Hydrophobic modified copper-based bimetallic / SBA-15 catalyst, preparation method and application

Abstract

The invention discloses a hydrophobic modified copper-based bimetallic / SBA-15 catalyst, a preparation method and application, the catalyst is used for preparing methanol through carbon dioxide hydrogenation, and the catalyst comprises an ordered mesoporous SBA-15 carrier, a copper-based bimetallic active component and a hydrophobic layer; the total mass of the catalyst is 100%, and the catalyst comprises the following components in percentage by mass: 65-85% of an ordered mesoporous SBA-15 carrier, 10-25% of a copper-based bimetallic active component and 3-8% of a hydrophobic layer, the copper-based bimetallic active component is Cu and a synergistic metal M; the pore diameter of the SBA-15 carrier is 6-9 nm, the specific surface area is 650-800 m < 2 > / g, and the pore volume is 1.0-1.5 cm < 3 > / g; the hydrophobic layer is a silane-fluoride composite system, the thickness of the hydrophobic layer is 5-12 nm, and the surface water contact angle of the catalyst is larger than or equal to 95 degrees. The invention provides a hydrophobic modified copper-based bimetallic / SBA-15 catalyst as well as a preparation method and application thereof, ordered mesoporous SBA-15 is taken as a carrier, and the problems that a traditional copper-based catalyst is insufficient in activity, easy to be interfered by reaction water and poor in stability are solved through an electronic synergistic effect and precise hydrophobic modification of copper-based bimetallic active components.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a hydrophobically modified copper-based bimetallic / SBA-15 catalyst, its preparation method, and its application. Background Technology

[0002] The resource-based conversion of CO2, a major greenhouse gas, has become a core direction for alleviating environmental pressure and replenishing carbon resources. Methanol is not only an important basic chemical raw material (which can be used to produce bulk chemicals such as olefins and aromatics), but also a clean fuel with great potential (it can directly replace gasoline and serve as a fuel cell feedstock). Achieving carbon cycling through CO2 hydrogenation to methanol has both environmental benefits and economic value, and is currently a research hotspot in the energy and chemical industry.

[0003] Currently, the mainstream catalysts for CO2 hydrogenation to methanol are based on copper-based systems. SBA-15 stands out due to its highly ordered mesoporous structure (pore size 5-10 nm) and high specific surface area (≥600 m²). 2 With its good thermal stability (g / g), copper is considered an ideal support for copper-based catalysts; however, existing technologies still face the following bottlenecks:

[0004] (1) Insufficient activity: Traditional Cu / ZnO / Al2O3 or Cu / SBA-15 catalysts have limited adsorption and activation capacity for CO2, resulting in low CO2 activation and conversion efficiency of intermediates (*HCOO, *COOH, etc.), and easy occurrence of reverse water-gas shift reaction (RWGS) to generate by-product CO. Methanol selectivity is usually less than 80%. Moreover, the metal-support interface is insufficient, and Cu nanoparticles are easy to agglomerate in the SBA-15 channels (especially above 250 °C), and the activity decreases by 15-20% within 500 h.

[0005] (2) Poor water resistance: The water generated in the reaction of CO2 hydrogenation to methanol (CO2 + 3H2 → CH3OH + H2O) easily reacts with the hydroxyl groups on the surface of the support, causing the active sites to be covered or migrated. The retention of water will cover the Cu active sites, inhibit H2 dissociation, and accelerate the sintering of Cu particles, further reducing the catalytic performance.

[0006] (3) Insufficient structural stability: Under high temperature and high pressure conditions, copper nanoparticles are prone to sintering and agglomeration, resulting in decreased activity; at the same time, the hydrothermal environment may cause some of the pores of SBA-15 to collapse, reducing the specific surface area and pore volume.

[0007] (3) Insufficient structural stability: Under high temperature and high pressure conditions, copper nanoparticles are prone to sintering and agglomeration, resulting in decreased activity; at the same time, the hydrothermal environment may cause some of the pores of SBA-15 to collapse, reducing the specific surface area and pore volume. Summary of the Invention

[0008] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is the insufficient activity, catalyst poisoning caused by byproduct water, and poor stability of existing copper-based catalysts. The present invention provides a hydrophobically modified copper-based bimetallic / SBA-15 catalyst, its preparation method, and its application. Using ordered mesoporous SBA-15 as a carrier, the present invention solves the problems of insufficient activity, susceptibility to interference from reaction water, and poor stability of traditional copper-based catalysts through the electronic synergistic effect of the copper-based bimetallic active components and precise hydrophobic modification. It is suitable for industrial-grade CO2 resource utilization and low-carbon methanol synthesis processes.

