CN111068779A - Preparation of noble metal magnetic nano catalyst based on polymerized ionic liquid loading - Google Patents
Preparation of noble metal magnetic nano catalyst based on polymerized ionic liquid loading Download PDFInfo
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Abstract
The invention discloses a noble metal magnetic nano catalyst based on polymerized ionic liquid loading and a preparation method thereof. The catalyst is used for synthesizing ionic liquid containing carboxyl, amino is introduced on the surface of the magnetic ferroferric oxide nano microsphere through modification of a silane coupling agent, and amide bond is formed through dehydration condensation reaction between the amino and the carboxyl in the ionic liquid, so that the ionic liquid is directionally anchored on the surface of the magnetic ferroferric oxide nano microsphere. And then, adding a cross-linking agent, an initiator and an antioxidant to form a polymerized ionic liquid, carrying out chemical reduction by utilizing the ion exchange effect between the polymerized ionic liquid and a noble metal precursor to obtain uniformly dispersed noble metal nano particles, and preparing the noble metal magnetic nano catalyst which is applied to the selective oxidation reaction of benzyl alcohol. The catalyst has good stability, high catalytic activity, easy recovery, long service life and good application prospect.
Description
Technical Field
The invention relates to a precious metal magnetic nano catalyst based on polymerized ionic liquid loading and a preparation method thereof, belonging to the catalyst preparation technology in the technical field of industrial catalysis.
Background
The selective oxidation of alcohols into aldehydes or ketones is an important reaction in the field of fine chemistry, wherein benzaldehyde prepared by the selective oxidation of benzyl alcohol is an important organic intermediate in organic chemical synthesis of flavors, fragrances, cosmetics, pesticides, medicines and the like, and has a large market demand. However, the reaction has the problems of easy deep oxidation and the like under the conventional conditions, and the reaction selectivity and the conversion rate are low. Therefore, a novel high-activity catalyst is actively explored, high-efficiency synthesis under mild reaction conditions is realized, and the method has important research significance in the application of the catalyst in the field of catalytic industry.
Patent CN109731573A provides a preparation method of a high-activity Au/nano-carbon catalyst for preparing benzaldehyde by benzyl alcohol oxidation, wherein the Au/nano-carbon catalyst is prepared by chemically reducing chloroauric acid aqueous solution and simply adding an element-doped carbon material. Although the preparation method of the catalyst is simple and convenient to operate, the prepared Au nanoparticles are easy to agglomerate on the carrier, and the dispersity of the noble metal particles needs to be further improved. Patent CN107042108A reports a method for preparing benzaldehyde by catalytic oxidation of benzyl alcohol with Pt/BiOCL-metal oxide as catalyst. It should be noted that the metal particles prepared by the method have relatively large particle size and wide particle size distribution, which is not beneficial to improving the stability of the noble metal. Compared with a catalyst prepared by loading components such as nano carbon, metal oxide and the like, the ionic liquid has the characteristic of stabilizing metal nano particles, and the metal stability of the catalyst prepared by taking the ionic liquid as a carrier can be improved to a certain extent. Patent CN107570210A provides an ionic liquid-polymer supported Pd-M based catalyst, and a preparation method and application thereof. Patent CN107486240A reports an ionic liquid crosslinked polymer supported nano palladium metal catalytic material, and a preparation method and application thereof. However, in the catalytic system, the ionic liquid itself is liable to absorb moisture in the air, thereby impairing the stabilizing effect on the metal particles. The polymerized ionic liquid is polymerized by the ionic liquid and has the properties of both the ionic liquid and the polymer. Through the functionalized and structured design of the polymerized ionic liquid monomer, the properties of the polymerized ionic liquid such as the chain length of the anionic and cationic side chains, the type of functional groups and the like can be regulated and controlled, so that the thermal stability and the chemical stability of the polymerized ionic liquid are obviously improved, the effective control of the polymerized ionic liquid on the dispersibility and the particle size of the nano metal particles is realized, and the reaction activity and the selectivity of a subsequently prepared catalyst are improved. Currently, there are few reports of the preparation of metal catalysts by using the polymeric ionic liquid loading technology, which limits the application thereof to some extent.
