Fe-cha catalyst, method for preparing the same, and method for partial oxidation of methane

Abstract

This invention relates to the field of methane partial oxidation technology, specifically to a Fe-CHA catalyst, its preparation method, and a method for methane partial oxidation. The Fe-CHA catalyst has a silicon-to-aluminum atomic ratio of 8-10; the Fe-CHA catalyst... 29 In the Si solid-state NMR, within the chemical shift range of -90 ppm to -120 ppm, there are four resonance peaks with increasing chemical shifts, δ1 to δ4. The normalized peak area of ​​δ1 is 6% ± 1%, that of δ2 is 8% ± 1%, that of δ3 is 11% ± 1%, and that of δ4 is 75% ± 1%. The content of tetrahedral coordination mononuclear Fe is 29%–31%, that of octahedral coordination mononuclear Fe is 47%–49%, and that of oligomeric Fe is 21%–23%. This catalyst, when used for the partial oxidation of methane, can achieve high methane conversion at low temperatures while also exhibiting high selectivity for methanol and dimethyl ether.

Description

Technical Field

[0001] This invention relates to the field of methane partial oxidation technology, specifically to an Fe-CHA catalyst, its preparation method, and a method for methane partial oxidation. Background Technology

[0002] Methane, a major component of natural gas (70–90%) and an important part of biogas, is a globally abundant carbon resource. Currently, its large-scale utilization mainly follows an indirect route: first, methane is converted into syngas (CO / H2) through energy-intensive steam reforming processes; then, the syngas is further upgraded through processes such as Fischer-Tropsch synthesis or methanol synthesis to produce higher-value fuel and chemical feedstocks. This multi-step process not only requires high investment and operating costs and demanding reaction conditions in the syngas preparation stage, but also suffers from cumulative efficiency losses.

[0003] Low-temperature partial oxidation of methane can directly and selectively oxidize methane into oxygen-containing chemicals such as methanol and dimethyl ether. This direct conversion route is expected to simplify the process, reduce energy consumption, and improve overall efficiency, thereby bringing significant economic and environmental benefits.

[0004] Low-temperature partial oxidation of methane currently faces challenges such as low methane conversion rates and the existence of multiple oxidation pathways, making it difficult to control various oxidation products. There is an urgent need to develop a catalyst that can improve the selectivity of products with higher economic value (methanol and dimethyl ether). Summary of the Invention

[0005] To achieve the above objectives, the present invention provides a Fe-CHA catalyst for the partial oxidation of methane, which can achieve high methane conversion at low temperatures, while also having the advantages of high selectivity for methanol and dimethyl ether.

[0006] To achieve the above objectives, the first aspect of the present invention provides a Fe-CHA catalyst having a silicon-to-aluminum atomic ratio of 8-10.

[0007] The Fe-CHA catalyst 29 In the NMR of Si solid-state, within the chemical shift range of -90 ppm to -120 ppm, there are four resonance peaks with increasing chemical shifts, δ1 to δ4. The normalized peak area of ​​δ1 is 6% ± 1%, the normalized peak area of ​​δ2 is 8% ± 1%, the normalized peak area of ​​δ3 is 11% ± 1%, and the normalized peak area of ​​δ4 is 75% ± 1%.

[0008] The content of tetrahedral coordination mononuclear Fe is 29%-31%, the content of octahedral coordination mononuclear Fe is 47%-49%, and the content of oligomeric Fe is 21%-23%.

[0009] A second aspect of this invention provides a method for preparing a Fe-CHA catalyst, the method comprising:

[0010] (1) A mixture containing USY molecular sieve, aluminum hydroxide, N,N,N-trimethyl-1-adamantyl ammonium hydroxide and water was crystallized, and the solid was separated. The solid was washed, dried and calcined to obtain H-CHA.

[0011] The USY molecular sieve, calculated as Si and in molar ratio, has the following composition: USY:Al:N,N,N-trimethyl-1-adamantyl ammonium hydroxide:H2O = 1:0.06-0.085:0.023-0.363:1.023-1.032, and the silicon-to-aluminum atomic ratio of the USY molecular sieve is 60-80.

