Supported metal catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the field of catalytic synthesis, and particularly relates to a supported metal catalyst as well as a preparation method and application thereof. A reaction device for preparing the supported metal catalyst is built by adopting a continuous flow type photoreaction system, a method for preparing the supported metal catalyst by using photodeposition is provided, turbid liquid enters a transparent plastic pipe through a peristaltic pump, a reaction pipe adopts a spiral structure, a light source is arranged at the center of the spiral structure, and the inner diameter of the pipe is small; and meanwhile, the light source uniformly irradiates outwards from eight surfaces, so that the reaction liquid in the reaction tube can be irradiated, the light deposition time is shortened, and the reaction efficiency is improved. The method does not need high-temperature calcination and reduction, and the reaction time is short; green, environment-friendly, non-toxic and harmless; and in addition, step-by-step deposition of various metals can be carried out to obtain a multi-metal supported catalyst, or multiple deposition of single metal in different time periods can be carried out. The catalyst obtained through the reaction is good in catalytic performance.

Description

Technical Field

[0001] The invention belongs to the field of catalytic synthesis, and specifically relates to a supported metal catalyst and a preparation method and application thereof. Background Art

[0002] Since the 20th century, the huge growth in the variety and scale of the modern chemical industry has become increasingly dependent on catalysts. From the industrialization of synthetic ammonia at the beginning of the century, the rise of the petrochemical industry and polymer industry after the 1950s, and even the solution to environmental protection problems after the 1960s, they are all related to the use of catalysts (JC Védrine. The past, present and future of heterogeneous catalysis. Catal. Today, 2012, 189, 2-27; DJ Cole-Hamilton. Homogeneous Catalysis--New Approaches to Catalyst Separation, Recovery, and Recycling. Science, 2003, 299, 1702-1706.). According to statistics, more than 90% of modern chemical and petroleum processing processes, more than 80% of conversion processes, and more than 60% of products now use catalytic technology (W. Karim. Catalyst Support Effects on Hydrogen Spillover. Nature, 2017, 541, 68-71). Since the application of metal catalysts such as platinum and palladium in reforming reactions, metal catalysts have been widely used in industries such as modern chemical industry and petroleum processing (AMRuppert. Hydrogenolysis goes bio: from carbohydrates and sugar alcohols to platform chemicals. Angew. Chem. Int. Ed. 2012, 51, 2564-2601.). In the research and development process of various metal catalysts, supported metal catalysts have attracted a large number of catalytic researchers as a new type of catalyst. The reason is that metal complexes act on homogeneous catalytic reaction systems, and there are many problems such as difficulty in separating the catalyst from the reaction system after the reaction is completed and poor reusability, and metal ions are easily lost during the catalytic process, which not only leads to a decrease in the quality of the catalytic product, but also shortens the service life of the catalyst. The above factors have a serious impact on the practical application of homogeneous catalysts in industrial production.

[0003] In order to solve the problems existing in practical applications of homogeneous catalysts, supported metal catalysts are developed to a greater extent because they can overcome the shortcomings of homogeneous catalysts. Metal particles are loaded on inorganic carriers, while maintaining their catalytic reaction activity and selectivity, and after the catalytic reaction is completed, the recovery of supported metal catalysts can be achieved by filtering, which not only improves the quality of the catalytic product but also increases the number of reuses of the catalyst (L.Liu, A.Corma.MetalCatalysts for Heterogeneous Catalysis:From Single Atoms to Nanoclusters andNanoparticles.Chem.Rev.2018,118,10,4981-5079;L.Prati et al.SelectiveOxidation of Glycerol under Acidic Conditions Using Gold Catalysts.Angew.Chem.Int.Ed.2010,49,4499-4502.). Supported metal catalysts have the characteristics of high selectivity, high activity, high stability and reusability, and these properties are closely related to their structure. Through the study of atomic-level characterization technology of supported metal catalysts, we can deeply understand their structure and action mechanism, and provide the possibility for realizing the actual industrial value of catalysts (GJ Hutchings et al. Selective Oxidation of Glycerol by Highly Active Bimetallic Catalysts at Ambient Temperature under Base-Free Conditions. Angew. Chem. Int. Ed. 2011, 50, 10136-10139.).

[0004] Supported metal catalysts not only have high catalytic activity, selectivity and stability, but are therefore widely used in catalytic reactions such as hydrogenation and dehydrogenation. Supported metal catalysts are usually composed of carriers and metals. Such catalysts can be prepared by a variety of methods, such as impregnation, solvated metal atom impregnation (SMAD), solid phase precipitation, etc. Among them, impregnation is a commonly used preparation method, but the dispersion of active components of metal catalysts prepared by solution impregnation is usually low, and the reaction conditions of the preparation process are often harsh.

