Preparation process of bifunctional Ru / C catalyst applied to coupling thermocatalytic methanol dehydrogenation and electrocatalytic hydroxidation reaction

Abstract

The invention relates to a preparation process of a bifunctional Ru / C catalyst applied to coupling thermocatalytic methanol dehydrogenation and electrocatalytic hydroxidation reaction, belonging to the technical field of methanol hydrogen production. TDI industrial waste residue is used as a raw material, and through the links of pyrolysis activation, supercritical methanol modification, bimetal freezing loading, activation, interface bonding construction, hydrophobic layer coating and the like, the Ru / C catalyst is prepared. The catalyst solves the problems that an existing Ru / C catalyst is sensitive to CO poisoning, easy to sinter at a high temperature, high in component and the like, the Ru utilization rate is high, the activity attenuation is reduced after long-time operation, the components are effectively reduced, and the catalyst is suitable for the process requirements of methanol hydrogen production-synthesis gas co-production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical industry, and particularly relates to methanol hydrogen production, and specifically relates to a preparation process of a bifunctional Ru / C catalyst for preparing high-purity H2 and CO by coupling thermal catalytic methanol dehydrogenation and electrocatalytic hydrogen oxidation reaction. BACKGROUND

[0002] Methanol has the advantages of high hydrogen content and convenient transportation, but the methanol hydrogen production process is usually accompanied by a large amount of carbon dioxide emission, and the selective conversion of methanol into H2 provides a promising strategy for valuable chemical raw materials, however, it is limited by harsh operating conditions and low conversion efficiency. The heterogeneous methanol dehydrogenation reaction can continuously release H2 and CO at normal pressure, however, the methanol dehydrogenation process is thermodynamically and kinetically unfavorable.

[0003] The document Electrocatalysis Boosts the Methanol Thermocatalytic Dehydrogenation for High-Purity H2 and CO Production (DOI: 10.1021 / jacs.3c13240) discloses a scheme for realizing the efficient conversion of methanol into high-purity hydrogen and carbon monoxide by coupling thermal catalytic methanol dehydrogenation and electrocatalytic hydrogen oxidation reaction on a bifunctional Ru / C catalyst, the mechanism is that a double-layer Ru / C+Pd / C electrode is designed, the thermal catalytic methanol dehydrogenation reaction occurring on the Ru surface:

[0004]

[0005] Among them, the Ru nanoparticles provide active sites to catalyze the methanol dehydrogenation to generate CO and H2; the electrocatalytic hydrogen oxidation reaction occurring at the interface of the Ru / C electrode:

[0006] Anode end: 2H ads → H2 + 2e -

[0007] The adsorbed hydrogen generated by dehydrogenation is oxidized to H2 at the electrode interface, and the generated adsorbed hydrogen is directly utilized, avoiding the high energy consumption of traditional water electrolysis;

[0008] Cathode end: 2H2O + 2e - → H2 + 2OH -

[0009] The cathode reduces water to supplement H2, achieving hydrogen balance in the system.

[0010] The above process optimizes the reaction pathway, coupling thermocatalytic dehydrogenation and electrocatalytic oxidation on the same catalyst surface, eliminating the diffusion limitations of intermediate products, and promptly removing adsorbed hydrogen in the electrochemical step, promoting the forward dehydrogenation reaction, improving methanol conversion rate, and obtaining highly selective products. Electrochemical oxidation directly generates H2, avoiding side reactions, resulting in H2 purity of over 99.9%. The Ru surface inhibits further hydrogenation or oxidation of CO, with no CO2 generation and CO selectivity exceeding 95%. Meanwhile, the electrocatalytic step only requires a voltage of 0.2-0.5V, saving more than 50% energy compared to traditional water electrolysis processes.

[0011] However, the above-mentioned process also has several technical bottlenecks, such as the catalyst: although Ru nanoparticles have high activity for methanol dehydrogenation, they have strong adsorption capacity for CO, which can easily lead to the covering of active sites and reduce the hydrogenation efficiency. In its double-layer electrode structure, Pd weakens CO adsorption and reduces CO toxicity to a certain extent, but CO accumulation may still cause slow deactivation during long-term operation; the reaction needs to be carried out at 200℃, and the high temperature environment can easily cause Ru to aggregate and grow, reducing the active surface area. At the same time, the carbon support may be oxidized and corroded, leading to the collapse of the catalyst structure; it is highly dependent on Ru, a precious metal, and Ru reserves are low and its price is expensive, which increases the production cost of the process. The existing technology CN119456017A uses carbon support derived from toluene diisocyanate (TDI) process waste, which can effectively reduce costs, but it does not perform surface modification, has too many acidic groups on the support surface, a carboxyl content of 0.82 mmol / g, and insufficient metal dispersion.

