JP6004850B2 - Method for producing MFI type zeolite catalyst and method for producing p-xylene - Google Patents

Description

  The present invention relates to a method for producing an MFI-type zeolite catalyst capable of selectively producing p-xylene and a method for producing p-xylene.

  Xylenes are important compounds as starting materials for producing polyester raw materials such as terephthalic acid, isophthalic acid, and phthalic acid, and are produced by various production methods. Among these, p-xylene is useful as a raw material for producing terephthalic acid, which is a monomer raw material for polyethylene terephthalate, and various methods for selectively producing p-xylene have been proposed.

  In order to selectively produce p-xylene, it has been studied to use the shape selectivity of MFI-type zeolite. However, xylene other than p-xylene is used due to the aluminum in the framework existing on the outer surface of MFI-type zeolite. A technique for removing aluminum as an acid surface on the outer surface or a technique for coating modification has been proposed.

  Patent Document 1 discloses a catalyst in which the outer surface of an MFI-type zeolite having a predetermined crystallite diameter is coated with aluminum, which is an active site, by modifying the outer surface with a silicate having a predetermined thickness. Alternatively, p-xylene is produced by methylation or disproportionation of toluene.

  However, the MFI-type zeolite catalyst of Patent Document 1 uses MFI-type zeolite produced using a structure-directing agent, which requires the cost of using the structure-directing agent and is used as a catalyst. In addition, since the firing at a high temperature is essential to remove the structure-directing agent, there is a problem that the production cost is increased. In addition, not only the MFI type zeolite catalyst of Patent Document 1, but also in reactions such as alkylation and disproportionation of aromatic hydrocarbons using a zeolite catalyst, if the amount of precipitated carbon increases due to side reactions, the catalyst is lost. There was also a problem that the life span was shortened.

  On the other hand, Non-Patent Document 1 discloses the catalytic behavior of MFI-type zeolite synthesized without using a structure-directing agent. The MFI-type theolite is steam-treated or steam-treated, and then further acid-treated. It is disclosed that the aluminum in the framework can be removed. However, Non-Patent Document 1 is an MFI-type zeolite that does not use a structure-directing agent, and it is possible to remove aluminum in the framework by steam treatment or steam treatment + acid treatment, and n- by steam treatment under a certain condition. Although it discloses that the hexane conversion can be improved, it does not disclose any p-xylene selectivity or carbon deposition amount of the MFI type zeolite catalyst after the treatment.

JP 2010-221095

Francisco J. Machado et al. Applied Catalysis A: General 181 (1999), 29-38

  The present applicant has studied various methods for selectively invalidating the outer surface acid sites in order to enhance the selectivity of p-xylene in reactions such as alkylation and disproportionation of aromatic hydrocarbons. It has been found that an MFI type zeolite catalyst obtained by acid-treating an MFI type zeolite prepared without using a regulating agent improves p-xylene selectivity and can also suppress carbon deposition.

  The present invention has been made in view of the above, and provides a method for producing p-xylene selectively and producing an MFI-type zeolite catalyst capable of suppressing carbon deposition in a simple and inexpensive manner. is there.

  In order to solve the above-mentioned problems and achieve the object, the present invention is a method for producing an MFI type zeolite catalyst capable of selectively producing p-xylene, which is crystallized without using a structure-directing agent. And an acid treatment step of treating the MFI-type zeolite with heating to a temperature range of 80 ° C to 200 ° C.

  Moreover, the manufacturing method of the MFI type | mold zeolite catalyst of this invention is performed in the said invention, performing the said acid treatment step, heating in the temperature range of 120 to 185 degreeC within a pressure-resistant container.

  The MFI zeolite catalyst production method of the present invention is characterized in that, in the above invention, the acid treatment step comprises acid-treating the MFI zeolite with an inorganic acid.

  The MFI type zeolite catalyst production method of the present invention is the above invention, wherein the MFI type zeolite comprises an alkali metal hydroxide aqueous solution, an alkali metal aluminate and fumed silica in distilled water at a predetermined ratio. A mixing step of obtaining an amorphous mixture by mixing, and a step of crystallizing the aluminosilicate by heating and stirring the mixture obtained in the mixing step at 130 ° C. to 200 ° C. in a pressure resistant vessel. It is characterized by that.

  The MFI type zeolite catalyst production method of the present invention is characterized in that, in the above invention, the MFI type zeolite before the acid treatment step has a Si / Al molar ratio of 12-30.

  In addition, the method for producing p-xylene of the present invention selects p-xylene by alkylating or disproportionating benzene and / or toluene in the presence of the MFI-type zeolite catalyst produced by the above-described method. It is characterized by manufacturing.

