Method for regulating metal falling position by activating ammonium type ZSM-5 molecular sieve through low-temperature plasma and application of method

Abstract

The invention provides a method for activating an ammonium type ZSM-5 molecular sieve by using low-temperature plasma, and mainly solves the problems of collapse of a molecular sieve framework, reduction of acidity and influence on activity in the traditional high-temperature calcination activation process. According to the method, the synthesized ammonium type molecular sieve is placed in the low-temperature plasma for treatment, and the ammonium type ZSM-5 molecular sieve is converted into the hydrogen type molecular sieve with catalytic activity by utilizing collision and bombardment effects between high-energy particles generated by the plasma and the molecular sieve, so that the activation temperature is reduced, and the damage to the framework structure of the molecular sieve is reduced; more framework Al is reserved, the acidity of the molecular sieve is improved, and the catalytic activity and the target product selectivity of low-carbon olefin prepared by cracking light alkane through the molecular sieve can be improved. The method for activating the molecular sieve is high in efficiency, mild in condition, low in energy consumption and simple and convenient to operate, more B acid sites exist, and the performance of cracking C4-C10 light alkane to prepare low-carbon olefin is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the chemical industry field, and particularly relates to a new method for quickly deammoniating ammonium-type ZSM-5 molecular sieve into catalytically active hydrogen-type ZSM-5 molecular sieve at low temperature, with high efficiency, low energy consumption. Background Art

[0002] With the continuous development of renewable energy technologies, the demand for lower-carbon olefins (especially ethylene and propylene) in industries such as batteries and electronic materials is increasing. As an efficient lower-carbon olefin production technology, catalytic cracking of naphtha significantly reduces energy consumption and carbon emissions compared with the steam cracking process. In addition, by adjusting the properties of the catalyst, the product distribution of the catalytic cracking process can be flexibly controlled to better meet market demands. The development and optimization of the catalyst are the core of this process, directly determining the selectivity and yield of the product and the overall efficiency of the process.

[0003] ZSM-5 molecular sieve containing abundant acidic sites is one of the most widely used catalytic materials in catalytic cracking. The unique cross-shaped ten-membered ring system of sinusoidal pores and straight pores in ZSM-5 molecular sieve endows it with the ability of "shape-selective catalysis", which can improve the selectivity of lower-carbon olefins (C2-C4). During the synthesis of ZSM-5 molecular sieve, after obtaining the ammonium-type molecular sieve through ion exchange, it needs to be calcined at a high temperature (>500 °C) to convert it into a hydrogen-type ZSM-5 molecular sieve with acid catalytic activity. However, the high temperature will damage the framework structure of the molecular sieve, thereby affecting its stability and acid properties and reducing the catalytic cracking activity.

[0004] Plasma is a highly reactive substance composed of high-energy particles such as high-energy electrons, ions, atoms, molecules, and free radicals. It has unique physical and chemical properties and is known as the fourth state of matter. According to the energy state of its system and the relationship between the electron temperature and the bulk temperature, it can be divided into thermal plasma and cold plasma. Thermal plasma is often applied to high-energy physical processes such as nuclear fusion and aerospace engines, while cold plasma is widely used in research and production processes. In cold plasma, dielectric barrier discharge (DBD) technology is a form of non-equilibrium gas discharge. By inserting an insulating medium into the discharge space, when a sufficiently high alternating voltage is applied, the gas between the electrodes will be broken down to generate discharge, forming dielectric barrier discharge. During the discharge process, the temperature of high-energy particles can reach tens of thousands of degrees, but the system temperature remains between room temperature and 200 °C. The unique physical and chemical properties of DBD enable it to play a unique role in catalyst synthesis and surface modification. For example, plasma etching treatment of nickel-based electrolytic water catalytic materials improves their electrocatalytic oxygen evolution performance (CN118326434A), and plasma modification of iron-doped nickel sulfide improves its degradation ability for acid lake blue A (CN115520938B). The process of treating catalytic materials with DBD plasma has the advantages of low temperature, low energy consumption, simple operation, and high efficiency, and is a very promising method for molecular sieve activation. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for gently activating ammonium-type ZSM-5 molecular sieve to solve the problems existing in the calcination activation process, such as the easy destruction of the molecular sieve framework structure, reduction of acid amount, high energy consumption, and long time, and at the same time improve the performance of ZSM-5 molecular sieve in catalyzing the cracking of light alkanes.

