A heteroatomic molecular sieve confined molybdenum oxide catalyst and a preparation method thereof

Abstract

The present application relates to the technical fields of molecular sieve catalyst preparation and application, and particularly relates to a kind of heteroatomic molecular sieve confined molybdenum oxide catalyst and preparation method.The catalyst of the present application includes molecular sieve carrier, metal element implanted in molecular sieve skeleton and molybdenum oxide, and the implanted metal is Ta, Ti, V, Nb, Zr, Hf, Sn and the like.Beta topology structure heteroatomic molecular sieve is used as carrier, which has regular three-dimensional pore structure, larger specific surface area and excellent thermal stability, and the confinement effect of molybdenum oxide by molecular sieve rigid skeleton can resist sintering or loss of oxide, and molybdenum oxide and molecular sieve skeleton metal show synergistic catalytic effect.The obtained catalyst is used for oxidative desulfurization, and the sulfides in fuel oil are removed by catalytic oxidation method, which can realize deep and efficient desulfurization, and the catalyst can be recycled and reused, and shows good recycling property.The reaction condition is mild, the operation is simple, molecular oxygen is used as oxidant, and it has good application prospect.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve catalyst preparation and application technology, and in particular to a heteroatom molecular sieve confined molybdenum oxide catalyst and its preparation method. Background Technology

[0002] Currently, with the development of modern industrial systems, the demand for energy is constantly increasing. Although various new energy sources, including wind, solar, and hydrogen energy, are becoming increasingly popular, fuel oils such as gasoline and diesel remain one of the main energy sources. However, the combustion of organic sulfur compounds in fuel oil in engines leads to the emission of pollutants such as sulfur oxides. To address the pollution problem of sulfur oxides, many countries have established strict standards for the sulfur content in gasoline and diesel. Therefore, the development of new green fuel oil desulfurization technologies is urgently needed. Current desulfurization technologies mainly include hydrodesulfurization and non-hydrodesulfurization. Traditional hydrodesulfurization systems can effectively remove active sulfur such as mercaptans and hydrogen sulfide; however, due to steric hindrance, the removal effect on inactive sulfur such as benzothiophene, dibenzothiophene, and 4,6-dimethylbenzothiophene is not ideal. Compared with traditional hydrodesulfurization technologies, non-hydrodesulfurization technologies, such as adsorption desulfurization, extraction desulfurization, ultrasonic desulfurization, and oxidative desulfurization (ODS), can overcome the problems of high temperature, high pressure, large H2 consumption, and high requirements for reaction equipment associated with hydrodesulfurization. ODS (Optical Desulfurization) is considered a promising method due to its advantages such as mild reaction conditions, high desulfurization efficiency for aromatic sulfides, low cost, and lack of hydrogen requirement. These aromatic sulfides are oxidized to polar sulfoxides or sulfones by suitable oxidants, such as hydrogen peroxide, molecular oxygen, air, organic peroxy acids, or ozone, and then removed by extraction or adsorption. Therefore, research on ODS mainly focuses on constructing novel catalytic systems and selecting inexpensive and safe oxidants.

[0003] To date, various homogeneous and heterogeneous catalysts have been applied to ODS processes, including homogeneous catalysts such as peroxy organic acids, ionic liquids, and polyoxometalates. However, recovering homogeneous catalysts from the reaction system is difficult, and their recyclability is poor, severely limiting their industrial application. Chinese patent CN113713857A discloses a polyoxometalate oxidative desulfurization catalyst, its preparation method, and its application. The reaction results disclosed in the specification show that the desulfurization rate reaches 100%. However, the catalyst preparation steps are complex, requiring strong acid conditions (pH=1.5), and the catalyst is difficult to recover, which is detrimental to industrial production.

[0004] Building upon this foundation, heterogeneous catalysts have emerged, such as metal-organic frameworks, metal oxides, and metal clusters. MoO3 possesses abundant free electrons, enabling it to generate numerous unsaturated metal sites, readily reacting with oxidants to form electrophilic reaction intermediates, which is highly advantageous for the oxidation of aromatic sulfides. However, low loading of a single metal results in low catalytic activity, while high loading easily leads to agglomeration, pore blockage, and reduced metal atom utilization (Advanced Functional Materials, 2021, 31, 2100442). To improve activity, molybdenum oxide needs to be highly dispersed on a support. Molecular sieves possess periodically tunable pore structures, excellent thermal and chemical stability, and unique Lewis and... Acidic sites not only serve as heterogeneous catalysts but also as excellent supports. Chinese patent CN107777702B discloses a method for preparing a hierarchical porous heteroatom aluminum phosphate molecular sieve for oxidative desulfurization. The reaction results disclosed in the specification show that the catalyst achieves removal rates of thiophene, benzothiophene, and dibenzothiophene of 72.48%, 79.16%, and 84.67%, respectively. Chinese patent CN1583965A discloses a method for gasoline oxidative desulfurization using metal ion-modified titanium-silicon molecular sieves as catalysts. The desulfurization rates of modified titanium-silicon molecular sieve catalysts with different metal ion supports fluctuate significantly (3.0–96.4%), and the patent does not provide preparation processes for various supported catalysts. Chen et al. anchored the dual active sites of transition metals and heteropolyacids on the Beta molecular sieve support to improve the support utilization and enhance the oxidative desulfurization activity. However, the oxidant used in this process is tert-butyl hydroperoxide, which is expensive, has poor safety, and is not easy to transport (Applied Catalysis B: Environmental, 2022, 305, 121044).

