A graphene-based desulfurization catalyst and a preparation method thereof

Abstract

The present application relates to the technical field of catalyst, in particular to a kind of desulfurization catalyst based on graphene and preparation method thereof.The present application uses graphene oxide as carrier, first introduces initiation group, builds short brush and long brush amphoteric polymer gradient modification layer in turn by atom transfer radical polymerization, fuses ammonium molybdate-urea complex deposition, realizes the uniform nucleation of metal precursor.Preparation process uses two-stage vulcanization, controls the crystallization process of precursor at different temperatures, optimizes the size and dispersity of molybdenum disulfide sheet.The conversion rate of the catalyst is high in hydrogenation desulfurization model system, the total sulfur of discharge is low, and the activity retention rate is excellent after multiple cycles.The present application can be widely applied in the field of fuel oil deep desulfurization, realizes the efficient, environmental protection industrial catalysis demand.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a graphene-based desulfurization catalyst and its preparation method. Background Technology

[0002] With increasingly stringent environmental regulations and continuously lowering standards for sulfur content in fuel oil, hydrodesulfurization technology faces greater technical challenges. Traditional desulfurization catalysts are mainly based on cobalt-molybdenum or nickel-molybdenum sulfide systems supported on alumina. Under high-temperature and high-pressure hydrogenation conditions, these catalysts suffer from problems such as active phase sintering and loss of active sites, leading to shortened catalyst lifespan, increased regeneration frequency, and higher operating costs.

[0003] Molybdenum disulfide (MoD) is the main active phase in hydrodesulfurization catalysts, and its catalytic activity primarily originates from its edge active sites. However, under actual reaction conditions, MoD particles are prone to sintering and agglomeration, reducing the number of active edge sites and leading to a decrease in catalytic activity. Traditional preparation methods typically involve impregnation to load the metal precursor onto a support, followed by sulfidation. This method suffers from problems such as uneven distribution of the metal precursor and particle growth during sulfidation, making it difficult to obtain a highly dispersed, small-sized active phase.

[0004] The support material has a significant impact on catalyst performance. While alumina supports have a large specific surface area, their strong surface acidity easily leads to carbon deposition and coking, affecting catalyst stability. Graphene, as an emerging carbon-based support material, possesses excellent thermal and electrical conductivity and a unique two-dimensional layered structure. Its surface oxygen-containing functional groups can provide anchoring sites for metal precursors, which is beneficial for the uniform dispersion of the active phase. However, the interaction mechanism between the graphene support and the active phase is still unclear, and how to control the morphology and dispersion state of the active phase through interface engineering remains a technical challenge.

[0005] In traditional catalyst preparation processes, the sulfidation process is typically a one-step process, involving prolonged treatment at a fixed temperature. This method makes it difficult to precisely control the kinetics of the sulfidation reaction, easily leading to problems such as excessive growth of the active phase and poor crystallinity. Although stepwise sulfidation processes have been reported, there is a lack of optimization studies for different supports and modification systems, and the selection of process parameters often relies on experience without scientific basis.

[0006] Furthermore, existing desulfurization catalysts suffer from severe activity decay and low regeneration efficiency during recycling. The main causes of catalyst deactivation include active phase sintering, carbon poisoning, and support structure damage. Although air roasting-resulfurization is a commonly used regeneration method, the catalyst activity recovery rate gradually decreases after multiple regenerations, severely impacting the economic viability of industrial applications. Improving the cyclic stability of catalysts through catalyst structure design and preparation process optimization is a significant challenge currently facing the development of desulfurization technology.

[0007] Therefore, there is an urgent need to develop a new desulfurization catalyst preparation technology that, through the synergistic effect of carrier selection, interface modification, and process optimization, can achieve high dispersion loading of the active phase and long-term stable operation, thereby meeting the requirements for deep desulfurization under strict environmental protection standards. Summary of the Invention

[0008] In view of this, the purpose of this invention is to propose a graphene-based desulfurization catalyst and its preparation method, so as to solve the problems of easy sintering and deactivation of existing desulfurization catalysts such as molybdenum disulfide and difficulty in recycling and regeneration.

[0009] To achieve the above objectives, this invention provides a method for preparing a graphene-based desulfurization catalyst, comprising the following steps:

[0010] (1) Introduction of initiating groups: Initiating groups are introduced on the surface of graphene oxide by dibromoisobutyryl bromide and triethylamine to obtain graphene oxide with initiating groups.

