Bifunctional catalyst for direct synthesis and catalytic oxidation of hydrogen peroxide and preparation method thereof

Abstract

The embodiment of the invention discloses a bifunctional catalyst for direct synthesis and catalytic oxidation of hydrogen peroxide and a preparation method of the bifunctional catalyst. The catalyst with the dual functions is provided with Pd-based alloy nanoparticles and high-dispersion monatomic transition metal sites at the same time. The preparation method comprises the following steps: preparing a zeolite-like molecular sieve carrier taking transition metal as link ions through a rolling hydrothermal method; then loading gold and palladium metals on the zeolite-like molecular sieve carrier by adopting a low-temperature liquid phase reduction method to obtain a bifunctional catalyst; the bifunctional catalyst for direct synthesis of hydrogen peroxide and preparation of methanol through methane oxidation has high methane conversion rate, methanol selectivity and yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and particularly relates to a bifunctional catalyst for direct synthesis of hydrogen peroxide and catalytic oxidation, and a preparation method thereof. Background Art

[0002] Hydrogen peroxide (H2O2) is an important green oxidant, which is widely used in the fields of chemical industry, environmental protection, medicine, etc. At present, H2O2 is mainly produced industrially by the anthraquinone process, but this process has problems such as high energy consumption, many organic by-products, and safety hazards. Therefore, the development of a catalytic process for the direct synthesis of H2O2 from hydrogen and oxygen (H2 + O2 → H2O2) has become a research hotspot. However, this reaction faces challenges such as low selectivity of H2O2, easy formation of water (H2O) by-products, etc., and there is an urgent need for an efficient and stable catalyst system. On the other hand, methane (CH4), as the main component of natural gas, still has problems that it is difficult to balance the conversion rate and selectivity in the selective oxidation to high-value chemicals (such as methanol, formaldehyde). Traditional processes usually require high temperature and high pressure, and are prone to over-oxidation to produce CO2. Therefore, the development of a method for efficient catalytic partial oxidation of CH4 under mild conditions is of great significance.

[0003] In view of the fact that H2O2 can be used as a mild oxidant for the selective oxidation of methane, the present invention proposes an innovative coupling process: combining the direct synthesis of H2O2 from H2 / O2 with the reaction of CH4 oxidation to methanol, and using the in-situ generated H2O2 to promote the efficient and highly selective conversion of CH4. The key to this process lies in the design of a bifunctional palladium (Pd)-based catalyst, and by regulating the electronic structure and the interaction with the support of the Pd active site, the following advantages can be achieved:

[0004] 1. Efficient synthesis of H2O2: Inhibiting the side reaction of H2O, and improving the selectivity and yield of H2O2;

[0005] 2. Controllable oxidation of CH4: Using the in-situ generated H2O2 to activate the C-H bond of methane under mild conditions and direct the formation of methanol;

[0006] 3. Synergistic catalytic mechanism: The coupling reaction can optimize the reaction thermodynamic equilibrium, reduce energy consumption, and avoid the safety risks of H2O2 storage and transportation.

[0007] At present, there is no report on a Pd-based catalyst with both H2O2 synthesis and CH4 oxidation bifunction and a coupling process. Through the innovation of the catalyst structure and the integration of the process, the present invention provides a new strategy for the green and efficient production of H2O2 and methanol, and has significant industrial application prospects.

[0008] In addition, on the one hand, there are differences in the understanding of those skilled in the art; on the other hand, when the inventor made this invention, a large number of documents and patents were studied, but due to space limitations, not all details and contents were listed in detail. However, this by no means means that this invention does not possess the features of these prior arts. On the contrary, this invention already possesses all the features of the prior arts, and the applicant reserves the right to add relevant prior arts in the background art. Summary of the Invention

[0009] To solve the technical problems in the prior art, such as low selectivity and yield of H2O2 caused by side reactions, low CH4 conversion rate, methanol selectivity and yield, and poor catalyst stability, the embodiments of the present invention provide a bifunctional catalyst and its preparation method to improve the generation efficiency of H2O2, CH4 conversion rate, methanol selectivity and yield.