According to the method, ionic liquid with carboxyl is synthesized, the surface of the ferroferric oxide nano microsphere is modified through an amination function, an amido bond is formed through dehydration condensation reaction between amino and carboxyl in the synthesized ionic liquid, and the ionic liquid is directionally anchored on the surface of the ferroferric oxide nano microsphere. The polymerization of the polymerized ionic liquid on the surface of the ferroferric oxide nano-particles is realized by introducing a cross-linking agent, an initiator and an antioxidant, the uniform dispersion of the nano-metal particles is realized through the ion exchange action between the polymerized ionic liquid and a metal precursor and the chemical reduction, and finally the noble metal magnetic nano-catalyst is prepared. And the influence of the reaction on the liquid-phase selective oxidation of the benzyl alcohol is explored to improve the conversion rate of the benzyl alcohol and the selectivity of benzaldehyde.
Disclosure of Invention
The technical problem is as follows: the invention aims to provide a precious metal magnetic nano catalyst based on polymerized ionic liquid loading and a preparation method thereof.
The technical scheme is as follows: the invention relates to a preparation method of a precious metal magnetic nano catalyst based on polymerized ionic liquid loading, which comprises the following steps: firstly synthesizing carboxyl-containing ionic liquid, introducing amino on the surface of the magnetic ferroferric oxide nano microsphere modified by a silane coupling agent, forming amido bond by utilizing dehydration condensation reaction between the amino and carboxyl in the ionic liquid, thus realizing the directional anchoring of the ionic liquid on the surface of the magnetic ferroferric oxide nano microsphere, then adding a cross-linking agent, an initiator and an antioxidant to form polymeric ionic liquid, and obtaining uniformly dispersed noble metal nano particles after chemical reduction through ion exchange between the polymeric ionic liquid and a noble metal precursor, thereby preparing the noble metal magnetic nano catalyst.
The specific preparation method of the catalyst comprises the following steps:
step a) preparation of ionic liquid: dissolving 1-vinylimidazole and halogenated acid in an ethanol solution, wherein the mass ratio of 1-vinylimidazole to bromo-acid to ethanol is 1:1: 2-1: 2:10, stirring at 60-90 ℃ for 20-30 h, removing the solvent, washing for multiple times to obtain a white solid, and drying the obtained product at 60-70 ℃ in vacuum for 6-8 h to obtain a carboxyl-containing ionic liquid;
step b), stirring ferric trichloride hexahydrate and ethylene glycol in a mass ratio of 1: 7-1: 12 for 0.5-2 hours until FeCl3Completely dissolving to form a clear solution, and adding sodium acetate and polyethylene glycol into the solution, wherein the mass ratio of ferric trichloride hexahydrate to sodium acetate to polyethylene glycol is 1:0.9: 0.25-1: 1.1: 0.35; stirring for 20-60 min, transferring the mixture into a stainless steel autoclave with a Teflon lining, reacting for 10-16 h at 150-250 ℃, then moving out of the autoclave, collecting the product by using a magnet, washing the product with distilled water and absolute ethyl alcohol for multiple times, and drying in vacuum for 12-24 h at 60-80 ℃ to obtain magnetic nano microspheres;
suspending the magnetic nano-microspheres prepared in the step b) in an anhydrous toluene solution, wherein the mass ratio of the magnetic nano-microspheres to the anhydrous toluene is 1: 10-1: 100, adding a silane coupling agent to prepare a suspension, wherein the volume ratio of the silane coupling agent to the anhydrous toluene is 1: 12-1: 24, stirring the suspension at 100-110 ℃ for 12-24 h, washing the suspension with toluene, anhydrous ethanol and distilled water for multiple times, and performing vacuum drying at 60-80 ℃ for 12-24 h to prepare amino-modified magnetic nano-microspheres;
step d), ultrasonically dispersing the ionic liquid containing carboxyl prepared in the step a) and the amino modified magnetic nano-microspheres prepared in the step c) in an ethanol solution according to the mass ratio of 2: 1-6: 1, then adding a cross-linking agent, an initiator and an antioxidant, stirring for 10-18 h at the temperature of 60-80 ℃, washing for multiple times by using ionic water and absolute ethyl alcohol, and drying for 20-24 h at the temperature of 40-50 ℃ to prepare the magnetic nano-microspheres loaded with the polymeric ionic liquid;
step e), dispersing the magnetic nano-microspheres loaded with the polymeric ionic liquid prepared in the step d) and the aqueous solution containing the noble metal acid in deionized water according to the mass ratio of 10: 1-6: 1 at room temperature, and stirring for 6-10 hours; and then adding 10-20 mL of sodium borohydride aqueous solution, stirring for 20-30 min, wherein the mass concentration of the sodium borohydride aqueous solution is 5mg/mL, centrifuging, washing, and drying in vacuum at 50-60 ℃ for 10-12 h to obtain the polymeric ionic liquid loaded noble metal magnetic nano catalyst.
