supporting it. that's all,
The catalyst prepared as described above was dried prior to use and subsequently calcined.

Drying at 50-250℃, preferably 100-200℃
．． It is carried out for 1 hour or more, preferably 0.5 to 48 hours. Firing is carried out at 300-700°C for 0.1 hour or more, preferably at 400-600°C for 0.5-24 hours. The ammonium ions introduced into the mordenite zeolite through such calcination are converted into hydrogen ions,
Furthermore, hydrogen ions are converted into a decationized form as the calcination temperature is increased, and of course catalysts in this form can also be used satisfactorily.

The catalyst prepared as described above is used under the following reaction conditions.

That is, the reaction operation temperature is 300 to 600°C, preferably 3
The temperature is 50-550°C. Reaction operating pressure is from atmospheric pressure to 10
0kg/(1-J mo VFG preferably 50Vd from atmospheric pressure
It is G. Reaction time factor W/F (F71C
atW/f-MOl feedstock) (W: catalyst weight, F: 1
molar feedstock per hour) is 1:200, preferably 5 to 150. Hydrogen in the reaction system is an essential component for dealkylating ethylbenzene. If the hydrogen concentration is too low, the dealkylation reaction of ethylbenzene will not proceed sufficiently, and furthermore, the activity will deteriorate over time due to the deposition of carbonaceous components on the catalyst soil. On the other hand, if the hydrogen concentration is excessively increased, it is undesirable that the hydrogenolysis reaction increases.
Therefore, there is a preferable range for hydrogen concentration. The hydrogen concentration is determined by the molar ratio of hydrogen and feedstock in the reaction system (H2/
F) is 1 to 50, preferably 3 to 30. A xylene mixture containing ethylbenzene is used as the feedstock, but there is no particular restriction on the concentration of ethylbenzene in the xylene mixture.

The concentration of paraxylene in the xylene mixture used is below the thermodynamic equilibrium concentration, but even if it contains paraxylene at the thermodynamic equilibrium concentration, it can be used as a feedstock for the purpose of reducing the ethylbenzene concentration. Of course, this is possible as an embodiment of the present invention. Even if the feedstock contains other aromatic components such as benzene, toluene, trimethylbenzene, ethyltoluene, diethylbenzene, ethylxylene, etc., there is no problem as long as the concentration is within a low range.

EXAMPLES Hereinafter, the present invention will be explained using Examples, but the present invention is not limited by these. Example 1 and Comparative Example 1 Synthetic mordenite "Zeolon NA" manufactured by Norton
-100° powder was heated to 80 to 90° C. with a 0.187 normal ammonium chloride aqueous solution at a solid-liquid ratio of 5 (l/1<g), and subjected to ion exchange treatment in batches for 30 minutes.

Thereafter, it was thoroughly washed with distilled water and dried at 110°C overnight. This ion-exchanged Zeolon NA-100 powder was extracted with nitric acid, and the sodium content was measured by flame analysis. As a result, the dealkalization rate was 36.4%. To this mordenite powder, 15% by weight of alumina sol was added as a binder in terms of alumina (Al2O3), and 0.1% by weight of perrhenic acid aqueous solution was added thereto in terms of rhenium element, followed by kneading and molding. 10-24 meshes after molding (J
IS blue). It was dried at 110°C overnight, and then fired at 500°C for 2 hours.

This catalyst is abbreviated as catalyst "A". On the other hand, as a comparative example, a catalyst prepared without adding perrhenic acid was abbreviated as catalyst 6B. Catalyst “A”. Ethylbenzene was supplied alone to 6B, and the results shown in Table 3 were obtained.

BZ: Benzene C8NP: C8 naphthene, paraffin TOL: Toluene ET: Ethyltoluene DEB: Diethylbenzene EB: Ethylbenzene R. L. :Ring loss (loss of aromatic ring) It can be seen that the catalyst 6A'' containing rhenium has a higher conversion rate of ethylbenzene than '''B'' and that the selective dealkylation to benzene is significantly improved. .

Example 2 and Comparative Examples 2 and 3 Synthetic mordenite “Zeolon NA-100” manufactured by Norton
'' powder was heated to 80 to 90°C in a 0.281 N ammonium chloride aqueous solution at 5 (1/Kg), and
The sample was subjected to ion exchange* treatment in batches for 0 minutes.

Thereafter, it was thoroughly washed with distilled water and dried at 110°C overnight. The dealkalization rate of this ion-exchanged 6zeolon NA-100'5 was 43.5%. Alumina sol (Al2O3) is added to this mordenite powder as a binder.
), and 0.1% by weight (calculated as rhenium element) of a perrhenic acid aqueous solution was added thereto, kneaded for about 1 hour, and extruded.

After molding, it was classified into 10 to 24 meshes, dried at 110°C overnight, and fired at 500°C for 2 hours. The catalyst thus prepared is abbreviated as catalyst "C". Using an aqueous solution of chloroplatinic acid instead of perrhenic acid and adding 0.05% by weight of platinum as a catalyst "D" - Using an aqueous solution of nickel nitrate and adding 0.2% by weight of nickel as a catalyst "E" It is abbreviated as

Catalyst support C low\DD-? Table 4 shows the reaction results when benzene was supplied to FEFF. It can be seen from Table 4 that rhenium as a hydrogenation component improves the selectivity for the dealkylation reaction of ethylbenzene to benzene over components such as platinum and nickel.

Claims (1)

[Claims] 1. xylene containing ethylbenzene in the presence of hydrogen,
A method for converting xylenes containing ethylbenzene, which comprises contacting with a mordenite-type zeolite containing rhenium. 2 Mordenite-type zeolites contain 0 hydrogen ions and/or hydrogen ion precursors per gram atom of aluminum.
．． The method for converting xylenes containing ethylbenzene according to claim 1, which is a zeolite having 5 equivalents or less.