[0010] The object of the present invention is achieved by the following technical solutions:

[0011] In the first aspect, the present invention provides a bifunctional catalyst for direct synthesis of hydrogen peroxide and catalytic oxidation, which has Pd-based alloy nanoparticles and highly dispersed single-atom transition metal sites at the same time.

[0012] In the second aspect, the present invention provides a bifunctional catalyst for direct synthesis of hydrogen peroxide and catalytic oxidation, which includes a carrier and a supported active metal. The carrier is a zeolite-like molecular sieve with MoO6 octahedra as the structural unit, and Fe, Mn, Zn, Ni, Co as the linking ions, and NH4 and Na as the charge-balancing cations respectively. The supported active metal is Au, Pd, and Pd-Au, Pd-Pt, Pd-Ru, Pd-Ir, Pd-Rh alloys. Preferably, calculated by mass percentage of the catalyst, the content of the supported active metal Au is 0-1%, the content of metal Pd is 0-1%, the content of Pt is 0-1%, the content of Ru is 0-1%, the content of Ir is 0-1%, and the content of Rh is 0-1%.

[0013] In the third aspect, the present invention provides a bifunctional catalyst for direct synthesis of hydrogen peroxide and catalytic oxidation, and the active metal includes active palladium, gold or a palladium-based alloy.

[0014] Fourth aspect, the present invention provides a preparation method of a bifunctional catalyst for direct synthesis of hydrogen peroxide and catalytic oxidation, including: adding a carrier, a salt containing Mo and a transition metal oxide into distilled water, then adding Mo powder, adjusting the pH with or without sulfuric acid and stirring evenly, then pouring it into a hydrothermal reactor and fixing it in a homogeneous reactor, and tumbling and heating at a high temperature. After the reaction is completed, after the hydrothermal reactor is cooled to room temperature, the solid is obtained by magnetic attraction or multiple centrifugations combined with washing with distilled water, and is placed in a drying oven to dry to obtain a zeolite-like molecular sieve carrier. Weigh the zeolite-like molecular sieve carrier, and add solutions containing PdCl2, HAuCl4 or PdCl2 and HAuCl4, PdCl2 and H2PtCl4, PdCl2 and RuCl2, PdCl2 and IrCl3, PdCl2 and RhCl3 by mass respectively and stir vigorously, then slowly add a dilute NaBH4 solution and stir. After the reaction is completed, the solid is obtained by washing and centrifuging with distilled water multiple times, and then dried in a drying oven to obtain a bifunctional catalyst with zeolite-like molecular sieves respectively loaded with Pd, Au, Pd-Au, Pd-Pt, Pd-Ru, Pd-Ir, Pd-Rh.

[0015] Fifth aspect, the present invention provides the use of the bifunctional catalyst involved in the present invention in the direct synthesis of hydrogen peroxide and catalytic oxidation. Specific embodiments

[0016] In the description of the present invention, the terms are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. In the description of the present invention, "a plurality" means two or more, unless otherwise specifically defined.

[0017] Example 1

[0018] Weigh 4.234 g of Na2MoO4·2H2O and 0.383 g of Fe3O4 and dissolve them in 52 mL of distilled water, then add 0.300 g of molybdenum powder. Use H2SO4 to adjust the pH value of the mixture to 5.5. After stirring at room temperature for 10 min, fix the hydrothermal reactor in a homogeneous reactor and tumble and heat at 175 °C for 48 h, and set the tumbling speed to 2 rpm. After the reaction is completed, after the hydrothermal reactor is naturally cooled to room temperature, completely remove the remaining unreacted Fe3O4 with a magnet, transfer the remaining suspension to a centrifuge tube, and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake well and centrifuge at 1500 rpm for 2 min, and collect about 70% of the liquid in the upper part of the suspension. This operation is repeated three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a 60 °C forced-air drying oven and dry overnight.

[0019] Weigh 0.200 g of the above material and disperse it in a beaker containing 50 mL of deionized water, and sonicate for 10 min. Weigh 0.0813 g of PdCl2 (Pd: 2.46 wt%) solution and add it to the beaker (Au:Pd = 0:1 molar ratio, Pd: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash it with water, and centrifuge again. Repeat this operation three times. Finally, place the obtained solid in a blast drying oven at 60 °C and dry it overnight. The obtained catalyst is denoted as C01.

