Porous SnO2 Materials, Their Preparation Methods and Applications

Abstract

The application relates to the field of methane oxidation coupling technology, and discloses a SnO2 material with a porous structure and a preparation method and application thereof. The preparation method comprises the following steps: mixing a tin source and alcohol, and then calcining the mixed product at 300-700 DEG C. The method for preparing C2 hydrocarbon by methane oxidation coupling comprises the following steps: under the methane oxidation coupling reaction condition, raw material gas is contacted with the SnO2 material with a porous structure in the second aspect. When the SnO2 material with a porous structure prepared by the application is used as a catalyst for the reaction of preparing C2 hydrocarbon by methane oxidation coupling, the conversion rate of methane is above 28%.

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 a novel functional material, is a typical semiconductor material widely used in optics, electronics, and magnetism. Furthermore, SnO2 possesses advantages such as active vacant oxygen sites, reducible surface lattice oxygen, and excellent stability, making its applications in catalysis increasingly attractive. By making SnO2 materials porous, the number of surface defects increases, the specific surface area expands, and unique properties are exhibited.

[0003] There are many methods for preparing porous tin dioxide materials, including the template method, hydrothermal method, and solvothermal method. Each method has its advantages and disadvantages. For example, the template method has the advantage of high controllability, but the yield is small and currently limited to laboratory research. The hydrothermal and solvothermal methods are simple, but the reproducibility is poor and the yield is also low. Therefore, the development of high-performance porous SnO2 materials is extremely urgent.

[0004] The ethylene industry is the core of the petrochemical industry, often referred to as the "mother of petrochemicals," and holds a vital position in the national economy. Ethylene production has become an important indicator of a country's petrochemical development level. In recent years, with rapid economic development, China's ethylene industry has grown rapidly, with its production capacity increasing quickly, making it the world's second-largest ethylene producer after the United States. However, my country's current ethylene production mainly relies on naphtha and coal-based routes, which suffer from drawbacks such as large project investments, long process routes, and low product yields. Natural gas-to-ethylene methods are simpler and have shorter process routes, and the methane oxidative coupling process is one of the simplest natural gas-to-ethylene processes discovered to date. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor reproducibility in the preparation of porous SnO2 materials by hydrothermal and solvent methods, and low yield in the preparation of porous SnO2 materials by template agent methods, and to provide a SnO2 material with a porous structure, its preparation method, and its applications. This invention uses a pyrolysis method to prepare porous SnO2 materials. This method is simple and reproducible, and the obtained porous SnO2 exhibits good catalytic performance.

[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 a tin source with an alcohol and then calcining the mixture at 300-700°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 prepared by this invention has the following advantages: the raw materials used are inexpensive, the preparation process is simple, the preparation process is easy to control, the equipment requirements are low, and the product reproducibility is good. Furthermore, the porous SnO2 material prepared by the method of this invention has a high yield, exceeding 95%. As a catalyst, the yield of C2 hydrocarbons remains essentially unchanged after 40 hours of reaction, therefore the prepared material exhibits good stability in the methane oxidative coupling reaction. Attached Figure Description

[0011] Figure 1 This is a scanning electron microscope image of the SnO2 material with a porous structure 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] The first aspect of the present invention provides a method for preparing a SnO2 material with a porous structure, the method comprising mixing a tin source with an alcohol and then calcining the mixture at 300-700°C.

[0014] According to the present invention, preferably, the calcination temperature is 500-700°C (for example, the calcination temperature can be 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, or any value between the above values). When the calcination temperature is limited to the above range, the SnO2 material with a porous structure obtained can be used as a catalyst in the oxidative coupling reaction of methane to C2 hydrocarbons, which can improve the conversion rate of methane and the selectivity of C2 hydrocarbons, and reduce the selectivity of carbon oxides (CO+CO2).

[0015] According to the present invention, the type of alcohol is not particularly limited, but in order to enable the SnO2 material with a porous structure to better catalyze the preparation of C2 hydrocarbons from methane and oxygen, the alcohol is preferably a diol, more preferably a C2-C4 diol, and even more preferably ethylene glycol and / or propylene glycol.

