阅读说明：本技术 一种过渡金属磷化物/卤氧化铋光催化剂及其制备方法和应用 (Transition metal phosphide/bismuth oxyhalide photocatalyst and preparation method and application thereof ) 是由 万俊 孙凯龙 付峰 王雪敏 刘琳 张悦 刘佳庆 于 2020-04-17 设计创作，主要内容包括：本发明提供了一种过渡金属磷化物/卤氧化铋光催化剂及其制备方法和应用,属于催化剂技术领域。本发明提供的过渡金属磷化物/卤氧化铋光催化剂,包括卤氧化铋和负载在所述卤氧化铋表面的过渡金属磷化物；所述卤氧化铋具有二维纳米片结构；所述过渡金属磷化物具有纳米颗粒结构。本发明提供的过渡金属磷化物/卤氧化铋光催化剂,卤氧化铋的比表面积大,可见光响应性能好,能够在可见光照将噻吩硫化物氧化为强极性的亚砜或砜；过渡金属磷化物能够增强光催化剂对可见光范围内的光吸收,还能够提高光催化剂的光生电子空穴分离效率,增强对燃油中芳香杂环类噻吩硫化物的选择性催化脱除活性,具有良好的光催化氧化脱硫活性和选择性。(The invention provides a transition metal phosphide/bismuth oxyhalide photocatalyst as well as a preparation method and application thereof, belonging to the technical field of catalysts. The transition metal phosphide/bismuth oxyhalide photocatalyst provided by the invention comprises bismuth oxyhalide and transition metal phosphide loaded on the surface of the bismuth oxyhalide; the bismuth oxyhalide has a two-dimensional nanosheet structure; the transition metal phosphide has a nanoparticle structure. The transition metal phosphide/bismuth oxyhalide photocatalyst provided by the invention has the advantages that the specific surface area of bismuth oxyhalide is large, the visible light response performance is good, and thiophene sulfide can be oxidized into strong-polarity sulfoxide or sulfone under visible light illumination; the transition metal phosphide can enhance the light absorption of the photocatalyst in a visible light range, can also improve the separation efficiency of photo-generated electron holes of the photocatalyst, enhances the selective catalytic removal activity of the aromatic heterocyclic thiophene sulfide in fuel oil, and has good photocatalytic oxidation desulfurization activity and selectivity.)

1. A transition metal phosphide/bismuth oxyhalide photocatalyst comprising bismuth oxyhalide and a transition metal phosphide supported on the surface of the bismuth oxyhalide; the bismuth oxyhalide has a two-dimensional nanosheet structure; the transition metal phosphide has a nanoparticle structure.

2. The transition metal phosphide/bismuth oxyhalide photocatalyst of claim 1, wherein the transition metal phosphide is supported at a level of 5 to 25 wt%.

3. A process for preparing a transition metal phosphide/bismuth oxyhalide photocatalyst as claimed in any one of claims 1 to 2, which comprises the steps of:

(1) dissolving bismuth salt and halide salt in an alcohol solvent, mixing the obtained mixed solution with an alkaline reagent aqueous solution, and carrying out a first hydrothermal reaction to obtain bismuth oxyhalide;

(2) mixing transition metal salt, a phosphorus source, a surfactant and an alcohol-water mixed solvent, and carrying out a second hydrothermal reaction to obtain a transition metal phosphide;

(3) mixing the bismuth oxyhalide, the transition metal phosphide and the oxygen-containing reagent, and carrying out liquid phase assembly to obtain a transition metal phosphide/bismuth oxyhalide photocatalyst;

and (3) no time sequence limitation exists between the step (1) and the step (2).

4. The preparation method according to claim 2, wherein in the step (1), the molar ratio of the bismuth salt to the halide salt is (1-4): (1-4).

5. The preparation method according to claim 2 or 4, wherein in the step (1), the temperature of the first hydrothermal reaction is 140-200 ℃ and the time is 16-24 h.

6. The method according to claim 3, wherein in the step (2), the molar ratio of the transition metal salt to the phosphorus source is 1: (5-15);

the ratio of the molar weight of the transition metal salt to the mass of the surfactant is 1 mmol: 0.1 to 0.3 g.

7. The preparation method according to claim 3 or 6, wherein in the step (2), the temperature of the second hydrothermal reaction is 140-200 ℃ and the time is 10-20 h.

8. The production method according to claim 3, wherein in the step (3), the mass ratio of the bismuth oxyhalide to the transition metal phosphide is 1: (0.05-0.25).

