CN109999873B

CN109999873B - A kind of preparation method and application of boron nitride supported molybdenum dioxide material

Info

Publication number: CN109999873B
Application number: CN201910172684.6A
Authority: CN
Inventors: 姚晓玉; 朱文帅; 王超; 何静; 吴沛文; 刘辉; 李华明
Original assignee: Jiangsu University
Current assignee: Jiangsu University
Priority date: 2019-03-07
Filing date: 2019-03-07
Publication date: 2022-05-17
Anticipated expiration: 2039-03-07
Also published as: CN109999873A

Abstract

The invention belongs to the field of heterogeneous catalysts, and relates to a preparation method of a boron nitride supported molybdenum dioxide material and its application in the oxidative desulfurization of fuel oil. The steps include: mixing and stirring boron nitride, molybdenum-based ionic liquid and dichloromethane, then vacuum filtration and drying to obtain a precursor; then placing the obtained precursor in a tube furnace and calcining at a high temperature in a nitrogen atmosphere for a certain period of time to obtain nitrogen Boronide supported molybdenum dioxide material. The process of the invention is simple, the material has high and lasting catalytic activity for the removal of sulfides in fuel oil, can effectively improve the desulfurization rate of oil products, reduce production costs, improve oil product quality, and can be recycled and reused to reduce environmental pollution.

Description

Preparation method and application of boron nitride loaded molybdenum dioxide material

Technical Field

The invention belongs to the field of heterogeneous catalysts, and particularly relates to a preparation method of a boron nitride loaded molybdenum dioxide material and application of the boron nitride loaded molybdenum dioxide material in fuel oil desulfurization.

Background

Environmental problems such as haze, acid rain and PM 2.5 are of great concern today. Sulfur oxides produced by the combustion of sulfur-containing fuel oil are one of the major sources of these environmental pollutants. The main purposes of reducing the sulfur content in fuel oil, improving the quality of the fuel oil and relieving the environmental pollution problem are the current fuel oil desulfurization. At present, the traditional industrial desulfurization technology is hydrodesulfurization, which requires harsh conditions such as high temperature, high pressure, hydrogen atmosphere and the like and has low activity on aromatic sulfides. The oxidative desulfurization method is considered to be one of the most promising desulfurization technologies due to mild reaction conditions, low energy consumption and high desulfurization efficiency. The catalyst commonly used in the oxidative desulfurization at present comprises organic acid, ionic liquid, polyoxometallate, transition metal oxide, molecular sieve and the like.

Transition Metal Oxides (TMO) have received a great deal of attention from various catalytic fields due to their unique electronic properties and relatively low cost (Small 2015,11, 1144-1149). However, bulk TMO (e.g., bulk molybdenum oxide) generally exhibits lower catalytic activity due to its fewer active sites and tendency to agglomerate. The loading can solve the problem well, so that it is very important to find a proper carrier to load the carrier. Recently, boron nitride (g-BN) has received increasing attention due to its large specific surface area and high chemical stability (angelw. chem., int. ed.2016,55, 10766-. Notably, several studies have shown that boron nitride has excellent adsorption capacity and can form high local concentrations of sulfide on the catalyst. Meanwhile, the boron nitride can generate a good synergistic effect with active sites on the catalyst, so that the catalytic performance of the catalyst is obviously improved.

At present, no relevant report is found on a boron nitride-supported molybdenum dioxide material.

Disclosure of Invention

The invention aims to solve the technical problem of providing a boron nitride loaded molybdenum dioxide catalyst, and a preparation method and application thereof in fuel oil oxidation desulfurization.

In order to solve the above technical problem (i.e. the above mentioned background art problem), the technical solution adopted by the present invention is as follows: a boron nitride supported molybdenum dioxide catalyst is prepared by taking molybdenum-based ionic liquid as a molybdenum source, taking boric acid and urea as a boron source and a nitrogen source to prepare boron nitride as a carrier, and then combining an impregnation method with high-temperature calcination.