  The method for producing an MFI-type zeolite catalyst according to the present invention comprises a framework of the outer surface of an MFI-type zeolite catalyst by acid-treating an MFI-type zeolite prepared without using a structure-directing agent while heating to a predetermined temperature. Since only aluminum can be removed, in the disproportionation reaction and methylation reaction of toluene using the catalyst, the xylene isomerization reaction on the outer surface of the catalyst is suppressed, and p-xylene conversion in the pores The reaction can be performed selectively. In addition, when the MFI-type zeolite produced by the production method according to the present invention is used for the disproportionation reaction and methylation reaction of toluene, it is possible to reduce the amount of coke (carbonaceous material) produced with the reaction. Therefore, the life of the catalyst can be extended. Coke is a substance that causes catalyst deterioration, and is mainly produced on the acid surface of the catalyst outer surface. Therefore, the amount of coke can be reduced by the catalyst from which the outer surface aluminum is removed.

FIG. 1 is a flowchart of a manufacturing process of an MFI type zeolite catalyst according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the acid concentration and the aluminum removal rate in the acid treatment of the ZSM-5 type zeolite catalyst according to the embodiment of the present invention. 3A is a graph showing the conversion rate of 1,3,5-triisopropylbenzene (hereinafter referred to as TIPB) or cumene of the ZSM-5 type zeolite catalyst according to Example 4. FIG. 3B is a graph showing the conversion rate of TIPB or cumene of the ZSM-5 type zeolite catalyst according to Comparative Example 1. FIG.

  Below, the manufacturing method of the MFI type | mold zeolite catalyst which concerns on embodiment of this invention is demonstrated in detail with reference to drawings. Note that the present invention is not limited to the embodiments.

<Catalyst>
The MFI-type zeolite catalyst according to the present embodiment is produced by acid-treating MFI-type zeolite crystallized without using a structure-directing agent while heating it to a predetermined temperature range.

  The MFI type zeolite catalyst according to the present embodiment can selectively produce p-xylene by the reaction of benzene and / or toluene with a methylating agent or the disproportionation reaction of toluene. Examples of the MFI type zeolite include ZSM-5, TS-1, TSZ, SSI-10, USC-4, NU-4 and the like. Since these MFI-type zeolites have pore sizes that are substantially the same as the minor axis of the p-xylene molecule (about 0.55 nm), only p-xylene is selectively adsorbed in the pores, It does not adsorb o-xylene or m-xylene having a molecular diameter larger than that of p-xylene.

  The MFI-type zeolite catalyst according to the present embodiment uses MFI-type zeolite crystallized without using a structure-directing agent.

  The production method of the MFI-type zeolite crystallized without using a structure directing agent is not particularly limited. For example, it is represented by an alkali metal hydroxide aqueous solution typified by an aqueous sodium hydroxide solution, sodium aluminate, etc. Alkali metal aluminate, fumed silica, and distilled water are mixed to obtain a mixed solution, and the mixed solution is heated and stirred at 130 ° C. to 200 ° C. for 1 to 10 days in a pressure vessel such as an autoclave. Crystallize and the resulting crystals are dried at 60-120 ° C. for 3-48 hours.

The mixing ratio of each component in the mixed solution is a molar ratio of 18 to 120 for SiO ₂ / Al ₂ O ₃ , 0.10 to 0.16 for Na ₂ O / SiO ₂ , and H ₂ O / SiO _2. it is preferable to be 18 to 43, _further, SiO 2 / _Al 2 _{O 3} is _20~60, Na ₂ O / SiO 2 is _0.12-0.14, and H ₂ O / SiO 2 20 to 30 It is preferable to do this. Crystallization is preferably performed by heating amorphous aluminosilicate in an autoclave in a temperature range of 130 ° C. to 200 ° C. for 24 to 72 hours, and more preferably in a temperature range of 160 ° C. to 180 ° C. It is preferably performed by heating for ~ 48 hours. The obtained crystal is not necessarily baked, but may be baked to remove the adsorbed impurities. When baking, it is preferable to bake in the temperature range of 500-700 degreeC for 1 to 10 hours, and also it is preferable to bake in the temperature range of 550-600 degreeC for 4 to 6 hours. As the aluminum source, aluminum hydroxide, aluminum nitrate, and aluminum sulfate can be suitably used in addition to the alkali metal aluminate.

  Furthermore, a conventionally known method may be used as a method for producing a crystallized MFI type zeolite without using a structure-directing agent. As one of such known methods, the method described in JP-B-2-44771 is exemplified. The method for producing zeolite described in JP-B-2-44771 includes a mixing step of continuously supplying an alkali metal silicate aqueous solution and an aluminum-containing aqueous solution to obtain an amorphous aluminosilicate homogeneous phase compound, And a crystallization step in which the amorphous aluminosilicate obtained in the mixing step is crystallized by heating at 120 ° C. to 220 ° C. in an aqueous solution to which a mineralizer is added.

