Catalyst, process for its preparation and use

Abstract

The application discloses a catalyst and a preparation method and application thereof, and belongs to the technical field of catalysts. The catalyst comprises a catalyst carrier and a transition metal, the loading amount of the transition metal is 1wt%-50wt% based on the mass of the catalyst, the transition metal is dispersed on the catalyst carrier, the particle size of the transition metal is less than or equal to 2.5nm, and the dispersion degree of the transition metal on the catalyst carrier is greater than or equal to 85%. The catalyst provided by the application has small transition metal particle size and uniform dispersion, which is beneficial to improving the active sites of the catalyst and further improving the activity and rate of the catalytic reaction.

Description

Technical Field

[0001] This application belongs to the field of catalyst technology, specifically relating to a catalyst, its preparation method, and its application. Background Technology

[0002] Catalysts can selectively react with macromolecular hydrocarbons, sulfur-containing, nitrogen-containing, oxygen-containing heteroatom compounds, and unsaturated components in heavy oil products to remove impurities, improve oil stability, and increase the yield of light oil.

[0003] In related technologies, catalysts include catalyst supports and transition metals, with the transition metals dispersed in the catalyst support, constituting the active sites of the reaction.

[0004] However, when preparing catalysts using the solution impregnation method, transition metal ions are easily hydrolyzed and agglomerate in the catalyst support, resulting in uneven size of the formed transition metal particles and low dispersion in the catalyst support, which in turn reduces the number of active sites exposed in the catalyst. At the same time, because the agglomerated transition metal particles are large in size, they may block some of the pores of the catalyst support, hindering the mass transfer between reactants and products, and ultimately affecting the efficiency of the reaction. Summary of the Invention

[0005] This application discloses a catalyst, its preparation method, and its application, to solve the problems of uneven transition metal particle size and low dispersion on the catalyst support surface in the prior art.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows: This application provides a catalyst comprising a catalyst support and a transition metal, wherein the transition metal is dispersed on the catalyst support; Based on the mass of the catalyst, the loading of the transition metal is 1wt%~50wt%, the particle size of the transition metal is ≤2.5nm, and the dispersion of the transition metal on the catalyst support is ≥85%.

[0007] In some embodiments, the catalyst further includes a binder that connects adjacent catalyst supports; The catalyst support comprises mesoporous silica or molecular sieve, and the binder comprises at least one of olivine and attapulgite.

[0008] This application also provides a method for preparing a catalyst, comprising: The first catalyst support was pretreated with an alkaline compound to obtain the second catalyst support; A transition metal precursor is reacted with a complexing agent to generate a complex solution; The second catalyst support is impregnated in the complexing solution to obtain the catalyst precursor; The catalyst precursor was calcined and reduced to obtain the catalyst.

[0009] In some embodiments, the first catalyst support is pretreated with an alkaline compound to obtain a second catalyst support, comprising: The alkaline compound is mixed with the first catalyst support and pretreated at a temperature of 40-80°C for 3-6 hours. The pretreated material is filtered, washed until neutral, and dried at 80~120℃ to obtain the second catalyst support, wherein the zeta potential of the second catalyst support is -30~-40mV.

[0010] In some embodiments, the second catalyst support is impregnated in the complexing solution to obtain a catalyst precursor, comprising: The second catalyst support is impregnated in the complexing solution to obtain a catalyst precursor complex; The catalyst precursor complex is mixed with a binder to obtain a catalyst precursor, wherein the binder includes at least one of olivine and attapulgite.

[0011] In some embodiments, the catalyst precursor is calcined and reduced to obtain a catalyst, comprising: The catalyst precursor was calcined at a temperature of 300-350°C for 3-4 hours to obtain a catalyst intermediate. Hydrogen gas is introduced into the catalyst intermediate to carry out a reduction reaction. The reduction reaction temperature is 450~550℃ and the reduction reaction time is 4~5h to obtain the catalyst.

[0012] In some embodiments, the alkaline compound includes at least one selected from ammonia monohydrate, ammonium carbonate, ethylenediamine, and triethylamine; And / or, the first catalyst support comprises mesoporous silica or molecular sieve; And / or, the complexing agent includes at least one of triamine citrate, ethylenediaminetetraacetic acid, and aminotriacetic acid.

