Bimetal supported catalyst, preparation method and application thereof, and methane catalytic oxidation method

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a bimetallic supported catalyst, a preparation method and application thereof, and a methane catalytic oxidation method. The bimetallic supported catalyst provided by the invention comprises a carrier, and platinum and iron which are supported in the carrier, the carrier is an H-Beta molecular sieve, the mass percentage content of platinum in the bimetallic supported catalyst is 0.15-0.6 wt%, and the mass percentage content of iron in the bimetallic supported catalyst is 0.25-1.0 wt%. Pt and Fe are adjacent in spatial position on the carrier, and the yield and selectivity of methanol prepared by catalytic oxidation of methane are improved under the synergistic effect of Pt and Fe; meanwhile, the Fe species can inhibit oxidation of the Pt species. When the bimetallic supported catalyst provided by the invention is used for preparing methanol through catalytic oxidation of methane, the yield and selectivity of methanol can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a bimetallic supported catalyst, a preparation method and application thereof, and a method for catalytic oxidation of methane. Background Art

[0002] Methane, abundant globally, is the second most potent greenhouse gas after carbon dioxide. Currently, its primary use is direct combustion, resulting in low efficiency and far from fully utilizing its role as a platform molecule in the chemical industry. Therefore, efficiently converting methane into high-value-added chemicals or other clean energy sources that are easily storable and transportable is crucial. Research has led to the development of a method for producing methanol from methane via catalytic oxidation. Currently, the main oxidants used for direct methane oxidation are H2O2, N2O, and O2. H2O2 is a green and efficient oxidant suitable for a variety of catalysts, but its price is significantly higher than that of products like methanol, limiting its industrial application. N2O primarily originates from agricultural activities, fossil fuel combustion, and wastewater treatment. It is also a major waste product from the industrial production of adipic acid and nitric acid. The large amounts of N2O emitted by human activities have made it the third most potent greenhouse gas after carbon dioxide and methane. Fe- and Cu-based catalysts can promote the decomposition of N2O at high temperatures to produce reactive oxygen species, which activate methane to produce oxygen-containing compounds. However, these gas-solid reactions are limited by product desorption and the catalysts are easily deactivated by the formation of large amounts of carbon deposits. O2, activated by Cu and noble metals such as Rh, Au, Pd, Ir, and Pt, can oxidize methane under relatively mild conditions. This is typically done in aqueous solution, where water promotes product desorption and facilitates separation of the catalyst and product. Oxygen's widespread availability makes it a popular oxidant for methane oxidation. However, the yield and selectivity of existing catalysts for the catalytic oxidation of methane to methanol using oxygen as an oxidant still need to be improved. Summary of the Invention

[0003] In view of this, the present invention provides a bimetallic supported catalyst, a preparation method and application thereof, and a method for catalytic oxidation of methane. The use of the catalyst provided by the present invention for catalytic oxidation of methane to produce methanol can improve the yield and selectivity of methanol.

[0004] In order to solve the above technical problems, the present invention provides a bimetallic supported catalyst, comprising a carrier and platinum and iron supported on the carrier;

[0005] The carrier is H-Beta molecular sieve, the mass percentage of the platinum in the bimetallic supported catalyst is 0.15-0.6 wt%, and the mass percentage of the iron in the bimetallic supported catalyst is 0.25-1.0 wt%.

[0006] Preferably, the mass percentage of platinum in the bimetallic supported catalyst is 0.3-0.5 wt%, and the mass percentage of iron is 0.5-0.75 wt%.

[0007] Preferably, the total specific surface area of ​​the bimetallic supported catalyst is 600 to 700 m 2 / g, with a total pore volume of 0.60-0.70 cm 3 / g.

[0008] The present invention also provides a method for preparing the bimetallic supported catalyst described in the above technical solution, including method 1, method 2 or method 3;

[0009] The method 1 comprises the following steps:

[0010] Mixing H-Beta molecular sieve and platinum source aqueous solution, performing a first impregnation and then a first reduction calcination to obtain a first primary catalyst;

[0011] Mixing the first primary catalyst and an iron source aqueous solution, performing a second impregnation, and then performing a second reduction calcination to obtain the bimetallic supported catalyst;

[0012] The method 2 comprises the following steps:

[0013] Mixing the H-Beta molecular sieve and the iron source aqueous solution, performing a third impregnation and then a third reduction calcination to obtain a second primary catalyst;

[0014] mixing the second primary catalyst and a platinum source aqueous solution, performing a fourth impregnation and then a fourth reduction calcination to obtain the bimetallic supported catalyst;

[0015] The method 3 comprises the following steps:

[0016] dissolving an iron source and a platinum source in water to obtain a composite aqueous solution;

[0017] The composite aqueous solution and H-Beta molecular sieve are mixed, and a fifth impregnation is performed followed by a fifth reduction calcination to obtain the bimetallic supported catalyst.

[0018] Preferably, the platinum source in the platinum source aqueous solution includes one or more of PtCl2, PtCl4, H2PtCl6, Pt(NH3)4Cl2, H2Pt(OH)6, Pt(NO3)2, Pt(NH3)4(NO3)2 and Pt(SO3)2; the mass concentration of the platinum element in the platinum source aqueous solution is 0.15 to 0.6 g / L;

[0019] The iron source in the iron source aqueous solution includes one or more of Fe(NO3)3, Fe(SO4)3, FeCl3, ferric acetate and ferric acetylacetonate; the mass concentration of the iron element in the iron source aqueous solution is 0.25~1g / L.

[0020] Preferably, the solid-liquid ratio of the first impregnation, the second impregnation, the third impregnation, the fourth impregnation and the fifth impregnation is independently 1g / 8~12mL; the first impregnation, the second impregnation, the third impregnation, the fourth impregnation and the fifth impregnation are respectively carried out under stirring conditions, the stirring speed is 750~850rpm, and the stirring time is 22~26h.

[0021] Preferably, the temperature of the first reduction calcination, the second reduction calcination, the third reduction calcination, the fourth reduction calcination and the fifth reduction calcination are independently 580-620° C., and the time is independently 4-6 hours;

[0022] The heating rates for heating to the temperatures required for the first reduction calcination, the second reduction calcination, the third reduction calcination, the fourth reduction calcination, and the fifth reduction calcination are independently 2.3-2.7° C. / min.

[0023] The present invention also provides the use of the bimetallic supported catalyst described in the above technical solution or the bimetallic supported catalyst prepared by the preparation method described in the above technical solution in the catalytic oxidation of methane.

[0024] The present invention also provides a method for catalytic oxidation of methane, comprising the following steps:

[0025] Methane, oxygen and carbon monoxide are introduced into a mixture of catalyst and water for catalytic oxidation to obtain methanol;

[0026] The catalyst is the bimetallic supported catalyst described in the above technical solution or the bimetallic supported catalyst prepared by the preparation method described in the above technical solution.

[0027] Preferably, the methane partial pressure is 0.5-2 MPa, the oxygen partial pressure is 0.1-0.5 MPa, and the carbon monoxide partial pressure is 0.1-0.5 MPa;

[0028] The reaction temperature of the catalytic oxidation is 120-210° C., and the reaction time is 0.8-1.2 h.

[0029] The present invention provides a bimetallic supported catalyst, comprising a carrier and platinum and iron supported on the carrier; the carrier is an H-Beta molecular sieve, the mass percentage of platinum in the bimetallic supported catalyst is 0.15-0.6wt%, and the mass percentage of iron in the bimetallic supported catalyst is 0.25-1.0wt%. In the present invention, Pt and Fe are spatially adjacent (less than or equal to) on the carrier. ), the combined action of the two (favoring the breaking of the O=O bond in the oxygen molecule and the generation of active oxygen species) promotes the yield and selectivity of methanol production from the catalytic oxidation of methane. Simultaneously, the Fe species inhibits the oxidation of the Pt species. The present invention limits the iron content in the bimetallic supported catalyst to 0.25-1.0 wt%, allowing the Pt-Fe to be spatially close, thereby significantly improving methanol selectivity. Using the bimetallic supported catalyst provided by the present invention for the catalytic oxidation of methane to produce methanol can improve the yield and selectivity of methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 XRD spectra of the catalysts prepared in Examples 1 to 6 and Comparative Examples 1 to 2;

[0031] Figure 2 The UV-visible diffuse reflectance spectra of the catalysts of Example 1 and Comparative Examples 1-2 are shown;

[0032] Figure 3 TEM and EDX images of the catalysts of Example 1 and Comparative Examples 1-2;

[0033] Figure 4 This is the enlarged TEM image of the clusters on the PtFe / Beta (0.3, 0.5) catalyst;

[0034] Figure 5 NH3-TPD results of catalysts with different topological structures prepared in Example 1 and Comparative Examples 6 to 8;

[0035] Figure 6 The XPS spectra of Pt4f and / or Al 2p in the catalysts of Example 1 and Comparative Examples 1-2 and H-Beta molecular sieve;

[0036] Figure 7 The XPS spectra of Fe 2p in the catalysts of Example 1 and Comparative Example 2 are shown;

