A core-shell catalyst and a preparation method and application thereof

Abstract

The application provides a core-shell catalyst and a preparation method and application thereof, and relates to the technical field of catalysts. 11 The core-shell catalyst is composed of a Pr6O 11 inner core and an inert material shell, and is used for preparing long-chain alpha-olefin compounds by selectively dehydrating long-chain alpha-alcohol compounds. The preparation method of the catalyst is simple, the reaction efficiency is high, the process flow is simple, no by-products are generated, the environment is not adversely affected, the product separation and purification process is simple, and the production cost of the target product is effectively reduced. The praseodymium oxide wrapped by the inert material is used as the catalyst, the adsorption configuration of the substrate can be effectively controlled, the substrate can only be adsorbed in a vertical configuration, the carbon-carbon double bond in the generated long-chain alpha-olefin compound molecule can be effectively avoided from moving internally, other functional groups can be effectively reduced from being adsorbed and activated to cause side reactions, and therefore the selectivity of the target product is improved.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a core-shell catalyst, its preparation method, and its application. Background Technology

[0002] Long-chain α-olefins have wide applications in the fine chemical industry, mainly including long-chain α-enols and long-chain α-enic acids and their corresponding esters. The uses of these products vary depending on the carbon chain length in the molecule. α-olefins with 4–8 carbon atoms are mainly used for copolymerization with common olefins to produce polyolefin materials with special structures and properties; long-chain α-olefins with 6–15 carbon atoms are mainly used in the production of specialty lubricants, high-performance plasticizers, and other products; in addition, they are frequently used as raw materials for synthesizing high-value-added pharmaceuticals, pesticides, and fragrances. Social development and progress have placed increasing demands on the field of new materials, leading to a gradual increase in the demand for α-olefins with 4–10 carbon atoms, making the improvement of existing production processes of great significance.

[0003] Currently, long-chain α-enols and long-chain α-encarboxylic acids and their esters are mainly prepared by organic synthesis, which has disadvantages such as high raw material prices, harsh reaction conditions, high risk factors, many by-products, and difficult purification. At the same time, the production process also generates a large amount of waste, which will pollute the environment.

[0004] The literature (ACS Catal., 2013, 3, 721) reports that rare earth metal oxides with specific crystal forms can efficiently catalyze the selective dehydration of different diols to produce enols. However, this reaction system cannot effectively prevent the migration of C=C double bonds. Since the boiling point difference between various enols is very small, it is difficult to obtain pure products through simple distillation, which limits the application and development of catalysts.

[0005] Chinese patents with application numbers CN201510752921.8 and CN201910518848.6 both report a method for catalytic cracking to produce olefins. In this method, 1,10-decanediol and percarbonic acid first undergo esterification in a reactor to obtain the corresponding diester, followed by cracking. This can efficiently and in high yields produce dienes and enols. However, these methods require the addition of percarbonic acid, the catalyst is prone to deactivation, and they are not suitable for feedstocks with fewer than 10 carbon atoms. Therefore, by designing a suitable catalyst system, the direct catalytic selective dehydration of long-chain α-alcohols to prepare long-chain α-olefins in a fixed-bed continuous reactor has great appeal and application prospects. Summary of the Invention

[0006] This invention provides a core-shell catalyst, its preparation method, and its application. The preparation method provided by this invention is simple, highly stable, and has a highly efficient catalytic reaction process with no by-products. The product is easy to separate and purify, which can effectively reduce the production cost of long-chain α-olefin compounds and is suitable for industrial production.

[0007] The core-shell catalyst of this invention consists of a core and an outer shell, wherein the core is Pr6O. 11 The outer shell is made of an inert material;

[0008] The core content is 5wt% to 30wt%, and the shell content is 70wt% to 95wt%.

[0009] The inert material is one or both of SiO2 and activated carbon.

