Process for the preparation of acetophenone by solvent-free ethylbenzene oxidation and catalysts and uses thereof

Abstract

The application discloses a kind of catalyst and method and application of preparation of phenylethanone by solvent-free ethylbenzene oxidation, belong to phenylethanone preparation technical field.The method of the present application regulates the efficiency of the catalyst by adjusting the content of Pd incorporated;And the introduction of oxygen-containing functional group-rich organic compounds is beneficial to the adsorption of oxygen and thus generates more active oxygen species.The preparation method is simple, the raw materials are cheap, no complex equipment is needed, the process is pollution-free, and is suitable for industrial mass production.The Pd / CNb2O5 catalyst can be used to prepare phenylethanone compounds by photocatalytic oxidation of ethylbenzene under solvent-free conditions, with high phenylethanone yield and selectivity, making it have broad industrial application prospects.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of acetophenone preparation, and particularly relates to a catalyst and method for preparing acetophenone by solvent-free ethylbenzene oxidation and application. BACKGROUND

[0002] Acetophenone, as an aromatic ketone most widely used in industry, has important application value in the fields of agriculture, medicine, perfume, material and dye, etc. Many systems for preparing acetophenone by catalyzing ethylbenzene oxidation need organic solvents such as water-methanol, acetonitrile, trifluorotoluene, toluene, hexafluoroisopropanol and 1,4-dioxane, which makes it difficult to separate the product in industry and increases the reaction cost. Therefore, it is of great theoretical and practical significance to explore an efficient, environmentally friendly and low-cost way for preparing acetophenone by solvent-free photocatalytic oxidation of ethylbenzene.

[0003] Gao Wenqiang et al. used an organic small molecule N-hydroxyphthalimide as a catalyst, and under the condition of normal pressure and room temperature, N-hydroxyphthalimide was first interchanged into N-oxyphthalimide radical, then the benzyl hydrogen of ethylbenzene was captured to generate benzyloxy radical, then the chain growth occurred with ozone to generate peroxy radical, which was decomposed into benzyloxy radical and oxygen, and finally the benzyloxy radical generated product acetophenone under the action of PINO (202211129644.1). Hao Yan et al. disclosed a method for preparing acetophenone by catalyzing ethylbenzene oxidation with nano-gold catalyst, 20 mg of nano-gold catalyst, 4 mmol of ethylbenzene and 6 mL of water were added into a reactor, and the target product acetophenone was prepared by reacting at 80℃ and normal pressure for 2 h (201910408501.6). The above prior art mainly has problems such as expensive catalyst, which cannot be recycled, complex preparation method, poor stability of catalyst, serious environmental pollution and low substrate conversion rate and product selectivity, which is not conducive to industrial practical application. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a catalyst and method for preparing acetophenone by solvent-free ethylbenzene oxidation and application, so as to solve the technical problems of low production efficiency, low conversion rate and selectivity, need for solvent, high treatment cost and environmental pollution in the synthesis of acetophenone by ethylbenzene oxidation.

[0005] In order to achieve the above purpose, the following technical solutions are adopted in the present application:

[0006] The present application discloses a method for preparing a catalyst for preparing acetophenone by solvent-free ethylbenzene oxidation, which comprises the following steps:

[0007] S1: After the niobium source solution and the template agent solution are mixed under heating and stirring, a hydrothermal reaction is carried out to obtain a reaction product; the reaction product is post-treated to obtain a niobium oxide carrier powder;

[0008] S2: dispersing the niobium oxide carrier powder in water, then adding the PdCl2 solution and urea while stirring, and calcining the obtained precipitate to obtain the Pd / CNb2O5 catalyst.

[0009] Further, in S1, the niobium source solution is obtained by mixing a niobium source and water, and the template solution is obtained by mixing a template and water; the niobium source is niobium oxalate or anhydrous niobium chloride; the template is arginine; and the molar ratio of the niobium oxalate to arginine is (10-20):10.

