Integral cordierite carrier hydrodechlorination catalyst, preparation method and application thereof
阅读说明：本技术 一种整体式堇青石载体加氢脱氯催化剂、其制备方法及应用 (Integral cordierite carrier hydrodechlorination catalyst, preparation method and application thereof ) 是由 李玲 卢春山 刘武灿 石能富 金佳敏 李小年 聂娟娟 于 2021-01-21 设计创作，主要内容包括：本发明公开了一种整体式堇青石载体加氢脱氯催化剂、其制备方法及应用,所述整体式堇青石载体加氢脱氯催化剂包括：载体,所述载体为氮掺杂炭涂覆的整体式堇青石载体；负载于载体的活性金属,所述活性金属选自钯、铂、铱、镍的至少一种；负载于载体的第二金属,所述第二金属选自铜、锡、银、锌中的一种；所述催化剂为呈核壳结构的包裹型双金属粒子,核部为活性金属,壳层为第二金属。本发明的催化剂具有高活性和稳定性,应用于加氢脱氯反应中,能提高反应选择性。(The invention discloses a monolithic cordierite carrier hydrodechlorination catalyst, a preparation method and application thereof, wherein the monolithic cordierite carrier hydrodechlorination catalyst comprises: the carrier is an integral cordierite carrier coated with nitrogen-doped carbon; an active metal supported on a carrier, the active metal being at least one selected from the group consisting of palladium, platinum, iridium, and nickel; a second metal supported on a carrier, wherein the second metal is selected from one of copper, tin, silver and zinc; the catalyst is wrapped bimetallic particles in a core-shell structure, the core part is active metal, and the shell layer is second metal. The catalyst has high activity and stability, and can be applied to hydrodechlorination reaction to improve the reaction selectivity.)
1. A monolithic cordierite carrier hydrodechlorination catalyst is characterized in that: the catalyst comprises:
the carrier is a monolithic cordierite carrier;
an active metal supported on a carrier, the active metal being at least one selected from the group consisting of palladium, platinum, iridium, and nickel;
a second metal supported on a carrier, wherein the second metal is selected from one of copper, tin, silver and zinc;
the catalyst is wrapped bimetallic particles in a core-shell structure, the core part is active metal, and the shell layer is second metal.
2. The monolithic cordierite substrate hydrodechlorination catalyst of claim 1, wherein: the monolithic cordierite carrier is a nitrogen-doped carbon-coated monolithic cordierite carrier, the mass of the nitrogen-doped carbon coating accounts for 0.1-5.0 wt% of the monolithic cordierite carrier, and the nitrogen content accounts for 0.1-8.0 wt% of the mass of the carbon coating.
3. The monolithic cordierite substrate hydrodechlorination catalyst of claim 2, wherein: the integral cordierite carrier has a pore density of 10-50 pores/cm2The specific surface area is more than or equal to 900m2/g。
4. The monolithic cordierite substrate hydrodechlorination catalyst of claim 1, wherein: the loading capacity of the active metal is 0.01-4.5%, the loading capacity of the second metal is 0.01-5.5%, and the loading capacity of the second metal is not lower than that of the active metal.
5. The monolithic cordierite substrate hydrodechlorination catalyst of claim 4, wherein: the mass ratio of the active metal to the second metal is 1: 1-5.
6. The monolithic cordierite substrate hydrodechlorination catalyst of claim 1, wherein: the size of the active metal particles at the core part is less than or equal to 100nm, and the thickness of the shell layer is less than or equal to 5 nm.
7. A process for the preparation of a monolithic cordierite-supported hydrodechlorination catalyst of any one of claims 1 to 6, wherein: the preparation method comprises the following steps:
A1. active metal loading
Soaking the integral cordierite carrier coated with nitrogen-doped carbon in an active metal salt solution to form a soaking solution, taking out after soaking for 2-6 hours at 25-85 ℃, standing, draining, and purging by adopting nitrogen flow; the volume ratio of the total volume of the impregnation liquid to the integral cordierite carrier is 2-5: 1;
A2. second metal load
Immersing the integral cordierite carrier loaded with active metal in ethylene glycol, introducing hydrogen into the ethylene glycol, stirring, controlling the temperature to be 20-95 ℃, the pressure to be 0.1-0.2 Mpa, and the time to be 1-10 hours;
dripping a second metal salt solution, heating and boosting the temperature for reaction, wherein the reaction temperature is 150-350 ℃, the reaction pressure is 0.5-4.0 Mpa, the reaction time is 3-10 hours, and taking out and draining the solution after the reaction is finished;
A3. drying
Placing the integral cordierite carrier loaded with the active metal and the second metal in a nitrogen atmosphere, heating from room temperature at the speed of 0.5-2.0 ℃/min, and drying at constant temperature for 2-5 hours after the temperature is increased to 110-150 ℃ to obtain a catalyst precursor;
A4. reduction of
And (3) placing the catalyst precursor in a hydrogen atmosphere, heating to 250-450 ℃ at the speed of 0.1-2.0 ℃/min, and keeping the temperature for 1-5 hours to obtain the hydrodechlorination catalyst.