[0012] Therefore, people still need to explore and improve from different directions to meet the needs. Summary of the Invention

[0013] To address the shortcomings of existing technologies, this invention proposes a method for preparing a highly active, highly stable, and low-cost bifunctional Ru / C catalyst, which solves the problems of traditional catalysts such as CO poisoning sensitivity, easy high-temperature sintering, and high cost.

[0014] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0015] A process for preparing a bifunctional Ru / C catalyst for coupled thermocatalytic methanol dehydrogenation and electrocatalytic hydrogenation reactions includes the following steps:

[0016] (1) Using toluene diisocyanate waste residue as raw material, nitrogen-doped porous carbon support was prepared by washing with hydrochloric acid, controlled pyrolysis and KOH activation;

[0017] (2) The carrier is subjected to supercritical methanol surface modification treatment;

[0018] (3) A Ru-Cu bimetallic precursor solution was loaded onto a modified support by a freeze-drying-assisted impregnation method.

[0019] (4) Activate the loaded catalyst;

[0020] (5) A Ru-OC bonded structure was constructed on the activated catalyst, and a hydrophobic SiO2 protective layer was prepared on its surface to obtain Ru@CuCl. x / SiO2@NPC core-shell structure catalyst.

[0021] In this invention, TDI industrial waste residue is used as the carbon and nitrogen source. Metal impurities are removed by washing with hydrochloric acid. The residue is then pyrolyzed at 700°C for 2 hours under a nitrogen atmosphere with a programmed temperature increase of 5°C / min. KOH is added at 800°C for 1 hour according to the mass ratio of waste residue to KOH = 1:2. After acid washing to neutrality, a carrier with a nitrogen content greater than 4 at% and a hierarchical pore structure is obtained, with a micropore / mesopore ratio of approximately 1:2.

[0022] In this invention, the supercritical methanol treatment conditions for the carrier are: temperature 280-320℃, pressure 10-15MPa, treatment time 10-15h, and the oxygen-containing acidic groups of the carrier after treatment are ≤0.3mmol / g.

[0023] In this invention, the Ru-Cu bimetallic precursor contains Ru acetylacetone as the Ru source and copper nitrate as the Cu source, with a Ru:Cu molar ratio of 3:1.

[0024] Ruthenium acetylacetonate Ru(acac)3 and copper nitrate Cu(NO3)2 were used as precursors and a precursor solution was prepared at a solid-liquid ratio of 1:10. The precursor was loaded by a freeze-drying-assisted impregnation method: after ultrasonic mixing of the carrier and the precursor solution, the carrier was rapidly frozen at -50℃ to form an ice crystal template, and then freeze-dried under vacuum for 24 hours to achieve uniform distribution of the metal precursor in the pores of the carrier.

[0025] In this invention, the method for activating the loaded catalyst is the magnetic induction Joule thermal shock method, with the following parameters: induction current 280-320A, heating rate ≥1000℃ / s, peak temperature 850-950℃, holding time 5-15s, and activation atmosphere is an argon-hydrogen mixture containing 5% H2.

[0026] Using a high-frequency induction heating system of 200-300kHz, at a current of 300A, 10 4 Activation in an argon-hydrogen mixed atmosphere at a heating rate of ℃ / s and a peak temperature of 900℃ resulted in the formation of Ru nanocrystals embedded in CuCl. x Ru@CuCl matrix x / C structure, Ruδ + The proportion is ≥35%, and the average particle size is 2.3±0.7nm.

[0027] In this invention, the Ru-OC bonding structure is constructed by treating the activated catalyst in an air atmosphere at 200°C for 30 minutes, followed by slow cooling to room temperature with nitrogen gas containing 5% O2. This forms an atomic-level Ru-OC bonding channel at the interface between the Ru nanocrystals and the carbon support, achieving a Ru-O coordination number of 2.1 and increasing the metal-support interaction force by three times.

[0028] In this invention, the hydrophobic SiO2 protective layer is prepared by vapor deposition, and the thickness of the obtained hydrophobic SiO2 protective layer is 1.2-1.8 nm, the surface contact angle is ≥130°, and the pore size is 0.35-0.45 nm.

