Solid core-shell catalysts, methods of making and using the same

Abstract

The application provides a solid core-shell catalyst and a preparation method and application thereof, and belongs to the technical field of organic synthesis. The solid core-shell catalyst provided by the application has the following general formula: xM@yShell, wherein M represents a transition metal, Shell represents an oxide shell layer, x is 20-50wt%, and y is 50-80wt% in terms of mass fraction. The solid core-shell catalyst provided by the application is simple to prepare, stable in structure, low in storage requirement, and has good catalytic activity and stability, and can be effectively used in isomerization of allyl alcohol.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a solid core-shell catalyst and a preparation method and application thereof. Background Art

[0002] The catalytic isomerization of allylic alcohols to their corresponding carbonyl compounds is a widely explored transformation in organic synthesis. This process offers the significant advantage of converting readily available allylic alcohols into versatile carbonyls in an economical, redox-sensitive manner.

[0003] Currently, the isomerization reaction of allylic alcohols is typically carried out homogeneously under certain conditions using metal-organic ligands as catalysts. This process is simple, highly selective, and produces few byproducts, but it also results in high catalyst separation costs. Ahlsten et al. added the water-soluble ligand 1,3,5-triaza-7-phosphaadamantane (PTA) to a Rh(COD)(CH3CN)2-BF4 reaction system, achieving the isomerization of simple allylic alcohols at room temperature. When the double bond is mono- or di-substituted, a yield of 99% is achieved. However, as the number of substituents increases, a moderate increase in temperature is often required to achieve isomerization (Ahlsten, N.; Lundberg, H.; Martín-Mature, B. Green Chem. 2010, 12, 1628).

[0004] Kuraray disclosed in CN104583168B a production process for the isomerization of 2,7-diene-1-octanol to 7-octenal using Cu-Fe-Al / γ-Al2O3 as a catalyst. Under a nitrogen atmosphere and at a temperature of 200±5°C, the conversion of 2,7-diene-1-octanol reached over 97%, with product selectivity reaching nearly 81%. However, due to the similar boiling points of the byproduct 2,7-octenal and the target product 7-octenal, product separation was difficult and the isomerization reaction was incomplete.

[0005] Kuraray disclosed in EP 908441B1 the production of 7-octenal using the E26L catalyst produced by Nikki Kagaku Co., Ltd. Under a nitrogen-hydrogen mixed atmosphere, the conversion of 2,7-octadienal reached 99%, the product selectivity reached over 85%, and the catalyst stability was good. However, under a nitrogen atmosphere, the catalyst stability was poor. At the beginning of the reaction, the conversion of 2,7-octadienal was 93.6%. After 100 hours of continuous operation on a fixed bed, the raw material conversion dropped to 76.6%, the product selectivity also decreased, and the byproduct 2,7-octadienal content increased from 10% to 13.1%.

[0006] As can be seen from the above, the current isomerization reaction using homogeneous catalysts suffers from high costs, difficult separation, and difficulty in industrialization. The use of heterogeneous catalysts, on the other hand, suffers from disadvantages such as easy agglomeration of active metal components, high storage requirements, poor selectivity, and poor stability. Therefore, it is particularly important to provide a catalyst for the isomerization reaction of allyl alcohol that is simple to prepare, has a stable structure, has low storage requirements, and exhibits good catalytic activity and stability. Summary of the Invention

[0007] The present invention provides a solid core-shell catalyst, a preparation method thereof, and an application thereof. The obtained catalyst is simple to prepare, has a stable structure, has low storage requirements, and has good catalytic activity and stability, and can be effectively used in the isomerization reaction of allyl alcohol.

[0008] In order to achieve the above object, the present invention provides a solid core-shell catalyst having the following general formula:

[0009] xM@yShell,

[0010] Wherein, M represents a transition metal, Shell represents an oxide shell, and by mass fraction, x is 20 to 50 wt %, and y is 50 to 80 wt %.

[0011] Preferably, the transition metal is selected from at least one of Cr, Mn, Fe, Ru, Pd, Pt, Ni, Co, Cu, and Zn; and the oxide shell is selected from at least one of titanium dioxide, zirconium dioxide, and silicon dioxide.

