A method for preparing a modified mordenite catalyst, the catalyst prepared thereby, and use thereof

Abstract

The application discloses a preparation method of a modified mordenite catalyst, the catalyst prepared by the method, and application of the catalyst. The preparation method comprises the following steps: 1) adding mordenite into acid, soaking, and roasting to obtain acid-modified mordenite; 2) fully contacting the acid-modified mordenite with TiCl4 vapor to obtain Ti-modified titanium mordenite; 3) mixing the Ti-modified titanium mordenite with tungsten metal salt, zirconium metal salt and molybdenum metal salt in a solution, adding ammonia water to age, filtering out solid, and washing, drying and roasting the solid to obtain a supported catalyst; and 4) immersing the obtained supported catalyst in acid, filtering and roasting to obtain the modified mordenite catalyst. The modified mordenite catalyst has high catalytic activity for catalytic nitration of aromatic hydrocarbons, high product yield, reusability and long service life.

Description

Technical Field

[0001] This invention relates to a catalyst for the catalytic nitration of aromatics and its preparation, and more particularly to a method for preparing a modified mordenite catalyst and the catalyst obtained therefrom, and its applications. Background Technology

[0002] The nitration products of aromatics are widely used in modern chemical industries such as pharmaceuticals, explosives, rubber, dyes, and pesticides, and are a class of organic synthetic products with extremely high industrial value. Currently, most aromatic nitration processes both domestically and internationally utilize mixed acids composed of sulfuric acid and nitric acid. Scholars worldwide have conducted in-depth and extensive research on this method, finding that nitration processes using sulfuric acid as a catalyst offer stable yields and relatively simple reaction processes. However, national regulations on the approval and supervision of hazardous processes such as nitration are becoming increasingly stringent. Furthermore, this technology suffers from problems such as poor selectivity of reaction products, large-scale emissions of waste acid and gas causing environmental pollution, difficulties in waste acid and gas recovery, and severe equipment corrosion. With the continuous promotion of green chemistry and green chemical engineering concepts, developing more efficient, environmentally friendly, and economical green nitration processes, especially green nitration catalysts for aromatic nitration reactions, has extremely high practical significance.

[0003] Catalysts for nitration reactions mainly include molecular sieves, heteropoly acids, clays, solid acids such as solid superacids, ionic liquids, transition metal catalysts, ion exchange resins, and biological enzymes.

[0004] Zeolite molecular sieves have attracted considerable attention from researchers as environmentally friendly solid acid catalysts in the study of aromatic nitration reactions. For example, patent CN117861692A proposes a Lewis acid catalyst using sepiolite as a support. Zeolite molecular sieves are crystalline porous materials composed of tetrahedral coordinating elements such as silicon and aluminum linked by oxygen bridges. They possess unique crystal structures, good hydrothermal stability, and strong acidity. Mordenite, in particular, exhibits excellent heat resistance, acid resistance, and moisture resistance, and is widely used as a catalyst and adsorbent in petrochemical, fine chemical, environmental, and catalytic fields. However, the catalytic activity of zeolite catalysts gradually weakens and deactivates as the reaction proceeds. To improve the catalytic performance of mordenite in aromatic nitration reactions, it is necessary to modify it to enhance its catalytic performance in these reactions. Summary of the Invention

[0005] The purpose of this invention is to propose a method for preparing a modified mordenite zeolite catalyst, the catalyst obtained therefrom, and its application, in order to solve problems such as waste acid treatment, difficulty in product separation, and equipment corrosion in traditional aromatic catalytic nitration reactions.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a modified mordenite zeolite catalyst includes the following steps:

[0008] 1) Add mordenite to acid, soak, and calcine to obtain acid-modified mordenite;

[0009] 2) Acid-modified mordenite was brought into full contact with TiCl4 vapor to obtain Ti-modified titanium mordenite;

[0010] 3) Ti-modified titanium mordenite zeolite was mixed with tungsten metal salt, zirconium metal salt and molybdenum metal salt in solution, ammonia water was added for aging, the solid was filtered out, washed, dried and calcined to obtain a supported catalyst;

[0011] 4) The obtained supported catalyst was immersed in acid, filtered, and then calcined to obtain the modified mordenite zeolite catalyst.

[0012] Crucite, also known as luminescent zeolite, is one of the main mineral components of zeolite minerals. This paper does not specifically limit the type of cressite; various known cressites can be used in this invention without departing from the inventive concept of this application.

[0013] This invention first acid-modifies mordenite and then treats it with TiCl4 steam. By removing aluminum and adding titanium, a Ti-modified titanium mordenite with a porous structure and altered catalytic performance is obtained. After co-precipitation with metals W, Zr, and Mo, a supported metal solid superacid zeolite catalyst can be obtained.

