CN103586048B - A kind of nano Pd particle magnetic catalyst, preparation and react for liquid-phase catalysis - Google Patents

Abstract

A kind of nano Pd particle magnetic catalyst, preparation and for liquid-phase catalysis reaction, belong to nanometer magnetic catalyst technical field.Make superparamagnetism Fe ₃o ₄core, using softex kw as template, using sodium metasilicate as silicon source, adopts hyperacoustic method, in magnetic Fe ₃o ₄core surface forms the mesoporous SiO of one deck ₂, at N after drying ₂the lower roasting removed template method of protection, prepares magnetic SiO ₂fe ₃o ₄nanosphere.Then with magnetic SiO ₂fe ₃o ₄nanosphere is core, adopts ultrasonic method, Pd catalytic active component is assembled in magnetic core SiO ₂fe ₃o ₄the mesoporous SiO on surface ₂on shell, prepare magnetic Pd/SiO ₂fe ₃o ₄catalyst.Pd catalytic active component particle of the present invention has been embedded in mesoporous SiO ₂on, define the nano Pd particle catalytic active component of high dispersive, improve the activity of catalyst, avoid the loss of Pd in course of reaction.

Description

A kind of nano Pd magnetic catalyst, preparation and use in liquid phase catalytic reaction

technical field

The invention relates to a preparation method of a magnetic catalyst for assembling nano Pd catalytic active component particles on the surface of a magnetic core carrier and its use in a liquid phase catalytic reaction, belonging to the technical field of nano magnetic catalysts.

Background technique

Under the action of a catalyst, bromobenzene and butyl acrylate can form C-C coupled organic compounds, which are widely used in the synthesis of dyes, medicines, pesticides, and fine chemicals. Most of the traditional catalysts for this type of C-C coupling reaction are homogeneous catalysts with noble metal Pd as the main active component. However, due to the difficulty in separation and recovery of homogeneous catalysts, Pd catalytically active components are loaded on various commonly used catalyst supports. On the other hand, the prepared supported Pd-based catalyst can realize the separation of the catalyst and the reactant by filtering after the reaction, and some good progress has been made (Liu Hongfei, Jia Zhigang, Ji Shengfu. Research progress of supported Heck reaction catalysts. Journal of Catalysis, 2012 , 33(5):757-767). But for nanoscale catalysts, the process of filtration operation is more complicated.

The magnetic catalyst prepared by using superparamagnetic Fe ₃ O ₄ as the core and supporting catalytic active components can easily separate the catalyst and reactants by using an external magnetic field after the liquid-phase catalytic reaction is completed, and the recovery of the catalyst is relatively simple. The Cu/Fe ₃ O ₄ SiO ₂ magnetic catalyst prepared by us with superparamagnetic Fe ₃ O ₄ as the nucleus, in the reaction process of catalytic conversion of low-concentration formaldehyde to hydrogen production, the catalyst is recovered by an external magnetic field and recycled 8 times. Has very good performance (JunhongJi, PenghuiZeng, ShengfuJi, WeiYang, HongfeiLiu, YingyiLi.Catalytic activityofcore–shellstructuredCu/Fe ₃ O ₄ SiO ₂ microspherecatalysts.CatalysisToday,2010,158:305-309); prepared TiO ₂ /SiO ₂ Fe ₃ O ₄ magnetic photocatalyst can effectively degrade organic dye pollutants in wastewater (Hongfei Liu, Zhigang Jia, Shengfu Ji, Yuanyuan Zheng, Ming Li, Hao Yang. Synthesis of TiO ₂ /SiO ₂ Fe ₃ O ₄ magnetic microspheres and their properties of photocatalytic degradation dyestuff. Catalysis Today, 2011, 175: 283) , in the photocatalytic degradation of the organic dye Rhodamine B, the catalyst was recovered by an external magnetic field and recycled 8 times and still had good degradation performance.