[0016] According to the present invention, the type of tin source is not particularly limited, but in order to enable the SnO2 material with porous structure to better catalyze the preparation of C2 hydrocarbons from methane and oxygen, preferably, the tin source is an organotin source with 10-18 carbon atoms, more preferably dibutyltin diacetate.

[0017] According to the present invention, preferably, the weight ratio of the tin source to the alcohol is 1:6-25 (for example, the weight ratio of the tin source to the alcohol can be 1:6, 1:7, 1:10, 1:12, 1:15, 1:18, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, or any value between the above values). When the weight ratio of the tin source to the alcohol is limited to the above range, the SnO2 material with a porous structure prepared can be used as a catalyst in the oxidative coupling reaction of methane to C2 hydrocarbons, which can improve the conversion rate of methane and the selectivity of C2 hydrocarbons, and reduce the selectivity of carbon oxides (CO+CO2).

[0018] 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 3-10℃ / min (for example, the heating rate can be 3℃ / min, 3.5℃ / min, 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).

[0019] 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 3-8 hours (for example, the roasting time can be 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, or any value between the above values).

[0020] According to the present invention, in order to make the pyrolysis more complete, the calcination is preferably carried out in an air atmosphere.

[0021] 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.

[0022] According to the present invention, preferably, the pore size of the SnO2 material with a porous structure is 200-1500 nm.

[0023] 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.

[0024] 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 720-780℃, preferably 730-780℃, and the space velocity of the feed gas is 3000-8000 mL / (g·h).

[0025] According to the present invention, preferably, the volume ratio of methane to oxygen in the raw material gas is 2-10:1.

[0026] The present invention will be described in detail below through embodiments. In the following embodiments,

[0027] "Alkoxy ratio" refers to the volume ratio of methane to oxygen in the feed gas.

[0028] Methane conversion rate = (molar amount of methane consumed in the reaction) / (initial molar amount of methane) × 100%.

[0029] Ethylene selectivity = (molar amount of methane consumed to produce ethylene / total molar amount of methane consumed) × 100%.

[0030] Ethane selectivity = (Moles of methane consumed to produce ethane) / (Total moles of methane consumed) × 100%.

[0031] C2 hydrocarbon selectivity = ethane selectivity + ethylene selectivity.

[0032] COx(CO+CO2) selectivity = (molar amount of methane consumed by CO and CO2 generated) / (total molar amount of methane consumed) × 100%.

[0033] C2 hydrocarbon yield = methane conversion rate × (ethane selectivity + ethylene selectivity) × 100%.

[0034] The manufacturer of dibutyltin diacetate is Guangdong Wengjiang Reagent Co., Ltd., product number WB08270, with a purity of 95wt%.

[0035] The purity of the ethylene glycol is 95 wt%.

[0036] The purity of propylene glycol is 95 wt%.

[0037] 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.

[0038] Preparation Example 1

[0039] This preparation example illustrates the preparation of SnO2 materials with porous structures.

[0040] (1) Take 1g of the precursor dibutyltin diacetate and add it to 10g of ethylene glycol. Stir for 10min to form solution A.

[0041] (2) The solution A was placed in a muffle furnace and heated to 600°C at a heating rate of 5°C / min, and then calcined at this temperature (calcination atmosphere is air) for 5 h to obtain the SnO2 porous material of the present invention.

[0042] Scanning electron microscope image of SnO2 porous material as shown below Figure 1 As shown, from Figure 1 It can be seen that the material produced has a three-dimensional porous structure, similar to a petal-shaped structure, with pores in a polyhedral shape and a diameter of about 300-1000nm.

[0043] Preparation Example 2

[0044] This preparation example illustrates the preparation of SnO2 materials with porous structures.

[0045] (1) Take 1g of the precursor dibutyltin diacetate and add it to 20g of propylene glycol. Stir for 10min to form solution A.

[0046] (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 3 hours to obtain the SnO2 porous material of the present invention.

[0047] Preparation Example 3

[0048] This preparation example illustrates the preparation of SnO2 materials with porous structures.

[0049] (1) Take 1g of the precursor dibutyltin diacetate and add it to 6g of ethylene glycol. Stir for 10min to form solution A.

