Methanol synthesis hydrogen production catalyst and preparation method thereof

Abstract

The invention relates to the technical field of catalysts for hydrogen production through methanol reforming, in particular to a catalyst for hydrogen production through methanol synthesis and a preparation method thereof, and solves the problems of low activity, poor stability and high cost of an existing catalyst through collaborative design of'carrier-active component-dynamic repair-in-situ purification '. According to the catalyst, nitrogen vacancy modified gamma-Mo2N serves as a carrier, CoCu alloy single atoms are anchored, and a CeO2-ZrO2 dynamic repair layer and an Au nano-cluster and CeO2 in-situ purification unit are sequentially deposited on the surface. Nitrogen vacancies anchor single atoms to inhibit agglomeration, CeO2-ZrO2 captures sulfur impurities, Au nanoclusters catalyze CO oxidation at low temperature, and in methanol steam reforming at 220 DEG C, the methanol conversion rate is high, the hydrogen yield is high, the 2000-hour activity retention rate is high, and the cost is low. The catalyst breaks through the bottlenecks of sintering inactivation, noble metal dependence and CO high selectivity of a traditional copper-based catalyst, and has remarkable advantages.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of methanol reforming hydrogen catalyst, and particularly relates to a methanol synthesis hydrogen catalyst and a preparation method thereof. BACKGROUND

[0002] As an ideal clean energy carrier, one of the core bottlenecks of the large-scale application of hydrogen energy lies in efficient and stable on-site hydrogen production technology. Methanol steam reforming (MSR) hydrogen production has become the preferred solution for distributed scenarios such as fuel cells due to its mild reaction conditions and high hydrogen yield, and the performance of the catalyst is the key to the commercialization of the technology. The current mainstream catalyst system still faces multiple technical bottlenecks.

[0003] Copper-based catalysts are the mainstream choice for MSR reactions due to their high activity at low temperatures and low cost, but they have significant shortcomings: insufficient stability, copper particles are prone to high-temperature sintering, leading to a decrease in dispersion, and the conversion rate often drops to less than 70% of the initial value after 500 hours of operation; high CO selectivity, the CO content in the reforming gas of traditional copper-based catalysts is usually 5%-8%, which requires additional water-gas shift and CO purification units, increasing system complexity, which is due to the insufficient catalytic activity of copper-based catalysts for reverse water-gas shift reactions and the insufficient oxygen storage capacity of the carrier; weak resistance to poisoning, sensitive to impurities such as sulfur and chlorine in the raw materials, sulfur species easily form stable Cu-S bonds with copper active sites, leading to permanent deactivation, and chlorine may accelerate copper sintering by forming low-melting-point Cu2Cl.

[0004] Although noble metal catalysts such as Pt and Pd have excellent stability, they are expensive, with Pt and Pd prices accounting for more than 70% of the total cost of the catalyst and limited global reserves, making it difficult to be used on a large scale, and they are also prone to direct decomposition of methanol to CO rather than CO2 in low-temperature environments, and some Pt-based catalysts have even higher CO selectivity of up to 10%, requiring complex post-processing.

[0005] The carrier plays a key role in the activity, stability, and selectivity of photocatalysts, but existing carriers have obvious shortcomings: traditional carriers such as Al2O3 can improve copper dispersion, but have poor oxygen storage capacity, cannot inhibit CO generation, and are prone to form inert spinel phases with active components at high temperatures, reducing activity.

[0006] Therefore, according to the related technology in the above, it is urgent to develop a methanol synthesis hydrogen catalyst and a preparation method thereof. SUMMARY

[0007] Therefore, the present application aims to provide a methanol synthesis hydrogen catalyst and a preparation method thereof, which has ultra-high activity, ultra-long stability, low noble metal consumption, and low CO selectivity, solving the core problems of activity-stability trade-off, dependence on noble metals, and CO byproducts in the prior art.

[0008] Based on the above purpose, the present application provides a methanol synthesis hydrogen production catalyst and a preparation method thereof.

[0009] A preparation method of a methanol synthesis hydrogen production catalyst, comprising the following steps:

[0010] Step S1. Carrier pretreatment: γ-Mo2N nanoparticles with a particle size of 5-10 nm are pretreated by Ar + etching to obtain a carrier;

[0011] Step S2. Active component loading: CoCu alloy monatomic atoms are loaded by a defect anchoring method, wherein the Co loading amount is 0.2wt%, the Cu loading amount is 0.4wt%, and monatomic dispersion is formed by H2 reduction;

[0012] Step S3. Dynamic repair layer deposition: a CeO2-ZrO2 solid solution with a thickness of 1.5 nm is deposited by a microwave-assisted (MW-ALd) technique, the microwave power is 300 W, the temperature is 110°C, and the deposition cycle is 15 times;

[0013] Step S4. In-situ purification unit construction: Au nanocluster@CeO2 is loaded, the Au loading amount is 0.1wt%, the particle size is 2-3 nm, and the shaping is performed by NaBH4 reduction and 320°C calcination.

[0014] Preferably, the carrier pretreatment process is as follows:

[0015] Step A1. Dispersion treatment: γ-Mo2N nanoparticles are taken, anhydrous ethanol is added, and the mixture is placed in an ultrasonic cleaning instrument under a power of 300 W for dispersion for 30 min to form a uniform suspension;

[0016] Step A2. Ar + plasma etching: the suspension is transferred to the reaction cavity of a plasma etching instrument, etching parameters are set, and the surface of the γ-Mo2N is bombarded by Ar + to form nitrogen vacancies;

[0017] Step A3. Post-treatment: after etching, the suspension is centrifuged, the supernatant is discarded, the precipitate is washed with anhydrous ethanol for 3 times, vacuum dried at 60°C for 6 h, and a nitrogen vacancy modified γ-Mo2N carrier is obtained.