Wherein:
the halogenated acid in the step a) is any one of bromoacetic acid, 3-bromopropionic acid, 4-bromobutyric acid, chloroacetic acid, 3-chloropropionic acid or 4-chlorobutyric acid.
The acid aqueous solution containing noble metal in the step e) is one or a compound of two of chloroauric acid, chloropalladite or chloroplatinic acid, and the mass concentration of metal in the aqueous solution is 0.1-2 mg/mL.
The noble metal is one or the combination of platinum and palladium alloy, and the mass of the loaded noble metal is 1-10 wt% of the prepared nano catalyst.
The carboxyl-containing ionic liquid is one or a combination of more of 3-acetic acid-1-vinyl imidazole bromide, 3-propionic acid-1-vinyl imidazole bromide, 3-butyric acid-1-vinyl imidazole bromide, 3-acetic acid-1-vinyl imidazole chloride, 3-propionic acid-1-vinyl imidazole chloride or 3-butyric acid-1-vinyl imidazole chloride.
The silane coupling agent is one or a combination of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane or N- (2-aminoethyl) -3-aminopropyltrimethoxysilane.
The cross-linking agent is any one of divinylbenzene and ethylene glycol dimethacrylate.
The initiator is any one of azodiisobutyronitrile or diacyl peroxide.
The antioxidant is any one of butyl hydroxy anisol, dibutyl hydroxy toluene and tert-butyl hydroquinone.
Has the advantages that: the invention aims to provide a precious metal magnetic nano catalyst based on polymerized ionic liquid loading and a preparation method thereof.
The invention has the characteristics that:
(1) an amido bond is formed through dehydration condensation reaction between carboxyl of the synthetic ionic liquid and amino of the modified magnetic iron tetroxide nano-microsphere, and the amido bond can firmly and orderly anchor the ionic liquid on the surface of the magnetic iron tetroxide nano-microsphere, thereby realizing uniform loading of the ionic liquid and greatly reducing the loss of the ionic liquid in the loading process.
(2) In the polymerization reaction process, except adding an initiator and a cross-linking agent, an antioxidant is also introduced. The presence of the antioxidant can effectively prevent double bonds in the ionic liquid from being oxidized and promote the polymerization reaction.
(3) The exchange reaction between the polymeric ionic liquid and metal precursor ions is fully utilized to realize the uniform adsorption of the metal precursor, which is beneficial to controlling the size of the nano metal particles and realizing the uniform dispersion of the nano metal particles. Compared with the traditional catalyst, the catalyst is easy to separate from the product, convenient to recover and high in recycling rate.
Detailed Description
The invention relates to a noble metal magnetic nano catalyst based on polymerized ionic liquid loading, which is characterized in that ionic liquid with carboxyl is synthesized, then magnetic ferric oxide nano microspheres are used as a substrate, and amino groups are introduced through modification of a silane coupling agent. The method comprises the steps of forming an amido bond by utilizing a dehydration condensation reaction between an amino group and a carboxyl group in the synthetic ionic liquid, adding a cross-linking agent, an initiator and an antioxidant to realize the polymerization of the ionic liquid on the surface of the ferric oxide nano microsphere, and obtaining the uniformly dispersed noble metal nano particles after chemical reduction according to the ion exchange effect between the polymerized ionic liquid and a nano metal precursor.
Example 1:
13.90g of bromoacetic acid and 9.42g of 1-vinylimidazole were weighed out and dissolved in 30mL of ethanol solution, stirred for 10min, heated to 80 ℃, then stirred for 24h under nitrogen atmosphere, the solvent was removed, and the ionic liquid 3-acetic acid-1-vinylimidazole bromide was obtained by washing several times with acetonitrile.
4.0g ferric chloride hexahydrate is weighed and dissolved in 30mL ethylene glycol and stirred for 1h until FeCl3And (2) completely dissolving to form a clear solution, adding 3.6g of sodium acetate and 1.0g of polyethylene glycol into the solution, stirring for 40 minutes, transferring the solution into a stainless steel autoclave with a teflon lining, reacting for 14 hours at 200 ℃, then removing the reaction kettle, collecting a product by using a magnet, washing the product by using distilled water and absolute ethyl alcohol for multiple times, and drying the product in vacuum for 15 hours at 60 ℃ to obtain the magnetic nano microspheres.