8. The method of preparing a monolithic cordierite substrate hydrodechlorination catalyst of claim 7, wherein: the coating method of the nitrogen-doped carbon coating on the surface of the nitrogen-doped carbon-coated monolithic cordierite carrier comprises the following steps of:
mixing starch, glucose, ethylenediamine and water according to the proportion of 1: 1-3: 1-3: 1-2, immersing the integral cordierite carrier into the aqueous solution, uniformly coating the surface of the integral cordierite carrier, taking out, drying at a constant temperature of 110-150 ℃ for 2-3 hours, and roasting at 400-800 ℃ for 3-8 hours in a nitrogen atmosphere to obtain the nitrogen-doped carbon coated integral cordierite carrier.
9. The method of preparing a monolithic cordierite substrate hydrodechlorination catalyst of claim 8, wherein: and carrying out repeated dipping coating, drying and roasting on the integral cordierite carrier for 2-5 times to obtain the nitrogen-doped carbon-coated cordierite carrier.
10. The method of preparing a monolithic cordierite substrate hydrodechlorination catalyst of claim 7, wherein: the active metal salt solution is an active metal nitrate solution or an active metal chloride solution; the second metal salt solution is a second metal nitrate solution or a second metal chloride solution, and the concentration of the solution is 0.5-2.0 mol/L.
11. The method of preparing a monolithic cordierite substrate hydrodechlorination catalyst of claim 7, wherein: in the active metal loading step, standing for 10-20 hours at 20-35 ℃ in an environment with air humidity less than or equal to 80%, draining, and purging in nitrogen flow with flow rate of 0.1-2.0 m/s and oxygen content of 0.1-1.0 v/v% for 0.5-2 hours.
12. A process for the preparation of a monolithic cordierite substrate hydrodechlorination catalyst according to any one of claims 7 to 11, wherein: in the prepared hydrodechlorination catalyst, more than or equal to 90 percent of active metal particles are in a wrapped bimetallic structure.
13. Use of a monolithic cordierite-supported hydrodechlorination catalyst according to any one of claims 1 to 6, wherein: the catalyst is used for the hydrogenation dechlorination reaction of trifluorotrichloroethane, 1,1, 2-trichloro-fluoroethane, 1, 2-dichlorotetrafluoroethane and 2, 3-dichloro-1, 1,1,4,4, 4-hexafluoro-2-butene.
14. A continuous preparation method of chlorotrifluoroethylene is characterized in that: the monolithic cordierite carrier hydrodechlorination catalyst of any one of claims 1-8 is used to prepare chlorotrifluoroethylene from trifluorotrichloroethane and hydrogen by a hydrodechlorination reaction.
15. The continuous process for the preparation of chlorotrifluoroethylene according to claim 14, characterized in that: the molar ratio of the trifluorotrichloroethane to the hydrogen is as follows: 1:1 to 4.
16. The continuous process for the preparation of chlorotrifluoroethylene according to claim 14, characterized in that: the reaction temperature is 150-300 ℃, and the space velocity of the raw material is 10-1500 h-1。
Technical Field
The invention relates to the field of catalysts, in particular to a monolithic cordierite carrier hydrodechlorination catalyst, a preparation method thereof, and application of the monolithic cordierite carrier hydrodechlorination catalyst in gas-phase hydrodechlorination reaction, especially application in preparation of chlorotrifluoroethylene from trichlorotrifluoroethane.
Background
Catalytic hydrodechlorination technology replacing the traditional chemical reduction method has attracted people's attention in important monomer reaction for synthesizing fluorine-containing materials such as hydrofluorocarbon and the like, and is considered to be one of the most economical, green and promising methods at present. At present, a common hydrodechlorination catalyst is prepared by mainly taking palladium as a main active component and taking magnesium, cobalt, copper, bismuth and the like as auxiliaries and loading the active component, the cobalt, the copper, the bismuth and the like on carriers such as activated carbon, silicon dioxide, magnesium fluoride and the like, and has good hydrodechlorination performance.
European patent EP0053657B1 discloses that a platinum group metal is loaded on basic magnesium fluoride (such as sodium magnesium fluoride and potassium magnesium fluoride) to prepare a hydrodechlorination catalyst, the catalyst can be used for preparing chlorotrifluoroethylene by CFC-113, the conversion rate of the CFC-113 is up to 84%, and the product selectivity is 82-84%.
European patent EP0747337B1 and Chinese patent CN1065261A disclose a bimetallic composite carbon-supported catalyst, wherein the bimetallic is formed by compounding at least one VIII group metal and copper, and the copper accounts for 12-22% of the total mass of the catalyst; the bimetallic composite catalyst can be used for the hydrodechlorination reaction of CFC-113, but the reaction products are chlorotrifluoroethylene and trifluoroethylene or tetrafluoroethylene, and the chlorotrifluoroethylene cannot be selectively obtained. European patent EP0416615A1 discloses a catalyst which takes Fe, Ni, Cu, Sn, Zn, Cr or oxides thereof as active components of the catalyst, and takes silicon dioxide, magnesium oxide, aluminum oxide, zirconium oxide, Y-type zeolite, silicon dioxide-aluminum oxide, silicon carbide, diatomite and the like as carriers, the catalyst can be applied to CFC-113 hydrodechlorination to prepare chlorotrifluoroethylene, but the selectivity of the catalyst is greatly different when different active components or carriers are used, and the maximum selectivity is only about 80%, so that the application of the catalyst has certain limitation.