[0011] (2) Short brush polymerization: using sulfobetaine methacrylate as monomer, cuprous bromide and N,N,N′,N″,N″-pentamethyldiethylenetriamine as catalyst, surface-initiated atom transfer radical polymerization was carried out on graphene oxide with initiating groups. The reaction was carried out at room temperature for 0.25-0.5 h to obtain graphene oxide modified with short brush amphoteric polymer.

[0012] (3) Complex deposition: Graphene oxide modified with short brush amphoteric polymer is dispersed in the aqueous phase, ammonium molybdate and urea are added, and complex deposition is carried out by stirring at 95°C for 5-7 h to obtain the precursor;

[0013] (4) First sulfidation: The precursor is sulfided in an atmosphere of 10% hydrogen sulfide / 90% hydrogen by volume to obtain molybdenum disulfide supported powder.

[0014] (5) Surface treatment and secondary initiation: After mild surface treatment of the molybdenum disulfide loaded powder with dilute sodium hydroxide methanol solution, initiation groups were introduced again with dibromoisobutyryl bromide and triethylamine to obtain molybdenum disulfide loaded powder with initiation groups.

[0015] (6) Long brush polymerization: using sulfobetaine methacrylate as monomer, cuprous bromide and N,N,N′,N″,N″-pentamethyldiethylenetriamine as catalyst, surface-initiated atom transfer radical polymerization was carried out on molybdenum disulfide supported powder with initiating groups. The reaction was carried out at room temperature for 1.5-2.5 h to obtain amphoteric polymer gradient modified powder with both short and long brushes.

[0016] (7) Second sulfidation: The amphoteric polymer gradient modified powder with both short and long brushes is sulfided in an atmosphere of 10% hydrogen sulfide / 90% hydrogen by volume to obtain a graphene-based desulfurization catalyst.

[0017] Preferably, in step (1), the mass ratio of 2-bromoisobutyryl bromide, triethylamine cuprous bromide, N,N,N′,N″,N″-pentamethyldiethylenetriamine and graphene oxide is 5-10:8-12:1.8-2.2.

[0018] Preferably, the average diameter of the graphene oxide in step (1) is 3-5 μm and the average thickness is 3-5 nm.

[0019] Preferably, in step (2), the mass ratio of sulfobetaine methacrylate, cuprous bromide, N,N,N′,N″,N″-pentamethyldiethylenetriamine and graphene oxide with initiating groups is 15-25:0.8-1.2:1.5-2.5:0.9-1.1.

[0020] Preferably, in step (3), the mass ratio of the short-brush amphoteric polymer-modified graphene oxide, aqueous phase, ammonium molybdate, and urea is 0.9-1.1:200:1.6-2.4:8-12.

[0021] Preferably, in step (4), the vulcanization is carried out by heating at 20°C / min to 320°C and holding at that temperature for 60-75 min.

[0022] Preferably, in step (5), the mass ratio of molybdenum disulfide supported powder, dilute sodium hydroxide methanol solution, dibromoisobutyryl bromide and triethylamine is 2.7-3.3:40-60:5-8:8-12.

[0023] Preferably, the concentration of the dilute sodium hydroxide methanol solution in step (5) is 0.008-0.012M.

[0024] Preferably, in step (6), the mass ratio of sulfobetaine methacrylate, cuprous bromide, N,N,N′,N″,N″-pentamethyldiethylenetriamine and molybdenum disulfide loaded powder with initiating groups is 24-36:0.8-1.2:5-8:2.7-3.3.

[0025] Preferably, in step (7), the vulcanization is carried out by heating at 20°C / min to 340°C and holding at that temperature for 25-40 min.

[0026] Furthermore, the present invention also provides a graphene-based desulfurization catalyst, which is obtained by the above-described method for preparing a graphene-based desulfurization catalyst.

[0027] This invention utilizes a unique short-brush and long-brush amphoteric polymer gradient modification technology, combined with a graphene support and a two-stage sulfidation process, to achieve a significant improvement in the performance of desulfurization catalysts, resulting in the following beneficial effects:

[0028] Interfacial confinement enhances the dispersion of the active phase: The short-brush amphoteric polymer layer provides a high-density near-interfacial ion hydration environment and spatial confinement during the precursor complex deposition stage, effectively suppressing the rapid migration and spontaneous aggregation tendency of the molybdenum precursor on the support surface. The long-brush polymer layer forms a thicker solvation barrier and a flexible mechanical binding network during sulfidation and reaction, significantly reducing the probability of lateral flaking of molybdenum disulfide sheets and the driving force for interlayer aggregation, thereby maintaining the highly dispersed state and fine size characteristics of the active phase.

