A palladium-zinc-bismuth oxide catalyst and a preparation method and application thereof in oxidation of beta-hydroxy ester

Abstract

The application provides a palladium-zinc-bismuth oxide catalyst and a preparation method and application thereof in beta-hydroxy ester oxidation, and the preparation steps of the catalyst comprise the following steps: dissolving a bismuth salt and an alkali into water, adding carbon powder to be ultrasonically dispersed, then heating to reflux to perform reaction, and then performing filtration and drying to obtain Bi2O3 / C; dissolving a palladium salt, a zinc salt, L-ascorbic acid and polyvinyl pyrrolidone into water, adding Bi2O3 / C to be ultrasonically dispersed, then heating to reflux to perform reaction, and then performing filtration, drying and calcination to obtain the palladium-zinc-bismuth oxide catalyst. The obtained catalyst can be used in beta-hydroxy ester oxidation reaction, and beta-keto ester products can be obtained with high yield and high selectivity. The catalyst has novel structure, simple preparation process, can efficiently catalyze beta-hydroxy ester oxidation to obtain beta-keto ester products, has the advantages of fast reaction speed, high raw material conversion rate and high product selectivity, and has important application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalysis and fine chemical industry, and particularly relates to a palladium-zinc-bismuth oxide catalyst and a preparation method, and application of the catalyst in preparation of beta-keto ester by oxidation of beta-hydroxy ester BACKGROUND

[0002] Beta-keto ester compounds are very important intermediates in organic synthesis, such as well-known methyl acetoacetate and ethyl acetoacetate. Due to the special molecular structure, the beta-keto ester compounds have both the properties of ketone and the reaction characteristics of enol, and are very active in chemical properties, and can be used to synthesize a series of alkylated products and heterocyclic compounds, and are widely used in the fields of medicine, dye, pesticide, etc., and are also used in the production of food additives and flavor and fragrance.

[0003] There are multiple synthesis methods for methyl acetoacetate and ethyl acetoacetate, among which the most commonly used method is the diacetylene ketone method: under the action of a base catalyst, diacetylene ketone reacts with methanol and ethanol respectively, and methyl acetoacetate and ethyl acetoacetate can be obtained in high yield.

[0004]

[0005] The synthesis method of methyl acetoacetate and ethyl acetoacetate is relatively mature and simple, but the synthesis method of other high-level beta-keto esters is relatively complex. For example, ethyl butyryl acetate, first, diethyl malonate and butyryl chloride undergo condensation reaction to obtain a beta-keto diester intermediate, and then hydrolysis decarboxylation occurs under the action of an equivalent base to obtain the ethyl butyryl acetate product. Other high-level beta-keto esters can be synthesized by using similar methods. The synthesis route is relatively long, and both steps produce a large amount of waste, and the atom economy is poor.

[0006]

[0007] Oxidation of the hydroxyl group in the beta-hydroxy ester molecule is a simple method to obtain beta-keto ester, but the relevant literature and patents report is not too much; for example, patent CN110183327A uses vanadium-based nitrogen-doped carbon material as catalyst, realizes the oxidation of 3-hydroxy butyric acid methyl ester in acetonitrile solvent at 120 DEG C, and the conversion rate and selectivity are 94% and 95% respectively, the effect is good, the shortage is that the catalyst dosage is large, which needs 5wt%. Patent CN108863796A reports a method for oxidizing lactic acid ester to obtain pyruvic acid ester, which uses KBr and Amberlyst-15 resin as a composite catalyst, hydrogen peroxide as an oxidant, the raw material conversion rate is 96%, and the product selectivity is 98%; Although the effect is good, but the metal halide addition amount is large. Patent CN105130807B uses phenyl seleninic acid as catalyst, air as oxidant to oxidize methyl mandelate, and the oxidation yield is only 73%, the yield is low.

[0008]

[0009] In summary, at present, the synthesis method of simple beta-keto esters such as methyl acetoacetate and ethyl acetoacetate is mature, and the cost is low; but some higher beta-keto esters such as methyl propionyl acetoacetate and methyl butyryl acetoacetate have relatively few synthesis methods, and have the disadvantages of low yield, much waste, etc., resulting in high cost of beta-keto ester, which limits its potential application. Oxidation of the hydroxyl group in the beta-hydroxy ester molecule is a simple method to obtain beta-keto ester, but the related literature reports less, and the catalyst dosage is also large, which is not economical. Therefore, it is of important application value and economic value to develop a new beta-hydroxy ester oxidation catalyst system, overcome the shortcomings of the existing beta-keto ester synthesis method, and prepare beta-keto ester compounds from simple and low-cost raw materials with higher yield. SUMMARY

[0010] In view of the above problems existing in the prior art, the purpose of the present application is first to provide a palladium-zinc-bismuth oxide catalyst and a preparation method, which has a novel structure and a simple preparation process.