The preparation method of the boron nitride supported molybdenum dioxide catalyst comprises the following steps:

(1) preparation of boron nitride g-BN and molybdenum-based Ionic liquids (C) separately₁₆mim)₂Mo₂O₁₁And is ready for use;

(2) proportionally mixing the boron nitride obtained in the step (1) and the molybdenum-based ionic liquid (C)₁₆mim)₂Mo₂O₁₁Uniformly dispersing the mixture in dichloromethane, stirring for 1-4 h, and then performing vacuum filtration and drying;

(3) and (3) under the nitrogen atmosphere, heating the product obtained in the step (2) to the calcining temperature by a program in a tubular furnace, calcining at a high temperature, cooling, washing with deionized water, and drying to obtain the boron nitride loaded molybdenum dioxide material.

In the step (1), for preparing g-BN, the using amount ratio of boric acid to urea is 1:20, the solvent is ultrapure water, and the synthesis temperature is 50-60 ℃. In the step (1), the molybdenum-based ionic liquid (C)₁₆mim)₂Mo₂O₁₁Is obtained by the following method: adding 5mmol of NaMoO₄2H₂O is dissolved in 10mL of water, and 6mL of 30% H is added with stirring under ice-water bath conditions₂O₂Then, dilute hydrochloric acid was added dropwise to adjust the pH to 4.2. Then, 10mmol (C) is weighed₁₆mim) Cl was dissolved in 15mL of 95% ethanol, added to the above solution to obtain a white precipitate, filtered under reduced pressure, washed with 10mL of water and 10mL of diethyl ether, respectively, and the resulting solid was dried in a vacuum oven at 50 ℃ for 24 hours to obtain a pale yellow powder (C)₁₆mim)₂Mo₂O₁₁。

In the step (2), the boron nitride and the molybdenum-based ionic liquid (C)₁₆mim)₂Mo₂O₁₁The mass ratio of (A) to (B) is 3: 1.

In the step (3), the temperature programming rate is 5 ℃/min, the high-temperature calcination temperature is 500-700 ℃, and the time is 1-5 h.

In the step (3), the washing and drying process is to wash the fabric with deionized water for three times and then place the fabric in a vacuum drying oven at 50 ℃ for drying for 12 hours.

The boron nitride loaded molybdenum dioxide material prepared by the invention is used for removing aromatic sulfide in fuel oil by catalytic oxidation. The boron nitride loaded molybdenum dioxide as the catalyst has good stability, and the desulfurization rate can still reach 98% after the catalyst is recycled for 8 times.

The specific application method is as follows: respectively adding a certain amount of simulated oil and a certain amount of boron nitride loaded molybdenum dioxide catalyst into a self-made double-neck flask under the condition of stirring, and then adding 30 wt.% of H₂O₂And (3) carrying out oxidative desulfurization reaction on the solution under the water bath condition, standing the reaction mixture after the reaction is finished, and carrying out solid-liquid separation to realize the separation of the catalyst and the fuel oil. Wherein, V (H)₂O₂) 24 mul, reaction time 90min, reaction temperature 60 ℃, catalyst amount 0.05g, oil amount 5 mL.

The boron nitride loaded molybdenum dioxide catalyst is used as a solid catalyst, is insoluble in oil products in the whole reaction process, has good lipophilicity, is beneficial to the contact of the catalyst and oil-containing substrates in the oil products, and improves the catalytic activity.

The invention has the beneficial effects that:

(1) the invention takes molybdenum-based ionic liquid as a molybdenum source for the first time to prepare the boron nitride loaded molybdenum dioxide catalyst.

(2) The prepared catalyst has high catalytic activity and can efficiently remove sulfides in fuel oil in a short time.

(3) The catalyst and the oil product are not mutually soluble, the catalyst and the fuel oil are simply separated after the reaction is finished, and the catalyst can be circulated for many times.

(4) The environment-friendly hydrogen peroxide is selected as the oxidant, and in addition, the reaction condition is mild, and other organic solvents are not needed.