[0012] (2) With the Fe element content being 0.3 wt%-0.4 wt% of the total weight of the catalyst, in an inert atmosphere, H-CHA is reacted with Fe-containing catalyst. 2+ The solution was subjected to ion exchange to separate the solid, which was then washed, dried, and calcined. The calcined product was then contacted with steam for modification to obtain the Fe-CHA catalyst.

[0013] The steam contains 5-10 vol% water, the modification temperature is 700-800℃, and the modification time is 4-10h.

[0014] A third aspect of the present invention provides a method for the partial oxidation of methane, the method comprising:

[0015] In the presence of the Fe-CHA catalyst described in this invention or the Fe-CHA catalyst prepared by the preparation method described in this invention, water, and an oxidant, methane is incompletely oxidized to methanol and dimethyl ether.

[0016] Through the above technical solution, this invention uses USY molecular sieve as raw material to synthesize CHA molecular sieve, and then loads iron element through ion exchange, followed by steam modification to obtain Fe-CHA catalyst. The CHA molecular sieve in the catalyst has a high para-aluminum content, as well as a specific distribution of tetrahedral coordinated mononuclear Fe, octahedral coordinated mononuclear Fe, and oligomeric Fe content. The Fe-CHA catalyst of this invention is used for the partial oxidation of methane, and can achieve the advantages of high methane conversion rate and high selectivity for methanol and dimethyl ether under low temperature conditions. Attached Figure Description

[0017] Figure 1 This is the UV-Vis spectrum of the Fe-CHA catalyst in Comparative Example 1;

[0018] Figure 2 The Fe-CHA catalyst in Comparative Example 1 29 NMR images of Si solid-state;

[0019] Figure 3 This is the UV-Vis spectrum of the Fe-CHA catalyst in Comparative Example 2;

[0020] Figure 4 The Fe-CHA catalyst in Comparative Example 2 29 NMR images of Si solid-state;

[0021] Figure 5 This is the UV-Vis spectrum of the Fe-CHA catalyst in Comparative Example 3;

[0022] Figure 6 The Fe-CHA catalyst in Comparative Example 3 29 NMR images of Si solid-state;

[0023] Figure 7 This is the UV-Vis spectrum image of the Fe-CHA catalyst in Example 1;

[0024] Figure 8 It is the Fe-CHA catalyst of Example 1. 29 NMR image of Si solid. Detailed Implementation

[0025] 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.

[0026] The first aspect of this invention provides an Fe-CHA catalyst, wherein the silicon-to-aluminum atomic ratio of the Fe-CHA catalyst is 8-10;

[0027] The Fe-CHA catalyst 29 In the Si solid-state NMR, within the chemical shift range of -90 ppm to -120 ppm, there are four resonance peaks with increasing chemical shifts, δ1 to δ4. The normalized peak area of ​​δ1 is 6% ± 1%, that of δ2 is 8% ± 1%, that of δ3 is 11% ± 1%, and that of δ4 is 75% ± 1%. The content of tetrahedral coordination mononuclear Fe is 29%-31%, that of octahedral coordination mononuclear Fe is 47-49%, and that of oligomeric Fe is 21%-23%.

[0028] 29 In Si solid-state NMR, δ1 represents the Q in the material. 4The Si(2Al) signal represents the Al-O-(Si-O)-Al configuration in CHA molecular sieves, which is a type of aluminum.

[0029] According to a preferred embodiment of the present invention, the chemical shift of δ1 is -100.1ppm ± 0.1ppm.

[0030] According to a preferred embodiment of the present invention, the chemical shift of δ2 is -103.1ppm ± 0.1ppm.

[0031] According to a preferred embodiment of the present invention, the chemical shift of δ3 is -109.9ppm ± 0.1ppm.

[0032] According to a preferred embodiment of the present invention, the chemical shift of δ4 is -111.2 ppm ± 0.1 ppm.

[0033] According to a preferred embodiment of the present invention, the Fe element content in the catalyst is 0.3wt%-0.4wt% of the total weight of the catalyst.