[0006] To solve the above problems, the present invention uses dielectric barrier discharge plasma treatment to replace the calcination process, and activates ammonium-type ZSM-5 molecular sieve under certain conditions to obtain hydrogen-type ZSM-5 molecular sieve. The specific technical solutions are as follows:

[0007] 1) Place ammonium-type ZSM-5 molecular sieve in a dielectric barrier discharge plasma reactor;

[0008] 2) Perform plasma discharge treatment under certain preset conditions

[0009] Preferably, the silicon-aluminum ratio of ammonium-type ZSM-5 molecular sieve is 50, 100, 200, 300.

[0010] Among them, the specific conditions of dielectric barrier discharge plasma include:

[0011] The plasma discharge mode is dielectric barrier discharge;

[0012] The atmosphere of the plasma treatment is air;

[0013] Preferably, the input voltage of the plasma power supply is 100 - 200V;

[0014] Preferably, the input current of the plasma power supply is 1 - 2A;

[0015] Preferably, the plasma treatment time is 20 - 80 min;

[0016] The beneficial effects that can be produced by this application include:

[0017] 1) The activation method of the ammonium-type ZSM-5 molecular sieve provided by this application uses dielectric barrier discharge plasma with air as the discharge atmosphere to activate the ammonium-type ZSM-5 molecular sieve into a hydrogen-type molecular sieve, retaining the molecular sieve framework structure and framework Al, and significantly improving the acid properties and B / L acid ratio of the hydrogen-type ZSM-5 molecular sieve.

[0018] 2) The activation method of the ammonium-type ZSM-5 molecular sieve provided by this application significantly improves the performance of the activated hydrogen-type ZSM-5 molecular sieve in catalyzing the cracking of light alkanes to produce light olefins. Description of the Drawings

[0019] To more clearly illustrate the technical solutions of the present invention, the plasma activation process of the present invention and some characterization results in the examples are introduced with the accompanying drawings.

[0020] Figure 1 It is a schematic diagram of the plasma activation process of the present invention.

[0021] Description of the Reference Numerals in the Drawings

[0022] 1 - Plasma high-voltage power supply 2 - High-voltage electrode 3 - Grounding electrode

[0023] 4 - Quartz barrier medium 5 - Plasma 6 - Ammonium-type ZSM-5 molecular sieve

[0024] Figure 2 It is the Fourier transform infrared spectroscopy spectrum of the hydrogen-type ZSM-5 molecular sieve obtained in Examples 1 - 3.

[0025] Figure 3 It is the Fourier transform infrared spectroscopy spectrum of the hydrogen-type ZSM-5 molecular sieve obtained in Examples 3, 7 - 9.

[0026] Figure 4 It is the 27 Al NMR spectrum of the hydrogen-type ZSM-5 molecular sieve obtained in Example 3 and Comparative Example 1.

[0027] Figure 5 It is the pyridine infrared spectrum of the hydrogen-type ZSM-5 molecular sieve obtained in Example 3 and Comparative Example 1. Detailed implementation manners

[0028] The present invention will be described in detail below through specific examples, but the present application is not limited to the listed specific embodiments.

[0029] In the examples and comparative examples of the present application, ammonium-type ZSM-5 molecular sieves with different silicon-aluminum ratios were synthesized by a hydrothermal method. The specific synthesis steps are as follows:

[0030] Step 1: Weigh tetraethyl orthosilicate (TEOS, 25 g), tetrapropylammonium hydroxide (TPAOH, 40 wt% aqueous solution, 15 g) and add them to deionized water (H 2 O, 47.8 g). Stir at 80 °C for 24 h to fully hydrolyze and form a uniform mixed solution A.