[0005] Highly dispersed supported metal catalysts are prepared by a specific method to make the metal active components highly dispersed on the carrier, thereby improving their catalytic performance, showing excellent activity and selectivity in many chemical reactions, especially in applications requiring high atomic utilization and stability. The methods reported so far mainly include photochemical precipitation, co-precipitation, sedimentation precipitation, ion exchange and colloidal deposition. Photodeposition (PD method for short) was first introduced into the catalysis field in 1978 for the preparation of supported metal catalysts (B. Kraeutler, AJ Bard. Heterogeneous photocatalytic preparation of supported catalysts. Photodeposition of platinum on titanium dioxide powder and other substrates. J. Am. Chem. Soc. 1978, 100, 4317-4318). These catalysts have the advantages of low loading, high dispersity, effective placement, mild conditions and long life, so they are widely used in photocatalysis and electrocatalysis (K. Wenderich, G. Mul. Chem. Rev. 2016, 116, 14587-14619). The method mainly irradiates semiconductors dispersed in metal ion solutions, and metals are loaded on semiconductor carriers under sufficient time irradiation. Through the photodeposition method, metals can be loaded on semiconductors under mild conditions, because high temperature reduction treatment is avoided, thereby avoiding high temperature sintering or high temperature decomposition of semiconductors, and retaining the high specific surface area and high dispersibility of semiconductors, especially nano-semiconductor materials. When the metal catalyst is prepared by photochemical precipitation, the particle size of the metal component is relatively easy to control, the reaction conditions are mild, the reaction time is short, and several metal components can be deposited on the carrier surface at the same time, which is an efficient and mild multi-metal loading method. However, in the suspension containing the photocatalyst, the penetration depth of light is limited, about several millimeters, and most of the light is scattered, that is, the utilization rate of light is low, which seriously limits the practical application of the photodeposition method. Therefore, it is necessary to build a new photoreaction system to improve utilization and prepare catalysts simply and efficiently. Summary of the invention

[0006] The present invention uses a continuous flow photoreaction system to build a reaction device for preparing a supported metal catalyst, and proposes a method for preparing a supported metal catalyst using photodeposition, which does not require high-temperature calcination and reduction, has a short reaction time, and can also perform step-by-step deposition of multiple metals to obtain a supported multi-metal catalyst. Based on this, the present invention is completed.

[0007] In the first aspect, the present invention provides a supported metal catalyst, wherein the supported metal catalyst structure is Mn / S, wherein M is a metal substance; n is a natural number starting from 1; S is a semiconductor carrier; when n is 1, the supported metal catalyst is M1 / S; when n is 2, the supported metal catalyst is M1M2 / S; when n is 3, the supported metal catalyst is M1M2M3 / S, and so on.

[0008] Furthermore, the M metal substance includes but is not limited to Au, Pt, Cu, In, Ru, Ni, Rh, Ag and / or Pd; preferably Au and / or Pt.

[0009] Furthermore, the semiconductor carrier is selected from metal oxides, metal sulfides and / or nitrides.

[0010] Furthermore, when the semiconductor carrier is a metal oxide, the semiconductor carrier includes but is not limited to TiO2, ZnO, WO3, Ta2O5, Ga2O3, Bi2O3, SrTiO3, Bi2WO6 and / or BiVO4.

[0011] Furthermore, when the semiconductor carrier is a metal sulfide compound, the semiconductor carrier includes but is not limited to CdS, ZnS and / or ZnIn2S4.

[0012] Furthermore, when the semiconductor carrier is a nitride, the semiconductor carrier includes but is not limited to carbon nitride and gallium nitride zinc oxide solid solution.

[0013] Furthermore, the particle size of the semiconductor carrier is selected from 1-1000 nm, preferably 20-100 nm.

[0014] Furthermore, in the supported metal catalyst Mn / S, the weight ratio of the supported metal in the catalyst to the weight ratio of the semiconductor carrier is 0.1-10 wt%, preferably 0.4-0.6 wt%.

[0015] Furthermore, when the supported metal is Au, the supported metal Au accounts for 0.6 wt % in the catalyst.

[0016] Furthermore, when the supported metal is Pt, the supported metal Pt accounts for 0.4 wt % in the catalyst.

[0017] In one embodiment of the present invention, when the metal M is Au and the semiconductor carrier is TiO2, the supported metal catalyst is Au / TiO2.

[0018] In one embodiment of the present invention, when the metal M is Pt and the semiconductor carrier is TiO2, the supported metal catalyst is Pt / TiO2.

[0019] In one embodiment of the present invention, when the metal M1 is Au, the metal M2 is Pt, and the semiconductor carrier is TiO2, the supported metal catalyst is AuPt / TiO2.

[0020] In one embodiment of the present invention, when the metal M1 is Au, the metal M2 is Pt, and the semiconductor carrier is ZnO, the supported metal catalyst is AuPt / ZnO.

[0021] In one embodiment of the present invention, when the metal M1 is Au, the metal M2 is Pt, and the semiconductor carrier is SrTiO3, the supported metal catalyst is AuPt / SrTiO3.

[0022] In a second aspect, the present invention provides a reaction device for preparing a supported metal catalyst as described in the first aspect, wherein the reaction device comprises an inert atmosphere device, a circulation reactor, a photoreaction system and a sealed exhaust device; the reactor comprises a circulation reactor A and a circulation reactor B, which are connected, and the two ends of the circulation reactor A and the circulation reactor B are respectively connected to the inert atmosphere device and the sealed exhaust device; the photoreaction system comprises a peristaltic pump, a light source and a reaction tube; the peristaltic pump, the light source and the reaction tube are arranged on the pipeline between the circulation reactor A and the circulation reactor B; the reaction tube is in a spiral structure; and the light source is arranged at the center of the spiral structure of the spiral reaction tube.

[0023] Furthermore, the gas of the inert atmosphere device includes but is not limited to nitrogen, nitrogen and / or argon.

[0024] Furthermore, the reaction tube is light-transmissive.

