Methane oxidative coupling reactor and application thereof

Abstract

The invention relates to the technical field of methane oxidative coupling, and discloses a methane oxidative coupling reactor and application thereof. The reactor provided by the invention comprises a reactor cavity comprising an inner pipe (1) and an outer pipe (2) nested on the outer side of the inner pipe, the inner pipe (1) is provided with holes in the pipe wall of a catalyst bed layer position (4), and a partition plate (3) is arranged at the tail end of the inner pipe at the catalyst bed layer position (4) in the gas flowing direction so as to prevent gas introduced into the inner pipe from continuously flowing forwards along the inner pipe. When the reactor provided by the invention is used for carrying out methane oxidative coupling reaction, the dispersity of feed gas can be improved, the center temperature of a catalyst bed layer is effectively reduced, on one hand, the reaction safety is improved, on the other hand, the conversion rate of methane and the selectivity of C2 hydrocarbon are improved, and a foundation is laid for industrial application of a methane oxidative coupling technology.

Description

Technical Field

[0001] The invention relates to the technical field of methane oxidative coupling, and in particular to a methane oxidative coupling reactor and application thereof. Background Art

[0002] The methane oxidative coupling reaction is a direct conversion reaction of methane, which can use the cheap and widely available methane as a raw material to prepare a variety of high-value chemical raw materials. The preparation of carbon dihydrogen by the methane oxidative coupling reaction is one of the most promising processes for the methane oxidative coupling reaction. However, as a gas with stable chemical properties, methane has a high activation energy, and even under aerobic conditions, it still requires a relatively high temperature (usually >700°C) to participate in the coupling reaction. Moreover, as a high-temperature and highly exothermic reaction, the methane oxidative coupling reaction releases a large amount of heat, and the axial temperature gradient and hot spot effect generated during the reaction bring many problems to the engineering scale-up and process flow of the process. In addition, the current conversion rate of carbon dihydrogen by the methane oxidative coupling reaction is still relatively low, which is difficult to meet the needs of industrial production. Summary of the invention

[0003] The purpose of the present invention is to provide a methane oxidative coupling reactor and its application in order to overcome the problems in the prior art that the methane oxidative coupling reaction releases a large amount of heat, industrial production is prone to safety problems, and the conversion rate of carbon dihydrocarbons is insufficient and cannot meet the requirements of industrialization. The reactor provided by the present invention can effectively reduce the center temperature of the bed layer, improve the safety of the methane oxidative coupling reaction, and lay a foundation for the industrial application of the reaction.

[0004] In order to achieve the above-mentioned object, the present invention provides a methane oxidative coupling reactor, which comprises a reactor cavity including an inner tube (1) and an outer tube (2) nested outside the inner tube.

[0005] The inner tube (1) has a hole in the tube wall at the catalyst bed position (4), and a partition (3) is provided at the end of the inner tube at the catalyst bed position (4) along the gas flow direction to prevent the gas introduced into the inner tube from continuing to flow forward along the inner tube.

[0006] The second aspect of the present invention provides a method for preparing carbon dihydrocarbons by methane oxidative coupling, the method comprising introducing methane and oxygen into the reactor described in the first aspect, and reacting under methane oxidative coupling reaction conditions;

[0007] Among them, one of methane and oxygen is introduced through the inner tube, and the other is introduced through the outer tube.

[0008] The third aspect of the present invention provides the reactor described in the first aspect, and / or the use of the method described in the second aspect in improving the safety of the methane oxidative coupling reaction and / or improving at least one of the reaction gas conversion rate, the C2H selectivity and the C2H yield of the methane oxidative coupling reaction.

[0009] Through the above technical solution, the present invention can at least achieve the following beneficial effects:

[0010] (1) The reactor and method provided by the present invention can effectively reduce the center temperature of the bed of methane oxidative coupling reaction, avoid safety problems caused by uneven temperature in the reactor, improve reaction safety, and facilitate industrial testing and application.

