JPH0321528B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for isomerizing dimethylnaphthalenes. More specifically, the present invention relates to a method of isomerizing dimethylnaphthalenes by contacting them with a specific crystalline aluminosilicate zeolite. Prior Art Various so-called isomerization methods are known in which dimethylnaphthalenes are isomerized to obtain a mixture rich in a particular isomer. Dimethylnaphthalene (DMN)
) has 10 isomers, of which 2,6-DMN and 2,7-DMN are
DMN is a particularly valuable compound industrially. That is, 2,6-DMN gives 2,6-naphthalene dicarboxylic acid by oxidation, and also gives 2,7-
DMN gives 2,7-naphthalene dicarboxylic acid through oxidation, and polyesters containing these dicarboxylic acids as dibasic acid components can be formed into synthetic fibers and films with excellent properties. Therefore, the so-called isomerization method is a method of isomerizing the obtained DMN isomer mixture after separating it from a certain DMN isomer mixture as described above to increase the target specific DMN content. This is an essential process for industrially obtaining Many inventions have been proposed in the past regarding such DMN isomerization methods (for example, Japanese Patent Publication No. 1973-
37415, 47-50622 and 50-37194). In these conventionally known isomerizations of DMN, in order to obtain specific DMN, it is necessary to use a certain limited isomer, and it is virtually impossible to obtain specific DMN from other isomers. There is a characteristic that there is no For example, if you want to obtain 2,6-DMN by isomerization, 1,5-DMN and/or 1,6-DMN
and/or 1,7-DMN and/or 1,8-DMN if you want to obtain 2,7-DMN.
- Had to use DMN. In other words, the isomerization of these DMN isomers can be classified into the following series, for example, and although mutual isomerization occurs within each series, isomerization between each series is said to hardly occur. () 2,6-DMN1,6-DMN1,
5-DMN () 2, 7-DMN1, 7-DMN1,
8-DMN Thus, the object of the present invention is to provide a method capable of causing not only the conventionally known isomerization reaction in DMN but also the isomerization between each series, which was thought not to occur. Another object is to provide a method for isomerizing DMN to target DMN at a high conversion rate and high reaction rate. Still another object is to provide an isomerization method that causes fewer side reactions other than isomerization, and therefore produces less dimethylnaphthalene. Yet another purpose is to extract 2,6-DMN or 2,6-DMN from a DMN mixture.
An object of the present invention is to provide an industrially advantageous method for producing 7-DMN. Further objects of the invention will become apparent from the description below. According to the research of the present inventors, the object of the present invention is to (i) have a molar ratio of SiO ₂ /Al ₂ O ₃ in the range of 10 to 100, and (ii) improve the X-ray lattice spacing. (d) by contacting a catalyst containing a crystalline aluminosilicate zeolite characterized by having the characteristics shown in Table A below with a raw material mixture containing dimethylnaphthalenes. I found out that it can be achieved. According to the present invention, by using the crystalline aluminosilicate, 1,5- or 1,6-
Isomerization of 2,6-DMN from DMN, 1,7-DMN or 1,8-DMN to 2,7-DMN as well as 2,6-DMN from 2,3- or 2,7-DMN - Transfer of a methyl group from β-position to β-position on the same ring, such as isomerization to DMN, isomerization from 2,3-DMN or 2,6-DMN to 2,7-DMN, and between rings. 2,6 from various DMN mixtures.
It has now become possible to provide an industrially extremely advantageous method for producing - or 2,7-DMN. The method of the present invention will be explained in more detail below, but first, the isomerization method will be explained about the catalyst of the present invention. [] Catalyst used in the method of the present invention and its production and preparation The crystalline aluminosilicate zeolite used as an active component of the catalyst in the method of the present invention has the characteristics (i) and (ii) above. This zeolite has a high SiO ₂ /Al ₂ O ₃ (molar ratio) composition like the conventionally known zeolite ZSM-5, but
It is clearly distinguished from that of ZSM-5 in the line diffraction grating spacing (d). Hereinafter, in this specification, crystalline aluminosilicate zeolite may be simply referred to as "zeolite". The zeolite of the present invention has a high SiO ₂ /Al ₂ O ₃ (molar ratio) similar to zeolite ZSM-5,
The proportion is in the range 10-100, preferably in the range 15-70, more preferably in the range 20-50. Furthermore, the zeolite of the present invention has the characteristics of the X-ray lattice spacing shown in Table A below, but according to the analysis of the present inventors, the X-ray diffraction chart of the zeolite of the present invention is ZSM-5. A detailed comparison with that of the above revealed that there were some differences. One major difference is that the X-ray lattice spacing d (Å) that gives the strongest peak of ZSM-5 is dÅ = 3.85 (2θ
= 23.14), but the strongest peak of the zeolite of the present invention is branched, with dÅ = 3.86 and
3.83 (2θ=23.05 and 23.25). Another major difference is that one peak at dÅ = 3.00 (2θ = 29.76) observed in ZSM-5 is the same in the zeolite of the present invention, dÅ = 3.00 (2θ = 29.76).
This is observed as a branched concave peak at 3.00 (2θ=29.75). This latter concave peak is not observed in all zeolites of the invention, but in most cases. Next, the X-ray lattice spacing dÅ of the zeolite of the present invention and its relative intensity are shown. This relative intensity (I/I ₀ ) is d
When the intensity (I ₀ ) of Å = 3.86 (2θ = 23.05) is taken as 100, the relative intensity of each peak [I/I ₀ (%)] is 100.
~60 is VS (very strong), 60-40 is S (strong), 40
~20 is represented by M (moderate), and 20 to 10 is represented by W (weak).