[0013] In some embodiments, the molar ratio of the complexing agent to the transition metal ions of the transition metal precursor is (1~4):1; And / or, the mass ratio of the transition metal precursor to the first catalyst support is 1:(1~99).

[0014] In some embodiments, in the mixture of the catalyst precursor complex and the binder, the mass percentage of the catalyst precursor complex is 85% to 95%, and the mass percentage of the binder is 5% to 15%. And / or, when the binder comprises olivine and attapulgite, the mass ratio of the olivine to the attapulgite is (1~1.2):1.

[0015] This embodiment also provides the application of the above-described catalyst or the catalyst prepared by the above-described catalyst preparation method in coal tar, residual oil, biomass or polymers.

[0016] The catalyst in this application includes a catalyst support and a transition metal dispersed on the catalyst support. The transition metal has catalytic activity. Based on the mass of the catalyst, the loading of the transition metal is 1~50wt%, and the dispersion of the transition metal on the catalyst support reaches more than 85%, which improves the utilization efficiency of the transition metal, avoids the reduction of active sites due to transition metal agglomeration, and thus improves the activity, selectivity and stability of the catalyst. Furthermore, when the particle size of the transition metal is controlled below 2.5nm, it is beneficial for it to be dispersed on the surface and in the pores of the catalyst support, thereby exposing more active sites and improving the catalytic efficiency of the catalyst. Furthermore, when the dispersion of the transition metal is high, the amount of transition metal used can be reduced, thereby reducing the cost of the catalyst. Detailed Implementation

[0017] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the fixed scope of this application.

[0018] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0019] This application provides a catalyst comprising a catalyst support and a transition metal. Based on the mass of the catalyst, the loading of the transition metal is 1 wt% to 50 wt%, and the transition metal is dispersed in the catalyst support. The particle size of the transition metal is ≤2.5 nm, and the dispersion of the transition metal in the catalyst support is ≥85%.

[0020] In this embodiment, the catalyst includes a catalyst support and a transition metal dispersed on the catalyst support. The transition metal is derived from a transition metal precursor and has catalytic activity, specifically dispersed on the surface and within the pores of the catalyst support.

[0021] In this embodiment, the transition metal serves as an active site for a series of reactions, including hydrogenation, hydrodesulfurization, and hydrodenitrogenation, involving saturated aromatics, carbon-carbon double bonds, carbonyl groups, aldehyde groups, and unsaturated alkanes. When the loading of the transition metal is 1 wt% to 50 wt%, it provides sufficient active sites, improving reaction activity and efficiency, while avoiding the problems of reduced dispersion and fewer active sites caused by agglomeration due to excessive loading. Exemplarily, the transition metal includes at least one of nickel, copper, cobalt, and tungsten. The preferred loading of the transition metal is 20 wt% to 50 wt%, more preferably 25 wt% to 40 wt%.

[0022] It should be noted that when the dispersion of transition metals on the catalyst support reaches more than 85%, the utilization efficiency of transition metals is improved, and the number of active sites is reduced due to transition metal agglomeration, thereby improving the activity, selectivity and stability of the catalyst. At the same time, when the dispersion of transition metals is high, the amount of transition metals used can be reduced, thereby reducing the cost of the catalyst. Furthermore, when transition metals with a particle size controlled below 2.5 nm are dispersed on the surface and in the pores of the catalyst support, it is beneficial to expose more active sites and improve the catalytic efficiency of the catalyst.

[0023] Therefore, when the loading of transition metal is 1wt%~50wt%, the particle size of the transition metal is controlled below 2.5nm and the dispersion is controlled above 85%, so that the particle size of the transition metal in the catalyst is small and the dispersion is relatively uniform, which is beneficial to improve the active sites of the catalyst and thus improve the reaction rate.

[0024] In some embodiments, the catalyst further includes a binder connected between adjacent catalyst supports; the support body comprises mesoporous silica or molecular sieves, and the binder comprises at least one of olivine and attapulgite.

