CN112275284A - Method for regulating interaction between metal nanoparticles and carrier by using plasma - Google Patents

Method for regulating interaction between metal nanoparticles and carrier by using plasma Download PDF

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CN112275284A
CN112275284A CN202011127794.XA CN202011127794A CN112275284A CN 112275284 A CN112275284 A CN 112275284A CN 202011127794 A CN202011127794 A CN 202011127794A CN 112275284 A CN112275284 A CN 112275284A
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catalyst
plasma
carrier
metal
interaction
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CN112275284B (en
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朱斌
张璐瑶
朱益民
闫妍
高亚楠
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Dalian Maritime University
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
    • B01J37/349—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of flames, plasmas or lasers
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    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/06—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents
    • C01B3/12—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents by reaction of water vapour with carbon monoxide
    • C01B3/16—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents by reaction of water vapour with carbon monoxide using catalysts
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    • C07C5/09—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by hydrogenation of carbon-to-carbon triple bonds to carbon-to-carbon double bonds
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    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
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    • C07C2523/44—Palladium
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    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Abstract

The invention discloses a method for regulating and controlling interaction between metal nanoparticles and a carrier by plasma, which comprises the following steps: s1, loading the metal precursor on a carrier by adopting an impregnation method or a deposition-precipitation method, and washing and drying to obtain the catalyst; s2, placing the obtained catalyst in a plasma generating device, and pretreating the catalyst by adopting plasma in a reducing atmosphere; s3, activating the catalyst by adopting plasma in an oxidizing atmosphere; and S4, after the activation treatment, treating the catalyst by adopting plasma in a reducing atmosphere to obtain the supported metal catalyst. The method of the invention utilizes plasmas generated by discharging under different atmospheres to carry out pretreatment, activation and retreatment on the supported catalyst in sequence, realizes effective modulation of the interaction between the metal nanoparticles and the carrier, and obviously enhances the stability of the nano catalyst while controlling the size of the metal particles.

Description

Method for regulating interaction between metal nanoparticles and carrier by using plasma
Technical Field
The invention belongs to the technical field of plasma surface engineering, and particularly relates to a method for regulating and controlling interaction between metal nanoparticles and a carrier by using plasma.
Background
The supported nano catalyst has excellent catalytic performance and plays an important role in industrial catalytic processes in the fields of environment, energy and the like. Generally, the heterogeneous catalyst formed by loading metal nanoparticles on the surface of a carrier with high specific surface area is a common and effective method for improving catalytic activity. However, it has been found that the interaction between the metal nanoparticles and the support also has a significant effect on the catalytic performance. The interaction between the metal nanoparticles and the carrier can not only control the particle size and regulate and control the carrier effect between the metal nanoparticles and the carrier, but also is the key point for obtaining the high-stability nano catalyst.
At present, the method for preparing the supported nano catalyst by adopting a heat treatment method is the most common. For example, by treating the supported noble metal catalyst at high temperature in a reducing atmosphere, strong interaction (SMSI) between the noble metal and the carrier can be generated, and noble metal particles can be effectively stabilized, so that the defect of unstable catalyst production is overcome. However, the heat treatment method sacrifices the size of active particles while regulating and controlling the interaction between the metal and the carrier, and the noble metal nanoparticles are easy to agglomerate due to high temperature, thereby reducing the activity. In recent years, in order to improve the catalytic activity of the supported nano-catalyst, the application of the plasma technology to the preparation of the catalyst has received general attention. Due to their non-equilibrium nature (low temperature, high activity), plasma treated catalysts generally achieve smaller sized metal particles and thus higher activity. The patent documents CN107008511A, CN103691428A, CN105032408A, etc. all adopt plasma technology to obtain metal nanoparticles with higher activity, i.e. the advantage is that metal nanoparticles with small size are obtained by reduction, but the method cannot regulate and control the interaction between metal and carrier, so the stability of the obtained catalyst is poor in long-term use, which is a key factor limiting the practical application.