[0037] Figure 8 The catalysts of Example 1 and Comparative Examples 1 to 2 and H-Beta molecular sieve 1 H NMR spectrum;

[0038] Figure 9This is a ToF-SIMS analysis result diagram of the catalyst PtFe / Beta (0.3, 0.5) in Example 1;

[0039] Figure 10 Comparative graph of the yields and selectivities of methanol, formic acid, and acetic acid prepared by Example 1, Comparative Examples 1-2, and a mixed catalyst of Comparative Example 1 and Comparative Example 2;

[0040] Figure 11 Comparative graph of the yields and selectivities of methanol, formic acid, and acetic acid prepared by catalytic oxidation reactions of the catalysts of Examples 1 to 3;

[0041] Figure 12 This is a comparison chart of the yields and selectivities of methanol, formic acid and acetic acid produced by catalytic oxidation reactions using the catalysts prepared in Comparative Examples 1 and 3 to 5;

[0042] Figure 13 A comparison chart of the yields and selectivities of methanol, formic acid, and acetic acid produced by catalytic oxidation reactions of the catalysts prepared in Examples 1 and Examples 4 to 6 and Pt / Beta (0.3) without additional impregnation and loading of Fe;

[0043] Figure 14 This is a comparison chart of the yields and selectivities of methanol, formic acid, and acetic acid produced by catalytic oxidation reactions using the catalysts prepared in Comparative Examples 1 and 9;

[0044] Figure 15 This is a comparison chart of the yields and selectivities of methanol, formic acid, and acetic acid produced by catalytic oxidation reactions using the catalysts prepared in Example 1 and Comparative Examples 6 to 8;

[0045] Figure 16 This is a comparison chart of the yields and selectivities of methanol, formic acid, and acetic acid produced by the catalytic oxidation reaction of the catalyst in Example 1 at different rotation speeds;

[0046] Figure 17 This is a comparison chart of the yields and selectivities of methanol, formic acid, and acetic acid produced by the catalytic oxidation reaction of the catalyst in Example 1 at different reaction temperatures;

[0047] Figure 18 This is a comparison chart of the yields and selectivities of methanol, formic acid, and acetic acid produced by the catalytic oxidation reaction of the catalyst in Example 1 at different methane partial pressures;

[0048] Figure 19 This is a comparison chart of the yields and selectivities of methanol, formic acid, and acetic acid produced by the catalytic oxidation reaction of the catalyst of Example 1 at different carbon monoxide partial pressures;

[0049] Figure 20 This is a comparison chart of the yields and selectivities of methanol, formic acid, and acetic acid produced by the catalytic oxidation reaction of the catalyst in Example 1 at different oxygen partial pressures;

[0050] Figure 21 This is a comparison chart of the yields and selectivities of methanol, formic acid and acetic acid produced by the catalytic oxidation reaction of the catalyst in Example 1 at different total reaction pressures. DETAILED DESCRIPTION

[0051] The invention provides a bimetallic supported catalyst, comprising a carrier and platinum and iron supported on the carrier.

[0052] In the present invention, the carrier is H-Beta molecular sieve. In the present invention, the H-Beta molecular sieve contains Acid, platinum and iron can replace the molecular sieve The acid sites form catalysts with good catalytic performance.

[0053] In the present invention, the mass percentage of platinum in the bimetallic supported catalyst is 0.15-0.6wt%, and can also be 0.3-0.5wt%, and can specifically be 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.4wt%, 0.5wt% or 0.6wt%; the mass percentage of iron in the bimetallic supported catalyst is 0.25-1.0wt%, and can also be 0.5-0.75wt%, and can specifically be 0.25wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.75wt%, 0.8wt% or 1.0wt%.

[0054] As a specific embodiment of the present invention, the total specific surface area of ​​the bimetallic supported catalyst can be 600 to 700 m 2 / g, which can be specifically 620m 2 / g、640m 2 / g、658.46m 2 / g or 680m 2 / g; the total pore volume can be 0.60~0.70cm 3 / g, specifically 0.62cm 3 / g, 0.65cm 3 / g, 0.66cm 3 / g or 0.68cm 3 / g.

[0055] The present invention also provides a method for preparing the bimetallic supported catalyst described in the above technical solution, including method 1, method 2 or method 3.

[0056] In the present invention, the method 1 comprises the following steps:

[0057] Mixing H-Beta molecular sieve and platinum source aqueous solution, performing a first impregnation and then a first reduction calcination to obtain a first primary catalyst;

[0058] The first primary catalyst and the iron source aqueous solution are mixed, and a second impregnation is performed followed by a second reduction calcination to obtain the bimetallic supported catalyst.

[0059] The present invention mixes H-Beta molecular sieve and platinum source aqueous solution, performs a first impregnation and then performs a first reduction calcination to obtain a first primary catalyst. As a specific embodiment of the present invention, the platinum source in the platinum source aqueous solution may include one or more of PtCl2, PtCl4, H2PtCl6, Pt(NH3)4Cl2, H2Pt(OH)6, Pt(NO3)2, Pt(NH3)4(NO3)2 and Pt(SO3)2, which can be specifically PtCl2, PtCl4, H2PtCl6, Pt(NH3)4Cl2, H2Pt(OH)6, Pt(NO3)2, Pt(NH3)4(NO3)2 or Pt(SO3)2; the mass concentration of platinum element in the platinum source aqueous solution can be 0.15~0.6g / L, specifically 0.15g / L, 0.3g / L, 0.4g / L, 0.45g / L, 0.5g / L or 0.6g / L; the solid-liquid ratio of the H-Beta molecular sieve and the platinum source aqueous solution can be 1g / 8~12mL, specifically 1g / 10mL.

[0060] As a specific embodiment of the present invention, before the first impregnation, the method may further include: subjecting the H-Beta molecular sieve to a vacuum treatment, wherein the vacuum degree of the vacuum treatment may be 0.05 to 0.10 MPa, specifically 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, or 0.10 MPa; and the vacuum treatment time may be 1.8 to 2.2 hours, specifically 2 hours. The present invention can remove adsorbed gas in the pores of the H-Beta molecular sieve through the vacuum treatment, which is conducive to the subsequent sufficient impregnation of the H-Beta molecular sieve with the platinum source aqueous solution.

[0061] As a specific embodiment of the present invention, the first impregnation can be carried out under stirring conditions, and the stirring speed can be 750-850 rpm, and can be specifically 750 rpm, 800 rpm or 850 rpm; the stirring time can be 22-26 h, and can be specifically 22 h, 24 h or 26 h; the stirring temperature can be room temperature, and the room temperature can be 20-35 ° C, and can also be 25-30 ° C.

[0062] As a specific embodiment of the present invention, the first impregnation may further include: grinding the system after the first impregnation to remove the solvent, and performing the first reduction calcination; the solvent removal method may include rotary evaporation and drying in sequence; the temperature of the rotary evaporation may be 65-75°C, specifically 70°C; the present invention has no special limitation on the time of the rotary evaporation, as long as most of the water in the system can be removed. As a specific embodiment of the present invention, the temperature of the drying may be 75-85°C, specifically 80°C; the time of the drying may be 10-14h, specifically 12h. As a specific embodiment of the present invention, the average particle size after grinding is <65 mesh. The present invention is conducive to fully carrying out the first reduction calcination after grinding.

[0063] As a specific embodiment of the present invention, before the first reduction calcination, the process may further include: replacing the apparatus for the first reduction calcination with a reducing atmosphere, wherein the reducing atmosphere may be a mixture of hydrogen and nitrogen, wherein the volume percentage of hydrogen in the mixture of hydrogen and nitrogen may be 4.8-5.2%, and may specifically be 5%; the flow rate of the reducing atmosphere during the replacement process may be 40-80 mL / min, and may specifically be 40 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, or 80 mL / min; and the product of the time for the reduction atmosphere replacement and the flow rate of the reducing atmosphere is at least twice the volume of the apparatus for the first reduction calcination. The present invention can remove air from the apparatus through the reduction atmosphere replacement.

[0064] As a specific embodiment of the present invention, the reducing atmosphere used for the first reduction calcination can be a mixed gas of hydrogen and nitrogen, and the volume percentage of hydrogen in the mixed gas of hydrogen and nitrogen can be 4.8-5.2%, and can be specifically 5%; the temperature of the first reduction calcination can be 580-620°C, and can be specifically 600°C; the time of the first reduction calcination can be 4-6h, and can be specifically 5h; the heating rate for heating to the temperature required for the first reduction calcination can be 2.3-2.7°C / min, and can be specifically 2.5°C / min.

[0065] As a specific embodiment of the present invention, the first reduction calcination may further include: cooling the product after the first reduction calcination to room temperature to obtain the first primary catalyst; the room temperature may be 20-35°C, or 25-30°C; the present invention has no special requirements for the cooling method, as long as it can naturally cool down to the required temperature. In the present invention, the first primary catalyst is an H-Beta molecular sieve loaded with platinum, and the platinum exists in the form of spherical nanocrystals with an average diameter of 0.9-2.2 nm, or 1.4-1.6 nm, and can be specifically in the form of spherical nanocrystals with an average diameter of 1.53 nm; the valence of the platinum is between 0 and +4.