Chinese patent CN1351903A discloses a quaternary catalyst using noble metal ruthenium or palladium or platinum and copper as main active components, lanthanum-rich mischmetal or metal lanthanum and alkali metal lithium as a modifying assistant, and coconut shell activated carbon as a carrier, wherein the service life of the catalyst is about 600 hours, but the selectivity of the catalyst is only 70-80% under the condition of lacking the modifying assistant, and the method provided by the patent is relatively limited in the selection of the active components and the modifying assistant.
Chinese patent CN105457651B discloses a hydrodechlorination catalyst which takes Pd and Cu as main catalysts and takes at least one of Mg, Ca, Ba, Co, Mo, Ni, Sm and Ce as an auxiliary agent and is loaded on activated carbon, wherein the catalyst can be used for preparing chlorotrifluoroethylene by CFC-113 catalytic hydrodechlorination, the conversion rate can reach 95%, the selectivity is 95%, and the service life of the catalyst is 2000 hours.
The hydrodechlorination catalysts are low in catalytic activity and poor in stability, and when the hydrodechlorination catalysts are applied to a hydrodechlorination reaction, the problem of low reaction selectivity generally exists, so that the development of a novel catalyst with high activity, high selectivity and high stability is particularly important.
Disclosure of Invention
In order to solve the technical problems, the invention provides a monolithic cordierite carrier hydrodechlorination catalyst with high activity and high stability, which is applied to the hydrodechlorination reaction of fluorochloroalkane and can obviously improve the selectivity of the product.
The purpose of the invention is realized by the following technical scheme:
a monolithic cordierite support hydrodechlorination catalyst, comprising:
the carrier is a monolithic cordierite carrier;
an active metal supported on a carrier, the active metal being at least one selected from the group consisting of palladium, platinum, iridium, and nickel;
a second metal supported on a carrier, wherein the second metal is selected from one of copper, tin, silver and zinc;
the catalyst is wrapped bimetallic particles in a core-shell structure, the core part is active metal, and the shell layer is second metal.
Generally, the active metal and the second metal in the catalyst are supported on the carrier, and each form an alloy in an ionic form, or both, whereas the active metal and the second metal in the catalyst of the present invention mainly exist in a simple substance form, the active metal becomes a core portion in a simple substance form, the second metal becomes a shell portion in a simple substance form, the active metal and the second metal form bimetallic particles, and the non-coated particles exist in a form of active metal monometal particles and second metal monometal particles or alloy particles.
Preferably, the monolithic cordierite carrier is a nitrogen-doped carbon-coated monolithic cordierite carrier, the mass of the nitrogen-doped carbon coating accounts for 0.1-5.0 wt% of the monolithic cordierite carrier, and the nitrogen content accounts for 0.1-8.0 wt% of the mass of the carbon coating. More preferably, the mass of the nitrogen-doped carbon coating accounts for 0.2-4.0 wt% of the mass of the monolithic cordierite carrier, and the nitrogen content accounts for 0.15-7.0 wt% of the mass of the carbon coating.
Further, the method can be used for preparing a novel materialThe pore density of the integral cordierite carrier is 10-50 pores/cm2The specific surface area is more than or equal to 900m2(ii) in terms of/g. Preferably, the monolithic cordierite carrier has a pore density of 13-48 pores/cm2The specific surface area is more than or equal to 1100m2/g。
The coating method of the nitrogen-doped carbon coating on the surface of the integral cordierite carrier coated with the nitrogen-doped carbon comprises the following steps:
mixing starch, glucose, ethylenediamine and water according to the proportion of 1: 1-3: 1-3: 1-2, immersing the integral cordierite carrier into the aqueous solution, uniformly coating the surface of the integral cordierite carrier, taking out, drying at a constant temperature of 110-150 ℃ for 2-3 hours, and roasting at 400-800 ℃ for 3-8 hours in a nitrogen atmosphere to obtain the nitrogen-doped carbon coated integral cordierite carrier.
For better coating, further, the monolithic cordierite carrier is subjected to repeated dipping coating, drying and roasting for 2-5 times to obtain the nitrogen-doped carbon-coated cordierite carrier.
Furthermore, in the monolithic cordierite carrier hydrodechlorination catalyst, the loading amount of the active metal is 0.01-4.5%, the loading amount of the second metal is 0.01-5.5%, and the loading amount of the second metal is not lower than that of the active metal. Preferably, the loading amount of the active metal is 0.05-4.5%, and the loading amount of the second metal is 0.05-5.0%.
Furthermore, the mass ratio of the active metal to the second metal is 1: 1-5. Preferably, the mass ratio of the active metal to the second metal is 1:2 to 1: 5.
The size of active metal particles at the core part of the integral cordierite carrier hydrodechlorination catalyst is less than or equal to 100nm, and the thickness of a shell layer is less than or equal to 5 nm. Preferably, the size of the active metal particle at the core part is less than or equal to 80nm, and the thickness of the shell layer is less than or equal to 4.8 nm.