[0014] In a preferred embodiment of the present invention, in step 1), the mordenite is soaked in an acid solution with a concentration of 6-8 mol / L for 3-4 hours.

[0015] Preferably, the roasting conditions in step 1) are 180-90℃ for 2-6 hours.

[0016] In a preferred embodiment of the present invention, step 2) is specifically processed as follows:

[0017] Acid-modified mordenite was placed in a vertical quartz tube reactor, preheated by purging with nitrogen, and then modified by introducing a mixture of TiCl4 and nitrogen steam to obtain Ti-modified titanium mordenite.

[0018] Preferably, the nitrogen preheating conditions are: preheating at 400-600℃ for 3-6 hours;

[0019] Preferably, the volume ratio of TiCl4 to nitrogen in the mixed steam is 1:(3-5); preferably, the temperature of the mixed steam is 500-700℃, and the modification treatment time is 15-24h.

[0020] Preferably, after modification, the nitrogen is purged at a high temperature for a certain period of time, preferably using nitrogen at 500-600℃ for 4-6 hours;

[0021] Preferably, in step 2), the gas flow rate is always maintained at 30-50 ml / min.

[0022] In a preferred embodiment of the present invention, in step 3), the tungsten metal salt is at least one of ammonium tungstate, sodium tungstate, and sodium metatungstate; the zirconium metal salt is at least one of zirconium nitrate, zirconium sulfate, and zirconium chloride; and the molybdenum metal salt is at least one of ammonium molybdate and sodium molybdate.

[0023] Preferably, the mass ratio of Ti-modified titanium mordenite to tungsten metal salt, zirconium metal salt and molybdenum metal salt is 1:(2-5):(2-4):(2-4).

[0024] In a preferred embodiment of the present invention, in step 3), the amount of ammonia water used is adjusted to adjust the pH of the solution to 10-12.

[0025] In a preferred embodiment of the present invention, in step 3), the aging treatment conditions are: treatment at 20-50℃ for 20-30 hours;

[0026] Preferably, in step 3), the calcination conditions are calcination at 550-750℃ for 2-5 hours.

[0027] In a preferred embodiment of the present invention, in step 4), the mordenite is immersed in an acid solution with a concentration of 1-2 mol / L for 10-24 hours.

[0028] Preferably, the roasting conditions in step 4) are 500-700℃ for 2-5 hours.

[0029] In a preferred embodiment of the present invention, in step 1), the acid is one or more of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid.

[0030] Preferably, in step 4), the acid is sulfuric acid and / or phosphoric acid.

[0031] Step 4) Post-treatment of the supported catalyst with sulfuric acid and / or phosphoric acid can stabilize the catalyst structure by forming chelate complexes with metals, thereby reducing sulfate loss from the catalyst and improving the reusability of the catalyst.

[0032] The present invention also provides a modified mordenite zeolite catalyst prepared according to the method described above.

[0033] The present invention also provides the application of a modified mordenite zeolite catalyst prepared according to the method described above in the catalytic nitration reaction of aromatics.

[0034] As a specific example of an aromatic hydrocarbon catalytic nitration reaction provided by the present invention, the process includes the following steps:

[0035] In the presence of the modified mordenite catalyst provided above, benzene and nitric acid are subjected to a nitration reaction; the reaction temperature is 140-160℃ and the pressure is absolute 0.05-0.5 MPa.

[0036] Preferably, the aromatic hydrocarbon is one or more of benzene, toluene, xylene, chlorobenzene, bromobenzene, and dichlorobenzene.

[0037] The modified mordenite catalyst in this invention exhibits high catalytic activity and high product yield in the nitration reaction of aromatics. It is reusable and, compared to traditional sulfuric acid catalysts, can reduce the environmental pollution caused by waste acid emissions during the nitration reaction, reduce equipment corrosion, lower equipment costs, and is beneficial to environmental protection. Attached Figure Description

[0038] Figure 1 The image shows the TEM mapping of the prepared modified mordenite zeolite catalyst. Detailed Implementation

[0039] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0040] Unless otherwise specified, the raw materials and reagents used in the following embodiments of the present invention can be obtained through commercial channels.

[0041]

Example 1

[0042] (1) Add 1g of mordenite to 20mL of 8mol / L hydrochloric acid solution, soak for 3h, filter, wash with deionized water until neutral, dry, and calcine at 180℃ for 4h to obtain acid-modified mordenite.