Disclosure of Invention
Aiming at the problems, the invention researches and designs a method for regulating and controlling the interaction between metal nano particles and a carrier by using plasma, so as to solve the defect of poor stability of a catalyst prepared by using a plasma technology. The technical means adopted by the invention are as follows:
a method for regulating and controlling interaction between metal nanoparticles and a carrier by plasma comprises the following steps:
s1, loading of the metal precursor on the carrier: loading a metal precursor (which may be salt, acid or alkali according to the type of metal) on a carrier by adopting an impregnation method or a deposition-precipitation method, cleaning by adopting an acidic/neutral/alkaline solution, and drying to obtain a catalyst;
s2, pretreatment of the catalyst: placing the cleaned catalyst in a plasma generating device, discharging hydrogen or a mixed gas consisting of hydrogen and inert gas to produce a reducing atmosphere, and pretreating the catalyst by adopting plasma;
s3, surface activation of the catalyst: replacing the reducing atmosphere in step S2 with an oxidizing atmosphere produced by discharge of oxygen or a mixed gas of oxygen and an inert gas, and activating the catalyst with plasma;
s4, regulation and control of interaction between metal nanoparticles and a carrier: after the activation treatment, the catalyst is further treated with plasma in place of the oxidizing atmosphere in step S3 with a reducing atmosphere produced by discharge of hydrogen or a mixed gas of hydrogen and an inert gas, to obtain a supported metal catalyst.
Preferably, in step S1, the metal precursor is a soluble metal salt, specifically a soluble noble metal salt, and the support is a reducible metal oxide, specifically a semiconductive metal oxide.
Preferably, in step S1, the metal precursor is a soluble salt of a noble metal of group IB and group VIII, and the support is a reducible metal oxide such as alumina, silica, ceria, titania, or the like. The metal precursor can be one soluble metal salt or a mixture of soluble metal salts, and the support can be a single or composite metal oxide.
Preferably, in step S1, the metal precursor may be impregnated on the surface of the metal oxide support in an equal volume or in an excess amount, or the metal precursor may be supported on the surface of the metal oxide support by a deposition precipitation method.
Preferably, in step S1, the number of times of cleaning the catalyst obtained by the impregnation method and the deposition precipitation method is determined by the component concentration of the cleaning solution after cleaning, and the component concentration of the cleaning solution can be determined by chemical titration, that is, after each cleaning, AgNO is used3And titrating the cleaning solution until no precipitate is generated, wherein the cleaning solution almost contains no solute, the cleaning can be stopped, and the corresponding cleaning times are the minimum cleaning times.
Preferably, in step S1, the pH values of the metal precursor solution and the cleaning solution are both higher than the isoelectric point of the metal oxide support, but the difference is less than 2.
Preferably, in steps S2-S4, the plasma generating device generates plasma through dielectric barrier discharge or corona discharge, and the discharge treatment time in each step is 1-30 min. Specifically, the plasma generating device can be a dielectric barrier or corona discharge reactor, the structure of the device is a flat plate or a wire cylinder, and the catalyst is placed in the center of the discharge reactor.
Preferably, the energy supply source for dielectric barrier discharge is an alternating current power source or a pulse power source, and the energy supply source for corona discharge is a direct current power source or a pulse power source. The frequency of the alternating current power supply is 5-20kHz, the applied voltage is 5-10kV, the applied voltage of the direct current power supply is 3-12kV, and the pulse width of the pulse power supply is less than 1000 ns.
Preferably, the instantaneous discharge power of the alternating current power supply and the direct current power supply is greater than 10W, and the instantaneous discharge power of the pulse power supply is greater than 5 kW.
Preferably, the discharge treatment time of the pulse power supply is 5-15 min.
Preferably, in the steps S2-S4, the inert gas is a mixture of helium and argon, the reducing atmosphere and the oxidizing atmosphere are both in a continuous gas flow condition, and the space velocity is 1000--1。
Preferably, in step S2, the volume ratio of hydrogen in the mixed gas is more than 5%; in step S3, the volume ratio of oxygen in the mixed gas is more than 30%; in step S4, the volume ratio of hydrogen in the mixed gas is greater than 10%.
Compared with the prior art, the method for regulating and controlling the interaction between the metal nanoparticles and the carrier by using the plasma has the beneficial effects that:
1. the catalyst is prepared by dipping or depositing the metal precursor on the surface of the metal oxide carrier, and removing toxic and harmful species on the surface of the catalyst by a cleaning method, so that the preparation process is simple, the operation is convenient, and the preparation repeatability of the catalyst is high.
2. According to the invention, the catalyst is pretreated by utilizing reductive plasma, then the catalyst is activated by adopting oxidative plasma, and the combination of the pretreatment and the activation steps not only ensures that a metal precursor is converted into metal nano particles with controllable sizes, but also can obviously enhance the coordination unsaturation degree at the metal-carrier interface and improve the catalytic activity of the catalyst.
