Reactors with silica deposited on their inner surface and their preparation methods, and methods for producing C2 hydrocarbons by oxidative coupling of methane.

Abstract

This invention relates to the field of catalysis technology, disclosing a reactor with silica-coated inner surface, its preparation method, and a method for the oxidative coupling of methane to produce C2 hydrocarbons. The reactor includes a stainless steel reaction tube and a silica film attached to the inner surface of the stainless steel reaction tube. The silica film has a thickness of 0.5-15 μm and a coverage of at least 60% on the inner surface of the stainless steel reaction tube. The reactor also includes a catalyst filled within the cavity of the stainless steel reaction tube. The catalyst includes a support and an active component loaded on the support, wherein the active component includes Na2WO4 and / or K2WO4, and oxides of Mn. The reactor provided by this invention can reduce the formation of byproducts during the oxidative coupling reaction of methane, and, combined with the specific catalyst filled within the reactor, can further improve the product yield and selectivity.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, specifically to a reactor with silica deposited on its inner surface, a method for preparing the same, and a method for the oxidative coupling of methane to produce C2 hydrocarbons. Background Technology

[0002] Natural gas plays a vital role in modern industrial energy. Methane is the main component of natural gas, comprising over 90% of its composition. With advancements in natural gas development technology, activating methane to convert it into chemical feedstocks has become an important research topic in C1 chemistry. The main utilization pathways for methane include oxidative coupling and syngas production. Since Keller and Bhasin first studied methane oxidative coupling in 1982, the importance of ethylene in the petrochemical industry has driven continuous research in this field, resulting in significant progress in catalyst systems and methane conversion mechanisms.

[0003] Currently, methane oxidative coupling catalysts are primarily at the laboratory microscale, requiring further industrial-scale testing. The methane oxidative coupling reaction is a high-temperature, strongly exothermic reaction, presenting many challenges for engineering scale-up, particularly regarding the reactor material, which is a key difficulty in methane oxidative coupling technology. Industrially used stainless steel reactor tubes typically contain iron. Under high temperatures, the iron on the surface of the reactor tube can cause methane to react with oxygen in an oxygen atmosphere to form CO. x Therefore, stainless steel reaction tubes have a significant impact on the oxidative coupling reaction of methane. When Kou Yuan's research group synthesized Fe / SiO2 as a catalyst for the oxidative coupling reaction of methane, the methane conversion rate was only 10%, while CO... x The selectivity is as high as 93.3%. Currently, the reaction tubes used in laboratory micro-scale methane oxidative coupling reactions are mainly quartz tubes. However, the inherent properties of quartz tubes limit further scale-up of methane oxidative coupling experiments. It is well known that quartz tubes are extremely impractical as reaction tubes in industrial scale-up experiments due to their fragility and low strength. Therefore, improving the mechanical strength of reaction tubes is one of the urgent problems to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the technical problems existing in the prior art and to provide a reactor with silica attached to its inner surface, its preparation method, and a method for producing C2 hydrocarbons by oxidative coupling of methane.

[0005] To achieve the above objectives, the first aspect of the present invention provides a reactor with silica attached to its inner surface. The reactor includes a stainless steel reaction tube and a silica film attached to the inner surface of the stainless steel reaction tube, wherein the thickness of the silica film is 0.5-15 μm and the coverage of the silica film on the inner surface of the stainless steel reaction tube is greater than or equal to 60%.

[0006] The reactor further includes a catalyst filled in a stainless steel reaction tube cavity. The catalyst includes a support and an active component supported on the support. The support is selected from silica and / or barium titanate. The active component includes a first active component and a second active component. The first active component is Na2WO4 and / or K2WO4, and the second active component is an oxide of Mn.

[0007] A second aspect of the present invention provides a method for preparing the reactor described in the first aspect, the method comprising the following steps:

[0008] (1) A silica film is attached to the inner surface of a stainless steel reaction tube to obtain a reactor precursor;

[0009] (2) A catalyst section is filled in the reactor front body to obtain the reactor.

[0010] A third aspect of the present invention provides a method for producing C2 hydrocarbons by oxidative coupling of methane, the method comprising: introducing methane and oxygen into the aforementioned reactor to carry out an oxidative coupling reaction.