[0050] (2) The solution A was placed in a muffle furnace and heated to 500°C at a heating rate of 3°C / min, and then calcined at this temperature (calcination atmosphere was air) for 8 hours to obtain the SnO2 porous material of the present invention.

[0051] Preparation Example 4

[0052] This preparation example illustrates the preparation of SnO2 materials with porous structures.

[0053] The SnO2 material with a porous structure was prepared according to the method of Preparation Example 1, except that 1g of the precursor dibutyltin diacetate was added to 4g of ethylene glycol.

[0054] Preparation Example 5

[0055] This preparation example illustrates the preparation of SnO2 materials with porous structures.

[0056] The SnO2 material with a porous structure was prepared according to the method of Preparation Example 1, except that it was heated to 300°C at a heating rate of 5°C / min and then calcined at that temperature (calcination atmosphere was air) for 5 hours.

[0057] Preparation Example 6

[0058] This preparation example is used to illustrate the preparation of SnO2 materials.

[0059] SnO2 materials were prepared according to the method of Preparation Example 1, except that dibutyltin diacetate was replaced with tin nitrate.

[0060] Example 1

[0061] The material obtained in Preparation Example 1 was used as a catalyst for the oxidative coupling of methane to C2 hydrocarbons. 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 C2 hydrocarbons after 1 hour of reaction are listed in Table 1.

[0062] Example 2

[0063] The material obtained in Preparation Example 2 was used as a catalyst for the oxidative coupling of methane to C2 hydrocarbons. 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 C2 hydrocarbons after 1 hour of reaction are listed in Table 1.

[0064] Example 3

[0065] The material obtained in Preparation Example 3 was used as a catalyst for the oxidative coupling of methane to C2 hydrocarbons. 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 780 °C, the alkane-to-oxygen ratio was 3, and the total space velocity of methane and oxygen was 3000 mL / (g·h). The catalyst performance evaluation results for the oxidative coupling of methane to C2 hydrocarbons after 1 hour of reaction are listed in Table 1.

[0066] Example 4

[0067] The catalyst performance was tested in accordance with the method of Example 1, except that the material obtained in Preparation Example 4 was used as a catalyst for the oxidative coupling of methane to C2 hydrocarbons. The reaction performance evaluation is shown in Table 1.

[0068] Example 5

[0069] The catalyst performance was tested in accordance with the method of Example 1, except that the material obtained in Preparation Example 5 was used as a catalyst for the oxidative coupling of methane to C2 hydrocarbons. The reaction performance evaluation is shown in Table 1.

[0070] Example 6

[0071] The catalyst performance was tested in accordance with the method of Example 1, except that the material obtained in Preparation Example 6 was used as a catalyst for the oxidative coupling of methane to C2 hydrocarbons. The reaction performance evaluation is shown in Table 1.

[0072] Table 1

[0073]

[0074] As shown 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, the methane conversion rate is above 28%. Among them, the methane conversion rate of Examples 1-3 is higher than 35%, and the C2 hydrocarbon selectivity is higher than 19%, showing better catalytic effect.

[0075] 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 the oxidative coupling of methane to produce C2 hydrocarbons, characterized in that, The method includes: contacting the feed gas with a SnO2 material having a porous structure under methane oxidative coupling reaction conditions; A method for preparing SnO2 materials with porous structures, characterized in that the preparation method includes mixing a tin source with an alcohol, and then calcining the mixture at 500-700°C; The tin source is dibutyltin diacetate; The alcohol is ethylene glycol and / or propylene glycol; The weight ratio of the tin source to the alcohol is 1:6-25.

2. The method according to claim 1, wherein, The calcination temperature was achieved at a heating rate of 3-10℃ / min.

3. The method according to claim 1, wherein, The roasting time is 3-8 hours.

4. The method according to claim 1, wherein, The conditions for the methane oxidative coupling reaction include: the feed gas is methane and oxygen, the reaction temperature is 720-780℃, and the space velocity of the feed gas is 3000-8000 mL / (g·h).

5. The method according to claim 1, wherein, The volume ratio of methane to oxygen in the feed gas is 2-10:

1.

6. The method according to claim 5, wherein, The volume ratio of methane to oxygen in the feed gas is 2-6:1.

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