[0020] Example 2

[0021] Weigh 4.234 g of Na2MoO4·2H2O and 0.383 g of Fe3O4 and dissolve them in 52 mL of distilled water, then add 0.300 g of molybdenum powder. Use H2SO4 to adjust the pH value of the mixture to 5.5. After stirring at room temperature for 10 min, pour it into a hydrothermal reactor and fix it in a homogeneous reactor, and heat it by tumbling at 175 °C for 48 h, and set the tumbling speed to 2 rpm. After the reaction is completed, wait for the hydrothermal reactor to cool naturally to room temperature, and completely remove the remaining unreacted Fe3O4 with a magnet. Transfer the remaining suspension to a centrifuge tube and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake it evenly and centrifuge at 1500 rpm for 2 min, and collect about 70% of the liquid in the upper part of the suspension. Repeat this operation three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a blast drying oven at 60 °C and dry it overnight.

[0022] Weigh 0.200 g of the above material and disperse it in a beaker containing 50 mL of deionized water, and sonicate for 10 min. Weigh 0.0423 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0232 g of HAuCl4·xH2O (Au: 4.14 wt%) solution and add them to the beaker (Au:Pd = 0.5:1 molar ratio, Au-Pd: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash it with water, and centrifuge again. Repeat this operation three times. Finally, place the obtained solid in a blast drying oven at 60 °C and dry it overnight. The obtained catalyst is denoted as C02.

[0023] Example 3

[0024] Weigh 4.234 g of Na2MoO4·2H2O and 0.383 g of Fe3O4 and dissolve them in 52 mL of distilled water. Then add 0.300 g of molybdenum powder. Use H2SO4 to adjust the pH value of the mixture to 5.5. After stirring at room temperature for 10 min, fix the hydrothermal reactor in a homogeneous reactor and heat it by tumbling at 175 °C for 48 h, with the tumbling speed set at 2 rpm. After the reaction is completed, wait for the hydrothermal reactor to cool naturally to room temperature, completely remove the remaining unreacted Fe3O4 with a magnet, transfer the remaining suspension to a centrifuge tube, and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake well, and centrifuge at 1500 rpm for 2 min. Collect about 70% of the liquid in the upper part of the suspension. Repeat this operation three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a blast drying oven at 60 °C and dry it overnight.

[0025] Weigh 0.200 g of the above material and disperse it in a beaker containing 50 mL of deionized water, and ultrasonically treat it for 10 min. Weigh 0.0285 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0314 g of HAuCl4·xH2O (Au: 4.14 wt%) solution and add them to the beaker (Au:Pd = 1:1 molar ratio, Au-Pd: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash it with water, and centrifuge again. Repeat this operation three times. Finally, place the obtained solid in a blast drying oven at 60 °C and dry it overnight. The obtained catalyst is denoted as C03.

[0026] Example 4

[0027] Weigh 4.234 g of Na2MoO4·2H2O and 0.383 g of Fe3O4 and dissolve them in 52 mL of distilled water. Then add 0.300 g of molybdenum powder. Use H2SO4 to adjust the pH value of the mixture to 5.5. After stirring at room temperature for 10 min, fix the hydrothermal reactor in a homogeneous reactor and heat it by tumbling at 175 °C for 48 h, with the tumbling speed set at 2 rpm. After the reaction is completed, wait for the hydrothermal reactor to cool naturally to room temperature, completely remove the remaining unreacted Fe3O4 with a magnet, transfer the remaining suspension to a centrifuge tube, and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake well, and centrifuge at 1500 rpm for 2 min. Collect about 70% of the liquid in the upper part of the suspension. Repeat this operation three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a blast drying oven at 60 °C and dry it overnight.