[0025] In this embodiment, olivine can enhance the mechanical strength of the catalyst and prevent breakage and wear. At the same time, olivine connects between the carrier particles, promotes the accumulation between the carrier particles, and helps to form larger pores, thereby expanding the pore size of the catalyst and promoting the diffusion of reactants and products, and preventing the micropores of the catalyst from being blocked. The porous structure of attapulgite itself can increase the internal specific surface area of ​​the catalyst, and attapulgite has adhesiveness, which can enhance the connection strength between the carrier particles. This application provides a method for preparing a catalyst, comprising: Step 1: The first catalyst support is pretreated with an alkaline compound to obtain the second catalyst support.

[0026] In this step, the alkaline compound is dissolved in a solvent to prepare an alkaline compound solution, which is then mixed with the first catalyst support for pretreatment. The pretreatment temperature is 40~80℃ and the pretreatment time is 3~6 h. Since the pretreated material is alkaline, it needs to be filtered and washed until neutral to remove residual alkaline compounds. It can also be dried at 80~120℃ to finally obtain a second catalyst support with a zeta potential that meets the requirements and a neutral pH.

[0027] In this step, by fully contacting the alkaline compound with the first catalyst support, the alkaline compound is promoted to fully migrate to the surface and pores of the first catalyst support, thereby causing the alkaline compound to deprotonate the hydroxyl groups on the surface and pores of the first catalyst support, thus obtaining a second catalyst support with negative charges on both the surface and the pores.

[0028] The zeta potential of the second catalyst support is controlled at -30 to -40 mV, and it carries a strong negative charge, which is conducive to the rapid and thorough adsorption of complexes containing transition metal ions onto the surface of the second catalyst support, thereby increasing the loading of transition metals. At the same time, the pretreatment temperature is 40 to 80 °C and the pretreatment time is 3 to 6 h. The pretreatment time and temperature are both suitable, which can perform relatively uniform deprotonation on the catalyst support, so that the surface and pores of the second catalyst support have a relatively uniform and stable negative charge.

[0029] In some embodiments, the alkaline compound includes at least one selected from ammonia monohydrate, ammonium carbonate, ethylenediamine, and triethylamine, preferably ammonia monohydrate.

[0030] The concentration of the alkaline compound solution is 8~12wt%. The alkalinity of the alkaline compound solution at this concentration is slightly stronger, which is beneficial for the deprotonation reaction of the hydroxyl groups on the first catalyst support, while also avoiding the erosion of the surface of the first catalyst support caused by excessive alkalinity.

[0031] Step 2: The transition metal precursor is reacted with a complexing agent to generate a complex solution.

[0032] After the transition metal precursor is dissolved in water, transition metal ions are released. These transition metal ions coordinate with the lone pair electrons on the carboxyl and / or amino groups in the complexing agent to form stable and water-soluble complexes. This avoids the aggregation of transition metal ions due to easy hydrolysis, and thus prevents the formation of aggregated transition metal particles with large particle sizes in the catalyst.

[0033] In this embodiment, the complexing agent includes at least one of triamine citrate, ethylenediaminetetraacetic acid, and aminotriacetic acid. These complexing agents are polydentate ligands with multiple carboxyl and / or amino groups in their molecules, exhibiting high complexing capacity and stronger complexing ability. Therefore, the complexes formed after complexing with transition metal ions are more stable. Furthermore, during the subsequent calcination process, these complexing agents can be decomposed into gases and escape to avoid introducing heteroatoms into the catalyst, thus affecting the catalyst's purity.

[0034] In this embodiment, the molar ratio of the complexing agent to the transition metal ions of the transition metal precursor is (1~4):1. The complexing agent is in excess, which can increase the probability of the transition metal ions in the transition metal precursor undergoing a complexation reaction with the complexing agent, reduce the content of free transition metal ions, avoid the aggregation of free transition metal ions due to hydrolysis, and thus promote the uniform dispersion of transition metals on the catalyst and reduce the particle size of transition metals.

[0035] The transition metal precursors include compounds containing transition metal elements. For example, transition metal precursors include at least one of nickel nitrate, nickel acetate, cobalt nitrate, cobalt acetate, copper nitrate, copper acetate, sodium metatungstate, and ammonium tungstate.

