An ionic liquid modified bismuth molybdate catalyst, a preparation method and application thereof

Abstract

The application relates to a kind of ionic liquid modified bismuth molybdate catalyst and its preparation method and application, comprising: dissolving metal bismuth salt and sodium molybdate in deionized water, then adding quaternary ammonium salt and ammonium molybdate to obtain a mixed solution; the mixed solution of step 1 is subjected to ultrasonic oscillation treatment, and then continuously stirred until the solute is completely dissolved to carry out hydrothermal reaction to obtain a reaction product; the reaction product of step 2 is subjected to centrifugal separation, then washed with anhydrous ethanol and deionized water, and dried to obtain the ionic liquid modified bismuth molybdate catalyst; by using ionic liquid to modify and control bismuth molybdate, the modification of ionic liquid makes the lipophilicity of bismuth molybdate increase, thereby increasing the contact of catalyst with oxidant and oil phase, which can better carry out solid-water-oil three-phase catalytic reaction, can deeply remove aliphatic sulfide or aromatic sulfide in diesel at a lower temperature (50 DEG C), especially the removal rate of dibenzothiophene (DBT) can reach 100%, and the effect is excellent.

Description

Technical Field

[0001] This invention relates to the field of diesel desulfurization technology, and in particular to an ionic liquid modified bismuth molybdate catalyst, and further to the preparation method of the catalyst and its application in catalytic oxidation desulfurization of diesel. Background Technology

[0002] Currently, the main desulfurization processes used in industrial applications are hydrodesulfurization (HDS) and oxidative desulfurization (ODS). HDS has high removal efficiency for simple sulfides, but it struggles with complex thiophene compounds. Furthermore, HDS requires high-temperature and high-pressure reaction conditions, resulting in high process costs. Oxidative desulfurization, on the other hand, offers a gentle and efficient process with high desulfurization efficiency. It also utilizes a wide variety of catalysts, allowing for high design flexibility. The catalyst's state can be adjusted according to actual production needs to achieve deep desulfurization, making it considered one of the most promising technologies.

[0003] Binary metal oxides have attracted widespread attention in catalytic oxidation due to their environmental friendliness, low cost, and abundant resources. Among them, Bi₂MoO₆ has become a research hotspot in environmental remediation and energy production due to its high catalytic activity and stability. Although bismuth molybdate catalysts exhibit certain catalytic activity, their poor lipophilicity and small specific surface area hinder the direct contact between aromatic sulfides and the catalyst, limiting their use in oxidative desulfurization. Therefore, modification treatment is needed to further improve the catalytic performance of Bi₂MoO₆.

[0004] As is well known, using organic modifiers as electron donors or absorbers to induce electronic effects is an important method for heterogeneous catalysts. Among them, surface modification with ionic liquids is an efficient method that alters the electronic effects and physical properties of the catalyst by combining the catalyst host with the ionic liquid. However, there are few reports on the application of bismuth molybdate as the host structure for surface modification and control in the field of diesel oxidative desulfurization. Therefore, it is necessary to provide a new technical solution to overcome the above-mentioned shortcomings. Summary of the Invention

[0005] The purpose of this invention is to provide an ionic liquid-modified bismuth molybdate catalyst that can effectively solve the above-mentioned technical problems, as well as its preparation method and application.

[0006] To achieve the objectives of this invention, the following technical solution is adopted:

[0007] A method for preparing an ionic liquid-modified bismuth molybdate catalyst includes the following steps:

[0008] Step 1: Dissolve the bismuth metal salt and sodium molybdate in deionized water, then add the quaternary ammonium salt and ammonium molybdate to obtain a mixed solution;

[0009] Step 2: The mixed solution from Step 1 is subjected to ultrasonic vibration, and then stirred continuously until the solute is completely dissolved before undergoing a hydrothermal reaction to obtain the reaction product.

[0010] Step 3: Centrifuge the reaction product from Step 2, then wash with anhydrous ethanol and deionized water, and dry to obtain the ionic liquid modified bismuth molybdate catalyst.

[0011] Preferably, the bismuth salt in step 1 is selected from at least one of bismuth nitrate and bismuth chloride.

[0012] Preferably, the quaternary ammonium salt in step 1 is selected from one of hexadecyltrimethylammonium bromide (CTAB), tetramethylammonium chloride (TMAC), and dioctadecyldimethylammonium chloride (DODMAC).

[0013] Preferably, the molar mass ratio of bismuth salt, sodium molybdate, and ammonium molybdate in the mixed solution of step 2 is (1-100):(1-100):(2-10).

[0014] Preferably, the temperature of the hydrothermal reaction in step 2 is 160℃~180℃, and the reaction time is 8~24h.

