Method for plasma production of olefins

Abstract

The present application relates to the field of energy conversion, and discloses a method for preparing olefins by plasma, which comprises: contacting alkane with active material of alkane generated by plasma electric field and catalyst to convert alkane into olefins, wherein the catalyst comprises a carrier and an active component loaded on the carrier, the active component contains a first active component and a second active component, the first active component is at least one selected from non-noble metals of group VIII and metals of group IB, the second active component is at least one selected from noble metals of group VIII, and the weight ratio of the first active component to the second active component is 0.1-200:1 in terms of metal elements. The method can adapt to the composition change of the reaction tail gas of alkane after plasma, improve the problem of uneven temperature of the catalyst bed layer caused by the reaction tail gas, and effectively and stably improve the selectivity of olefins.

Description

Technical Field

[0001] This invention relates to the field of olefin preparation, and more specifically to a method for preparing olefins using plasma. Background Technology

[0002] Ethylene, as one of the most important basic raw materials in the petrochemical industry, mainly originates from petroleum hydrocarbon cracking technology. With significant fluctuations in oil prices, the ethylene market is heavily dependent on oil prices. Currently, my country is focusing on developing non-petroleum-based ethylene production processes, among which the coal-to-methanol-to-low-carbon-olefins (CTO) process is well-developed. However, coal chemical processes consume large amounts of water and energy during the coal gasification stage, and water shortages are common in coal-rich areas, severely limiting the development of coal-to-olefins. With the development of combustible ice and shale gas, natural gas reserves are abundant, and natural gas conversion and utilization technologies have become a hot topic. Converting natural gas into ethylene can serve as a national energy strategic reserve and represents a new direction for technological development.

[0003] The natural gas-to-ethylene reaction can be carried out mainly through anaerobic coupling and aerobic coupling. Aerobic coupling, however, has not yet been industrialized due to the risk of combustion and explosion when the combustible gas is mixed with the oxidizer, and the demanding operating conditions. Natural gas can produce hydrogen and high-value-added olefins through anaerobic coupling. In traditional processes, under high temperature and pressure, methane is converted through adsorption activation coupling on the catalyst surface, but this produces many byproducts and cannot be directionally converted to ethylene. Plasma conversion of natural gas utilizes electron collisions to activate methane under an electric field, leading to free radical collision coupling and product formation. Plasma technology can convert methane at ambient temperature and pressure, with relatively mild operating conditions and high selectivity for specific products, primarily acetylene. Internationally, the United States and Germany have conducted research on plasma cracking for acetylene production. The German company ISP has built a 3000 t / a industrial-scale natural gas plasma-to-acetylene plant. Domestic institutions such as the Chengdu Institute of Organic Chemistry of the Chinese Academy of Sciences, Sichuan University, Tsinghua University, and the Institute of Metal Research of the Chinese Academy of Sciences have also conducted research on plasma pyrolysis devices and processes for producing acetylene. However, there is still no complete industrial-scale device in China capable of achieving the entire process. CN109503310 discloses a process for producing high-concentration acetylene and hydrogen from natural gas, using a plasma pyrolysis reactor. After thermal pyrolysis, carbon black, acetylene, and hydrogen are separated through a series of measures. CN109264671, CN106185806, CN105451874, and CN1176051 disclose the conversion of methane by plasma in various discharge forms, which can produce multiple products with complex compositions. However, the selectivity for ethylene still needs to be improved. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of numerous byproducts and low olefin selectivity in the production of olefins from alkanes in the existing technology, and to provide a method for preparing olefins. This method is characterized by its ability to adapt to the compositional changes of the reaction tail gas after natural gas passes through plasma and the uneven temperature of the catalyst bed caused by the reaction tail gas, and can effectively and stably improve olefin selectivity.

[0005] To achieve the above objectives, the present invention provides a method for plasma-based olefin preparation. The method includes: contacting an active substance generated from an alkane by a plasma electric field with a catalyst to convert the alkane into an olefin. The catalyst comprises a Ti oxide-doped support and an active component supported on the support. The active component contains a first active component and a second active component. The first active component is selected from at least one non-noble metal of Group VIII and a metal of Group IB. The second active component is selected from at least one noble metal of Group VIII. The weight ratio of the first active component to the second active component, based on metal elements, is 0.1-200:1.

