Preparation method and application of surface-hydrophobized bismuth molybdate catalyst
By introducing synergistic modification of organic acids and amines into the hydrothermal synthesis of bismuth molybdate catalysts, a dense hydrophobic layer was constructed, solving the hydrophilicity problem of the bismuth molybdate catalyst surface. This achieved high efficiency and selectivity in the olefin epoxidation reaction, simplified the modification steps, and improved the stability of the catalyst.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU UNIV
- Filing Date
- 2026-01-07
- Publication Date
- 2026-04-28
AI Technical Summary
The surface hydrophilicity of existing bismuth molybdate catalysts limits their activity and selectivity in olefin epoxidation reactions, and existing hydrophobic modification methods are complex and unstable.
In the hydrothermal synthesis system of bismuth molybdate, organic acids and organic amines in a specific molar ratio are introduced simultaneously as composite modifiers. Through acid-base interactions and synergistic coordination with metal precursors, a dense hydrophobic layer is constructed on the catalyst surface, achieving one-step modification.
The modification steps were simplified, the hydrophobicity and stability of the catalyst were improved, the conversion and selectivity of the olefin epoxidation reaction were enhanced, and the catalyst showed good recycling stability in heterogeneous reactions.
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Figure CN121927587A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of olefin epoxidation technology, and in particular to a surface-hydrophobicated bismuth molybdate catalyst. Background Technology
[0002] The epoxidation of olefins has long been a research hotspot, attributed to the importance of target epoxides as key chemical intermediates in the synthesis of polymers, pharmaceuticals, and fine chemicals. However, the presence of an unsaturated C=C double bond and multiple reactive α-H atoms in olefins (such as 1-hexene) presents significant challenges, as oxidation can lead to the formation of a variety of products. Therefore, designing and developing novel catalysts capable of achieving high activity and selectivity in olefin epoxidation remains a major challenge.
[0003] Chalcopyrite is widely used as a selective oxidation catalyst for unsaturated olefins, such as the selective oxidation of propylene to acrolein and the ammoxidation of propylene to acrylonitrile. It has been reported that the nucleophilic lattice oxygen and its migration properties in chalcopyrite catalysts play a crucial role in selective oxidation processes. Inspired by this, the use of bismuth molybdate as an olefin epoxidation catalyst is reasonable, as the reaction involves the addition of active oxygen species to the C=C double bond. Furthermore, the application of bismuth molybdates as olefin epoxidation catalysts has received little attention. However, the inherent hydrophilicity of its surface severely limits its application in heterogeneous systems: the hydrophilic catalyst surface induces ring-opening of epoxide products, leading to low activity, which becomes a key bottleneck restricting its catalytic performance.
[0004] In existing technologies, hydrophobic modification of catalysts is a feasible solution, such as post-treatment using silanizing agents. However, these methods often suffer from problems such as complex processes, insufficient stability of the modified layer, or high costs. Therefore, developing a simple, effective, and stable hydrophobic modification method for bismuth molybdate has significant practical application value. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a surface-hydrophobic bismuth molybdate catalyst that is simple to process, has significant hydrophobic effect, and excellent catalytic performance.
[0006] This invention creatively discovers that in the hydrothermal synthesis system of bismuth molybdate, simultaneously introducing organic acids and organic amines in a specific molar ratio as composite modifiers allows them to directly and in situ construct a dense and stable organic hydrophobic layer on the surface of newly formed bismuth molybdate nanocrystals during hydrothermal crystallization through acid-base interactions and synergistic coordination with metal precursors. This process is completed in one step, avoiding problems such as uneven modification layers and weak bonding that may occur in subsequent modification steps. By precisely controlling the type, chain length, and ratio of organic acids / amines, continuous and fine-tuning of the hydrophobicity (water contact angle) of the catalyst surface can be achieved, thereby optimally matching the mass transfer requirements of the multiphase catalytic reaction interface.
[0007] To achieve the objectives of this invention, the following experimental scheme is employed:
[0008] A method for preparing a surface-hydrophobicated bismuth molybdate catalyst, comprising the following steps:
[0009] Step S1: Dissolve sodium molybdate and bismuth source in deionized water to form a precursor solution;
[0010] Step S2: The precursor solution from step S1 is subjected to ultrasonic or vortex oscillation treatment, and then organic acid and organic amine are added to the precursor solution simultaneously. The mixture is stirred continuously until the solute is completely dissolved to obtain a mixed solution.