[0028] Weigh 0.200 g of the above material and disperse it in a beaker containing 50 mL of deionized water, and perform ultrasonic treatment for 10 min. Weigh 0.0174 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0380 g of HAuCl4·xH2O (Au: 4.14 wt%) solution and add them to the beaker (Au:Pd = 2:1 molar ratio, Au-Pd: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash it with water, and centrifuge again. Repeat this operation three times. Finally, place the obtained solid in a blast drying oven at 60 °C and dry it overnight. The obtained catalyst is denoted as C04.

[0029] Example 5

[0030] Weigh 4.234 g of Na2MoO4·2H2O and 0.383 g of Fe3O4 and dissolve them in 52 mL of distilled water, then add 0.300 g of molybdenum powder. Use H2SO4 to adjust the pH value of the mixture to 5.5. After stirring at room temperature for 10 min, fix the hydrothermal reactor in a homogeneous reactor and heat it by tumbling at 175 °C for 48 h, and set the tumbling speed to 2 rpm. After the reaction is completed, wait for the hydrothermal reactor to cool naturally to room temperature, completely remove the remaining unreacted Fe3O4 with a magnet, transfer the remaining suspension to a centrifuge tube, and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake it evenly, and centrifuge at 1500 rpm for 2 min to collect about 70% of the liquid in the upper part of the suspension. Repeat this operation three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a blast drying oven at 60 °C and dry it overnight.

[0031] Weigh 0.200 g of the above material and disperse it in a beaker containing 50 mL of deionized water, and perform ultrasonic treatment for 10 min. Weigh 0.0125 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0409 g of HAuCl4·xH2O (Au: 4.14 wt%) solution and add them to the beaker (Au:Pd = 3:1 molar ratio, Au-Pd: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash it with water, and centrifuge again. Repeat this operation three times. Finally, place the obtained solid in a blast drying oven at 60 °C and dry it overnight. The obtained catalyst is denoted as C05.

[0032] Example 6

[0033] Weigh 4.234 g of Na2MoO4·2H2O and 0.383 g of Fe3O4 and dissolve them in 52 mL of distilled water. Then add 0.300 g of molybdenum powder. Use H2SO4 to adjust the pH value of the mixture to 5.5. After stirring at room temperature for 10 min, fix the hydrothermal reactor in a homogeneous reactor and heat it by tumbling at 175 °C for 48 h, with the tumbling speed set at 2 rpm. After the reaction is completed, wait for the hydrothermal reactor to cool naturally to room temperature, and then completely remove the remaining unreacted Fe3O4 with a magnet. Transfer the remaining suspension into a centrifuge tube and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake well, and centrifuge at 1500 rpm for 2 min. Collect 70% of the liquid in the upper part of the suspension. Repeat this operation three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a blast drying oven at 60 °C and dry it overnight.

[0034] Weigh 0.200 g of the above material and disperse it in a beaker containing 50 mL of deionized water, and ultrasonically treat it for 10 min. Weigh 0.0483 g of HAuCl4·xH2O (Au: 4.14 wt%) solution and add it to the beaker (Au:Pd = 1:0 molar ratio, Au: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash it with water, and centrifuge again. Repeat this operation three times. Finally, place the obtained solid in a blast drying oven at 60 °C and dry it overnight. The obtained catalyst is denoted as C06.

[0035] Example 7

[0036] Weigh 4.234 g of Na2MoO4·2H2O and 0.352 g of MnO and dissolve them in 52 mL of distilled water. Then add 0.300 g of molybdenum powder. Use H2SO4 to adjust the pH value of the mixture to 5.5. After stirring at room temperature for 10 min, fix the hydrothermal reactor in a homogeneous reactor and heat it by tumbling at 175 °C for 24 h, with the tumbling speed set at 2 rpm. After the reaction is completed, wait for the hydrothermal reactor to cool naturally to room temperature, and then transfer the suspension into a centrifuge tube and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake well, and centrifuge at 1500 rpm for 2 min. Collect about 70% of the liquid in the upper part of the suspension. Repeat this operation three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a blast drying oven at 60 °C and dry it overnight.

