Radial gradient distribution of ni-mo-fe hydrofining catalyst and its preparation method and application

Abstract

This invention belongs to the field of hydrorefining catalysts, specifically relating to a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst, its preparation method, and its application. In the catalyst, Ni and Mo are enriched in the outer layer of the support, while Fe is enriched in the sub-outer to middle layers. The preparation method includes the following steps: First, a strongly acidic molybdenum-containing impregnation solution is used for outer layer pre-deposition, enriching Mo in the outer region of the support. Then, a near-neutral nickel-containing impregnation solution is used for outer layer anchoring, causing Ni to be mainly distributed in the Mo-rich outer layer and form a synergistic enrichment shell with it. Next, a moderately acidic iron-containing complex impregnation solution is used, combined with reduced pressure suction and atmospheric pressure aging treatment, to distribute Fe in the sub-outer to middle layers of the support. Subsequently, the catalyst is obtained through segmented drying, curing, and calcination. When applied to the hydrorefining of styrene tar, the catalyst of this invention can preferentially achieve rapid hydrogenation stabilization of highly active unsaturated components, reduce polymerization and coking tendencies, and improve operational stability.

Description

Technical Field

[0001] This invention belongs to the field of hydrorefining catalyst preparation technology, specifically, it relates to a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst, its preparation method, and its application. Background Technology

[0002] Hydrorefining is one of the core technologies in the petroleum refining and chemical industries for stabilizing feedstocks, removing impurities, and improving quality. In the deep processing of various sulfur-containing, nitrogen-containing, and unsaturated hydrocarbon feedstocks, catalytic hydrogenation can effectively saturate unsaturated components such as olefins and aromatics, remove heteroatoms, and improve oil stability, providing qualified feedstocks for subsequent storage, transportation, and further processing.

[0003] Styrene tar is a high-boiling-point heavy component byproduct produced in ethylbenzene dehydrogenation to styrene production units. It mainly contains styrene, ethylbenzene, α-methylstyrene, dimers, oligomers, and various high-boiling-point unsaturated aromatic hydrocarbons. This type of feedstock has a high degree of unsaturation, poor thermal stability, and a strong tendency to polymerize. During storage and transportation, it is highly susceptible to polymerization, coking, and the formation of gum deposits, severely impacting feedstock stability and subsequent high-value utilization. Therefore, hydrorefining is a crucial technological pathway for achieving the stabilization and high-value utilization of styrene tar.

[0004] Selective hydrogenation to reduce the content of alkenyl aromatics and highly active unsaturated components can effectively suppress their polymerization and coking tendency, improving feedstock stability and processing adaptability. However, highly unsaturated and easily polymerizable feedstocks such as styrene tar are prone to causing concentrated exothermic reactions, increased pressure drop, and rapid catalyst deactivation in the actual hydrogenation refining process. Therefore, higher requirements are placed on the catalyst's hydrogenation activity, anti-coking ability, and long-term operational stability.

[0005] Among existing hydrorefining catalysts, the Ni-Mo system is widely used due to its excellent hydrogenation activity and mature industrial application. To further improve performance, existing technologies typically control the dispersion state of the active metals through co-impregnation, stepwise impregnation, or the introduction of promoters. For example, CN 102974362 A discloses a catalyst and its preparation method for hydrogen production from bio-oil catalytic reforming. The catalyst's active component is a composite of Ni, Mo, and Fe, and the support is a mixed clay mineral of attapulgite and sepiolite. Here, Fe is introduced into the Ni-Mo system as a promoter, and its modulating effect on the structure and electronic properties of the active phase can improve the catalyst's hydrogenation activity and selectivity to a certain extent. However, the active metals are often uniformly distributed, making it difficult to achieve precise control over the spatial distribution of multiple metals.