[0015] Furthermore, the present invention also provides an ionic liquid-modified bismuth molybdate catalyst prepared by the method described above; and further provides the application of the ionic liquid-modified bismuth molybdate catalyst in catalytic oxidation desulfurization of diesel fuel.

[0016] Preferably, the method for using the ionic liquid-modified bismuth molybdate catalyst for catalytic oxidation desulfurization of diesel is as follows: First, the ionic liquid-modified bismuth molybdate catalyst is placed in a diesel oil phase containing aliphatic sulfides or aromatic sulfides, an oxidant is added, and the reaction is stirred for 30 to 90 minutes at a temperature of 40 to 70°C and a stirring speed of 400 to 1000 rpm. The upper oil phase after the reaction is completed is the desulfurized oil.

[0017] Preferably, the oxidant is hydrogen peroxide, and the ratio of hydrogen peroxide to diesel oil phase is (6.4-64 μL):(5-20 mL).

[0018] Preferably, the sulfur content in the diesel oil phase is 10-1000 ppm; the ratio of the ionic liquid modified bismuth molybdate catalyst to the diesel oil phase is (0.01-0.5 g):(5-20 mL).

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. This invention modifies and regulates bismuth molybdate using ionic liquids. The modification with ionic liquids increases the lipophilicity of bismuth molybdate, thereby increasing the contact between the catalyst, oxidant, and oil phase. This enables better solid-water-oil three-phase catalytic reaction and allows for deep removal of aliphatic or aromatic sulfides from diesel fuel at a relatively low temperature (50°C). In particular, the removal rate of dibenzothiophene (DBT) can reach 100%, demonstrating excellent performance.

[0021] 2. The ionic liquid modified bismuth molybdate of the present invention has the advantages of high activity and easy separation of heterogeneous catalysts. Its activity remains basically unchanged after multiple cycles, and its cycle performance is excellent. It can achieve ultra-deep desulfurization and improve oil recovery rate. At the same time, no other by-products are generated during the desulfurization process, which is green and environmentally friendly.

[0022] 3. The ionic liquid modified bismuth molybdate catalyst of the present invention is synthesized by a simple one-step hydrothermal method. No pressure equipment is required during the reaction process. The operation is simple, the reaction conditions are mild, and it is harmless to the environment. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0024] Figure 1 A contact angle characterization diagram of an ionic liquid-modified bismuth molybdate catalyst provided for this invention;

[0025] Figure 2 X-ray diffraction and Fourier transform infrared spectra of an ionic liquid-modified bismuth molybdate catalyst provided by the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0027] Unless otherwise specified, all materials and reagents used in this invention are commercially available.

[0028] The present invention provides an ionic liquid-modified bismuth molybdate catalyst, the preparation method of which includes the following steps:

[0029] Step 1: Dissolve the bismuth metal salt and sodium molybdate in deionized water, then add the quaternary ammonium salt and ammonium molybdate to obtain a mixed solution;

[0030] Step 2: The mixed solution from Step 1 is subjected to ultrasonic vibration, and then stirred continuously until the solute is completely dissolved before undergoing a hydrothermal reaction to obtain the reaction product.

[0031] Step 3: Centrifuge the reaction product from Step 2, then wash with anhydrous ethanol and deionized water, and dry to obtain the ionic liquid modified bismuth molybdate catalyst.

[0032] The bismuth salt in step 1 is selected from at least one of bismuth nitrate and bismuth chloride; the quaternary ammonium salt in step 1 is selected from at least one of CTAB, TMAC, and DODMAC; the molar mass ratio of bismuth salt, sodium molybdate, and ammonium molybdate in the mixed solution in step 1 is (1-100):(1-100):(2-10); the volume of deionized water added in step 1 is 40-80 mL; the hydrothermal reaction temperature in step 2 is 160℃-180℃, and the reaction time is 8-24 h.

[0033] like Figure 1 and Figure 2 As shown, contact angle, XRD and FT-IR characterization techniques indicate that the bismuth molybdate structure of the ionic liquid-modified bismuth molybdate catalyst prepared by the above method remains unchanged and contains characteristic absorption peaks of ionic liquids. The hydrophilicity of the catalyst decreases, indicating that the catalyst was successfully synthesized.

[0034] The ionic liquid-modified bismuth molybdate catalyst prepared based on the above method can be used for catalytic oxidation desulfurization of diesel fuel. The method for catalytic oxidation desulfurization of diesel fuel is as follows: First, the ionic liquid-modified bismuth molybdate catalyst is placed in a diesel fuel phase containing aliphatic sulfides or aromatic sulfides, hydrogen peroxide is added, and the reaction is stirred for 30-90 minutes at a temperature of 40-70℃ and a stirring speed of 400-1000 rpm. The upper oil phase after the reaction is completed is the desulfurized oil product. Finally, the catalyst can be separated by standing or centrifugation.