9. The use of the transition metal phosphide/bismuth oxyhalide photocatalyst according to any one of claims 1 to 2 or the transition metal phosphide/bismuth oxyhalide photocatalyst prepared by the preparation method according to any one of claims 3 to 8 in selective catalytic oxidation removal of heteroaromatic thiophene sulfides in fuel oil under visible light.

10. Use according to claim 9, wherein the oxidant used for oxidation comprises air or oxygen.

Technical Field

The invention relates to the technical field of catalysts, in particular to a transition metal phosphide/bismuth oxyhalide photocatalyst as well as a preparation method and application thereof.

Background

SO produced by combustion of fuel oil_xThe diesel oil is a main factor causing atmospheric pollution such as acid rain, haze and the like, and along with the increasing shortage of global petroleum resources and the increasing of environmental awareness of people, the sulfur content of the fuel oil is strictly regulated, the development and utilization of clean fuel oil become important problems for solving energy and environmental problems, and low-sulfur and even zero-sulfur diesel oil becomes a necessary direction for developing clean fuel oil.

The existing desulfurization technologies mainly comprise hydrodesulfurization technology and non-hydrodesulfurization technology. The traditional hydrodesulfurization technology has harsh operating conditions, needs high temperature (300-400 ℃), high pressure (4-7 MPa) and large amount of hydrogen, has high operating cost, and is difficult to remove sulfur-containing compounds (such as Benzothiophene (BT), Dibenzothiophene (DBT), 4, 6-dimethyldibenzothiophene (4,6-DMDBT) and the like) of heteroaromatic thiophene and alkyl substituted derivatives thereof in fuel oil. The non-hydrodesulfurization technology is low in cost, environment-friendly and more concerned, wherein the photocatalytic oxidation desulfurization technology is used for oxidizing thiophene sulfur into sulfoxide or sulfone with strong polarity under the action of a photocatalyst under the excitation of light, and then the thiophene sulfur is extracted and separated.

At present, the number of the current day,photocatalytic desulfurization technique mostly uses H₂O₂Using H as an oxidant or using ultraviolet light as a light source₂O₂In the reaction process, OH oxidized thiophene sulfur compounds are generated, but OH oxidizing capability is too strong and almost no selectivity exists, so that components such as aromatic hydrocarbon, olefin and the like in the fuel oil are subjected to oxidative decomposition; and the ultraviolet light is easy to initiate the photochemical reaction of aromatic hydrocarbon, olefin and cyclane in the diesel oil, which causes the reduction of the fuel quality.

Disclosure of Invention

In view of the above, the present invention aims to provide a transition metal phosphide/bismuth oxyhalide photocatalyst, and a preparation method and an application thereof, and the transition metal phosphide/bismuth oxyhalide photocatalyst provided by the present invention realizes high selectivity and high efficiency removal of heteroaromatic thiophene sulfides in fuel oil under visible light irradiation.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a transition metal phosphide/bismuth oxyhalide photocatalyst, which comprises bismuth oxyhalide and transition metal phosphide loaded on the surface of the bismuth oxyhalide; the bismuth oxyhalide has a two-dimensional nanosheet structure; the transition metal phosphide has a nanoparticle structure.

Preferably, the loading amount of the transition metal phosphide is 5-25 wt%.

The invention provides a preparation method of the transition metal phosphide/bismuth oxyhalide photocatalyst in the technical scheme, which comprises the following steps:

(1) dissolving bismuth salt and halide salt in an alcohol solvent, mixing the obtained mixed solution with an alkaline reagent aqueous solution, and carrying out a first hydrothermal reaction to obtain bismuth oxyhalide;

(2) mixing transition metal salt, a phosphorus source, a surfactant and an alcohol-water mixed solvent, and carrying out a second hydrothermal reaction to obtain a transition metal phosphide;

(3) mixing the bismuth oxyhalide, the transition metal phosphide and the oxygen-containing reagent, and carrying out liquid phase assembly to obtain a transition metal phosphide/bismuth oxyhalide photocatalyst;

and (3) no time sequence limitation exists between the step (1) and the step (2).

Preferably, in the step (1), the molar ratio of the bismuth salt to the halide salt is (1-4): (1-4).

Preferably, in the step (1), the temperature of the first hydrothermal reaction is 140-200 ℃ and the time is 16-24 h.

Preferably, in the step (2), the molar ratio of the transition metal salt to the phosphorus source is 1: (5-15);

the ratio of the molar weight of the transition metal salt to the mass of the surfactant is 1 mmol: 0.1 to 0.3 g.

Preferably, the temperature of the second hydrothermal reaction is 140-200 ℃ and the time is 10-20 h.