[0025] Furthermore, the material of the reaction tube includes but is not limited to FEP and / or PTFE.

[0026] Furthermore, the inner diameter of the reaction tube is selected from 0.3-4 mm, preferably 0.8 mm or 2 mm.

[0027] Furthermore, the length of the reaction tube is selected from 5-15 m, preferably 13 m.

[0028] Furthermore, the light source is a parallel light reactor selected from LED lamps and / or xenon lamps and mercury lamps.

[0029] Furthermore, the light source excitation light is ultraviolet light, the wavelength of the light source is 365nm, and the power is 40W.

[0030] In a third aspect, the present invention provides a method for preparing the supported metal catalyst as described in the first aspect, the method comprising the following steps:

[0031] S1. Connecting the reaction device according to the second aspect of the present invention;

[0032] S2. The semiconductor carrier is added to water to prepare a suspension, which is placed in a circulation reactor A;

[0033] S3. adding the metal precursor solution and the sacrificial agent to the suspension in step S2;

[0034] S4. In step S3, an inert gas is introduced into the system to make the interior of the reaction device an oxygen-free environment;

[0035] S5. The peristaltic pump adds the liquid in step S4 to the photoreaction system, and all the liquid in the circulation reactor A enters the system and enters the circulation reactor B after sufficient reaction;

[0036] S6. After the reaction is completed, adjust the direction of the peristaltic pump so that the liquid flows from the circulation reactor B through the photoreaction system back to the circulation reactor A;

[0037] S7. The suspension after the reaction in step S6 is centrifuged, washed, and vacuum dried to obtain a supported metal catalyst Mn / S.

[0038] Furthermore, in step S2, the semiconductor carrier is selected from metal oxides, metal sulfides and / or nitrides.

[0039] Furthermore, when the semiconductor carrier is a metal oxide, the semiconductor carrier includes but is not limited to TiO2, ZnO, WO3, Ta2O5, Ga2O3, Bi2O3, SrTiO3, Bi2WO6 and / or BiVO4.

[0040] Furthermore, when the semiconductor carrier is a metal sulfide compound, the semiconductor carrier includes but is not limited to CdS, ZnS and / or ZnIn2S4.

[0041] Furthermore, when the semiconductor carrier is a nitride, the semiconductor carrier includes but is not limited to carbon nitride and gallium nitride zinc oxide solid solution.

[0042] Furthermore, in step S2, the ratio of the mass (g) of the semiconductor carrier to the volume (L) of the required solution is 1:1.

[0043] Furthermore, in step S3, the volume of the sacrificial agent in the solution required for the reaction is 2%.

[0044] Furthermore, the sacrificial agent in step S3 includes but is not limited to isopropanol, methanol, ethanol, triethylamine and / or triethanolamine.

[0045] Furthermore, in the metal precursor solution in step S3, the metal substance includes but is not limited to Au, Pt, Cu, In, Ru, Ni, Rh, Ag and / or Pd; preferably Au and / or Pt.

[0046] Furthermore, when the metal substance is Au, the Au-loaded metal precursor includes but is not limited to chloroauric acid and / or chloroaurate; the metal precursor solution includes but is not limited to chloroauric acid solution and / or chloroaurate solution, preferably NaAuCl4·2H2O solution.

[0047] Furthermore, when the metal substance is Pt, the Pt-loaded metal precursor includes but is not limited to chloroplatinic acid and / or chloroplatinate; the metal precursor solution includes but is not limited to chloroplatinic acid solution and / or chloroplatinate solution, preferably K2PtCl4·4H2O solution.

[0048] Furthermore, in the step S3, the volume of the metal precursor solution added is determined according to the metal loading amount in the loaded metal catalyst.

[0049] Furthermore, the inert gas in step S4 includes but is not limited to nitrogen, nitrogen and / or argon.

[0050] Furthermore, in step S5, the liquid is added to the photoreaction system, and the reaction pump controls the liquid flow rate to be selected from 1-100 mL / min, preferably 12 mL / min.

[0051] Further, when multiple supported metal catalysts are prepared, steps S3 to S6 are repeated.

[0052] Furthermore, when preparing a single supported metal catalyst, steps S3-S6 are repeated when multiple depositions are performed.

[0053] Furthermore, in the step S7, the supported metal catalyst Mn / S has a mass ratio of supported metal to semiconductor carrier of 0.1-10wt%, preferably 0.4-0.6wt%.

[0054] Furthermore, when the supported metal is Au, the supported metal Au accounts for 0.6 wt % in the catalyst.

[0055] Furthermore, when the supported metal is Pt, the supported metal Pt accounts for 0.4 wt % in the catalyst.

[0056] In a fourth aspect, the present invention provides use of the supported metal catalyst as described in the first aspect of the present invention in a selective oxidation reaction of organic matter.

[0057] Beneficial Effects

[0058] The present invention provides a method for preparing a metal-supported catalyst by using photodeposition, which has the following advantages:

[0059] (1) This method does not require high-temperature calcination or reduction, has a simple reaction, can be expanded, has low cost, and is suitable for daily life and production;

[0060] (2) The reaction time is short;

[0061] (3) The reaction is green, environmentally friendly, non-toxic and harmless;

[0062] (4) Multiple metals can be deposited step by step. After the first metal is loaded, the precursor of the second metal can be added, that is, multiple metals can be deposited step by step to obtain a multi-metal supported catalyst; or a single metal can be deposited multiple times at different time periods;

[0063] (5) The present invention adopts a continuous flow photoreaction system. The suspension enters the transparent plastic tube through a peristaltic pump, and the light source irradiates the plastic tube.