[0011] (2) The reactor and method provided by the present invention avoid side reactions caused by local high temperature in the reactor, thereby improving the selectivity and yield of carbon dihydrocarbons in the methane oxidative coupling reaction.

[0012] (3) When the reactor provided by the present invention is used for the methane oxidative coupling reaction, the reaction raw materials are fed uniformly and the dispersion of the reaction gas is improved, which further improves the conversion rate of the raw materials and the selectivity and yield of carbon dihydrocarbons. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of the reactor provided by the present invention.

[0014] Description of Reference Numerals

[0015] 1 inner tube; 2 outer tube; 3 partition; 4 catalyst bed;

[0016] A is raw gas A (i.e. one of methane and oxygen); B is raw gas B (i.e. the other of methane and oxygen). DETAILED DESCRIPTION

[0017] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0018] In the present invention, unless otherwise specified, "carbon dihydrocarbon" refers to ethane and / or ethylene.

[0019] The inventor of the present invention cleverly discovered in research that by setting the reaction tube in the methane oxidative coupling reactor to a "double-layer" structure with two inner and outer tubes nested, introducing a reaction raw gas (i.e., methane and oxygen) into the inner tube and the outer tube respectively, and opening holes at the catalyst bed position so that the raw gas can contact and react in the catalyst bed, the bed center temperature can be effectively reduced and the reaction safety can be improved. Moreover, after further research, the inventor also found that when such a reactor is used for methane oxidative coupling reaction, the reaction raw gas has better dispersion, so that the raw material conversion rate is improved, while the side reactions are reduced, and the selectivity and yield of carbon dihydrocarbons are also greatly improved.

[0020] Based on the above findings, the first aspect of the present invention provides a methane oxidative coupling reactor, referring to Figure 1 The reactor comprises a reactor cavity including an inner tube (1) and an outer tube (2) nested outside the inner tube,

[0021] The inner tube (1) has a hole in the tube wall at the catalyst bed position (4) (the catalyst is loaded in the annular space between the outer tube and the inner tube at this position), and a partition (3) is provided at the end of the inner tube at the catalyst bed position (4) along the gas flow direction to prevent the gas introduced into the inner tube from continuing to flow forward along the inner tube.

[0022] During use of the reactor provided by the present invention, one component of the raw gas can be introduced into the inner tube, and another component of the raw gas can be introduced into the outer tube. For example, methane can be introduced into the inner tube, and oxygen can be introduced into the outer tube, or vice versa. The reactor provided by the present invention can improve the dispersibility of the raw gas through the above-mentioned feeding method, thereby improving the raw material conversion rate, carbon dihydrocarbon selectivity and yield of the methane oxidative coupling reaction.

[0023] It should be noted that, in the present invention, unless otherwise specified, "introducing a certain gas into the outer tube" (such as "introducing methane into the outer tube") means introducing the gas into the annular space formed by the inner wall of the outer tube and the outer wall of the inner tube between the outer tube and the inner tube, and the gas does not enter the inner tube when introduced.

[0024] In the present invention, the purpose of opening holes at the catalyst bed position of the inner tube is to allow the raw gas introduced from the outer tube to contact and react with the raw gas introduced from the inner tube in the catalyst bed. The present invention has no particular restrictions on the specific opening conditions (such as opening rate, hole size, etc.) of the inner tube, as long as the above purpose can be achieved, and can be adjusted according to actual production conditions and needs, such as the particle size of the catalyst used, the size of the catalyst bed (such as length, tube diameter, etc.), the requirements for the reaction effect, etc.

[0025] According to a preferred embodiment of the present invention, the opening rate of the inner tube at the catalyst bed position is 40-70%. The opening rate refers to the percentage of the area of ​​the holes opened at the catalyst bed position to the tube wall area, that is, the opening rate = the total area of ​​the openings at the catalyst bed position / the total tube wall area of ​​the inner tube at the catalyst bed position × 100%.

[0026] Preferably, the diameter of a single hole opened in the inner tube at the catalyst bed position is 2-4 mm.

