Reactor for oxidative coupling reaction of methane as well as preparation method and application of reactor

Abstract

The invention relates to the technical field of methane oxidative coupling, and discloses a reactor for methane oxidative coupling reaction and a preparation method and application thereof.The reactor comprises a metal shell and a composite oxide film layer attached to the inner surface of the metal shell, and the composite oxide film layer comprises Mg, Al, Ca and Si. According to the invention, the inner surface of the metal shell is coated, and Mg, Al, Ca and Si are adopted as main components of the composite oxide film layer, so that the side reaction of methane and oxygen can be effectively avoided, and the conversion rate of methane and the selectivity of C2 and above hydrocarbons are improved.

Description

Reactors for methane oxidative coupling reactions, their preparation methods, and applications Technical Field

[0001] This invention relates to the field of methane oxidative coupling technology, specifically to a reactor for methane oxidative coupling reaction, its preparation method, and its application. Background Technology

[0002] The oxidative coupling of methane to ethylene and ethane is one of the most challenging and closely watched research topics in the field of catalysis due to its academic significance and potential for enormous economic value. Since its initial report by Keller and Bhasin in 1982, it has been a focus of attention in catalysis, the chemical industry, and the oil and gas sector. Methane oxidative coupling is an exothermic reaction, producing mainly ethylene, ethane, and water. This technology boasts good atom economy and environmental friendliness, making it a target of intense research by scientific researchers and major companies for the past four decades. Currently, quartz reactors are used in laboratory research for methane oxidative coupling catalysts. This is mainly because conventional stainless steel reactors increase side reactions between methane and oxygen, easily leading to deep oxidation and the formation of carbon monoxide and carbon dioxide. Quartz tube reactors, due to their inherent properties, are currently unsuitable for industrial applications. Therefore, finding a material that can replace quartz tubes, has industrial application prospects, and produces no side effects for the methane oxidative coupling reaction is a pressing issue. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems of quartz tubes being fragile and metal reaction tubes increasing methane and oxygen side reactions in the prior art, and to provide a reactor for methane oxidative coupling reaction, its preparation method, and its application.

[0004] To achieve the above objectives, a first aspect of the present invention provides a reactor for a methane oxidative coupling reaction, the reactor comprising a metal shell and a composite oxide film layer attached to the inner surface of the metal shell, wherein the composite oxide film layer comprises Mg, Al, Ca and Si.

[0005] A second aspect of the present invention provides a method for preparing a reactor for methane oxidative coupling reaction, the method comprising: depositing a coating on the inner surface of a metal shell using a coating solution containing Mg precursor, Al precursor, Ca precursor and Si precursor, followed by drying and calcination.

[0006] A third aspect of the present invention provides a reactor for methane oxidative coupling reaction prepared by the method described above.

[0007] A fourth aspect of the present invention provides a method for methane oxidative coupling, the method comprising: contacting methane with a catalyst in the reactor described above to carry out a methane oxidative coupling reaction.

[0008] The above technical solution has achieved the following beneficial effects:

[0009] This invention effectively avoids the side reaction between methane and oxygen by coating the inner surface of the metal shell with Mg, Al, Ca and Si as the main components of the composite oxide film, thereby improving the conversion rate of methane and the selectivity of C2 and above hydrocarbons. At the same time, the reactor of this invention is not easily broken and has the advantages of high temperature resistance and fast heat conduction. Detailed Implementation

[0010] 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.

[0011] The first aspect of the present invention provides a reactor for a methane oxidative coupling reaction, the reactor comprising a metal shell and a composite oxide film layer attached to the inner surface of the metal shell, wherein the composite oxide film layer comprises Mg, Al, Ca and Si.

[0012] The inventors of this invention discovered that coating the inner surface of a metal shell with Mg, Al, Ca, and Si as the main components of the composite oxide film can effectively prevent the side reaction between methane and oxygen, thereby improving the conversion rate of methane and the selectivity of C2 and above hydrocarbons. At the same time, the reactor of this invention is not easily broken and has the advantages of high temperature resistance and fast heat conduction.