[0011] Compared with existing technologies, the reactor provided by this invention utilizes a thin film (silica film) formed on the inner wall surface to effectively cover the iron content on the inner surface of the stainless steel reaction tube, thereby reducing the formation of byproducts during the methane oxidative coupling reaction. Combined with a specific catalyst packed within the reactor, this further improves product yield and selectivity. Furthermore, the reactor preparation method (with a silica film attached to the surface) provided by this invention is simple to operate, suitable not only for laboratory-scale reactions but also offering a new approach to reactor material selection for industrial scale-up experiments. 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 reactor with silica attached to its inner surface. The reactor includes a stainless steel reaction tube and a silica film attached to the inner surface of the stainless steel reaction tube. The silica film has a thickness of 0.5-15 μm and a coverage of the silica film on the inner surface of the stainless steel reaction tube of ≥60%.

[0014] The reactor further includes a catalyst filled in a stainless steel reaction tube cavity. The catalyst includes a support and an active component supported on the support. The support is selected from silica and / or barium titanate. The active component includes a first active component and a second active component. The first active component is Na2WO4 and / or K2WO4, and the second active component is an oxide of Mn.

[0015] According to some embodiments of the present invention, the thickness of the silica film is 1-8 μm, and the coverage of the silica film on the inner surface of the stainless steel reaction tube is 80-90%.

[0016] In this invention, "coverage rate" refers to the effective area of ​​the silica film covering the inner surface of the stainless steel reaction tube.

[0017] According to some embodiments of the present invention, the elemental composition of the stainless steel reaction tube material, by weight percentage, includes 12-30 wt% chromium, 5-20 wt% nickel, 0.5-5 wt% manganese, 0.1-2 wt% silicon, 0-8 wt% trace elements, 0-2 wt% carbon, and 60-95 wt% iron.

[0018] According to some embodiments of the present invention, the elemental composition of the stainless steel reaction tube material, by weight percentage, includes 16-18 wt% chromium, 10-14 wt% nickel, 1-3 wt% manganese, 0.5-1 wt% silicon, 0-4 wt% trace elements and 0-0.3 wt% ultra-trace elements, 0-0.2 wt% carbon and 70-90 wt% iron.

[0019] According to some embodiments of the present invention, the trace element is selected from at least one of titanium, molybdenum, niobium and vanadium, more preferably selected from titanium and / or molybdenum.

[0020] According to some embodiments of the present invention, the trace element is selected from sulfur and / or phosphorus.

[0021] According to some embodiments of the present invention, in the catalyst, the content of W is 3-40g, the content of Mn is 1-20g, and the content of Na and / or K is 0.5-10g relative to 100g of support.

[0022] According to some embodiments of the present invention, the catalyst contains 5-30g of W, 3-15g of Mn, and 1-5g of Na and / or K relative to 100g of support.

[0023] In this invention, there are no particular limitations on the preparation method of the catalyst, as long as it meets the requirements of this invention. For example, it can be prepared by the following method: adding a manganese source to deionized water, adding a support (preferably silica and / or barium titanate), stirring for 1-4 hours, and drying at 100-120°C for 2-12 hours to obtain solid A; then dissolving a sodium source and / or a potassium source in deionized water, adding solid A, stirring for 1-4 hours, and drying at 100-120°C for 2-12 hours to obtain solid B; then calcining solid B at 500-550°C for 4-5 hours, and then calcining at 850-880°C for 4-8 hours to obtain the catalyst of this invention. The manganese source is preferably manganese nitrate; the sodium source is preferably selected from sodium tungstate and sodium nitrate; and the potassium source is preferably potassium tungstate.

[0024] A second aspect of the present invention provides a method for preparing the reactor described in the first aspect, the method comprising the following steps:

[0025] (1) A silica film is attached to the inner surface of a stainless steel reaction tube to obtain a reactor precursor;

[0026] (2) A catalyst section is filled in the reactor front body to obtain the reactor.

[0027] According to some embodiments of the present invention, in step (1), the method of attaching the silica film can be: contacting the material to be coated with the inner surface of the stainless steel reaction tube.