[0011] Step S3: Adjust the pH of the mixed solution to the range of 1-5 using dilute acid and dilute alkali solutions, and then carry out a hydrothermal reaction to obtain the reactants;
[0012] Step S4: Centrifuge the reaction product from step S3 at 6000-10000 rpm for 3-10 min, adding deionized water and ethanol respectively and centrifuging 2-5 times to obtain a solid product.
[0013] Step S5: Use an organic solvent to initially remove the adsorbed, unreacted organic modifiers and organic byproducts adsorbed on the surface of the solid product, including ethanol, methanol, and acetone; then use deionized water to remove residual inorganic salt ions to obtain the washed solid.
[0014] Step S6: Place the washed solid in a drying device for drying to obtain the surface hydrophobic bismuth molybdate catalyst. The drying is vacuum drying, the drying temperature is controlled at 50-80°C, and the drying time is 6-24 h.
[0015] Furthermore, the bismuth source is a compound that provides bismuth ions under hydrothermal reaction conditions, including soluble bismuth salts and bismuth-containing compounds. The soluble bismuth salts include bismuth nitrate, bismuth chloride, and bismuth sulfate; the bismuth-containing compounds refer to compounds that decompose in the aqueous phase and generate Bi during the reaction. 3+Bismuth compounds, including bismuth salts of organic acids such as basic carbonic acid or bismuth acetate, and bismuth citrate.
[0016] Furthermore, the organic acid is selected from aliphatic organic acids (i.e., monocarboxylic acids) and aromatic organic acids (i.e., monocarboxylic acids) with hydrophobic chains. The aliphatic organic acid is a straight-chain or branched alkyl carboxylic acid with 2 to 18 carbon atoms, including acetic acid, valeric acid, and oleic acid. The aromatic organic acid includes benzoic acid. The organic amine is selected from aliphatic primary amines and aromatic primary amines. The aliphatic primary amine is a straight-chain or branched alkyl primary amine with 3 to 18 carbon atoms, including propylamine, dodecylamine, and oleylamine. The aromatic organic amine includes aniline.
[0017] Furthermore, the molar ratio of the organic acid to the organic amine is 0.8:1 to 1.2:1.
[0018] Furthermore, the total amount of the organic acid and organic amine added, in molar terms, is 10% to 50% of the molar amount of the bismuth source.
[0019] Furthermore, in step S3, the temperature of the hydrothermal reaction is 160 °C to 180 °C, and the reaction time is 12 to 24 hours.
[0020] Furthermore, this invention proposes an application of a surface-hydrophobicated bismuth molybdate catalyst, applicable to the aforementioned method for preparing the surface-hydrophobicated bismuth molybdate catalyst. The application involves using the surface-hydrophobicated bismuth molybdate catalyst to catalyze the epoxidation of olefins, with the specific steps as follows:
[0021] First, the surface-hydrophobic bismuth molybdate catalyst is placed in a solution containing olefins, polar solvents, and oxidants;
[0022] Then, the reaction was stirred for 1–3 h at a temperature of 40–70 °C and a stirring speed of 200–600 rpm.
[0023] Finally, the supernatant collected after the reaction is complete is the epoxy product solution.
[0024] Furthermore, the oxidant is hydrogen peroxide, and the ratio of hydrogen peroxide to olefin is (5-15 mmol): (5-15 mmol).
[0025] Furthermore, the olefin substrate is propylene, 1-pentene, 1-hexene, cyclohexene, or 1-octene, wherein the test temperature for 1-pentene is 30–60 °C, and the test temperatures for 1-hexene, cyclohexene, and 1-octene are 50 °C–70 °C.
[0026] Furthermore, the ratio of the surface-hydrophobic bismuth molybdate catalyst to the olefin is (0.02–0.5 g):(5–15 mmol).