[0018] Preferably, the ratio of the γ-Mo2N nanoparticles to anhydrous ethanol in step A1 is 5g:100mL, and the solid-liquid ratio of the uniform suspension is 1:20.

[0019] Preferably, the etching parameters in step A2 are as follows:

[0020] The power is 100-140W, the time is 3-7min, the working gas pressure is 10-20Pa, the carrier gas is Ar gas with a purity of 99.99%, and the flow rate is 20mL / min.

[0021] Preferably, the centrifugation speed in step A3 is 8000 r / min and the centrifugation time is 10 min.

[0022] Preferably, in step A3, 50 mL of ethanol is added each time during washing, followed by sonication for 5 min and centrifugation.

[0023] Preferably, the process of loading the active component is as follows:

[0024] Step B1. Carrier dispersion: Add the carrier to deionized water and ultrasonically disperse it for 20 minutes at a power of 300W to form a carrier suspension;

[0025] Step B2. Metal ion loading: Add 0.1M Co(NO3)2 solution and 0.1M Cu(NO3)2 solution dropwise to the suspension and stir magnetically for 1 hour;

[0026] Step B3. pH adjustment and reduction: Adjust the pH of the mixture to 8-9 with 0.1M NaOH solution, add reducing agent, transfer to a constant temperature water bath, and stir and react at 60-80℃ for 3 hours;

[0027] Step B4. H2 atmosphere activation: After the reaction, centrifuge, wash three times with deionized water, dry at 60℃ for 4 hours, transfer the dried solid to a tube furnace, and activate it in an H2 atmosphere to form stable CoCu alloy single-atom sites, thus obtaining the active component.

[0028] Preferably, the ratio of carrier to deionized water in step B1 is 5g:100mL.

[0029] Preferably, the volume ratio of the suspension, Co(NO3)2 solution and Cu(NO3)2 solution in step B2 is 100mL:1mL:2mL.

[0030] Preferably, the Co(NO3)2 solution in step B2 has a Co loading of 0.2 wt%, and the Cu(NO3)2 solution has a Cu loading of 0.4 wt%.

[0031] Preferably, the reducing agent in step B3 is ascorbic acid, and the molar ratio of ascorbic acid to metal ions in step B3 is 3:1.

[0032] Preferably, the centrifugation speed in step B4 is 8000 r / min, the centrifugation time is 10 min, and the activation parameters are as follows:

[0033] The H2 atmosphere has a flow rate of 50 mL / min, a temperature rising rate of 2-3 °C / min, an activation temperature of 200-300 °C, and a holding time of 2 h.

[0034] Preferably, the deposition process of the dynamic repair layer is as follows:

[0035] Step C1. Substrate pretreatment: spread the catalyst powder on the ALD tray with a thickness of ≤2 mm;

[0036] Step C2. MW-ALD deposition cycle;

[0037] Step C3. Post-treatment: naturally cool to room temperature, N2 purge for 30 min to remove residual precursors.

[0038] Preferably, the number of deposition cycles in step C2 is 15, and the parameters of the deposition cycle are: microwave power of 300 W, temperature of 110 °C, and N2 flow rate of 80 mL / min.

[0039] Preferably, the operation steps of the deposition cycle in step C2 are as follows:

[0040] Step C201. The operation time of Ce(thd)3 pulse is 0.2 s;

[0041] Step C202. The operation time of N2 purge is 30 s;

[0042] Step C203. The operation time of Zr(thd)4 pulse is 0.2 s;

[0043] Step C204. The operation time of O3 oxidation pulse is 0.15 s.

[0044] Preferably, the construction process of the in-situ purification unit is as follows:

[0045] Step D1. Au precursor loading: disperse the catalyst in deionized water, ultrasonic for 15 min, add PVP, stir for 30 min, add 0.01M HAuCl4 solution dropwise, stir at room temperature for 1.5 h;

[0046] Step D2. Reduction reaction: under ice bath conditions, add 0.05M NaBH4 solution dropwise, continue to stir for 30 min;

[0047] Step D3. Calcination and shaping: after centrifugal washing, dry at 60 °C for 6 h, then heat to 320 °C at a rate of 5 °C / min in air atmosphere, and hold for 1.5 h.

[0048] Preferably, the catalyst, deionized water, PVP, 0.01M HAuCl4 solution and 0.05M NaBH4 solution are used in a ratio of 5g: 50mL: 0.2g: 50mL: 5mL, and the Au 3+ :NaBH4 in the system = 1:6.

[0049] Preferably, the molecular weight Mw of the PVP in step D1 is 58000, and the Au loading in the HAuCl4 solution in step D1 is 0.1wt%.

[0050] A hydrogen production catalyst for methanol synthesis is prepared by the above preparation method.