[0006] Furthermore, some technologies improve mass transfer and active site utilization efficiency under diffusion-limited conditions by controlling the spatial or radial distribution of active components in the support particles. This approach highlights the importance of controlling the spatial distribution of active components. For example, CN 101927197 A discloses a hydrogenation catalyst and its preparation method in which the concentrations of active metal and acidic auxiliaries decrease in a gradient. The catalyst is sprayed in order of decreasing concentration, so that the concentrations of active metal components and acidic auxiliaries decrease from the center to the surface of the particles. However, for feedstocks such as styrene tar, which have a particularly strong tendency to polymerize, conventionally distributed catalysts or simple stepwise impregnation / spraying catalysts still have certain shortcomings in practical applications: on the one hand, highly active unsaturated components are difficult to be preferentially and rapidly hydrogenated and stabilized on the outer layer of the particles, and polymerization and coking easily occur at the bed inlet and particle pore area; on the other hand, existing technologies focus more on controlling the total metal loading, metal ratio, or support properties, and research on optimizing the spatial distribution of active components through programmed impregnation and drying curing, while systematically taking into account both the preferential stabilization of highly active components and the long-term operational stability of the catalyst, is still relatively limited.

[0007] Therefore, there is an urgent need to develop a Ni-Mo-Fe hydrorefining catalyst and its preparation method suitable for the hydrorefining of styrene tar. By specifically controlling the spatial distribution of active components in the support particles, the preferential hydrogenation stabilization efficiency of highly active unsaturated components can be improved, the polymerization and coking tendencies can be reduced, and the long-term operational stability of the catalyst can be improved. Summary of the Invention

[0008] The purpose of this invention is to overcome the deficiencies in the prior art and provide a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst, its preparation method, and its application. By programmatically controlling the pH, complexation state, diffusion process, and drying and curing process of different impregnation steps, the spatial distribution of active components within the support particles is optimized, so that Ni and Mo are preferentially enriched in the outer layer region of the support, while Fe is mainly distributed in the sub-outer to middle layer region, forming a catalyst structure with radial functional partitioning characteristics. This improves the preferential hydrogenation stabilization efficiency of highly active unsaturated components in styrene tar, reduces polymerization and coking tendencies, and improves the long-term operational stability of the catalyst.

[0009] The objective of this invention can be achieved through the following technical solutions: The present invention provides a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst, wherein the content of each component in the Ni-Mo-Fe hydrorefining catalyst, based on oxides, comprises by mass percentage: 10-25 wt% MoO3, 2-10 wt% NiO, 0.2-6 wt% Fe2O3, with the balance being a support; and Ni and Mo in MoO3 and NiO are enriched in the outer layer region of the support, while Fe in Fe2O3 is enriched in the sub-outer to middle layer region of the support; The average concentration of Ni in the outer region of the catalyst is 1.2 to 3.0 times its overall average concentration, and the average concentration of Mo in the outer shell region is 1.1 to 2.5 times its overall average concentration. The overall average concentration refers to the average value obtained by dividing the total molar amount of elements in the catalyst particles (from the core to the sub-outer layer and then to the outer layer) by the total volume of the catalyst particles.

[0010] In some embodiments of the present invention, the carrier is γ-Al2O3 or η / γ composite alumina, and its shape is any one of strip, clover-shaped, or four-leaf clover-shaped extrusion strips, and the specific surface area of ​​the carrier is 120-300 m². 2 / g, with a water absorption pore volume of 0.35~0.90mL / g and an average pore size of 6~20nm.

[0011] In some embodiments of the present invention, the active ingredients contain, by mass percentage, 0.01 to 4.0 wt% P2O5, calculated as oxides.

[0012] Furthermore, in some preferred embodiments, the active ingredient contains 0.2 to 2.0 wt% P2O5 by mass percentage, calculated as oxides.

