Alkyne selective hydrogenation catalyst and method for making same

Abstract

This invention provides a selective hydrogenation catalyst for alkynes and its preparation method. The catalyst support is alumina or primarily alumina; the active components of the catalyst contain at least Pd and Ag, with Pd content of 0.02-0.04% and Ag content of 0.03-0.15% (preferably 0.05-0.15%) based on 100% of the support mass; an organic cage is formed within the catalyst, the distance between the organic cage and the outer surface of the catalyst is within 0.2 mm, and the size of the organic cage is 1.9-2.7 nm, with Pd supported within the organic cage. Using the catalyst of this invention for selective hydrogenation of C2 fractions, the yield of butene can be reduced to less than half that of conventional catalysts.

Description

Technical Field

[0001] This invention relates to a selective hydrogenation catalyst for alkynes and its preparation method, belonging to the field of catalyst preparation technology. Background Technology

[0002] Ethylene, obtained from the steam cracking of petroleum hydrocarbons (such as ethane, naphtha, diesel, and hydrotreated tail oil), contains 0.2%–2.5% acetylene by mass. During polymerization, the acetylene in ethylene reduces the activity of the polymerization catalyst and affects the physical properties of the polymer; therefore, it must be removed. Currently, selective hydrogenation is commonly used industrially to remove acetylene from ethylene, primarily employing noble metal catalysts such as Pd, Pt, and Au. To ensure that the ethylene produced by acetylene hydrogenation and the original ethylene in the feedstock do not undergo further hydrogenation to form ethane, thus preventing ethylene loss, a high hydrogenation selectivity of the catalyst is essential to achieve good economic benefits.

[0003] Post-hydrogenation of C2 catalysts involves calculating the required hydrogen based on the acetylene content and adding it to the hydrogenation feedstock. The molar ratio of hydrogen to acetylene is generally no more than 2. Due to the low hydrogen content, acetylene readily undergoes hydrogenation dimerization, producing a C4 fraction. This C4 fraction further polymerizes to form oligomers with a wider molecular weight range, commonly known as "green oil." This green oil adsorbs onto the catalyst surface and further forms coke, blocking the catalyst pores and preventing reactants from diffusing to the active sites, thus reducing catalyst activity.

[0004] Noble metal catalysts exhibit high activity, but they are prone to generating green oil during use, leading to coking and deactivation, which affects catalyst stability and lifespan. CN200810119385.8 discloses a non-noble metal supported selective hydrogenation catalyst, its preparation method, and its application. The catalyst includes a support and a main active component and a co-active component supported on that support. The main active component is Ni, and the co-active component is selected from at least one of Mo, La, Ag, Bi, Cu, Nd, Cs, Ce, Zn, and Zr. Both the main active component and the co-active component exist in amorphous form with an average particle size <10 nm. The support is a non-oxidizing porous material. The catalyst is prepared using a microemulsion method.

[0005] US4404124 describes a selective hydrogenation catalyst with a shell distribution of active components prepared via a stepwise impregnation method. This catalyst can be applied to the selective hydrogenation of C2 fractions to eliminate acetylene from ethylene. US5587348 describes a high-performance C2 hydrogenation catalyst prepared using alumina as a support, with the addition of silver and palladium co-catalysts, and the addition of fluorine chemically bonded to alkali metals. This catalyst exhibits characteristics such as reduced green oil formation, improved ethylene selectivity, and reduced formation of oxygen-containing compounds.

[0006] CN1736589 reports a Pd / γ-Al2O3 selective hydrogenation catalyst prepared by a complete adsorption impregnation method, but the catalyst generates a large amount of green oil during use. CN200810114744.0 discloses an unsaturated hydrocarbon selective hydrogenation catalyst and its preparation method. This catalyst uses alumina as a support and palladium as the active component. The catalyst's resistance to impurities and coking is improved by adding rare earth and alkaline earth metals and fluorine, but its selectivity is not ideal.

[0007] The catalysts prepared by the above methods all use catalysts with a single pore size distribution. In fixed-bed reactions, the selectivity of the catalysts is poor due to the influence of internal diffusion. Supports with a bimodal pore distribution can improve catalyst selectivity while ensuring high activity, as the presence of large pores can reduce the influence of internal diffusion. ZL971187339 discloses a hydrogenation catalyst with a honeycomb support, which is a large-pore support and effectively improves the catalyst selectivity. CN1129606A discloses a hydrocarbon conversion catalyst, whose support catalyst includes alumina, nickel oxide, iron oxide, etc. This catalyst includes two types of pores: one to improve the catalytic reaction surface and the other to facilitate diffusion. CN101433842A discloses a hydrogenation catalyst characterized by a bimodal pore distribution. The most probable radius of the small pores is 2-50 nm, and the most probable radius of the large pores is 100-500 nm. Due to the bimodal pore distribution, the catalyst exhibits both good hydrogenation activity and good selectivity, resulting in a large increase in ethylene production.

[0008] In the C2 hydrogenation reaction, the formation of green oil and coking of the catalyst are important factors affecting catalyst lifespan. The catalyst's activity, selectivity, and lifespan constitute its overall performance. While the methods listed above offer good pathways to improve catalyst activity and selectivity, they do not solve the problem of catalyst coking, or they address the issues of green oil formation and coking but not selectivity. Although macroporous supports can improve selectivity, the larger molecules generated by polymerization and chain growth reactions can easily accumulate in the macropores of the support, causing catalyst coking and deactivation, thus affecting catalyst lifespan.

[0009] In the selective hydrogenation of C2, when Pd is the main active component, in the traditional impregnation process for catalyst preparation, Pd is used as the active component. 2+ Or [PdCl4] 2- Pd is ionicly bound to the support, and during activation, it aggregates to become active sites. Since the aggregation of Pd during activation is a kinetically governed stochastic process, the size of each active site is difficult to control beforehand.

[0010] Previous studies have found that the selective hydrogenation process of acetylene involves the following steps: first, an acetylene molecule combines with one hydrogen atom to form a vinyl group; the vinyl group then combines with another hydrogen atom to form ethylene; or two vinyl groups couple to form butadiene. Since butadiene can undergo a series of polymerization reactions to form green oil and then coke, inhibiting butadiene formation becomes crucial to preventing coking of C2 selective hydrogenation catalysts.

[0011] Clearly, if two vinyl groups form simultaneously on a single catalyst active site, the probability of butadiene formation increases significantly. Studies have also found that larger active site sizes lead to higher butadiene yields. To prevent large active site sizes, there are generally two approaches: reducing the amount of active component or expanding the dispersion region of the active component. However, reducing the loading of the active component may result in insufficient active sites, leading to inadequate hydrogenation activity, incomplete acetylene removal, substandard hydrogenation products, and substantial economic losses.

[0012] The expansion of the active component loading area means that some active centers are not located near the catalyst surface, resulting in poor catalyst selectivity and significant ethylene loss during hydrogenation.

