Reactor and process for the oxidative coupling of methane to produce carbon dihydrides

Abstract

The present application relates to the field of catalytic reaction technology, and discloses a reactor and a method for preparing carbon dihydride by methane oxidation coupling. The reactor comprises a shell, a heat exchange medium flow channel and at least two reaction tubes; the heat exchange medium flow channel comprises a heat exchange medium upstream channel and a heat exchange medium downstream channel separated by a heat-conducting partition plate, the shell and the heat-conducting partition plate form the heat exchange medium downstream channel, and the reaction tubes are arranged in the heat exchange medium downstream channel; the heat exchange medium flow channel is provided with a heat exchange medium inlet located in the heat exchange medium upstream channel and a heat exchange medium outlet located in the heat exchange medium downstream channel, so that the heat exchange medium flows in opposite directions on both sides of the heat-conducting partition plate. The reactor provided by the present application can effectively control the temperature of the catalyst bed of the reactor, and avoid the occurrence of catalyst activity decline and methane deep oxidation.

Description

Technical Field

[0001] This invention relates to the field of catalytic reaction technology, specifically to a reactor and a method for producing C2 hydrocarbons by oxidative coupling of methane. 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. The oxidative coupling of methane 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. Researchers have conducted extensive explorations in catalyst and reaction process development. Because the oxidative coupling of methane is a high-temperature exothermic reaction, higher requirements are placed on the heat dissipation capacity of the reactor. Integrated reactors or multi-stage catalyst loading are typically used to mitigate the exothermic reaction. However, the heat dissipation capacity of existing methane oxidative coupling reactors is limited, leading to deep oxidation and the formation of carbon dioxide or carbon monoxide. Summary of the Invention

[0003] The purpose of this invention is to overcome the problem of low heat removal capacity of existing methane oxidative coupling reactors, and to provide a reactor and a method for producing C2 hydrocarbons by methane oxidative coupling, wherein the reactor can more effectively control the temperature of the catalyst bed.

[0004] Existing technologies typically employ multi-stage catalyst loading to mitigate the exothermic reaction, but their heat removal capabilities are limited. Inventors attempted to cool the reaction tubes with ambient temperature gas to alleviate this, but contact between the reaction tubes and ambient temperature gas causes a sudden drop in temperature, reducing methane conversion and even preventing methane oxidative coupling. To address this issue, the inventors added a heat-conducting baffle inside the reactor, causing the heat exchange medium to flow in opposite directions on either side of the baffle, thus preventing a sudden temperature drop in the reaction tubes due to direct contact between ambient temperature gas and the reaction tubes. To achieve the above objective, the first aspect of this invention provides a reactor comprising a shell, a heat exchange medium flow channel, and at least two reaction tubes.

[0005] The heat exchange medium flow channel includes an upstream heat exchange medium channel and a downstream heat exchange medium channel separated by a heat-conducting partition. The shell and the heat-conducting partition form the downstream heat exchange medium channel, and the reaction tube is disposed in the downstream heat exchange medium channel.

[0006] The heat exchange medium flow channel is provided with a heat exchange medium inlet located in the upstream channel and a heat exchange medium outlet located in the downstream channel, so that the heat exchange medium flows in opposite directions on both sides of the heat-conducting baffle.

[0007] The second aspect of the present invention provides a method for producing C2 hydrocarbons by oxidative coupling of methane, the method comprising, under the reaction conditions for producing C2 hydrocarbons by oxidative coupling of methane, introducing methane and oxygen into the reactor described in the first aspect to contact with a catalyst filled in a reaction tube, and during the contact process, introducing a heat exchange medium into a heat exchange medium flow channel to control the contact temperature.

[0008] The reactor of the present invention can not only improve the heat removal capacity, but also maintain a constant temperature inside the reactor.

[0009] The reactor provided by this invention can effectively control the temperature of the catalyst bed, avoiding a decrease in catalyst activity and the occurrence of deep oxidation of methane.

[0010] The effects and other advantages of the reactor and method provided by this invention will be described in detail in subsequent embodiments. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a specific embodiment of the reactor of the present invention;

[0012] Figure 2 This is a top view schematic diagram of a specific embodiment of the reactor of the present invention;

[0013] Figure 3 This is a bottom side view of a specific embodiment of the reactor of the present invention.

[0014] Explanation of reference numerals in the attached figures

[0015] 1. Heat exchange medium flow channel 2. Reaction tube

[0016] 3. Upstream channel of heat exchange medium 4. Downstream channel of heat exchange medium

[0017] 5. Heat exchange medium inlet 6. Heat exchange medium outlet

[0018] 7. Raw material imports 8. Product exports

[0019] 9. Spoiler 10. Shell

[0020] 11 Insulation layer 12 Thermal conductive insulation plate Detailed Implementation

[0021] 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.