[0066] After obtaining the first primary catalyst, the present invention mixes the first primary catalyst with an iron source aqueous solution, performs a second impregnation, and then performs a second reduction calcination to obtain the bimetallic supported catalyst. As a specific embodiment of the present invention, the iron source in the iron source aqueous solution may include one or more of Fe(NO3)3, Fe(SO4)3, FeCl3, ferrous acetate, and ferric acetylacetonate, and may specifically be Fe(NO3)3, Fe(SO4)3, FeCl3, ferrous acetate, or ferric acetylacetonate; the mass concentration of the iron element in the iron source aqueous solution may be 0.25 to 1 g / L, and may specifically be 0.25 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.75 g / L, 0.8 g / L, or 1 g / L; the solid-to-liquid ratio of the first primary catalyst to the iron source aqueous solution may be 1 g / 8 to 12 mL, and may specifically be 1 g / 10 mL.

[0067] As a specific embodiment of the present invention, before the second impregnation, the first primary catalyst may be subjected to a vacuum treatment. The vacuum degree of the vacuum treatment may be 0.05 to 0.10 MPa, specifically 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, or 0.10 MPa. The vacuum treatment time may be 1.8 to 2.2 hours, specifically 2 hours. The present invention can remove adsorbed gas in the pores of the first primary catalyst through the vacuum treatment, which facilitates the subsequent impregnation of the first primary catalyst with the iron source aqueous solution.

[0068] As a specific embodiment of the present invention, the second impregnation can be carried out under stirring conditions, and the stirring speed can be 750-850 rpm, specifically 750 rpm, 800 rpm or 850 rpm; the stirring time can be 22-26 h, specifically 22 h, 24 h or 26 h; the stirring temperature can be room temperature, and the room temperature can be 20-35 ° C, and can also be 25-30 ° C.

[0069] As a specific embodiment of the present invention, the second impregnation may further include: grinding the system after the second impregnation to remove the solvent, and performing a second reduction calcination; the solvent removal method may include rotary evaporation and drying in sequence; the temperature of the rotary evaporation may be 65-75°C, specifically 70°C; the present invention has no special limitation on the time of the rotary evaporation, as long as most of the water in the system can be removed. As a specific embodiment of the present invention, the temperature of the drying may be 75-85°C, specifically 80°C; the time of the drying may be 10-14h, specifically 12h. As a specific embodiment of the present invention, the average particle size after grinding is <65 mesh. The present invention is conducive to fully carrying out the second reduction calcination after grinding.

[0070] As a specific embodiment of the present invention, before the second reduction calcination, the process may further include: replacing the apparatus for the second reduction calcination with a reducing atmosphere, wherein the reducing atmosphere may be a mixture of hydrogen and nitrogen, wherein the volume percentage of hydrogen in the mixture of hydrogen and nitrogen may be 4.8-5.2%, and may be specifically 5%; the flow rate of the reducing atmosphere during the replacement process may be 40-80 mL / min, and may be specifically 40 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, or 80 mL / min; and the product of the time for the reduction atmosphere replacement and the flow rate of the reducing atmosphere is at least twice the volume of the apparatus for the first reduction calcination. The present invention can remove air from the apparatus through the reduction atmosphere replacement.

[0071] As a specific embodiment of the present invention, the reducing atmosphere used for the second reduction calcination can be a mixed gas of hydrogen and nitrogen, and the volume percentage of hydrogen in the mixed gas of hydrogen and nitrogen can be 4.8-5.2%, and can be specifically 5%; the temperature of the second reduction calcination can be 580-620°C, and can be specifically 600°C; the time of the second reduction calcination can be 4-6h, and can be specifically 5h; the heating rate for heating to the temperature required for the second reduction calcination can be 2.3-2.7°C / min, and can be specifically 2.5°C / min.

[0072] As a specific embodiment of the present invention, the second reduction calcination may further include: cooling the product after the second reduction calcination to room temperature to obtain the bimetallic supported catalyst; the room temperature may be 20-35°C, or 25-30°C; the present invention has no special requirements for the cooling method, as long as the temperature can be reduced to the required temperature. In the present invention, the bimetallic supported catalyst is an H-Beta molecular sieve loaded with platinum and iron, the platinum exists in the form of nanocrystals with an average diameter of 0.9-2.2nm, or 1.4-1.6nm (specifically 1.53nm), and the valence of the platinum is between 0 and +4; the iron is uniformly dispersed in the H-Beta molecular sieve in the form of +3 valence.

[0073] In the present invention, the method 2 comprises the following steps:

[0074] Mixing the H-Beta molecular sieve and the iron source aqueous solution, performing a third impregnation and then a third reduction calcination to obtain a second primary catalyst;

[0075] The second primary catalyst and the platinum source aqueous solution are mixed, and a fourth impregnation is performed followed by a fourth reduction calcination to obtain the bimetallic supported catalyst.

[0076] In the present invention, the conditions and parameters of method 2 are basically the same as those of method 1, except that the order of impregnation is that in method 1, the primary catalyst is first impregnated in a platinum source aqueous solution and then impregnated in an iron source aqueous solution, while in method 2, the primary catalyst is first impregnated in an iron source aqueous solution and then impregnated in a platinum source aqueous solution. In the present invention, method 2 is carried out with reference to method 1 and will not be repeated here.

[0077] In the present invention, the method 3 comprises the following steps:

[0078] dissolving an iron source and a platinum source in water to obtain a composite aqueous solution;

[0079] The composite aqueous solution and H-Beta molecular sieve are mixed, and a fifth impregnation is performed followed by a fifth reduction calcination to obtain the bimetallic supported catalyst.

[0080] The present invention dissolves an iron source and a platinum source in water to obtain a composite aqueous solution. As a specific embodiment of the present invention, the platinum source may include one or more of PtCl2, PtCl4, H2PtCl6, Pt(NH3)4Cl2, H2Pt(OH)6, Pt(NO3)2, Pt(NH3)4(NO3)2, and Pt(SO3)2, and may specifically be PtCl2, PtCl4, H2PtCl6, Pt(NH3)4Cl2, H2Pt(OH)6, Pt(NO3)2, Pt(NH3)4(NO3)2, or Pt(SO3)2; the iron source may include one or more of Fe(NO3)3, Fe(SO4)3, FeCl3, ferric acetate, and ferric acetylacetonate, and may specifically be Fe(NO3)3, Fe(SO4)3, FeCl3, ferric acetate, or ferric acetylacetonate. As a specific embodiment of the present invention, the mass concentration of iron element in the composite aqueous solution can be 0.25-1 g / L, specifically 0.25 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.75 g / L, and 1 g / L; the mass concentration of platinum element in the composite aqueous solution can be 0.15-0.6 g / L, specifically 0.15 g / L, 0.3 g / L, 0.4 g / L, 0.45 g / L, 0.5 g / L or 0.6 g / L; the solid-liquid ratio of the H-Beta molecular sieve and the composite aqueous solution can be 1 g / 8-12 mL, specifically 1 g / 10 mL.

[0081] The present invention has no special requirements for the dissolution, as long as it can be completely dissolved.

[0082] After obtaining the composite aqueous solution, the present invention mixes the composite aqueous solution and H-Beta molecular sieve for a fifth impregnation and then performs a fifth reduction calcination to obtain the bimetallic supported catalyst. As a specific embodiment of the present invention, the fifth impregnation may also include: vacuuming the H-Beta molecular sieve, and the vacuum degree of the vacuum treatment may be 0.05 to 0.10 MPa, specifically 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa or 0.10 MPa; the time of the vacuum treatment may be 1.8 to 2.2 hours, specifically 2 hours. The present invention can remove the adsorbed gas in the pores of the H-Beta molecular sieve through the vacuum treatment, which is conducive to the subsequent full impregnation of the H-Beta molecular sieve with the composite aqueous solution.

[0083] As a specific embodiment of the present invention, the fifth impregnation can be carried out under stirring conditions, and the stirring speed can be 750-850rpm, specifically 750rpm, 800rpm or 850rpm; the stirring time can be 22-26h, specifically 22h, 24h or 26h; the stirring temperature can be room temperature, and the room temperature can be 20-35°C, and can also be 25-30°C.

[0084] As a specific embodiment of the present invention, the fifth impregnation may further include: grinding the system after the fifth impregnation to remove the solvent, and performing the fifth reduction calcination; the solvent removal method may include rotary evaporation and drying in sequence; the temperature of the rotary evaporation may be 65-75°C, specifically 70°C; the present invention has no special limitation on the time of the rotary evaporation, as long as most of the water in the system can be removed. As a specific embodiment of the present invention, the temperature of the drying may be 75-85°C, specifically 80°C; the time of the drying may be 10-14h, specifically 12h. As a specific embodiment of the present invention, the average particle size after grinding is <65 mesh. The present invention is conducive to fully carrying out the fifth reduction calcination after grinding.

