Preparation method and application of molybdate-loaded mesoporous silica composite material

Abstract

The present invention discloses a preparation method and application of a molybdate-loaded mesoporous silica composite material. The preparation process comprises the steps of sequentially mixing a template, a metal source, methanol, water, and a silicon source, and continuously stirring the resulting solution. The resulting solution is then subjected to alternating vacuum drying and ground into powder. The powder is then calcined at high temperature in a muffle furnace to obtain a highly dispersed mesoporous silica composite material containing molybdenum as an active center. The advantages are: greatly simplifying the synthesis process, reducing the cost of synthesis, and improving the utilization and recovery efficiency of raw materials. This allows for high dispersion of the catalyst's active sites and enhances the catalyst's high-temperature resistance in a high-temperature environment. The material has high catalytic activity against sulfur-containing compounds in oil products and can effectively improve the desulfurization efficiency of oil products. Based on ease of preparation and easy recovery, the material can effectively reduce production costs, improve oil product quality, and protect the environment to the greatest extent possible.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a molybdate-loaded mesoporous silica composite material, belonging to the technical field of heterogeneous catalysis. Background Art

[0002] As society develops, energy demand continues to rise. Oil, as a traditional energy source, remains irreplaceable. As people demand a better living environment, countries around the world are implementing stricter controls on environmental pollution caused by traditional energy sources. Sulfur oxides in fuel can cause a range of hazards when burned, damaging the living environment. Consequently, countries are increasingly tightening regulations on sulfur content in fuel, making it particularly important to limit sulfur content in fuel.

[0003] Oxidative desulfurization (ODS) is considered one of the most promising desulfurization methods for industrial applications due to its hydrogen-free nature, mild reaction conditions, and low energy consumption. Oxidative desulfurization effectively removes thiophenes from fuel oils. With the advancement of various research, the main catalysts currently used in ODS include ionic liquids, metal oxides, molecular sieves, and metal oxoates.

[0004] Among the catalysts involved in many research institutes at home and abroad, compared with metal catalysts, the raw materials of non-metallic catalysts are very abundant and easy to synthesize. Among the many non-metallic materials, polyionic liquids have the advantages of strong designability, easy separation and recovery, and strong thermal stability. This type of polymer combines some properties of polymers and ionic liquids, has high thermal stability and mechanical strength, and can be used as a carrier in catalytic processes. Metal oxoates have been found in previous reports to be used as active centers for catalytic oxidative desulfurization, but no matter which method is used, there are problems such as cumbersome synthesis process, high synthesis cost, inconvenient raw material utilization and low recovery efficiency. Summary of the Invention

[0005] The present invention provides a method for preparing a molybdate-loaded mesoporous silica composite material with low synthesis cost, simple raw material utilization and high recovery efficiency. Another object of the present invention is to provide an application of the above-mentioned material, which has excellent performance in catalytic oxidation desulfurization.

[0006] In order to solve the above technical problems, the preparation method of the molybdate-loaded mesoporous silica composite material of the present invention comprises the following steps:

[0007] A. Dissolve molybdate in a bottle filled with deionized water, keep stirring in a low-temperature water bath, and dropwise add hydrogen peroxide and concentrated hydrochloric acid to deeply oxidize the molybdate to obtain a solution containing a molybdenum metal source;

[0008] B. self-polymerizing the ionic liquid under a nitrogen atmosphere for 23-25 ​​hours, and dissolving the resulting polyionic liquid in ethanol to form a polyionic liquid solution;

[0009] C. Add the solution obtained in step A dropwise to the solution obtained in step B, complete the reaction to obtain a solid precipitate, filter, wash, dry, and grind to obtain a powder;

[0010] D. Dissolve the powder obtained in step C in methanol, and then add deionized water dropwise to obtain a prepared solution;

[0011] E. Add the silicon source dropwise to the prepared solution obtained in step D, and then add aqueous ammonia to the prepared solution while stirring to hydrolyze the silicon source;

[0012] F. Filtering, washing, drying, and grinding the solution treated in step E into a powdery state to obtain a solid powder;

[0013] G. The solid powder obtained in step F is calcined in a programmed temperature muffle furnace to 300, 400, and 500° C., respectively, and the constant temperature calcination is maintained for 3-5 hours to obtain a molybdate-loaded mesoporous silica composite material.

