Plasma reactor, its applications and methods for improving conversion of lower alkane hydrocarbons and / or selectivity of target products

Abstract

The present application relates to the technical field of methane conversion, in particular to a kind of plasma reactor and its application and the method for improving low carbon alkane conversion rate and / or target product selectivity, the plasma reactor includes reactor body and at least one electrode arranged in the reactor body, it further includes at least one side line feed pipe, at least one side line feed pipe extends to below or side of the electrode through the reactor body, the included angle α between each side line feed pipe and the reactor body side wall is each independently 10-90 °.The plasma reactor of the present application can improve low carbon alkane conversion rate, reaction product selectivity in low carbon alkane conversion, and reaction product can be adjusted wide range.

Description

Technical Field

[0001] This invention relates to the field of methane conversion technology, specifically to a plasma reactor and its application, and methods for improving the conversion rate of low-carbon alkanes and / or the selectivity of target products. Background Technology

[0002] Plasma methane conversion technologies include, for example, a method for producing gasoline from methane and carbon dioxide using plasma, disclosed in CN1180058C, in which CO2 is added as another reactant and gasoline is the main product. A method for producing acetylene from methane-containing gas using thermal plasma cracking, disclosed in CN1235846C, mainly uses methane as a raw material and acetylene as the main byproduct. CN100999432B discloses a method for producing C2 hydrocarbons from methane using plasma catalysis catalyzed by ionic liquids. CN101734620B discloses a method for producing hydrogen from methane-rich plasma.

[0003] Plasma cracking of methane, such as CN210367505U, CN109294284B, CN106478332B, and CN101921163B, is mainly developed for the plasma conversion of methane to produce carbon black or acetylene and hydrogen, with a greater emphasis on process design and optimization.

[0004] Plasma pyrolysis coal-to-acetylene processes, such as CN203582763U, CN102068953B, CN101734620B, CN101550057A, CN101734995B, and CN1240647C, mainly use coal as raw material, with natural gas as an auxiliary agent to produce acetylene and hydrogen. The working gas is hydrogen.

[0005] CN104056828A and CN104056829B are mainly developed for online plasma decoking methods, which can introduce CO2 or H2 to remove carbon deposits on the electrode surface. A rotating arc plasma method for pyrolyzing methane to produce acetylene (CN103333044B and CN101844744B) was also developed. The working gas rotates into the discharge gap, and an external magnetic field drives the process to cause millisecond-level pyrolysis.

[0006] CN106925086A discloses a plasma degradation treatment device for organic waste gas. This plasma treatment device is a plasma reactor, including a reactor cylinder, a gas inlet at the top of the reactor cylinder, a gas outlet at the bottom of the reactor, a plasma discharge electrode located inside the reactor cylinder, and a power interface for supplying power to the plasma discharge device. The reactor cylinder is equipped with an energy utilization device that expands the area and length of the sliding arc. The energy utilization device is an arc-expanding rod, an arc-expanding plate, or a combination of both. However, when this reactor is used for the directional conversion of methane, the methane conversion rate is low, and the olefin selectivity is low.

[0007] In summary, existing plasma reactors used in methane conversion processes all suffer from drawbacks such as low methane conversion rate, low product selectivity, and a narrow range of controllable product parameters. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing plasma reactors used in methane conversion processes, which have low methane conversion rates, low product selectivity, and narrow controllable product ranges. This invention provides a plasma reactor, its application, and a method for improving the conversion rate and / or target product selectivity of low-carbon alkanes. This plasma reactor, when used in methane conversion, can improve methane conversion rates, product selectivity, and has a wide controllable product range.

[0009] To achieve the above objectives, a first aspect of the present invention provides a plasma reactor, comprising a reactor body and at least one electrode disposed within the reactor body, and further comprising at least one side feed pipe extending through the reactor body to below or to the side of the electrode, wherein the included angle α between each side feed pipe and the sidewall of the reactor body is independently 10-90°.

[0010] Preferably, the plasma reactor further includes a jacket for the flow of heat exchange medium, the jacket being disposed outside the reactor body.

[0011] The second aspect of the present invention provides the application of the plasma reactor described in the first aspect above in the conversion of low-carbon alkane.

[0012] A third aspect of the present invention provides a method for improving the conversion rate and / or selectivity of low-carbon alkanes, the method comprising: introducing low-carbon alkanes into the reactor body for a discharge reaction in the aforementioned plasma reactor, and then contacting the product of the discharge reaction with hydrogen or a CO-containing gas for a hydrogenation or carbonylation reaction.

[0013] The hydrogen or CO-containing gas is introduced into the reactor body of the plasma reactor through a side feed pipe.

[0014] Preferably, the method further includes: filling or not filling the bottom of the reactor body with a catalyst;

[0015] And / or, the heat exchange medium may or may not be introduced into a jacket located outside the reactor body.

[0016] The plasma reactor provided by this invention, by introducing a specific side feed pipe and limiting the angle between the side feed pipe and the reactor body to the aforementioned specific range, enables the plasma reactor to improve the conversion rate of low-carbon alkanes and the selectivity of reaction products in the conversion of low-carbon alkanes. Moreover, the reaction products have a wide range of controllability. For example, it can use low-carbon alkanes as raw materials to prepare hydrocarbon products (e.g., alkanes and / or unsaturated hydrocarbons) and olefinic acids (e.g., C2-C5 olefinic acids), thereby increasing the variety and output of high-value-added products from the conversion of low-carbon alkanes.

[0017] In a preferred embodiment of the present invention, by setting a jacket for the flow of heat exchange medium, it is possible to flexibly cool or heat different reaction systems, thereby adjusting the required temperature of the system according to different processes, and introducing raw materials in conjunction with side streams to further improve methane conversion rate and reaction product selectivity.