If the Pd active component is supported on the surface of the superparamagnetic Fe ₃ O ₄ core to prepare a magnetic catalyst, the catalyst can be easily separated, recovered, and recycled by using an external magnetic field, thereby greatly improving the utilization efficiency of the catalyst. Based on this idea, the present invention firstly prepares a Fe ₃ O ₄ core with superparamagnetism, and then wraps a SiO ₂ shell on the surface of the Fe ₃ O ₄ core to prepare magnetic SiO ₂ Fe ₃ O ₄ nanospheres. Nano-Pd catalytic active components were assembled on the surface of SiO ₂ Fe ₃ O ₄ nanospheres, and a series of new magnetic Pd/SiO ₂ Fe ₃ O ₄ catalysts were prepared.

The novel magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst prepared by the method of the present invention not only has good liquid-phase catalytic reaction performance, but also uses an external magnetic field to easily realize the separation of the catalyst and the reactant after the reaction, and the recovery and repeated circulation of the catalyst Operations such as use are also relatively simple, so it has important industrial application value.

Contents of the invention

The object of the present invention is to provide a method for preparing a Pd/SiO ₂ Fe ₃ O ₄ catalyst with a superparamagnetic Fe ₃ O ₄ core. Using FeCl ₃ 6H ₂ O to make superparamagnetic Fe ₃ O ₄ core, hexadecyltrimethylammonium bromide as template, and cheap sodium silicate as magnetic Fe ₃ O ₄ core surface coated with SiO ₂ shell silicon source, using ultrasonic method, quickly form a layer of mesoporous SiO ₂ shell layer on the surface of magnetic Fe ₃ O ₄ core, after drying, roast under the protection of N ₂ to remove the template agent, so as to prepare a Mesoporous _SiO2 shells and magnetic _{SiO2Fe3O4 nanospheres} with large specific surface area _. Then, using magnetic SiO ₂ Fe ₃ O ₄ nanospheres as the core, the Pd catalytic active component was assembled on the mesoporous SiO ₂ shell on the surface of the magnetic core SiO ₂ Fe ₃ O ₄ by ultrasonic method, and then the magnetic Pd/ SiO ₂ Fe ₃ O ₄ catalyst.

A magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst with nano-Pd catalytic active components, characterized in that the magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst uses superparamagnetic Fe ₃ O ₄ as the core, and the magnetic Fe ₃ The surface of the O ₄ core is coated with a mesoporous SiO ₂ shell, forming magnetic SiO ₂ Fe ₃ O ₄ nanospheres. On the mesoporous SiO ₂ shell layer on the surface of magnetic SiO ₂ Fe ₃ O ₄ nanospheres, the nano-Pd catalytic active component is assembled, which is the magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst. Preferably, the mass percent content of the Pd catalytically active component in the Pd/SiO ₂ Fe ₃ O ₄ catalyst is 1%-7%.

The above-mentioned magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst of the present invention is prepared by the following methods:

( ₁ ) Preparation of magnetic _Fe3O4 nanoparticles:

Preferably: dissolving FeCl ₃ ·6H ₂ O in water to prepare a solution with a mass content of FeCl ₃ of 10% to 30%. Sodium acetate is dissolved in ethylene glycol to prepare an ethylene glycol solution with a mass content of sodium acetate of 5% to 20%. At 30°C, under the protection of _N2 and stirring, add the FeCl3 solution dropwise to the ethylene glycol solution of sodium acetate, wherein the mass ratio of FeCl3 to sodium acetate is preferably ₃ : ₁ . After the dropwise addition, add The mixed solution was placed in an autoclave, crystallized at 180°C for 8 hours, then cooled naturally, washed with deionized water and ethanol respectively, and dried in vacuum at 60°C to obtain magnetic Fe ₃ O ₄ particles;