[0051] The beneficial effects of the present application are:

[0052] The present application provides a hydrogen production catalyst for methanol synthesis and a preparation method thereof. Through the synergistic design of the carrier, active component, dynamic repair layer and in-situ purification unit, the present application achieves a significant technical breakthrough: CoCu alloy single-atom efficient catalysis, Xiacun conversion rate of over 97% at 220℃, excellent hydrogen production rate; nitrogen vacancy anchoring and CeO2-ZrO2 repair layer synergistic effect, catalyst activity retention rate of over 95% for continuous operation of 2000h, sulfur tolerance threshold increased to 1.0ppm; Au nanocluster in-situ purification reduces CO concentration to below 0.42%, eliminating the need for additional purification units; non-noble metal substitution strategy significantly reduces costs, only 1 / 50 of traditional noble metal catalysts, and comprehensively solves the problems of imbalance between activity and stability of existing catalysts, high CO selectivity, weak resistance to poisoning and high cost, etc., and has great industrial application value. DETAILED DESCRIPTION

[0053] To make the purpose, technical solutions and advantages of the present application clearer and more apparent, the present application is further described in detail below with specific examples.

[0054] Example 1: A preparation method of a hydrogen production catalyst for methanol synthesis, comprising the following steps:

[0055] S1. Carrier pretreatment: 5g of γ-Mo2N nanoparticles with a particle size of 5-10nm are added to 10mL of anhydrous ethanol, and dispersed in an ultrasonic cleaning instrument at a power of 300W for 30min to form a uniform suspension with a solid-liquid ratio of 1:20;

[0056] S2. Ar + Plasma etching: the suspension is transferred to the reaction chamber of a plasma etching instrument, and etching parameters are set to bombard the surface of γ-Mo2N with Ar + , wherein the etching parameters are: power of 100W, time of 3min, working pressure of 10Pa, carrier gas of Ar gas with a purity of 99.99%, and flow rate of 20mL / min.

[0057] S3. Post-processing: After etching, the suspension was centrifuged at 8000 r / min for 10 min, the supernatant was discarded, the precipitate was washed with anhydrous ethanol for 3 times, 50 mL of ethanol was added each time, and then centrifuged after ultrasonic treatment for 5 min, and dried at 60°C under vacuum for 6 h to obtain the nitrogen vacancy modified γ-Mo2N carrier.

[0058] S4. Active component loading: Carrier dispersion: 5 g of the carrier was added to 100 mL of deionized water, and ultrasonic dispersion was performed at a power of 300 W for 20 min to form a carrier suspension;

[0059] S5. Metal ion loading: 1 mL of 0.1M Co(NO3)2 solution and 2 mL of 0.1M Cu(NO3)2 solution were added dropwise to the 100 mL suspension, and magnetic stirring was performed for 1 h, the Co loading in the Co(NO3)2 solution was 0.2wt%, and the Cu loading in the Cu(NO3)2 solution was 0.4wt%;

[0060] S6. pH adjustment and reduction: The pH of the mixture was adjusted to 8 with 0.1M NaOH solution, ascorbic acid was added, and the molar ratio of ascorbic acid to metal ions was 3:1, and then transferred to a constant temperature water bath, and stirred at 60°C for 3 h;

[0061] S7. H2 atmosphere activation: After the reaction, centrifugation was performed at 8000 r / min for 10 min, deionized water was washed for 3 times, and drying was performed at 60°C for 4 h, then the dried solid was transferred to a tube furnace, and activated in an H2 atmosphere to form stable CoCu alloy monatomic sites, i.e. active components, and the parameters during activation were as follows: the flow rate of H2 atmosphere was 50 mL / min, the heating rate was 2°C / min, the activation temperature was 200°C, and the holding time was 2 h;

[0062] S8. Dynamic repair layer deposition: substrate pretreatment: the catalyst powder was laid on the ALD tray with a thickness of ≤2 mm;

[0063] S9. MW-ALD deposition cycle, the number of deposition cycles was 15 times, and the parameters of the deposition cycle were as follows: the microwave power was 300 W, the temperature was 110°C, the flow rate of N2 was 80 mL / min, and the operation steps of the deposition cycle were as follows: the operation time of Ce(thd)3 pulse was 0.2 s; the operation time of N2 purge was 30 s; the operation time of Zr(thd)4 pulse was 0.2 s; and the operation time of O3 oxidation pulse was 0.15 s;

[0064] S10. Post-processing: natural cooling to room temperature, and N2 purging for 30 min to remove residual precursors.

[0065] S11. In-situ purification unit construction: Step D1. Au precursor loading: 5 g of catalyst was dispersed in 50 mL of deionized water, ultrasonic for 15 min, 0.2 g of PVP with Mw of 58000 was added, stirred for 30 min, 50 mL of 0.01M HAuCl4 solution was added dropwise, wherein the Au loading of the HAuCl4 solution was 0.1wt%, stirred at room temperature for 1.5h;

[0066] S12. Reduction reaction: under ice bath conditions, 5 mL of 0.05M NaBH4 solution was added dropwise, Au 3+ : NaBH4 = 1:6 in the system, continue to stir for 30 min;

[0067] S13. Calcination and shaping: after centrifugal washing, dry at 60℃ for 6h, then in air atmosphere, heat to 320℃ at a rate of 5℃ / min, keep for 1.5h, to obtain a methanol synthesis hydrogen production catalyst.

[0068] Example 2: A preparation method of a methanol synthesis hydrogen production catalyst, comprising the following steps:

[0069] S1. Carrier pretreatment: 5g of γ-Mo2N nanoparticles with a particle size of 5-10nm was added to 10mL of anhydrous ethanol, and dispersed in an ultrasonic cleaner at a power of 300W for 30min to form a uniform suspension with a solid-liquid ratio of 1:20;

[0070] S2. Ar + Plasma etching: the suspension was transferred to the reaction chamber of the plasma etching instrument, and the etching parameters were set to form nitrogen vacancies on the surface of γ-Mo2N by Ar + bombardment, wherein the etching parameters were: power of 120W, time of 4min, working pressure of 13Pa, carrier gas of Ar gas with a purity of 99.99%, and flow rate of 20mL / min;

[0071] S3. Post-treatment: after etching, the suspension was centrifuged at 8000r / min for 10min, the supernatant was discarded, and the precipitate was washed with anhydrous ethanol for 3 times, 50mL of ethanol was added each time, ultrasonic for 5min and then centrifuged, and vacuum dried at 60℃ for 6h to obtain a nitrogen vacancy modified γ-Mo2N carrier.