【table】

[Table] Furthermore, the intensity (I ₀ ) of the peak at dÅ = 3.86 (2θ = 23.05), which is characteristic of the more preferred zeolite of the present invention
The relative intensity (I/I ₀ ) of the peak at dÅ = 3.83 (2θ = 23.25) is at least 70, preferably at least 75, more typically between 77 and 80. There is a correlation within the range. Furthermore, more preferred zeolites of the present invention exhibit unique properties in terms of chemical activity, such as:
The zeolite in an activated state has a cyclohexane decomposition index ratio of at least 1.1, preferably at least 1.5, and more preferably 1.7 or more, as measured by the definition below. In this specification, the above-mentioned "activated state"
This means that most of the alkali metal ions contained in the zeolite of the present invention immediately after synthesis are replaced with hydrogen ions according to a known method. This means that more than 70%, preferably more than 90%, of the alumina-based cation exchange sites of the zeolite are substantially occupied by hydrogen ions, thereby making the zeolite in an activated state (the zeolite in such a state (sometimes called "H-type zeolite") is obtained. Generally, zeolite has its SiO ₂ /Al ₂ O ₃ (molar ratio)
Its activity, especially its acidity, has roughly determined values. However, one feature of the zeolite of the present invention is that it has almost the same SiO ₂ /Al ₂ O ₃ (molar ratio).
The activity of ZSM-5 is higher than that of ZSM-5. In other words, if the cyclohexane decomposition activity of a certain standard ZSM-5 is set to 1, then the cyclohexane decomposition activity of the zeolite of the present invention having almost the same SiO ₂ /Al ₂ O ₃ molar ratio is cyclohexane decomposition activity as described above. Expressed as an index ratio, it is 1.1 or more, preferably 1.5 or more. This means that the zeolite of the present invention is ZSM-5
The present inventors conjecture that this is due to the fact that the acid strength within the pores is greater than that of the pores. The upper limit of the cyclohexane decomposition index ratio of the zeolite of the present invention is generally 3, preferably 2.5 or less. The zeolite used in the present invention is
has a ratio of SiO ₂ /Al ₂ O ₃ (molar ratio) and
Any material having the characteristic of line lattice spacing may be used.
It is not particularly affected by the type of synthesis method. Among them, preferred zeolites are those whose cyclohexane decomposition index ratio is at least 1.1, preferably at least 1.5, and more preferred are zeolites synthesized by the following method, but the synthesis method shown below is This is just an example, and the method for producing zeolite used in the present invention is not limited thereto. Method A Method A is a method previously proposed by the present inventors and will be described in detail below. That is, this method uses SiO ₂ /Al ₂ O ₃ (molar ratio)
crystalline aluminosilicate zeolite ZSM-5 having a crystalline aluminosilicate of 20 to 300 per gram of the zeolite ZSM-5.
This method involves heating to a temperature between 80 and 250°C in an aqueous solution containing 0.1 to 1 g of alkali metal hydroxide. This method was developed by the inventors on June 17, 1981.
This method is specifically explained in detail in Japanese Patent Application No. 107,635/1989 (title of the invention: "Novel crystalline aluminosilicate zeolite and method for producing the same") filed in Japan. ZSM-5, the raw material for this method, was
It can be produced by the method described in Japanese Patent No. 10064, and it can also be used since it is commercially produced by Mobil Oil Corporation. This ZSM-5 SiO ₂ /
Al ₂ O ₃ molar ratios in the range from 20 to 300, preferably in the range from 30 to 200, are advantageously used to prepare the zeolites of process A. _{SiO2 / Al2O3}
ZSM-5, which has a molar ratio lower than 20, is not only extremely difficult to produce, but also not easy to obtain. However, according to this method A, zeolite with a SiO ₂ /Al ₂ O ₃ molar ratio of 20 or less can be easily produced using ZSM-5 with a SiO ₂ /Al ₂ O ₃ molar ratio of 20 or more, preferably 30 or more as a raw material. It is surprising that not only is it possible to do so, but that such zeolites exhibit the unique activities described above. Examples of the alkali metal hydroxide used in the treatment of the raw material zeolite ZSM-5 include sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. Among them, sodium hydroxide is particularly preferred. The amount of such alkali metal hydroxide used is 0.1 g to 1 g per 1 g of ZSM-5 used.
g, preferably in the range of 0.2 g to 0.7 g, more preferably in the range of 0.3 g to 0.5 g. The alkali metal hydroxide is generally brought into contact with the raw zeolite ZSM-5 particles in the form of an aqueous solution.
In this case the amount of water is not critical and the ZSM used
-5 and/or alkali metal hydroxide, etc., but usually the amount is at least sufficient to fully immerse the entire amount of supplied ZSM-5 in the aqueous solution. That's fine. The concentration of the alkali metal hydroxide in the aqueous solution is not limited and can be varied over a wide range, but is generally in the range of 1 to 10% by weight, preferably 2 to 7% by weight. The reaction is carried out by heating to a temperature ranging from 80 to 250°C, preferably from 100°C to 200°C. The reaction can be carried out until a zeolite having the above characteristics is substantially produced.
The weight ratio of ZSM-5 can be used. That is, the reaction is carried out at a weight ratio of 10 to 80%, preferably 20 to 70%, more preferably 30 to 60%.
This can be continued until the range is reached. The zeolite thus obtained has the above characteristics and its chemical composition is represented by the following formula. xM ₂ /nO・Al ₂ O ₃・ySiO ₂ ...() [However, the formula is expressed in the form of an oxide in an anhydrous state, and M is one or more n-valent cations, x has a value of 0.5 to 4, y has a value of 10 to 200] where M represents an alkali metal, especially sodium, in the direct zeolite produced by method A; Therefore,
It can be exchanged for cations such as hydrogen ions, ammonium ions, and other metal ions. Of course, even if the zeolite is exchanged with cations other than sodium ions, it essentially meets the requirements of the zeolite of the present invention. In the above formula (), x is an index of the amount of cations bonded to the zeolite, and in the case of the zeolite of the present invention, it is 0.5 to 4, preferably 0.9 to 4.