[0018] The method for improving the conversion rate of low-carbon alkanes and / or the selectivity of target products provided by this invention utilizes the plasma reactor of this invention, enabling flexible control of the target product and achieving flexible process control and market adaptability. Compared with the traditional methane-to-olefins process (i.e., the aerobic coupling of methane to olefins process, whose CO2 selectivity is generally 30-60%), the method of this invention produces no CO2, has a high ethylene yield, and eliminates the risk of combustion and explosion, thus achieving a safe, green, and environmentally friendly methane-to-olefins process.

[0019] Furthermore, by employing preferred methods of loading or not loading catalyst, or introducing or not introducing heat exchange medium, the required temperature of different catalysts can be adopted according to different reactions. By combining the introduction or not of heat exchange medium, the catalyst bed temperature can be adjusted, thereby further controlling the selectivity of the target product. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a specific embodiment of the plasma reactor of the present invention;

[0021] Figure 2 yes Figure 1 A schematic diagram of the structure in which the middle electrode and the insulating base cooperate.

[0022] Explanation of reference numerals in the attached figures

[0023] Detailed Implementation

[0024] 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.

[0025] In this invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upstream or downstream direction along the material flow direction, and "inner" and "outer" refer to the inner and outer sides based on the contour of the corresponding component.

[0026] The first aspect of the present invention provides a plasma reactor, such as Figure 1 As shown, the reactor includes a reactor body 101 and at least one electrode 3 disposed within the reactor body 101, and also includes at least one side feed pipe 4. The at least one side feed pipe 4 extends through the reactor body 101 to the bottom or side of the electrode 3, and the included angle α between each side feed pipe 4 and the side wall of the reactor body 101 is independently 10-90°.

[0027] In this invention, the at least one side feed pipe 4 extending through the reactor body 101 to the side of the electrode 3 means that it can be located on the outside or inside of the electrode 3, preferably on the inside of the electrode 3 (it can be understood that the side of the electrode 3 near the central axis of the reactor body 101 is the inside, and the side near the tube wall of the reactor body 101 is the outside).

[0028] In this invention, the included angle α refers to the angle between the extended section of each side feed pipe 4 and the lower sidewall of the reactor body 101 (the lower part refers to the lower part with the intersection of the side feed pipe 4 and the reactor body 101 as the dividing point). It can be understood that the connection between the intersection of the side feed pipe 4 and the reactor body 101 is sealed.

[0029] In this invention, within the reactor body 101, the region near the electrode 3 is designated as the first reaction zone (i.e., the plasma zone), used for discharge reactions; optionally, the region located below the side feed pipe 4 is designated as the second reaction zone, used for reactions such as hydrogenation or carbonylation. It is understood that each side feed pipe 4 extends downwards from the reactor body 101, preferably conveying raw materials to the second reaction zone.

[0030] In a preferred embodiment, the included angle α is 30-90°, more preferably 40-90°. This preferred embodiment is more conducive to improving the conversion rate of low-carbon alkanes and the selectivity of reaction products (e.g., acrylic acid selectivity).

[0031] According to the present invention, preferably, the ratio of the distance m between the extended end of the side feed pipe 4 and the side wall of the reactor body 101 to the radius d of the reactor body 101 is 0.1-0.9:1, more preferably 0.3-0.6:1. This preferred embodiment facilitates the thorough mixing of the material introduced by the side feed pipe (e.g., hydrogen or CO) with the material obtained from the discharge reaction (also known as tail gas), while appropriate cooling of the tail gas further facilitates subsequent hydrogenation or carbonylation reactions, thereby further improving methane conversion rate and reaction product selectivity.

[0032] In this invention, the extended end of the side feed pipe 4 refers to the end of the side feed pipe 4 located inside the reactor body 101. The term m refers to the distance between the center of the outermost end face of the extended end of the side feed pipe 4 and the side wall of the reactor body 101, such as... Figure 1 As shown. The radius d refers to 1 / 2 of the maximum inner diameter D of the reactor body 101. When the reactor body 101 is cylindrical, the maximum inner diameter D is the inner diameter of the reactor body 101.

[0033] According to the present invention, the position of the extension end of the side feed pipe 4 in the length direction of the reactor body 101 can be selected from a wide range. In order to enable the material introduced by the side feed pipe to participate in the reaction better and more fully to improve product selectivity, preferably, the extension end of the side feed pipe 4 is located below the middle position of the electrode 3 (referring to the middle of the maximum length of the electrode).

[0034] More preferably, the extension end of at least one side feed pipe 4 is located below the electrode 3 (meaning directly below the entire electrode 3).

[0035] Preferably, in the vertical direction, the distance between the extended end of the side feed pipe 4 and the middle part of the electrode 3 is 0.1-1 times the total length of the electrode 3. In this invention, the total length of the electrode 3 refers to the total length of all electrodes in the vertical direction, and the length of a single electrode refers to its length in the vertical direction, for example... Figure 1 The length of the blade 302 shown in the vertical direction (understandably, excluding the length of the electrode rod 303).

[0036] According to the present invention, preferably, the side feed pipe 4 is disposed within 1-5 horizontal planes from top to bottom of the reactor body 101. More preferably, the distance between two adjacent horizontal planes is 0.1-0.3 times the length of the reactor body 101. In the present invention, the horizontal plane in which the side feed pipe 4 is disposed refers to the horizontal plane where the center of the bottom end (i.e., the lower end) of the side feed pipe 4 is located.

[0037] In this invention, the number of side feed pipes 4 can be selected from a wide range. Preferably, in the same horizontal plane, the side feed pipes 4 are arranged in pairs with a total number of 2-10 (which can be understood as 1-5 pairs), more preferably 2-8, and even more preferably 4-6. The preferred embodiment of this invention is more conducive to introducing raw materials from multiple directions, which is beneficial to the homogenization of the reaction, thereby further improving the conversion rate of low-carbon alkanes and the selectivity of reaction products.

