CN112657507B

CN112657507B - High-selectivity hydrodechlorination catalyst, and preparation method and application thereof

Info

Publication number: CN112657507B
Application number: CN202011408886.5A
Authority: CN
Inventors: 刘武灿; 李小年; 李玲; 马超峰; 石能富; 卢春山; 聂娟娟
Original assignee: Zhejiang Chemical Industry Research Institute Co Ltd; Zhejiang Lantian Environmental Protection Hi Tech Co Ltd; Sinochem Lantian Co Ltd
Current assignee: Zhejiang Chemical Industry Research Institute Co Ltd; Zhejiang Lantian Environmental Protection Hi Tech Co Ltd; Sinochem Lantian Co Ltd
Priority date: 2020-12-04
Filing date: 2020-12-04
Publication date: 2022-07-08
Anticipated expiration: 2040-12-04
Also published as: CN112657507A

Abstract

The invention discloses a high-selectivity hydrodechlorination catalyst, a preparation method and application thereof, wherein the catalyst comprises the following components in parts by weight: the carrier is activated 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.

Description

High-selectivity hydrodechlorination catalyst, and preparation method and application thereof

Technical Field

The invention relates to the field of catalysts, in particular to a high-selectivity hydrodechlorination catalyst with a core-shell structure, a preparation method thereof, and application of the 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 bimetal composite carbon-supported catalyst, wherein the bimetal 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 hydrodechlorination catalyst with a core-shell structure, which has high activity and high stability, and can obviously improve the selectivity of products when being applied to the hydrodechlorination reaction of fluorochloroalkane.

The purpose of the invention is realized by the following technical scheme:

a high selectivity hydrodechlorination catalyst, the catalyst comprising:

the carrier is activated 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 mainly coated bimetallic particles with a core-shell structure, the core part is active metal, the shell layer is second metal, the active metal and the second metal form coated bimetallic particles, and the non-coated particles exist in the form of active metal single metal particles and second metal single metal particles or alloy particles.

Generally, the active metal and the second metal in the catalyst are supported on the carrier, each in an ionic form, or both form an alloy, whereas the active metal and the second metal in the catalyst of the present invention both exist in a simple substance form, the active metal becomes the core portion in the simple substance form, the second metal becomes the shell portion in the simple substance form, and the active metal and the second metal form the bimetal particles.

Furthermore, the loading capacity of the active metal is 0.05-5.0%, the loading capacity of the second metal is 0.1-8.0%, and the loading capacity of the second metal is not lower than that of the active metal. Preferably, the loading amount of the active metal is 0.1-4.5%, and the loading amount of the second metal is 0.1-5.0%.

Further, the mass ratio of the active metal to the second metal is 1:1 to 6. Preferably, the mass ratio of the active metal to the second metal is 1:1 to 5.

In the high-selectivity hydrodechlorination catalyst, the size of active metal particles at the core part is less than or equal to 65nm, and the thickness of a shell layer is less than or equal to 10 nm. Preferably, the size of the active metal particle at the core part is less than or equal to 55nm, and the thickness of the shell layer is less than or equal to 8.0 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. The surface average particle diameter is calculated as: d_s＝Σn_id_i ³/Σn_id_i ². Wherein n is_iDenotes the diameter d_iThe number of the metal particles is not less than 200.

The carrier of the high-selectivity hydrodechlorination catalyst is granular activated carbon or columnar activated carbon, and the material is selected from coconut shellsWood or coal based activated carbon. Preferably, the specific surface area of the activated carbon carrier is more than or equal to 1000m²The ash content is less than or equal to 3.0wt percent. More preferably, the specific surface area of the activated carbon support is not less than 1100m²The ash content is less than or equal to 2.8wt percent.