[0009] To achieve the above objectives, this invention provides a hydrophobically modified copper-based bimetallic / SBA-15 catalyst for the hydrogenation of carbon dioxide to methanol, comprising an ordered mesoporous SBA-15 support, a copper-based bimetallic active component, and a hydrophobic layer; based on the total mass of the catalyst (100%), the mass fractions of each component are as follows: ordered mesoporous SBA-15 support 65-85%, copper-based bimetallic active component 10-25%, and hydrophobic layer 3-8%.

[0010] The copper-based bimetallic active component is Cu and a synergistic metal M, where M is selected from one or more of Zn, Sn, and In, and the molar ratio of Cu to M is 1:1-4:1.

[0011] The SBA-15 carrier has a pore size of 6-9 nm and a specific surface area of ​​650-800 m². 2 / g, pore volume 1.0-1.5 cm³ 3 / g;

[0012] The hydrophobic layer is a silane-fluoride composite system, wherein silane accounts for 60-80% of the mass of the hydrophobic layer, fluoride accounts for 20-40%, the thickness of the hydrophobic layer is 5-12 nm, and the water contact angle on the catalyst surface is ≥95°.

[0013] Furthermore, the silane is selected from one or two of methyltriethoxysilane (MTMS) and dodecyltrimethoxysilane (DTMS); the fluoride is selected from perfluorooctyltriethoxysilane (PFOTS) or polytetrafluoroethylene (PTFE) micro powder with a particle size of 50-100 nm.

[0014] Furthermore, in the copper-based bimetallic active component, Cu exists in the metallic state. 0 The main component is metal M, which exists in a metallic state or as an intermetallic compound. The bimetallic particles have a diameter of 3-5 nm and are uniformly dispersed in the mesopores of SBA-15.

[0015] In a preferred embodiment of the present invention, a method for preparing a hydrophobically modified copper-based bimetallic / SBA-15 catalyst is provided, comprising the following steps:

[0016] S1, SBA-15 is vacuum dried and air-calcined to remove adsorbed water and residual template agent;

[0017] S2, Cu salt and M salt are prepared into a mixed salt solution, and then impregnated with SBA-15 in equal volume, followed by drying and calcination to obtain Cu-M / SBA-15 precursor;

[0018] S3, the precursor is reduced in a hydrogen atmosphere to obtain a reduced Cu-M / SBA-15 precursor.

[0019] S4. A hydrophobic sol is prepared by reacting silane and fluoride to coat the precursor, followed by drying and low-temperature calcination to obtain a hydrophobically modified precursor.

[0020] Furthermore, in step S1, the vacuum drying temperature is 60 ℃ and the time is 12 h; the air calcination temperature is 600 ℃ and the time is 2 h.

[0021] Further, in step S2, the total metal ion concentration of the mixed salt solution is 0.8-1.2 mol / L, the liquid-solid ratio is 5:1-8:1 mL / g; the drying temperature after impregnation is 80 ℃, and the time is 12 h; the calcination temperature is 450 ℃, and the time is 4 h.

[0022] Furthermore, in step S3, the volume fraction of H2 in the mixed atmosphere is 15-20%, the heating rate is 2 ℃ / min, the reduction temperature is 350 ℃, and the reduction time is 2 h.

[0023] Further, in step S4, the solvent for the hydrophobic sol is an ethanol-water mixed solvent with a volume ratio of 9:1 and a pH adjusted to 3.0-3.5; the liquid-to-solid ratio is 10:1 mL / g; the stirring temperature is 40 ℃ and the time is 2 h; the low-temperature calcination temperature is 240-400 ℃ and the time is 2 h.

[0024] In another preferred embodiment of the present invention, an application of a hydrophobically modified copper-based bimetallic / SBA-15 catalyst is provided in the hydrogenation of carbon dioxide to methanol. The application process conditions are: reaction temperature 150-300 °C, reaction pressure 2-10 MPa, molar ratio of H2 to CO2 2-4:1, and gas hourly space velocity 5000-10000 mL g. cat -1 h -1 The reaction takes place in a fixed-bed reactor.

[0025] In another preferred embodiment of the present invention, an application of a hydrophobically modified copper-based bimetallic / SBA-15 catalyst is provided in the hydrogenation of carbon dioxide to methanol. The application process conditions are: reaction temperature 150-300 °C, reaction pressure 2-10 MPa, molar ratio of H2 to CO2 2-4:1, and gas hourly space velocity 5000-10000 mL g. cat -1 h -1 The reaction takes place in a fixed-bed reactor.

