Multilayer core-shell structure catalyst, preparation method and application thereof, and method for synthesizing 1,3-propanediol

Abstract

The application relates to the field of catalyst material synthesis, and discloses a core-shell structure catalyst, a preparation method and application thereof, and a 1,3-propanediol synthesis method. The catalyst comprises a core, a sandwich layer and a shell. The core of the catalyst comprises a heat-resistant inorganic oxide and / or a molecular sieve, the sandwich layer comprises W oxide and Pt nanoparticles, and the shell comprises a mesoporous molecular sieve. The catalyst has high hydrothermal stability, and the selectivity of the product 1,3-propanediol in a catalytic reaction is high.

Description

Technical Field

[0001] This invention relates to the field of catalyst material synthesis, specifically to a multilayer core-shell structure catalyst, its preparation method and application, and a method for synthesizing 1,3-propanediol. Background Technology

[0002] Glycerin is a major byproduct of biodiesel production from renewable animal and vegetable oils, accounting for up to 10%. The effective utilization of glycerin, such as its use in the production of high-value-added high-end chemicals, is an excellent choice from an economic, environmental, and resource recycling perspective. Among these, the selective synthesis of high-value-added 1,3-propanediol from glycerin is one of the most economically promising and socially valuable pathways. 1,3-Propanediol is an important monomer for the production of poly(1,3-propanediol) terephthalate (PTT). PTT combines the easy processing of polyethylene terephthalate (PET) with the high performance of polybutylene terephthalate (PBT), making it a high-end polymer that can be used to produce high-end plastic medical products and textiles. Therefore, utilizing glycerin, a byproduct of biodiesel production, to synthesize high-value-added 1,3-propanediol aligns perfectly with the development of a green, environmentally friendly, and sustainable development path.

[0003] Industrial production methods for 1,3-propanediol include chemical and biological methods. Chemical methods include Shell's ethylene oxide carbonylation hydrogenation method and Degussa and DuPont's acrolein hydration hydrogenation method. However, these methods have been discontinued due to environmental pollution, catalyst issues, and complex production processes. DuPont (CN200380104657.2) disclosed a pathway for converting sugar sources into 1,3-propanediol through bio-fermentation, but this method requires the addition of expensive vitamin B12, resulting in high costs. Tsinghua University (CN200510011867.8) disclosed a method for biologically converting glycerol into 1,3-propanediol using Clostridiurn bacteria; however, this method is affected by the bio-metabolic activity, resulting in low production efficiency and complex products containing vitamins, salts, bacteria, and other impurities. Separation requires multiple procedures, leading to high energy consumption and costs. Conversely, the direct hydrogenolysis of glycerol to produce 1,3-propanediol provides a more optimized method and pathway for high-value-added conversion and upgrading, with potential economic benefits and scientific research value.

[0004] The key technical obstacle to the industrialization of this technology lies in the lack of highly efficient and stable catalysts. Current catalysts still suffer from the following problems: While catalysts with good activity primarily use W and Pt as active components, water is used as the solvent in this reaction system, and the W component is easily leached out under hydrothermal conditions, forming H₂. 2x WO 3-xSpecies loss is a significant issue, as Pt tends to aggregate and bleed under hydrothermal reaction conditions, leading to catalyst deactivation. Currently available and reported catalysts also exhibit poor stability. Therefore, a catalyst with both good catalytic activity and stability is needed. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that the active components of catalysts for the synthesis of 1,3-propanediol are prone to agglomeration and loss during hydrothermal reactions, resulting in catalyst deactivation. This invention provides a multilayer core-shell structure catalyst, its preparation method and application, and a method for synthesizing 1,3-propanediol. This catalyst has high hydrothermal stability and high selectivity for the catalytic reaction product 1,3-propanediol.

[0006] To achieve the above objectives, the first aspect of the present invention provides a core-shell structured catalyst, the catalyst comprising a core, a sandwich layer, and a shell, wherein the core of the catalyst comprises heat-resistant inorganic oxides and / or molecular sieves, the sandwich layer comprises W oxides and Pt nanoparticles, and the shell comprises mesoporous molecular sieves.

[0007] Preferably, the core comprises at least one of alumina, Beta molecular sieve, ZSM-5 molecular sieve, and HY molecular sieve.

[0008] A second aspect of the present invention provides a method for preparing a core-shell structured catalyst, wherein the method includes:

[0009] (1) Loading W oxide and Pt nanoparticles onto the core to obtain the first preproduct;

[0010] (2) A mixture containing a first preproduct, a first template agent, an optional acid, an optional first base source, a silicon source and water is subjected to a hydrothermal reaction to obtain a second preproduct;

[0011] (3) The second preproduct is calcined to obtain the catalyst.

[0012] A third aspect of the present invention provides a core-shell structured catalyst prepared by the preparation method described in the second aspect, the catalyst comprising a core, a sandwich layer and a shell.

[0013] The fourth aspect of this invention provides the application of the core-shell structured catalyst described in the first or third aspect in the synthesis of 1,3-propanediol.