The conventional catalyst preparation method cannot obtain a wrapped catalyst structure. The invention provides a preparation method of a high-selectivity hydrodechlorination catalyst with a core-shell structure, which comprises the following steps:

A1. reactive metal particle preparation

Preparing an impregnation liquid of active metal salt according to the loading amount, impregnating for 0.5-10 hours at 25-95 ℃ under ultrasound, and then performing centrifugal separation to obtain active metal particles; the steeping fluid is at least one of ethylene glycol aqueous solution, formaldehyde aqueous solution or glucose aqueous solution;

A2. second metal particle coating

Adding active metal particles and a second metal salt solution configured according to the loading amount into a reducing reagent aqueous solution, introducing hydrogen under stirring, controlling the hydrogen pressure to be 0.1-2.0 MPa, controlling the temperature to be 100-300 ℃, and performing centrifugal separation after 1-10 hours to obtain wrapped bimetallic particles;

A3. bimetallic particle loading

Putting the wrapped bimetallic particles into deionized water, adding an activated carbon carrier under a stirring state, and impregnating, filtering and washing to obtain activated carbon loaded bimetallic particles; the dipping temperature is 20-80 ℃, and the dipping time is 1-10 hours;

A4. drying

Putting the activated carbon loaded bimetallic particles 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;

A5. 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.

And the step A1 is carried out impregnation and reduction under ultrasound, so that the system is uniformly dispersed, and active metal agglomeration is avoided. The ultrasonic frequency is 30-50 kHz, and the power is 300-1000 w.

As a preferred embodiment, the active metal salt is an active metal nitrate or an active metal chloride, more preferably an active metal chloride such as nickel chloride, and a complex of a chloride ion and a noble metal such as [ PdCl [ ]₄]^2-、[PtCl₄]^2-、[IrCl₄]^2-. The content of one or more of the ethylene glycol aqueous solution, the formaldehyde aqueous solution and the glucose aqueous solution as the impregnation liquid is 1 to 20wt%, and more preferably 2 to 18 wt%. The dipping temperature is 35-80 ℃, and the dipping time is 2-8 h. After the impregnation is finished, centrifugal separation is adopted, and the obtained active metal particles are washed to be neutral by deionized water.

In order to promote the wrapping and reduction of the second metal ions, in the step a2, hydrogen gas is introduced into the reducing agent under stirring, preferably, the hydrogen gas is introduced from the bottom of the reactor through a gas distributor; the reactor is preferably a kettle type reactor, magnetons are placed at the bottom of the reactor for stirring, and the stirring speed is preferably 1000-3000 r/min. The second metal salt solution is a second metal nitrate solution or a second metal chloride solution, and the concentration of the solution is 0.1-2.0 mol/L; the reducing agent is at least one of ethylene glycol, sodium borohydride or hydrazine hydrate, the solution of the reducing agent is 5-50 wt% of water solution, and the mass ratio of the reducing agent to the second metal is 1: 20-100. More preferably, the aqueous solution of the reducing agent is 10-40 wt% of an aqueous solution of ethylene glycol, sodium borohydride or hydrazine hydrate, and the mass ratio of the reducing agent to the second metal is 1: 30-90.

In a preferred embodiment, in the step A2, the hydrogen pressure is preferably 0.2 to 1.8MPa, the temperature is controlled to be 150 to 250 ℃, and the reaction is carried out for 2 to 5 hours. And after the reaction is finished, performing centrifugal separation, and washing the obtained coated bimetallic particles to be neutral by using deionized water.

In order to realize uniform loading of the bimetallic particles on the carrier, in the step A3, the wrapped bimetallic particles are firstly placed in deionized water, subjected to ultrasonic treatment for 5-20 minutes and stirred for 1-3 hours to uniformly disperse the bimetallic particles, and then the activated carbon carrier is added under the stirring state, wherein the stirring speed is 1000-3000 r/min. The ratio of the volume of the activated carbon carrier to the total volume of the impregnation liquid is 1: 1-5, and the preferred volume ratio is 1: 2-4.5.

After the bimetallic particles are uniformly loaded on the activated carbon carrier, the bimetallic particles are filtered and washed to be neutral, and further drying and reduction are needed. Preferably, the temperature rise rate in the A4 drying step is 0.8-1.8 ℃/min, the constant-temperature drying is carried out for 2.5-4.5 hours after the temperature is 115-140 ℃, and the space velocity is more than 100h^-1Obtaining a catalyst precursor; in the step A5, heating to 280-430 ℃ at a speed of 0.2-1.9 ℃/min, keeping the temperature for 1-4 hours, and keeping the space velocity higher than 100 hours^-1Obtaining the hydrodechlorination catalyst.