[0029] A 1.5±0.2 nm amorphous SiO2 thin layer was prepared by vapor deposition-self-confined passivation process, and then modified by hexamethyldisilazane (HMDS) vapor hydrophobicity modification to form a protective layer with a contact angle greater than 130° and a pore size of 0.4 nm, which inhibits Ru dissolution and CO poisoning and allows H2 / CO free diffusion.

[0030] A bifunctional Ru / C catalyst obtained using the above process, exhibiting Ru@CuCl x / SiO2@NPC core-shell structure, Ru particles with an average size of 2.3±0.7 nm, Ruδ + The proportion is ≥35%.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] (1) The catalyst prepared in this application has a Ru utilization rate of 58%, an extended operating voltage window for CO poisoning resistance to 0.1-0.3V, an activity decay of less than 8% after 1000h of operation at 200℃, and a methanol dehydrogenation TOF of 3.2s. -1 The hydrogen oxidation reaction has an overpotential of only 31 mV @ 10 mA / cm. 2 It has strong performance advantages;

[0033] (2) The catalyst obtained in this application has a Ru loading of 2wt%, a catalyst cost of 32%, a production cycle of 2.5h, and an energy consumption of 45%, which is very economical.

[0034] (3) The preparation process of this application realizes the resource utilization of TDI waste residue and the supercritical methanol treatment solvent recovery rate is greater than 95%, which is in line with the dual-carbon environmental protection strategy. Attached Figure Description

[0035] Figure 1 This is a flowchart of the carrier pretreatment process in this application;

[0036] Figure 2XPS spectra of the product obtained in this application;

[0037] Figure 3 The XRD pattern of the product obtained in this application;

[0038] Figure 4 The gas phase diffusion spectrum of the product obtained in this application;

[0039] Figure 5 The TPR spectrum of the product obtained in this application. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0041] Example 1

[0042] This embodiment provides a technical analysis of the technical solution of this application.

[0043] A process for preparing a bifunctional Ru / C catalyst for coupled thermocatalytic methanol dehydrogenation and electrocatalytic hydrogenation reactions includes:

[0044] 1. Selection of raw materials and carrier pretreatment

[0045] 1.1 Preparation of nitrogen-doped porous carbon support derived from industrial waste

[0046] 1.1.1 Specific steps: Using TDI industrial waste residue as carbon and nitrogen source, metal impurities are removed by washing with hydrochloric acid. The residue is then pyrolyzed at 700℃ for 2 hours under a nitrogen atmosphere with a programmed temperature increase of 5℃ / min. KOH is added at a mass ratio of waste residue:KOH = 1:2 and activated at 800℃ for 1 hour. After acid washing to neutrality, a carrier with a nitrogen content greater than 4 at% and a hierarchical pore structure is obtained.

[0047] 1.1.2 Selection Criteria for TDI Waste Residue: TDI waste residue contains a large amount of nitrogen-containing organic polymers. After pyrolysis, nitrogen-doped carbon structures can be produced in situ, with a nitrogen content of 8-12 wt%, far exceeding the 0.5-2 wt% of traditional activated carbon carriers. The waste residue contains approximately 0.3-0.5 wt% Fe and Zn metal impurities. After washing three times with 5% hydrochloric acid, the residual metal content is less than 0.01 wt%.

[0048] 1.1.3 Selection of Pyrolysis-Activation Process Parameters

[0049] (i) Determination of 700℃ pyrolysis temperature: Through TG-DTA analysis of TDI waste residue, the weight loss rate of TDI waste residue reached 65% in the range of 500-700℃, the carbon yield was stable at 32% at 700℃, and the nitrogen retention rate was >70%; the heating rate of 5℃ / min can avoid the collapse of the pore structure caused by local overheating.

[0050] (ii) Advantages of a KOH activator ratio of 1:2: When the mass ratio of KOH to waste residue is <1:2, the specific surface area increases slowly, less than 800m². 2 When the ratio is greater than 1:2, excessive etching leads to thinning of the pore walls and a decrease in mechanical strength. Activation at 800℃ for 1 hour can form a hierarchical pore structure with micropore diameters of 0.8-1.5 nm, mesopore diameters of 2-50 nm, and a pore volume of up to 1.2 cm³. 3 / g.

[0051] (iii) Selection of hydrochloric acid concentration for pickling: less than 5% is not efficient enough for washing, and more than 10% will cause corrosion of the carbon skeleton.

[0052] 1.1.4 Nitrogen doping morphology regulation: After pyrolysis and activation, nitrogen exists in the form of 45-50% pyridine nitrogen, 35-40% pyrrole nitrogen and 15-20% graphitic nitrogen. Among them, pyridine nitrogen is the main active site, and its anchoring barrier to Ru atoms is 0.32 eV lower than that of graphitic nitrogen.