[0013] The second invention provides a method for preparing a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst, comprising the following steps: S1. The carrier is pre-dried; the pre-dried carrier is first impregnated with a molybdenum-containing impregnation solution with a pH of 0.8 to 2.5, so that molybdenum is preferentially deposited in the outer layer of the carrier particles, and then dried to obtain a Mo-containing intermediate. S2. The Mo-containing intermediate obtained in step S1 is impregnated a second time with a nickel-containing complex impregnation solution with a pH of 6.0 to 8.5, so that nickel is mainly distributed in the outer region enriched by molybdenum. After drying, a Ni-Mo-containing intermediate is obtained. S3. The Ni-Mo intermediate obtained in step S2 is impregnated for the third time with an iron-containing complex impregnation solution with a pH of 2.5 to 4.5, and then subjected to vacuum aspiration treatment and normal pressure aging treatment in sequence, so that the iron is mainly distributed in the sub-outer layer to the middle layer region of the carrier particles. The sample is dried in stages to obtain the Ni-Mo-Fe primary sample. S4. The Ni-Mo-Fe primary sample obtained in step S3 is subjected to segmented calcination to obtain the radially gradient distributed Ni-Mo-Fe hydrogenation refining catalyst.

[0014] In some preferred embodiments of the present invention, the pH of the molybdenum-containing impregnation solution in step S1 is 1.0 to 2.2.

[0015] In some preferred embodiments of the present invention, the pH of the nickel-containing complex impregnation solution in step S2 is 6.8 to 7.2.

[0016] In some preferred embodiments of the present invention, the pH of the iron-containing complex impregnation solution in step S3 is 3.2 to 3.8.

[0017] In some embodiments of the present invention, the molybdenum precursor used in the molybdenum-containing impregnation solution in step S1 is selected from any one or more of ammonium heptamolybdate, ammonium paramolybdate, ammonium metamolybdate, molybdic acid, and molybdenum trioxide.

[0018] Furthermore, in some preferred embodiments, the molybdenum-containing impregnation solution is a mixture obtained by reacting molybdenum trioxide with hydrogen peroxide solution or a mixture obtained by reacting molybdic acid with hydrogen peroxide solution.

[0019] In some embodiments of the present invention, the nickel-containing complex impregnation solution in step S2 is prepared by mixing nickel precursor, complexing agent and deionized water; the iron-containing complex impregnation solution in step S3 is prepared by mixing iron precursor, complexing agent and deionized water.

[0020] Furthermore, the nickel precursor used in the nickel-containing complex impregnation solution in step S2 is selected from any one or more of nickel nitrate, nickel acetate, and nickel carbonate; the iron precursor used in the iron-containing complex impregnation solution in step S3 is selected from any one or more of ferric nitrate, ferric citrate, ferric oxalate, and ferric acetylacetone.

[0021] Furthermore, the complexing agent used in the impregnation solution is selected from any one or more of citric acid, malic acid, ethylenediaminetetraacetic acid, and tartaric acid.

[0022] Furthermore, the nickel nitrate (in Ni) 2+ The molar ratio of the ferric nitrate (calculated as Fe) to the complexing agent is 1:0.2 to 1:0.5; the ferric nitrate nonahydrate (in Fe) 3+ The molar ratio of the complexing agent to the complexing agent is 1:0.5 to 0.85.

[0023] Adding complexing agents to nickel-containing complexing impregnation solutions and iron-containing complexing impregnation solutions can reduce the tendency of instantaneous hydrolysis and rapid surface deposition of metal ions such as nickel and iron, and enhance the controllable migration and anchoring of metal precursors.

[0024] In some embodiments of the present invention, the vacuum degree of the depressurization inhalation treatment in step S3 is -0.04 to -0.09 MPa, and the holding time is 3 to 20 min; the time of the atmospheric pressure aging treatment is 20 to 120 min.

[0025] The present invention, through the introduction of a weakly acidic iron-containing complex impregnation solution and subsequent reduced pressure intake and atmospheric pressure aging treatment, is beneficial to optimizing the spatial distribution of Fe components in the support particles and improving the local interface environment and operational stability of the catalyst.

[0026] In some embodiments of the present invention, the segmented drying in step S3 includes at least two of the following stages: holding at 40-60°C for 0.5-3 hours, holding at 60-80°C for 1-4 hours, holding at 80-100°C for 1-4 hours, and holding at 100-120°C for 2-8 hours; the segmented calcination in step S4 includes at least two of the following stages: holding at 120-250°C for 0.5-3 hours, holding at 250-350°C for 1-8 hours, and holding at 350-600°C for 1-8 hours.