In the high-selectivity hydrodechlorination catalyst prepared by the method, more than or equal to 80 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, more than or equal to 85 percent of active metal particles are in a wrapped bimetallic structure.

The active metal has stronger hydrogen dissociation performance, hydrogen can be dissociated into active hydrogen on active metal particles, and second metal ions are induced to be reduced on the surfaces of the active metal particles, so that a wrapping structure is formed. After the formation of the primary wrapping structure, the hydrogen dissociation performance is reduced, and the difficulty of further deposition of the second metal is gradually increased. Therefore, the invention further adopts the water solution of ethylene glycol, sodium borohydride or hydrazine hydrate as the reducing reagent, and the reducing reagent can show reducibility at high temperature, thereby solving the problem that the deposition difficulty of the second metal is gradually increased, and ensuring that the second metal can be continuously deposited outside the active metal. The invention realizes the preparation of the wrapped high-selectivity hydrodechlorination catalyst under the combined action of the reducing agent and hydrogen.

The present invention also provides the use of any one of the above-mentioned highly selective hydrodechlorination catalysts, which can be used for the hydrodechlorination of chlorofluoroalkanes such as trifluorotrichloroethane, 1,1, 2-trichloro-fluoroethane, and 1, 2-dichlorotetrafluoroethane, and also can be used for the hydrodechlorination of chlorofluoroalkenes 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 high-selectivity hydrogenation dechlorination catalyst is adopted, and trifluorotrichloroethane and hydrogen are used as raw materials to prepare chlorotrifluoroethylene through hydrogenation dechlorination reaction.

Further, the molar ratio of the trifluorotrichloroethane to the hydrogen is 1: 1-4, preferably 1:1 to 3.5.

Further, the reaction temperature is 150-300 ℃, and the space velocity of the raw materials is 10-1200 h^-1(ii) a Preferably, the reaction temperature is 180-290 ℃, and the space velocity of the raw materials is 10-900 h^-1。

Compared with the prior art, the invention has the beneficial effects that:

1. in the preparation process of the hydrodechlorination catalyst, the wrapped bimetallic particles are formed firstly, and then the wrapped bimetallic particles are loaded on the activated carbon carrier, so that the size control of the metal particles and the generation of a wrapped structure are facilitated, and more than 80% of the active metal particles in the prepared hydrodechlorination catalyst are in the wrapped bimetallic structure.

2. 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.

3. 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.

Drawings

FIG. 1 is a TEM representation of the highly selective hydrodechlorination catalyst obtained in example 1 according to 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.

Example 1

Preparation of a hydrodechlorination catalyst:

s1, preparing active metal particles: preparing chloroplatinic acid aqueous solution according to the load amount of 1.5 wt%, adding ethylene glycol aqueous solution of 5.0 wt%, performing ultrasonic impregnation at 35 ℃, 30kHz of ultrasonic frequency and 300w of power, performing centrifugal separation after ultrasonic impregnation for 1 hour, and washing (washing for multiple times) with deionized water to be neutral to obtain active metal particles;

s2, wrapping second metal particles: adding active metal particles and a copper chloride solution prepared according to a loading amount of 2.0 wt% into a 25 wt% ethylene glycol solution, wherein the mass ratio of ethylene glycol to a second metal is 1:30, and the concentration of a second metal salt is 0.1 mol/L; introducing hydrogen under stirring at 3000r/min, maintaining hydrogen pressure at 2.0MPa, controlling temperature at 200 deg.C, reacting for 5 hr, centrifuging, washing with deionized water (multiple times) to neutrality to obtain coated bimetallic particles;