(2) Preparation of magnetic SiO ₂ Fe ₃ O ₄ nanospheres: Weigh a certain amount of magnetic Fe ₃ O ₄ particles and add them to ethanol with a mass concentration of 95% to make Fe ₃ O ₄ with a mass concentration of 10%~ 20% solution, under the condition of stirring at 40°C, add dropwise sodium silicate solution with a mass concentration of 5% to 20% and cetyltrimethylammonium bromide (CTAB) ethanol solution (preferably with a mass concentration of 0.2 %), the amount added dropwise is Fe ₃ O ₄ to sodium silicate, cetyltrimethylammonium bromide mass ratio is 1: (0.1~0.3): (0.001~0.005), so that sodium silicate can Evenly disperse on the surface of Fe ₃ O ₄ particles, after fully stirring, add ammonia solution dropwise until the pH value is 10, continue to stir for ₃ hours, and then use ultrasonic power of 50W~200W for 10min~40min to complete the _Fe3O4 particles The process of coating the surface with a mesoporous _SiO2 shell, then cooling naturally, washing with deionized water and ethanol to neutrality, drying in vacuum at 60°C, and finally baking at 450°C for 6 hours under the protection of _N2 to remove the template agent, which is the prepared magnetic SiO ₂ Fe ₃ O ₄ nanospheres with mesoporous SiO ₂ shells;

(3) Preparation of magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst: Weigh a certain amount of magnetic SiO ₂ Fe ₃ O ₄ nanospheres and disperse them in deionized water to make SiO ₂ Fe ₃ O ₄ with a mass concentration of 10%-20 % of the dispersion liquid; take a certain amount of palladium chloride, palladium nitrate or palladium acetate and dissolve it in deionized water to make a solution with a mass concentration of palladium chloride, palladium nitrate or palladium acetate of 1% to 5%; under stirring, Add palladium chloride, palladium nitrate or palladium acetate solution dropwise to the magnetic SiO ₂ Fe ₃ O ₄ nanosphere dispersion, wherein the mass ratio of SiO ₂ Fe ₃ O ₄ : (palladium chloride, palladium nitrate or palladium acetate) is 1: (0.01 ~ 0.15), fully stirred, so that palladium chloride, palladium nitrate or palladium acetate can be evenly dispersed on the surface of SiO ₂ Fe ₃ O ₄ , and then under the ultrasonic power of 50W ~ 100W, ultrasonic 30min ~ 50min, complete SiO ₂ The process of assembling Pd on the surface of Fe ₃ O ₄ core, then washing with deionized water and ethanol, and vacuum drying at 80°C is the prepared magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst with nano-Pd catalytic active components.

The present invention adopts the prepared magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst, which is used for the liquid-phase catalytic reaction of bromobenzene and butyl acrylate after reduction, and evaluates the catalytic performance and post-reaction performance of the magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst. The external magnetic field separation, recovery, and recycle performance of the catalyst show that the magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst has good catalytic performance and recycle performance.

The magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst prepared by the present invention has the following significant advantages:

(1) During the process of assembling the Pd catalytic active component on the mesoporous SiO ₂ shell on the surface of the magnetic core SiO ₂ Fe ₃ O ₄ , due to the use of ultrasonic technology, the Pd catalytic active component particles were embedded in the mesoporous SiO ₂ , a highly dispersed nano-Pd catalytic active component is formed, which not only improves the activity of the catalyst, but also avoids the loss of the Pd catalytic active component during the reaction.

(2) The prepared magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst can be easily separated from the reaction product in the liquid-phase catalytic reaction with an external magnetic field, which can greatly improve the catalyst reuse efficiency of the liquid-phase catalytic reaction and reduce The separation cost of the liquid-phase catalytic reaction has important industrial application value.

Description of drawings

Fig. 1 is a transmission electron micrograph of the catalyst of Example 1, the diameter of the Pd catalytically active component particles is between 5nm and 15nm.

detailed description

The present invention will be further described below in conjunction with the examples, but the present invention is not limited thereto.

Example 1

(1) Weigh 13.4g FeCl ₃ 6H ₂ O and dissolve it in 86.6g deionized water to make a solution, weigh 4.1g sodium acetate and dissolve it in 45.9g ethylene glycol to make a solution. Add it dropwise to the reactor protected by _N2 at the same time. After the dropwise addition, put the mixed solution into the autoclave, crystallize it at 180°C for 8 hours, then cool it naturally, wash it with deionized water and ethanol three times respectively, Vacuum drying at 60°C for 8 hours is the obtained magnetic Fe ₃ O ₄ particles.