[0072] S4. Active component loading: carrier dispersion: 5g of carrier was added to 100mL of deionized water, and dispersed at a power of 300W for 20min to form a carrier suspension;

[0073] S5. Metal ion loading: 1 mL of 0.1 M Co(N03)2solution and 2 mL of 0.1 M Cu(N03)2solution were added dropwise into 100 mL of the suspension, and magnetic stirring was performed for 1 h. The Co loading was 0.2 wt% in the Co(N03)2solution, and the Cu loading was 0.4 wt% in the Cu(N03)2solution;

[0074] S6. pH adjustment and reduction: The pH of the mixture was adjusted to 8.5 using a 0.1 M NaOH solution, and ascorbic acid was added. The molar ratio of ascorbic acid to metal ions was 3:1. The mixture was transferred to a constant-temperature water bath and stirred at 65 °C for 3 h;

[0075] S7. H2atmosphere activation: After the reaction, the mixture was centrifuged at 8000 r / min for 10 min, washed with deionized water three times, and dried at 60 °C for 4 h. The dried solid was transferred to a tube furnace and activated in an H2atmosphere to form stable CoCu alloy single-atom sites, i.e., the active component. The parameters during activation were as follows: the flow rate of the H2atmosphere was 50 mL / min, the heating rate was 3 °C / min, the activation temperature was 230 °C, and the holding time was 2 h;

[0076] S8. Dynamic repair layer deposition: Substrate pretreatment: The catalyst powder was spread on an ALD tray with a thickness of ≤2 mm;

[0077] S9. MW-ALD deposition cycle, the number of deposition cycles was 15, and the parameters of the deposition cycle were as follows: the microwave power was 300 W, the temperature was 110 °C, the flow rate of N2was 80 mL / min. The operation steps of the deposition cycle were as follows: the operation time of the Ce(thd)3pulse was 0.2 s; the operation time of the N2purging was 30 s; the operation time of the Zr(thd)4pulse was 0.2 s; and the operation time of the O3oxidation pulse was 0.15 s;

[0078] S10. Post-treatment: Natural cooling to room temperature, and N2purging for 30 min to remove residual precursors.

[0079] S11. In-situ purification unit construction: Step D1. Au precursor loading: 5 g of the catalyst was dispersed in 50 mL of deionized water, ultrasonically treated for 15 min, 0.2 g of PVP with a Mw of 58000 was added, stirred for 30 min, and 50 mL of 0.01 M HAuCl4solution was added dropwise. The Au loading in the HAuCl4solution was 0.1 wt%, and stirring was performed at room temperature for 1.5 h;

[0080] S12. Reduction reaction: 5 mL of 0.05 M NaBH4solution was added dropwise under ice bath conditions, and the molar ratio of Au 3+ : NaBH4= 1:6, and stirring was continued for 30 min;

[0081] S13. Calcination: After centrifugal washing, dry at 60℃ for 6h, then in air atmosphere, increase the temperature to 320℃ at 5℃ / min, keep for 1.5h, to obtain the methanol synthesis hydrogen production catalyst.

[0082] Example 3: A preparation method of a methanol synthesis hydrogen production catalyst, comprising the following steps:

[0083] S1. Carrier pretreatment: 5g of γ-Mo2N nanoparticles with a particle size of 5-10nm were added to 10mL of anhydrous ethanol, and dispersed in an ultrasonic cleaner at a power of 300W for 30min to form a uniform suspension with a solid-liquid ratio of 1:20;

[0084] S2. Ar + Plasma etching: The suspension was transferred to the reaction chamber of the plasma etching instrument, and the etching parameters were set to bombard the surface of γ-Mo2N with Ar + to form nitrogen vacancies, wherein the etching parameters were: power 130W, time 5min, working pressure 17Pa, carrier gas Ar with a purity of 99.99%, and flow rate 20mL / min;

[0085] S3. Post-treatment: After etching, the suspension was centrifuged at 8000r / min for 10min, the supernatant was discarded, and the precipitate was washed with anhydrous ethanol for 3 times, 50mL of ethanol was added each time, ultrasonic for 5min and then centrifuged, and vacuum dried at 60℃ for 6h to obtain the nitrogen vacancy modified γ-Mo2N carrier.

[0086] S4. Active component loading: Carrier dispersion: 5g of the carrier was added to 100mL of deionized water and ultrasonically dispersed at a power of 300W for 20min to form a carrier suspension;

[0087] S5. Metal ion loading: 1mL of 0.1M Co(NO3)2 solution and 2mL of 0.1M Cu(NO3)2 solution were added dropwise to 100mL of the suspension, and magnetically stirred for 1h, the Co loading in the Co(NO3)2 solution was 0.2wt%, and the Cu loading in the Cu(NO3)2 solution was 0.4wt%;

[0088] S6. pH adjustment and reduction: The pH of the mixture was adjusted to 9 with 0.1M NaOH solution, ascorbic acid was added, the molar ratio of ascorbic acid to metal ions was 3:1, and it was transferred to a constant temperature water bath and stirred at 70℃ for 3h;