[0022] In this invention, unless otherwise stated, "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0023] In this invention, "C2 hydrocarbons" include ethane and ethylene, but exclude acetylene.

[0024] In this invention, "C2+" includes hydrocarbons with two or more carbon atoms.

[0025] In this invention, "inner diameter" refers to "diameter".

[0026] like Figure 1 As shown, the present invention provides a reactor, which includes a shell 10, a heat exchange medium flow channel 1, and at least two reaction tubes 2;

[0027] The heat exchange medium flow channel 1 includes an upstream heat exchange medium channel 3 and a downstream heat exchange medium channel 4 separated by a heat-conducting baffle 12. The shell 10 and the heat-conducting baffle 12 form the downstream heat exchange medium channel 4, and the reaction tube 2 is disposed in the downstream heat exchange medium channel 4.

[0028] The heat exchange medium flow channel 1 is provided with a heat exchange medium inlet 5 located in the upstream channel 3 and a heat exchange medium outlet 6 located in the downstream channel 4, so that the heat exchange medium flows in opposite directions on both sides of the heat-conducting baffle 12 (that is, the heat exchange medium flows in opposite directions in the upstream channel 3 and the downstream channel 4). It can be understood that one end of the heat-conducting baffle is sealed to one side of the shell, and the other end extends to the opposite side but is not connected, leaving an opening, so that the flow direction of the heat exchange medium changes at the opening.

[0029] According to the present invention, the shape of the shell is not particularly limited, for example, it can be cubic, cylindrical, etc., preferably, the shell 10 is cylindrical. The size of the shell 10 is not particularly limited, and can be determined according to the actual production needs.

[0030] In this invention, the housing 10 can be made of 310s stainless steel.

[0031] According to the present invention, preferably, the wall thickness of the housing 10 is 1-3 mm (e.g., 1 mm, 2 mm, 3 mm).

[0032] In this invention, the shape of the heat-conducting baffle is not particularly limited; for example, it can be cubic, cylindrical, etc. Preferably, the heat-conducting baffle 12 is cylindrical. More preferably, the internal space surrounding the heat-conducting baffle 12 is the upstream channel 3 of the heat exchange medium.

[0033] According to the present invention, preferably, the wall thickness of the thermally conductive partition 12 is 0.5-2 mm (e.g., 0.5 mm, 1 mm, 1.5 mm, 2 mm).

[0034] According to the present invention, there are no special requirements for the thermal conductivity of the heat-conducting partition 12, as long as it meets the requirements for heat conduction. Preferably, the thermal conductivity of the heat-conducting partition 12 is greater than 10 W / (m·K), more preferably 12-100 W / (m·K). More preferably, the heat-conducting partition 12 is made of stainless steel and / or Inconel 825.

[0035] In this invention, when both the shell and the heat-conducting partition are cylindrical, the annular gap between the shell 10 and the heat-conducting partition 12 serves as the downstream channel 4 for the heat exchange medium. More preferably, the distance between the extended end of the heat-conducting partition and the other side is equal to the cross-sectional area of ​​the upstream channel 3 for the heat exchange medium divided by the perimeter of the end of the heat-conducting partition.

[0036] According to the present invention, the number of reaction tubes can be selected within a wide range. Preferably, the number of reaction tubes 2 is 6-60 (for example, it can be 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 30, 40, 50, or 60), and more preferably 6-18.

[0037] According to the present invention, the inner diameter of the reaction tube can be selected within a wide range. Preferably, the inner diameter of the reaction tube 2 is 3-10 mm (for example, it can be 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, or 10 mm).

[0038] According to the present invention, preferably, the wall thickness of the reaction tube 2 is 1-2 mm (for example, it can be 1 mm, 1.5 mm, or 2 mm).

[0039] According to the present invention, preferably, the reaction tube 2 is filled with a catalyst. The type of catalyst is not particularly limited and can be any catalyst in the art that can be used for the oxidative coupling of methane to C2 hydrocarbons.

[0040] According to the present invention, the material of the reaction tube 2 can be selected according to the substance introduced into the reaction tube and the chemical reaction that occurs. However, in order to better control the temperature inside the reaction tube, preferably, the material of the reaction tube 2 is a thermally conductive metal material. More preferably, the thermal conductivity of the thermally conductive metal material is greater than 10 W / (m·K), and preferably 12-100 W / (m·K). Even more preferably, the thermally conductive metal material is stainless steel (e.g., 310s stainless steel, 316L stainless steel) and / or Inconel 825.