[0014] The fifth aspect of the present invention provides a method for synthesizing 1,3-propanediol, wherein the method comprises: reacting an aqueous glycerol solution with a core-shell structured catalyst as described in the first or third aspect.

[0015] Preferably, the reaction conditions include: a reaction temperature of 120-200°C, a hydrogen pressure of 1-6 MPa, and a glycerol concentration of 10-90 wt% in the aqueous glycerol solution.

[0016] Preferably, the mass ratio of the catalyst to the glycerol is 1:(0.5-5), and the reaction time is 4-720 h.

[0017] Preferably, the reactor is a fixed-bed reactor with a liquid hourly space velocity (LHSV) of 0.05-5 h⁻¹. -1 Preferably 0.1-2h -1 .

[0018] The beneficial effects achieved through the above technical solution are as follows:

[0019] (1) The core-shell structure catalyst provided by the present invention has a multi-layer core-shell structure with W oxide and Pt nanoparticles as active components. The outer shell is made of mesoporous molecular sieve to fix the active components, which has a more stable structure and avoids the aggregation and loss of active components.

[0020] (2) In this invention, the outer shell is a mesoporous molecular sieve. The ordered mesoporous channels of the mesoporous molecular sieve are more conducive to the mass transfer efficiency of raw materials and products, significantly improving the activity of the catalyst and the high conversion rate of glycerol. At the same time, the 1,3-propanediol product can migrate rapidly, reducing the occurrence of the side reaction of the generated 1,3-propanediol being further hydrogenated and deoxygenated to generate n-propanol, resulting in high selectivity of the synthesized product 1,3-propanediol.

[0021] (3) In this invention, preferably, the method for preparing the core-shell structure catalyst is simple. W oxide and Pt nanoparticles are loaded onto the core of the catalyst using a specific loading method. The loading amount of W oxide and Pt nanoparticles can be flexibly adjusted. The mesoporous molecular sieve of the outer shell is synthesized through hydrothermal reaction, which plays a better role in fixing the W oxide and Pt nanoparticles in the interlayer. Attached Figure Description

[0022] Figure 1 This is a TEM image of the core-shell structured catalyst prepared in Example 1;

[0023] Figure 2 This is the small-angle XRD pattern of the core-shell structured catalyst prepared in Example 1. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] The first aspect of the present invention provides a core-shell structured catalyst, wherein the catalyst includes a core, a sandwich layer and a shell, the core of the catalyst includes heat-resistant inorganic oxides and / or molecular sieves, the sandwich layer includes W oxides and Pt nanoparticles, and the shell includes mesoporous molecular sieves.

[0026] In this invention, the innermost layer of the core-shell structure is the core, the middle interlayer covers the core, and the interlayer is covered by the outermost shell. The core-shell structure catalyst of this invention has a more stable structure and higher hydrothermal stability. The interlayer uses W oxide and Pt nanoparticles as active components, and the mesoporous molecular sieve of the shell plays a role in fixing the Pt nanoparticles, preventing the aggregation and loss of active components.

[0027] According to the present invention, the type of heat-resistant inorganic oxide is not particularly limited, and any conventional heat-resistant inorganic oxide in the art can be used as a core carrier. Preferably, the heat-resistant inorganic oxide is selected from at least one of alumina, zirconium oxide, titanium dioxide, and silicon dioxide.

[0028] According to the present invention, the type of molecular sieve is not particularly limited, and it can be a conventional molecular sieve used as a carrier core. Preferably, the molecular sieve is selected from at least one of Beta molecular sieve, ZSM-5 molecular sieve, and HY molecular sieve. In the present invention, the molar ratio of SiO2 / Al2O3 of the molecular sieve seed core is not particularly limited, but is preferably 5-200, more preferably 10-100.

[0029] According to the present invention, preferably, the core comprises at least one of alumina, Beta molecular sieve, ZSM-5 molecular sieve and HY molecular sieve.

[0030] According to the present invention, preferably, the average particle size of the core is 0.1-10 μm, for example, 0.1 μm, 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, 7 μm, 10 μm, or any range between the two, preferably 0.2-2 μm. Loading the active component with interlayers on the above-mentioned core, with the active component uniformly dispersed on the core surface, can effectively improve the catalytic activity of the catalyst. The average particle size of the core refers to the average particle size of the core particles, which can be a single particle or a particle aggregated from several small particles.

[0031] In this invention, the average particle size of the kernel is measured using scanning electron microscopy (SEM). The average value is obtained by randomly measuring the size of 100 kernel particles using NanoMeasurer software. During the measurement process, the average particle size has the conventional interpretation in the art, referring to the particle size; for spherical particles, it refers to the diameter of the sphere; for irregular particles, it refers to the maximum straight-line distance within the particle.

[0032] According to the present invention, preferably, the average particle size of the Pt nanoparticles in the interlayer is 0.5-6 nm, for example, 0.5 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 6 nm, or any range between the two, preferably 2-4 nm. In this invention, limiting the average particle size of the Pt nanoparticles in the interlayer enables a more uniform distribution of Pt nanoparticles in the interlayer and better stability of the active component loading. In this invention, the average particle size of the Pt nanoparticles is measured by transmission electron microscopy (TEM), and the average value is taken from the particle size of 100 randomly measured Pt nanoparticles in the TEM image.