[0053] 1.2 Surface Modification of Supercritical Methanol

[0054] 1.2.1 Specific steps: The carrier is loaded into a supercritical reactor, methanol is injected to a filling rate of 80%, the temperature is increased to 300℃ at 10℃ / min, and the pressure is maintained at 12MPa for 12h.

[0055] 1.2.2 Analysis of supercritical fluid characteristics: At 300℃ and 12MPa, methanol is in a supercritical state. Its dielectric constant and surface tension are close to zero, and its diffusion coefficient is 100 times that of the liquid state. It can efficiently penetrate into the 2nm micropores of the carrier and undergo esterification reaction with acidic groups.

[0056] 1.2.3 Mechanism of acid group reduction: The acid functional group determination method on activated carbon surface was used. After supercritical treatment, the number of carboxyl groups (-COOH) on the support surface decreased from 0.82 mmol / g to 0.24 mmol / g, phenolic hydroxyl groups (-OH) from 0.56 mmol / g to 0.18 mmol / g, and lactone groups (-COO-) from 0.31 mmol / g to 0.09 mmol / g, resulting in a 70% reduction in total acid groups. The reaction formula is as follows:

[0057] R-COOH + CH3OH → R-COOCH3 + H2O (esterification reaction)

[0058] R-OH + CH3OH → R-OCH3 + H2O (etherification reaction)

[0059] 1.2.4 Enhancement effect of basic nitrogen functional groups: Supercritical treatment promotes the migration of nitrogen atoms from the interior of the carbon skeleton to the surface, forming more basic nitrogen sites, which increase the proportion of total nitrogen from 48% before treatment to more than 65%. NH3-TPD test shows that the number of strong basic sites on the support surface increases by 2.3 times.

[0060] 2. Active component loading and structural regulation

[0061] 2.1 Bimetallic Ru-Cu precursor

[0062] 2.1.1 Specific steps: Prepare a 0.1 mol / L Ru(acca)3-Cu(NO3)2 solution according to the Ru:Cu = 3:1 molar ratio. Take 50 g of the carrier and mix it with 500 mL of the solution. Sonicate for 30 min, freeze rapidly to -50 °C and then vacuum dry for 24 h.

[0063] 2.1.2 Selection of Ru(acca)3: Compared with RuCl3, ruthenium acetylacetonate has a lower degree of dissociation in water, with a dissociation constant Kd = 1.2 × 10⁻⁶. -5 To avoid Cl - Poisoning of active sites caused by adsorption on the carrier surface.

[0064] 2.1.3 Structure Orientation of Cu(NO3)2: DFT calculations show that Cu 2+ The coordination energy (-2.1 eV) with pyridine nitrogen on the support surface is higher than that of Ru. 3+ (-1.8eV) preferentially occupies high-energy sites on the support surface, forming a Cu-anchored-Ru-filled distribution pattern, which promotes the reduction of Ru particle size. When the molar ratio Ru:Cu = 3:1, the center of the d-band shifts from -1.2eV to -1.5eV, thus optimizing the H adsorption energy.

[0065] 2.1.4 Freeze-drying assisted impregnation method:

[0066] (i) Ice crystal template effect: When frozen at -50℃, water molecules in the solution form hexagonal ice crystals, and their growth direction produces channels with a diameter of 5-100nm, which restricts the migration of metal precursors and achieves uniform distribution.

[0067] (ii) Selection of vacuum drying parameters: vacuum degree <10Pa, temperature -40℃, drying for 24h, which can avoid the agglomeration of precursors during the heating process, and the precursor particle size after freeze drying is <5nm.

[0068] 2.2 Activation of the supported catalyst by magnetic induction Joule thermal shock method

[0069] 2.2.1 Specific steps: Place the carrier of the load precursor in a graphite crucible, introduce a mixed gas with a volume ratio of Ar:H2 = 95:5, apply an induced current of 300A, heat up to 900℃ within 10s, hold for 10s and then rapidly cool.

[0070] 2.2.2 High-frequency induction heating principle: When a high-frequency current of 200-300kHz passes through the coil, an eddy current effect is generated in the graphite crucible. The Joule heating formula is Q = I 2 Rt, where I = 300A and R is the graphite resistivity, can achieve a heating rate of 10000℃ / s, which is more than a thousand times that of traditional tube furnaces, thus inhibiting the Ostwald ripening of nanoparticles.