In Japanese Patent Publication No. 2-44771, an aqueous solution of an alkali metal silicate selected from an aqueous solution of sodium silicate, potassium silicate, lithium silicate, etc., an alkaline aqueous solution in which silicic acid is dissolved, sodium aluminate, potassium aluminate, aluminum chloride, nitric acid By reacting an aqueous solution of aluminum, aluminum hydroxide, or the like, or an aqueous solution containing aluminum selected from an alkaline aqueous solution or a mineral acid aqueous solution in which aluminum oxide is dissolved, the aluminum is reacted with Al ₂ O ₃ (anhydride equivalent) simultaneously and continuously. As a result, an amorphous aluminosilicate homogeneous phase compound containing 0.5 to 5.85% by mass is obtained. The resulting amorphous aluminosilicate is separated by filtration.

  The crystallization step is performed in an aqueous solution containing the filtered aluminosilicate containing an alkali metal hydroxide or alkali metal silicate as a mineralizer. The aluminosilicate is crystallized by heating at 120 to 220 ° C. in an alkali metal hydroxide aqueous solution or an alkali metal silicate aqueous solution of 1.5 to 5% by mass (anhydrous conversion). The alkali metal hydroxide aqueous solution is selected from sodium hydroxide, potassium hydroxide or lithium hydroxide aqueous solution. The alkali metal silicate aqueous solution is an aqueous solution comprising 0.5 to 5% by mass of alkali (for example, sodium hydroxide, potassium hydroxide, calcium hydroxide, etc.) in terms of alkali metal hydroxide and 10% by mass of silica in terms of silicon dioxide. It is. Crystallization is performed by heating amorphous aluminosilicate in an alkaline aqueous solution at a temperature range of 120 ° C. to 220 ° C. for 10 to 200 hours.

  As another method for producing MFI-type zeolite crystallized without using a structure-directing agent, Japanese Patent Publication No. 56-49851 and Applied Catalysis A: General 181 (1999), 29-38 by Francisco J. Machado et al. Is described as an example.

  The manufacturing method by Francisco J. Machado et al. Is an aqueous solution of an alkali metal aluminate in which sodium aluminate as an alkali metal aluminate is dissolved in an aqueous sodium hydroxide solution as an alkali metal hydroxide aqueous solution. A mixing step for supplying amorphous aluminosilicate and a crystallization step for crystallizing the amorphous aluminosilicate obtained in the mixing step by heating at 130 ° C. to 200 ° C.

The mixing ratio of each component in the mixing step is as follows: SiO ₂ / Al ₂ O ₃ molar ratio is 18 to 120, Na ₂ O / SiO ₂ molar ratio is 0.10 to 0.16, H ₂ O / SiO ₂ mole The ratio is preferably 18 to 43. Crystallization is performed by heating amorphous aluminosilicate in an autoclave at a temperature range of 130 ° C. to 200 ° C. for 24 to 72 hours.

MFI-type zeolite crystallized without using a structure-directing agent obtained by various production methods described above has a Si / Al molar ratio of 12 to 30 (SiO ₂ / Al ₂ O ₃ molar ratio of 24 to 60). It is preferably 12 to 25 (SiO ₂ / Al ₂ O ₃ molar ratio is 24 to 50), and 12 to 20 (SiO ₂ / Al ₂ O ₃ molar ratio is 24 to 40). More preferably it is.

  In the present embodiment, the MFI-type zeolite crystallized without using a structure-directing agent as described above is subjected to an acid treatment while being heated to a temperature range of 80 ° C. to 200 ° C., whereby the outer surface of the MFI-type zeolite is obtained. Remove only the aluminum present in In the present invention, the outer surface aluminum can be effectively removed by only subjecting the MFI-type zeolite crystallized without using a structure-directing agent to heat acid treatment. In the present invention, since it is not necessary to perform other post-treatment such as steam treatment, an MFI-type zeolite catalyst can be easily prepared.

  As the acid used for the acid treatment, organic acids can be used in addition to inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid. The concentration of the acid used is preferably in the range of 0.1 mol / L to 15.0 mol / L. When the acid concentration is lower than 0.1 mol / L, the ability to remove skeletal aluminum on the outer surface is lowered, so 0.1 mol / L or more is preferable, 1.0 mol / L or more is more preferable, and 2.0 mol / L. The above is more preferable. On the other hand, even if the acid concentration is higher than 15.0 mol / L, improvement in the removal performance of skeletal aluminum on the outer surface is not recognized, and the cost is increased, so 15.0 mol / L or less is preferable. The acid treatment is preferably performed with an inorganic acid, more preferably with nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, particularly phosphoric acid.

  The mixing ratio of the MFI zeolite and the acid to be used is preferably 5 to 100, more preferably 15 to 60, and more preferably 20 to 40 with respect to the MFI zeolite 1 in terms of mass ratio. A range is further preferred.