[0038] In this invention, the number of side feed pipes 4 can be the same or different on different horizontal planes of the reactor body 101. Those skilled in the art can choose freely according to their needs, as long as it is conducive to improving product selectivity and raw material conversion rate.

[0039] In a preferred embodiment of the present invention, each of the side feed pipes 4 is evenly arranged along the circumferential direction of the reactor body 101 in the same horizontal plane, and the included angle α between each side feed pipe 4 and the side wall of the reactor body 101 is the same.

[0040] According to a specific embodiment of the present invention, the plasma reactor further includes a gas nozzle 9, a reactant outlet 8, and an insulating base 102 connected to the reactor body 101. The gas nozzle 9 is disposed on the insulating base 102, and the reactant outlet 8 is disposed on one end of the reactor body 101 away from the insulating base 102. The electrode 3 is connected to the insulating base 102, and the extension end of the side feed pipe 4 is located between the electrode 3 and the reactant outlet 8. It is understood that the gas nozzle 9 and the reactant outlet 8 are located on opposite sides of the reactor body 101, such that the gas inlet direction of the reactor body 101 is top-inlet and bottom-outlet. Of course, the gas inlet direction can also be adjusted to bottom-inlet and top-outlet according to actual needs. It is understood that the gas nozzle 9 is used to transport raw material gas (e.g., at least one of hydrogen, nitrogen, and methane).

[0041] In this invention, those skilled in the art can select the position and size of the gas nozzle 9 according to actual needs. The gas nozzle 9 is preferably located at the center of the insulating base 102. The diameter of the gas nozzle 9 is preferably 1-2 mm.

[0042] In this invention, it is understood that the reactor body 101 and the insulating base 102 together constitute the reactor shell 1. Of course, the reactor body 101 can be a one-piece molded cylinder with an opening only at the top (or a cylindrical structure with an irregular shape at the bottom, such as...). Figure 1The inverted conical shape shown can also be composed of a cylindrical shape (i.e., a cylinder open at both ends) and a bottom part. Generally, it is required that the gaps between the two ends of the cylinder (i.e., the upper and lower ends) and the electrodes (which can be understood as the distance from the end of the electrode blade) must each be greater than twice the minimum discharge gap (which can be understood as the minimum distance between the two electrodes) to avoid affecting the normal generation of plasma. This is existing technology and will not be elaborated further here. The length of the reactor body 101 is preferably 150-300 mm. In this invention, this length refers to... Figure 1 The length of the cylindrical portion shown in the vertical direction does not include the length of the inverted conical portion at the bottom of the reactor body 101. It is understood that when the reactor body 101 is a conventional cylindrical structure, the length refers to the overall length of the cylindrical structure. This invention does not limit the length of the inverted conical portion; those skilled in the art can freely choose it as needed.

[0043] In this invention, the material of the reactor body 101 can be selected according to actual needs, such as quartz glass or corundum, to facilitate providing a sealed space for the reaction. Those skilled in the art can select the shape and size of the insulating base 102 according to actual needs; for example, it can be circular, with a preferred diameter of 70-100 mm. It is understood that, according to actual needs, the insulating base 102 can have a power supply groove and terminals for connecting the electrodes, and the distance between the electrode mounting position and the outer edge of the insulating base 102 must ensure that the discharge is not affected.

[0044] In this invention, the plasma reactor further includes an inlet pipe connected to the gas nozzle 9 for supplying a raw material gas (e.g., at least one of hydrogen, nitrogen, and methane). It is understood that the inlet pipe can control the flow rate of the raw material gas; this is prior art and will not be elaborated upon here.

[0045] According to the present invention, preferably, the number of electrodes 3 is two or more.

[0046] Preferably, the electrodes 3 are arranged in pairs, with the two electrodes symmetrically distributed on opposite sides of the axis of the gas nozzle 9. The distance between the two electrodes gradually increases in the direction from the gas nozzle 9 to the reactant outlet 8, which facilitates better guidance of the raw material gas for reaction in the plasma region. It is understood that the electrodes 3 extend along the direction from the gas nozzle 9 to the reactant outlet 8.

[0047] Preferably, the maximum inner diameter D of the reactor body 101 is 70-100 mm, and the length is 150-300 mm. More preferably, the minimum distance h between the two electrodes in the paired electrodes is 1-4 mm. This preferred embodiment is more conducive to forming an electric arc between the electrodes. More preferably, the shortest distance H between the electrode 3 and the gas nozzle 9 is 10-50 mm, more preferably 20-30 mm.

[0048] Preferably, the included angle β between the two electrodes in the paired electrodes is 20°-70°, more preferably 30°-60°, and even more preferably 35-55°. In this invention, the included angle β between the two electrodes refers to the angle between the tangents of the inner surfaces of the two electrodes. For example, when the inner surfaces of the two electrodes are planes (understood as straight lines), the included angle β refers to the angle formed by extending the inner surfaces of the two electrodes. This preferred embodiment is more conducive to extending the sliding distance of the electric arc, thereby enabling the raw materials to undergo plasma reactions better and more efficiently.

[0049] According to the present invention, preferably, the electrode 3 is movably connected to the insulating base 102 for adjusting the position of the electrode 3 in the horizontal or vertical direction, thereby facilitating the adjustment of the spacing parameters between the gas nozzle 9 and the electrode 3 (e.g., minimum spacing h, shortest distance H between the electrode 3 and the gas nozzle 9).