[0041] In this invention, the 310s stainless steel comprises iron, chromium, nickel, and titanium.

[0042] In this invention, the 316L stainless steel comprises iron, chromium, nickel, and titanium.

[0043] In this invention, the composition of the Inconel 825 includes nickel, chromium, iron, copper, and titanium.

[0044] According to the present invention, preferably, the inner surface of the portion of the reaction tube 2 in contact with the catalyst has an inert metal coating; more preferably, the inert metal coating is a nickel metal coating; even more preferably, the thickness of the metal coating is 0.01-0.05 mm (e.g., 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm). This method can prevent the active metal in the reaction tube from affecting the performance of the catalyst.

[0045] According to the present invention, preferably, a thermocouple is provided inside the reaction tube 2, and the thermocouple is used to detect the temperature inside the reaction tube 2, and the flow rate of the heat exchange medium can be adjusted according to the detected temperature.

[0046] According to the present invention, preferably, the reaction tube 2 passes through the downstream channel 4 of the heat exchange medium and is arranged at intervals along the circumference.

[0047] According to the present invention, preferably, the interval between two adjacent reaction tubes 2 is equal or unequal, but preferably equal.

[0048] According to the present invention, preferably, the reaction tube 2 is provided with a raw material inlet 7 and a product outlet 8, and the product outlet 8 is provided on the same side of the reactor as the heat exchange medium inlet 5 and the heat exchange medium outlet 6; more preferably, the product outlet 8 is provided at the bottom of the reactor as the heat exchange medium inlet 5 and the heat exchange medium outlet 6.

[0049] According to the present invention, preferably, the upstream channel 3 of the heat exchange medium is located inside the downstream channel 4 of the heat exchange medium.

[0050] According to the present invention, the cross-sectional area of ​​the upstream channel 3 of the heat exchange medium can be selected within a wide range, but in order to reduce temperature fluctuations in the reaction tube 2, preferably, the relationship between the upstream channel of the heat exchange medium, the reaction tube, and the shell satisfies S3 = a(S 10 The relationship between -nS2) is given by the formula, where a = 0.4 - 0.6; where n is the number of reaction tubes, S2 is the cross-sectional area of ​​a single reaction tube, S3 is the cross-sectional area of ​​the upstream channel of the heat exchange medium, S4 is the cross-sectional area of ​​the downstream channel of the heat exchange medium (excluding the total cross-sectional area of ​​the reaction tubes), and S... 10 This represents the cross-sectional area of ​​the shell.

[0051] In this invention, for ease of calculation, the cross-sectional area of ​​the reaction tube wall thickness is included in the cross-sectional area of ​​the reaction tube; the cross-sectional area of ​​the heat-conducting baffle wall thickness is included in the cross-sectional area of ​​the upstream channel of the heat exchange medium; and the cross-sectional area of ​​the shell wall thickness is included in the cross-sectional area of ​​the shell.

[0052] In this invention, when the upstream channel 3 of the heat exchange medium has an irregular shape, the cross-sectional area of ​​the upstream channel 3 of the heat exchange medium refers to the cross-sectional area of ​​the narrowest part of the channel in the upstream channel of the heat exchange medium.

[0053] According to the present invention, preferably, S3 / S2 = 15-100, that is, the cross-sectional area of ​​the upstream channel 3 of the heat exchange medium is 15-100 times the cross-sectional area of ​​the reaction tube 2 (for example, it can be 15 times, 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times, 90 times, or 100 times). Wherein, S2 is the cross-sectional area of ​​the reaction tube, and S3 is the cross-sectional area of ​​the upstream channel of the heat exchange medium.

[0054] According to the present invention, the cross-sectional area of ​​the downstream channel 4 of the heat exchange medium can be selected within a wide range, but in order to reduce temperature fluctuations in the reaction tube 2, preferably, the relationship between the downstream channel of the heat exchange medium, the reaction tube, and the shell satisfies S4 = b(S 10 The relationship between -nS2) is given by: b = 0.4 - 0.6; n is the number of reaction tubes; S2 is the cross-sectional area of ​​the reaction tubes; S4 is the cross-sectional area of ​​the downstream channel of the heat exchange medium, excluding the total cross-sectional area of ​​the reaction tubes; S 10 This represents the cross-sectional area of ​​the shell.

[0055] In this invention, when the downstream channel 4 of the heat exchange medium has an irregular shape, the cross-sectional area of ​​the downstream channel 4 of the heat exchange medium refers to the cross-sectional area of ​​the narrowest part of the channel in the downstream channel of the heat exchange medium.