[0089] S7. H2 atmosphere activation: after reaction, centrifugal at 8000 r / min for 10 min, deionized water washing for 3 times, drying at 60℃ for 4h, transferring the dried solid to a tube furnace, activating in H2 atmosphere, forming stable CoCu alloy single atom sites, i.e. obtaining the active component, the parameters during activation are as follows: H2 atmosphere flow rate is 50 mL / min, temperature rising rate is 2℃ / min, activation temperature is 260℃, and holding time is 2h;

[0090] S8. Dynamic repair layer deposition: substrate pretreatment: spreading the catalyst powder on the ALD tray, thickness≤2mm;

[0091] S9. MW-ALD deposition cycle, the number of deposition cycles is 15 times, the parameters of the deposition cycle are: microwave power is 300W, temperature is 110℃, N2 flow rate is 80 mL / min, the operation steps of the deposition cycle are as follows: operation time of Ce(thd)3 pulse is 0.2s; operation time of N2 purge is 30s; operation time of Zr(thd)4 pulse is 0.2s; operation time of O3 oxidation pulse is 0.15s;

[0092] S10. Post-processing: natural cooling to room temperature, N2 purging for 30 min to remove residual precursors.

[0093] S11. In-situ purification unit construction: step D1. Au precursor loading: dispersing 5g catalyst in 50mL deionized water, ultrasonic for 15min, adding 0.2g PVP with Mw of 58000, stirring for 30min, adding 50mL 0.01M HAuCl4 solution dropwise, wherein the Au loading in the HAuCl4 solution is 0.1wt%, stirring at room temperature for 1.5h;

[0094] S12. Reduction reaction: under ice bath condition, adding 5mL 0.05M NaBH4 solution dropwise, Au 3+ : NaBH4=1:6, continue stirring for 30min;

[0095] S13. Calcination and shaping: after centrifugal washing, drying at 60℃ for 6h, then in air atmosphere, heating to 320℃ at 5℃ / min, holding for 1.5h, obtaining the methanol synthesis hydrogen production catalyst.

[0096] Example 4: a preparation method of a methanol synthesis hydrogen production catalyst, comprising the following steps:

[0097] S1. Carrier pretreatment: adding 5g γ-Mo2N nanoparticles with particle size of 5-10nm into 10mL anhydrous ethanol, dispersing in an ultrasonic cleaning instrument under a power of 300W for 30min, forming a uniform suspension with solid-liquid ratio of 1:20;

[0098] S2.Ar + Plasma etching: The suspension is transferred to the reaction chamber of the plasma etching instrument, etching parameters are set, and etching is performed using Ar... + The surface of γ-Mo2N was bombarded to form nitrogen vacancies. The etching parameters were: power of 140W, time of 7min, working pressure of 20Pa, carrier gas of 99.99% pure Ar gas, and flow rate of 20mL / min.

[0099] S3. Post-processing: After etching, the suspension was centrifuged at 8000 r / min for 10 min, the supernatant was discarded, and the precipitate was washed 3 times with anhydrous ethanol, with 50 mL of ethanol added each time. After sonication for 5 min, the suspension was centrifuged and dried under vacuum at 60℃ for 6 h to obtain the nitrogen-vacancy modified γ-Mo2N support.

[0100] S4. Active component loading: Carrier dispersion: Add 5g of carrier to 100mL of deionized water and ultrasonically disperse at 300W for 20min to form a carrier suspension;

[0101] S5. Metal ion loading: Add 1 mL of 0.1 M Co(NO3)2 solution and 2 mL of 0.1 M Cu(NO3)2 solution to 100 mL of suspension, stir magnetically for 1 h, the Co loading in the Co(NO3)2 solution is 0.2 wt%, and the Cu loading in the Cu(NO3)2 solution is 0.4 wt%.

[0102] S6. pH adjustment and reduction: Adjust the pH of the mixture to 9 with 0.1M NaOH solution, add ascorbic acid, the molar ratio of ascorbic acid to metal ions is 3:1, transfer to a constant temperature water bath, and stir and react at 80℃ for 3h.

[0103] S7. H2 atmosphere activation: After the reaction, centrifuge at 8000 r / min for 10 min, wash three times with deionized water, dry at 60℃ for 4 h, transfer the dried solid to a tube furnace, and activate it in H2 atmosphere to form stable CoCu alloy single-atom sites, thus obtaining the active component. The activation parameters are as follows: H2 atmosphere flow rate of 50 mL / min, heating rate of 3℃ / min, activation temperature of 300℃, and holding time of 2 h.

[0104] S8. Dynamic repair layer deposition: Substrate pretreatment: Spread the catalyst powder evenly on the ALD tray with a thickness ≤2mm;

[0105] S9. MW-ALD deposition cycle, the number of deposition cycles is 15, the parameters of the deposition cycle are: microwave power is 300 W, temperature is 110 DEG C, N2 flow rate is 80 mL / min, the operation steps of the deposition cycle are as follows: the operation time of Ce(thd)3 pulse is 0.2 s; the operation time of N2 purging is 30 s; the operation time of Zr(thd)4 pulse is 0.2 s; the operation time of O3 oxidation pulse is 0.15 s;

[0106] S10. Post-processing: natural cooling to room temperature, N2 purging for 30 min to remove residual precursors.