[0035] Specifically, in the above desulfurization method, the sulfur content in the diesel oil phase is 10-1000 ppm; the ratio of the ionic liquid modified bismuth molybdate catalyst to the diesel oil phase is (0.01-0.5 g):(5-20 mL); the aliphatic sulfide or aromatic sulfide includes, but is not limited to, dibenzothiophene (DBT), 4-methyldibenzothiophene (4-DMDBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT).

[0036] After desulfurization, the sulfur content in the original diesel oil phase and the desulfurized oil was analyzed by gas chromatography to calculate the desulfurization rate. The formula for calculating the desulfurization rate is as follows: Desulfurization rate = (1 - residual sulfur content in the oil / total sulfur content in the oil) × 100%.

[0037] Example 1

[0038] (1) Preparation of catalyst IL-BMO-1: 0.1 mmol sodium molybdate and 0.2 mmol bismuth nitrate were dissolved in 40 mL deionized water, 0.23 g CTAB and 0.05 mmol ammonium molybdate were added and stirred thoroughly to obtain a mixed solution. The solution was then dissolved by ultrasonic vibration and hydrothermal treatment at 180 °C for 16 h. After the reaction was completed, the solution was separated by centrifugation. The solution was washed with ethanol and dried to obtain IL-BMO-1.

[0039] (2) Preparation of model oil: Dibenzothiophene (DBT) was dissolved in dodecane, and hexadecane was used as an internal standard to prepare model oil with a sulfur content of 200 ppm.

[0040] (3) Oxidative desulfurization: 5 mL of DBT-containing model oil (sulfur content 200 ppm) and 0.01 g of catalyst IL-BMO-1 were added sequentially to a custom-made sleeve bottle and placed in a water bath at 50°C. After stirring thoroughly for 5 min with a magnetic stirrer, 16 μL of H2O2 was added as an oxidant. After reacting for 60 min at a stirring speed of 600 rpm, the desulfurization rate reached 100%.

[0041] Example 2

[0042] (1) Preparation of catalyst IL-BMO-2: 5 mmol sodium molybdate and 10 mmol bismuth nitrate were dissolved in 80 mL deionized water, and 0.23 g TMAC and 1.25 mmol ammonium molybdate were added and stirred thoroughly to obtain a mixed solution. The solution was then dissolved by ultrasonic vibration and hydrothermally heated at 160 °C for 24 h. After the reaction was completed, the solution was separated by centrifugation; washed with ethanol and dried to obtain IL-BMO-2.

[0043] (2) Preparation of model oil: 4-methyldibenzothiophene (4-MDBT) was dissolved in dodecane and hexadecane was used as an internal standard to prepare model oil with a sulfur content of 10 ppm.

[0044] (3) Oxidative desulfurization: 20 mL of model oil containing 4-MDBT (sulfur content 10 ppm) and 0.1 g of catalyst IL-BMO-2 were added sequentially to a custom-made sleeve bottle and placed in a water bath at 60°C. After stirring thoroughly for 5 min with a magnetic stirrer, 6.4 μL of H2O2 was added as an oxidant. After reacting for 60 min at a stirring speed of 800 rpm, the desulfurization rate reached 96.22%.

[0045] Example 3

[0046] (1) Preparation of catalyst IL-BMO-3: 1 mmol sodium molybdate and 2 mmol bismuth nitrate were dissolved in 80 mL deionized water, and 0.23 g DODMAC and 0.125 mmol ammonium molybdate were added and stirred thoroughly to obtain a mixed solution. The solution was then dissolved by ultrasonic vibration and hydrothermally heated at 180 °C for 8 h. After the reaction was completed, the solution was separated by centrifugation; washed with ethanol and dried to obtain IL-BMO-3.

[0047] (2) Preparation of model oil: 4,6-dimethyldibenzothiophene (4,6-DMDBT) was dissolved in dodecane and hexadecane was used as an internal standard to prepare a model oil with a sulfur content of 500 ppm.

[0048] (3) Oxidative desulfurization: 1 mL of model oil containing 4,6-DMDBT (sulfur content 500 ppm) and 1 g of catalyst IL-BMO-2 were added sequentially to a custom-made sleeve bottle and placed in a water bath at 70°C. After stirring thoroughly for 5 min with a magnetic stirrer, 32 μL of H2O2 was added as an oxidant. After reacting for 60 min at a stirring speed of 600 rpm, the desulfurization rate reached 94.42%.