The particle size, shell thickness and size distribution calculation method comprises the following steps: two to three regions were randomly selected in a Transmission Electron Microscope (TEM) photograph, magnified, and then statistically analyzed using Image-Pro Plus software. Surface average particleThe particle diameter is calculated by the formula: ds＝Σnidi 3/Σnidi 2. Wherein n isiDenotes the diameter diThe number of the metal particles is not less than 200.
The integral cordierite carrier hydrodechlorination catalyst disclosed by the invention adopts the integral cordierite carrier, and compared with a conventional activated carbon carrier, the integral cordierite carrier can improve the fluidity of fluid in the catalyst and improve the catalytic efficiency. The integral cordierite carrier coated with nitrogen-doped carbon can effectively regulate and control the tissue structure and the chemical composition of the surface of the carrier, and further improve the catalytic activity and the stability of the surface of the carrier.
Conventional catalyst preparation methods cannot obtain a wrapped catalyst structure. The invention provides a preparation method of a monolithic cordierite carrier hydrodechlorination catalyst, which comprises the following steps:
A1. active metal loading
Soaking the integral cordierite carrier coated with nitrogen-doped carbon in an active metal salt solution to form a soaking solution, taking out after soaking for 2-6 hours at 25-85 ℃, standing, draining, and purging by adopting nitrogen flow;
A2. second metal load
Immersing the integral cordierite carrier loaded with active metal into ethylene glycol, introducing hydrogen into the ethylene glycol, stirring, controlling the temperature to be 20-95 ℃, the pressure to be 0.1-0.2 Mpa, and the time to be 1-10 hours, wherein the active metal ions are reduced into active metal simple substances;
dripping a second metal salt solution, heating and boosting for reaction, wherein the reaction temperature is 150-350 ℃, the reaction pressure is 0.5-4.0 Mpa, the reaction time is 3-10 hours, the second metal salt solution is taken out after the reaction is finished, and is drained, and second metal ions are reduced into a second metal simple substance which is wrapped outside the active metal simple substance;
A3. drying
Placing the integral cordierite carrier loaded with the active metal and the second metal in a nitrogen atmosphere, heating from room temperature at the speed of 0.5-2.0 ℃/min, and drying at constant temperature for 2-5 hours after the temperature is increased to 110-150 ℃ to obtain a catalyst precursor;
A4. reduction of
The catalyst precursor is placed in a hydrogen atmosphere at a space velocity of not less than 100h-1And heating to 250-450 ℃ at the speed of 0.1-2.0 ℃/min, and keeping the temperature for 1-5 hours to obtain the hydrodechlorination catalyst.
Preferably, the impregnation of the active metal in the step A1 is carried out in a stirring state, the impregnation temperature is 35-70 ℃, the impregnation time is 3-5 hours, and the volume ratio of the total volume of the impregnation liquid to the volume of the monolithic cordierite carrier is 2-5: 1.
Further, the monolithic cordierite carrier loaded with active metal and taken out in the step A1 is kept stand for 10-20 hours at the temperature of 20-35 ℃ and under the environment that the air humidity is less than or equal to 80%, drained and then blown in nitrogen flow with the flow rate of 0.1-2.0 m/s and the oxygen content of 0.1-1.0 v/v% for 0.5-2 hours.
Preferably, when the active metal is reduced in the step A2, the temperature is controlled to be 60-90 ℃, the pressure is 0.1-0.15 Mpa, and the time is 2-5 hours; when the second metal ions are loaded in the step A2, the reaction temperature is 250-350 ℃, the reaction pressure is 0.5-3.5 MPa, and the reaction time is 5-7 hours.
In order to promote the reduction of the active metal ion and the second metal ion, it is more preferable that the hydrogen gas is introduced into the ethylene glycol from the bottom of the reactor through a gas distributor to stir the reaction. The reactor is preferably a kettle type reactor, magnetons are placed at the bottom of the reactor for stirring reaction, and the integral cordierite carrier loaded with active metal ions is placed above the magnetons.
In the preparation process of the monolithic cordierite carrier hydrodechlorination catalyst, the active metal salt solution is an active metal nitrate solution or an active metal chloride solution. Preferably, the active metal salt solution is a metal chloride solution, such as a nickel chloride solution, and a complex solution of chloride ions and noble metals, such as [ PdCl4]2-、[PtCl4]2-、[IrCl4]2-。
The second metal salt solution is a second metal nitrate solution or a second metal chloride solution, and the concentration of the solution is 0.5-2.0 mol/L. Preferably, the second metal salt solution is at least one selected from silver nitrate, zinc chloride and copper nitrate, and the solution concentration is 1.0-1.5 mol/L.
Preferably, the temperature rise rate in the step A3 is 1.0-1.5 ℃/min, and after the temperature rises to 120-140 ℃, drying is carried out for 2.5-4.8 hours at constant temperature, so as to obtain a catalyst precursor; in the step A4, the space velocity is 100-1000 h-1And heating to 300-400 ℃ at the speed of 0.5-1.5 ℃/min, and keeping the temperature for 2-3.8 hours to obtain the hydrodechlorination catalyst.
