Methanation catalysts and processes for treating tail gas from ethylene production by oxidative coupling of methane

Abstract

The present application relates to the field of methane oxidation coupling reaction, and in particular to a methanation catalyst and a preparation method and application thereof.The catalyst provided by the present application can synthesize methane by using methane oxidation coupling reaction tail gas as raw material, realizes recovery and recycling of the raw material of the methane oxidation coupling reaction, improves the overall carbon atom utilization rate of the industrial application of the methane oxidation coupling reaction, reduces the production cost, and realizes sustainable production.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of methane oxidation coupling reaction, in particular, to a methanation catalyst and a method for treating tail gas of methane oxidation coupling reaction for ethylene production by methanation method. BACKGROUND

[0002] Methane oxidation coupling reaction is the most direct and effective way for methane utilization, and with the progress of global natural gas reserves and natural gas exploration technology, the research on methane oxidation coupling reaction, especially the industrial application of methane oxidation coupling reaction, is becoming more and more popular. At present, the research on methane oxidation coupling process mainly aims to improve the reaction conversion rate and selectivity, and the research on the recycling of reaction raw materials is less.

[0003] The main components of the tail gas produced after the separation of the target products such as ethylene from the methane oxidation coupling reaction product are unreacted CO, H2, CH4, etc. The content of CO and H2 in them is low, and the volume ratio of H2 and CO is low. Generally, the treatment method for the tail gas of methane oxidation coupling reaction is oxidation combustion method, which converts it into CO2 and H2O, but this method not only has low carbon atom utilization efficiency, but also causes waste of raw materials. However, the recycling of each component in the tail gas for methane oxidation coupling reaction will greatly increase the cost, which is not conducive to the industrialization of methane oxidation coupling reaction. If the methane oxidation coupling reaction tail gas can be directly treated by methanation to convert it into CH4, the recycling of reaction raw materials can be realized, which not only reduces the cost of industrialization of methane oxidation coupling reaction, but also meets the needs of sustainable development. However, due to the low volume ratio of H2 and CO in the methane oxidation coupling reaction tail gas and the large amount of CH4, the methanation reaction using only the methane oxidation coupling reaction tail gas as raw material faces great obstacles in thermodynamics, and the reaction efficiency and raw material conversion rate are low. SUMMARY

[0004] The purpose of the present application is to overcome the problem of low reaction efficiency and raw material conversion rate in the preparation of methane using methane oxidation coupling reaction tail gas as raw material, and to provide a methanation catalyst and a method for treating tail gas of methane oxidation coupling reaction for ethylene production by methanation method. The catalyst provided by the present application can convert the low content of CO and H2 in the methane oxidation coupling reaction tail gas into raw material methane, realize the recycling and recycling of methane oxidation coupling reaction raw materials, improve the carbon atom utilization rate, and improve the economic feasibility of industrialization of methane oxidation coupling reaction.

[0005] In order to achieve the above-mentioned purpose, the present application provides a methanation catalyst in one aspect, the catalyst comprising a carrier, an active component and an optional auxiliary agent, wherein the carrier is selected from Al2O3 and / or a full-silica molecular sieve, the active component is Ni, and the auxiliary agent is selected from La and / or Mn.

[0006] The present application provides a method for preparing a methanation catalyst in a second aspect, the method comprising loading an active component precursor and an optional auxiliary agent precursor on a carrier, and then sequentially performing drying and calcination.

[0007] The carrier is selected from Al2O3 and / or a full-silica molecular sieve, the active component precursor is a Ni precursor, and the auxiliary agent precursor is selected from a La precursor and / or a Mn precursor.

[0008] The present application provides a methanation catalyst prepared by the method as described above in a third aspect.

[0009] The present application provides an application of the methanation catalyst as described above in a fourth aspect in tail gas treatment of a methane oxidative coupling reaction.

[0010] The present application provides a method for treating tail gas of a methane oxidative coupling reaction in a fifth aspect, the method comprising: contacting the tail gas of the methane oxidative coupling reaction with the methanation catalyst as described above, and allowing a methanation reaction to occur under methanation conditions.

[0011] The present application provides an application of the catalyst and the method as described above in a sixth aspect in a methane catalytic coupling reaction, in particular in an industrial methane catalytic coupling reaction.

[0012] The present application can achieve the following beneficial effects through the above technical solutions:

[0013] (1) The catalyst provided by the present application can use raw material gas with a low H2 / CO ratio, such as tail gas of a methane oxidative coupling reaction, to perform a methanation reaction and prepare methane, and the conversion rate of H2 and CO and the methane yield are high.