[0033] According to the present invention, preferably, the Pt nanoparticles have a mass percentage content of 0.2-4 wt%, more preferably 1-2 wt%, based on the total weight of the catalyst.

[0034] According to the present invention, preferably, the mass percentage of W oxide is 0.5-10 wt%, more preferably 0.8-8 wt%, based on the total weight of the catalyst. In the present invention, the mass percentage of Pt nanoparticles and the mass percentage of W oxide in the catalyst interlayer are obtained by ICP testing.

[0035] In this invention, Pt nanoparticles and W oxide are loaded onto the core. The W oxide provides highly dispersed W adsorption sites, while the Pt nanoparticles provide highly efficient hydrogen active sites. Both work synergistically as active components to enhance the catalytic activity of the catalyst. The W oxide and Pt nanoparticles are uniformly dispersed on the core surface.

[0036] According to the present invention, preferably, the thickness of the outer shell is 5-100 nm, for example, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any range between the two, preferably 10-30 nm. This preferred embodiment is more conducive to forming a stable multilayer core-shell structure, fixing the interlayer active components, and improving the hydrothermal stability of the catalyst.

[0037] In this invention, the thickness of the catalyst shell is obtained using transmission electron microscopy. For example... Figure 1As shown, a curve can be drawn based on the outer edge position of the Pt nanoparticles. The distance between this curve and the entire outer edge of the catalyst is the thickness of the catalyst shell. The average value of ten randomly selected positions is recorded as the thickness of the shell.

[0038] According to the present invention, preferably, the pore volume of the mesoporous molecular sieve is 0.01-0.1 m³. 3 / g, preferably 0.03-0.08m 2 / g. The mesopore volume of the mesoporous molecular sieve was measured using the low-temperature nitrogen adsorption capacity method. The experimental instrument was a Micromeritics ASAP2400 static nitrogen adsorption instrument. Experimental conditions: The sample was degassed under vacuum at 1.33 Pa and 300 °C for 4 h, then contacted with liquid nitrogen at 77 K for isothermal adsorption and desorption. Adsorption and desorption isotherms were measured, and the mesopore volume was calculated using the BET formula.

[0039] In this invention, a mesoporous molecular sieve is used as a shell to cover the outside of the interlayer, which plays a role in fixing the active components of the interlayer, resulting in a catalyst with a stable core-shell structure, thus avoiding the aggregation and loss of active components.

[0040] According to the present invention, the type of mesoporous molecular sieve for the outer shell is not particularly limited, as long as it can cover the outer layer to form an outer shell. Those skilled in the art can adjust the type of mesoporous molecular sieve according to the core and sandwich structure of the catalyst. Preferably, the mesoporous molecular sieve is MCM-41 mesoporous molecular sieve and / or SBA-15 mesoporous molecular sieve.

[0041] A second aspect of the present invention provides a method for preparing a core-shell structured catalyst, wherein the method includes:

[0042] (1) Loading W oxide and Pt nanoparticles onto the core to obtain the first preproduct;

[0043] (2) A mixture containing a first preproduct, a first template agent, an optional acid, an optional first base source, a silicon source and water is subjected to a hydrothermal reaction to obtain a second preproduct;

[0044] (3) The second preproduct is calcined to obtain the catalyst.

[0045] In this invention, the interlayer and shell are loaded onto the core to form a catalyst with a stable multilayer core-shell structure. The preparation method is simple and the loading of W oxide and Pt nanoparticles in the interlayer can be flexibly adjusted. The mesoporous molecular sieve of the shell is synthesized through hydrothermal reaction, and the structure of the mesoporous molecular sieve is controllable.

[0046] According to the present invention, preferably, the loading process in step (1) includes:

[0047] (1-1) The W precursor is coated onto the core and subjected to a first heat treatment to obtain a core loaded with W oxide;

[0048] (1-2) The core loaded with W oxide and the solution of Pt nanoparticles were mixed and ultrasonically treated, and then subjected to a second heat treatment to obtain the first preproduct.

[0049] In this invention, step (1) employs a special loading method to load Pt nanoparticles onto the core. Compared with loading Pt nanoparticles using the equal-volume impregnation method with Pt salt, the synthesized Pt nanoparticles have controllable size, uniform distribution, and higher activity and selectivity.

[0050] According to the present invention, preferably, the heat-resistant inorganic oxide is selected from at least one of alumina, zirconium oxide, titanium dioxide, and silicon dioxide. Preferably, the molecular sieve is selected from at least one of Beta molecular sieve, ZSM-5 molecular sieve, and HY molecular sieve.

[0051] According to the present invention, preferably, the core comprises at least one of alumina, Beta molecular sieve, ZSM-5 molecular sieve and HY molecular sieve.

[0052] According to the present invention, the type of the W precursor is not particularly limited, but preferably, the W precursor is selected from at least one of ammonium metatungstate, ammonium paratungstate, and sodium tungstate.