[0107] S11. In-situ purification unit construction: step D1. Au precursor loading: 5 g of catalyst is dispersed in 50 mL of deionized water, ultrasonic for 15 min, 0.2 g of PVP with a molecular weight of 58000 is added, stirring for 30 min, 50 mL of 0.01M HAuCl4 solution is added dropwise, wherein the Au loading of the HAuCl4 solution is 0.1wt%, stirring at room temperature for 1.5 h;

[0108] S12. Reduction reaction: under ice bath conditions, 5 mL of 0.05M NaBH4 solution is added dropwise, the Au 3+ : NaBH4 = 1:6, continue stirring for 30 min;

[0109] S13. Calcination and shaping: after centrifugal washing, dry at 60 DEG C for 6 h, then in an air atmosphere, heat to 320 DEG C at a rate of 5 DEG C / min, and keep for 1.5 h, to obtain a methanol synthesis hydrogen production catalyst.

[0110] Comparative example 1: traditional copper-based catalyst (without nitrogen vacancy, without dynamic repair):

[0111] Preparation method:

[0112] 1. Support: γ-Mo2N nanoparticles (not etched, without nitrogen vacancy).

[0113] 2. Active component: CuO / ZnO is loaded by coprecipitation method (Cu loading is 20wt%, Zn loading is 10wt%), and calcination is performed at 500 DEG C for 4 h.

[0114] 3. Without dynamic repair layer and purification unit: the active component is directly loaded on the support, without CeO2-ZrO2 and Au nanoclusters.

[0115] Comparative example 2: high-loading Pt-based catalyst (without synergistic design):

[0116] Preparation method:

[0117] 1. Support: γ-Al2O3 (not etched).

[0118] 2. Active component: 3.0 wt% Pt nanoparticles (particle size 5-8 nm) by impregnation method.

[0119] 3. No dynamic repair layer: No CeO2-ZrO2 deposited.

[0120] 4. No purification unit: No Au nanoclusters loaded.

[0121] Comparative Example 3: Catalyst without dynamic repair layer:

[0122] Preparation method

[0123] 1. Support: Nitrogen vacancy modified γ-Mo2N (same as patent example steps S1-S3).

[0124] 2. Active component: CoCu alloy monatomic (same as patent example steps S4-S7).

[0125] 3. No dynamic repair layer: Skip steps S8-S10, directly load Au nanoclusters.

[0126] 4. Purification unit: Same as patent example steps S11-S13.

[0127] Comparative Example 4: Catalyst without in-situ purification unit:

[0128] Preparation method:

[0129] 1. Support to dynamic repair layer: Same as patent example steps S1-S10.

[0130] 2. No purification unit: Skip steps S11-S13, no Au nanoclusters@CeO2.

[0131] Comparative Example 5: Existing low copper catalyst:

[0132] Preparation method:

[0133] Refer to patent CN115888754A, prepare Cu / ZnO / Al2O3 catalyst with Cu content of 23 wt% (tablet method, no support etching and dynamic repair).

[0134] Performance test:

[0135] Test equipment and sample preparation:

[0136] Reaction device: Fixed bed microreactor (inner diameter 8 mm) equipped with gas chromatograph (GC-2014, Shimadzu), thermal conductivity detector (TCD), flame ionization detector (FID), and infrared gas analyzer (Gasmet DX4000).

[0137] Catalyst loading: 0.5 g catalyst (particle size 40-60 mesh) was mixed with equal mass of quartz sand and loaded into the reactor, with quartz wool fixed at both ends.

[0138] Test conditions:

[0139] Reaction system: methanol steam reforming (MSR), the feed was methanol-water solution (molar ratio of methanol / water 1:1.2).

[0140] Operating parameters: reaction temperature 220℃, pressure 1 atm, mass space velocity (WHSV) 2.0 h-1, carrier gas N2(flow rate 50 mL / min).

[0141] Stability test: continuous operation for 2000 h, sampling and analysis every 24 h.

[0142] Sulfur resistance test: 1.0 ppm H2S was added to the feed, and the change in catalyst activity was monitored within 24 h.

[0143] Cost accounting: based on the cost of Example 1 (set as 1), the relative cost was calculated according to the raw material price and loading.

[0144] 3. Test indicators and methods

[0145] Methanol conversion rate: the methanol content in the feed and product was analyzed by GC-FID, and the conversion rate was calculated (conversion rate = (amount of reacted methanol / initial methanol amount) x 100%).

[0146] Hydrogen yield: the H2 concentration in the product was detected by GC-TCD, and the yield was calculated (unit: mmol·g -1 ·s -1 ).

[0147] CO concentration: the CO volume fraction in the product was directly measured by an infrared gas analyzer.

[0148] Stability: based on the initial activity, the activity retention rate after continuous operation was calculated (retention rate = (conversion rate at time t / initial conversion rate) x 100%).

[0149] The results are shown in Tables 1 and 2 below:

[0150] Table 1 Test results of Examples 1-4 and Comparative Examples 1-5

[0151]

[0152]

[0153] Table 2 Test results of Examples 1-4 and Comparative Examples 1-5

[0154]

[0155]

[0156] Data analysis:

[0157] 1. Performance differences and reasons for Examples 1-4:

[0158] The core parameters (etching power, activation temperature, reduction temperature) of Examples 1-4 are fine-tuned within the preferred range, resulting in slight differences in performance:

[0159] Example 2 (etching power 120W, activation temperature 230℃, reduction temperature 65℃) performs best: methanol conversion rate 98.1%, hydrogen yield 3.1mmol·g -1 ·s -1 , CO concentration 0.38%. The reason is that under this parameter combination, the nitrogen vacancy concentration (8.5at%) and CoCu monatomic dispersion (100%) match best, the CeO2-ZrO2 cover layer density is highest (40%), and the oxygen migration efficiency is improved.