1.5g of magnetic nanospheres were weighed and ultrasonically dispersed in 30mL of anhydrous toluene, followed by the addition of 2mL of 3-aminopropyltrimethoxysilane. Stirring the suspension at 100 ℃ for 12h, respectively centrifugally washing with anhydrous toluene, anhydrous ethanol and deionized water for three times, and vacuum drying at 70 ℃ for 24h to obtain the amino-modified magnetic nano-microspheres.
100mg of the amino-modified magnetic nanospheres prepared above, 0.46g of ionic liquid 3-acetic acid-1-vinylimidazolium bromide and 0.26g of divinylbenzene were weighed out and mixed in 10mL of ethanol, stirred for 20min, added with 24.6mg of azobisisobutyronitrile and 10mg of butylated hydroxyanisole for polymerization, heated to 70 ℃, and stirred under nitrogen atmosphere for 12 h. And after the reactants are cooled to room temperature, sequentially carrying out centrifugal washing for a plurality of times by using deionized water and absolute ethyl alcohol, and finally carrying out vacuum drying for 24h at the temperature of 60 ℃ to obtain the magnetic nano-microsphere loaded by the polymeric ionic liquid.
Weighing the magnetic nano-microsphere prepared by preparing the 50mg polymeric ionic liquid load into 50mL of deionized water, then adding 6mL of chloroauric acid aqueous solution (the concentration is 1mg/mL), stirring at room temperature for 7h, then adding 12mL of sodium borohydride solution (the concentration is 5mg/mL), stirring for 20min, respectively centrifugally washing with deionized water and absolute ethyl alcohol for 3 times, and drying in vacuum at 60 ℃ for 10h to obtain the Au magnetic nano-catalyst loaded by the polymeric ionic liquid.
Evaluation conditions were as follows: 25mg of the prepared catalyst was weighed and ultrasonically dispersed in a 25mL three-necked flask reactor containing 0.6g of potassium carbonate, 5mL of benzyl alcohol and 15mL of deionized water so that the flow rate of oxygen was 60mL/min, the reaction temperature was 150 ℃ and the reaction time was 6 hours. After the reaction is finished, the reaction product is treated, sampled and analyzed in a gas chromatograph, and the conversion rate of the benzyl alcohol and the selectivity of the benzaldehyde are inspected.
The results show that the catalyst has a conversion of 82% of benzyl alcohol and a selectivity of 95% of benzaldehyde.
Example 2:
7.65g of bromopropionic acid and 4.70g of 1-vinylimidazole were weighed out and dissolved in 50mL of ethanol solution, mechanically stirred for 20min, warmed to 75 ℃, then stirred for 24h under nitrogen atmosphere, the solvent was removed, and the ionic liquid 3-propionic acid-1-vinylimidazole bromide was obtained by washing several times with acetonitrile.
4.0g ferric chloride hexahydrate was weighed into 35mL ethylene glycol and stirred for 1.5h until FeCl3And (2) completely dissolving to form a clear solution, adding 4.4g of sodium acetate and 1.2g of polyethylene glycol into the solution, stirring for 50min, transferring the solution into a stainless steel autoclave with a teflon lining, reacting for 16h at 180 ℃, then moving out of the reaction kettle, collecting a product by using a magnet, washing the product by using distilled water and absolute ethyl alcohol for multiple times, and drying the product in vacuum for 20h at 50 ℃ to obtain the magnetic nano microspheres.
2g of magnetic nanospheres were weighed and ultrasonically dispersed in 40mL of anhydrous toluene, followed by 3mL of 3-aminopropyltriethoxysilane. And stirring the suspension for 15h at 105 ℃, respectively centrifugally washing the suspension for three times by using anhydrous toluene, anhydrous ethanol and deionized water, and drying the suspension for 24h in vacuum at 60 ℃ to obtain the amino-modified magnetic nano-microspheres.