[0013] According to the present invention, preferably, the composite oxide film layer does not contain detectable amounts of Fe and Ni.

[0014] The inventors of this invention further discovered that when the amount of Mg in the composite oxide film is higher than that of Al, Ca, and Si (i.e., the molar ratio of Mg to Al is greater than 1, the molar ratio of Mg to Ca is greater than 1, and the molar ratio of Mg to Si is greater than 1), the conversion rate of methane and the selectivity of C2 and above hydrocarbons can be further improved.

[0015] According to the present invention, preferably, the molar ratio of Mg, Al, Ca, and Si is 10:2-5:0.1-2:2-6, more preferably 10:2-4:0.1-2:2-5. The inventors of the present invention have further discovered that when Mg, Al, Ca, and Si are limited to the above ranges, the conversion rate of methane and the selectivity for C2 and higher hydrocarbons can be further improved. In the present invention, the molar ratio of Mg, Al, Ca, and Si in the composite oxide film layer is calculated based on the feed amount.

[0016] According to the present invention, in order to ensure the density and uniformity of the composite oxide coating, preferably, the thickness of the composite oxide film is 2-200 μm, more preferably 2-100 μm, and even more preferably 3-30 μm. The thickness of the composite oxide film is tested by X-ray fluorescence spectrometry (XRF).

[0017] According to the present invention, the metal shell can be made of a metal commonly used in reactors, such as a material with high-temperature resistance. Preferably, the metal shell is made of stainless steel; more preferably, it is at least one of stainless steel 304, stainless steel 316L, and Inconel 825. In the present invention, the stainless steel material can withstand temperatures of 650°C or higher, preferably not lower than 750°C; the stainless steel material of the present invention is suitable for use in high-temperature reactions (e.g., methane oxidative coupling reaction).

[0018] According to the present invention, preferably, the thickness of the metal casing is 2-5 mm.

[0019] The reactor of the present invention can be sold as a product alone or together with the catalyst. Therefore, the reactor of the present invention may also include a catalyst packed inside the reactor. The catalyst may be a lanthanum-containing catalyst, such as (nano)lanthanum oxycarbonate.

[0020] A second aspect of the present invention provides a method for preparing a reactor for methane oxidative coupling reaction, the method comprising: depositing a coating on the inner surface of a metal shell using a coating solution containing Mg precursor, Al precursor, Ca precursor and Si precursor, followed by drying and calcination.

[0021] In this invention, there are no particular limitations on the types of Mg precursor, Al precursor, Ca precursor, and Si precursor, as long as they can provide the elements of Mg, Al, Ca, and Si in the composite oxide film. The Mg precursor, Al precursor, Ca precursor, and Si precursor can be, respectively, Mg salt, Al salt, Ca salt, and silica sol; for example, the Mg precursor can be Mg nitrate, sulfate, chloride, etc.; the Al precursor can be Al nitrate, sulfate, chloride, etc.; the Ca precursor can be Ca nitrate, sulfate, chloride, etc.; the silica content in the Si silica sol can be 15-40% by weight, and the solvent in the silica sol can be water and / or an organic solvent (e.g., ethanol).

[0022] In this invention, the method of obtaining the coating solution can be selected within a wide range. For example, the coating solution can be obtained by mixing Mg precursor, Al precursor, Ca precursor, and Si precursor with water to obtain a mixture, then adding a gelling agent (e.g., citric acid, aluminum hydroxide), and then adding ammonia until a gel is formed, at which point the addition of ammonia is stopped, thus obtaining the coating solution. The amount of gelling agent used is 1-30g per 100g of the mixture. The weight ratio of Mg precursor to water is 0.05-0.15:1.

[0023] According to the present invention, preferably, the molar ratio of Mg precursor, Al precursor, Ca precursor and Si precursor in the coating solution is 10:2-5:0.1-2:2-6, more preferably 10:2-4:0.1-2:2-5.