[0027] Compared with the prior art, the present invention has the following beneficial effects:
[0028] (1) The present invention proposes a method for preparing a surface hydrophobic bismuth molybdate catalyst and its application, which simultaneously completes the synthesis of bismuth molybdate and surface hydrophobic modification in a hydrothermal reactor, avoiding complex post-modification steps, eliminating the need for pressurization equipment, and making the operation simple, the process convenient, and easy to scale up production.
[0029] (2) The present invention proposes a method for preparing a surface-hydrophobic bismuth molybdate catalyst and its application. By adjusting the amount of oleylamine and oleic acid added, the hydrophobicity (contact angle) of the catalyst surface can be precisely controlled, thereby achieving controllable optimization of the microenvironment of the multiphase reaction interface.
[0030] (3) The hydrophobic bismuth molybdate catalyst prepared in this invention can achieve an olefin conversion rate of 55% and a selectivity of 85% within 2 hours in the olefin epoxidation reaction.
[0031] (4) The present invention proposes a method for preparing a surface-hydrophobicated bismuth molybdate catalyst and its application, wherein oleylamine and oleic acid synergistically modify the catalyst through hydrophobic modification. Organic acid molecules undergo strong coordination with the metal center on the surface of bismuth molybdate through their carboxyl groups, achieving initial anchoring; organic amine molecules form hydrogen bonds and ion pair interactions with the carboxyl groups of organic acids through their amino groups. This strong intermolecular force between acid and amine allows them to assemble together during hydrothermal crystallization, forming a dense composite organic monolayer on the surface of the catalyst particles through a network of coordination bonds and hydrogen bonds. The inner side of this monolayer is firmly anchored by chemical bonds, while the outer side is provided with hydrophobicity by long alkyl chains, thus achieving a unity of hydrophobicity, stability, and accessibility of active sites. The modified layer is not easily detached during the reaction, and the catalyst exhibits good stability for repeated use. Attached Figure Description
[0032] Figure 1 This is a flowchart of a method for preparing a surface-hydrophobic bismuth molybdate catalyst according to the present invention.
[0033] Figure 2 The X-ray diffraction pattern of the catalyst prepared in this invention.
[0034] Figure 3 X-ray diffraction patterns of catalysts modified with single organic amines and organic acids provided in this invention.
[0035] Figure 4 The image shows a scanning electron microscope (SEM) image of the catalyst prepared according to the present invention.
[0036] Figure 5 The scanning electron microscope elemental distribution diagram of the catalyst prepared in this invention.
[0037] Figure 6 A comparison diagram of the static water contact angle of the catalyst prepared in this invention. Detailed Implementation
[0038] 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.
[0039] Unless otherwise specified, all materials and reagents used in this invention are commercially available.
[0040] To achieve the objectives of this invention, the following experimental scheme is employed:
[0041] A method for preparing a surface-hydrophobicated bismuth molybdate catalyst, comprising the following steps:
[0042] Step S1: Dissolve sodium molybdate and bismuth source in deionized water to form a precursor solution;
[0043] Step S2: Process the precursor solution from step S1, and then simultaneously add organic acid and organic amine to the precursor solution, stirring continuously until the solute is completely dissolved to obtain a mixed solution.
[0044] Step S3: Use dilute acid such as nitric acid and dilute alkali solution such as ammonia to adjust the pH value of the mixed solution to the range of 1 to 5, and then carry out a hydrothermal reaction to obtain the reactants;
[0045] Step S4: Centrifuge the reaction product from step S3 at 6000-10000 rpm for 3-10 min, adding deionized water and ethanol respectively and centrifuging 2-5 times to obtain a solid product.
[0046] Step S5: Use an organic solvent to initially remove the adsorbed, unreacted organic modifiers and organic byproducts adsorbed on the surface of the solid product, including ethanol, methanol, and acetone; then use deionized water to remove residual inorganic salt ions to obtain the washed solid.
[0047] Step S6: Place the washed solid in a drying device for drying to obtain the surface hydrophobic bismuth molybdate catalyst. The drying is vacuum drying, the drying temperature is controlled at 50-80°C, and the drying time is 6-24 h.
[0048] Furthermore, the bismuth source in step S1 is a soluble bismuth salt. Those skilled in the art will understand that any bismuth source available in a hydrothermal reaction system... Bismuth salts that combine with molybdate ions to form bismuth molybdate can be used. The examples primarily use bismuth nitrate as an example, but this is not intended to limit the invention.