[0011] The purpose of the present application is also to provide the application of the catalyst in the oxidation of beta-hydroxy ester to prepare beta-keto ester. The present application introduces Zn component and nitrogen oxide additive into the palladium-bismuth oxide catalyst to synergistically act, which can effectively shorten the initiation time of the oxidation reaction of hydroxy ester, has high product yield, and maintains good catalytic activity, and can realize cyclic application.

[0012] To achieve the above purposes and achieve the above technical effects, the present application adopts the following technical solutions:

[0013] On the one hand, the present application provides a preparation method of a palladium-zinc-bismuth oxide catalyst, which comprises the following steps:

[0014] 1) Dissolve bismuth salt and base in water, add carbon powder, ultrasonic dispersion, then heat to reflux to react, filter, dry to obtain Bi2O3 / C;

[0015] 2) Dissolve palladium salt, zinc salt, L-ascorbic acid and polyvinylpyrrolidone (PVP) in water, add Bi2O3 / C prepared in step 1) for ultrasonic dispersion, then heat to reflux to react, filter, dry, calcine to obtain palladium-zinc-bismuth oxide catalyst (i.e. Pd-Zn-Bi2O3 / C catalyst).

[0016] In the present application, the bismuth salt in step 1) is selected from at least one of bismuth nitrate, bismuth phosphate, bismuth sulfate, bismuth subnitrate and the like;

[0017] The base is selected from at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium phosphate and the like;

[0018] The source of the carbon powder is not particularly limited, for example, it can be selected from at least one of carbon powder derived from coconut shell, fruit shell, wood, coal and the like;

[0019] Preferably, the particle size of the carbon powder is 1-100 μm, preferably 10-50 μm.

[0020] In the present application, the molar ratio of the bismuth salt to base in step 1) is 1:5-20, preferably 1:5-10;

[0021] The mass ratio of the carbon powder to bismuth salt is 20-100:1, preferably 50-100:1;

[0022] The total concentration of the bismuth salt and base dissolved in water is 0.008-0.02 g / ml, preferably 0.01-0.02 g / ml.

[0023] In the present application, the ultrasonic dispersion in step 1) is for 10-30 min, preferably 20-30 min;

[0024] The reaction is at a temperature of 95-110°C, preferably 99-102°C, for 6-12 h, preferably 6-8 h.

[0025] In the present application, the palladium salt in step 2) is selected from at least one of palladium chloride, palladium bromide, palladium acetate, palladium acetylacetonate, palladium nitrate, palladium trifluoroacetate and the like;

[0026] The zinc salt is selected from at least one of zinc acetate, zinc acetylacetonate, zinc nitrate, zinc chloride, zinc propionate and the like.

[0027] The molar ratio of the zinc salt to palladium salt is 1:0.5-3, preferably 1:0.5-2;

[0028] The molar ratio of the L-ascorbic acid to the palladium salt is 2-10:1, preferably 2-5;

[0029] The mass ratio of the polyvinylpyrrolidone to the palladium salt is 1-3:1, preferably 2-3;

[0030] The total concentration of the palladium salt, the zinc salt, the L-ascorbic acid and the polyvinylpyrrolidone in water is 0.010-0.015 g / ml, preferably 0.012-0.015 g / ml;

[0031] The dispersion concentration of the Bi2O3 / C prepared in step 1) in water is 0.1-0.4 g / ml, preferably 0.2-0.4 g / ml.

[0032] In the present application, the ultrasonic dispersion in step 2) is performed for 10-30 min, preferably 20-30 min.

[0033] The reaction is performed at a temperature of 95-110℃, preferably 99-102℃, for 2-6 h, preferably 2-3 h.

[0034] In the present application, the filtration, drying and calcination involved in steps 1) and 2) are conventional operations in the art, wherein, preferably, the drying in step 1) is performed at a temperature of 40-80℃, preferably 60-80℃, for 6-12 h, preferably 6-8 h.

[0035] The drying in step 2) is performed at a temperature of 40-80℃, preferably 60-80℃, for 6-12 h, preferably 6-8 h; and the calcination is performed at a temperature of 200-400℃, preferably 300-400℃, for 2-6 h, preferably 2-4 h.

[0036] In another aspect, the present application also provides a palladium-zinc-bismuth oxide catalyst prepared by the above method.

[0037] In still another aspect, the present application also provides a use of the above palladium-zinc-bismuth oxide catalyst in the preparation of β-keto ester from β-hydroxy ester.

[0038] In the present application, the β-hydroxy ester is one or more of the compounds having the structure shown in the following formula 1:

[0039]

[0040] In the formula, R1, R2 are independently selected from C1-C10 alkyl, C2-C10 alkenyl, C6-C12 aryl, C5-C12 heterocyclic substituent, heteroatom selected from N, O, S, etc., preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, isopentyl, phenyl, naphthyl, furanyl, pyrrolyl, pyridyl, thienyl, quinoline, quinoxaline, etc.; R1, R2 can be the same or different.