3. The zeolite obtained by this method A has the above-mentioned characteristics as well as a known zeolite.
Compared to ZSM-5 and other similar zeolites, it has the following characteristics: One of its characteristics is
(Cyclohexane/n-hexane) adsorption ratio is abnormally large. The zeolite according to method A has an adsorption ratio of at least 0.7, preferably at least 0.8, more preferably 0.9 or more. The adsorption ratio (cyclohexane/n-hexane) is a value measured according to the definition described below, and for ZSM-5, all of the values are lower than 0.7, and those of 0.7 or more are in accordance with the present invention. As far as we know, it doesn't exist. This adsorption ratio is a value indicating the adsorption ratio of cyclohexane to n-hexane, and is an index indicating that the higher the value, the larger the diameter (size) of the pores in the zeolite. The upper limit of the adsorption ratio of zeolite according to method A is generally about 1.3, typically
The pore size is about 1.2, and this zeolite has an appropriate pore size. Next, an index expressing the characteristics of the zeolite obtained by this method A is "(cyclohexane/n
-hexane) adsorption ratio" and the above-mentioned "cyclohexane decomposition index ratio" and the measurement method will be explained in detail. (1) (Cyclohexane/n-hexane) adsorption ratio (hereinafter sometimes abbreviated as CNA value): This (cyclohexane/n-hexane) adsorption ratio is the n- adsorbed per unit weight of zeolite.
It represents the weight ratio of cyclohexane to the weight of hexane, and is a parameter that defines the pore diameter of zeolite. As this value increases, molecules with a large molecular cross section, such as cyclohexane, will more easily diffuse into the pores. represents something. The amount of adsorption per unit weight of zeolite is measured as follows. That is, pellet-shaped zeolite calcined at 450° C. for 8 hours in an electric furnace is accurately weighed using a spring balance of an adsorption device. Next, after evacuating the interior of the adsorption tube, cyclohexane or n-hexane is introduced in gaseous form until the pressure reaches 60±2 mmHg, and the mixture is maintained at 20±1° C. until equilibrium is reached (at least 2 hours). The amount of cyclohexane or n-hexane adsorbed on zeolite can be measured from the difference in spring balance length before and after adsorption. (2) Cyclohexane decomposition index ratio (hereinafter sometimes abbreviated as CDR value): The cyclohexane decomposition index ratio is
It is defined as the ratio of the cyclohexane decomposition index of the H-type zeolite obtained in the present invention to the activated state H-type ZSM-5 having alumina (molar ratio). The cyclohexane decomposition index is calculated by calcining 10 to 20 mesh pellets of zeolite containing 50 weight percent γ-alumina at 450°C for 8 hours in an electric furnace, and then filling a fixed bed reactor with a certain weight of the zeolite pellets. Under the conditions of 350℃ and 1 atm (weight unit hourly space velocity WHSV = 2HR ^-1 (total weight basis) cyclohexane and hydrogen/cyclohexane = 2/1
(molar ratio) of hydrogen. The amount of cyclohexane converted (per 100 weight of feed) at this time is called the cyclohexane decomposition index. Note that WHSV is a value calculated from the following formula: weight of hydrocarbon feedstock supplied per unit time/weight of catalyst. Method B This method B is also a method previously proposed by the present inventors, and the application was filed on July 5, 1982.
The invention was filed under the title ``Method for producing crystalline aluminosilicate zeolite and novel crystalline aluminosilicate zeolite.'' The contents are specifically and detailedly explained in the specification of Japanese Patent Application No. 58-120953, and the gist thereof will be explained below. This method B comprises a silica source, an alumina source, and a zeolite selected from zeolite ZSM-5 and zeolites with the properties shown below in an aqueous solution containing 1 to 200 mmol of alkali metal hydroxide per gram of said zeolite. maintained under conditions of temperature, pressure and time such that a crystalline aluminosilicate zeolite is formed, characterized in that: (a) the silica/alumina molar ratio is in the range 10 to 100; b) the X-ray lattice spacing d is as shown in Table A of the specification; and (c) the specific adsorption amount of n-hexane is at least 0.07.
g/g.This is a method for producing crystalline aluminosilicate zeolite. In other words, this method B does not substantially use organic amines as in the conventional production of ZSM-5, and in other words, the ZSM
The essential feature is that the zeolite is produced in the presence of the zeolite previously produced by method B or method B. This method B uses as raw materials an aqueous solution of a silica source, an alumina source, and an alkali metal hydroxide, which are usually used in the synthesis of zeolite, and zeolite ZSM-
Zeolites can be synthesized in very high yields, several times higher than the starting zeolites selected from zeolites prepared by method B and method B, and even several times higher under suitable conditions. In this method B, any silica source commonly used in zeolite production can be used, such as silica powder, colloidal silica, water-soluble silicon compounds, and silicic acid. To explain these specific examples in detail, as the silica powder, precipitated silica produced by a precipitation method from an alkali metal silicate such as aerosil silica, fumed silica, and silica gel is suitable, and as the colloidal silica, various For example, particles having a particle size of 10 to 50 microns can be advantageously used. In addition, as a water-soluble silicon compound, SiO ₂ 1 per mole of alkali metal oxide
Alkali metal silicates containing ~5 mol, especially 2 to 4 mol, such as water glass, sodium silicate,
Examples include potassium silicate. Colloidal silica or water glass is particularly preferred as the silica source. On the other hand, any alumina source that is generally used in the production of zeolite can be used, such as alumina, aluminum mineral salts, aluminates, etc. Specifically,
Alumina in a hydrated or hydrateable state such as colloidal alumina, pseudoboehmite, boehmite, γ-alumina, α-alumina, β-alumina trihydrate; aluminum chloride, aluminum nitrate, aluminum sulfate; Examples include sodium aluminate and potassium aluminate, among which sodium aluminate or aluminum mineral acid salts are preferred. Common sources of silica and alumina include aluminosilicate compounds such as naturally occurring feldspars, kaolin, acid clay, bentonite,
It is also possible to use montmorillonite and the like, and these aluminosilicates may be substituted for part or all of the silica source and/or the silica source described above. The amount of silica source in the raw material mixture of the present invention is
In terms of _SiO2 , it is generally in the range of 0.1 to 200 mmol, preferably in the range of 1 to 100 mmol, more preferably 5 mmol per gram of starting zeolite as raw material.