[0024] According to the present invention, preferably, the amount of the coating solution is such that the thickness of the composite oxide film layer formed after calcination is 2-200 μm, more preferably 2-100 μm, and more preferably 3-10 μm.

[0025] According to the present invention, the coating method is not particularly limited, as long as a composite oxide film layer can be formed on the inner surface of the metal casing. The coating method can be physical coating, chemical coating, vacuum coating, spray coating, electrochemical coating, atomic layer plating, etc. Preferably, the coating method includes spray coating and / or atomic layer plating.

[0026] According to a preferred embodiment of the present invention, the coating method is a spraying method. Preferably, the spraying method includes: spraying a coating solution onto the inner surface of a metal casing using an ultrasonic sprayer. The spraying can be performed in multiple applications (e.g., 1-200 times). When spraying in multiple applications, each application needs to be dried before the next application. The drying conditions are not particularly limited, as long as the water in the coating solution evaporates.

[0027] According to the present invention, preferably, the calcination conditions include a temperature of 800-1100°C and a time of 2-10 hours. Typically, the calcination is carried out in an oxidizing atmosphere (e.g., air).

[0028] According to the present invention, the metal shell can be made of a metal commonly used in reactors, such as a material with high-temperature resistance. Preferably, the metal shell is made of stainless steel; more preferably, it is at least one of stainless steel 304, stainless steel 316L, and Inconel 825. In the present invention, the stainless steel material can withstand temperatures of 650°C or higher, preferably not lower than 750°C; the stainless steel material of the present invention is suitable for use in high-temperature reactions (e.g., methane oxidative coupling reaction).

[0029] According to the present invention, preferably, the thickness of the metal casing is 2-5 mm.

[0030] According to the present invention, preferably, the method further includes polishing the inner surface of the metal casing before coating.

[0031] A third aspect of the present invention provides a reactor for methane oxidative coupling reaction prepared by the method described above.

[0032] A fourth aspect of the present invention provides a method for methane oxidative coupling, the method comprising: contacting methane with a catalyst in the reactor described above to carry out a methane oxidative coupling reaction.

[0033] According to the present invention, preferably, the conditions for the methane oxidative coupling reaction include: a reaction temperature of 500-750°C; a molar ratio of methane to oxygen of 3-10:1; and a reaction space velocity of 5000-200000 ml / gh (calculated as methane).

[0034] According to the present invention, preferably, the catalyst is lanthanum oxycarbonate. The inventors of the present invention have further discovered that when nano-lanthanum oxycarbonate is used as a catalyst packed in the reactor, the deep oxidation reaction of methane can be further avoided.

[0035] The present invention will be described in detail below through embodiments. In the following embodiments,

[0036] The silicon source is silica sol, in which the silica content is 25% by weight; the magnesium source is magnesium nitrate; the aluminum source is aluminum nitrate; and the calcium source is calcium nitrate.

[0037] Example 1

[0038] This embodiment illustrates the preparation method of the coated metal reactor in this invention.

[0039] Commercially available 304 stainless steel pipe (3mm thick) was selected as the metal pipe to be coated, and the interior was polished for later use. A mixture of magnesium source, aluminum source, calcium source, and silicon source (calculated as silicon element) in a molar ratio of 10:2:0.1:2 was prepared with 100g of deionized water, wherein the amount of magnesium source used was 10.37g. Then, a gelling agent (citric acid) was added and stirred until homogeneous. Ammonia water was then gradually added dropwise to adjust the solution until a gel-like solution was obtained; the amount of gelling agent used was 25g per 100g of the mixture.

[0040] A gel-like solution was ultrasonically sprayed onto the polished inner surface of a metal reactor. After the first spraying and thorough drying, a second spraying was performed, followed by thorough drying. This process was repeated multiple times, followed by thorough drying. The reactor was then placed in a tube furnace and heated to 850°C at a rate of 1°C / min, and held for 8 hours to obtain a metal reactor with an inner composite oxide film, denoted as G1. The thickness of the composite oxide film is shown in Table 1.