100mg of the amino-modified magnetic nanosphere prepared above, 0.5g of ionic liquid 3-propionic acid-1-vinylimidazole bromide and 0.40g of ethylene glycol dimethacrylate were weighed and mixed in 20mL of ethanol, stirred for 30min, added with 30mg of diacyl peroxide and 15mg of dibutylhydroxytoluene for polymerization, heated to 80 ℃, and stirred for 10h under a nitrogen atmosphere. And after the reactants are cooled to room temperature, sequentially carrying out centrifugal washing for a plurality of times by using deionized water and absolute ethyl alcohol, and finally carrying out vacuum drying for 24h at 40 ℃ to obtain the magnetic nano-microsphere loaded by the polymeric ionic liquid.
Weighing the magnetic nano-microsphere prepared by preparing 50mg of the polymeric ionic liquid load into 50mL of deionized water, then adding 5mL of chloroplatinic acid aqueous solution (with the concentration of 1.5mg/mL), stirring at room temperature for 5h, then adding 15mL of sodium borohydride solution (with the concentration of 5mg/mL), stirring for 30min, respectively centrifugally washing with deionized water and absolute ethyl alcohol for 3 times, and vacuum drying at 50 ℃ for 11h to obtain the polymeric ionic liquid load Pt magnetic nano-catalyst.
Evaluation conditions were as follows: 25mg of the prepared catalyst was weighed and ultrasonically dispersed in a 25mL three-necked flask reactor containing 0.6g of potassium carbonate, 5mL of benzyl alcohol and 15mL of deionized water so that the flow rate of oxygen was 50mL/min, the reaction temperature was 160 ℃ and the reaction time was 7 hours. After the reaction is finished, the reaction product is treated, sampled and analyzed in a gas chromatograph, and the conversion rate of the benzyl alcohol and the selectivity of the benzaldehyde are inspected.
The results show that the catalyst has a benzyl alcohol conversion of 81% and a benzaldehyde selectivity of 92%.
Example 3:
8.35g of bromopropionic acid and 4.70g of 1-vinylimidazole were weighed out in 40mL of ethanol solution, mechanically stirred for 30min, warmed to 70 ℃, then stirred for 24h under nitrogen atmosphere, the solvent was removed, and the ionic liquid 3-propionic acid-1-vinylimidazole bromide was obtained by washing several times with acetonitrile.
4.0g ferric chloride hexahydrate was weighed out and dissolved in 38mL ethylene glycol and stirred for 0.5h until FeCl3Dissolving completely to obtain clear solution, adding 4.0g sodium acetate and 1.4g polyethylene glycol into the solution, stirring for 60min, transferring into stainless steel autoclave with Teflon lining, reacting at 160 deg.C for 12 hr, removing the autoclave, collecting the product with magnet, washing with distilled water and anhydrous ethanol for several times, and vacuum-drying at 70 deg.CDrying for 16h to obtain the magnetic nano-microsphere.
2.5g of magnetic nanospheres were weighed out and ultrasonically dispersed in 60mL of anhydrous toluene, followed by the addition of 2.5mL of N- (2-aminoethyl) -3-aminopropyltrimethoxysilane. Stirring the suspension at 110 ℃ for 18h, respectively centrifugally washing the suspension with anhydrous toluene, anhydrous ethanol and deionized water for three times, and drying the suspension at 80 ℃ in vacuum for 24h to obtain a product, thus obtaining the amino-modified magnetic nano-microsphere.
100mg of the amino-modified magnetic nanospheres prepared above, 0.48g of ionic liquid 3-propionic acid-1-vinylimidazolium bromide and 0.26g of divinylbenzene were weighed and mixed in 40mL of ethanol, stirred for 40min, added with 26.4mg of azobisisobutyronitrile and 20mg of tert-butylhydroquinone for polymerization, heated to 80 ℃, and stirred for 10h under a nitrogen atmosphere. And after the reactant of 26.4mg is cooled to room temperature, sequentially carrying out centrifugal washing on the reactant by using deionized water and absolute ethyl alcohol for a plurality of times, and finally carrying out vacuum drying at 50 ℃ for 20 hours to obtain the magnetic nano microsphere loaded by the polymeric ionic liquid.
Weighing the magnetic nano-microsphere prepared by preparing 50mg of the polymeric ionic liquid load into 50mL of deionized water, then adding 7mL of chloropalladate aqueous solution (with the concentration of 0.8mg/mL), stirring at room temperature for 5h, then adding 20mL of sodium borohydride solution (with the concentration of 5mg/mL), stirring for 30min, respectively centrifugally washing with deionized water and absolute ethyl alcohol for 3 times, and drying in vacuum at 60 ℃ for 12h to obtain the polymeric ionic liquid load Pd magnetic nano-catalyst.