Advantageously within the range ~80 mmol;
The amount of the alumina source is generally 0.01 _to 20 mmol, preferably 0.1 to 10 mmol, more preferably 0.5 to 5 mmol per 1 g of starting zeolite in terms of _Al2O3 .
It is preferable to keep it within the millimole range. Although the mixing ratio of the silica source and the alumina source is not limited, generally, the molar ratio of SiO ₂ /Al ₂ O ₃ in terms of SiO ₂ and Al ₂ O ₃ is 1 to 200.
, preferably within the range of 5 to 100. If this molar ratio is less than 1, the desired zeolite cannot be obtained;
When it exceeds 200, the rate of degeneration decreases. Particularly suitable alkali metal hydroxides are sodium hydroxide and potassium hydroxide, and each of these may be used alone or in combination. Such alkali metal hydroxides are used in amounts ranging from 1 to 200 mmol, preferably from 5 to 100 mmol, more preferably from 10 to 80 mmol per gram of starting zeolite. Further, the alkali metal hydroxide with respect to the silica source and alumina source is generally 0.1 to 10, preferably 0.2 to 5, in terms of alkali metal hydroxide/(SiO ₂ + Al ₂ O ₃ ) molar ratio. More preferably, it is used in an amount within the range of 0.3-1. The above alkali metal hydroxide is usually used in the form of an aqueous solution, and the concentration of the alkali metal hydroxide in the aqueous solution is generally 1 to 100 mmol per mol of water based on the total amount of water in the reaction system. , preferably 5 to 50 mmol, more preferably 10 to 50 mmol
Conveniently, it is 40 mmol. Furthermore, in this method B, the starting ZSM-5 that can be the crystal matrix of the produced zeolite is a known one, in which a certain organic cation is combined with an alkali metal cation, and it is hydrothermally heated in an alkaline aqueous solution together with a silica source and an alumina source. It can be obtained according to a known method for synthesis under synthetic conditions (see, for example, Japanese Patent Publication No. 10064/1983). Zeolite ZSM synthesized by this known method
Organic cations are removed by generally washing the material 5 thoroughly with water and then calcining it at a temperature in the range of, for example, 300 to 700°C, preferably 400 to 600°C. However, the ZSM-5 used in this method B may be one in which such organic cations are incinerated or in which they remain. In addition, ZSM-5 zeolite, which is a raw material mixture, is prepared by converting some or all of the ions originally present in the zeolite into other cations such as lithium, silver, ammonium, etc. in accordance with a known method after the above-mentioned calcination operation. Monovalent cation; magnesium,
It may be ion-exchanged with divalent alkaline earth cations such as calcium and barium; group metal cations such as cobalt, nickel, platinum, and palladium; and group cations such as rare earth metals. Furthermore, in this method B, the object of the present invention can also be achieved by using the zeolite obtained in this method B as the starting zeolite instead of the above ZSM-5 zeolite. The form of such zeolite may be in the form of a slurry immediately after synthesis, or it may be separated from a liquid and subjected to a drying and calcination process. Furthermore, the zeolite is
As with ZSM-5 zeolite, it is perfectly acceptable even if the zeolite is ion-exchanged with the metal cations mentioned above. In method B, a silica source, as described above,
By preparing a raw material mixture of an alumina source, an alkali metal hydroxide, a zeolite, and water in the proportions described above, and maintaining the mixture under conditions of temperature, pressure, and time sufficient to form crystalline zeolite. Zeolite synthesis takes place. In addition to keeping the silica source, alumina source, alkali metal hydroxide, and water in the proportions described above, the silica source, alumina source, and alkali metal hydroxide in the raw material mixture were adjusted to SiO ₂ , Al ₂ O ₃ , and alkali metal hydroxide, respectively. SiO ₂ /Al ₂ O ₃ = 1 to 200, preferably 5 to 100, more preferably 10 to 80, OH ^- / (SiO ₂ + Al ₂ O ₃ ) = 0.1 ^to 10, preferably
0.2-5, more preferably 0.3-1, OH ^- _{/H2O=0.001-0.1} , preferably 0.005-1
It is more advantageous to use a proportion satisfying 0.05, more preferably 0.01 to 0.04. The temperature of the above zeolite synthesis reaction is not limited and can be set to essentially the same range as the temperature conditions for conventional ZSM-5 production, usually 90°C or higher, preferably 100 to 250°C, more preferably teeth
Temperatures in the range 120-200°C are advantageously used. Furthermore, if this method B is used, the reaction rate is significantly accelerated compared to the conventional method, so the reaction time is usually 30 minutes to 7 days, preferably 1 hour to 2 days.
A day, particularly preferably 2 hours to 1 day, is sufficient.
The pressure applied is the autoclave's autogenous pressure or higher pressure, and the autoclaving is generally carried out under the autoclave, and may also be carried out under an inert gas atmosphere such as nitrogen gas. When synthesizing zeolite according to this method, a batch method can be used in which all of the above-mentioned raw material components are charged as a mixture into a reaction vessel and the reaction is carried out under the above-mentioned conditions. Alternatively, a continuous method may be used in which a slurry of silica source and alumina source is continuously fed into a reaction vessel in which an aqueous solution of an alkali metal hydroxide and a starting zeolite are charged in advance, and the reaction is carried out in stages. Furthermore, a part of the product obtained by the above method is taken out, and a new aqueous solution of alkali metal hydroxide, a silica source, and an alumina source are fed batchwise or continuously to cause the reaction to occur. You can also do it. The zeolite formation reaction is continued by heating the raw material mixture to the desired temperature and, if necessary, stirring, until the zeolite is formed. After crystals have thus formed, the reaction mixture is cooled to room temperature and filtered until the ionic conductivity is 50μ.