s3, loading of bimetallic particles: putting the coated bimetallic particles into deionized water, performing ultrasonic treatment for 5 minutes, stirring at 3000r/min for 1 hour, and adding an activated carbon carrier (wood, with a specific surface area of 1200 m) which is washed clean by deionized water²The volume ratio of the activated carbon carrier to the impregnation liquid is 1:5, the activated carbon carrier is impregnated for 3 hours at 80 ℃, the activated carbon carrier is filtered and washed to be neutral by deionized water, and the activated carbon-loaded bimetallic particles are obtained (sealed preservation);

s4, drying: placing the activated carbon loaded bimetallic particles in a tube furnace under the nitrogen atmosphere (the space velocity is 300 h)^-1) The catalyst precursor was obtained by drying at a constant temperature for 2 hours at a rate of 0.5 ℃/min from room temperature to 150 ℃.

S5, stillOriginal: the obtained catalyst precursor was placed under a hydrogen atmosphere (space velocity 300 h)^-1) And raising the temperature from room temperature to 250 ℃ at the speed of 0.1 ℃/min, and keeping the temperature for 1 hour 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, 85% of active metal particles in the hydrodechlorination catalyst prepared by the implementation method are in a wrapped bimetallic structure.

Example 2

The operation of this example is the same as example 1 except that: the loading of the active metal was reduced to 1.0% and the loading of the second metal was reduced to 1.5% and a hydrodechlorination catalyst was prepared and designated cat 2.

According to TEM, 82% of active metal particles in the hydrodechlorination catalyst prepared by the implementation method are in a wrapped bimetallic structure.

Example 3

The operation of this example is the same as example 1 except that: the loading of the active metal was 1.5% and the loading of the second metal was reduced to 4.5% to produce a hydrodechlorination catalyst, designated cat 3.

According to TEM representation, in the hydrodechlorination catalyst prepared by the method, 94% of active metal particles are in a wrapped bimetallic structure.

Example 4

The operation of this example is the same as example 1 except that: the active metal is platinum and the second metal is changed into zinc. The hydrodechlorination catalyst was prepared and is designated as cat 4.

According to TEM, 95% of active metal particles in the hydrodechlorination catalyst prepared by the implementation method are in a wrapped bimetallic structure.

Example 5

The operation of this example is the same as example 1 except that: the active metal is changed into nickel, and the second metal is changed into zinc. The hydrodechlorination catalyst was prepared and is designated as cat 5.

According to TEM, 88% of active metal particles in the hydrodechlorination catalyst prepared by the implementation method are in a wrapped bimetallic structure.

Example 6

The operation of this example is the same as example 1 except that: the active metal solution (active metal precursor) is palladium nitrate and the second metal solution is zinc chloride. The hydrodechlorination catalyst was prepared and is designated as cat 6.

According to TEM, 89% of active metal particles in the hydrodechlorination catalyst prepared by the implementation method are in a wrapped bimetallic structure.

Example 7

The operation of this example is the same as example 1 except that: the active metal solution (active metal precursor) used chloropalladite and the second metal solution used zinc nitrate. The hydrodechlorination catalyst was prepared and is designated as cat 7.

According to TEM, 87% of active metal particles in the hydrodechlorination catalyst prepared by the implementation method are in a wrapped bimetallic structure.

Example 8

The operation of this example is the same as example 1 except that: in the step S1, the dipping temperature was raised to 60 ℃. The hydrodechlorination catalyst was prepared and is designated as cat 8.

According to TEM, 96% of active metal particles in the hydrodechlorination catalyst prepared by the implementation are in a wrapped bimetallic structure.

Example 9

The operation of this example is the same as example 1 except that: in step S1, the dipping time was increased to 6 hours. The hydrodechlorination catalyst was prepared and is designated as cat 9.

According to TEM, 90% of active metal particles in the hydrodechlorination catalyst prepared by the implementation method are in a wrapped bimetallic structure.

Example 10

The operation of this example is the same as example 1 except that: in the step S2, the hydrogen pressure during the reduction of the bimetallic particles was 1.5 MPa. The hydrodechlorination catalyst was prepared and is designated as cat 10.

According to TEM representation, 88% of active metal particles in the hydrodechlorination catalyst prepared by the method are in a wrapped bimetallic structure.

