Porous SnO2 Materials, Their Preparation Methods and Applications
The preparation of porous SnO2 materials doped with alkali metals by high-temperature decomposition solves the problem of poor catalytic performance of existing SnO2 catalysts in the oxidative coupling reaction of methane, and realizes efficient and stable C2 hydrocarbon production, which is suitable for large-scale preparation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-12-08
- Publication Date
- 2026-04-07
AI Technical Summary
Existing SnO2 catalysts have poor catalytic performance in the oxidative coupling of methane to C2 hydrocarbons, and traditional preparation methods suffer from low yield and poor reproducibility.
Porous SnO2 materials doped with alkali metals were prepared by high-temperature decomposition. The mixture of alkyltin laurylate, acid and alkali metal source was calcined at 500-700℃ to form a porous structure with a pore size of 0.2-1.8 μm, which was used for methane oxidative coupling reaction.
The prepared porous SnO2 material has high yield and good stability. As a catalyst, the yield of C2 hydrocarbons remains basically unchanged after 35 h of reaction, which improves the methane conversion rate and C2 hydrocarbon selectivity. The operation is simple and easy to produce on a large scale.
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Figure CN116237033B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of methane oxidative coupling technology, specifically to a SnO2 material with a porous structure, its preparation method, and its application. Background Technology
[0002] SnO2, as an N-type semiconductor material, possesses stable chemical properties and has been widely used in gas sensors, electrode materials, and other fields. Due to its abundant oxygen vacancies and acidic sites on its surface, SnO2 has been used to catalyze reactions such as CO oxidation and methane oxidation. Wang Zhongquan's research group prepared a highly stable SnO2 catalyst for the methane oxidative coupling reaction and investigated the effect of LiCl content on the catalyst activity and selectivity.
[0003] Porous catalysts are functional materials that combine excellent catalytic performance with good adsorption properties. Compared with traditional catalysts, porous catalysts have a high specific surface area, which is beneficial for accelerating catalytic reactions. There are various methods for preparing porous catalysts, commonly including template methods, hydrothermal methods, and precipitation methods. Each method has its advantages and disadvantages. For example, template methods have the advantage of high controllability, but the yield is small and currently limited to laboratory research. Hydrothermal and solvothermal methods are simple, but have poor reproducibility.
[0004] Oxidative coupling of methane to C2 hydrocarbons is an important pathway for the direct conversion of methane into C2 hydrocarbons. In recent years, various catalytic systems for the oxidative coupling of methane to C2 hydrocarbons have been studied. It has been found that SnO2 catalyzes the reaction of methane and oxygen to produce C2 hydrocarbons, but the catalytic effect is poor and needs further improvement. Summary of the Invention
[0005] The purpose of this invention is to overcome the problem of poor catalyst performance of ordinary SnO2 in the oxidative coupling of methane to C2 hydrocarbons in the prior art, and to provide a SnO2 material with a porous structure, its preparation method and application. This invention uses a high-temperature decomposition method to prepare Na / SnO2 with a porous structure. The method is simple, easy to operate, and convenient for large-scale preparation, and has good application prospects.
[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a SnO2 material with a porous structure, the method comprising mixing alkyltin laurylate, an acid and an optional alkali metal source, and then calcining the mixture at 500-700°C.
[0007] The second aspect of the present invention provides a SnO2 material with a porous structure, which is prepared by the preparation method described in the first aspect.
[0008] The third aspect of the present invention provides a method for the reaction of methane oxidative coupling to produce C2 hydrocarbons, the method comprising: contacting a feed gas with a SnO2 material having a porous structure as described in the second aspect under methane oxidative coupling reaction conditions.
[0009] In this invention, "C2 hydrocarbon" refers to ethane and ethylene.
[0010] The porous SnO2 material doped with alkali metals prepared by this invention has the following advantages: the raw materials used are inexpensive, the method is simple and convenient to operate, and the yield of the obtained porous SnO2 material is high, making it easy to prepare on a large scale (the yield in a single preparation can reach more than 10g), providing a direction for the development of efficient, simple, inexpensive and practical catalysts. Furthermore, when the porous SnO2 material is used as a catalyst for the oxidative coupling of methane to C2 hydrocarbons, the yield of C2 hydrocarbons remains essentially unchanged after 35 hours of reaction. Therefore, the porous SnO2 material prepared by this invention exhibits good stability and catalytic performance. Attached Figure Description
[0011] Figure 1 This is a scanning electron microscope image of the SnO2 material with a porous structure doped with alkali metal prepared in Preparation Example 1 of the present invention. Detailed Implementation
[0012] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0013] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a SnO2 material with a porous structure, the method comprising mixing alkyltin laurylate, an acid and an optional alkali metal source, and then calcining the mixture at 500-700°C.