[0085] As a specific embodiment of the present invention, before the fifth reduction calcination, the process may further include: replacing the apparatus for the fifth reduction calcination with a reducing atmosphere, wherein the reducing atmosphere may be a mixture of hydrogen and nitrogen, wherein the volume percentage of hydrogen in the mixture of hydrogen and nitrogen may be 4.8-5.2%, and may specifically be 5%; the flow rate of the reducing atmosphere during the replacement process may be 40-80 mL / min, and may specifically be 40 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, or 80 mL / min; and the product of the time for the reducing atmosphere replacement and the reducing atmosphere flow rate is at least twice the volume of the apparatus for the first reduction calcination. The present invention can remove air from the apparatus by replacing the reducing atmosphere.

[0086] As a specific embodiment of the present invention, the reducing atmosphere used for the fifth reduction calcination can be a mixed gas of hydrogen and nitrogen, and the volume percentage of hydrogen in the mixed gas of hydrogen and nitrogen can be 4.8-5.2%, specifically 5%; the temperature of the fifth reduction calcination can be 580-620°C, specifically 600°C, and the time of the fifth reduction calcination can be 4-6h, specifically 5h; the heating rate for heating to the temperature required for the fifth reduction calcination can be 2.3-2.7°C / min, specifically 2.5°C / min.

[0087] As a specific embodiment of the present invention, the fifth reduction calcination may further include: cooling the product after the fifth reduction calcination to room temperature to obtain the bimetallic supported catalyst; the room temperature may be 20-35°C, or 25-30°C; the present invention has no special requirements for the cooling method, as long as the temperature can be reduced to the required temperature.

[0088] In the present invention, the condition parameters of method 3 are basically the same as those of method 1, except that the platinum source and the iron source are mixed and impregnated in one step.

[0089] The present invention also provides the use of the bimetallic supported catalyst described in the above technical solution or the bimetallic supported catalyst prepared by the preparation method described in the above technical solution in the catalytic oxidation of methane. In the present invention, the bimetallic supported catalyst can be used to catalytically oxidize methane to produce methanol.

[0090] The present invention also provides a method for catalytic oxidation of methane, comprising the following steps:

[0091] Methane, oxygen and carbon monoxide are introduced into a mixture of catalyst and water for catalytic oxidation to obtain methanol;

[0092] The catalyst is the bimetallic supported catalyst described in the above technical solution or the bimetallic supported catalyst prepared by the preparation method described in the above technical solution.

[0093] As a specific embodiment of the present invention, the total pressure of the catalytic oxidation reaction can be 1.35-5.4 MPa, specifically 1.35 MPa, 2.7 MPa or 5.4 MPa; the partial pressure of methane can be 0.5-2 MPa, specifically 0.5 MPa, 1 MPa, 1.5 MPa or 2 MPa; the partial pressure of oxygen can be 0.1-0.5 MPa, specifically 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MP or 0.5 MP; the partial pressure of carbon monoxide can be 0.1-0.5 MPa, specifically 0.1 MPa, 0.3 MP or 0.5 MP; the temperature of the catalytic oxidation can be 120-210°C, specifically 120°C, 150°C, 180°C or 210°C; the time of the catalytic oxidation can be 0.8-1.2 h, specifically 1 h.

[0094] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0095] In the examples, the values ​​in brackets in the catalyst abbreviations are the mass percentages of the preceding loaded elements. For example, PtFe / Beta(0.3,0.5) means that Pt and Fe are loaded sequentially, and the loading amounts of Pt and Fe (as a percentage of the mass of the bimetallic supported catalyst) are 0.3 wt% and 0.5 wt%, respectively; FePt / Beta(0.5,0.3) means that Fe and Pt are loaded sequentially, and the loading amounts of Fe and Pt are 0.5 wt% and 0.3 wt%, respectively; (PtFe) / Beta(0.3,0.5) means that Pt and Fe are loaded simultaneously (one-step impregnation), and the loading amounts of Pt and Fe are 0.3 wt% and 0.5 wt%, respectively.

[0096] Example 1

[0097] Prepare an H2PtCl6 aqueous solution with a Pt element mass concentration of 0.3 g / L, weigh 1 g of H-Beta molecular sieve and place it in a 100 mL pear-shaped flask, place a magnetic stirrer and seal it with a rubber stopper, and evacuate (vacuum degree is 0.08 MPa) for 2 h. Use a pipette to transfer 10 mL of H2PtCl6 aqueous solution with a Pt mass concentration of 0.3 g / L into the pear-shaped flask after vacuum treatment. Stir for 24 h at room temperature (25 ° C) to complete the first impregnation at a stirring rate of 800 rpm; the impregnated system is subjected to rotary evaporation at 70 ° C to remove most of the water and then placed in an 80 ° C oven for further drying for 12 h; the dried product is ground to an average particle size of < After 65 mesh, it was transferred to a corundum boat, placed in a tubular furnace with a volume of 7L, sealed, and passed through 60mL / min of H2 / N2 (hydrogen volume content of 5%) mixed gas for 4 hours. The purpose was to replace the air in the tubular furnace to avoid danger caused by air and hydrogen under heating conditions; after completion of the replacement, the flow rate of H2 / N2 (5%) mixed gas was adjusted to 20mL / min, and the temperature was increased to 600℃ at a heating rate of 2.5℃ / min. After the first reduction calcination for 5 hours, it was naturally cooled to room temperature (25℃) to obtain the primary catalyst Pt / Beta (0.3).

[0098] Prepare an FeCl3 aqueous solution with an Fe element mass concentration of 0.5 g / L, place 1 g of Pt / Beta (0.3) catalyst in a pear-shaped bottle, put in a magnetic stirrer and seal it with a rubber stopper, perform vacuum treatment (vacuum degree is 0.08 MPa) for 2 hours, use a pipette to transfer 10 mL of FeCl3 aqueous solution with an Fe mass concentration of 0.5 g / L into the pear-shaped bottle, stir for 24 hours at room temperature (25 ° C) to complete the second impregnation, and the stirring rate is 800 rpm; the impregnated system is rotary evaporated at 70 ° C, and after removing most of the water, it is placed in an 80 ° C oven for further drying for 12 hours; the dried product is ground After grinding to an average particle size of <65 mesh, it was transferred to a corundum boat and placed in a 7L tubular furnace. After sealing, 60mL / min of H2 / N2 (hydrogen volume content of 5%) mixed gas was introduced for 4 hours. The purpose was to replace the air in the tubular furnace to avoid the danger of air and hydrogen under heating conditions. After the replacement was completed, the flow rate of H2 / N2 (5%) mixed gas was adjusted to 20mL / min, and the temperature was increased to 600℃ at a heating rate of 2.5℃ / min. After the second reduction calcination for 5 hours, it was naturally cooled to room temperature (25℃) to obtain a bimetallic supported catalyst PtFe / Beta (0.3, 0.5).

[0099] Example 2

[0100] A bimetallic supported catalyst was prepared according to the method of Example 1, except that the impregnation order was adjusted, first impregnating with FeCl3 aqueous solution and then impregnating with H2PtCl6 aqueous solution. The obtained bimetallic supported catalyst was recorded as FePt / Beta (0.5, 0.3).

[0101] Example 3

[0102] A bimetallic supported catalyst was prepared according to the method of Example 1, except that the two-step impregnation was adjusted to a one-step impregnation. The specific process was as follows: H2PtCl6 and FeCl3 were dissolved in deionized water to obtain a composite aqueous solution of H2PtCl6 and FeCl3 with a Pt element mass concentration of 0.3 g / L and an Fe element mass concentration of 0.5 g / L;

[0103] Weigh 1g H-Beta molecular sieve and place it in a 100mL pear-shaped bottle, put in a magnetic stirrer and seal it with a rubber stopper, vacuumize it (vacuum degree is 0.08MPa) for 2h, use a pipette to transfer 10mL of the composite aqueous solution into the pear-shaped bottle after vacuum treatment and stir it for 24h at room temperature (25℃) to complete the fifth impregnation, with a stirring rate of 800rpm; the impregnated system is rotary evaporated at 70℃ to remove most of the water and then placed in an 80℃ oven for further drying for 12h; the dried product is ground to an average particle size of <65 mesh and then transferred to a corundum boat and placed in a body A tubular furnace with a volume of 7 L was sealed and introduced with a flow rate of 60 mL / min of H2 / N2 (hydrogen volume content of 5%) for 4 hours. The purpose was to replace the air in the tubular furnace to avoid danger from air and hydrogen under heating conditions. After the replacement was completed, the flow rate of the H2 / N2 (5%) mixed gas was adjusted to 20 mL / min, and the temperature was raised to 600°C at a heating rate of 2.5°C / min. After the fifth reduction calcination for 5 hours, it was naturally cooled to room temperature (25°C) to obtain a bimetallic supported catalyst (PtFe) / Beta (0.3, 0.5).