[0049] Furthermore, the organic acid is selected from aliphatic monocarboxylic acids and aromatic monocarboxylic acids having hydrophobic chains. The aliphatic organic acid is a straight-chain or branched alkyl carboxylic acid with 2 to 18 carbon atoms, including acetic acid, valeric acid, and oleic acid. The aromatic organic acid includes benzoic acid. The organic amine is selected from aliphatic primary amines or aromatic primary amines. The aliphatic primary amine is a straight-chain or branched alkyl primary amine with 3 to 18 carbon atoms, including propylamine, dodecylamine, and oleylamine. The aromatic organic amine includes aniline.
[0050] Furthermore, the molar ratio of the organic acid to the organic amine is 0.8:1 to 1.2:1.
[0051] Furthermore, the total amount of the organic acid and organic amine added, in molar terms, is 10% to 50% of the molar amount of the bismuth source.
[0052] Furthermore, in step S3, the temperature of the hydrothermal reaction is 160°C to 180°C, and the reaction time is 12 to 24 hours.
[0053] Furthermore, the precursor treatment in step S2 is selected from one or a combination of the following two methods:
[0054] (a) Ultrasonic oscillation treatment: The precursor solution is placed in an ultrasonic cleaner or probe-type ultrasonic processor for treatment. The ultrasonic power is 100-500 W, the frequency is 20-40 kHz, and the treatment time is 10-60 min.
[0055] (b) Vortex oscillation treatment: The precursor solution is placed in a closed container and oscillated. The vortex oscillator speed is 200-3000 rpm and the treatment time is 10 s-10 min.
[0056] Furthermore, this invention also proposes an application of a surface-hydrophobic bismuth molybdate catalyst, applicable to the preparation method of the aforementioned surface-hydrophobic bismuth molybdate catalyst. The specific steps for using the surface-hydrophobic bismuth molybdate catalyst to catalyze the epoxidation of olefins are as follows:
[0057] First, 10 mmol of olefin, 10 mmol of hydrogen peroxide, 10 mL of acetonitrile, and 0.05 g of catalyst H-BMO-0.1 were sequentially added to a 50 mL micro reactor equipped with a magnetic stirrer.
[0058] Then, the reaction was stirred for 1–3 h at a temperature of 30–70 °C and a stirring speed of 200–600 rpm.
[0059] Finally, the supernatant collected after the reaction is complete is the epoxy product solution.
[0060] Furthermore, the oxidant is hydrogen peroxide, and the ratio of hydrogen peroxide to olefin is (5-15 mmol): (5-15 mmol).
[0061] Furthermore, the olefin substrates are 1-pentene, 1-hexene, cyclohexene, and 1-octene, with 1-pentene being tested at a temperature of 30–60 °C, while 1-hexene, cyclohexene, and 1-octene are tested at temperatures of 50 °C–70 °C.
[0062] Furthermore, the ratio of the surface-hydrophobic bismuth molybdate catalyst to the olefin is (0.02–0.5 g): (5–15 mmol).
[0063] In this invention, adjusting the pH value is a preferred step. Under acidic conditions (e.g., pH 1-3), it is beneficial for organic acids to exist in molecular form and react with each other. Specific coordination patterns can occur; under weakly acidic conditions (such as pH 3–5), the polymerization state of molybdate ions may be affected, thereby regulating the crystallization process of bismuth molybdate and the synergistic assembly of organic modifiers. By adjusting the pH, the hydrophobicity, specific surface area, and exposure of active sites of the catalyst can be further optimized.
[0064] The following examples illustrate the preparation process of surface-hydrophobicated bismuth molybdate:
[0065] Example 1:
[0066] (1) 2 mmol and 1 mmol Dissolve in 80 mL of deionized water and stir for 0.5 hours.
[0067] (2) Add 0.1 mmol of oleylamine and 0.1 mmol of oleic acid to the resulting solution and continue stirring for 0.5 hours.
[0068] (3) Transfer the mixture to a 100 mL high-pressure reactor and react at 160 °C for 16 hours.