  Moreover, it is preferable to heat an acid treatment in the temperature range of 80 to 200 degreeC. When the temperature is lower than 80 ° C., the removal performance of the skeletal aluminum on the outer surface is low, and even if the heating temperature is higher than 200 ° C., the improvement of the removal performance of the skeleton aluminum on the outer surface is not recognized, and the cost increases. . The heating temperature is more preferably in the temperature range of 120 ° C to 185 ° C, and further preferably in the temperature range of 135 ° C to 175 ° C.

  The acid treatment is performed by heating and stirring at the above temperature using a pressure vessel such as an autoclave, preferably 1 hour to 100 hours, more preferably 3 hours to 50 hours, further preferably 10 hours to 30 hours. After completion of the acid treatment, the MFI zeolite is filtered, washed with water and dried to prepare an MFI zeolite catalyst that does not use a structure-directing agent.

  Hereinafter, the manufacturing process of the MFI type zeolite catalyst according to the present embodiment will be described with reference to the drawings. FIG. 1 is a flowchart of a manufacturing process of an MFI type zeolite catalyst according to an embodiment of the present invention.

  As shown in FIG. 1, in the manufacturing process of the MFI-type zeolite catalyst according to the embodiment of the present invention, first, a predetermined material is mixed at a predetermined ratio by the above-described method or the like to form an amorphous aluminosilicate. Is generated (step S101). The produced aluminosilicate-containing mixture is heated under predetermined conditions in the presence or absence of a mineralizer to crystallize the aluminosilicate (step S102).

  The crystallized MFI-type zeolite is separated by filtration, washed with water and dried, and then calcined at a temperature range of 500 to 700 ° C. for 2 hours to 10 hours (step S103).

  The calcined MFI-type zeolite is acid-treated while being heated to a predetermined temperature range (Step S104). In this way, the MFI type zeolite catalyst according to the present embodiment can be manufactured. In addition, since the MFI type zeolite catalyst according to the present embodiment is crystallized without using a structure directing agent, it is separated by filtration, washed with water, and dried at 60 ° C. to 120 ° C. in Step S103. Can be produced by acid treatment without firing.

  The generation and crystallization of the amorphous aluminosilicate described above (steps S101 and S102) are merely examples, and an MFI type zeolite having a Si / Al molar ratio of 12 to 30 without using a structure-directing agent. Can be included in the manufacturing process of the MFI-type zeolite catalyst according to the present embodiment.

<Alkylation or disproportionation reaction of aromatic hydrocarbon>
The production of p-xylene by the aromatic hydrocarbon alkylation reaction or aromatic hydrocarbon disproportionation reaction using the MFI-type zeolite catalyst according to the embodiment of the present invention will be described.

  Examples of the raw material for producing p-xylene include benzene and / or toluene. As the alkylating agent used in the alkylation reaction, methanol and dimethyl ether are preferable. Commercial products can be used for these, but methanol or dimethyl ether produced from a mixed gas of hydrogen and carbon monoxide may be used, or dimethyl ether produced by dehydrating methanol may be used. . Moreover, although benzene, toluene, methanol, and dimethyl ether which are raw materials can contain water, an olefin, a sulfur compound, and a nitrogen compound as an impurity, it is preferable that impurity content is small. The water content is preferably 200 mass ppm or less, and more preferably 100 mass ppm or less. Further, the olefin content is preferably 1% by mass or less, and more preferably 0.5% by mass or less. Furthermore, the sulfur compound and nitrogen compound contents are preferably 1 mass ppm or less, and more preferably 0.1 mass ppm or less.

  The mixing ratio of the alkylating agent and the aromatic hydrocarbon raw material is preferably a molar ratio of 5: 1 to 1:20, more preferably 2: 1 to 1:10, and 1: 1 to 1: 5. The range of is optimal. If the mixing ratio of the alkylating agent is too large, the reaction between the alkylating agents proceeds, which may cause coking that causes catalyst deterioration, which is not preferable. If the mixing ratio of the alkylating agent is too small, it is not preferable because the alkylation reaction does not proceed easily.

The aromatic hydrocarbon alkylation reaction and disproportionation reaction are carried out by supplying aromatic hydrocarbon in the range of weight space velocity (WHSV) 1h ^{−1 to} 30h ⁻¹ , and MFI type zeolite catalyst according to the present embodiment. It is preferable to contact with.

  The alkylation reaction and disproportionation reaction of aromatic hydrocarbons are preferably carried out by heating in the range of 200 ° C to 550 ° C. If the reaction temperature is lower than 200 ° C., the reaction hardly proceeds, and if the reaction temperature is higher than 550 ° C., the selectivity for p-xylene decreases and the amount of carbon deposition increases, which is not preferable. The reaction temperature is more preferably 230 ° C to 530 ° C, and most preferably 260 ° C to 510 ° C. The reaction pressure is preferably from atmospheric pressure to 10 MPa, more preferably from 0.5 MPa to 5 MPa. The alkylation reaction may be performed in the presence of an inert gas such as nitrogen or helium, and may be performed by flowing hydrogen through the reaction system from the viewpoint of preventing coking.