[0010] The preparation method of the core-shell catalyst of the present invention includes the following steps:

[0011] S1. Dissolve soluble praseodymium salt and polyvinyl alcohol in deionized water to obtain a salt solution;

[0012] S2. Under vigorous stirring, ammonia solution is added dropwise to the salt solution to adjust the pH value of the solution to ≥9, and the solution is aged at room temperature to obtain a mixed solution;

[0013] S3. Filter the mixed solution, and wash the filter cake until the pH of the filtrate is 7. Disperse the washed filter cake in deionized water by ultrasonication to form a sol.

[0014] S4. Add the calculated amount of SiO2 and activated carbon precursor to the sol, stir evenly, heat to crystallize, and filter to obtain a precipitate; the content of SiO2 is calculated based on the mass ratio of the core and the shell.

[0015] S5. The precipitate is dried and then calcined to obtain the core-shell catalyst.

[0016] Furthermore, in S1, the soluble praseodymium salt is one or more of Pr2(SO4)3, Pr(NO3)3·6H2O, and PrCl3·7H2O.

[0017] Furthermore, in S1, the molar ratio of soluble praseodymium salt to polyvinyl alcohol is 1:10.

[0018] Furthermore, in S1, the concentration of the salt solution is 10 g / L.

[0019] Furthermore, in S2, the concentration of the ammonia solution is 1 mol / L, and the aging time is 4 h.

[0020] Furthermore, in S4, the SiO2 precursor is one or more of methyl orthosilicate, ethyl orthosilicate, and dichlorodimethylsilane.

[0021] Furthermore, in S4, the activated carbon precursor is one or more of glucose, sucrose, and cellulose.

[0022] Furthermore, in S4, the crystallization temperature is 180°C and the crystallization time is 20 hours.

[0023] Furthermore, in step S5, the drying temperature is 110°C and the drying time is 12 hours.

[0024] Furthermore, in step S5, the calcination temperature is 600°C, the calcination time is 4 hours, and the calcination is carried out in a nitrogen atmosphere.

[0025] The core-shell catalyst described in this invention is used for the selective dehydration of long-chain alcohols to prepare long-chain α-olefins.

[0026] Furthermore, the selective dehydration reaction of the long-chain alcohol compound to prepare the long-chain α-olefin compound is carried out in a fixed-bed continuous flow reactor at a reaction temperature of 400°C, a reaction pressure of 3 MPa, and a mass hourly space velocity (WHSV) of 0.1–1 h⁻¹ for the long-chain alcohol compound. -1 .

[0027] Furthermore, the long-chain alcohol is a long-chain α-ol compound.

[0028] Furthermore, the long-chain α-ol compound is a long-chain α,ω-diol or a long-chain α-ol-ω-carboxylic acid.

[0029] Furthermore, the long-chain α,ω-diol is one or more of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol.

[0030] Furthermore, the long-chain α-ol-ω-carboxylic acid is one or more of 4-hydroxybutyric acid, 5-hydroxyvalerate, 6-hydroxyhexanoic acid, 7-hydroxyheptanoic acid, 8-hydroxyoctanoic acid, 9-hydroxynonanoic acid, and 10-hydroxydecanoic acid.

[0031] Furthermore, the long-chain α-olefin compound is a long-chain α-olefin-ω-ol or a long-chain α-olefin-ω-carboxylic acid.

[0032] Furthermore, the long-chain α-olefin-ω-ol is one or more of 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 6-hepten-1-ol, 7-octen-1-ol, 8-nonen-1-ol, and 9-decen-1-ol.

[0033] Furthermore, the long-chain α-olefin-ω-carboxylic acid is one or more of 3-butenoic acid, 4-pentenoic acid, 5-hexenoic acid, 6-heptenoic acid, 37-octenic acid, 8-nonenoic acid, and 9-decenoic acid.

[0034] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0035] The catalyst of this invention has a simple preparation method. In a fixed-bed continuous flow reactor, it can achieve selective dehydration of long-chain α-alcohols to prepare long-chain α-olefins. The reaction efficiency is high, the process is simple, no by-products are generated, and there is no adverse impact on the environment. The product separation and purification process is simple, which effectively reduces the production cost of the target product.