[0028] According to some embodiments of the present invention, the material to be coated may be a silicate compound.

[0029] According to some embodiments of the present invention, the contact conditions may include: a temperature of 500-900°C, preferably 650-800°C; and a time of 1-10 hours, preferably 3-7 hours.

[0030] In this invention, the contact method can be vapor deposition, for example, depositing the material to be coated as a deposition liquid on the inner surface of a stainless steel reaction tube.

[0031] In this invention, before the material to be coated comes into contact with the inner surface of the stainless steel reaction tube, the material to be coated is preheated at 30-70°C for 10-30 minutes.

[0032] According to some embodiments of the invention, the contact is carried out in the presence of air.

[0033] Preferably, the air flow rate can be 200-1000 mL / min relative to the stainless steel reaction tube with a cross-sectional diameter of 10 mm, more preferably 300-850 mL / min, and even more preferably 300-700 mL / min.

[0034] The present invention does not impose a specific limitation on the amount of the material to be coated, as long as it can meet the requirements of the present invention. Preferably, the amount of the material to be coated is such that the thickness of the silica film attached to the inner surface of the stainless steel reaction tube is 0.5-15 μm, preferably 1-8 μm; the amount of the material to be coated is such that the coverage of the silica film on the inner surface of the stainless steel reaction tube is greater than or equal to 60%, preferably 80-90%.

[0035] According to some embodiments of the present invention, the material to be coated is selected from at least one of tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane, preferably selected from tetraethoxysilane and / or tetrapropoxysilane.

[0036] According to some embodiments of the present invention, in step (2), the volume is 20 cm³ relative to the cavity volume. 3 The stainless steel reaction tube contains a catalyst section, the amount of which can be 0.1-0.5g, preferably 0.15-0.3g.

[0037] In this invention, there are no particular restrictions on the length, diameter of the cross-section, and thickness of the stainless steel reaction tube (these can be selected according to actual needs), as long as they meet the requirements of this invention.

[0038] In this invention, the contact between the material to be coated and the inner surface of the stainless steel reaction tube is preferably carried out in the following manner: The material to be coated (e.g., tetraethoxysilane deposition solution) is preheated at 30-70°C for 10-30 minutes at 650-800°C. Air is then introduced into the material to be coated, which is carried into the stainless steel reaction tube by the air, and deposited on the inner surface of the reaction tube for 3-7 hours (residue may remain), resulting in the reactor precursor. The stainless steel reaction tube has a cross-sectional diameter of 10 mm, and the air flow rate is 300-700 mL / min. The volume relative to the cavity is 20 cm³. 3 The stainless steel reaction tube, wherein the amount of the material to be coated is 25-150g.

[0039] A third aspect of the present invention provides a method for producing C2 hydrocarbons by oxidative coupling of methane, the method comprising: introducing methane and oxygen into the aforementioned reactor to carry out an oxidative coupling reaction.

[0040] According to some embodiments of the present invention, prior to the oxidative coupling reaction, the reactor is further subjected to a filling process with an inert material.

[0041] According to some embodiments of the present invention, the filling process is carried out by filling the catalyst section in the reactor with a first inert material section and a second inert material section, respectively.

[0042] According to some embodiments of the present invention, the cavity volume is 20 cm³. 3 The stainless steel reaction tube has a first inert material section with a filling amount of 10-40g, preferably 15-30g, and a second inert material section with a filling amount of 10-40g, preferably 15-30g.

[0043] According to some embodiments of the present invention, in the direction of the reaction stream, the length ratio of the first inert material segment, the second inert material segment and the catalyst segment can be 1:(1-2):(0.02-0.15), preferably 1:(1-1.5):(0.03-0.13).

[0044] According to some embodiments of the present invention, the inert materials filled in the first inert material segment and the second inert material segment may each be independently selected from silicon dioxide and / or aluminum oxide.

[0045] According to some embodiments of the present invention, the conditions for the oxidative coupling reaction may include: a temperature of 600-900°C, preferably 700-850°C; and a time of 0.2-15 h, preferably 0.5-8 h.