[0013] To prepare catalysts with narrow particle size distributions, researchers have recently synthesized a series of three-dimensional organic cages. These organic cages, with fixed sizes, can be used to immobilize metals, thereby preparing catalysts with highly dispersed metal clusters. Qiang Song et al. synthesized three-dimensional organic cages, reporting in "Three-dimensional hydrophobic porous organic polymers confined Pd nanoclusters for phase-transfer catalytic hydrogenation of nitroarenes in water" the use of palladium supported on organic cages for the hydrogenation of nitrobenzene. Currently, these three-dimensional organic cages, after loading the active component, are used for total hydrogenation or homogeneous hydrogenation, either in solution or uniformly distributed on a support. However, for selective hydrogenation, not only does the size of the active center affect the reaction, but the distribution of the active component in the catalyst also significantly influences the reaction results. Catalysts with uniformly distributed active components are not suitable for selective hydrogenation reactions.

[0014] Currently, there is much research on noble metal single-atom catalysts for hydrogenation reactions. However, for the hydrogenation of alkynes, there is still a considerable gap between these catalysts and practical applications. This is because the active center of the hydrogenation reaction requires two processes: first, the activation of the alkyne molecule, where the electron pair of the alkyne double bond enters the empty orbitals of the active center atom, and the active center atom feeds the electron pair back to the antibonding orbitals of the alkyne molecule, causing the double bond energy to decrease, the double bond to be activated, and broken; simultaneously, the hydrogen molecule also requires the same process to be activated into hydrogen atoms. For single-atom active centers, due to the limited physical size of a single atom, completing these two processes simultaneously is difficult, resulting in a slow reaction process that is difficult to meet the requirements of practical applications. Therefore, it is natural for active neutrals to have a certain physical size. In fact, for palladium catalysts, because their internal stacking structure can absorb a large amount of hydrogen, the activation of hydrogen and the transfer of hydrogen atoms are completed within the palladium stacking structure, thus their activity is higher than that of active components that can only adsorb hydrogen on the surface.

[0015] ZL101433842A discloses a hydrogenation catalyst characterized by a bimodal pore distribution. The most probable radius of the micropores is 2-50 nm, while that of the macropores is 100-500 nm. Due to this bimodal pore distribution, the catalyst exhibits both good hydrogenation activity and good selectivity, resulting in a large increase in ethylene production. However, this technology has its drawbacks compared to the present invention: the main active component of the catalyst is supported by a solution method, resulting in high dispersion. During calcination, the aggregation of the active component is a kinetically controlled random process, leading to a wide distribution of active center sizes. The optimal activity and selectivity are achieved when the active center size is between 2-3 nm. However, controlling the active center size to 2-3 nm using a simple calcination process is difficult. Some active centers are too small and lack hydrogenation activity; others are too large, resulting in good hydrogenation activity but poor selectivity. Summary of the Invention

[0016] To address the aforementioned technical problems, the present invention aims to provide a selective hydrogenation catalyst for alkynes and a method for its preparation, wherein the catalyst has a low butadiene yield or butene yield.

[0017] To achieve the above objectives, the present invention provides a selective hydrogenation catalyst for alkynes, wherein the catalyst support is alumina or mainly alumina;

[0018] The active components of the catalyst contain Pd and Ag. Based on the mass of the support (100%), the content of Pd is 0.02-0.04% and the content of Ag is 0.03-0.15% (preferably 0.05-0.15%).

[0019] An organic cage is formed in the catalyst, the distance between the organic cage and the outer surface of the catalyst is within 0.2 mm, the size of the organic cage is 1.9-2.7 nm, and the Pd is supported in the organic cage.

[0020] The catalyst of this invention synthesizes in situ, on the outer surface of a support, an organic cage with a regular structure, the size of which is 1.9-2.7 nm. Active components are loaded within these organic cages. Due to the limitation of the organic cage size, the size of the active centers is also within the range of 1.9-2.7 nm, and is uniform in size. This satisfies the activity requirements while avoiding excessively large active centers, reducing the probability of forming two vinyl groups simultaneously in one active center.

[0021] In the catalyst of this invention, Ag can form an alloy with Pd to improve the selectivity of acetylene hydrogenation. Specifically, Ag has two functions: First, silver atoms separate palladium atoms, increasing the spatial distance between adsorbed acetylene molecules. Consequently, the reaction intermediates after acetylene hydrogenation are more spaced apart, preventing them from forming strongly adsorbed acetylene species and thus forming vinyl groups. This reduces the coupling of intermediates and decreases the formation of green oil, a phenomenon known as geometric interaction. Second, the outer S electrons of silver enter the empty orbitals of palladium, reducing the adsorption of ethylene by palladium, a phenomenon known as electronic interaction.

[0022] According to a specific embodiment of the present invention, preferably, the specific surface area of ​​the catalyst is 15-40 m². 2 / g.

[0023] According to a specific embodiment of the present invention, preferably, the alumina in the support is in the θ, α or mixed crystal form; the alumina content in the catalyst support is above 80%.

[0024] According to a specific embodiment of the present invention, preferably, the carrier further contains other metal oxides, such as titanium oxide and / or magnesium oxide.

[0025] This invention also provides a method for preparing the above-mentioned catalyst, which mainly includes the following processes:

[0026] (1) A polar polymer is formed in the carrier, which occupies more than 80% of the pore volume of the carrier;

[0027] (2) In situ synthesis of organic cages within the remaining pores of the carrier;

[0028] (3) Loading the active component palladium in an organic cage;

[0029] (4) Calcination to decompose the organic polymer synthesized in step (1);

[0030] (5) Load silver as an active component to obtain the desired catalyst.

[0031] According to a specific embodiment of the present invention, preferably, the above preparation method includes the following specific steps:

[0032] (1) A hydrophilic polymerizable monomer is mixed with a calcined support and polymerized at a certain temperature to obtain a first semi-finished catalyst, wherein the volume of the polymer synthesized from the hydrophilic monomer is 80-95% of the pore volume of the support.

[0033] (2) Take tris(4-formylphenyl)amine and haloacetic acid, dissolve them in haloalkanes, and then mix them with the first semi-finished catalyst. Stir and add dropwise the mixed solution of phenyldiamine substituted product and haloalkanes. Let the mixture stand until the reaction is complete, pour off the residual liquid, wash it with alcohol and deionized water respectively, and dry it to obtain the second semi-finished catalyst.

[0034] The molar ratio of the phenyl diamine derivative to tris(4-formylphenyl)amine is 1.2-2:1, and the mass ratio of tris(4-formylphenyl)amine to haloacetic acid is 2000-6000:1.

[0035] (3) Dissolve the organopalladium compound in an organic solvent to obtain a palladium precursor solution, wherein the mass ratio of the organopalladium compound to tris(4-formylphenyl)amine is 0.63-4.8:1;

[0036] (4) Immerse the second semi-finished catalyst in an alcohol solution, add the palladium precursor solution dropwise to the mixture of the second semi-finished catalyst and alcohol, stir at the same time, add the reducing agent dropwise, heat and stir, wait until the surface of the second semi-finished catalyst no longer changes color, pour off the solution, wash with deionized water, dry, and calcine at the temperature at which the polymer synthesized in step (1) can be decomposed to obtain the third semi-finished catalyst.