[0071] 2.2.3 Temperature-Time Parameter Selection:

[0072] (i) Determination of the peak temperature of 900℃: Experiments and tests show that RuO2 is completely reduced to metal at 900℃, and Cu(NO3)2 decomposes to form CuCl. x The matrix, while Cu below 850°C 2+ Insufficient reduction leads to the Ru particles beginning to sinter at temperatures above 950°C.

[0073] (ii) Balance of 10s holding time: When the holding time is less than 5s, the reduction reaction is incomplete; when it is greater than 15s, the average particle size of Ru particles increases from 2.3nm to 3.5nm.

[0074] 2.2.4Ru@CuCl x Structure formation: In-situ monitoring shows that Ru during the heating process 3+ Reduction begins at 300℃, with H2 adsorption reaching 80% of the theoretical value, and Cu... 2+ Partial reduction begins at 600℃, forming Cu. + / Cu 2+ Mixed valence states ultimately lead to the formation of Ru nanocrystals embedded in CuCl. x The core-shell structure of the matrix allows electrons to transfer from Ru to Cu, forming Ruδ. + Active center.

[0075] 3. Interface Engineering and Stability Enhancement

[0076] 3.1 Constructing the Ru-OC bonding structure

[0077] 3.1.1 Specific steps: The activated catalyst is treated in an air atmosphere at 200℃ for 30 min, and then slowly cooled to room temperature by introducing nitrogen gas containing 5% O2.

[0078] 3.1.2 Selection of process parameters for low-temperature oxidation stabilization:

[0079] (i) Effect of treatment in air atmosphere at 200℃ for 30 min: O2 partial pressure is controlled at 0.21 atm. At this temperature, Ru nanocrystals preferentially oxidize to form a RuO2 thin layer with a thickness of 1-2 nm, which reacts with C-OH groups on the surface of the support to form Ru-OC bonds.

[0080] (ii) Necessity of slow cooling with 5% O2 / N2: The cooling rate is controlled at 1℃ / min to avoid interfacial stress cracking caused by rapid cooling.

[0081] 3.1.3 Metal-support interaction: After Ru-OC bonding, the interaction force is 3 times higher than that of traditional Ru / C catalysts, forming a stable structure similar to anchor points, which inhibits Ru particle migration.

[0082] 3.2 Design of Gradient Core-Shell Hydrophobic Protective Layer

[0083] 3.2.1 Specific steps: TEOS steam is introduced for 30 minutes at a temperature of 250℃, followed by HMDS steam hydrophobication for 1 hour at a temperature of 150℃ to obtain the final product.

[0084] 3.2.2 SiO2 Thin-Layer Deposition:

[0085] (i) TEOS vapor concentration control: Under the conditions of 250℃ and N2 carrier gas flow rate of 50mL / min, the partial pressure of TEOS (tetraethoxysilane) was maintained at 0.05atm. The reaction rate was determined by the number of surface hydroxyl -OH. The molar ratio of the reaction between the carrier surface -OH and TEOS was 1:1.2, forming an amorphous SiO2 layer of 1.5±0.2nm, which uniformly covered the carrier pores.

[0086] (ii) Gradient annealing: Treatment in nitrogen at 300℃ for 1 h promotes the condensation of CO bonds between the SiO2 layer and the support surface: Si-OH + C-OH → Si-O-C + H2O, reducing the interfacial bonding energy from 0.5 J / m 2 Increased to 1.2 J / m 2 The adhesion of the protective layer is increased by 4 times.

[0087] 3.2.3 Hydrophobic modification and shape selection:

[0088] (i) HMDS treatment mechanism: HMDS vapor was treated at 150℃ for 1h. HMDS and -OH on the surface of SiO2 underwent a substitution reaction: Si-OH+(CH3)3Si-NH-Si(CH3)3→Si-O-Si(CH3)3+NH3. The contact angle increased from 85° before treatment to 135°, and the water adsorption capacity decreased from 0.8mL / g to 0.1mL / g.

[0089] (ii) Molecular sieving effect: The protective layer has a pore size of 0.4 nm, which matches the kinetic diameter of H2 (0.28 nm) and CO (0.33 nm), allowing free diffusion. The CH3OH molecule has a diameter of 0.38 nm, which is close to the pore size, reducing the diffusion coefficient by 3 orders of magnitude. The diffusion activation energy of CH3OH in the protective layer is 28 kJ / mol, which is 4.5 times that of H2, thus achieving the "anti-poisoning" function.

[0090] Example 2

[0091] This embodiment sets up different cases for comparative experiments.