(2) Weigh 5.8g of the prepared magnetic Fe ₃ O ₄ particles, add them to 44.2g of ethanol, and add 20g of sodium silicate solution with a mass concentration of 5% and mass Concentration is 0.2% cetyltrimethylammonium bromide (CTAB) ethanol solution 5g, after dropwise addition, dropwise ammonia solution under stirring fully to pH value is 10, continue to stir for 3 hours, then in 50W ultrasonic power The process of coating the surface of Fe ₃ O ₄ particles with mesoporous SiO ₂ shell was completed by ultrasonication for 40 min. Then cool naturally, wash with deionized water and ethanol to neutrality, vacuum dry at 60°C for 8 hours, and finally bake at 450°C for 6 hours under the protection of _N2 to remove the template agent, that is, the prepared mesoporous Magnetic _{SiO2Fe3O4 nanospheres} with _SiO2 shells _.

(3) Weigh 11.5 g of the prepared magnetic SiO ₂ Fe ₃ O ₄ nanospheres, add 88.5 g of deionized water to make a dispersion solution with a SiO ₂ Fe ₃ O ₄ mass concentration of 11.5%; weigh 1.8 g of palladium chloride g was dissolved in 98.2g deionized water to make a solution with a mass concentration of palladium chloride of 1.8%. Under stirring, add 35g of 1.8% palladium chloride solution dropwise into the magnetic SiO ₂ Fe ₃ O ₄ dispersion, stir well so that palladium chloride can be evenly dispersed on the surface of SiO ₂ Fe ₃ O ₄ , and then under 100W ultrasonic power , sonicated for 30 minutes, completed the assembly process of palladium on the surface of SiO ₂ Fe ₃ O ₄ core, washed with deionized water and ethanol, and dried in vacuum at 60°C, which is the prepared magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst, wherein The mass content of palladium is 3.12%.

The magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst was used for the liquid-phase catalytic reaction of equimolar bromobenzene and butyl acrylate, the conversion rate of p-bromobenzene was 98.6%, and the product selectivity was 97.8%. The catalyst was reused 8 times, the conversion rate of p-bromobenzene did not drop significantly, and the catalyst was basically not lost.

Example 2

(1) Weigh 20.3g FeCl ₃ 6H ₂ O and dissolve it in 79.7g deionized water to make a solution, weigh 6.2g sodium acetate and dissolve it in 43.8g ethylene glycol to make a solution. Add it dropwise to the reactor protected by _N2 at the same time. After the dropwise addition, put the mixed solution into the autoclave, crystallize it at 180°C for 8 hours, then cool it naturally, wash it with deionized water and ethanol three times respectively, Vacuum drying at 60°C for 8 hours is the obtained magnetic Fe ₃ O ₄ particles.

(2) Weigh 6.9 g of the prepared magnetic Fe ₃ O ₄ particles, add them into 43.1 g of ethanol, and add 20 g of sodium silicate solution with a mass concentration of 10% and mass Concentration is 10g of cetyltrimethylammonium bromide (CTAB) ethanol solution 10g of 0.2%, after the dropwise addition is completed, the ammonia solution is added dropwise under sufficient stirring until the pH value is 10, and the stirring is continued for 3 hours, and then the solution is added under 150W ultrasonic power The process of coating the surface of Fe ₃ O ₄ particles with a mesoporous SiO ₂ shell was completed by ultrasonication for 30 min. Then cool naturally, wash with deionized water and ethanol to neutrality respectively, vacuum dry at 60°C for 8 hours, and finally bake at 450°C for 6 hours under the protection of _N2 to remove the template agent, that is, the prepared mesoporous Magnetic _{SiO2Fe3O4 nanospheres} with _SiO2 shells _.

(3) Weigh 11.5 g of the prepared magnetic SiO ₂ Fe ₃ O ₄ nanospheres, add 88.5 g of deionized water to make a dispersion solution with a SiO ₂ Fe ₃ O ₄ mass concentration of 11.5%; weigh 1.8 g of palladium chloride g was dissolved in 98.2g deionized water to make a solution with a mass concentration of palladium chloride of 1.8%. Under stirring, add 12g of 1.8% palladium chloride solution dropwise into the magnetic SiO ₂ Fe ₃ O ₄ dispersion, stir well so that palladium chloride can be evenly dispersed on the surface of SiO ₂ Fe ₃ O ₄ , and then under 50W ultrasonic power , sonicated for 50 minutes, completed the assembly process of palladium on the surface of SiO ₂ Fe ₃ O ₄ core, washed with deionized water and ethanol, and dried in vacuum at 60°C, which was the prepared magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst, in which The mass content of palladium is 1.09%.

The magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst was used for the liquid-phase catalytic reaction of equimolar bromobenzene and butyl acrylate, the conversion rate of p-bromobenzene was 93.8%, and the selectivity of the product was 96.5%. The catalyst was reused 8 times, the conversion rate of p-bromobenzene did not drop significantly, and the catalyst was basically not lost.

Example 3

(1) Weigh 27.0g FeCl ₃ 6H ₂ O and dissolve it in 73.0g deionized water to make a solution, weigh 8.2g sodium acetate and dissolve it in 41.8g ethylene glycol to make a solution. Add it dropwise to the reactor protected by _N2 at the same time. After the dropwise addition, put the mixed solution into the autoclave, crystallize it at 180°C for 8 hours, then cool it naturally, wash it with deionized water and ethanol three times respectively, Vacuum drying at 60°C for 8 hours is the obtained magnetic Fe ₃ O ₄ particles.

(2) Weigh 9.3 g of the prepared magnetic Fe ₃ O ₄ particles, add them to 40.7 g of ethanol, and add 15 g of sodium silicate solution with a mass concentration of 15% and mass Concentration is 0.2% cetyltrimethylammonium bromide (CTAB) ethanol solution 15g, after the dropwise addition is completed, under full stirring, dropwise add ammonia solution to a pH value of 10, continue to stir for 3 hours, and then use 50W ultrasonic power The process of coating the surface of Fe ₃ O ₄ particles with mesoporous SiO ₂ shell was completed by ultrasonication for 40 min. Then cool naturally, wash with deionized water and ethanol to neutrality respectively, vacuum dry at 60°C for 8 hours, and finally bake at 450°C for 6 hours under the protection of _N2 to remove the template agent, that is, the prepared mesoporous Magnetic _{SiO2Fe3O4 nanospheres} with _SiO2 shells _.

(3) Weigh 15.0 g of the prepared magnetic SiO ₂ Fe ₃ O ₄ nanospheres and add them into 85 g of deionized water to prepare a dispersion with a mass concentration of SiO ₂ Fe ₃ O ₄ of 15.0%; weigh 3.5 g of palladium nitrate to dissolve In 96.5g deionized water, a solution with a mass concentration of palladium nitrate of 3.5% was prepared. Under stirring, add 20 g of 3.5% palladium nitrate solution dropwise into the magnetic SiO ₂ Fe ₃ O ₄ dispersion, stir well so that palladium chloride can be evenly dispersed on the surface of SiO ₂ Fe ₃ O ₄ , and then under 70W ultrasonic power, Ultrasound for 40 minutes to complete the assembly process of palladium on the surface of the SiO ₂ Fe ₃ O ₄ core, wash with deionized water and ethanol, and dry under vacuum at 60°C to obtain the magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst, in which the palladium The mass content is 2.07%.

The magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst was used for the liquid-phase catalytic reaction of equimolar bromobenzene and butyl acrylate, the conversion rate of p-bromobenzene was 95.7%, and the product selectivity was 97.3%. The catalyst was reused 8 times, the conversion rate of p-bromobenzene did not drop significantly, and the catalyst was basically not lost.

Example 4

(1) Weigh 20.3g FeCl ₃ 6H ₂ O and dissolve it in 69.7g deionized water to make a solution, weigh 6.2g sodium acetate and dissolve it in 43.8g ethylene glycol to make a solution. Add it dropwise to the reactor protected by _N2 at the same time. After the dropwise addition, put the mixed solution into the autoclave, crystallize it at 180°C for 8 hours, then cool it naturally, wash it with deionized water and ethanol three times respectively, Vacuum drying at 60°C for 8 hours is the obtained magnetic Fe ₃ O ₄ particles.