[0031] Step 2: Add aluminum nitrate nonahydrate (Al(NO 3 ) 3 ·9H 2 O, with addition amounts of 0.1125 g, 0.225 g, 0.45 g, 0.9 g respectively to synthesize ZSM-5 molecular sieves with different Si / Al ratios), sodium hydroxide (NaOH, 0.48 g), and deionized water (H 2 O, 8 g), and stir evenly to form a uniform mixed solution B.

[0032] Step 3: Transfer the mixed solution B obtained in Step 2 to a stainless-steel hydrothermal autoclave with a polytetrafluoroethylene inner lining, and crystallize at 170 °C for 24 h. Centrifuge, wash and collect the solid product, dry at 110 °C for 10 h, transfer to a muffle furnace and calcine at 550 °C for 3 h to obtain Na-type ZSM-5 molecular sieve.

[0033] Step 4: Transfer the Na-type ZSM-5 molecular sieve obtained in Step 3 to a flask, and perform ammonium ion exchange with 1 M ammonium chloride solution (solid-liquid ratio of 1:10) for 4 h, and repeat twice. Centrifuge, wash and collect the solid product, dry at 110 °C for 10 h to obtain ammonium-type ZSM-5 molecular sieve.

[0034] In the context of this specification, including all examples and comparative examples, the crystallinity of the molecular sieve was measured by an X-ray diffractometer from Rigaku Corporation, Japan. Using Cu-Kα radiation, the operating voltage was 40 KV, the current was 20 mA, the scanning speed was 10 ° / min, the scanning range was 2θ = 5 - 80 °, and the step size was 0.01 °. The relative crystallinity was calculated with ammonium-type ZSM-5 molecular sieve with a silicon-aluminum ratio of 300 as the reference.

[0035] In the context of this specification, including all the examples and comparative examples, the ammonium removal effect of the molecular sieve was detected by a Nicolet-380 Fourier transform infrared spectrometer from Thermo Fisher Scientific, USA. The scanning resolution was 4 cm -1 , and the scanning range was 4000 - 400 cm -1 .

[0036] In the context of this specification, including all the examples and comparative examples, the framework aluminum content and non-framework aluminum content of the molecular sieve were determined by an AVANCE III HD 500 MHz nuclear magnetic resonance spectrometer from Bruker Corporation 27 using Al NMR.

[0037] In the context of this specification, including all the examples and comparative examples, the acid type of the molecular sieve was detected by in-situ pyridine infrared (Py-IR) using a Nicolet-710 Fourier transform infrared spectrometer from Thermo Fisher Scientific, USA. After pressing 20 mg of the sample to be tested into a tablet, it was fixed in an in-situ infrared reactor, pretreated under vacuum at 400 °C for 1 h, adsorbed pyridine vapor for 3 min after cooling to room temperature, and then the infrared spectra were recorded at 150 °C and 300 °C. The scanning resolution was 4 cm -1 , the number of scans was 64 times, and the scanning range was 4000 - 400 cm -1 .

[0038]

Example 1

[0039] Take 1 g of ammonium-type ZSM-5 molecular sieve with a silica-alumina ratio of 50 and place it evenly in a dielectric barrier discharge plasma reactor. Set the plasma input voltage to 120 V, the input current to 1.5 A, and treat for 30 min to obtain a hydrogen-type ZSM-5 molecular sieve. Examine the ammonium removal effect of the molecular sieve and evaluate its performance in cracking n-hexane.

[0040]

Example 2

[0041] Take 1 g of ammonium-type ZSM-5 molecular sieve with a silica-alumina ratio of 50 and place it evenly in a dielectric barrier discharge plasma reactor. The plasma input voltage is 120 V, the input current is 1.5 A, and treat for 45 min to obtain a hydrogen-type ZSM-5 molecular sieve. Examine the ammonium removal effect of the molecular sieve and evaluate its performance in cracking n-hexane.

[0042]

Example 3

[0043] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 50 and evenly place it in a dielectric barrier discharge plasma reactor. The plasma input voltage is 120 V, the input current is 1.5 A, and it is treated for 60 min to obtain hydrogen-type ZSM-5 zeolite. Examine the properties of the zeolite such as ammonium removal effect, crystallinity, framework aluminum content, and acid properties, and evaluate its performance in cracking n-hexane.