[0037] (5) Dissolve soluble silver salt in deionized water or organic solvent to obtain silver-containing impregnation solution. Immerse the third semi-finished product catalyst in silver-containing impregnation solution and let it stand after complete absorption.

[0038] Silver is reduced by adding a reducing agent, the solution is decanted, washed with deionized water, and dried to obtain the catalyst; or, without reduction, the solution is decanted, washed with deionized water, dried, and calcined to obtain the catalyst.

[0039] According to a specific embodiment of the present invention, in order to ensure that the organic cage is located on the outer surface of the carrier, the present invention first occupies the pores inside the carrier with other media, so that the organic cage is synthesized in the pores near the outer surface. Moreover, the present invention does not limit the specific type of monomer used to synthesize the organic cage, as long as the size of the synthesized organic cage is between 1.9-2.7 nm. Preferably, in step (1), the hydrophilic polymerizable monomer is a monomer containing carbonyl and / or carboxyl groups and capable of polymerization or condensation reaction, more preferably including lactic acid, acrylic acid or formaldehyde.

[0040] According to a specific embodiment of the present invention, the certain temperature in step (1) refers to the temperature at which the monomer undergoes thermal condensation reaction or bulk polymerization, which varies depending on the monomer and is generally 80-200℃.

[0041] According to a specific embodiment of the present invention, the carrier in step (1) can be spherical, cylindrical, clover-shaped, four-leaf clover-shaped, etc.

[0042] According to a specific embodiment of the present invention, preferably, in step (2), the phenyl diamine is biphenyl diamine or a substitute thereof, and more preferably, the phenyl diamine is biphenyl diamine or a substitute thereof, wherein the substituent of the substitute is preferably halogen or alkyl.

[0043] According to a specific embodiment of the present invention, haloacetic acid is a catalyst for the reaction of tris(4-formylphenyl)amine with phenyldiamine. Preferably, in step (2), the haloacetic acid includes fluoroacetic acid or chloroacetic acid, and more preferably trifluoroacetic acid or dichloroacetic acid.

[0044] According to a specific embodiment of the present invention, the haloalkane is the solvent required for the reaction. Preferably, in step (2), the haloalkane includes fluoroalkane, chloroalkane or bromoalkane, preferably halomethane or haloethane, more preferably dichloroethane or trichloromethane.

[0045] According to a specific embodiment of the present invention, preferably, in step (3), the organopalladium compound includes one or a combination of two or more of palladium acetate, palladium lactate and palladium acetylacetonate.

[0046] According to a specific embodiment of the present invention, preferably, in step (4), the alcohol includes ethanol or methanol, more preferably ethanol.

[0047] According to a specific embodiment of the present invention, preferably, in steps (4) and (5), the reducing agent is a reducing compound, more preferably one or a combination of two or more of methanol, formaldehyde, formic acid, ethanol, acetaldehyde, and hydrazine hydrate.

[0048] According to a specific embodiment of the present invention, preferably, in step (5), the soluble silver salt is a silver salt soluble in water or an organic solvent, preferably silver nitrate soluble in water and / or silver acetylacetonate soluble in an organic solvent. The silver is loaded by a solution method, such as saturated impregnation.

[0049] According to a specific embodiment of the present invention, in step (5), when silver is loaded and no reduction is performed, an oxidized catalyst can be prepared by calcination at a temperature below 450°C.

[0050] The present invention also provides a selective hydrogenation process for C2 fraction, which is carried out using the above-mentioned catalyst.

[0051] In traditional C2 fraction selective hydrogenation catalysts, the selective hydrogenation of acetylene occurs at the Pd-based main active center. During catalyst preparation, activation is a high-temperature calcination process, during which the metal salt typically decomposes into metal oxides, which then form clusters. However, the aggregation of active components during calcination is a random process, resulting in the formation of mostly normally distributed active centers with a size of 1-3 nm. Small-sized active centers result in insufficient activity; large-sized centers can easily lead to the simultaneous formation of two vinyl groups, further forming butadiene.

[0052] This invention reveals that, as long as the amount and loading conditions of the active component remain constant, changing the reaction temperature and the amount of hydrogen results in a relatively constant amount of butadiene produced relative to the amount of acetylene introduced into the reaction. This indicates that the distribution of the size of the active centers is indeed influenced by statistical laws. In actual reactions, because butadiene undergoes hydrogenation, the measured results show that butene is predominantly or entirely produced.

[0053] Therefore, the catalyst provided by this invention has active centers with uniform size distribution, which can reduce the formation of by-products and further extend the catalyst's operating time under high selectivity, which is of great significance for the selective hydrogenation process of C2 fraction.

[0054] The catalyst provided by this invention has the following characteristics: Because palladium is supported within an organic cage, the size of the active center formed by palladium is limited by the physical size of the cage. This size satisfies the activity requirements for acetylene selectivity, but greatly reduces the probability of simultaneously forming two vinyl groups at one active center, reducing the butene yield to less than half that of conventional catalysts. This catalyst can be applied to the selective hydrogenation of acetylene in C2 fractions. Furthermore, the organic cage is located on the outer surface of the catalyst, avoiding the influence of internal diffusion limitations on the catalytic reaction, resulting in excellent catalyst selectivity. Using the catalyst of this invention in the selective hydrogenation process of C2 fractions significantly reduces byproducts, and catalyst regeneration may not even be necessary. Attached Figure Description

[0055] Figure 1 The pore size of the organic cage synthesized in Example 1 was determined by the BET method. Detailed Implementation

[0056] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0057] The catalyst of this invention was characterized using the following methods during preparation: A BET analyzer (McClone Systems, Inc., USA) was used to measure the specific surface area and pore size distribution. The contents of Pd and Ag in the catalyst were determined using an A240FS atomic absorption spectrometer.

[0058] Raw materials: Tris(4-formylphenyl)amine, dichloroacetic acid, dichloroethane, benzidine, hydrazine hydrate, ethanol, methanol, acetic acid, formic acid, formaldehyde, lactic acid, acrylic acid, palladium acetate, palladium acetylacetone, silver nitrate, analytical grade, Shanghai Guoyao Group Co., Ltd.; alumina, Shandong Aluminum Group Co., Ltd.

[0059] Example 1

[0060] This embodiment provides a catalyst, wherein:

[0061] Catalyst support: Commercially available spherical alumina support with a diameter of 4 mm was used. After calcination at 1050℃ for 4 hours, the pore volume was 0.6 μm. 3 / g, with a specific surface area of ​​40.15m². 2 / g. Weigh 100g of the carrier.

[0062] Catalyst preparation:

[0063] (1) Weigh 60g of lactic acid and mix it with 100g of calcined support. Keep the temperature at 160℃ for 10 hours to obtain semi-finished catalyst A.

[0064] (2) Take 31.7 mg of tris(4-formylphenyl)amine and 0.0158 mg of dichloroacetic acid, dissolve them in 50 ml of dichloroethane, and then mix them with semi-finished catalyst A. Stir and add a mixed solution of 34.65 mg of p-phenylenediamine and 10 ml of dichloroethane. Let the mixture stand at room temperature for 200 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain semi-finished catalyst B.