[0160] Example 4 (etching power 140W, activation temperature 300℃) performs slightly lower: excessive etching power causes partial destruction of the carrier structure, and 300℃ activation causes a small amount of CoCu atoms to agglomerate, resulting in decreased activity.

[0161] 2. Comparative analysis of performance between comparative examples and examples:

[0162] (1) Comparative Example 1 (traditional copper-based catalyst)

[0163] Defects: no nitrogen vacancy anchoring, Cu particles prone to sintering (particle size increases from 10nm to 50nm after 500h), CO selectivity as high as 4.2% (due to insufficient oxygen storage capacity of the carrier), sulfur tolerance threshold only 0.3ppm (Cu-S bond irreversible formation).

[0164] Conclusion: Traditional copper-based catalysts cannot balance activity and stability, and require additional purification units, making them unsuitable for fuel cell scenarios.

[0165] (2) Comparative Example 2 (high-loading Pt-based catalyst)

[0166] Defects: Pt loading 3.0wt% (30 times that of the example), cost 50 times higher; Pt particles sinter after 500h (particle size increases from 5nm to 15nm), activity retention rate only 72%; CO concentration 1.2% (high proportion of direct methanol decomposition path at low temperature).

[0167] Conclusion: Precious metal catalysts rely on high loading, with cost and stability imbalance, and performance limitations due to lack of synergistic design.

[0168] (3) Comparative Example 3 (without dynamic repair layer)

[0169] Defects: After the CeO2-ZrO2 layer was missing, sulfur impurities directly combined with CoCu monomers (Co-S bonds were detected by XPS), and the sulfur tolerance threshold decreased to 0.5 ppm; CoCu agglomerated after 1000h (particle size 3-5nm), and the activity retention rate was 85% (96% for Example 2).

[0170] Conclusion: The dynamic repair layer is the core of sulfur poisoning resistance and structural stability, and its Ce 4+ / Ce 3+ redox cycle can "preferentially" capture sulfur to protect active sites.

[0171] (4) Comparative Example 4 (without in-situ purification unit)

[0172] Defects: Without Au nanoclusters@CeO2, the CO concentration increased from 0.38% to 1.2% (an additional PROX reactor was required, increasing equipment costs by 30%); due to the lack of oxygen migration channels, the utilization rate of byproduct O2 decreased by 20%.

[0173] Conclusion: The in-situ purification unit realizes deep purification of CO through the synergy of Au catalytic CO oxidation + CeO2-ZrO2 oxygen migration, simplifying the system structure.

[0174] (5) Comparative Example 5 (existing low-copper catalyst)

[0175] Defects: Cu loading was 23wt% (38 times that of the example), with high cost; without nitrogen vacancy anchoring, the activity retention rate was 88% after 1000h (96% for Example 2); although the CO concentration was 0.25%, high-temperature calcination (500°C) was required, increasing energy consumption.

[0176] Conclusion: The existing low-copper catalyst has not solved the problems of monomer dispersion and dynamic stability, and its comprehensive performance is still inferior to that of the present application.

[0177] 3. Summary of the core advantages of the present application:

[0178] Through the synergistic design of "nitrogen vacancy anchoring CoCu monomers + CeO2-ZrO2 dynamic repair + Au nanocluster purification", the present application realizes:

[0179] Activity: methanol conversion rate increased by 10-25% (relative to traditional catalysts), and hydrogen production rate reached 3.1 mmol·g -1 ·s -1 ;

[0180] Stability: 2000h activity retention rate exceeded 95% (traditional catalysts only 65-72% for 500h);

[0181] Product purity: CO concentration is reduced to below 0.4%, without additional purification;

[0182] Economy: the cost is only 1 / 50 of the noble metal catalyst, and the sulfur resistance is increased by 2-3 times.

[0183] The synergistic mechanism breaks through the existing catalyst "activity-stability-cost" triangular restriction, and provides a feasible scheme for commercialization of methanol hydrogen production.

[0184] Those skilled in the art should understand that the above discussion of any embodiment is only exemplary, and is not intended to imply that the scope of the present application is limited to these examples; under the idea of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above. In order to be brief, they are not provided in details.

[0185] The present application is intended to cover all such alternatives, modifications, and variations as fall within the broad scope of the appended claims. Accordingly, any and all such modifications, variations, omissions, and equivalents are intended to fall within the scope of the present application.

Claims

1. A method for preparing a catalyst for methanol-to-hydrogen synthesis, characterized in that, Includes the following steps: Step S1. Support pretreatment: γ-Mo2N nanoparticles with a particle size of 5-10 nm are subjected to Ar... + Etching creates a substrate; Step S2. Loading of active components: CoCu alloy single atoms are loaded using the defect anchoring method, with Co loading at 0.2 wt% and Cu loading at 0.4 wt%, and single-atom dispersion is formed by H2 reduction; Step S3. Dynamic repair layer deposition: A CeO2-ZrO2 solid solution with a thickness of 1.5 nm was deposited using microwave-assisted (MW-ALd) technology at a microwave power of 300 W and a temperature of 110 °C, with 15 deposition cycles. Step S4. In-situ purification unit construction: Au nanoclusters@CeO2 are loaded with an Au loading of 0.1 wt% and a particle size of 2-3 nm. They are shaped by reduction with NaBH4 and calcination at 320 °C.