[0041] As preferred, the present application provides a method for preparing β-keto ester by oxidizing β-hydroxy ester, which is prepared by oxidizing β-hydroxy ester with an oxidant in a solvent environment under the action of the above-mentioned palladium-zinc-bismuth oxide catalyst.

[0042] The reaction equation for preparing β-keto ester by oxidizing β-hydroxy ester is shown as follows:

[0043]

[0044] In the present application, the oxidant is selected from at least one of air, oxygen, hydrogen peroxide, hypochlorous acid, alkyl peroxide, alkyl peroxy ether, peroxy acid, etc., preferably at least one of air and oxygen;

[0045] The amount of the oxidant is generally excessive, and the specific upper limit is not limited, for example, the amount can be 2-10 times the molar amount of β-hydroxy ester, or when the oxidant is gaseous, it can be controlled by the pressure of the reaction system.

[0046] In the present application, the solvent is selected from at least one of methanol, ethanol, isopropanol, ethyl acetate, dichloromethane, chloroform, dichloroethane, acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, toluene, acetone, preferably at least one of acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide;

[0047] The amount of the solvent is 1.0-4.0 M based on the concentration of the substrate β-hydroxy ester.

[0048] In the present application, the amount of the palladium-zinc-bismuth oxide catalyst is 0.1-2.0 wt% of β-hydroxy ester.

[0049] In the present application, the reaction temperature of the oxidation reaction is 80-150°C, preferably 80-100°C, and the time is 1-4 h, preferably 1-2 h.

[0050] The reaction pressure is 0.5-3.0 MPa, preferably 0.5-2.0 MPa.

[0051] In the present application, an auxiliary agent can also be added to promote the reaction and shorten the reaction initiation time.

[0052] The auxiliary agent is at least one selected from morpholine N-oxide, N-methyl morpholine N-oxide, triethylamine N-oxide, nitric oxide, dinitrogen monoxide, trimethylamine oxide and the like, preferably morpholine N-oxide, N-methyl morpholine N-oxide, triethylamine N-oxide;

[0053] The amount of the auxiliary agent is 1.0-3.0 mol% of the substrate β-hydroxy ester.

[0054] In the present application, after the oxidation reaction is completed, the catalyst is recovered by filtering the reaction solution, and then can be directly used in the next step reaction after washing and drying.

[0055] Compared with the prior art, the technical scheme of the present application has the following positive effects:

[0056] 1. The palladium-zinc-bismuth oxide catalyst prepared by the present application has a novel structure, a simple preparation process, and good catalytic oxidation activity.

[0057] 2. The zinc element introduced in the catalyst exists in the form of zinc oxide, which has Lewis base sites and can promote the surface adsorption of the β-hydroxy ester substrate, thereby promoting the oxidation reaction, improving the reaction rate and selectivity. After the β-hydroxy ester is adsorbed, the palladium catalyst dehydrogenates it to obtain a β-keto ester product, and the palladium is changed from a high-valence state to a low-valence palladium hydrogen species. The palladium hydrogen is oxidized to a high-valence state by the oxidizing agent and then catalyzing again, and the catalyst activity remains good, which can realize recycling.

[0058] 3. The further introduction of nitrogen oxide auxiliary agent in the present application can oxidize the palladium on the surface of the palladium-zinc-bismuth oxide catalyst to a high-valence state, thereby effectively shortening the oxidation reaction initiation time, promoting the reaction to proceed quickly, and shortening the reaction time to 1-2h, which is significantly lower than the current literature report level, and the conversion rate and selectivity are high, generally above 95%.

[0059] 4. The oxidation method of the present application has the advantages of high yield, less waste, green environmental protection, etc. DETAILED DESCRIPTION

[0060] The following examples will further illustrate the method provided by the present application, but the present application is not limited to the listed examples, and any other known changes within the scope of the claimed rights of the present application should also be included.

[0061] The main raw material source information in the examples and comparative examples of the present application is as follows, and other materials not specifically mentioned are obtained from ordinary commercial channels:

[0062] Bismuth nitrate, bismuth phosphate, bismuth nitrite, Anjieji Chemical, AR;

[0063] Carbon powder, Aldrich reagent, 99%;

[0064] Urea, ammonium bicarbonate, National Reagent, AR;

[0065] Palladium acetate, trifluoro palladium acetate, Little Chili reagent;

[0066] L-ascorbic acid, North China Pharmaceutical;

[0067] Polyvinyl pyrrolidone K30, New Kaiyuan;

[0068] Zinc acetate, zinc propionate, zinc nitrate, acetylacetone cadmium, National Reagent, 98%;

[0069] 3-hydroxyhexanoic acid ethyl ester, 3-hydroxy-4-methyl valeric acid methyl ester, Bailingwei reagent, AR;

[0070] 3-hydroxy valeric acid methyl ester, Wengjiang reagent, AR;

[0071] 3-hydroxyheptanoic acid ethyl ester, Kamel medicine, AR;

[0072] 3-hydroxydecanoic acid ethyl ester, Aoboke biological, AR;

[0073] 3-hydroxyhexanoic acid n-butyl ester, Yuanda reagent, AR;

[0074] 3-hydroxy-3-phenylpropionic acid methyl ester, Aladdin reagent, AR;

[0075] Acetonitrile, N, N-dimethylformamide, dimethyl sulfoxide, Xilong reagent, AR;

[0076] N-methyl morpholine N-oxide, trimethylamine oxide, Aldrich reagent, 99%.