[0014] (2) The catalyst provided by the present application can realize recycling of raw materials in the industrial application process of a methane oxidative coupling reaction, improve the overall carbon atom utilization rate of the methane oxidative coupling process, reduce costs, realize sustainable development of industrial production, and improve the economic feasibility of industrialization of the methane oxidative coupling reaction.

[0015] (3) The preparation method of the catalyst provided by the present application is simple, raw materials are easy to obtain, and is suitable for industrial large-scale production and promotion. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1XRD patterns of catalysts A1, A2, A8 prepared by embodiments of the present application and Al2O3 carrier used. DETAILED DESCRIPTION

[0017] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are provided as approximate descriptions of the ranges and are understood to be open-ended. Each range endpoint is thus actually a point of reference (albeit an inaccurate one) towards a first side of a given continuous range that is understood to include values of or adjacent to the first-mentioned value, and a point of reference (albeit an inaccurate one) towards a second side of the given continuous range that is understood to include values of or adjacent to the second-mentioned value. In each such range, every value between the first and second mentioned values includes the first and second mentioned values. For values and points that are not within the typical range given, the same principles apply to the extent that some imprecision can exist in the definition of the actually stated value or point.

[0018] In the present application, unless otherwise specified, the "catalyst" refers to the methanation catalyst provided by the present application.

[0019] The volume of H2 and CO in the tail gas of the methane oxidation coupling reaction (OCM reaction) is relatively low, and a large amount of CH4 is contained. Therefore, when the OCM reaction tail gas is used as a raw material, the use of a conventional methanation catalyst will face greater obstacles in reaction thermodynamics, and the reaction will be difficult to proceed, and the reaction efficiency and raw material conversion rate will be low. The inventors of the present application ingeniously found that a catalyst composed of a specific carrier, an active component and an additive can use the OCM reaction tail gas as a raw material to realize a methanation reaction with a high conversion rate.

[0020] The present application provides a methanation catalyst, which comprises a carrier, an active component and an optional additive, wherein the carrier is selected from Al2O3 and / or a full-silica molecular sieve, the active component is Ni, and the additive is selected from La and / or Mn.

[0021] Any of the above carriers available in the art for the preparation of a methanation catalyst can be used in the present application. According to a preferred embodiment of the present application, the particle size of the carrier is 100-500 nm. The carrier can be a carrier within the above particle size range, or a carrier within the above particle size range obtained by crushing a carrier with a larger particle size.

[0022] Any of the full-silica molecular sieves available in the art for the preparation of a methanation catalyst can be used in the present application. According to a preferred embodiment of the present application, the full-silica molecular sieve can be selected from silicalite-1 molecular sieve.

[0023] Preferably, the carrier is a pretreated carrier. Preferably, the pretreatment comprises calcining the carrier at 500-800℃ for 5-10h.

[0024] In the present application, the content of the active component in the catalyst is not particularly limited. In order to obtain better reaction activity / stability, preferably, the content of the active component (in terms of elements) is 20-35% by weight, based on the total weight of the catalyst. For example, it can be 20% by weight, 22% by weight, 24% by weight, 25% by weight, 26% by weight, 28% by weight, 30% by weight, 32% by weight, 35% by weight, or it can also be an intermediate value between any two of the above values.

[0025] More preferably, the content of the active component can be 20-25% by weight.

[0026] In the present application, the content of the auxiliary agent in the catalyst is not particularly limited. Preferably, the total content of the auxiliary agent is 1-5% by weight, based on the total weight of the catalyst. The "total content of the auxiliary agent" is the sum of the contents of all auxiliary agents (in terms of elements) in the catalyst.

[0027] More preferably, the content of La is 1-5% by weight, preferably 1-3% by weight, based on the total weight of the catalyst.

[0028] More preferably, the content of Mn is 1-5% by weight, preferably 1-3% by weight, based on the total weight of the catalyst.

[0029] The second aspect of the present application provides a method for preparing a methanation catalyst, the method comprising loading an active component precursor and optionally an auxiliary agent precursor on a carrier, and then sequentially drying and calcining;

[0030] In the present application, the carrier is selected from at least one of Al2O3 and / or a full-silica molecular sieve, the active component precursor is a Ni precursor, and the auxiliary agent precursor is selected from a La precursor and / or a Mn precursor.

[0031] According to a preferred embodiment of the present application, the particle size of the carrier is 100-500 nm.