[0010] Further, in S1, the template solution is added to the niobium source solution, and stirring is performed at 60-100℃ for 2-4h.

[0011] Further, in S1, the temperature of the hydrothermal reaction is 180-200℃, and the time is 12-16h; after the hydrothermal reaction, the reaction product is naturally cooled to room temperature, and then post-treatment is performed; the post-treatment includes sequentially performing cooling, suction filtration, washing, and drying; the temperature of the drying is 80-100℃, and the time is 12-16h.

[0012] Further, in S2, the mass fraction of palladium in the PdCl2 solution is 0.089-0.44%.

[0013] Further, in S2, the amount ratio of the niobium oxide carrier powder, water, PdCl2 solution, and urea is 1.0g:30mL:(0.5-2.5)mL:(2.0-10.0)g.

[0014] Further, in S2, the niobium oxide carrier powder is dispersed in water, then the PdCl2 solution and urea are added while stirring, and the obtained precipitate is aged at 65℃ for 3h, and then the precipitate is subjected to centrifugal and drying treatment, and then calcination treatment.

[0015] Further, in S2, the process parameters of the calcination are as follows: the temperature is increased to 400-600℃ at a temperature increasing rate of 5-10℃ / min in an air atmosphere, and the calcination is performed at a constant temperature for 4h, and then the temperature is naturally cooled to room temperature.

[0016] The application further discloses a phenacetin catalyst prepared by the preparation method.

[0017] The application further discloses application of the phenacetin catalyst, and the phenacetin catalyst is used in combination with ethylbenzene to serve as a reaction catalyst for preparing phenacetin in a photocatalytic reaction container.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] The application discloses a method for preparing acetophenone by solvent-free ethylbenzene oxidation, adopts a niobium source solution, a template agent solution and arginine as raw materials to synthesize a porous Pd / CNb2O5 catalyst, increases the surface area of the catalyst, and thus improves the photocatalytic reaction activity; the introduction of carbon elements in the CNb2O5 can be beneficial to the adsorption of oxygen, and the surface of the CNb2O5 has certain hydrophilicity, which can effectively adsorb the intermediate phenethyl alcohol generated in the solvent-free ethylbenzene reaction process on the surface of the catalyst; the oxygen adsorbed on the surface of the catalyst is rapidly reduced into a peroxide free radical by electrons and is rapidly oxidized into acetophenone. Meanwhile, the introduction of carbon can make the niobium oxide carrier have high-concentration oxygen defects, and the existence of the oxygen defects can accelerate the separation of photo-generated carriers, and thus more active substances are generated, and the activity of the catalyst is improved. The preparation method disclosed by the application has simple preparation process, cheap raw materials and low cost, and is suitable for industrial batch production.

[0020] The application further discloses the acetophenone catalyst prepared by the above preparation method, PdO is uniformly introduced into the CNb2O5 structure, the low electron migration efficiency is overcome, and the migration of photo-generated electrons between material junctions is facilitated, so that the photo-generated electrons and holes can be effectively separated, the photocatalytic reaction activity is improved, the catalyst can be recycled after use, and the catalyst stability is good; the PdO is highly dispersed on the CNb2O5 carrier by the preparation method, which provides a prerequisite for the migration of photo-generated carriers; the catalyst has a large specific surface area and a surface rich in oxygen functional groups, which is beneficial to the generation of active substances, the adsorption of intermediate products and the desorption of products.