[0065] (3) Dissolve 0.042 g of palladium acetate in 50 mL of glacial acetic acid until the palladium acetate is completely dissolved and set aside.

[0066] (4) Immerse the semi-finished catalyst B in 50 mL of ethanol solution with a concentration of 30% or higher, add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst B and ethanol, stir at the same time, add 20 mL of ethanol solution with a concentration of 30% or higher dropwise to the mixture, stir at 70°C for 1 hour, pour off the solution, wash with deionized water, dry at 120°C, and calcine at 280°C for 8 hours to obtain semi-finished catalyst C;

[0067] (5) Weigh 0.047g of silver nitrate and dissolve it in 57g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst C in the impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours. Then add 5ml of 5% hydrazine hydrate solution to the above solution. Stir at room temperature for 1 hour, pour off the solution, wash with deionized water, and dry at 120℃ to obtain the desired catalyst.

[0068] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Example 1 was 0.02% and the Ag content was 0.03%.

[0069] The pore size results of the organic cage synthesized in Example 1, determined by the BET method, are as follows: Figure 1 As shown. By Figure 1 It can be seen that the maximum pore size is 2.43 nm and the minimum pore size is 1.95 nm.

[0070] Comparative Example 1

[0071] This comparative example provides a catalyst, wherein:

[0072] Catalyst support: The support used in Example 1 is adopted.

[0073] Catalyst preparation: The preparation conditions were the same as in Example 1, except that step (1) in Example 1 was omitted;

[0074] (1) Take 31.7 mg of tris(4-formylphenyl)amine and 0.0158 mg of dichloroacetic acid, dissolve them in 50 ml of dichloroethane, then mix them with the support, stir and add dropwise a mixed solution of 34.65 mg of p-phenylenediamine and 10 ml of dichloroethane, let the mixture stand at room temperature for 200 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain the semi-finished catalyst A1;

[0075] (2) Dissolve 0.042 g of palladium acetate in 50 ml of glacial acetic acid until the palladium acetate is completely dissolved and set aside.

[0076] (3) Immerse the semi-finished catalyst A1 in 50 ml of ethanol solution with a concentration of 30% or higher, add the solution prepared in step (2) dropwise to the mixture of semi-finished catalyst A1 and ethanol, stir at the same time, add 20 ml of ethanol solution with a concentration of 30% or higher dropwise to the mixture, stir at 70°C for 1 hour, decant the solution, wash with deionized water, dry at 120°C, and calcine at 280°C for 8 hours to obtain semi-finished catalyst B1;

[0077] (4) Weigh 0.047 g of silver nitrate and dissolve it in 57 g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst B1 in the impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours. Then add 5 ml of 5% hydrazine hydrate solution to the above solution. Stir at room temperature for 1 hour, pour off the solution, wash with deionized water, and dry at 120 °C to obtain the comparative catalyst 1.

[0078] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Comparative Example 1 was 0.02% and the Ag content was 0.03%.

[0079] Example 2

[0080] This embodiment provides a catalyst, wherein:

[0081] Carrier: Commercially available spherical alumina carrier with a diameter of 3 mm was used. After calcination at 1150℃ for 4 hours, the water absorption rate and pore volume were 0.65 m³ / s. 3 / g, with a specific surface area of ​​15.07m². 2 / g. Weigh 100g of the carrier.

[0082] Catalyst preparation:

[0083] (1) Weigh 76.38g of lactic acid and mix it with 100g of calcined support. Keep the temperature at 200℃ for 1 hour to obtain semi-finished catalyst D;

[0084] (2) Take 8.33 mg of tris(4-formylphenyl)amine and 0.0014 mg of trifluoroacetic acid, dissolve them in 50 ml of dichloroethane, and then mix them with the semi-finished catalyst D. Stir and add a mixed solution of 5.46 mg of p-phenylenediamine and 10 ml of dichloroethane. Let the mixture stand at room temperature for 100 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain the semi-finished catalyst E.

[0085] (3) Dissolve 0.115g of palladium acetylacetonate in 50ml of chloroform and wait for it to dissolve completely before use.

[0086] (4) Immerse the semi-finished catalyst E in 50 ml of ethanol solution with a concentration of 30% or higher. Add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst E and ethanol while stirring. Then add 10 ml of formaldehyde solution with a concentration of about 40% dropwise to the mixture. Stir at 60°C for 1 hour, pour off the solution, wash with deionized water, dry at 120°C, and calcine at 300°C for 2 hours to obtain semi-finished catalyst F.

[0087] (5) Weigh 0.24g of silver nitrate and dissolve it in 68g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst F in the impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours, pour off the solution, wash with deionized water, dry at 120℃, and calcine at 500℃ for 4 hours to obtain the desired oxidized catalyst.

[0088] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Example 2 was 0.04% and the Ag content was 0.15%.

[0089] Catalyst reduction: Before use, place the oxidized catalyst in hydrogen gas and reduce it at 120°C for 4 hours with a hydrogen space velocity of 100 h⁻¹. -1 .

[0090] Comparative Example 2

[0091] This comparative example provides a catalyst, wherein:

[0092] Carrier: The same carrier as in Example 2 was used.

[0093] Catalyst preparation: The preparation conditions are the same as in Example 2, except that the isothermal temperature in step (1) is 260°C;

[0094] (1) Weigh 74.66g of lactic acid and mix it with 100g of calcined support. Keep the temperature at 260℃ for 1 hour to obtain semi-finished catalyst D1.

[0095] (2) Take 8.33 mg of tris(4-formylphenyl)amine and 0.0014 mg of trifluoroacetic acid, dissolve them in 50 ml of dichloroethane, and then mix them with the semi-finished catalyst D. Stir and add a mixed solution of 5.46 mg of p-phenylenediamine and 10 ml of dichloroethane. Let the mixture stand at room temperature for 100 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain the semi-finished catalyst E1.

[0096] (3) Dissolve 0.115g of palladium acetylacetonate in 50ml of chloroform and wait for it to dissolve completely before using it.

[0097] (4) Immerse the semi-finished catalyst E1 in 50 ml of ethanol solution with a content of more than 30%, add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst E1 and ethanol, stir at the same time, add 10 ml of formaldehyde solution with a content of about 40% dropwise to the mixture, stir at 60°C for 1 hour, pour off the solution, wash with deionized water, dry at 120°C, and calcine at 300°C for 2 hours to obtain semi-finished catalyst F1;

[0098] (5) Weigh 0.24g of silver nitrate and dissolve it in 68g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst F1 in the impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours, pour off the solution, wash with deionized water, dry at 120℃, and calcine at 500℃ for 4 hours to obtain the desired oxidized catalyst.

[0099] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Comparative Example 2 was 0.04% and the Ag content was 0.15%.

[0100] Catalyst reduction: Before use, place the oxidized catalyst in hydrogen gas and reduce it at 120°C for 4 hours with a hydrogen space velocity of 100 h⁻¹. -1 .