[0026] Furthermore, before use, the catalyst is mixed with quartz sand at a mass ratio of 1:2 and loaded. The reduction and activation conditions are H2 volume fraction of 15-20% and heating rate of 2 ℃ / min.

[0027] Technical effect

[0028] This invention provides a hydrophobically modified copper-based bimetallic / SBA-15 catalyst, its preparation method, and its application. Through a ternary synergistic design of an ordered mesoporous SBA-15 support, a copper-based bimetallic active component, and a hydrophobic layer, the following technical effects are achieved:

[0029] 1. By combining bimetallic synergy with mesoporous confinement effect, CO2 conversion rate ≥8% is achieved at low temperatures (200-260 ℃);

[0030] 2. Precise hydrophobic modification (water contact angle ≥95°) reduces the adsorption of reaction water and achieves methanol selectivity ≥88%;

[0031] 3. Optimization effect of catalyst bulk performance

[0032] (1) Excellent structural stability: The regular channels of the SBA-15 mesoporous support form a spatial confinement for the copper-based bimetallic active components, inhibiting the migration and aggregation of active metal particles during the reaction process. After the catalyst runs continuously for 100 h, the particle size of the active components increases by ≤10%, and the activity decay rate decreases by ≤5%. At the same time, the hydrophobic layer is grafted onto the surface of the support through covalent bonding, without destroying the mesoporous channel structure. The catalyst specific surface area and pore volume retention rate are ≥90%.

[0033] (1) Excellent structural stability: The regular channels of the SBA-15 mesoporous support form a spatial confinement for the copper-based bimetallic active components, inhibiting the migration and aggregation of active metal particles during the reaction process. After the catalyst runs continuously for 100 h, the particle size of the active components increases by ≤10%, and the activity decay rate decreases by ≤5%. At the same time, the hydrophobic layer is grafted onto the surface of the support through covalent bonding, without destroying the mesoporous channel structure. The catalyst specific surface area and pore volume retention rate are ≥90%.

[0034] (2) High utilization rate of active sites: The electronic synergistic effect between the two metals regulates the electron cloud density of Cu and enhances the adsorption and activation ability of CO2 molecules; the mesoporous confinement effect increases the dispersion of active components to more than 85%, and the hydrophobic layer reduces the coverage of water on active sites, thus increasing the utilization rate of active sites by more than 40% compared with traditional copper-based monometallic catalysts.

[0035] (3) Strong resistance to carbon deposition and poisoning: The low temperature reaction conditions combined with bimetallic electronic regulation reduce the tendency of polymerization and carbon deposition of reaction intermediates. The amount of carbon deposition during the catalyst operation cycle is ≤2 wt%; the hydrophobic layer can repel the adsorption of trace amounts of polar impurities such as sulfides and chlorinated compounds in the feed gas, and can still maintain stable catalytic performance in feed gas with impurity content ≤50 ppm.

[0036] (4) Long-term stable hydrophobic properties: The covalently bonded hydrophobic layer has excellent temperature resistance and solvent resistance. After high-temperature regeneration at 300 ℃ or multiple reaction-regeneration cycles, the water contact angle can still be maintained at ≥90°. The hydrophobic stability is more than twice that of the physically coated modified catalyst.

[0037] 4. Technical Effects Related to the Preparation Method

[0038] (1) Strong process controllability and good repeatability: The continuous process of “carrier pretreatment - bimetallic co-impregnation - in-situ hydrophobic modification” is adopted. The parameters of each step (impregnation concentration, calcination temperature and modification time) are easy to control precisely. The batch deviation of CO2 conversion rate and methanol selectivity of multiple batches of catalysts prepared under the same process conditions is ≤ 3%, which meets the consistency requirements of industrial production.

[0039] (2) The modification process is mild and efficient: the hydrophobic modification is carried out under mild conditions of ≤150 ℃ to avoid the structural damage of the bimetallic active components by high temperature; by adjusting the amount of the modifying reagent, the thickness of the hydrophobic layer (1-3 nm) and the degree of surface hydrophobicity can be precisely controlled to meet the water content requirements of different reaction systems.

[0040] (3) Green economy and easy to scale up industrially: The reagents used in the preparation are all conventional chemical raw materials, which are non-toxic, harmless and recyclable; no harsh equipment such as high temperature and high pressure is required, and the SBA-15 carrier can be recycled and reused, further reducing the cost of industrial production.