[0029] Gradient modification optimizes the mass transfer environment: The gradient polymer modification layer with both short and long brushes constructs a unique microenvironment gradient on the catalyst surface. The near-surface short brush layer provides dense interfacial anchoring and initial confinement, while the outer long brush layer provides extended solvation space and dynamic regulation capability. This gradient structure facilitates the orderly transport of reactant molecules and product desorption, while the electrostatic sieving effect of the amphoteric groups inhibits the persistent retention of non-reactive heavy aromatic components near the active sites.

[0030] Uniform nucleation is achieved through complex-based slow-release deposition: An ammonium molybdate-urea complex system is used instead of direct impregnation to achieve slow release and uniform deposition of the metal precursor by controlling temperature and time. The complexing effect of urea reduces the instantaneous supersaturation of free molybdenum ions in the solution, effectively inhibiting the rapid formation of coarse crystal nuclei and promoting uniform nucleation and miniaturization of the precursor at oxygen-containing functional group sites on the graphene support.

[0031] A two-stage sulfidation process optimizes the crystal structure: Pre-sulfidation is performed at a lower temperature to promote mild transformation of the precursor and initial nucleation, followed by short-term crystallization at a slightly higher temperature to achieve a balance between low-layer molybdenum disulfide lamellars and moderate crystallinity. This stepwise sulfidation strategy avoids over-crystallization and lateral growth problems caused by long-term high-temperature processing, and helps maintain high density and accessible active edge sites.

[0032] Synergistic effect of graphene support: The layered structure and abundant oxygen-containing functional groups of graphene provide dense anchoring sites for metal precursors. Its excellent in-plane thermal and electrical conductivity effectively dissipates reaction hotspots and charge accumulation. Combined with the confined solvation effect of polymer brush layers, it synergistically maintains the structural stability of the molybdenum disulfide active phase during sulfidation and long-term operation.

[0033] Significantly improved regeneration performance: The stable confined structure constructed through interface engineering design enables the catalyst to maintain a high activity recovery rate during multiple air calcination-resulfurization cycles. The antifouling properties and flexible adjustment capabilities of the amphoteric polymer brush layer effectively mitigate structural damage and irreversible loss of active sites during regeneration, significantly extending the catalyst's lifespan. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0035] Figure 1 The nitrogen adsorption-desorption curve of the graphene-based desulfurization catalyst provided in Example 2 of the present invention is shown.

[0036] Figure 2 The X-ray photoelectron spectroscopy spectrum of the graphene-based desulfurization catalyst provided in Example 2 of this invention is shown. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0038] In a specific embodiment of the present invention, the average sheet diameter of the graphene oxide is 4.2 μm and the average thickness is 4.5 nm.

[0039] Example 1:

[0040] (1) 1.8 g of graphene oxide was dispersed in 200 mL of anhydrous dimethylformamide. After ultrasonic dispersion, 8 g of triethylamine and 5 g of 2-bromoisobutyryl bromide were slowly added dropwise in an ice bath. After stirring for 45 min, the mixture was moved to room temperature and stirred for 10 h. The mixture was washed alternately with anhydrous diethyl ether and methanol and dried under vacuum at 40 °C for 12 h to obtain graphene oxide with initiating groups.

[0041] (2) 0.9 g of graphene oxide with initiating groups was added to a solvent mixture consisting of 125 mL methanol and 125 mL deionized water. After nitrogen removal, 15 g of sulfobetaine methacrylate monomer, 0.8 g of cuprous bromide and 1.5 g of N,N,N′,N″,N″-pentamethyldiethylenetriamine were added. The mixture was stirred at room temperature for 15 min. After the reaction was terminated, the mixture was thoroughly washed with deionized water and methanol and dried under vacuum at 40 °C for 12 h to obtain graphene oxide modified with short-brush amphoteric polymer.

[0042] (3) 0.9g of graphene oxide modified with short brush amphoteric polymer was dispersed in 200mL of deionized water, 1.6g of ammonium molybdate tetrahydrate and 8g of urea were added, and the mixture was stirred at 95℃ for 5h. After the mixture was stirred, it was filtered, washed and dried under vacuum at 80℃ for 8h to obtain a precursor containing ammonium molybdate and urea complexed and deposited.