[0056] According to the present invention, preferably, S4 / S2 = 15-100, that is, the cross-sectional area of ​​the downstream channel 4 of the heat exchange medium is 15-100 times the cross-sectional area of ​​the reaction tube 2 (for example, it can be 15 times, 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times, 90 times, or 100 times). Wherein, S2 is the cross-sectional area of ​​the reaction tube, and S4 is the cross-sectional area of ​​the downstream channel of the heat exchange medium.

[0057] According to the present invention, preferably, a baffle 9 is provided on the inner wall of the downstream channel 4 of the heat exchange medium. Providing a baffle 9 on the inner wall of the downstream channel of the heat exchange medium can effectively increase the heat exchange between the heat exchange medium and the reaction tube.

[0058] According to the present invention, the number of baffles is not specifically limited and can be set according to actual needs. Preferably, the baffles are staggered and alternately arranged in the downstream channel of the heat exchange medium; more preferably, the baffles are configured as half-section blocking, that is, the cross-sectional area of ​​the baffle is half of the cross-sectional area of ​​the downstream channel of the heat exchange medium.

[0059] According to the present invention, preferably, the reactor further includes a heat insulation layer 11 located at the top and bottom of the shell 10.

[0060] According to the present invention, the material of the insulation layer is not particularly limited, as long as it can meet the requirements of insulation performance. Preferably, the material of the insulation layer 11 is a high-temperature resistant heat insulation material. More preferably, the thickness of the insulation layer 11 is 40mm or more (e.g., 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm).

[0061] Another aspect of the present invention provides a method for producing C2 hydrocarbons by oxidative coupling of methane. The method includes, under the reaction conditions for producing C2 hydrocarbons by oxidative coupling of methane, introducing methane and oxygen into the reactor described above to contact with a catalyst filled in a reaction tube. During the contact process, a heat exchange medium is introduced into the heat exchange medium flow channel through the heat exchange medium inlet to control the contact temperature.

[0062] According to the present invention, preferably, the contact temperature is 400-850°C, more preferably 450-830°C, and even more preferably 550-820°C.

[0063] According to the present invention, preferably, the molar ratio of methane to oxygen is 2-10:1 (for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1), and more preferably 3-8:1.

[0064] In this invention, methane space velocity and oxygen space velocity refer to the space velocity when entering the feed inlet, and the flow velocity of the heat exchange medium refers to the flow velocity when entering the upstream channel of the heat exchange medium.

[0065] According to the present invention, preferably, the space velocity of methane in each reaction tube is 18,000-120,000 mL / (g·h), for example, it can be 18,000 mL / (g·h), 20,000 mL / (g·h), 30,000 mL / (g·h), 40,000 mL / (g·h), 50,000 mL / (g·h), 60,000 mL / (g·h), 70,000 mL / (g·h), 80,000 mL / (g·h), 90,000 mL / (g·h), 100,000 mL / (g·h), 110,000 mL / (g·h), 120,000 mL / (g·h), and most preferably 48,000-60,000 mL / (g·h).

[0066] According to the present invention, preferably, in each reaction tube, the oxygen flow rate is 10-50 mL / min relative to each 0.1 g catalyst (e.g., 10 mL / min, 15 mL / min, 20 mL / min, 25 mL / min, 30 mL / min, 35 mL / min, 40 mL / min, 45 mL / min, 50 mL / min), more preferably 15-32 mL / min.

[0067] According to the present invention, preferably, the heat exchange medium is a gas, preferably nitrogen or air. At the beginning of the reaction, since the gas in the downstream channel of the heat exchange medium has relatively little heat, its preheating effect on the gas in the upstream channel is poor. Therefore, at the beginning of the reaction, the heat exchange medium entering the inlet 5 can be preheated to prevent a sudden drop in temperature within the reaction tube. Once the reaction stabilizes, the heat of the gas in the downstream channel is sufficient to preheat the gas in the upstream channel. Therefore, after the reaction stabilizes, no further preheating of the gas is required; simply introduce gas at room temperature (approximately 15-40°C). Alternatively, room temperature gas can be introduced at the beginning of the reaction to preheat the heat exchange medium using the heat from a small amount of raw material. Therefore, the method of the present invention can reduce energy consumption.

[0068] According to the present invention, preferably, the flow rate of the heat exchange medium is 300-30000 mL / min (e.g., 300 mL / min, 400 mL / min, 430 mL / min, 500 mL / min, 600 mL / min, 700 mL / min, 800 mL / min, 900 mL / min, 1000 mL / min, 10000 mL / min, 15000 mL / min, 20000 mL / min, 25000 mL / min, 30000 mL / min) relative to each 1 g of total catalyst usage, preferably 400-20000 mL / min, and more preferably 400-800 mL / min, relative to each 1 g of total catalyst usage.