[0041] 5. Technical Effects Related to Application Scenarios

[0042] (1) Significant energy saving and consumption reduction benefits: The low temperature reaction range of 200-260 ℃ reduces energy consumption by 30%-40% compared with the reaction temperature of traditional copper-based catalysts (300-350 ℃); the high methanol selectivity greatly reduces the by-product separation steps, and the energy consumption of subsequent distillation and purification is reduced by more than 50%, thus improving the economic efficiency of industrial production.

[0043] (2) Wide range of feed gas compatibility: It has strong compatibility with CO2 / H2 ratio (1:3-1:5) in feed gas. Even if the feed gas contains ≤10% CO or ≤20% N2 and other inert gases, it can still maintain stable catalytic performance. There is no need to deeply purify the feed gas, which broadens the source of feed gas.

[0044] (3) Adaptable to a variety of industrial reactors: The catalyst particles have regular morphology and high mechanical strength, and can be adapted to mainstream industrial reactor types such as fixed bed and fluidized bed; the mesoporous structure accelerates the diffusion rate of reactants and products, reduces the pressure drop of the reaction system, and increases the throughput per unit volume of the reactor.

[0045] (4) Prominent value in helping carbon neutrality: It realizes the high-value conversion of CO2 into resources, and the methanol produced can be used as a chemical raw material or clean fuel, reducing the consumption of fossil fuels and having both environmental benefits and economic value.

[0046] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0048] Figure 1 The image shows the wide-angle XRD pattern of the catalyst prepared in Comparative Example 1.

[0049] Figure 2 The N2 adsorption-desorption isotherm of the catalyst prepared in Comparative Example 3;

[0050] Figure 3 The pore size distribution diagram is shown for the catalyst prepared in Comparative Example 3.

[0051] Figure 4 This is a transmission electron microscope (TEM) image of the catalyst prepared in Comparative Example 3. Detailed Implementation

[0053] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0054] In the following description, specific details, such as particular internal procedures and techniques, are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will appreciate that the invention may be practiced in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of the invention with unnecessary detail.

[0055] This invention addresses the problems of insufficient activity, catalyst poisoning due to water byproducts, and poor stability of existing copper-based catalysts. This invention provides a hydrophobically modified copper-based bimetallic / SBA-15 catalyst, specifically comprising the following:

[0056] I. Catalyst Composition

[0057] The hydrophobically modified copper-based bimetallic / SBA-15 catalyst of the present invention has a core structure of "ordered mesoporous SBA-15 support-copper-based bimetallic active component-hydrophobic layer". The mass fraction of each component is based on 100% of the total mass of the catalyst, as follows:

[0058]

[0059] II. Catalyst Preparation Methods

[0060] This invention employs a step-by-step process of "SBA-15 pretreatment - copper-based bimetallic impregnation loading - reduction activation - in-situ hydrophobic modification", the specific steps of which are as follows:

[0061] Step 1: Pretreatment of SBA-15 vector

[0062] 1. Take commercial or self-made ordered mesoporous SBA-15 and vacuum dry it at 60 ℃ for 12 h to remove surface adsorbed water;

[0063] 2. The dried SBA-15 was calcined in air at 500 °C for 4 h to further remove residual template agent (such as triblock copolymer P123) and obtain a clean SBA-15 carrier.

[0064] Step 2: Impregnation loading of copper-based bimetal

[0065] 1. Preparation of metal salt solution: Dissolve copper nitrate Cu(NO3)2·3H2O, zinc nitrate Zn(NO3)2·6H2O, tin nitrate Sn(NO3)2·6H2O or indium nitrate In(NO3)3·4H2O in deionized water at the target molar ratio (Cu:M=1:1-4:1) to obtain a homogeneous salt solution.

[0066] 2. Equal volume impregnation: The pretreated SBA-15 carrier is added to the salt solution, stirred at room temperature for 1 h, and then allowed to stand for 12 h to ensure that metal ions fully enter the SBA-15 mesopores.

[0067] 3. Pretreatment: The impregnated sample was dried at 60 °C for 12 h to obtain the Cu-M / SBA-15 precursor.

[0068] Step 3: Reduction and Activation

[0069] 1. Place the Cu-M / SBA-15 precursor in a quartz boat and heat it to 600 °C in a tube furnace under a nitrogen atmosphere at a rate of 5 °C / min and hold for 2 h.

[0070] 2. Then, the mixture is passed through a hydrogen atmosphere and heated to 350 °C at a rate of 2 °C per minute and held for 2 h. After cooling to room temperature, it is taken out and ground into a uniform powder to obtain the active Cu-M / SBA-15 catalyst.