[0043] (4) Place 2.7g of the precursor containing ammonium molybdate and urea complexed and deposited in a tubular furnace quartz boat, introduce a mixed gas of 10% hydrogen sulfide and 90% hydrogen by volume at a flow rate of 100mL / min, and heat it to 320℃ at 20℃ / min, hold it at that temperature for 45min, and then cool it to room temperature under nitrogen protection to obtain molybdenum disulfide loaded powder.

[0044] (5) 1.8 g of molybdenum disulfide loaded powder was treated with 50 mL of 0.008 M sodium hydroxide methanol solution at room temperature for 8 min, then neutralized and washed with water, dried under vacuum at 80 °C for 8 h, and then dispersed in 200 mL of anhydrous dimethylformamide. 8 g of triethylamine and 5 g of 2-bromoisobutyryl bromide were added under ice bath conditions. The mixture was stirred for 45 min and then moved to room temperature and stirred for another 10 h. After the reaction was completed, the powder was washed with anhydrous diethyl ether and methanol and dried under vacuum at 40 °C for 12 h to obtain molybdenum disulfide loaded powder with initiating groups.

[0045] (6) 0.9 g of molybdenum disulfide loaded powder with initiating groups was added to a solvent consisting of 150 mL methanol and 150 mL deionized water. After nitrogen deoxygenation, 24 g of sulfobetaine methacrylate monomer, 0.8 g of cuprous bromide and 2.5 g of N,N,N′,N″,N″-pentamethyldiethylenetriamine were added. The mixture was stirred at room temperature for 90 min. After the reaction was terminated, the mixture was washed with deionized water and methanol and dried under vacuum at 40 °C for 12 h to obtain an amphoteric polymer gradient modified powder with both short and long brushes.

[0046] (7) Place 1.8g of amphoteric polymer gradient modified powder with both short and long brushes in a tube furnace, introduce a mixed gas of 10% hydrogen sulfide and 90% hydrogen by volume at a flow rate of 100mL / min, heat to 340℃ at 20℃ / min, hold for 25min, and cool to room temperature in nitrogen to obtain a graphene-based desulfurization catalyst.

[0047] Example 2:

[0048] (1) 2g of graphene oxide was dispersed in 200mL of anhydrous dimethylformamide. After ultrasonic dispersion, 10g of triethylamine and 8g of 2-bromoisobutyryl bromide were slowly added dropwise in an ice bath. After stirring for 60min, the mixture was moved to room temperature and stirred for 12h. The mixture was washed alternately with anhydrous diethyl ether and methanol and dried under vacuum at 40℃ for 12h to obtain graphene oxide with initiating groups.

[0049] (2) 1g of graphene oxide with initiating groups was added to a solvent mixture consisting of 125mL methanol and 125mL deionized water. After nitrogen was introduced to remove oxygen, 20g of sulfobetaine methacrylate monomer, 1g of cuprous bromide and 2g of N,N,N′,N″,N″-pentamethyldiethylenetriamine were added. The mixture was stirred at room temperature for 20min. After the reaction was terminated, the mixture was thoroughly washed with deionized water and methanol and dried under vacuum at 40℃ for 12h to obtain graphene oxide modified with short-brush amphoteric polymer.

[0050] (3) 1g of graphene oxide modified by short brush amphoteric polymer was dispersed in 200mL of deionized water, 2g of ammonium molybdate tetrahydrate and 10g of urea were added, and the mixture was stirred at 95℃ for 6h. After the mixture was stirred, it was filtered, washed and dried under vacuum at 80℃ for 8h to obtain a precursor containing ammonium molybdate and urea complexed and deposited.

[0051] (4) Place 3g of the precursor containing ammonium molybdate and urea complexed and deposited in a tubular furnace quartz boat, introduce a mixed gas of 10% hydrogen sulfide and 90% hydrogen by volume at a flow rate of 100mL / min, and heat it to 320℃ at 20℃ / min, keep it at that temperature for 60min, and then cool it to room temperature under nitrogen protection to obtain molybdenum disulfide loaded powder.

