A manganese oxide octahedral molecular sieve Na-OMS-2 catalyst and its preparation method and application

Abstract

The present invention relates to the technical field of catalyst material preparation, and in particular to a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst and a preparation method and application thereof. The catalyst is composed of sodium, manganese and oxygen elements, and is specifically a pore structure. The pore structure is formed by MnO6 octahedrons forming a chain through 2×2 shared edges, and the chains are connected by oxygen atoms at the vertices of the octahedrons. The pores are formed by a single metal ion Na + The preparation process provided by the present invention is simple, the synthesis method is novel, and the pores of the manganese oxide octahedral molecular sieve are single metal ions Na + The present invention uses the prepared manganese oxide octahedral molecular sieve Na‑OMS‑2 catalyst to catalyze the combustion of carbon smoke particles and exhibits high catalytic activity and stability. The preparation method provided has the advantages of simple preparation process, strong practicality, and easy large-scale production.

Description

Technical Field

[0001] The invention discloses a catalyst material preparation technology field, and in particular, relates to a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst and a preparation method and application thereof. Background Art

[0002] In recent years, diesel engines have been widely used in various fields such as transportation, construction, agriculture, manufacturing and power generation due to their advantages such as low fuel consumption, high fuel efficiency, high reliability and safety. However, pollutants such as carbon monoxide, nitrogen oxides, hydrocarbons and soot particles in diesel engine exhaust have caused certain harm to the environment. Among them, soot particles are one of the main sources of PM2.5. PM2.5 can directly enter the human respiratory system and cause a series of respiratory diseases such as asthma, bronchitis, lung cancer, etc., posing a serious threat to human health. Diesel engine exhaust emission aftertreatment technology is one of the most effective ways to remove soot particles, and the development of highly active catalysts is the main task facing diesel engine exhaust aftertreatment technology.

[0003] At present, various types of catalysts such as precious metal catalysts, Mn-based catalysts, Ce-based catalysts and perovskite oxide catalysts are widely used in the catalytic combustion of soot particles. Among them, the manganese oxide octahedral molecular sieve OMS-2 in the Mn-based oxide catalyst has a one-dimensional tunnel structure with rich pores, ion exchange capacity, manganese mixed valence state and lattice oxygen mobility, which makes it show high catalytic activity in the catalytic combustion reaction of soot particles (He HB, Wang YS, Fu WY, et al, Ceramics International, 2021, 47, 33120-33126; Tao LY, Bi XR, Zhang LP, et al, Applied Catalysis A: General, 2020, 605, 117813).

[0004] Manganese oxide octahedral molecular sieve (OMS-2) is a microporous nanostructured material. It is composed of MnO6 octahedrons that form chains through 2×2 shared edges. The chains are connected by oxygen atoms at the vertices of the octahedrons to form a one-dimensional pore structure. It has a unique Mn (Mn 4+ , Mn 3+ , Mn 2+ ) mixed valence state and 2×2 open tunnel structure, the pores of which contain K + To balance the overall valence state and support the pore structure. Studies have shown that the K-OMS-2 catalyst has excellent redox performance and the K contained in its pores + It has strong fluidity, and this synergistic effect makes it show higher catalytic performance in the catalytic combustion of soot particles. +,Na + Mg 2+ ,Al 3+ ,Co 2+ ,Ni 2+ ,Ag + Introducing various metal cations into the pores or on the framework to regulate the catalytic activity of OMS-2 has gradually become a research hotspot (Liu P, Duan JH, Ye Q, et al, Journal of Catalysis, 2018, 367, 115-125; Liu Y, Hou JT, Materials Research Bulletin, 2019, 118, 11049). At present, researchers often use KMnO4 as a raw material to obtain manganese oxide octahedral molecular sieve K-OMS-2, and dope various metal ions into its precursor solution to replace potassium ions in its tunnels or manganese ions in its framework. For example, Wang et al. used KMnO4, Mn(CH3COO)2·4H2O and SbCl3 as raw materials and prepared a series of Sb n -OMS-2 (n = 0.1-0.4) catalyst; Yao et al. used KMnO4, MnSO4·H2O, HNO3 and sodium phosphotungstate as raw materials to synthesize a series of nanorod-shaped OMS-2 catalysts by reflux method; Ming et al. also used reflux method to synthesize a series of nanorod-shaped OMS-2 catalysts by Mn 2+ A series of M-OMS-2(Li + ,Na + Mg 2 + ,Ca 2+ ,Al 3+ ,Fe 3+ ,Co 2+ ,Ni 2+ ,Cu 2+ ,Zn 2+ and Ag +) catalyst; In addition, Hong et al. used MnO2 precursor instead of potassium permanganate as the manganese source, and added an appropriate amount of MNO3 (M=Na, K, Rb, Cs) by heating-rotary evaporation-calcination-washing to prepare a series of M-OMS-2 catalysts (Wang YS, Zhang C, Zhang L, et al, Applied Catalysis A, General, 2022, 641, 118684; Ming SJ, Wang PP, Liu P, et al, Chemical Engineering Journal, 2020, 379, 122287; Yao N, Bi XR, Zhang LP, et al, Molecular Catalysis, 2021, 504, 111499; Hong W, Zhu TL, Sun Y, et al, Environmental Science&Technology, 2019, 53, 13332-13343). In the above-mentioned metal-doped M-OMS-2 catalysts, Na + Tunnel K, which replaced OMS-2 + The crystal stability can be greatly improved, thereby significantly improving the catalytic stability of Na-OMS-2 catalyst in heterogeneous catalytic reactions.