[0014] According to the present invention, preferably, the acid is a monobasic acid, more preferably a C2-C3 monobasic acid, and even more preferably acetic acid.
[0015] According to the present invention, preferably, the acid is mixed with alkyltin laurylate in the form of a solution, and the mass fraction of the acid in the acid solution is 40-80 wt%. The solvent in the acid solution is water.
[0016] According to the present invention, an alkali metal source is preferably used, and the weight ratio of the organotin laurate to the alkali metal source is 1:0.03-0.21. Preferably, the weight ratio of the organotin laurate to the acid is 1:6-35. When the weights of the organotin laurate, the alkali metal-containing salt, and the acid are limited to the above ranges, the prepared alkali metal-doped SnO2 material with a porous structure, when used as a catalyst in the oxidative coupling reaction of methane to C2 hydrocarbons, can improve the conversion rate of methane and the selectivity of C2 hydrocarbons, and reduce the selectivity of carbon oxides.
[0017] According to the present invention, in order to enable the obtained SnO2 material with porous structure doped with alkali metal to better catalyze the preparation of C2 hydrocarbons from methane and oxygen, preferably, the alkyl group in the alkyltin laurylate is a C1-C10 alkyl group; more preferably, the alkyltin laurylate is dibutyltin laurylate and / or dioctyltin laurylate.
[0018] According to the present invention, the type of alkali metal source is not particularly limited and can be a commonly used alkali metal source in the art. Preferably, the alkali metal source is an alkali metal nitrate. More preferably, the alkali metal in the alkali metal source is Na and / or K. Even more preferably, the alkali metal source is sodium nitrate.
[0019] According to the present invention, in order to improve the selectivity of C2 hydrocarbons, preferably, the calcination temperature is reached at a heating rate of 4-10℃ / min (for example, the heating rate can be 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min, 6℃ / min, 6.5℃ / min, 7℃ / min, 7.5℃ / min, 8℃ / min, 9℃ / min, 9.5℃ / min, 10℃ / min, or any value between the above values).
[0020] According to the present invention, the roasting time can be selected within a wide range. In order to further improve the selectivity of C2 hydrocarbons, the roasting time is preferably 5-10 h (for example, the roasting time can be 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, or any value between the above values).
[0021] According to the present invention, in order to make the calcination more complete, expose the covered active centers, and improve the reaction performance of the catalyst, the calcination is preferably carried out in an air atmosphere.
[0022] The second aspect of the present invention provides a SnO2 material with a porous structure, which is prepared by the preparation method described in the first aspect.
[0023] According to the present invention, preferably, the pore size distribution of the SnO2 material with porous structure is in the range of 0.2-1.8 μm, and more preferably in the range of 0.5-1.5 μm.
[0024] The third aspect of the present invention provides a method for the reaction of methane oxidative coupling to produce C2 hydrocarbons, the method comprising: contacting a feed gas with a SnO2 material having a porous structure as described in the second aspect under methane oxidative coupling reaction conditions.
[0025] According to the present invention, preferably, the conditions for the methane oxidative coupling reaction include: the feed gas is methane and oxygen, the reaction temperature is 700-800℃, and the space velocity of the feed gas is 5000-20000 mL / (g·h).
[0026] According to the present invention, preferably, the volume ratio of methane to oxygen in the raw material gas is 2-5:1.
[0027] The present invention will be described in detail below through embodiments. In the following embodiments,
[0028] "Alkoxy ratio" refers to the volume ratio of methane to oxygen in the feed gas.
[0029] Methane conversion rate = (molar amount of methane consumed in the reaction) / (initial molar amount of methane) × 100%.
[0030] Ethylene selectivity = (molar amount of methane consumed to produce ethylene / total molar amount of methane consumed) × 100%.
[0031] Ethane selectivity = (Moles of methane consumed to produce ethane) / (Total moles of methane consumed) × 100%.
[0032] C2 hydrocarbon selectivity = ethane selectivity + ethylene selectivity.
[0033] COx(CO+CO2) selectivity = (molar amount of methane consumed by CO and CO2 generated) / (total molar amount of methane consumed) × 100%.
[0034] C2 hydrocarbon yield = methane conversion rate × (ethane selectivity + ethylene selectivity) × 100%.