Evaluation conditions were as follows: 25mg of the prepared catalyst was weighed and ultrasonically dispersed in a 25mL three-necked flask reactor containing 0.6g of potassium carbonate, 5mL of benzyl alcohol and 15mL of deionized water so that the flow rate of oxygen was 40mL/min, the reaction temperature was 170 ℃ and the reaction time was 5 hours. After the reaction is finished, the reaction product is treated, sampled and analyzed in a gas chromatograph, and the conversion rate of the benzyl alcohol and the selectivity of the benzaldehyde are inspected.
The results show that the catalyst has a benzyl alcohol conversion of 75% and a benzaldehyde selectivity of 92%.
Example 4:
7.65g of bromopropionic acid and 4.70g of 1-vinylimidazole were weighed out and dissolved in 50mL of ethanol solution, mechanically stirred for 20min, warmed to 75 ℃, then stirred for 24h under nitrogen atmosphere, the solvent was removed, and the ionic liquid 3-propionic acid-1-vinylimidazole bromide was obtained by washing several times with acetonitrile.
4.0g ferric chloride hexahydrate was weighed into 35mL ethylene glycol and stirred for 1.5h until FeCl3And (2) completely dissolving to form a clear solution, adding 4.4g of sodium acetate and 1.2g of polyethylene glycol into the solution, stirring for 50min, transferring the solution into a stainless steel autoclave with a teflon lining, reacting for 16h at 180 ℃, then moving out of the reaction kettle, collecting a product by using a magnet, washing the product by using distilled water and absolute ethyl alcohol for multiple times, and drying the product in vacuum for 20h at 50 ℃ to obtain the magnetic nano microspheres.
2g of magnetic nanospheres were weighed and ultrasonically dispersed in 40mL of anhydrous toluene, followed by 3mL of 3-aminopropyltriethoxysilane. And stirring the suspension for 15h at 105 ℃, respectively centrifugally washing the suspension for three times by using anhydrous toluene, anhydrous ethanol and deionized water, and drying the suspension for 24h in vacuum at 60 ℃ to obtain a product, thus obtaining the amino-modified magnetic nano-microsphere.
100mg of the amino-modified magnetic nanosphere prepared above, 0.45g of ionic liquid 3-propionic acid-1-vinylimidazole bromide and 0.35g of ethylene glycol dimethacrylate were weighed and mixed in 20mL of ethanol, stirred for 30min, added with 30mg of diacyl peroxide and 15mg of dibutylhydroxytoluene for polymerization, heated to 80 ℃, and stirred for 10h under a nitrogen atmosphere. And after the reactants are cooled to room temperature, sequentially carrying out centrifugal washing for a plurality of times by using deionized water and absolute ethyl alcohol, and finally carrying out vacuum drying for 24h at 40 ℃ to obtain the magnetic nano-microsphere loaded by the polymeric ionic liquid.
Weighing the magnetic nano-microsphere prepared by preparing 50mg of the polymeric ionic liquid load into 50mL of deionized water, then adding 5mL of chloroplatinic acid aqueous solution (with the concentration of 1.5mg/mL), stirring at room temperature for 5h, then adding 15mL of sodium borohydride solution (with the concentration of 5mg/mL), stirring for 30min, respectively centrifugally washing with deionized water and absolute ethyl alcohol for 3 times, and vacuum drying at 50 ℃ for 11h to obtain the polymeric ionic liquid load Pt magnetic nano-catalyst.
The evaluation conditions were the same as in example 2. The results show that the catalyst has a conversion of benzyl alcohol of 85% and a selectivity of benzaldehyde of 94%. Compared with example 3, the catalytic reaction activity and stability are improved.
Example 5:
8.35g of bromopropionic acid and 4.70g of 1-vinylimidazole were weighed out in 40mL of ethanol solution, mechanically stirred for 30min, warmed to 70 ℃, then stirred for 24h under nitrogen atmosphere, the solvent was removed, and the ionic liquid 3-propionic acid-1-vinylimidazole bromide was obtained by washing several times with acetonitrile.
4.0g ferric chloride hexahydrate was weighed out and dissolved in 38mL ethylene glycol and stirred for 0.5h until FeCl3And (2) completely dissolving to form a clear solution, adding 4.0g of sodium acetate and 1.4g of polyethylene glycol into the solution, stirring for 60min, transferring the solution into a stainless steel autoclave with a teflon lining, reacting at 160 ℃ for 12h, then removing the reaction kettle, collecting a product by using a magnet, washing the product by using distilled water and absolute ethyl alcohol for multiple times, and drying the product in vacuum at the temperature of 70 h to prepare the magnetic nano microspheres.