Preferably, in the step (3), the mass ratio of the bismuth oxyhalide to the transition metal phosphide is 1: (0.05-0.25).

The invention also provides an application of the transition metal phosphide/bismuth oxyhalide photocatalyst prepared by the technical scheme or the transition metal phosphide/bismuth oxyhalide photocatalyst prepared by the preparation method in the technical scheme in selective catalytic oxidation removal of heteroaromatic thiophene sulfides in fuel oil under visible light.

Preferably, the oxidizing agent used for the oxidation comprises air or oxygen.

The invention provides a transition metal phosphide/bismuth oxyhalide photocatalyst, which comprises bismuth oxyhalide and transition metal phosphide loaded on the surface of the bismuth oxyhalide; the bismuth oxyhalide has a two-dimensional nanosheet structure; the transition metal phosphide has a nanoparticle structure. In the transition metal phosphide/bismuth oxyhalide photocatalyst provided by the invention, bismuth oxyhalide has a two-dimensional nanosheet structure, a large specific surface area and good visible light response performance, and the reduction potential of conduction band electrons of the bismuth oxyhalide is higher than that of E (O)₂ ^-/O₂) The photoproduction electrons can effectively activate O₂Forming a superoxide radical (O2-) with strong oxidation activity, and oxidizing thiophene sulfide adsorbed on the surface of the photocatalyst into a sulfoxide or sulfone with strong polarity; after the transition metal phosphide is loaded on the surface of the bismuth oxyhalide, on one hand, the visible light of the photocatalyst can be enhancedThe light absorption in the range can improve the photoproduction electron hole separation efficiency of the photocatalyst, provide more effective photoproduction charges for the photocatalytic oxidation desulfurization reaction, and on the other hand, the transition metal phosphide has the selective adsorption effect on sulfur-containing compounds, so that the adsorbability on other substances in oil products is reduced, the adsorption selectivity of the photocatalyst on thiophenic sulfur is enhanced, and the catalytic removal activity and selectivity on thiophenic sulfides in fuel oil are improved. Therefore, the transition metal phosphide/bismuth oxyhalide photocatalyst provided by the invention has good photocatalytic oxidation desulfurization activity and selectivity.

The invention provides a preparation method of the transition metal phosphide/bismuth oxyhalide photocatalyst, which is simple to operate, low in raw material cost and suitable for industrial production.

The invention adopts visible light and uses air or oxygen as oxidant, which can effectively avoid the influence of light source on the oil composition, and meanwhile, the air is clean and easy to obtain, no by-product is generated, and the desulfurization process is green and mild.

Drawings

FIG. 1 shows Bi prepared in example 1₄O₅Br₂And Ni₂XRD pattern of P;

FIG. 2 shows Ni prepared in example 1₂P/Bi₄O₅Br₂SEM picture of (1);

FIG. 3 shows Bi prepared in example 2₂₄O₃₁Br₁₀And the XRD pattern of NiCoP;

FIG. 4 shows NiCoP/Bi prepared in example 2₂₄O₃₁Br₁₀SEM picture of (1);

FIG. 5 shows Bi prepared in example 2₂₄O₃₁Br₁₀And NiCoP/Bi₂₄O₃₁Br₁₀UV-vis absorption spectrum of (1);

FIG. 6 shows Bi prepared in example 2₂₄O₃₁Br₁₀And NiCoP/Bi₂₄O₃₁Br₁₀Photocurrent response spectrum of;

FIG. 7 is a graph showing the desulfurization effect of the photocatalyst prepared in examples 1 to 4 on fuel oil by visible light catalytic oxidation.

Detailed Description

The invention provides a transition metal phosphide/bismuth oxyhalide photocatalyst, which comprises bismuth oxyhalide and transition metal phosphide loaded on the surface of the bismuth oxyhalide; the bismuth oxyhalide has a two-dimensional nanosheet structure; the transition metal phosphide has a nanoparticle structure.

In the present invention, the bismuth oxyhalide preferably comprises Bi₄O₅Br₂、Bi₂₄O₃₁Br₁₀、Bi₂₄O₃₁Cl₁₀Or Bi₄O₅I₂. In the invention, the bismuth oxyhalide has a two-dimensional nanosheet structure, and the diameter of the two-dimensional nanosheet is preferably 200-2000 nm, more preferably 400-1500 nm, and most preferably 500-1000 nm; the thickness of the two-dimensional nanosheet is preferably 10-30 nm, more preferably 15-25 nm, and most preferably 20-25 nm. In the invention, the bismuth oxyhalide two-dimensional nanosheet structure has large specific surface area and good visible light response performance, and the reduction potential of conduction band electrons of the bismuth oxyhalide two-dimensional nanosheet structure is higher than that of E (O)₂ ^-/O₂) The photoproduction electrons can effectively activate O₂Formation of superoxide radical (. O) with strong oxidative activity₂ ^-) And oxidizing the thiophene sulfide adsorbed on the surface of the photocatalyst into the strongly polar sulfoxide or sulfone.