[0052] (5) 2g of molybdenum disulfide-supported powder was treated with 50mL of 0.01M sodium hydroxide methanol solution at room temperature for 10min, then neutralized and washed with water, dried under vacuum at 80℃ for 8h, and then dispersed in 200mL of anhydrous dimethylformamide. 10g of triethylamine and 6g of 2-bromoisobutyryl bromide were added under ice bath conditions. The mixture was stirred for 60min and then moved to room temperature and stirred for 12h. After the reaction was completed, the powder was washed with anhydrous diethyl ether and methanol and dried under vacuum at 40℃ for 12h to obtain molybdenum disulfide-supported powder with initiating groups.

[0053] (6) 1g of molybdenum disulfide loaded powder with initiating group was added to a solvent consisting of 150mL methanol and 150mL deionized water. After nitrogen deoxygenation, 30g of sulfobetaine methacrylate monomer, 1g of cuprous bromide and 3g of N,N,N′,N″,N″-pentamethyldiethylenetriamine were added. The mixture was stirred at room temperature for 120min. After the reaction was terminated, the mixture was washed with deionized water and methanol and dried under vacuum at 40℃ for 12h to obtain an amphoteric polymer gradient modified powder with both short and long brushes.

[0054] (7) Place 2g of amphoteric polymer gradient modified powder with both short and long brushes in a tube furnace, introduce a mixed gas of 10% hydrogen sulfide and 90% hydrogen by volume at a flow rate of 100mL / min, heat to 340℃ at 20℃ / min, hold for 30min, and cool to room temperature in nitrogen to obtain a graphene-based desulfurization catalyst.

[0055] Example 3:

[0056] (1) 2.2 g of graphene oxide was dispersed in 200 mL of anhydrous dimethylformamide. After ultrasonic dispersion, 12 g of triethylamine and 10 g of 2-bromoisobutyryl bromide were slowly added dropwise in an ice bath. After stirring for 90 min, the mixture was moved to room temperature and stirred for 16 h. The mixture was washed alternately with anhydrous diethyl ether and methanol and dried under vacuum at 40 °C for 12 h to obtain graphene oxide with initiating groups.

[0057] (2) 1.1 g of graphene oxide with initiating groups was added to a solvent mixture consisting of 125 mL methanol and 125 mL deionized water. After nitrogen removal, 25 g of sulfobetaine methacrylate monomer, 1.2 g of cuprous bromide and 2.5 g of N,N,N′,N″,N″-pentamethyldiethylenetriamine were added. The mixture was stirred at room temperature for 30 min. After the reaction was terminated, the mixture was thoroughly washed with deionized water and methanol and dried under vacuum at 40 °C for 12 h to obtain graphene oxide modified with short-brush amphoteric polymer.

[0058] (3) 1.1g of graphene oxide modified with short brush amphoteric polymer was dispersed in 200mL of deionized water, 2.4g of ammonium molybdate tetrahydrate and 12g of urea were added, and the mixture was stirred at 95℃ for 7h. After the mixture was stirred, it was filtered, washed and dried under vacuum at 80℃ for 8h to obtain a precursor containing ammonium molybdate and urea complexed and deposited.

[0059] (4) Place 3.3g of the precursor containing ammonium molybdate and urea complexed and deposited in a tubular furnace quartz boat, introduce a mixed gas of 10% hydrogen sulfide and 90% hydrogen by volume at a flow rate of 100mL / min, and heat it to 320℃ at 20℃ / min, hold it at that temperature for 75min, and then cool it to room temperature under nitrogen protection to obtain molybdenum disulfide loaded powder.

[0060] (5) 2.2 g of molybdenum disulfide-supported powder was treated with 60 mL of 0.012 M sodium hydroxide methanol solution at room temperature for 12 min, then neutralized and washed with water, dried under vacuum at 80 °C for 8 h, and then dispersed in 200 mL of anhydrous dimethylformamide. 12 g of triethylamine and 8 g of 2-bromoisobutyryl bromide were added under ice bath conditions, and the mixture was stirred for 90 min. After stirring at room temperature for 16 h, the mixture was washed with anhydrous diethyl ether and methanol and dried under vacuum at 40 °C for 12 h to obtain molybdenum disulfide-supported powder with initiating groups.