[0005] Using heteroatom molecular sieves as supports for molybdenum oxide results in a synergistic effect, significantly enhancing the catalytic activity of ODS. However, if metal oxides are loaded onto the outer surface of the molecular sieve crystals, uneven dispersion of the active material can clog the pores of the support, reducing contact with reactants and decreasing activity; loss or sintering may also occur. Chinese patent CN102294236B discloses a method for preparing a supported Mo-based oxidative desulfurization catalyst. This catalyst requires an inert gas atmosphere to react, producing H2 and CH4, using expensive cumene peroxide as the oxidant, but the desulfurization rate is only 65-85%. Impregnation and ion exchange are the most commonly used methods for preparing molecular sieve-supported metal catalysts, but loss or sintering often occurs during the reaction, leading to unsatisfactory catalytic effects. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] The present invention aims to solve the technical problem that supported catalysts prepared by impregnation and ion exchange methods may be lost or sintered during the reaction process, resulting in unsatisfactory catalytic effects.

[0008] (II) Technical Solution

[0009] To solve the above technical problems, the present invention provides a heteroatom molecular sieve confined molybdenum oxidation catalyst, wherein the catalyst is nMoO3@M-Beta-y, the Mo loading n is 2-8wt%, and the Si to M molar ratio y is 30-200.

[0010] Secondly, this invention provides a method for preparing a heteroatom molecular sieve-confined molybdenum oxide catalyst. A metal element with variable valence characteristics is implanted into the molecular sieve framework via isomorphic substitution. Ligands stabilize the molybdenum species, restricting their movement under solvent-free conditions, thus confining molybdenum oxide in situ within the heteroatom molecular sieve. The specific steps of the preparation method are as follows: Preparation of a deeply dealufted Beta molecular sieve: The Beta molecular sieve is acid-washed, washed, and dried. The deeply dealufted Beta molecular sieve, template agent, metal salt, and water are mixed and treated at 110–160°C for 1 hour to obtain a mixed gel. The obtained mixed gel is mixed with a polyvinylpyrrolidone solution containing molybdenum salt and stirred evenly. Fluoride is added, and the mixture is dehydrated at 80°C for 8–12 hours until a dry gel is formed. It is then treated at 110–160°C for 12–24 hours. The product is filtered, washed, dried, and calcined at 550°C for 3–6 hours to obtain the nMoO3@M-Beta-y catalyst.

[0011] Furthermore, the implanted metal M is one or more of Ta, Ti, V, Nb, Zr, Hf, and Sn.

[0012] Furthermore, the pickling treatment uses nitric acid with a concentration of 6-11 mol / L, and the mass ratio of the silica-alumina type Beta molecular sieve to the nitric acid solution is 1:30-50; the pickling temperature is 80-130℃, the time is 6-12 hours, and the pickling treatment is repeated 2-3 times.

[0013] Furthermore, the molar ratio of SiO2 to template agent in the deep dealuded Beta molecular sieve is 1:0.2-0.7; the template agent is one or more of tetraethylammonium hydroxide and tetraethylammonium fluoride; the metal salt solution is one of metal chloride, nitrate, and organometallic salt.

[0014] Furthermore, fluorides are selected as mineralizing agents, wherein the fluorides are one or more of NH4F, HF, and NH4HF2; the molar ratio of SiO2 to fluorides in the deep dealuded Beta molecular sieve is 1:0.1 to 0.8; and the soluble molybdenum salt is one or more of ammonium heptamolybdate and ammonium molybdate.

[0015] Thirdly, the present invention provides an application of a heteroatom molecular sieve confined molybdenum oxidation catalyst, characterized by the following steps: preparing a eutectic solvent, treating p-toluenesulfonic acid and PEG2000 at a molar ratio of 1:2 at 80°C for 1 h; adding model oil to the eutectic solvent and extracting at 90°C for 0.5 h; adding a catalyst and an oxidant, and stirring to carry out the reaction.

[0016] Furthermore, the amount of eutectic solvent used is 4g.

[0017] Furthermore, the model oil is made by dissolving organic sulfides in decahydronaphthalene solvent, with a volume of 20 mL; the total sulfur content in the model oil is 500 μg / mL.

[0018] Furthermore, the oxidant is one or more of O2, H2O2, and O3; the temperature of the oxidative desulfurization reaction is 90℃, and the pressure is 1 atm.