[0032] Preferably, the full-silica molecular sieve is selected from a silicalite-1 molecular sieve.

[0033] In the method provided by the present application, the amount of the active component precursor is not particularly limited. Preferably, the amount of the active component precursor is such that the content of the active component is 20-35% by weight, based on the total weight of the catalyst. For example, it can be 20% by weight, 22% by weight, 24% by weight, 25% by weight, 26% by weight, 28% by weight, 30% by weight, 32% by weight, 35% by weight, or it can also be an intermediate value between any two of the above values. More preferably, it is 20-25% by weight.

[0034] The amount of the assistant precursor in the method provided by the present application is not particularly limited. Preferably, the amount of the assistant precursor is such that the total content of the assistant is 1-5% by weight based on the total weight of the catalyst.

[0035] The inventors of the present application have ingeniously found that, by loading the active component precursor and the assistant precursor on the carrier in a specific manner, the catalytic activity / stability of the obtained methanation catalyst is better.

[0036] Any method for loading the active component precursor and the assistant precursor on the carrier available in the art can be applied to the present application. According to a preferred embodiment of the present application, the loading method is selected from impregnation (preferably isovolumetric impregnation) and / or vacuum rotary evaporation (impregnation).

[0037] Preferably, the loading method can be that the carrier, the active component precursor and the optional assistant precursor are mixed and placed in a rotary evaporator, and the active component precursor is loaded on the carrier under vacuum rotary evaporation conditions.

[0038] More preferably, the vacuum rotary evaporation conditions include a temperature of 50-60℃, a time of 1-3h, a vacuum degree of 20-60Pa, a stirring speed of 60-100rpm, a concentration of the aqueous solution of the active component precursor of 10-20% by weight, a concentration of the aqueous solution of the assistant precursor of 1-2% by weight, and an initial amount of the impregnation solution of 5-10mL per gram of the carrier.

[0039] In the method provided by the present application, any drying method available in the art can be applied. According to a preferred embodiment of the present application, the drying method is selected from oven drying.

[0040] Preferably, the drying conditions include a temperature of 100-150℃ and a time of 10-15h.

[0041] In the method provided by the present application, the calcination method is not particularly limited. According to a preferred embodiment of the present application, the calcination method includes increasing the temperature to 500-600℃ at a temperature increasing rate of 1-5℃ / min (preferably 1-3℃ / min), and then calcining at the temperature for 10-15h.

[0042] The inventors of the present application have ingeniously found that, by pretreating the carrier before loading the active component precursor and the assistant precursor, the catalytic activity / stability of the prepared catalyst can be further improved.

[0043] According to a preferred embodiment of the present application, the method further includes pretreating the carrier, and preferably the pretreatment includes calcining the carrier at 500-800℃ for 5-10h.

[0044] The third aspect of the present application provides a methanation catalyst prepared according to the method as described above. The characteristics of the methanation catalyst are as described above, which will not be repeated here.

[0045] The fourth aspect of the present application provides the use of the methanation catalyst as described above in the treatment of tail gas of oxidative coupling of methane reaction.

[0046] The fifth aspect of the present application provides a method for treating tail gas of oxidative coupling of methane reaction (OCM reaction tail gas), which comprises: contacting the tail gas of oxidative coupling of methane reaction with the methanation catalyst as described above, and under the methanation conditions, a methanation reaction occurs.

[0047] In the method provided by the present application, the OCM reaction tail gas is the part remaining after the ethylene, ethane and other products in the OCM reaction product are separated out. According to the preferred embodiment of the present application, the components of the tail gas of oxidative coupling of methane reaction include at least one of CH4, CO and H2.

[0048] Any OCM reaction tail gas can be applied to the method provided by the present application, and there is no particular limitation on the content of each component (such as CH4, CO, H2, etc.).

[0049] Preferably, the content of CH4 is 50-80% by volume based on the total volume of the tail gas of oxidative coupling of methane reaction.

[0050] Preferably, the content of CO is 5-15% by volume based on the total volume of the tail gas of oxidative coupling of methane reaction.

[0051] Preferably, the content of H2 is 2-5% by volume based on the total volume of the tail gas of oxidative coupling of methane reaction.

[0052] More preferably, the volume ratio of CO to H2 in the tail gas of oxidative coupling of methane reaction is 1:1-5. For example, it can be 1:1, 1:2, 1:3, 1:4, 1:5, or also an intermediate value between any two of the above values.

