Catalyst and process for the oxidative conversion of methane to methanol

Abstract

The present application relates to the field of catalysts, in particular to a catalyst for preparing methanol by methane oxidation conversion, the catalyst containing a molecular sieve carrier and an active metal element supported on the molecular sieve carrier, and the active metal being Au.The catalyst of the present application has a simple preparation process, high preparation repeatability, high stability and can be repeatedly used for multiple times.A method for preparing methanol by methane oxidation conversion is also disclosed.The method generates hydrogen peroxide in situ by using carbon monoxide, oxygen and water, and then reacts with methane to realize one-step direct oxidation to prepare methanol.The carbon monoxide in the route of the present application is easy to obtain and low in price, and the explosion limit range is narrower than that of hydrogen, thereby improving the operation safety;and the route of the present application has excellent methane conversion rate and methanol selectivity, and has certain industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more specifically to a catalyst and a method for the oxidative conversion of methane to methanol. Background Technology

[0002] Methanol is a crucial chemical raw material, holding a fundamental position in the chemical industry. It is widely used in the synthesis of dimethyl ether, methylamine, chloromethane, formaldehyde, and low-carbon olefins. Particularly in coal chemical engineering, the MTO (methanol-to-olefins) technology is of great significance in alleviating the shortage of petroleum resources. Methane reserves are vast; converting it into methanol could also reduce heavy dependence on petroleum resources. Currently, the process of converting methane to methanol via steam reforming and then further converting the syngas into methanol can achieve this conversion. However, this indirect process involves numerous steps and high energy consumption. Furthermore, methane has higher structural stability than methanol, and the oxidation of methane also leads to the peroxidation of methanol, generating carbon dioxide. Therefore, developing a one-step direct conversion route from methane to methanol and efficient selective oxidation catalysts are the main research directions.

[0003] Grundner et al. (Nature Communications, 2015, 6, 1) reported a direct conversion of methane to methanol via a copper ion-exchange MOR molecular sieve catalyst, achieving a maximum concentration of 180 μmol / g after 4 hours of reaction at 200 °C. -1 The methanol yield of this technique is relatively low. Luo et al. (ACS Catalysis, 2021, 11, 6684) prepared a high-performance copper-modified monomeric iron / ZSM-5 catalyst that directly converts methane to methanol in the liquid phase under mild conditions using H2O2 as an oxidant, achieving a methanol yield of 431 mol. MeOH mol -1 Fe h -1While exhibiting excellent performance with a methanol selectivity of around 80%, the transportation and storage of H2O2 in this technology may pose certain safety hazards. Xiao et al. (Science, 2020, 367, 193) developed a heterogeneous catalyst system capable of catalyzing the in-situ generation of hydrogen peroxide from hydrogen and oxygen under mild conditions of 70℃, followed by the selective oxidation of methane to methanol. This catalyst was synthesized by immobilizing AuPd alloy nanoparticles within the pores of a ZSM-5 molecular sieve and then modifying the outer surface of the zeolite with organosilanes. This catalyst structure exhibits a "molecular fence effect," effectively increasing the concentration of hydrogen peroxide around the active metal, thereby improving the methane conversion rate. The catalyst achieved a maximum methane conversion rate of 17.3% and a methanol selectivity of 92%, equivalent to a methanol yield of 91.6 mmol g. AuPd -1 h -1 This article successfully achieved selective oxidation of methane with excellent performance using the in-situ synthesis of hydrogen peroxide. However, the high explosion limit of hydrogen necessitates the use of concentrated hydrogen gas to operate outside this limit, which restricts the upper limit of methane conversion. Therefore, it is necessary to explore other safer direct synthesis routes and develop highly efficient catalysts to achieve high conversion and high selectivity in the oxidation of methane to methanol. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of complex process, high safety risks and low methanol yield in the existing technology of methane to methanol production, and to provide a catalyst and method for the oxidative conversion of methane to methanol.

