Preparation method of hierarchical pore H-type ZSM-5 molecular sieve loaded manganese samarium metal oxide

Abstract

The invention relates to a preparation method of a hierarchical pore H-type ZSM-5 molecular sieve loaded manganese samarium metal oxide, which belongs to the field of catalytic material preparation, and by investigating the reaction performance of the hierarchical pore H-type ZSM-5 molecular sieve loaded manganese samarium metal oxide on propane catalytic combustion, compared with commercial gas-phase S O < 2 > and conventional microporous H-type ZSM-5 molecular sieves, the catalytic combustion performance of the hierarchical pore H-type ZSM-5 molecular sieve is greatly improved. The H-type ZSM-5 carrier prepared by the invention has a typical micro-mesoporous hierarchical porous structure and a higher specific surface area, is beneficial to uniform dispersion of manganese-samarium composite oxide nanoparticles, and remarkably improves the catalytic activity of the catalyst. The catalyst can completely convert propane into carbon dioxide and water at the temperature of 350 DEG C, no by-product is generated, the excellent propane catalytic combustion performance is shown, the mass transfer efficiency of the molecular sieve is remarkably improved through the design of the hierarchical pore structure, macromolecular reactants can more smoothly enter and exit the catalyst and effectively make contact with active sites, and the catalytic combustion efficiency of propane is improved. Therefore, the catalytic performance is improved.

Description

Technical Field

[0001] The invention relates to the field of catalytic material preparation, and in particular to a method for preparing a multi-level pore H-type ZSM-5 molecular sieve loaded with manganese and samarium metal oxide. Background Art

[0002] ZSM-5 molecular sieve, as a type of microporous material with excellent shape-selective catalytic performance, has shown broad application prospects in many fields such as petroleum refining, fine chemical synthesis, and environmental protection since its introduction in the 1970s due to its unique three-dimensional cross-channel structure, good thermal stability and hydrothermal stability, and adjustable acidity. However, the limitation of the microporous structure is that for macromolecular reactants, the diffusion resistance is large, which easily leads to carbon deposition and affects the activity and life of the catalyst. Summary of the invention

[0003] In order to solve the problem in the prior art that the microporous structure of the existing ZSM-5 molecular sieve has a large diffusion resistance for macromolecular reactants, which easily leads to carbon deposition and affects the activity and life of the catalyst, the present application provides a preparation method of a multi-level pore H-type ZSM-5 molecular sieve loaded with manganese and samarium metal oxide to solve the above problem.

[0004] In order to achieve the above purpose, the technical solution adopted in this application is:

[0005] A method for preparing a multi-level pore H-type ZSM-5 molecular sieve loaded with manganese and samarium metal oxide, the method comprising:

[0006] (1) Weigh manganese nitrate tetrahydrate (Mn(NO3)2) and samarium nitrate (Sm(NO3)3), dissolve them in deionized water, and stir them to form a metal salt solution;

[0007] (2) Weighing an H-type ZSM-5 molecular sieve carrier and placing it in a metal salt solution, stirring and mixing it evenly, placing it in a 70° C. water and stirring until the water evaporates to obtain a solid product;

[0008] The preparation method of the H-type ZSM-5 molecular sieve carrier comprises:

[0009] Sodium aluminate (NaA l O2) is dissolved in deionized water to form a clear solution, tetrapropylammonium hydroxide (TPAOH) and tetraethyl orthosilicate (TEOS) are added to the clear solution, stirred and mixed, and aged to obtain an initial mixed solution;

[0010] The initial mixed solution is transferred to a hydrothermal reactor, and after crystallization and cooling, it is centrifugally washed to neutrality, and after drying, it is placed in a muffle furnace for heating to obtain Na-type ZSM-5 powder;

[0011] The Na-type ZSM-5 powder is ion exchanged with an ammonium acetate solution, and then centrifuged, dried, and calcined in a muffle furnace to obtain a multi-level pore H-type ZSM-5 molecular sieve;

[0012] (3) The solid product was placed in an oven to dry overnight, and then placed in a muffle furnace for calcination to obtain a multi-level pore H-type ZSM-5 molecular sieve loaded with manganese and samarium oxide.