[0043] (2) The acid-modified mordenite was placed in a vertical quartz tube reactor. It was preheated with nitrogen at 500°C for 5 hours, and then a mixture of TiCl4 and nitrogen at 600°C (volume ratio 1:4) was introduced for 18 hours. Finally, it was purged with nitrogen at 550°C for 5 hours. The gas flow rate was kept at 40 ml / min throughout the process to obtain Ti-modified titanium mordenite.

[0044] (3) Ti-modified titanium mordenite zeolite, ammonium tungstate hexahydrate, zirconium nitrate pentahydrate, and ammonium molybdate tetrahydrate were mixed in water at a mass ratio of 1:2.34:3.73:2.33. After complete dissolution, 12% wt ammonia was slowly added until the pH reached 10. The mixture was stirred for 1 hour and then transferred to a 35°C water bath for aging for 24 hours. After filtration, the mixture was washed with deionized water and anhydrous ethanol until neutral, dried, and calcined at 650°C for 3 hours to obtain the supported catalyst.

[0045] (4) Add 1g of the supported catalyst to 15mL of 2mol / L sulfuric acid solution and soak for 15h. After filtration and drying, calcine at 620℃ for 3h to obtain the modified mordenite zeolite catalyst.

[0046] The TEM-mapping image of the modified mordenite zeolite catalyst prepared in this embodiment is shown below. Figure 1 As shown, the catalyst sample contains W, Zr, and Mo elements, and these elements are evenly distributed.

[0047]

Example 2

[0048] (1) Add 1g of mordenite to 20mL of 6mol / L hydrochloric acid solution, soak for 4h, filter, wash with deionized water until neutral, dry, and calcine at 180℃ for 4h to obtain acid-modified mordenite.

[0049] (2) The acid-modified mordenite was placed in a vertical quartz tube reactor. It was preheated with nitrogen at 500°C for 5 hours, and then a mixture of TiCl4 and nitrogen at 500°C (volume ratio 1:5) was introduced for 24 hours. Finally, it was purged with nitrogen at 550°C for 5 hours. The gas flow rate was kept at 40 ml / min throughout the process to obtain Ti-modified titanium mordenite.

[0050] (3) Ti-modified titanium mordenite zeolite, sodium tungstate dihydrate, zirconium sulfate tetrahydrate, and ammonium molybdate tetrahydrate were mixed in water at a mass ratio of 1:5:3.08:2.33. After complete dissolution, 12% wt ammonia was slowly added until the pH reached 12. The mixture was stirred for 1 hour and then transferred to a 35°C water bath for aging for 24 hours. After filtration, the mixture was washed with deionized water and anhydrous ethanol until neutral, dried, and calcined at 750°C for 5 hours to obtain the supported catalyst.

[0051] (4) Add 1g of the supported catalyst to 15mL of 2mol / L sulfuric acid solution and soak for 10h. After filtration and drying, calcine at 620℃ for 3h to obtain the modified mordenite zeolite catalyst.

[0052]

Example 3

[0053] (1) Add 1g of mordenite to 20mL of 8mol / L hydrochloric acid solution, soak for 3h, filter, wash with deionized water until neutral, dry, and calcine at 180℃ for 6h to obtain acid-modified mordenite.

[0054] (2) The acid-modified mordenite was placed in a vertical quartz tube reactor. It was preheated with nitrogen at 500°C for 3 hours, and then a mixture of TiCl4 and nitrogen at 700°C (volume ratio 1:3) was introduced for 18 hours. Finally, it was purged with nitrogen at 550°C for 4 hours. The gas flow rate was kept at 40 ml / min throughout the process to obtain Ti-modified titanium mordenite.

[0055] (3) Ti-modified titanium mordenite zeolite, ammonium tungstate hexahydrate, zirconium nitrate pentahydrate, and ammonium dimolybdate were mixed in water at a mass ratio of 1:2.34:4:2. After complete dissolution, 12% wt ammonia was slowly added until the pH reached 10. The mixture was stirred for 1 hour and then transferred to a 20°C water bath for aging for 24 hours. After filtration, the mixture was washed with deionized water and anhydrous ethanol until neutral, dried, and calcined at 550°C for 2 hours to obtain the supported catalyst.

[0056] (4) Add 1g of the supported catalyst to 15mL of 1mol / L sulfuric acid solution and soak for 15h. After filtration and drying, calcine at 620℃ for 3h to obtain the modified mordenite zeolite catalyst.

[0057]

Example 4

[0058] (1) Add 1g of mordenite to 20mL of 8mol / L hydrochloric acid solution, soak for 3h, filter, wash with deionized water until neutral, dry, and calcine at 180℃ for 2h to obtain acid-modified mordenite.