[0069] (4) After the reaction was completed, the catalyst was centrifuged, washed and air-dried to obtain hydrophobic bismuth molybdate catalyst H-BMO-0.1, and the water contact angle was measured to be 87.5°.
[0070] (5) Epoxidation of olefins: 10 mmol of olefin, 10 mmol of hydrogen peroxide, 10 mL of acetonitrile and 0.05 g of catalyst H-BMO-0.1 were added sequentially to a 50 mL micro reactor with magnetic stirring. The reaction was carried out at the target temperature of 40 °C and 200 rpm for 2 h. The olefin epoxidation conversion rate / selectivity (% / %) was measured. The specific results were: 1-pentene (27% / 91%).
[0071] Example 2:
[0072] (1) 1 mmol and 0.5 mmol Dissolve in 80 mL of deionized water and stir for 0.5 hours.
[0073] (2) Add 0.3 mmol of oleylamine and 0.3 mmol of oleic acid to the resulting solution and continue stirring for 0.5 hours.
[0074] (3) Adjust the pH of the mixed solution to 2.5 using a 0.1 mol / L dilute nitric acid solution.
[0075] (4) Transfer the mixture to a 100 mL high-pressure reactor and react at 180 °C for 16 hours.
[0076] (5) After the reaction was completed, the catalyst was centrifuged, washed and dried to obtain the hydrophobic bismuth molybdate catalyst H-BMO-0.3, and the water contact angle was measured to be 102.2°.
[0077] (6) Olefin epoxidation: 10 mmol olefin, 10 mmol hydrogen peroxide, 10 mL acetonitrile, and 0.05 g catalyst H-BMO-0.3 were added sequentially to a 50 mL micro reactor with magnetic stirring. The reaction was carried out at the target temperature of 60 °C and 200 rpm for 2 h. The olefin epoxidation conversion / selectivity (% / %) was measured. The specific results were: 1-hexene (40% / 94%).
[0078] Example 3:
[0079] (1) Take 0.2 mmol and 0.1 mmol Dissolve in 40 mL of deionized water and stir for 0.5 hours.
[0080] (2) Add 0.03 mmol oleylamine and 0.03 mmol oleic acid to the resulting solution and continue stirring for 0.5 hours.
[0081] (3) Transfer the mixture to a 100 mL high-pressure reactor and react at 160 °C for 16 hours.
[0082] (4) After the reaction was completed, the catalyst was centrifuged, washed and dried to obtain hydrophobic bismuth molybdate catalyst H-BMO-0.03, and the water contact angle was measured to be 97.6°.
[0083] (5) Olefin epoxidation: 10 mmol olefin, 10 mmol hydrogen peroxide, 10 mL acetonitrile, and 0.05 g catalyst H-BMO-0.03 were added sequentially to a 50 mL micro reactor with magnetic stirring. The reaction was carried out at the target temperature of 60 °C and 200 rpm for 2 h. The olefin epoxidation conversion rate / selectivity (% / %) was measured. The specific results were: 1-octene (28% / 95%).
[0084] Example 4:
[0085] (1) Take 0.2 mmol and 0.1 mmol Dissolve in 40 mL of deionized water and stir for 0.5 hours.
[0086] (2) Add 0.3 mmol dodecylamine and 0.3 mmol oleic acid to the resulting solution at the same time, and continue stirring for 0.5 hours.
[0087] (3) Transfer the mixture to a 100 mL high-pressure reactor and react at 160 °C for 16 hours.
[0088] (4) After the reaction was completed, the catalyst was centrifuged, washed and dried to obtain hydrophobic bismuth molybdate catalyst S-BMO-0.3OA, and the water contact angle was measured to be 100.1°.
[0089] (5) Olefin epoxidation: 10 mmol olefin, 10 mmol hydrogen peroxide, 10 mL acetonitrile, and 0.05 g catalyst S-BMO-0.3OA were added sequentially to a 50 mL micro reactor with magnetic stirring. The reaction was carried out at the target temperature of 40 °C and 200 rpm for 2 h. The olefin epoxidation conversion rate / selectivity (% / %) was measured. The specific results were: 1-pentene (32% / 93%).
[0090] Example 5:
[0091] (1) Take 0.2 mmol and 0.1 mmol Dissolve in 60 mL of deionized water and stir for 0.5 hours.