[0077] The main analysis method used in the examples and comparative examples of the present application:

[0078] The gas chromatography test conditions are as follows:

[0079] Instrument model: Shimadzu gas chromatograph 2010; chromatographic column Agilent DB-5 (30m x 0.25mm x 0.25um); column temperature: initial temperature 50℃, temperature rising to 100℃ at 5℃ / min, then temperature rising to 150℃ at 10℃ / min, finally temperature rising to 240℃ at 20℃ / min, keeping for 5min; injection port temperature: 280℃; FID detector temperature: 280℃; split injection, split ratio 45:1; injection amount: 2.0uL; H2flow: 30mL / min; air flow: 200mL / min.

[0080] Example 1

[0081] Preparation of palladium-zinc-bismuth oxide catalyst:

[0082] 1) Bismuth nitrate (0.395 g, 1.0 mmol) and sodium hydroxide (0.200 g, 5.0 mmol) were dissolved in 50 mL of deionized water at room temperature and stirred to dissolve; then 19.8 g of carbon powder (average particle size 20 μm) was added to the above aqueous solution at one time, and after ultrasonic dispersion for 20 minutes, the aqueous solution was heated to reflux in an oil bath at 100°C, and the temperature was maintained at 100°C for 6 hours with uniform stirring; finally, the suspension was cooled to room temperature, filtered, and dried at 40°C for 12 hours to obtain about 20 g of carbon powder loaded bismuth oxide carrier Bi2O3 / C.

[0083] 2) Palladium acetate (0.225 g, 1.0 mmol), zinc acetate (0.184 g, 1.0 mmol), L-ascorbic acid (0.881 g, 5.0 mmol), and polyvinylpyrrolidone (0.225 g) were dissolved in 100 mL of deionized water at room temperature to obtain a uniform solution, and then 20.0 g of Bi2O3 / C prepared in step 1) was added to the above aqueous solution, and after ultrasonic dispersion for 15 minutes, the temperature was heated to 100°C for reflux reaction for 2 hours, and the catalyst precursor was obtained by cooling, filtering, and drying. The catalyst precursor was dried at 80°C for 6 hours, and then calcined (400°C, 2 hours) under N2protection to obtain 20.2 g of carbon powder loaded palladium-zinc-bismuth oxide catalyst, which was named PdZn-Bi2O3 / C-1.

[0084] Example 2

[0085] Preparation of palladium-zinc-bismuth oxide catalyst:

[0086] 1) Bismuth nitrate (0.198 g, 0.5 mmol) and potassium hydroxide (0.140 g, 2.5 mmol) were dissolved in 30 mL of deionized water at room temperature and stirred to dissolve; then 9.9 g of carbon powder (average particle size 50 μm) was added to the above aqueous solution at one time, and after ultrasonic dispersion for 20 minutes, the aqueous solution was heated to reflux in an oil bath at 102°C, and the temperature was maintained at 102°C for 6 hours with uniform stirring; finally, the suspension was cooled to room temperature, filtered, and dried at 80°C for 6 hours to obtain about 10 g of carbon powder loaded bismuth oxide carrier Bi2O3 / C.

[0087] 2) PdZn-Bi203 / C-2: Pd(II) acetate (0.112 g, 0.5 mmol), zinc propionate (0.106 g, 0.5 mmol), L-ascorbic acid (0.176 g, 1.0 mmol), polyvinylpyrrolidone (0.224 g) were dissolved in 50 mL of deionized water to form a homogeneous solution. Then, 10.0 g of Bi203 / C prepared in step 1) was added into the above aqueous solution, and ultrasonically dispersed for 15 min. After that, the temperature was raised to 105 °C and the reaction was carried out under reflux for 6 h. After cooling, the catalyst precursor was obtained by filtration and drying. The catalyst precursor was dried at 40 °C for 12 h, and then calcined under N2atmosphere (350 °C, 2 h) to obtain the carbon powder supported Pd-Zn-Bi203catalyst (10.1 g), which was named as PdZn-Bi203 / C-2.