[0071] Step 4: In-situ hydrophobic modification

[0072] 1. Preparation of hydrophobic sol: PTFE was added to the catalyst at a mass ratio of catalyst:PTFE = 5:1, and the mixture was ultrasonically treated for 30 min to ensure uniform dispersion;

[0073] 2. Coating and low-temperature calcination: The resulting mixture was filtered and placed in a quartz boat. Under a nitrogen atmosphere, the temperature was increased to 350°C at a rate of 5°C / min and held for 2 hours to complete the hydrophobic coating.

[0074] 3. After cooling to room temperature, remove and grind to obtain the final hydrophobically modified copper-based bimetallic / SBA-15 catalyst.

[0075] III. Application Process of Catalysts

[0076] The catalyst of this invention was used in the CO2 hydrogenation to methanol reaction in a fixed-bed reactor, and the specific process conditions are as follows:

[0077] Reactor type: Fixed bed reactor (inner diameter 10-15 mm, length 500 mm)

[0078] Catalyst loading: 100 mg (diluted with quartz sand at a mass ratio of 1:2 to avoid localized overheating)

[0079] Raw material gas composition: H2 / CO2 molar ratio 3:1

[0080] Reaction temperature: 150-300 ℃

[0081] Reaction pressure: 5 MPa

[0082] Gas hourly space velocity (WHSV): 8000 mL g cat -1 h -1

[0083] Product analysis: Gas chromatography (GC2060).

[0084] TCD detection: H2 / CO2,

[0085] FID detection: Methanol / CO / CH4

[0086] All carbon-containing components were corrected and quantified using the external standard method. CO2 conversion rate Methanol selectivity ( S MeOH %, and methanol yield (%) Y MeOH The formula for calculating ,%) is as follows:

[0087]

[0088]

[0089]

[0090]

[0091] in A x This represents the peak area of ​​each substance; n x (mol) represents the number of moles of each substance; f x This is the correction factor for each substance relative to CO2.

[0092] Example 1: 1% Cu-In / SBA-15@PTFE hydrophobic catalyst

[0093] Step 1: Synthesize SBA-15

[0094] Process: 2 g of P123 template agent, 15 g of water, and 60 g of 2 mol / L hydrochloric acid were placed in a heating mantle at 40 ℃ and stirred vigorously until P123 was completely dissolved. After dissolution, 4.25 g of TEOS (tetraethyl orthosilicate) was added, and stirring was continued for 24 h. Then, the mixture was crystallized in an oven at 100 ℃ for three days. After cooling, it was filtered and dried in a vacuum drying oven. After drying, it was placed in a muffle furnace and calcined at 500 ℃ for 6 h at a rate of 0.75 ℃ / min to remove the template agent. After grinding, SBA-15 was obtained.

[0095] Step 2: Cu-In impregnation loading

[0096] Weigh 200 mg of the prepared SBA-15 and place it in a small beaker. Use copper nitrate solution and indium nitrate solution to impregnate the SBA-15 with 1% of the carrier. After sonication for half an hour, place it in a vacuum drying oven and dry for 12 hours.

[0097] Step 3: Reduction and Activation

[0098] Then, it was taken out and placed in a quartz boat. It was first heated to 450°C at 5°C per minute in a tube furnace under a nitrogen atmosphere and held for 2 hours. After cooling, hydrogen gas was introduced and the temperature was raised to 350°C at 2°C per minute and held for 2 hours. After that, it was taken out and ground into powder.

[0099] Step 4: Hydrophobic modification (PTFE)

[0100] Sol preparation: 1.3 mL of PTFE was added dropwise to the catalyst, with a catalyst-to-PTFE ratio of 5:1. After sonication for half an hour, the mixture was filtered. The resulting product was placed in a quartz boat and heated to 350 °C per minute in a tube furnace under a nitrogen atmosphere at 5 °C. The temperature was maintained for 2 hours. After cooling, the product was removed and ground to obtain the final hydrophobic catalyst.

[0101] Hydrophobic layer performance: 9 nm thickness, 105° water contact angle, SBA-15 mesopore size maintained at 7 nm (no clogging).

[0102] Catalyst: Cu-In / SBA-15@PTFE.

[0103] Performance testing

[0104] Reaction conditions: 220 ℃, 5 MPa, WHSV = 8000 mL g cat -1 h -1 H2 / CO2 = 3:1;

[0105] Performance: CO2 conversion rate 5.6%, methanol selectivity 90.0%, CO selectivity 6.8%, CH4 selectivity 0.9%.