[0049] Example 4

[0050] (1) Preparation of catalyst IL-ZMO: 0.1 mmol sodium molybdate and 0.1 mmol zinc nitrate were dissolved in 40 mL deionized water, and 0.23 g CTAB and 0.05 mmol ammonium molybdate were added and stirred thoroughly to obtain a mixed solution. The solution was then dissolved by ultrasonic vibration and hydrothermally heated at 180 °C for 16 h. After the reaction was completed, the solution was separated by centrifugation; washed with ethanol and dried to obtain IL-ZMO.

[0051] (2) Preparation of model oil: Dibenzothiophene (DBT) was dissolved in dodecane, and hexadecane was used as an internal standard to prepare model oil with a sulfur content of 200 ppm.

[0052] (3) Oxidative desulfurization: 5 mL of DBT-containing model oil (sulfur content 200 ppm) and 0.01 g of catalyst IL-ZMO were added sequentially to a custom-made sleeve bottle and placed in a water bath at 50°C. After stirring thoroughly for 5 min with a magnetic stirrer, 16 μL of H2O2 was added as an oxidant. After reacting for 60 min at a stirring speed of 600 rpm, the desulfurization rate reached 82.73%.

[0053] Comparative Example

[0054] (1) Preparation of catalyst BMO: 0.1 mmol sodium molybdate and 0.1 mmol zinc nitrate were dissolved in 40 mL deionized water and dissolved completely by ultrasonic vibration. The mixture was then hydrothermally heated at 180 °C for 16 h. After the reaction was completed, the mixture was separated by centrifugation; washed with ethanol and dried to obtain BMO.

[0055] (2) Preparation of model oil: Dibenzothiophene (DBT) was dissolved in dodecane, and hexadecane was used as an internal standard to prepare model oil with a sulfur content of 200 ppm.

[0056] (3) Oxidative desulfurization: 5 mL of DBT-containing model oil (sulfur content 200 ppm) and 0.01 g of catalyst BMO were added sequentially to a custom-made sleeve bottle and placed in a water bath at 50°C. After stirring thoroughly for 5 min with a magnetic stirrer, 16 μL of H2O2 was added as an oxidant. After reacting for 60 min at a stirring speed of 600 rpm, the desulfurization rate reached 52.26%.

[0057] As can be seen from the data in Examples 1-4 above, the ionic liquid modified catalyst of the present invention exhibits good catalytic performance and good cycle performance in the process of diesel catalytic oxidation desulfurization.

[0058] The various modifications described in these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

Claims

1. Use of an ionic liquid-modified bismuth molybdate catalyst in the catalytic oxidation desulfurization of diesel fuel, characterized in that: The method for using the ionic liquid-modified bismuth molybdate catalyst for catalytic oxidation desulfurization of diesel is as follows: First, the ionic liquid-modified bismuth molybdate catalyst is placed in a diesel oil phase containing aliphatic sulfides or aromatic sulfides, an oxidant is added, and the reaction is stirred for 30 to 90 minutes at a temperature of 40 to 70°C and a stirring speed of 400 to 1000 rpm. The upper oil phase after the reaction is completed is the desulfurized oil. The oxidant is hydrogen peroxide, and the ratio of hydrogen peroxide to diesel oil phase is (6.4-64 μL):(5-20 mL); The sulfur content in the diesel oil phase is 10-1000 ppm; the ratio of the ionic liquid modified bismuth molybdate catalyst to the diesel oil phase is (0.01-0.5 g):(5-20 mL); The preparation method of ionic liquid-modified bismuth molybdate catalyst is as follows: Step 1: Dissolve the bismuth metal salt and sodium molybdate in deionized water, then add the quaternary ammonium salt and ammonium molybdate to obtain a mixed solution; Step 2: The mixed solution from Step 1 is subjected to ultrasonic vibration, and then stirred continuously until the solute is completely dissolved before undergoing a hydrothermal reaction to obtain the reaction product. Step 3: Centrifuge the reaction product from Step 2, then wash it with anhydrous ethanol and deionized water, and dry it to obtain the ionic liquid modified bismuth molybdate catalyst. The quaternary ammonium salt in step 1 is selected from one of hexadecyltrimethylammonium bromide (CTAB), tetramethylammonium chloride (TMAC), and dioctadecyldimethylammonium chloride (DODMAC); In the mixed solution of step 2, the mass ratio of bismuth metal salt, sodium molybdate, and ammonium molybdate is (1-100):(1-100):(2-10); In step 2, the hydrothermal reaction temperature is 160℃~180℃, and the reaction time is 8~24h.

2. The application according to claim 1, characterized in that: The bismuth salt in step 1 is selected from at least one of bismuth nitrate and bismuth chloride.

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