[0088] Example 3

[0089] Preparation of Pd-Zn-Bi203catalyst:

[0090] 1) Pd-Bi203 / C: Bismuth phosphate (0.091 g, 0.3 mmol) and potassium hydroxide (0.135 g, 2.4 mmol) were dissolved in 30 mL of deionized water at room temperature, and stirred to dissolve at room temperature. Then, 9.1 g of carbon powder (average particle size 100 μm) was added into the above aqueous solution at one time, and ultrasonically dispersed for 20 min. After that, the temperature was raised to 99 °C and the reaction was carried out under reflux for 6 h. After cooling, the catalyst precursor was obtained by filtration and drying at 40 °C for 8 h to obtain about 9.2 g of carbon powder supported Bi203carrier (Bi203 / C).

[0091] 2) PdZn-Bi203 / C-3: Pd(II) trifluoroacetate (0.05 g, 0.2 mmol), zinc nitrate (0.076 g, 0.4 mmol), L-ascorbic acid (0.352 g, 2.0 mmol), polyvinylpyrrolidone (0.1 g) were dissolved in 40 mL of deionized water to form a homogeneous solution. Then, 9.2 g of Bi203 / C prepared in step 1) was added into the above aqueous solution, and ultrasonically dispersed for 15 min. After that, the temperature was raised to 102 °C and the reaction was carried out under reflux for 3 h. After cooling, the catalyst precursor was obtained by filtration and drying. The catalyst precursor was dried at 60 °C for 12 h, and then calcined under N2atmosphere (400 °C, 4 h) to obtain the carbon powder supported Pd-Zn-Bi203catalyst (9.3 g), which was named as PdZn-Bi203 / C-3.

[0092] Comparative Example 1

[0093] Pd-Bi203 / C: The catalyst was prepared according to the catalyst preparation method of Example 1, except that no zinc acetate was added in step 2). The catalyst was named as Pd-Bi203 / C.

[0094] Comparative Example 2

[0095] The catalyst was prepared according to the method of Example 1, except that in Step 2) the zinc acetate was replaced by magnesium acetate, and the other operations and conditions were unchanged. The catalyst was named PdMg-Bi2O3 / C.

[0096] Examples 4-6

[0097] Ethyl butyrylacetate was prepared by oxidation of ethyl 3-hydroxyhexanoate using the PdZn-Bi2O3 / C catalyst prepared in Examples 1-3, respectively:

[0098] A 200 mL autoclave was charged with a magnetic stir bar, ethyl 3-hydroxyhexanoate (16.0 g, 0.1 mol), solvent acetonitrile (40 mL) at room temperature in air. After the mixture was stirred to homogeneity, the PdZn-Bi2O3 / C catalyst (0.16 g, 1.0 wt% relative to the starting material ethyl 3-hydroxyhexanoate) and N-methylmorpholine N-oxide (0.23 g, 2 mmol) were added. After the 200 mL autoclave was sealed, the gas inlet line was connected to an oxygen cylinder, and 0.3 MPa of oxygen was slowly charged. The pressure was then released to normal pressure, and this was repeated three times. Finally, 0.5 MPa of oxygen was charged. The autoclave was placed in an oil bath, and the stirring was started (600 rpm). The reaction temperature was raised to 80 °C, and the reaction was carried out for 2 hours. When the pressure decreased, the gas inlet valve was opened to supplement oxygen to 0.5 MPa. The sample was analyzed by gas chromatography, and decahydronaphthalene was added as an internal standard for quantitative analysis. The conversion of the starting material ethyl 3-hydroxyhexanoate and the selectivity of the product ethyl butyrylacetate are shown in Table 1.

[0099] Example 7

[0100] The method of Example 4 was followed, except that the additive N-methylmorpholine N-oxide was not added, and the other operations and conditions were unchanged. The results of the sample analysis are shown in Table 1.

[0101] Comparative Examples 3-4

[0102] The method of Example 4 was followed, except that the catalyst was replaced by Pd-Bi2O3 / C prepared in Comparative Example 1, PdMg-Bi2O3 / C prepared in Comparative Example 2, respectively, and the other operations and conditions were unchanged. The results of the sample analysis are shown in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] Example 8

[0107] The reaction solution of Example 4 was filtered to recover the catalyst, and then the recovered catalyst was repeatedly used to catalyze the oxidation of ethyl 3-hydroxyhexanoate to prepare ethyl butyrylacetate according to the procedure of Example 4, and other operations and conditions were unchanged. The sampling analysis results are shown in Table 2:

[0108] Table 2

[0109] times conversion / % selectivity / % 1 99％ 99％ 2 99％ 98％ 3 98％ 98％ 4 98％ 98％ 5 97％ 99％ 6 98％ 99％ 7 98％ 98％ 8 97％ 98％

[0110] Example 9

[0111] The palladium-zinc-bismuth oxide PdZn-Bi2O3 / C-1 prepared in Example 1 was used to catalyze the oxidation of methyl 3-hydroxypentanoate to prepare methyl propionylacetate:

[0112] At room temperature in air, a magnetic stirrer was sequentially added to a 200 mL autoclave, methyl 3-hydroxypentanoate (13.2 g, 0.1 mol), a solvent acetonitrile (25 mL), and after stirring and mixing, a palladium-zinc-bismuth oxide catalyst (0.16 g, 1.0 wt% relative to the raw material methyl 3-hydroxypentanoate) and N-methylmorpholine N-oxide (0.12 g, 1 mmol) were added. After the 200 mL autoclave was sealed, the gas inlet line was connected to an oxygen cylinder, 0.3 MPa of oxygen was slowly filled, and then it was placed at normal pressure, and this was repeated 3 times, and finally 0.5 MPa of oxygen was filled. The autoclave was placed in an oil bath, stirring (600 rpm) was started, the reaction temperature was raised to 80°C, and the pressure was reduced to 0.5 MPa. Sampling analysis was performed. The conversion rate of the raw material methyl 3-hydroxypentanoate was 99%, and the selectivity of the product methyl propionylacetate was 98%.

[0113] After the catalyst PdZn-Bi2O3 / C-1 was used for 9 times, the conversion rate was 98%, and the selectivity was 98%.

[0114] Example 10

[0115] The palladium-zinc-bismuth oxide PdZn-Bi2O3 / C-1 prepared in Example 1 was used to catalyze the oxidation of methyl 3-hydroxypentanoate to prepare methyl propionylacetate:

[0116] A 200 mL autoclave was charged with a magnetic stir bar, 3-hydroxy-4- methylpentanoic acid methyl ester (14.6 g, 0.1 mol), solvent acetonitrile (100 mL), and stirred to mix well. Then, palladium-zinc-bismuth oxide catalyst (0.29 g, 2.0 wt% relative to 3-hydroxy-4-methylpentanoic acid methyl ester) and dinitrogen monoxide (0.09 g, 2.0 mmol) were added. After the 200 mL autoclave was sealed, the inlet line was connected to an oxygen cylinder, and the autoclave was charged with 0.3 MPa of oxygen. The pressure was released to the atmosphere, and the process was repeated three times. Finally, the autoclave was charged with 1.5 MPa of oxygen. The autoclave was placed in an oil bath, and the stirring was started (600 rpm). The reaction temperature was increased to 150 °C, and the reaction was carried out for 2 h. When the pressure decreased, the inlet valve was opened to charge the autoclave with 1.5 MPa of oxygen. The reaction mixture was analyzed by GC. The conversion of 3-hydroxy-4-methylpentanoic acid methyl ester was 99%, and the selectivity to isobutyryl acetic acid methyl ester was 99%.

[0117] After the catalyst PdZn-Bi2O3 / C-1 was reused for 12 times, the conversion was 97%, and the selectivity was 97%.

[0118] Example 11

[0119] Palladium-zinc-bismuth oxide catalyst PdZn-Bi2O3 / C-1 prepared in Example 1 was used to catalyze the oxidation of 3-hydroxyheptanoic acid ethyl ester to prepare n-pentanoyl acetic acid ethyl ester:

[0120] A 200 mL autoclave was charged with a magnetic stir bar, 3-hydroxyheptanoic acid ethyl ester (17.4 g, 0.1 mol), solvent N,N-dimethylformamide (50 mL), and stirred to mix well. Then, palladium-zinc-bismuth oxide catalyst (0.09 g, 0.5 wt% relative to 3-hydroxyheptanoic acid ethyl ester, which was recovered from Example 10) and N-methylmorpholine-N-oxide (0.12 g, 1.0 mmol) were added. After the 200 mL autoclave was sealed, the inlet line was connected to an oxygen cylinder, and the autoclave was charged with 0.3 MPa of oxygen. The pressure was released to the atmosphere, and the process was repeated three times. Finally, the autoclave was charged with 0.5 MPa of oxygen. The autoclave was placed in an oil bath, and the stirring was started (600 rpm). The reaction temperature was increased to 100 °C, and the reaction was carried out for 1.5 h. When the pressure decreased, the inlet valve was opened to charge the autoclave with 0.5 MPa of oxygen. The reaction mixture was analyzed by GC. The conversion of 3-hydroxyheptanoic acid ethyl ester was 99%, and the selectivity to n-pentanoyl acetic acid ethyl ester was 98%.

[0121] After the catalyst PdZn-Bi2O3 / C-1 was reused for 15 times, the conversion was 96%, and the selectivity was 98%.