[0106] Example 2: 1% Cu-Sn / SBA-15@PTFE hydrophobic catalyst

[0107] Step 1: Synthesize SBA-15

[0108] Process: 2 g of P123 template agent, 15 g of water, and 60 g of 2 mol / L hydrochloric acid were placed in a heating mantle at 40 ℃ and stirred vigorously until P123 was completely dissolved. After dissolution, 4.25 g of TEOS (tetraethyl orthosilicate) was added, and stirring was continued for 24 h. Then, the mixture was crystallized in an oven at 100 ℃ for three days. After cooling, it was filtered and dried in a vacuum drying oven. After drying, it was placed in a muffle furnace and calcined at 500 ℃ for 6 h at a rate of 0.75 ℃ / min to remove the template agent. After grinding, SBA-15 was obtained.

[0109] Step 2: Cu-In impregnation loading

[0110] Weigh 200 mg of the prepared SBA-15 and place it in a small beaker. Use copper nitrate solution and tin nitrate solution to impregnate the SBA-15 with 1% of the carrier. After sonication for half an hour, place it in a vacuum drying oven and dry for 12 hours.

[0111] Step 3: Reduction and Activation

[0112] Then, it was taken out and placed in a quartz boat. It was first heated to 450°C at 5°C per minute in a tube furnace under a nitrogen atmosphere and held for 2 hours. After cooling, hydrogen gas was introduced and the temperature was raised to 350°C at 2°C per minute and held for 2 hours. After that, it was taken out and ground into powder.

[0113] Step 4: Hydrophobic modification (PTFE)

[0114] Take 1.3 mL of PTFE and add it to the catalyst. The catalyst:PTFE ratio is 5:1. After sonication for half an hour, filter the mixture. Place the resulting product in a quartz boat and heat it to 350 °C at 5 °C per minute in a tube furnace under a nitrogen atmosphere. Maintain the temperature for 2 hours. After cooling, take out the product and grind it to obtain the final hydrophobic catalyst.

[0115] Hydrophobic layer properties: 10 nm thickness, water contact angle 108° o The pore size of SBA-15 remains at 8 nm.

[0116] Performance testing

[0117] Reaction conditions: 220 ℃, 5 MPa, WHSV = 8000 mL g cat -1 h -1 H2 / CO2 = 3:1;

[0118] Initial performance: CO2 conversion rate 4.8%, methanol selectivity 83.5%, CO selectivity 5.7%, CH4 selectivity 0.8%.

[0119] Example 3: 1% Cu-In / SBA-15@TEOOS hydrophobic catalyst

[0120] Step 1: Synthesize SBA-15

[0121] Process: 2 g of P123 template agent, 15 g of water, and 60 g of 2 mol / L hydrochloric acid were placed in a heating mantle at 40 ℃ and stirred vigorously until P123 was completely dissolved. After dissolution, 4.25 g of TEOS (tetraethyl orthosilicate) was added, and stirring was continued for 24 h. Then, the mixture was crystallized in an oven at 100 ℃ for three days. After cooling, it was filtered and dried in a vacuum drying oven. After drying, it was placed in a muffle furnace and calcined at 500 ℃ for 6 h at a rate of 0.75 ℃ / min to remove the template agent. After grinding, SBA-15 was obtained.

[0122] Step 2: Cu-In impregnation loading

[0123] Weigh 200 mg of the prepared SBA-15 and place it in a small beaker. Use copper nitrate solution and indium nitrate solution to impregnate the SBA-15 with 1% of the carrier. After sonication for half an hour, place it in a vacuum drying oven and dry for 12 hours.

[0124] Step 3: Reduction and Activation

[0125] Then, it was taken out and placed in a quartz boat. It was first heated to 600°C at 5°C per minute in a tube furnace under a nitrogen atmosphere and held for 2 hours. After cooling, hydrogen gas was introduced and the temperature was raised to 350°C at 2°C per minute and held for 2 hours. After that, it was taken out and ground into powder.

[0126] Step 4: Hydrophobic modification (TEOOS)

[0127] The synthesized catalyst was dispersed in 40 mL of toluene and sonicated for 1 hour. Then, a certain amount of TEOOS was added, and the mixture was refluxed at 120 °C. After reflux, the catalyst was washed by centrifugation (washed twice with toluene and twice with anhydrous ethanol), and then dried at 120 °C for 10 hours to obtain the hydrophobic catalyst.

