Noble metal pre-hydrogenation catalyst, method for preparing the same and use thereof

Abstract

The present application relates to the technical field of aromatic hydrocarbon selective hydrogenation catalyst, and discloses a noble metal pre-hydrogenation catalyst and a preparation method and application thereof.The noble metal pre-hydrogenation catalyst comprises a carrier and an active component loaded on the carrier; the active component is a noble metal, and the carrier is amorphous silicon aluminum; the pore volume of the noble metal pre-hydrogenation catalyst is 0.65-0.95 cm 3 / g, the pore size is 6-9.5 nm, the acid amount is 0.13-0.18 mmol / g, the content of the noble metal is 0.5-2 wt%, and the average particle size of the noble metal is 1.2-1.8 nm.The noble metal pre-hydrogenation catalyst of the present application is directly prepared in situ from a noble metal organic complex and silicon and aluminum raw materials through a hydrothermal aging process, and the noble metal pre-hydrogenation catalyst has obvious advantages in the selective hydrogenation saturation process of heavy aromatic hydrocarbons (C10+ aromatic hydrocarbons).

Description

Technical Field

[0001] This invention relates to the field of selective hydrogenation catalysts for aromatics, specifically to noble metal pre-hydrogenation catalysts, their preparation methods, and applications. Background Technology

[0002] With the expansion of refining and chemical technologies such as ethylene cracking units and aromatics complexes in my country, the amount of by-product aromatics resources, especially C10+ heavy aromatics, is increasing. Their high-value utilization is one of the pressing issues that needs to be addressed. The sources of heavy aromatics resources include C10+ heavy aromatics by-products of catalytic reforming units, C10+ heavy aromatics by-products of ethylene cracking units, aromatics disproportionation and isomerization to produce oil, and heavy aromatics by-products of high-temperature coal coking. Currently, heavy aromatics can be separated into higher-value compounds such as mesitylene, pseudotrimethylbenzene, and naphthalene through simple distillation. The majority of the remainder is used as low-cost fuel, with only a small portion used to produce aromatic solvent oils or gasoline blending components. Therefore, the utilization of heavy aromatics resources faces challenges such as low raw material utilization rates and difficulty in comprehensively utilizing the potential economic value of polycyclic aromatic hydrocarbons. In recent years, the domestic market has seen strong and rapid demand for benzene, toluene, and xylene, gradually revealing a high dependence on imports, and is currently in a situation of supply falling short of demand. In addition, with the increasing demand for catalytic reforming and other units, the quality of heavy aromatics feedstocks is becoming increasingly inferior. How to utilize heavy aromatics cleanly and efficiently to achieve increased production of high-value-added light aromatics such as benzene, toluene, and xylene is one of the urgent issues that petrochemical workers need to address.

[0003] Heavy aromatic hydrocarbon lightening technology is one of the key technologies for the conversion and utilization of heavy aromatic hydrocarbon resources. Its core lies in the performance of its catalysts and their preparation methods. Heavy aromatic hydrocarbon lightening technology mainly involves heavy aromatic hydrocarbon hydrogenation saturation reactions, ring-opening cracking reactions, and isomerization reactions. Existing heavy aromatic hydrocarbon lightening catalysts with non-precious metals such as nickel, molybdenum, and tungsten as active components generally suffer from problems such as poor C10+ heavy aromatic hydrocarbon processing capacity, poor selectivity for light aromatic hydrocarbons, and poor catalyst stability. Precious metal nanoparticles have many edge catalytic active sites on their surface, making them a high-quality metal active center with high hydrogenation activity under low pressure.

[0004] Patent CN114437818B discloses a method for processing heavy aromatic oil. This method mainly uses a combined distillation / extraction / hydrogenation process to process monocyclic aromatics and polycyclic aromatics (PAA) compounds separately. However, the PAA portion is converted into liquefied petroleum gas (LPG) through hydrogenation, thus not fully utilizing the potential economic value of PAA resources.

[0005] Patent CN102746091B discloses a method for producing BTX aromatics and trimethylbenzene from heavy aromatics, using a microporous molecular sieve as the support and C9+ heavy aromatic feedstock as the raw material. However, when faced with the even lower quality C10+ feedstock, the microporous structure makes it difficult to efficiently hydrogenate and convert polycyclic aromatic components.