[0005] In summary, it is very meaningful to provide a new preparation method to obtain a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst material. Summary of the invention

[0006] In view of this, the present invention discloses a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst and its preparation method and application. In order to provide a new preparation method to successfully synthesize a Na-OMS-2 catalyst material with stable performance;

[0007] In a first aspect, the present invention provides a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst, wherein the catalyst is composed of sodium, manganese, and oxygen elements.

[0008] Furthermore, the catalyst has a pore structure, wherein the pore structure is formed by MnO6 octahedrons forming chains through 2×2 shared edges, and the chains are connected by oxygen atoms at the vertices of the octahedrons, and the pores are formed by a single metal ion Na + Balance the overall valence and support the pore structure.

[0009] In a second aspect, the present invention provides a method for preparing the above-mentioned manganese oxide octahedral molecular sieve Na-OMS-2 catalyst, comprising: using an aqueous solution of manganese nitrate and sodium nitrate as metal precursors and glucose as a complexing agent, and preparing a layered sodium manganese composite oxide Na2Mn3O7 catalyst by dissolving-mixing-drying-calcining;

[0010] The sodium manganese composite oxide Na2Mn3O7 catalyst is hydrothermally treated to obtain a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst.

[0011] Furthermore, the above preparation method specifically comprises the following steps:

[0012] Dissolve 0.1-5g 50% Mn(NO3)2 and 0.05-2g NaNO3 in 10-50ml water at room temperature. After dissolution, add 0.5-10g glucose to the solution and stir on a magnetic stirrer for 2h.

[0013] The above solution is placed in 60-90°C and dried for 12-24 hours. The dried sample is calcined in a muffle furnace to remove glucose. The solid product obtained is a sodium manganese composite oxide Na2Mn3O7 catalyst;

[0014] Weigh 0.1-2g of the above-mentioned sodium manganese composite oxide Na2Mn3O7 catalyst and put it into 10-200mL of 0-1mol / L HCl solution and stir for 0-60min. After sufficient stirring, transfer it to a high-pressure reactor, and then place it in a 60-200℃ constant temperature drying oven for hydrothermal 2-24h. After cooling to room temperature, wash with water and filter to remove the solution. The obtained solid is placed in a 50-100℃ constant temperature drying oven for drying. The dried sample is placed in a muffle furnace and calcined at 450-900℃ for 2-10h to obtain a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst material.

[0015] Furthermore, the calcination conditions for removing glucose are: a heating rate of 1-10°C / min, heating from room temperature to 450-950°C, and calcining at 450-950°C for 2-10h.

[0016] Finally, the present invention also provides an application of a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst, wherein the catalyst is applied to catalyze the combustion of carbon smoke particles.

[0017] The present invention provides a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst and a preparation method and application thereof. The method selects and utilizes a low-cost manganese nitrate aqueous solution and sodium nitrate as metal precursors, and glucose as a complexing agent, and prepares a layered sodium-manganese composite oxide Na2Mn3O7 catalyst by dissolving-mixing-drying-calcining. Subsequently, the layered Na2Mn3O7 catalyst is hydrothermally treated to successfully synthesize the manganese oxide octahedral molecular sieve Na-OMS-2 catalyst.

[0018] The preparation process provided by the invention is simple, the synthesis method is novel, and the pores of the manganese oxide octahedral molecular sieve are single metal ions Na + The present invention uses the prepared manganese oxide octahedral molecular sieve Na-OMS-2 catalyst to catalyze the combustion of carbon smoke particles and exhibits high catalytic activity and stability. The preparation method provided has the advantages of simple preparation process, strong practicality, and easy large-scale production.