[0036] This invention uses praseodymium oxide encapsulated in an inert material as a catalyst, which can effectively control the adsorption configuration of the substrate, ensuring that the substrate can only be adsorbed in a steric configuration. This effectively avoids the inward migration of carbon-carbon double bonds in the generated long-chain α-olefin compound molecules, and also reduces side reactions caused by the adsorption and activation of other functional groups, thereby improving the selectivity of the target product. Detailed Implementation

[0037] The technical solution provided by the present invention will be further described below with reference to the embodiments.

[0038] Example 1

[0039] A core-shell catalyst, wherein the core active component is Pr6O by mass fraction. 11 The content is 20%, and the outer shell inert material SiO2 is 80%.

[0040] The preparation method of the core-shell catalyst:

[0041] 10.22 g of Pr(NO3)3·6H2O and 10.35 g of polyvinyl alcohol were weighed and dissolved in 1000 mL of deionized water to obtain a 10 g / L salt solution. Under vigorous stirring, a 1 mol / L ammonia solution was added dropwise to the salt solution until the pH of the salt solution was 9. After aging at room temperature for 4 h, the solution was filtered, and after repeated slurry washing, it was ultrasonically dispersed in 1000 mL of deionized water. Then, 40.54 g of methyl orthosilicate (152.22 g) was added, and the mixture was stirred evenly. The solution was then heated to 180 °C and crystallized for 20 h. After filtration, a precipitate was obtained. The precipitate was dried at 110 °C for 12 h and then calcined at 600 °C in a nitrogen atmosphere for 4 h to obtain core-shell catalyst A.

[0042] Evaluation method: Core-shell catalyst A was pressed into tablets and ground to 40-60 mesh. 10g was placed in the reaction tube of a fixed-bed continuous flow reactor. 1,6-hexanediol was preheated and mixed with nitrogen gas, and then passed through the catalyst bed for selective dehydration to produce 5-hexen-1-ol. The reaction temperature was 400℃, the reaction pressure was 3MPa, and the mass hourly space velocity (WHSV) of 1,6-hexanediol was 0.3h. -1 Testing showed that the conversion rate of 1,6-hexanediol was >99%, and the selectivity of 5-hexen-1-ol was 90.1%.

[0043] Example 2

[0044] A core-shell catalyst, wherein the core active component is Pr6O by mass fraction. 11 The content is 30%, and the outer shell inert material SiO2 is 70%.

[0045] The preparation method of the core-shell catalyst:

[0046] 10.04 g of Pr2(SO4)3 and 15.52 g of polyvinyl alcohol were weighed and dissolved in 1000 mL of deionized water to obtain a 10 g / L salt solution. Under vigorous stirring, a 1 mol / L ammonia solution was added dropwise to the salt solution until the pH of the salt solution was 9. After aging at room temperature for 4 h, the solution was filtered, and after repeated slurry washing, it was ultrasonically dispersed in 1500 mL of deionized water. Then, 48.54 g of tetraethyl orthosilicate was added, and the mixture was stirred evenly. The solution was then heated to 180 °C and crystallized for 20 h. After filtration, a precipitate was obtained. The precipitate was dried at 110 °C for 12 h and then calcined at 600 °C in a nitrogen atmosphere for 4 h to obtain core-shell catalyst B.

[0047] Evaluation method: Core-shell catalyst B was pressed into tablets and ground to 40-60 mesh. 10g was placed in the reaction tube of a fixed-bed continuous flow reactor. 1,4-Butanediol was preheated and mixed with nitrogen gas, and then passed through the catalyst bed for selective dehydration to produce 5-hexen-1-ol. The reaction temperature was 400℃, the reaction pressure was 3MPa, and the mass hourly space velocity (WHSV) of 1,4-butanediol was 0.1h. -1 Testing showed that the conversion rate of 1,4-butanediol was >99%, and the selectivity of 3-buten-1-ol was 84.3%.

[0048] Example 3

[0049] A core-shell catalyst, wherein the core active component is Pr6O by mass fraction. 11 The content is 5%, and the inert outer shell material SiO2 is 95%.