[0013] As a further improvement of the present invention, the aging temperature is 50-100°C.

[0014] As a further improvement of the present invention, the mass ratio of Mn element to Sm element in Mn(NO3)2 and Sm(NO3)3 is 4:1.

[0015] As a further improvement of the present invention, the total mass of the Mn and Sm elements is 10% by mass fraction compared with the H-type ZSM-5 molecular sieve carrier.

[0016] Compared with the prior art, the technical solution provided by the present invention has the following advantages and effects:

[0017] 1. The design of the multi-level pore structure in this application, i.e., the introduction of mesopores on the basis of micropores, significantly improves the mass transfer efficiency of the molecular sieve, allowing macromolecular reactants to enter and exit the catalyst more smoothly and effectively contact the active sites, thereby improving the catalytic performance. H-type ZSM-5 molecular sieve, i.e., replacing metal cations (such as sodium ions) in the molecular sieve with hydrogen ions through ion exchange, further enhances its acidity and catalytic activity, and is suitable for a variety of acid-catalyzed reactions.

[0018] 2. The manganese-samarium composite metal oxide in this application is widely used in the field of environmental catalysis due to its high activity, good thermal stability and cost-effectiveness in redox reactions. In the propane catalytic combustion reaction, the manganese-samarium composite metal oxide can provide abundant active sites to promote the activation and oxidation of propane molecules, converting them into harmless carbon dioxide and water. At the same time, the manganese-samarium composite metal oxide also has good anti-carbon deposition performance and can maintain high activity during long-term catalytic processes. The composite catalyst formed by loading the manganese-samarium composite metal oxide on a multi-level pore H-type ZSM-5 molecular sieve combines the acid activation effect of the molecular sieve, the pore adsorption characteristics and the redox properties of the manganese-samarium metal oxide, and achieves a significant improvement in the catalytic combustion efficiency of propane. The main technical advantages of the catalyst include:

[0019] (1) Multi-level pore structure design of molecular sieve carrier: By precisely controlling the synthesis conditions, introducing the mesoporous structure, optimizing the pore distribution, and improving the mass transfer efficiency, propane molecules can enter the catalyst more efficiently;

[0020] (2) Effective loading technology: using an over-impregnation process to ensure that manganese and samarium metal oxides are evenly and firmly loaded on the surface and pores of the molecular sieve, maximizing the use of active sites and improving catalytic efficiency;

[0021] (3) Anti-carbon deposition performance: The synergistic effect of manganese and samarium metal oxides and the multi-level pore structure of ZSM-5 molecular sieve effectively reduces the formation of carbon deposition during the reaction and prolongs the service life of the catalyst;

[0022] (4) Environmentally friendly: The propane catalytic combustion process does not cause secondary pollution, and the generated carbon dioxide and water are harmless to the environment, which is in line with the concept of green chemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 The X-ray diffraction (XRD) diagram of the H-type ZSM-5 molecular sieve carrier in the preparation method of the multi-level pore H-type ZSM-5 molecular sieve loaded with manganese and samarium metal oxide provided in an embodiment of the present invention;

[0025] Figure 2 A scanning electron microscope (SEM) image of the multi-level pore H-type ZSM-5 molecular sieve provided in an embodiment of the present invention;

[0026] Figure 3 The nitrogen adsorption and desorption isotherms and pore size distribution diagram of the multi-level pore H-type ZSM-5 molecular sieve provided in the embodiment of the present invention;

[0027] Figure 4 The propane catalytic combustion activity and related conversion temperature diagram of the H-type ZSM-5 molecular sieve carrier in the preparation method of the multi-level pore H-type ZSM-5 molecular sieve loaded with manganese and samarium metal oxide provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application, and ordinary technicians in the field can understand the specific meanings of the above terms in the present application according to specific circumstances.