Example 11

The operation of this example is the same as example 1 except that: in step S2, the time for reducing the bimetal particles is reduced to 3 hours. The hydrodechlorination catalyst was prepared and is designated as cat 11.

According to TEM, 94% of active metal particles in the hydrodechlorination catalyst prepared by the preparation method are in a wrapped bimetallic structure.

Example 12

The operation of this example is the same as example 1 except that: in step S2, the temperature is 150 ℃. The hydrodechlorination catalyst was prepared and is designated as cat 12.

Example 13

The operation of this example is the same as example 1 except that: in the step S2, the mass ratio of the ethylene glycol to the second metal is 1: 60. The hydrodechlorination catalyst was prepared and is designated as cat 13.

Example 14

The operation of this example is the same as example 1 except that: in the step S3, the stirring speed was decreased to 2000 r/min. The hydrodechlorination catalyst was prepared and is designated as cat 14.

Example 15

The operation of this example is the same as example 1 except that: in step S3, the stirring time was increased to 2 hours. The hydrodechlorination catalyst was prepared and designated as cat 15.

According to TEM representation, 95% of active metal particles in the hydrodechlorination catalyst prepared by the method are in a wrapped bimetallic structure.

Example 16

The operation of this example is the same as example 1 except that: in step S3, sonication is performed for 15 minutes. The hydrodechlorination catalyst was prepared and is designated as cat 16.

According to TEM, 93% of active metal particles in the hydrodechlorination catalyst prepared by the implementation method are in a wrapped bimetallic structure.

Example 17

The operation of this example is the same as example 1 except that: in the step S3, the ratio of activated carbon to impregnation solution is 1: 3. the hydrodechlorination catalyst was prepared and designated as cat 17.

According to TEM, 92% of active metal particles in the hydrodechlorination catalyst prepared by the implementation method are in a wrapped bimetallic structure.

Example 18

The operation of this example is the same as example 1 except that: the constant temperature drying time in the S4 drying step was increased to 3 hours. The hydrodechlorination catalyst was prepared and is designated as cat 18.

According to TEM, 91% of active metal particles in the hydrodechlorination catalyst prepared by the implementation method are in a wrapped bimetallic structure.

Example 19

The operation of this example is the same as example 1 except that: the temperature rise rate in the drying step of S4 was 1.25 deg.C/min. The hydrodechlorination catalyst was prepared and is designated as cat 19.

Example 20

The operation of this example is the same as example 1 except that: in the step S5, the reduction of the catalyst precursor in a hydrogen atmosphere is performed for a constant temperature of 2 hours. The hydrodechlorination catalyst was prepared and is designated as cat 20.

Example 21

The operation of this example is the same as example 1 except that: in step S5, the temperature increase rate is 1.0 ℃/min. The hydrodechlorination catalyst was prepared and is designated as cat 21.

Example 22

The operation of this example is the same as example 1 except that: in the step S5, the final temperature was 400 ℃. The hydrodechlorination catalyst was prepared and is designated as cat 22.

Comparative example 1

The comparative example was conducted as in example 1 except that: ultrasonic treatment is not adopted in the preparation process of the active metal particles, the prepared catalyst is marked as B1, and 46 percent of the active metal particles are in a wrapped bimetallic structure.

Comparative example 2

The comparative example was conducted as in example 1 except that: in the process of wrapping the second metal particles, the temperature is controlled to be 80 ℃, the prepared catalyst is marked as B2, and 42 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: in the process of wrapping the second metal particles, the temperature is controlled to be 350 ℃, the prepared catalyst is marked as B3, and 51 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 process of wrapping the second metal particles, no hydrogen is introduced, the prepared catalyst is marked as B4, and 41% of active metal particles are in a wrapped bimetallic structure.

Comparative example 5

The comparative example was conducted as in example 1 except that: in the process of wrapping the second metal particles, no glycol solution is added, the prepared catalyst is marked as B5, and 58% of active metal particles are in a wrapped bimetallic structure.