[0006] The above technical solutions can effectively and stably improve olefin selectivity and can adapt to problems such as changes in the composition of the reaction tail gas after natural gas passes through plasma and uneven catalyst bed temperature caused by the reaction tail gas. Detailed Implementation

[0007] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0008] 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.

[0009] This invention provides a method for plasma-based olefin preparation. The method includes: contacting an active substance generated by passing an alkane through a plasma electric field with a catalyst to convert the alkane into an olefin. The catalyst includes a Ti oxide-doped support and an active component supported on the support. The active component contains a first active component and a second active component. The first active component is selected from at least one non-noble metal of Group VIII and a metal of Group IB. The second active component is selected from at least one noble metal of Group VIII. The weight ratio of the first active component to the second active component, based on metal elements, is 0.1-200:1.

[0010] According to a preferred embodiment of the present invention, the weight ratio of the first active component to the second active component, based on metal elements, is 0.1-10:1. More preferably, it is 0.5-5:1. For example, it can be 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, or any intermediate value between any two of the above ratios.

[0011] According to the present invention, preferably, the first active component is selected from at least one of Cu, Ag, Au, Ni and Fe.

[0012] According to the present invention, preferably, the second active component is selected from at least one of Pt, Rh, Pd and Ir.

[0013] According to a preferred embodiment of the present invention, the weight ratio of the first active component to the support is 0.1-2:100, and the weight of the first active component is calculated in terms of metal elements. That is, the first active component accounts for 0.1-2% by weight of the total weight of the catalyst. For example, it can be 0.1% by weight, 0.3% by weight, 0.5% by weight, 0.8% by weight, 1% by weight, 1.2% by weight, 1.5% by weight, 1.8% by weight, 2% by weight, or any intermediate value between any two of the above values.

[0014] According to the present invention, there are no special restrictions on the choice of support, and any conventional catalyst support in the art can be used in the present invention.

[0015] The advantage of the Ti oxide-doped support used in the method provided by this invention is that the doping of Ti in the support can effectively increase the Lewis acid (L acid) content on the support surface. The ratio of L acid (B acid) to Brønsted acid is adjusted to improve the selectivity of the catalyst for olefins. According to a preferred embodiment of the invention, the molar ratio of L acid to Brønsted acid in the Ti oxide-doped support is 0.1-50:1. Preferably, it is 1-20:1. More preferably, it is 5-18:1.

[0016] More preferably, the support is a conventional oxide support doped with Ti oxide. The amount of Ti (by element) doping per gram of conventional oxide support can be 0.1-5 g, preferably 0.1-1 g.

[0017] More preferably, the support is at least one of Ti oxide-doped Al2O3, SiO2, MgO, and molecular sieve.

[0018] According to a preferred embodiment of the present invention, the carrier may be a commercially available carrier that meets the above conditions, or it may be synthesized by the present invention based on existing technology.

[0019] Specifically, the synthesis method of the support may include: dispersing a conventional oxide support (preferably at least one of Al2O3, SiO2, MgO, and molecular sieve) in an organic solvent (such as anhydrous ethanol), then adding a titanium precursor solution (such as tetrabutyl titanate) dropwise, and reacting at 150-200°C for 10-60 minutes. After the reaction is complete, the precipitate is collected, washed 1-5 times each with water and anhydrous ethanol, and dried in an oven at 75-90°C for 20-30 hours.

[0020] More specifically, the synthesis method of the support may include: adding a conventional oxide support to 20-100 mL of anhydrous ethanol and ultrasonically dispersing it for 1-3 hours, followed by dropwise addition of a titanium precursor. After stirring under magnetic stirring for 1-2 hours, the mixture is transferred to a 50-100 mL hydrothermal reactor (Teflon-lined), and then placed in a microwave digester and reacted at 150-200°C for 10-60 minutes. During the synthesis, the microwave power is 180-220 W × the number of reactors. After the reaction is complete, the precipitate is collected, washed 1-5 times each with water and anhydrous ethanol, and dried in an oven at 75-90°C for 20-30 hours. The "number of reactors" refers to the number of reactors contained in the hydrothermal reactor.

[0021] According to a preferred embodiment of the present invention, the particle size of the active component in the catalyst is 3-20 nm, more preferably 5-15 nm. Further preferably, it is 5-12 nm. For example, it can be 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, or 12 nm, or it can be an intermediate value between any two of the above values.