Drawings

FIG. 1 shows the molybdenum-based ionic liquid (C) obtained in example 1₁₆mim)₂Mo₂O₁₁TG-DTG picture of (1);

FIG. 2 is a scanning electron microscope and EDS pictures of the boron nitride support and boron nitride supported molybdenum dioxide catalyst of example 1;

FIG. 3 is a graph showing the removal efficiency of boron nitride supported molybdenum dioxide catalysts obtained in example 1 for different sulfur-containing substrates;

FIG. 4 is a graph showing the cycle effect of DBT removal of the boron nitride supported molybdenum dioxide catalyst obtained in example 1.

Detailed Description

The present invention is described by the following examples, but the present invention is not limited to the following examples, and variations and implementations are included in the technical scope of the present invention without departing from the spirit of the invention described above and below.

Formulation of the oils used in the following examples: dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT), 4, 6-dimethyldibenzothiophene (4,6-DMDBT) were dissolved in dodecane, respectively, to prepare a model oil having a sulfur content of 200 ppm.

Adding simulated oil and a catalyst into a self-made double-neck flask, magnetically stirring at a set water bath temperature, and adding hydrogen peroxide as an oxidant to react. The catalyst is kept insoluble in oil products in the reaction process, the catalyst and the oil products are separated by a simple dumping method after the reaction, the content of sulfide in the oil is detected by adopting gas chromatography (GC-FID), and the desulfurization rate is calculated according to the following formula:

example 1:

0.2g of synthesized boron nitride and 0.0688g (C) were taken₁₆mim)₂Mo₂O₁₁The ionic liquid is dissolved in 40mL dichloromethane, stirred for 1h at room temperature and then dried by suction filtration under reduced pressure. Then the dried powder is put into a tube furnace, the temperature is raised to 700 ℃ from the room temperature at the speed of 5 ℃/min, the temperature is kept for 1h under the nitrogen atmosphere, and then the powder is naturally cooled to the room temperature. And washing the collected powder with deionized water at 50 ℃ for three times, and drying in a vacuum drying oven for 12 hours to obtain the boron nitride supported molybdenum dioxide catalyst.

Example 2:

0.2g of synthesized boron nitride and 0.0688g (C) were taken₁₆mim)₂Mo₂O₁₁Dissolving the ionic liquid in 40mL of dichloromethane, stirring for 3h at room temperature, and then carrying out vacuum filtrationAnd (5) drying. Then the dried powder is put into a tube furnace, the temperature is raised to 600 ℃ from room temperature at the speed of 5 ℃/min, the temperature is kept for 2h under the nitrogen atmosphere, and then the powder is naturally cooled to the room temperature. And washing the collected powder with deionized water at 50 ℃ for three times, and drying in a vacuum drying oven for 12 hours to obtain the boron nitride supported molybdenum dioxide catalyst.

Example 3:

0.2g of synthesized boron nitride and 0.0688g (C) were taken₁₆mim)₂Mo₂O₁₁The ionic liquid is dissolved in 40mL dichloromethane, stirred for 4h at room temperature and then dried by suction filtration under reduced pressure. Then the dried powder is put into a tube furnace, the temperature is raised to 500 ℃ from the room temperature at the speed of 5 ℃/min, the powder is kept for 5h under the nitrogen atmosphere, and then the powder is naturally cooled to the room temperature. And washing the collected powder with deionized water at 50 ℃ for three times, and drying in a vacuum drying oven for 12 hours to obtain the boron nitride supported molybdenum dioxide catalyst.

Example 4:

the sulfide (dibenzothiophene) content in the oil was 200ppm, 0.05g of the boron nitride-supported molybdenum dioxide catalyst prepared in example 1, 5mL of the oil, stirring with a magnetic stirrer, and 24. mu.L of 30 wt.% H₂O₂And (3) reacting the solution at the reaction temperature of 60 ℃ for 60min, and pouring out the upper sulfur-free oil after the catalyst is precipitated to the bottom layer, wherein the desulfurization rate reaches 100%.

Example 5:

the oil product had a sulfide (dibenzothiophene) content of 200ppm, 0.05g of the boron nitride-supported molybdenum dioxide catalyst prepared in example 2, 5mL of a simulated oil, stirred with a magnetic stirrer, and 24. mu.L of 30 wt.% H₂O₂The solution reacts for 60min at the reaction temperature of 60 ℃, and after the catalyst is precipitated to the bottom layer, the oil without sulfur in the upper layer is poured out, and the desulfurization rate reaches 87.4%.