Wash with water until the crystals are less than / cm and separate the crystals. Further, if necessary, the crystals are kept at 50° C. or higher for 5 to 24 hours under normal pressure or reduced pressure in order to dry them. Thus, according to the above method B, the silica source which is usually used for the synthesis of zeolite as a raw material,
In addition to the alumina source and aqueous alkali metal solution, only zeolite ZSM-5 or zeolite obtained by method B is used, which is equivalent to several times the amount of zeolite used as a raw material in the batch method, and several times under suitable conditions. The amount of zeolite can be synthesized in a continuous manner, and it is also possible to synthesize 100 times more zeolite. The zeolite thus obtained contains an alkali metal ion as a cation, and can be ion-exchanged by a method known per se, for example, by treating it with an aqueous ammonium chloride solution to replace the cation sites with ammonium ions. If this is further fired, the ammonium ions can be converted to hydrogen ions in an activated state. Furthermore, some or all of the alkali metal ions in the obtained zeolite can be exchanged with other cations. As cations that can be ion-exchanged,
For example, monovalent metal cations such as lithium, potassium, silver; alkaline earth metal cations such as magnesium, calcium, barium; manganese, iron,
Divalent transition metal cations such as cobalt, nickel, copper, and zinc; cations containing noble metals such as rhodium, palladium, and platinum; and rare earth metal cations such as lanthanum and cerium. When exchanging with the various cations mentioned above, it may be carried out according to a known method, and the zeolite may be contacted with a water-soluble or water-insoluble medium containing an aqueous solution containing the desired cation. Such contacting can be accomplished in either a batch or continuous manner. The zeolite thus obtained may be calcined at a temperature of 100 to 600°C, preferably 300 to 500°C, for 5 to 40 hours, preferably 8 to 24 hours, and this calcined product can also be used as the zeolite of the present invention. Ru. The zeolite obtained by this method B is a known zeolite having the above-mentioned characteristics.
Compared to ZSM-5 and other similar zeolites, it has the following characteristics: One of its characteristics is that the specific adsorption amount of n-hexane is at least 0.07.
It has an extremely high value of g/g. The specific absorption capacity of n-hexane is a value measured according to the definition below. The specific adsorption amount of n-hexane is a factor related to the pore volume of the zeolite, and a large value means that the pore volume of the channels of the zeolite is large. However, there is naturally an upper limit to the specific adsorption amount of n-hexane, and the upper limit of the specific adsorption amount of n-hexane in the zeolite produced by method B is generally 0.1.
g/g, typically around 0.08 g/g,
It preferably has a specific adsorption amount of n-hexane in the range of 0.07 to 0.09 g/g. Yet another characteristic of the zeolite produced by method B is (2-methylpentane/
(cyclohexane) adsorption ratio.
This adsorption ratio is a value measured by the method described below, but this zeolite generally has a (2-methylpentane/cyclohexane) adsorption ratio in the range of 1.1 to 1.6, preferably 1.2 to 1.5, and more preferably 1.25 to 1.45. You can have it. This (2-methylpentane/cyclohexane)
The adsorption ratio is a factor related to the pore size of the zeolite channel, and a large value means that molecules with a large cross section, such as cyclohexane molecules, have difficulty entering the zeolite channel; This means that methylpentane molecules can easily enter that channel. Therefore, when a zeolite having a channel pore size with an adsorption ratio in the above range is used as a catalyst, it exhibits unique shape selectivity and becomes a novel catalyst of high industrial value. Next, the definition and measurement method of "n-hexane specific adsorption amount" and "(2-methylpentane/cyclohexane) adsorption ratio", which are indicators representing the characteristics of the zeolite of method B, will be explained in detail. (i) Specific adsorption amount of n-hexane This index is defined as the weight of n-hexane adsorbed on 1 g of zeolite under the following constant conditions, and is measured as follows. That is, pelletized zeolite calcined at 450° C. for 8 hours in an electric Matsufuru furnace is accurately weighed using a spring balance of an adsorption device. Next, the inside of the adsorption tube was evacuated (0 mmHg) for 1 hour, and then n-hexane was introduced in gaseous form until the inside of the adsorption tube reached 50 ± 1 mmHg, and then kept at room temperature (20 ± 1°C) until equilibrium was reached (at least 2 hours). )Hold. The weight of adsorbed n-hexane can be calculated from the difference in the length of the spring balance before and after adsorption. (ii) (2-Methylpentane/cyclohexane) adsorption ratio This index is expressed as the weight ratio of 2-methylpentane to the weight of cyclohexane adsorbed per gram of zeolite under certain conditions. The method for measuring the adsorption amount of each component is exactly the same as in section (i) above. Note that the chemical composition of the zeolite obtained by the method B is almost the same as that of the zeolite obtained by the method A, so a description thereof will be omitted here. Method C Method for zeolite obtained by the method described in JP-A-56-17926 D Method for zeolite obtained by the method described in JP-A-57-123815 E Zeolite described in JP-A-51-67299 These The zeolites of Methods C to E have the characteristics specified in the present invention, but one other characteristic is that the (cyclohexane/n-hexane) adsorption ratio is less than 0.7, generally between 0.4 and 0.7. It is one. Another feature is that the specific adsorption amount of n-hexane is relatively small, ranging from 0.03 to 0.06 g/g. Among the specific examples of the zeolite synthesis method described above,
By using the zeolites obtained by Method A and Method B, it is possible to obtain a catalyst that has higher isomerization activity of dimethylnaphthalene, which is the object of the present invention, and is capable of more selective isomerization. More preferred. The zeolite used in the catalyst of the invention is one in which at least 50%, preferably at least 70% of its total cation sites are occupied by hydrogen cations (H ⁺ ). A zeolite having hydrogen cations in the above range can be prepared by a method known per se in which cations of a zeolite having a hydrogen cation (H ⁺ ) proportion lower than this range are ion-exchanged into hydrogen cations. That is, the cation sites can be converted to hydrogen cations (H ⁺ ) in the range described above by immersion treatment with a mineral acid such as hydrochloric acid, nitric acid, or sulfuric acid, or by exchange with ammonium ions (NH ₄ ⁺ ) and subsequent calcination. Cations other than hydrogen cations (H ⁺ ) in the above range may be occupied by various metal cations. For example, it may be occupied by alkaline earth metal cations such as Be, Mg, Ca, Sr, and Ba, and lanthanide metal cations such as La and Ce. Also Fe,
May be ion-exchanged with Group 8 metals of the periodic table such as Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, etc.