In the invention, the transition metal phosphide has a nanoparticle structure, and the particle size of the nanoparticles is preferably 10-40 nm, more preferably 15-35 nm, and most preferably 20-30 nm. In the present invention, the chemical composition of the transition metal phosphide is a transition metal and phosphorus; the transition metal preferably comprises one or more of nickel, cobalt, iron, molybdenum and tungsten, and more preferably nickel, cobalt, iron or nickel-cobalt mixed transition metal; the chemical composition of the transition metal phosphide is further preferably Ni₂P、Co₂P、Fe₂P or NiCoP.

In the invention, the loading amount of the transition metal phosphide is preferably 5-25 wt%, more preferably 10-20 wt%, and most preferably 15-20 wt%. In the invention, after the transition metal phosphide is loaded on the surface of the two-dimensional nanosheet of bismuth oxyhalide, on one hand, the light absorption of the photocatalyst in a visible light range can be enhanced, the separation efficiency of photo-generated electron holes of the photocatalyst is improved, on the other hand, the selective adsorption effect of the photocatalyst on sulfur-containing compounds can be promoted, and the selective removal effect on heteroaromatic thiophene sulfides in fuel oil is enhanced.

In the present invention, the chemical composition of the transition metal phosphide/bismuth oxyhalide photocatalyst preferably includes: ni₂P/Bi₄O₅Br₂、Co₂P/Bi₂₄O₃₁Br₁₀、Co₂P/Bi₂₄O₃₁Cl₁₀Or Fe₂P/Bi₄O₅I₂. The transition metal phosphide/bismuth oxyhalide photocatalyst provided by the invention has high selectivity and catalytic removal activity on heteroaromatic thiophene sulfides in fuel oil under the irradiation of visible light.

The invention provides a preparation method of the transition metal phosphide/bismuth oxyhalide photocatalyst in the technical scheme, which comprises the following steps:

(1) dissolving bismuth salt and halide salt in an alcohol solvent, mixing the obtained mixed solution with an alkaline reagent aqueous solution, and carrying out a first hydrothermal reaction to obtain bismuth oxyhalide;

(2) mixing transition metal salt, a phosphorus source, a surfactant and an alcohol-water mixed solvent, and carrying out a second hydrothermal reaction to obtain a transition metal phosphide;

(3) mixing the bismuth oxyhalide, the transition metal phosphide and the oxygen-containing reagent, and carrying out liquid phase assembly to obtain a transition metal phosphide/bismuth oxyhalide photocatalyst;

and (3) no time sequence limitation exists between the step (1) and the step (2).

In the present invention, all the raw material components are commercially available products well known to those skilled in the art unless otherwise specified.

Bismuth salt and halide salt are dissolved in an alcohol solvent, the obtained mixed solution is mixed with an alkaline reagent aqueous solution, and a first hydrothermal reaction is carried out to obtain bismuth oxyhalide.

In the present invention, the bismuth salt preferably includes bismuth nitrate and/or bismuth chloride. In the present invention, the halide salt preferably includes a chloride salt, a bromide salt or an iodide salt; the chloride salt preferably comprises potassium chloride, sodium chloride or ammonium chloride; the bromide salt preferably comprises potassium bromide, sodium bromide or ammonium bromide; the iodine salt preferably comprises potassium iodide, sodium iodide or ammonium iodide. In the present invention, the molar ratio of the bismuth salt to the halide salt is preferably (1 to 4): (1-4), more preferably (1.5-3.5): (1.5 to 3.5), preferably (2 to 3) and (2 to 3).

In the present invention, the alcohol solvent is not particularly limited in kind, and may be one capable of dissolving the bismuth salt and the halide salt, and in the embodiment of the present invention, the alcohol solvent is preferably ethylene glycol. In the invention, the ratio of the volume of the alcohol solvent to the molar weight of the bismuth salt is preferably 5-20 mL: 1mmol, more preferably 6-15 mL: 1mmol, most preferably 6.5-10 mL: 1 mmol.