[0012] The present invention also provides a method for preparing the solid core-shell catalyst according to any of the above technical solutions, comprising the following steps:

[0013] A precipitant is added dropwise to a transition metal salt solution to obtain a flocculent precipitate, which is then washed, dried, and calcined to obtain a transition metal oxide;

[0014] The obtained transition metal oxide is added to an organic solvent, dispersed by ultrasonication, and then added to a colloidal liquid containing a coupling agent, and reacted at 60-90°C for 1-3 hours to allow the coupling agent to undergo a dehydration reaction to obtain a precipitate coated with the transition metal;

[0015] The obtained precipitate is washed, dried, calcined and reduced to obtain a solid core-shell catalyst.

[0016] Preferably, the transition metal salt is derived from at least one of nitrate, bicarbonate, hydrogen phosphate, chloride and sulfate, the precipitant is selected from at least one of ammonia water, sodium hydroxide solution and ammonium bicarbonate solution, and the added precipitant adjusts the pH value of the solution to 7-10.

[0017] Preferably, the coupling agent is selected from at least one of a silicate coupling agent, a titanate coupling agent, and a zirconate coupling agent, wherein the silicate coupling agent is selected from at least one of ethyl orthosilicate, butyl orthosilicate, and phenyl-3-aminopropyltrimethoxysilane; the titanate coupling agent is selected from at least one of tetrabutyl titanate, tetraisopropyl titanate, and neoalkoxy tris (p-aminophenoxy) titanate; and the zirconate coupling agent is selected from at least one of tetrabutyl zirconate, tetraisopropyl zirconate, and neoalkoxy tris (p-aminophenoxy) zirconate.

[0018] Preferably, the molar ratio of the added coupling agent to the active metal in the transition metal oxide is 5-20.

[0019] Preferably, in the step of obtaining the transition metal oxide, the sample can be washed several times by centrifugation at 11000 r / min with water to remove impurities, and then dried and calcined at 200-600° C. to obtain the transition metal oxide;

[0020] In the step of obtaining the solid core-shell catalyst, the drying temperature is 60-120°C and the drying time is 3-10 hours; the calcination temperature is 200-600°C and the calcination time is 2-6 hours; the reduction temperature is 200-600°C and the reduction time is 1-5 hours, and the reducing gas is an argon-hydrogen mixture with a hydrogen volume concentration of 10-99%.

[0021] The present invention also provides a use of the solid core-shell catalyst according to any of the above technical solutions in the isomerization reaction of allyl alcohol.

[0022] Preferably, the specific steps include:

[0023] Using allyl alcohol as raw material and solid core-shell catalyst as catalyst, the corresponding carbonyl compound is produced by isomerization reaction in a fixed bed;

[0024] In the above reaction, the operating conditions are: liquid space velocity is 1.8-2.8h -1 , reaction temperature is 120-200℃, nitrogen space velocity is 200-600h -1 .

[0025] Preferably, when the allyl alcohol is selected from methyl allyl alcohol or 2,7-diene-1-octanol, the raw material conversion rate of the reaction is ≥98.3%, and the product selectivity is ≥88.1%;

[0026] The catalytic activity of the solid core-shell catalyst remains substantially unchanged after running for 100 hours.

[0027] Compared with the prior art, the advantages and positive effects of the present invention are:

[0028] 1. The present invention uses transition metal elements as the core of a core-shell structure and oxides as the shell to construct a solid core-shell catalyst called xM@yShell. This catalyst is simple to prepare, has a stable structure, and can significantly improve the agglomeration problem of the catalyst, avoiding the high separation cost of homogeneous catalysts and facilitating separation. Furthermore, the core-shell catalyst has a porous structure, which solves the problem of agglomeration of the active metal center (the core of the core-shell structure). Furthermore, by controlling the shell thickness of the core-shell structure, the mass transfer efficiency of the reaction can be enhanced, the adsorption capacity of byproducts on the catalyst can be reduced, the catalytic activity can be improved, and the catalyst stability can be enhanced.