[0046] According to some embodiments of the present invention, the gas hourly space velocity (HSV) of the reaction between methane and oxygen is 5000-30000 mL / (g·h), preferably 10000-20000 mL / (g·h).

[0047] According to some embodiments of the present invention, the amount of methane used is 2-10 mol relative to 1 mol of oxygen, in terms of the molar amount of oxygen.

[0048] The present invention will be described in detail below through embodiments.

[0049] Unless otherwise specified, all reagents used in the following examples and comparative examples are commercially available analytical grade reagents.

[0050] Preparation Example 1

[0051] 65g of a 50wt% manganese nitrate solution was added to deionized water, followed by 100g of silica. The mixture was stirred for 1 hour and dried at 120℃ for 2 hours to obtain solid A. Then, 26.9g of sodium tungstate and 0.9g of sodium nitrate were dissolved in deionized water, and solid A was added. The mixture was stirred for 1 hour and dried at 120℃ for 2 hours. Then, it was calcined at 550℃ for 4 hours to obtain solid B. Solid B was then heated to 850℃ and calcined for 8 hours to obtain catalyst C1, which has the composition of 4wt% Na-15wt% W-10wt% Mn / SiO2.

[0052] Preparation Example 2

[0053] 19.5 g of a 50 wt% manganese nitrate solution was added to deionized water, followed by 100 g of silica. The mixture was stirred for 4 hours and dried at 100 °C for 12 hours to obtain solid A. Then, 9 g of sodium tungstate and 2.7 g of sodium nitrate were dissolved in deionized water, and solid A was added. The mixture was stirred for 4 hours and dried at 100 °C for 12 hours. Then, it was calcined at 500 °C for 5 hours to obtain solid B. Solid B was then heated to 880 °C and calcined for 4 hours to obtain catalyst C2, which has the composition of 2 wt% Na-5 wt% W-3 wt% Mn / SiO2.

[0054] Preparation Example 3

[0055] 104g of a 50wt% manganese nitrate solution was added to deionized water, followed by 100g of silica. The mixture was stirred for 2 hours and dried at 110℃ for 6 hours to obtain solid A. Then, 62.8g of sodium tungstate and 8.3g of sodium nitrate were dissolved in deionized water, and solid A was added. The mixture was stirred for 2 hours and dried at 110℃ for 6 hours. Then, it was calcined at 550℃ for 5 hours to obtain solid B. Solid B was then heated to 860℃ and calcined for 6 hours to obtain catalyst C3, which has the composition of 10wt% Na-35wt% W-16wt% Mn / SiO2.

[0056] Preparation Example 4

[0057] The preparation was carried out in the same manner as in Example 1, except that the amount of active component and the calcination temperature were changed to obtain catalyst C4 (15wt% Na-1wt% W-0.5wt% Mn / SiO2).

[0058] Preparation Example 5

[0059] The preparation was carried out in the same manner as in Example 1, except that the active component was changed to obtain catalyst C5 (1wt% Mn / SiO2).

[0060] Example 1

[0061] The stainless steel reaction tube used in this embodiment has the following composition: 16 wt% chromium, 10 wt% nickel, 2 wt% manganese, 0.5 wt% silicon, 1 wt% carbon, 2 wt% molybdenum, 2 wt% titanium, 0.1 wt% sulfur, 0.2 wt% phosphorus and 66.2 wt% iron.

[0062] (1) A stainless steel reaction tube with a length of 530 mm, a cross-sectional diameter of 10 mm (outer diameter), and a thickness of 0.15 cm was heated to 700 °C and kept at that temperature for 20 min. 75 g of tetraethoxysilane deposition solution was preheated at 60 °C for 20 min. Air was introduced into the tetraethoxysilane deposition solution at 700 °C, and the air flow rate was controlled to be 500 mL / min. The tetraethoxysilane was carried into the stainless steel reaction tube by the air and deposited in contact with the inner surface of the reaction tube for 5 h (with residual deposition solution) to obtain the reactor precursor. The thickness of the silica film was 2 μm, and the coverage of the silica film on the inner surface of the stainless steel reaction tube was 90%.

