JP2000007588A - Reaction mixture composed of para-xylene and meta- xylene and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject reaction mixture useful for the joint production of isophthalic acid and/or dimethyl isophthalate and terephthalic acid and/or dimethyl terephthalate by subjecting p-xylene to isomerization reaction using a zeolite catalyst. SOLUTION: This reaction mixture is obtained by subjecting p-xylene (pref. >=99.0% purity) to isomerization reaction using a zeolite catalyst (pref. in a fixed bed continuous reaction style). This reaction mixture thus obtained meets the requirements A to D described below: (A) m-xylene accounts for 1-40 wt.% of the whole weight of the reaction mixture; (A) the content of o-xylene is <=25 wt.% based on the whole weight of the m-xylene; (C) the content of hydrocarbons except o-xylene, m-xylene and p-xylene is <=2 wt.% based on the whole weight of the reaction mixture; and (D) in the reaction mixture, the component other than the components A to C is occupied by p-xylene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a reaction mixture comprising para-xylene and meta-xylene starting from para-xylene and a method for producing the same. Even without purification, the content of hydrocarbons other than para-xylene and meta-xylene, which are impurities, is small, and is useful for producing isophthalic acid and / or dimethyl isophthalate together with terephthalic acid and / or dimethyl terephthalate And a reaction mixture comprising para-xylene and meta-xylene and a method for producing the same.

[0002]

2. Description of the Related Art Xylene isomers are composed of para-xylene, meta-xylene, ortho-xylene and ethylbenzene. Para-xylene is a polyester fiber / polyester film. Each is industrially important as a raw material.

Among other uses, meta-xylene has recently been used as isophthalic acid or dimethyl isophthalate in recent years, is mixed with terephthalic acid or dimethyl terephthalate at an appropriate ratio, and then subjected to a condensation polymerization reaction with ethylene glycol to obtain a copolymerized polyester. Therefore, the demand has been increasing in recent years.

Hitherto, several methods for producing substantially pure meta-xylene have been proposed. A method for selectively extracting meta-xylene from a mixed xylene raw material by forming a complex has been proposed by Mitsubishi Gas Chemical and Petroleum Refinery. Of meta-xylene, which is contained in a concentration close to the thermodynamic equilibrium composition in mixed xylene obtained from crude oil or cracked gasoline, by means of orthoxylene in the presence of a catalyst containing crystalline alumina silicate zeolite Various methods have been proposed, such as a method for selectively isomerizing the compound to meta-xylene, but all of these methods require enormous costs for distillation purification and the like, and it is difficult to produce pure meta-xylene.

The reaction for oxidizing meta-xylene to obtain isophthalic acid and / or dimethyl isophthalate and the reaction for oxidizing para-xylene to obtain terephthalic acid and / or dimethyl terephthalate have very similar reaction conditions and catalysts. A method is known in which a mixture of para-xylene and meta-xylene is used as a starting material in a single production facility to produce isophthalic acid and / or dimethyl isophthalate together with terephthalic acid and / or dimethyl terephthalate. (JP-B-39-30275, JP-A-9-3098)
No. 62, etc.).

Using the above method, para-xylene and / or para-xylene
Alternatively, equipment capable of producing at least one of isophthalic acid, dimethyl isophthalate, terephthalic acid, and dimethyl terephthalate (hereinafter sometimes collectively abbreviated as “active ingredient”) by oxidizing meta-xylene. For those who possess isophthalic acid and / or dimethyl isophthalate, if a mixture of para-xylene and meta-xylene, which is low in substances other than para-xylene and meta-xylene, can be obtained at low cost, high price, high price There is no need to obtain and use pure meta-xylene.

However, no means for producing such a mixture at low cost has been proposed so far. Therefore, in order to carry out the above co-production method, pure para-xylene and meta-xylene must be obtained respectively. There is a problem that the mixing method has to be adopted and the raw material is expensive.