[0053] The inventors of the present application ingeniously found in the research process that the catalyst provided by the present application can further improve the reactivity (conversion rate of raw materials and CH4 selectivity) / stability in combination with specific methanation reaction conditions.

[0054] In the method provided by the present application (except for the volume ratio of CO to H2), any existing methanation reaction condition in the art can be used. Preferably, the methanation conditions include: temperature 300-400℃, pressure 0.5-1MPa, and the space velocity of the tail gas of oxidative coupling of methane reaction is 8000-12000mL·g-1·h-1.-1 ·h -1 , the unit mL·g -1 ·h -1 The meaning of the unit mL·g

[0055] More preferably, the methanation conditions include: temperature 330-380℃ (for example, it can be 330℃, 335℃, 340℃, 345℃, 350℃, 355℃, 360℃, 365℃, 370℃, 375℃, 380℃, or any intermediate value between any two of the above-mentioned values), pressure 0.8-1MPa, and the methane oxidative coupling reaction tail gas space velocity is 8000-12000 mL·g -1 ·h -1 .

[0056] The method provided by the present application further includes a step of reducing the catalyst before the reaction. According to a preferred embodiment of the present application, the reducing method includes: placing the catalyst in a reducing atmosphere under reducing conditions to reduce the catalyst. Preferably, the reducing atmosphere is provided by a reducing gas (a gas with reducing property), for example, it can be provided by H2.

[0057] Preferably, the reducing conditions include: temperature 450-500℃, pressure 0.1-2MPa, and reducing gas space velocity 800-15000 mL·g -1 ·h -1 .

[0058] More preferably, the reducing method can further include: under an inert atmosphere, increasing the temperature to the reduction temperature at a temperature increasing rate of 1-3℃ / min, and then switching to the reducing atmosphere to reduce the catalyst. The inert atmosphere can be provided by N2 and / or an inert gas.

[0059] The sixth aspect of the present application provides the use of the catalyst and the method as described above in the methane oxidative coupling reaction, especially in the industrial methane catalytic coupling reaction.

[0060] The present application will be described in detail below through examples. It should be understood that the following examples are only used to exemplarily further explain and illustrate the content of the present application in detail, and are not used to limit the present application.

[0061] In the following examples, the γ-Al2O3 powder is purchased from a national pharmaceutical company, the particle size is 350±100nm, and the BET specific surface area is 250m 2g. Unless otherwise stated, the chemical reagents used are commercially available from a regular chemical supplier and are of chemical purity. In the following examples, the content of active components and promoters in the catalysts is the percentage of the active components and promoters in the total weight of the catalysts, in terms of elements.

[0062] Example 1

[0063] According to the method in Example 1, except that the amount of Ni(NO3)2-6H2O is such that the content of Ni in the catalyst is 30% by weight. Other operation steps and conditions are the same as in Example 1. Catalyst A4 is obtained. Figure 1

[0064] Example 2

[0065] According to the method in Example 1, except that the amount of La(NO3)3-6H2O is such that the content of La in the catalyst is 2% by weight. Other operation steps and conditions are the same as in Example 1. Catalyst Al is obtained.

[0066] Example 3

[0067] According to the method in Example 1, except that La(NO3)3-6H2O is replaced by a mixture of La(NO3)3-6H2O and Mn(NO3)2, with the content of La and Mn in the catalyst being both 1% by weight. Other operation steps and conditions are the same as in Example 1. Catalyst A3 is obtained.

[0068] Example 4

[0069] According to the method in Example 1, except that the amount of Ni(NO3)2-6H2O is such that the content of Ni in the catalyst is 30% by weight. Other operation steps and conditions are the same as in Example 1. Catalyst A4 is obtained. ​

[0070] Example 5

[0071] The method in Example 1 was followed, except that the amount of Ni(NO3)2-6H2O was such that the content of Ni in the catalyst was 20% by weight. The other operating steps and conditions were the same as in Example 1. Catalyst A5 was obtained.

[0072] Example 6

[0073] The method in Example 1 was followed, except that the amount of Ni(NO3)2-6H2O was such that the content of Ni in the catalyst was 15% by weight. The other operating steps and conditions were the same as in Example 1. Catalyst A6 was obtained.

[0074] Example 7

[0075] The method in Example 1 was followed, except that the amount of Ni(NO3)2-6H2O was such that the content of Ni in the catalyst was 35% by weight. The other operating steps and conditions were the same as in Example 1. Catalyst A7 was obtained.