[0064] Material tube, because the diameter of the plastic tube is relatively thin (0.3-2mm), it ensures that light can penetrate the reaction liquid and shortens the light deposition time;

[0065] (6) The reaction tube adopts a spiral structure, and the light source is set at the center of the spiral structure. The light source irradiates outward evenly from 8 sides, so that the reaction liquid in the reaction tube can be irradiated, shortening the light deposition time and improving the reaction efficiency;

[0066] (7) The catalyst obtained by the reaction is stable and has good catalytic performance.

[0067] In summary, the metal loading method of the present invention successfully prepares a highly dispersed catalyst by optimizing the photodeposition reactor. By using a coil and a peristaltic pump device, the method of photodeposition loading of metals is precisely regulated, and by achieving a more efficient photoreaction, a higher light energy utilization rate, a variety of metal distribution deposition and milder operating conditions, the energy waste caused by the low utilization rate of incident photons in conventional photodeposition is avoided. The multi-metal catalyst synthesized by this invention has a higher metal dispersion, exposing more metal active sites, which is conducive to the adsorption of oxygen, participating in the oxidation reaction of glycerol, and improving the conversion rate and selectivity of glycerol to glyceric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 This is a diagram of the continuous photodeposition reaction system.

[0069] Note: 1. Peristaltic pump; 2. Three-necked blue-capped glass bottle; 3. N2 gas cylinder; 4. Low-temperature constant temperature system; 5. Bubble generator; 6. Light source; 7. Coil tube.

[0070] Figure 2 This is the full XPS spectrum of the catalyst AuPt / TiO2.

[0071] Figure 3 This is the XPS Au4f spectrum of the catalyst AuPt / TiO2.

[0072] Figure 4 This is the XPS Pt4f spectrum of the catalyst AuPt / TiO2.

[0073] Figure 5 This is the full XPS spectrum of the catalyst AuPt / ZnO.

[0074] Figure 6 This is the XPS Au4f spectrum of the catalyst AuPt / ZnO.

[0075] Figure 7 This is the XPS Pt4f spectrum of the catalyst AuPt / ZnO.

[0076] Figure 8 This is the full XPS spectrum of the catalyst AuPt / SrTiO3.

[0077] Fig. 9 This is the XPS Au4f spectrum of the catalyst AuPt / SrTiO3.

[0078] Fig.10 This is the XPS Pt4f spectrum of the catalyst AuPt / SrTiO3. DETAILED DESCRIPTION

[0079] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the embodiments described below can be combined with each other as long as they do not conflict with each other.

[0080] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0081] Explanation of terms

[0082] Glycerol oxidation reaction: It is an important chemical process to convert glycerol into high value-added chemicals. In the glycerol oxidation reaction, commonly used catalysts include precious metals such as platinum (Pt), palladium (Pd), gold (Au), etc., as well as some polyoxometalates (POMs) and composite catalysts. These catalysts show different activities and selectivities under different reaction conditions. As a by-product in the biodiesel production process, the effective conversion of glycerol has important economic and environmental significance.

[0083] XPS full spectrum: It is an important analysis result in X-ray photoelectron spectroscopy (XPS) technology, which is used to study the chemical composition and structure of the material surface. XPS provides information about its chemical state by measuring the binding energy of elements on the sample surface. This technology is widely used in materials science, chemistry, physics and other fields to analyze the element types, chemical valence states and chemical environment on the surface of solid samples.

[0084] Sacrificial agent: plays an important role in photocatalytic hydrogen production. Its main function is to consume photogenerated holes, thereby improving the photocatalytic efficiency of semiconductor materials. The selection of sacrificial agent has an important influence on the efficiency of photocatalytic hydrogen production. Different types of sacrificial agents have different oxidation potentials and chemical properties. Therefore, in practical applications, it is necessary to select a suitable sacrificial agent according to the specific photocatalytic system and reaction conditions to optimize the hydrogen production performance.

[0085] Example 1 Construction of the reaction device

[0086] The reaction device comprises an inert atmosphere device, a circulation reactor, a photoreaction system and a sealed exhaust device; the reactor comprises a circulation reactor A and a circulation reactor B, which are connected, and the two ends of the circulation reactor A and the circulation reactor B are respectively connected to the inert atmosphere device and the sealed exhaust device; the photoreaction system comprises a peristaltic pump, a light source and a reaction tube; the peristaltic pump, the light source and the reaction tube are arranged on the pipeline between the circulation reactor A and the circulation reactor B; the reaction tube is in a spiral structure; the light source is arranged at the center of the spiral structure of the spiral reaction tube and is perpendicular to the reaction tube; the light source is evenly diffused outwards from 8 faces.

[0087] like Figure 1 As shown, the reaction device is constructed as follows: the circulation reactor A and the circulation reactor B can use three-mouth blue-covered glass bottles (2) for reaction, the circulation reactor A is respectively connected to the peristaltic pump (1), the circulation reactor B and the inert atmosphere device, the inert atmosphere device inputs gas through the N2 gas cylinder (3), the peristaltic pump (1) is connected between the circulation reactor and the low-temperature constant temperature system (4), the low-temperature constant temperature system is a 13m Teflon hard tube spirally formed into a spiral tube (7) structure, the light reaction system is arranged in the low-temperature constant temperature system (4), wherein the light source 6 is an LED light source box, providing a parallel light source; the circulation reactor B is respectively connected to the low-temperature constant temperature system (4), the circulation reactor A and the sealed exhaust device, and the sealed exhaust device is a bubbler (5) for isolating air and discharging waste gas.