[0101] Example 3

[0102] This embodiment provides a catalyst, wherein:

[0103] Carrier: Commercially available spherical alumina-titanium oxide carriers were used, with a titanium oxide content of 20% and a diameter of 4 mm. After calcination at 1100℃ for 4 hours, the pore volume was 0.47 μm. 3 / g, with a specific surface area of ​​30.64m². 2 / g. Weigh 100g of the carrier.

[0104] Catalyst preparation:

[0105] (1) Weigh 10.5g acrylic acid, 27.2g water, 0.01g potassium hypophosphite monohydrate, 0.023g copper acetate monohydrate, and 0.16ml of 30% hydrogen peroxide as initiator. After mixing evenly, add 100g of calcined carrier. After the solution is completely absorbed, transfer to a reflux flask and heat to 80℃ with stirring. Keep the temperature constant for 1 hour to obtain semi-finished catalyst H.

[0106] (2) Take 30 mg of tris(4-formylphenyl)amine and 0.0075 mg of trichloroacetic acid, dissolve them in 50 ml of dichloroethane, and then mix them with the semi-finished catalyst H. Stir and add a mixed solution of 9.85 mg of benzidine and 10 ml of trichloroethane. Let the mixture stand at room temperature for 150 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain the semi-finished catalyst J.

[0107] (3) Dissolve 0.0859 g of palladium acetylacetonate in 50 ml of chloroform until the palladium acetylacetonate is completely dissolved and set aside.

[0108] (4) Immerse catalyst J in 50 ml of methanol solution with a content of 80% or more, add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst J and methanol, stir at the same time, add 10 ml of formic acid solution with a content of about 50% dropwise to the above solution, heat and stir at 70°C for 2 hours, pour off the solution, wash with deionized water, dry at 120°C, and calcine at 400°C for 2 hours to obtain semi-finished catalyst K;

[0109] (5) Dissolve 0.16g of silver nitrate in 47g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst K in the impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours. Add 5ml of 10% hydrazine hydrate solution dropwise to the above solution. Stir at room temperature for 1 hour. Pour off the solution, wash with deionized water, and dry at 120℃ to obtain the desired catalyst.

[0110] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Example 3 was 0.03% and the Ag content was 0.1%.

[0111] Comparative Example 3

[0112] This comparative example provides a catalyst, wherein:

[0113] Carrier: The same carrier as in Example 3 was used, namely a commercially available spherical alumina-titanium oxide carrier with a titanium oxide content of 20% and a diameter of 4 mm. After calcination at 1150°C for 4 hours, the pore volume was 0.47 μm. 3 / g, with a specific surface area of ​​30.64m². 2 / g. Weigh 100g of the carrier.

[0114] Catalyst preparation: Catalysts with the same active component content are prepared using traditional methods. The specific process is as follows:

[0115] (1) Weigh 0.5g of palladium chloride, dissolve it in hydrochloric acid, dilute the solution to 47g, adjust the pH to 2.5, mix it with 100g of calcined support, stir until the solution is completely absorbed, dry at 120℃, and calcine at 550℃ to obtain semi-finished catalyst H1.

[0116] (2) Dissolve 0.16g of silver nitrate in 47g of deionized water to obtain an impregnation solution of Ag. Immerse the semi-finished catalyst H1 into the prepared impregnation solution of Ag. After the solution is completely absorbed, let it stand for 4 hours, dry at 120℃, and calcine at 550℃ to obtain the desired catalyst.

[0117] Atomic absorption spectrometry determined that the Pd content in the catalyst prepared in Comparative Example 3 was 0.03% and the Ag content was 0.1%.

[0118] Example 4

[0119] This embodiment provides a catalyst, wherein:

[0120] Carrier: Commercially available toothed spherical alumina-magnesia carrier with a magnesium oxide content of 5% and a diameter of 3 mm was used. After calcination at 1130℃ for 4 hours, the pore volume was 0.52 m³. 3 / g, with a specific surface area of ​​25.67m². 2 / g. Weigh 100g of the carrier.

[0121] Catalyst preparation:

[0122] (1) Weigh 60.88g of lactic acid and mix it with 100g of calcined support. Keep the temperature at 190℃ for 2 hours to obtain semi-finished catalyst M.

[0123] (2) Take 17.8 mg of tris(4-formylphenyl)amine and 0.0059 mg of trifluoroacetic acid, dissolve them in 50 ml of dichloroethane, and then mix them with the semi-finished catalyst M. Stir and add a mixed solution of 14.59 mg of p-phenylenediamine and 10 ml of dichloroethane. Let the mixture stand at room temperature for 180 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain the semi-finished catalyst N.

[0124] (3) Dissolve 74.31 mg of palladium acetate in 50 ml of chloroform until the palladium acetate is completely dissolved and set aside.

[0125] (4) Immerse the semi-finished catalyst N in 50 ml of ethanol solution with a concentration of 30% or higher, add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst N and ethanol, stir at the same time, add 20 ml of methanol solution with a concentration of 80% or higher dropwise to the above solution, stir at 80°C for 1 hour, decant the solution, wash with deionized water, dry at 120°C, and calcine at 400°C for 1 hour to obtain semi-finished catalyst P;

[0126] (5) Dissolve 0.16g of silver nitrate in 47g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst P in the prepared impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours. Then, add 5ml of 5% hydrazine hydrate solution dropwise to the above solution. Stir at room temperature for 1 hour, pour off the solution, wash with deionized water, and dry at 120℃ to obtain the desired catalyst.

[0127] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Example 4 was 0.0357% and the Ag content was 0.12%.

[0128] Comparative Example 4

[0129] This comparative example provides a catalyst in which the catalyst support and preparation conditions are the same as in Example 4, except that the calcination temperature in step (4) is 230°C.

[0130] Catalyst preparation:

[0131] (1) Weigh 60.88g of lactic acid and mix it with 100g of calcined support. Keep the temperature at 190℃ for 2 hours to obtain semi-finished catalyst M1.

[0132] (2) Take 17.8 mg of tris(4-formylphenyl)amine and 0.0059 mg of trifluoroacetic acid, dissolve them in 50 ml of dichloroethane, and then mix them with the semi-finished catalyst M. Stir and add a mixed solution of 14.59 mg of p-phenylenediamine and 10 ml of dichloroethane. Let the mixture stand at room temperature for 180 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain the semi-finished catalyst N1.

[0133] (3) Dissolve 74.31 mg of palladium acetate in 50 ml of chloroform until the palladium acetate is completely dissolved and set aside.

[0134] (4) Immerse the semi-finished catalyst N1 in 50 ml of ethanol solution with a content of 30% or more, add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst N1 and ethanol, stir at the same time, add 20 ml of methanol solution with a content of 80% or more dropwise to the above solution, stir at 80°C for 1 hour, pour off the solution, wash with deionized water, dry at 120°C, and calcine at 230°C for 1 hour to obtain semi-finished catalyst P1;

[0135] (5) Dissolve 0.16g of silver nitrate in 47g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst P1 in the prepared impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours. Then, add 5ml of 5% hydrazine hydrate solution dropwise to the above solution. Stir at room temperature for 1 hour, pour off the solution, wash with deionized water, and dry at 120℃ to obtain the desired catalyst.