In the present invention, the aqueous alkaline reagent solution preferably includes aqueous ammonia or an aqueous hydroxide solution. In the present invention, the concentration of the ammonia water is preferably 5 to 25 wt%, more preferably 8 to 22.4 wt%, and most preferably 10 to 20 wt%. In the present invention, the concentration of the hydroxide aqueous solution is preferably 0.1 to 0.5mol/L, more preferably 0.15 to 0.45mol/L, and most preferably 0.2 to 0.4 mol/L; the hydroxide preferably comprises sodium hydroxide or potassium hydroxide. In the present invention, the aqueous solution of the alkaline reagent serves to provide an alkaline environment for dehalogenation of bismuth oxyhalide formed from the bismuth salt and the halide salt.

In the present invention, the dissolving of the bismuth salt and the halide salt in the alcohol solvent preferably includes first dissolving the bismuth salt in the alcohol solvent and then adding the halide salt to the solution for second dissolution to obtain a mixed solution. In the present invention, the dissolution is preferably carried out under stirring conditions, and the speed of stirring in the present invention is not particularly limited, and the raw material may be dissolved in an alcohol solvent. The first dissolving time is not particularly limited, and the bismuth salt can be dissolved in an alcohol solvent; the second dissolving time is preferably 20-40 min, and more preferably 25-35 min.

In the present invention, the mixing is preferably carried out by dropwise adding an aqueous alkaline reagent solution under stirringAnd adding into the mixed solution. The stirring and mixing speed is not particularly limited, and the raw materials can be uniformly mixed. The dropping speed is not particularly limited in the invention, and the dropping can be carried out dropwise. In the invention, the mixing time is preferably 2-4 h, and the mixing time is preferably counted after the alkaline reagent aqueous solution is added. In the present invention, in the mixing process, Bi is added after the alkaline reagent is added³⁺Halogen ion X^-(X ═ Cl, Br, I) will produce a BiOX precipitate under alkaline conditions, forming a cloudy solution, as shown in equations 1 and 2:

Bi³⁺+3OH^-→Bi(OH)₃(s) (formula 1);

Bi(OH)₃(s)+X^-→BiOX(s)+H₂O+OH^-(formula 2).

In the invention, the temperature of the first hydrothermal reaction is preferably 140-200 ℃, more preferably 150-190 ℃, and most preferably 150-180 ℃; the time of the first hydrothermal reaction is preferably 16-24 hours, more preferably 18-22 hours, and most preferably 20-22 hours. In the present invention, the first hydrothermal reaction is preferably a static hydrothermal reaction. The reactor used in the first hydrothermal reaction is not particularly limited, and a hydrothermal reactor known to those skilled in the art may be used, specifically, a hydrothermal reactor. In the present invention, during the first hydrothermal reaction, BiOX is further reacted with OH^-The dehalogenation reaction that occurs forms bismuth-rich bismuth oxyhalide, the reaction formula is shown in formula (3):

BiOX(s)+OH-→Bi_mO_nXp(s)+X^-+H₂o formula (3).

The dehalogenation reaction is dependent on the temperature of the first hydrothermal reaction and thus at different temperatures different stoichiometries of the bismuth oxyhalide are obtained.

After the first hydrothermal reaction is completed, the method preferably further comprises the steps of carrying out solid-liquid separation on a system of the first hydrothermal reaction, and sequentially carrying out water washing, alcohol washing and drying on an obtained solid product to obtain bismuth oxyhalide. The solid-liquid separation method is not particularly limited, and specifically includes centrifugal separation or suction filtration. The washing frequency is not particularly limited, and ions or impurities which are attached to the surface of the product and dissolved in water can be removed, specifically 3-5 times. In the present invention, the alcohol used for the alcohol washing preferably includes ethanol or ethylene glycol; the number of times of alcohol washing is not particularly limited, and organic impurities which are attached to the surface of a product and dissolved in alcohol can be removed, specifically 3-5 times. In the present invention, the preferred method of drying is vacuum drying; the temperature of the vacuum drying is preferably 60-100 ℃, more preferably 70-90 ℃, and the drying time is preferably 6-12 hours, more preferably 8-10 hours.

According to the invention, transition metal salt, phosphorus source, surfactant and alcohol-water mixed solvent are mixed for a second hydrothermal reaction to obtain transition metal phosphide.

In the present invention, the transition metal preferably includes one or more of nickel, cobalt, iron, molybdenum and tungsten; the transition metal salt preferably comprises one or more of transition metal chloride, transition metal nitrate and transition metal acetate, and more preferably comprises one or more of nickel chloride, nickel nitrate, nickel acetate, cobalt chloride, cobalt nitrate, cobalt acetate, ferric chloride, ferric nitrate, ferric acetate, cupric chloride, cupric nitrate, cupric acetate, zinc chloride, zinc nitrate and zinc acetate. In the present invention, when the transition metal salt is a mixture of two or more transition metal salts, the molar ratio of the different transition metal salts is not particularly limited, and may be any ratio. In embodiments of the present invention, the transition metal salt preferably comprises nickel chloride, a mixture of nickel chloride and cobalt chloride, cobalt nitrate or ferric chloride.