[0053] According to the present invention, preferably, the amount of the W precursor added is based on tungsten oxide, and the mass ratio of the W precursor to the core is 1:5-200, for example 1:5, 1:10, 1:15, 1:20, 1:30, 1:40, 1:50, 1:80, 1:100, 1:150, 1:200, or any range between the two, preferably 1:10-150.

[0054] According to the present invention, preferably, the conditions for the first heat treatment include: a heating temperature of 100-800°C, more preferably 500-600°C; and a heating time of 1-10 h, more preferably 2-6 h. Performing the first heat treatment under the above conditions enables the W oxide to be uniformly loaded onto the core surface, forming highly dispersed W active sites.

[0055] According to the present invention, preferably, the mass ratio of the supported W oxide core to the Pt nanoparticles is 1:0.002-0.04, for example 1:0.002, 1:0.005, 1:0.01, 1:0.012, 1:0.015, 1:0.018, 1:0.02, 1:0.03, 1:0.04, or any range between the two, preferably 1:0.01-0.02. Using the above Pt nanoparticle solution, the synthesized catalyst exhibits controllable Pt nanoparticle size, uniform distribution, and higher activity and selectivity.

[0056] This invention does not specifically limit the conditions for mixing and sonication in steps (1-2), which can be appropriately selected according to specific circumstances. Preferably, mixing is carried out by stirring, and the stirring rate is not particularly limited, as long as the purpose of uniform mixing is achieved. In this invention, the method of adding each substance in steps (1-2) is not particularly limited; they can be added separately or together.

[0057] Preferably, this invention further includes a process of separating the ultrasonic products and then subjecting them to a second heat treatment. The separation method is not particularly limited; according to a specific embodiment of the invention, centrifugal separation can be used. The conditions for centrifugal separation are not particularly limited, and those skilled in the art can adjust them adaptively according to the separation situation.

[0058] According to the present invention, preferably, the conditions for the second heat treatment include: a heating temperature of 40-120°C, more preferably 60-100°C; and a heating time of 1-15 hours, more preferably 3-10 hours. In the present invention, performing the second heat treatment under the above conditions does not destroy the activity of the Pt nanoparticles, while ensuring that the Pt nanoparticles are uniformly distributed in the interlayer.

[0059] According to the present invention, preferably, the method for preparing the Pt nanoparticle solution includes: mixing a Pt source, a second template agent and a solvent, and refluxing the mixture to obtain a Pt nanoparticle solution.

[0060] According to the present invention, preferably, the amount of Pt source added is based on elemental Pt, and the mass ratio of Pt source: second template agent: solvent is 1:(1-50):(500-10000), more preferably 1:(5-30):(1000-5000). Adding the above substances according to the above amounts enables the preparation of a Pt nanoparticle solution with a more uniform average particle size distribution.

[0061] According to the present invention, preferably, the reflux conditions include: a reflux temperature of 60-200°C, preferably 80-160°C, under a protective atmosphere; and a reflux time of 0.5-6 h, preferably 2-4 h. Reflux under these conditions yields Pt nanoparticles with a more uniform average particle size distribution and a stable Pt nanoparticle solution.

[0062] In this invention, the type of protective atmosphere is not particularly limited, but is preferably selected from at least one of argon, nitrogen and helium.

[0063] According to the present invention, the type of Pt source is not particularly limited, and is a conventional Pt-containing compound in the art. Preferably, the Pt source is selected from at least one of chloroplatinic acid, tetraammineplatinum nitrate, and potassium chloroplatinate.

[0064] According to the present invention, the type of the second template agent is not particularly limited, but preferably, the second template agent is selected from at least one of polyvinylpyrrolidone, polyethyleneimine and oleylamine.

[0065] According to the present invention, the solvent is an aqueous solution of an alcohol selected from at least one of a saturated monohydric alcohol having 1-3 carbon atoms and an aqueous solution of a saturated dihydric alcohol having 1-3 carbon atoms, preferably selected from at least one of an aqueous solution of methanol, an aqueous solution of ethanol, and an aqueous solution of propanol. The volume ratio of alcohol to water in the aqueous solution is 1:0.05-2, preferably 1:0.1-1.

[0066] According to the present invention, preferably, in step (2), the amount of silicon source added to the mixture is SiO2, and the mass ratio of the first preproduct: the first template agent: the first alkali source: the acid: the silicon source: the water is 1:(0.02-2):(0-2):(0-2):(0.05-1):(20-200), preferably 1:(0.05-1):(0-1):(0-1):(0.1-0.5):(50-100).

[0067] According to the present invention, the type of the first template agent is not particularly limited, and it can be a conventional template agent for synthesizing mesoporous molecular sieves. Those skilled in the art can select it based on the type of mesoporous molecular sieve to be synthesized. Preferably, the first template agent is a quaternary ammonium bromide with 15-20 carbon atoms and / or a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer. Using the above-mentioned first template agent is beneficial for controlling the type and structure of the mesoporous molecular sieve obtained by the hydrothermal reaction.