[0021] The application further discloses the application of the above acetophenone catalyst, the catalyst has very excellent activity and selectivity in the preparation of ketone compounds by solvent-free ethylbenzene and derivatives thereof oxidation and the oxidation of solvent-free benzyl alcohol and derivatives thereof into aldehydes, and when the catalyst is applied to the preparation of acetophenone in a photocatalytic reaction container, according to relevant experimental results, when the doping amount of Pd is 0.27%, the catalyst shows the best catalytic activity in the preparation of acetophenone by solvent-free oxidation of ethylbenzene. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 X-ray diffraction (XRD) spectra of Pd / CNb2O5 catalysts (acetophenone catalysts) prepared in the embodiments of the application and pure CNb2O5 and Nb2O5 prepared for comparison;

[0023] Figure 2 Fourier infrared spectra (FT-IR) of Pd / CNb2O5 catalysts (acetophenone catalysts) prepared in the embodiments of the application and pure CNb2O5 and Nb2O5 prepared for comparison;

[0024] Figure 3 The photocurrent spectrum of the Pd / CNb2O5 catalyst (acetophenone catalyst) prepared in the embodiments of the present application with different contents, and the pure CNb2O5 and the Nb2O5 prepared for comparison, and the impedance (ESI) spectrum of the Nb2O5 of the Pd / CNb2O5 catalyst (acetophenone catalyst) prepared in the embodiments of the present application with different contents, and the pure CNb2O5 and the Nb2O5 prepared for comparison.

[0025] Figure 4 The photocurrent spectrum of the Pd / CNb2O5 catalyst (acetophenone catalyst) prepared in the embodiments of the present application with different contents, and the pure CNb2O5 and the Nb2O5 prepared for comparison, and the impedance (ESI) spectrum of the Nb2O5 of the Pd / CNb2O5 catalyst (acetophenone catalyst) prepared in the embodiments of the present application with different contents, and the pure CNb2O5 and the Nb2O5 prepared for comparison. DETAILED DESCRIPTION

[0026] To enable persons skilled in the art to understand the features and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used herein have their usual meanings to those skilled in the art of the present application, and in the event of conflict, the definitions in the present specification shall prevail.

[0027] Theories or mechanisms described and disclosed herein, whether correct or not, should not be considered limiting the scope of the present application, i.e., the present application can be practiced without relying on any particular theory or mechanism.

[0028] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are for the sake of brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have encompassed and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0029] In this document, unless otherwise specified, "comprise", "include", "contain", "have", or similar words encompass the meaning of "consist of" and "consist essentially of", for example, "A comprises a" encompasses the meaning of "A comprises a and other" and "A comprises only a".

[0030] In this document, for the sake of brevity, not all possible combinations of the technical features in each embodiment or example are described. Therefore, as long as there is no contradiction in the combination of technical features, each technical feature in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope disclosed in the present specification.

[0031] The present application provides a method for preparing acetophenone catalyst by solvent-free ethylbenzene oxidation, and the preparation process is as follows:

[0032] a: dissolve niobium oxalate (or anhydrous niobium chloride) and arginine in a solvent respectively to obtain a niobium oxalate solution (or anhydrous niobium chloride solution) and an arginine solution;

[0033] b: stirring the niobium oxalate solution and the arginine solution under heating conditions;

[0034] c: heating and stirring the solution obtained in step b to make it completely dissolved;

[0035] d: hydrothermal treatment of the mixture obtained in step c in a hydrothermal kettle, cooling, suction filtration, washing, drying to obtain niobium oxide (CNb20s) carrier powder;

[0036] e: dispersing the niobium oxide carrier powder obtained in step d in water, adding PdCl2 solution and urea for precipitation while stirring, obtaining a precipitate after aging, and centrifugally drying the precipitate for standby;

[0037] f: calcining and grinding the solid powder obtained in step e in a muffle furnace under air atmosphere to obtain Pd / CNb20s catalyst.

[0038] Preferably, the solvent described above is deionized water; in step a, the molar ratio of the niobium oxalate to arginine is 20-10:10; and in step b, the stirring time of the respective solutions at 60°C is 2 h.

[0039] Preferably, in step c, the arginine solution is added to the niobium oxalate solution, and stirring at 60°C for 2 h is to make it mixed uniformly and clear.

[0040] Preferably, in step d, the clear solution in c is placed in a 100 mL polytetrafluoroethylene-lined hydrothermal kettle, hydrothermal treatment is carried out at a reaction temperature of 180°C for 12 h, natural cooling is carried out, suction filtration is carried out with deionized water, and drying is carried out at 80°C overnight to obtain niobium oxide (CNb20s) carrier powder.