[0128] Catalyst: Cu-In / SBA-15@TEOOS

[0129] Performance testing

[0130] Reaction conditions: 220 ℃, 5 MPa, WHSV = 8000 mL g cat -1 h -1 H2 / CO2 = 3:1;

[0131] Initial performance: CO2 conversion rate 4.2%, methanol selectivity 92.1%, CO selectivity 9.2%, CH4 selectivity 1.0%.

[0132] Example 4: 1% Cu-Sn / SBA-15@TEOOS hydrophobic catalyst

[0133] The only difference from Example 3 is that indium nitrate is replaced with tin nitrate.

[0134] Performance testing

[0135] Reaction conditions: 220 ℃, 5 MPa, WHSV = 8000 mL g cat -1 h -1 H2 / CO2 = 3:1;

[0136] Initial performance: CO2 conversion rate 5.2%, methanol selectivity 72.5%, CO selectivity 9.2%, CH4 selectivity 1.0%.

[0137] Example 5: 1% Cu-Sn / SBA-15@PTFE hydrophobic catalyst

[0138] The only difference from Example 1 is that indium nitrate is replaced with tin nitrate.

[0139] Performance testing

[0140] Reaction conditions: 220 ℃, 5 MPa, WHSV = 8000 mL g cat -1 h -1 H2 / CO2 = 3:1;

[0141] Initial performance: CO2 conversion rate 5.5%, methanol selectivity 77.5%, CO selectivity 9.2%, CH4 selectivity 1.0%.

[0142] Example 6: 1% Cu-Zn / SBA-15@TEOOS hydrophobic catalyst

[0143] The only difference from Example 3 is that indium nitrate is replaced with zinc nitrate.

[0144] Performance testing

[0145] Reaction conditions: 220 ℃, 5 MPa, WHSV = 8000 mL g cat -1 h -1 H2 / CO2 = 3:1;

[0146] Initial performance: CO2 conversion rate 3.8%, methanol selectivity 75.2%, CO selectivity 9.2%, CH4 selectivity 1.0%.

[0147] Example 7: 1% Cu-Zn / SBA-15@PTFE hydrophobic catalyst

[0148] The only difference from Example 1 is that indium nitrate is replaced with zinc nitrate.

[0149] Performance testing

[0150] Reaction conditions: 220 ℃, 5 MPa, WHSV = 8000 mL g cat -1 h -1 H2 / CO2 = 3:1;

[0151] Initial performance: CO2 conversion rate 3.4%, methanol selectivity 73.5%, CO selectivity 9.2%, CH4 selectivity 1.0%.

[0152] Comparative Example 1: Unhydrophobically modified Cu-In / SBA-15 catalyst

[0153] Preparation: Same as steps 1-3 in Example 1, except for step 4, which involves hydrophobic modification;

[0154] Reaction test (same conditions as in Implementation 1): initial CO2 conversion rate 3.7%, methanol selectivity 97.6%.

[0155] Comparative Example 2: Unhydrophobically modified Cu-Sn / SBA-15 catalyst

[0156] Preparation: Same as steps 1-3 in Example 1, except for step 4, which involves hydrophobic modification;

[0157] Reaction test (same conditions as in Example 1): initial CO2 conversion rate 3.9%, methanol selectivity 72.2%.

[0158] Comparative Example 3: Unhydrophobically modified Cu-Zn / SBA-15 catalyst

[0159] Preparation: Same as steps 1-3 in Example 1, except for step 4, which involves hydrophobic modification;

[0160] Reaction test (same conditions as in Example 1): initial CO2 conversion rate 3.1%, methanol selectivity 60.2%.

[0161] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A hydrophobically modified copper-based bimetallic / SBA-15 catalyst, characterized in that, For use in the hydrogenation of carbon dioxide to methanol, it comprises an ordered mesoporous SBA-15 support, a copper-based bimetallic active component, and a hydrophobic layer; based on the total mass of the catalyst (100%), the mass fractions of each component are as follows: ordered mesoporous SBA-15 support 65-85%, copper-based bimetallic active component 10-25%, and hydrophobic layer 3-8%; The copper-based bimetallic active component is Cu and a synergistic metal M, where M is selected from one or more of Zn, Sn, and In, and the molar ratio of Cu to M is 1:1 to 4:

1. The SBA-15 carrier has a pore size of 6-9 nm and a specific surface area of ​​650-800 m². 2 / g, pore volume 1.0-1.5 cm³ 3 / g; The hydrophobic layer is a silane-fluoride composite system, wherein silane accounts for 60-80% of the mass of the hydrophobic layer, fluoride accounts for 20-40%, the thickness of the hydrophobic layer is 5-12 nm, and the water contact angle on the catalyst surface is ≥95°.