In the hydrodechlorination catalyst prepared by the method, more than or equal to 90 percent of active metal particles are in a wrapped bimetallic structure, and the rest active metal particles are in a state of dispersion or mutual embedding. More preferably, in the hydrodechlorination catalyst prepared by the preparation method, not less than 95% of active metal particles are in a wrapped bimetallic structure.
The active metal has stronger hydrogen dissociation performance, and after hydrogen is filled into the glycol impregnation liquid, the hydrogen is dissociated into active hydrogen on the active metal particles to induce the second metal ions to be reduced on the surfaces of the active metal particles, so that a wrapping type structure is formed. After the formation of the primary inclusion type structure, the hydrogen dissociation performance is decreased, and the further deposition of the second metal is gradually increased. Therefore, the invention further adopts the ethylene glycol as the impregnation liquid, and the ethylene glycol can show reducibility at high temperature, thereby solving the problem that the difficulty of the second metal deposition is gradually increased, and leading the second metal to be continuously deposited outside the active metal. Under the combined action of glycol impregnation liquid and hydrogen, the wrapped monolithic cordierite carrier hydrodechlorination catalyst is realized.
The invention also provides application of any monolithic cordierite carrier hydrodechlorination catalyst, and the catalyst can be used for hydrodechlorination of fluorochloroalkanes such as trifluorotrichloroethane, 1,1, 2-trichloro-fluoroethane and 1, 2-dichlorotetrafluoroethane, and can also be used for hydrodechlorination of fluorochloroalkenes such as 2, 3-dichloro-1, 1,1,4,4, 4-hexafluoro-2-butene (CFO-1316).
The invention also provides a continuous preparation method of chlorotrifluoroethylene, which comprises the following steps:
the integral cordierite carrier hydrodechlorination catalyst is adopted, and trifluorotrichloroethane and hydrogen are used as raw materials to prepare chlorotrifluoroethylene through a hydrodechlorination reaction.
Further, the molar ratio of the trifluorotrichloroethane to the hydrogen is 1:1 to 4, preferably 1:1 to 3.5.
Further, the reaction temperature is 150-300 ℃, and the space velocity of the raw materials is 10-1500 h-1(ii) a Preferably, the reaction temperature is 170-280 ℃, and the space velocity of the raw materials is 10-1200 h-1。
Compared with the prior art, the invention has the beneficial effects that:
1. the catalyst is of a core-shell structure, the core part is made of active metal, the shell part is made of second metal, a wrapped bimetallic structure is formed, electrons deviate between the two metal structures, and the hydrogen dissociation performance and the carbon-chlorine bond (C-Cl) activation performance are modulated, so that the catalyst has high activity and high stability.
2. The catalyst of the invention can improve the selectivity of products when used in the hydrodechlorination reaction, and particularly, when used in the hydrodechlorination reaction of trifluorotrichloroethane, the selectivity of chlorotrifluoroethylene is more than or equal to 99 percent, and can reach more than 99.8 percent at most.
3. The catalyst adopts the monolithic cordierite carrier, so that the lamination of the catalyst is reduced, the fluidity of fluid in the catalyst is improved, and the catalytic efficiency is further improved; and the integral cordierite carrier is coated with nitrogen-doped carbon, so that the tissue structure and the chemical composition of the surface of the carrier can be effectively regulated and controlled, and the catalytic activity and the stability of the surface of the carrier can be further improved.
Drawings
FIG. 1 is a TEM representation of a monolithic cordierite substrate hydrodechlorination catalyst prepared according to example 1 of the present invention.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to limit the invention to these embodiments. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.
Preparation example
Preparation of nitrogen-doped carbon-coated monolithic cordierite carrier:
mixing starch, glucose, ethylenediamine and water according to the proportion of 1: 2: 2: 2, immersing the integral cordierite carrier in the aqueous solution, uniformly coating the integral cordierite carrier on the surface, taking out, drying at 110 ℃ for 3 hours, placing in a nitrogen atmosphere, and roasting at 400 ℃ for 5 hours. And continuously repeating the dip coating, drying and roasting under the same conditions. Obtaining the nitrogen-doped carbon-coated integral cordierite carrier after three times of coating, drying and roasting, wherein the specific surface area of the nitrogen-doped carbon-coated integral cordierite carrier is 1270m2Per g, the carbon coating content is 4.0 wt%, wherein the nitrogen content is 5.0 wt%.
The coating conditions of the nitrogen-doped carbon coating are changed to obtain the integral cordierite carriers with different specific surface areas, carbon contents and nitrogen contents, which are specifically shown in the following table 1:
TABLE 1 Nitrogen-doped carbon-coated monolithic cordierite Supports
Example 1
Preparation of a hydrodechlorination catalyst:
s1, active metal loading: the nitrogen-doped carbon-coated monolithic cordierite carrier 1 obtained by the preparation method is washed clean with deionized water and then immersed in a chloropalladite acid aqueous solution, wherein the palladium content is 0.08 percent of that of the monolithic cordierite carrier, and the volume ratio of the total volume of the immersion liquid to that of the monolithic cordierite carrier is 2: 1. Starting stirring, heating to 50 ℃, soaking for 3 hours, and taking out; after allowing to stand at 30 ℃ and 70% air humidity for 15 hours, the mixture was drained and then purged with a nitrogen stream (containing 0.1v/v oxygen) at a flow rate of 0.5m/s for 1 hour.