[0005] To achieve the above objectives, the present invention provides a catalyst for the oxidative conversion of methane to methanol, wherein the catalyst contains a molecular sieve support and an active metal element supported on the molecular sieve support, and the active metal element is Au.

[0006] The catalyst of this invention can effectively catalyze the selective oxidation of methane to methanol. The preparation process is simple, the preparation is highly reproducible, and the catalyst has high stability and can be reused multiple times.

[0007] A second aspect of the present invention provides a method for the oxidative conversion of methane to methanol, the method comprising: reacting CH4, CO, O2 and an aqueous solvent in the presence of the catalyst described in the present invention.

[0008] This invention utilizes carbon monoxide, oxygen, and water to generate hydrogen peroxide in situ, which then reacts with methane to produce methanol. In this route, carbon monoxide is readily available and inexpensive, has a narrower explosion limit range than hydrogen, and offers improved operational safety. The route of this invention exhibits high methane conversion rate and methanol selectivity. Detailed Implementation

[0009] 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.

[0010] This invention provides a catalyst for the oxidative conversion of methane to methanol, wherein the catalyst contains a molecular sieve support and an active metal element supported on the molecular sieve support, and the active metal element is Au.

[0011] In this invention, as long as the objective of the invention can be achieved, there are no special requirements for the loading amount of the active metal Au. According to a preferred embodiment of the invention, the loading amount of Au element is 0.1 to 5.0 wt%. By adopting the aforementioned preferred scheme, the conversion rate of methane and the selectivity of methanol can be further improved when the catalyst is used for the oxidative conversion of methane to methanol.

[0012] To further improve the conversion rate of methane and the selectivity of methanol, according to a preferred embodiment of the present invention, the loading of Au element is 0.6 to 3 wt%.

[0013] In this invention, as long as the objective of this invention can be achieved, there are no special requirements for the support of the catalyst. According to a preferred embodiment of this invention, the support of the catalyst is at least one of ZSM-5 molecular sieve and TS-1 molecular sieve.

[0014] According to a particularly preferred embodiment of the present invention, the support is a composite of ZSM-5 molecular sieve and TS-1 molecular sieve, and the mass ratio of ZSM-5 molecular sieve to TS-1 molecular sieve in the support is 9:1 to 1:9. By employing the aforementioned preferred embodiment, the selectivity of methanol as a product can be further improved when the catalyst is used for the oxidative conversion of methane to methanol.

[0015] In this invention, there are no special requirements for the ZSM-5 molecular sieve as long as the objective of the invention can be achieved. According to a particularly preferred embodiment of the invention, the physicochemical parameters of the ZSM-5 molecular sieve include: Si / Al (molar ratio) = 30-200, and specific surface area of ​​150-600 m². 2 / g. By employing the aforementioned preferred embodiments, the selectivity of methanol as a product can be further improved when the catalyst is used for the oxidative conversion of methane to methanol.

[0016] In this invention, there are no special requirements for the TS-1 molecular sieve as long as the objective of the invention can be achieved. According to a particularly preferred embodiment of the invention, the physicochemical parameters of the TS-1 molecular sieve include: Si / Ti (molar ratio) = 20-80, and a specific surface area of ​​100-550 m². 2 / g. By employing the aforementioned preferred embodiments, the selectivity of methanol as a product can be further improved when the catalyst is used for the oxidative conversion of methane to methanol.

[0017] In this invention, catalysts possessing the aforementioned characteristics can achieve the objectives of this invention. There are no particular requirements for the preparation method of the catalyst. According to a particularly preferred embodiment of this invention, the preparation method of the catalyst includes: contacting and impregnating a gold-containing solution with a molecular sieve support, followed by drying and calcination. By employing the aforementioned preferred catalyst preparation method, the selectivity of methanol as a product can be further improved when the catalyst is used for the oxidative conversion of methane to methanol.

[0018] According to a particularly preferred embodiment of the present invention, the method for preparing the catalyst includes:

[0019] 1) Prepare a solution with a concentration of 5–30 mg using the gold-containing compound HAuCl4·4H2O. Au A gold-containing aqueous solution of / mL was prepared by taking an appropriate amount of gold-containing aqueous solution on the molecular sieve support according to the predetermined Au element loading and completing the impregnation treatment.