[0014] In step A, the molybdate is Na2MoO4·2H2O, the molar ratio of Na2MoO4·2H2O to hydrogen peroxide is 10:12.88, the stirring speed is 600 rpm, and the low-temperature water bath is 0-1°C.

[0015] In the step B, the ionic liquid is 1-vinyl-3-butylimidazolium bromide ([VBIm]Br), and the molar ratio of the ionic liquid to ethanol is 1:26.

[0016] In step E, the silicon source is tetraethyl orthosilicate; the molar ratio of tetraethyl orthosilicate, ammonia water, and the powder obtained in step C is 2:3:0.1, and the stirring speed is 600 rpm.

[0017] In the step G, the programmed heating rate is 5°C / min.

[0018] The molybdate-loaded mesoporous silica composite material has a mesoporous structure.

[0019] The application of the molybdate-supported mesoporous silica composite material in the catalytic oxidation desulfurization of sulfur compounds in oil products is mainly to catalytically remove aromatic sulfides and aliphatic sulfides from fuel oil, such as the oxidation reaction of dibenzothiophene (DBT). The reaction process can be expressed by the following formula:

[0020]

[0021] The carbon-doped silica composite material containing molybdenum source has a high desulfurization rate for different sulfur-containing substrates in oil products. The desulfurization rates of aromatic sulfides: 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) can reach 80.02% and 99.34% within 30 minutes, and the desulfurization rate of dibenzothiophene (DBT) can reach 99.36% within 30 minutes.

[0022] The advantages of the present invention are:

[0023] The carbon-doped silica composite material containing a molybdenum source of the present invention exhibits high catalytic activity for removing sulfur compounds from oil products. Its excellent activity is mainly attributed to the following factors:

[0024] (1) The carbon-doped silica composite material containing a molybdenum source has a large specific surface area, a mesoporous structure, and a uniform pore size distribution. These factors enable a relatively uniform dispersion of molybdenum on it, and also ensure more complete contact between the catalyst and the sulfur-containing substrate.

[0025] (2) The molybdenum source is dispersed more evenly in various parts of the catalyst without crystallization, thus having higher activity.

[0026] (3) The catalyst of the present invention utilizes 1-vinyl-3-butylimidazolium bromide as a template and carbon source, silicon dioxide as a silicon source, and molybdenum-doped polyionic liquid as a metal source, which greatly simplifies the synthesis process, reduces the cost of synthesis, improves the utilization and recovery efficiency of raw materials, and provides a new idea for metal-loaded polyionic liquid as a catalyst; the high specific surface area, mesoporous structure, uniform dispersion of active sites, and high catalytic activity can solve the problems existing in the prior art; it can achieve high dispersion of the catalyst active sites and enhance the high temperature resistance of the catalyst in a high temperature environment. The material has high catalytic activity for sulfur-containing compounds in oil products and can effectively improve the desulfurization efficiency of oil products. During the process of the catalyst desulfurizing the sulfur-containing substrate, no other organic solvent is needed. During the catalytic process, the active center and the sulfur-containing substrate can be fully contacted. After the catalytic process is completed, the recovery and reuse of the catalyst is also extremely simple, which greatly improves the recycling capacity of the catalyst. On the basis of easy preparation and easy recovery, it can effectively reduce production costs, improve oil quality, and protect the environment to the greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 1 is the X-ray diffraction pattern of the molybdate-loaded mesoporous silica composite material obtained in Example 1 under different states;

[0028] Figure 2These are the catalytic activity results of the molybdate-supported mesoporous silica composite material obtained in Example 1 on different sulfur-containing substrates.

[0029] Figure 3 The catalytic oxidation activity results of the molybdate-loaded mesoporous silica composite material obtained in Example 1 for DBT at different temperatures.