3. According to the method, the interaction between the metal nanoparticles and the carrier is regulated by adopting the reducing plasma in the last step, the carrier can be partially reduced while the stable valence state of the metal nanoparticles is ensured by the reducing atmosphere, the carrier effect between the metal and the carrier and the riveting effect of the carrier on the nanoparticles are generated, the surface migration of the metal nanoparticles in the use process of the catalyst is avoided, and the stability of the catalyst is obviously improved on the premise of ensuring the activity of the catalyst.
4. The reduction and activation of the metal precursor by the plasma and the regulation and control of the metal-carrier interaction are realized by regulating the discharge atmosphere and instantaneous power of the generated plasma, the regulation mode is flexible and has strong pertinence, the advantages in the aspects of effectively reducing the metal precursor and accurately regulating and controlling the metal-carrier interaction are obvious, and the defect that the conventional plasma treatment method does not selectively reduce metal is overcome.
5. The method adopts the combination of plasmas in different atmospheres to continuously treat the catalyst, is more efficient and rapid compared with the traditional method for regulating and controlling the interaction of metal and carrier by thermal reduction, and has extremely low energy consumption in the treatment process; the combined method can not only reduce to obtain the metal nano particles, but also break through the limitation of poor stability of the catalyst obtained by conventional plasma treatment, and simultaneously improve the catalytic activity and stability of the catalyst by changing the surface property of the metal-carrier and modulating the interaction characteristics between the metal nano particles and the carrier.
6. The invention adopts the plasma to process the catalyst, has low manufacturing cost of the processing device and simple assembly, is not only suitable for the preparation of fine chemical catalysts, but also is easy for large-scale application.
Drawings
FIG. 1 shows Au-Pt/TiO obtained in example 1 of the present invention2The CO removal effect of the composite nano catalyst is compared with that of the composite nano catalyst.
FIG. 2 shows Au/CeO obtained in example 2 of the present invention2Catalytic activity of the catalyst is compared.
FIG. 3 shows Au/CeO obtained in example 2 of the present invention2Transmission electron micrographs of the catalyst before and after the water-vapor conversion reaction experiment.
FIG. 4 shows Pd/Al obtained in example 3 of the present invention2O3The result chart of acetylene selective hydrogenation reaction experiment carried out by the nano catalyst.
Detailed Description
The invention provides a plasma method capable of effectively regulating and controlling interaction between metal nano particles and a carrier, which is implemented aiming at a supported metal nano catalyst and comprises the following operation steps: (1) loading a metal precursor on the surface of the carrier by adopting a dipping or deposition precipitation method; (2) pretreating the catalyst by adopting a reducing atmosphere plasma to remove toxic species remained on the surface of the catalyst by a metal precursor; (3) selecting proper plasma oxidation atmosphere composition and instantaneous discharge power according to the characteristics of the surface interface property of the catalyst, and carrying out activation treatment on the catalyst; (4) and then the activated catalyst is treated by utilizing the reducing atmosphere plasma, and the interaction between the metal nano particles and the carrier is regulated and controlled by regulating key parameters such as discharge atmosphere composition, instantaneous discharge power, action time and the like.
Compared with the conventional regulation and control method of the interaction between the metal and the carrier, the plasma method can ensure that the supported nano catalyst obtains higher activity, and has the advantages of simplicity, convenience, flexibility, rapidness, low energy consumption and the like, and the main reason is the non-equilibrium characteristic of the plasma. For the supported catalyst, the metal precursor must be converted into nanoparticles on the surface of the carrier, so that the nanoparticles can show high activity in catalytic reaction. Although the conventional treatment method can reduce the precursor into the metal nanoparticles, the conventional treatment method usually requires a more rigorous and complicated process. For example, for noble metal catalysts, a large amount of chemical reducing agents are wasted in the liquid phase reduction method, and noble metal nanoparticles can be obtained through a more complicated procedure; the thermal reduction method reduces the metal precursor under the reducing atmosphere with higher temperature, and has long period and high energy consumption. In contrast, the plasma method of the invention has simple process, the treatment time required by the catalyst in each step is less than 30min, the treatment process can be started instantly, the average power required by the process is less than 10W, and the energy consumption is extremely low. In the pretreatment stage, the effective reduction of the metal precursor can be realized by means of active species such as high-energy electrons generated by non-equilibrium discharge, and the size of the reduced nano particles is smaller due to the low temperature of the plasma.