[0029] 2. The present invention uses allyl alcohol and 2,7-diene-1-octanol as raw materials and a solid core-shell catalyst as a catalyst for isomerization reaction. The raw material conversion rate of the reaction is ≥98.3%, and the product selectivity is ≥88.1%. High activity and catalytic stability are achieved, and the catalytic activity remains basically unchanged after about 100 hours of operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a transmission electron microscope (TEM) photograph of the catalyst provided in Example 1.

[0031] Figure 2 A stability experiment of the catalyst prepared in Example 6 is provided for the performance test of the present invention. DETAILED DESCRIPTION

[0032] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0033] Example 1 Preparation of Cu@TiO2 Catalyst

[0034] Weigh 9.6 g (0.06 mol) of anhydrous CuSO4 and add it to 200 ml of deionized water, stirring to obtain solution A;

[0035] An appropriate amount of ammonia water was weighed to prepare a 1 mol / L alkaline solution B, and solution B was added dropwise to solution A to precipitate it until the pH was about 7. The reaction was continued at 60°C for 3 hours. After the reaction was completed, the sample was centrifuged with water for multiple times at 11000 r / min to remove impurities, and then dried and calcined to obtain a solid to obtain a transition metal oxide, which was then ground into powder using a ball mill;

[0036] Weigh 1.0 g of the above powder and add it to 100 mL of anhydrous ethanol, then perform ultrasonic dispersion to obtain slurry C;

[0037] Measure 10 g of tetrabutyl titanate and 100 mL of anhydrous ethanol into a 300 mL beaker to obtain solution D;

[0038] After adding all of solution C to solution D, the mixture was stirred at 60°C for 3 h to obtain a precipitate coated with transition metals, which was then washed three times with ethanol and water and dried in vacuum at 60°C for 8 h.

[0039] Finally, the dried solid powder was placed in a muffle furnace, heated to 200 °C at a rate of 1 °C / min in an air atmosphere and calcined for 2 h, and finally reduced at 600 °C for 5 h to obtain the Cu@TiO2 catalyst, such as Figure 1 shown.

[0040] Example 2 Preparation of Fe@TiO2 Catalyst

[0041] Weigh 24.2 g (0.06 mol) of Fe(NO3)3·9H2O and add it to 200 ml of deionized water. Stir and obtain solution A.

[0042] An appropriate amount of sodium hydroxide was weighed to prepare a 1 mol / L alkaline solution B, and solution B was added dropwise to solution A to precipitate it until the pH was about 10. The reaction was continued at 60°C for 3 hours. After the reaction was completed, the sample was centrifuged with water for multiple times at 11000 r / min to remove impurities, and then dried and calcined to obtain a solid to obtain a transition metal oxide, which was then ground into powder using a ball mill;

[0043] Weigh 2.0 g of the above powder and add it to 100 mL of anhydrous ethanol, then perform ultrasonic dispersion to obtain slurry C;

[0044] Measure 10 g of tetraisopropyl titanate and 100 mL of anhydrous ethanol into a 300 mL beaker to obtain solution D;

[0045] After adding all of solution C to solution D, the mixture was stirred at 90°C for 1 h to obtain a precipitate coated with transition metals, which was then washed three times with ethanol and water and dried in vacuum at 60°C for 5 h.

[0046] Finally, the dried solid powder was placed in a muffle furnace, heated to 600°C at a rate of 1°C / min in an air atmosphere, and calcined for 2 h. Finally, it was reduced at 600°C for 5 h to obtain the Fe@TiO2 catalyst.

[0047] Example 3 Preparation of Fe-Cu@ZrO2 Catalyst

[0048] 8.34 g (0.03 mol) of FeSO4·7H2O and 14.5 g (0.06 mol) of Cu(NO3)2·3H2O were weighed and added to 200 ml of deionized water to obtain a mixed solution A.

[0049] An appropriate amount of ammonium bicarbonate was weighed to prepare a 1 mol / L alkaline solution B, and solution B was added dropwise to solution A to precipitate the solution until the pH reached about 9. The solution was reacted at 60°C for 3 h. After the reaction was completed, the sample was centrifuged with water several times at 11,000 r / min to remove impurities, and then dried and calcined to obtain a solid to obtain a transition metal oxide, which was then ground into powder using a ball mill.