[0006] Currently, most pre-hydrogenation catalysts suitable for the hydrogenation saturation reaction of heavy aromatics are prepared by impregnation, resulting in less interaction between the metal and the support, which means that the hydrogenation performance of the noble metal active center is not fully utilized. Summary of the Invention

[0007] The purpose of this invention is to overcome the poor hydrogenation performance of existing pre-hydrogenation catalysts for the hydrogenation saturation reaction of heavy aromatics, and to provide a noble metal pre-hydrogenation catalyst, its preparation method, and its application. This noble metal pre-hydrogenation catalyst involves a sol-gel reaction between a noble metal organic complex and silicon / aluminum raw materials, resulting in an interaction between the noble metal organic complex and the silicon / aluminum support framework. Following calcination and reduction, a noble metal pre-hydrogenation catalyst with strong host-guest interactions is obtained. This catalyst exhibits high hydrogenation reactivity and selectivity.

[0008] To achieve the above objectives, the present invention provides a noble metal pre-hydrogenation catalyst, which includes a support and an active component supported on the support; the active component is a noble metal, and the support is amorphous silicon-aluminum.

[0009] The pore volume of the noble metal pre-hydrogenation catalyst is 0.65-0.95 cm³. 3 / g, pore size of 6-9.5nm, acidity of 0.13-0.18mmol / g, and precious metal content of 0.5-2wt%;

[0010] The average particle size of the precious metal is 1.2-1.8 nm.

[0011] Preferably, the precious metal is selected from one or more of platinum, palladium, rhodium and ruthenium.

[0012] A second aspect of the present invention provides a method for preparing the above-mentioned noble metal pre-hydrogenation catalyst, the method comprising the following steps:

[0013] (1) Mix the noble metal salt, the organic complex and water to obtain a noble metal complex solution;

[0014] (2) Mix water glass, sodium aluminate and water to obtain a silicon-aluminum precursor solution; wherein, in the silicon-aluminum precursor solution, the total content of water glass and sodium aluminate is 8-10 wt%, and the weight ratio of water glass to sodium aluminate is 17-22:1, wherein water glass is calculated as SiO2 and sodium aluminate is calculated as Al2O3.

[0015] (3) The noble metal complex solution is mixed with the silicon-aluminum precursor solution, and then subjected to hydrothermal aging treatment, followed by filtration, washing, drying, calcination and reduction in sequence.

[0016] Preferably, in step (1), the noble metal salt is selected from one or more of platinum nitrate, palladium nitrate, rhodium chloride, ruthenium chloride, and platinum chloride;

[0017] Preferably, the organic complex is selected from one or more of N,N-dimethylformamide, 1,4,7,10-tetraazacyclododecane and hexamethylenediamine.

[0018] Preferably, in step (1), the molar ratio of the organic complex to the noble metal salt is 1.1-2.2:1.

[0019] Preferably, in step (3), the conditions for the hydrothermal aging treatment include: pH value of 8-9, temperature of 50-60℃, and time of 3-5h.

[0020] Preferably, in step (3), the calcination conditions include: heating to 450-600℃ at a heating rate of 0.5-2℃ / min and calcining for 5-7 hours.

[0021] Preferably, in step (3), the reduction conditions include: reducing to 300-450℃ for 3-5 hours at a heating rate of 0.5-2℃ / min under an H2 atmosphere.

[0022] A third aspect of the present invention provides the application of the above-mentioned noble metal pre-hydrogenation catalyst in the selective hydrogenation of heavy aromatics.

[0023] The fourth aspect of the present invention provides a method for selective hydrogenation of heavy aromatics, wherein heavy aromatics and hydrogen are contacted with the above-mentioned noble metal pre-hydrogenation catalyst to carry out a hydrogenation reaction;

[0024] Preferably, the conditions for the hydrogenation reaction include: a pressure of 4-7 MPa and a reaction space velocity of 1.5-4 h⁻¹. -1 The inlet temperature of the pre-hydrogenation reactor is 120-240℃, and the hydrogen-to-hydrogen volume ratio is 600-1100.