[0041] Preferably, in step e, specifically: 177.33 mg of PdCl2 and 2.0 g of NaCl are dissolved in 100 mL of deionized water to prepare a PdCl2 solution of 1.7733 mg / mL; 1.0 g of the solid powder obtained in step d is dispersed in 30 mL of water, 0.5-2.5 mL (theoretical palladium content is about 0.089-0.44%) of the PdCl2 solution and 2.0-10.0 g of urea are added to the dispersion; then, the mixture is stirred for 4 h, and aged at 65°C for 3 h; after centrifugation and drying, a gray solid powder is obtained.

[0042] Preferably, in step f, the obtained gray solid powder is placed in a crucible, heated to 400°C at a heating rate of 5°C / min under air atmosphere, calcined at constant temperature for 4 h, and then naturally cooled to room temperature to obtain a white Pd / CNb20s catalyst, which is ground for standby.

[0043] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not intended to limit the scope of the application. Furthermore, it should be understood that after reading the present application, those skilled in the art can make various modifications or changes to the application, and these equivalent forms also fall within the scope of the appended claims.

[0044] The following examples use the instruments and equipment that are conventional in the art. The experimental methods in the following examples, unless otherwise specified, are generally carried out according to the conventional conditions, or according to the conditions recommended by the manufacturer. The following examples use various raw materials, unless otherwise specified, all use conventional commercially available products, which are conventional specifications in the art. In the specification of the present application and in the following examples, unless otherwise specified, "%" means weight percent, "parts" means weight parts, and the ratio means weight ratio.

[0045] Example 1

[0046] A method for preparing acetophenone by solvent-free oxidation of ethylbenzene, comprising the following steps:

[0047] S1: After mixing niobium oxalate and water, stirring at 60°C for 2h, a niobium oxalate solution is obtained; after mixing arginine and water, stirring at 60°C for 2h, an arginine solution is obtained; the arginine solution is added to the niobium oxalate solution, and stirring at 60°C for 2h is to make it mixed uniformly and clear; wherein the molar ratio of niobium oxalate to arginine in the arginine solution and the niobium oxalate solution is 10:10; the clear solution is moved to a 100mL polytetrafluoroethylene-lined hydrothermal kettle, hydrothermal at a reaction temperature of 180°C for 12h, naturally cooled, washed with deionized water while filtering, and dried at 80°C overnight to obtain a niobium oxide carrier powder (CNb2O5 catalyst);

[0048] S2: 177.33mg PdCl2 and 2.0g NaCl are dissolved in 100mL deionized water to prepare a 1.7733mg / mL PdCl2 solution; 1.0g of the niobium oxide carrier powder is dispersed in 30mL water, then 1.5mL (theoretical palladium content is about 0.27%) PdCl2 solution and 2.0g urea are added while stirring, the mixture is stirred for 4h, and aged at 65°C for 3h to obtain a precipitate, which is centrifuged, dried and placed in a crucible, heated to 400°C at a heating rate of 5°C / min under air atmosphere, and calcined at constant temperature for 4h, then naturally cooled to room temperature to prepare a white Pd / CNb2O5 catalyst.

[0049] Example 2

[0050] A method for preparing acetophenone by solvent-free oxidation of ethylbenzene, comprising the following steps:

[0051] S1: mix niobium oxalate and water, stir at 60°C for 2h to obtain a niobium oxalate solution; mix arginine and water, stir at 60°C for 2h to obtain an arginine solution; add the arginine solution to the niobium oxalate solution, stir at 60°C for 2h to make it mixed uniformly and clear; wherein the molar ratio of niobium oxalate to arginine in the niobium oxalate solution and the arginine solution used is 10:20; move the clear solution to a 100mL polytetrafluoroethylene-lined hydrothermal kettle, hydrothermal at a reaction temperature of 180°C for 12h, naturally cool, filter and wash with deionized water, dry at 80°C overnight to obtain a niobium oxide carrier powder (C-Nb2O5 catalyst);