[0050] Weigh 2.0 g of the above powder and add it to 100 mL of anhydrous ethanol, then perform ultrasonic dispersion to obtain slurry C;

[0051] Measure 12 g of tetraisopropyl zirconate and 100 mL of anhydrous ethanol into a 300 mL beaker to obtain solution D;

[0052] After adding all of solution C to solution D, the mixture was stirred at 80°C for 4 h to obtain a precipitate coated with transition metals, which was then washed three times with ethanol and water and dried in vacuum at 60°C for 5 h.

[0053] Finally, the dried solid powder was placed in a muffle furnace, heated to 400°C at a rate of 5°C / min in an air atmosphere and calcined for 3 h, and finally reduced at 400°C for 1 h to obtain the Fe-Cu@ZrO2 catalyst.

[0054] Example 4 Preparation of Zn-Cu@SiO2 Catalyst

[0055] 4.1 g (0.03 mol) ZnCl2 and 14.5 g (0.06 mol) Cu(NO3)2·3H2O were weighed and added to 200 ml deionized water to obtain a mixed solution A.

[0056] An appropriate amount of sodium hydroxide was weighed to prepare a 1 mol / L alkaline solution B, and solution B was added dropwise to solution A to precipitate it until the pH was about 10. The reaction was continued at 60°C for 3 hours. After the reaction was completed, the sample was centrifuged with water for multiple times at 11000 r / min to remove impurities, and then dried and calcined to obtain a solid to obtain a transition metal oxide, which was then ground into powder using a ball mill;

[0057] Weigh 2.0 g of the above powder and add it to 100 mL of anhydrous ethanol, then perform ultrasonic dispersion to obtain slurry C;

[0058] Measure 15 g of ethyl orthosilicate and 100 mL of anhydrous ethanol into a 300 mL beaker to obtain solution D;

[0059] After adding all of solution C to solution D, the mixture was stirred at 70°C for 3 h to obtain a precipitate coated with transition metals, which was then washed three times with ethanol and water and dried in vacuum at 60°C for 5 h.

[0060] Finally, the dried solid powder was placed in a muffle furnace, heated to 500°C at a rate of 5°C / min in an air atmosphere and calcined for 4 hours, and finally reduced at 500°C for 3 hours to obtain the Zn-Cu@TiO2 catalyst.

[0061] Example 5 Preparation of Fe-Ni@SiO2-TiO2 Catalyst

[0062] 7.5 g (0.05 mol) of FePO4 and 5.9 g (0.04 mol) of NiCl2·6H2O were weighed and added to 200 ml of deionized water to obtain a mixed solution A.

[0063] An appropriate amount of ammonium bicarbonate was weighed to prepare a 1 mol / L alkaline solution B, and solution B was added dropwise to solution A to precipitate it, and the pH was added until it was about 9. The reaction was continued at 60°C for 3 hours. After the reaction was completed, the sample was centrifuged with water for multiple times at 11000 r / min to remove impurities, and then dried and calcined to obtain a solid to obtain a transition metal oxide, which was then ground into powder using a ball mill.

[0064] Weigh 2.0 g of the above powder and add it to 100 mL of anhydrous ethanol, then perform ultrasonic dispersion to obtain slurry C;

[0065] Measure 15 g of butyl orthosilicate, 10 g of tetrabutyl titanate, and 100 mL of anhydrous ethanol into a 300 mL beaker to obtain solution D.

[0066] After adding all of solution C to solution D, the mixture was stirred at 70°C for 3 h to obtain a precipitate coated with transition metals, which was then washed three times with ethanol and water and dried in vacuum at 60°C for 5 h.

[0067] Finally, the dried solid powder was placed in a muffle furnace, heated to 400°C at a rate of 5°C / min in an air atmosphere and calcined for 2h, and finally reduced at 400°C for 4h to obtain the Fe-Ni@SiO2-TiO2 catalyst.