[0022] According to a preferred embodiment of the present invention, the method further includes the step of preparing the catalyst by loading the active component onto a support.

[0023] According to the present invention, preferably, the step of preparing the catalyst by loading the active component onto the support comprises: impregnating the support with an impregnation solution containing a precursor of the active component, and then sequentially drying and calcining.

[0024] According to the present invention, the precursor of the active component includes a precursor of a first active component and a precursor of a second active component. The precursor of the first active component is selected from at least one precursor of a non-noble metal element from Group VIII and a precursor of a metal element from Group IB. The precursor of the second active component is selected from at least one precursor of a noble metal element from Group VIII.

[0025] According to a preferred embodiment of the present invention, the precursor of the active component may be a water-soluble salt of the corresponding metal element, such as nitrate, chloride, etc.

[0026] Preferably, the precursor of the first active component is selected from at least one of Cu(NO3)2, AgNO3, Ni(NO3)2 and Fe(NO3)3.

[0027] Preferably, the precursor of the second component is selected from at least one of H2PtCl6, HAuCl4, Rh(NO3)3, PdNO3 and iridium acetate.

[0028] There are no particular restrictions on the order of impregnation of the first and second active components; they can be carried out simultaneously or in a specific order.

[0029] There are no particular restrictions on the concentration of the precursor of the active component in the impregnation solution. The impregnation method can be either excess impregnation or equal volume impregnation.

[0030] According to the present invention, there are no special limitations on the drying and calcining conditions, and any conventional drying and calcining conditions in the art can be used in the method described in the present invention.

[0031] According to the present invention, preferably, the drying conditions include: a drying temperature of 50-150°C and a drying time of 5-15 hours.

[0032] More preferably, the drying conditions include: a drying temperature of 80-120°C and a drying time of 8-12 hours.

[0033] According to the present invention, preferably, the drying can be carried out in a segmented drying manner.

[0034] According to a preferred embodiment of the present invention, the segmented drying method may employ the same drying method (e.g., oven drying, rotary evaporation drying, freeze drying, etc.) or may employ different drying methods respectively.

[0035] According to a preferred embodiment of the present invention, the drying can be carried out in the following segmented drying manner:

[0036] (1) First drying: Drying is carried out by rotary evaporation. The drying temperature is 50-100℃, preferably 70-90℃. The drying time is 1-5h, preferably 3-5h.

[0037] (2) Second drying: Drying is carried out by oven drying. The drying temperature is 100-150℃, preferably 100-120℃. The drying time is 5-10h, preferably 7-9h.

[0038] According to the present invention, preferably, the calcination conditions include: a calcination temperature of 450-500℃ and a calcination time of 2-6 hours.

[0039] According to a preferred embodiment of the present invention, the method further includes: pretreating the carrier before loading the active component onto the carrier to remove moisture and organic impurities that may be present in the carrier.

[0040] Preferably, the pretreatment includes drying and calcining the carrier to remove moisture and organic impurities.

[0041] More preferably, the pretreatment conditions include: drying temperature 100-120℃, drying time 8-12h, calcination temperature 450-500℃, heating rate 1-4℃ / min, and calcination time 2-6h.

[0042] According to a preferred embodiment of the present invention, the active component exists in an oxidized state on the support (after preparation). During use, the active component exists in a reduced state (metallic form) on the support. Therefore, the method provided by the present invention further includes a step of reducing the catalyst to reduce the active component loaded on it before use. The reduction treatment can be carried out using any method existing in the art for reducing catalysts. For example, the catalyst can be placed in a reducing atmosphere (provided by a reducing gas, such as H2) for a period of time to reduce the active component therein.

[0043] According to a preferred embodiment of the present invention, the active substance generated by the plasma electric field through the alkane is produced under the action of the plasma source.

[0044] A plasma source is a device capable of breaking at least one CH bond in an alkane, facilitating the conversion of alkanes into alkenes. Common plasma sources include: nonthermal plasma (low-temperature plasma), corona discharge, dielectric barrier discharge, microwave discharge, and normal glow discharge. Adjusting the plasma source settings, such as frequency and voltage, can have different effects on the reaction. Specific energy consumption is an important parameter of a plasma source, representing the electrical energy extracted by the source to produce a unit amount of plasma-state alkane.

[0045] According to the present invention, the plasma source can be any plasma source commonly used in the art.