[0008] Mixed xylene containing a large amount of substances other than para-xylene and meta-xylene, for example, ortho-xylene / ethylbenzene, etc., can be obtained at low cost, but it is used as it is to use isophthalic acid and / or dimethyl isophthalate. Is difficult to manufacture at low cost. This is because a large amount of by-products other than the active ingredient are generated from substances other than para-xylene and meta-xylene (the ratio of by-products in the product is about 35 to 60%), and the by-products are removed from the active ingredient. For this, a large amount of equipment and labor are required, so that a greater cost is required than a method of mixing pure para-xylene and meta-xylene as a raw material.

[0009] In addition, there is a problem that if the mixed xylene is simply distilled, the distillation cost becomes large.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a first object of the present invention is to provide isophthalic acid and / or dimethyl isophthalate with terephthalic acid and / or dimethyl terephthalate. An object is to provide a mixture consisting essentially of para-xylene and meta-xylene which is useful for co-production. A second object of the present invention is to provide a method for producing the above-mentioned mixture at low cost.

[0011]

Means for Solving the Problems In order to solve the above problems, the present inventors have focused on obtaining meta-xylene as a mixture with para-xylene by omitting purification treatments such as distillation and adsorption. As a result of intensive studies on a method of isomerizing para-xylene as a raw material, the present invention has been completed.

That is, a first object of the present invention is to provide a reaction mixture obtained by subjecting para-xylene to an isomerization reaction using a zeolite catalyst, and having the following requirements (A) to (D): It can be achieved by a reaction mixture comprising para-xylene and meta-xylene, which is useful for co-producing isophthalic acid and / or dimethyl isophthalate with terephthalic acid and / or dimethyl terephthalate. (A) Metaxylene accounts for 1 to 40% based on the total weight of the reaction mixture. (B) The content of ortho-xylene is 25% or less based on the total weight of meta-xylene. (C) The content of hydrocarbons other than ortho-xylene, meta-xylene, and para-xylene is 2% or less based on the total weight of the reaction mixture. (D) In the reaction mixture, para-xylene occupies other than the above (A) to (C).

A second object of the present invention is to provide a reaction mixture having the following requirements (A) to (D) when para-xylene is subjected to an isomerization reaction using a zeolite catalyst. Of a reaction mixture comprising para-xylene and meta-xylene useful for co-producing isophthalic acid and / or dimethyl isophthalate with terephthalic acid and / or dimethyl terephthalate, wherein Achieved by the method. (A) Metaxylene accounts for 1 to 40% based on the total weight of the reaction mixture. (B) The content of ortho-xylene is 25% or less based on the total weight of meta-xylene. (C) The content of hydrocarbons other than ortho-xylene, meta-xylene, and para-xylene is 2% or less based on the total weight of the reaction mixture. (D) In the reaction mixture, para-xylene occupies other than the above (A) to (C).

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a reaction mixture obtained by subjecting para-xylene to an isomerization reaction using a zeolite catalyst must satisfy the following requirements (A) to (D). (A) Metaxylene accounts for 1 to 40% based on the total weight of the reaction mixture. (B) The content of ortho-xylene is 25% or less based on the total weight of meta-xylene. (C) The content of hydrocarbons other than ortho-xylene, meta-xylene, and para-xylene is 2% or less based on the total weight of the reaction mixture. (D) In the reaction mixture, para-xylene occupies other than the above (A) to (C).

If the requirements (A) to (D) are sequentially described, in the requirement (A), if the proportion of meta-xylene is less than 1%, the amount of meta-xylene in the mixture is too small. The object of the present invention of obtaining a mixture cannot be achieved. On the other hand, if the isomerization reaction is performed so as to exceed 40%, ortho-xylene by-product due to sequential isomerization also occurs at the same time.

In the requirement (B), if the proportion occupied by orthoxylene exceeds 25%, the reaction mixture cannot be used as it is as the raw material for oxidation, and must be purified and separated by costly means such as distillation. .

In the requirement (C), when the amount of hydrocarbons other than ortho-xylene, meta-xylene, and para-xylene exceeds 2%, the reaction mixture can be used as it is as an oxidation raw material as in the requirement (B). It is not possible, and it is necessary to perform purification and separation by costly means such as distillation.