[0104] Example 4

[0105] A bimetallic supported catalyst was prepared according to the method of Example 1, except that the Fe loading amount was adjusted, specifically, the concentration of the FeCl3 aqueous solution was adjusted from 0.5 g / L to 1 g / L. The obtained bimetallic supported catalyst was recorded as PtFe / Beta (0.3, 1.0).

[0106] Example 5

[0107] A bimetallic supported catalyst was prepared according to the method of Example 1, except that the Fe loading amount was adjusted, specifically, the concentration of the FeCl3 aqueous solution was adjusted from 0.5 g / L to 0.75 g / L. The obtained bimetallic supported catalyst was recorded as PtFe / Beta (0.3, 0.75).

[0108] Example 6

[0109] A bimetallic supported catalyst was prepared according to the method of Example 1, except that the Fe loading amount was adjusted, specifically, the concentration of the FeCl3 aqueous solution was adjusted from 0.5 g / L to 0.25 g / L. The obtained bimetallic supported catalyst was recorded as PtFe / Beta (0.3, 0.25).

[0110] Comparative Example 1

[0111] The primary catalyst Pt / Beta (0.3) prepared in Example 1 was used as a comparative example, and its preparation method was specifically as follows:

[0112] Prepare an H2PtCl6 aqueous solution with a Pt mass concentration of 0.3 g / L, weigh 1 g of H-Beta molecular sieve and place it in a 100 mL pear-shaped bottle, put in a magnetic stirrer and seal it with a rubber stopper, vacuumize it (vacuum degree is 0.08 MPa) for 2 h, and pipette 10 mL An H2PtCl6 aqueous solution with a Pt mass concentration of 0.3 g / L was placed in a pear-shaped bottle after vacuum treatment and stirred at room temperature (25°C) for 24 hours to complete impregnation at a stirring rate of 800 rpm; the impregnated system was rotary evaporated at 70°C to remove most of the water and then placed in an 80°C oven for further drying for 12 hours; the dried product was ground to an average particle size of <65 mesh and then transferred to a corundum boat, placed in a tubular furnace with a volume of 7L, sealed and passed through a 60 mL / min H2 / N2 (hydrogen volume content of 5%) mixed gas for 4 hours to replace the air in the tubular furnace and avoid the danger of air and hydrogen under heating conditions; after completion of the replacement, the flow rate of the H2 / N2 (5%) mixed gas was adjusted to 20 mL / min, and the temperature was increased to 600°C at a heating rate of 2.5°C / min, and then naturally cooled to room temperature (25°C) for reduction calcination for 5 hours to obtain the catalyst Pt / Beta (0.3).

[0113] Comparative Example 2

[0114] The primary catalyst Fe / Beta (0.5) prepared in Example 2 was used as a comparative example, and its preparation method was specifically as follows:

[0115] Prepare an FeCl3 aqueous solution with an Fe mass concentration of 0.5 g / L, weigh 1 g of H-Beta molecular sieve and place it in a 100 mL pear-shaped bottle, put in a magnetic stirrer and seal it with a rubber stopper, and perform vacuum treatment (vacuum degree is 0.08 MPa) for 2 hours, use a pipette to transfer 10 mL of FeCl3 aqueous solution with an Fe mass concentration of 0.5 g / L and place it in the pear-shaped bottle, stir for 24 hours at room temperature (25 ° C) to complete the impregnation, and the stirring rate is 800 rpm; the impregnated system is rotary evaporated at 70 ° C, and after removing most of the water, it is placed in an 80 ° C oven and continued to dry for 12 hours; the dried product is ground to an average particle size of <65 The mixture was then transferred to a corundum boat, placed in a 7L tubular furnace, sealed, and introduced with a 60mL / min H2 / N2 (H2 volume content of 5%) mixed gas for 4 hours to replace the air in the tubular furnace and avoid danger from air and hydrogen under heating conditions. After the replacement was completed, the flow rate of the H2 / N2 (5%) mixed gas was adjusted to 20mL / min, and the temperature was increased to 600°C at a heating rate of 2.5°C / min. After reduction calcination for 5 hours, the mixture was naturally cooled to room temperature (25°C) to obtain the catalyst Fe / Beta (0.5).

[0116] Comparative Example 3

[0117] The catalyst was prepared according to the method of Comparative Example 1, except that the Pt loading was adjusted, specifically, the concentration of the H2PtCl6 aqueous solution was adjusted from 0.3 g / L to 0.6 g / L. The obtained catalyst was recorded as Pt / Beta (0.6).

[0118] Comparative Example 4

[0119] The catalyst was prepared according to the method of Comparative Example 1, except that the Pt loading was adjusted, specifically, the concentration of the H2PtCl6 aqueous solution was adjusted from 0.3 g / L to 0.45 g / L. The obtained catalyst was recorded as Pt / Beta (0.45).

[0120] Comparative Example 5

[0121] The catalyst was prepared according to the method of Comparative Example 1, except that the Pt loading was adjusted, specifically, the concentration of the H2PtCl6 aqueous solution was adjusted from 0.3 g / L to 0.15 g / L. The obtained catalyst was recorded as Pt / Beta (0.15).

[0122] Comparative Example 6

[0123] The catalyst was prepared according to the method of Example 1, except that H-Beta was replaced with H-ZSM-5. The prepared catalyst was recorded as PtFe / ZSM-5 (0.3, 0.5).

[0124] Comparative Example 7

[0125] The catalyst was prepared according to the method of Example 1, except that H-Beta was changed to H-SSZ-13. The prepared catalyst was recorded as PtFe / SSZ-13 (0.3, 0.5).

[0126] Comparative Example 8

[0127] A catalyst was prepared according to the method of Example 1, except that H-Beta was adjusted to H-MOR. The prepared catalyst was recorded as PtFe / MOR (0.3, 0.5).

[0128] Comparative Example 9

[0129] The catalysts were prepared according to the method of Comparative Example 1, except that H-Beta was adjusted to H-ZSM-5, H-SSZ-13, and H-MOR, respectively. The prepared catalysts were respectively recorded as Pt / ZSM-5 (0.3) catalyst, Pt / SSZ-13 (0.3) catalyst, and Pt / MOR (0.3) catalyst.

[0130] The specific surface area and pore volume of the H-Beta molecular sieve and the catalysts prepared in Example 1 and Comparative Examples 1-2 were tested, and the results are listed in Table 1.

[0131] Table 1 Physical and chemical properties of the catalysts and H-Beta molecular sieves prepared in Example 1 and Comparative Example 1

[0132]

[0133] a S BET =BET specific surface area;

[0134] b Calculated using the t-plot method; c Total pore volume, value at 0.99P / P0; d The element contents in the catalyst samples were determined by ICP-OES.

[0135] The test results in Table 1 show that the specific surface area, micropore specific surface area, total pore volume, and micropore volume of the PtFe / Beta catalyst all show a certain degree of decrease compared to the H-Beta molecular sieve support. This is due to the incorporation of some metal species into the molecular sieve pores. Quantitative analysis of Pt and Fe in the catalyst using inductively coupled plasma optical emission spectroscopy indicates that the unloaded H-Beta contains a trace amount of Fe (0.02 wt%), an impurity introduced during the synthesis process. The actual metal loadings in the PtFe / Beta catalyst (Pt: 0.30 wt%; Fe: 0.51 wt%) are very close to the theoretical loadings (Pt: 0.3 wt%; Fe: 0.5 wt%), indicating successful Pt and Fe loading.

[0136] The catalysts prepared in Examples 1 to 6 and Comparative Examples 1 to 5 were subjected to X-ray diffraction detection, and the XRD spectra were as follows: Figure 1 As shown. Figure 1 It can be seen that only the characteristic peaks of the BEA topological structure of the H-Beta molecular sieve itself were observed in the catalysts with different loading sequences and different Pt and Fe loading amounts, and no signals of any phases containing Pt and Fe elements were generated, indicating that the Pt and Fe elements were well dispersed or the formed grain size was lower than the instrument detection limit.

[0137] The catalysts prepared in Example 1 and Comparative Examples 1-2 were subjected to UV-Vis diffuse reflectance spectroscopy (DR UV-Vis) detection in the range of 200-800 nm, and the UV-Vis diffuse reflectance spectra were as follows: Figure 2 As shown. Figure 2 It can be seen that there is an absorption peak at 280 nm in both the Fe / Beta (0.5) catalyst and the PtFe / Beta (0.3, 0.5) catalyst, which is attributed to the isolated hexacoordinated octahedral Fe 3+The Pt / Beta (0.3) and PtFe / Beta (0.3, 0.5) catalysts have a broad absorption band at approximately 400-800 nm, which is related to the presence of Pt species.