[0020] 2) Stir dry at room temperature, then place in an oven at 60-100℃ to dry for 6-12 hours, and then calcine.

[0021] By employing the aforementioned preferred catalyst preparation method, the reproducibility of the catalyst can be guaranteed.

[0022] According to a particularly preferred embodiment of the invention, the contact impregnation is carried out in the presence of an organic compound.

[0023] According to a particularly preferred embodiment of the present invention, the organic compound is one or more of ethanol, methanol, acetone and isopropanol.

[0024] According to a particularly preferred embodiment of the present invention, the weight ratio of the organic compound to the gold-containing aqueous solution is (10-75):100.

[0025] By adopting the aforementioned preferred embodiments, the dispersion of precious metals on the carrier can be effectively improved.

[0026] In this invention, the calcination conditions in step 2) can be conventionally chosen in the art. According to a preferred embodiment of the invention, the calcination conditions in step 2) include: calcination at 200–600°C for 2–5 hours in an air atmosphere. By adopting the aforementioned preferred scheme, the selectivity of methanol as a product can be further improved when the catalyst is used for the oxidative conversion of methane to methanol.

[0027] The catalyst of this invention can effectively catalyze the selective oxidation of methane to methanol. The preparation process is simple, the preparation is highly reproducible, and the catalyst has high stability and can be reused multiple times.

[0028] A second aspect of the present invention provides a method for the oxidative conversion of methane to methanol, the method comprising: reacting CH4, CO, O2 and an aqueous solvent in the presence of the catalyst described in the present invention.

[0029] According to a particularly preferred embodiment of the present invention, the conditions for the contact reaction include a reaction temperature of 20–85°C.

[0030] According to a particularly preferred embodiment of the present invention, the conditions for the contact reaction include a reaction pressure of 2 to 6 MPa.

[0031] According to a particularly preferred embodiment of the present invention, the conditions for the contact reaction include: solvent mass: catalyst mass = 50 to 3000.

[0032] In this invention, the reaction time is determined based on temperature and pressure. According to a particularly preferred embodiment of the invention, the contact reaction conditions include a reaction time of 2–120 min, preferably 15–120 min. Using the aforementioned preferred embodiment can improve the conversion rate of methane and the selectivity of methanol.

[0033] According to a particularly preferred embodiment of the present invention, the method wherein the aqueous solvent contains 99.8 to 100% by weight water and 0 to 0.2% by weight inorganic acid.

[0034] In this invention, the inorganic acid can be any conventional choice in the art, as long as it achieves the objective of the invention. According to a particularly preferred embodiment of the invention, the inorganic acid is selected from one or more of sulfuric acid, phosphoric acid, and hydrochloric acid. By employing the aforementioned preferred embodiment, the stability of the intermediate product hydrogen peroxide can be improved, thereby increasing the conversion rate of methane.

[0035] According to a particularly preferred embodiment of the present invention, the method wherein, based on the total amount of substance of all gases, the CH4 content is 1–5 mol%.

[0036] According to a particularly preferred embodiment of the present invention, the method wherein, based on the total amount of substance of all gases, the total content of CO and O2 is 10 to 90 mol% of the total amount of all gases.

[0037] According to a particularly preferred embodiment of the present invention, the method wherein the molar ratio of O2 to CO is 2 to 25.

[0038] By employing the aforementioned preferred embodiments, the selectivity of the product methanol can be improved.

[0039] According to a particularly preferred embodiment of the present invention, the method wherein the contact is carried out in the presence of a protective inert gas.

[0040] According to a particularly preferred embodiment of the present invention, the method wherein the protective gas is preferably selected from one or more of N2, He and Ar.

[0041] According to a particularly preferred embodiment of the present invention, in the method, the molar content of the protective gas is preferably 5 to 89 mol% of the total gas molar content.