[0092] Experimental Example 1

[0093] Preparation of bifunctional Ru / C catalysts:

[0094] (1) Carrier preparation: 1 kg of TDI waste residue with a water content of 30% was washed three times with 5% hydrochloric acid, and then pyrolyzed at 700℃ for 2 h under N2 atmosphere with a heating rate of 5℃ / min. The resulting semi-coke was mixed with KOH at a mass ratio of 1:2, activated at 800℃ for 1 h, and then acid-washed and dried to obtain a nitrogen-doped carbon carrier with a specific surface area of ​​1280 m². 2 / g, pore volume 1.2cm 3 / g;

[0095] (2) Supercritical methanol treatment: The carrier was loaded into a supercritical reactor and methanol was injected to a filling rate of 80%. The temperature was increased to 300℃ at 10℃ / min and the pressure was maintained at 12MPa for 12h. After depressurization and methanol recovery, the oxygen group content of the carrier was reduced to 0.24mmol / g.

[0096] (3) Bimetallic loading: Prepare a 0.1 mol / L Ru(acac)3-Cu(NO3)2 solution according to the Ru:Cu molar ratio, take 50 g of the support and mix it with 500 mL of the solution, sonicate for 30 min, quickly freeze to -50℃ and then vacuum dry for 24 h;

[0097] (4) Magnetic induction activation: The carrier of the load precursor is placed in a graphite crucible, Ar / H2 (95:5) mixed gas is introduced, an induction current of 300A is applied, the temperature is raised to 900℃ within 10s, and the temperature is held for 10s before rapid cooling.

[0098] (5) Interface engineering: After air treatment at 200℃ for 30 min, slow cooling was followed by the introduction of TEOS steam at 250℃ for 30 min, and then hydrophobication was achieved by HMDS steam at 150℃ for 1 h to obtain Ru@CuCl. x / SiO2@NPC catalyst.

[0099] Experimental Example 2

[0100] Effect of different Ru:Cu molar ratios on catalyst performance:

[0101] (1) Support preparation: Same as in Experiment 1, nitrogen-doped porous carbon support was obtained with a nitrogen content of 4.2 at%.

[0102] (2) Bimetallic loading: Precursor solutions with Ru:Cu molar ratios of 1:1, 2:1, 3:1 and 4:1 were prepared, with Ru concentration of 0.1 mol / L. The solutions were loaded onto the carrier using a freeze-drying-assisted impregnation method with a solid-liquid ratio of 1:10.

[0103] (3) Magnetic induction activation: Parameters are the same as in Experiment 1;

[0104] (4) Performance test results:

[0105] ① When Ru:Cu = 3:1, the average particle size of Ru is 2.3 nm, and Ruδ + The proportion is 35%, and the time-to-hydrogen (TOF) of methanol dehydrogenation is 3.2 s. -1 ;

[0106] ② When Ru:Cu = 1:1, the excessive Cu content leads to Ru particle agglomeration, with an average particle size of 4.8 nm and a TOF of 1.8 s⁻¹. -1 ;

[0107] ③ When Ru:Cu = 4:1, the structure-directing effect of Cu is insufficient, the particle size distribution becomes wider, reaching 2.3-5.0 nm, and the TOF = 2.5 s. -1 ;

[0108] Therefore, 3:1 is the optimal molar ratio, which verifies the optimal value for the downward shift of the d-band center calculated by DFT.

[0109] Experimental Example 3

[0110] The effect of supercritical methanol treatment temperature on carrier performance:

[0111] (1) Carrier preparation: Same as in Experiment 1, the carrier was obtained after pyrolysis-activation;

[0112] (2) Supercritical treatment: fixed pressure 12MPa, treatment time 1h, and temperatures of 280℃, 300℃ and 320℃ respectively;

[0113] (3) Characterization structure:

[0114] ① At 280℃, the residual oxygen-containing acidic groups are 0.35 mmol / g, the basic nitrogen content is 58%, and the contact angle is 115°;

[0115] ②At 300℃, the acidic group is 0.24 mmol / g, the basic nitrogen is 65%, and the contact angle is 120°;

[0116] ③ At 320℃, the carrier partially carbonizes, and the specific surface area decreases to 1050 m².2 / g, acidic groups 0.21mmol / g, but the destruction of the pore structure led to a 15% decrease in metal loading;

[0117] Therefore, 300℃ is the optimal temperature, balancing the modification effect with the stability of the carrier.