[0061] (6) 1.1 g of molybdenum disulfide loaded powder with initiating group was added to a solvent consisting of 150 mL methanol and 150 mL deionized water. After nitrogen deoxygenation, 36 g sulfobetaine methacrylate monomer, 1.2 g cuprous bromide and 3.5 g N,N,N′,N″,N″-pentamethyldiethylenetriamine were added. The mixture was stirred at room temperature for 150 min. After the reaction was terminated, the mixture was washed with deionized water and methanol and dried under vacuum at 40 °C for 12 h to obtain an amphoteric polymer gradient modified powder with both short and long brushes.

[0062] (7) 2.2g of amphoteric polymer gradient modified powder with short and long brushes coexisting was placed in a tube furnace, and a mixed gas of 10% hydrogen sulfide and 90% hydrogen was introduced at a flow rate of 100mL / min and heated to 340℃ at 20℃ / min. The temperature was held for 40min and then cooled to room temperature in nitrogen to obtain a graphene-based desulfurization catalyst.

[0063] Comparative Example 1:

[0064] The difference between Comparative Example 1 and Example 2 is that the second surface initiation and polymerization were cancelled, the long brush layer was not constructed, and only the first amphoteric polymer short brush was retained. The other conditions were the same as in Example 2.

[0065] Comparative Example 2:

[0066] The difference between Comparative Example 2 and Example 2 is that sulfobetaine methacrylate was replaced with methyl methacrylate monomer, and the resulting brush layer was a neutral polymer brush layer. All other conditions were the same as in Example 2.

[0067] Comparative Example 3:

[0068] The difference between Comparative Example 3 and Example 2 is that urea was omitted, and the metal precursor was directly deposited using an aqueous solution of ammonium molybdate. All other conditions were the same as in Example 2.

[0069] Comparative Example 4:

[0070] The difference between Comparative Example 4 and Example 2 is that the graphene oxide carrier was replaced with alumina powder, while the other conditions were the same as in Example 2.

[0071] Comparative Example 5:

[0072] The difference between Comparative Example 5 and Example 2 is that the vulcanization temperature in step (4) is 340°C and the time is 30 min, while the vulcanization temperature in step (7) is 320°C and the time is 60 min.

[0073] Performance testing:

[0074] Model oil hydrodesulfurization activity test: A 316L stainless steel fixed-bed tubular reactor with an inner diameter of 9.0 mm and an effective length of 400 mm was used. α-Al2O3 (50 mesh) and catalyst were uniformly wet-mixed at a volume ratio of 1:2, dried, and then loaded. The feed was dibenzothiophene-n-hexadecane model oil (sulfur content 800 mg / kg), the temperature was 340℃, the hydrogenation pressure was 3 MPa, and the mass hourly space velocity was 1 h⁻¹. -1 The hydrogen-to-oil volume ratio was 500. The total sulfur in the discharge was determined by ultraviolet fluorescence method, and the conversion rate was calculated. The results are shown in Table 1.

[0075] Accelerated aging and regeneration: Aging conditions: 10% hydrogen sulfide / 90% hydrogen, 340℃, 24h; Regeneration process: calcination in air at 350℃ for 2h, followed by sulfidation at 340℃ with 10% hydrogen sulfide / 90% hydrogen for 0.5h; cycled 5 times, and the hydrodesulfurization activity test of the model oil was repeated after each regeneration. The activity retention rate was calculated based on the conversion rate after regeneration and the initial conversion rate.

[0076] BET specific surface area test: Following the gas adsorption BET method, the nitrogen adsorption-desorption curve is shown below. Figure 1 As shown in Table 1, the specific surface area is as follows.

[0077] X-ray photoelectron spectroscopy (XPS) detection: The peak positions of Mo3d and S2p were detected by XPS, and the results are as follows: Figure 2 As shown.

[0078] Table 1 Performance Test Results

[0079]

[0080] Data Analysis:

[0081] As can be seen from the data in Examples 1-3 in Table 1, the graphene-based desulfurization catalyst prepared by this invention achieves high sulfide conversion, low total sulfur content in the output, and maintains high activity even after multiple regenerations. It is speculated that the combination of the short / long brush amphoteric polymer gradient and the two-stage sulfidation provides a synergistic interface effect. Specifically, the short brush layer forms dense near-interface hydration and spatial confinement during the complexation deposition stage, reducing the probability of precursor migration and spontaneous aggregation. The subsequent long brush layer forms a considerable solvation barrier and flexible mechanical restraint during sulfidation and the reaction process, suppressing the lateral merging and interlayer aggregation kinetics of the generated molybdenum disulfide sheets. Simultaneously, the stepwise release of the metal source using urea-containing complexation-slow-release deposition, combined with the anchoring of oxygen-containing functional groups on the graphene oxide support, promotes uniform nucleation and miniaturization of the precursor on the support surface. The two-stage sulfidation achieves a balance between low layer number and moderate crystallinity through low-temperature nucleation / high-temperature short-time crystallization, thereby maintaining a high density of accessible active sites.