[0063] (2) 0.2g of catalyst C1 (4wt% Na-15wt% W-10wt% Mn / SiO2) is filled into the reactor prebody prepared in step (1); reactor S1 with silica attached to its inner surface is obtained.

[0064] Example 2

[0065] The stainless steel reaction tube used in this embodiment has the following composition: 18wt% chromium, 15wt% nickel, 3wt% manganese, 1wt% silicon, 2wt% carbon, 1wt% molybdenum, 1wt% titanium, 0.1wt% sulfur, 0.1wt% phosphorus and 58.8wt% iron.

[0066] (1) A stainless steel reaction tube with a length of 530 mm, a cross-sectional diameter of 8 mm, and a thickness of 0.1 cm was heated to 800 °C and kept at that temperature for 20 min. 100 g of tetrapropoxysilane deposition solution was preheated at 70 °C for 15 min. At 800 °C, air was introduced into the tetraethoxysilane deposition solution, and the air flow rate was controlled to be 700 mL / min. The tetrapropoxysilane was carried into the stainless steel reaction tube by the air and deposited in contact with the inner surface of the reaction tube for 7 h (there was residual deposition solution) to obtain the reactor precursor. The thickness of the silica film was 4 μm and the coverage of the silica film on the inner surface of the stainless steel reaction tube was 90%.

[0067] (2) 0.2g of catalyst C2 (2wt% Na-5wt% W-3wt% Mn / SiO2) was filled into the reactor prebody prepared in step (1); reactor S2 with silica attached to its inner surface was obtained.

[0068] Example 3

[0069] The stainless steel reaction tube used in this embodiment has the following composition: 25 wt% chromium, 17 wt% nickel, 4 wt% manganese, 2 wt% silicon, 2 wt% carbon, 0.5 wt% molybdenum, 1 wt% titanium, 0.2 wt% sulfur, 0.05 wt% phosphorus and 66.2 wt% iron.

[0070] (1) A stainless steel reaction tube with a length of 530 mm, a cross-sectional diameter of 10 mm, and a thickness of 0.1 cm was heated to 650 °C and kept at that temperature for 20 min. 40 g of tetraethoxysilane deposition solution was preheated at 30 °C for 30 min. At 650 °C, air was introduced into the tetraethoxysilane deposition solution, and the air flow rate was controlled to be 300 mL / min. The tetraethoxysilane was carried into the stainless steel reaction tube by the air and deposited in contact with the inner surface of the reaction tube for 3 h (there was residual deposition solution) to obtain the reactor precursor. The thickness of the silica film was 1 μm and the coverage of the silica film on the inner surface of the stainless steel reaction tube was 86%.

[0071] (2) Fill the reactor prebody prepared in step (1) with 0.2g of C3 (10wt% Na-35wt% W-16wt% Mn / SiO2) catalyst; and obtain reactor S3 with silica attached to its inner surface.

[0072] Examples 4-7

[0073] The process was carried out in accordance with Example 1, except that Examples 4-7 changed one or more parameters, such as the contact temperature or time in step (1), the air flow rate, the type or amount of silicon source, and the composition or filling amount of the catalyst in step (2), as shown in Table 1. Reactors S4-S7 with silica adhering to their inner surfaces were finally obtained.

[0074] Comparative Example 1

[0075] The procedure was carried out as in Example 1, except that no silica film was attached to the inner surface of the stainless steel reactor, as detailed in Table 1. Reactor D1 was thus obtained.

[0076] Comparative Example 2

[0077] The process was carried out in accordance with Example 1, except that the contact deposition time of tetraethoxysilane on the inner surface of the stainless steel reaction tube was changed to 0.5 h. Ultimately, the thickness of the silica film was 0.2 μm, and the coverage of the silica film on the inner surface of the stainless steel reaction tube was 50%, as detailed in Table 1. Reactor D2 was thus obtained.

[0078] Comparative Example 3

[0079] The procedure was carried out as in Example 1, except that the catalyst composition was changed to C5 (1wt% Mn / SiO2), as detailed in Table 1. Reactor D3 was obtained.

[0080] Comparative Example 4

[0081] The process was carried out in the same manner as Comparative Example 1, except that the catalyst composition was changed to C5 (1wt% Mn / SiO2). Reactor D4 was obtained.