  The method for producing an MFI type zeolite catalyst and the method for producing p-xylene according to the present embodiment are a simple method of acid-treating MFI type zeolite crystallized without using a structure-directing agent at a predetermined temperature. A catalyst from which aluminum, which is an acid point on the surface, is removed can be produced. Furthermore, by using the catalyst produced by this method for alkylation or disproportionation reaction such as toluene, p-xylene can be produced with high selectivity and coking can be suppressed.

  Hereinafter, the present invention will be described in detail with reference to examples. The present invention is not limited to the examples described below.

<Catalyst preparation>
First, ZSM-5 that does not use a structure directing agent (OSDA) (hereinafter referred to as “OSDA-free ZSM-5”) and ZSM-5 that uses a structure directing agent (OSDA) (hereinafter referred to as “OSDA using ZSM-”). 5)).

(OSDA free ZSM-5: Comparative Example 1)
OSDA free ZSM-5 was produced as follows.
Fumed silica, sodium aluminate (NaAlO ₂ ), sodium hydroxide (NaOH), and distilled water in a molar ratio of SiO ₂ : Al ₂ O ₃ : NaOH: H ₂ O = 1: 0.016: 0.23: Each compound was mixed so that it might be set to 30. This mixture was treated in an autoclave with stirring at 20 rpm at 170 ° C. for 4 days, and the resulting solid was washed with water, dried at 80 ° C., and calcined at 630 ° C. for 10 hours to obtain OSDA-free ZSM-5. Obtained. In Comparative Example 1 where no acid treatment was performed thereafter, the treatment was repeated twice with an ammonium nitrate aqueous solution at 80 ° C. for 24 hours, and then calcined at 550 ° C. for 6 hours to obtain proton-type OSDA-free ZSM-5.

(OSDA use ZSM-5: Comparative Example 2)
OSDA using ZSM-5 was prepared using tetrapropylammonium hydroxide (TPAOH) as the structure directing agent (OSDA).
Tetraethoxysilane (Si (OEt) ₄ ), aluminum nitrate nonahydrate, sodium hydroxide, tetrapropylammonium hydroxide (TPAOH), and distilled water in a molar ratio of SiO ₂ : Al ₂ O ₃ : NaOH: TPAOH: _{H 2 O = 1: 0.010:} 0.10: 0.25: a mixture of the compound so that 8.3. After this mixture was treated at 80 ° C. for 6 hours, ethanol produced by hydrolysis of Si (OEt) ₄ was removed. Furthermore, it processed at 170 degreeC for 1 day, stirring at 20 rpm in an autoclave, and the obtained solid was washed with water, dried at 80 degreeC, and baked at 550 degreeC for 10 hours, and OSDA use ZSM-5 was obtained. In Comparative Example 2 where no acid treatment was performed thereafter, the treatment was repeated twice with an ammonium nitrate aqueous solution at 80 ° C. for 24 hours, and then calcined at 550 ° C. for 6 hours to obtain proton-type OSDA-use ZSM-5.

Example 1
1 g of OSDA-free ZSM-5 and 30 g of a 0.1 mol / L nitric acid aqueous solution were introduced into a 23 ml autoclave, and the catalyst was acid-treated with stirring at 160 ° C. for 24 hours at 20 rpm. After the treatment, the acid-treated OSDA-free ZSM-5 was washed and filtered and dried to produce a catalyst.

(Example 2)
1 g of OSDA-free ZSM-5 and 30 g of a 1.0 mol / L nitric acid aqueous solution were introduced into a 23 ml autoclave, and the catalyst was acid-treated while stirring at 160 ° C. for 24 hours at 20 rpm. After the treatment, the acid-treated OSDA-free ZSM-5 was washed and filtered and dried to produce a catalyst.

(Example 3)
1 g of OSDA-free ZSM-5 and 30 g of a 2.0 mol / L nitric acid aqueous solution were introduced into a 23 ml autoclave, and the catalyst was acid-treated with stirring at 160 ° C. for 24 hours at 20 rpm. After the treatment, the acid-treated OSDA-free ZSM-5 was washed and filtered and dried to produce a catalyst.

Example 4
1 g of OSDA free ZSM-5 and 30 g of 6.0 mol / L nitric acid aqueous solution were introduced into a 23 ml autoclave, and the catalyst was acid-treated with stirring at 160 ° C. for 24 hours at 20 rpm. After the treatment, the acid-treated OSDA-free ZSM-5 was washed and filtered and dried to produce a catalyst.

(Example 5)
10 g of OSDA-free ZSM-5 and 100 g of a 13.4 mol / L nitric acid aqueous solution were introduced into a 150 ml autoclave, and the catalyst was acid-treated with stirring at 170 ° C. for 24 hours at 20 rpm. After the treatment, the acid-treated OSDA-free ZSM-5 was washed and filtered and dried to produce a catalyst.