[0036] In this embodiment, the mass ratio of the transition metal precursor to the first catalyst support is 1:(1~99). At this ratio, the transition metal ions are relatively abundant and can be dispersed on the surface and pores of the second catalyst support, thereby helping to ensure the loading of transition metal in the catalyst, providing more active sites, and improving the activity and catalytic efficiency of the catalyst. At the same time, it can also avoid the problem of transition metal agglomeration in the catalyst due to excessive transition metal precursor, which would reduce the dispersion and increase the particle size of the transition metal. The mass ratio of the transition metal precursor to the first catalyst support is preferably 1:(1~4), more preferably 1:(1.5~3).

[0037] Step 3: The second catalyst support is immersed in the complexation solution to obtain the catalyst precursor.

[0038] In this step, since the surface and pores of the second catalyst support have a relatively uniform and stable negative charge, when it is immersed in the complexing solution, the positively charged complexes in the complexing solution are electrostatically adsorbed onto the surface of the second catalyst support and gradually diffused and adsorbed into the pores through electrostatic attraction, thereby achieving uniform dispersion of transition metal ions on the second catalyst support. Furthermore, the adsorption between the transition metal ions and the second catalyst support is electrostatic adsorption, which makes it less likely to migrate and aggregate during subsequent drying and calcination, thus improving the loading and dispersion uniformity of the transition metal.

[0039] The impregnation temperature is 30~40℃ and the time is 4~5h. The impregnation process can be accompanied by relatively slow stirring, for example, it can be carried out in a slow-rotating rotary evaporator to ensure that the second catalyst support and the complexing solution are in full contact. After impregnation, washing is performed to remove physical adsorbates, impurity ions and excess complexing agent. Then, solid-liquid separation is performed by vacuum filtration or centrifugation. The solid obtained after filtration is the catalyst precursor, which is loaded with transition metal ions.

[0040] In this step, a binder may also be added. Specifically, the second catalyst support is impregnated in a complexing solution to obtain a catalyst precursor complex; the catalyst precursor complex is mixed with a binder to obtain a catalyst precursor.

[0041] The binder includes at least one of olivine and attapulgite. Olivine, when combined with the catalyst precursor complex, enhances the mechanical strength of the catalyst and prevents breakage and wear. Simultaneously, olivine connects the catalyst precursor complex, promoting its accumulation and facilitating the formation of larger pores. This ultimately expands the pore size of the catalyst, promoting the diffusion of reactants and products and preventing the micropores of the catalyst from becoming clogged. Attapulgite itself, with its porous structure, increases the internal specific surface area of ​​the catalyst. Furthermore, its adhesive properties enhance the bonding strength between catalyst precursor particles and improve the formability of the catalyst precursor, facilitating the preparation of catalyst precursors in strip or spherical shapes.

[0042] In the mixture of catalyst precursor complex and binder, the mass percentage of catalyst precursor complex is 85%~95% and the mass percentage of binder is 5%~15%. Under this ratio, the mechanical strength and formability of the catalyst are guaranteed, and it is also beneficial to expand the pores of the catalyst, improve the diffusion efficiency of reactants and products, and thus promote the reaction rate of the catalyst.

[0043] When the binder includes olivine and attapulgite, the mass ratio of olivine to attapulgite is (1~1.2):1. Olivine mainly provides a strong skeleton and wear resistance, while attapulgite provides adhesion with its fibrous structure. The two work synergistically in this ratio, which also gives the catalyst suitable mechanical strength and formability.

[0044] Step four: The catalyst precursor is calcined and reduced to obtain the catalyst.

[0045] In this step, the catalyst precursor is first calcined at a temperature of 300-350℃ for 3-4 hours to obtain a catalyst intermediate. Then, hydrogen is introduced into the catalyst intermediate to carry out a reduction reaction at a temperature of 450-550℃ for 4-5 hours to obtain the catalyst.

[0046] During the calcination process, transition metal ions on the catalyst precursor react with oxygen to form transition metal oxides. Due to the high adsorption capacity caused by electrostatic adsorption, the transition metal ions are not easy to migrate or aggregate during calcination, which allows the generated transition metal oxides to be dispersed relatively uniformly on the surface and pores of the catalyst support. Meanwhile, the complexing agent on the catalyst precursor decomposes upon heating to generate gas that escapes. Furthermore, a calcination temperature of 300~350℃ and a calcination time of 3~4 hours are beneficial for the complete decomposition of the complexing agent and can also prevent the transition metal oxides from being over-sintered. In addition, the sintering process can also enhance the bonding strength of the binder, thereby enhancing the mechanical strength of the catalyst.