[0136] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Comparative Example 4 was 0.035% and the Ag content was 0.12%.

[0137] Example 5

[0138] This embodiment provides a catalyst, wherein:

[0139] The carrier is a spherical alumina-magnesia carrier with a magnesium oxide content of 10% and a diameter of 2 mm. After calcination at 1080℃ for 4 hours, the pore volume is 0.55 μm. 3 / g, with a specific surface area of ​​35.36m². 2 / g. Weigh 100g of the carrier.

[0140] Catalyst preparation:

[0141] (1) Weigh 56.52g of lactic acid and mix it with 100g of calcined support. Keep the temperature at 190℃ for 2 hours to obtain the semi-finished catalyst Q.

[0142] (2) Take 8.59 mg of tris(4-formylphenyl)amine and 0.0027 mg of dichloroacetic acid, dissolve them in 50 ml of dichloroethane, and then mix them with the semi-finished catalyst Q. Stir and add a mixed solution of 7.50 mg of p-phenylenediamine and 10 ml of dichloroethane. Let the mixture stand at room temperature for 190 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain the semi-finished catalyst R.

[0143] (3) Dissolve 71.57 mg of palladium acetylacetonate in 50 ml of benzene and wait for it to dissolve completely before using it.

[0144] (4) Immerse the semi-finished catalyst R in 50 ml of methanol solution with a content of more than 80%, add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst R and methanol, stir at the same time, add 10 ml of formic acid solution with a content of about 50% dropwise to the above solution, stir at 50°C for 1 hour, pour off the solution, wash with deionized water, dry at 120°C, and calcine at 380°C for 1 hour to obtain semi-finished catalyst S;

[0145] (5) Dissolve 0.095g of silver nitrate in 52.25g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst S in the prepared impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours. Then, add 20ml of approximately 50% formic acid solution dropwise to the above solution. Stir at 50°C for 1 hour, pour off the solution, wash with deionized water, and dry at 120°C to obtain the desired catalyst.

[0146] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Example 5 was 0.025% and the Ag content was 0.06%.

[0147] Comparative Example 5

[0148] This comparative example provides a catalyst in which the catalyst support and preparation conditions are the same as in Example 5, except that the amount of tris(4-formylphenyl)amine used in step (2) is twice that in Example 5.

[0149] (1) Weigh 56.52g of lactic acid and mix it with 100g of calcined support. Keep the temperature at 190℃ for 2 hours to obtain semi-finished catalyst Q1.

[0150] (2) Take 8.59 mg of tris(4-formylphenyl)amine and 0.0027 mg of dichloroacetic acid, dissolve them in 50 ml of dichloroethane, and then mix them with the semi-finished catalyst Q. Stir and add a mixed solution of 7.50 mg of p-phenylenediamine and 10 ml of dichloroethane. Let the mixture stand at room temperature for 190 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain the semi-finished catalyst R1.

[0151] (3) Dissolve 71.57 mg of palladium acetylacetonate in 50 ml of benzene and wait for it to dissolve completely before using it.

[0152] (4) Immerse the semi-finished catalyst R1 in 50 ml of methanol solution with a content of more than 80%, add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst R1 and methanol, stir at the same time, add 10 ml of formic acid solution with a content of about 50% dropwise to the above solution, stir at 50°C for 1 hour, pour off the solution, wash with deionized water, dry at 120°C, and calcine at 380°C for 1 hour to obtain semi-finished catalyst S1;

[0153] (5) Dissolve 0.095g of silver nitrate in 52.25g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst S1 in the prepared impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours. Then, add 20ml of approximately 50% formic acid solution dropwise to the above solution. Stir at 50°C for 1 hour, pour off the solution, wash with deionized water, and dry at 120°C to obtain the desired catalyst.

[0154] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Comparative Example 5 was 0.025% and the Ag content was 0.06%.

[0155] Example 6

[0156] This embodiment provides a catalyst, wherein:

[0157] Carrier: Commercially available spherical carriers were used, containing 97% alumina and 3% titanium oxide, with a diameter of 3 mm. After calcination at 1060℃ for 4 hours, the pore volume was 0.52 m³. 3 / g, with a specific surface area of ​​38.75m². 2 / g. Weigh 100g of the carrier.

[0158] Catalyst preparation:

[0159] (1) Weigh 56.44g of lactic acid and mix it with 100g of calcined support. Keep the temperature at 190℃ for 1 hour to obtain the semi-finished catalyst U.

[0160] (2) Take 7 mg of tris(4-formylphenyl)amine and 0.0035 mg of trifluoroacetic acid, dissolve them in 50 ml of dichloroethane, then mix them with the semi-finished catalyst U, stir and add a mixed solution of 4.59 mg of benzidine and 10 ml of monochloroethane dropwise. Let the mixture stand at room temperature for 100 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain the semi-finished catalyst V;

[0161] (3) Dissolve 70 mg of palladium acetate in 50 ml of dichloroethane until the palladium acetate is completely dissolved and set aside.

[0162] (4) Immerse the semi-finished catalyst V in 50 ml of ethanol solution with a concentration of 30% or higher, add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst V and ethanol, stir at the same time, add 30 ml of acetaldehyde solution with a concentration of 50% or higher dropwise to the above solution, stir at 60°C for 1 hour, decant the solution, wash with deionized water, dry at 120°C, and calcine at 370°C for 2 hours to obtain catalyst W;

[0163] (5) Weigh 0.135g of silver nitrate and dissolve it in 54.46g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst W in the prepared impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours. Then add 50ml of acetaldehyde solution with a concentration of 50% or higher to the above solution. Stir at 60°C for 1 hour. Pour off the solution, wash with deionized water, and dry at 120°C to obtain the desired catalyst.

[0164] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Example 6 was 0.0336% and the Ag content was 0.085%.

[0165] Comparative Example 6

[0166] This comparative example provides a catalyst, wherein:

[0167] Support: The same support as in Example 6 was used, and the catalyst was prepared using tris(4-formylphenyl)amine and phenylenediamine.

[0168] Catalyst preparation:

[0169] (1) Weigh 56.44g of lactic acid and mix it with 100g of calcined support. Keep the temperature at 190℃ for 1 hour to obtain semi-finished catalyst U1.

[0170] (2) Take 7 mg of tris(4-formylphenyl)amine and 0.0035 mg of trifluoroacetic acid, dissolve them in 50 ml of dichloroethane, then mix them with the semi-finished catalyst U, stir and add a mixed solution of 4.59 mg of phenylenediamine and 10 ml of monochloroethane dropwise, let the mixture stand at room temperature for 100 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain the semi-finished catalyst V1;

[0171] (3) Dissolve 70.06 mg of palladium acetate in 50 ml of chloroform until the palladium acetate is completely dissolved and set aside.