[0076] Example 8

[0077] The method in Example 1 was followed, except that the precursor solution contained only Ni(NO3)2-6H2O, and the amount of Ni(NO3)2-6H2O was such that the content of Ni in the catalyst was 24% by weight. The other operating steps and conditions were the same as in Example 1. Catalyst A8 was obtained.

[0078] Example 9

[0079] The method in Example 1 was followed, except that the calcination temperature was 700°C. The other operating steps and conditions were the same as in Example 1. Catalyst A9 was obtained.

[0080] Example 10

[0081] The method in Example 1 was followed, except that the support was replaced by silicalite-1 zeolite (particle size 250 nm, BET surface area 450 m 2 / g, purchased from Nanhua Catalyst Co., Ltd.). The other operating steps and conditions were the same as in Example 1. Catalyst A10 was obtained.

[0082] Test Example 1

[0083] A simulated OCM tail gas treatment test was performed using a mixed gas of CO, H2 and CH4 mixed in a ratio of 15:5:80 by volume to simulate the OCM reaction tail gas as the reaction gas. Catalyst A1 obtained in the above examples was evaluated. The catalyst evaluation was performed in a stainless steel reaction tube with an inner diameter of 8 mm, in which a thermocouple with an outer diameter of 3 mm was installed in the middle. The catalyst loading amount was 0.3 ± 0.1 g, and in order to protect the reactor, the catalyst was pressed into particles with a particle size of 500 ± 100 μm before loading. The specific method is as follows:

[0084] The catalyst bed was slowly heated to 450°C at 1°C / min in a high-purity N2 atmosphere, and high-purity N2 was switched to pure H2 gas. The reduction of the catalyst was performed under the conditions of a pressure of 1 ± 0.2 MPa and a space velocity of 10000 mL·g -1 ·h -1 . After reduction, the reactor temperature was lowered to the reaction temperature, and then the reaction gas (space velocity 10000 mL·g -1 ·h -1 ) was switched to perform the reaction. Agilent gas chromatography was used to analyze the reaction products (after cold trap condensation) online.

[0085] A 3-detector chromatograph was used to detect the raw materials and products online, 1 FID and 2 TCDs. FID was used to detect hydrocarbons, Al2O3 capillary column; thermal conductivity detector (TCD1) carrier used H2 to detect the volume content of CO, CO2, N2, CH4 in the gas, and the chromatographic column was Q+ carbon molecular sieve; auxiliary TCD2 used N2 as carrier gas to detect H2 and CH4 in the gas, and the chromatographic column selected Q+ 5A molecular sieve. Auxiliary TCD2 used N2 as carrier gas to detect H2 and CH4 in the gas, and the chromatographic column selected Q+ 5A molecular sieve.

[0086] After the reaction reached steady state, the reaction results were calculated from the chromatographic analysis data. The water produced by the reaction was collected and measured by a cold trap. The temperature of the catalyst bed was measured by a K-type thermocouple.

[0087] The reaction conditions (temperature and pressure) and results are shown in Table 1. The specific results were calculated as follows:

[0088] (1) All three detectors were associated with CH4, and the calculation was normalized

[0089] Association constant β1 = CH4 area (FID) x correction factor (benzene) / CH4 area (TCD1) x 100% Association constant β2 = CH4 area (FID) x correction factor (benzene) / CH4 area (TCD2) x 100% All calculations were made to FID, and each gas molar fraction, carbon atom percentage, and H2 molecule percentage were calculated and normalized respectively.

[0090] (2) CO conversion % (calculated on the basis of carbon balance)

[0091] CO conversion % = (1 - % of carbon atoms of CO in tail gas / % of carbon atoms of CO in feed gas) x 100%

[0092] Total moles of carbon atoms = CO area x correction factor (methane) x β1 + CO2 area x correction factor (methane) x β1 + CH4 area x correction factor (benzene) + 2 x C2H6 area x correction factor (benzene) + 2 x C2H4 area x correction factor (benzene)

[0093] % of carbon atoms of CO = CO area x correction factor (methane) x β1 / total moles of carbon atoms

[0094] (3) H2conversion % (calculated on the basis of H2balance)

[0095] H2conversion % = (1 - % of H2 molecules of H2 in tail gas / % of H2 molecules of H2 in feed gas) x 100%

[0096] Total moles of H2 molecules = H2 area x correction factor (methane) x β2 + 2 x CH4 area x correction factor (benzene) + 3 x C2H6 area x correction factor (benzene) + 2 x C2H4 area x correction factor (benzene)

[0097] % of H2 molecules = H2 area x correction factor (methane) x β2 / total moles of H2 molecules In the above calculation process, the generation of product H2O is not considered. It has been proved by experiments that almost no water is generated when H2 is insufficient (i.e. the volume ratio of H2 to CO in the feed gas is low, for example, lower than 3:1 in conventional methanation reaction).