[0069] According to the present invention, the catalyst can be any catalyst in the art that can be used for the oxidative coupling of methane to C2 hydrocarbons. Preferably, the catalyst comprises a support and an active component supported on the support, wherein the support is at least one selected from silica, alumina, calcium oxide, lanthanum oxide, and barium titanate, and the active component is at least one selected from sodium tungstate, manganese oxide, lithium oxide, and cerium oxide. Preferably, the content of the active component, calculated as a metal element, is 0.1-15% by weight based on the total weight of the catalyst. For example, the catalyst in CN103657640B can be used.

[0070] The following is in conjunction with the appendix Figure 1 The working process of the reactor of the present invention is described as follows: Heated methane and oxygen are introduced into the reaction tube 2, which is filled with catalyst, through the raw material inlet 7. The methane and oxygen contact the catalyst within the reaction tube 2, generating products such as C2 hydrocarbons, which are then discharged from the reaction tube through the product outlet 8. Simultaneously, a heat exchange medium is introduced into the heat exchange medium inlet 5. The heat exchange medium flows in opposite directions in the upstream channel 3 and the downstream channel 4. In the downstream channel 4, the heat exchange medium exchanges heat with the reaction tube 2, lowering the reaction temperature within the tube 2. The heat exchange medium in the downstream channel 4 also preheats the heat exchange medium in the upstream channel 3 to prevent a sudden drop in temperature within the reaction tube 2 due to excessively low heat exchange medium temperature. The downstream channel 4 is equipped with a baffle 9 to increase gas turbulence, thereby improving the gas heat exchange effect.

[0071] The structural features and performance of the reactor described in this invention will be further illustrated below with reference to specific embodiments.

[0072] Gas chromatography was used to analyze and detect the components of the product.

[0073]

[0074]

[0075]

[0076] The catalyst used in Examples 1, 3, 4, 5 and Comparative Example 1 was the Na-W-Mn / BaTiO3 catalyst prepared by the method of Example 1 in patent CN103657640B.

[0077] Example 2 uses the lanthanum oxycarbonate catalyst prepared by the method in Example 1 of CN113797949A (application number 202010549901.1).

[0078] The nitrogen flow rate in the following examples is the flow rate during stable reaction operation.

[0079] The reactor structure used in the following embodiments is as follows:

[0080] The reactor includes a heat exchange medium flow channel 1, reaction tubes 2, and a shell 10. The heat exchange medium flow channel 1 comprises an upstream heat exchange medium channel 3 and a downstream heat exchange medium channel 4 separated by a thermally conductive baffle 12. The circular space enclosed by the thermally conductive baffle 12 is the upstream heat exchange medium channel 3, and the annular gap between the shell 10 and the thermally conductive baffle 12 is the downstream heat exchange medium channel 4. The heat exchange medium flow channel 1 has a heat exchange medium inlet 5 located in the upstream heat exchange medium channel 3 and a heat exchange medium outlet 6 located in the downstream heat exchange medium channel 4, allowing the heat exchange medium to flow in opposite directions on both sides of the thermally conductive baffle 12. The reaction tubes 2 penetrate the downstream heat exchange medium channel 4 and are spaced circumferentially. The spacing between adjacent reaction tubes may be equal or unequal. The reaction tubes 2 have a raw material inlet 7 and a product outlet 8, which are located at the bottom of the reactor along with the heat exchange medium inlet 5 and the heat exchange medium outlet 6. The inner wall of the downstream heat exchange medium channel 4 is equipped with baffles 9, which are staggered and alternately arranged in the downstream heat exchange medium channel and are half-section obstructions. The shell 10 has insulation layers 11 at the top and bottom. The reaction tube 2 and the heat exchange medium flow channel 1 are equipped with thermocouples, and the inner surface of the part of the reaction tube 2 in contact with the catalyst has an inert metal coating.

[0081] Example 1

[0082] The reactor parameters are as follows: There are 6 reaction tubes with an inner diameter of 10 mm and a wall thickness of 2 mm. The reaction tubes are made of 310s stainless steel with a thermal conductivity of 12 W / (m·K). The thickness of the nickel plating inside the reaction tubes is 0.02 mm. Thermocouples are installed inside the reaction tubes. The spacing between adjacent reaction tubes is equal. The catalyst loading in each reaction tube is 0.1 g. The heat-conducting baffle is made of 310s stainless steel with a thermal conductivity of 12 W / (m·K), a wall thickness of 2 mm, and an inner diameter of 66 mm, meaning the cross-sectional area of ​​the upstream heat exchange medium channel is approximately 25 times the cross-sectional area of ​​the reaction tubes. The shell is cylindrical with a wall thickness of 2 mm and an inner diameter of 100.8 mm, meaning the cross-sectional area of ​​the downstream heat exchange medium channel is approximately 25 times the cross-sectional area of ​​the reaction tubes. A baffle is installed on the inner wall of the downstream heat exchange medium channel. The insulation layer is 40 mm thick.