(2) Weigh 11.6g of the prepared magnetic Fe ₃ O ₄ particles, add them to 88.4g of ethanol, and add 15g of sodium silicate solution with a mass concentration of 20% and mass Concentration is 25g of cetyltrimethylammonium bromide (CTAB) ethanol solution 25g of 0.2%, after dropwise addition, ammonia solution is added dropwise under sufficient stirring to pH value is 10, continue to stir for 3 hours, then in 150W ultrasonic power The process of coating the surface of Fe ₃ O ₄ particles with a mesoporous SiO ₂ shell was completed by ultrasonication for 20 min. Then cool naturally, wash with deionized water and ethanol to neutrality respectively, vacuum dry at 60°C for 8 hours, and finally bake at 450°C for 6 hours under the protection of _N2 to remove the template agent, that is, the prepared mesoporous Magnetic _{SiO2Fe3O4 nanospheres} with _SiO2 shells _.

(3) Weigh 15.0 g of the prepared magnetic SiO ₂ Fe ₃ O ₄ nanospheres and add them into 85 g of deionized water to prepare a dispersion with a mass concentration of SiO ₂ Fe ₃ O ₄ of 15.0%; weigh 3.5 g of palladium nitrate to dissolve In 96.5g deionized water, a solution with a mass concentration of palladium nitrate of 3.5% was prepared. Under stirring, add 46g of 3.5% palladium nitrate solution dropwise into the magnetic SiO ₂ Fe ₃ O ₄ dispersion, stir well so that palladium chloride can be evenly dispersed on the surface of SiO ₂ Fe ₃ O ₄ , and then under 80W ultrasonic power, Ultrasound for 40 minutes to complete the assembly process of palladium on the surface of the SiO ₂ Fe ₃ O ₄ core, wash with deionized water and ethanol, and dry under vacuum at 60°C to obtain the magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst, in which the palladium The mass content is 4.72%.

The magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst was used for the liquid-phase catalytic reaction of equimolar bromobenzene and butyl acrylate, the conversion rate of p-bromobenzene was 97.5%, and the product selectivity was 98.3%. The catalyst was reused 8 times, the conversion rate of p-bromobenzene did not drop significantly, and the catalyst was basically not lost.

Example 5

(1) Weigh 27.0g FeCl ₃ 6H ₂ O and dissolve it in 73.0g deionized water to make a solution, weigh 8.2g sodium acetate and dissolve it in 41.8g ethylene glycol to make a solution. Add it dropwise to the reactor protected by _N2 at the same time. After the dropwise addition, put the mixed solution into the autoclave, crystallize it at 180°C for 8 hours, then cool it naturally, wash it with deionized water and ethanol three times respectively, Vacuum drying at 60°C for 8 hours is the obtained magnetic Fe ₃ O ₄ particles.

(2) Weigh 13.8g of the prepared magnetic Fe ₃ O ₄ particles, add them into 86.2g of ethanol, and add 20g of sodium silicate solution with a mass concentration of 20% and mass Concentration is 30g of cetyltrimethylammonium bromide (CTAB) ethanol solution 30g of 0.2%, after the dropwise addition is completed, drip ammonia solution under sufficient stirring to a pH value of 10, continue to stir for 3 hours, and then use 100W ultrasonic power The process of coating the surface of Fe ₃ O ₄ particles with a mesoporous SiO ₂ shell was completed by ultrasonication for 30 min. Then cool naturally, wash with deionized water and ethanol to neutrality respectively, vacuum dry at 60°C for 8 hours, and finally bake at 450°C for 6 hours under the protection of _N2 to remove the template agent, that is, the prepared mesoporous Magnetic _{SiO2Fe3O4 nanospheres} with _SiO2 shells _.

(3) Weigh 12.7 g of the prepared magnetic SiO ₂ Fe ₃ O ₄ nanospheres, add 87.3 g of deionized water to make a dispersion with a SiO ₂ Fe ₃ O ₄ mass concentration of 12.7%; weigh 4.5 g of palladium acetate Dissolve in 95.5g deionized water to make a solution with a mass concentration of palladium acetate of 4.5%. Under stirring, add 40g of 4.5% palladium acetate solution dropwise into the magnetic SiO ₂ Fe ₃ O ₄ dispersion, stir well so that palladium chloride can be evenly dispersed on the surface of SiO ₂ Fe ₃ O ₄ , and then under 100W ultrasonic power, Ultrasound for 30 minutes to complete the assembly process of palladium on the surface of SiO ₂ Fe ₃ O ₄ nuclei, wash with deionized water and ethanol, and dry in vacuum at 60°C to obtain the magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst, in which palladium The mass content is 6.28%.

The magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst was used for the liquid-phase catalytic reaction of equimolar bromobenzene and butyl acrylate, the conversion rate of p-bromobenzene was 97.8%, and the product selectivity was 98.5%. The catalyst was reused 8 times, the conversion rate of p-bromobenzene did not drop significantly, and the catalyst was basically not lost.

Example 6

(1) Weigh 20.3g FeCl ₃ 6H ₂ O and dissolve it in 69.7g deionized water to make a solution, weigh 6.2g sodium acetate and dissolve it in 43.8g ethylene glycol to make a solution. Add it dropwise to the reactor protected by _N2 at the same time. After the dropwise addition, put the mixed solution into the autoclave, crystallize it at 180°C for 8 hours, then cool it naturally, wash it with deionized water and ethanol three times respectively, Vacuum drying at 60°C for 8 hours is the obtained magnetic Fe ₃ O ₄ particles.

(2) Weigh 20.0 g of the prepared magnetic Fe ₃ O ₄ particles, add them to 80.0 g of ethanol, and add 20 g of sodium silicate solution with a mass concentration of 20% and mass Concentration is 30g of cetyltrimethylammonium bromide (CTAB) ethanol solution 30g of 0.2%, after the dropwise addition is completed, the ammonia solution is added dropwise under sufficient stirring until the pH value is 10, and the stirring is continued for 3 hours, and then the solution is added under 150W ultrasonic power The process of coating the surface of Fe ₃ O ₄ particles with a mesoporous SiO ₂ shell was completed by ultrasonication for 30 min. Then cool naturally, wash with deionized water and ethanol to neutrality respectively, vacuum dry at 60°C for 8 hours, and finally bake at 450°C for 6 hours under the protection of _N2 to remove the template agent, that is, the prepared mesoporous Magnetic _{SiO2Fe3O4 nanospheres} with _SiO2 shells _.

(3) Weigh 12.7 g of the prepared magnetic SiO ₂ Fe ₃ O ₄ nanospheres, add 87.3 g of deionized water to make a dispersion with a SiO ₂ Fe ₃ O ₄ mass concentration of 12.7%; weigh 4.5 g of palladium acetate Dissolve in 95.5g deionized water to make a solution with a mass concentration of palladium acetate of 4.5%. Under stirring, add 20 g of 4.5% palladium acetate solution dropwise into the magnetic SiO ₂ Fe ₃ O ₄ dispersion, stir well so that palladium chloride can be evenly dispersed on the surface of SiO ₂ Fe ₃ O ₄ , and then under 60W ultrasonic power, Ultrasound for 50 minutes to complete the assembly process of palladium on the surface of SiO ₂ Fe ₃ O ₄ core, wash with deionized water and ethanol, and dry in vacuum at 60°C, that is, the prepared magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst, in which palladium The mass content is 3.24%.

The magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst was used for the liquid-phase catalytic reaction of equimolar bromobenzene and butyl acrylate, the conversion rate of p-bromobenzene was 97.4%, and the selectivity of the product was 98.2%. The catalyst was reused 8 times, the conversion rate of p-bromobenzene did not drop significantly, and the catalyst was basically not lost.