S2, second metal loading: 1) reduction of active metal ions: placing an integral cordierite carrier loaded with active metal and blown by nitrogen flow in a high-pressure reaction kettle, immersing the integral cordierite carrier in an ethylene glycol solution, adding a magnet at the bottom of the kettle for stirring (the rotation number is 1500r/min), continuously introducing hydrogen into the ethylene glycol solution, heating to 80 ℃, keeping the temperature for 5 hours, and controlling the pressure to be 0.1 MPa; 2) and (3) loading a second metal: the temperature is raised to 250 ℃, the pressure is increased to 1.0MPa, 1mol/L of copper chloride solution is transferred according to the load of 0.08 percent, the copper chloride solution is dripped into the high-pressure kettle through a constant-pressure funnel, and the constant-temperature reaction is continued for 5 hours.
S3, drying: the monolithic cordierite carrier loaded with the active metal and the second metal was placed in a tube furnace, raised from room temperature to 120 ℃ at a rate of 0.5 ℃/min under a nitrogen atmosphere, and dried at a constant temperature for 5 hours to obtain a catalyst precursor.
S4, reduction: the obtained catalyst precursor was placed under a hydrogen atmosphere (space velocity of 200 h)-1) And raising the temperature from room temperature to 350 ℃ at the speed of 0.1 ℃/min, and keeping the temperature for 5 hours to obtain the hydrodechlorination catalyst which is recorded as cat 1.
FIG. 1 shows a TEM representation of the hydrodechlorination catalyst prepared in this example, in which the hydrodechlorination catalyst of this example forms a wrapped structure, the core is palladium and the shell is copper.
According to TEM, 91% of active metal particles in the cat1 are in a wrapped bimetallic structure.
Example 2
The operation of this example is the same as example 1 except that: the carrier 3 is adopted to replace the carrier 1 for the preparation of the hydrodechlorination catalyst, the loading capacity of the active metal is 0.8 percent, the loading capacity of the second metal is reduced to 1.5 percent, and the prepared catalyst is marked as cat 2.
According to TEM, 93 percent of active metal particles in the cat2 are in a wrapped bimetallic structure.
Example 3
The operation of this example is the same as example 1 except that: the carrier 8 is adopted to replace the carrier 1 for the preparation of the hydrodechlorination catalyst, the loading capacity of the active metal is 0.3 percent, the loading capacity of the second metal is reduced to 1.5 percent, and the prepared catalyst is marked as cat 3.
According to TEM, 90% of active metal particles in the cat3 have a wrapped bimetallic structure.
Example 4
The operation of this example is the same as example 1 except that: the carrier 12 is adopted to replace the carrier 1 for the preparation of the hydrodechlorination catalyst, the active metal is platinum, the second metal is changed into zinc, and the prepared catalyst is marked as cat 4.
According to TEM, 97 percent of active metal particles in the cat4 are in a wrapped bimetallic structure.
Example 5
The operation of this example is the same as example 1 except that: the carrier 18 is adopted to replace the carrier 1 for the preparation of the hydrodechlorination catalyst, the active metal is changed into nickel, the second metal is changed into zinc, and the prepared catalyst is marked as cat 5.
By TEM, 96 percent of active metal particles in the cat5 have a wrapped bimetallic structure.
Example 6
The operation of this example is the same as example 1 except that: the carrier 2 is adopted to replace the carrier 1 to prepare the hydrodechlorination catalyst, the load capacity of the active metal palladium is 1 percent, and the load capacity of the second metal copper is 1.5 percent. The hydrodechlorination catalyst was prepared and is designated as cat 6.
According to TEM, 95% of active metal particles in the cat6 have a wrapped bimetallic structure.
Example 7
The operation of this example is the same as example 1 except that: the carrier 7 is adopted to replace the carrier 1 for the preparation of the hydrodechlorination catalyst, the active metal solution (active metal precursor) adopts palladium nitrate, the second metal solution adopts zinc chloride, and the prepared catalyst is marked as cat 7.
According to TEM, 93 percent of active metal particles in the cat7 are in a wrapped bimetallic structure.
Example 8
The operation of this example is the same as example 1 except that: the carrier 4 is adopted to replace the carrier 1 for the preparation of the hydrodechlorination catalyst, the active metal solution (active metal precursor) adopts palladium nitrate, the second metal solution adopts zinc nitrate, and the prepared catalyst is marked as cat 8.
By TEM, 96 percent of active metal particles in the cat8 have a wrapped bimetallic structure.
Example 9
The operation of this example is the same as example 1 except that: the preparation of the hydrodechlorination catalyst is carried out by adopting the carrier 9 instead of the carrier 1, in the step S1, the impregnation temperature is increased to 60 ℃, and the catalyst obtained by the preparation is marked as cat 9.
According to TEM, 92 percent of active metal particles in the cat9 are in a wrapped bimetallic structure.