[0068] According to the present invention, the type of the first alkali source is not particularly limited, as long as it can hydrolyze the silicon source and promote the synthesis of mesoporous molecular sieves. Those skilled in the art can adaptively select the type of the first alkali source. Preferably, the first alkali source is selected from at least one of ammonia, sodium hydroxide, and potassium hydroxide. Those skilled in the art can determine whether to add the first alkali source and adjust the amount of the first alkali source added based on the synthesis of the mesoporous molecular sieves. Sodium hydroxide and / or potassium hydroxide can be added as compounds or as aqueous solutions. When the alkali source is added in the form of an aqueous solution, the amount of alkali source added is based on the mass of the solute.

[0069] According to the present invention, the type of acid is not particularly limited, as long as it can hydrolyze the silicon source and promote the synthesis of mesoporous molecular sieves. Those skilled in the art can make adaptive selections. Preferably, the acid is selected from at least one of hydrogen bromide, hydrogen chloride, and sulfuric acid. Those skilled in the art can determine whether to add acid and adjust the amount of acid added based on the synthesis of the mesoporous molecular sieves. The acid can be added as a compound or as an aqueous solution. When the acid is added in the form of an aqueous solution, the amount of acid added is based on the mass of the solute.

[0070] According to the present invention, the type of silicon source is not particularly limited, and it is a conventional silicon source capable of synthesizing mesoporous molecular sieves. Preferably, the silicon source is tetraethyl orthosilicate and / or methyl orthosilicate.

[0071] In this invention, preferably, the mixing method of each substance in step (2) is not particularly limited, as long as a mixture is obtained. According to a specific embodiment of this invention, the mixture is obtained by stirring at room temperature. The stirring rate and stirring time are not particularly limited, and those skilled in the art can make adaptive adjustments.

[0072] According to the present invention, preferably, the conditions for the hydrothermal reaction in step (2) include: a reaction temperature of 60-240℃, for example 60℃, 70℃, 80℃, 90℃, 100℃, 120℃, 140℃, 160℃, 180℃, 200℃, 220℃, 240℃, or any range between the two, preferably 80-160℃; and a reaction time of 2-72h, for example 2h, 4h, 6h, 8h, 10h, 12h, 16h, 20h, 24h, 28h, 32h, 36h, 40h, 48h, 56h, 64h, 72h, or any range between the two, preferably 12-36h.

[0073] In this invention, the equipment for the hydrothermal reaction is not particularly limited, as long as it can carry out the reaction under hydrothermal conditions. Those skilled in the art can select the appropriate equipment as needed. According to a preferred embodiment of the invention, the hydrothermal reaction is carried out in a reaction vessel, preferably a hydrothermal reaction vessel.

[0074] In this invention, preferably, the reactor is cooled (preferably to room temperature) after the hydrothermal reaction is completed before opening it. This preferred embodiment avoids the safety hazards associated with opening the reactor at high temperatures due to the self-generated pressure inside the reactor caused by the hydrothermal reaction under elevated temperatures.

[0075] Preferably, this invention further includes a process of separating and drying the second preproduct, followed by calcination. The conditions for separation and drying are not particularly limited, and those skilled in the art can make adaptive adjustments.

[0076] According to the present invention, preferably, in step (3), the calcination conditions include: a calcination temperature of 200-600℃, preferably 300-500℃; and a calcination time of 1-10h, preferably 3-6h.

[0077] A third aspect of the present invention provides a core-shell structured catalyst prepared by the preparation method described in the second aspect, the catalyst comprising a core, a sandwich layer and a shell.

[0078] The fourth aspect of this invention provides the application of the core-shell structured catalyst described in the first or third aspect in the synthesis of 1,3-propanediol.

[0079] A fifth aspect of this invention provides a method for synthesizing 1,3-propanediol, wherein the method comprises reacting an aqueous glycerol solution with a core-shell structured catalyst as described in the first or third aspect. In this invention, the reaction conditions and reaction equipment are not particularly limited, and those skilled in the art can select them according to the actual reaction conditions for the synthesis of 1,3-propanediol from glycerol.

[0080] According to the present invention, preferably, the reaction conditions include: a reaction temperature of 120-200°C, preferably 130-170°C, a hydrogen pressure of 1-6 MPa, preferably 3-5 MPa, and a glycerol concentration of 10-90 wt%, preferably 30-80 wt%, in the glycerol aqueous solution.

[0081] According to the present invention, preferably, the mass ratio of the catalyst to the glycerol is 1:(0.5-5), more preferably 1:(1-2), and the reaction time is 4-720h, more preferably 8-360h.

[0082] According to the present invention, preferably, the reactor can be a fixed-bed reactor, and when the reactor is a fixed-bed reactor, the liquid hourly space velocity is 0.05-5 h⁻¹. -1 Preferably 0.1-2h -1 .

[0083] In this invention, the liquid phase refers to an aqueous solution of glycerol.

[0084] The present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, the reagents and materials used in the following examples and comparative examples are commercially available, and the room temperature is 25°C.

[0085] Polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) Aladdin brand, with an average molecular weight of 5000-6000.