[0019] (III) Beneficial Effects

[0020] The above-mentioned technical solution of the present invention has the following advantages: The catalyst of the present invention includes a molecular sieve support, a metal element implanted in the molecular sieve framework, and molybdenum oxide. The implanted metal is Ta, Ti, V, Nb, Zr, Hf, Sn, etc. Using a Beta topological heteroatom molecular sieve as the support, it possesses a regular three-dimensional pore structure, a large specific surface area, and excellent thermal stability. The rigid framework of the molecular sieve confines the molybdenum oxide, resisting sintering or loss of the oxide. Simultaneously, the molybdenum oxide and the molecular sieve framework metal exhibit a synergistic catalytic effect. The resulting catalyst is used for oxidative desulfurization, removing sulfides from fuel oil through catalytic oxidation, achieving deep and efficient desulfurization. The catalyst is recyclable and exhibits good recyclability. The reaction conditions are mild, the operation is simple, and molecular oxygen is used as the oxidant, showing promising application prospects. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0022] Figure 1 The X-ray diffraction pattern of the 2MoO3@M-Beta-50 molecular sieve catalyst in the embodiment of the present invention is shown below.

[0023] Figure 2 This is a scanning electron microscope image of the 2MoO3@Ta-Beta-50 molecular sieve catalyst in the embodiments of the present invention;

[0024] Figure 3 This is a transmission electron microscope image of the 2MoO3@Ta-Beta-50 molecular sieve catalyst in the embodiments of the present invention;

[0025] Figure 4 This is a line graph showing the desulfurization removal rate of 2MoO3@Ti-Beta-50 in an embodiment of the present invention.

[0026] Figure 5 This is a line graph showing the desulfurization removal rate of 2MoO3@Zr-Beta-50 in an embodiment of the present invention.

[0027] Figure 6 This is a line graph showing the desulfurization removal rate of 2MoO3@Sn-Beta-50 in an embodiment of the present invention.

[0028] Figure 7 This is a line graph showing the desulfurization removal rate of 2MoO3@Hf-Beta-50 in an embodiment of the present invention.

[0029] Figure 8 This is a line graph showing the desulfurization removal rate of 2MoO3@Nb-Beta-50 in an embodiment of the present invention.

[0030] Figure 9 This is a line graph showing the desulfurization removal rate of 2MoO3@Ta-Beta-50 in an embodiment of the present invention.

[0031] Figure 10 This is a line graph showing the desulfurization removal rate of 2MoO3@Ta-Beta-200 in an embodiment of the present invention.

[0032] Figure 11 This is a line graph showing the desulfurization removal rate of 2MoO3@Ta-Beta-30 in an embodiment of the present invention.

[0033] Figure 12 This is a line graph showing the desulfurization removal rate of 8MoO3@Ta-Beta-50 in an embodiment of the present invention.

[0034] Figure 13 This is a line graph showing the desulfurization removal rate of 2MoO3@Ta-Beta-50 in a cyclic experiment according to an embodiment of the present invention. Detailed Implementation

[0035] The specific embodiments of the present invention will be further described in detail below with reference to the examples. The detailed description of the following examples is only used to illustrate the technical solutions of the present invention and is not intended to limit the scope of protection of the present invention. That is, the present invention is not limited to the specific embodiments described in the examples, and covers any modifications, substitutions and improvements to the raw materials and means without departing from the spirit of the present invention.

[0036] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. The raw materials, equipment, etc., used in the following embodiments and experimental examples are all commercially available products.

[0037] Please refer to Figures 1-3 The present invention provides a heteroatom molecular sieve confined molybdenum oxidation catalyst, wherein the catalyst is nMoO3@M-Beta-y, the Mo loading n is 2-8 wt%, and the Si to M molar ratio y in the molecular sieve is 30-200.

[0038] Secondly, this invention provides a method for preparing a heteroatom molecular sieve-confined molybdenum oxide catalyst. A metal element with variable valence characteristics is implanted into the molecular sieve framework via isomorphic substitution. Ligands stabilize the molybdenum species, restricting their movement under solvent-free conditions, thus confining molybdenum oxide in situ within the heteroatom molecular sieve. The specific steps of the preparation method are as follows: Preparation of a deeply dealufted Beta molecular sieve: The Beta molecular sieve is acid-washed, washed, and dried. The deeply dealufted Beta molecular sieve, template agent, metal salt, and water are mixed and treated at 110–160°C for 1 hour to obtain a mixed gel. The obtained mixed gel is mixed with a polyvinylpyrrolidone solution containing molybdenum salt and stirred evenly. Fluoride is added, and the mixture is dehydrated at 80°C for 8–12 hours until a dry gel is formed. It is then treated at 110–160°C for 12–24 hours. The product is filtered, washed, dried, and calcined at 550°C for 3–6 hours to obtain the nMoO3@M-Beta-y catalyst.

[0039] In some embodiments, the implanted metal M is one or more of Ta, Ti, V, Nb, Zr, Hf, and Sn.