[0082] As can be seen from the data in Table 1 for Example 2 and Comparative Example 1, their specific surface areas are similar, but Example 2 performs better in terms of initial conversion, total sulfur output, and cycle retention, with a more gradual decline. It is speculated that the long brush layer provides additional spatial confinement and solvation layers during the sulfidation and operation stages, reducing the probability of lateral lamination of the molybdenum disulfide crystal layer, and mitigating sintering behavior under hydrogen and high-temperature conditions through flexible confinement. Furthermore, the amphoteric groups of the long brush layer form a stable ion hydration shell, which helps suppress the persistent adsorption of non-reactive heavy aromatics near the catalytic site, thereby reducing the apparent activity loss due to surface covering.

[0083] As can be seen from the data in Table 1 for Example 2 and Comparative Example 2, although the specific surface area of ​​Comparative Example 2 is slightly higher, its total sulfur content in the output is significantly higher, and its conversion rate and activity retention rate after multiple regenerations are lower than those of Example 2. This indicates that the chemical properties of the brush layer, rather than the external specific surface area, play a decisive role in performance. Comparative Example 2 uses a neutral polymer, which lacks the ion hydration and electrostatic sieving effects brought about by amphoteric groups. This may lead to insufficient interfacial wettability, a poor microenvironment for the transfer of reactants and hydrogen at the solid-liquid-gas three-phase interface, and is also not conducive to suppressing the retention of heavy components near the active sites.

[0084] As can be seen from the data in Table 1 for Example 2 and Comparative Example 3, Comparative Example 3, by omitting urea and directly depositing only with an aqueous metal source solution, exhibits a significantly lower specific surface area, increased residual sulfur, and a synchronous weakening of conversion and recycling. This indicates that the precursor formation behavior during the deposition stage has a crucial impact on the final catalytic structure. Example 2, employing a metal source-urea complex deposition, is more conducive to uniform nucleation near the oxygen-containing functional groups of the support, resulting in precursors with smaller particle sizes and narrower distributions. The subsequent two-stage sulfidation completes short-term crystallization and defect regulation based on this fine precursor, enabling the active sites to possess high density and good accessibility from the outset.

[0085] As can be seen from the data in Table 1 for Example 2 and Comparative Example 4, although Comparative Example 4 used alumina as the carrier, it exhibited higher total sulfur output, lower conversion, and faster decay, despite having a higher specific surface area. It is speculated that the layered structure and abundant oxygen-containing functional groups of the graphene oxide in Example 2 provide dense anchoring points for the metal precursor, and reduce local hot spots and charge accumulation through in-plane thermal and electrical conductivity. Combined with the confinement and solvation effects of the amphoteric brush layer, this allows molybdenum disulfide to remain fine and uniformly dispersed during sulfidation and operation. While alumina provides a high specific surface area, its surface acid-base and functional group characteristics have limited synergistic effects with the amphoteric brush layer and metal precursor, potentially leading to non-uniform nucleation and an enhanced tendency for subsequent lamellar aggregation.

[0086] As can be seen from the data in Table 1 for Example 2 and Comparative Example 5, Comparative Example 5 reversed the temperature sequence of the two-stage vulcanization, initially using a high temperature followed by a low temperature, resulting in a significant deterioration in the initial conversion and residual sulfur. Although there was a brief rebound after one regeneration during the cycle, the overall retention rate was still lower than that of Example 2. It is speculated that if a higher temperature is applied in the early stage, the precursor is more likely to crystallize rapidly and undergo lateral growth, making it difficult to reverse the already formed large crystal domains in the subsequent lower temperature stage. At the same time, premature high-temperature treatment may weaken the integrity and confinement effect of the brush layer, increasing the tendency for sintering and lamination during the operation stage.

[0087] from Figure 1 It can be seen that the nitrogen adsorption-desorption isotherms of the sample exhibit typical Type IV characteristics, and a distinct H3-type hysteresis loop appears in the medium-high relative pressure region: the capillary condensation step of the adsorption branch appears at P / P0 of 0.55-0.65, and the desorption branch closes near P / P0 of 0.40-0.50, indicating that the slit-like mesopores formed by the stacking of lamellar plates are dominant; the BET linearity is good in the P / P0 range of 0.05-0.30.