[0041] Example 2

[0042] This embodiment illustrates the preparation method of the coated metal reactor in this invention.

[0043] Select 316L stainless steel as the metal tube to be coated (the thickness of the metal tube is 2mm), and polish the inside for later use. Mix magnesium source: aluminum source: calcium source: silicon source in a molar ratio of 10:3:1:4 with 100g of deionized water, wherein the amount of magnesium source is 10.68g. Then add gelling agent (citric acid) and stir evenly, then gradually add ammonia water dropwise to adjust the solution until a gel-like solution is formed; wherein, 30g of citric acid is added for every 100g of mixture.

[0044] A gel-like solution was ultrasonically sprayed onto the polished inner surface of a metal reactor. After the first spraying and thorough drying, a second spraying was performed, followed by thorough drying. This process was repeated multiple times, followed by thorough drying. The reactor was then placed in a tube furnace and heated to 950°C at a rate of 1°C / min, and held for 12 hours to prepare a metal reactor with an inner composite oxide film, denoted as G2. The thickness of the composite oxide film is shown in Table 1.

[0045] Example 3

[0046] This embodiment illustrates the preparation method of the coated metal reactor in this invention.

[0047] Inconel 825 was selected as the metal tube to be coated (the thickness of the metal tube is 4mm), and the inside was polished for later use. A mixture of magnesium source, aluminum source, calcium source, and silicon source (based on elemental silicon) in a molar ratio of 10:4:2:5 was mixed with 100g of deionized water, wherein the amount of magnesium source used was 8.8g. Then, a gelling agent (citric acid) was added and stirred evenly, and then ammonia water was gradually added dropwise to adjust the solution until a gel-like solution was formed; wherein, the amount of gelling agent used was 30g per 100g of the mixture.

[0048] A gel-like solution was ultrasonically sprayed onto the polished inner surface of a metal reactor. After the first spray and thorough drying, a second spray was applied, followed by thorough drying. This process was repeated multiple times, followed by thorough drying. The reactor was then placed in a tube furnace and heated to 1050°C at a rate of 1°C / min, and held for 12 hours to prepare an Inconel 825 metal reactor with an internally plated composite oxide film, denoted as G3. The thickness of the composite oxide film is shown in Table 1.

[0049] Example 4

[0050] This embodiment illustrates the preparation method of the coated metal reactor in this invention.

[0051] Inconel 825 was selected as the metal tube to be coated (the thickness of the metal tube is 5mm), and the inside was polished for later use. A mixture of magnesium source, aluminum source, calcium source, and silicon source (based on elemental silicon) in a molar ratio of 10:2:2:6 was mixed with 100g of deionized water, wherein 10g of magnesium source was used. Then, a gelling agent (citric acid) was added and stirred evenly. Ammonia water was then gradually added dropwise to adjust the solution until a gel-like solution was formed; the amount of gelling agent used was 30g per 100g of the mixture.

[0052] A gel-like solution was ultrasonically sprayed onto the polished inner surface of a metal reactor. After the first spraying and thorough drying, a second spraying was performed, followed by thorough drying. This process was repeated multiple times, followed by thorough drying. The reactor was then placed in a tube furnace and heated to 1050°C at a rate of 1°C / min, and held for 12 hours to prepare an Inconel 825 metal reactor with an internally plated composite oxide film, denoted as G4. The thickness of the composite oxide film is shown in Table 1.

[0053] Example 5

[0054] The coated metal reactor was prepared according to the method of Example 4, except that the molar ratio of magnesium source: aluminum source: calcium source: silicon source (calculated as silicon element) was 10:2:2:10.

[0055] Example 6

[0056] The coated metal reactor was prepared according to the method of Example 4, except that the molar ratio of magnesium source: aluminum source: calcium source: silicon source (calculated as silicon element) was 10:10:2:4.