[0042] By employing the aforementioned preferred embodiments, the selectivity of the product methanol can be improved.

[0043] According to a particularly preferred embodiment of the present invention, the method wherein the contact is carried out in a high-pressure reactor, and the reaction is stirred by a magnetic stirrer at a rotation speed of 500–1200 rpm. By employing the aforementioned preferred embodiment, the conversion rate of methane can be improved.

[0044] This invention first utilizes carbon monoxide, oxygen, and water to synthesize hydrogen peroxide in situ. Subsequently, the generated hydrogen peroxide reacts with methane to produce methanol, exhibiting both high methane conversion rate and high methanol selectivity.

[0045] The technical solution of the present invention will be further described below through embodiments, but the scope of protection of the present invention is not limited by the embodiments.

[0046] Example 1

[0047] ZSM-5 (physicochemical parameters: Si / Al (molar ratio, same for other examples) = 80, specific surface area 200 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti (molar ratio, same for other examples) = 50, specific surface area is 200m² 2 Using molecular sieves with a mass ratio of 1:1 (g / g) as the carrier, 5 mg of Au was taken according to an Au loading of 1 wt%. AuA 1 wt% Au / 1ZSM-5 / 1TS-1 catalyst was prepared by impregnating a 1 mL / mL aqueous solution of HAuCl4·4H2O with methanol (50:100 weight ratio of methanol to the gold-containing aqueous solution). After impregnation, the catalyst was dried at room temperature and then dried in an 80℃ oven for 9 h. After drying, it was calcined at 400℃ for 3 h in air to obtain the catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% phosphoric acid) were weighed and added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70℃. A gas was introduced at 4 MPa according to the molar ratio of 4% CO / 80% O2 / 1% CH4 / 15% He. The reaction was stopped after 30 min, and the product was analyzed. The CH4 conversion rate was 16.8%, and the methanol selectivity was 86%.

[0048] Example 2

[0049] ZSM-5 (physicochemical parameters: Si / Al = 130, specific surface area 350 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti=30, specific surface area is 150m²) 2 Using molecular sieves with a mass ratio of 7:1 (g / g) as the carrier, 15 mg of Au was taken according to an Au loading of 2.5 wt%. Au A 2.5 wt% Au / 7ZSM-5 / 1TS-1 catalyst was prepared by impregnating a HAuCl4·4H2O aqueous solution (at a weight ratio of 20:100) with ethanol (an organic compound). After impregnation, the solution was dried at room temperature and then dried in a 65°C oven for 11 hours. Following drying, the solution was calcined at 550°C for 2 hours in air to obtain the catalyst. 100 mg of the catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% sulfuric acid) were added to a 50 mL high-pressure reactor. The reaction speed was adjusted to 900 rpm, and the reaction temperature was raised to 40°C. A gas mixture of 10% CO / 60% O2 / 5% CH4 / 25% N2 was introduced at a pressure of 6 MPa. The reaction was stopped after 110 minutes. Product analysis showed a CH4 conversion rate of 13.2% and a methanol selectivity of 80%.

[0050] Example 3

[0051] ZSM-5 (physicochemical parameters: Si / Al = 180, specific surface area 500 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti=70, specific surface area is 450m²) 2 Using molecular sieves with a mass ratio of 1:8 (g / g) as the carrier, 25 mg of Au was taken according to an Au loading of 0.6 wt%. AuA 0.6 wt% Au / 1ZSM-5 / 8TS-1 catalyst was prepared by impregnating a HAuCl4·4H2O aqueous solution with acetone (70:100 weight ratio to the gold-containing aqueous solution). After impregnation, the solution was dried at room temperature and then placed in a 95°C oven for 7 hours. After drying, the solution was calcined at 250°C for 2 hours in air to obtain the catalyst. 200 mg of the catalyst and 10 g of aqueous solvent (containing 99.8 wt% water and 0.2 wt% hydrochloric acid) were added to a 50 mL high-pressure reactor. The reaction speed was adjusted to 600 rpm, and the reaction temperature was raised to 80°C. A gas mixture of 7% CO / 58% O2 / 3% CH4 / 32% Ar was introduced at 2 MPa. The reaction was stopped after 60 minutes, and the product was analyzed. The CH4 conversion rate was 12.8%, and the methanol selectivity was 83%.