[0050] The preparation method of the core-shell catalyst:

[0051] 2.19 g of PrCl3·7H2O and 2.59 g of polyvinyl alcohol were weighed and dissolved in 220 mL of deionized water to obtain a 10 g / L salt solution. Under vigorous stirring, a 1 mol / L ammonia solution was added dropwise to the salt solution until the pH of the salt solution was 9. After aging at room temperature for 4 h, the solution was filtered, and after repeated slurry washing, it was ultrasonically dispersed in 500 mL of deionized water. Then, 40.81 g of dichlorodimethylsilane (129.06 g) was added, and the mixture was stirred evenly. The solution was then heated to 180 °C and crystallized for 20 h. After filtration, a precipitate was obtained. The precipitate was dried at 110 °C for 12 h and then calcined at 600 °C in a nitrogen atmosphere for 4 h to obtain the core-shell catalyst C.

[0052] Evaluation method: Core-shell catalyst C was pressed into tablets and ground to 40-60 mesh. 10g was placed in the reaction tube of a fixed-bed continuous flow reactor. 1,10-decanediol was preheated and mixed with nitrogen gas, and then passed through the catalyst bed for selective dehydration to produce 9-decen-1-ol. The reaction temperature was 400℃, the reaction pressure was 3MPa, and the mass hourly space velocity (WHSV) of 1,10-decanediol was 1.0 h⁻¹. -1 Testing showed that the conversion rate of 1,10-decanediol was 95.2%, and the selectivity of 9-decen-1-ol was 95.6%.

[0053] Example 4

[0054] A core-shell catalyst, wherein the core active component is Pr6O by mass fraction. 11 The content is 20%, and the outer shell inert material is 80% activated carbon.

[0055] The preparation method of the core-shell catalyst is as follows: 10.22g of Pr(NO3)3·6H2O and 10.35g of polyvinyl alcohol are weighed and dissolved in 1000mL of deionized water to obtain a 10g / L salt solution; under vigorous stirring, a 1mol / L ammonia solution is added dropwise to the salt solution until the pH of the salt solution is 9. After aging at room temperature for 4h, the solution is filtered, and after repeated slurry washing, it is ultrasonically dispersed in 1000mL of deionized water. Then, 48.00g of glucose is added, and after stirring evenly, the solution is heated to 180℃ for crystallization for 20h. After filtration, a precipitate is obtained; the precipitate is dried at 110℃ for 12h and then calcined at 600℃ in a nitrogen atmosphere for 4h to obtain the core-shell catalyst D.

[0056] Evaluation method: Core-shell catalyst D was pressed into tablets and ground to 40-60 mesh. 10g was placed in the reaction tube of a fixed-bed continuous flow reactor. 1,8-Octanediol was preheated and mixed with nitrogen gas, and then passed through the catalyst bed for selective dehydration to produce 7-octen-1-ol. The reaction temperature was 400℃, the reaction pressure was 3MPa, and the mass hourly space velocity (WHSV) of 1,8-octanediol was 0.3h. -1Testing showed that the conversion rate of 1,8-octanediol was >99%, and the selectivity of 7-octen-1-ol was 92.6%.

[0057] Example 5

[0058] A core-shell catalyst, wherein the core active component is Pr6O by mass fraction. 11 The content is 20%, and the outer shell inert material is 80% activated carbon.

[0059] The preparation method of the core-shell catalyst:

[0060] 10.22 g of Pr(NO3)3·6H2O and 10.35 g of polyvinyl alcohol were weighed and dissolved in 1000 mL of deionized water to obtain a 10 g / L salt solution. Under vigorous stirring, a 1 mol / L ammonia solution was added dropwise to the salt solution until the pH of the salt solution was 9. After aging at room temperature for 4 h, the solution was filtered, and after repeated slurry washing, it was ultrasonically dispersed in 1000 mL of deionized water. Then, 45.60 g of sucrose was added, and the mixture was stirred evenly. The solution was then heated to 180 °C and crystallized for 20 h. After filtration, a precipitate was obtained. The precipitate was dried at 110 °C for 12 h and then calcined at 600 °C in a nitrogen atmosphere for 4 h to obtain the core-shell catalyst E.