[0025] The noble metal pre-hydrogenation catalyst of the present invention is prepared directly in situ from noble metal organic complexes and silicon and aluminum raw materials through a hydrothermal aging process. This noble metal pre-hydrogenation catalyst has significant advantages in the selective hydrogenation saturation process of heavy aromatics (C10+ aromatics). In the in-situ preparation process, the noble metal center and the support framework form a strong host-guest interaction, which makes the noble metal more dispersed and significantly enhances the reaction activity and selectivity. Attached Figure Description

[0026] Figure 1 This is a transmission electron microscope (TEM) characterization image of the noble metal pre-hydrogenation catalyst obtained in Example 1. Detailed Implementation

[0027] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] The present invention provides a noble metal pre-hydrogenation catalyst, which includes a support and an active component supported on the support; the active component is a noble metal, and the support is amorphous silicon-aluminum.

[0030] In this invention, the pore volume of the noble metal pre-hydrogenation catalyst is 0.65-0.95 cm³. 3 / g, pore size is 6-9.5nm, acidity is 0.13-0.18mmol / g.

[0031] Furthermore, the noble metal content in the noble metal pre-hydrogenation catalyst of the present invention is 0.5-2 wt%. When the noble metal content is within this range, the noble metal pre-hydrogenation catalyst has good hydrogenation reaction activity and hydrogenation selectivity.

[0032] In a specific embodiment, the content of noble metal in the noble metal pre-hydrogenation catalyst can be 0.5wt%, 1wt%, 1.5wt%, or 2wt%.

[0033] In a preferred embodiment, the average particle size of the noble metal is 1.2-1.8 nm. When the average particle size of the noble metal is within this range, the noble metal can have good dispersion, which further enables the noble metal pre-hydrogenation catalyst to have good hydrogenation reaction activity and hydrogenation selectivity.

[0034] In a preferred embodiment, the precious metal is selected from one or more of platinum, palladium, rhodium and ruthenium.

[0035] A second aspect of the present invention provides a method for preparing the above-mentioned noble metal pre-hydrogenation catalyst, the method comprising the following steps:

[0036] (1) Mix the noble metal salt, the organic complex and water to obtain a noble metal complex solution;

[0037] (2) Mix water glass, sodium aluminate and water to obtain a silicon-aluminum precursor solution; wherein, in the silicon-aluminum precursor solution, the total content of water glass and sodium aluminate is 8-10 wt%, and the weight ratio of water glass to sodium aluminate is 17-22:1, wherein water glass is calculated as SiO2 and sodium aluminate is calculated as Al2O3.

[0038] (3) The noble metal complex solution is mixed with the silicon-aluminum precursor solution, and then subjected to hydrothermal aging treatment, followed by filtration, washing, drying, calcination and reduction in sequence.

[0039] Preferably, in step (1), the precious metal salt is selected from one or more of platinum nitrate, palladium nitrate, rhodium chloride, ruthenium chloride and platinum chloride.

[0040] Preferably, in step (1), the organic complex is selected from one or more of N,N-dimethylformamide, 1,4,7,10-tetraazacyclododecane and hexamethylenediamine.

[0041] In step (1) of the present invention, the noble metal salt reacts with the organic complex to generate the noble metal complex. In order to promote a full reaction, in a preferred case, the noble metal salt is first fully mixed with water in step (1) and then fully mixed with the organic complex.

[0042] In the specific implementation of step (1), the amount of water used is sufficient to fully dissolve the precious metal salt.

[0043] In step (1) of the present invention, the amount of organic complex and noble metal salt is determined according to the relationship between the number of nitrogen-containing functional groups of the complex and the coordination number of the noble metal. In a preferred case, in order to ensure sufficient reaction, the molar ratio of the organic complex to the noble metal salt is 1.1-2.2:1, specifically 1.1:1, 1.5:1, 1.7:1, 2:1 or 2.2:1.

[0044] In step (2), in order to ensure that the pore volume and pore size of the prepared noble metal pre-hydrogenated catalyst meet the corresponding requirements, it is necessary to control the total content of water glass and sodium aluminate in the silicon-aluminum precursor solution, wherein the water glass is calculated as SiO2 and the sodium aluminate is calculated as Al2O3.

[0045] In the preferred embodiment of step (2), the total content of water glass and sodium aluminate in the silicon-aluminum precursor solution is 8-10 wt%, with water glass calculated as SiO2 and sodium aluminate calculated as Al2O3.

[0046] In the specific implementation of step (2), the total content of water glass and sodium aluminate in the silicon-aluminum precursor solution can be 8 wt%, 9 wt%, or 10 wt%.