Comparative example 6

The comparative example was conducted as in example 1 except that: in the second metal particle coating process, methanol is used to replace ethylene glycol solution, the prepared catalyst is marked as B6, and 43% of active metal particles are in a coating type bimetal structure.

Comparative example 7

The comparative example was conducted as in example 1 except that: the S3 bimetal particle loading step was omitted and the prepared catalyst was not loaded with a carrier. The prepared catalyst is recorded as B7, the size of the obtained metal particles is 70-600 nm, the size distribution is uneven, and 59% 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 catalyst precursor obtained was not reduced and the catalyst obtained was prepared and designated B8, with 47% of the active metal particles being in the wrapped bimetallic structure.

Comparative example 9

Mixing activated carbon carrier (wood, specific surface area 1200 m)²1.5 wt% of ash) is washed by deionized water and immersed in an aqueous solution of palladium chloride acid and copper chloride, the content of palladium and copper is 1.5 percent and 2.0 percent of the active carbon carrier, and the volume ratio of the total volume of the impregnating solution to the active carbon carrier is 5: 1. Stirring, heating to 50 deg.C, soaking for 3 hr, taking out, and oven drying at 110 deg.C for 4 hr.

The drying and reduction steps were performed in the same manner as in example 1.

The prepared catalyst is marked as B9, 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 23

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 (particle size 0.5-1 mm) obtained 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 99.38%.

Examples 24 to 46

Examples 24-46 were performed as in example 23, except that: the catalysts prepared in examples 2-15 and comparative examples 1-9 are used for replacing cat1 to carry out hydrodechlorination reaction.

The hydrogenation product was analyzed by Agilent 7890A gas chromatography, and the results are shown in Table 1 below:

TABLE 1 results of the Trifluorotrichloroethane hydrodechlorination reaction over different catalysts

Examples 47 to 68

The procedure of examples 47 to 68 is the same as that of example 30 except that: cat8 is used as a hydrodechlorination catalyst, and the reaction conditions are changed to carry out 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 under different reaction conditions

Example 69

Example 69 is a stability experiment conducted under the reaction conditions of example 26.

The hydrogenation product was analyzed by Agilent 7890A gas chromatography, and the results are shown in Table 3 below:

TABLE 3 hydrodechlorination stability results

Time/day	Conversion rate/%	Selectivity/%)
			10	100	99.53
20	100	99.74
			30	100	99.72
40	100	99.28
			50	100	99.68
60	100	99.57
			70	100	99.68
80	100	99.70
			90	100	99.68
100	100	99.59
			110	100	99.81
120	100	99.48
			130	100	99.49
140	100	99.55
			150	100	99.67
160	100	99.90
			170	100	99.65
180	100	99.58

Claims

1. A high-selectivity hydrodechlorination catalyst is characterized in that: the catalyst comprises:

the carrier is activated carbon;

a second metal supported on a carrier, the second metal being one selected from 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 preparation method of the catalyst comprises the following steps:

A1. reactive metal particle preparation

Preparing an impregnation liquid of active metal salt according to the loading amount, impregnating for 0.5-10 hours at 25-95 ℃ under ultrasonic waves, and then performing centrifugal separation to obtain active metal particles; the steeping liquid is at least one of ethylene glycol aqueous solution, formaldehyde aqueous solution or glucose aqueous solution;

A2. second metal particle coating

Adding active metal particles and a second metal salt solution configured according to the load amount into a reducing reagent, introducing hydrogen under stirring, controlling the pressure of the hydrogen to be 0.1-2.0 MPa, controlling the temperature to be 100-300 ℃, and performing centrifugal separation after 1-10 hours to obtain coated bimetallic particles; the reducing reagent is at least one of ethylene glycol, sodium borohydride or hydrazine hydrate;

A3. bimetallic particle loading

Putting the coated bimetallic particles into deionized water, adding an activated carbon carrier under a stirring state, and impregnating, filtering and washing to obtain activated carbon-loaded bimetallic particles; the dipping temperature is 20-80 ℃, and the dipping time is 1-10 hours;

A4. drying

A5. reduction of

2. The highly selective hydrodechlorination catalyst according to claim 1, wherein: the loading capacity of the active metal is 0.05-5.0%, the loading capacity of the second metal is 0.1-8.0%, and the loading capacity of the second metal is not lower than that of the active metal.