[0037] Weigh 0.200 g of the above materials and disperse them in a beaker containing 50 mL of deionized water, and ultrasonically treat for 10 min. Weigh 0.0280 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0317 g of RuCl3 (Ru: 4.14 wt%) solution and add them to the beaker (Ru:Pd = 2:1 molar ratio, Ru-Pd: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash with water, and centrifuge again. Repeat this operation three times. Finally, place the obtained solid in a blast drying oven at 60 °C and dry overnight. The obtained catalyst is denoted as C07.

[0038] Example 8

[0039] Weigh 4.234 g of Na2MoO4·2H2O and 0.680 g of ZnCl2 and dissolve them in 52 mL of distilled water, and then add 0.300 g of molybdenum powder. Use H2SO4 to adjust the pH value of the mixture to 5.5. After stirring at room temperature for 10 min, fix the hydrothermal reactor in a homogeneous reactor and heat it by tumbling at 175 °C for 24 h, and set the tumbling speed to 2 rpm. After the reaction is completed, wait for the hydrothermal reactor to cool naturally to room temperature, then transfer the suspension to a centrifuge tube and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake well and centrifuge at 1500 rpm for 2 min, and collect about 70% of the liquid in the upper part of the suspension. Repeat this operation three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a blast drying oven at 60 °C and dry overnight.

[0040] Weigh 0.200 g of the above materials and disperse them in a beaker containing 50 mL of deionized water, and ultrasonically treat for 10 min. Weigh 0.0174 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0380 g of H2PtCl6·xH2O (Pt: 4.14 wt%) solution and add them to the beaker (Pt:Pd = 2:1 molar ratio, Pt-Pd: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash with water, and centrifuge again. Repeat this operation three times. Finally, place the obtained solid in a blast drying oven at 60 °C and dry overnight. The obtained catalyst is denoted as C08.

[0041] Example 9

[0042] Weigh 4.234 g of Na2MoO4·2H2O and 1.236 g of Co(CH3COO)2·4H2O and dissolve them in 52 mL of distilled water. Then add 0.300 g of molybdenum powder. Use H2SO4 to adjust the pH value of the mixture to 5.5. After stirring at room temperature for 10 min, fix the hydrothermal reactor in a homogeneous reactor and heat it by tumbling at 175 °C for 48 h, with the tumbling speed set at 2 rpm. After the reaction is completed, wait for the hydrothermal reactor to cool naturally to room temperature, then transfer the suspension to a centrifuge tube and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake well and centrifuge at 1500 rpm for 2 min, and collect 70% of the liquid in the upper part of the suspension. Repeat this operation three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a blast drying oven at 60 °C and dry overnight.

[0043] Weigh 0.200 g of the above material and disperse it in a beaker containing 50 mL of deionized water, and ultrasonically treat it for 10 min. Weigh 0.0277 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0319 g of RhCl3 (Rh: 4.14 wt%) solution and add them to the beaker (Rh:Pd = 2:1 molar ratio, Rh-Pd: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash it with water, and centrifuge again. Repeat this operation three times. Finally, place the obtained solid in a blast drying oven at 60 °C and dry overnight. The obtained catalyst is denoted as C09.

[0044] Example 10

[0045] Weigh 4.234 g of Na2MoO4·2H2O and 1.180 g of NiCl2·6H2O and dissolve them in 52 mL of distilled water. Then add 0.300 g of molybdenum powder. Use H2SO4 to adjust the pH value of the mixture to 5.5. After stirring at room temperature for 10 min, fix the hydrothermal reactor in a homogeneous reactor and heat it by tumbling at 175 °C for 96 h, with the tumbling speed set at 2 rpm. After the reaction is completed, wait for the hydrothermal reactor to cool naturally to room temperature, then transfer the suspension to a centrifuge tube and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake well and centrifuge at 1500 rpm for 2 min, and collect 70% of the liquid in the upper part of the suspension. Repeat this operation three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a blast drying oven at 60 °C and dry overnight.

[0046] Weigh 0.200 g of the above materials and disperse them in a beaker containing 50 mL of deionized water, and sonicate for 10 min. Weigh 0.0176 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0379 g of IrCl3 (Ir: 4.14 wt%) solution and add them to the beaker (Ir:Pd = 2:1 molar ratio, Ir-Pd: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash with water, and centrifuge again. Repeat this operation three times. Finally, dry the obtained solid overnight in a blast drying oven at 60 °C. The obtained catalyst is denoted as C10.