[0047] In the reduction reaction, the transition metal oxide is reduced by hydrogen to produce transition metal and water. The transition metal is uniformly dispersed in the catalyst to form transition metal particles with small particle size. Furthermore, since the metal-oxygen bond energy is relatively strong, higher energy is required for breaking. Therefore, the reduction temperature is set to 450~550℃ and the reduction reaction time is 4~5h to ensure that the transition metal oxide can be fully reduced.

[0048] This application also provides an application of a catalyst, which is the same as the catalyst or the catalyst prepared by the method described in the above embodiments, and has similar beneficial effects. This catalyst can be applied to coal tar, residual oil, biomass, or polymers. Because the catalyst in this embodiment has high transition metal dispersion and small particle size, it exhibits high catalytic activity, allowing the reaction to proceed under relatively mild reaction conditions.

[0049] The technical solution of this application will now be described in detail with reference to embodiments and comparative examples.

[0050] Example 1 Step 1: The first catalyst support is completely immersed in a 12 wt% ammonia monohydrate solution, stirred, and pretreated at 60°C for 5 h. The pretreated material is then filtered, washed until neutral, and dried at 100°C to obtain the second catalyst support. The first catalyst support is mesoporous silica.

[0051] Step 2: The transition metal precursor solution is reacted with a complexing agent to obtain a complexed solution. The mass ratio of the transition metal precursor to the first catalyst support is 1:3, the molar ratio of the complexing agent to the transition metal ions of the transition metal precursor is 1.5:1, the transition metal precursor solution includes nickel nitrate solution, and the complexing agent is triamine citrate.

[0052] Step 3: Immerse the second catalyst support in the complexation solution and stir continuously at a speed of 80 rpm to ensure full contact between the two. The immersion temperature is 40℃ and the time is 5 hours. After immersion, wash and filter to finally obtain the catalyst precursor.

[0053] Step 4: The catalyst precursor is calcined at 350℃ for 4 hours to obtain the catalyst intermediate.

[0054] Step 5: Heat to 450℃, introduce hydrogen gas into the catalyst intermediate to carry out the reduction reaction, and the reaction time is 5 hours. After the reduction reaction is completed, the catalyst is obtained.

[0055] Step 6: Weigh 10.0 g of medium-low temperature coal tar and add it to the reactor. Then add 1.0 g of catalyst to the reactor. Seal the reactor and replace the air inside the reactor with nitrogen three times, then replace the nitrogen with hydrogen three times. Finally, fill with hydrogen and start heating to increase the pressure inside the reactor to 6.0 MPa and the temperature to 380~430℃ and maintain stability. The reaction time is 1 hour. After the reaction is completed, place the reactor in an ice-water bath to cool to room temperature, release the residual pressure, collect the material inside the reactor, and filter and separate the material to obtain the liquid product.

[0056] Example 2 The difference from Example 1 is that the concentration of the ammonia monohydrate solution in step 1 is 8 wt%, and the mass ratio of the transition metal precursor to the first catalyst support in step 2 is 1:99.

[0057] Example 3 The difference from Example 1 is that the ammonia monohydrate solution in step 1 is replaced with ethylenediamine, and the mass ratio of the transition metal precursor to the first catalyst support in step 2 is 1:9.

[0058] Example 4 The difference from Example 1 is that the ammonia monohydrate solution in step 1 is replaced with ethylenediamine, and the mass ratio of the transition metal precursor to the first catalyst support in step 2 is 1:1.

[0059] Example 5 The difference from Example 1 is that in step 2, the transition metal precursor solution includes nickel nitrate solution and cobalt nitrate, the molar ratio of nickel ions to cobalt ions is 1:1, and the complexing agent is ethylenediaminetetraacetic acid.