In the requirement (D), the above requirements (A) to
With para-xylene occupying other than (C),
The object of the present invention of obtaining a mixture consisting essentially of para-xylene and meta-xylene can be achieved.

In the production method of the present invention, when para-xylene is subjected to an isomerization reaction using a zeolite catalyst, the isomerization reaction is carried out to obtain a reaction mixture satisfying the above-mentioned requirements (A) to (D). The reaction conditions for the isomerization to obtain the reaction mixture are as follows.

In the production method of the present invention, para-xylene is used as a starting material. The purity of para-xylene to be supplied is not particularly limited, but for the purpose of the present invention, a substance containing less components other than meta-xylene is used.
It is preferably at least 9% by weight. Usually, paraxylene available as a product has a purity of 99% by weight or more, and the product can be supplied as a starting material as it is.

Further, the para-xylene is subjected to an isomerization reaction using a zeolite catalyst. Here, the zeolite catalyst refers to a catalyst component containing a crystalline aluminosilicate zeolite as a component, and may contain, as other components, a binder or an inorganic salt or metal for improving performance. Good.

The zeolite catalyst is not limited in its shape, but is preferably a molded product from a practical viewpoint, and a binder such as clay, alumina or silica may be used for molding.

The zeolite catalyst can be used in any of a fixed bed, a fluidized bed and a suspension bed, but it is preferable to use the zeolite catalyst in a fixed bed form from the viewpoint of easy operation.

As the reaction form in the isomerization reaction, any of a continuous type and a batch type can be used, but a continuous type reaction is preferred from the viewpoint of simplicity of operation.

The weight hourly space velocity of para-xylene during the isomerization reaction (hereinafter sometimes referred to as WHSV).
Is preferably in the range of 0.1 to 100 h ^-1 ,
Here, the weight hourly space velocity indicates the flow velocity of para-xylene in the layer filled with the zeolite catalyst, and when it is within the above range, the balance between the improvement in selectivity and the equipment cost is good.

Further, the temperature of the isomerization reaction is not particularly limited, but is preferably in the range of 100 to 300 ° C. When the reaction temperature is within the above range, the conversion of the raw material is further increased, and the by-products of orthoxylene and toluene and trimethylbenzene due to the disproportionation reaction are further suppressed.

In the production method of the present invention, the contact between the zeolite catalyst and the starting material, para-xylene, can be carried out arbitrarily in a gas phase or a liquid phase. However, it may be carried out at a gauge pressure within a range of 0 to 5,000,000 Pa.

Further, a carry gas may be further used for the purpose of pressurization, vaporization, and the like, and examples of usable gases include inert gases such as hydrogen, nitrogen, helium, and argon.

Regarding the reaction time of the above isomerization reaction,
What is necessary is just to select suitably from the required ratio of para-xylene and meta-xylene.

[0030]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, each value in an Example was measured according to the following method. In Examples, pX represents para-xylene, oX represents ortho-xylene, and mX represents meta-xylene. (1) WHSV (hr ^-1 ): determined based on the following equation. WHSV = (hourly supply amount of pX) / (catalyst amount) (2) H ₂ / HC ratio (molar ratio): determined according to the following equation. H ₂ / HC ratio = (hourly feed rate of H ₂₎ / (hourly feed amount of pX) (3) pX conversion (%): was determined based on the following equation. pX conversion rate (%) = (pX conversion amount) / (pX supply amount) × 100 (4) oX / mX ratio (%): It was determined based on the following equation. oX / mX ratio (%) = (amount of oX in reaction mixture) /
(MX amount in reaction mixture) × 100

Reference Example US Pat. No. 3,965,207
Zeolite (Z) according to the method disclosed in US Pat.
SM-5) was synthesized. At the time of synthesis, water glass as a silica source, aluminum sulfate as an alumina source, tri-n-propylamine and n-propyl bromide as organic nitrogen cation sources, and further adding methyl ethyl ketone, in an autoclave under predetermined conditions. Reacted. After the product was filtered and sufficiently washed with water, it was dried in an electric dryer at 100 ° C. overnight. As a result of X-ray diffraction, the product was identified as ZSM-5. As a result of chemical analysis, the silica / alumina ratio of the product was 70.