It may also be supported on these metals. When this zeolite ion-exchanged or supported with Group 8 metal is used in the isomerization reaction of the present invention, the generation of carbonaceous substances on the catalyst surface is suppressed as the reaction progresses, and the activity can be maintained for a long time. It has this effect. The zeolite of the present invention can be used in the form of powder itself, or can be used in the form of molded products, such as pellets or tablets. When used as a molded product, the content of zeolite in the molded product is 1 to 100% by weight,
Preferably a range from 10 to 90% is advantageous. Furthermore, to form zeolite, refractory inorganic oxides, such as silica, alumina, silica-alumina, silica-magnesium, and kaolin, which are generally used as binders for zeolite, are used.
Alumina is particularly preferred. When the catalyst contains a metal, it is subjected to a reductive heat treatment at a temperature of, for example, 200 to 600°C, preferably 250 to 550°C under a reducing atmosphere (for example, a hydrogen-containing gas atmosphere) before being subjected to the reaction of the present invention. It is preferable to do so. This reduction heat treatment may be performed before or after the catalyst is charged into the reactor. [] Isomerization reaction of the present invention The zeolite produced and prepared as described above or the catalyst containing the same can be used for the isomerization of DMNs, for example, the isomerization of 1,6-DMN to 2,6-DMN. , isomerization of 2,7-DMN to 2,6-DMN, 2,6- or 2,7- of 2,3-DMN
Used as a catalyst in reactions such as isomerization to DMN. In particular, as mentioned above, the zeolite of the present invention
It is unique in that it exhibits unique reactivity in the isomerization reaction of DMN, which is not seen in conventional catalysts. That is, in the isomerization of DMNs, it was conventionally thought that only the transfer of a methyl group from the α-position to the β-position or from the β-position to the α-position on the same ring was possible. However, when using the zeolite of the present invention, the rearrangement of the methyl group onto a different ring (e.g. rearrangement from the 3-position to the 6- or 7-position),
and from α- position (1-position) on the same ring
It also becomes possible to rearrange the methyl group from the (4-position) or the β-position (2-position) to the β-position (3-position).
Therefore, the zeolite of the present invention replaces the less useful 2,7-DMN with the industrially valuable 2,6-DMN.
Reactions that convert 2,3-DMN to DMN and 2,3-DMN to 2,3-DMN
It can be advantageously used as a catalyst in the isomerization reaction to 6- or 2,7-DMN. Thus, in carrying out the method of the present invention,
40% by weight or more of various DMN isomers, preferably
A raw material mixture containing 60% by weight or more, particularly preferably 80% by weight or more, may be brought into contact with the catalyst, and in particular, one having a target DMN having a thermal equilibrium composition or less is advantageously used. For example, when trying to obtain 2,6-DMN or 2,7-DMN by isomerization, 2,6-DMN or 2,7-DMN is
6-DMN or 2,7-DMN is 10% by weight or less,
It is desirable to use one containing preferably 5% by weight or less. The isomerization according to the invention can be carried out either in the liquid phase or in the gas phase, and is generally advantageously carried out at a temperature in the range of 200 to 500°C. The preferred range of reaction conditions differs depending on whether the reaction is carried out in a liquid phase or a gas phase. In liquid phase, 200-450℃, especially 250-350℃
The weight unit hourly space velocity (WHSV) in the catalytic reaction is from 0.1 to 20, preferably from 1 to
It is advantageous to carry out the reaction within the range of 10 Kg/cm 2 and at a reaction pressure of normal pressure to 30 Kg/cm ² , preferably 2 Kg/cm ² to 10 Kg/cm ² . On the other hand, when the reaction is carried out in the gas phase, 250 to 500℃,
Preferably at a temperature in the range of 300-400℃, from 0.05 to
It is suitable to carry out at a WHSV of 20, preferably from 0.1 to 5, and at a pressure ranging from normal pressure to 20 kg/cm ² , preferably from 1 kg/cm ² to 10 kg/cm ² . Especially when carrying out the reaction in the gas phase, nitrogen (N ₂ ) is introduced into the raw material mixture.