[0034] A second aspect of this invention provides a method for preparing a Fe-CHA catalyst, the method comprising:

[0035] (1) A mixture containing USY molecular sieve, aluminum hydroxide, N,N,N-trimethyl-1-adamantyl ammonium hydroxide and water was crystallized, and the solid was separated. The solid was washed, dried and calcined to obtain H-CHA.

[0036] The USY molecular sieve, calculated as Si and in molar ratio, has the following composition: USY:Al:N,N,N-trimethyl-1-adamantyl ammonium hydroxide:H2O = 1:0.06-0.085:0.023-0.363:1.023-1.032, and the silicon-to-aluminum atomic ratio of the USY molecular sieve is 60-80.

[0037] (2) With the Fe element content being 0.3wt%-0.4wt% of the total weight of the catalyst, in an inert atmosphere, H-CHA is reacted with Fe-containing... 2+ The solution was subjected to ion exchange to separate the solid, which was then washed, dried, and calcined. The calcined product was then contacted with steam for modification to obtain the Fe-CHA catalyst.

[0038] The steam contains 5-10 vol% water, the modification temperature is 700-800℃, and the modification time is 4-10h.

[0039] In this invention, there are no particular limitations on the crystallization conditions. According to a preferred embodiment of the present invention, in step (1), the crystallization conditions include: a temperature of 140-160°C and a time of 96-144h.

[0040] According to a preferred embodiment of the present invention, a mixture containing USY molecular sieve, aluminum hydroxide, N,N,N-trimethyl-1-adamantyl ammonium hydroxide and water is placed in a forced convection oven for crystallization.

[0041] In this invention, there are no particular limitations on the drying conditions after crystallization, as long as water is removed. In the examples, drying at 100 °C for 12 h is used as an example.

[0042] In this invention, there are no particular limitations on the calcination conditions in step (1). According to a preferred embodiment of this invention, the calcination conditions include: a temperature of 500-600℃ and a time of 3-10h. In this embodiment of the invention, static air calcination at 600℃ for 6h is used as an example.

[0043] According to a preferred embodiment of the present invention, in step (2), H-CHA is reacted with Fe... 3+ The ion exchange of the solution includes: forming a suspension of H-CHA with water, adjusting the pH of the suspension to 2.5-3, and adding a soluble divalent Fe salt in an inert atmosphere to carry out ion exchange at 60-80°C; in this embodiment of the invention, ion exchange is carried out at 80°C as an example.

[0044] According to one embodiment of the present invention, nitrogen gas is continuously introduced to form an inert atmosphere.

[0045] According to a preferred embodiment of the present invention, the soluble divalent Fe salt is ferrous sulfate.

[0046] In this invention, there are no particular limitations on the drying conditions after ion exchange; it is only necessary to remove moisture under conditions that isolate oxygen. In the examples, vacuum drying at 80°C for 30 min is used as an example.

[0047] In this invention, there are no particular limitations on the calcination conditions in step (2). According to a preferred embodiment of this invention, the calcination conditions include: a temperature of 500-600℃ and a time of 3-10h. In this embodiment of the invention, static air calcination at 550℃ for 5h is used as an example.

[0048] A third aspect of the present invention provides a method for the partial oxidation of methane, the method comprising:

[0049] In the presence of the Fe-CHA catalyst described in this invention or the Fe-CHA catalyst prepared by the preparation method described in this invention, water, and an oxidant, methane is incompletely oxidized to methanol and dimethyl ether.

[0050] According to a preferred embodiment of the present invention, the oxidant is selected from N2O and / or O2.

[0051] According to a preferred embodiment of the present invention, the conditions for incomplete oxidation of methane include a temperature of 250-350°C.

[0052] According to a preferred embodiment of the present invention, the volume ratio of methane to oxidant is 1:1-2.

[0053] According to a preferred embodiment of the present invention, the volume ratio of methane to water is 1:0.1-0.2.

[0054] According to a preferred embodiment of the present invention, the total gas hourly space velocity is 150-250 mL / (g·min).

[0055] According to a preferred embodiment of the present invention, the Fe-CHA catalyst has a particle size of 20 to 40 mesh when in use.