[0030] Figure 4 and Figure 5 The diagram shows the nitrogen isothermal adsorption and desorption of the molybdate-loaded mesoporous silica composite material obtained in Example 1 under a series of changing conditions, as well as the specific surface area, pore size, and pore volume data. DETAILED DESCRIPTION

[0031] The preparation method and application of the molybdate-loaded mesoporous silica composite material of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] The present invention designs an ionic liquid by using tetraethyl orthosilicate as a soft template agent, successfully loads molybdenum as an active center on the polyionic liquid, and after calcination to remove the organic carbon chain skeleton, obtains the in-situ controllable synthesis of highly dispersed molybdenum-doped silica composite materials, and effectively increases the thermal stability of the mesoporous material.

[0033] Example 1

[0034] The preparation method of the molybdate-loaded mesoporous silica composite material of this embodiment comprises the following steps:

[0035] 1) Weigh 2.42 g (10 mmol) of sodium molybdate dihydrate into a vial, add 10 mL of deionized water, and connect to an ice-water bath at 0.1°C. After dissolution, add 12 mL of 30% hydrogen peroxide dropwise. Stir continuously and add concentrated hydrochloric acid dropwise until a light yellow color forms. 11 Solution, at this time the pH value of the solution is approximately between 3 and 4.

[0036] 2) 2.31 g (10 mmol) of 1-vinyl-3-butylimidazolium bromide ([VBIm]Br) was added to 0.0693 g of azobisisobutyronitrile (AIBN) under a nitrogen atmosphere at 70°C for 24 h to obtain P[VBIm]Br. After the polymerization was completed, the solution was transferred to 15 mL of ethanol solution and dissolved at 50°C to form a P[VBIm]Br solution.

[0037] 3) P[VBIm]Br solution was added dropwise to the H2Mo2O 11 After the reaction is complete, a yellow solid is formed in the solution. The solution is filtered, washed three times with deionized water, and dried in vacuo at 50°C for 6 h. After drying, the solid is ground to obtain powder P[VBIm]2Mo2O 11 .

[0038] 4) Take 0.2328g P[VBIm]2Mo2O 11 Dissolve in 15 mL of methanol at 50 °C, stir for 20 min to form a light yellow solution, and add the solution dropwise to 13 mL of deionized water.

[0039] 5) 1 mL of tetraethyl orthosilicate (TEOS) was added dropwise to the solution in step (4), and 0.5 mL of aqueous ammonia (NH3·H2O) was added to the solution using a pipette. The solution was stirred at 600 rpm for 30 min until a gel appeared, and then allowed to stand for 30 min.

[0040] 6) The solution of step (5) was filtered, washed with deionized water 3 times, dried under vacuum at 50°C for 6 h, and ground to obtain powder P[VBIm]2Mo2O 11 -SiO2.

[0041] 7) P[VBIm]2Mo2O 11 -SiO2 powder was placed in a programmed temperature muffle furnace, heated to 400°C at a heating rate of 5°C / min, maintained at 400°C in the muffle furnace for calcination for 6 hours, and completely cooled to obtain a molybdate-loaded mesoporous silica composite material.

[0042] Example 2

[0043] The preparation method of the molybdate-loaded mesoporous silica composite material of this embodiment comprises the following steps:

[0044] 1) Weigh 2.42 g (10 mmol) of sodium molybdate dihydrate into a vial, add 10 mL of deionized water, and connect to an ice-water bath at 0.1°C. After dissolution, add 12 mL of 30% hydrogen peroxide dropwise. Stir continuously and add concentrated hydrochloric acid dropwise until a light yellow color forms. 11 Solution, at this time the pH value of the solution is approximately between 3 and 4.

[0045] 2) 2.31 g (10 mmol) of 1-vinyl-3-butylimidazolium bromide ([VBIm]Br) was added to 0.0693 g of azobisisobutyronitrile (AIBN) under a nitrogen atmosphere at 70°C for 24 h to obtain P[VBIm]Br. After the polymerization was completed, the solution was transferred to 15 mL of ethanol solution and dissolved at 50°C to form a P[VBIm]Br solution.

[0046] 3) P[VBIm]Br solution was added dropwise to the H2Mo2O 11 After the reaction is complete, a yellow solid is formed in the solution. The solution is filtered, washed three times with deionized water, and dried in vacuo at 50°C for 6 h. After drying, the solid is ground to obtain powder P[VBIm]2Mo2O 11.