[0118] Test Example 4

[0119] The effect of magnetic induction Joule heating rate on Ru particle size:

[0120] (1) Carrier preparation and loading: Same as in Experiment 1, a carrier for loading precursor was obtained;

[0121] (2) Activation parameters: fixed peak temperature of 900℃, holding time of 10s, and heating rate of 10 3 ℃ / s, 10 4 ℃ / s, 10 5 ℃ / s;

[0122] (3) Test results:

[0123] ①10 3 At ℃ / s, the average particle size of Ru is 3.8 nm, with a wide particle size distribution of 1-8 nm;

[0124] ②10 4 At ℃ / s, the particle size is 2.3±0.7nm, with a narrow distribution;

[0125] ③10 5 At ℃ / s, the rapid temperature rise leads to local overheating, resulting in a small number of large particles of 5-10nm with an average particle size of 2.8nm.

[0126] Therefore, 10 4 The optimal heating rate is ℃ / s, which balances rapid reduction with the avoidance of sintering.

[0127] Comparative Example 1

[0128] A comparison is made between the traditional tube furnace activation process and the process described in this application:

[0129] (1) Catalyst preparation: The support preparation and loading process of Experiment 1 were adopted, and then activation was carried out by conventional tube furnace heating and magnetic induction heating (MIH) respectively. The parameters of the tube furnace were 300℃ / 2h, H2 reduction, and magnetic induction heating activation were the same as those of Experiment 1.

[0130] (2) Comparison of differences:

[0131] ① Tube furnace activation: Ru average particle size 5.2 nm, Ruδ +The proportion is 28%, and the activity decreases by 42% after running at 200℃ for 1000 hours;

[0132] ②MIH activation: Ru average particle size 2.3 nm, Ruδ + With a concentration of 35%, the activity decreased by 7.5% after 1000 hours of operation at 200℃.

[0133] The slow heating in the tube furnace leads to Ostwald ripening of Ru particles, while the ultra-rapid heating in the MIH inhibits atomic diffusion, resulting in a more stable Ru@CuCl. x structure.

[0134] Example 3

[0135] This embodiment verifies the structure of the catalyst through testing experiments.

[0136] 1. Figure 2 XPS Ru 3d spectrum, used to verify Ru@CuCl x Electron transfer in the kernel and Ruδ + Active center formation.

[0137] The figure shows a bimodal splitting characteristic: the peak at 280.0 eV corresponds to the metallic Ru (Ru 0 The peak at 280.5 eV corresponds to electron-deficient Ru (Ruδ). + ), and by calculating the peak area, the latter accounts for approximately 35%. Ruδ + The existence of electrons from Ru to CuCl x Matrix transfer, forming a strong Xianghu Town Ouyong, is the key to improving hydrogen adsorption activity.

[0138] Evidence regarding Cu valence state: This is supported by the Cu 2p spectrum (not shown), specifically the 932.5 (Cu) value. + ) and 934.0 eV (Cu 2+ The mixed peaks of CuCl confirm that CuCl x (x=1.5-2) The matrix exists and forms a core-shell electronic coupling structure with Ru.

[0139] Ruδ + Its formation originates directly from Ru@CuCl x The electronic delocalization effect at the interface is the theoretical basis for bimetallic synergistic catalysis.

[0140] 2. Figure 3 XRD patterns were used to verify the interaction between Ru nanocrystals and CuCl. x Coexistence of crystalline phases in the matrix and crystallinity of the core-shell structure.

[0141] Characteristic diffraction peaks in the figure:

[0142] 2θ = 44.7° corresponds to the Ru(101) crystal plane (metallic Ru), and the peak broadening indicates that the nanocrystal size is 2-3 nm;

[0143] 2θ = 29.5° corresponds to the CuCl2(110) crystal plane, confirming that CuCl x The matrix exists and forms a core-shell crystalline structure with Ru;

[0144] The broad peak at 2θ = 22.0° is characteristic of the amorphous layer of SiO2, which corroborates the amorphous structure of the shell.

[0145] Compared to the traditional Ru / C spectrum (with only a 44.7° peak), the coexistence of two peaks in this spectrum proves that Ru@CuCl x The structure remains stable after activation at high temperature (900℃) without obvious sintering.

[0146] Ru and CuCl x The characteristic peaks exist independently and do not overlap, indicating that the two form a core-shell structure with a clear interface, rather than a disordered alloy.

[0147] 3. Figure 4 The gas-phase diffusion pattern is used to verify the molecular sieving function and hydrophobic protection of the SiO2@NPC shell.