[0056] According to a preferred embodiment of the invention, the oxidation is carried out in a fixed-bed reactor.

[0057] In the context of this invention specification, including the following embodiments, the silicon-to-aluminum atomic ratio refers to the molar ratio of silicon atoms to aluminum atoms in the sample; the deconvolution used all achieves r 2 = 0.999 goodness of fit.

[0058] In the context of this invention specification, including the following embodiments, the Fe loading and silicon-to-aluminum atomic ratio data in Fe-CHA were measured using an inductively coupled plasma optical emission spectrometer (ICP-OES, analytikjena PQ9000).

[0059] Using Cu K α Powder X-ray diffraction patterns were collected using a Bruker D8 Advance X-ray diffractometer with a X-ray source (λ = 1.5406 Å), with a scanning range of 2θ from 5° to 40° and a step size of 0.02°.

[0060] A PerkinElmer Lambda 750S spectrophotometer equipped with an integrating sphere was used to collect ultraviolet-visible spectra in the wavelength range of 200 to 800 nm. Reflectance data were converted to apparent absorbance using the Kubelka-Munk function.

[0061] Solid-state magic angle rotation (MAS) NMR spectra were measured using a 600 MHz wide-cavity solid-state NMR spectrometer (Bruker AVANCE III) with a 4 mm probe, and data were acquired at the resonance frequency of 119.3 MHz. 29 Si signal. Sample rotation speed was set to 7 kHz.² 9The Si chemical shift was calibrated with reference to -91.5 ppm for kaolinite (Al2Si2O3(OH)4).

[0062] The present invention will be described in detail below through embodiments.

[0063] In the following examples, a fixed-bed reactor was used for the low-temperature partial oxidation of methane: 200 mg of sample (20-40 mesh) was packed into a quartz reaction tube with an inner diameter of 6 mm and placed in a tube furnace. The temperature was raised to 300 °C and the reaction was carried out for 6 h. Unless otherwise specified, the feed gas composition was 30 vol% CH4, 30 vol% N2O, and 5 vol% H2O, with helium (He) as the equilibrium gas. The reaction was carried out at atmospheric pressure. The total gas flow rate was 40 mL / min (mass hourly space velocity WHSV = 12000 mL·g). - ¹·h - ¹), precisely controlled by a mass flow controller. The reaction tail gas is analyzed every 30 minutes by an online gas chromatograph (PANA, A60Pro) equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD). Specifically, the FID connected to a KB-PLOT Q packed column (30 m × 0.32 mm × 20 μm) is used for quantitative analysis of CH4, methanol (MeOH), dimethyl ether (DME), alkenes, and alkanes with fewer than five carbon atoms. The TCD is used to analyze CO, CO2, N2O, O2, and N2.

[0064] In this invention, the formulas for calculating methane conversion rate, methanol and dimethyl ether selectivity are as follows:

[0065]

[0066] in C CH4 (%) represents the conversion rate of methane. c CH4 This represents the initial concentration of methane. c i The concentration of carbon-containing products. i The number of carbon atoms in a carbon-containing product;

[0067]

[0068] S i (%) is included i Selectivity of carbon-containing products per carbon atom c i For methanol, the concentration of carbon-containing products is... i =1, for dimethyl ether i = 2.

[0069] The present invention will be described in detail below through embodiments.

[0070] Comparative Example 1

[0071] (1) First, Na-CHA was synthesized using a hydrothermal synthesis method based on amorphous precursors. The specific implementation steps are as follows: according to the atomic ratio Si: Al: Na + TMAda + The raw materials were mixed in a ratio of H2O = 1: 0.091: 0.046: 0.132: 15.432. Sodium hydroxide was first dissolved in deionized water and stirred for approximately 15 min. Then, sodium aluminate, as the aluminum source, was added while stirring. After stirring for 2 h, colloidal silica (SiO2), as the silicon source, was added dropwise. Stirring continued for approximately 2 h until a homogeneous mixture was obtained. The resulting slurry was transferred to a 100 mL PTFE-lined stainless steel reactor and crystallized at 160°C for 4 days. After crystallization, the reactor was cooled to room temperature. The solid product was recovered by centrifugation (12000 rpm, 5 min) and washed at least three times with deionized water until the pH of the supernatant was less than 9. The solid was dried at 100°C for 12 h and calcined in static air at 600°C for 6 h to obtain CHA.