[0088] Example 2 Preparation of supported metal catalyst Au / TiO2

[0089] The reaction device constructed in Example 1 was used; the inner diameter of the plastic coil in the photoreaction system was set to 0.8 mm, the length was set to 13 m, the light source was set to a 365 nm LED light source, and the peristaltic pump flow rate was set to 12 mL / min.

[0090] (1) Add 0.400 g of TiO2 and deionized water into the circulation reactor A and mix them to form a suspension;

[0091] (2) Add 98 μL NaAuCl4·2H2O solution (Au loading in the catalyst is 0.6 wt%) and 2 mL isopropanol to (1).

[0092] Medium suspension;

[0093] (3) continuously introducing nitrogen into the circulation reactor A to remove oxygen from the circulation reactor A;

[0094] (4) The liquid in the circulation reactor A will enter the photoreaction system through the peristaltic pump and finally flow into the circulation reactor B;

[0095] (5) After all the liquid in the circulation reactor A flows into the circulation reactor B and the reaction is complete, the direction of the peristaltic pump is reversed so that the liquid flows from the circulation reactor B into the photoreaction system and finally flows into the circulation reactor A;

[0096] (6) The suspension obtained in (5) is centrifuged, washed with deionized water and anhydrous ethanol, and dried to obtain the supported metal catalyst Au / TiO2.

[0097] When the same metal needs to be loaded multiple times, NaAuCl4·2H2O solution and isopropanol are added to the circulation reactor B, the direction of the peristaltic pump is adjusted, and the test is repeated, alternating between the circulation reactor A and the circulation reactor B.

[0098] Example 3 Preparation of supported metal catalyst Pt / TiO2

[0099] The reaction device constructed in Example 1 was used; the inner diameter of the plastic coil in the photoreaction system was set to 0.8 mm, the length was set to 13 m, the light source was set to a 365 nm LED light source, and the peristaltic pump flow rate was set to 12 mL / min.

[0100] (1) Add 0.400 g of TiO2 and deionized water into the circulation reactor A and mix them to form a suspension;

[0101] (2) 72 μL of K2PtCl4·4H2O solution (Pt loading in the catalyst is 0.4 wt%) was added to the suspension in (1);

[0102] (3) continuously introducing nitrogen into the circulation reactor A to remove oxygen from the circulation reactor A;

[0103] (4) The liquid in the circulation reactor A will enter the photoreaction system through the peristaltic pump and finally flow into the circulation reactor B;

[0104] (5) After all the liquid in the circulation reactor A flows into the circulation reactor B and the reaction is complete, the direction of the peristaltic pump is reversed so that the liquid flows from the circulation reactor B into the photoreaction system and finally flows into the circulation reactor A;

[0105] (6) The suspension obtained in (5) is centrifuged, washed with deionized water and anhydrous ethanol, and dried to obtain a supported metal catalyst Pt / TiO2.

[0106] When the same metal needs to be loaded multiple times, NaAuCl4·2H2O solution and isopropanol are added to the circulation reactor B, the direction of the peristaltic pump is adjusted, and the test is repeated, alternating between the circulation reactor A and the circulation reactor B.

[0107] Example 4 Preparation of supported metal catalyst AuPt / TiO2-1

[0108] The reaction device constructed in Example 1 was used; the inner diameter of the plastic coil in the photoreaction system was set to 0.8 mm, the length was set to 13 m, the light source was set to a 365 nm LED light source, and the peristaltic pump flow rate was set to 12 mL / min.

[0109] (1) Add 0.200 g of TiO2 and deionized water into the circulation reactor A and mix them to form a suspension;

[0110] (2) 49 μL NaAuCl4·2H2O solution (0.6 wt% Au loading in the catalyst) was added to the suspension in (1);

[0111] (3) continuously introducing nitrogen into the circulation reactor A to remove oxygen from the circulation reactor A;

[0112] (4) The liquid in the circulation reactor A will enter the photoreaction system through the peristaltic pump and finally flow into the circulation reactor B;

[0113] (5) After all the liquid in the circulation reactor A flows into the circulation reactor B and the reaction is complete, the direction of the peristaltic pump is reversed so that the liquid flows from the circulation reactor B into the photoreaction system and finally flows into the circulation reactor A;

[0114] (6) After the liquid has passed through the continuous photoreaction system twice, 36 μL of K2PtCl4·4H2O (Pt loading in the catalyst is 0.4 wt%) solution is extracted and injected into the circulation reactor A, and (3)-(5) are repeated;

[0115] (7) The suspension obtained in (6) was centrifuged, washed with deionized water and anhydrous ethanol, and dried to obtain the supported metal catalyst AuPt / TiO2-1.

[0116] Example 5 Preparation of supported metal catalyst AuPt / TiO2-2

[0117] The reaction device constructed in Example 1 was used; the inner diameter of the plastic coil in the photoreaction system was set to 0.8 mm, the length was set to 13 m, the light source was set to a 365 nm LED light source, and the peristaltic pump flow rate was set to 12 mL / min.