[0068] Example 6 Preparation of Fe-Mn@SiO2-TiO2 Catalyst

[0069] 24.2 g (0.06 mol) of Fe(NO3)3·9H2O and 15.1 g (0.06 mol) of Mn(NO3)2·4H2O were weighed and added to 200 ml of deionized water to obtain a mixed solution A.

[0070] An appropriate amount of sodium hydroxide was weighed to prepare a 1 mol / L alkaline solution B, and solution B was added dropwise to solution A to precipitate it, and the pH was added until it was about 9. The reaction was continued at 60°C for 3 hours. After the reaction was completed, the sample was centrifuged with water for multiple times at 11000 r / min to remove impurities, and then dried and calcined to obtain a solid to obtain a transition metal oxide, which was then ground into powder using a ball mill.

[0071] Weigh 2.0 g of the above powder and add it to 100 mL of anhydrous ethanol, then perform ultrasonic dispersion to obtain slurry C;

[0072] Measure 15 g of butyl orthosilicate, 10 g of tetrabutyl titanate, and 100 mL of anhydrous ethanol into a 300 mL beaker to obtain solution D.

[0073] After adding all of solution C to solution D, the mixture was stirred at 70°C for 3 h to obtain a precipitate coated with transition metals, which was then washed three times with ethanol and water and dried in vacuum at 60°C for 5 h.

[0074] Finally, the dried solid powder was placed in a muffle furnace, heated to 400°C at a rate of 5°C / min in an air atmosphere and calcined for 4 h, and finally reduced at 400°C for 4 h to obtain the Fe-Cu@SiO2-TiO2 catalyst.

[0075] Performance Testing

[0076] Isomerization reaction test

[0077] The catalyst prepared in Examples 1-6 was used to carry out the isomerization reaction of 2,7-diene-1-octanol in a fixed bed having an inner diameter of 9 mm. The reaction conditions corresponded to those in Examples 7-12 in Table 1 below. The specific operation process was as follows:

[0078] Weigh 5 ml of the catalyst prepared in the above example and fill it into the constant temperature zone of the reaction tube. Fill the rest of the tube with quartz sand. Connect the nitrogen cylinder and open the cylinder to fill the tube with gas. Maintain the nitrogen GHSV: 400h -1 After the nitrogen pressure in the pipeline stabilizes, the temperature begins to rise. When the temperature reaches the preset reaction temperature of 200°C, the feed pump is turned on and the liquid space velocity of the raw material is maintained at 2.3h -1 The reaction liquid was condensed and then stored in a storage tank. Samples were taken every 1.5 hours and analyzed by gas chromatography. The raw material conversion rate was over 98%, and the product selectivity was over 88%.

[0079] Table 1 Summary of reaction conditions for isomerization reaction test

[0080]

[0081] As can be seen from the data in Table 1, the core-shell catalyst synthesized by the method of the present invention has better catalytic performance in product selectivity for the isomerization reaction of allyl alcohol than the solid catalyst in the prior art, avoiding the high separation cost of homogeneous catalysts. At the same time, the two-component core-shell structure enhances the reaction activity of the catalyst and improves the raw material conversion rate.

[0082] Reaction effects of different reaction substrates

[0083] 5 ml of the catalyst prepared in Example 6 was weighed and filled into the constant temperature zone of the reaction tube. The remainder was filled with quartz sand to fill the entire tube. A nitrogen cylinder was connected and opened to fill the tube. The nitrogen space velocity was adjusted. After the nitrogen pressure in the tube stabilized, the temperature was increased. When the temperature reached the preset reaction temperature, the feed pump was turned on to start feeding. The reaction liquid was condensed and then entered into a storage tank. Samples were taken every 2 hours for gas chromatography analysis, and the results were averaged five times. The test results are shown in Table 2.

[0084] Table 2 Reaction effects of different reaction substrates

[0085]

[0086]

[0087] As can be seen from the data in Table 2, the core-shell catalyst synthesized by the present invention was used to evaluate the effect of the isomerization reaction of different allylic raw materials. It was found that different allylic raw materials all had good raw material conversion rates and product selectivities, indicating that the solid core-shell catalyst of the present invention has good universality for the allylic isomerization reaction.