In the present invention, the phosphorus source preferably comprises red phosphorus or sodium hypophosphite. In the present invention, the molar ratio of the transition metal salt to the phosphorus source is preferably 1: (5-15), more preferably 1: (8-15), most preferably 1: (8-12); the amount of the phosphorus source is calculated as P.

In the invention, the surfactant preferably comprises Cetyl Trimethyl Ammonium Bromide (CTAB) and Sodium Dodecyl Benzene Sulfonate (SDBS), and the mass ratio of CTAB to SDBS is preferably 1 (1-2), and more preferably 1 (1-1.5). In the present invention, the ratio of the transition metal salt molar amount to the surfactant mass is preferably 1 mmol: (0.1 to 0.3) g, more preferably 1 mmol: (0.15-0.28) g, most preferably 1 mmol: (0.6-0.25) g. In the present invention, the surfactant can inhibit crystal growth of the product, enabling it to form a nanoparticle morphology.

In the present invention, the alcohol in the alcohol-water mixed solvent preferably includes ethanol or ethylene glycol; the volume ratio of the alcohol to the water in the alcohol-water mixed solvent is preferably 1 (1-3), and more preferably 1 (1.5-2.5). In the present invention, the ratio of the molar amount of the transition metal salt to the volume of the alcohol-water mixed solvent is preferably (0.5 to 4) mmol: 50mL, more preferably (1-3) mmol: 50 mL.

In the present invention, the mixing of the transition metal salt, the phosphorus source, the surfactant, and the alcohol-water mixed solvent preferably includes fourth mixing the transition metal salt and the alcohol-water mixed solvent to obtain a transition metal salt solution; and mixing the transition metal salt solution, the phosphorus source and the surfactant for the fifth time. In the present invention, the fourth mixing and the fifth mixing are preferably stirring mixing, and the speed of the stirring mixing is not particularly limited in the present invention, and the raw materials may be uniformly mixed. In the present invention, the time for the fourth mixing is not particularly limited, and the alcohol-water mixed solvent may be one that can completely dissolve the transition metal salt. In the present invention, the time for the fifth mixing is preferably 30 to 60min, and more preferably 40 to 50 min.

In the invention, the temperature of the second hydrothermal reaction is preferably 140 to 200 ℃, more preferably 150 to 200 ℃, and most preferably 180 to 200 ℃; the time of the second hydrothermal reaction is preferably 10-20 h, more preferably 10-18 h, and most preferably 12-18 h. The reactor used in the second hydrothermal reaction is not particularly limited, and a hydrothermal reactor known to those skilled in the art may be used, specifically, the hydrothermal reactor is used. In the present invention, the phosphorus source undergoes a disproportionation reaction to form negative phosphorus (pH) during the second hydrothermal reaction₃) And then combined with a transition metal to form a transition metal phosphide.

After the second hydrothermal reaction is completed, the method preferably further comprises the steps of carrying out solid-liquid separation on a system of the second hydrothermal reaction, and sequentially carrying out water washing, alcohol washing and drying on an obtained solid product to obtain the transition metal phosphide. The solid-liquid separation method is not particularly limited, and specifically includes centrifugal separation or suction filtration. The washing frequency is not particularly limited, and ions or impurities which are attached to the surface of the product and dissolved in water can be removed, specifically 3-5 times. In the present invention, the alcohol used for the alcohol washing preferably includes ethanol; the number of times of alcohol washing is not particularly limited, and impurities which are attached to the surface of a product and dissolved in alcohol can be removed, specifically 3-5 times. In the present invention, the preferred method of drying is vacuum drying; the temperature of the vacuum drying is preferably 60-80 ℃, more preferably 65-75 ℃, and the drying time is preferably 6-12 hours, more preferably 8-10 hours.

After the bismuth oxyhalide and the transition metal phosphide are obtained, the bismuth oxyhalide, the transition metal phosphide and the oxygen-containing reagent are mixed and subjected to liquid phase assembly to obtain the transition metal phosphide/bismuth oxyhalide photocatalyst.

In the present invention, the mass ratio of the bismuth oxyhalide to the transition metal phosphide is preferably 1: (0.05 to 0.25), more preferably 1: (0.1 to 0.2), most preferably 1: (0.1-0.15).