More importantly, compared with the existing reported catalyst plasma preparation method, the plasma method disclosed by the invention makes a breakthrough in the aspect of regulating and controlling the interaction between the metal nanoparticles and the carrier, and the fundamental reason is that the method realizes the accurate regulation and control of the surface interface characteristics of the supported nano catalyst through the optimized combination of key parameters such as discharge atmosphere, instantaneous discharge power and the like.
The conventional plasma preparation method mainly stays in the pretreatment stage of the invention, and essentially realizes the conversion of the metal precursor to the smaller metal nanoparticles, but the obtained metal nanoparticles have poor stability due to weak interaction with the carrier. Although partial coating of the carrier on the nanoparticles can be realized by changing discharge parameters to enhance the reducibility of the plasma, the method has the defect that the catalytic activity of the nanoparticles is sacrificed while the rivet effect of the carrier on the nanoparticles is enhanced. Therefore, the optimization scheme of the invention is as follows: in the pretreatment stage, aiming at the characteristics of the metal precursor and the carrier, the reduction of the metal precursor is controlled by regulating and controlling parameters such as discharge power, reducing atmosphere composition, processing time and the like, so that the reduction of the carrier is avoided while the precursor is fully reduced and converted into the nano particles. Further, the nano-catalyst is activated by utilizing the oxidative atmosphere discharge plasma, the main function of the step is to form a large amount of active oxygen and oxygen vacancies at the interface of the metal nano-particles and the carrier, and the length of the metal-carrier interface is increased by enhancing the function of the nano-particles and the carrier; due to the control of oxygen content and instantaneous power during the activation process, the size and chemical valence of the metal nanoparticles are not affected when the properties of the interfacial structure of the structured catalyst are processed. And finally, adopting reducing atmosphere discharge plasma to process the nano catalyst, wherein the step has the function of realizing controllable coating and riveting of the carrier on the metal nano particles and charge transfer between the metal nano particles and the carrier by controlling the plasma to act on the metal oxide carrier at the interface and partially micro-reducing the carrier, thereby achieving the function of effectively regulating and controlling the action strength and the carrier effect between the metal nano particles and the carrier.
Example 1:
a method for regulating and controlling interaction between metal nanoparticles and a carrier by plasma comprises the following steps:
a. 5g of chloroauric acid are weighed and dissolved in 500ml of water to prepare 2.4X 10-2The standard solution of chloroauric acid (gold precursor) in mol/L is prepared by dissolving 10mg of platinum chloride in 100mL of deionized water-3Dissolving 1g of sodium hydroxide in 50mL of deionized water to prepare 0.5mol/L of sodium hydroxide solution;
b. weighing 2gTiO2(rutile and anatase mixed crystal) is added into a beaker filled with 100mL of platinum nitrate and chloroauric acid solution (the volume ratio of the two is 1:1), the mixture is evenly mixed under the condition of 1000r/min, and 0.5mol/L sodium hydroxide solution is used for adjusting the pH value to be 8 (more than TiO)2Isoelectric point 6), mixing the samples for 1 hour to fully load the gold-platinum precursor on TiO2A surface;
c. ultrasonic washing the mixed solution with deionized water for 2 times until 2.0 × 10-2mol/L AgNO3Solution titration is carried out without generating precipitates, and the solution is centrifuged for 10min at the rotating speed of 10000r/min to obtain a solid sample;
d. drying the obtained solid sample in an oven at the temperature of 80 ℃ for 6h to obtain Au-Pt/TiO2A catalyst;
e. in a dielectric barrier discharge reactor, using H2And Ar dielectric barrier discharge plasma pretreatment Au-Pt/TiO2Catalyst 5min, gas flow rate 100mL/min, H2The volume ratio of Ar to Ar is 1:5, the energy supply power supply of the discharge reactor is a 5kHz alternating current power supply, and the input power is 10W;
f. by using O2And Au-Pt/TiO pretreated by Ar dielectric barrier discharge plasma activation2Catalyst 5min, gas flow rate 100mL/min, O2And Ar in a volume ratio of 3:2The energy supply power supply of the electric reactor is a 5kHz alternating current power supply, and the input power is 15W;
g. by means of H2And the activated Au-Pt/TiO is retreated by the Ar dielectric barrier discharge plasma2Catalyst 7min, gas flow rate 100mL/min, H2The volume ratio of the energy source to Ar is 1:9, the energy supply source is an alternating current power supply with 5kHz, the input power is 15W, and Au-Pt/TiO is obtained2A composite nanocatalyst.