(Example 6)
10 g of OSDA-free ZSM-5 and 100 g of a 14.7 mol / L phosphoric acid aqueous solution were introduced into a 150 ml autoclave, and the catalyst was acid-treated while stirring at 170 ° C. for 24 hours at 20 rpm. After the treatment, the acid-treated OSDA-free ZSM-5 was washed and filtered and dried to produce a catalyst.

(Comparative Example 3)
1 g of ZSM-5 using OSDA and 30 g of a 0.1 mol / L nitric acid aqueous solution were introduced into a 23 ml autoclave, and the catalyst was acid-treated while stirring at 160 ° C. for 24 hours at 20 rpm. After the treatment, the acid-treated OSDA-use ZSM-5 was washed and filtered and dried to produce a catalyst.

(Comparative Example 4)
1 g of ZSM-5 using OSDA and 30 g of a 1.0 mol / L nitric acid aqueous solution were introduced into a 23 ml autoclave, and the catalyst was acid-treated while stirring at 160 ° C. for 24 hours at 20 rpm. After the treatment, the acid-treated OSDA-use ZSM-5 was washed and filtered and dried to produce a catalyst.

(Comparative Example 5)
1 g of ZSM-5 using OSDA and 30 g of a 2.0 mol / L nitric acid aqueous solution were introduced into a 23 ml autoclave, and the catalyst was acid-treated while stirring at 160 ° C. for 24 hours at 20 rpm. After the treatment, the acid-treated OSDA-use ZSM-5 was washed and filtered and dried to produce a catalyst.

(Comparative Example 6)
1 g of ZSM-5 using OSDA and 30 g of 6.0 mol / L nitric acid aqueous solution were introduced into a 23 ml autoclave, and the catalyst was acid-treated while stirring at 160 ° C. for 24 hours at 20 rpm. After the treatment, the acid-treated OSDA-use ZSM-5 was washed and filtered and dried to produce a catalyst.

<Catalyst characteristics>
For the catalysts of Examples 1 to 4 and Comparative Examples 1, 2 and 6 obtained as described above, the Si / Al (molar ratio) of the catalyst was measured by inductively coupled plasma atomic emission spectrometer (ICP-AES) and ²⁷ Al MAS NMR. ), Al content (mmol / g) and Al content (pieces / unit cell). Moreover, about the catalyst of Examples 1-4, the comparative example 1, and the comparative example 6, the X-ray-diffraction figure was measured and crystallinity degree (%) was calculated | required. Table 1 shows Si / Al (molar ratio), Al content (mmol / g), Al content (pieces / unit cell) and crystallization for the catalysts of Examples 1 to 4 and Comparative Examples 1, 2 and 6. Degrees.

表１中、Ａｌ含有量（個／単位格子）は、触媒の結晶単位格子内に存在する骨格アルミニウム量を意味し、Ｓｉ／Ａｌ（モル比）およびＡｌ含有量（ｍｍｏｌ／ｇ）におけるアルミニウム量は、触媒の結晶単位格子内の骨格アルミニウムおよび骨格外のアルミニウムを含む数値である。

In Table 1, the Al content (pieces / unit cell) means the amount of skeletal aluminum present in the crystal unit cell of the catalyst, and the aluminum content in Si / Al (molar ratio) and Al content (mmol / g). Is a numerical value including skeletal aluminum in the crystal unit cell of the catalyst and aluminum outside the skeleton.

  In Table 1, Comparative Example 1 is OSDA-free ZSM-5, and Examples 1 to 6 are catalysts obtained by acid-treating OSDA-free ZSM-5. The Si / Al (molar ratio) before acid treatment (Comparative Example 1) is 15.4, whereas the Si / Al (molar ratio) after acid treatment (Examples 1 to 6) is 16.1, 20.3, 22.8, 19.8, 31.8, 21.5 and larger than before acid treatment. From this result, it can be seen that the aluminum in the catalyst was removed by heat treatment with a nitric acid solution of 0.1 mol / L to 13.4 mol / L and a phosphoric acid solution of 14.7 mol / L.

  The crystallinity (%) of Examples 1 to 6 was as high as 84% to 94%, and it was found that even when aluminum in the skeleton was removed by acid treatment, the crystal structure was still retained.

  Comparative Example 2 is an OSDA-use ZSM-5, and Comparative Example 6 is a catalyst obtained by acid-treating the OSDA-use ZSM-5 of Comparative Example 2. The Si / Al (molar ratio) before the acid treatment (Comparative Example 2) is 52.4, whereas the Si / Al (molar ratio) after the acid treatment (Comparative Example 6) is 323 and before the acid treatment. It is very big. From this result, it can be seen that a large amount of aluminum in the catalyst was removed by heat treatment with a 6.0 mol / L nitric acid solution.