[0047] Example 11

[0048] Weigh 3.090 g of (NH4)6Mo7O 24 ·4H2O and 0.383 g of Fe3O4 and dissolve them in 52 mL of distilled water, then add 0.300 g of molybdenum powder. After stirring at room temperature for 10 min, fix the hydrothermal reactor in a homogeneous reactor and heat it by tumbling at 175 °C for 48 h, and set the tumbling speed to 2 rpm. After the reaction is completed, wait for the hydrothermal reactor to cool naturally to room temperature, and completely remove the remaining unreacted Fe3O4 with a magnet. Transfer the remaining suspension to a centrifuge tube and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake well and centrifuge at 1500 rpm for 2 min, and collect 70% of the liquid on the upper part of the suspension. Repeat this operation three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a blast drying oven at 60 °C and dry it overnight.

[0049] Weigh 0.200 g of the above materials and disperse them in a beaker containing 50 mL of deionized water, and sonicate for 10 min. Weigh 0.0428 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0483 g of RuCl3 (Ru: 4.14 wt%) solution and add them to the beaker (Ru:Pd = 2:1 molar ratio, Ru: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash with water, and centrifuge again. Repeat this operation three times. Finally, dry the obtained solid overnight in a blast drying oven at 60 °C. The obtained catalyst is denoted as C11.

[0050] Example 12

[0051] Weigh 3.090 g of (NH4)6Mo7O 240.352 g of MnO and 4H₂O were dissolved in 52 mL of distilled water, and then 0.300 g of molybdenum powder was added. After stirring at room temperature for 10 min, the hydrothermal reactor was fixed in a homogeneous reactor and heated with tumbling at 175 °C for 24 h, and the tumbling speed was set at 2 rpm. After the reaction, when the hydrothermal reactor was naturally cooled to room temperature, the suspension was transferred into a centrifuge tube and centrifuged at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then an appropriate amount of deionized water was added, shaken well and centrifuged at 1500 rpm for 2 min, and 70% of the liquid in the upper part of the suspension was collected. This operation was repeated three times. Finally, the collected liquid was centrifuged at 4000 rpm for 1 h. The centrifuge tube was placed in a blast drying oven at 60 °C and dried overnight.

[0052] 0.200 g of the above material was weighed and dispersed in a beaker containing 50 mL of deionized water and ultrasonicated for 10 min. 0.0222 g of PdCl₂ (Pd: 2.46 wt%) solution and 0.0483 g of H₂PtCl₆·xH₂O (Pt: 4.14 wt%) solution were added to the beaker (Pt:Pd = 2:1 molar ratio, Pt: 1 wt%), and vigorously stirred at room temperature for 2 h. Then 2 mL of freshly prepared 0.1 M NaBH₄ solution was slowly added, and then stirred at room temperature for 1 h. The solid was collected by centrifugation at 8000 rpm for 10 min, washed with water and centrifuged again. This operation was repeated three times. Finally, the obtained solid was placed in a blast drying oven at 60 °C and dried overnight. The obtained catalyst was denoted as C12.

[0053] Example 13

[0054] 3.090 g of (NH₄)₆Mo₇O 24 0.680 g of ZnCl₂ and 4H₂O were dissolved in 52 mL of distilled water, and then 0.300 g of molybdenum powder was added. After stirring at room temperature for 10 min, the hydrothermal reactor was fixed in a homogeneous reactor and heated with tumbling at 175 °C for 24 h, and the tumbling speed was set at 2 rpm. After the reaction, when the hydrothermal reactor was naturally cooled to room temperature, the suspension was transferred into a centrifuge tube and centrifuged at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then an appropriate amount of deionized water was added, shaken well and centrifuged at 1500 rpm for 2 min, and 70% of the liquid in the upper part of the suspension was collected. This operation was repeated three times. Finally, the collected liquid was centrifuged at 4000 rpm for 1 h. The centrifuge tube was placed in a blast drying oven at 60 °C and dried overnight.