[0050] The present invention offers a wide range of possible connection methods between the electrode 3 and the insulating base 102, as long as it allows for adjustment of the electrode 3 in either the horizontal or vertical direction; for example, such as Figure 2 As shown, the electrode 3 is fixed to the position by a positioning screw 304. Figure 1 The electrode rod 303 shown has multiple positioning holes in the horizontal direction on the positioning screw 304, which are used to fix the electrode rod 303 on the electrode 3. The horizontal position of the electrode 3 can be adjusted by changing the relative position between the positioning hole and the electrode 3. The electrode 3 is connected to the insulating base 102 through the electrode rod 303 (e.g., threaded connection). The position of the electrode 3 in the vertical direction can be adjusted by adjusting the position of the electrode rod 303 up and down.

[0051] In this invention, preferably, the electrode 3 is a blade electrode (it is understood that, as Figure 1 As shown, electrode 3 includes a blade, which comprises a cutting edge 301 and a blade body 302. The cutting edge 301 of the blade electrode faces the first reaction zone. The cutting edge 301 can be curved or straight, preferably the former. This invention does not limit the material of electrode 3; for example, the cutting edge can be made of 316L stainless steel or tungsten-cerium alloy. The preferred size of electrode 3 is 50-100 mm in length (length refers to...). Figure 1The blade of the electrode shown is 2-4 mm thick and has a vertical length.

[0052] Preferably, within the same horizontal plane, the paired electrodes 3 are arranged in one or three pairs, and the one or three pairs of electrodes are evenly distributed along the circumference of the reactor body 101. When the paired electrodes 3 are one pair, the included angle between the two electrodes is 180°, and when the paired electrodes 3 are three pairs, the included angle between two adjacent electrodes is 60°.

[0053] According to a preferred embodiment of the present invention, the plasma reactor further includes a jacket 2 for the flow of heat exchange medium, the jacket 2 being disposed outside the reactor body 101. The inventors further discovered that this preferred embodiment allows for flexible cooling or heating of different reaction systems, thereby adjusting the required system temperature according to different processes, thus improving methane conversion rate and reaction product selectivity; simultaneously, the heat generated by the discharge reaction occurring in the plasma region can be recovered and utilized, for example, by first introducing the raw materials into the jacket 2 for preheating before introducing them into the reactor body 101.

[0054] It is understood that the jacket 2 is located outside the first reaction zone (i.e., the plasma zone).

[0055] According to the present invention, preferably, the plasma reactor further includes a heat exchange medium outlet 6 disposed on the upper part of the jacket 2 and a heat exchange medium inlet 7 disposed on the lower part of the jacket 2, thereby achieving convective cooling and achieving better cooling effect.

[0056] According to a preferred embodiment of the present invention, a catalyst bed 5 filled with catalyst is provided at one end of the reactor body 101 away from the electrode 3.

[0057] Preferably, the jacket 2 is also located outside the catalyst bed 5 to further cool or heat the catalyst reaction, thereby hydrogenating or carbonylating the plasma exhaust gas (which is understood to be a gas mixture after the reaction in the first reaction zone) to finally obtain the target product (e.g., unsaturated hydrocarbons or acrylic acid).

[0058] In this invention, the plasma reactor can be used in any field where a reaction can be carried out via a plasma reactor; the invention has no limitations in this regard, and it is particularly applicable to methane conversion reactions. The detailed description of the plasma reactor above uses methane conversion as an example, but the invention is not limited thereto.

[0059] The second aspect of the present invention provides the application of the plasma reactor described in the first aspect above in the conversion of low-carbon alkane.

[0060] In this invention, the low-carbon alkane can be C1-C4 alkane, and this invention is not limited thereto. For example, the plasma reactor is used in methane conversion. On the one hand, it can be used to prepare unsaturated hydrocarbons (e.g., ethylene) or alkanes (e.g., ethane). In this case, the feedstock introduced into the side feed pipe 4 can be hydrogen gas. Hydrogen gas can both cool the tail gas obtained from the discharge reaction and serve as a feedstock for subsequent hydrogenation reactions, thereby improving the methane conversion rate and the selectivity of reaction products. On the other hand, it can also be used to prepare products such as acrylic acid (understandably, these can be downstream products of methane or acetylene). In this case, the feedstock introduced into the side feed pipe 4 can be CO-containing gas to prepare acrylic acid.

[0061] A third aspect of the present invention provides a method for improving the conversion rate and / or selectivity of low-carbon alkanes, the method comprising: introducing low-carbon alkanes into the reactor body 101 in the aforementioned plasma reactor for a discharge reaction, and then contacting the product of the discharge reaction with hydrogen or CO-containing gas for a hydrogenation or carbonylation reaction; wherein the hydrogen or CO-containing gas is introduced into the reactor body 101 of the plasma reactor through a side feed pipe 4.

[0062] It is understood that the target product refers to the target product after the conversion of low-carbon alkanes.

[0063] It is understandable that when hydrogen is introduced into the side feed pipe 4, a hydrogenation reaction occurs, and the product of the hydrogenation reaction can be an alkane or an unsaturated hydrocarbon, such as an olefin. When CO gas is introduced, a carbonylation reaction occurs, and the product of the carbonylation reaction is an olefinic acid, such as acrylic acid obtained after carbonylation of methane as a raw material.

[0064] According to the present invention, preferably, the conditions for the discharge reaction include: a discharge voltage of 1-5 kV, a discharge frequency of 5-30 kHz, and a discharge input energy of 20-100 kJ / L low-carbon alkanes. It is understood that the discharge reaction is continuous.

[0065] According to the present invention, preferably, the conditions for the hydrogenation or carbonylation reaction include: a volume ratio of hydrogen feed flow rate to low-carbon alkane feed flow rate of 0-1:1, and a hydrogenation reaction temperature of 30-200°C; or, a volume ratio of CO feed flow rate to low-carbon alkane feed flow rate of 0.5-1.5:1, and a carbonylation reaction temperature of 50-250°C.