[0052] Example 4

[0053] ZSM-5 (physicochemical parameters: Si / Al = 80, specific surface area 200 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti=50, specific surface area is 200m²) 2 Using a molecular sieve with a mass ratio of 1:1 (g / g) as the carrier, 5 mg of Au was taken according to an Au loading of 5 wt%. Au A 5wt% Au / 1ZSM-5 / 1TS-1 catalyst was prepared by impregnating a 1 mL / mL aqueous solution of HAuCl4·4H2O with methanol (50:100 weight ratio of methanol to the gold-containing aqueous solution). After impregnation, the catalyst was dried at room temperature and then dried in an 80℃ oven for 9 h. After drying, it was calcined at 400℃ for 3 h in air to obtain the catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% phosphoric acid) were weighed and added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70℃. Gas was introduced at 4 MPa according to the molar ratio of 4% CO / 80% O2 / 1% CH4 / 15% He. The reaction was stopped after 30 min, and the product was analyzed. The CH4 conversion rate was 9.1%, and the methanol selectivity was 68%.

[0054] Example 5

[0055] ZSM-5 (physicochemical parameters: Si / Al = 200, specific surface area 200 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti=10, specific surface area is 50m²) 2 Using molecular sieves with a mass ratio of 1:1 (g / g) as the carrier, 5 mg of Au was taken according to an Au loading of 1 wt%. AuA 1 wt% Au / 1ZSM-5 / 1TS-1 catalyst was prepared by impregnating a 1 mL / mL aqueous solution of HAuCl4·4H2O with methanol (50:100 weight ratio of the organic compound to the gold-containing aqueous solution). After impregnation, the catalyst was dried at room temperature and then dried in an oven at 80°C for 9 h. After drying, it was calcined at 400°C for 3 h in air to obtain the catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% phosphoric acid) were weighed and added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70°C. Gas was introduced at 4 MPa according to the molar ratio of 4% CO / 80% O2 / 1% CH4 / 15% He. The reaction was stopped after 30 min, and the product was analyzed. The CH4 conversion rate was 8.9%, and the methanol selectivity was 74%.

[0056] Example 6

[0057] ZSM-5 (physicochemical parameters: Si / Al = 30, specific surface area 100 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti=10, specific surface area is 200m²) 2 Using molecular sieves with a mass ratio of 1:1 (g / g) as the carrier, 5 mg of Au was taken according to an Au loading of 1 wt%. Au A 1 wt% Au / 1ZSM-5 / 1TS-1 catalyst was prepared by impregnating a 1 mL / mL aqueous solution of HAuCl4·4H2O with methanol (50:100 weight ratio of the organic compound to the gold-containing aqueous solution). After impregnation, the catalyst was dried at room temperature and then dried in an 80℃ oven for 9 h. After drying, it was calcined at 400℃ for 3 h in air to obtain the catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% phosphoric acid) were weighed and added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70℃. Gas was introduced at 4 MPa according to the molar ratio of 4% CO / 80% O2 / 1% CH4 / 15% He. The reaction was stopped after 30 min, and the product was analyzed. The CH4 conversion rate was 12.1%, and the methanol selectivity was 55%.