Claims (5)

1. A magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst with nanometer Pd catalytically active components, characterized in that, the magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst is based on superparamagnetic Fe ₃ O ₄ as the core, in magnetic The surface of the Fe ₃ O ₄ core is coated with a mesoporous SiO ₂ shell to form a magnetic SiO ₂ Fe ₃ O ₄ nanosphere, and on the mesoporous SiO ₂ shell on the surface of the magnetic SiO ₂ Fe ₃ O ₄ nanosphere, assemble the nano The Pd catalytic active component is the magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst; The mass percent content of the Pd catalytic active component in the Pd/SiO ₂ Fe ₃ O ₄ catalyst is 1%-7%. 2. prepare a kind of magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst method with nano-Pd catalytic active component described in claim 1, it is characterized in that, comprises the following steps: (1) Preparation of magnetic Fe ₃ O ₄ nanoparticles; (2) Preparation of magnetic SiO ₂ Fe ₃ O ₄ nanospheres: Weigh a certain amount of magnetic Fe ₃ O ₄ particles and add them into ethanol with a mass concentration of 95% to make Fe ₃ O ₄ with a mass concentration of 10% to 20% solution, under the condition of stirring at 40°C, add dropwise sodium silicate solution and cetyltrimethylammonium bromide (CTAB) ethanol solution with a mass concentration of 5% to 20% at the same time, and the amount added dropwise is The mass ratio of Fe ₃ O ₄ to sodium silicate and cetyltrimethylammonium bromide is 1: (0.1~0.3): (0.001~0.005), so that sodium silicate can be evenly dispersed in Fe ₃ O ₄ particles After fully stirring, add ammonia solution dropwise until the pH value is 10, continue to stir for 3 hours, and then use ultrasonic power of 50W~200W for 10min~40min to finish coating the surface of Fe ₃ O ₄ particles with mesoporous SiO ₂ shell layer, then cooled naturally, washed with deionized water and ethanol to neutrality, dried in vacuum at 60°C, and finally baked at 450°C for 6 hours under the protection of _N2 to remove the template agent, which is the obtained Magnetic SiO ₂ Fe ₃ O ₄ nanospheres with mesoporous SiO ₂ shell; (3) Preparation of magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst: Weigh a certain amount of magnetic SiO ₂ Fe ₃ O ₄ nanospheres and disperse them in deionized water to make SiO ₂ Fe ₃ O ₄ with a mass concentration of 10% to 20% % dispersion liquid; take a certain amount of palladium chloride, palladium nitrate or palladium acetate and dissolve it in deionized water to make palladium chloride, palladium nitrate or palladium acetate mass concentration as a solution of 1% to 5%; under stirring, Add palladium chloride, palladium nitrate or palladium acetate solution dropwise to magnetic SiO ₂ Fe ₃ O ₄ nanosphere dispersion liquid, wherein SiO ₂ Fe ₃ O ₄ : the mass ratio of (palladium chloride, palladium nitrate or palladium acetate) is 1: (0.01 ~ 0.15), fully stirred, so that palladium chloride, palladium nitrate or palladium acetate can be uniformly dispersed on the surface of SiO ₂ Fe ₃ O ₄ , and then under the ultrasonic power of 50W ~ 100W, ultrasonic 30min ~ 50min, complete SiO ₂ The process of assembling Pd on the surface of Fe ₃ O ₄ core, then washing with deionized water and ethanol, and vacuum drying at 80°C is the prepared magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst with nano-Pd catalytic active components. 3. according to the method for claim 2, it is characterized in that, the preparation of magnetic Fe ₃ O ₄ nanoparticles: FeCl ₃ .6H ₂ O is dissolved in water, make FeCl _The solution that mass content is 10%～30%, will Sodium acetate is dissolved in ethylene glycol to make an ethylene glycol solution with a mass content of 5% to 20% of sodium acetate. At 30°C, under the protection of N ₂ and stirring, the FeCl ₃ solution is added dropwise to the sodium acetate In the ethylene glycol solution, the mass ratio of FeCl3 and sodium acetate is ₃ :1. After the dropwise addition, the mixed solution is placed in an autoclave, and crystallized at 180°C for 8 hours, then cooled naturally, and deionized water and ethanol, and vacuum-dried at 60°C to obtain magnetic Fe ₃ O ₄ particles. 4. according to the method for claim 2, it is characterized in that, cetyltrimethylammonium bromide (CTAB) ethanolic solution mass concentration is 0.2%. 5. A magnetic Pd/SiO ₂ Fe ₃ O ₄ catalyst with nano-Pd catalytic active components as claimed in claim 1 is used for the liquid-phase catalytic reaction of bromobenzene and butyl acrylate.