[0052] S2: dissolve 177.33mg PdCl2 and 2.0g NaCl in 100mL deionized water to prepare a 1.7733mg / mL PdCl2 solution; disperse 1g of the niobium oxide carrier powder in 30mL water, then add 0.5mL (palladium content is about 0.089%) PdCl2 solution and 2.0g urea while stirring, stir the mixture for 4h, age at 65°C for 3h to obtain a precipitate, centrifuge and dry the precipitate, then place it in a crucible, heat to 400°C at a heating rate of 5°C / min under an air atmosphere, heat at constant temperature for 4h, then naturally cool to room temperature to prepare a white PdO / C-Nb2O5 catalyst.

[0053] Example 3

[0054] A method for preparing acetophenone by solvent-free ethylbenzene oxidation, comprising the following steps:

[0055] S1: mix niobium oxalate and water, stir at 60°C for 2h to obtain a niobium oxalate solution; mix arginine and water, stir at 60°C for 2h to obtain an arginine solution; add the arginine solution to the niobium oxalate solution, stir at 60°C for 2h to make it mixed uniformly and clear; wherein the molar ratio of niobium oxalate to arginine in the niobium oxalate solution and the arginine solution used is 10:20; move the clear solution to a 100mL polytetrafluoroethylene-lined hydrothermal kettle, hydrothermal at a reaction temperature of 200°C for 12h, naturally cool, filter and wash with deionized water, dry at 80°C overnight to obtain a niobium oxide carrier powder (C-Nb2O5 catalyst);

[0056] S2: 177.33 mg of PdCl2 and 2.0 g of NaCl were dissolved in 100 mL of deionized water to prepare a PdCl2 solution of 1.7733 mg / mL; 1 g of the niobium oxide carrier powder was dispersed in 30 mL of water, then 0.5 mL (theoretical palladium content of about 0.089%) of the PdCl2 solution and 2.0 g of urea were added while stirring, the mixture was stirred for 4 h, aged at 65°C for 3 h to obtain a precipitate, the precipitate was centrifuged and dried, then placed in a crucible, heated to 400°C at a heating rate of 5°C / min under an air atmosphere, calcined at constant temperature for 4 h, and then naturally cooled to room temperature to prepare a white PdO / C-Nb2O5 catalyst.

[0057] Example 4

[0058] A method for preparing a catalyst for the solvent-free oxidation of ethylbenzene to acetophenone, comprising the following steps:

[0059] S1: niobium oxalate and water were mixed and stirred at 60°C for 2 h to obtain a niobium oxalate solution; arginine and water were mixed and stirred at 60°C for 2 h to obtain an arginine solution; the arginine solution was added to the niobium oxalate solution, which was stirred at 60°C for 2 h to make the mixture uniform and clear; the molar ratio of niobium oxalate to arginine in the arginine solution and the niobium oxalate solution was 10:20; the clear solution was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal kettle, hydrothermally treated at a reaction temperature of 180°C for 12 h, naturally cooled, washed with deionized water while suction filtering, and dried at 80°C overnight to obtain a niobium oxide carrier powder (C-Nb2O5 catalyst);

[0060] S2: 177.33 mg of PdCl2 and 2.0 g of NaCl were dissolved in 100 mL of deionized water to prepare a PdCl2 solution of 1.7733 mg / mL; 1 g of the niobium oxide carrier powder was dispersed in 30 mL of water, then 0.5 mL (theoretical palladium content of about 0.089%) of the PdCl2 solution and 2.0 g of urea were added while stirring, the mixture was stirred for 4 h, aged at 65°C for 3 h to obtain a precipitate, the precipitate was centrifuged and dried, then placed in a crucible, heated to 400°C at a heating rate of 5°C / min under an air atmosphere, calcined at constant temperature for 4 h, and then naturally cooled to room temperature to prepare a white PdO / C-Nb2O5 catalyst.