[0086] Example 1

[0087] (1-1) Ammonium metatungstate was coated on the core of Beta molecular sieve. The amount of ammonium metatungstate added was based on WO3. The mass ratio of Beta molecular sieve to WO3 was 1:0.01. The silicon-aluminum ratio SiO2 / Al2O3 was 30. The average particle size of the core was 0.3 μm. The core was heat-treated at 600℃ for 3 h to obtain a core loaded with W oxide.

[0088] (1-2) Take 20 mL of water and 180 mL of ethanol and place them in a 500 mL round-bottom flask. Add 0.1 g of Pt and 0.6 g of polyvinylpyrrolidone (PVP) through an 8 wt% chloroplatinic acid aqueous solution. Stir for 5 minutes, then heat to 100 °C and reflux for 3 hours under an argon atmosphere to obtain a Pt nanoparticle solution.

[0089] 2g of the core loaded with W oxide was added to the above solution containing 0.04g of Pt nanoparticles. The mixture was stirred under ultrasonic conditions for 3 hours, centrifuged, and then heated at 80°C for 6 hours to obtain the first preproduct Beta@W-Pt.

[0090] (2) Disperse 2g of the first preproduct in 100mL of ethanol, then add 0.5g of cetyltrimethylammonium bromide, 0.66g of SiO2 via tetraethyl orthosilicate (TEOS), and 1g of ammonium hydroxide (NH4OH), and stir at room temperature for 4.5 hours, then transfer to a hydrothermal reactor and hydrothermally react at 100℃ for 24 hours to obtain the second preproduct;

[0091] (3) The second preproduct was centrifuged, dried, and calcined at 500℃ for 3h to obtain the Beta@W-Pt@MCM-41 catalyst. The physicochemical properties of the catalyst are shown in Table 1.

[0092] Figure 1 This is a TEM image of the core-shell structured catalyst prepared in Example 1. Figure 1 The lattice fringes and substrate depth can be used to determine the core and shell; the yellow dashed line in the diagram represents the interface between the two.

[0093] Figure 2 This is the small-angle XRD pattern of the core-shell structure catalyst from Example 1. Figure 2 It can be proven that the MCM-41 mesoporous molecular sieve structure was generated.

[0094] Example 2

[0095] The catalyst was prepared according to the method of Example 1, except that in step (2), hexadecyltrimethylammonium bromide was replaced with an equal mass of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), and 1g of ammonium hydroxide was replaced with 0.3g of hydrogen chloride, to obtain Beta@W-Pt@SBA-15 catalyst. The physicochemical properties of the catalyst are shown in Table 1.

[0096] Example 3

[0097] The catalyst was prepared according to the method of Example 1, except that the loading of Pt nanoparticles was adjusted in step (1) to obtain the Beta@W-Pt@MCM-41 catalyst. The physicochemical properties of the catalyst are shown in Table 1.

[0098] Example 4

[0099] (1-1) Ammonium metatungstate was coated on the alumina core. The amount of ammonium metatungstate added was based on WO3. The mass ratio of alumina to WO3 was 1:0.1. The average particle size of the core was 0.5 μm. The core was heat-treated at 600℃ for 4 h to obtain a core loaded with W oxide.

[0100] (1-2) Take 250 mL of water and 250 mL of propanol and place them in a 1 L round bottom flask. Add 0.1 g of Pt and 2 g of polyvinylpyrrolidone (PVP) through tetraammineplatinum nitrate (Pt source). Stir for 5 minutes, then heat to 120 °C and reflux for 3 hours under an argon atmosphere to obtain a Pt nanoparticle solution.

[0101] Add 5g of the core loaded with W oxide to the above solution containing 0.1g of Pt nanoparticles, stir under ultrasonic conditions for 3 hours, centrifuge, and heat at 100℃ for 6 hours to obtain the first preproduct Al2O3@W-Pt.

[0102] (2) Disperse 1g of the first preproduct in 60mL of ethanol, then add 0.8g of tetradecyltrimethylammonium bromide, and add 0.25g of SiO2 via tetramethyl silicate. 2， Add 0.25 g of sodium hydroxide and stir at room temperature for 4.5 hours, then transfer to a hydrothermal reactor and react hydrothermally at 120 °C for 24 hours to obtain the second preproduct;

[0103] (3) The second preproduct was centrifuged, dried, and calcined at 450°C for 3 hours to obtain the Al2O3@W-Pt@MCM-41 catalyst. The physicochemical properties of the catalyst are shown in Table 1.

[0104] Example 5

[0105] The catalyst was prepared according to the method of Example 1, except that in steps (1-2), the same volume impregnation method was used to load the same mass of Pt nanoparticles onto the core of the W oxide loaded with the same mass. Other conditions were the same as in Example 1, and the Beta@W-Pt@MCM-41 catalyst was obtained. The physicochemical properties of the catalyst are shown in Table 1.

[0106] Example 6

[0107] The catalyst was prepared according to the method of Example 1, except that step (1-1) was omitted. Instead, ammonium metatungstate of the same mass as in Example 1 was directly added to the Pt nanoparticle solution in step (1-2) and loaded onto the same mass of Beta molecular sieve cores. Other conditions were the same as in Example 1, and the Beta@W-Pt@MCM-41 catalyst was obtained. The physicochemical properties of the catalyst are shown in Table 1.