In the present invention, the oxygen-containing reagent preferably comprises water, ethanol or nitrogen methyl pyrrolidone. In the present invention, the ratio of the mass of the bismuth oxyhalide to the volume of the oxygen-containing reagent is preferably 0.3 g: 40-60 mL, more preferably 0.3 g: 50 mL. In the invention, the oxygen-containing reagent can effectively improve the dispersion degree of the bismuth oxyhalide and the transition metal phosphide, and provides a sufficient contact site for the bismuth oxyhalide and the transition metal phosphide.

In the present invention, the mixing preferably includes ultrasonic dispersion and agitation mixing which are sequentially performed. The power of the ultrasonic dispersion is not particularly limited in the invention, and the power of the ultrasonic dispersion known by the person skilled in the art can be adopted; the time for ultrasonic dispersion is preferably 10-60 min, and more preferably 20-40 min; the ultrasonic dispersion instrument adopted by the ultrasonic dispersion instrument is not particularly limited, and an ultrasonic instrument well known to a person skilled in the art can be adopted, and in the embodiment of the invention, the ultrasonic dispersion is preferably carried out by using a Ningbo Xinzhi JY92-IIDN ultrasonic disruptor; the ultrasonic mixing can effectively improve the dispersion and mixing degree of the bismuth oxyhalide and the transition metal phosphide in the oxygen-containing reagent, prevent the self-aggregation of the bismuth oxyhalide and the transition metal phosphide, and ensure that the bismuth oxyhalide and the transition metal phosphide can be fully dispersed and mixed together. The stirring speed is not particularly limited, and the stirring speed known by the person skilled in the art can be adopted; the stirring and mixing time is preferably 6-36 h, more preferably 10-30 h, and most preferably 20-24 h; the stirring and mixing can enable bismuth oxyhalide and transition metal phosphide to be fully and effectively contacted together, so that transition metal phosphide nano-particles are uniformly attached to the surface of the bismuth oxyhalide nano-sheet. .

In the invention, in the liquid phase assembly process, the transition metal phosphide is loaded on the surface of the bismuth oxyhalide through the adsorption action, so as to obtain the transition metal phosphide/bismuth oxyhalide photocatalyst.

After the liquid phase assembly is completed, the method preferably further comprises the steps of carrying out solid-liquid separation on a liquid phase assembly system, and sequentially carrying out water washing, alcohol washing and drying on the obtained solid product to obtain the transition metal phosphide/bismuth oxyhalide photocatalyst. The solid-liquid separation method is not particularly limited, and specifically includes centrifugal separation or suction filtration. The washing frequency is not particularly limited, and ions or impurities which are attached to the surface of the product and dissolved in water can be removed, specifically 3-5 times. In the present invention, the alcohol used for the alcohol washing preferably includes ethanol; the number of times of alcohol washing is not particularly limited, and impurities which are attached to the surface of a product and dissolved in alcohol can be removed, specifically 3-5 times. In the present invention, the preferred method of drying is vacuum drying; the temperature of the vacuum drying is preferably 60-100 ℃, more preferably 70-90 ℃, and the drying time is preferably 6-12 hours, more preferably 8-10 hours.

According to the invention, the bismuth oxyhalide and the transition metal phosphide are prepared by a hydrothermal method respectively, and the transition metal phosphide/bismuth oxyhalide photocatalyst is prepared by a liquid-phase assembly method. The photocatalyst provided by the invention is used for photocatalytic oxidation fuel oil desulfurization under visible light, and the transition metal phosphide in the photocatalyst can effectively enhance the light absorption of the catalyst in the visible light range, improve the electron hole separation efficiency of the catalyst, and enhance the selectivity and removal effect on the aromatic heterocyclic thiophene sulfide in the fuel oil.

The invention also provides an application of the transition metal phosphide/bismuth oxyhalide photocatalyst prepared by the technical scheme or the transition metal phosphide/bismuth oxyhalide photocatalyst prepared by the preparation method in the technical scheme in selective catalytic oxidation removal of heteroaromatic thiophene sulfides in fuel oil under visible light.

In the invention, the heteroaromatic thiophene sulfide is preferably one or more of Benzothiophene (BT), Dibenzothiophene (DBT) and 4, 6-dimethyldibenzothiophene (4, 6-DMDBT).

In the present invention, the fuel is preferably gasoline and/or diesel.