[0057] Example 7

[0058] The coated metal reactor was prepared according to the method of Example 4, except that the coating thickness was 2 μm.

[0059] Comparative Example 1

[0060] The coated metal reactor was prepared according to the method of Example 4, except that "aluminum" was replaced with an equimolar amount of "magnesium".

[0061] Comparative Example 2

[0062] The coated metal reactor was prepared according to the method of Example 4, except that "calcium" was replaced with an equimolar amount of "magnesium".

[0063] Comparative Example 3

[0064] The coated metal reactor was prepared according to the method of Example 4, except that "calcium" was replaced with an equimolar amount of "iron".

[0065] Comparative Example 4

[0066] A standard 316L metal reaction tube was used as the metal reactor.

[0067] Test Example 1

[0068] The application of the coated metal reactor prepared in the above examples and comparative examples in the oxidative coupling reaction of methane was tested. 1 g of catalyst (nano-lanthanum oxycarbonate) was loaded into the coated metal reactor, and methane and oxygen were introduced at an alkane-to-oxygen ratio of 8. The reaction temperature was 650 °C, and the reaction space velocity (HSV) was 140,000 ml / gh (based on methane). The composition of the reaction products was analyzed by Agilent gas chromatography. The methane conversion and selectivity for C2 and higher hydrocarbons are shown in Table 1.

[0069] Table 1

[0070]

[0071] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. (1240214)

[0072] I95560BHY

[0073] Within the scope of the technical concept of this invention, various simple modifications can be made to the technical solution of this invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed in this invention and are all within the protection scope of this invention.

Claims

1. A reactor for methane oxidative coupling reaction, characterized in that, The reactor includes a metal shell and a composite oxide film layer attached to the inner surface of the metal shell, wherein the composite oxide film layer is composed of Mg, Al, Ca and Si.

2. The reactor according to claim 1, wherein, The molar ratio of Mg, Al, Ca and Si is 10:2-5:0.1-2:2-6, preferably 10:2-4:0.1-2:2-5.

3. The reactor according to claim 1, wherein, The thickness of the composite oxide film is 2-200 μm, preferably 2-100 μm, and more preferably 3-30 μm.

4. The reactor according to claim 1, wherein, The metal casing is made of stainless steel; and / or the thickness of the metal casing is 2-5 mm.

5. A method for preparing a reactor for methane oxidative coupling reaction, characterized in that, The method includes: depositing a coating on the inner surface of a metal casing using a coating solution containing Mg precursor, Al precursor, Ca precursor and Si precursor, and then calcining it.

6. The method according to claim 5, wherein, The molar ratio of Mg precursor, Al precursor, Ca precursor and Si precursor in the coating solution is 10:2-5:0.1-2:2-6, preferably 10:2-4:0.1-2:2-5.

7. The method according to claim 5, wherein, The amount of the coating solution used is such that the thickness of the composite oxide film layer formed after calcination is 2-200 μm, preferably 2-100 μm, and more preferably 3-30 μm; And / or, the coating method includes: spray coating and / or atomic layer electroplating.

8. The method according to claim 5, wherein, The roasting conditions include a temperature of 800-1100℃ and a time of 2-12 hours.

9. The method according to claim 5, wherein, The metal casing is made of a high-temperature resistant material; preferably stainless steel; and / or, the thickness of the metal casing is 2-5 mm. And / or, the method further includes polishing the inner surface of the metal casing before coating.

10. A reactor for methane oxidative coupling reaction prepared by the method of any one of claims 5-9.

11. A method for oxidative coupling of methane, characterized in that, The method comprises: contacting methane with a catalyst in a reactor according to any one of claims 1-4 and 10 to carry out a methane oxidative coupling reaction.

12. The method according to claim 11, wherein, The conditions for the methane oxidative coupling reaction include: a reaction temperature of 500-750℃; a molar ratio of methane to oxygen of 3-10:1; and a reaction space velocity of 5000-200000 ml / gh (based on methane). Preferably, the catalyst is lanthanum oxycarbonate.

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