3. The highly selective hydrodechlorination catalyst according to claim 2, wherein: the mass ratio of the active metal to the second metal is 1:1 to 6.

4. The highly selective hydrodechlorination catalyst according to claim 1, wherein: the size of the active metal particles at the core part is less than or equal to 65nm, and the thickness of the shell layer is less than or equal to 10 nm.

5. The highly selective hydrodechlorination catalyst according to claim 1, wherein: the carrier is granular active carbon or columnar active carbon, and the specific surface area is more than or equal to 1000m²The ash content is less than or equal to 3.0wt percent.

6. A process for the preparation of a highly selective hydrodechlorination catalyst according to any one of claims 1 to 5, wherein: the preparation method comprises the following steps:

A1. reactive metal particle preparation

A2. second metal particle coating

Adding active metal particles and a second metal salt solution configured according to the loading capacity into a reducing reagent, introducing hydrogen under stirring, controlling the hydrogen pressure to be 0.1-2.0 MPa, controlling the temperature to be 100-300 ℃, and performing centrifugal separation after 1-10 hours to obtain wrapped bimetallic particles; the reducing reagent is at least one of ethylene glycol, sodium borohydride or hydrazine hydrate;

A3. bimetallic particle loading

A4. drying the mixture

A5. reduction of

7. The process for preparing a highly selective hydrodechlorination catalyst according to claim 6, wherein: the ultrasonic frequency of the step A1 is 30-50 kHz, and the power is 300-1000 w.

8. The process for preparing a highly selective hydrodechlorination catalyst according to claim 6, wherein: the active metal salt is active metal nitrate or active metal chloride; the second metal salt solution is a second metal nitrate solution or a second metal chloride solution, and the concentration of the second metal nitrate solution or the second metal chloride solution is 0.1-2.0 mol/L.

9. The process for preparing a highly selective hydrodechlorination catalyst according to claim 6, wherein: the mass content of the ethylene glycol aqueous solution, the formaldehyde aqueous solution or the glucose aqueous solution is 1-20 wt%.

10. The process of claim 6, wherein the catalyst is prepared by the following steps: the mass ratio of the reducing agent to the second metal is 1: 20-100.

11. The process for preparing a highly selective hydrodechlorination catalyst according to claim 10, wherein: the reducing agent is 5-50 wt% of reducing agent water solution.

12. The process for preparing a highly selective hydrodechlorination catalyst according to claim 6, wherein: and A3, putting the wrapped bimetallic particles into deionized water, performing ultrasonic treatment for 5-20 minutes, stirring for 0.5-1 hour, and adding an activated carbon carrier under a stirring state.

13. The process for preparing a highly selective hydrodechlorination catalyst according to claim 6, wherein: and washing the product to be neutral by using deionized water after centrifugal separation in the steps A1 and A2.

14. The process for the preparation of the highly selective hydrodechlorination catalyst according to any one of claims 6 to 13, wherein: in the prepared hydrodechlorination catalyst, more than or equal to 80 percent of active metal particles are in a wrapped bimetallic structure.

15. Use of a highly selective hydrodechlorination catalyst according to any one of claims 1 to 5, 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.

16. A continuous preparation method of chlorotrifluoroethylene is characterized in that: the method adopts the hydrodechlorination catalyst with the core-shell structure as in any one of claims 1 to 5, and uses trifluorotrichloroethane and hydrogen as raw materials to prepare chlorotrifluoroethylene through hydrodechlorination reaction.

17. The continuous process for the preparation of chlorotrifluoroethylene according to claim 16, characterized in that: the molar ratio of the trifluorotrichloroethane to the hydrogen is 1:1 to 4.

18. The continuous process for the preparation of chlorotrifluoroethylene according to claim 16, characterized in that: the reaction temperature is 150-300 ℃, and the space velocity of the raw material is 10-1200 h^-1。