[0040] In some embodiments, the pickling treatment uses nitric acid with a concentration of 6-11 mol / L, and the mass ratio of the silica-alumina type Beta molecular sieve to the nitric acid solution is 1:30-50; the pickling temperature is 80-130°C, the time is 6-12 h, and the pickling treatment is repeated 2-3 times.

[0041] In some embodiments, the molar ratio of SiO2 to template agent in the deep dealuded Beta molecular sieve is 1:0.2-0.7; the template agent is one or more of tetraethylammonium hydroxide and tetraethylammonium fluoride; the metal salt solution is one of metal chloride, nitrate, and organometallic salt.

[0042] In some embodiments, fluorides are selected as mineralizing agents, wherein the fluorides are one or more of NH4F, HF, and NH4HF2; the molar ratio of SiO2 to fluoride in the deep dealuded Beta molecular sieve is 1:0.1 to 0.8; and the soluble molybdenum salt is one or more of ammonium heptamolybdate and ammonium molybdate.

[0043] Thirdly, the present invention provides an application of a heteroatom molecular sieve confined molybdenum oxidation catalyst, characterized by the following steps: preparing a eutectic solvent, treating p-toluenesulfonic acid and PEG2000 at a molar ratio of 1:2 at 80°C for 1 h; adding model oil to the eutectic solvent and extracting at 90°C for 0.5 h; adding a catalyst and an oxidant, and stirring to carry out the reaction.

[0044] In some embodiments, the amount of eutectic solvent used is 4g.

[0045] In some embodiments, the model oil is made by dissolving an organic sulfide in a decahydronaphthalene solvent, with a volume of 20 mL; the total sulfur content in the model oil is 500 μg / mL.

[0046] In some embodiments, the oxidant is one or more of O2, H2O2, and O3; the temperature of the oxidative desulfurization reaction is 90°C and the pressure is 1 atm.

[0047] The catalyst of this invention comprises a molecular sieve support, a metal element embedded in the molecular sieve framework, and molybdenum oxide. The embedded metal can be Ta, Ti, V, Nb, Zr, Hf, Sn, etc. Using a Beta-topological heteroatom molecular sieve as the support, which possesses a regular three-dimensional pore structure, a large specific surface area, and excellent thermal stability, the rigid framework of the molecular sieve confines the molybdenum oxide, resisting sintering or loss of the oxide. Simultaneously, the molybdenum oxide and the metal in the molecular sieve framework exhibit a synergistic catalytic effect. The resulting catalyst is used for oxidative desulfurization, removing sulfides from fuel oil through catalytic oxidation. It achieves deep and efficient desulfurization, is recyclable, and exhibits good recyclability. The reaction conditions are mild, the operation is simple, and molecular oxygen is used as the oxidant, showing promising application prospects.

[0048] Example 1

[0049] In this embodiment, the heteroatom molecular sieve-confined molybdenum oxidation catalyst is 2MoO3@Ti-Beta-50, and its preparation method includes the following steps:

[0050] (1) Acid elution and aluminum removal using Beta molecular sieves.

[0051] Weigh 6g of commercially purchased Beta molecular sieve and 180g of 65wt% concentrated nitric acid, pour them into 250mL round-bottom flasks, heat-treat them in an oil bath at 130℃ for 12h, then filter, wash, and dry. Repeat the above steps twice to obtain deeply dealullated Beta-DA molecular sieve.

[0052] (2) Synthesis of 2MoO3@Ti-Beta-50 catalyst.

[0053] 0.3 g Beta-DA, 1.1784 g TEAOH, and 0.034 g tetrabutyl titanate were weighed and placed into the lining of a hydrothermal reactor. The mixture was stirred for 10 min, the reactor was sealed, and the mixture was treated at 140 °C for 1 h to obtain mixture A. Separately, 0.08 g polyvinylpyrrolidone (PVP) and 0.1 g ammonium heptamolybdate were added sequentially to 5 g of deionized water to prepare solution B. Solution B was slowly added to mixture A and stirred until homogeneous. Then, 0.0926 g NH4F was added and stirred for 0.5 h. The gel was dehydrated at 80 °C for 12 h, and then crystallized at 140 °C for 24 h. Finally, the gel was filtered, washed, dried, and calcined at 550 °C for 5 h to obtain the 2MoO3@Ti-Beta-50 catalyst.

[0054] The X-ray diffraction pattern of the Ti-Beta molecular sieve confined molybdenum oxide catalyst in this embodiment is as follows: Figure 1 As shown. From Figure 1 It can be seen that the 2MoO3@Ti-Beta-50 catalyst has a Beta topology, and the characteristic peaks of MoO3 are not obvious, indicating that it is highly dispersed on the molecular sieve support.

[0055] The application of the 2MoO3@Ti-Beta-50 catalyst in oxidative desulfurization in this embodiment includes the following steps:

[0056] (1) Preparation of eutectic solvent.

[0057] Weigh 0.0929g of p-toluenesulfonic acid and 3.9071g of PEG2000, add them to 100mL three-necked flasks respectively, and incubate in an oil bath at 80℃ for 1h.