[0027] The inventors of the present invention also found during the research process that when the diameters of the inner tube and the outer tube of the reactor have a certain proportional relationship, better reaction effects (such as improved conversion rate, C2H selectivity, C2H yield, etc.) can be obtained.

[0028] According to a preferred embodiment of the present invention, in the reactor, the ratio of the inner diameter of the outer tube to the outer diameter of the inner tube is 1.3-2:1.

[0029] The present invention has no particular limitation on the material of the reactor, and any material commonly used in methane oxidative coupling reactors in the art can be applied to the present invention. According to some preferred embodiments of the present invention, the material of the inner tube and / or the outer tube is at least one of quartz, stainless steel and corundum.

[0030] The second aspect of the present invention provides a method for preparing carbon dihydrocarbons by methane oxidative coupling, the method comprising introducing a raw gas containing methane and oxygen into the reactor described in the first aspect, and reacting under methane oxidative coupling reaction conditions;

[0031] Among them, one of methane and oxygen is introduced through the inner tube, and the other is introduced through the outer tube.

[0032] In the method provided by the present invention, there is no particular restriction on the specific introduction positions of methane and oxygen, as long as the two are introduced from the inner tube and the outer tube respectively. For example, oxygen can be introduced from the inner tube and methane can be introduced from the outer tube, or methane can be introduced from the inner tube and oxygen can be introduced from the outer tube.

[0033] In order to obtain better reaction effect, according to some preferred embodiments of the present invention, the volume ratio of methane to oxygen is 2-6:1, preferably 2.2-4:1.

[0034] The method provided by the present invention effectively reduces the center temperature of the catalyst bed of the methane oxidative coupling reaction, so that the method can also have good safety and reaction effect at a higher reaction temperature. According to some preferred embodiments of the present invention, the methane oxidative coupling reaction conditions include a reaction temperature of 700-900°C and a time of 0.5-20h. The preferred reaction temperature is 780-830°C.

[0035] According to a preferred embodiment of the present invention, the methane oxidative coupling reaction conditions further include a feed gas hourly space velocity of 5000-20000 mL / (g·h) based on methane and oxygen. "mL / (g·h)" refers to the total amount of methane and oxygen used (mL) in 1 hour relative to a catalyst mass of 1 g.

[0036] According to a preferred embodiment of the present invention, in the reactor, a catalyst is loaded in the catalyst bed, and a filler is loaded at both ends of the catalyst (to fix the catalyst), and the filler is selected from inert materials (i.e., materials that will not participate in the methane oxidative coupling reaction).

[0037] Preferably, the inert material is silicon dioxide (eg, quartz sand) and / or aluminum oxide.

[0038] The third aspect of the present invention provides the reactor described in the first aspect, and / or the use of the method described in the second aspect in improving the safety of the methane oxidative coupling reaction and / or improving at least one of the reaction gas conversion rate, the C2H selectivity and the C2H yield of the methane oxidative coupling reaction.

[0039] The present invention will be described in detail below by way of examples. It should be understood that the following examples are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0040] In the following examples, unless otherwise specified, all reagents used were commercial products purchased from regular chemical suppliers and were of analytical grade.

[0041] In the following embodiments, unless otherwise specified, the reactor used includes a quartz reaction chamber (the structure of which can be referred to in Figure 1 ), which includes an inner tube 1 and an outer tube 2, the raw gas A is introduced from the annular channel between the outer tube 1 and the inner tube 2 and does not enter the inner tube 1, and the raw gas B is introduced from the inner tube 1. The inner tube 1 is nested in the outer tube 2 along the axial center, and the catalyst is loaded in the annular space between the inner tube and the outer tube. Holes are evenly opened on the wall of the inner tube at the catalyst loading position (i.e., the catalyst bed position 4), and a partition 3 is provided at the end of the inner tube at the catalyst bed position 4 to prevent the raw gas B from continuing to flow backward from the inner tube 1. The length of the inner tube 1 and the outer tube 2 are both 530mm. 80mm of quartz sand is loaded before and after the catalyst to fix the catalyst. The porosity is calculated using the following formula:

[0042] Opening rate = total opening area / total wall area of ​​inner tube at catalyst bed position × 100%

[0043] The catalysts used in the following examples were prepared as follows:

[0044] According to the selection and content of the active components in Table 1, the precursor of the active component (the precursor of W is ammonium tungstate, and the precursors of the other active components are all nitrates thereof) is weighed and added to 25g of deionized water (50°C), and the carrier is added, stirred for 2 hours, dried at 120°C for 24 hours, and solid A is obtained, and then calcined at 750°C for 6 hours to obtain a catalyst. The elemental composition of the catalyst is determined by X-ray fluorescence method, and the specific detection is carried out in accordance with GB / T 30905-2014.

[0045] Table 1

[0046]

[0047] Note: The content of each active component in the catalyst is the relative content calculated based on 100g of carrier.

[0048] Example 1

[0049] A quartz reaction tube with an inner diameter of 12 mm was used as the outer tube, and a quartz reaction tube with an outer diameter of 6 mm and an inner diameter of 3 mm was used as the inner tube. 0.4 g of 1# catalyst was loaded in the catalyst bed, and the layer height was 17 mm. The opening rate of the inner tube wall at the catalyst bed position was 60%, and the single hole diameter was 3 mm.

[0050] Raw gas A is methane, raw gas B is oxygen, and the volume ratio of methane to oxygen is 2.2:1. The methane oxidative coupling reaction is carried out under the conditions of a reaction temperature of 800°C, a reaction pressure that is the pressure generated by the raw materials themselves (0.01MPa), and a raw gas hourly space velocity of 10000mL / (g·h) based on methane and oxygen. The reaction product is collected after 1 hour of reaction.

[0051] Example 2

[0052] A quartz reaction tube with an inner diameter of 12 mm was used as the outer tube, and a quartz reaction tube with an outer diameter of 8 mm and an inner diameter of 4 mm was used as the inner tube. 0.4 g of 2# catalyst was loaded in the catalyst bed, and the layer height was 19 mm. The opening rate of the inner tube wall at the catalyst bed position was 70%, and the single hole diameter was 2 mm.

[0053] The raw material gas A is methane, the raw material gas B is oxygen, and the volume ratio of methane to oxygen is 3:1. The methane oxidative coupling reaction is carried out under the conditions of a reaction temperature of 830°C, a reaction pressure that is the pressure generated by the raw material itself (0.01MPa), and a raw material gas hourly space velocity of 5000mL / (g·h) based on methane and oxygen. The reaction product is collected after 1 hour of reaction.

[0054] Example 3

[0055] A quartz reaction tube with an inner diameter of 12 mm was used as the outer tube, and a quartz reaction tube with an outer diameter of 6 mm and an inner diameter of 3 mm was used as the inner tube. 0.4 g of 3# catalyst was loaded in the catalyst bed, and the layer height was 17 mm. The opening rate of the inner tube wall at the catalyst bed position was 40%, and the single hole diameter was 4 mm.

[0056] The raw material gas A is methane, the raw material gas B is oxygen, and the volume ratio of methane to oxygen is 4:1. The methane oxidative coupling reaction is carried out under the conditions of a reaction temperature of 780°C, a reaction pressure that is the pressure generated by the raw material itself (0.01MPa), and a raw material gas hourly space velocity of 8000mL / (g·h) based on methane and oxygen. The reaction product is collected after 1 hour of reaction.

[0057] Example 4

[0058] A quartz reaction tube with an inner diameter of 12 mm was used as the outer tube, and a quartz reaction tube with an outer diameter of 8 mm and an inner diameter of 4 mm was used as the inner tube. 0.4 g of 4# catalyst was loaded in the catalyst bed, and the layer height was 20 mm. The opening rate of the inner tube wall at the catalyst bed position was 50%, and the single hole diameter was 2.5 mm.