[0092] (2) Add 0.3 mmol of oleylamine and 0.3 mmol of valerate to the resulting solution and continue stirring for 0.5 hours.
[0093] (3) Transfer the mixture to a 100 mL high-pressure reactor and react at 160 °C for 18 hours.
[0094] (4) After the reaction was completed, the catalyst was centrifuged, washed and dried to obtain hydrophobic bismuth molybdate catalyst S-BMO-0.3OLA, and the water contact angle was measured to be 82.8°.
[0095] (5) Olefin epoxidation: 10 mmol olefin, 10 mmol hydrogen peroxide, 10 mL acetonitrile, and 0.05 g catalyst S-BMO-0.3OLA were added sequentially to a 50 mL micro reactor with magnetic stirring. The reaction was carried out at the target temperature of 60 °C and 200 rpm for 2 h. The olefin epoxidation conversion rate / selectivity (% / %) was measured. The specific results were: 1-hexene (23% / 95%).
[0096] Example 6:
[0097] (1) Take 0.2 mmol and 0.1 mmol Dissolve in 60 mL of deionized water and stir for 0.5 hours.
[0098] (2) Add 0.2 mmol dodecylamine and 0.2 mmol propionic acid to the resulting solution at the same time, and continue stirring for 0.5 hours.
[0099] (3) Transfer the mixture to a 100 mL high-pressure reactor and react at 160 °C for 16 hours.
[0100] (4) After the reaction was completed, the catalyst was centrifuged, washed and dried to obtain hydrophobic bismuth molybdate catalyst S-BMO-0.2, and the water contact angle was measured to be 91.4°.
[0101] (5) Olefin epoxidation: 10 mmol olefin, 10 mmol hydrogen peroxide, 10 mL acetonitrile and 0.05 g catalyst S-BMO-0.2 were added sequentially to a 50 mL micro reactor with magnetic stirring. The reaction was carried out at the target temperature of 60 °C and 200 rpm for 2 h. The olefin epoxidation conversion / selectivity was measured. The specific results were: cyclohexene (27% / 95%).
[0102] Example 7:
[0103] (1) 2 mmol and 1 mmol Dissolve in 80 mL of deionized water and stir for 0.5 hours.
[0104] (2) Add 0.1 mmol of oleylamine and 0.1 mmol of oleic acid to the resulting solution and continue stirring for 0.5 hours.
[0105] (3) Transfer the mixture to a 100 mL high-pressure reactor and react at 160 °C for 16 hours.
[0106] (4) After the reaction was completed, the catalyst was centrifuged, washed and air-dried to obtain hydrophobic bismuth molybdate catalyst H-BMO-0.1, and the water contact angle was measured to be 87.5°.
[0107] (5) Olefin epoxidation: 10 mmol olefin, 10 mmol hydrogen peroxide, 10 mL acetonitrile and 0.05 g catalyst H-BMO-0.1 were added sequentially to a 50 mL micro reactor with magnetic stirring. The reaction was carried out at the target temperature of 40 °C and 200 rpm for 2 h. The olefin epoxidation conversion rate / selectivity (% / %) was measured. The specific results were: propylene (87% / 99%).
[0108] Comparative Example 1:
[0109] (1) Take 1 mmol and 0.5 mmol Dissolve in 80 mL of deionized water and stir for 0.5 hours.
[0110] (2) Do not add oleylamine and oleic acid, and continue stirring for 0.5 hours.
[0111] (3) Transfer the mixture to a 100 mL high-pressure reactor and react at 180 °C for 16 hours.
[0112] (4) After the reaction was completed, the catalyst was centrifuged, washed and dried to obtain the hydrophobic bismuth molybdate catalyst BMO, and the water contact angle was measured to be 27.8°.
[0113] (5) Olefin epoxidation: 10 mmol olefin, 10 mmol hydrogen peroxide, 10 mL acetonitrile and 0.05 g catalyst BMO were added sequentially to a 50 mL micro reactor with magnetic stirring. The reaction was carried out at the target temperature of 60 °C and 200 rpm for 2 h. The olefin epoxidation conversion / selectivity was measured. The specific results were: 1-hexene (15% / 45%).