[0047] In step (2), in order to ensure that the acid content of the prepared noble metal pre-hydrogenation catalyst meets the corresponding requirements, it is necessary to control the weight ratio of water glass and sodium aluminate in the silicon-aluminum precursor solution.

[0048] Therefore, in the preferred embodiment of step (2), the weight ratio of water glass to sodium aluminate in the silicon-aluminum precursor solution is 17-22:1, where water glass is calculated as SiO2 and sodium aluminate is calculated as Al2O3.

[0049] In the specific implementation of step (2), the weight ratio of water glass and sodium aluminate in the silicon-aluminum precursor solution can be 17:1, 18:1, 19:1, 20:1, 21:1 or 22:1.

[0050] In step (3) of this invention, the amount of noble metal complex solution and silicon-aluminum precursor solution used is sufficient to ensure that the content of noble metal in the final noble metal pre-hydrogenation catalyst meets the requirements.

[0051] In a preferred embodiment of the present invention, in step (3), the conditions for the hydrothermal aging treatment include: pH value of 8-9, temperature of 50-60℃, and time of 3-5h.

[0052] In a specific embodiment of the present invention, in step (3), after the noble metal complex solution is mixed with the silicon-aluminum precursor solution, an inorganic acid is added, and then hydrothermal aging treatment is performed. The pH value of the system during hydrothermal aging treatment is controlled by adding an inorganic acid.

[0053] In this invention, the inorganic acid is sulfuric acid and / or nitric acid.

[0054] In the specific implementation of step (3), the temperature of the hydrothermal aging treatment can be 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃ or 60℃, and the time of the hydrothermal aging treatment can be 3h, 4h or 5h.

[0055] Preferably, in step (3), the calcination conditions include: heating to 450-600℃ at a heating rate of 0.5-2℃ / min and calcining for 5-7 hours.

[0056] In the specific implementation of step (3), the heating rate of calcination can be 0.5℃ / min, 1℃ / min, 1.5℃ / min or 2℃ / min, the calcination temperature can be 450℃, 500℃, 550℃ or 600℃, and the calcination time can be 5h, 6h or 7h.

[0057] Preferably, in step (3), the reduction conditions include: reducing to 300-450℃ for 3-5 hours at a heating rate of 0.5-2℃ / min under an H2 atmosphere.

[0058] In the specific implementation of step (3), the reduction heating rate can be 0.5℃ / min, 1℃ / min, 1.5℃ / min or 2℃ / min, the calcination temperature can be 300℃, 350℃, 400℃ or 450℃, and the calcination time can be 3h, 4h or 5h.

[0059] A third aspect of the present invention provides the application of the above-mentioned noble metal pre-hydrogenation catalyst in the selective hydrogenation of heavy aromatics.

[0060] The fourth aspect of the present invention provides a method for selective hydrogenation of heavy aromatics, wherein heavy aromatics and hydrogen are contacted with the above-mentioned noble metal pre-hydrogenation catalyst to carry out a hydrogenation reaction;

[0061] Preferably, the conditions for the hydrogenation reaction include: a pressure of 4-7 MPa and a reaction space velocity of 1.5-4 h⁻¹. -1 The inlet temperature of the pre-hydrogenation reactor is 120-240℃, and the hydrogen-to-hydrogen volume ratio is 600-1100.

[0062] In this invention, since the hydrogenation reaction is an exothermic reaction, the actual reaction temperature will be slightly higher than the inlet temperature of the pre-hydrogenation reactor. Therefore, by controlling the inlet temperature of the pre-hydrogenation reactor within the above-mentioned range, the degree of reaction can be controlled, and overheating during the hydrogenation reaction can be avoided, which would affect the hydrogenation reaction effect.

[0063] In a specific embodiment, the pressure of the hydrogenation reaction can be 4 MPa, 5 MPa, 6 MPa, or 7 MPa, and the reaction space velocity can be 1.5 h⁻¹. -1 2h -1 3h -1 or 4h -1 The inlet temperature of the pre-hydrogenation reactor can be 120℃, 150℃, 180℃, 200℃ or 240℃, and the hydrogen-to-hydrogen volume ratio can be 600, 700, 800, 900, 1000 or 1100.

[0064] In this invention, the pressure is absolute pressure, and the airspeed refers to mass airspeed.