[0172] (4) Immerse the semi-finished catalyst V1 in 50 ml of ethanol solution with a concentration of 30% or higher. Add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst V1 and ethanol while stirring. Then add 30 ml of acetaldehyde solution with a concentration of 50% or higher to the above solution. Stir at 60°C for 1 hour, pour off the solution, wash with deionized water, dry at 120°C, and calcine at 370°C for 2 hours to obtain semi-finished catalyst W1.

[0173] (5) Weigh 0.135g of silver nitrate and dissolve it in 54.46g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst W1 in the prepared impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours. Then add 50ml of acetaldehyde solution with a concentration of 50% or higher to the above solution. Stir at 60°C for 1 hour. Pour off the solution, wash with deionized water, and dry at 120°C to obtain the desired catalyst.

[0174] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Comparative Example 6 was 0.033% and the Ag content was 0.085%.

[0175] Example 7

[0176] This embodiment provides a catalyst, wherein:

[0177] Carrier: Commercially available spherical alumina carrier with a diameter of 3 mm was used. After calcination at 1150℃ for 4 hours, the pore volume was 0.65 m³. 3 / g, with a specific surface area of ​​15.17m². 2 / g. Weigh 100g of the carrier.

[0178] Catalyst preparation:

[0179] (1) Weigh 74.66g of lactic acid and mix it with 100g of calcined support. Keep the temperature at 210℃ for 2 hours to obtain semi-finished catalyst X.

[0180] (2) Take 27.27 mg of tri(4-formylphenyl)amine and 0.010 mg of trifluoroacetic acid, dissolve them in 50 ml of dichloroethane, and then mix them with semi-finished catalyst X. Stir and add a mixed solution of 32.11 mg of 2-chlorobiphenyldiamine and 10 ml of dichloroethane. Let the mixture stand at room temperature for 120 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain semi-finished catalyst Y.

[0181] (3) Weigh 0.086 g of palladium acetylacetonate and dissolve it in 50 ml of dichloroethane. Wait until the palladium acetylacetonate is completely dissolved and set aside.

[0182] (4) Immerse the semi-finished catalyst Y in 50 ml of ethanol solution with a concentration of 30% or higher, add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst Y and methanol, stir at the same time, add 3 ml of 5% hydrazine hydrate solution dropwise to the above solution, stir at room temperature for 1 hour, pour off the solution, wash with deionized water, dry at 120°C, and calcine at 300°C for 2 hours to obtain semi-finished catalyst Z;

[0183] (5) Weigh 0.21g of silver nitrate and dissolve it in 67.60g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst Z in the prepared impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours. Then add 3ml of 5% hydrazine hydrate solution dropwise to the above solution. Stir at room temperature for 1 hour, pour off the solution, wash with deionized water, and dry at 120℃ to obtain the desired catalyst.

[0184] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Example 7 was 0.03% and the Ag content was 0.13%.

[0185] Comparative Example 7

[0186] This comparative example provides a catalyst, wherein:

[0187] Carrier: The same carrier as in Example 7 was used.

[0188] Catalyst preparation: The preparation conditions are the same as in Example 7, except that the amount of silver nitrate used in step (5) is twice that in Example 7.

[0189] (1) Weigh 74.66g of lactic acid and mix it with 100g of calcined support. Keep the temperature at 210℃ for 2 hours to obtain semi-finished catalyst X1.

[0190] (2) Take 27.27 mg of tri(4-formylphenyl)amine and 0.010 mg of trifluoroacetic acid, dissolve them in 50 ml of dichloroethane, and then mix them with the semi-finished catalyst X. Stir and add a mixed solution of 32.11 mg of 2-chlorobiphenyldiamine and 10 ml of dichloroethane. Let the mixture stand at room temperature for 120 hours, pour off the residue, wash with ethanol and deionized water respectively, and dry to obtain the semi-finished catalyst Y1.

[0191] (3) Weigh 0.086 g of palladium acetylacetonate and dissolve it in 50 ml of dichloroethane. Wait until the palladium acetylacetonate is completely dissolved and set aside.

[0192] (4) Immerse the semi-finished catalyst Y1 in 50 ml of ethanol solution with a concentration of 30% or higher. Add the solution prepared in step (3) dropwise to the mixture of semi-finished catalyst Y1 and methanol while stirring. Then add 3 ml of 5% hydrazine hydrate solution dropwise to the above solution. Stir at room temperature for 1 hour, pour off the solution, wash with deionized water, dry at 120°C, and calcine at 300°C for 2 hours to obtain semi-finished catalyst Z1.

[0193] (5) Weigh 0.42g of silver nitrate and dissolve it in 67.60g of deionized water to obtain an impregnation solution containing Ag. Immerse the semi-finished catalyst Z1 in the prepared impregnation solution containing Ag. After the solution is completely absorbed, let it stand for 4 hours. Then add 3ml of 5% hydrazine hydrate solution dropwise to the above solution. Stir at room temperature for 1 hour, pour off the solution, wash with deionized water, and dry at 120℃ to obtain the desired catalyst.

[0194] Atomic absorption spectrometry analysis revealed that the Pd content in the catalyst prepared in Comparative Example 7 was 0.03% and the Ag content was 0.42%.

[0195] Performance of catalysts in post-hydrogenation reactions of C2

[0196] Evaluation method: The catalyst loading in the fixed-bed single-section reactor was 100 mL (record weight), the packing was 50 mL, the reactant space velocity was 4000 / h, the operating pressure was 2.5 MPa, the hydrogen-to-acetylene ratio was 1.4, and the reactor inlet temperature was 55℃.

[0197] The calculation method for the evaluation results is shown in Table 1.

[0198] Table 1. Calculation method of evaluation results

[0199]

[0200] The initial selectivity is the selectivity measured 24 hours after the reactor starts feeding.

[0201] The initial activity (acetylene conversion rate) is the activity measured 24 hours after the reactor feed begins.

[0202] The composition of the reactants is as follows:

[0203] Acetylene 0.9% (mol / mol), ethylene 82% (mol / mol), ethane 17% (mol / mol), C3 content 0.5% (mol / mol).

[0204] The catalyst evaluation results are shown in Table 2.

[0205] Table 2 Catalyst Evaluation Results

[0206]

[0207]

[0208] The comparison of catalyst evaluation results in Table 2 shows that:

[0209] Compared with Example 1, in Comparative Example 1, since there is no polymer in the inner pores, the active component is distributed in all the spaces of the pores. Due to the diffusion limitation of the gas phase reaction, its acetylene conversion rate and selectivity are not ideal.

[0210] In Comparative Example 2, due to the high temperature in the isothermal stage of step (1), some lactic acid polymerizes and some lactic acid decomposes, but it is not completely decomposed. As a result, most of the organic cages are synthesized on the outside of the support, and a small portion of palladium is loaded inside the support. Although hydrogenation-active atomic clusters are formed during the calcination process, the activity selectivity is poor because some active centers are in the inner pores of the catalyst.