[0114] Comparative Example 2:
[0115] (1) Take 1 mmol and 0.5 mmol Dissolve in 80 mL of deionized water and stir for 0.5 hours.
[0116] (2) Add only 0.3 mmol of oleylamine and continue stirring for 0.5 hours.
[0117] (3) Transfer the mixture to a 100 mL high-pressure reactor and react at 180 °C for 16 hours.
[0118] (4) After the reaction was completed, the catalyst was centrifuged, washed and dried to obtain the hydrophobic bismuth molybdate catalyst BMO-OLA, and the water contact angle was measured to be 45.1°.
[0119] (5) Olefin epoxidation: 10 mmol olefin, 10 mmol hydrogen peroxide, 10 mL acetonitrile and 0.05 g catalyst BMO-OLA were added sequentially to a 50 mL micro reactor with magnetic stirring. The reaction was carried out at the target temperature of 60 °C and 200 rpm for 2 h. The olefin epoxidation conversion / selectivity was measured. The specific results were: cyclohexene (17% / 42%).
[0120] Comparative Example 3:
[0121] (6) Take 1 mmol and 0.5 mmol Dissolve in 80 mL of deionized water and stir for 0.5 hours.
[0122] (7) Do not add oleylamine and oleic acid, and continue stirring for 0.5 hours.
[0123] (8) Transfer the mixture to a 100 mL high-pressure reactor and react at 180 °C for 16 hours.
[0124] (9) After the reaction was completed, the catalyst was centrifuged, washed and dried to obtain the hydrophobic bismuth molybdate catalyst BMO, and the water contact angle was measured to be 27.8°.
[0125] (10) Epoxidation of olefins: 10 mmol of olefin, 10 mmol of hydrogen peroxide, 10 mL of acetonitrile and 0.05 g of catalyst BMO were added sequentially to a 50 mL micro reactor with magnetic stirring. The reaction was carried out at the target temperature of 60 °C and 200 rpm for 2 h. The olefin epoxidation conversion / selectivity was measured. The specific result was 1-octene (16% / 41%).
[0126] Comparative Example 4:
[0127] (1) 1 mmol and 0.5 mmol Dissolve in 80 mL of deionized water and stir for 0.5 hours.
[0128] (2) Add only 0.3 mmol of oleylamine and continue stirring for 0.5 hours.
[0129] (3) Transfer the mixture to a 100 mL high-pressure reactor and react at 180 °C for 16 hours.
[0130] (4) After the reaction was completed, the catalyst was centrifuged, washed and dried to obtain the hydrophobic bismuth molybdate catalyst BMO-OLA, and the water contact angle was measured to be 45.1°.
[0131] (5) Olefin epoxidation: 10 mmol olefin, 10 mmol hydrogen peroxide, 10 mL acetonitrile and 0.05 g catalyst BMO-OLA were added sequentially to a 50 mL micro reactor with magnetic stirring. The reaction was carried out at the target temperature of 40 °C and 200 rpm for 2 h. The olefin epoxidation conversion / selectivity was measured. The specific results were: 1-pentene (16% / 54%).
[0132] Examples 1-6 exhibited excellent catalytic performance against various olefins within 2 hours, while Comparative Examples 1-4 showed a significant decrease in activity under the same conditions. This demonstrates that the modification effect of using organic amines or organic acids alone is minimal, or even harmful; however, when both are used synergistically in a specific ratio, the epoxidation performance is dramatically improved. This proves that the synergistic modification mechanism of this invention produces unexpected technical effects, rather than being a simple additive effect.
[0133] 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. A method for preparing a surface-hydrophobicated bismuth molybdate catalyst, characterized in that, The steps are as follows: Step S1: Dissolve sodium molybdate and bismuth source in deionized water to form a precursor solution; Step S2: The precursor solution from step S1 is subjected to ultrasonic and vortex oscillation treatment, and then organic acid and organic amine are added to the precursor solution simultaneously. The mixture is stirred continuously until the solute is completely dissolved to obtain a mixed solution. Step S3: Adjust the pH of the mixed solution to the range of 1-5 using dilute acid and dilute alkali solutions, and then carry out a hydrothermal reaction to obtain the reactants; Step S4: Centrifuge the reaction product from step S3 at 6000-10000 rpm for 3-10 min, adding deionized water and ethanol respectively and centrifuging 2-5 times to obtain a solid product. Step S5: Use an organic solvent to initially remove the adsorbed, unreacted organic modifiers and organic byproducts adsorbed on the surface of the solid product, including ethanol, methanol, and acetone; then use deionized water to remove residual inorganic salt ions to obtain the washed solid. Step S6: Place the washed solid in a drying device for drying to obtain the surface hydrophobic bismuth molybdate catalyst. The drying is vacuum drying, the drying temperature is controlled at 50-80°C, and the drying time is 6-24 h.