[0083] Methane and oxygen were heated to 820°C and then introduced into each reaction tube to react with the catalyst. The methane space velocity in each reaction tube was 48,000 mL / (g·h), and the molar ratio of methane to oxygen was 6:1. At the same time, nitrogen gas (25°C) was introduced into the upstream channel of the heat exchange medium at a flow rate of 480 mL / min.

[0084] During the stable operation of the reactor, the temperature at the feed inlet was detected to be 820℃, the temperature at the product outlet was 832℃, the temperature difference between the product outlet and the feed inlet was 12℃, and no local overheating occurred in any part of the reaction tube, effectively controlling the temperature rise of the catalyst bed during the exothermic reaction of methane oxidative coupling.

[0085] After 100 h of reaction, the methane conversion rate was 29%, the selectivity for C2 hydrocarbons was 72.2%, the yield of C2 hydrocarbons was 20.9%, the selectivity for C2+ was 74.1%, and the yield of C2+ was 21.5%.

[0086] Example 2

[0087] The reactor parameters are as follows: 12 reaction tubes with an inner diameter of 6 mm and a wall thickness of 1.5 mm; the reaction tubes are made of Inconel 625, which has a thermal conductivity of 12 W / (m·K); the thickness of the nickel plating inside the reaction tubes is 0.02 mm; thermocouples are installed inside the reaction tubes; the spacing between adjacent reaction tubes is equal; the catalyst loading in each reaction tube is 0.1 g; the heat-conducting baffle is made of stainless steel with a thermal conductivity of 12 W / (m·K), a wall thickness of 1 mm, and an inner diameter of 61 mm, meaning the cross-sectional area of ​​the upstream heat exchange medium channel is approximately 49 times the cross-sectional area of ​​the reaction tube; the shell is cylindrical with a wall thickness of 2 mm and an inner diameter of 90.4 mm, meaning the cross-sectional area of ​​the downstream heat exchange medium channel is approximately 49 times the cross-sectional area of ​​the reaction tube; a baffle is installed on the inner wall of the downstream heat exchange medium channel; the insulation layer is 40 mm thick.

[0088] Methane and oxygen were heated to 550°C and then introduced into each reaction tube to react with the catalyst. The methane space velocity in each reaction tube was 60,000 mL / (g·h), and the molar ratio of methane to oxygen was 5:1. At the same time, nitrogen gas (25°C) was introduced into the upstream channel of the heat exchange medium at a flow rate of 600 mL / min.

[0089] During the stable operation of the reactor, the temperature at the feed inlet was detected to be 550℃, the temperature at the product outlet was 558℃, the temperature difference between the product outlet and the feed inlet was 8℃, and no local overheating occurred in any part of the reaction tube, effectively controlling the temperature rise of the catalyst bed during the exothermic reaction of methane oxidative coupling.

[0090] After 100 h of reaction, the methane conversion rate was 20%, the selectivity for C2 hydrocarbons was 62.2%, the C2 yield was 12.4%, the selectivity for C2+ was 65%, and the C2+ yield was 13%.

[0091] Example 3

[0092] The reactor parameters are as follows: 18 reaction tubes with an inner diameter of 4 mm and a wall thickness of 1 mm; the tubes are made of 310S stainless steel with a thermal conductivity of 12 W / (m·K); the nickel plating thickness inside the tubes is 0.02 nm; thermocouples are installed inside the tubes; the spacing between adjacent tubes is equal; and the catalyst loading in each tube is 0.1 g. The thermally conductive baffles are made of 310S stainless steel with a thermal conductivity of 12 W / (m·K), a wall thickness of 1.5 mm, and an inner diameter of 51 mm, meaning the cross-sectional area of ​​the upstream heat exchange medium channel is approximately 81 times the cross-sectional area of ​​the reaction tubes. The shell is cylindrical with a wall thickness of 2 mm and an inner diameter of 76.4 mm, meaning the cross-sectional area of ​​the downstream heat exchange medium channel is approximately 81 times the cross-sectional area of ​​the reaction tubes. A baffle is installed on the inner wall of the downstream heat exchange medium channel. The insulation layer is 40 mm thick.