Alternatively, hydrogen (H ₂ ), preferably hydrogen (H ₂ ), can be introduced. Introduction of hydrogen is industrially advantageous because it can extend the life of catalyst activity. The appropriate amount of hydrogen used in this case is 0.1 to 100 mol, preferably 1 to 50 mol, per mol of the raw material mixture. In carrying out the isomerization reaction, the catalyst and the raw material mixture may be contacted in either a fixed bed reactor or a fluidized bed reactor, but the former is preferably used. According to the isomerization reaction of the present invention, the use of the zeolite-containing catalyst provides the following advantages. (i) It is possible not only to substitute methyl groups between α and β positions on the same ring of the naphthalene skeleton, but also to replace methyl groups between β and β positions on the same ring, and between rings. becomes. In particular, in the conventional isomerization of DMN, the isomerization does not occur, or even if it occurs, it occurs only to a very small extent, and for example, the following isomerization can be carried out easily and at a good conversion rate. 2,3-DMN → 2,6-DMN or 2,7
-DMN 2,6-DMN→2,7-DMN 2,7-DMN→2,6-DMN (ii) Therefore, in the conventional isomerization method, after the isomerization reaction,
After separating the target isomer, isomers that cannot undergo an isomerization reaction are separated and removed from the system as by-products or those with no utility value, but with the isomerization of the present invention, Other isomers from which the desired isomer has been separated can be recycled and used as raw materials. (iii) Conventionally, the types of raw material isomers were limited depending on the type of target isomer. However, according to the present invention, it has become possible to obtain a wide range of DMN from a wide range of types of DMN, so the source of DMN as a raw material can be arbitrarily selected. That is, a DMN isomer-containing mixture obtained from petroleum or coal fractions, a DMN isomer-containing mixture obtained by methylation of naphthalene or methylnaphthalene, etc. can be freely selected. (iv) Since the zeolite-containing catalyst of the present invention has high activity and low activity against side reactions such as disproportionation and demethylation, it is possible to obtain the desired dimethylnaphthalene at a high conversion rate and high selectivity. Example 1 (a) A silica/alumina molar ratio of 71.9 was prepared according to the method disclosed in U.S. Pat. No. 3,766,093.
ZSM-5 zeolite was synthesized. That is, tri-n-propylamine and n-propyl bromide were added as organic cation sources during the synthesis. After filtering and thoroughly washing the resulting composite with water, it was heated in an electric dryer at 100°C for 16 hours, then at 200°C.
The mixture was dried for 8 hours and then fired for 16 hours at 500°C under air circulation. Next, 10 g of the above ZSM-5 was taken and suspended in 50 ml of an aqueous solution containing 1.5 g of sodium hydroxide in a flask. This was maintained at 90°C for 3 hours with stirring, and the residue was filtered, thoroughly washed with water, and dried in an electric dryer at 100°C for 16 hours.
The weight after drying was 5.7 g, the silica/alumina molar ratio of this product decreased to 39.2, and Cu
- In the X-ray diffraction pattern obtained by irradiation with Kα rays, ZSM
The strongest peak at dÅ = 3.84 obtained at -5 is dÅ
A clear separation was observed between dA = 3.86 and dA = 3.83 (zeolite A-1). Furthermore, ion exchange of the powdered zeolite A-1 was performed at 70° C. for 16 hours using a 5 wt % ammonium chloride aqueous solution. The amount of ammonium chloride aqueous solution used is
The amount was 5 ml per gram of zeolite, and this operation was repeated twice. After ion exchange, the zeolite was washed and dried as described above, and then placed in an electric furnace.
H ⁺ type zeolite was obtained by calcining at 450°C for 8 hours under air circulation (zeolite A-
2). (b) After molding the above zeolite A-1 into a size of 10 to 20 meshes, it was molded in an electric Matsufuru furnace.
It was baked at 450°C for 8 hours. Approximately 0.5 g of the zeolite was placed on a spring balance suspended inside the adsorption tube, and the weight of the zeolite was precisely measured from the elongation of the spring. Next, after evacuating the inside of the adsorption tube, n-hexane or cyclo-hexane filled in a gas holder was introduced into the adsorption tube. Adsorption is 20℃, 60mmHg
I went for 2 hours under these conditions. The weight of adsorbate adsorbed on zeolite was calculated from the difference in spring balance length before and after adsorption. The amount of n-hexane and cyclohexane adsorbed on the zeolite is 6.8 wt% and 6.4 wt%, respectively, based on the weight of the zeolite.
The adsorption ratio of cyclo-hexane to n-hexane was 0.94. (c) Alumina gel for chromatography (300 mesh or less) was added to the zeolite A-2 at a weight ratio of 1/1, thoroughly mixed, and molded into a size of 10 to 20 mesh. After the molded part was fired at 450° C. for 8 hours in an electric Matsufuru furnace, 4 g was filled into a fixed bed reaction tube. After setting the catalyst bed temperature to 350°C, cyclohexane 8g/Hr and hydrogen/
When hydrogen was supplied at a ratio of cyclohexane=2/1 (molar ratio), the cyclohexane decomposition index was measured and found to be 21.5. The cyclohexane decomposition index of ZSM-5, which has the same silica/alumina (molar ratio) as zeolite A-2, is 11.3 from the correlation curve in Figure 1, and therefore the cyclohexane decomposition index ratio of zeolite A-2 is 1.9. I understand. Example 2 (a) Sodium hydroxide (special grade reagent manufactured by Wako Pure Chemical Industries)
Add aluminum sulfate 16 to 18 as an alumina source to an alkaline aqueous solution in which 10.5 g is dissolved in 210 ml of pure water.
Add 3.1 g of hydrate (special grade reagent manufactured by Wako Pure Chemical Industries),
Further, 69.4 g of silica sol (Kakuroid S-30L SiO ₂ 30 wt %, manufactured by Catalyst Kasei Co., Ltd.) was added as a silica source to prepare a gel. Next, this gel was charged into a 300 ml stainless steel autoclave, and then 6.9 g of ZSM-5 zeolite synthesized in Example 1-(a) was added. The composition of the feed material is SiO ₂ = 50.0 mmol, M ₂ O ₃ = 0.714 mmol, NaOH = 38.0 mmol, expressed per 1 g of ZSM-5, and SiO ₂ /Al ₂ O ₃ = 70, OH expressed in molar ratio. ^- /SiO ₂ +Al ₂ O ₃ = 0.75, OH ^- /H ₂ O = 0.018. 180℃ while stirring the ingredients gently
The reaction was carried out at autogenous pressure for 6 hours. After removing and separating the reactants, they were thoroughly washed with pure water until the washing solution became 50 μ/cm or less, dried at 90°C overnight, and weighed 10.0 g, which was the same as the preparation ZSM-5.