[0058] (2) Oxidative desulfurization reaction of model oil.

[0059] Add 20 mL of model oil (with benzothiophene as the substrate and decahydronaphthalene as the solvent, concentration 500 μg / mL) to the above three-necked flask, place it in a 90℃ oil bath, and extract for 0.5 h; then add 20 mg of 2MoO3@Ti-Beta-50 catalyst, install a low-temperature condenser, introduce O2 at atmospheric pressure, adjust the flow rate to 60 mL / min, start timing, and react for a certain time. The catalytic results are as follows. Figure 4 As shown, the desulfurization rate of the extraction process is 15.7%. With the increase of reaction time, the desulfurization rate shows an increasing trend. At 5 hours, the sulfide removal rate is 97.3%.

[0060] Example 2

[0061] In this embodiment, the heteroatom molecular sieve-confined molybdenum oxidation catalyst is 2MoO3@Zr-Beta-50, and its preparation method includes the following steps:

[0062] (1) The pickling method is the same as in Example 1.

[0063] (2) Synthesis of 2MoO3@Zr-Beta-50 catalyst.

[0064] Weigh out 0.3g Beta-DA, 1.1784g TEAOH and 0.0339g Zr(NO3)4. . 5H2O was added to the lining of a hydrothermal reactor and stirred for 10 min. The reactor was then sealed and treated at 140 °C for 1 h to obtain mixture A. Separately, 0.08 g PVP and 0.1 g ammonium heptamolybdate were added sequentially to 5 g of deionized water to prepare solution B. Solution B was slowly added to mixture A and stirred until homogeneous. Then, 0.0926 g NH4F was added and stirred for 0.5 h. The gel was dehydrated at 80 °C for 12 h and then crystallized at 140 °C for 24 h. Finally, the gel was filtered, washed, dried, and calcined at 550 °C for 5 h to obtain the 2MoO3@Zr-Beta-50 catalyst.

[0065] The X-ray diffraction pattern of the Zr-Beta molecular sieve-confined molybdenum oxide catalyst in this embodiment is as follows: Figure 1 As shown. From Figure 1 It can be seen that the 2MoO3@Zr-Beta-50 catalyst has a Beta topology, and the characteristic peaks of MoO3 are not obvious, indicating that it is highly dispersed on the molecular sieve support.

[0066] The application of the 2MoO3@Zr-Beta-50 catalyst in oxidative desulfurization in this embodiment includes the following steps:

[0067] (1) The preparation method of the eutectic solvent is the same as in Example 1.

[0068] (2) Oxidative desulfurization reaction of model oil.

[0069] Add 20 mL of model oil (with benzothiophene as the substrate and decahydronaphthalene as the solvent, concentration 500 μg / mL) to the above three-necked flask, place it in a 90℃ oil bath, and extract for 0.5 h; then add 20 mg of 2MoO3@Zr-Beta-50 catalyst, install a low-temperature condenser, introduce O2 at atmospheric pressure, adjust the flow rate to 60 mL / min, start timing, and react for a certain time. The catalytic results are as follows. Figure 5 As shown, the desulfurization rate of the extraction process was 16.7%. With the increase of reaction time, the desulfurization rate showed an increasing trend. At 5 h, the sulfide removal rate was 91.1%.

[0070] Example 3

[0071] In this embodiment, the heteroatom molecular sieve confined molybdenum oxidation catalyst is 2MoO3@Sn-Beta-50, and its preparation method includes the following steps:

[0072] (1) The pickling method is the same as in Example 1.

[0073] (2) Synthesis of 2MoO3@Sn-Beta-50 catalyst.

[0074] Weigh out 0.3g Beta-DA, 1.1784g TEAOH and 0.0260g SnCl4. . 5H2O was added to the lining of a hydrothermal reactor and stirred for 10 min. The reactor was then sealed and treated at 140 °C for 1 h to obtain mixture A. Separately, 0.08 g PVP and 0.1 g ammonium heptamolybdate were added sequentially to 5 g of deionized water to prepare solution B. Solution B was slowly added to mixture A and stirred until homogeneous. Then, 0.0926 g NH4F was added and stirred for 0.5 h. The gel was dehydrated at 80 °C for 12 h and then crystallized at 140 °C for 24 h. Finally, the gel was filtered, washed, dried, and calcined at 550 °C for 5 h to obtain the 2MoO3@Sn-Beta-50 catalyst.

[0075] The X-ray diffraction pattern of the Sn-Beta molecular sieve-confined molybdenum oxide catalyst in this embodiment is as follows: Figure 1 As shown. From Figure 1 It can be seen that the 2MoO3@Sn-Beta-50 catalyst has a Beta topology, and the characteristic peaks of MoO3 are not obvious, indicating that it is highly dispersed on the molecular sieve support.

[0076] The application of the 2MoO3@Sn-Beta-50 catalyst in oxidative desulfurization in this embodiment includes the following steps:

[0077] (1) The preparation method of the eutectic solvent is the same as in Example 1.