[0035] The manufacturer of dibutyltin laurylate is Alfa, and the product number is 071130.
[0036] The manufacturer of dioctyltin laurate is Adamas, and the product number is 98967B.
[0037] The mass fraction of acetic acid in the aqueous acetic acid solution is 80 wt%.
[0038] The reaction products were analyzed online using a gas chromatograph (Agilent Technologies, model 7890A). A dual-detection-channel, three-valve, four-column system was employed for analysis, with the FID detector connected to an alumina column for the analysis of CH4, C2H6, C2H4, C3H8, C3H6, and C4H. 10 C4H8, C n H m The TCD detector is mainly used to detect CO, CO2, N2, O2, and CH4.
[0039] Preparation Example 1
[0040] This preparation example illustrates the preparation of porous SnO2 materials doped with alkali metals.
[0041] (1) Take 2g of the precursor dibutyltin laurylate and 0.2g of sodium nitrate and add them to 25g of acetic acid aqueous solution. Stir for 10min to form solution A.
[0042] (2) The solution A was placed in a muffle furnace and heated to 600°C at a heating rate of 6°C / min, and then calcined at this temperature (calcination atmosphere was air) for 7 h to obtain the Na / SnO2 porous material of the present invention.
[0043] Scanning electron microscope image of Na / SnO2 porous material as follows: Figure 1 As shown, from Figure 1 The product exhibits a honeycomb-like porous structure with numerous interconnected pores, the pore size of which ranges from 0.5 to 1.5 μm.
[0044] Preparation Example 2
[0045] This preparation example illustrates the preparation of porous SnO2 materials doped with alkali metals.
[0046] (1) Take 2g of the precursor dioctyltin laurylate and 0.1g of sodium nitrate and add them to 16g of acetic acid aqueous solution. Stir for 10min to form solution A.
[0047] (2) The solution A was placed in a muffle furnace and heated to 700°C at a heating rate of 10°C / min. Then it was calcined at this temperature (calcination atmosphere was air) for 5 hours to obtain the Na / SnO2 porous material of the present invention.
[0048] Preparation Example 3
[0049] This preparation example illustrates the preparation of porous SnO2 materials doped with alkali metals.
[0050] (1) Take 2g of the precursor dioctyltin laurylate and 0.4g of sodium nitrate and add them to 65g of acetic acid aqueous solution. Stir for 10min to form solution A.
[0051] (2) The solution A was placed in a muffle furnace and heated to 500°C at a heating rate of 5°C / min, and then calcined at this temperature (calcination atmosphere is air) for 10 h to obtain the Na / SnO2 porous material of the present invention.
[0052] Preparation Example 4
[0053] This preparation example illustrates the preparation of porous SnO2 materials doped with alkali metals.
[0054] (1) Take 2g of the precursor dibutyltin laurylate and 0.01g of sodium nitrate and add them to 5g of acetic acid aqueous solution, stir for 10min, and mix to form solution A.
[0055] (2) Solution A was placed in a muffle furnace and heated to 600°C at a heating rate of 5°C / min. Then it was calcined at this temperature (calcination atmosphere was air) for 5 h to obtain Na / SnO2 material.
[0056] Preparation Example 5
[0057] This preparation example illustrates the preparation of SnO2 materials with porous structures.
[0058] SnO2 materials were prepared according to the method of Preparation Example 1, except that sodium nitrate was not added.
[0059] Comparative Preparation Example 1
[0060] This preparation example illustrates the preparation of alkali metal-doped SnO2 materials.
[0061] The Na / SnO2 material was prepared according to the method in Example 1, except that dibutyltin laurylate was replaced with tin nitrate. Na / SnO2 particles were ultimately obtained, but no porous material was produced.
[0062] Example 1
[0063] The material obtained in Preparation Example 1 was used as a catalyst for the oxidative coupling of methane to olefins. The reaction was carried out in a continuous flow fixed bed reactor, which was a quartz tube with an inner diameter of 10 mm and a length of 530 mm. The catalyst loading was 0.5 g, the reaction pressure was the pressure generated by the feed gas itself, the reaction temperature was 750 °C, the alkane-to-oxygen ratio was 2, and the total space velocity of methane and oxygen was 5000 mL / (g·h). The catalyst performance evaluation results for the oxidative coupling of methane to ethylene after 1 hour of reaction are listed in Table 1.