[0030] Embodiment 1:

[0031] Weigh 0.165g of sodium aluminate and dissolve it in 40mL of deionized water to form a clear solution. Slowly add 5g of tetrapropylammonium hydroxide template and 8.34g of tetraethyl orthosilicate to the solution and stir at room temperature for 30min until it is evenly dispersed. Transfer the above mixture to a hydrothermal reactor and crystallize at 180℃ for 72h, then cool to room temperature, centrifuge and wash until neutral, dry in an oven at 100℃, place in a muffle furnace, and heat at 2℃min -1 The temperature was raised to 550℃ and calcined for 5h to obtain Na-type ZSM-5 powder. -1 The dried powder was ion exchanged three times with ammonium acetate solution, stirred at 80 °C for 2 h each time, centrifuged and dried, and then heated in a muffle furnace at 2 °C min -1 The temperature was raised to 550°C and calcined for 5 hours to obtain a multi-level pore H-type ZSM-5 molecular sieve, which was marked as HZ5.

[0032] Weigh 0.7310g of manganese nitrate tetrahydrate (Mn(NO3)2) and 0.1182g of samarium nitrate hexahydrate (Sm(NO3)3) respectively and dissolve them in 30mL of deionized water, and stir them evenly to form a metal salt solution. Weigh 2.0g of HZ5 molecular sieve carrier and place it in the metal salt solution, stir and mix evenly, and place it in 70℃ water and stir until the water evaporates. Place the above solid product in a 60℃ oven to dry overnight, and then place it in a muffle furnace at 5℃min -1 The temperature was raised to 500°C and calcined for 5 hours. The obtained catalyst was marked as MnSm / HZ5.

[0033] A fixed bed reactor at atmospheric pressure was loaded with 150 mg of catalyst particles (40-60 mesh) to investigate its low-temperature catalytic combustion activity of propane. The total gas flow rate was 50 mL min -1 , containing 0.2% propane, 2% oxygen and 97.8% argon, corresponding to a mass space velocity of 20000 mL g -1 h -1 The catalytic reaction products are only carbon dioxide and water, and the reaction temperature (T 90 ) is 371℃.

[0034] Embodiment 2:

[0035] Weigh 0.165g of sodium aluminate and dissolve it in 40mL of deionized water to form a clear solution. Slowly add 5g of tetrapropylammonium hydroxide template and 8.34g of tetraethyl orthosilicate to the solution, stir at room temperature for 30min until it is evenly dispersed, and then age at 50℃ for 3h. Transfer the above mixture to a hydrothermal reactor, crystallize at 180℃ for 72h, then cool to room temperature, centrifuge and wash until neutral, dry in an oven at 100℃, place in a muffle furnace, and heat at 2℃min. -1 The temperature was raised to 550℃ and calcined for 5h to obtain Na-type ZSM-5 powder. -1 The dried powder was ion exchanged three times with ammonium acetate solution, stirred at 80 °C for 2 h each time, centrifuged and dried, and then heated in a muffle furnace at 2 °C min -1 The temperature was raised to 550°C and calcined for 5 hours to obtain a multi-level pore H-type ZSM-5 molecular sieve, which was marked as HZ5 / 50.

[0036] Weigh 0.7310g of manganese nitrate tetrahydrate (Mn(NO3)2) and 0.1182g of samarium nitrate hexahydrate (Sm(NO3)3) respectively and dissolve them in 30mL of deionized water, and stir them evenly to form a metal salt solution. Weigh 2.0g of HZ5 / 50 molecular sieve carrier and place it in the metal salt solution, stir and mix evenly, and place it in 70℃ water and stir until the water evaporates. Place the above solid product in a 60℃ oven to dry overnight, and then place it in a muffle furnace at 5℃min -1 The temperature was raised to 500°C and calcined for 5 hours. The obtained catalyst was marked as MnSm / HZ5 / 50.