[0072] (2) Before preparing Fe-CHA by ion exchange, NH4+ was used. 4+ The preparation of NH4-type CHA for ion exchange loading of Fe is carried out by the following steps: 0.1 M ammonium chloride solution is used for two exchanges at 80 °C. Each time, 100 mg of catalyst is used with 100 mL of ammonium chloride solution. After each exchange, filtration, washing and drying of the solid at 100 °C for 12 h are required.

[0073] (3) Preparation of Fe-CHA by ion exchange: The obtained NH4-type CHA was dispersed in deionized water. Specifically, 100 mL of deionized water was used for every 100 mg of NH4-type CHA. A few drops of 2 M HNO3 solution were added to adjust the pH of the suspension to about 3. Under the condition of continuous N2 introduction and heating to 80 °C, ferrous sulfate heptahydrate was added. After sufficient exchange at 80 °C, the solution was filtered, washed, vacuum dried at 80 °C for 30 min, and calcined in static air at 550 °C for 5 h to obtain the Fe-CHA catalyst.

[0074] The Fe-CHA catalyst has a silicon-to-aluminum atomic ratio of 9.9 and an Fe loading of 0.38 wt%.

[0075] Its ultraviolet-visible spectrum is as follows Figure 1As shown in the table below, the peak areas of A1, A2, A3, and their normalized peaks are as follows: A1 corresponds to the content of tetrahedral coordination mononuclear Fe, A2 corresponds to the content of octahedral coordination mononuclear Fe, and A3 corresponds to the content of oligomeric Fe.

[0076]

[0077] That 29 Si solid NMR spectrum as shown Figure 2 As shown, the peak areas of δ1, δ2, δ3, δ4 and their normalized peaks are shown in the table below:

[0078]

[0079] Comparative Example 2

[0080] The method is the same as that in Comparative Example 1, except that in step (3), the calcined solid is treated at 750°C for 6 h in a nitrogen-water mixed atmosphere containing 10 vol% H2O to obtain the Fe-CHA catalyst.

[0081] The Fe-CHA catalyst has a silicon-to-aluminum atomic ratio of 10.1 and an Fe loading of 0.38 wt%; its UV-Vis spectrum is as follows: Figure 3 As shown in the table below, the peak areas of A1, A2, A3, and their normalized peaks are:

[0082]

[0083] That 29 Si solid NMR spectrum as shown Figure 4 As shown, the peak areas of δ1, δ2, δ3, δ4 and their normalized peaks are shown in the table below:

[0084]

[0085] Example 1

[0086] (1) USY is based on Si, and the molar ratio of USY:Al:TMAda is calculated as follows: + The ratio of H2O was 1:0.075:0.343:1.029, where USY molecular sieve (silicon-to-aluminum atomic ratio 40) was used. The organic structure-directing agent N,N,N-trimethyl-1-adamantyl ammonium hydroxide (TMAdaOH, 25 wt% aqueous solution) was mixed with USY molecular sieve in deionized water. Then, aluminum hydroxide was added under vigorous stirring and mixed thoroughly. The resulting gel was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel reactor and placed in a forced convection oven. After crystallization at 160 °C for 6 days, the gel was filtered, washed with deionized water, dried at 100 °C for 12 h, and calcined in static air at 600 °C for 6 h to obtain H-CHA.

[0087] (2) Disperse the obtained H-CHA in deionized water. The specific dosage is 100 mL of deionized water for every 100 mg H-CHA. Add a few drops of 2 M HNO3 solution to adjust the pH of the suspension to 3. Under the condition of continuous N2 introduction and heating to 80 °C, add ferrous sulfate heptahydrate. After sufficient exchange at 80 °C, filter, wash, vacuum dry at 80 °C for 30 min, calcine in static air at 550 °C for 5 h, and treat at 750 °C for 6 h in a nitrogen-water mixed atmosphere containing 10 vol% H2O to obtain Fe-CHA catalyst.