[0061] Evaluation method: Core-shell catalyst E was pressed into tablets and ground to 40-60 mesh. 10g was placed into the reaction tube of a fixed-bed continuous flow reactor. 5-Hydroxyvalerate was mixed with preheated nitrogen gas and passed through the catalyst bed for selective dehydration to produce 4-pentenoic acid. The reaction temperature was 400℃, the reaction pressure was 3MPa, and the mass hourly space velocity (WHSV) of 5-hydroxyvalerate was 0.3h. -1 Testing showed that the conversion rate of 5-hydroxyvalerate was >99%, and the selectivity of 4-pentenoic acid was 86.4%.

[0062] Example 6

[0063] A core-shell catalyst, wherein the core active component is Pr6O by mass fraction. 11 The content is 20%, and the outer shell inert material is 80% activated carbon.

[0064] The preparation method of the core-shell catalyst:

[0065] 10.22 g of Pr(NO3)3·6H2O and 10.35 g of polyvinyl alcohol were weighed and dissolved in 1000 mL of deionized water to obtain a 10 g / L salt solution. Under vigorous stirring, a 1 mol / L ammonia solution was added dropwise to the salt solution until the pH of the salt solution was 9. After aging at room temperature for 4 h, the solution was filtered, and after repeated slurry washing, it was ultrasonically dispersed in 1000 mL of deionized water. Then, 50 g of hydroxypropyl methylcellulose was added, and the mixture was stirred evenly. The solution was then heated to 180 °C and crystallized for 20 h. After filtration, a precipitate was obtained. The precipitate was dried at 110 °C for 12 h and then calcined at 600 °C in a nitrogen atmosphere for 4 h to obtain the core-shell catalyst F.

[0066] Evaluation method: Core-shell catalyst F was pressed into tablets and ground to 40-60 mesh. 10g was placed into the reaction tube of a fixed-bed continuous flow reactor. 7-hydroxyheptanoic acid was mixed with preheated nitrogen gas and passed through the catalyst bed for selective dehydration to produce 6-heptenic acid. The reaction temperature was 400℃, the reaction pressure was 3MPa, and the mass hourly space velocity (WHSV) of 7-hydroxyheptanoic acid was 0.3h⁻¹. -1 Testing showed that the conversion rate of 7-hydroxyheptanoic acid was >99%, and the selectivity of 6-heptenoic acid was 89.1%.

[0067] Example 7

[0068] A core-shell catalyst, wherein the core active component is Pr6O by mass fraction. 11 The content is 20%, and the outer shell inert material is 80% activated carbon.

[0069] The preparation method of the core-shell catalyst is the same as in Example 1.

[0070] Evaluation method: Core-shell catalyst A was pressed into tablets and ground to 40-60 mesh. 10g was placed into the reaction tube of a fixed-bed continuous flow reactor. 9-hydroxynonanoic acid was mixed with preheated nitrogen gas and passed through the catalyst bed for selective dehydration to produce 8-nonenoic acid. The reaction temperature was 400℃, the reaction pressure was 3MPa, and the mass hourly space velocity (WHSV) of 9-hydroxynonanoic acid was 0.3h. -1 Testing showed that the conversion rate of 9-hydroxynonanoic acid was >99%, and the selectivity of 8-nonenoic acid was 90.6%.

[0071] Comparative Example 1

[0072] A Pr6O 11 Catalyst preparation methods:

[0073] 10.22 g of Pr(NO3)3·6H2O and 10.35 g of polyvinyl alcohol were weighed and dissolved in 1000 mL of deionized water to obtain a 10 g / L salt solution. Under vigorous stirring, a 1 mol / L ammonia solution was added dropwise to the salt solution until the pH of the solution reached 9. After aging at room temperature for 4 h, the solution was filtered and precipitated after repeated slurry washing. The precipitate was dried at 110 °C for 12 h and then calcined at 600 °C under a nitrogen atmosphere for 4 h to obtain the catalyst Pr6O. 11 .