[0108] Comparative Example 1

[0109] The catalyst was prepared according to the method of Example 1, except that step (2) was omitted. The first preproduct of step (1) was directly centrifuged, dried and calcined, and other conditions were the same as in Example 1 to obtain the Beta@W-Pt catalyst. The physicochemical performance parameters of the catalyst are shown in Table 1.

[0110] Test Example 1

[0111] The structural parameters and active component contents of the catalysts prepared in the examples and comparative examples are shown in Table 1.

[0112] Table 1

[0113]

[0114] As can be seen from Table 1, after 360 hours of long-term operation, the Pt content loss rate of the mesoporous molecular sieve catalyst is less than 1%, while the comparative catalyst without shell protection loses 10 wt% of Pt content after 360 hours of reaction.

[0115] Test Example 2

[0116] 1g of the catalyst obtained in the examples and comparative examples was weighed and placed in a fixed-bed reactor. Under the conditions of a reaction temperature of 160°C, a hydrogen pressure of 3MPa, and a mass hourly space velocity (WHSV) of 1.5h⁻¹ for the glycerol aqueous solution, the reaction was carried out at a mass hourly space velocity (WHSV) of 1.5h⁻¹. -1 A 30wt% aqueous glycerol solution was introduced, and the liquid from the outlet at 8h and 360h of reaction was analyzed by gas chromatography. The results are shown in Table 2.

[0117] Table 2

[0118]

[0119]

[0120] As can be seen from the results in Table 2, the catalyst prepared using the embodiments of the present invention for the hydrogenolysis of glycerol to 1,3-propanediol has significantly improved glycerol conversion, selectivity for 1,3-propanediol in the product, and catalyst stability compared to catalysts synthesized by existing methods. The outer mesoporous molecular sieve can fix Pt active sites and inhibit Pt loss. At the same time, the mesoporous channels are more conducive to mass transfer than the microporous channels. The conversion rate, selectivity for 1,3-propanediol in the product, and catalyst stability are significantly improved, and the conversion rate decreases less after 360 h of reaction.

[0121] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A core-shell structured catalyst, characterized in that, The catalyst comprises a core, a sandwich layer, and a shell. The core of the catalyst comprises heat-resistant inorganic oxides and / or molecular sieves, the sandwich layer comprises W oxides and Pt nanoparticles, and the shell comprises mesoporous molecular sieves. The average particle size of the Pt nanoparticles is 2-4 nm; the thickness of the outer shell is 10-30 nm; the mesoporous molecular sieve is MCM-41 mesoporous molecular sieve and / or SBA-15 mesoporous molecular sieve; the heat-resistant inorganic oxide is selected from at least one of alumina, zirconium oxide, titanium dioxide, and silicon dioxide; the molecular sieve is selected from at least one of Beta molecular sieve, ZSM-5 molecular sieve, and HY molecular sieve; the average particle size of the core is 0.1-10 μm; the pore volume of the mesoporous molecular sieve is 0.01-0.1 μm. 3 / g.

2. The catalyst according to claim 1, wherein, The core comprises at least one of alumina, Beta molecular sieve, ZSM-5 molecular sieve, and HY molecular sieve.

3. The catalyst according to claim 1, wherein, The average particle size of the kernel is 0.2-2 μm.

4. The catalyst according to any one of claims 1-3, wherein, The Pt nanoparticles comprise 0.2-4 wt% of the total weight of the catalyst. And / or, based on the total weight of the catalyst, the W oxide content is 0.5-10 wt% by mass.

5. The catalyst according to claim 4, wherein, The Pt nanoparticles comprise 1-2 wt% of the total weight of the catalyst. And / or, based on the total weight of the catalyst, the W oxide has a mass percentage content of 0.8-8 wt%.

6. The catalyst according to claim 1, wherein, The mesoporous molecular sieve has a pore volume of 0.03-0.08 m³. 2 / g.

7. A method for preparing a core-shell structured catalyst according to any one of claims 1-6, characterized in that, The method includes: (1) W oxide and Pt nanoparticles were loaded onto the core to obtain the first preproduct; (2) A mixture containing the first preproduct, the first template agent, an optional acid, an optional first base source, a silicon source and water is subjected to a hydrothermal reaction to obtain the second preproduct; (3) The second preproduct is calcined to obtain the catalyst; The load process described in step (1) includes: (1-1) The W precursor is coated onto the core and subjected to a first heat treatment to obtain a core loaded with W oxide; (1-2) The core loaded with W oxide and the solution of Pt nanoparticles were mixed and sonicated, and then subjected to a second heat treatment to obtain the first preproduct.

8. The preparation method according to claim 7, wherein, The W precursor is selected from at least one of ammonium metatungstate, ammonium paratungstate, and sodium tungstate.

9. The preparation method according to claim 7, wherein, The amount of the W precursor added is based on tungsten oxide, and the mass ratio of the W precursor to the core is 1:5-200; And / or, the conditions for the first heat treatment include: a heating temperature of 100-800℃; and a heating time of 1-10h.