5.0g of magnetic nanospheres were weighed out and ultrasonically dispersed in 50mL of anhydrous toluene, followed by addition of 4.0mL of N- (2-aminoethyl) -3-aminopropyltrimethoxysilane. Stirring the suspension at 103 ℃ for 20h, respectively centrifugally washing the suspension with anhydrous toluene, anhydrous ethanol and deionized water for three times, and drying the suspension at 60 ℃ in vacuum for 20h to obtain a product, thus obtaining the amino-modified magnetic nano-microsphere.
100mg of the amino-modified magnetic nanospheres prepared above, 0.52g of ionic liquid 3-propionic acid-1-vinylimidazolium bromide and 0.26g of divinylbenzene were weighed and mixed in 40mL of ethanol, stirred for 40min, added with 26.4mg of azobisisobutyronitrile and 20mg of tert-butylhydroquinone for polymerization, heated to 80 ℃, and stirred for 10h under a nitrogen atmosphere. And after the reactant of 26.4mg is cooled to room temperature, sequentially carrying out centrifugal washing on the reactant by using deionized water and absolute ethyl alcohol for a plurality of times, and finally carrying out vacuum drying at 50 ℃ for 20 hours to obtain the magnetic nano microsphere loaded by the polymeric ionic liquid.
Weighing the magnetic nano-microsphere prepared by preparing 50mg of the polymeric ionic liquid load into 50mL of deionized water, then adding 7mL of chloropalladate aqueous solution (with the concentration of 0.8mg/mL), stirring at room temperature for 5h, then adding 20mL of sodium borohydride solution (with the concentration of 5mg/mL), stirring for 30min, respectively centrifugally washing with deionized water and absolute ethyl alcohol for 3 times, and drying in vacuum at 60 ℃ for 12h to obtain the polymeric ionic liquid load Pd magnetic nano-catalyst.
The evaluation conditions were the same as in example 3. The results show that the catalyst has a conversion of benzyl alcohol of 76.5% and a selectivity of benzaldehyde of 94%. Compared with example 3, the catalytic reaction activity and stability are improved.
Claims (10)
1. A preparation method of a noble metal magnetic nano catalyst based on polymeric ionic liquid loading is characterized by comprising the steps of firstly synthesizing ionic liquid containing carboxyl, then modifying the surface of a magnetic ferroferric oxide nano microsphere through a silane coupling agent to introduce amino, forming amido bond through dehydration condensation reaction between the amino and the carboxyl in the ionic liquid, realizing directional anchoring of the ionic liquid on the surface of the magnetic ferroferric oxide nano microsphere, then adding a cross-linking agent, an initiator and an antioxidant to form polymeric ionic liquid, and obtaining uniformly dispersed noble metal nano particles after chemical reduction through ion exchange between the polymeric ionic liquid and a noble metal precursor, thereby preparing the noble metal magnetic nano catalyst.