[0074] Evaluation method: The catalyst Pr6O 11 After tableting, the product is ground to 40-60 mesh. 5g of the product is placed in the reaction tube of a fixed-bed continuous flow reactor. 1,6-Hexanediol is preheated and mixed with nitrogen gas, then passed through the catalyst bed for a selective dehydration reaction to produce 5-hexen-1-ol. The reaction temperature is 400℃, the reaction pressure is 3MPa, and the 1,6-hexanediol mass hourly space velocity (WHSV) is 0.3h⁻¹. -1 The conversion rate of 1,6-hexanediol was >99%, and the selectivity for 5-hexen-1-ol was 32.7%.

[0075] Comparative Example 2

[0076] The preparation method of the core-shell catalyst: Commercial Al2O3 was used as the catalyst (purchased from Anaiji Reagent Company, item number: A16013).

[0077] Evaluation method: Same as in Implementation 1. Testing showed that the conversion rate of 1,6-hexanediol was >99%, and the selectivity of 5-hexen-1-ol was 10.9%.

[0078] The performance evaluation of the core-shell catalysts obtained in Examples 1-7 and Comparative Examples 1-2 for the selective dehydration of long-chain α-alcohols to long-chain α-olefins shows that, under appropriate reaction conditions, the core-shell catalysts of the present invention have excellent conversion rates of long-chain α-alcohols and selectivity for long-chain α-olefins, and have promising prospects for industrial application.

[0079] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. The application of a core-shell catalyst in the selective dehydration of long-chain alcohols to prepare long-chain α-olefins, characterized in that, The preparation of the long-chain α-olefin compound was carried out in a fixed-bed continuous flow reactor at a reaction temperature of 400°C, a reaction pressure of 3 MPa, and a mass hourly space velocity (WHSV) of 0.1–1 h⁻¹ for the long-chain alcohol compound. -1 ; The long-chain α-olefin compound is a long-chain α-olefin-ω-ol or a long-chain α-olefin-ω-carboxylic acid; The catalyst consists of a core and a shell, the core being Pr6O. 11 The outer shell is made of SiO2 and / or activated carbon; The core content is 5wt%~30wt%, and the shell content is 70wt%~95wt%. The core-shell catalyst is used for the selective dehydration of long-chain alcohols to prepare long-chain α-olefins. The preparation method of the core-shell catalyst includes the following steps: S1. Dissolve soluble praseodymium salt and polyvinyl alcohol in deionized water to obtain a salt solution; S2. Under vigorous stirring, ammonia solution is added dropwise to the salt solution to adjust the pH value of the solution to ≥9, and the solution is aged at room temperature to obtain a mixed solution; S3. Filter the mixed solution, and wash the filter cake until the pH of the filtrate is 7. Disperse the washed filter cake in deionized water by ultrasonication to form a sol. S4. Add a calculated amount of SiO2 and / or activated carbon precursor to the sol, stir until uniform, heat to crystallize, and filter to obtain a precipitate. S5. After drying the precipitate, calcine it in a nitrogen atmosphere to obtain the core-shell catalyst.

2. The application according to claim 1, characterized in that, The soluble praseodymium salt is one or more of Pr2(SO4)3, Pr(NO3)3•6H2O, and PrCl3•7H2O.

3. The application according to claim 1, characterized in that, The molar ratio of the soluble praseodymium salt to polyvinyl alcohol is 1:

10.

4. The application according to claim 1, characterized in that, The SiO2 precursor is one or more of methyl orthosilicate, ethyl orthosilicate, and dichlorodimethylsilane.

5. The application according to claim 1, characterized in that, The activated carbon precursor is one or more of glucose, sucrose, and cellulose.

6. The application according to claim 1, characterized in that, The long-chain alcohol is a long-chain α,ω-diol or a long-chain α-ol-ω-carboxylic acid.