[0064] Example 2
[0065] The material obtained in Preparation Example 2 was used as a catalyst for the oxidative coupling of methane to olefins. The reaction was carried out in a continuous flow fixed bed reactor, which was a quartz tube with an inner diameter of 10 mm and a length of 530 mm. The catalyst loading was 0.5 g, the reaction pressure was the pressure generated by the feed gas itself, the reaction temperature was 730 °C, the alkane-to-oxygen ratio was 4, and the total space velocity of methane and oxygen was 8000 mL / (g·h). The catalyst performance evaluation results for the oxidative coupling of methane to ethylene after 1 hour of reaction are listed in Table 1.
[0066] Example 3
[0067] The material obtained in Preparation Example 3 was used as a catalyst for the oxidative coupling of methane to olefins. The reaction was carried out in a continuous flow fixed bed reactor, which was a quartz tube with an inner diameter of 10 mm and a length of 530 mm. The catalyst loading was 0.5 g, the reaction pressure was the pressure generated by the feed gas itself, the reaction temperature was 800 °C, the alkane-to-oxygen ratio was 3, and the total space velocity of methane and oxygen was 20000 mL / (g·h). The catalyst performance evaluation results for the oxidative coupling of methane to ethylene after 1 hour of reaction are listed in Table 1.
[0068] Example 4
[0069] The catalyst performance was tested in accordance with the method of Example 1, except that the Na / SnO2 material prepared in Preparation Example 4 was used instead of the porous SnO2 material doped with alkali metal prepared in Example 1. The reaction performance evaluation is shown in Table 1.
[0070] Example 5
[0071] The catalyst performance was tested in accordance with the method of Example 1, except that the SnO2 material prepared in Preparation Example 5 was used instead of the porous SnO2 material with alkali metal doping prepared in Example 1. The reaction performance evaluation is shown in Table 1.
[0072] Comparative Example 1
[0073] The catalyst performance was tested according to the method of Example 1, except that the Na / SnO2 particles prepared in Comparative Preparation Example 1 were used instead of the porous SnO2 material with alkali metal doping prepared in Example 1. The reaction performance evaluation is shown in Table 1.
[0074] Table 1
[0075]
[0076] As can be seen from the results in Table 1, when the porous SnO2 material prepared according to this invention is used as a catalyst for the oxidative coupling of methane to C2 hydrocarbons, high methane conversion, C2 hydrocarbon selectivity, and C2 hydrocarbon yield can be obtained. Particularly preferred, using the methods of Examples 1-3 of this invention, the methane conversion is above 36%, the C2 hydrocarbon selectivity is above 28%, and the C2 hydrocarbon yield selectivity is above 10%, demonstrating better catalytic performance.
[0077] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for preparing a SnO2 material with a porous structure, characterized in that, The preparation method includes mixing alkyltin laurylate, an acid and an alkali metal source, and then calcining the mixture at 500-700°C. The acid is a C2-C3 monobasic acid; The weight ratio of the alkyltin laurylate to the alkali metal source is 1:0.03-0.21; The alkali metal in the alkali metal source is Na and / or K; The weight ratio of the alkyltin laurylate to the acid is 1:6-35; The alkali metal source is an alkali metal nitrate; The calcination temperature was achieved at a heating rate of 4-10℃ / min; The roasting time is 5-10 hours; The pore size distribution of the SnO2 material with a porous structure is in the range of 0.5-1.5 μm.
2. The preparation method according to claim 1, wherein, The acid is mixed with alkyltin laurylate in solution, and the mass fraction of the acid in the acid solution is 40-80 wt%.
3. The preparation method according to claim 1, wherein, The alkyl group in the alkyltin laurylate is a C1-C10 alkyl group; And / or, the alkali metal source is sodium nitrate.
4. The preparation method according to claim 3, wherein, The alkyltin laurylate is dibutyltin laurylate and / or dioctyltin laurylate.
5. A SnO2 material with a porous structure, characterized in that, The SnO2 material with a porous structure is prepared by any one of the preparation methods described in claims 1-4.
6. A method for the oxidative coupling of methane to produce C2 hydrocarbons, characterized in that, The method includes contacting the feed gas with the SnO2 material with a porous structure as described in claim 5 under methane oxidative coupling reaction conditions.
7. The method according to claim 6, wherein, The conditions for the methane oxidative coupling reaction include: the feed gas is methane and oxygen, the reaction temperature is 700-800℃, and the space velocity of the feed gas is 5000-20000 mL / (g·h).
8. The method according to claim 7, wherein, The volume ratio of methane to oxygen in the feed gas is 2-5:1.