[0061] Example 5

[0062] A method for preparing a catalyst for the solvent-free oxidation of ethylbenzene to acetophenone, comprising the following steps:

[0063] S1: After mixing niobium oxalate and water, stirring at 60°C for 2h, niobium oxalate solution was obtained; after mixing arginine and water, stirring at 60°C for 2h, arginine solution was obtained; arginine solution was added to niobium oxalate solution, stirring at 60°C for 2h to make it mixed uniformly and clear; wherein the molar ratio of niobium oxalate to arginine in the used niobium oxalate solution and arginine solution was 10:20; the clear solution was moved to a 100mL polytetrafluoroethylene-lined hydrothermal kettle, hydrothermal at a reaction temperature of 180°C for 12h, naturally cooled, washed with deionized water while filtering, dried at 80°C overnight to obtain niobium oxide carrier powder (C-Nb2O5 catalyst);

[0064] S2: 177.33mg PdCl2 and 2.0g NaCl were dissolved in 100mL deionized water to prepare a 1.7733mg / mL PdCl2 solution; 1g niobium oxide carrier powder was dispersed in 30mL water, then 1.5mL (theoretical palladium content was about 0.27%) PdCl2 solution and 2.0g urea were added while stirring, the mixture was stirred for 4h, aged at 65°C for 3h to obtain a precipitate, the precipitate was centrifuged, dried and placed in a crucible, heated to 600°C at a heating rate of 5°C / min under air atmosphere, calcined at constant temperature for 4h, then naturally cooled to room temperature to prepare a white PdO / C-Nb2O5 catalyst.

[0065] Application Example 1

[0066] The acetophenone catalyst prepared in Example 1 and ethylbenzene were placed in a photocatalytic reaction container, 100mg Pd / CNb2O5 catalyst was added per 20mmol of ethylbenzene, 1bar of oxygen was introduced, irradiated under a LED light source with a power of 10W and a wavelength of λ=400-405nm, the stirring speed was 1500rpm, the reaction temperature was 25°C, and the reaction time was 12h, the conversion rate of ethylbenzene was 67.4%, and the selectivity of acetophenone was 97.7%.

[0067] Application Example 2

[0068] The acetophenone catalyst prepared in Example 2 and ethylbenzene were placed in a photocatalytic reaction container, 100mg Pd / CNb2O5 catalyst was added per 20mmol of ethylbenzene, 1bar of air was introduced, irradiated under a LED light source with a power of 10W and a wavelength of λ=400-405nm, the stirring speed was 1500rpm, the reaction temperature was 25°C, and the reaction time was 12h, the conversion rate of ethylbenzene was 37.4%, and the selectivity of acetophenone was 94.8%.

[0069] Application Example 3

[0070] The acetophenone catalyst prepared in Example 3 and ethylbenzene were placed in a photocatalytic reactor vessel, 100 mg of Pd / C Nb2O5 catalyst was added per 20 mmol of ethylbenzene, 1 bar of nitrogen was bubbled in, the reaction was carried out under irradiation with a LED light source with a power of 10 W and a wavelength of λ = 400-405 nm, the stirring speed was 1500 rpm, the reaction temperature was 25 °C, the reaction time was 12 h, the conversion of ethylbenzene was 4.6% and the selectivity to styrene was 100%.

[0071] Application Example 4

[0072] The acetophenone catalyst prepared in Example 4 and ethylbenzene were placed in a photocatalytic reactor vessel, 100 mg of CNb2O5 catalyst was added per 20 mmol of ethylbenzene, 1 bar of nitrogen was bubbled in, the reaction was carried out under irradiation with a LED light source with a power of 10 W and a wavelength of λ = 400-405 nm, the stirring speed was 1500 rpm, the reaction temperature was 25 °C, the reaction time was 12 h, the conversion of ethylbenzene was 25.8% and the selectivity to acetophenone was 97.5%.