[0058] Example 7

[0059] ZSM-5 (physicochemical parameters: Si / Al = 80, specific surface area 200 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti=50, specific surface area is 200m²) 2 Using molecular sieves with a mass ratio of 1:1 (g / g) as the carrier, 5 mg of Au was taken according to an Au loading of 1 wt%. AuA 1 wt% Au / 1ZSM-5 / 1TS-1 catalyst was prepared by impregnating a 1 mL / mL aqueous solution of HAuCl4·4H2O with a tetrahydrofuran (50:100 weight ratio of the gold-containing aqueous solution). After impregnation, the catalyst was dried at room temperature and then dried in an oven at 80°C for 9 h. After drying, it was calcined at 400°C for 3 h in air to obtain the catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% phosphoric acid) were weighed and added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70°C. A gas was introduced at 4 MPa according to the molar ratio of 4% CO / 80% O2 / 1% CH4 / 15% He. The reaction was stopped after 30 min, and the product was analyzed. The CH4 conversion rate was 9.4%, and the methanol selectivity was 80%.

[0060] Example 8

[0061] ZSM-5 (physicochemical parameters: Si / Al = 80, specific surface area 200 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti=50, specific surface area is 200m²) 2 Using molecular sieves with a mass ratio of 1:1 (g / g) as the carrier, 5 mg of Au was taken according to an Au loading of 1 wt%. Au A 1 wt% Au / 1ZSM-5 / 1TS-1 catalyst was prepared by impregnating a 1 mL / mL aqueous solution of HAuCl4·4H2O with methanol (200:100 by weight) containing an organic compound. After impregnation, the catalyst was dried at room temperature and then dried in an oven at 80°C for 9 h. After drying, it was calcined at 400°C for 3 h in air to obtain the catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% phosphoric acid) were weighed and added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70°C. Gas was introduced at 4 MPa according to the molar ratio of 4% CO / 80% O2 / 1% CH4 / 15% He. The reaction was stopped after 30 min, and the product was analyzed. The CH4 conversion rate was 11.9%, and the methanol selectivity was 79%.

[0062] Example 9

[0063] ZSM-5 (physicochemical parameters: Si / Al = 80, specific surface area 200 m²) 2 / g) Molecular sieve as carrier, take 5mg according to Au loading of 1wt% AuA 1 wt% Au / ZSM-5 catalyst was prepared by impregnating a 1 mL / mL aqueous solution of HAuCl4·4H2O with methanol (50:100 weight ratio of methanol to the gold-containing aqueous solution). After impregnation, the catalyst was dried at room temperature and then dried in an oven at 80°C for 9 h. After drying, it was calcined at 400°C for 3 h in air to obtain the catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% phosphoric acid) were weighed and added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70°C. Gas was introduced at 4 MPa according to the molar ratio of 4% CO / 80% O2 / 1% CH4 / 15% He. The reaction was stopped after 30 min, and the product was analyzed. The CH4 conversion rate was 8.7%, and the methanol selectivity was 82%.

[0064] Example 10

[0065] ZSM-5 (physicochemical parameters: Si / Al = 80, specific surface area 200 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti=50, specific surface area is 200m²) 2 Using a molecular sieve with a mass ratio of 1:12 (g / g) as the carrier, 5 mg of Au was taken according to an Au loading of 1 wt%. Au A 1 wt% Au / 1ZSM-5 / 12TS-1 catalyst was prepared by impregnating a 1 mL / mL aqueous solution of HAuCl4·4H2O with methanol (50:100 weight ratio of methanol to the gold-containing aqueous solution). After impregnation, the catalyst was dried at room temperature and then dried in an 80℃ oven for 9 h. After drying, it was calcined at 400℃ for 3 h in air to obtain the catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% phosphoric acid) were weighed and added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70℃. Gas was introduced at 4 MPa according to the molar ratio of 4% CO / 80% O2 / 1% CH4 / 15% He. The reaction was stopped after 30 min, and the product was analyzed. The CH4 conversion rate was 7.9%, and the methanol selectivity was 76%.