[0019] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0021] In order to more clearly illustrate the embodiments of the present invention 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, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 XRD diffraction patterns of NaMnO-n catalysts prepared under different hydrothermal time conditions provided in Example 1 of the present invention;

[0023] Figure 2 XRD diffraction patterns of NaMnO-T catalysts prepared under different hydrothermal temperature conditions provided in Example 2 of the present invention;

[0024] Figure 3 XRD diffraction patterns of NaMnO-m catalysts prepared under different acid concentration conditions provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0025] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present invention. Instead, they are merely examples of systems consistent with some aspects of the present invention as detailed in the appended claims.

[0026] Different from the method for preparing metal-doped M-OMS-2 disclosed in the prior art, this embodiment successfully synthesized a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst material through a new preparation method, and the pores of the catalyst material are composed of a single metal ion Na + Balance the overall valence and support pore structure.

[0027] First, this embodiment provides a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst, wherein the material is a one-dimensional pore structure formed by MnO6 octahedrons forming chains through 2×2 shared edges, and the chains are connected by oxygen atoms at the vertices of the octahedrons, and the pores contain a single metal ion Na + To balance the overall valence and support the pore structure.

[0028] In the second aspect, the present embodiment provides a method for synthesizing a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst which is easy to operate. The method uses a low-cost aqueous solution of manganese nitrate and sodium nitrate as metal precursors and glucose as a complexing agent to prepare a layered sodium manganese composite oxide Na2Mn3O7 catalyst by dissolution-mixing-drying-calcination. Subsequently, the layered Na2Mn3O7 catalyst is hydrothermally treated to successfully synthesize a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst. The method has the advantages of simple preparation process, readily available raw materials, low cost, strong practicability, and easy large-scale production.

[0029] Finally, this embodiment applies the above-prepared manganese oxide octahedral molecular sieve Na-OMS-2 catalyst material to the catalytic combustion reaction of carbon soot particles in diesel engine exhaust. The catalyst has high catalytic activity and stability, and the carbon soot particles can be completely burned and eliminated below 390°C.

[0030] The preparation method uses 50% manganese nitrate aqueous solution, sodium nitrate, glucose and concentrated hydrochloric acid as raw materials to prepare Na-OMS-2 catalyst and uses it as a catalyst to catalyze the combustion of soot particles in diesel engine exhaust, and specifically includes the following steps:

[0031] 0.1-5g 50% Mn(NO3)2 and 0.05-2g NaNO3 are dissolved in 10-50ml water at room temperature, and 0.5-10g glucose is added to the solution after dissolution, and stirred on a magnetic stirrer for 2h. The solution is then dried at 60-90°C for 12-24h, and the dried sample is calcined in a muffle furnace to remove glucose, and the temperature is raised from room temperature to 450-950°C at 1-10°C / min, and calcined at 450-950°C for 2-10h to obtain a solid product, which is a sodium manganese composite oxide Na2Mn3O7 catalyst. Subsequently, 0.1-2g of the above-mentioned Na2Mn3O7 catalyst is weighed and placed in 10-200mL of 0-1mol / L HCl solution and stirred for 0-60min. After sufficient stirring, it is transferred to a high-pressure reactor and then placed in a 60-200°C constant temperature drying oven for hydrothermal treatment for 2-24h. After cooling to room temperature, the solution is removed by water washing and filtration. The obtained solid is placed in a 50-100°C constant temperature drying oven for drying. The dried sample is placed in a muffle furnace and calcined at 450-900°C for 2-10h to obtain a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst material.

[0032] In order to better illustrate the technical means and product effects of the present invention, the preferred embodiments of the present invention are described below.