[0066] More preferably, the hydrogenation reaction temperature is 50-150°C, or the carbonylation reaction temperature is 100-200°C.

[0067] In this invention, the discharge reaction and the hydrogenation reaction or carbonylation reaction are both carried out within the reactor body 101. The temperature of the hydrogenation reaction or carbonylation reaction can be provided by the temperature provided by the discharge reaction, or it can be provided by the heat exchange medium in conjunction with the temperature provided by the discharge reaction. Those skilled in the art can freely choose according to actual needs.

[0068] The present invention does not impose any restrictions on the duration of the discharge reaction, or the duration of the hydrogenation or carbonylation reaction; those skilled in the art can freely choose according to actual needs.

[0069] In this invention, the time for the hydrogenation or carbonylation reaction is preferably the same as the time for the discharge reaction. This is because the discharge reaction and the hydrogenation or carbonylation reaction occur in the upper and lower parts of the reactor body 101, respectively. After the discharge reaction is completed, the products of the discharge reaction naturally flow to the catalyst bed for hydrogenation or carbonylation reaction.

[0070] In this invention, the hydrogenation or carbonylation reaction can proceed stably and continuously. It is understood that the discharge voltage, discharge frequency, and discharge power of the hydrogenation or carbonylation reaction are the same as those of the discharge reaction, because the carbonylation reaction and the discharge reaction occur almost simultaneously.

[0071] In this invention, the hydrogenation or carbonylation reaction is preferably carried out in the presence of a reduced catalyst. There are no restrictions on the reduction conditions; conventional reduction conditions in the art can be used, as long as the catalyst can be reduced. Preferably, the catalyst reduction is carried out in a plasma reactor.

[0072] According to a preferred embodiment of the present invention, the method further includes: loading or not loading a catalyst at the bottom of the reactor body 101. This preferred embodiment can control the type of target product; for example, loading a catalyst yields olefins or alkanes, while not loading a catalyst yields alkynes.

[0073] According to another preferred embodiment of the present invention, the method further includes: introducing or not introducing a heat exchange medium into a jacket 2 disposed outside the reactor body 101. More preferably, the heat exchange medium is selected according to the target product requirements.

[0074] The heat exchange medium can be water (e.g., saturated water) or reaction raw materials, such as at least one of the following: raw material gas, boiling water, heat transfer oil, and cooling water. Using raw material gas for heat exchange can lower the temperature inside the reactor body 101 and effectively utilize the heat generated by the plasma, further reducing plasma energy consumption. Using boiling water for heat exchange can maintain a constant temperature in the reactor body 101, suitable for temperatures above 200°C, and can generate steam as a byproduct of the heat, improving the economic efficiency of the plasma process. Heat transfer oil is mainly used to cool or provide the catalyst with the temperature required for the reaction, suitable for reactions with temperatures above 100°C but below 200°C. Ordinary water can be used for temperature requirements below 100°C. The heat exchange medium is preferably at least one of boiling water, cooling water, and heat transfer oil.

[0075] According to a preferred embodiment of the present invention, the method further includes: first introducing a heat exchange medium into a jacket 2 disposed outside the reactor body 101, then loading a catalyst at the bottom of the reactor body 101, and then introducing the low-carbon alkane.

[0076] According to another preferred embodiment of the present invention, a catalyst is first loaded at the bottom of the reactor body 101, then a heat exchange medium is introduced into the jacket 2 located outside the reactor body 101, and then the low-carbon alkane is introduced. This preferred scheme is beneficial for improving methane conversion and balancing the selectivity of the target product.

[0077] Further research by the inventors revealed that the above-mentioned method can be used to flexibly control the selectivity of the target product in the reactor provided by this invention, thereby meeting different market demands.

[0078] In this invention, there are no limitations on the catalyst used. Those skilled in the art can select existing catalysts according to their needs, such as hydrogenation catalysts or carbonylation catalysts, as long as they can achieve the purpose of hydrogenation or carbonylation reaction. Preferably, the catalyst is at least one of Pd-based catalysts, Ag-based catalysts, and Ni-based catalysts. The catalyst is preferably in particulate form, and more preferably, the particle size is 1-5 mm.

[0079] According to the present invention, those skilled in the art can select the heat exchange medium according to the reaction temperature required by the corresponding catalyst. For example, warm water can be used for heating or heat extraction in Pd-based catalysts, heat transfer oil can be used for heating in Ag-based high-temperature catalysts, and boiling water is required for heating in Ni-based catalysts.

[0080] This invention does not limit the CO content in the CO-containing gas; those skilled in the art can freely choose according to their needs. Preferably, the CO-containing gas is CO or syngas. This invention also does not limit the hydrogen-to-carbon volume ratio in the syngas; those skilled in the art can freely choose according to their needs, for example, it can be 0.5-2:1.

[0081] Preferably, the discharge reaction and the hydrogenation or carbonylation reaction are carried out in an oxygen-free environment. This preferred approach is safer.

[0082] More preferably, the method further includes: first introducing oxygen-free gas to replace the gas in the plasma reactor, and then introducing the low-carbon alkane to provide an oxygen-free environment.

[0083] According to a preferred embodiment of the present invention, such as Figure 1 As shown, the method for improving the conversion rate of low-carbon alkanes and / or the selectivity of target products includes the following steps:

[0084] (1) In the aforementioned plasma reactor, the electrode structure is adjusted to meet the required electrode structure parameters (e.g., the shortest distance H between the electrode 3 and the gas nozzle 9, and the minimum spacing h between the two electrodes in a pair).

[0085] (2) A catalyst is packed in the lower part of the reactor body 101 to form a catalyst bed 5;

[0086] (3) First, heat exchange medium is introduced into the jacket 2; then oxygen-free gas (e.g., inert gas, preferably nitrogen) is introduced into the reactor body 101 through the gas nozzle 9 to replace the oxygen in the reactor body 101 and obtain an oxygen-free environment.