[0047] 4) Take 0.2328g P[VBIm]2Mo2O 11 Dissolve in 15 mL of methanol at 50 °C, stir for 20 min to form a light yellow solution, and add the solution dropwise to 13 mL of deionized water.

[0048] 5) 1 mL of tetraethyl orthosilicate (TEOS) was added dropwise to the solution in step (4), and 0.5 mL of aqueous ammonia (NH3·H2O) was added to the solution using a pipette. The solution was stirred at 600 rpm for 30 min until a gel appeared, and then allowed to stand for 30 min.

[0049] 6) The solution of step (5) was filtered, washed with deionized water 3 times, dried under vacuum at 50°C for 6 h, and ground to obtain powder P[VBIm]2Mo2O 11 -SiO2.

[0050] 7) P[VBIm]2Mo2O 11 -SiO2 powder was placed in a programmed temperature muffle furnace, heated to 300°C at a heating rate of 5°C / min, maintained at 300°C in the muffle furnace for calcination for 6 hours, and completely cooled to obtain a molybdate-loaded mesoporous silica composite material.

[0051] Example 3

[0052] The preparation method of the molybdate-loaded mesoporous silica composite material of this embodiment comprises the following steps:

[0053] 1) Weigh 2.42 g (10 mmol) of sodium molybdate dihydrate into a vial, add 10 mL of deionized water, and connect to an ice-water bath at 0.1°C. After dissolution, add 12 mL of 30% hydrogen peroxide dropwise. Stir continuously and add concentrated hydrochloric acid dropwise until a light yellow color forms. 11 Solution, at this time the pH value of the solution is approximately between 3 and 4.

[0054] 2) 2.31 g (10 mmol) of 1-vinyl-3-butylimidazolium bromide ([VBIm]Br) was added to 0.0693 g of azobisisobutyronitrile (AIBN) under a nitrogen atmosphere at 70°C for 24 h to obtain P[VBIm]Br. After the polymerization was completed, the solution was transferred to 15 mL of ethanol solution and dissolved at 50°C to form a P[VBIm]Br solution.

[0055] 3) P[VBIm]Br solution was added dropwise to the H2Mo2O 11 After the reaction is complete, a yellow solid is formed in the solution. The solution is filtered, washed three times with deionized water, and dried in vacuo at 50°C for 6 h. After drying, the solid is ground to obtain powder P[VBIm]2Mo2O11 .

[0056] 4) Take 0.2328g P[VBIm]2Mo2O 11 Dissolve in 15 mL of methanol at 50 °C, stir for 20 min to form a light yellow solution, and add the solution dropwise to 13 mL of deionized water.

[0057] 5) 1 mL of tetraethyl orthosilicate (TEOS) was added dropwise to the solution in step (4), and 0.5 mL of aqueous ammonia (NH3·H2O) was added to the solution using a pipette. The solution was stirred at 600 rpm for 30 min until a gel appeared, and then allowed to stand for 30 min.

[0058] 6) The solution of step (5) was filtered, washed with deionized water 3 times, dried under vacuum at 50°C for 6 h, and ground to obtain powder P[VBIm]2Mo2O 11 -SiO2.

[0059] 7) P[VBIm]2Mo2O 11 -SiO2 powder was placed in a programmed temperature muffle furnace, heated to 500°C at a heating rate of 5°C / min, maintained at 500°C in the muffle furnace for calcination for 6 hours, and completely cooled to obtain a molybdate-loaded mesoporous silica composite material.

[0060] Example 4

[0061] The preparation method of the molybdate-loaded mesoporous silica composite material of this embodiment comprises the following steps:

[0062] 1) Weigh 2.42 g (10 mmol) of sodium molybdate dihydrate into a vial, add 10 mL of deionized water, and connect to an ice-water bath at 0.1°C. After dissolution, add 12 mL of 30% hydrogen peroxide dropwise. Stir continuously and add concentrated hydrochloric acid dropwise until a light yellow color forms. 11 Solution, at this time the pH value of the solution is approximately between 3 and 4.