[0037] A fixed bed reactor at atmospheric pressure was loaded with 150 mg of catalyst particles (40-60 mesh) to investigate its low-temperature catalytic combustion activity of propane. The total gas flow rate was 50 mL min -1 , containing 0.2% propane, 2% oxygen and 97.8% argon, corresponding to a mass space velocity of 20000 mL g -1 h -1 The catalytic reaction products are only carbon dioxide and water, and the reaction temperature (T 90 ) is 363℃.

[0038] Embodiment 3:

[0039] Weigh 0.165g of sodium aluminate and dissolve it in 40mL of deionized water to form a clear solution. Slowly add 5g of tetrapropylammonium hydroxide template and 8.34g of tetraethyl orthosilicate to the solution, stir at room temperature for 30min until it is evenly dispersed, and then age at 100℃ for 3h. Transfer the above mixture to a hydrothermal reactor, crystallize at 180℃ for 72h, then cool to room temperature, centrifuge and wash until neutral, dry in an oven at 100℃, place in a muffle furnace, and heat at 2℃min. -1 The temperature was raised to 550℃ and calcined for 5h to obtain Na-type ZSM-5 powder. -1 The dried powder was ion exchanged three times with ammonium acetate solution, stirred at 80 °C for 2 h each time, centrifuged and dried, and then heated in a muffle furnace at 2 °C min -1 The temperature was raised to 550°C and calcined for 5 hours to obtain a hierarchical pore H-type ZSM-5 molecular sieve, which was marked as HZ5 / 100.

[0040] Weigh 0.7310g of manganese nitrate tetrahydrate (Mn(NO3)2) and 0.1182g of samarium nitrate hexahydrate (Sm(NO3)3) respectively and dissolve them in 30mL of deionized water, and stir them evenly to form a metal salt solution. Weigh 2.0g of HZ5 / 100 molecular sieve carrier and place it in the metal salt solution, stir and mix evenly, and place it in 70℃ water and stir until the water evaporates. Place the above solid product in a 60℃ oven to dry overnight, and then place it in a muffle furnace at 5℃min -1 The temperature was raised to 500°C and calcined for 5 hours. The obtained catalyst was marked as MnSm / HZ5 / 100.

[0041] A fixed bed reactor at atmospheric pressure was loaded with 150 mg of catalyst particles (40-60 mesh) to investigate its low-temperature catalytic combustion activity of propane. The total gas flow rate was 50 mL min -1 , containing 0.2% propane, 2% oxygen and 97.8% argon, corresponding to a mass space velocity of 20000 mL g -1 h -1 The catalytic reaction products are only carbon dioxide and water, and the reaction temperature (T 90 ) is 347℃.

[0042] Embodiment 4:

[0043] Weigh 0.7310g of manganese nitrate tetrahydrate (Mn(NO3)2) and 0.1182g of samarium nitrate hexahydrate (Sm(NO3)3) respectively and dissolve them in 30mL of deionized water, and stir them evenly to form a metal salt solution. Weigh 2.0g of commercial grade gas phase SiO2 carrier and place it in the metal salt solution, stir and mix evenly, and place it in 70℃ water and stir until the water evaporates. Place the above solid product in a 60℃ oven to dry overnight, and then place it in a muffle furnace at 5℃min -1 The temperature was raised to 500°C and calcined for 5 hours. The obtained catalyst was marked as MnSm / SiO2.

[0044] A fixed bed reactor at atmospheric pressure was loaded with 150 mg of catalyst particles (40-60 mesh) to investigate its low-temperature catalytic combustion activity of propane. The total gas flow rate was 50 mL min -1 , containing 0.2% propane, 2% oxygen and 97.8% argon, corresponding to a mass space velocity of 20000 mL g -1 h -1 The catalytic reaction products are only carbon dioxide and water, and the reaction temperature (T 90 ) is 400℃.