[0065] The heavy aromatic hydrocarbons mentioned in this invention refer to polycyclic aromatic hydrocarbons with ≥10 carbon atoms.

[0066] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto.

[0067] Example 1

[0068] (1) Add 3.45g of noble metal salt (platinum chloride) to 100g of deionized water and let it dissolve completely. Then add 1.65g of organic complex (N,N-dimethylformamide) and stir until homogeneous to obtain a noble metal organic complex solution. The molar ratio of the organic complex to the noble metal salt is 2.2:1.

[0069] (2) 9.52g of sodium aluminate (calculated as Al2O3) was added to 190.48g of water glass (calculated as SiO2), and then deionized water was added. After stirring evenly, a silicon-aluminum precursor solution was obtained; wherein, in the silicon-aluminum precursor solution, the total content of water glass (SiO2) and sodium aluminate (Al2O3) was 8wt%, and the weight ratio of water glass (SiO2) to sodium aluminate (Al2O3) was 20:1;

[0070] (3) The noble metal complex solution was slowly added to the prepared silicon-aluminum precursor solution. After stirring evenly, nitric acid was added for hydrothermal aging treatment. The conditions for hydrothermal aging treatment included: pH value of 8, temperature of 55℃, and time of 3.5h. After the hydrothermal aging treatment, the solid phase obtained by suction filtration was washed with a large amount of deionized water. Then it was dried at 100℃ for 15h. Subsequently, it was calcined at 500℃ for 6h at a heating rate of 1℃ / min in air atmosphere. Then it was cooled and reduced at 400℃ for 4h at a heating rate of 1℃ / min in H2 atmosphere to obtain noble metal pre-hydrogenation catalyst A1, wherein the active component is noble metal (platinum) and the support is amorphous silicon-aluminum.

[0071] A1 was characterized and analyzed using transmission electron microscopy, and the results are as follows: Figure 1 As shown, according to Figure 1 It can be seen that in the noble metal pre-hydrogenation catalyst obtained in this embodiment, the noble metal is uniformly loaded on the support.

[0072] Example 2

[0073] The method of Example 1 was implemented, except that in step (1), the organic complex was 1,4,7,10-tetraazacyclododecane, the amount of the organic complex was 1.94 g, and the molar ratio of the organic complex to the noble metal salt was 1.1:1; a noble metal pre-hydrogenation catalyst A2 was obtained, wherein the active component was a noble metal (platinum) and the support was amorphous silicon-aluminum.

[0074] Example 3

[0075] The method of Example 1 was implemented, except that in step (1), the organic complex was hexamethylenediamine, the amount of the organic complex was 2.62 g, and the molar ratio of the organic complex to the noble metal salt was 2.2:1; a noble metal pre-hydrogenation catalyst A3 was obtained, wherein the active component was a noble metal (platinum) and the support was amorphous silicon-aluminum.

[0076] Example 4

[0077] The method was implemented according to Example 1, except that in step (1), 4.33g of noble metal salt (palladium nitrate) was added to 100g of deionized water and after it was fully dissolved, 3.56g of organic complex (1,4,7,10-tetraazacyclododecane) was added and stirred evenly to obtain a noble metal organic complex solution; the molar ratio of the organic complex to the noble metal salt was 1.1:1; and a noble metal pre-hydrogenation catalyst A4 was obtained, wherein the active component was noble metal (palladium) and the support was amorphous silicon-aluminum.

[0078] Example 5

[0079] The method was implemented according to Example 1, except that in step (1), 4.10g of noble metal salt (ruthenium chloride) was added to 100g of deionized water and after it was fully dissolved, 3.75g of organic complex (1,4,7,10-tetraazacyclododecane) was added and stirred evenly to obtain a noble metal organic complex solution; the molar ratio of the organic complex to the noble metal salt was 1.1:1; and a noble metal pre-hydrogenation catalyst A5 was obtained, wherein the active component was noble metal (ruthenium) and the support was amorphous silicon-aluminum.

[0080] Example 6

[0081] The method was implemented according to Example 5, except that in step (1), the amount of noble metal used was 5.12 g (rhodium chloride trihydrate), the amount of organic complex (1,4,7,10-tetraazacyclododecane) used was 3.68 g, and the molar ratio of the organic complex to the noble metal salt was 1.1:1; a noble metal pre-hydrogenation catalyst A6 was obtained, wherein the active component was noble metal (rhodium), and the support was amorphous silicon aluminum.