[0122] Example 12

[0123] PdZn-Bi2O3 / C-1 prepared in Example 1 was used to catalyze the oxidation of ethyl 3-hydroxydecanoate to prepare ethyl n-octanoylacetate:

[0124] A magnetic stirrer was added into a 200 mL autoclave, followed by ethyl 3-hydroxydecanoate (21.6 g, 0.1 mol) and dimethyl sulfoxide (40 mL) as solvent. After stirring and mixing, PdZn-Bi2O3 catalyst (0.11 g, 0.5 wt% relative to ethyl 3-hydroxydecanoate) and N-methylmorpholine N-oxide (0.35 g, 3.0 mmol) were added. After sealing the 200 mL autoclave, the gas inlet line was connected to an oxygen cylinder, and 0.3 MPa of oxygen was slowly filled into the autoclave. After the pressure was released to normal pressure, the process was repeated three times, and finally 0.5 MPa of oxygen was filled into the autoclave. The autoclave was placed in an oil bath, and the stirring (600 rpm) was started. The reaction temperature was increased to 100 °C, and the reaction was carried out for 2 h. When the pressure decreased, the gas inlet valve was opened to supplement oxygen to 0.5 MPa. The sample was analyzed. The conversion of ethyl 3-hydroxydecanoate was 99%, and the selectivity of ethyl n-octanoylacetate was 97%.

[0125] After the catalyst PdZn-Bi2O3 / C-1 was reused for 13 times, the conversion was 98%, and the selectivity was 96%.

[0126] Example 13

[0127] PdZn-Bi2O3 / C-1 prepared in Example 1 was used to catalyze the oxidation of ethyl 3-hydroxydecanoate to prepare ethyl n-octanoylacetate:

[0128] A magnetic stirrer was added into a 200 mL autoclave, followed by ethyl 3-hydroxydecanoate (21.6 g, 0.1 mol) and dimethyl sulfoxide (40 mL) as solvent. After stirring and mixing, PdZn-Bi2O3 catalyst (0.11 g, 0.5 wt% relative to ethyl 3-hydroxydecanoate) and N-methylmorpholine N-oxide (0.35 g, 3.0 mmol) were added. After sealing the 200 mL autoclave, the gas inlet line was connected to an oxygen cylinder, and 0.3 MPa of oxygen was slowly filled into the autoclave. After the pressure was released to normal pressure, the process was repeated three times, and finally 0.5 MPa of oxygen was filled into the autoclave. The autoclave was placed in an oil bath, and the stirring (600 rpm) was started. The reaction temperature was increased to 100 °C, and the reaction was carried out for 2 h. When the pressure decreased, the gas inlet valve was opened to supplement oxygen to 0.5 MPa. The sample was analyzed. The conversion of ethyl 3-hydroxydecanoate was 99%, and the selectivity of ethyl n-octanoylacetate was 97%.

[0129] After the catalyst PdZn-Bi2O3 / C-1 was reused for 13 times, the conversion was 98%, and the selectivity was 96%.

[0130] Example 14

[0131] Example 14

[0132] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example 14

[0133] Example

Claims

1. A method for preparing a palladium-zinc-bismuth oxide catalyst, characterized in that the step... include: 1) Dissolve bismuth salt and alkali in water, add carbon powder and disperse ultrasonically, then heat to reflux to react, and then filter and dry to obtain Bi2O3 / C; 2) Dissolve palladium salt, zinc salt, L-ascorbic acid and polyvinylpyrrolidone in water, add Bi2O3 / C prepared in step 1) and ultrasonically disperse, then heat to reflux for reaction, and then filter, dry and calcine to obtain palladium zinc-bismuth oxide catalyst.

2. The preparation method according to claim 1, characterized in that, Step 1) The bismuth salt is selected from at least one of bismuth nitrate, bismuth phosphate, bismuth sulfate, and bismuth hyponitrate; and / or Step 1) The alkali is selected from at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide; and / or Step 1) The charcoal powder is selected from at least one of the following: charcoal powder derived from fruit shells, wood, and coal; and / or Step 2) The palladium salt is selected from at least one of palladium chloride, palladium bromide, palladium acetate, palladium acetylacetone, palladium nitrate, and palladium trifluoroacetate; and / or Step 2) The zinc salt is selected from at least one of zinc acetate, zinc acetylacetonate, zinc nitrate, zinc chloride, and zinc propionate.

3. The preparation method according to claim 2, characterized in that, The carbon powder has a particle size of 1-100 μm.

4. The preparation method according to claim 3, characterized in that, The carbon powder has a particle size of 10-50 μm.

5. The preparation method according to claim 2, characterized in that, The shell mentioned in step 1) is a coconut shell.

6. The preparation method according to claim 1, characterized in that, Step 1) The molar ratio of the bismuth salt to the alkali is 1:5-20; and / or Step 1) The mass ratio of carbon powder to bismuth salt is 20-100:1; and / or Step 1) The total concentration of the bismuth salt and alkali dissolved in water is 0.008-0.02 g / mL; and / or Step 2) The molar ratio of zinc salt to palladium salt is 1:0.5-3; and / or Step 2) The molar ratio of L-ascorbic acid to palladium salt is 2-10:1; and / or Step 2) The mass ratio of polyvinylpyrrolidone to palladium salt is 1-3:1; and / or Step 2) The total concentration of palladium salt, zinc salt, L-ascorbic acid, and polyvinylpyrrolidone dissolved in water is 0.010-0.015 g / mL; and / or Step 2) The dispersion concentration of Bi2O3 / C prepared in step 1) in water is 0.1-0.4 g / mL.