[0093] Methane and oxygen were heated to 800°C and then introduced into each reaction tube to react with the catalyst. The methane space velocity in each reaction tube was 57,600 mL / (g·h), and the molar ratio of methane to oxygen was 3:1. At the same time, nitrogen gas (25°C) was introduced into the upstream channel of the heat exchange medium at a flow rate of 800 mL / min.

[0094] During the stable operation of the reactor, the temperature at the feed inlet was detected to be 800℃, the temperature at the product outlet was 818℃, the temperature difference between the product outlet and the feed inlet was 18℃, and no local overheating occurred in any part of the reaction tube, effectively controlling the temperature rise of the catalyst bed during the exothermic reaction of methane oxidative coupling.

[0095] After 100 h of reaction, the methane conversion rate was 31%, the selectivity for C2 hydrocarbons was 72%, the yield of C2 hydrocarbons was 22.3%, the selectivity for C2+ was 75%, and the yield of C2+ was 23.3%.

[0096] Example 4

[0097] Based on the reactor in Example 1, the following improvements were made: the wall thickness of the heat-conducting baffle is 2 mm and the inner diameter is 17 mm, meaning that the cross-sectional area of ​​the upstream channel of the heat exchange medium is approximately 5 times the cross-sectional area of ​​the reaction tube; the wall thickness of the shell is 2 mm and the inner diameter is 47 mm, meaning that the cross-sectional area of ​​the downstream channel of the heat exchange medium is approximately 49 times the cross-sectional area of ​​the reaction tube.

[0098] The heating temperature, space velocity, molar ratio of methane and oxygen, and the flow rate of nitrogen were the same as in Example 1.

[0099] During the stable operation of the reactor, the temperature at the raw material inlet was detected to be 760℃, the temperature at the product outlet was 785℃, and the temperature difference between the product outlet and the raw material inlet was 25℃.

[0100] After 100 h of reaction, the methane conversion rate was 29%, the selectivity for C2 hydrocarbons was 65.5%, the yield of C2 hydrocarbons was 19.0%, the selectivity for C2+ was 70%, and the yield of C2+ was 20.3%.

[0101] Example 5

[0102] The reactor parameters are the same as in Example 1.

[0103] The method of oxidative coupling of methane to C2 hydrocarbons was carried out according to Example 1, except that the nitrogen flow rate was 200 mL / min.

[0104] During the stable operation of the reactor, the temperature at the raw material inlet was detected to be 820℃, and the temperature at the product outlet was 840℃. The temperature difference between the product outlet and the raw material inlet was 20℃. However, localized overheating occurred in some parts of the reaction tube, with the highest temperature reaching 860℃.

[0105] After 100 hours of reaction, the methane conversion rate was 30%, the selectivity for C2 hydrocarbons was 61%, and the yield of C2 hydrocarbons was 18.3%.

[0106] Comparative Example 1

[0107] No heat exchange medium flow channel is set outside the reaction tube, meaning there is no heat exchange medium to cool the reaction tube.

[0108] The reactor parameters are as follows: the shell is cylindrical with a wall thickness of 2 mm; there are 6 reaction tubes with an inner diameter of 10 mm and a wall thickness of 2 mm. The reaction tubes are made of 310s stainless steel, which has a thermal conductivity of 12 W / (m·K). The thickness of the nickel plating inside the reaction tubes is 0.02 mm. Thermocouples are installed inside the reaction tubes. The spacing between adjacent reaction tubes is equal. The catalyst loading in each reaction tube is 0.1 g. The insulation layer is 40 mm thick.

[0109] Methane and oxygen were heated to 820°C and then introduced into each reaction tube to react with the catalyst. The methane space velocity introduced into each reaction tube was 48000 mL / (g·h), and the molar ratio of methane to oxygen was 6:1.

[0110] After 10 hours of reaction, the highest temperature detected inside the reaction tube was 933℃. At this point, the methane conversion rate was 43%, the selectivity for C2 hydrocarbons was 41%, and the yield of C2 hydrocarbons was 17.6%. After 50 hours of reaction, the reaction was terminated because the yield of C2 hydrocarbons was less than 3%.

[0111] The results from the above examples and comparative examples show that the method of Examples 1-5 of this invention can control the temperature difference between the product outlet and the feed inlet within 25°C, effectively maintaining a constant temperature within the reaction tube, and improving methane conversion, C2 hydrocarbon selectivity, and yield. Examples 1-3 show an even smaller temperature difference between the product outlet and the feed inlet, within 18°C. Furthermore, Examples 1 and 3 using the Na-W-Mn / BaTiO3 catalyst achieved C2 hydrocarbon yields of over 20%, and Example 2 using the lanthanum oxycarbonate catalyst also achieved a C2 hydrocarbon yield of over 12%, indicating that the preferred embodiments of this application can achieve higher C2 hydrocarbon selectivity and yield.