2. The method for preparing the methanol-to-hydrogen catalyst according to claim 1, characterized in that, The carrier pretreatment process is as follows: Step A1. Dispersion treatment: Take γ-Mo2N nanoparticles, add anhydrous ethanol, and disperse them in an ultrasonic cleaner at a power of 300W for 30 minutes to form a uniform suspension. Step A2.Ar + Plasma etching: The suspension is transferred to the reaction chamber of the plasma etching instrument, etching parameters are set, and etching is performed using Ar... + Bombarding the γ-Mo2N surface creates nitrogen vacancies; Step A3. Post-processing: After etching, the suspension is centrifuged, the supernatant is discarded, the precipitate is washed three times with anhydrous ethanol, and then vacuum dried at 60°C for 6 hours to obtain the nitrogen-vacancy-modified γ-Mo2N support.

3. The method for preparing the methanol-to-hydrogen catalyst according to claim 2, characterized in that, In step A1, the ratio of γ-Mo2N nanoparticles to anhydrous ethanol is 5g:100mL, and the solid-liquid ratio of the uniform suspension is 1:

20. The etching parameters described in step A2 are as follows: The power is 100-140W, the time is 3-7min, the working gas pressure is 10-20Pa, the carrier gas is Ar gas with a purity of 99.99%, and the flow rate is 20mL / min; The centrifugation speed in step A3 is 8000 r / min, and the centrifugation time is 10 min; In step A3, 50 mL of ethanol is added each time during washing, followed by sonication for 5 min and centrifugation.

4. The method for preparing the methanol-to-hydrogen catalyst according to claim 1, characterized in that, The process of loading the active component is as follows: Step B1. Carrier dispersion: Add the carrier to deionized water and ultrasonically disperse it for 20 minutes at a power of 300W to form a carrier suspension; Step B2. Metal ion loading: Add 0.1M Co(NO3)2 solution and 0.1M Cu(NO3)2 solution dropwise to the suspension and stir magnetically for 1 hour; Step B3. pH adjustment and reduction: Adjust the pH of the mixture to 8-9 with 0.1M NaOH solution, add reducing agent, transfer to a constant temperature water bath, and stir and react at 60-80℃ for 3 hours; Step B4. H2 atmosphere activation: After the reaction, centrifuge, wash three times with deionized water, dry at 60℃ for 4 hours, transfer the dried solid to a tube furnace, and activate it in an H2 atmosphere to form stable CoCu alloy single-atom sites, thus obtaining the active component.

5. The method for preparing the methanol-to-hydrogen catalyst according to claim 4, characterized in that, The ratio of carrier to deionized water in step B1 is 5g:100mL; The volume ratio of the suspension, Co(NO3)2 solution, and Cu(NO3)2 solution in step B2 is 100 mL: 1 mL: 2 mL; In step B2, the Co(NO3)2 solution has a Co loading of 0.2 wt%, and the Cu(NO3)2 solution has a Cu loading of 0.4 wt%. The reducing agent mentioned in step B3 is ascorbic acid, and the molar ratio of ascorbic acid to metal ions in step B3 is 3:1; The centrifugation speed in step B4 is 8000 r / min, the centrifugation time is 10 min, and the activation parameters are as follows: The flow rate of H2 atmosphere is 50 mL / min, the heating rate is 2-3℃ / min, the activation temperature is 200-300℃, and the holding time is 2h.

6. The method for preparing the methanol-to-hydrogen catalyst according to claim 1, characterized in that, The process of depositing the dynamic repair layer is as follows: Step C1. Substrate pretreatment: Spread the catalyst powder evenly on the ALD tray with a thickness ≤2mm; Step C2. MW-ALD deposition cycle; Step C3. Post-treatment: Allow to cool naturally to room temperature, then purge with N2 for 30 minutes to remove residual precursors.

7. The method for preparing the methanol-to-hydrogen catalyst according to claim 6, characterized in that, The deposition cycle in step C2 is repeated 15 times. The parameters of the deposition cycle are: microwave power of 300W, temperature of 110℃, and N2 flow rate of 80mL / min. The operation steps of the deposition cycle described in step C2 are as follows: The operation time of the C201.Ce(thd)3 pulse is 0.2s; The C202.N2 purging operation time is 30 seconds; The operation time of the C203.Zr(thd)4 pulse is 0.2s; The operation time of the C2O4.O3 oxidation pulse in step 0.15s.

8. The method for preparing the methanol-to-hydrogen catalyst according to claim 1, characterized in that, The construction process of the in-situ purification unit is as follows: Step D1. Au precursor loading: Disperse the catalyst in deionized water, sonicate for 15 min, add PVP, stir for 30 min, add 0.01 M HAuCl4 solution dropwise, and stir at room temperature for 1.5 h; Step D2. Reduction reaction: Under ice bath conditions, add 0.05M NaBH4 solution dropwise and continue stirring for 30 min; Step D3. Calcination and shaping: After centrifugation and washing, dry at 60℃ for 6 hours, then heat to 320℃ in air at 5℃ / min and hold for 1.5 hours.

9. The method for preparing the methanol-to-hydrogen catalyst according to claim 8, characterized in that, The ratio of catalyst, deionized water, PVP, 0.01M HAuCl4 solution, and 0.05M NaBH4 solution is 5g:50mL:0.2g:50mL:5mL. The system contains Au... 3+ :NaBH4=1:6; The molecular weight (Mw) of the PVP mentioned in step D1 is 58,000, and the Au loading in the HAuCl4 solution mentioned in step D1 is 0.1 wt%.

10. A catalyst for methanol-to-hydrogen synthesis, characterized in that, The methanol-to-hydrogen catalyst is prepared by the preparation method according to any one of claims 1-9.

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