Next, the cation of the obtained zeolite
The site was converted from sodium ions to ammonium ions. That is, the mixture was treated for 16 hours under reflux with 10 ml of a 10% aqueous ammonium chloride solution per 1 g of the zeolite. This operation was repeated twice. After a while, filtration,
After washing with water and drying at 100 ° C. for 16 hours, ammonium zeolite (ZSM-5) was obtained.

[Example 1] To the ammonium-type zeolite obtained by the operation of the reference example, 1/3 amount of gel-like γ-alumina (“ACP1” manufactured by Catalysis Kasei Co., Ltd.) was added based on the weight of the zeolite. After sufficient mixing, the mixture was molded into a size of 10 to 20 mesh. The molded product was fired in an electric furnace at 500 ° C. under an air flow, and 1 g of the fired product was filled in a downflow glass vertical reaction tube. After the catalyst bed temperature was adjusted to 250 ° C. while flowing hydrogen under normal pressure, pX (composition: p
X = 99.90% by weight, mX = 0.06% by weight, oX =
(0.02% by weight, toluene = 0.02% by weight) to carry out an isomerization reaction of para-xylene. The product obtained after a certain period of time was collected and analyzed by gas chromatography. Table 1 shows the results.

Example 2 The same operation as in Example 1 was carried out except that the catalyst bed temperature was changed from 250 ° C. to 200 ° C., to carry out an isomerization reaction of pX. Table 1 shows the results.

[0035]

[Table 1]

[0036]

According to the method of the present invention, a mixture consisting essentially of meta-xylene and para-xylene can be produced at a low cost, and the mixture can be obtained by isophthalic acid and / or para-xylene.
Alternatively, it is useful as a starting material for co-producing dimethyl isophthalate with terephthalic acid and / or dimethyl terephthalate.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G069 AA02 BA01B BA07A BA07B BB01B BD01B BD06B CB01 CB41 DA06 EB18Y ZA32B 4H006 AA01 AA02 AC27 BA71

Claims (4)

[Claims] 1. A reaction mixture obtained by subjecting para-xylene to an isomerization reaction using a zeolite catalyst, characterized by having the following requirements (A) to (D):
A reaction mixture comprising para-xylene and meta-xylene useful for co-producing isophthalic acid and / or dimethyl isophthalate with terephthalic acid and / or dimethyl terephthalate. (A) Metaxylene accounts for 1 to 40% based on the total weight of the reaction mixture. (B) The content of ortho-xylene is 25% or less based on the total weight of meta-xylene. (C) The content of hydrocarbons other than ortho-xylene, meta-xylene, and para-xylene is 2% or less based on the total weight of the reaction mixture. (D) In the reaction mixture, para-xylene occupies other than the above (A) to (C). 2. When para-xylene is subjected to an isomerization reaction using a zeolite catalyst, the isomerization reaction is carried out so as to obtain a reaction mixture satisfying the following requirements (A) to (D). A method for producing a reaction mixture comprising para-xylene and meta-xylene useful for simultaneously producing isophthalic acid and / or dimethyl isophthalate and terephthalic acid and / or dimethyl terephthalate. (A) Metaxylene accounts for 1 to 40% based on the total weight of the reaction mixture. (B) The content of ortho-xylene is 25% or less based on the total weight of meta-xylene. (C) The content of hydrocarbons other than ortho-xylene, meta-xylene, and para-xylene is 2% or less based on the total weight of the reaction mixture. (D) In the reaction mixture, para-xylene occupies other than the above (A) to (C). 3. The production method according to claim 2, wherein the purity of para-xylene subjected to the isomerization reaction is 99.0% or more. 4. The production method according to claim 2, wherein the isomerization reaction is carried out in a fixed bed continuous reaction mode.