[0033] Example 1

[0034] Preparation of NaMnO-n catalysts at different hydrothermal times

[0035] 1.79g 50% Mn(NO3)2 and 0.42g NaNO3 were dissolved in 40mL water at room temperature. After dissolution, 3.96g glucose was added to the solution and stirred on a magnetic stirrer for 2h. The solution was then dried at 90°C for 12h. The dried sample was calcined in a muffle furnace to remove glucose. The temperature was raised from room temperature to 550°C at 2°C / min and calcined at 550°C for 6h. The solid product obtained was a sodium manganese composite oxide Na2Mn3O7 catalyst. Subsequently, 0.8 g of the above-mentioned Na2Mn3O7 catalyst was weighed and placed in 80 mL of 0.01 mol / L HCl solution and stirred for 60 min. After sufficient stirring, it was transferred to a high-pressure reactor and then placed in a 120°C constant temperature drying oven. After cooling to room temperature, the solution was removed by water washing and filtration. The obtained solid was placed in a 80°C constant temperature drying oven for drying. The dried sample was placed in a muffle furnace and calcined at 650°C for 6 h to obtain NaMnO-n catalyst materials under different hydrothermal time conditions. The catalysts obtained under different hydrothermal time conditions are recorded as NaMnO-n, where n is 2, 4, 8 and 12 h. Figure 1 is the XRD diffraction pattern of NaMnO-n. Figure 1It can be observed that the catalysts prepared under the hydrothermal conditions all have manganese oxide octahedral molecular sieve Na 2-x Mn8O 16 Table 1 shows the activity of NaMnO-n catalyst in catalytic combustion of soot particles. The catalysts prepared under different hydrothermal time conditions have good activity in the combustion of soot particles.

[0036] Table 1 Catalytic combustion activity of soot particles by catalysts prepared under different hydrothermal time conditions

[0037]

[0038] Example 2

[0039] Preparation of NaMnO-T catalysts under different hydrothermal temperature conditions

[0040] 1.79g 50% Mn(NO3)2 and 0.42g NaNO3 were dissolved in 40mL water at room temperature. After dissolution, 3.96g glucose was added to the solution and stirred on a magnetic stirrer for 2h. The solution was then dried at 90°C for 12h. The dried sample was calcined in a muffle furnace to remove glucose. The temperature was raised from room temperature to 550°C at 2°C / min and calcined at 550°C for 6h. The solid product obtained was a sodium manganese composite oxide Na2Mn3O7 catalyst. Subsequently, 0.8 g of the above Na2Mn3O7 catalyst was weighed and placed in 80 mL of 0.01 mol / L HCl solution and stirred for 60 min. After sufficient stirring, it was transferred to a high-pressure reactor and then hydrothermally heated in a constant temperature drying oven for 8 h. After cooling to room temperature, the solution was removed by water washing and filtration. The obtained solid was placed in a constant temperature drying oven at 80 ° C for drying. The dried sample was placed in a muffle furnace and calcined at 650 ° C for 6 h to obtain NaMnO-T catalyst materials under different hydrothermal times. The catalysts obtained under different hydrothermal time conditions are recorded as NaMnO-T, where T is 80, 120 and 160 ° C. Figure 2 The XRD diffraction pattern of NaMnO-T can be observed from the figure. The catalyst prepared under the hydrothermal temperature of 80 and 120 ° C has a manganese oxide octahedral molecular sieve Na 2-x Mn8O 16 When the hydrothermal temperature is increased to 160 °C, the catalyst obtained has Na 2-x Mn8O 16 Table 2 shows the activity of NaMnO-T catalyst in catalytic combustion of soot particles. The catalysts prepared under different hydrothermal time conditions have good activity in the combustion of soot particles.

[0041] Table 2 Catalytic combustion activity of soot particles of the catalysts prepared under different hydrothermal temperature conditions

[0042]

[0043] Example 3

[0044] Preparation of NaMnO-m catalysts under different acid concentrations

[0045] 1.79g 50% Mn(NO3)2 and 0.42g NaNO3 were dissolved in 40mL water at room temperature. After dissolution, 3.96g glucose was added to the solution and stirred on a magnetic stirrer for 2h. The solution was then dried at 90°C for 12h. The dried sample was calcined in a muffle furnace to remove glucose. The temperature was raised from room temperature to 550°C at 2°C / min and calcined at 550°C for 6h. The solid product obtained was a sodium manganese composite oxide Na2Mn3O7 catalyst. Subsequently, 0.8 g of the above-mentioned Na2Mn3O7 catalyst was weighed and placed in 80 mL of HCl solution and stirred for 60 min. After sufficient stirring, it was transferred to a high-pressure reactor and then placed in a constant temperature drying oven for hydrothermal treatment for 8 h. After cooling to room temperature, the solution was removed by filtration and the obtained solid was placed in a constant temperature drying oven for drying at 80 ° C. The dried sample was placed in a muffle furnace and calcined at 650 ° C for 6 h to obtain NaMnO-m catalyst materials under different acid concentrations. The catalysts obtained under different acid concentrations are recorded as NaMnO-m, where m is 0, 0.01, 0.05 and 0.1 mol / L. Figure 3 It can be observed from the figure that the catalyst prepared under 0 mol / L HCl (H2O) has Na2Mn5O 10 When the acid concentration is increased to 0.01 mol / L, the catalyst obtained is a manganese oxide octahedral molecular sieve Na 2-x Mn8O 16 When the acid concentration is further increased to 0.05 and 0.1 mol / L, the obtained catalyst is a catalyst with a Mn2O3 crystal form. Table 3 shows the activity of NaMnO-m catalyst in catalytic combustion of soot particles. It can be seen from the table that the catalytic activity of the catalysts prepared under different acid concentration conditions has obvious differences, which shows a trend of first increasing and then decreasing with the increase of acid concentration.