[0088] Stability test

[0089] The catalyst prepared in Example 6 was used in the isomerization reaction of 2,7-octadienol using a fixed bed reactor.

[0090] Reaction conditions: reaction temperature 200℃, liquid space velocity 2.3h -1 , nitrogen space velocity 400h -1 The quantitative analysis of the products was carried out on an Agilent 7890B gas chromatograph using a chromatographic column HP-5 and a FID detector. Figure 2 Under a nitrogen atmosphere, the solid core-shell catalyst synthesized by the method of the present invention maintained a raw material conversion rate of over 98%, and a product selectivity of over 88%. Moreover, the catalyst activity remained essentially unchanged after 100 hours of continuous operation on a fixed bed, indicating broad prospects for industrialization.

Claims

1. Use of a solid core-shell catalyst in the isomerization reaction of methylallyl alcohol or 2,7-diene-1-octanol, characterized in that: The specific steps of the isomerization reaction include: Using methyl allyl alcohol or 2,7-diene-1-octanol as raw material and solid core-shell catalyst as catalyst, an isomerization reaction is carried out in a fixed bed to produce the corresponding carbonyl compound; The solid core-shell catalyst has the following general formula: xM@yShell, Wherein, M represents a transition metal, Shell represents an oxide shell, and by mass fraction, x is 20 to 50 wt%, and y is 50 to 80 wt%; The preparation method of the solid core-shell catalyst comprises the following steps: A precipitant is added dropwise to a transition metal salt solution to obtain a flocculent precipitate, the sample is washed by centrifugation at 11,000 r / min for multiple times to remove impurities, and then dried and calcined at 200-600°C to obtain a transition metal oxide; The obtained transition metal oxide is added to an organic solvent, dispersed by ultrasonication, and then added to a colloidal liquid containing a coupling agent. The reaction is carried out at 60°C to 90°C for 1 to 3 hours, and the coupling agent undergoes a dehydration reaction to obtain a precipitate coated with the transition metal; The obtained precipitate is washed, dried at 60-120° C. for 3-10 hours, calcined at 200-600° C. for 2-6 hours, and reduced at 200-600° C. for 1-5 hours to obtain a solid core-shell catalyst; wherein the reducing gas is an argon-hydrogen mixture with a hydrogen volume concentration of 10-99%; The transition metal is selected from at least one of Cr, Mn, Fe, Ru, Pd, Pt, Ni, Co, Cu, and Zn; and the oxide shell is selected from at least one of titanium dioxide, zirconium dioxide, and silicon dioxide.

2. The use according to claim 1, characterized in that The operating conditions of the isomerization reaction are: liquid space velocity of 1.8-2.8 h -1 , reaction temperature is 120-200℃, nitrogen space velocity is 200-600 h -1 .

3. The use according to claim 2, characterized in that The raw material conversion rate of the isomerization reaction is ≥98.3%, and the product selectivity is ≥88.1%.

4. The use according to claim 1, characterized in that The transition metal salt is derived from at least one of nitrate, bicarbonate, hydrogen phosphate, chloride and sulfate; the precipitant is selected from at least one of ammonia water, sodium hydroxide solution and ammonium bicarbonate solution; and the added precipitant adjusts the pH value of the solution to 7-10.

5. The use according to claim 1, characterized in that The coupling agent is selected from at least one of a silicate coupling agent, a titanate coupling agent, and a zirconate coupling agent, wherein the silicate coupling agent is selected from at least one of ethyl orthosilicate, butyl orthosilicate, and phenyl-3-aminopropyltrimethoxysilane; the titanate coupling agent is selected from at least one of tetrabutyl titanate, tetraisopropyl titanate, and neoalkoxy tris (p-aminophenoxy) titanate; and the zirconate coupling agent is selected from at least one of tetrabutyl zirconate, tetraisopropyl zirconate, and neoalkoxy tris (p-aminophenoxy) zirconate.

6. The use according to claim 5, characterized in that The molar ratio of the added coupling agent to the active metal in the transition metal oxide is 5-20.

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