[0059] The raw material gas A is methane, the raw material gas B is oxygen, and the volume ratio of methane to oxygen is 4:1. The methane oxidative coupling reaction is carried out under the conditions of a reaction temperature of 750°C, a reaction pressure that is the pressure generated by the raw material itself (0.01MPa), and a raw material gas hourly space velocity of 12000mL / (g·h) based on methane and oxygen. The reaction product is collected after 1 hour of reaction.

[0060] Example 5

[0061] The method in Example 1 was used, except that the openings of the catalyst bed were set according to the opening ratio and single hole diameter in Table 1. The mode and conditions of the methane oxidative coupling reaction were the same as those in Example 1, and the reaction product was collected after 1 hour of reaction.

[0062] Table 1

[0063] serial number Opening rate / % Single hole diameter / mm 5-1 60 5 5-2 60 1 5-3 60 4 5-4 10 3 5-5 85 3 5-6 40 3 5-7 70 3 5-8 20 4.5 5-9 75 1.5

[0064] Example 6

[0065] The method in Example 1 was used, except that the inner tube and the outer tube were selected according to Table 2. The manner and conditions of the methane oxidative coupling reaction were the same as those in Example 1, and the reaction product was collected after 1 hour of reaction.

[0066] Table 2

[0067] serial number Outer tube inner diameter / mm Inner tube outer diameter / mm 6-1 12 10 6-2 12 9 6-3 18 5

[0068] Example 7

[0069] The method in Example 1 was used, except that the methane oxidative coupling reaction was carried out according to the conditions in Table 3, wherein the alkoxy ratio refers to the volume ratio of methane to oxygen, and the feed gas space velocity is calculated based on the total amount of methane and oxygen. The reactor structure and catalyst loading were the same as those in Example 1, and the reaction product was collected after 1 hour of reaction.

[0070] Table 3

[0071] serial number Alkyl oxygen ratio Temperature / ℃ <![CDATA[Raw material gas space velocity / mL·g -1 ·h -1 > 7-1 2:1 800 10000 7-2 6:1 800 10000 7-3 4:1 800 10000 7-4 5:1 800 10000 7-5 8:1 800 10000 7-6 2.2:1 700 10000 7-7 2.2:1 900 10000 7-8 2.2:1 780 10000 7-9 2.2:1 830 10000 7-10 2.2:1 850 10000 7-11 2.2:1 800 5000 7-12 2.2:1 800 20000 7-13 2.2:1 800 3000 7-14 2.2:1 800 25000

[0072] Example 8

[0073] The method in Example 1 was used, except that the partition in the inner tube was set 2 cm below the end of the catalyst bed. The methane oxidative coupling reaction was carried out in the same manner and under the same conditions as in Example 1, and the reaction product was collected after 1 hour of reaction.

[0074] Comparative Example 1

[0075] The method in Example 1 was used, except that the reactor was not provided with an inner tube, and methane and oxygen were introduced into the reactor cavity at the same time. The method and conditions of the methane oxidative coupling reaction were the same as those in Example 1, and the reaction product was collected after 1 hour of reaction.

[0076] Comparative Example 2

[0077] The method in Example 1 was used, except that no partition was provided in the inner tube. The mode and conditions of the methane oxidative coupling reaction were the same as those in Example 1, and the reaction product was collected after the reaction for 1 hour.

[0078] Comparative Example 3

[0079] The method in Example 1 was used, except that the catalyst was loaded in the inner tube, the catalyst loading was adjusted so that the bed height was the same as in Example 1, and a partition was set in the annular space between the outer tube and the inner tube at the catalyst bed position. The mode and conditions of the methane oxidative coupling reaction were the same as in Example 1, and the reaction product was collected after 1 hour of reaction.