[0060] Example 6 The difference from Example 1 is that only step 3 is adjusted as follows: The second catalyst support was immersed in the complexing solution and stirred continuously at 80 rpm to ensure full contact between the two. The immersion temperature was 40°C and the immersion time was 5 h. After immersion, the catalyst precursor complex was obtained by washing and filtering. A binder is added to the catalyst precursor complex, and after kneading and conditioning, it is extruded on an extruder to obtain the catalyst precursor. The mass ratio of the binder to the second catalyst support is 10:90. The binder includes olivine and attapulgite, and the mass ratio of olivine and attapulgite is 1:1.

[0061] Comparative Example 1 The first catalyst support was dispersed in a nickel nitrate solution. After the solvent was evaporated, the catalyst was calcined at 350°C for 4 hours to obtain a catalyst intermediate. The temperature was then increased to 450°C, and hydrogen gas was introduced into the catalyst intermediate to carry out a reduction reaction for 5 hours. After the reduction reaction was completed, the catalyst was obtained. The mass ratio of nickel nitrate to the first catalyst support was 1:3.

[0062] The Zeta potential of the second catalyst support prepared in the above examples was tested. The particle size, dispersity, and loading of transition metals in the catalysts prepared in the above examples and examples were also tested. The test results are shown in Table 1. The yield of liquid products, aromatic saturation, and light oil yield in the above examples and comparative examples were also tested. The test results are shown in Table 1. The test methods included: (1) Zeta potential test of the second catalyst support: The second catalyst support was dispersed in the clarified mother liquor to prepare a suspension with a solid concentration of 0.1 mg / mL. The clarified mother liquor was the supernatant obtained by low-speed centrifugation of the mixture of ammonia monohydrate and the first catalyst support after pretreatment. The suspension was then injected into the sample cell of the Zeta potential and nanoparticle size analyzer (DLS) for testing. The Zeta potential value was recorded. The test method was repeated three times, and the average value of the Zeta potential value was calculated.

[0063] (2) Particle size test of transition metals in catalyst: The catalyst powder was ultrasonically dispersed in ethanol for 3 min to prepare a dilute suspension; the dilute suspension was dropped onto a copper grid supported by an ultrathin carbon film and dried under an infrared lamp (after drying, the catalyst particles are sparse and separated). After drying, the sample was placed on the stage of a transmission electron microscope (TEM) and images of different regions under at least 5 fields of view were obtained by scanning with an electron beam. The images were analyzed using the built-in analysis software of the TEM. Specifically, the scale bar (nm / pixel) was marked on the image, and at least 100 clearly distinguishable transition metal particle outlines were manually or semi-automatically drawn. The equivalent diameter of each transition metal particle was automatically calculated by the software, and the average particle size of the transition metal was calculated based on each equivalent diameter.

[0064] (3) Dispersion test of transition metals in catalyst: The metal dispersion is evaluated by scanning with an electron beam and observing the morphology of the metal particles.

[0065] (4) Test of transition metal loading in catalyst: Weigh 0.1 g of catalyst powder and digest it with aqua regia until the solution is completely clear; dilute the cooled solution with deionized water to a fixed volume; measure the concentration of each transition metal in the solution using inductively coupled plasma optical emission spectrometry (ICP-OES) and calculate the loading (wt%) of each transition metal = (measured concentration × fixed volume) / sample mass × 10 -4 The loading of transition metals in the catalyst is the sum of the loadings of each transition metal.

[0066] (5) Yield of liquid product The yield of the liquid product is a percentage of the mass of the liquid product to the mass of the medium- and low-temperature coal tar.

[0067] (6) Aromatic saturation of liquid products The liquid product is analyzed by gas chromatography to obtain the number of saturated C-H bonds and the total number of C-H bonds in the aromatic molecules. The aromatic saturation rate of the liquid product is calculated, which is equal to the percentage of the number of saturated C-H bonds in the aromatic molecules to the total number of C-H bonds.

[0068] (7) Test of light oil yield Distill the liquid product and calculate the percentage of the mass of the fraction with a distillation range below 350℃ relative to the mass of medium- and low-temperature coal tar.