[0046] Preferably, the specific energy consumption of the plasma source is 5-100 kJ / L. The unit "kJ / L" represents the electrical energy (kJ) absorbed by the plasma source when converting a unit volume (L) of alkane into plasma-state alkane.

[0047] According to the present invention, the alkane may be C1-C60.10 The alkane is preferably at least one of C1-C5 alkanes, more preferably at least one of methane, ethane, propane, butane and pentane.

[0048] According to the present invention, the olefin may be C2-C 20 The olefin is preferably at least one of C2-C4 olefins, more preferably at least one of ethylene, propylene, butadiene, isoprene, 1-butene and isobutene.

[0049] According to the present invention, there are no particular limitations on the contact conditions between the plasma-state alkane and the catalyst, and any conventional contact conditions in the art can be applied to the method provided by the present invention.

[0050] To further improve the selectivity of olefins, preferably, the contact conditions include: a temperature of 25-35°C, a pressure of 0.05-0.25 MPa, and a time of more than 8 hours.

[0051] More preferably, the contact conditions include: temperature 25-30°C, pressure 0.08-0.15 MPa, and time 8-20 h.

[0052] According to a preferred embodiment of the present invention, the contact can be carried out in the presence of hydrogen gas for the purpose of accelerating the reaction.

[0053] More preferably, the volume ratio of hydrogen to alkane is 0-10:1, more preferably 1-5:1.

[0054] The present invention will be described in detail below through specific embodiments. It should be noted that the following embodiments are only used to further explain and illustrate the present invention by way of example, and are not intended to limit the present invention.

[0055] Unless otherwise specified, all chemicals used in the following examples were purchased from reputable chemical reagent suppliers and were of analytical grade. The Al2O3, SBA-13, SiO2, MgO supports, and ZSM-5 molecular sieve used in the preparation of the Ti oxide doping support were all purchased from Sinopharm Reagent Company.

[0056] The Ti oxide doped support preparation method used in the following examples is as follows:

[0057] 10 g of a conventional oxide support was ultrasonically dispersed in 60 mL of anhydrous ethanol for 2 hours. Then, 40 g of tetrabutyl titanate was added dropwise. After stirring magnetically for 1 hour, the mixture was transferred to a 100 mL Teflon-lined hydrothermal reactor. The reactor was then placed in a microwave digester and reacted at 200 °C for 60 minutes. The microwave power during the synthesis was 200 W. After the reaction was complete, the precipitate was collected, washed three times each with water and anhydrous ethanol, and dried in an oven at 80 °C for 24 hours.

[0058] The molar ratios of L acid to Brønsted acid on the surface of the TiO2-Al2O3 support, TiO2-SBA-13 support, TiO2-SiO2 support, TiO2-MgO support, and TiO2-ZSM-5 support prepared by the above methods were found to be 17.5:1, 7.7:1, 3.6:1, 1.2:1, and 5.5:1, respectively.

[0059] In the following examples, a fully automated surface area and porosity analyzer (Micromeritics, USA, model ASAP2020) was used to detect the particle size of the active component in the catalyst using CO pulse adsorption. The specific procedure was as follows: 1g of catalyst was placed in a U-tube, argon gas was introduced, and the temperature was raised to 350°C and maintained for 1 hour to remove moisture and impurities. The temperature was then lowered to room temperature, hydrogen gas was introduced, and the temperature was raised again to 350°C and maintained for 2 hours to reduce the catalyst. The temperature was then lowered to 50°C, and He gas was introduced to purge for 30 minutes to remove physically adsorbed H2. After baseline stabilization, a fixed volume of CO was intermittently injected into the sample tube until adsorption saturation was achieved. After the operation was completed, the particle size data of the active component was obtained by reading the instrument.

[0060] Example 1

[0061] Palladium nitrate was dissolved in deionized water to form a palladium nitrate solution (palladium content 18 wt%), and copper nitrate was dissolved in deionized water to form a copper nitrate solution (copper content 30 wt%). The mixing ratio of the palladium nitrate solution and the copper nitrate solution was such that the palladium loading accounted for 0.5 wt% of the carrier mass and the copper loading accounted for 1 wt% of the carrier mass. A TiO2-Al2O3 carrier was used. The two solutions were mixed and impregnated for 12 h using an excess impregnation method. The mixture was then dried by rotary evaporation at 80 °C for 4 h, followed by further drying in an oven at 120 °C for 8 h. Finally, the mixture was calcined in a muffle furnace at 450 °C for 5 h to obtain catalyst 1, the chemical composition of which is shown in Table 1.