[0082] In Table 1, “thickness” refers to the thickness of the silica film attached to the inner surface of the stainless steel reaction tube, which was measured by scanning electron microscopy (FEI XL-30 field emission environmental scanning electron microscope, USA); “coverage” refers to the coverage of the silica film on the inner surface of the stainless steel reaction tube, which was measured by scanning electron microscopy (FEI XL-30 field emission environmental scanning electron microscope, USA).

[0083] Table 1

[0084]

[0085] The methane oxidative coupling reaction was evaluated using reactors (S1-S7, D1-D4) obtained in the above examples and comparative examples.

[0086] Test Example 1

[0087] The reactor prepared in Example 1 was used for the oxidative coupling of methane to C2 hydrocarbons. The reaction was carried out in a continuous flow fixed bed. Both ends of the catalyst in the tube were filled with inert material, quartz sand, with a loading amount of 42 g. The length ratio of the first inert material section, the second inert material section, and the catalyst section was 1:1:0.05. The reaction pressure was the pressure generated by the raw materials themselves, the reaction temperature was 800 °C, the alkane-oxygen ratio (molar ratio of methane to oxygen) was 2.2, and the gas hourly space velocity (GHSV) based on methane and oxygen was 20000 mL / (g·h). After 1 hour of reaction, the performance evaluation results of the oxidative coupling of methane to ethylene are listed in Table 2.

[0088] Test Example 2

[0089] The reactor prepared in Example 1 was used for the oxidative coupling of methane to C2 hydrocarbons. The reaction was carried out in a continuous flow fixed bed. Both ends of the catalyst in the tube were filled with inert material, which was quartz sand. The amount of inert material was 40 g. The length ratio of the first inert material section, the second inert material section and the catalyst section was 1:1.5:0.1. The reaction pressure was the pressure generated by the raw materials themselves. The reaction temperature was 830 °C. The alkane-to-oxygen ratio was 4. The gas hourly space velocity (GHSV) of the reaction, calculated as methane and oxygen, was 10000 mL / (g·h). After 1 hour of reaction, the performance evaluation results of the oxidative coupling of methane to ethylene are listed in Table 2.

[0090] Test Example 3

[0091] The reactor prepared in Example 1 was used for the oxidative coupling of methane to C2 hydrocarbons. The reaction was carried out in a continuous flow fixed bed. Both ends of the catalyst in the tube were filled with inert material, which was quartz sand. The amount of inert material was 45g. The length ratio of the first inert material section, the second inert material section and the catalyst section was 1:1.2:0.06. The reaction pressure was the pressure generated by the raw materials themselves. The reaction temperature was 780℃. The alkane-to-oxygen ratio was 3. The gas hourly space velocity (GHSV) of the reaction, calculated as methane and oxygen, was 15000mL / (g·h). After 1 hour of reaction, the performance evaluation results of the oxidative coupling of methane to ethylene are listed in Table 2.

[0092] Test Case 4-7 and Comparative Test Case 1-4

[0093] The test was conducted in the same manner as in Test Example 1, except that S4-S7 and D1-D4 were used instead of S1. The performance test results are shown in Table 2.

[0094] Comparative Test Example 5

[0095] The process was similar to Test Example 1, except that a quartz reactor was used and a C1 catalyst was employed for the oxidative coupling of methane to C2 hydrocarbons. The reaction performance evaluation is shown in Table 2.

[0096] Comparative Test Case 6

[0097] The process was similar to Test Example 1, except that a quartz reactor was used and a C5 catalyst was employed for the oxidative coupling of methane to C2 hydrocarbons. The reaction performance evaluation is shown in Table 2.

[0098] The reaction products obtained from Test Examples 1-7 and Comparative Test Examples 1-5 were analyzed using a gas chromatograph (Gas Chromatograph, Model 7890A, Agilent Technologies). The products were determined using a dual-detection-channel, three-valve, four-column system, with the FID detector connected to an alumina column for analyzing 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.