[0055] Weigh 0.200 g of the above materials and disperse them in a beaker containing 50 mL of deionized water, and ultrasonically treat for 10 min. Weigh 0.0420 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0483 g of RhCl3 (Rh: 4.14 wt%) solution and add them to the beaker (Rh:Pd = 2:1 molar ratio, Rh: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash with water, and centrifuge again. Repeat this operation three times. Finally, place the obtained solid in a blast drying oven at 60 °C and dry overnight. The obtained catalyst is denoted as C13.

[0056] Example 14

[0057] Weigh 3.090 g of (NH4)6Mo7O 24 ·4H2O and 1.236 g of Co(CH3COO)2·4H2O and dissolve them in 52 mL of distilled water, and then add 0.300 g of molybdenum powder. After stirring at room temperature for 10 min, fix the hydrothermal reactor in a homogeneous reactor and heat it by tumbling at 175 °C for 48 h, and set the tumbling speed to 2 rpm. After the reaction is completed, wait for the hydrothermal reactor to cool naturally to room temperature, then transfer the suspension to a centrifuge tube and centrifuge at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then add an appropriate amount of deionized water, shake well and centrifuge at 1500 rpm for 2 min, and collect 70% of the liquid on the upper part of the suspension. Repeat this operation three times. Finally, centrifuge the collected liquid at 4000 rpm for 1 h. Place the centrifuge tube in a blast drying oven at 60 °C and dry overnight.

[0058] Weigh 0.200 g of the above materials and disperse them in a beaker containing 50 mL of deionized water, and ultrasonically treat for 10 min. Weigh 0.0225 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0483 g of IrCl3 (Ir: 4.14 wt%) solution and add them to the beaker (Ir:Pd = 2:1 molar ratio, Ir: 1 wt%). Stir vigorously at room temperature for 2 h. Then slowly add 2 mL of freshly prepared 0.1 M NaBH4 solution, and then stir at room temperature for 1 h. Centrifuge at 8000 rpm for 10 min to collect the solid, wash with water, and centrifuge again. Repeat this operation three times. Finally, place the obtained solid in a blast drying oven at 60 °C and dry overnight. The obtained catalyst is denoted as C14.

[0059] Example 15

[0060] Weigh 3.090 g of (NH4)6Mo7O 24· 4H2O and 1.180 g of NiCl2·6H2O were dissolved in 52 mL of distilled water, and then 0.300 g of molybdenum powder was added. After stirring at room temperature for 10 min, the hydrothermal reactor was fixed in a homogeneous reactor and heated by tumbling at 175 °C for 96 h, with the tumbling speed set at 2 rpm. After the reaction, when the hydrothermal reactor cooled naturally to room temperature, the suspension was transferred into a centrifuge tube and centrifuged at 4000 rpm for 30 min to obtain the solid at the bottom of the centrifuge tube. Then an appropriate amount of deionized water was added, shaken well and centrifuged at 1500 rpm for 2 min, and 70% of the liquid in the upper part of the suspension was collected. This operation was repeated three times. Finally, the collected liquid was centrifuged at 4000 rpm for 1 h. The centrifuge tube was placed in a forced-air drying oven at 60 °C and dried overnight.

[0061] 0.200 g of the above material was weighed and dispersed in a beaker containing 50 mL of deionized water and ultrasonicated for 10 min. 0.0220 g of PdCl2 (Pd: 2.46 wt%) solution and 0.0483 g of HAuCl4·xH2O (Au: 4.14 wt%) solution were added to the beaker (Au:Pd = 2:1 molar ratio, Au: 1 wt%), and stirred vigorously at room temperature for 2 h. Then 2 mL of freshly prepared 0.1 M NaBH4 solution was slowly added, and then stirred at room temperature for 1 h. The solid was collected by centrifugation at 8000 rpm for 10 min, washed with water and centrifuged again. This operation was repeated three times. Finally, the obtained solid was placed in a forced-air drying oven at 60 °C and dried overnight. The obtained catalyst was denoted as C15.