  FIG. 2 is a graph showing the relationship between the concentration of nitric acid during the acid treatment and the aluminum removal rate of the ZSM-5 type zeolite catalyst. ○ is the result of OSDA use ZSM-5, and □ is the result of OSDA free ZSM-5.

  As shown in FIG. 2, it can be seen that OSDA use ZSM-5 having a larger Si / Al (molar ratio) before acid treatment (small aluminum content) has a higher aluminum removal rate than OSDA free ZSM-5. It was also found that both the OSDA-free ZSM-5 and the OSDA-use ZSM-5 had a substantially constant aluminum removal rate at an acid concentration of 1 mol / L or higher.

<Catalyst performance evaluation test 1>
Using a pulse reactor, cracking of 1,3,5-triisopropylbenzene (TIPB) and cumene was carried out in the presence of the catalysts of Examples 1 to 6 and Comparative Examples 1 and 6, and the conversion rate was measured. did. Cumene has the same diameter as p-xylene, and the cracking reaction proceeds in the pores and on the outer surface of the ZSM-5 type zeolite catalyst. Since TIPB has a larger diameter than p-xylene, it is not adsorbed in the pores, and the cracking reaction proceeds only on the outer surface of the ZSM-5 type zeolite catalyst. Therefore, by performing the cracking reaction of TIPB and cumene, and measuring the conversion rate, the amount of aluminum which is the acid point in the pores and on the outer surface of the ZSM-5 type zeolite catalyst can be evaluated. In order to improve the selectivity of p-xylene, the amount of aluminum at the outer surface acid point of the ZSM-5 type zeolite catalyst is small (TIPB conversion is small) and the amount of aluminum at the acid point in the pore is large. Preferred (high conversion of cumene). In addition, since the coke that causes catalyst deterioration is mainly generated at the outer surface acid point, the amount of aluminum at the outer surface acid point is small (the conversion rate of TIPB is small) to reduce the amount of coke. It is preferable that the amount of aluminum at the acid point is large (the conversion rate of cumene is large).

  A fixed bed flow reactor is filled with 20 mg of catalyst and helium gas is circulated (30 ml / min), and 0.6 μL / pulse TIPB or cumene is supplied to the fixed bed flow reactor at 300 ° C. under atmospheric pressure. did. The product and / or unproducted product at the outlet of the fixed bed flow reactor was analyzed by gas chromatography.

Measuring device: Shimadzu gas chromatograph GC-8A
Column: Silicone OV-1 (2%), Uniport HP, 60-80mesh, ID 3mm, length 6m
Temperature conditions: column initial temperature 80 ° C. (2 minutes), heating rate 20 ° C./minute (5 minutes), 180 ° C. (1 minute)

The cumene conversion rate and TIPB conversion rate were calculated by the following equations.
Cumene conversion (mol%) = 100− [unreacted cumene (mol) / (unreacted cumene (mol) + benzene (mol))] × 100
TIPB conversion (mol%) = 100− [unreacted TIPB (mol) / (unreacted TIPB (mol) + DIPB (mol) + cumene (mol) + benzene (mol))] × 100
In the above formula, DIPB means 1,3-diisopropylbenzene.

<Catalyst performance evaluation test 2>
In the presence of the catalysts of Examples 1 to 6 and Comparative Examples 1 and 6, toluene was disproportionated and the toluene conversion and p-xylene selectivity were measured.

Toluene disproportionation was carried out under conditions of 400 ° C., WHSV = 15.1 h ⁻¹ , and toluene partial pressure of 18.3 kPa while charging a fixed bed flow reactor with 100 mg of catalyst and circulating argon gas (30 ml / min). Reaction was performed. The product at the outlet of the reactor was analyzed by gas chromatography to determine toluene conversion and p-xylene selectivity. Moreover, after performing toluene disproportionation reaction for 45 minutes, the catalyst was extracted and the amount of carbon deposited on the catalyst was measured by thermogravimetric analysis. Further, the carbon deposition amount was calculated as the carbon deposition amount (mg) per 1 g of the catalyst.

Measuring device: GC-2014 manufactured by Shimadzu Corporation
Column: Capillary column Xylene Master, inner diameter 0.32 mm, length 50 m
Temperature conditions: column initial temperature 50 ° C., heating rate 2 ° C./min, detector (FID) temperature 250 ° C.
Carrier gas: helium

The toluene conversion rate and p-xylene selectivity were calculated by the following equations.
Toluene conversion rate (mol%) = 100− (unreacted toluene (mol) / raw material toluene (mol)) × 100
p-xylene selectivity (mol%) = 100- (product p-xylene (mol) / product C8 aromatic hydrocarbon (mol)) × 100

  Table 2 below shows the results of the catalyst performance evaluation tests 1 and 2. 3A and 3B show the conversion rate of TIPB or cumene of the OSDA-free ZSM-5 type zeolite catalyst with and without acid treatment (Example 4) and without acid treatment (Comparative Example 1). In FIG. 3A and FIG. 3B, ◯ indicates the conversion rate of TIPB, and □ indicates the conversion rate of cumene.