Example 6:

the oil product had a sulfide (dibenzothiophene) content of 200ppm, 0.05g of the boron nitride-supported molybdenum dioxide catalyst prepared in example 3, 5mL of a simulated oil, stirred with a magnetic stirrer, and 24. mu.L of 30 wt.% H₂O₂Solutions ofReacting for 60min at the reaction temperature of 60 ℃, pouring out the oil without sulfur on the upper layer after the catalyst is precipitated to the bottom layer, and ensuring that the desulfurization rate reaches 66.4 percent.

Table 1 examples the results of the experiments are as follows

The catalytic activity results for different sulfur-containing substrates are shown in fig. 3, and it can be seen that the boron nitride-loaded molybdenum dioxide catalyst has higher removal efficiency for different sulfur-containing substrates.

After the oxidation desulfurization reaction is finished, the boron nitride loaded molybdenum dioxide catalyst is separated from the reaction phase, and then is recycled by a decantation separation mode, and then fresh H is added into the reactor₂O₂And carrying out next cycle experiment on the model oil product. The cyclic activity investigation result is shown in figure 4, and the result shows that the desulfurization activity is not obviously reduced after the catalyst is recycled for 8 times, deep desulfurization can still be achieved, and the desulfurization rate is 97.2%.

Claims

1. a preparation method of boron nitride supported molybdenum dioxide material, is characterized in that, adopts following steps to prepare:

(1) respectively preparing boron nitride g-BN and molybdenum-based ionic liquid (C ₁₆ mim) ₂ Mo ₂ O ₁₁ for use;

The molybdenum-based ionic liquid (C ₁₆ mim) ₂ Mo ₂ O ₁₁ was obtained by the following method: 5 mmol NaMoO ₄ .2H ₂ O was dissolved in 10 mL of water, and 6 mL of 30% H ₂ O was added with stirring in an ice-water bath. _2. Then, dilute hydrochloric acid was added dropwise to adjust the pH to 4.2; 10 mmol (C ₁₆ mim) Cl was then weighed and dissolved in 15 mL of 95% ethanol, added to the solution obtained above to obtain a white precipitate, which was filtered under reduced pressure and filtered with 10 ml of water, respectively. Wash with 10 mL of diethyl ether, then dry the obtained solid in a vacuum drying oven at 50° C. for 24 h, and the obtained pale yellow powder is (C ₁₆ mim) ₂ Mo ₂ O ₁₁ ;

(2) uniformly dispersing the boron nitride and molybdenum-based ionic liquid (C ₁₆ mim) ₂ Mo ₂ O ₁₁ obtained in step (1) in dichloromethane in proportion to stir for 1 to 4 hours, then filter and dry under reduced pressure;

(3) Under a nitrogen atmosphere, the product obtained in step (2) is heated to a calcination temperature of 500-700° C. in a tube furnace, calcined at a high temperature for 1-5 hours, cooled, washed with deionized water and dried to obtain boron nitride. Loaded molybdenum dioxide material.

2. The preparation method of a boron nitride supported molybdenum dioxide material according to claim 1, wherein in step (2), the boron nitride and molybdenum-based ionic liquid (C ₁₆ mim) _The mass ratio of _2Mo2O11 is ₃ :1.

3 . The method for preparing a boron nitride supported molybdenum dioxide material according to claim 1 , wherein, in step (3), the temperature-programmed rate is 5° C./min. 4 .

4. the preparation method of a kind of boron nitride supported molybdenum dioxide material according to claim 1, is characterized in that, in step (3), described washing and drying process is to be placed in 50 after washing three times with deionized water ℃ vacuum drying oven for 12h.

5 . A boron nitride supported molybdenum dioxide material, prepared by the method according to any one of claims 1 to 4 .

6. Use of the boron nitride supported molybdenum dioxide material of claim 5 for catalytic oxidation to remove aromatic sulfides in fuel oil.