[0066] Example 11

[0067] ZSM-5 (physicochemical parameters: Si / Al = 80, specific surface area 200 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti=50, specific surface area is 200m²) 2 Using molecular sieves with a mass ratio of 1:1 (g / g) as the carrier, 5 mg of Au was taken according to an Au loading of 1 wt%. AuA 1 wt% Au / 1ZSM-5 / 1TS-1 catalyst was prepared by impregnating a 1 mL / mL aqueous solution of HAuCl4·4H2O with methanol (50:100 weight ratio of methanol to the gold-containing aqueous solution). After impregnation, the catalyst was dried at room temperature and then placed in an 80℃ oven for 9 h. After drying, it was calcined at 400℃ for 3 h in air to obtain the catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing only 100 wt% water) were weighed and added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70℃. Gas was introduced at 4 MPa according to the molar ratio of 4% CO / 80% O2 / 1% CH4 / 15% He. The reaction was stopped after 30 min, and the product was analyzed. The CH4 conversion rate was 7.2%, and the methanol selectivity was 73%.

[0068] Example 12

[0069] ZSM-5 (physicochemical parameters: Si / Al = 80, specific surface area 200 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti=50, specific surface area is 200m²) 2 Using molecular sieves with a mass ratio of 1:1 (g / g) as the carrier, 5 mg of Au was taken according to an Au loading of 1 wt%. Au A 1 wt% Au / 1ZSM-5 / 1TS-1 catalyst was prepared by impregnating a 1 mL / mL aqueous solution of HAuCl4·4H2O with methanol (in an organic compound solution at a weight ratio of 50:100 to the gold-containing aqueous solution). After impregnation, the catalyst was dried at room temperature and then placed in an oven at 80°C for 9 h. After drying, it was calcined at 400°C for 3 h in air to obtain the catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% phosphoric acid) were weighed and added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70°C. A gas was introduced at 4 MPa according to the molar ratio of 5% CO / 93% O2 / 2% CH4. The reaction was stopped after 30 min, and the product was analyzed. The CH4 conversion rate was 12.1%, and the methanol selectivity was 76%.

[0070] Comparative Example 1

[0071] Using Al2O3 as a carrier, 10 mg of Au was taken at a loading of 1 wt%. AuImpregnated with a HAuCl4·4H2O aqueous solution ( / mL), the catalyst was dried at room temperature and then placed in an 80℃ oven for 9 hours. After drying, it was calcined at 400℃ for 3 hours in air to obtain a 1wt% Au / Al2O3 catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% phosphoric acid) were added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70℃. Gas was introduced at 4 MPa according to the molar ratio of 4% CO / 80% O2 / 1% CH4 / 15% He. The reaction was stopped after 30 minutes, and the product was analyzed. The CH4 conversion rate was 0.4%, and the methanol selectivity was 10%.

[0072] Comparative Example 2

[0073] ZSM-5 (physicochemical parameters: Si / Al = 80, specific surface area 200 m²) 2 / g) and TS-1 (physicochemical parameters: Si / Ti=50, specific surface area is 200m²) 2 Using molecular sieves with a mass ratio of 1:1 ( / g) as the carrier, 5 mg of Pd was taken according to a Pd loading of 1 wt%. Pd A 1 wt% Pd / 1ZSM-5 / 1TS-1 catalyst was prepared by impregnating a 1 mL Pd(NO3)2 aqueous solution with methanol (at a weight ratio of 30:100 to the palladium-containing aqueous solution). After impregnation, the solution was dried at room temperature and then dried in an 80°C oven for 9 h. After drying, the solution was calcined at 400°C for 3 h in air to obtain the catalyst. 10 mg of the above catalyst and 10 g of aqueous solvent (containing 99.9 wt% water and 0.1 wt% phosphoric acid) were weighed and added to a 50 mL high-pressure reactor. The rotation speed was adjusted to 1200 rpm, and the reaction temperature was raised to 70°C. Gas was introduced at 4 MPa according to the molar ratio of 4% CO / 80% O2 / 1% CH4 / 15% He. The reaction was stopped after 30 min, and the product was analyzed. The CH4 conversion rate was 1.0%, and the methanol selectivity was 13%.

[0074] As can be seen from Examples 1-12 and Comparative Examples 1-2, the catalyst of the present invention, when applied to the novel route of methane oxidation to methanol, exhibits significantly higher catalytic performance than supported Au catalysts with oxide supports. The preferred example 1 demonstrates a CH4 conversion of 16.8% and a methanol selectivity of 86%, exhibiting excellent methane conversion and methanol selectivity.