[0073] Application Example 5

[0074] The acetophenone catalyst prepared in Example 5 and ethylbenzene were placed in a photocatalytic reactor vessel, 1000 mg of Pd / C Nb2O5 catalyst was added per 200 mmol of ethylbenzene, 1 bar of oxygen was bubbled in, the reaction was carried out under irradiation with a Xe light source with a power of 200 W and a wavelength of λ > 400 nm, the stirring speed was 1500 rpm, the reaction temperature was 25 °C, the reaction time was 12 h, the conversion of ethylbenzene was 34.5% and the selectivity to acetophenone was 94.3%.

[0075] Comparative Example 1

[0076] In this comparative example, a Nb2O5 catalyst was prepared, which comprised the following steps:

[0077] Anhydrous niobium chloride was accurately weighed at 4 mmol and dispersed in 40 mL of deionized water, 10 mL of 25-27% ammonia water was added while stirring to obtain a white precipitate, the white mixture was stirred for 4 h and aged at 65 °C for 3 h. After centrifugation and drying, a white solid powder was obtained.

[0078] The obtained white solid powder was placed in a crucible and heated to 400 °C at a heating rate of 5 °C / min under an air atmosphere, calcined at 400 °C for 4 h, and then naturally cooled to room temperature to obtain a white Nb2O5 catalyst, which was ground and used.

[0079] The obtained Nb2O5catalyst, 100 mg of Nb2O5catalyst was added per 20 mmol of ethylbenzene, 1 bar of nitrogen was introduced, and the reaction was carried out under irradiation of a LED light source with a power of 10 W and a wavelength of λ = 400-405 nm, at a stirring speed of 1500 rpm, a reaction temperature of 25°C, and a reaction time of 12 h. The conversion rate of ethylbenzene was 8.2%, and the selectivity of acetophenone was 91.9%.

[0080] Comparative Example 2

[0081] In this comparative example, a Pd / Nb2O5-Commercial catalyst was prepared, which included the following steps:

[0082] 1 g of commercial Nb2O5was weighed and dispersed in 40 mL of deionized water, 1.5 mL of prepared PdCl2solution (177.33 mg of PdCl2and 2.0 g of NaCl were dissolved in 100 mL of deionized water to prepare a PdCl2solution with a concentration of 1.7733 mg / mL), and 2.0 g of urea were removed. Then, the mixture was stirred for 4 h and aged at 65°C for 3 h. After centrifugation and drying, a gray solid powder was obtained.

[0083] The obtained gray solid powder was placed in a crucible and heated to 400°C at a heating rate of 5°C / min under an air atmosphere, and then calcined at a constant temperature for 4 h. After natural cooling to room temperature, a white Pd / Nb2O5-Commercial catalyst was prepared, which was ground and reserved.

[0084] The obtained Pd / Nb2O5-Commercial catalyst, 100 mg of Pd / Nb2O5-commercial catalyst was added per 20 mmol of ethylbenzene, 1 bar of nitrogen was introduced, and the reaction was carried out under irradiation of a LED light source with a power of 10 W and a wavelength of λ = 400-405 nm, at a stirring speed of 1500 rpm, a reaction temperature of 25°C, and a reaction time of 12 h. The conversion rate of ethylbenzene was 28.8%, and the selectivity of acetophenone was 85.9%.

[0085] The Pd / CNb2O5catalysts prepared in Examples 1-5, the Nb2O5catalysts prepared in Comparative Examples 1-2, and the Pd / Nb2O5-Commercial catalyst were subjected to XRD, FT-IR, photocurrent, and impedance tests, and the test patterns are shown in Figure 1 、 Figure 2 、 Figure 3 、 Figure 4

[0086] Figure 1 ​The XRD spectrum of the sample shows that the sample is partially composed of niobia, wherein the peaks of the niobia are shifted and the peaks of PdO are not detected, indicating that Pd is successfully incorporated into the crystal lattice of niobia and the content is low, and compared with the prepared Nb2O5, the crystal phase of Pd / CNb2O5 and CNb2O5 has disorder, and the disordered niobia is beneficial to the adsorption of oxygen.