[0138] The catalysts prepared in Example 1 and Comparative Examples 1-2 were examined by transmission electron microscopy, and the TEM images were as follows: Figure 3 As shown. Figure 3 It can be observed that the molecular sieve pore structure is clearly visible on the Fe / Beta (0.5) support, indicating that the selected Beta molecular sieve has a high degree of crystallinity, which is consistent with the XRD test results. In addition, no obvious clusters are observed, indicating that the Fe element in the Fe / Beta (0.5) catalyst has a good dispersion, which is consistent with the DR UV-Vis results. In addition to the molecular sieve pore structure, many white bright spots are also observed in Pt / Beta (0.3) and PtFe / Beta (0.3,0.5). Combined with the electron microscope signal intensity and the square of the atomic number (Z 2 ), these bright spots are attributed to Pt nanoclusters. The particle size of the clusters on the Pt / Beta(0.3) catalyst and the PtFe / Beta(0.3,0.5) catalyst was statistically analyzed. The average particle size of the particles on the Pt / Beta(0.3) catalyst was 1.47nm, while the average particle size of the particles on the PtFe / Beta(0.3,0.5) catalyst was 1.53nm. It can be concluded that the introduction of Fe species has no significant effect on the dispersion of Pt species. EDX results of Fe / Beta(0.5), Pt / Beta(0.3) and PtFe / Beta(0.3,0.5) catalysts ( Figure 3 The images (below) show that Fe is well dispersed on the Fe / Beta (0.5) and PtFe / Beta (0.3, 0.5) catalysts, with no significant agglomeration observed. However, Pt is clearly agglomerated on the Pt / Beta (0.3) and PtFe / Beta (0.3, 0.5) catalysts. The locations of the Pt elements correspond to the white bright spots in the HAADF-STEM images, further confirming that these bright spots are Pt nanoclusters. Fe signals are observed near Pt aggregations on the PtFe / Beta catalyst, indicating that some Fe and Pt species are spatially close.

[0139] The PtFe / Beta (0.3, 0.5) catalyst was analyzed at a high rate. Figure 4 As shown, there are clearly visible lattice fringes. The measurement shows that the lattice fringes spacing is 0.23nm, which is consistent with the (111) crystal plane of the face-centered cubic structure of Pt crystal, preliminarily confirming that these bright spots are Pt nanoclusters.

[0140] Ammonia temperature programmed desorption experiment (NH3-TPD) was conducted on the catalysts with different topological structures prepared in Example 1 and Comparative Examples 6 to 8, and the NH3-TPD results were as follows: Figure 5 As shown. Figure 5 All four catalysts exhibit a sharp desorption peak around 200°C, a signal associated with the weak acid in the zeolite. A broad peak is observed above 400°C for the PtFe / ZSM-5 (0.3, 0.5) catalyst, the PtFe / SSZ-13 (0.3, 0.5) catalyst, and the PtFe / MOR (0.3, 0.5) catalyst, associated with the strong acid in the zeolite. However, no significant signal is observed for the PtFe / Beta catalyst at the same position, indicating that the PtFe / Beta catalyst contains no strong acid or only a very small amount. The application test results shown below indicate that the PtFe / Beta (0.3, 0.5) catalyst exhibits the highest reactivity compared to the PtFe / ZSM-5 (0.3, 0.5), PtFe / SSZ-13 (0.3, 0.5), and PtFe / MOR (0.3, 0.5) catalysts, indicating that the strong acid in the zeolite framework is detrimental to the reaction.

[0141] X-ray photoelectron spectroscopy (XPS): X-ray photoelectron spectroscopy was used to measure the Pt, Fe and Al on the catalyst surfaces of Example 1, Comparative Examples 1-2 and H-BETA to explore the elemental composition and valence state of the catalyst surface; the XPS spectra obtained are shown in FIG. Figure 6 and Figure 7 shown. Figure 6 The XPS spectra of Pt4f and Al 2p in the catalyst are shown in Figure 2. Figure 6 The data were subjected to peak fitting. The fitting results of Pt 4f in Pt / Beta (0.3) and PtFe / Beta (0.3, 0.5) catalysts showed that there were two valence states of Pt species in the catalysts, namely Pt 2+ and Pt 0 The ratio of different species was calculated using the peak area. The results are shown in Table 2. Compared with the Pt / Beta (0.3) catalyst, the Pt in the PtFe / Beta (0.3, 0.5) catalyst is 2+ The decrease in species content is due to the partial coverage of Pt clusters by the introduction of Fe species, which inhibits the growth of Pt 0 Oxidation of species.

[0142] Figure 7 The XPS spectra of Fe 2p of Fe / Beta(0.5) and PtFe / Beta(0.3,0.5) catalysts are shown in Figure 2. The data were fitted by peak separation. The results show that the valence state of Fe in the catalyst is +3 and there are two forms: Fe 3+-OM (M=Si, Al, Fe, 711.9, 725.2eV) and Fe 3+ -(OH) x (715.3, 728.9 eV). In addition, a weak Fe 3+ The existence of satellite peaks is related to the aggregation of Fe elements.

[0143] The catalysts of Example 1 and Comparative Examples 1-2 and H-BETA catalyst were subjected to solid state nuclear magnetic resonance 1 H spectrum detection, solid nuclear magnetic 1 H spectrum, such as Figure 8 Based on Figure 8 and Figure 9 The XPS signal of Al 2p was fitted into two species: Al-OM (M = Si, Fe, 75.1eV) and -Al-OH (76.3eV). By calculating the ratio of the two species, it was found that the -Al-OH signal decreased significantly after the introduction of Fe (Pt / Beta (0.3) 31.5% vs PtFe / Beta (0.3, 0.5) 15.6%; H-Beta 33.63% vs Fe / Beta (0.5)

[0144] 11.18%), indicating that Fe species reacted with -Al-OH.

[0145] Table 2 The ratio of different Pt and Al species in the catalyst.

[0146]

[0147] The PtFe / Beta (0.3, 0.5) catalyst was analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) to explore the atomic bonding mode in the catalyst. The results are as follows Figure 9 As shown in the figure, * indicates that one Fe atom in the fragment is replaced by two Si atoms (1Fe m / z=55.935; 2Si m / z=55.965). + The presence of fragments indicates that Pt is aggregated on the catalyst, which is consistent with the TEM results. + 、PtO2 + The presence of fragments indicates that some Pt ​​exists in an oxidized form. + The fragments indicate the presence of mononuclear Fe species in the catalyst, while Fe2O2 + 、Fe3O3 + The fragments indicate that some Fe species in the catalyst are Fe x O y In addition, SiOAlFe+ 、SiO2AlFe + fragments, indicating that the monodispersed Fe species are anchored on the molecular sieve framework and interact with the molecular sieve framework. It is worth noting that PtFe was also detected in the PtFe / Beta catalyst. + The fragments indicate that some Pt ​​species and Fe species are located adjacent to each other on the support.

[0148] Application Example 1

[0149] 30 mg of the catalyst prepared in each embodiment and comparative example was weighed and placed in a high-pressure reactor. A magnetic stirrer and 20 mL of deionized water were added, and the reactor was tightened and sealed with a wrench. Methane gas was filled into the reactor to 2.0 MPa, and then evacuated to replace the air in the reactor. The replacement operation was repeated twice. Methane (2 MPa), oxygen (0.2 MPa), and carbon monoxide (0.5 MPa) at the required pressures were filled, stirring was started (1000 rpm), the temperature was raised to the target reaction temperature (150 ° C), and the timing was started after the temperature was reached. The catalytic oxidation reaction was carried out for 1 hour. After the reaction was completed, the reactor was removed from the heating jacket and cooled to room temperature (25 ° C) with an electric fan. After cooling, the reacted gas was collected using an air bag and quantitatively analyzed using a gas chromatograph. The chromatographic column model used was a TDX-01 packed column. The solid-liquid mixture after the reaction was collected and centrifuged, 0.4 mL of the supernatant was accurately transferred to a nuclear magnetic resonance tube using a pipette, and 0.1 mL of D2O (containing 0.02 wt% DSS) was added, and quantitative analysis was performed using a liquid nuclear magnetic resonance spectrometer.

[0150] Figure 10 The following is a comparison of the yields and selectivities of methanol, formic acid, and acetic acid prepared by Example 1 (PtFe / Beta(0.3,0.5)), Comparative Example 1 (Pt / Beta(0.3)), Comparative Example 2 (Fe / Beta(0.5)), and the mixed catalyst of Comparative Example 1 and Comparative Example 2 (Fe / Beta(0.5)+Pt / Beta(0.3)); wherein the total mass of the mixed catalyst is 60 mg, including 30 mg of Pt / Beta(0.3) and 30 mg of Fe / Beta(0.5). Figure 10 It can be seen that after the Fe / Beta (0.5) catalytic oxidation reaction, three liquid products, CH3OH, HCOOH, and CH3COOH, were detected, with yields of 27.5, 12.6, and 13.1 μmol·g, respectively. cat -1 ·h -1, indicating that Fe has a very weak ability to activate O2, with methanol selectivity in the liquid phase being 51.6%. In addition, CO2 was detected in the gas after the reaction. Using a Pt / Beta (0.3) catalyst for methane oxidation under the same reaction conditions, the liquid products were still CH3OH, HCOOH, and CH3COOH, with yields of 156.0, 102.0, and 17.6 μmol·g, respectively. cat -1 ·h -1 The selectivity of CH3OH was 56.0%. Under the same reaction conditions, the yields of CH3OH, HCOOH, and CH3COOH were 405.3, 56.0, and 20.1 μmol·g, respectively, using PtFe / Beta (0.3, 0.5) as the catalyst. cat -1 ·h -1 , with a CH3OH selectivity of 84.2%. Experimental results show that, compared with Pt / Beta, the introduction of Fe significantly improves the CH3OH yield of the PtFe / Beta bimetallic catalyst, while reducing the HCOOH yield to half of its original value and slightly decreasing the CH3COOH yield. The significant increase in methanol yield and the change in product selectivity suggest a synergistic effect between Fe and Pt in the PtFe / Beta catalyst.