[0075] 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 catalyst for the oxidative conversion of methane to methanol, characterized in that, The catalyst contains a molecular sieve support and an active metal element supported on the molecular sieve support, wherein the active metal element is Au; The support is a composite of ZSM-5 molecular sieve and TS-1 molecular sieve; The mass ratio of ZSM-5 molecular sieve to TS-1 molecular sieve in the carrier is 9:1 to 1:

9.

2. The catalyst according to claim 1, wherein, The loading of Au element is 0.1~5.0 wt% based on the total weight of the catalyst.

3. The catalyst according to claim 2, wherein, The loading of Au element is 0.6~3 wt% based on the total weight of the catalyst.

4. The catalyst according to claim 1, wherein, The physicochemical parameters of the ZSM-5 molecular sieve include: Si / Al molar ratio of 30 to 200, and specific surface area of ​​150 to 600 m². 2 / g.

5. The catalyst according to claim 1, wherein, The physicochemical parameters of TS-1 molecular sieve include: Si / Ti molar ratio of 20 to 80, and specific surface area of ​​100 to 550 m². 2 / g.

6. The catalyst according to any one of claims 1-5, wherein, The catalyst is prepared by contacting and impregnating a gold-containing solution with a molecular sieve support, followed by drying and calcination.

7. The catalyst according to claim 6, wherein, The method for preparing the catalyst includes: 1) Use gold-containing compound HAuCl4 The concentration of 4H2O is prepared as 5~30 mg. Au A gold-containing aqueous solution of / mL was prepared by taking an appropriate amount of gold-containing aqueous solution on the molecular sieve support according to the predetermined Au element loading and completing the impregnation treatment. 2) Stir dry at room temperature, then place in an oven at 60~100 ℃ to dry for 6~12 h, and then calcine.

8. The catalyst according to claim 7, wherein, The calcination conditions include: calcination at 200-600°C for 2-5 hours in air; and / or The contact impregnation is carried out in the presence of an organic compound.

9. The catalyst according to claim 8, wherein, The organic compound is one or more of ethanol, methanol, acetone and isopropanol.

10. The catalyst according to claim 9, wherein, The weight ratio of the organic compound to the gold-containing aqueous solution is (10-75):

100.

11. A method for the oxidative conversion of methane to methanol, characterized in that, The method comprises: reacting CH4, CO, O2 and an aqueous solvent in the presence of the catalyst described in any one of claims 1-10.

12. The method according to claim 11, wherein, The conditions for a contact reaction include: The reaction temperature is 20~85℃; and / or The reaction pressure is 2-6 MPa; and / or Solvent mass: Catalyst mass = 50~3000; and / or The reaction time is 2~240 min.

13. The method according to claim 12, wherein, The conditions for a contact reaction include: The reaction time is 15~120 min.

14. The method according to claim 11, wherein, The aqueous solvent contains 99.8-100% by weight water and 0.01-0.2% by weight inorganic acid, with the sum of the weight percentages of water and inorganic acid being 100%.

15. The method according to claim 14, wherein, The inorganic acid is selected from one or more of sulfuric acid, phosphoric acid, and hydrochloric acid.

16. The method according to claim 11, wherein, Based on the total amount of substance of all gases, The CH4 content is 1~5 mol%; and / or The total content of CO and O2 is 10 to 90 mol of the total content of all gases.

17. The method according to claim 16, wherein, The molar ratio of O2 to CO is 2 to 25.

18. The method according to claim 11, wherein, The contact is carried out in the presence of a protective gas selected from one or more of N2, He, and Ar.

19. The method according to claim 18, wherein, The molar content of the protective gas is 5-89 mol of the total gas molar content.

20. The method according to claim 11, wherein, The contact is carried out in a high-pressure reactor, and the reaction is stirred by a magnetic stirrer at a speed of 500-1200 rpm.