Example 10
The operation of this example is the same as example 1 except that: the preparation of the hydrodechlorination catalyst was carried out using the carrier 10 instead of the carrier 1, and in the step of S1, the impregnation time was increased to 6 hours, and the catalyst obtained by the preparation was designated as cat 10.
According to TEM, 95% of active metal particles in the cat10 have a wrapped bimetallic structure.
Example 11
The operation of this example is the same as example 1 except that: and (3) replacing the carrier 1 with the carrier 11 to prepare the hydrodechlorination catalyst, wherein in the step S2, the reduction pressure of active metal ions is 0.2MPa, and the prepared catalyst is recorded as cat 11.
By TEM, 94% of active metal particles in the cat11 have a wrapped bimetallic structure.
Example 12
The operation of this example is the same as example 1 except that: and (3) replacing the carrier 1 with the carrier 5 to prepare the hydrodechlorination catalyst, wherein in the step of S2, active metal ions are reduced for 3 hours, and the prepared catalyst is named as cat 12.
By TEM, 98% of active metal particles in the cat12 have a wrapped bimetallic structure.
Example 13
The operation of this example is the same as example 1 except that: and (3) replacing the carrier 1 with the carrier 5 to prepare the hydrodechlorination catalyst, wherein in the step S2, the reduction temperature of the second metal ions is 200 ℃, and the prepared catalyst is recorded as cat 13.
According to TEM, 93 percent of active metal particles in the cat13 are in a wrapped bimetallic structure.
Example 14
The operation of this example is the same as example 1 except that: and (3) replacing the carrier 1 with the carrier 5 to prepare the hydrodechlorination catalyst, wherein in the step S2, the reduction pressure of the second metal ions is 3.0MPa, and the prepared catalyst is recorded as cat 14.
According to TEM, 93 percent of active metal particles in the cat14 are in a wrapped bimetallic structure.
Example 15
The operation of this example is the same as example 1 except that: and (3) replacing the carrier 1 with the carrier 13 to prepare the hydrodechlorination catalyst, wherein in the step S3, the constant-temperature drying time is 3 hours, and the prepared catalyst is named as cat 15.
According to TEM, 97 percent of active metal particles in the cat15 are in a wrapped bimetallic structure.
Example 16
The operation of this example is the same as example 1 except that: the preparation of the hydrodechlorination catalyst is carried out by adopting the carrier 14 to replace the carrier 1, in the step S3, the heating rate is changed to 1.5 ℃/min, and the prepared catalyst is recorded as cat 16.
According to TEM, 91 percent of active metal particles in the cat16 are in a wrapped bimetallic structure.
Example 17
The operation of this example is the same as example 1 except that: the carrier 15 is adopted to replace the carrier 1 for the preparation of the hydrodechlorination catalyst, in the step S3, the temperature rise and the final temperature are changed to 140 ℃, and the catalyst obtained by the preparation is recorded as cat 17.
By TEM, 96 percent of active metal particles in the cat17 have a wrapped bimetallic structure.
Example 18
The operation of this example is the same as example 1 except that: the carrier 16 is adopted to replace the carrier 1 for the preparation of the hydrodechlorination catalyst, in the step S4, the temperature rise and the final temperature are changed to 400 ℃, and the catalyst obtained by the preparation is recorded as cat 18.
According to TEM, 93 percent of active metal particles in the cat18 are in a wrapped bimetallic structure.
Example 19
The operation of this example is the same as example 1 except that: the preparation of the hydrodechlorination catalyst is carried out by adopting the carrier 17 to replace the carrier 1, in the step S4, the heating rate is changed to 1.5 ℃/min, and the prepared catalyst is recorded as cat 19.
By TEM, 94% of active metal particles in the cat19 have a wrapped bimetallic structure.
Example 20
The operation of this example is the same as example 1 except that: the preparation of the hydrodechlorination catalyst is carried out by adopting the carrier 6 to replace the carrier 1, the constant temperature time is changed to 3 hours in the step S4, and the prepared catalyst is recorded as cat 20.
According to TEM, 91% of active metal particles in the cat120 are in a wrapped bimetallic structure.
Comparative example 1
The comparative example was conducted as in example 1 except that: the catalyst obtained by using columnar activated carbon to replace an integral cordierite carrier is marked as B1, and 56% of active metal particles are in a wrapped bimetallic structure.
Comparative example 2
The comparative example was conducted as in example 1 except that: the monolithic cordierite carrier taken out from the impregnation solution in the step S1 was directly placed in a nitrogen stream to be purged, and the standing draining process was omitted. The catalyst obtained by the preparation is marked as B2, and 54 percent of active metal particles are in a wrapped bimetallic structure.
Comparative example 3
The comparative example was conducted as in example 1 except that: the monolithic cordierite substrate removed from the impregnation solution in step S1 was left to stand and drain, and then directly subjected to the second metal loading without being purged with a nitrogen stream. The catalyst obtained by the preparation is marked as B3, and 58 percent of active metal particles are in a wrapped bimetallic structure.