[0088] The Fe-CHA catalyst has a silicon-to-aluminum atomic ratio of 9.6 and an Fe loading of 0.37 wt%.

[0089] Its ultraviolet-visible spectrum is as follows Figure 7 As shown in the table below, the peak areas of A1, A2, A3, and their normalized peaks are:

[0090]

[0091] That 29 Si solid NMR spectrum as shown Figure 8 As shown, the peak areas of δ1, δ2, δ3, δ4 and their normalized peaks are shown in the table below:

[0092]

[0093] Comparative Example 3

[0094] The method is the same as in Example 1, except that it is not treated in a nitrogen-water mixed atmosphere containing 10 vol% H2O. Specifically:

[0095] (1) USY is based on Si, and the molar ratio of USY:Al:TMAda is calculated as follows: + The ratio of H2O was 1:0.075:0.343:1.029, where USY molecular sieve (silicon-to-aluminum atomic ratio 40) was used. The organic structure-directing agent N,N,N-trimethyl-1-adamantyl ammonium hydroxide (TMAdaOH, 25 wt% aqueous solution) was mixed with USY molecular sieve in deionized water. Then, aluminum hydroxide was added under vigorous stirring and mixed thoroughly. The resulting gel was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel reactor and placed in a forced convection oven. After crystallization at 160 °C for 6 days, the gel was filtered, washed with deionized water, dried at 100 °C for 12 h, and calcined in static air at 600 °C for 6 h to obtain H-CHA.

[0096] (2) Disperse the obtained H-CHA in deionized water. The specific dosage is 100 mL of deionized water for every 100 mg H-CHA. Add a few drops of 2 M HNO3 solution to adjust the pH of the suspension to 3. Under the condition of continuous N2 introduction and heating to 80 °C, add ferrous sulfate heptahydrate. After sufficient exchange at 80 °C, filter, wash, vacuum dry at 80 °C for 30 min, and calcine in static air at 550 °C for 5 h to obtain Fe-CHA catalyst.

[0097] The Fe-CHA catalyst has a silicon-to-aluminum atomic ratio of 9.6 and an Fe loading of 0.37 wt%.

[0098] Its ultraviolet-visible spectrum is as follows Figure 5 As shown in the table below, the peak areas of A1, A2, A3, and their normalized peaks are:

[0099]

[0100] That 29 Si solid NMR spectrum as shown Figure 6 As shown, the peak areas of δ1, δ2, δ3, δ4 and their normalized peaks are shown in the table below:

[0101]

[0102] Catalyst performance evaluation:

[0103] 200 mg of Fe-CHA (20-40 mesh) was packed into a quartz reaction tube with an inner diameter of 6 mm and placed in a tube furnace. The temperature was raised to 300 °C and the reaction was carried out for 6 h. The composition of the reaction feed gas was 30 vol% CH4, 30 vol% N2O and 5 vol% H2O. Helium (He) was used as the balance gas. The reaction was carried out at atmospheric pressure and the total gas flow rate was 40 mL / min. The test results are shown in Table 1.

[0104] Table 1

[0105]

[0106] 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 Fe-CHA catalyst, characterized in that, The Fe-CHA catalyst has a silicon-to-aluminum atomic ratio of 8-10; The Fe-CHA catalyst 29 In the NMR of Si solid-state, within the chemical shift range of -90 ppm to -120 ppm, there are four resonance peaks δ1 to δ4, with the chemical shift shifting sequentially towards higher fields. The normalized peak area of ​​δ1 is 6% ± 1%, the normalized peak area of ​​δ2 is 8% ± 1%, the normalized peak area of ​​δ3 is 11% ± 1%, and the normalized peak area of ​​δ4 is 75% ± 1%. The content of tetrahedral coordination mononuclear Fe is 29%-31%, the content of octahedral coordination mononuclear Fe is 47-49%, and the content of oligomeric Fe is 21%-23%; the δ1 chemical shift is -100.1ppm ± 0.1ppm; and / or The chemical shift of δ2 is -103.1 ppm ± 0.1 ppm; and / or The chemical shift of δ3 is -109.9 ppm ± 0.1 ppm; and / or The chemical shift of δ4 is -111.2 ppm ± 0.1 ppm.