[0046] Table 3 Catalytic combustion activity of soot particles of the catalysts prepared under different acid concentrations

[0047]

[0048] Specific implementation 3

[0049] Catalyst activity evaluation method: using gas chromatography detection system, the catalyst adopts fixed bed method

[0050] Specific steps: Place the weighed catalyst and carbon smoke particles on weighing paper, stir evenly with a spatula to make the catalyst and carbon smoke particles loosely contact, and load them into a 6mm quartz reaction tube, wherein the gas flow rate is controlled to be 50mL / min, the volume content of NO in the gas is 2000ppm, the volume content of O2 is 10%, and the balance is Ar; the heating rate is controlled to be about 2℃ / min.

[0051] Evaluation method: The oxidation ability of the catalyst is expressed by the combustion temperature of the soot particles, where the ignition temperature of the soot particles (T 10 ), the temperature corresponding to the maximum burning rate (T 50 ) and burnout temperature (T 90 ), respectively represent the temperature points corresponding to 10%, 50% and 90% of the soot combustion completion. The calculation method is to integrate the curves of CO2 and CO produced by the combustion of carbon black in the programmed temperature oxidation reaction. The temperature point corresponding to 10%, 50% and 90% of the sum of the integral areas of CO2 and CO is T 10 、T 50 and T 90 . Where S CO2 m The catalytic combustion results of pure soot particles are shown in Table 4. It can be seen from the table that in the absence of a catalyst, the combustion temperature of pure soot is higher, indicating that the sodium manganese composite oxide Na prepared by the present invention has a high CO2 selectivity. x Mn y O z The catalyst has high catalytic activity for the catalytic combustion of soot particles.

[0052] Table 4 Catalytic combustion activity of pure soot particles

[0053]

[0054] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the claims.

Claims

1. A method for preparing a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst, characterized in that: The catalyst is composed of sodium, manganese and oxygen elements; The catalyst has a pore structure, wherein the pore structure is formed by MnO6 octahedrons forming chains through 2×2 shared edges, and the chains are connected by oxygen atoms at the vertices of the octahedrons. + Balancing the overall valence and supporting the pore structure; The method for preparing a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst comprises: using a manganese nitrate aqueous solution and sodium nitrate as metal precursors and glucose as a complexing agent, and preparing a layered sodium manganese composite oxide Na2Mn3O7 catalyst by dissolving-mixing-drying-calcining; The sodium manganese composite oxide Na2Mn3O7 catalyst is hydrothermally treated to obtain a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst.

2. The method for preparing a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst according to claim 1, characterized in that: The specific steps include: Dissolve 0.1-5 g 50% Mn(NO3)2 and 0.05-2 g NaNO3 in 10-50 ml water at room temperature to obtain a dissolved solution, add 0.5-10 g glucose to the dissolved solution, and stir on a magnetic stirrer for 2 h; The stirred solution was placed in a temperature of 60-90 °C and dried for 12-24 h. The dried sample was calcined in a muffle furnace to remove glucose. The solid product obtained was a sodium manganese composite oxide Na2Mn3O7 catalyst. Weigh 0.1-2 g of the sodium manganese composite oxide Na2Mn3O7 catalyst and put it into 10-200 mL of 0-1 mol / L HCl solution and stir for 0-60 min, wherein the concentration of the HCl solution is not 0, and the stirring time is not 0. After sufficient stirring, transfer it to a high-pressure reactor, and then place it in a 60-200 ° C constant temperature drying oven for hydrothermal 2-24 h, cool it to room temperature, wash it with water, and filter it to remove the solution. The obtained solid is placed in a 50-100 ° C constant temperature drying oven for drying, and the dried sample is placed in a muffle furnace and calcined at 450-900 ° C for 2-10 h to obtain a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst material.

3. The method for preparing a manganese oxide octahedral molecular sieve Na-OMS-2 catalyst according to claim 2, characterized in that: The calcination conditions for removing glucose are: heating rate of 1-10 ℃ / min, heating from room temperature to 450-950 ℃, and calcining at 450-950 ℃ for 2-10 h.

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