[0118] (1) Add 0.200 g TiO2 and 200 mL deionized water into the circulation reactor A and mix them to form a suspension;

[0119] (2) Add 49 μL NaAuCl4·2H2O solution (Au loading in the catalyst is 0.6 wt%) and 2 mL isopropanol to (1).

[0120] Medium suspension;

[0121] (3) continuously introducing nitrogen into the circulation reactor A to remove oxygen from the circulation reactor A;

[0122] (4) The liquid in the circulation reactor A will enter the photoreaction system through the peristaltic pump and finally flow into the circulation reactor B;

[0123] (5) After all the liquid in the circulation reactor A flows into the circulation reactor B and the reaction is complete, the direction of the peristaltic pump is reversed so that the liquid flows from the circulation reactor B into the photoreaction system and finally flows into the circulation reactor A;

[0124] (6) After the liquid has passed through the continuous photoreaction system twice, 36 μL of K2PtCl4·4H2O (Pt loading in the catalyst is 0.4 wt%) solution is extracted and injected into the circulation reactor A, and (3)-(5) are repeated;

[0125] (7) The suspension obtained in (6) is centrifuged, washed with deionized water and anhydrous ethanol, and dried to obtain the supported metal catalyst AuPt / TiO2-2.

[0126] Example 6 Preparation of supported metal catalyst AuPt / TiO2-3

[0127] The reaction device constructed in Example 1 was used; the inner diameter of the plastic coil in the photoreaction system was set to 0.8 mm, the length was set to 13 m, the light source was set to a 365 nm LED light source, and the peristaltic pump flow rate was set to 12 mL / min.

[0128] (1) Add 0.400 g TiO2 and 400 mL deionized water into the circulation reactor A and mix them to form a suspension;

[0129] (2) Add 98 μL NaAuCl4·2H2O solution (Au loading in the catalyst is 0.6 wt%) and 2 mL isopropanol to (1).

[0130] Medium suspension;

[0131] (3) continuously introducing nitrogen into the circulation reactor A to remove oxygen from the circulation reactor A;

[0132] (4) The liquid in the circulation reactor A will enter the photoreaction system through the peristaltic pump and finally flow into the circulation reactor B;

[0133] (5) After all the liquid in the circulation reactor A flows into the circulation reactor B and the reaction is complete, the direction of the peristaltic pump is reversed so that the liquid flows from the circulation reactor B into the photoreaction system and finally flows into the circulation reactor A;

[0134] (6) After the liquid has passed through the continuous photoreaction system twice, 72 μL of K2PtCl4·4H2O (Pt loading in the catalyst is 0.4 wt%) solution is extracted and injected into the circulation reactor A, and (3)-(5) are repeated;

[0135] (7) The suspension obtained in (6) is centrifuged, washed with deionized water and anhydrous ethanol, and dried to obtain the supported metal catalyst AuPt / TiO2-3.

[0136] Example 7 Preparation of supported metal catalyst AuPt / ZnO

[0137] The reaction device constructed in Example 1 was used; the inner diameter of the plastic coil in the photoreaction system was set to 0.8 mm, the length was set to 13 m, the light source was set to a 365 nm LED light source, and the peristaltic pump flow rate was set to 12 mL / min.

[0138] (1) Add 0.400 g ZnO and 400 mL deionized water into the circulation reactor A and mix them to form a suspension;

[0139] (2) Add 98 μL NaAuCl4·2H2O solution (Au loading in the catalyst is 0.6 wt%) and 2 mL isopropanol to (1).

[0140] Medium suspension;

[0141] (3) continuously introducing nitrogen into the circulation reactor A to remove oxygen from the circulation reactor A;

[0142] (4) The liquid in the circulation reactor A will enter the photoreaction system through the peristaltic pump and finally flow into the circulation reactor B;

[0143] (5) After all the liquid in the circulation reactor A flows into the circulation reactor B and the reaction is complete, the direction of the peristaltic pump is reversed so that the liquid flows from the circulation reactor B into the photoreaction system and finally flows into the circulation reactor A;

[0144] (6) After the liquid has passed through the continuous photoreaction system twice, 72 μL of K2PtCl4·4H2O (Pt loading in the catalyst is 0.4 wt%) solution is extracted and injected into the circulation reactor A, and (3)-(5) are repeated;

[0145] (7) The suspension obtained in (6) is centrifuged, washed with deionized water and anhydrous ethanol, and dried to obtain the supported metal catalyst AuPt / ZnO.

[0146] Example 8 Preparation of supported metal catalyst AuPt / SrTiO3

[0147] The reaction device constructed in Example 1 was used; the inner diameter of the plastic coil in the photoreaction system was set to 0.8 mm, the length was set to 13 m, the light source was set to a 365 nm LED light source, and the peristaltic pump flow rate was set to 12 mL / min.

[0148] (1) Add 0.400 g SrTiO2 and deionized water into the circulation reactor A and mix them to form a suspension;

[0149] (2) Add 98 μL NaAuCl4·2H2O solution (Au loading in the catalyst is 0.6 wt%) and 2 mL isopropanol to (1).