[0062] Example 2

[0063] Palladium nitrate was dissolved in deionized water to form a palladium nitrate solution (palladium content 18 wt%), and silver nitrate was dissolved in deionized water to form a silver nitrate solution (silver concentration 30 wt%). The mixing ratio of the palladium nitrate solution and the silver nitrate solution was such that the palladium loading accounted for 0.5 wt% of the carrier mass and the silver loading accounted for 1 wt% of the carrier mass. TiO2-Al2O3 carrier was used, and the two solutions were mixed and impregnated for 12 h using the excess impregnation method. The mixture was then dried by rotary evaporation at 80 °C for 4 h, followed by further drying in an oven at 120 °C for 8 h, and then calcined in a muffle furnace at 450 °C for 5 h to obtain catalyst 2. Its chemical composition is shown in Table 1.

[0064] Example 3

[0065] The method described in Example 1 was used, except that nickel nitrate solution (nickel concentration 30 wt%) and palladium nitrate solution (palladium content 18 wt%) were selected as the precursor solutions for the first and second active components, respectively. The mixing ratio of the two solutions was such that the palladium loading in the catalyst accounted for 0.5 wt% of the support mass, and the nickel loading accounted for 1 wt% of the support mass. TiO2-SBA-13 support was used. The remaining steps and conditions were the same as in Example 1. Catalyst 3 was obtained, and its chemical composition is shown in Table 1.

[0066] Example 4

[0067] Chloroplatinic acid and copper nitrate were uniformly dissolved in deionized water to form a homogeneous mixed solution. The mixing ratio of chloroplatinic acid solution and copper nitrate solution was such that the platinum loading accounted for 0.5 wt% of the support mass and the copper loading accounted for 1 wt% of the support mass. TiO2-MgO support was used. The solution was impregnated with copper nitrate solution using an excess impregnation method. The solution was dried by rotary evaporation at 80°C for 4 hours, then further dried in an oven at 120°C for 8 hours, and then calcined in a muffle furnace at 450°C for 5 hours. The solution was then impregnated with chloroplatinic acid solution, dried by rotary evaporation at 80°C for 4 hours, then further dried in an oven at 120°C for 8 hours, and then calcined in a muffle furnace at 450°C for 5 hours to obtain catalyst 4. Its chemical composition is shown in Table 1.

[0068] Example 5

[0069] The method described in Example 1 was used, except that copper nitrate solution (copper concentration 30 wt%) and rhodium nitrate solution (rhodium content 18 wt%) were selected as the precursor solutions for the first and second active components, respectively. The mixing ratio of the two solutions was such that the rhodium loading in the catalyst accounted for 0.5 wt% of the support mass, and the copper loading accounted for 1 wt% of the support mass. A TiO2-SiO2 support was used. The remaining steps and conditions were the same as in Example 1. Catalyst 5 was obtained, and its chemical composition is shown in Table 1.

[0070] Example 6

[0071] The method described in Example 1 was used, except that ferric nitrate solution (iron concentration 30 wt%) and palladium nitrate solution (rhodium content 18 wt%) were selected as the precursor solutions for the first and second active components, respectively. The mixing ratio of the two solutions was such that the palladium loading in the catalyst accounted for 0.5 wt% of the support mass, and the iron loading accounted for 1 wt% of the support mass. The remaining steps and conditions were the same as in Example 1. Catalyst 6 was obtained, and its chemical composition is shown in Table 1.

[0072] Example 7

[0073] The method described in Example 1 was used, except that chloroauric acid solution (gold concentration 30 wt%) and iridium acetate solution (iridium content 18 wt%) were selected as precursor solutions for the active components. The mixing ratio of the two solutions resulted in an iridium loading of 0.5 wt% and a gold loading of 1 wt% of the support in the catalyst. TiO2-ZSM-5 support was used. The remaining steps and conditions were the same as in Example 1. Catalyst 7 was obtained, and its chemical composition is shown in Table 1.

[0074] Comparative Example 1

[0075] The same method as in Example 2 was used, except that the support was replaced with Al2O3. All other steps and conditions were the same as in Example 2. Catalyst 8 was obtained, and its chemical composition is shown in Table 1.