[0088] from Figure 2 It can be seen that in the XPS high-resolution spectrum, the Mo3d region is dominated by Mo 4+ Mainly 3D 5 / 2 With 3D 3 / 2 The peaks are located at approximately 229.5 eV and 232.7 eV, respectively, with a spin-orbit splitting of approximately 3.2 eV; simultaneously, weak Mo peaks are observed at approximately 232.8 / 236.0 eV. 6+ The composition indicates that only a small amount of oxidation state exists on the surface. The S2p region exhibits a typical sulfide bimodal distribution, while the 2p region... 3 / 2 With 2p 1 / 2 Located at approximately 161.9 eV and approximately 163.1 eV (area ratio approximately 2:1), a weak S(VI) component is visible at approximately 168.6 / 169.8 eV on the high binding energy side, which may originate from surface residues or slight oxidation; overall, it indicates that the active phase mainly exists in the form of MoS2 with low content of oxidized impurities, which meets the requirements of high activity and stability.

[0089] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing a graphene-based desulfurization catalyst, characterized in that, Including the following steps: (1) Introduction of initiating groups: 2-bromoisobutyryl bromide and triethylamine are used to introduce initiating groups on the surface of graphene oxide to obtain graphene oxide with initiating groups; (2) Short brush polymerization: using sulfobetaine methacrylate as monomer, cuprous bromide and N,N,N′,N″,N″-pentamethyldiethylenetriamine as catalyst, surface-initiated atom transfer radical polymerization was carried out on graphene oxide with initiating groups. The reaction was carried out at room temperature for 0.25-0.5 h to obtain graphene oxide modified with short brush amphoteric polymer. (3) Complex deposition: Graphene oxide modified with short brush amphoteric polymer is dispersed in the aqueous phase, ammonium molybdate and urea are added, and complex deposition is carried out by stirring at 95°C for 5-7 h to obtain the precursor; (4) First sulfidation: The precursor is sulfided in an atmosphere of 10% hydrogen sulfide / 90% hydrogen by volume to obtain molybdenum disulfide supported powder. (5) Surface treatment and secondary initiation: After mild surface treatment of the molybdenum disulfide loaded powder with dilute sodium hydroxide methanol solution, 2-bromoisobutyryl bromide and triethylamine were used to introduce initiation groups to obtain molybdenum disulfide loaded powder with initiation groups. (6) Long brush polymerization: using sulfobetaine methacrylate as monomer, cuprous bromide and N,N,N′,N″,N″-pentamethyldiethylenetriamine as catalyst, surface-initiated atom transfer radical polymerization was carried out on molybdenum disulfide supported powder with initiating groups. The reaction was carried out at room temperature for 1.5-2.5 h to obtain amphoteric polymer gradient modified powder with both short and long brushes. (7) Second sulfidation: The amphoteric polymer gradient modified powder with both short and long brushes is sulfidated in an atmosphere of 10% hydrogen sulfide / 90% hydrogen by volume to obtain a graphene-based desulfurization catalyst. In step (2), the mass ratio of sulfobetaine methacrylate, cuprous bromide, N,N,N′,N″,N″-pentamethyldiethylenetriamine and graphene oxide with initiating groups is 15-25:0.8-1.2:1.5-2.5:0.9-1.

1. In step (4), the vulcanization is carried out by heating to 320°C at 20°C / min and holding for 60-75min. In step (7), the vulcanization is carried out by heating at 20℃ / min to 340℃ and holding at that temperature for 25-40min.

2. The method for preparing the graphene-based desulfurization catalyst according to claim 1, characterized in that, In step (1), the average diameter of the graphene oxide sheet is 3-5 μm and the average thickness is 3-5 nm.

3. The method for preparing the graphene-based desulfurization catalyst according to claim 1, characterized in that, In step (3), the mass ratio of the short-brush amphoteric polymer-modified graphene oxide, aqueous phase, ammonium molybdate, and urea is 0.9-1.1:200:1.6-2.4:8-12.

4. A graphene-based desulfurization catalyst, characterized in that, It is obtained by the preparation method of the graphene-based desulfurization catalyst according to any one of claims 1-3.

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