[0087] (4) Then hydrogen (and an inert gas, preferably nitrogen, can be introduced at the same time) is introduced through gas nozzle 9 to reduce the catalyst;

[0088] (5) Next, raw material gas (preferably low-carbon alkanes and hydrogen, to facilitate direct hydrogenation after conversion of low-carbon alkanes) is introduced through gas nozzle 9, and hydrogen or CO-containing gas (e.g., CO or syngas) is introduced into reactor body 101 through side feed pipe 4 for discharge reaction (when adjusting discharge reaction parameters, it is preferred to first increase the voltage and then decrease the voltage to the required voltage value, the difference between the increased voltage value and the required voltage value is 0.4-1kV). The tail gas obtained from the discharge reaction naturally enters catalyst bed 5 for hydrogenation or carbonylation reaction. Under this preferred scheme, the selectivity of olefins is higher, the conversion rate of low-carbon alkanes is higher, and the amount of carbon deposition is low or there is no obvious carbon deposition (generally, a carbon deposition of less than 1% is called no obvious carbon deposition).

[0089] The present invention will be described in detail below through embodiments. The formulas for calculating the selectivity of acrylic acid are: (molar amount of acrylic acid at the outlet) * 3 / (molar amount of methane at the inlet - molar amount of methane at the outlet); the formula for calculating the selectivity of ethylene is: (molar amount of ethylene at the outlet) * 2 / (molar amount of methane at the inlet - molar amount of methane at the outlet); the formula for calculating the selectivity of ethane is: (molar amount of ethane at the outlet) * 2 / (molar amount of methane at the inlet - molar amount of methane at the outlet); the formula for calculating the selectivity of acetylene is: (molar amount of acetylene at the outlet) * 2 / (molar amount of methane at the inlet - molar amount of methane at the outlet); C 3+ The formula for calculating selectivity is: Σ(C n (Export molar quantity) * n / (Methane import molar quantity - Methane export molar quantity), n = 3-5.

[0090] Example 1

[0091] This embodiment illustrates the plasma reactor and the method for converting methane into acrylic acid according to the present invention.

[0092] (1) In Figure 1 In the plasma reactor shown, the maximum inner diameter D (i.e., the diameter of the upper cylinder) of the reactor body 101 is 70 mm, and the length (i.e., the height of the upper cylinder) is 250 mm. There are eight side-feed pipes 4 (i.e., four pairs) evenly distributed along the circumference of the reactor body 101. The angle α between each side-feed pipe 4 and the side wall of the reactor body 101 is 45°. The side-feed pipes 4 are arranged in one layer (i.e., distributed within a horizontal plane of the reactor body 101). The extension end of the side-feed pipe 4 is located below the electrode 3. In the vertical direction, the distance between the extension end of the side-feed pipe 4 and the middle of the electrode 3 is 0.5 times the total length of the electrode 3. The ratio of the distance m between the extension end of the side-feed pipe 4 and the side wall of the reactor body 101 to the radius d (i.e., half of D) of the reactor body 101 is 0.5:1. The bottom of the reactor body 101 is an inverted cone shape. Electrode 3 consists of two blade-type electrodes (the included angle β of the paired electrodes is 45°, and the blade 301 is arc-shaped) and is arranged horizontally and symmetrically. Electrode 3 is adjusted so that the shortest distance H between electrode 3 and the gas nozzle 9 is 1cm and the minimum distance h between the two electrodes is 2mm.

[0093] (2) A carbonylation catalyst (specifically Rh-Fe / Al2O3, wherein, based on the total amount of catalyst and calculated as oxides, the content of Rh is 0.5 wt% and the content of Fe is 5 wt%) is packed into the lower part of the reactor body 101, approximately 60 g. The catalyst particle size is 3-5 mm.

[0094] (3) First, heat exchange medium heat transfer oil is introduced into the jacket 2 through the heat exchange medium inlet 7 for cooling; then oxygen-free gas (nitrogen, inlet flow rate of 3L / min) is introduced into the reactor body 101 through the gas nozzle 9 for 30min to replace the oxygen in the reactor body 101 and obtain an oxygen-free atmosphere.

[0095] (4) Then, hydrogen and nitrogen (2 L / min nitrogen and 1 L / min hydrogen) are introduced into the reactor body 101 through the gas nozzle 9. Turn on the power, adjust the voltage and frequency, first increase the voltage to 2 kV and adjust the frequency to 25 kHz, start the discharge, reduce the carbonylation catalyst for about 2 hours, the catalyst color turns basically black, end the reduction, and turn off the power.

[0096] (5) Next, the raw material gas (methane 1L / min, hydrogen 3L / min) is introduced into the reactor body 101 through the gas nozzle 9, and CO (the volume ratio of CO feed flow rate to methane feed flow rate is 0.75:1) is introduced into the reactor body 101 through the side feed pipe 4. The power is turned on, and the voltage and frequency are adjusted. First, the voltage is increased to 2kV and the frequency is adjusted to 25kHz (i.e., the discharge frequency). Discharge begins, and the voltage is adjusted to the specified 1.6kV (i.e., the discharge voltage). At this time, the power is about 300W (i.e., the discharge power). The discharge reaction is carried out, and the temperature of the catalyst bed (i.e., the carbonylation reaction temperature) packed in the lower part of the reactor body 101 is controlled between 150-300℃ by the heat exchange medium heat transfer oil. The product after plasma reaction and carbonylation (hereinafter referred to as tail gas) is discharged from the reactant outlet 8.