2. The method for preparing a surface-hydrophobicated bismuth molybdate catalyst according to claim 1, characterized in that, The bismuth source is a compound that provides bismuth ions under hydrothermal reaction conditions, including soluble bismuth salts and bismuth-containing compounds. The soluble bismuth salts include bismuth nitrate, bismuth chloride, and bismuth sulfate. The bismuth-containing compounds refer to compounds that decompose in the aqueous phase and generate Bi during the reaction. 3+ Bismuth compounds, including bismuth salts of organic acids such as basic carbonic acid or bismuth acetate, and bismuth citrate.
3. The method for preparing a surface-hydrophobicated bismuth molybdate catalyst according to claim 2, characterized in that, The organic acid is selected from aliphatic organic acids (i.e., monocarboxylic acids) and aromatic organic acids (i.e., monocarboxylic acids) with hydrophobic chains. The aliphatic organic acids are straight-chain and branched alkyl carboxylic acids with 2 to 18 carbon atoms, including acetic acid, valeric acid, and oleic acid. The aromatic organic acids include benzoic acid. The organic amine is selected from aliphatic primary amines and aromatic primary amines. The aliphatic primary amines are straight-chain and branched alkyl primary amines with 3 to 18 carbon atoms, including propylamine, dodecylamine, and oleylamine. The aromatic organic amines include aniline.
4. The method for preparing a surface-hydrophobicated bismuth molybdate catalyst according to claim 3, characterized in that, The molar ratio of the organic acid to the organic amine is 0.8:1 to 1.2:
1.
5. The method for preparing a surface-hydrophobicated bismuth molybdate catalyst according to claim 4, characterized in that, The total amount of organic acid and organic amine added, in molar terms, is 10% to 50% of the molar amount of bismuth source.
6. The method for preparing a surface-hydrophobicated bismuth molybdate catalyst according to claim 5, characterized in that, In step S3, the hydrothermal reaction temperature is 160 °C to 180 °C, and the reaction time is 12 to 24 h.
7. The application of a surface-hydrophobicated bismuth molybdate catalyst, applicable to the preparation method of the surface-hydrophobicated bismuth molybdate catalyst as described in any one of claims 1-6, characterized in that, The application involves using a surface-hydrophobicated bismuth molybdate catalyst to catalyze the epoxidation of olefins. No additional phase transfer agent is required during the reaction. The specific steps are as follows: First, the surface-hydrophobic bismuth molybdate catalyst is placed in a solution containing olefins, polar solvents, and oxidants; Then, the reaction was stirred for 1–3 h at a temperature of 40–70 °C and a stirring speed of 200–600 rpm. Finally, the supernatant collected after the reaction is complete is the epoxy product solution.
8. The application of the surface-hydrophobicated bismuth molybdate catalyst according to claim 7, characterized in that, The oxidant is hydrogen peroxide, and the ratio of hydrogen peroxide to olefin is (5-15 mmol): (5-15 mmol).
9. The application of the surface-hydrophobicated bismuth molybdate catalyst according to claim 8, characterized in that, The olefin substrates are propylene, 1-pentene, 1-hexene, cyclohexene, and 1-octene, wherein the test temperature for 1-pentene is 30–60 °C, and the test temperatures for 1-hexene, cyclohexene, and 1-octene are 50 °C–70 °C.
10. The application of the surface-hydrophobicated bismuth molybdate catalyst according to claim 9, characterized in that, The ratio of the surface-hydrophobic bismuth molybdate catalyst to the olefin is (0.02–0.5 g): (5–15 mmol).