[0069] Table 1

[0070] As can be seen from the data in Table 1, the absolute values ​​of the Zeta potential of the second catalyst support in Examples 1-6 are higher than those in Comparative Example 1, indicating that alkaline treatment enhances the negative charge on the catalyst support surface, which is beneficial to the dispersion of transition metals. The complexation reaction avoids the aggregation effect of transition metal ions, resulting in transition metal particle sizes ≤2.5 nm and dispersion ≥85% in all examples, demonstrating high dispersion characteristics. Among them, Examples 1, 5, and 6, with moderate loading and high dispersion, exhibit superior catalytic performance, with yields of 94%-96%, aromatic saturation of 91%-94%, and light oil yield of 92%-94%. Comparative Example 1, due to the lack of alkaline pretreatment and complexing agent treatment, has larger particle sizes (3.5 nm) and lower dispersion (70%), resulting in decreased performance in all aspects. It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0071] Although optional embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the optional embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0072] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used merely to distinguish one entity from another, and do not necessarily require or imply any such actual relationship or order between these entities. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or terminal device that includes that element.

[0073] The technical solutions provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the principles and implementation methods of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A catalyst, characterized in that, The catalyst comprises a catalyst support and a transition metal, wherein the transition metal is dispersed on the catalyst support; Based on the mass of the catalyst, the loading of the transition metal is 1wt%~50wt%, the particle size of the transition metal is ≤2.5nm, and the dispersion of the transition metal on the catalyst support is ≥85%.

2. The catalyst according to claim 1, characterized in that, The catalyst further includes a binder that connects adjacent catalyst supports; The catalyst support comprises mesoporous silica or molecular sieve, and the binder comprises at least one of olivine and attapulgite.

3. A method for preparing the catalyst according to any one of claims 1 to 2, characterized in that, include: The first catalyst support was pretreated with an alkaline compound to obtain the second catalyst support; A transition metal precursor is reacted with a complexing agent to generate a complex solution; The second catalyst support is impregnated in the complexing solution to obtain the catalyst precursor; The catalyst precursor was calcined and reduced to obtain the catalyst.

4. The method for preparing the catalyst according to claim 3, characterized in that, A second catalyst support is obtained by pretreating the first catalyst support with an alkaline compound, comprising: The alkaline compound is mixed with the first catalyst support and pretreated at a temperature of 40-80°C for 3-6 hours. The pretreated material is filtered, washed until neutral, and dried at 80~120℃ to obtain the second catalyst support, wherein the zeta potential of the second catalyst support is -30~-40mV.

5. The method for preparing the catalyst according to claim 3, characterized in that, The second catalyst support is impregnated in the complexing solution to obtain a catalyst precursor, comprising: The second catalyst support is impregnated in the complexing solution to obtain a catalyst precursor complex; The catalyst precursor complex is mixed with a binder to obtain a catalyst precursor, wherein the binder includes at least one of olivine and attapulgite.

6. The method for preparing the catalyst according to claim 3, characterized in that, The catalyst precursor is calcined and reduced to obtain a catalyst comprising: The catalyst precursor was calcined at a temperature of 300-350°C for 3-4 hours to obtain a catalyst intermediate. Hydrogen gas is introduced into the catalyst intermediate to carry out a reduction reaction. The reduction reaction temperature is 450~550℃ and the reduction reaction time is 4~5h to obtain the catalyst.

7. The method for preparing the catalyst according to claim 3, characterized in that, The alkaline compound includes at least one of ammonia monohydrate, ammonium carbonate, ethylenediamine, and triethylamine; And / or, the first catalyst support comprises mesoporous silica or molecular sieve; And / or, the complexing agent includes at least one of triamine citrate, ethylenediaminetetraacetic acid, and aminotriacetic acid.

8. The method for preparing the catalyst according to claim 4, characterized in that, The molar ratio of the complexing agent to the transition metal ions of the transition metal precursor is (1~4):1; And / or, the mass ratio of the transition metal precursor to the first catalyst support is 1:(1~99).

9. The method for preparing the catalyst according to claim 5, characterized in that, In the mixture of the catalyst precursor complex and the binder, the mass percentage of the catalyst precursor complex is 85% to 95%, and the mass percentage of the binder is 5% to 15%. And / or, when the binder comprises olivine and attapulgite, the mass ratio of the olivine to the attapulgite is (1~1.2):

1.

10. The application of the catalyst according to any one of claims 1 to 2 or the catalyst prepared by the preparation method according to any one of claims 3 to 9 in coal tar, residual oil, biomass or polymer.

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