A product 1.5 times the weight of zeolite was obtained. As a result of quantifying silica and alumina, the silica/alumina (molar ratio) = 23.8, and the X-ray diffraction pattern has the characteristics shown in Table A above, especially dÅ =
The strongest peak at 3.84 showed a significant separation between dA = 3.86 and dA = 3.83 (zeolite B-1). From this powdered zeolite B-1, Example 1
-H type zeolite (zeolite B-2) was obtained according to the method described in (a). (b) After molding the above zeolite B-1 into a size of 10 to 20 meshes, it was heated in an electric Matsufuru furnace for 450 min.
It was baked at ℃ for 8 hours. Approximately 0.5 g of zeolite was placed on a spring balance suspended in an adsorption tube, and the weight of the zeolite was accurately measured from the elongation of the spring. Next, after evacuating the inside of the adsorption tube, n-hexane, 2-methylpentane, or cyclohexane filled in a gas holder was introduced until the inside of the adsorption tube reached 50±1 mmHg. 2 at room temperature (20℃±1℃)
After holding for a period of time, the weight of adsorbate adsorbed on the zeolite was calculated from the difference in the length of the spring balance before and after adsorption. n- for the zeolite
The specific adsorption amounts of hexane, 2-methylpentane and cyclohexane are respectively per zeolite weight.
The adsorption ratio of n-hexane to cyclohexane was 1.50. Further, the cyclohexane decomposition index ratio of zeolite B-2 was measured according to the method described in Example 1(c) and was found to be 2.0. Example 3 H ⁺ type zeolite (A-
2) Gel-like γ-alumina (300 mesh or less)
were added in equal weight, thoroughly mixed, and molded into a size of 10 to 20 meshes. 5 g of this molded product was fired in an electric Matsufuru furnace at 450° C. in an air atmosphere, and then filled into a fixed bed reaction tube. After setting the catalyst bed temperature to 375℃, 1,5-dimethylnaphthalene was added at 2.5g/HR.
At the same time, hydrogen was supplied at a rate of 3/1 (mole ratio) of hydrogen/1,5-dimethylnaphthalene.
The same operation as above was performed on zeolite B-2 synthesized in Example-2, and for comparison, H-type ZSM-5 (synthesized in Example-1) and commercially available H-type mordenite. The product composition 5 hours after the start of oil passing is summarized in Table 1. This result shows that in the method of the present invention, dimethylnaphthalene undergoes not only normal methyl group transfer (conversion of 1,5-isomer to 1,6- or 2,6-isomer) but also αβ transfer of methyl group (1, conversion of the 5-isomer to the 1,7- or 2,7-isomer) and also transfer of the methyl group to a different ring (conversion of the 1,5-isomer to the 1,3- or 2,3-isomer). (conversion to)
This shows that the value is extremely high.

【table】

[Table] Example 4 H ⁺ type zeolite (B-
2) 1 g of the powder was charged into a small stainless steel reactor. 4 g of 2,3-dimethylnaphthalene (Wako Pure Chemical's special grade reagent) was added to the flask and the flask was sealed. After holding at 350°C for 6 hours, the product composition was analyzed and 5.6 mol% of 2,6-dimethylnaphthalene and 4.1 mol% of 2,7-dimethylnaphthalene were detected. This indicates that one of the two methyl groups on the same ring was intramolecularly transferred to a different ring. Example 5 In this example, a continuous oil passage test in the liquid phase was conducted. H-type zeolite (B
-2) 10g of the powder was filled into a stainless steel fixed bed reaction tube. After setting the catalyst bed temperature to 375℃ and pressurizing the reaction system to 15Kg/cm ² G with nitrogen,
-Dimethylnaphthalene was fed at a rate of 10 g/HR. Table 2 shows the changes in product composition over time. These results show that the method of the present invention exhibits a specific intramolecular methyl group transfer reaction of dimethylnaphthalene even in the liquid phase, and also exhibits little deterioration over time.

【table】

【table】

【table】 [Brief explanation of the drawing]

The attached drawing shows the cyclohexane decomposition index ratio (CD
This figure shows the correlation between the silica/alumina (molar ratio) of H-type ZSM-5 zeolite, which is the standard for calculating R), and the cyclohexane decomposition index.

Claims (1)

[Claims] 1 (i) the molar ratio of SiO ₂ /Al ₂ O ₃ is in the range of 10 to 100, and (ii) the X-ray lattice spacing (d) has the characteristics shown in the table below. 1. A method for isomerizing dimethylnaphthalenes, comprising contacting a catalyst containing a crystalline aluminosilicate zeolite characterized by having a raw material mixture containing dimethylnaphthalenes. [Table] 2 Crystalline aluminosilicate zeolite is
Intensity of peak at line lattice spacing d (Å) = 3.86 (I ₀ )
The isomerization method according to item 1, wherein the relative intensity (I/I ₀ ) of the peak of d (Å) = 3.83 is at least 70 when d (Å) = 100. 3 The crystalline aluminosilicate zeolite is
2. The isomerization method according to claim 1, wherein the cyclohexane decomposition index ratio in the activated state is at least 1.1. 4. The isomerization method according to item 1, wherein the contact is carried out at a temperature of 200 to 500°C. 5. The isomerization method according to item 1, wherein the raw material mixture contains at least 40% (by weight) of dimethylnaphthalenes. 6. The isomerization method according to item 1, wherein the contact is carried out in a gas phase. 7. The isomerization method according to item 6, wherein the contact is carried out in the presence of hydrogen. 8. The isomerization method according to item 1, wherein the contact is carried out in a liquid phase.