[0076] Comparative Example 2

[0077] The same method as in Example 5 was used, except that the support was replaced with TiO2. All other steps and conditions were the same as in Example 5. Catalyst 9 was obtained, and its chemical composition is shown in Table 1.

[0078] Comparative Example 3

[0079] The same method as in Example 3 was used, except that only a nickel nitrate solution was used as the precursor solution for the active component, wherein the nickel loading accounted for 1% by weight of the support. All other steps and conditions were the same as in Example 3. Catalyst 10 was obtained, and its chemical composition is shown in Table 1.

[0080] Comparative Example 4

[0081] The same method as in Example 4 was used, except that only a chloroplatinic acid solution was used as the precursor solution for the active component, wherein the platinum loading accounted for 0.5% by weight of the support. All other steps and conditions were the same as in Example 4. Catalyst 11 was obtained, and its chemical composition is shown in Table 1.

[0082] Comparative Example 5

[0083] The same method as in Example 6 was used, except that a copper nitrate solution was used instead of a palladium nitrate solution as the precursor solution for the second active component, and the amount used was such that the copper loading in the catalyst accounted for 1% by weight of the support. All other steps and conditions were the same as in Example 6. Catalyst 12 was obtained, and its chemical composition is shown in Table 1.

[0084] Comparative Example 6

[0085] The same method as in Example 7 was used, except that a rhodium nitrate solution was used instead of a chloroauric acid solution as the precursor solution for the active component, and the amount used was such that the rhodium loading in the catalyst accounted for 0.5% by weight of the support mass. The remaining steps and conditions were the same as in Example 7. Catalyst 13 was obtained, and its chemical composition is shown in Table 1.

[0086] Table 1. Chemical composition and characteristics of the catalyst

[0087] catalyst Chemical composition* (wt%) Particle size of active component (nm) L-acid / B-acid** 1 <![CDATA[1 Cu, 0.5 Pd, the balance being TiO2 - Al2O3]]> 5.4 15.6 2 <![CDATA[1Ag, 0.5Pd, the balance being TiO2 - Al2O3]]> 5.9 15.3 3 <![CDATA[1Ni, 0.5Pd, the balance is TiO2-SBA-13]]> 5.2 6.5 4 <![CDATA[1 Cu, 0.5 Pt, the balance is TiO2 - MgO]]> 7.1 1.4 5 <![CDATA[1 Cu, 0.5 Rh, balance TiO2 - SiO2]]> 10.3 3.1 6 <![CDATA[1Fe, 0.5Pd, the balance being TiO2 - Al2O3]]> 6.4 16.3 7 <![CDATA[1 Au, 0.5 Ir, balance TiO2-ZSM-5]]> 7.4 5.2 8 <![CDATA[1Ag, 0.5Pd, the balance being Al2O3]]> 7.7 6.1 9 <![CDATA[1Cu, 0.5Rh, balance TiO2]]> 9.4 35.5 10 <![CDATA[1Ni, the balance is TiO2-SBA-13]]> / 6.1 11 <![CDATA[0.5Pt, the balance is TiO2 - MgO]]> 8.9 1.7 12 <![CDATA[1Cu, 1Fe, the balance is TiO2 - Al2O3]]> / 16.9 13 <![CDATA[0.5Ir, 0.5Pd, the balance being TiO2-ZSM-5]]> 9.6 4.9

[0088] *Calculated based on a total weight of 100% by weight for the active component (by element) and the carrier.

[0089] **This refers to the molar ratio of Livic acid to Beta acid in the catalyst.

[0090] Test Example 1

[0091] More than 30g of the catalysts prepared in the examples and comparative examples were placed in a 1L plasma reactor (specific power consumption 40kJ / L) and reacted under the following conditions: temperature 25℃, pressure 0.15MPa, methane 0.5L / min, hydrogen 1.5L / min, and W 120W. A control group experiment was also conducted: no catalyst was added, and the reaction was carried out directly under the above conditions. The methane conversion rate and hydrocarbon selectivity in the products were detected and calculated according to the following method, and the results are detailed in Table 2.