[0097] After 8 hours, the tail gas was analyzed by gas chromatography. The results showed a methane conversion rate of 36%, acrylic acid selectivity of 80%, ethylene selectivity of 15%, and C3... + 5%, with no obvious carbon buildup.

[0098] Example 2

[0099] The method is carried out according to Example 1, except that the side feed pipes 4 are set differently. Specifically, there are a total of 8 side feed pipes 4, 4 in each layer, divided into two layers (distributed in two horizontal planes of the reactor body 101). The distance between the two layers is 0.2 of the length of the reactor body 101. The side feed pipes 4 in both layers are located below the electrode 3.

[0100] Analysis of the exhaust gas revealed a methane conversion rate of 36%, an acrylic acid selectivity of 85%, an ethylene selectivity of 8%, and a C3 conversion rate of [missing information]. + 7%, with no obvious carbon buildup.

[0101] Example 3

[0102] The method was carried out according to Example 1, except that α was 30°.

[0103] Analysis of the exhaust gas revealed a methane conversion rate of 35%, an acrylic acid selectivity of 63%, an ethylene selectivity of 35%, and a C3 concentration of [missing information]. + 2%, with no obvious carbon buildup.

[0104] Example 4

[0105] The method of Example 1 was followed, except that no heat exchange medium was introduced (i.e., the reaction was not cooled).

[0106] Analysis of the exhaust gas revealed a methane conversion rate of 37%, an acrylic acid selectivity of 20%, an ethylene selectivity of 31%, and a C3 conversion rate of [missing information]. + 35%, carbon deposits 15%.

[0107] Example 5

[0108] The method of Example 1 is followed, except that in step (2), a hydrogenation catalyst (specifically Pd-Ag / Al2O3, wherein based on the total amount of catalyst, the content of Pd is 0.1wt% and the content of Ag is 0.5wt% in terms of oxides) is used instead of the carbonylation catalyst of Example 1, in step (3), water is used instead of heat transfer oil for cooling, and in step (5), methane is introduced through gas nozzle 9 and hydrogen is introduced through side feed pipe 4 instead of CO (wherein, methane is 1L / min and hydrogen is 3L / min), and the temperature of the catalyst bed (i.e. the hydrogenation reaction temperature) packed in the lower part of the reactor body 101 is controlled between 50-100°C by heat exchange medium.

[0109] Analysis of the exhaust gas revealed a methane conversion rate of 35%, ethylene selectivity of 85%, ethane selectivity of 5%, and C3... + 10%, with no obvious carbon buildup.

[0110] Example 6

[0111] The procedure was carried out according to the method of Example 5, except that no catalyst was loaded in step (2).

[0112] Analysis of the exhaust gas showed a methane conversion rate of 37%, acetylene selectivity of 95%, ethylene selectivity of 3%, ethane selectivity of 2%, and no significant carbon deposits.

[0113] Example 7

[0114] The method of Example 5 is followed, except that in step (3), heat transfer oil is used to maintain the temperature inside the reactor at 150°C.

[0115] Analysis of the exhaust gas revealed a methane conversion rate of 37%, ethylene selectivity of 3%, ethane selectivity of 85%, and C3... + 12%, with no obvious carbon buildup.

[0116] Example 8

[0117] The method is carried out according to Example 5, except that water is not introduced in step (3).

[0118] Analysis of the exhaust gas revealed a methane conversion rate of 35%, ethylene selectivity of 63%, ethane selectivity of 29%, and C3... + 8%, with no obvious carbon buildup.

[0119] Example 9

[0120] The method of Example 5 is followed, except that the method of introducing water is different. Specifically, water is not introduced in step (3), but water is first introduced through the heat exchange medium inlet 7 for cooling in step (5), and then raw material gas is introduced through the gas nozzle 9. The rest is the same as in Example 5.

[0121] Analysis of the exhaust gas revealed a methane conversion rate of 36%, ethylene selectivity of 75%, acetylene selectivity of 20%, and C3... + 5%, with no obvious carbon buildup.

[0122] Example 10

[0123] The method was carried out according to Example 5, except that m / d = 0.1.

[0124] Analysis of the exhaust gas revealed a methane conversion rate of 35%, ethylene selectivity of 70%, acetylene selectivity of 25%, and C3... + 5%, with no obvious carbon buildup.

[0125] Comparative Example 1

[0126] The method of Example 5 is followed, except that the side feed pipe 4 is not set. Instead, in step (5), hydrogen is introduced into the reactor body 101 together with methane through the gas nozzle 9. The amount of hydrogen used is the same as in Example 5.

[0127] Analysis of the exhaust gas revealed a methane conversion rate of 20%, ethylene selectivity of 80%, acetylene selectivity of 20%, and C3... + 0%, no obvious carbon buildup.

[0128] The results above show that the embodiments using the specific plasma reactor of the present invention have the effects of high methane conversion rate, high selectivity of target product, and flexible adjustment of target product.

[0129] As can be seen from the comparison of Examples 1 and 5-9, the plasma reactor of the present invention and the method for converting low-carbon alkane using the reactor can flexibly adjust the target product. As can be seen from the comparison of Example 1 and Comparative Example 1, the preferred side-feed pipe scheme of the present invention results in higher methane conversion rate and higher target product selectivity.

[0130] By comparing Examples 1-2 with Examples 3 and 10, it can be seen that the preferred reactor with a specific structure of the present invention has a higher methane conversion rate and a higher selectivity for the target product.

[0131] It should be noted that the comparative examples of the present invention are not prior art, but are set up to highlight the effects of the present invention, and should not be regarded as a limitation of the present invention.

[0132] 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 plasma reactor, comprising a reactor body (101) and at least one electrode (3) disposed within the reactor body (101), characterized in that, It also includes at least one side feed pipe (4), which extends through the reactor body (101) to the bottom or side of the electrode (3), and the included angle α between each side feed pipe (4) and the side wall of the reactor body (101) is independently 10-90°; the ratio of the distance m between the extension end of the side feed pipe (4) and the side wall of the reactor body (101) to the radius d of the reactor body (101) is 0.1-0.9:

1.