[0063] 2) 2.31 g (10 mmol) of 1-vinyl-3-butylimidazolium bromide ([VBIm]Br) was added to 0.0693 g of azobisisobutyronitrile (AIBN) under a nitrogen atmosphere at 70°C for 24 h to obtain P[VBIm]Br. After the polymerization was completed, the solution was transferred to 15 mL of ethanol solution and dissolved at 50°C to form a P[VBIm]Br solution.

[0064] 3) P[VBIm]Br solution was added dropwise to the H2Mo2O 11After the reaction is complete, a yellow solid is formed in the solution. The solution is filtered, washed three times with deionized water, and dried in vacuo at 50°C for 6 h. After drying, the solid is ground to obtain powder P[VBIm]2Mo2O 11 .

[0065] 4) Take 0.2328g P[VBIm]2Mo2O 11 Dissolve in 15 mL of methanol at 50 °C, stir for 20 min to form a light yellow solution, and add the solution dropwise to 26 mL of deionized water.

[0066] 5) 2 mL of tetraethyl orthosilicate (TEOS) was added dropwise to the solution in step (4), and 0.5 mL of aqueous ammonia (NH3·H2O) was added to the solution using a pipette. The solution was stirred at 600 rpm for 30 min until a gel appeared, and then allowed to stand for 30 min.

[0067] 6) The solution of step (5) was filtered, washed with deionized water 3 times, dried under vacuum at 50°C for 6 h, and ground to obtain powder P[VBIm]2Mo2O 11 -SiO2.

[0068] 7) P[VBIm]2Mo2O 11 -SiO2 powder was placed in a programmed temperature muffle furnace, heated to 400°C at a heating rate of 5°C / min, maintained at 400°C in the muffle furnace for calcination for 6 hours, and completely cooled to obtain a molybdate-loaded mesoporous silica composite material.

[0069] Example 5

[0070] The preparation method of the molybdate-loaded mesoporous silica composite material of this embodiment comprises the following steps:

[0071] 1) Weigh 2.42 g (10 mmol) of sodium molybdate dihydrate into a vial, add 10 mL of deionized water, and connect to an ice-water bath at 0.1°C. After dissolution, add 12 mL of 30% hydrogen peroxide dropwise. Stir continuously and add concentrated hydrochloric acid dropwise until a light yellow color forms. 11 Solution, at this time the pH value of the solution is approximately between 3 and 4.

[0072] 2) 2.31 g (10 mmol) of 1-vinyl-3-butylimidazolium bromide ([VBIm]Br) was added to 0.1386 g of azobisisobutyronitrile (AIBN) at 70°C under a nitrogen atmosphere and self-polymerized for 24 h to obtain P[VBIm]Br. After the polymerization was completed, the solution was transferred to 15 mL of ethanol solution and dissolved at 50°C to form a P[VBIm]Br solution.

[0073] 3) P[VBIm]Br solution was added dropwise to the H2Mo2O11 After the reaction is complete, a yellow solid is formed in the solution. The solution is filtered, washed three times with deionized water, and dried in vacuo at 50°C for 6 h. After drying, the solid is ground to obtain powder P[VBIm]2Mo2O 11 .

[0074] 4) Take 0.0832g P[VBIm]2Mo2O 11 Dissolve in 15 mL of methanol at 50 °C, stir for 20 min to form a light yellow solution, and add the solution dropwise to 26 mL of deionized water.

[0075] 5) 2 mL of tetraethyl orthosilicate (TEOS) was added dropwise to the solution in step (4), and 0.5 mL of aqueous ammonia (NH3·H2O) was added to the solution using a pipette. The solution was stirred at 600 rpm for 30 min until a gel appeared, and then allowed to stand for 30 min.

[0076] 6) The solution of step (5) was filtered, washed with deionized water 3 times, dried under vacuum at 50°C for 6 h, and ground to obtain powder P[VBIm]2Mo2O 11 -SiO2.

[0077] 7) P[VBIm]2Mo2O 11 -SiO2 powder was placed in a programmed temperature muffle furnace, heated to 400°C at a heating rate of 5°C / min, maintained at 400°C in the muffle furnace for calcination for 6 hours, and completely cooled to obtain a molybdate-loaded mesoporous silica composite material.