[0044]

Example 4

[0045] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 100 and evenly place it in a dielectric barrier discharge plasma reactor. The plasma input voltage is 120 V, the input current is 1.5 A, and it is treated for 60 min to obtain hydrogen-type ZSM-5 zeolite. Examine the properties of the zeolite such as crystallinity, framework content, and acid properties, and evaluate its performance in cracking n-hexane.

[0046]

Example 5

[0047] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 200 and evenly place it in a dielectric barrier discharge plasma reactor. The plasma input voltage is 120 V, the input current is 1.5 A, and it is treated for 60 min to obtain hydrogen-type ZSM-5 zeolite. Examine the properties of the zeolite such as crystallinity, framework aluminum content, and acid properties, and evaluate its performance in cracking n-hexane.

[0048]

Example 6

[0049] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 300 and evenly place it in a dielectric barrier discharge plasma reactor. The plasma input voltage is 120 V, the input current is 1.5 A, and it is treated for 60 min to obtain hydrogen-type ZSM-5 zeolite. Examine the properties of the zeolite such as crystallinity, framework aluminum content, and acid properties, and evaluate its performance in cracking n-hexane.

[0050]

Example 7

[0051] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 50 and evenly place it in a dielectric barrier discharge plasma reactor. The plasma input voltage is 100 V, the input current is 1.5 A, and it is treated for 60 min to obtain hydrogen-type ZSM-5 zeolite. Examine the ammonium removal effect of the zeolite and evaluate its performance in cracking n-hexane.

[0052]

Example 8

[0053] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 50 and evenly place it in a dielectric barrier discharge plasma reactor. The plasma input voltage is 80 V, the input current is 1.5 A, and it is treated for 60 min to obtain hydrogen-type ZSM-5 zeolite. Examine the ammonium removal effect of the zeolite and evaluate its performance in cracking n-hexane.

[0054]

Example 9

[0055] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 50 and evenly place it in a dielectric barrier discharge plasma reactor. The plasma input voltage is 60 V, the input current is 1.5 A, and it is processed for 60 min to obtain hydrogen-type ZSM-5 zeolite. Examine the ammonium removal effect of the zeolite and evaluate its performance in cracking n-hexane.

[0056]

Example 10

[0057] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 50 and evenly place it in a dielectric barrier discharge plasma reactor. The plasma input voltage is 120 V, the input current is 1.5 A, and it is processed for 60 min to obtain hydrogen-type ZSM-5 zeolite. Examine the ammonium removal effect of the zeolite and evaluate its performance in cracking n-butane.

[0058]

Example 11

[0059] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 50 and evenly place it in a dielectric barrier discharge plasma reactor. The plasma input voltage is 120 V, the input current is 1.5 A, and it is processed for 60 min to obtain hydrogen-type ZSM-5 zeolite. Examine the ammonium removal effect of the zeolite and evaluate its performance in cracking n-decane.

[0060]

Comparative Example 1

[0061] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 50 and place it in a muffle furnace. Calcinate it at 550 °C for 3 h under an air atmosphere, examine properties such as the crystallinity of the zeolite, the content of framework aluminum, and the acid properties, and evaluate its performance in cracking n-hexane.

[0062]

Comparative Example 2

[0063] The ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 100 is placed in a muffle furnace and calcined at 550 °C for 3 h under an air atmosphere. Examine properties such as the crystallinity of the zeolite, the content of framework aluminum, and the acid properties, and evaluate its performance in cracking n-hexane.

[0064]

Comparative Example 3

[0065] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 200 and place it in a muffle furnace. Calcinate it at 550 °C for 3 h under an air atmosphere. Examine properties such as the crystallization of the zeolite, the content of framework aluminum, and the acid properties, and evaluate its performance in cracking n-hexane.

[0066]

Comparative Example 4

[0067] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 300 and place it in a muffle furnace. Calcinate it at 550 °C for 3 h under an air atmosphere. Examine the properties such as the crystallinity of the zeolite, the framework aluminum content, and the acid properties, and evaluate its performance in cracking n-hexane.