[0148] Permeability differences shown in the figure:

[0149] The permeability of H2 (0.28 nm) and CO (0.33 nm) is >90%, indicating that small molecules can freely pass through the shell channel with a pore size of 0.4 nm; the permeability of CH3OH (0.38 nm) is <5%, confirming that the shell has a "sieving effect" on molecules close to the pore size, preventing them from contacting the Ru active center and avoiding CO poisoning. Combined with the contact angle test (135°), the hydrophobic SiO2 layer - Si(CH3)3 groups reduce water molecule adsorption and inhibit Ru oxidation and dissolution.

[0150] The precise matching of shell pore size and molecular dynamic diameter (0.4nm vs 0.38nm) is the core design for achieving "selective protection".

[0151] 4. Figure 5 The TPR spectrum was used to verify the strengthening effect of Ru-OC interface bonding on metal-support interaction.

[0152] The reduction peak shift in the figure shows that the reduction peak temperature of the catalyst in the complete process is 240℃, which is 60℃ higher than that of the catalyst without Ru-OC bonding (180℃), proving that the metal-support interaction force is enhanced by 3 times (for every 10℃ increase in TPR peak temperature, the interaction is enhanced by about 50%). The peak temperature shift originates from the Ru-OC bond ( Figure 2The formation of the 280.5 eV peak in the bond acts as an "anchor point" to inhibit Ru particle migration, and the activity decay is less than 8% after 1000 h of operation at 200 °C.

[0153] Ru-OC bonding is the "intermediate anchoring layer" in the core-shell structure, connecting Ru@CuCl x The core and the SiO2 shell form a three-level stable structure.

[0154] In summary, XPS proves Ruδ + Formation, XRD evidence for Ru@CuCl x The crystal phase structure, TPR confirmation of Ru-OC bond enhancement interaction, and gas diffusion pattern revealing the sieving and hydrophobic properties of the SiO2 layer, all jointly demonstrate the Ru@CuCl prepared in this application. x The / SiO2@NPC catalyst forms a complete core-shell structure of "active center - stable interface - protective shell".

Claims

1. A process for preparing a bifunctional Ru / C catalyst for coupled thermocatalytic methanol dehydrogenation and electrocatalytic hydrogenation reactions, characterized in that: Includes the following steps: (1) Using toluene diisocyanate waste residue as raw material, nitrogen-doped porous carbon support was prepared by washing with hydrochloric acid, controlled pyrolysis and KOH activation; (2) The carrier is subjected to supercritical methanol surface modification treatment; (3) A Ru-Cu bimetallic precursor solution was loaded onto a modified support by a freeze-drying-assisted impregnation method. (4) Activate the loaded catalyst; (5) The activated catalyst is constructed with a Ru-OC bonded structure and a hydrophobic SiO2 protective layer is prepared on its surface to obtain the product catalyst.

2. The preparation process according to claim 1, characterized in that: The supercritical methanol treatment conditions for the carrier are: temperature 280-320℃, pressure 10-15MPa, treatment time 10-15h, and the oxygen-containing acidic groups of the carrier after treatment are ≤0.3mmol / g.

3. The preparation process according to claim 1, characterized in that: In the Ru-Cu bimetallic precursor, the Ru source is ruthenium acetylacetone, the Cu source is copper nitrate, and the Ru:Cu molar ratio is 3:

1.

4. The preparation process according to claim 1, characterized in that: The method for activating the loaded catalyst is magnetic induction Joule thermal shock method, with the following parameters: induction current 280-320A, heating rate ≥1000℃ / s, peak temperature 850-950℃, holding time 5-15s, and activation atmosphere is an argon-hydrogen mixture containing 5% H2.

5. The preparation process according to claim 1, characterized in that: The Ru-OC bonding structure was constructed as follows: the activated catalyst was treated in an air atmosphere at 200°C for 30 min, and then slowly cooled to room temperature by introducing nitrogen gas containing 5% O2. An atomic-level Ru-OC bonding channel was formed at the interface between the Ru nanocrystals and the carbon support, with a Ru-O coordination number of 2.1, and the metal-support interaction force was increased by 3 times.

6. The preparation process according to claim 1, characterized in that: The hydrophobic SiO2 protective layer was prepared by vapor deposition, and the thickness of the obtained hydrophobic SiO2 protective layer was 1.2-1.8 nm, the surface contact angle was ≥130°, and the pore size was 0.35-0.45 nm.

7. A catalyst obtained by the preparation process described in any one of claims 1-6, characterized in that: The catalyst has Ru@CuCl x / SiO2@NPC core-shell structure.

8. The catalyst according to claim 7, characterized in that: The catalyst contains Ru particles with an average particle size of 2.3 ± 0.7 nm and Ruδ... + The proportion is ≥35%.

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