2. The preparation method of the noble metal magnetic nano catalyst based on the polymeric ionic liquid loading as claimed in claim 1, characterized in that the specific preparation method of the catalyst is as follows:
step a) preparation of ionic liquid: dissolving 1-vinylimidazole and halogenated acid in an ethanol solution, wherein the mass ratio of 1-vinylimidazole to bromo-acid to ethanol is 1:1: 2-1: 2:10, stirring at 60-90 ℃ for 20-30 h, removing the solvent, washing for multiple times to obtain a white solid, and drying the obtained product at 60-70 ℃ in vacuum for 6-8 h to obtain a carboxyl-containing ionic liquid;
step b), stirring ferric trichloride hexahydrate and ethylene glycol in a mass ratio of 1: 7-1: 12 for 0.5-2 hours until FeCl3Dissolving completely to form clear solution, adding sodium acetate and polyethylene glycol into the solution, wherein ferric trichloride hexahydrate, sodium acetate and polyethylene glycolThe mass ratio is 1:0.9: 0.25-1: 1.1: 0.35; stirring for 20-60 min, transferring the mixture into a stainless steel autoclave with a Teflon lining, reacting for 10-16 h at 150-250 ℃, then moving out of the autoclave, collecting the product by using a magnet, washing the product with distilled water and absolute ethyl alcohol for multiple times, and drying in vacuum for 12-24 h at 60-80 ℃ to obtain magnetic nano microspheres;
suspending the magnetic nano-microspheres prepared in the step b) in an anhydrous toluene solution, wherein the mass ratio of the magnetic nano-microspheres to the anhydrous toluene is 1: 10-1: 100, adding a silane coupling agent to prepare a suspension, wherein the volume ratio of the silane coupling agent to the anhydrous toluene is 1: 12-1: 24, stirring the suspension at 100-110 ℃ for 12-24 h, washing the suspension with toluene, anhydrous ethanol and distilled water for multiple times, and performing vacuum drying at 60-80 ℃ for 12-24 h to prepare amino-modified magnetic nano-microspheres;
step d), ultrasonically dispersing the ionic liquid containing carboxyl prepared in the step a) and the amino modified magnetic nano-microspheres prepared in the step c) in an ethanol solution according to the mass ratio of 2: 1-6: 1, then adding a cross-linking agent, an initiator and an antioxidant, stirring for 10-18 h at the temperature of 60-80 ℃, washing for multiple times by using ionic water and absolute ethyl alcohol, and drying for 20-24 h at the temperature of 40-50 ℃ to prepare the magnetic nano-microspheres loaded with the polymeric ionic liquid;
step e), dispersing the magnetic nano-microspheres loaded with the polymeric ionic liquid prepared in the step d) and the aqueous solution containing the noble metal acid in deionized water according to the mass ratio of 10: 1-6: 1 at room temperature, and stirring for 6-10 hours; and then adding 10-20 mL of sodium borohydride aqueous solution, stirring for 20-30 min, wherein the mass concentration of the sodium borohydride aqueous solution is 5mg/mL, centrifuging, washing, and drying in vacuum at 50-60 ℃ for 10-12 h to obtain the polymeric ionic liquid loaded noble metal magnetic nano catalyst.
3. The preparation method of the magnetic nano catalyst based on the polymerized ionic liquid supported noble metal, according to claim 2, characterized in that the halogenated acid in the step a) is any one of bromoacetic acid, 3-bromopropionic acid, 4-bromobutyric acid, chloroacetic acid, 3-chloropropionic acid or 4-chlorobutyric acid.
4. The preparation method of the polymerized ionic liquid supported precious metal magnetic nano-catalyst according to claim 2, wherein the precious metal-containing aqueous solution in step e) is one or a compound of two of chloroauric acid, chloropalladite and chloroplatinic acid, and the mass concentration of metal in the aqueous solution is 0.1-2 mg/mL.
5. The preparation of the polymerized ionic liquid supported noble metal magnetic nano-catalyst according to the claim 1 or 2, characterized in that the noble metal is one or the combination of two of platinum and palladium alloy, and the mass of the supported noble metal is 1-10 wt% of the prepared nano-catalyst.
6. The preparation method of the magnetic nano catalyst based on the polymerized ionic liquid loaded precious metal, according to the claim 1 or 2, characterized in that the ionic liquid containing carboxyl is one or a combination of several of 3-acetic acid-1-vinyl imidazole bromide, 3-propionic acid-1-vinyl imidazole bromide, 3-butyric acid-1-vinyl imidazole bromide, 3-acetic acid-1-vinyl imidazole chloride, 3-propionic acid-1-vinyl imidazole chloride or 3-butyric acid-1-vinyl imidazole chloride.
7. The preparation method of the polymerized ionic liquid supported noble metal magnetic nano-catalyst according to claim 1 or 2, characterized in that the silane coupling agent is one or a combination of more of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane or N- (2-aminoethyl) -3-aminopropyltrimethoxysilane.
8. The preparation of the polymeric ionic liquid supported noble metal magnetic nanocatalyst according to claim 1 or 2, characterized in that the crosslinking agent is any one of divinylbenzene and ethylene glycol dimethacrylate.
9. The preparation method of the polymeric ionic liquid supported noble metal magnetic nanocatalyst according to claim 1 or 2, characterized in that the initiator is any one of azobisisobutyronitrile or diacyl peroxide.
10. The preparation method of the polymeric ionic liquid supported noble metal magnetic nano catalyst according to claim 1 or 2, wherein the antioxidant is any one of butylated hydroxyanisole, dibutylhydroxytoluene and tert-butylhydroquinone.
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