2. The plasma reactor according to claim 1, characterized in that, The included angle α is 40-90°.

3. The plasma reactor according to claim 1, characterized in that, The side feed pipe (4) is arranged in 1-5 horizontal planes from top to bottom of the reactor body (101), and the distance between two adjacent horizontal planes is 0.1-0.3 times the length of the reactor body (101).

4. The plasma reactor according to claim 3, characterized in that, Within the same horizontal plane, the side feed pipes (4) are arranged in pairs and the total number is 2-10.

5. The plasma reactor according to claim 3, characterized in that, Within the same horizontal plane, each side feed pipe (4) is evenly arranged along the circumference of the reactor body (101), and the included angle α between each side feed pipe (4) and the side wall of the reactor body (101) is the same.

6. The plasma reactor according to claim 1, characterized in that, The extension end of the side feed tube (4) is located below the middle position of the electrode (3), where the middle position refers to the middle of the maximum length of the electrode (3).

7. The plasma reactor according to claim 1, characterized in that, At least one side feed tube (4) has an extension end located below the electrode (3).

8. The plasma reactor according to claim 6, characterized in that, In the vertical direction, the distance between the extension end of the side feed tube (4) and the middle position of the electrode (3) is 0.1-1 of the total length of the electrode (3), and the middle position refers to the middle of the maximum length of the electrode (3).

9. The plasma reactor according to any one of claims 1-8, characterized in that, The plasma reactor also includes a gas nozzle (9), a reactant outlet (8), and an insulating seat (102) connected to the reactor body (101). The gas nozzle (9) is disposed on the insulating seat (102), and the reactant outlet (8) is disposed on the reactor body (101) and at one end away from the insulating seat (102). The electrode (3) is connected to the insulating base (102), and the extension end of the side feed pipe (4) is located between the electrode (3) and the reactant outlet (8).

10. The plasma reactor according to claim 9, characterized in that, The electrodes (3) are arranged in pairs, and the two electrodes in the pair are symmetrically distributed on opposite sides of the axis of the gas nozzle (9). The distance between the two electrodes gradually increases in the direction from the gas nozzle (9) to the reactant outlet (8).

11. The plasma reactor according to claim 10, characterized in that, The reactor body (101) has a maximum inner diameter D of 70-100 mm and a length of 150-300 mm; the minimum distance h between the two electrodes in the paired electrodes is 1-4 mm; and the shortest distance H between the electrode (3) and the gas nozzle (9) is 10-50 mm. And / or, in the same horizontal plane, the electrodes (3) are arranged in pairs, which are one or three pairs, and the one or three pairs of electrodes are evenly arranged along the circumferential direction of the reactor body (101).

12. The plasma reactor according to claim 11, characterized in that, The included angle β between the two electrodes in the paired electrodes is 20°-70°.

13. The plasma reactor according to claim 1, characterized in that, The plasma reactor also includes a jacket (2) for the flow of heat exchange medium, the jacket (2) being disposed outside the reactor body (101); And / or, a catalyst bed (5) filled with catalyst is provided at one end of the reactor body (101) away from the electrode (3). And / or, the end of the reactor body (101) away from the electrode (3) is an inverted cone.

14. The application of the plasma reactor according to any one of claims 1-13 in the conversion of low-carbon alkane.

15. A method for improving the conversion rate of low-carbon alkanes and / or the selectivity of a target product, the method comprising: In the plasma reactor according to any one of claims 1-13, low-carbon alkanes are introduced into the reactor body (101) for discharge reaction, and then the products of the discharge reaction are contacted with hydrogen or CO-containing gas for hydrogenation or carbonylation reaction. The hydrogen or CO-containing gas is introduced into the reactor body (101) of the plasma reactor through the side feed pipe (4).

16. The method according to claim 15, wherein, The method also includes: filling or not filling the bottom of the reactor body (101) with a catalyst; And / or, the heat exchange medium may or may not be introduced into the jacket (2) located outside the reactor body (101).

17. The method according to claim 16, wherein, The method further includes: first introducing the heat exchange medium into the jacket (2) located outside the reactor body (101), then loading the catalyst at the bottom of the reactor body (101), and then introducing the low-carbon alkane.

18. The method according to claim 16, wherein, First, a catalyst is loaded at the bottom of the reactor body (101), then the heat exchange medium is introduced into the jacket (2) located outside the reactor body (101), and then the low-carbon alkane is introduced.

19. The method according to claim 18, wherein, The catalyst is a hydrogenation catalyst or a carbonylation catalyst; And / or, the heat exchange medium is at least one of boiling water, cooling water, and heat transfer oil.

20. The method of claim 15, wherein, The conditions for the discharge reaction include: a discharge voltage of 1-5 kV, a discharge frequency of 5-30 kHz, and a discharge input energy of 20-100 kJ / L low-carbon alkanes. And / or, the conditions for the hydrogenation or carbonylation reaction include: a volume ratio of hydrogen feed flow rate to low-carbon alkane feed flow rate of 0-1:1, and a hydrogenation reaction temperature of 30-200°C; or, a volume ratio of CO feed flow rate to low-carbon alkane feed flow rate of 0.5-1.5:1, and a carbonylation reaction temperature of 50-250°C; And / or, the discharge reaction and the hydrogenation or carbonylation reaction are carried out in an oxygen-free environment.

21. The method according to claim 20, wherein, The hydrogenation reaction temperature is 50-150℃, or the carbonylation reaction temperature is 100-200℃.

22. The method according to claim 15, wherein, The CO-containing gas is CO or synthesis gas.

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