For the Au-Pt/TiO obtained in example 12The composite nano catalyst is used for carrying out a catalytic oxidation removal performance evaluation experiment of CO, and the experimental conditions are as follows: 1 vol% CO, 20 vol% O2And 79 vol% N2Gas composition at 100000h-1Is subjected to one-way flow of Au-Pt/TiO at the space velocity2The surface of the catalyst. As a comparative study, the calcination treatment at 300 ℃ was carried out with H2The plasma-treated catalyst was also subjected to test evaluation under the same conditions, and the results are shown in fig. 1.
The result shows that the Au-Pt/TiO treated by plasma regulation2The catalyst showed the highest CO conversion (85%), under the same conditions, conventional H2The activity of the plasma treated catalyst was 70%, the activity of the conventional calcined catalyst was 45%, and the activity of the untreated catalyst was only 7%. The highest activity of the catalyst regulated by the plasma is obtained because Au and Pt nano particles and TiO2The interaction between the two is effectively regulated and controlled. As shown in FIG. 1, the metal nanoparticles and TiO are mixed2Au-Pt/TiO regulated by reactant CO in plasma under the same condition through proper interaction between carriers2The surface adsorption amount is remarkably increased.
Example 2:
a. weighing 2g of chloroauric acid, dissolving in 200ml of water to prepare 2.4X 10-2A gold chloride acid standard solution (gold precursor standard solution) of mol/L;
b. weighing 2gCeO2Adding the powder into a beaker filled with 20mL of chloroauric acid solution with a certain concentration to realize the impregnation of the chloroauric acid solution on the carrier, and standing the sample for 12 hours to fully load the gold precursor on the CeO2；
c. For the obtained dipped articleAlternately washing with alkaline solution and neutral solution (deionized water) twice or more until 2.0 × 10 is adopted-2mol/L AgNO3Until no precipitate is generated by solution titration; the pH value of the alkaline solution is required to be more than or equal to 8 (higher than CeO)2Isoelectric point of powder 7.6); carrying out ultrasonic treatment for 10min after each washing, and then centrifuging for 10min to obtain a solid sample;
d. drying the washed solid sample in an oven at 80 ℃ for 12h to obtain Au/CeO2A catalyst;
e. in a dielectric barrier discharge reactor, using H2He dielectric barrier discharge plasma pretreatment of Au/CeO2Catalyst 10min, gas flow rate 300mL/min, H2The volume ratio of He to He is 3:7, the energy supply power supply of the discharge reactor is a 5kHz alternating current power supply, and the input power is 15W;
f. by using O2Au/CeO pretreated by dielectric barrier discharge plasma activation2The catalyst is 10min, the gas flow rate is 200mL/min, the energy supply power supply of the discharge reactor is a 2kHz alternating current power supply, and the input power is 10W;
g. by means of H2And Ar dielectric barrier discharge plasma retreating the activated Au/CeO2Catalyst 5min, gas flow rate 200mL/min, H2The volume ratio of Ar to Au is 1:4, the energy supply power of the discharge reactor is a 10kHz alternating current power supply, the input power is 10W, and Au/CeO is obtained2And (3) a nano catalyst.
For the Au/CeO obtained in example 22The nano catalyst is used for carrying out a water-vapor conversion reaction experiment, and the experimental conditions are as follows: 0.5gAu/CeO2The nano catalyst is placed in a tubular reactor, then the temperature of the reactor is raised to 150 ℃ under the He atmosphere (100mL/min), and after the reactor is stabilized for 30min, reaction gas (85 vol% He, 5 vol% CO, 10 vol% H) is added2O) was introduced into the reactor at a reaction gas flow rate of 100 mL/min. As a comparative study, the calcination treatment at 300 ℃ was carried out with O2The plasma-treated catalyst was also subjected to test evaluation under the same conditions, and the results are shown in fig. 2 and 3.