Comparative example 4
The comparative example was conducted as in example 1 except that: in the step of S2, hydrogen is not introduced into the glycol solution, the temperature is directly raised to 250 ℃, the pressure is raised to 1.0MPa, the second metal loading is carried out, and the active metal reduction step is not carried out. The catalyst obtained by the preparation is marked as B4, and 15 percent of active metal particles are in a wrapping bimetal structure.
Comparative example 5
The comparative example was conducted as in example 1 except that: in the step of S2, the hydrogen is introduced only in the step of reducing the active metal, and the introduction of the hydrogen is stopped when the second metal is impregnated. The catalyst obtained by the preparation is marked as B5, and 25 percent of active metal particles are in a wrapping bimetal structure.
Comparative example 6
The comparative example was conducted as in example 1 except that: when the second metal is loaded in the step S2, the reaction is carried out at normal temperature and normal pressure instead of the reaction conditions of 250 ℃ and 1.0 MPa. The catalyst obtained by the preparation is marked as B6, and 43 percent of active metal particles are in a wrapped bimetallic structure.
Comparative example 7
The comparative example was conducted as in example 1 except that: in the step S2, methanol is used to replace glycol solution, the prepared catalyst is marked as B7, and 31% of active metal particles are in a wrapped bimetallic structure.
Comparative example 8
The comparative example was conducted as in example 1 except that: the preparation process of the comparative example does not adopt a carrier, and the specific process comprises the following steps: adding a chloropalladate solution into an ethylene glycol solution, and continuously introducing hydrogen under a stirring state; adding a copper chloride solution, mixing, and heating and pressurizing for reaction; drying at constant temperature in nitrogen atmosphere; reducing under hydrogen atmosphere. The prepared catalyst is marked as B8, the size of the obtained metal particles is 60-700 nm, the size distribution is uneven, and 23% of active metal particles are in a wrapped bimetallic structure.
Comparative example 9
The comparative example was conducted as in example 1 except that: the monolithic cordierite supports were prepared without nitrogen doping (no ethylenediamine addition). The catalyst obtained by the preparation is marked as B9, and 57 percent of active metal particles are in a wrapped bimetallic structure.
Comparative example 10
The monolithic cordierite carrier 4 is washed clean with deionized water and then immersed in an aqueous solution of chloropalladate and copper chloride, wherein the content of palladium and copper is 1.0 percent and 1.0 percent of the monolithic cordierite carrier, and the volume ratio of the total volume of the immersion liquid to the monolithic cordierite carrier is 2: 1. Stirring is started, the temperature is increased to 50 ℃, and the mixture is taken out after 3 hours of immersion. After allowing to stand at 30 ℃ and 70% air humidity for 15 hours, the mixture was drained and then purged with a nitrogen stream (containing 0.1v/v oxygen) at a flow rate of 0.5m/s for 1 hour.
The drying and reduction steps were performed in the same manner as in example 1.
The prepared catalyst is marked as B10, and the palladium-copper bimetallic material does not form a wrapped core-shell structure and is in a bimetallic alloy state through TEM representation.
Example 21
The embodiment is an application of a hydrodechlorination catalyst in a reaction for preparing chlorotrifluoroethylene by trichlorotrifluoroethane hydrodechlorination, and the method comprises the following specific steps:
0.5g of Cat1 prepared in example 1 was charged into a fixed bed reactor having an inner diameter of 10 mm. Heating to 250 ℃, introducing a mixed gas consisting of hydrogen and trichlorotrifluoroethane with a molar ratio of 1:1, and keeping the space velocity at 300h-1Reaction at 250 ℃.
The hydrogenation product was analyzed by Agilent 7890A gas chromatography, and the conversion rate was 100% and the selectivity to chlorotrifluoroethylene was 99.58%.
Examples 22 to 48
Examples 22-48 were performed as in example 1, except that: the catalysts prepared in examples 2-20 and comparative examples 1-10 are used to replace cat1 for hydrodechlorination reaction.
The hydrogenation product was analyzed by Agilent 7890A gas chromatography, and the results are shown in Table 2 below:
TABLE 2 results of the Trifluorotrichloroethane hydrodechlorination reaction over different catalysts
Examples 49 to 72
The procedures of examples 49-72 were carried out in the same manner as in example 22, except that Cat3 was used as a hydrodechlorination catalyst and the hydrodechlorination reaction was carried out by changing the reaction conditions.
The hydrogenation product was analyzed by Agilent 7890A gas chromatography, and the results are shown in Table 3 below:
TABLE 3 results of the trichlorotrifluoroethane hydrodechlorination reaction under different reaction conditions
Example 73
Example 73 is a stability experiment conducted under the reaction conditions of example 56.
The hydrogenation product was analyzed by Agilent 7890A gas chromatography, the results of which are shown in Table 4 below:
TABLE 4 hydrodechlorination stability results
Time/day
Conversion rate/%
Selectivity/%)
10
100
99.67
20
100
99.64
30
100
99.77
40
100
99.68
50
100
99.58
60
100
99.57
70
100
99.58
80
100
99.70
90
100
99.57
100
100
99.56
110
100
99.71
120
100
99.58
130
100
99.59
140
100
99.55
150
100
99.77
160
100
99.80
170
100
99.69
180
100
99.57
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