[0082] Example 7

[0083] (1) Add 5.175g of noble metal salt (platinum chloride) to 150g of deionized water and after it is fully dissolved, add 2.91g of organic complex (1,4,7,10-tetraazacyclododecane) and stir until homogeneous to obtain a noble metal organic complex solution; the molar ratio of the organic complex to the noble metal salt is 1.1:1;

[0084] (2) 10.53g of sodium aluminate (calculated as Al2O3) was added to 189.47g of water glass (calculated as SiO2), and then a certain amount of deionized water was added. After stirring evenly, a silicon-aluminum precursor solution was obtained; wherein, in the silicon-aluminum precursor solution, the total content of water glass (SiO2) and sodium aluminate (Al2O3) was 10wt%, and the weight ratio of water glass (SiO2) to sodium aluminate (Al2O3) was 18:1;

[0085] (3) The noble metal complex solution was slowly added to the prepared silicon-aluminum precursor solution. After stirring evenly, sulfuric acid was added for hydrothermal aging treatment. The conditions for hydrothermal aging treatment included: pH value of 9, temperature of 60℃, and time of 5h. After the hydrothermal aging treatment, the solid phase obtained by suction filtration was washed with a large amount of deionized water. Then it was dried at 100℃ for 15h. Subsequently, it was calcined at 500℃ for 6h at a heating rate of 1℃ / min in air atmosphere. Then it was cooled and reduced at 400℃ for 5h at a heating rate of 1℃ / min in H2 atmosphere to obtain the noble metal pre-hydrogenation catalyst A7, wherein the active component is noble metal (platinum) and the support is amorphous silicon-aluminum.

[0086] Comparative Example 1

[0087] (1) 9.52g of sodium aluminate (calculated as Al2O3) was added to 190.48g of water glass (calculated as SiO2), and then a certain amount of deionized water was added. After stirring evenly, a silicon-aluminum precursor solution was obtained. In the silicon-aluminum precursor solution, the total content of water glass (SiO2) and sodium aluminate (Al2O3) was 8wt%, and the weight ratio of water glass (SiO2) to sodium aluminate (Al2O3) was 20:1. Nitric acid was added, and hydrothermal aging treatment was performed. The conditions of hydrothermal aging treatment included: pH value of 8, temperature of 55℃, and time of 3.5h. After the hydrothermal aging treatment was completed, the solid phase obtained by suction filtration was performed, and the solid phase obtained by suction filtration was washed with a large amount of deionized water. Then it was dried at 100℃ for 15h to obtain a silicon-aluminum support.

[0088] (2) Dissolve 3.5g of noble metal salt (platinum chloride) in 120g of deionized water. After complete dissolution, add it to the above-mentioned silica-alumina support, mix evenly, and leave it at room temperature (25℃) overnight. Then dry it at 100℃ for 10h. Then calcine it at 500℃ for 6h in air atmosphere at a heating rate of 1℃ / min. Then cool it and reduce it at 400℃ for 4h in H2 atmosphere at a heating rate of 1℃ / min to obtain noble metal pre-hydrogenation catalyst D1.

[0089] Test Example 1

[0090] The pore volume, pore size, acid content, precious metal content, and precious metal size of A1-A7 and D1 were measured respectively.

[0091] The pore volume, pore size and specific surface area of ​​A1-A7 and D1 were characterized by nitrogen adsorption / desorption. The instrument used was Micromeritics ASAP 2020Plus, the analysis temperature was 77K, and the degassing conditions were 350℃ under vacuum for 10h.

[0092] The precious metal content was detected using an iCAP 7000SERIES instrument;

[0093] The acid content was characterized by ammonia temperature-programmed desorption test. The instrument used was a Micromeritics Auto ChemII 2920 automated chemisorption. The pretreatment conditions were 300℃ for 5 h in a helium atmosphere.

[0094] Transmission electron microscopy was used to characterize the grain size of noble metals and to calculate the average grain size.

[0095] The results are shown in Table 1.