FIG. 2 shows the results of the plasma-modified Au/CeO2Catalyst and process for preparing sameNot only can show the highest catalytic activity (60% of H)2Conversion of O to H2) And the stability is extremely high at the reaction temperature, and the performance of the catalyst is not obviously attenuated after the catalyst is continuously operated for 100 hours. This means that the Au catalyst treated by plasma regulation and control has great breakthrough in both activity and stability. The stability of the nano Au catalyst is known to be a problem which troubles the application, just like the result given by the comparative experiment, under the same condition, the conventional O2The catalyst activity of the plasma treatment is high (H)2 O conversion 50%), but activity decayed to below 30% after 30min of reaction run; the activity of the catalyst in the conventional calcination treatment is lower than 15%, and the activity is continuously reduced with the prolonging of the reaction time (almost no activity after 40 h). Example 2 plasma conditioned Au/CeO2Au and CeO of catalyst2The interaction between the Au particles and the Au nanoparticles is effectively regulated, and the high-activity interface is increased, and the carrier effectively rivets the Au nanoparticles, so that the stability is improved. As shown in FIG. 3, the Au/CeO treated in example 2 was controlled2Transmission electron microscope images of the catalyst before and after reaction prove the excellent stability of the Au nano particles.
Example 3:
a. 1g of palladium chloride is weighed and dissolved in 200ml of water to prepare 3X 10-2Dissolving 1g of sodium hydroxide in 50ml of deionized water to prepare 0.5mol/L of sodium hydroxide solution;
b. weighing 2g of gamma-Al2O3Adding into a beaker containing 60ml of palladium chloride solution, mixing uniformly under the condition of 1000r/min, adjusting the pH value to 9 by using 0.5mol/L sodium hydroxide solution, mixing the samples for 1 hour, and depositing and precipitating a palladium precursor in gamma-Al2O3A surface;
c. alternately washing the precipitated sample with sodium hydroxide solution with pH of 9 and deionized water for more than 2 times until 2.0 × 10 is adopted-2mol/L AgNO3Solution titration is carried out without generating precipitates, and washing liquid is filtered out to obtain a solid sample;
d. drying the obtained solid sample in an oven at 70 ℃ for 10h to obtain Pd/Al2O3A catalyst;
e. by means of H2Plasma pretreatment of Pd/Al2O3The catalyst is used for 15min, the gas flow rate is 100mL/min, the energy supply power source is a square wave pulse power source, the input voltage is 10kV, and the pulse width is 800 ns;
f. by using O2And activating pretreated Pd/Al by Ar plasma2O3Catalyst 30min, gas flow 100mL/min, O2The volume ratio of Ar to Ar is 3:7, a square wave pulse power supply is supplied, the input voltage is 9kV, and the pulse width is 500 ns;
g. by means of H2Plasma reprocessing of activated Pd/Al2O3The catalyst is 10min, the gas flow rate is 300mL/min, the energy supply source is a sharp wave pulse power supply, the input peak voltage is 10kV, and the pulse width is 1000 ns.
For Pd/Al in example 32O3The nano catalyst is used for carrying out acetylene selective hydrogenation reaction experiments under the following experimental conditions: 0.3gPd/Al2O3The nano-catalyst is placed in a reactor and then reacts with N at 40 DEG C2After stabilization for 30min under atmosphere (200mL/min), the reaction gas (1 vol% C)2H2，3vol％H2，31vol％H2O，65vol％N2) And (3) introducing into a reactor, wherein the reaction space velocity is 200000 mL/h/g. As a comparative study, by H2Reduction treatment at 200 ℃ in an atmosphere and H2And Ar (volume ratio 3:7) plasma treated catalyst were also subjected to test evaluation under the same conditions.
The obtained result is shown in FIG. 4, and the Pd/Al treated by plasma regulation2O3The catalyst can not only show the highest catalytic activity (97 percent of C) at the reaction temperature2H2Conversion rate) and C)2H4The selectivity of the catalyst is up to 91%, and the performance of the catalyst is not obviously attenuated after the reaction is continuously operated for 48 hours. This shows that the activity and selectivity of the plasma-controlled Pd nano-catalyst are significantly improved. Generally, it is difficult to simultaneously obtain high conversion rate and selectivity when the nano Pd catalyst is used in acetylene hydrogenation reaction. For example, under the same reaction conditions, conventional H2Catalyst activity of thermal reductionLow sex and selectivity (C)2H2Conversion and C2H4Selectivity 62% versus 57%); h2The Pd catalyst plasma-treated with Ar (volume ratio 3:7) has high activity (C)2H2Conversion 92%), but C2H4The selectivity was 75% lower. In addition, from the stability of the catalyst in acetylene hydrogenation reaction, Pd/Al treated by plasma regulation2O3The nano-catalyst is also far superior to the other two catalysts. Pd/Al after plasma Conditioning in example 32O3The catalyst has the advantages of Pd particles and Al2O3Unique interactions between the vectors. Through the regulation and control treatment of the method, the Pd nanoparticles can show excellent adsorption and activation capacity on acetylene, which is beneficial to obtaining high activity; meanwhile, the metal-carrier interface has stronger interaction, so that the adsorption capacity of the ethylene obtained by primary hydrogenation at the interface is weakened, and the ethylene can rapidly leave an active site without further hydrogenation into ethane, thereby obviously improving the selectivity of the reaction ethylene. In contrast, conventionally treated Pd/Al2O3It is difficult to achieve both activity and selectivity.