[0099] The calculation methods for methane conversion rate, etc., are as follows:

[0100] Methane conversion rate = Amount of methane consumed in the reaction / Initial amount of methane × 100%

[0101] Ethylene selectivity = Amount of methane consumed to produce ethylene / Total methane consumption × 100%

[0102] Ethane selectivity = Amount of methane consumed to produce ethane / Total methane consumption × 100%

[0103] C2 hydrocarbon selectivity = ethane selectivity + ethylene selectivity

[0104] CO x (CO + CO2) selectivity = (Amount of methane consumed by the combined generation of CO and CO2) / (Total methane consumption) × 100%

[0105] C2 hydrocarbon yield = methane conversion rate × (ethane selectivity + ethylene selectivity)

[0106] Table 2

[0107]

[0108]

[0109] As can be seen from the test results in Table 2, compared with Comparative Test Example 1, Test Examples 1-7 showed higher selectivity for C2 hydrocarbons, higher yield of C2 hydrocarbons, and higher CO content. x The relatively low selectivity indicates that the reactor and method of this invention suppresses deep oxidation of methane and reduces side reactions during the oxidative coupling of methane to prepare C2 hydrocarbons. Compared to Comparative Test Example 2, Test Examples 1-7 show higher C2 hydrocarbon selectivity, higher C2 hydrocarbon yield, and higher CO2 content. x The relatively low selectivity indicates that only when the thickness of the silica film attached to the inner surface of the stainless steel reaction tube is within the range of this invention (i.e., 0.5-15 μm), the catalyst of this invention results in fewer side reactions and a higher yield of C2 hydrocarbons during the oxidative coupling of methane. Compared to comparative test examples 3, 4, and 6, the C2 hydrocarbon selectivity and yield of Examples 1-7 are both higher, indicating that only by using the technical solution of this invention with specific catalysts can superior catalytic effects be obtained.

[0110] Compared to Comparative Test Example 5, the data in Table 2 for Test Example 1 are not significantly different. However, the quartz tube used in Comparative Test Example 5 is fragile and would severely limit its further scale-up production. In contrast, the stainless steel reaction tube used in Test Example 1 is robust, has a long service life, and good thermal insulation properties, making it easy to use on a large scale.

[0111] 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: (1) A silica film is attached to the inner surface of a stainless steel reaction tube to obtain a reactor precursor; (2) A catalyst section is filled into the inlet of the reactor to obtain the reactor; (3) Methane and oxygen are introduced into a reactor with silica adhering to its inner surface to carry out an oxidative coupling reaction; The reactor includes a stainless steel reaction tube and a silica film attached to the inner surface of the stainless steel reaction tube. The silica film has a thickness of 0.5-15µm and a coverage of 60% or more on the inner surface of the stainless steel reaction tube. The catalyst in the catalyst section includes a support and an active component supported on the support. The support is selected from silica and / or barium titanate. The active component includes a first active component and a second active component. The first active component is Na2WO4 and / or K2WO4, and the second active component is an oxide of Mn. In step (1), the method of attaching the silica film is to bring the material to be coated into contact with the inner surface of the stainless steel reaction tube. The material to be coated is a silicate compound; The contact conditions include: a temperature of 500-900℃ and a time of 1-10 hours. The contact takes place in the presence of air.

2. The method according to claim 1, wherein, The thickness of the silica film is 1-8µm, and the coverage of the silica film on the inner surface of the stainless steel reaction tube is 80-90%.

3. The method according to claim 1, wherein, By weight percentage, the elemental composition of stainless steel reaction tubes includes 12-30 wt% chromium, 5-20 wt% nickel, 0.5-5 wt% manganese, 0.1-2 wt% silicon, 0-8 wt% trace elements, 0-2 wt% carbon, and 60-95 wt% iron.

4. The method according to claim 3, wherein, By weight percentage, the elemental composition of stainless steel reaction tubes includes 16-18 wt% chromium, 10-14 wt% nickel, 1-3 wt% manganese, 0.5-1 wt% silicon, 0-4 wt% trace elements and 0-0.3 wt% ultra-trace elements, 0-0.2 wt% carbon and 70-90 wt% iron.