[0150] Medium suspension;

[0151] (3) continuously introducing nitrogen into the circulation reactor A to remove oxygen from the circulation reactor A;

[0152] (4) The liquid in the circulation reactor A will enter the photoreaction system through the peristaltic pump and finally flow into the circulation reactor B;

[0153] (5) After all the liquid in the circulation reactor A flows into the circulation reactor B and the reaction is complete, the direction of the peristaltic pump is reversed so that the liquid flows from the circulation reactor B into the photoreaction system and finally flows into the circulation reactor A;

[0154] (6) After the liquid has passed through the continuous photoreaction system twice, 72 μL of K2PtCl4·4H2O (Pt loading in the catalyst is 0.4 wt%) solution is extracted and injected into the circulation reactor A, and (3)-(5) are repeated;

[0155] (7) The suspension obtained in (6) is centrifuged, washed with deionized water and anhydrous ethanol, and dried to obtain the supported metal catalyst AuPt / SrTiO3.

[0156] Example 9 Spectral Analysis of Supported Metal Catalysts

[0157] X-ray photoelectron spectroscopy was used to analyze the elemental composition and valence state of the sample surface distribution to prove that the photodeposition method of the present invention successfully deposited a variety of metals on the catalyst surface. The supported metal catalysts prepared in Examples 2-8 were analyzed by spectrogram, and the test included the following steps:

[0158] (1) The washed, dried and ground supported metal catalyst sample is evenly spread on the conductive glue.

[0159] (2) Measured using a Thermo Fisher Scientific instrument with an Al Kα radiation excitation source, using C1s (284.80 eV)

[0160] The peak was used as the calibration peak.

[0161] like Figure 2-10 As shown in FIG. 1 , the element composition and valence state of the surface distribution of different supported metal catalysts prepared in the examples were analyzed by X-ray photoelectron spectroscopy. The XPS spectra of the supported metal catalysts all observed response peaks at 87 eV, 83 eV, 74 eV, and 71 eV, which were respectively attributed to Au 4f 5 / 2 、Au 4f 7 / 2 、Pt 4f 5 / 2 、Pt 4f 7 / 2 The photodeposition method of the present invention successfully deposits a variety of metals on different catalyst surfaces, and the deposited metals are all in the form of simple substances.

[0162] Example 10 Performance Evaluation of Supported Metal Catalysts

[0163] The glycerol oxidation reaction was chosen as a method to evaluate the catalyst performance.

[0164] Control group: TiO2 catalyst without metal loading

[0165] Test group: catalysts prepared in Examples 2-8, Au / TiO2, Pt / TiO2, AuPt / TiO2-1, AuPt / TiO2-2, AuPt / TiO2-3, AuPt / ZnO and AuPt / SrTiO3

[0166] (1) Add 10 mL of glycerol aqueous solution (0.3 mol / L) and a certain amount of catalyst (the molar ratio of glycerol to Au and Pt is 500:1) into a stainless steel autoclave;

[0167] (2) Carrying out the reaction: the reaction temperature is 100°C, the oxygen pressure is 0.6MPa, and the reaction time is 8h;

[0168] (3) After the reaction is completed, the mixture is filtered with an aqueous phase filter and then analyzed by liquid chromatography. The glycerol conversion rate and the selectivity of glyceric acid are calculated by the external standard method.

[0169] The test results are shown in Table 1. Among the photo-deposited Au-based Pt-based catalysts prepared by the present invention, AuPt / TiO2-2 (Au 0.6wt% Pt 0.4wt%) has a higher catalytic performance in the reaction of glycerol oxidation to prepare glyceric acid, with a glycerol conversion rate of 83.6% and a glyceric acid selectivity of 46.3%.

[0170] Compared with AuPt / TiO2-2, AuPt / TiO2-1 did not add the sacrificial agent isopropanol during the preparation of the catalyst, resulting in the photodeposition efficiency of AuPt / TiO2-1 being lower than that of AuPt / TiO2-2 during the photodeposition process, which in turn resulted in its glycerol oxidation performance being worse than that of AuPt / TiO2-2.

[0171] AuPt / TiO2-3 and AuPt / TiO2-2 have the same experimental steps, but the amount of carrier added during the preparation of AuPt / TiO2-3 is twice that of AuPt / TiO2-2. The experimental results of glycerol oxidation are similar to those of AuPt / TiO2-2, which proves that the photodeposition method of the present invention is applicable to situations with different amounts of carriers, and the system can be enlarged or reduced according to needs without affecting the catalytic performance of the catalyst itself.

[0172] The results of glycerol oxidation of AuPt / SrTiO3 and AuPt / ZnO show that the multi-metal loading method of the invention is suitable for different carriers.

[0173] The results of glycerol oxidation with TiO2, Au / TiO2, and Pt / TiO2 show that the catalytic performance of glycerol oxidation to prepare glyceric acid is determined by the two precious metals. It also shows that the multi-metal preparation method of the invention can distribute and load multiple metals, and can also deposit a single metal on a carrier.