[0059] (2) The acid-modified mordenite was placed in a vertical quartz tube reactor. It was preheated with nitrogen at 500°C for 5 hours, and then a mixture of TiCl4 and nitrogen at 600°C (volume ratio 1:4) was introduced for 20 hours. Finally, it was purged with nitrogen at 500°C for 5 hours. The gas flow rate was kept at 50 ml / min throughout the process to obtain Ti-modified titanium mordenite.

[0060] (3) Ti-modified titanium mordenite zeolite, sodium metatungstate monohydrate, zirconium nitrate pentahydrate, and sodium molybdate dihydrate were mixed in water at a mass ratio of 1:3.68:3.73:4. After complete dissolution, 12% wt ammonia was slowly added until the pH reached 10. The mixture was stirred for 1 hour and then transferred to a 50°C water bath for 30 hours of aging. After filtration, the mixture was washed with deionized water and anhydrous ethanol until neutral, dried, and calcined at 650°C for 3 hours to obtain the supported catalyst.

[0061] (4) Add 1g of the supported catalyst to 15mL of 2mol / L sulfuric acid solution and soak for 24h. After filtration and drying, calcine at 620℃ for 3h to obtain the modified mordenite zeolite catalyst.

[0062]

Example 5

[0063] (1) Add 1g of mordenite to 20mL of 8mol / L hydrochloric acid solution, soak for 3h, filter, wash with deionized water until neutral, dry, and calcine at 180℃ for 5h to obtain acid-modified mordenite.

[0064] (2) The acid-modified mordenite was placed in a vertical quartz tube reactor. It was preheated with nitrogen at 600℃ for 5 hours, and then a mixture of TiCl4 and nitrogen at 600℃ (volume ratio 1:4) was introduced for 15 hours. Finally, it was purged with nitrogen at 550℃ for 6 hours. The gas flow rate was kept at 30 ml / min throughout the process to obtain Ti-modified titanium mordenite.

[0065] (3) Ti-modified titanium mordenite zeolite, ammonium tungstate hexahydrate, zirconium oxychloride octahydrate, and ammonium molybdate tetrahydrate were mixed in water at a mass ratio of 1:2:2:3. After complete dissolution, 12% wt ammonia was slowly added until the pH reached 10. The mixture was stirred for 1 hour and then transferred to a 35°C water bath for aging for 20 hours. After filtration, the mixture was washed with deionized water and anhydrous ethanol until neutral, dried, and calcined at 650°C for 3 hours to obtain the supported catalyst.

[0066] (4) Add 1g of the supported catalyst to 15mL of 2mol / L phosphoric acid solution and soak for 15h. After filtration and drying, calcine at 620℃ for 3h to obtain the modified mordenite zeolite catalyst.

[0067] Comparative Example 1

[0068] The catalyst was prepared in essentially the same manner as in Example 1, except that the sulfuric acid modification in step (4) was not performed.

[0069] Comparative Example 2

[0070] The catalyst was prepared in essentially the same manner as in Example 1, except that ammonium tungstate hexahydrate was not added in step (3).

[0071] Comparative Example 3

[0072] The catalyst was prepared in essentially the same manner as in Example 1, except that zirconium nitrate pentahydrate was not added in step (3).

[0073] Comparative Example 4

[0074] The catalyst was prepared in essentially the same manner as in Example 1, except that ammonium molybdate tetrahydrate was not added in step (3).

[0075] Comparative Example 5

[0076] The catalyst was prepared in basically the same way as in Example 1, except that the Ti modification in step (2) was not performed. That is, the supported catalyst in step (3) was directly prepared using the acid-modified mordenite prepared in step (1) as a carrier.

[0077] Benzene-catalyzed nitration reaction and catalytic performance evaluation

[0078] Nitrobenzene was prepared using the catalysts provided in the respective examples and comparative examples as nitration catalysts according to the following methods:

[0079] 5g of catalyst was loaded into a reaction tube (diameter-to-height ratio approximately 5), and the reaction tube was installed in a vertical tube furnace. Heating was started, and the temperature was set to 150℃. After reaching the predetermined temperature, the furnace was purged with nitrogen for 1 hour. The benzene and nitric acid feed pumps were turned on, and the benzene and nitric acid feed rates were controlled at 0.083g / min and 0.05g / min, respectively. The reaction temperature was controlled at 155℃ and the pressure at 0.1MPa. After stabilization for 1 hour, the product was collected in a cold trap and analyzed by gas chromatography. The initial performance evaluation results of the catalyst are shown in Table 1.