[0087] Figure 2 The FT-IR spectrum of the sample can show that compared with the prepared Nb2O5, the catalyst surface of Pd / CNb2O5 and CNb2O5 contains rich oxygen-containing functional groups, and the oxygen-containing functional groups are beneficial to the adsorption of intermediate products.

[0088] Figure 3 The broad current spectrum of the sample can show that compared with the prepared Nb2O5 and CNb2O5, the catalyst of Pd / CNb2O5 has a very high photoelectric current response signal, indicating that the introduction of Pd accelerates the separation of photo-generated carriers and improves the broad current efficiency.

[0089] Figure 4 The impedance spectrum of the sample can show that compared with the prepared Nb2O5 and CNb2O5, the catalyst of Pd / CNb2O5 has a small current impedance effect, indicating that the introduction of Pd indeed accelerates the separation of photo-generated carriers and improves the broad current efficiency. The above content is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application, and any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A process for the preparation of a catalyst for the solvent-free oxidation of ethylbenzene to acetophenone, characterized in that, The method comprises the following steps: S1: mixing a niobium source solution and a template solution under stirring and heating, and then performing a hydrothermal reaction to obtain a reaction product; and performing post-treatment on the reaction product to obtain a niobium oxide carrier powder; S2: dispersing the niobium oxide carrier powder in water, then adding a PdCl2 solution and urea under stirring, and then performing calcination treatment on the obtained precipitate to obtain a Pd / CNb2O5 catalyst.

2. The production method according to claim 1, characterized by, In S1, the niobium source solution is obtained by mixing a niobium source and water, and the template solution is obtained by mixing a template and water; the niobium source is niobium oxalate or anhydrous niobium chloride; the template is arginine; and the molar ratio of the niobium oxalate to the arginine is (10-20):

10.

3. The production method according to claim 1, characterized by, In S1, the template solution is added to the niobium source solution, and then stirring is performed at 60-100 DEG C for 2-4 hours.

4. The production method according to claim 1, characterized by, In S1, the temperature of the hydrothermal reaction is 180-200 DEG C, and the time is 12-16 hours; after the hydrothermal reaction, the reaction product is naturally cooled to room temperature, and then post-treatment is performed; the post-treatment comprises sequentially performing cooling, suction filtration, washing, and drying; the temperature of the drying is 80-100 DEG C, and the time is 12-16 hours.

5. The preparation method according to claim 1, characterized in that, In S2, the mass fraction of palladium in the PdCl2 solution is 0.089-0.44%.

6. The method of claim 1, wherein, In S2, the amount ratio of the niobium oxide carrier powder, water, the PdCl2 solution, and urea is 1.0 g:30 mL:(0.5-2.5) mL:(2.0-10.0) g.

7. The preparation method according to claim 1, characterized in that, In S2, the niobium oxide carrier powder is dispersed in water, then the PdCl2 solution and urea are added under stirring, and then the obtained precipitate is aged at 65 DEG C for 3 hours; then the precipitate is subjected to centrifugal treatment and drying treatment, and then calcination treatment is performed.

8. The method of claim 1, wherein, In S2, the process parameters of the calcination are as follows: the temperature is increased to 400-600 DEG C at a temperature increasing rate of 5-10 DEG C / min in an air atmosphere, and then the temperature is kept constant for 4 hours, and then the temperature is naturally cooled to room temperature.

9. A catalyst for the solvent-free oxidation of ethylbenzene to acetophenone, characterized in that, The catalyst is prepared by the preparation method in any one of claims 1-8.

10. Use of the catalyst according to claim 9 for the solvent-free oxidation of ethylbenzene to acetophenone, characterized in that, The catalyst is used in combination with ethylbenzene to prepare acetophenone in a photocatalytic reaction container.

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