[0096] Table 1

[0097]

[0098] Test Example 2

[0099] Evaluation of the selective hydrogenation saturation performance of heavy aromatics: A fixed-bed reactor was used for the hydrogenation reaction, introducing heavy aromatics and hydrogen gas. The heavy aromatics were naphthalene and methylnaphthalene. The type and content of heavy aromatics were determined by gas chromatography (GC) and GC-MS. 100 g of noble metal pre-hydrogenation catalyst was used. The inlet temperature of the pre-hydrogenation reactor was 150 °C, the hydrogenation reaction pressure was 5.0 MPa, and the reaction space velocity was 1.5 h⁻¹. 1 The hydrogen-to-hydrogen volume ratio was 800. The conversion rate of heavy aromatics and the selectivity of monocyclic aromatics in the hydrogenation reaction were detected. The performance evaluation results are shown in Table 2.

[0100] Conversion rate of heavy aromatics = (Weight of heavy aromatics before reaction - Weight of heavy aromatics after reaction) / Weight of heavy aromatics before reaction × 100%

[0101] Monocyclic aromatic hydrocarbon selectivity = (Weight of monocyclic aromatic hydrocarbon / (Weight of heavy aromatic hydrocarbon before reaction - Weight of heavy aromatic hydrocarbon after reaction)) × 100%

[0102] Table 2

[0103]

[0104] The results above show that the noble metal complex obtained in this invention plays two main roles in the preparation of the pre-hydrogenation catalyst. On the one hand, it hinders the aggregation of noble metal species during the calcination-reduction process, effectively reducing the size of the noble metal and thus improving its dispersion, resulting in higher hydrogenation activity and selectivity of the prepared noble metal pre-hydrogenation catalyst. On the other hand, it also acts as a directing agent, increasing the pore volume and pore size of the noble metal pre-hydrogenation catalyst, facilitating the rapid diffusion of reactants and products, and avoiding the occurrence of excessive hydrogenation saturation side reactions.

[0105] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a noble metal pre-hydrogenation catalyst, characterized in that, The method includes the following steps: (1) Mix the noble metal salt, the organic complex and water to obtain a noble metal complex solution; (2) Mix water glass, sodium aluminate and water to obtain a silicon-aluminum precursor solution; wherein, in the silicon-aluminum precursor solution, the total content of water glass and sodium aluminate is 8-10 wt%, and the weight ratio of water glass to sodium aluminate is 17-22:1, wherein water glass is calculated as SiO2 and sodium aluminate is calculated as Al2O3. (3) The noble metal complex solution is mixed with the silicon-aluminum precursor solution, and then subjected to hydrothermal aging treatment, followed by filtration, washing, drying, calcination and reduction in sequence; The organic complex is selected from one or more of N,N-dimethylformamide, 1,4,7,10-tetraazacyclododecane and hexamethylenediamine; In step (1), the molar ratio of the organic complex to the noble metal salt is 1.1-2.2:

1.

2. The method according to claim 1, characterized in that, In step (1), the precious metal salt is selected from one or more of platinum nitrate, palladium nitrate, rhodium chloride, ruthenium chloride and platinum chloride.

3. The method according to claim 1, characterized in that, In step (3), the conditions for the hydrothermal aging treatment include: pH value of 8-9, temperature of 50-60℃, and time of 3-5h.

4. The method according to claim 1 or 3, characterized in that, In step (3), the calcination conditions include heating to 450-600℃ at a heating rate of 0.5-2℃ / min and calcining for 5-7 hours.

5. The method according to claim 1 or 3, characterized in that, In step (3), the reduction conditions include: under H2 atmosphere, heating to 300-450℃ at a heating rate of 0.5-2℃ / min for 3-5 hours.

6. A noble metal prehydrogenation catalyst prepared by the method according to any one of claims 1-5.

7. The application of the noble metal pre-hydrogenation catalyst according to claim 6 in the selective hydrogenation of heavy aromatics.

8. A method for selective hydrogenation of heavy aromatics, characterized in that, Heavy aromatics and hydrogen are contacted with the noble metal pre-hydrogenation catalyst described in claim 6 to carry out a hydrogenation reaction.

9. The method according to claim 8, characterized in that, The conditions for the hydrogenation reaction include: a pressure of 4-7 MPa and a reaction space velocity of 1.5-4 h⁻¹. -1 The inlet temperature of the pre-hydrogenation reactor is 120-240℃, and the hydrogen-to-hydrogen volume ratio is 600-1100.

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