[0078] (2) Oxidative desulfurization reaction of model oil.

[0079] Add 20 mL of model oil (with benzothiophene as the substrate and decahydronaphthalene as the solvent, concentration 500 μg / mL) to the above three-necked flask, place it in a 90℃ oil bath, and extract for 0.5 h; then add 20 mg of 2MoO3@Sn-Beta-50 catalyst, install a low-temperature condenser, introduce O2 at atmospheric pressure, adjust the flow rate to 60 mL / min, start timing, and react for a certain time. The catalytic results are as follows. Figure 6 As shown, the desulfurization rate of the extraction process is 17.5%. With the increase of reaction time, the desulfurization rate shows an increasing trend. At 5 hours, the sulfide removal rate is 83.7%.

[0080] Example 4

[0081] In this embodiment, the heteroatom molecular sieve confined molybdenum oxidation catalyst is 2MoO3@Hf-Beta-50, and its preparation method includes the following steps:

[0082] (1) The pickling method is the same as in Example 1.

[0083] (2) Synthesis of 2MoO3@Hf-Beta-50 catalyst.

[0084] Weigh 0.3g Beta-DA, 1.1784g TEAOH, and 0.0320g HfCl4 and place them in the lining of a hydrothermal reactor. Stir for 10 min, seal the reactor, and treat at 140℃ for 1 h to obtain mixture A. Separately, add 0.08g PVP and 0.1g ammonium heptamolybdate to 5g deionized water to prepare solution B. Slowly add solution B to mixture A, stir until homogeneous, then add 0.0926g NH4F and stir for 0.5 h. The gel is dehydrated at 80℃ for 12 h, then crystallized at 140℃ for 24 h. Then, filter, wash, dry, and calcine at 550℃ for 5 h to obtain the 2MoO3@Hf-Beta-50 catalyst.

[0085] The X-ray diffraction pattern of the Hf-Beta molecular sieve-confined molybdenum oxide catalyst in this embodiment is as follows: Figure 1 As shown. From Figure 1 It can be seen that the 2MoO3@Hf-Beta-50 catalyst has a Beta topology, and the characteristic peaks of MoO3 are not obvious, indicating that it is highly dispersed on the molecular sieve support.

[0086] The application of the 2MoO3@Hf-Beta-50 catalyst in oxidative desulfurization in this embodiment includes the following steps:

[0087] (1) The preparation method of the eutectic solvent is the same as in Example 1.

[0088] (2) Oxidative desulfurization reaction of model oil.

[0089] Add 20 mL of model oil (with benzothiophene as the substrate and decahydronaphthalene as the solvent, concentration 500 μg / mL) to the three-necked flask, place it in a 90℃ oil bath, and extract for 0.5 h; then add 20 mg of 2MoO3@Hf-Beta-50 catalyst, install a low-temperature condenser, introduce O2 at atmospheric pressure, adjust the flow rate to 60 mL / min, start timing, and react for a certain time. The catalytic results are as follows. Figure 7 As shown, the desulfurization rate of the extraction process is 17.4%. With the increase of reaction time, the desulfurization rate shows an increasing trend. At 5h, the sulfide removal rate is 95.0%.

[0090] Example 5

[0091] In this embodiment, the heteroatom molecular sieve confined molybdenum oxidation catalyst is 2MoO3@Nb-Beta-50, and its preparation method includes the following steps:

[0092] (1) The pickling method is the same as in Example 1.

[0093] (2) Synthesis of 2MoO3@Nb-Beta-50 catalyst.

[0094] Weigh 0.3g Beta-DA, 1.1784g TEAOH, and 0.0270g NbCl5 and place them in the lining of a hydrothermal reactor. Stir for 10 min, seal the reactor, and treat at 140℃ for 1 h to obtain mixture A. Separately, add 0.08g PVP and 0.1g ammonium heptamolybdate to 5g deionized water to prepare solution B. Slowly add solution B to mixture A, stir until homogeneous, then add 0.0926g NH4F and stir for 0.5 h. The gel is dehydrated at 80℃ for 12 h, then crystallized at 140℃ for 24 h. Finally, filter, wash, dry, and calcine at 550℃ for 5 h to obtain the 2MoO3@Nb-Beta-50 catalyst.

[0095] The X-ray diffraction pattern of the Nb-Beta molecular sieve-confined molybdenum oxide catalyst in this embodiment is as follows: Figure 1 As shown. From Figure 1 It can be seen that the 2MoO3@Nb-Beta-50 catalyst has a Beta topology, and the characteristic peaks of MoO3 are not obvious, indicating that it is highly dispersed on the molecular sieve support.

[0096] The application of the 2MoO3@Nb-Beta-50 catalyst in oxidative desulfurization in this embodiment includes the following steps:

[0097] (1) The preparation method of the eutectic solvent is the same as in Example 1.

[0098] (2) Oxidative desulfurization reaction of model oil.