[0078] Example 6

[0079] The molybdate-supported mesoporous silica composites obtained in Examples 1-5 were used to catalytically remove sulfur compounds from oil bottles. The specific process was as follows: 4 mg of powdered catalyst, 40 μL of 30% H₂O₂, and 5 mL of a model oil with a sulfur content of 500 ppm were added to a homemade double-necked flask equipped with a reflux condenser. The mixture was heated and stirred in a water bath at 60°C. After the reaction was complete, the solution was allowed to stand until the catalyst completely settled to the bottom layer of the oil. The upper oil phase was collected and the sulfur content in the oil was quantitatively analyzed by GC.

[0080] Taking dibenzothiophene (DBT) as an example, the reaction formula is:

[0081]

[0082] Table 1 shows the efficiency of DBT removal under the above conditions for Examples 1 to 5.

[0083] Table 1. Catalytic activity of catalysts synthesized under different conditions for the oxidation of DBT

[0084] Catalyst type Desulfurization rate (%) Example 1 100 Example 2 95.47 Example 3 84.04 Example 4 94.15 Example 5 89.14

Claims

1. A method for preparing a molybdate-loaded mesoporous silica composite material, characterized in that: The steps include: A. Dissolve molybdate in a bottle filled with deionized water, keep stirring in a low-temperature water bath, and dropwise add hydrogen peroxide and concentrated hydrochloric acid to deeply oxidize the molybdate to obtain a solution containing a molybdenum metal source; B. self-polymerizing the ionic liquid under a nitrogen atmosphere for 23-25 ​​hours, and dissolving the resulting polyionic liquid in ethanol to form a polyionic liquid solution; C. Add the solution obtained in step A dropwise to the solution obtained in step B, complete the reaction to obtain a solid precipitate, filter, wash, dry, and grind to obtain a powder; D. Dissolve the powder obtained in step C in methanol, and then add deionized water dropwise to obtain a prepared solution; E. Add the silicon source dropwise to the prepared solution obtained in step D, and then add aqueous ammonia to the prepared solution while stirring to hydrolyze the silicon source; F. Filtering, washing, drying, and grinding the solution treated in step E into a powdery state to obtain a solid powder; G. The solid powder obtained in step F was calcined in a programmed temperature muffle furnace to 300, 400, 500 o C, maintaining constant temperature calcination for 3-5 hours to obtain a molybdate-loaded mesoporous silica composite material; In the step B, the ionic liquid is 1-vinyl-3-butylimidazolium bromide ([VBIm]Br), and the molar ratio of the ionic liquid to ethanol is 1:

26.

2. The method for preparing the molybdate-loaded mesoporous silica composite material according to claim 1, wherein: In step A, the molybdate is Na2MoO4·2H2O, the molar ratio of Na2MoO4·2H2O to hydrogen peroxide is 10:12.88, the stirring speed is 600 rpm, and the low temperature water bath is 0-1 o C.

3. The method for preparing the molybdate-loaded mesoporous silica composite material according to claim 1, wherein: In step E, the silicon source is tetraethyl orthosilicate; the molar ratio of tetraethyl orthosilicate, ammonia water, and the powder obtained in step C is 2:3:0.1, and the stirring speed is 600 rpm.

4. The method for preparing the molybdate-loaded mesoporous silica composite material according to claim 1, wherein: In step G, the programmed heating rate is 5 o C / min.

5. The method for preparing the molybdate-loaded mesoporous silica composite material according to claim 1, wherein: The molybdate-loaded mesoporous silica composite material has a mesoporous structure.

6. Use of a molybdate-supported mesoporous silica composite material prepared by the method for preparing a molybdate-supported mesoporous silica composite material according to any one of claims 1 to 5 in catalytic oxidative desulfurization to remove sulfur compounds from oil products, characterized in that: To catalytically remove aromatic sulfides and aliphatic sulfides from fuel, the oxidation reaction of dibenzothiophene (DBT) is used. The reaction process can be expressed as follows: 。

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