The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention by those skilled in the art should fall within the protection scope defined by the claims of the present invention without departing from the spirit of the present invention.

Claims (10)

1. A method for regulating and controlling the interaction between metal nano particles and a carrier by plasma is characterized in that: the method comprises the following steps:
s1, loading of the metal precursor on the carrier: loading a metal precursor on a carrier by adopting an impregnation method or a deposition-precipitation method, and cleaning and drying to obtain a catalyst;
s2, pretreatment of the catalyst: placing the obtained catalyst in a plasma generating device, and pretreating the catalyst by adopting plasma in the atmosphere of hydrogen or mixed gas consisting of hydrogen and inert gas;
s3, surface activation of the catalyst: activating the catalyst by adopting plasma in the atmosphere of oxygen or mixed gas consisting of oxygen and inert gas;
s4, regulation and control of interaction between metal nanoparticles and a carrier: and after the activation treatment, further treating the catalyst by adopting plasma in the atmosphere of hydrogen or the mixed gas of hydrogen and inert gas to obtain the supported metal catalyst.
2. The method of claim 1, wherein the step of modulating the interaction between the metal nanoparticles and the carrier comprises: in step S1, the metal precursor is a soluble metal salt and the carrier is a metal oxide.
3. The method of claim 2, wherein the step of modulating the interaction between the metal nanoparticles and the carrier comprises: in step S1, the metal precursor is a soluble salt of a group IB and group VIII noble metal, and the carrier is one or more of alumina, silica, ceria, and titania.
4. The method of claim 2 or 3, wherein the interaction between the metal nanoparticles and the carrier is controlled by plasma, and the method comprises the following steps: in step S1, the pH of the metal precursor solution is higher than the isoelectric point of the metal oxide support, but the difference is less than 2.
5. The method of claim 1, wherein the step of modulating the interaction between the metal nanoparticles and the carrier comprises: in steps S2-S4, the plasma generating device generates plasma through dielectric barrier discharge or corona discharge, and the discharge treatment time in each step is 1-30 min.
6. The method of claim 5, wherein the step of modulating the interaction between the metal nanoparticles and the carrier comprises: the energy supply power source for dielectric barrier discharge is an alternating current power source or a pulse power source, the energy supply power source for corona discharge is a direct current power source or a pulse power source, the frequency of the alternating current power source is 5-20kHz, the applied voltage is 5-10kV, the applied voltage of the direct current power source is 3-12kV, and the pulse width of the pulse power source is less than 1000 ns.
7. The method of claim 5 or 6, wherein the plasma-mediated interaction between the metal nanoparticles and the carrier comprises: the instantaneous discharge power of the alternating current power supply and the direct current power supply is larger than 10W, and the instantaneous discharge power of the pulse power supply is larger than 5 kW.
8. The method of claim 7, wherein the step of modulating the interaction between the metal nanoparticles and the carrier comprises: the discharge treatment time of the pulse power supply is 5-15 min.
9. The method of claim 1, wherein the step of modulating the interaction between the metal nanoparticles and the carrier comprises: in the steps S2-S4, the inert gas is one of helium and argon, the reducing atmosphere and the oxidizing atmosphere are both in the condition of continuous gas flow, and the space velocity is 1000--1。
10. The method of claim 9, wherein the step of modulating the interaction between the metal nanoparticles and the carrier comprises: in step S2, the volume ratio of hydrogen in the mixed gas is more than 5%; in step S3, the volume ratio of oxygen in the mixed gas is more than 30%; in step S4, the volume ratio of hydrogen in the mixed gas is greater than 10%.
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