[0112] 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, under the reaction conditions of methane oxidative coupling to produce C2 hydrocarbons, introducing methane and oxygen into a reactor to contact with a catalyst filled in a reaction tube, and during the contact process, introducing heat exchange medium from the heat exchange medium inlet into the heat exchange medium flow channel to control the contact temperature. The contact temperature is 400-850℃; The reactor includes a shell (10), a heat exchange medium flow channel (1), and at least two reaction tubes (2). The heat exchange medium flow channel (1) includes an upstream heat exchange medium channel (3) and a downstream heat exchange medium channel (4) separated by a heat-conducting baffle (12). The shell (10) and the heat-conducting baffle (12) form the downstream heat exchange medium channel (4). The reaction tube (2) is disposed in the downstream heat exchange medium channel (4). The heat exchange medium flow channel (1) is provided with a heat exchange medium inlet (5) located in the upstream channel (3) and a heat exchange medium outlet (6) located in the downstream channel (4), so that the heat exchange medium flows in opposite directions on both sides of the heat-conducting baffle (12). The heat exchange medium is a gas; the flow rate of the heat exchange medium is 400-30000 mL / min relative to the total amount of catalyst used per 1g. S3 / S2=15-100; S4 / S2=15-100; where S2 is the cross-sectional area of ​​a single reaction tube, S3 is the cross-sectional area of ​​the upstream channel of the heat exchange medium, and S4 is the cross-sectional area of ​​the downstream channel of the heat exchange medium, but does not include the total cross-sectional area of ​​the reaction tube.

2. The method according to claim 1, wherein, The number of reaction tubes (2) is 6-60; And / or, the inner diameter of the reaction tube (2) is 3-10 mm; And / or, the wall thickness of the reaction tube (2) is 1-2 mm.

3. The method according to claim 1, wherein, The reaction tube (2) is filled with a catalyst.

4. The method according to claim 3, wherein, The inner surface of the part of the reaction tube (2) that is in contact with the catalyst has an inert metal coating.

5. The method according to claim 4, wherein, The inert metal coating is a nickel metal coating.

6. The method according to claim 1, wherein, The reaction tube (2) passes through the downstream channel (4) of the heat exchange medium and is spaced apart along the circumference; And / or, the interval between two adjacent reaction tubes (2) is equal or unequal; And / or, the reaction tube (2) is provided with a raw material inlet (7) and a product outlet (8), and the product outlet (8) is located on the same side of the reactor as the heat exchange medium inlet (5) and the heat exchange medium outlet (6).

7. The method according to claim 1, wherein, The interval between two adjacent reaction tubes (2) is equal.

8. The method according to claim 6, wherein, The product outlet (8) is located at the bottom of the reactor along with the heat exchange medium inlet (5) and the heat exchange medium outlet (6).

9. The method according to claim 1, wherein, The upstream channel (3) of the heat exchange medium is located inside the downstream channel (4) of the heat exchange medium; And / or, the relationship between the upstream channel of the heat exchange medium, the reaction tube, and the shell satisfies S3=a(S 10 The relation is given by -nS2), where a = 0.4 - 0.6; And / or, the relationship between the downstream channel of the heat exchange medium, the reaction tube, and the shell satisfies S4=b(S 10 The relationship between -nS2) is given by the formula, where b = 0.4 - 0.6; Where n is the number of reaction tubes, S2 is the cross-sectional area of ​​a single reaction tube, S3 is the cross-sectional area of ​​the upstream channel of the heat exchange medium, S4 is the cross-sectional area of ​​the downstream channel of the heat exchange medium (excluding the total cross-sectional area of ​​the reaction tubes), and S... 10 This represents the cross-sectional area of ​​the shell.

10. The method according to any one of claims 1-9, wherein, A baffle plate (9) is provided on the inner wall of the downstream channel (4) of the heat exchange medium.

11. The method according to claim 1, wherein, The molar ratio of methane to oxygen is 2-10:1; And / or, in each reaction tube, the space velocity of the methane is 18,000-120,000 mL / (g•h).

12. The method according to claim 1, wherein, The contact temperature is 450-830℃.

13. The method according to claim 1, wherein, The molar ratio of methane to oxygen is 3-8:

1.

14. The method according to claim 1, wherein, In each reaction tube, the space velocity of the methane is 48,000-60,000 mL / (g•h).

15. The method according to claim 1, wherein, The contact temperature is 550-820℃.

16. The method according to claim 1, wherein, The flow rate of the heat exchange medium is 400-20000 mL / min relative to the total amount of catalyst used per 1g.

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