[0062] Catalyst performance test

[0063] The Au-Pd supported catalysts prepared in Examples 1-15 with different zeolite molecular sieves as carriers were respectively placed in a high-pressure batch reactor to test their catalytic performance. Before the test, the air in the reactor was exhausted with a high-purity argon stream, and then 3.0 MPa of raw material gas (1.5% CH4 / 3.0% H2 / 6.0% O2 / 89.5% Ar) was introduced. The catalyst dosage was 50 mg, the reaction solution was 20 mL of deionized water, the temperature was 70 °C, and the time was 0.5 h. The test results are shown in Table 1.

[0064] Table 1. Test results of CH4 selective oxidation performance in the examples of the present invention

[0065]

[0066]

[0067] As can be seen from Table 1, the catalysts obtained in Examples 1-15 all have high methanol selectivity. Among them, Example 4 has the highest methanol yield, and Example 7 has the highest methanol selectivity. The highest methanol selectivity can reach 98.5%, and the highest methanol yield can reach 5157 mmol CH4 g Pd或Au -1 ·h -1 . It can be seen therefrom that the examples of the present invention have high methane conversion rate, methanol selectivity and methanol yield, and relatively high reaction activity. At the same time, the examples of the present invention also have high H2 selectivity.

[0068] It should be noted that the above specific examples are exemplary. Those skilled in the art can come up with various solutions inspired by the disclosure of the present invention, and these solutions also belong to the disclosure scope of the present invention and fall within the protection scope of the present invention. Those skilled in the art should understand that the specification of the present invention is illustrative and does not constitute a limitation to the claims. The protection scope of the present invention is defined by the claims and their equivalents.

Claims

1. A bifunctional catalyst, characterized in that, The bifunctional catalyst includes a support and a supported active metal.

2. The bifunctional catalyst according to claim 1, wherein The support is a zeolite-like molecular sieve, with MoO6 octahedrons as structural units, Fe, Mn, Zn, Ni, and Co as linking ions respectively, and NH4 and Na as charge-balancing cations respectively.

3. The bifunctional catalyst according to claim 1, characterized in that, The supported active metals are Au, Pd, and Pd-Au, Pd-Pt, Pd-Ru, Pd-Ir, Pd-Rh alloys.

4. The bifunctional catalyst according to claim 1, wherein In terms of the mass percentage of the catalyst, the content of the supported active metal Au is 0 to 1%, the content of metal Pd is 0 to 1%, the content of Pt is 0 to 1%, the content of Ru is 0 to 1%, the content of Ir is 0 to 1%, and the content of Rh is 0 to 1%.

5. A method for preparing the bifunctional catalyst according to any one of claims 1 to 4, characterized in that, Comprising: Adding a Mo-containing salt and transition metal oxides to the support into distilled water, then adding Mo powder, adjusting the pH with or without sulfuric acid and stirring evenly, then pouring it into a hydrothermal autoclave and fixing it in a homogeneous reactor, and heating it by tumbling at a high temperature; After the reaction ends, after the hydrothermal autoclave cools to room temperature, a solid is obtained by magnetic attraction or multiple centrifugations combined with washing with distilled water, and is placed in a drying oven to be dried to obtain a zeolite-like molecular sieve support; Weigh the zeolite-like molecular sieve support, add solutions containing PdCl2, HAuCl4 or PdCl2 and HAuCl4, PdCl2 and H2PtCl4, PdCl2 and RuCl2, PdCl2 and IrCl3, PdCl2 and RhCl3 respectively by mass and stir vigorously, and then slowly add a dilute NaBH4 solution and stir; After the reaction ends, a solid is obtained by washing with distilled water and centrifuging multiple times; It is dried in a drying oven to obtain a bifunctional catalyst with zeolite-like molecular sieves respectively loaded with Pd, Au, Pd-Au, Pd-Pt, Pd-Ru, Pd-Ir, Pd-Rh.

6. Use of the bifunctional catalyst according to any one of claims 1 to 4 or the bifunctional catalyst prepared by the preparation method according to claim 5 in the direct synthesis of hydrogen peroxide and catalytic oxidation.

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