[0099] Add 20 mL of model oil (with benzothiophene as the substrate and decahydronaphthalene as the solvent, concentration 500 μg / mL) to the above three-necked flask, place it in a 90℃ oil bath, and extract for 0.5 h; then add 20 mg of 2MoO3@Nb-Beta-50 catalyst, install a low-temperature condenser, introduce O2 at atmospheric pressure, adjust the flow rate to 60 mL / min, start timing, and react for a certain time. The catalytic results are as follows. Figure 8 As shown, the desulfurization rate of the extraction process is 15.9%. With the increase of reaction time, the desulfurization rate shows an increasing trend. At 5 hours, the sulfide removal rate is 92.7%.

[0100] Example 6

[0101] In this embodiment, the heteroatom molecular sieve-confined molybdenum oxidation catalyst is 2MoO3@Ta-Beta-50, and its preparation method includes the following steps:

[0102] (1) The pickling method is the same as in Example 1.

[0103] (2) Synthesis of 2MoO3@Ta-Beta-50 catalyst.

[0104] Weigh 0.3g Beta-DA, 1.1784g TEAOH, and 0.0358g TaCl5 and place them in the lining of a hydrothermal reactor. Stir for 10 min, seal the reactor, and treat at 140℃ for 1 h to obtain mixture A. Separately, add 0.08g PVP and 0.1g ammonium heptamolybdate to 5g deionized water to prepare solution B. Slowly add solution B to mixture A, stir until homogeneous, then add 0.0926g NH4F and stir for 0.5 h. The gel is dehydrated at 80℃ for 12 h, then crystallized at 140℃ for 24 h. Finally, filter, wash, dry, and calcine at 550℃ for 5 h to obtain the 2MoO3@Ta-Beta-50 catalyst.

[0105] The X-ray diffraction pattern of the Ta-Beta molecular sieve-confined molybdenum oxide catalyst in this embodiment is as follows: Figure 1 As shown. From Figure 1 It can be seen that the 2MoO3@Ta-Beta-50 catalyst has a Beta topology, and the characteristic peaks of MoO3 are not obvious, indicating that it is highly dispersed on the molecular sieve support.

[0106] The scanning electron microscope image of the Ta-Beta molecular sieve-confined molybdenum oxide catalyst in this embodiment is as follows: Figure 2 As shown. From Figure 2 It can be seen that the 2MoO3@Ta-Beta-50 catalyst has the morphology of nanoparticles with a particle size of approximately 68–85 nm.

[0107] The transmission electron microscope (TEM) image of the Ta-Beta molecular sieve-confined molybdenum oxide catalyst in this embodiment is shown below. Figure 3 As shown. From Figure 3 It can be seen that MoO3 is highly dispersed and embedded in the support molecular sieve.

[0108] The application of the 2MoO3@Ta-Beta-50 catalyst in oxidative desulfurization in this embodiment includes the following steps:

[0109] (1) The preparation method of the eutectic solvent is the same as in Example 1.

[0110] (2) Oxidative desulfurization reaction of model oil.

[0111] Add 20 mL of model oil (with benzothiophene as the substrate and decahydronaphthalene as the solvent, concentration 500 μg / mL) to the three-necked flask, place it in a 90℃ oil bath, and extract for 0.5 h; then add 20 mg of 2MoO3@Ta-Beta-50 catalyst, install a low-temperature condenser, introduce O2 at atmospheric pressure, adjust the flow rate to 60 mL / min, start timing, and react for a certain time. The catalytic results are as follows. Figure 9 As shown, the desulfurization rate of the extraction process is 16.1%. With the increase of reaction time, the desulfurization rate shows an increasing trend. At 5 hours, the sulfide removal rate is 100%.

[0112] Example 7

[0113] Repeat Example 6, changing the amount of TaCl5 in step 2 to 0.0597 g, while keeping other conditions unchanged, to prepare the 2MoO3@Ta-Beta-200 catalyst. The catalytic results are as follows. Figure 10 As shown, the desulfurization rate of the extraction process is 15.8%. With the increase of reaction time, the desulfurization rate shows an increasing trend. At 5 hours, the sulfide removal rate is 92.2%.

[0114] Example 8

[0115] Repeat Example 6, changing the amount of TaCl5 in step 2 to 0.0089 g, while keeping other conditions unchanged, to prepare the 2MoO3@Ta-Beta-30 catalyst. The catalytic results are as follows. Figure 11 As shown, the desulfurization rate of the extraction process is 16.4%. With the increase of reaction time, the desulfurization rate shows an increasing trend. At 5h, the sulfide removal rate is 93.6%.

[0116] Example 9

[0117] Repeat Example 6, changing the amount of ammonium heptamolybdate in step 2 to 0.4 g, while keeping other conditions unchanged, to prepare the 8MoO3@Ta-Beta-50 catalyst. The catalytic results are as follows. Figure 12 As shown, the desulfurization rate of the extraction process is 16.7%. With the increase of reaction time, the desulfurization rate shows an increasing trend. At 5h, the sulfide removal rate is 98.4%.