10. The preparation method according to claim 9, wherein, The amount of the W precursor added is based on tungsten oxide, and the mass ratio of the W precursor to the core is 10-150. And / or, the conditions for the first heat treatment include: a heating temperature of 500-600℃; and a heating time of 2-6 hours.

11. The preparation method according to claim 7, wherein, The mass ratio of the W oxide-loaded core to the Pt nanoparticles is 1:0.002-0.04; And / or, the conditions for the second heat treatment include: a heating temperature of 40-120°C; and a heating time of 1-15 hours.

12. The preparation method according to claim 11, wherein, The mass ratio of the W oxide-loaded core to the Pt nanoparticles is 1:0.01-0.02; And / or, the conditions for the second heat treatment include: a heating temperature of 60-100°C; and a heating time of 3-10 hours.

13. The preparation method according to claim 7, wherein, The method for preparing the Pt nanoparticle solution includes: mixing a Pt source, a second template agent, and a solvent, and then refluxing the mixture to obtain a Pt nanoparticle solution.

14. The preparation method according to claim 13, wherein, The amount of Pt source added is based on elemental Pt, and the mass ratio of Pt source: second template agent: solvent is 1:(1-50):(500-10000).

15. The preparation method according to claim 14, wherein, The amount of Pt source added is based on elemental Pt, and the mass ratio of Pt source: second template agent: solvent is 1:(5-30):(1000-5000).

16. The preparation method according to claim 13, wherein, The reflux conditions include: under a protective atmosphere, a reflux temperature of 60-200℃; and a reflux time of 0.5-6h.

17. The preparation method according to claim 16, wherein, The reflux conditions include: a reflux temperature of 80-160℃ under a protective atmosphere; and a reflux time of 2-4 hours.

18. The preparation method according to claim 13, wherein, The Pt source is selected from at least one of chloroplatinic acid, tetraammineplatinum nitrate and potassium chloroplatinate. And / or, the second template agent is selected from at least one of polyvinylpyrrolidone, polyethyleneimine, and oleylamine.

19. The preparation method according to claim 13, wherein, The solvent is an aqueous solution of at least one of saturated monohydric alcohols having 1-3 carbon atoms and saturated dihydric alcohols having 1-3 carbon atoms. And / or, the volume ratio of alcohol to water in the alcohol-water solution is 1:0.05-2.

20. The preparation method according to claim 19, wherein, The solvent is selected from at least one of methanol aqueous solution, ethanol aqueous solution and propanol aqueous solution; And / or, the volume ratio of alcohol to water in the alcohol-water solution is 1:0.1-1.

21. The preparation method according to claim 7, wherein, In step (2), the amount of silicon source added to the mixture is SiO2, and the mass ratio of the first preproduct: the first template agent: the first alkali source: the acid: the silicon source: the water is 1: (0.02-2): (0-2): (0-2): (0.05-1): (20-200).

22. The preparation method according to claim 21, wherein, In step (2), the amount of silicon source added to the mixture is SiO2, and the mass ratio of the first preproduct: the first template agent: the first alkali source: the acid: the silicon source: the water is 1:(0.05-1):(0-1):(0-1):(0.1-0.5):(50-100).

23. The preparation method according to claim 7, wherein, The first template agent is a brominated quaternary ammonium salt with 15-20 carbon atoms and / or a polyoxyethylene-polypropylene-polyoxyethylene triblock copolymer; And / or, the first alkali source is selected from at least one of ammonia, sodium hydroxide, and potassium hydroxide; And / or, the acid is selected from at least one of hydrogen bromide, hydrogen chloride, and sulfuric acid; And / or, the silicon source is tetraethyl orthosilicate and / or methyl orthosilicate.

24. The preparation method according to claim 7, wherein, The conditions for the hydrothermal reaction in step (2) include: a reaction temperature of 60-240℃; and a reaction time of 2-72h. And / or, in step (3), the calcination conditions include: calcination temperature of 200-600℃; calcination time of 1-10h.

25. The preparation method according to claim 24, wherein, The conditions for the hydrothermal reaction in step (2) include: a reaction temperature of 80-160℃; and a reaction time of 12-36h. And / or, in step (3), the calcination conditions include: calcination temperature of 300-500℃; calcination time of 3-6h.

26. A method for synthesizing 1,3-propanediol, characterized in that, The method includes reacting an aqueous glycerol solution with a core-shell catalyst according to any one of claims 1-6.

27. The method according to claim 26, wherein, The reaction conditions include: a reaction temperature of 120-200℃, a hydrogen pressure of 1-6MPa, and a glycerol concentration of 10-90wt% in the glycerol aqueous solution.

28. The method according to claim 26, wherein, The mass ratio of the catalyst to the glycerol is 1:(0.5-5), and the reaction time is 4-720h.

29. The method according to claim 26, wherein, The reactor is a fixed-bed reactor with a liquid hourly space velocity (LHSV) of 0.05-5 h⁻¹. -1 .

30. The method according to claim 29, wherein, The liquid phase mass hourly space velocity is 0.1-2 h⁻¹. -1 .

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