[0098] Table 1

[0099]

[0100] Test Example 2

[0101] The catalyst A2 obtained in Example 2 was subjected to reaction activity test by using the method in Test Example 1. The results are shown in Table 2.

[0102] Table 2

[0103]

[0104] Test Example 3

[0105] The catalyst A8 obtained in Example 8 was subjected to reaction activity test by using the method in Test Example 1. The results are shown in Table 3.

[0106] Table 3

[0107]

[0108] Test Example 4

[0109] The catalysts obtained in the above examples were subjected to reaction activity test under the conditions of 1 MPa of pressure and 350°C of temperature using the method of Test Example 1. The results are shown in Table 4.

[0110] Table 4

[0111]

[0112]

[0113] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method of processing a tail gas of a methane oxidation coupling reaction, characterized in that, The method comprises: contacting a methane oxidative coupling reaction tail gas with a methanation catalyst, and under methanation conditions, a methanation reaction occurs; wherein the components of the methane oxidative coupling reaction tail gas include CH4, CO, and H2; the content of the CH4 is 50-80% by volume based on the total volume of the methane oxidative coupling reaction tail gas; The catalyst comprises a carrier, an active component, and optionally an additive, wherein the carrier is selected from Al2O3 and / or a full-silica molecular sieve, the active component is Ni, and the additive is selected from La and / or Mn; The particle size of the carrier is 100-500 nm; and the full-silica molecular sieve is selected from a silicalite-1 molecular sieve. The content of the active component is 24-35% by weight based on the total weight of the catalyst, and the total content of the additive is 1-5% by weight; The methanation conditions include: temperature 300-400℃, pressure 0.5-1MPa, reaction space velocity 8000-12000mL·g -1 ·h -1 .

2. The method of claim 1, wherein, The content of the CO is 5-15% by volume based on the total volume of the methane oxidative coupling reaction tail gas; And / or, the content of the H2 is 2-5% by volume based on the total volume of the methane oxidative coupling reaction tail gas.

3. The method of claim 1, wherein, The volume ratio of CO to H2 in the methane oxidative coupling reaction tail gas is 1:1-5.

4. The method of any of claims 1-3, wherein, The preparation method of the methanation catalyst comprises loading an active component precursor and optionally an additive precursor on a carrier, and then sequentially performing drying and calcination; The carrier is selected from Al2O3 and / or a full-silica molecular sieve, the active component precursor is a Ni precursor, and the amount of the active component precursor is such that the content of the active component is 24-35% by weight based on the total weight of the catalyst; the additive precursor is selected from a La precursor and / or a Mn precursor, and the amount of the additive precursor is such that the total content of the additive is 1-5% by weight based on the total weight of the catalyst.

5. The method of claim 4, wherein, The particle size of the carrier is 100-500 nm; And / or, the full-silica molecular sieve is selected from a silicalite-1 molecular sieve.

6. The method of claim 4, wherein, The loading mode is selected from an equal-volume impregnation method and / or a vacuum rotary evaporation method; And / or, the drying mode is selected from oven drying; And / or, the calcination mode comprises: increasing the temperature to 500-600°C at a temperature increase rate of 1-5°C / min, and then calcining at the temperature for 10-15 h.

7. The method of claim 6, wherein, The loading mode is to mix the carrier, the active component precursor, and the optional additive precursor in a rotary evaporator, and load the active component precursor on the carrier under vacuum rotary evaporation conditions.

8. The method of claim 6, wherein, The drying conditions comprise a temperature of 100-150°C and a time of 10-15 h.

9. The method of claim 7, wherein, The vacuum rotary evaporation conditions comprise a temperature of 50-60°C, a time of 1-3 h, a vacuum degree of 20-60 Pa, a stirring speed of 60-100 rpm, a concentration of the aqueous solution of the active component precursor of 10-20% by weight, a concentration of the aqueous solution of the additive precursor of 1-2% by weight, and an initial amount of the impregnation solution of 5-10 mL per gram of the carrier.

10. The method of claim 4, wherein, The method further comprises pretreatment of the carrier.

11. The method of claim 10, wherein, The pretreatment comprises calcining the carrier at 500-800°C for 5-10 h.

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