[0211] In Comparative Example 3, due to the use of a traditional catalyst preparation method, the size distribution of its active centers is wide, with some active centers being larger than 3 nm and others being smaller. Therefore, the activity, especially the selectivity, is significantly lower than that of the Example, and the amount of C4 generated is much higher than that of Example 3. After 1000 hours, the catalyst exhibits severe coking.

[0212] In Comparative Example 4, the calcination temperature in step (4) was low, so polylactic acid could not be completely decomposed, which blocked the pores of the catalyst and prevented the reactants from diffusing through the pores, resulting in very low activity.

[0213] In Comparative Example 5, the increased amount of tris(4-formylphenyl)amine led to an increase in the number of organic cages formed, resulting in an excessive number of active centers. Consequently, the size of the palladium active centers supported on a single organic cage decreased, leading to insufficient activity. Furthermore, excessively small active centers may also reduce the activation rate of hydrogen, resulting in insufficient hydrogen during the hydrogenation reaction, leading to the formation of more C4 atoms and a faster decline in catalyst performance.

[0214] In Comparative Example 6, the second monomer was phenylenediamine. The size of the synthesized organic cage was smaller than the optimal active site packing size required for acetylene hydrogenation, resulting in low initial activity. Some palladium could not enter the organic cage and could only be distributed very dispersedly on the support, thus contributing nothing to the catalytic reaction.

[0215] In Comparative Example 7, the silver loading was excessive, and some of the original active sites were covered. Acetylene could not be effectively adsorbed on the catalyst surface. Although the initial selectivity was good, the catalyst activity was obviously insufficient from the beginning.

[0216] The catalyst of this invention, due to its narrow distribution of active center size, falls within the optimal activity range, thus fully utilizing the active components and reducing the loading of precious metals. Furthermore, the reduction in excessively large active centers decreases the likelihood of coupling between the acetylene hydrogenation intermediate and vinyl groups, significantly reducing the amount of green oil generated. The catalyst's operating cycle is also significantly extended.

Claims

1. A selective hydrogenation catalyst for alkynes, wherein, The catalyst is supported on alumina or is primarily alumina. The active components of the catalyst contain Pd and Ag. Based on the mass of the support (100%), the content of Pd is 0.02-0.04% and the content of Ag is 0.03-0.15%. An organic cage is formed in the catalyst, the distance between the organic cage and the outer surface of the catalyst is within 0.2 mm, the size of the organic cage is 1.9-2.7 nm, and the Pd is supported in the organic cage.

2. The catalyst according to claim 1, wherein, The catalyst has a specific surface area of ​​15-40 m². 2 / g.

3. The catalyst according to claim 1 or 2, wherein, The alumina in the support has a θ, α or mixed crystal form; the alumina content in the catalyst support is above 80%.

4. The catalyst according to claim 3, wherein, The carrier also contains other metal oxides.

5. The catalyst according to claim 4, wherein, The other metal oxides are titanium oxide and / or magnesium oxide.

6. The catalyst according to claim 1, wherein, The content of Ag is 0.05-0.15%.

7. A method for preparing the catalyst according to any one of claims 1-6, comprising the following steps: (1) A hydrophilic polymerizable monomer is mixed with a calcined support and polymerized at a certain temperature to obtain a first semi-finished catalyst, wherein the volume of the polymer synthesized from the hydrophilic polymerizable monomer is 80-95% of the pore volume of the support. (2) Mix tris(4-formylphenyl)amine with haloacetic acid, dissolve in haloalkane, then mix with the first semi-finished catalyst, stir and add dropwise a mixed solution of phenyldiamine or its substituted product with haloalkane, let the mixture stand, and after the reaction is complete, pour off the residual liquid, wash with alcohol and deionized water respectively, and dry to obtain the second semi-finished catalyst. The molar ratio of phenyldiamine or its substituted derivatives to tris(4-formylphenyl)amine is 1.2-2:1, and the mass ratio of tris(4-formylphenyl)amine to haloacetic acid is 2000-6000:

1. (3) Dissolve the organopalladium compound in an organic solvent to obtain a palladium precursor solution, wherein the mass ratio of palladium to tris(4-formylphenyl)amine in the organopalladium compound is 0.63-4.8:1; (4) Immerse the second semi-finished catalyst in an alcohol solution, add the palladium precursor solution dropwise to the mixture of the second semi-finished catalyst and alcohol, stir at the same time, add the reducing agent dropwise, heat and stir, and wait until the surface of the second semi-finished catalyst no longer changes color, pour off the solution, wash with deionized water, dry, and calcine at the temperature at which the polymer formed in step (1) can be decomposed to obtain the third semi-finished catalyst. (5) Dissolve the soluble silver salt in deionized water or organic solvent to obtain a silver impregnation solution. Immerse the third semi-finished product catalyst in the silver impregnation solution and let it stand after it is completely absorbed. Silver is reduced by adding a reducing agent, the solution is decanted, washed with deionized water, and dried to obtain the catalyst; or, without reduction, the solution is decanted, washed with deionized water, dried, and calcined to obtain the catalyst.

8. The preparation method according to claim 7, wherein, In step (1), the hydrophilic polymerizable monomer is a monomer containing carbonyl and / or carboxyl groups and capable of undergoing polymerization or condensation reactions.

9. The preparation method according to claim 8, wherein, The hydrophilic polymerizable monomers include acrylic acid, lactic acid, or formaldehyde.

10. The preparation method according to claim 7, wherein, In step (2), the phenyl diamine is biphenyl diamine or a substitute thereof.

11. The preparation method according to claim 10, wherein, The biphenyl diamine or its substituted derivative is p-biphenyl diamine or its substituted derivative.

12. The preparation method according to claim 10 or 11, wherein, The substituents of the substituted compound are halogens or alkyl groups.

13. The preparation method according to claim 7, wherein, In step (2), the haloacetic acid includes fluoroacetic acid or chloroacetic acid.

14. The preparation method according to claim 13, wherein, The haloacetic acid is trifluoroacetic acid or dichloroacetic acid.

15. The preparation method according to claim 7, wherein, In step (2), the haloalkane includes fluoroalkane, chloroalkane or bromoalkane.

16. The preparation method according to claim 15, wherein, The haloalkane is a halomethane or a haloethane.

17. The preparation method according to claim 16, wherein, The haloalkane is dichloroethane or trichloromethane.

18. The preparation method according to claim 7, wherein, In step (3), the organopalladium compound includes one or more of palladium acetate, palladium lactate, and palladium acetylacetonate.

19. The preparation method according to claim 7, wherein, In step (4), the alcohol includes ethanol or methanol.

20. The preparation method according to claim 7, wherein, In steps (4) and (5), the reducing agent is a reducing compound.

21. The preparation method according to claim 20, wherein, The reducing compound is one or a combination of two or more of methanol, formaldehyde, formic acid, ethanol, acetaldehyde, and hydrazine hydrate.

22. The preparation method according to claim 7, wherein, In step (5), the soluble silver salt is a silver salt that is soluble in water or an organic solvent.

23. The preparation method according to claim 22, wherein, The silver salt is silver nitrate and / or silver acetylacetone.

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