5. The method according to claim 3, wherein, The trace element is selected from at least one of titanium, molybdenum, niobium and vanadium.

6. The method according to claim 5, wherein, The trace elements are selected from titanium and / or molybdenum.

7. The method according to claim 3, wherein, The trace elements are selected from sulfur and / or phosphorus.

8. The method according to claim 1, wherein, In the catalyst, relative to 100g of support, the content of W is 3-40g, the content of Mn is 1-20g, and the content of Na and / or K is 0.5-10g.

9. The method according to claim 8, wherein, In the catalyst, relative to 100g of support, the content of W is 5-30g, the content of Mn is 3-15g, and the content of Na and / or K is 1-5g.

10. The method according to claim 1, wherein, The contact conditions include: a temperature of 650-800℃ and a time of 3-7 hours.

11. The method according to claim 1, wherein, The air flow rate is 200-1000 mL / min relative to a stainless steel reaction tube with a cross-sectional diameter of 10 mm.

12. The method according to claim 11, wherein, The air flow rate is 300-850 mL / min relative to a stainless steel reaction tube with a cross-sectional diameter of 10 mm.

13. The method according to claim 1, wherein, The amount of material to be coated is such that the thickness of the silica film adhering to the inner surface of the stainless steel reaction tube is 0.5-15µm; the amount of material to be coated is such that the coverage of the silica film on the inner surface of the stainless steel reaction tube is greater than or equal to 60%.

14. The method according to claim 13, wherein, The amount of material to be coated results in a silica film thickness of 1-8µm adhering to the inner surface of the stainless steel reaction tube; the amount of material to be coated results in a silica film coverage of 80-90% on the inner surface of the stainless steel reaction tube.

15. The method according to claim 1, wherein, The material to be coated is selected from at least one of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane.

16. The method according to claim 15, wherein, The material to be coated is selected from tetraethoxysilane and / or tetrapropoxysilane.

17. The method according to claim 1, wherein, In step (2), the volume of the cavity is 20 cm³. 3 The stainless steel reaction tube contains a catalyst section with a loading amount of 0.1-0.5g.

18. The method according to claim 17, wherein, In step (2), the volume of the cavity is 20 cm³. 3 The stainless steel reaction tube contains a catalyst section with a loading amount of 0.15-0.3g.

19. The method according to claim 1, wherein, Prior to the oxidative coupling reaction, the reactor is filled with inert material.

20. The method according to claim 19, wherein, The filling process is as follows: a first inert material segment and a second inert material segment are respectively filled at both ends of the catalyst segment in the reactor.

21. The method according to claim 20, wherein, The cavity volume is 20cm 3 The stainless steel reaction tube has a first inert material section with a filling amount of 10-40g and a second inert material section with a filling amount of 10-40g.

22. The method according to claim 21, wherein, The cavity volume is 20cm 3 The stainless steel reaction tube has a first inert material section filled with 15-30g and a second inert material section filled with 15-30g.

23. The method of claim 20, wherein, In the direction of the reaction stream, the length ratio of the first inert material segment, the second inert material segment, and the catalyst segment is 1:(1-2):(0.02-0.15).

24. The method according to claim 23, wherein, In the direction of the reaction stream, the length ratio of the first inert material segment, the second inert material segment, and the catalyst segment is 1:(1-1.5):(0.03-0.13).

25. The method according to claim 20, wherein, The inert materials filled in the first and second inert material segments are each independently selected from silicon dioxide and / or aluminum oxide.

26. The method according to claim 1, wherein, The conditions for the oxidative coupling reaction include: a temperature of 600-900℃ and a time of 0.2-15h.

27. The method according to claim 26, wherein, The conditions for the oxidative coupling reaction include: a temperature of 700-850℃ and a time of 0.5-8h.

28. The method according to claim 1, wherein, The gas hourly space velocity (HSV) for the reaction of methane and oxygen is 5000-30000 mL / (g·h).

29. The method according to claim 28, wherein, The gas hourly space velocity (HSV) for the reaction of methane and oxygen is 10,000-20,000 mL / (g·h).

30. The method according to claim 1, wherein, The amount of methane used is 2-10 mol relative to 1 mol of oxygen.

Images