7. The preparation method according to claim 6, characterized in that, In step 1), the molar ratio of bismuth salt to alkali is 1:5-10.

8. The preparation method according to claim 6, characterized in that, In step 1), the mass ratio of carbon powder to bismuth salt is 50-100:

1.

9. The preparation method according to claim 6, characterized in that, In step 1), the total concentration of the bismuth salt and alkali dissolved in water is 0.01-0.02 g / mL.

10. The preparation method according to claim 6, characterized in that, In step 2), the molar ratio of zinc salt to palladium salt is 1:0.5-2.

11. The preparation method according to claim 6, characterized in that, In step 2), the molar ratio of L-ascorbic acid to palladium salt is 2-5.

12. The preparation method according to claim 6, characterized in that, In step 2), the mass ratio of polyvinylpyrrolidone to palladium salt is 2-3.

13. The preparation method according to claim 6, characterized in that, In step 2), the total concentration of palladium salt, zinc salt, L-ascorbic acid, and polyvinylpyrrolidone dissolved in water is 0.012-0.015 g / mL.

14. The preparation method according to claim 6, characterized in that, Step 2) The dispersion concentration of Bi2O3 / C prepared in step 1) in water is 0.2-0.4 g / mL.

15. The preparation method according to claim 1, characterized in that, Step 1) describes ultrasonic dispersion for a dispersion time of 10-30 minutes; and / or The reaction described in step 1) is carried out at a temperature of 95-110℃ for 6-12 hours; and / or Step 2) describes ultrasonic dispersion for a dispersion time of 10-30 minutes; and / or The reaction described in step 2) is carried out at a temperature of 95-110℃ for 2-6 hours.

16. The preparation method according to claim 15, characterized in that, The ultrasonic dispersion in step 1) takes 20-30 minutes.

17. The preparation method according to claim 15, characterized in that, The reaction described in step 1) is carried out at a temperature of 99-102℃ for 6-8 hours.

18. The preparation method according to claim 15, characterized in that, Step 2) describes ultrasonic dispersion, with a dispersion time of 20-30 minutes.

19. The preparation method according to claim 15, characterized in that, The reaction described in step 2) is carried out at a temperature of 99-102℃ for 2-3 hours.

20. A palladium-zinc-bismuth oxide catalyst prepared by the method according to any one of claims 1-19.

21. The use of a palladium zinc-bismuth oxide catalyst prepared by any one of claims 1-19 in the oxidation of β-hydroxy esters to prepare β-keto esters.

22. The application according to claim 21, characterized in that, The β-hydroxy ester is one or more compounds having the structure shown in Formula 1 below: In the formula, R1 and R2 are independently selected from C1-C10 alkyl, C2-C10 alkenyl, C6-C12 aryl, and C5-C12 heterocyclic substituents, respectively, and the heteroatoms are selected from N, O, and S; R1 and R2 can be the same or different.

23. The application according to claim 22, characterized in that, R1 and R2 are independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, phenyl, naphthyl, furanyl, pyrroleyl, pyridyl, thiophene, quinoline or quinoxaline.

24. A method for preparing β-keto esters by β-hydroxy ester oxidation, characterized in that, The method involves preparing β-keto esters by oxidizing β-hydroxy esters with an oxidant in a solvent environment under the action of a palladium-zinc bismuth oxide catalyst prepared according to any one of claims 1-19.

25. The method according to claim 24, characterized in that, The oxidant is selected from at least one of air, oxygen, hydrogen peroxide, hypochlorous acid, alkyl peroxide, alkyl peroxy ether, and peroxy acid; and / or The solvent is selected from at least one of methanol, ethanol, isopropanol, ethyl acetate, dichloromethane, chloroform, dichloroethane, acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, toluene, and acetone; and / or The amount of solvent used, based on the concentration of the β-hydroxy ester, is 1.0-4.0 M; and / or The amount of the palladium zinc-bismuth oxide catalyst is 0.1-2.0 wt% of the β-hydroxy ester; and / or The oxidation reaction is carried out at a temperature of 80-150℃ for 1-4 hours and at a pressure of 0.5-3.0 MPa.

26. The method according to claim 25, characterized in that, The oxidation reaction is carried out at a temperature of 80-100℃ for 1-2 hours and at a pressure of 0.5-2.0 MPa.

27. The method according to claim 24, characterized in that, An auxiliary agent may be added to the oxidation reaction; The adjuvant is selected from at least one of morpholine nitrogen oxide, N-methylmorpholine nitrogen oxide, triethylamine nitrogen oxide, nitric oxide, nitrous oxide, and trimethylamine oxide.

28. The method according to claim 27, characterized in that, The amount of the adjuvant is 1.0-3.0 mol% of the β-hydroxy ester.

Images