[0045] According to the attached drawings in the specification Figure 1-Figure 4 The above-mentioned embodiments 1-4 are explained as follows:

[0046] The XRD patterns of the H-type ZSM-5 molecular sieve and the supported manganese-samarium oxide catalyst prepared in Examples 1-4 are as follows: Figure 1 As shown, it can be seen that the H-type ZSM-5 molecular sieve prepared in this example and the manganese and samarium oxide catalyst loaded thereon have a typical MFI topological structure, and no characteristic diffraction peaks of manganese oxide and samarium oxide are detected, indicating good dispersion of the metal oxide component on the carrier surface.

[0047] The scanning electron microscope photograph of the H-type ZSM-5 molecular sieve prepared in Example 1-3 is as follows Figure 2 As shown, it can be seen that the HZ5 molecular sieve prepared in Example 1 has an irregular nano-spherical morphology, and the HZ5 / 50 and HZ5 / 100 molecular sieves after aging treatment in Examples 2 and 3 have more particle protrusions on the surface, showing a mulberry-like morphology.

[0048] The nitrogen adsorption-desorption isotherms and pore size distribution curves of the H-type ZSM-5 molecular sieve prepared in Examples 1-3 are shown in FIG. Figure 3 As shown, it can be seen that all molecular sieves have a large adsorption amount when the relative pressure p / p0 is close to 0, indicating the existence of a large number of micropores; the obvious hysteresis loop that appears indicates the existence of the molecular sieve mesoporous structure; the pore size distribution curve confirms the formation of the micro-mesoporous multi-level pore structure of the molecular sieve carrier.

[0049] The propane catalytic combustion activity of the H-type ZSM-5 molecular sieve and the supported manganese-samarium oxide catalyst prepared in Examples 1-4 is as follows: Figure 4 As shown in the figure, it can be seen that the MnSm / HZ5 / 100 catalyst prepared using the aged HZ5 / 100 molecular sieve carrier exhibits higher catalytic activity than MnSm / HZ5 and MnSm / SiO2. 90 The temperatures were reduced by 24 and 53°C respectively, and the complete conversion temperature of propane was 350°C.

[0050] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a multi-level pore H-type ZSM-5 molecular sieve loaded with manganese and samarium metal oxide, characterized in that: The method comprises: (1) Weigh manganese nitrate tetrahydrate (Mn(NO3)2) and samarium nitrate (Sm(NO3)3), dissolve them in deionized water, and stir them to form a metal salt solution; (2) Weighing an H-type ZSM-5 molecular sieve carrier and placing it in a metal salt solution, stirring and mixing it evenly, placing it in a 70° C. water and stirring until the water evaporates to obtain a solid product; The preparation method of the H-type ZSM-5 molecular sieve carrier comprises: Sodium aluminate (NaAlO2) is dissolved in deionized water to form a clear solution, tetrapropylammonium hydroxide (TPAOH) and tetraethyl orthosilicate (TEOS) are added to the clear solution, stirred, mixed, and aged to obtain an initial mixed solution; The initial mixed solution is transferred to a hydrothermal reactor, and after crystallization and cooling, it is centrifugally washed to neutrality, and after drying, it is placed in a muffle furnace for heating to obtain Na-type ZSM-5 powder; The Na-type ZSM-5 powder is ion exchanged with an ammonium acetate solution, and then centrifuged, dried, and calcined in a muffle furnace to obtain a multi-level pore H-type ZSM-5 molecular sieve; (3) The solid product was placed in an oven to dry overnight, and then placed in a muffle furnace for calcination to obtain a multi-level pore H-type ZSM-5 molecular sieve loaded with manganese and samarium oxide.

2. The preparation method according to claim 1, characterized in that: The aging temperature is 50-100°C.

3. The preparation method according to claim 1, characterized in that: The mass ratio of Mn element to Sm element in Mn(NO3)2 and Sm(NO3)3 is 4:

1.

4. The preparation method according to claim 3, characterized in that: The total mass of Mn and Sm elements is 10% by mass compared to the H-type ZSM-5 molecular sieve carrier.

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