2. The Fe-CHA catalyst according to claim 1, characterized in that, The Fe element content in the catalyst is 0.3 wt%-0.4 wt% of the total catalyst weight.

3. A method for preparing an Fe-CHA catalyst, characterized in that, The method includes: (1) A mixture containing USY molecular sieve, aluminum hydroxide, N,N,N-trimethyl-1-adamantyl ammonium hydroxide and water was crystallized, and the solid was separated. The solid was washed, dried and calcined to obtain H-CHA. The USY molecular sieve, calculated as Si and in molar ratio, has the following composition: USY:Al:N,N,N-trimethyl-1-adamantyl ammonium hydroxide:H2O = 1:0.06-0.085:0.023-0.363:1.023-1.032, and the silicon-to-aluminum atomic ratio of the USY molecular sieve is 60-80. (2) With the Fe element content being 0.3wt%-0.4wt% of the total weight of the catalyst, in an inert atmosphere, H-CHA is reacted with Fe-containing... 2+ The solution was subjected to ion exchange to separate the solid, which was then washed, dried, and calcined. The calcined product was then contacted with steam for modification to obtain the Fe-CHA catalyst. The steam contains 5-10 vol% water, the modification temperature is 700-800℃, and the modification time is 4-10 h.

4. The preparation method according to claim 3, characterized in that, In step (1), the crystallization conditions include: a temperature of 140-160℃ and a time of 96-144h; The calcination conditions include a temperature of 500-600℃ and a time of 3-10h.

5. The preparation method according to claim 3 or 4, characterized in that, In step (2), H-CHA is mixed with Fe... 2+ Ion exchange of the solution includes: forming a suspension of H-CHA with water, adjusting the pH of the suspension to 2-3, and carrying out ion exchange at 60-80℃ with the addition of soluble divalent Fe salt in an inert atmosphere. In step (2), the calcination conditions include: a temperature of 500-600℃ and a time of 3-10h.

6. The preparation method according to claim 3 or 4, characterized in that, The silicon-aluminum atomic ratio of the Fe-CHA catalyst is 8-10; The Fe-CHA catalyst 29 In the NMR spectrum of Si solid, there are four resonance peaks with increasing chemical shifts, δ1 to δ4, in the range of -90 ppm to -120 ppm. The normalized peak area of ​​δ1 is 6% ± 1%, the normalized peak area of ​​δ2 is 8% ± 1%, the normalized peak area of ​​δ3 is 11% ± 1%, and the normalized peak area of ​​δ4 is 75% ± 1%. The chemical shift of δ1 is -100.1 ppm ± 0.1 ppm; The chemical shift of δ2 is -103.1 ppm ± 0.1 ppm; The chemical shift of δ3 is -109.9 ppm ± 0.1 ppm; The chemical shift of δ4 is -111.2 ppm ± 0.1 ppm.

7. A method for the partial oxidation of methane, characterized in that, The method includes: In the presence of water and an oxidant, the Fe-CHA catalyst prepared by the method described in claim 1 or 2 or any one of claims 3-6 in the Fe-CHA catalyst in the Fe-CHA catalyst in the Fe-CHA catalyst prepared by the method described in any one of claims 3-6 in the Fe-CHA catalyst in the Fe-CHA catalyst in the Fe-CHA catalyst in the Fe-CHA catalyst prepared by the method described in any one of claims 3-6 in the Fe-CHA catalyst in the Fe-CHA catalyst prepared by ...

8. The method for partial oxidation of methane according to claim 7, characterized in that, The oxidizing agent is selected from N2O and / or O2; and / or Conditions for incomplete oxidation of methane include a temperature of 250-350℃.

9. The method for partial oxidation of methane according to claim 7, characterized in that, The volume ratio of methane to oxidant is 1:1-2; and / or The volume ratio of methane to water is 1:0.1-0.

2.

10. The method for partial oxidation of methane according to claim 7, characterized in that, The total gas hourly space velocity is 150-250 mL / (g·min).

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