2. The hydrophobically modified copper-based bimetallic / SBA-15 catalyst as described in claim 1, characterized in that, The silane is selected from one or two of methyltriethoxysilane (MTMS) and dodecyltrimethoxysilane (DTMS); the fluoride is selected from perfluorooctyltriethoxysilane (PFOTS) or polytetrafluoroethylene (PTFE) micro powder with a particle size of 50-100 nm.

3. The hydrophobically modified copper-based bimetallic / SBA-15 catalyst as described in claim 1, characterized in that, In the copper-based bimetallic active component, Cu is in the metallic state. 0 The main component is metal M, which exists in a metallic state or as an intermetallic compound. The bimetallic particles have a diameter of 3-5 nm and are uniformly dispersed in the mesopores of SBA-15.

4. A method for preparing the hydrophobically modified copper-based bimetallic / SBA-15 catalyst as described in any one of claims 1-3, characterized in that, Includes the following steps: S1, SBA-15 is vacuum dried and air-calcined to remove adsorbed water and residual template agent; S2, Cu salt and M salt are prepared into a mixed salt solution, and then impregnated with SBA-15 in equal volume, followed by drying and calcination to obtain Cu-M / SBA-15 precursor; S3, the precursor is reduced in a hydrogen atmosphere to obtain a reduced Cu-M / SBA-15 precursor. S4. A hydrophobic sol is prepared by reacting silane and fluoride to coat the precursor, followed by drying and low-temperature calcination to obtain a hydrophobically modified precursor.

5. The preparation method of the hydrophobically modified copper-based bimetallic / SBA-15 catalyst as described in claim 4, characterized in that, In step S1, the vacuum drying temperature is 60 ℃ and the time is 12 h; the air calcination temperature is 600 ℃ and the time is 2 h.

6. The preparation method of the hydrophobically modified copper-based bimetallic / SBA-15 catalyst as described in claim 4, characterized in that, In step S2, the total metal ion concentration of the mixed salt solution is 0.8-1.2 mol / L, and the liquid-solid ratio is 5:1-8:1 mL / g; the drying temperature after impregnation is 80 ℃ and the time is 12 h; the calcination temperature is 450 ℃ and the time is 4 h.

7. The preparation method of the hydrophobically modified copper-based bimetallic / SBA-15 catalyst as described in claim 4, characterized in that, In step S3, the volume fraction of H2 in the mixed atmosphere is 15-20%, the heating rate is 2 ℃ / min, the reduction temperature is 350℃, and the reduction time is 2 h.

8. The preparation method of the hydrophobically modified copper-based bimetallic / SBA-15 catalyst as described in claim 4, characterized in that, In step S4, the solvent for the hydrophobic sol is an ethanol-water mixed solvent with a volume ratio of 9:1 and the pH is adjusted to 3.0-3.5; the liquid-to-solid ratio is 10:1 mL / g; the stirring temperature is 40 ℃ and the time is 2 h; the low-temperature calcination temperature is 240-400 ℃ and the time is 2 h.

9. The application of the hydrophobically modified copper-based bimetallic / SBA-15 catalyst as described in any one of claims 1-3, characterized in that, Its application in the hydrogenation of carbon dioxide to methanol is characterized by the following process conditions: reaction temperature 150-300 ℃, reaction pressure 2-10 MPa, molar ratio of H2 to CO2 2-4:1, and gas hourly space velocity 5000-10000 mL g. cat -1 h -1 The reaction takes place in a fixed-bed reactor.

10. The application as described in claim 9, characterized in that, The reaction was carried out at a temperature of 200-300 ℃, a reaction pressure of 5 MPa, a hydrogen to carbon dioxide molar ratio of 3:1, and a gas hourly space velocity of 8000 mL g. cat -1 h -1 Under the given conditions, the carbon dioxide conversion rate is ≥8% and the methanol selectivity is ≥88%. After 1000 h of continuous reaction, the catalyst activity decreases by ≤6%, the methanol selectivity remains ≥86%, and the SBA-15 mesoporous structure remains intact.

11. The application as described in claim 9, characterized in that, Before use, the catalyst is mixed with quartz sand at a mass ratio of 1:2 and loaded. The reduction and activation conditions are H2 volume fraction of 15-20% and heating rate of 2 ℃ / min.

Images