[0080] Table 1. Initial performance evaluation of catalysts

[0081] catalyst Nitric acid conversion rate / % Nitrobenzene yield / % Example 1 91.2 89.9 Example 2 90.2 89.1 Example 3 89.9 89.0 Example 4 91.0 89.9 Example 5 90.7 89.7 Comparative Example 1 65.3 63.3 Comparative Example 2 77.9 73.9 Comparative Example 3 86.5 85.0 Comparative Example 4 82.1 80.7 Comparative Example 5 80.7 78.7

[0082] To test the long-term performance of the catalyst, the nitration products were sampled and analyzed after 100 hours of continuous operation with the feed rates of benzene and nitric acid controlled at 0.083 g / min and 0.05 g / min, respectively, the reaction temperature controlled at 155℃, and the pressure controlled at 0.1 MPa. The results of the long-term performance evaluation of the catalyst are shown in Table 2.

[0083] Table 2. Evaluation of the long-term performance of the catalyst

[0084]

[0085]

[0086] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified mordenite zeolite catalyst, characterized in that, Includes the following steps: 1) Add mordenite to acid, soak, and calcine to obtain acid-modified mordenite; 2) Acid-modified mordenite was brought into full contact with TiCl4 vapor to obtain Ti-modified titanium mordenite; 3) Ti-modified titanium mordenite zeolite was mixed with tungsten metal salt, zirconium metal salt and molybdenum metal salt in solution, ammonia water was added for aging, the solid was filtered out, washed, dried and calcined to obtain a supported catalyst; 4) The obtained supported catalyst was immersed in acid, filtered, and then calcined to obtain the modified mordenite zeolite catalyst.

2. The method for preparing the modified mordenite zeolite catalyst according to claim 1, characterized in that, In step 1), the mordenite is soaked in an acid solution with a concentration of 6-8 mol / L for 3-4 hours. Preferably, the roasting conditions in step 1) are 180-90℃ for 2-6 hours.

3. The method for preparing the modified mordenite zeolite catalyst according to claim 1, characterized in that, In step 2), the specific processing method is as follows: Acid-modified mordenite was placed in a vertical quartz tube reactor, preheated by purging with nitrogen, and then modified by introducing a mixture of TiCl4 and nitrogen steam to obtain Ti-modified titanium mordenite. Preferably, the nitrogen preheating conditions are: preheating at 400-600℃ for 3-6 hours; Preferably, the volume ratio of TiCl4 to nitrogen in the mixed steam is 1:(3-5); preferably, the temperature of the mixed steam is 500-700℃, and the modification treatment time is 15-24h. Preferably, after modification, the nitrogen is purged at a high temperature for a certain period of time, preferably using nitrogen at 500-600℃ for 4-6 hours; Preferably, in step 2), the gas flow rate is always maintained at 30-50 ml / min.

4. The method for preparing the modified mordenite zeolite catalyst according to any one of claims 1-3, characterized in that, In step 3), the tungsten metal salt is ammonium tungstate, the zirconium metal salt is at least one of zirconium nitrate, zirconium sulfate, zirconium chloride, and ammonium zirconate, and the molybdenum metal salt is ammonium molybdate. Preferably, the mass ratio of Ti-modified titanium mordenite to tungsten metal salt, zirconium metal salt and molybdenum metal salt is 1:(2-5):(2-4):(2-4).

5. The method for preparing the modified mordenite zeolite catalyst according to any one of claims 1-4, characterized in that, In step 3), the amount of ammonia water used is adjusted to adjust the pH of the solution to 10-12.

6. The method for preparing the modified mordenite zeolite catalyst according to any one of claims 1-5, characterized in that, In step 3), the aging treatment conditions are: treatment at 20-50℃ for 20-30 hours; Preferably, in step 3), the calcination conditions are calcination at 550-750℃ for 2-5 hours.

7. The method for preparing the modified mordenite zeolite catalyst according to any one of claims 1-6, characterized in that, In step 4), the mordenite is immersed in an acid solution with a concentration of 1-2 mol / L for 10-24 hours. Preferably, the roasting conditions in step 4) are 500-700℃ for 2-5 hours.

8. The method for preparing the modified mordenite zeolite catalyst according to any one of claims 1-7, characterized in that, In step 1), the acid is one or more of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid; Preferably, in step 4), the acid is sulfuric acid and / or phosphoric acid.

9. A modified mordenite zeolite catalyst prepared by the method according to any one of claims 1-8.

10. The application of a modified mordenite zeolite catalyst prepared by the method according to any one of claims 1-8 in the catalytic nitration reaction of aromatics.

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