[0080] Test Example 1

[0081] The components of the reaction products obtained in the above examples and comparative examples were detected by gas chromatograph (Agilent, 7890A), and the methane conversion rate, selectivity and yield of carbon dihydrocarbons, and CO conversion rate were calculated according to the following formulas: x (CO+CO2) selectivity, the results are shown in Table 4. The products were determined using a dual detection channel three-valve four-column system, in which the FID detector was connected to an alumina column for the analysis of CH4, C2H6, C2H4, C3H8, C3H6, C4H 10 、C4H8、C n H mAnd other components, TCD detector is mainly used to detect CO, CO2, N2, O2, CH4.

[0082] Methane conversion rate = amount of methane consumed by the reaction / initial amount of methane × 100%

[0083] Ethylene selectivity = amount of methane consumed by the generated ethylene / total methane consumption × 100%

[0084] Ethane selectivity = amount of methane consumed to produce ethane / total methane consumption × 100%

[0085] C2 selectivity = ethane selectivity + ethylene selectivity

[0086] CO x Selectivity = Amount of methane consumed by generated CO and CO2 / Total methane consumption × 100%

[0087] C2 hydrocarbon yield = methane conversion × (ethane selectivity + ethylene selectivity)

[0088] Table 4

[0089]

[0090] Test Example 2

[0091] The methods in Example 1, Comparative Example 1 and Comparative Example 2 were respectively used, except that the reaction time was extended to 20 h. The collected reaction products were tested according to the method in Test Example 1, and the methane conversion rate, the selectivity and yield of carbon dihydrocarbons, and the CO x The selectivity results are shown in Table 5.

[0092] Table 5

[0093] method Methane conversion rate / % Selectivity of C2H2O / % <![CDATA[CO x Selectivity / %]]> C2Hydrocarbon Yield / % Example 1 19.3 65.1 32.1 12.56 Comparative Example 1 16.5 51.2 42.3 8.44 Comparative Example 2 9.6 51.1 42 4.9

[0094] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A methane oxidative coupling reactor, characterized in that: The reactor comprises a reactor cavity including an inner tube (1) and an outer tube (2) nested outside the inner tube, The inner tube (1) has a hole in the tube wall at the catalyst bed position (4), and a partition (3) is provided at the end of the inner tube at the catalyst bed position (4) along the gas flow direction to prevent the gas introduced into the inner tube from continuing to flow forward along the inner tube.

2. The reactor according to claim 1, wherein The opening rate of the inner tube at the catalyst bed position is 40-70%, and the diameter of a single hole is preferably 2-4 mm.

3. The reactor according to claim 1, wherein In the reactor, the ratio of the inner diameter of the outer tube to the outer diameter of the inner tube is 1.3-2:

1.

4. The reactor according to any one of claims 1 to 3, wherein The material of the inner tube and / or the outer tube is at least one of quartz, stainless steel and corundum.

5. A method for preparing carbon dihydrocarbons by oxidative coupling of methane, characterized in that: The method comprises passing a feed gas containing methane and oxygen into a reactor according to any one of claims 1 to 4, and reacting under methane oxidative coupling reaction conditions; Among them, one of methane and oxygen is introduced through the inner tube, and the other is introduced through the outer tube.

6. The method according to claim 5, wherein: The volume ratio of methane to oxygen is 2-6:1, preferably 2.2-4:

1.

7. The method according to claim 5 or 6, wherein: The methane oxidative coupling reaction conditions include a reaction temperature of 700-900°C and a reaction time of 0.5-20 hours, and preferably a reaction temperature of 780-830°C.

8. The method according to claim 7, wherein: The methane oxidative coupling reaction conditions also include a raw gas hourly space velocity of 5000-20000 mL / (g·h) based on methane and oxygen.

9. The method according to any one of claims 5 to 7, wherein: In the reactor, a catalyst is loaded in the catalyst bed, and a filler is loaded at both ends of the catalyst. The filler is selected from inert materials, preferably silicon dioxide and / or aluminum oxide.

10. Use of the reactor described in any one of claims 1 to 4 and / or the method described in any one of claims 5 to 9 in improving the safety of methane oxidative coupling reaction and / or improving at least one of the reaction gas conversion rate, C2H selectivity and C2H yield of methane oxidative coupling reaction.

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