In the invention, taking dibenzothiophene as an example, the reaction principle of photocatalytic oxidation desulfurization of the transition metal phosphide/bismuth oxyhalide photocatalyst is shown in formula 4-formula 7, and the specific process is as follows: the transition metal phosphide/bismuth oxyhalide photocatalyst is excited by visible light to generate a photo-generated electron-hole pair with a certain oxidation-reduction potential, wherein the photo-generated electron activates O₂Form O with strong oxidation activity₂ ^-Thiophene sulfide can be selectively adsorbed on transition metal phosphide nano-particles of photocatalyst, and can be activated by cavity, and then activated by O₂ ^-Oxidizing thiophene sulfide adsorbed on the surface of the photocatalyst into strong-polarity sulfoxide or sulfone, and then separating the generated sulfide from an oil product by using an extracting agent. In the present invention, the extractant preferably comprises acetonitrile or N-methylpyrrolidone. The transition metal phosphide/bismuth oxyhalide photocatalyst provided by the invention improves the light absorption capacity and the photo-induced electron hole separation capacity of the photocatalystThe quantum efficiency of the desulfurization reaction is effectively improved, and more effective photo-generated charges are provided for the desulfurization reaction, so that the activity of the desulfurization reaction is improved; meanwhile, the selective chemical adsorption and activation process of the photocatalyst on organic sulfide is enhanced, so that the selectivity and the removal effect of the desulfurization reaction are further improved.

Photocatalyst + h v (light) → e^-(Electron) + h⁺(void) (formula 4)

e^-+O₂→·O₂ ^-(formula 5)

In the present invention, the step of photocatalytic oxidative desulfurization preferably includes: adding a transition metal phosphide/bismuth oxyhalide photocatalyst into a system to be desulfurized, adding an extracting agent, introducing an oxidizing agent, stirring in a dark environment, carrying out photocatalytic oxidation desulfurization reaction under visible light, and then standing for layering.

In the invention, the desulfurization effect of the transition metal phosphide/bismuth oxyhalide photocatalyst is preferably characterized according to the sulfur content in the upper liquid after standing and layering; the sulfur content is preferably measured by gas chromatography.

In the embodiment of the invention, in order to verify the catalytic effect of the photocatalyst, the system to be desulfurized is preferably self-made simulated diesel oil, and the composition of the simulated diesel oil preferably comprises dodecane, naphthalene and sulfide; the concentration of the sulfide is preferably 200-1000 ppm, and more preferably 500-800 ppm; the concentration of naphthalene is preferably 500 to 2000ppm, more preferably 1000 to 1500 ppm. In the invention, the sulfide preferably comprises one or more of Benzothiophene (BT), Dibenzothiophene (DBT) and 4, 6-dimethylbenzothiophene (4, 6-DMDBT); when the sulfide is a mixture of two or more types of sulfides, the mass ratio of the different types of sulfides is not particularly limited in the present invention, and may be any ratio. In the invention, the ratio of the mass of the transition metal phosphide/bismuth oxyhalide photocatalyst to the volume of the simulated diesel oil is preferably 5-10 mg/mL, and more preferably 6-8 mg/mL.

In the present invention, the extractant preferably comprises acetonitrile or nitrogen methyl pyrrolidone; the volume ratio of the extracting agent to the simulated diesel oil is preferably 1 (1-4), and more preferably 1 (2-3).

In the present invention, the oxidant preferably comprises air or oxygen; the introduction amount of the oxidant is preferably 20-100 mL/min, and more preferably 50-80 mL/min.

In the present invention, the stirring time in the dark is preferably 30 min.

In the invention, the wavelength of the visible light is preferably 400-760 nm; in the embodiment of the present invention, the visible light is preferably filtered by an ultraviolet filter to remove light below 420nm using a 300W xenon lamp (available from beijing, zhongzhi jinyuan technologies ltd) as a light source for simulating sunlight.

In the invention, the temperature of the photocatalytic oxidation desulfurization reaction is preferably 20-30 ℃, and the time is preferably 2-4 h; the temperature of the photocatalytic oxidative desulfurization reaction is preferably maintained by circulating water through the jacket of the reactor.

In the present invention, the sampling of the supernatant liquid is preferably performed by using a sampling needle with a filter. In the present invention, the pore size of the filter is preferably 0.22 to 0.45 μm.

The transition metal phosphide/bismuth oxyhalide photocatalyst provided by the invention is used for photocatalytic desulfurization, and has the characteristics of mild reaction conditions, simple process and equipment, high reaction selectivity, small loss of oil product quality, good desulfurization effect, good repeatability and the like. In addition, the transition metal phosphide/bismuth oxyhalide photocatalyst provided by the invention has a wide applicable spectrum range, and has high selectivity and catalytic activity to sulfides in diesel oil under the condition of visible light and high selectivity and catalytic activity to sulfides in diesel oil under the condition of ultraviolet light irradiation.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.