  As shown in FIG. 3A and FIG. 3B, in both OSDA-free ZSM-5 (Comparative Example 1) without acid treatment and OSDA-free ZSM-5 (Example 4) with 6.0 mol / L nitric acid treatment, The conversion rate of cumene is a number close to 100%, and both with and without acid treatment (Example 4; 6.0 mol / L nitric acid) and without acid treatment (Comparative Example 1). It can be seen that skeletal aluminum which is an acid point remains.

  On the other hand, the TIPB conversion rate of OSDA-free ZSM-5 without acid treatment (Comparative Example 1) decreases as the number of treatments increases, and the OSDA-free ZSM-5 with nitric acid treatment of 6.0 mol / L (Example 4). Then, only TIPB was slightly decomposed only in the first time, but no decomposition was observed after the second time. In OSDA-free ZSM-5 (Comparative Example 1) without acid treatment, decomposition of TIPB proceeds because acid sites remain on the outer surface, but the catalyst of Example 4 treated with 6.0 mol / L nitric acid. Then, since most of the skeletal aluminum on the outer surface is removed, it is considered that the decomposition of TIPB does not proceed. In addition, it is estimated that the fall of the TIPB conversion rate for every processing frequency in the comparative example 1 generate | occur | produced when the oligomer of the propylene produced | generated by coke, TIPB catalytic cracking, etc. deposited on an outer surface.

  From the above cumene conversion rate and TIPB conversion rate, the catalyst according to the present embodiment produced by acid treatment of OSDA-free ZSM-5 selectively removes only the aluminum on the outer surface, and the aluminum in the pores. It is presumed that p-xylene can be selectively produced while suppressing the reaction of p-xylene to other isomers catalyzed at acid points on the outer surface.

  In addition, the OSDA-free ZSM-5 (Examples 1 to 6) with acid treatment has a lower toluene conversion than the OSDA-free ZSM-5 (Comparative Example 1) without acid treatment, but has a p-xylene selectivity. Improvement and reduction of carbon deposition were observed. It is presumed that by treating with nitric acid or phosphoric acid, only the skeletal aluminum on the outer surface was selectively removed while retaining the skeletal aluminum inside the pores. In particular, in Example 6 treated with 14.7 mol / L phosphoric acid, the carbon deposition amount was reduced and the selectivity for p-xylene was greatly improved. However, the phosphoric acid treatment reduced the amount of OSDA-free ZSM-5. It is presumed that the acid sites near the hole entrance could be removed or inactivated by the reaction between phosphorus and aluminum.

  In Comparative Example 6 in which ZSM-5 using TPAOH was treated with 6 mol / L nitric acid, both toluene conversion and p-xylene selectivity were low, and not only skeletal aluminum on the outer surface but also pores by acid treatment. It can be presumed that the internal skeletal aluminum has also been removed.

  As described above, the method for producing an MFI-type zeolite catalyst according to the present invention is an industrially feasible embodiment, and is a process for producing p-xylene, particularly p-xylene produced by a disproportionation reaction of toluene. Useful for manufacturing.

Claims (6)

A method for producing an MFI-type zeolite catalyst capable of selectively producing p-xylene,
The crystallized MFI-type zeolite without the use of structure-directing agent, the acid treatment step of acid treatment with heating to a temperature range of 80 ° C. to 200 DEG ° C. seen including,
A method for producing an MFI-type zeolite catalyst, characterized by not performing steam treatment .   2. The method for producing an MFI-type zeolite catalyst according to claim 1, wherein the acid treatment step is performed while heating in a temperature range of 120 ° C. to 185 ° C. in a pressure vessel.   The method for producing an MFI-type zeolite catalyst according to claim 1 or 2, wherein the acid treatment step comprises acid-treating the MFI-type zeolite with an inorganic acid. The MFI zeolite is
A mixing step of mixing an aqueous alkali metal hydroxide solution, an alkali metal aluminate and fumed silica in distilled water at a predetermined ratio to obtain an amorphous mixture;
The mixture obtained in the mixing step is manufactured by heating and stirring in a pressure vessel at 130 ° C to 200 ° C to crystallize the aluminosilicate. The manufacturing method of the MFI type | mold zeolite catalyst as described in one.   The method for producing an MFI type zeolite catalyst according to any one of claims 1 to 4, wherein the MFI type zeolite before the acid treatment step has a Si / Al molar ratio of 12 to 30.   P-xylene is selectively produced by alkylating or disproportionating benzene and / or toluene in the presence of the MFI-type zeolite catalyst produced by the method according to any one of claims 1 to 5. A process for producing p-xylene,

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