[0151] When the Pt / Beta+Fe / Beta composite catalyst was used to catalyze oxidation reactions under the same reaction conditions, the yields of the three main products obtained were roughly equivalent to the sum of the yields of the Pt / Beta and Fe / Beta catalysts reacting separately, and the product selectivity did not change significantly. This indicates that even if Fe species and Pt species are simultaneously present in the reaction system, if their spatial positions are far apart, they can only act separately in the reaction and cannot produce an effective synergistic effect.

[0152] Figure 11 Table 3 shows a comparison of the yields and selectivities of methanol, formic acid, and acetic acid obtained by catalytic oxidation reactions using the catalysts of Example 1 (PtFe / Beta(0.3,0.5)), Example 2 (FePt / Beta(0.5,0.3)), and Example 3 ((PtFe) / Beta(0.3,0.5)). The yields and selectivities of catalysts with different impregnation sequences were investigated, and the specific results are listed in Table 3.

[0153] Table 3 Yield and selectivity of catalytic oxidation reaction of catalysts in Examples 1 to 3

[0154]

[0155] From Table 3 and Figure 11It can be seen that the yields of the three catalysts show different differences, and the PtFe / Beta catalyst shows the highest yield. There is no significant difference in the product selectivity of the three catalysts; this shows that anchoring Pt on the molecular sieve first and then introducing Fe can form a more active catalytic site.

[0156] The bimetallic supported catalysts with different iron loadings (Examples 1, 4-6) and the monometallic supported catalysts with different platinum loadings (Comparative Examples 1, 3-5) were subjected to catalytic oxidation reactions. The yields and selectivities of the synthesized products are listed in Table 4.

[0157] Table 4 Yield and selectivity of catalytic oxidation reaction of catalysts in Example 2 and Examples 7 to 9

[0158]

[0159]

[0160] Figure 12 This is a comparison chart of the yields and selectivities of methanol, formic acid and acetic acid produced by catalytic oxidation reactions using the catalysts prepared in Comparative Examples 1 and 3 to 5. Figure 13 The graph is a comparison of the yields and selectivities of methanol, formic acid and acetic acid produced by the catalytic oxidation reaction of the catalysts prepared in Examples 1 and Examples 4 to 6 and Pt / Beta (0.3) without additional impregnation and loading of Fe (Comparative Example 1).

[0161] From Table 4 and Figure 12 It can be seen that when the Pt loading of the single-metal supported catalyst increases from 0.15wt% to 0.3wt%, the yield of oxygenates increases accordingly. When the Pt loading increases from 0.3wt% to 0.45wt%, the yield does not change significantly. However, when the Pt loading is further increased from 0.45wt%, both the yield and methanol selectivity decrease slightly. This indicates that when the Pt loading is greater than 0.3wt%, further increasing the loading leads to reduced Pt dispersion, which cannot provide more reactive sites, and the catalytic performance is no longer improved.

[0162] Different loading amounts of Fe were introduced into the Pt / Beta (0.3) catalyst to synthesize PtFe / Beta catalysts with Fe loading amounts of 0.25 to 1 wt%. Catalytic tests were carried out under the same reaction conditions. The results are shown in Figure 2. Figure 13 As shown. The H-Beta molecular sieve carrier contains 0.02wt% Fe element, which may be an impurity introduced during the production process. Figure 3-4 The data of 0.02 wt% Fe in the catalyst are derived from the Pt / Beta (0.3) catalyst without additional impregnation of Fe (Comparative Example 1). Figure 13It can be seen that when the Fe loading is 0.25wt%, the yields of the three liquid products are all improved compared with the Pt / Beta (0.3) catalyst, but the product selectivity has not changed significantly. When the Fe loading is increased to 0.5wt%, the yield of CH3OH is further improved, while the production of HCOOH is significantly inhibited, and the selectivity of CH3OH is increased from 52.6% to 84.2%, indicating that the introduction of a small amount of Fe (0.25wt%) only promotes the reaction from a kinetic point of view, changes the yield of oxygen-containing compounds but does not affect the product distribution, while a sufficient amount of Fe (0.5wt%) interacts with Pt, resulting in certain changes in the reaction pathway and showing different product distributions. With the further increase of Fe loading, the yields of all products decrease, and the selectivity does not change significantly. This is because the higher Fe loading leads to a decrease in the dispersion of Fe species, and the formation of Fe on the catalyst. x O y Clusters are not conducive to the formation of products.

[0163] The bimetallic supported catalysts with different supports (Example 1, Comparative Examples 6 to 8) and the monometallic supported catalysts with different supports (Comparative Examples 1 and 9) were subjected to catalytic oxidation reactions. The yields and selectivities of the synthesized products are listed in Table 5.

[0164] Table 5 Yield and selectivity of catalytic oxidation reaction of Example 1 and Comparative Examples 1, 6 to 9 catalysts

[0165]

[0166]

[0167] Figure 14 This is a comparison chart of the yields and selectivities of methanol, formic acid and acetic acid produced by catalytic oxidation reactions of the catalysts prepared in Comparative Examples 1 and 9. Figure 15 This is a comparison chart of the yields and selectivities of methanol, formic acid and acetic acid produced by catalytic oxidation reactions using the catalysts prepared in Example 1 and Comparative Examples 6 to 8.

[0168] From Table 5 and Figure 14 It can be seen that the main products of the four catalysts are CH3OH, HCOOH, and CH3COOH, but the yields and selectivities of the various products are different. Among them, the Pt / Beta (0.3) catalyst shows the highest reaction activity, indicating that the reaction is affected by the topological structure of the molecular sieve.

[0169] Fe was impregnated onto Pt catalysts of different topologies, and catalytic activity was tested under the same reaction conditions. The results showed that the catalyst supported on H-Beta zeolite exhibited the highest activity. The introduction of Fe also improved the yields of catalysts with other topologies, demonstrating that Fe's promotion of the reaction is universal across Pt / zeolite catalysts of varying topologies. The total amount and strength of the acid in the zeolite are key factors influencing methane activation, and the differences in activity among catalysts with different topologies stem from the differences in acid strength on the zeolite.

[0170] The above test results show that the synergistic effect between Pt and Fe can only occur when the Pt and Fe species are spatially adjacent, and the impregnation sequence of Pt first and then Fe can form more active reaction sites; the catalyst with the best loading composition ratio is PtFe / Beta (0.3, 0.5); the PtFe / Beta catalyst supported by H-Beta molecular sieve exhibits the highest reaction activity and methanol selectivity.

[0171] Application Example 2

[0172] The PtFe / Beta (0.3, 0.5) prepared in Example 1 was selected as a catalyst and a methane catalytic oxidation reaction was carried out according to the method of Application Example 1, except that different stirring speeds were used during the reaction, namely 500 rpm, 750 rpm, 1000 rpm, 1250 rpm, and 1500 rpm. The yield and selectivity of the synthesized product are listed in Table 6.

[0173] Table 6 Yield and selectivity of the catalyst of Example 1 in catalytic oxidation reaction at different speeds

[0174]

[0175] Figure 16 The following is a comparison of the yields and selectivities of methanol, formic acid and acetic acid produced by the catalytic oxidation reaction of the catalyst in Example 1 at different speeds. Figure 16 It can be seen that, with all other reaction conditions remaining the same, the yield of oxygenated compounds exhibits a volcanic-like trend as the stirring speed increases. When the stirring speed is increased from 500 rpm to 1000 rpm, the yield increases accordingly, indicating that the rate-limiting step at this stage is the diffusion of the reactants from the water to the catalyst surface. However, when the stirring speed is further increased, the yield decreases slightly. When the speed is higher than 1000 rpm, catalyst powder is observed on the inner wall of the reactor above the liquid level after the reaction, indicating that the decrease in yield is related to catalyst splashing caused by vigorous stirring.

[0176] Application Example 3

[0177] The PtFe / Beta (0.3, 0.5) prepared in Example 1 was used as a catalyst to carry out a methane catalytic oxidation reaction according to the method of Application Example 1, except that different reaction temperatures, 120°C, 150°C, 180°C, and 210°C, were used during the reaction. The yield and selectivity of the synthesized product are listed in Table 7.