[0118] Example 10

[0119] Repeat Example 6 and perform a cyclical test, including the following steps:

[0120] (1) After the catalytic reaction, the mixture was allowed to stand, the supernatant was discarded, and the mixture was washed with deionized water and centrifuged to obtain the used 2MoO3@Ta-Beta-50 catalyst.

[0121] (2) The preparation method of the eutectic solvent is the same as in Example 1.

[0122] (3) Oxidative desulfurization reaction of model oil.

[0123] Add 20 mL of model oil (with benzothiophene as the substrate and decahydronaphthalene as the solvent, concentration 500 μg / mL) to the above three-necked flask, place it in a 90℃ oil bath, and extract for 0.5 h; then add the recovered 2MoO3@Ta-Beta-50 catalyst, install a low-temperature condenser, introduce O2 at atmospheric pressure, adjust the flow rate to 60 mL / min, start timing, and react for a certain time. The catalytic results are as follows. Figure 13 As shown, the desulfurization rate of the extraction process is 17.4%. With the increase of reaction time, the desulfurization rate shows an increasing trend. At 5 h, the sulfide removal rate is 100%, and the catalytic activity is the same as that of Example 6, indicating that this catalyst has good recyclability.

[0124] In summary, this invention uses Beta molecular sieves after deep dealumination as a support, leveraging their uniform pore structure, large specific surface area, regular three-dimensional pore structure, and high crystallinity. Based on their inherent confinement effect, an excellent metal-confined catalyst is obtained. The resulting molecular sieve catalyst is used for oxidative desulfurization. The catalyst includes a support and metal elements implanted into the molecular sieve framework. The implanted metals include Ta, Ti, V, Nb, Zr, Hf, Sn, etc.

[0125] The heteroatom molecular sieve-confined molybdenum oxidation catalyst provided by this invention removes sulfides from fuel oil via oxidation, achieving deep and efficient desulfurization. The catalyst is recyclable, and the recovered catalyst still possesses good catalytic oxidation performance. The reaction conditions are mild, the operation is simple, and it uses inexpensive molecular oxygen as the oxidant, eliminating the need for expensive hydrogen sources. Experimental results show that the oxidative desulfurization efficiency can reach up to 100%, and the catalyst is recyclable.

[0126] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a heteroatom molecular sieve-confined molybdenum oxidation catalyst, characterized in that, The heteroatom molecular sieve-confined molybdenum oxide catalyst is nMoO3@M-Beta-y, where M is the embedded molecular sieve framework metal, the Mo loading n is 2-8 wt%, the Si to M molar ratio y in the molecular sieve is 30-200, and the embedded molecular sieve framework metal M is one or more of Ta, Ti, V, Nb, Zr, Hf, and Sn. A metal element with variable valence characteristics is implanted into the molecular sieve framework through isomorphous substitution. Ligands stabilize the molybdenum species, restricting their movement under solvent-free conditions, thus confining molybdenum oxide in situ within the heteroatom molecular sieve. The specific steps of the preparation method are as follows: Preparation of deep dealuded Beta molecular sieves: The silica-alumina type Beta molecular sieves were acid-washed, washed, and then dried; Deeply dealuminated Beta molecular sieves, template agents, metal salts, and water were mixed and treated at 110–160 °C for 1 h to obtain a mixed gel. The metal in the metal salt was the embedded molecular sieve framework metal M. The obtained mixed gel was mixed with a polyvinylpyrrolidone solution containing molybdenum salt, stirred evenly, and then fluoride was added. The mixture was dehydrated at 80°C for 8–12 h until it became a dry gel. It was then treated at 110–160°C for 12–24 h. The product was filtered, washed, dried, and calcined at 550°C for 3–6 h to obtain the nMoO3@M-Beta-y catalyst.

2. The method for preparing the heteroatom molecular sieve-confined molybdenum oxidation catalyst according to claim 1, characterized in that, The pickling treatment uses nitric acid with a concentration of 6-11 mol / L, and the mass ratio of silica-alumina type Beta molecular sieve to nitric acid solution is 1:30-50; the pickling temperature is 80-130℃, the time is 6-12h, and the pickling treatment is repeated 2-3 times.

3. The method for preparing the heteroatom molecular sieve-confined molybdenum oxidation catalyst according to claim 1, characterized in that, In the deep dealuded Beta molecular sieve, the molar ratio of SiO2 to template agent is 1:0.2-0.7; the template agent is one or more of tetraethylammonium hydroxide and tetraethylammonium fluoride; the metal salt is one or more of metal chloride salt, nitrate salt, and organometallic salt.

4. The method for preparing the heteroatom molecular sieve-confined molybdenum oxidation catalyst according to claim 1, characterized in that, Fluorides are selected as mineralizing agents, and the fluorides are one or more of NH4F, HF, and NH4HF2; the molar ratio of SiO2 to fluoride in the deep dealuded Beta molecular sieve is 1:0.1 to 0.8; the soluble molybdenum salt is ammonium heptamolybdate.

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