[0068]

Comparative Example 5

[0069] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 50 and place it in a muffle furnace. Calcinate it at 550 °C for 3 h under an air atmosphere. Examine the properties such as the crystallinity of the zeolite, the framework aluminum content, and the acid properties, and evaluate its performance in cracking n-butane.

[0070]

Comparative Example 6

[0071] Take 1 g of ammonium-type ZSM-5 zeolite with a silica-alumina ratio of 50 and place it in a muffle furnace. Calcinate it at 550 °C for 3 h under an air atmosphere, and examine the properties such as the crystallinity of the zeolite, the framework aluminum content, and the acid properties, and evaluate its performance in cracking n-decane.

[0072] Table 1. Characterization results and catalytic light hydrocarbon cracking performance of the activated hydrogen-type ZSM-5 zeolites in Examples 3-6, 10-11 and Comparative Examples 1-6

[0073]

[0074] As can be seen from Table 1, by comparing Example 3 with Comparative Example 1, Example 4 with Comparative Example 2, Example 5 with Comparative Example 3, and Example 6 with Comparative Example 4, it can be known that the method of activating zeolite by plasma in the present invention can effectively reduce the damage to the zeolite structure and improve the relative crystallinity of the hydrogen-type ZSM-5 zeolite.

[0075] From Table 1 and Figure 4 , Figure 5 it can be seen that compared with the traditional calcination activation, the method of the present invention can regulate the location of framework aluminum, and significantly improve the framework aluminum content, B acid amount and total acid amount of the hydrogen-type ZSM-5 zeolite.

[0076] As can be seen from Table 1, the hydrogen-type ZSM-5 zeolite activated by the method of the present invention has better catalytic activity in the application of catalytic cracking of light alkanes compared with the traditional calcination method, and improves the conversion rate of light alkanes and the yield of light olefins.

Claims

1. A method for regulating metal placement by low-temperature plasma activated ammonium ZSM-5 molecular sieve, characterized in that The synthesized ammonium type molecular sieve is placed in a low-temperature plasma reactor and activated under certain conditions to obtain a hydrogen type ZSM-5 molecular sieve with metal Al distributed in the framework and having catalytic activity.

2. A method for regulating metal placement by low temperature plasma activated ammonium ZSM-5 molecular sieve according to claim 1, characterized in that: The molecular sieve framework contains silicon and aluminum elements and is an ammonium-type ZSM-5 microporous or mesoporous molecular sieve that has undergone ion exchange.

3. The method for controlling metal placement by low temperature plasma activated ammonium ZSM-5 molecular sieve according to claim 1, characterized in that: The silicon-aluminum ratio of the molecular sieve is 50-300.

4. The method for controlling metal placement by low temperature plasma activated ammonium ZSM-5 molecular sieve according to claim 1, characterized in that: The low-temperature plasma is generated by dielectric barrier discharge.

5. The method for controlling metal placement by low temperature plasma activated ammonium ZSM-5 molecular sieve according to claim 1, characterized in that: The atmosphere for plasma activation is air.

6. The method for controlling metal placement by low temperature plasma activated ammonium ZSM-5 molecular sieve according to claim 1, characterized in that: The input voltage of the plasma power supply is 100-200V, and the input current is 1-2A.

7. The method for controlling metal placement by low temperature plasma activated ammonium ZSM-5 molecular sieve according to claim 1, characterized in that: The dielectric barrier discharge gap of the plasma reactor is 8 mm.

8. The method for controlling metal placement by low temperature plasma activated ZSM-5 molecular sieve according to claim 1, characterized in that: The plasma treatment time is 20-80 minutes.

9. A hydrogen-type ZSM-5 molecular sieve activated according to claim 1.

10. Use of the hydrogen-type ZSM-5 molecular sieve as claimed in claim 9 in catalyzing cracking of light alkanes, characterized in that: The light alkane is one of C4-C10 alkanes, and the process conditions for the catalytic cracking reaction of the light alkane are: reaction temperature 500-700°C, mass space velocity 1-2h -1 .

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