[0174] Table 1. Performance of different catalysts in the selective oxidation of glycerol to glyceric acid

[0175]

[0176]

Claims

1. A supported metal catalyst, wherein the supported metal catalyst structure is Mn / S, wherein M is a metal substance; n is a natural number starting from 1; S is a semiconductor carrier; when n is 1, the supported metal catalyst is M1 / S; when n is 2, the supported metal catalyst is M1M2 / S; when n is 3, the supported metal catalyst is M1M2M3 / S, and so on; the M metal substance includes but is not limited to Au, Pt, Cu, In, Ru, Ni, Rh, Ag and / or Pd; preferably Au and / or Pt; the semiconductor carrier is selected from metal oxides, metal sulfides and / or nitrides; when the semiconductor carrier When the body is a metal oxide, the semiconductor carrier includes but is not limited to TiO2, ZnO, WO3, Ta2O5, Ga2O3, Bi2O3, SrTiO3, Bi2WO6 and / or BiVO4; when the semiconductor carrier is a metal sulfide compound, the semiconductor carrier includes but is not limited to CdS, ZnS and / or ZnIn2S4; further, when the semiconductor carrier is a nitride, the semiconductor carrier includes but is not limited to carbon nitride, gallium nitride zinc oxide solid solution; supported metal catalyst Mn / S, the mass of the supported metal in the catalyst to the mass of the semiconductor carrier ratio is 0.1-10wt%, preferably 0.4-0.6wt%.

2. The supported metal catalyst Mn / S as claimed in claim 1, when the supported metal is Au, the supported metal Au accounts for 0.6 wt% in the catalyst; when the supported metal is Pt, the supported metal Pt accounts for 0.4 wt% in the catalyst.

3. A reaction device for preparing a supported metal catalyst as claimed in claim 1, the reaction device comprising an inert atmosphere device, a circulation reactor, a photoreaction system and a sealed exhaust device; the reactor comprises a circulation reactor A and a circulation reactor B, the two are connected, and the two ends of the circulation reactor A and the circulation reactor B are respectively connected to the inert atmosphere device and the sealed exhaust device; the photoreaction system comprises a peristaltic pump, a light source and a reaction tube; the peristaltic pump, the light source and the reaction tube are arranged on the pipeline between the circulation reactor A and the circulation reactor B; the reaction tube is a spiral structure; the light source is arranged at the center of the spiral structure of the spiral reaction tube.

4. The reaction device as claimed in claim 3, wherein the material of the reaction tube includes but is not limited to FEP and / or PTFE; the inner diameter of the reaction tube is selected from 0.3-4 mm; and the length of the reaction tube is selected from 5-15 m.

5. The reaction device according to claim 3, wherein the light source is a parallel light reactor selected from LED lamps and / or xenon lamps, mercury lamps; The excitation light of the light source is ultraviolet light, the wavelength of the light source is 365nm, and the power is 40W.

6. The method for preparing a supported metal catalyst according to claim 1, comprising the steps of: S1. Connecting the reaction device according to claim 2; S2. The semiconductor carrier is added to water to prepare a suspension, which is placed in a circulation reactor A; S3. adding the metal precursor solution and the sacrificial agent to the suspension in step S2; S4. In step S3, an inert gas is introduced into the system to make the interior of the reaction device an oxygen-free environment; S5. The reaction pump adds the liquid in step S4 to the photoreaction system, and all the liquid in the circulation reactor A enters the system and fully reacts before entering the circulation reactor B; S6. After the reaction is completed, adjust the direction of the peristaltic pump so that the liquid flows from the circulation reactor B through the photoreaction system back to the circulation reactor A; S7. The suspension after the reaction in step S6 is centrifuged, washed, and vacuum dried to obtain a supported metal catalyst Mn / S.

7. The method for preparing a supported metal catalyst as claimed in claim 6, wherein the semiconductor carrier in step S2 is selected from metal oxides, metal sulfides and / or nitrides; when the semiconductor carrier is a metal oxide, the semiconductor carrier includes but is not limited to TiO2, ZnO, WO3, Ta2O5, Ga2O3, Bi2O3, SrTiO3, Bi2WO6 and / or BiVO4; when the semiconductor carrier is a metal sulfide, the semiconductor carrier includes but is not limited to CdS, ZnS and / or ZnIn2S4; further, when the semiconductor carrier is a nitride, the semiconductor carrier includes but is not limited to carbon nitride, gallium nitride zinc oxide solid solution; the ratio of the mass of the semiconductor carrier (g) to the volume of the required solution (L) is 1:

1.

8. The method for preparing a supported metal catalyst as claimed in claim 6, wherein the sacrificial agent in step S3 accounts for 2% of the volume of the suspension; the sacrificial agent includes but is not limited to isopropanol, methanol, ethanol, triethylamine and / or triethanolamine; the metal precursor solution in step S3, the metal substance includes but is not limited to Au, Pt, Cu, In, Ru, Ni, Rh, Ag and / or Pd; preferably Au and / or Pt; when the metal substance is Au, the Au-loaded metal precursor includes but is not limited to chloroauric acid and / or chloroaurate; the metal precursor solution includes but is not limited to chloroauric acid solution and / or chloroaurate solution, preferably NaAuCl4·2H2O solution; when the metal substance is Pt, the Pt-loaded metal precursor includes but is not limited to chloroplatinic acid and / or chloroplatinate; the metal precursor solution includes but is not limited to chloroplatinic acid solution and / or chloroplatinate solution, preferably K2PtCl4·4H2O solution.

9. The method for preparing a supported metal catalyst according to claim 6, wherein the inert gas in step S4 includes but is not limited to nitrogen, nitrogen and / or argon; in step S5, the liquid is added to the photoreaction system, and the reaction pump controls the liquid flow rate to be selected from 1-100 mL / min, preferably 12 mL / min.

10. Use of the supported metal catalyst as claimed in claim 1 in the selective oxidation reaction of organic matter.

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