[0178] Table 7 Yield and selectivity of the catalyst of Example 1 in catalytic oxidation reaction at different temperatures

[0179]

[0180] Figure 17 The following is a comparison of the yields and selectivities of methanol, formic acid and acetic acid produced by the catalytic oxidation reaction of the catalyst in Example 1 at different reaction temperatures. Figure 17 It can be seen that the yield increases continuously as the reaction temperature gradually increases from 120°C to 210°C, indicating that the reaction requires external energy to promote it and that higher temperatures lead to higher activity. Notably, when the reaction temperature is increased to 210°C, the formic acid yield increases significantly, resulting in a certain degree of decrease in methanol selectivity. This is because higher reaction temperatures facilitate deep oxidation, thereby promoting the production of formic acid.

[0181] Application Example 4

[0182] The PtFe / Beta (0.3, 0.5) prepared in Example 1 was selected as a catalyst and a methane catalytic oxidation reaction was carried out according to the method of Application Example 1. The difference was that different partial pressures of the reaction raw materials were used during the reaction. Specifically, when the oxygen partial pressure was 0.2 MPa and the carbon monoxide partial pressure was 0.5 MPa, the methane partial pressure increased from 0 MPa to 2 MPa; when the methane partial pressure was 2 MPa and the oxygen partial pressure was 0.2 MPa, the carbon monoxide partial pressure increased from 0 MPa to 0.5 MPa; when the methane partial pressure was 2 MPa and the carbon monoxide partial pressure was 0.5 MPa, the oxygen partial pressure increased from 0 MPa to 0.5 MPa; the reaction materials were introduced according to a partial pressure ratio of methane, carbon monoxide and oxygen of 2 / 0.5 / 0.2, and the total reaction pressure was 1.35 MPa, 2.7 MPa and 5.4 MPa; the results of the yield and selectivity of the synthetic products are listed in Tables 8 to 11.

[0183] Table 8 Yield and selectivity of the catalyst of Example 1 in catalytic oxidation reaction at different methane partial pressures

[0184]

[0185]

[0186] Figure 18The following is a comparison of the yields and selectivities of methanol, formic acid and acetic acid produced by the catalytic oxidation reaction of the catalyst in Example 1 at different methane partial pressures. Figure 18 It can be seen that when the methane partial pressure is 0 MPa, no liquid products are observed, indicating that methane is the source of various liquid oxides. When the methane partial pressure increases from 0.5 to 2 MPa, the yields of methanol and formic acid continue to increase, but the yield of acetic acid shows a downward trend, indicating that methanol and formic acid are not reaction intermediates of acetic acid.

[0187] Table 9 Yield and selectivity of catalytic oxidation reaction of the catalyst in Example 1 at different carbon monoxide partial pressures

[0188]

[0189] Figure 19 The following is a comparison of the yields and selectivities of methanol, formic acid and acetic acid produced by the catalytic oxidation reaction of the catalyst in Example 1 at different carbon monoxide partial pressures. Figure 19 It can be seen that when no CO partial pressure is introduced into the system, no liquid product is detected, indicating that the reaction requires CO "activation". When the CO partial pressure is increased from 0.1MPa to 0.3MPa, the yield increases significantly, but when the CO partial pressure is further increased, the yield does not change significantly, indicating that at a partial pressure of 0.3MPa, CO has reached adsorption saturation on the catalyst surface.

[0190] Table 10 Yield and selectivity of catalytic oxidation reaction of the catalyst in Example 1 under different oxygen partial pressures

[0191]

[0192] Figure 20 The following is a comparison chart of the yield and selectivity of methanol, formic acid and acetic acid produced by the catalytic oxidation reaction of the catalyst in Example 1 under different oxygen partial pressures. Figure 20 It can be seen that no liquid product was detected when no oxygen was introduced, indicating that all three feed gases are essential for the reaction. As the oxygen partial pressure increases, the product initially increases and then stabilizes, indicating that oxygen quickly reaches adsorption saturation on the catalyst surface. When the oxygen partial pressure reaches 0.5 MPa, methanol selectivity decreases slightly. This is because excessively high oxygen partial pressure favors deep oxidation of the product, thereby promoting the production of formic acid.

[0193] Table 11 Yield and selectivity of catalytic oxidation reaction of the catalyst in Example 1 at different total reaction pressures

[0194]

[0195]

[0196] Figure 21 The following is a comparison chart of the yield and selectivity of methanol, formic acid and acetic acid produced by the catalytic oxidation reaction of the catalyst in Example 1 at different total reaction pressures. Figure 21 It can be seen that the partial pressure ratio of the three reaction gases CH4, CO and O2 is maintained at 2 / 0.5 / 0.2. As the total reaction pressure increases, the yield continues to increase, indicating that a higher reaction pressure is conducive to the progress of the reaction. However, further increasing the total reaction pressure is conducive to the formation of by-product formic acid, which reduces the selectivity of the product methanol.

[0197] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A bimetallic supported catalyst, characterized in that: comprising a carrier and platinum and iron supported on the carrier; The carrier is H-Beta molecular sieve, the mass percentage of the platinum in the bimetallic supported catalyst is 0.15-0.6 wt%, and the mass percentage of the iron in the bimetallic supported catalyst is 0.25-1.0 wt%.

2. The bimetallic supported catalyst according to claim 1, characterized in that The mass percentage of platinum in the bimetallic supported catalyst is 0.3-0.5 wt%, and the mass percentage of iron is 0.5-0.75 wt%.

3. The bimetallic supported catalyst according to claim 1 or 2, characterized in that The total specific surface area of ​​the bimetallic supported catalyst is 600 to 700 m 2 / g, with a total pore volume of 0.60-0.70 cm 3 / g.

4. The method for preparing the bimetallic supported catalyst according to any one of claims 1 to 3, characterized in that: Including Method 1, Method 2 or Method 3; The method 1 comprises the following steps: Mixing H-Beta molecular sieve and platinum source aqueous solution, performing a first impregnation and then a first reduction calcination to obtain a first primary catalyst; Mixing the first primary catalyst and an iron source aqueous solution, performing a second impregnation, and then performing a second reduction calcination to obtain the bimetallic supported catalyst; The method 2 comprises the following steps: Mixing the H-Beta molecular sieve and the iron source aqueous solution, performing a third impregnation and then a third reduction calcination to obtain a second primary catalyst; mixing the second primary catalyst and a platinum source aqueous solution, performing a fourth impregnation and then a fourth reduction calcination to obtain the bimetallic supported catalyst; The method 3 comprises the following steps: dissolving an iron source and a platinum source in water to obtain a composite aqueous solution; The composite aqueous solution and H-Beta molecular sieve are mixed, and a fifth impregnation is performed followed by a fifth reduction calcination to obtain the bimetallic supported catalyst.

5. The preparation method according to claim 4, characterized in that: The platinum source in the platinum source aqueous solution includes one or more of PtCl2, PtCl4, H2PtCl6, Pt(NH3)4Cl2, H2Pt(OH)6, Pt(NO3)2, Pt(NH3)4(NO3)2 and Pt(SO3)2; the mass concentration of the platinum element in the platinum source aqueous solution is 0.15 to 0.6 g / L; The iron source in the iron source aqueous solution includes one or more of Fe(NO3)3, Fe(SO4)3, FeCl3, ferric acetate and ferric acetylacetonate; the mass concentration of iron element in the iron source aqueous solution is 0.25~1g / L.

6. The preparation method according to claim 4, characterized in that: The solid-liquid ratios of the first impregnation, the second impregnation, the third impregnation, the fourth impregnation and the fifth impregnation are independently 1 g / 8 to 12 mL; the first impregnation, the second impregnation, the third impregnation, the fourth impregnation and the fifth impregnation are respectively carried out under stirring conditions, the stirring speed is 750 to 850 rpm, and the stirring time is 22 to 26 hours.

7. The preparation method according to claim 4 or 6, characterized in that: The temperatures of the first reduction calcination, the second reduction calcination, the third reduction calcination, the fourth reduction calcination and the fifth reduction calcination are independently 580-620° C. and the times are independently 4-6 hours; The heating rates for heating to the temperatures required for the first reduction calcination, the second reduction calcination, the third reduction calcination, the fourth reduction calcination, and the fifth reduction calcination are independently 2.3-2.7° C. / min.

8. Use of the bimetallic supported catalyst according to any one of claims 1 to 3 or the bimetallic supported catalyst prepared by the preparation method according to any one of claims 4 to 7 in the catalytic oxidation of methane.

9. A method for catalytic oxidation of methane, characterized in that: The following steps are involved: Methane, oxygen and carbon monoxide are introduced into a mixture of catalyst and water for catalytic oxidation to obtain methanol; The catalyst is the bimetallic supported catalyst according to any one of claims 1 to 3 or the bimetallic supported catalyst prepared by the preparation method according to any one of claims 4 to 7.

10. The method for catalytic oxidation of methane according to claim 9, characterized in that: The methane partial pressure is 0.5-2 MPa, the oxygen partial pressure is 0.1-0.5 MPa, and the carbon monoxide partial pressure is 0.1-0.5 MPa; The reaction temperature of the catalytic oxidation is 120-210° C., and the reaction time is 0.8-1.2 h.

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