[0092] The reaction products were measured by gas chromatography. Based on the measurement results, the conversion rate of methane and the selectivity of hydrocarbons were calculated using the carbon balance method according to the following formula:

[0093]

[0094]

[0095]

[0096]

[0097]

[0098] S C3+ =S C3+S C4 +S C5 +S C6

[0099] In the formula, X CH4 S represents the conversion rate of methane. C2H4 S represents ethylene selectivity. C2H2 S indicates acetylene selectivity. C2H6 S represents ethane selectivity. C3+ Indicate C 3+ Selectivity, N CH4，in Indicates the molar amount of imported methane, N CH4，out N represents the molar amount of methane exported. C2H4，out N represents the molar quantity of exported ethylene. C2H2，out Indicates the molar amount of acetylene exported, N Cn，out This represents the molar quantity of the product with n carbon atoms exported.

[0100] Table 2 Comparison of reaction results

[0101] catalyst Methane conversion rate % Acetylene selectivity % Ethylene selectivity % Ethane selectivity % <![CDATA[C 3+ Selectivity % 1 12.3 0 87.5 9.2 3.3 2 13.7 0 84.6 7.5 7.9 3 12.8 0 85.3 8.3 6.4 4 14.2 10.3 60.4 10.4 18.9 5 13.4 5.7 83.9 6.5 3.9 6 14.1 0 86.8 2.8 10.4 7 13.5 5.1 80.5 9.7 4.7 8 14.1 0 80.4 9.1 10.5 9 14.6 13.2 62.9 8.5 15.4 10 14.2 65.2 20.4 8.3 6.1 11 12.5 6.1 53.8 25.6 4.5 12 13.7 53.8 25.6 6.1 14.5 13 13.5 0 20.3 69.1 10.6 control group 13.8 75.1 15.3 5.2 4.4

[0102] Further test results show that when catalysts 1-7 are used for the reaction, the temperature of the catalyst bed after plasma is relatively stable, with the temperature at the edge of the bed being about 85±15℃ and the temperature at the center of the bed being about 275±25℃.

[0103] 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. To avoid unnecessary repetition, the present invention will not describe all possible combinations separately. However, these simple modifications and combinations should also be considered as part of the content disclosed in this invention and are all within the protection scope of this invention.

Claims

1. A method for plasma-based preparation of olefins, characterized in that, The method includes: contacting an active material generated by passing an alkane through a plasma electric field with a catalyst to convert the alkane into an olefin. The catalyst comprises a Ti oxide-doped support and an active component supported on the support. The molar ratio of Li acid to B acid in the Ti oxide-doped support is 5-18:

1. The active component contains a first active component and a second active component. The first active component is selected from at least one of Cu, Ag, and Ni, and the second active component is selected from Pd. The weight ratio of the first active component to the second active component, based on metal elements, is 0.1-10:

1. The particle size of the active component is 5-7 nm.

2. The method according to claim 1, wherein, The weight ratio of the first active component to the carrier is 0.1-2:100, and the weight of the first active component is calculated in terms of metal elements.

3. The method according to claim 1, wherein, The support is selected from at least one of Ti oxide-doped Al2O3, SiO2, MgO, and molecular sieves.

4. The method according to claim 1, wherein, The method further includes the step of preparing the catalyst by loading the active component onto a support.

5. The method according to claim 4, wherein, The active component is loaded onto the support by impregnating the support with an impregnation solution containing a precursor of the active component, followed by drying and calcination.

6. The method according to claim 5, wherein, The drying conditions include: a drying temperature of 100-120℃ and a drying time of 8-12 hours; And / or, the calcination conditions include: a calcination temperature of 450-500℃ and a calcination time of 2-6h.

7. The method according to any one of claims 4-6, wherein, The method further includes pretreating the carrier before loading the active component onto it to remove any moisture and organic impurities that may be present in the carrier.

8. The method according to claim 1, wherein, The plasma electric field is provided by the plasma source.

9. The method according to claim 8, wherein, The specific power consumption of the plasma source is 5-100 kJ / L.

10. The method according to claim 1, wherein, The alkane is at least one of C1-C5 alkanes; And / or, the olefin is at least one of C2-C4 olefins.

11. The method according to claim 1, wherein, The contact conditions include: temperature 20-35℃, pressure 0.05-0.25MPa, and time 8 hours or more.

12. The method according to claim 11, wherein, The contact conditions include: temperature 25-30℃, pressure 0.08-0.15MPa, and time 8-20h.

13. The method according to claim 1 or 11, wherein, The contact is carried out in the presence of hydrogen gas, with a volume ratio of hydrogen to alkane of 0-10:1.

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