[0027] The third invention provides the application of a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst in the hydrorefining of styrene tar.

[0028] In some embodiments of the present invention, the application of the Ni-Mo-Fe hydrorefining catalyst in the hydrorefining of styrene tar follows the steps described below: (1) The Ni-Mo-Fe hydrorefining catalyst is packed into the reactor and a sulfiding agent is introduced for pre-sulfidation treatment to obtain a sulfidated catalyst; (2) After pre-sulfurization, styrene tar feedstock is introduced into the hydrogenation refining reaction under a hydrogen atmosphere. The reaction temperature is 260-400℃, the reaction pressure is 1.0-12.0MPa, and the liquid hourly space velocity is 0.1-5.0h. -1 The hydrogen-to-oil volume ratio is 50–2000 Nm³. 3 / m 3 .

[0029] In some embodiments of the present invention, the pre-vulcanization treatment in step (1) is carried out at a temperature of 280–380°C, a pressure of 1.0–8.0 MPa, a vulcanization time of 2–24 h, and a liquid hourly space velocity of 0.1–3.0 h. -1 The hydrogen-to-oil volume ratio is 50–1000 Nm. 3 / m 3 The vulcanizing agent is selected from any one or more of dimethyl disulfide, di-tert-butyl polysulfide, and vulcanized oil.

[0030] Furthermore, in some preferred embodiments, the reaction temperature in step (2) is 300–340°C; the reaction pressure is 2.0–8.0 MPa; and the liquid hourly space velocity is 0.2–2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 100–1000 Nm. 3 / m 3 .

[0031] Furthermore, the styrene tar is the bottom liquid, recovery column residue, evaporation residue, or a mixture thereof produced by the distillation system of the ethylbenzene dehydrogenation to styrene unit.

[0032] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves optimized spatial distribution of active components within the carrier particles by using a programmed introduction method of "acidic Mo outer layer pre-deposition - near-neutral Ni outer layer anchoring - weak acid complexed Fe internal diffusion / middle layer fixation", combined with segmented low-speed drying and curing and segmented calcination treatment, thus constructing a Ni-Mo-Fe hydrogenation refining catalyst with radial functional partitioning characteristics.

[0033] 2. In the preparation of the catalyst, this invention adjusts the pH of different impregnation steps to promote the preferential enrichment of Ni and Mo in the outer layer of the support, which is beneficial to the preferential hydrogenation and stabilization of highly active unsaturated components in styrene tar on the outer layer of the particles, thereby reducing the tendency of polymerization and coking. On the other hand, by combining reduced pressure intake and normal pressure aging treatment, the spatial distribution of Fe components in the support particles is optimized, thereby improving the local interface environment and operational stability of the catalyst.

[0034] 3. Compared with conventional uniformly distributed catalysts or simple stepwise impregnation catalysts, this invention has advantages in balancing the rapid stabilization of highly active unsaturated components with the long-term stability of the catalyst. Furthermore, the preparation process of this invention is clear and the process parameters are adjustable, making it suitable for the scale-up preparation of industrial-grade molded supports and demonstrating promising application prospects. Attached Figure Description

[0035] Figure 1 This is an XRD diagram of the Ni-Mo-Fe hydrogenation refining catalyst of Example 1.

[0036] Figure 2 This is a scanning electron microscope image of the Ni-Mo-Fe hydrorefining catalyst in Example 1 and a schematic diagram of its corresponding EDS elemental distribution. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0038] Unless otherwise specified, the experimental methods used in this embodiment are conventional methods, and the materials and reagents used are commercially available. The sources of the raw materials used in this invention are described below: Support: γ-Al2O3 extruded support, with a pore size distribution concentrated in the range of 10–20 nm and a specific surface area of ​​approximately 266 m². 2 / g.

[0039] Example 1 A method for preparing a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst includes the following steps: S1. The γ-Al2O3 extruded support was dried at 120℃ for 4h. 100g of the dried γ-Al2O3 extruded support was taken and naturally cooled to room temperature. The water absorption pore volume of the support was measured to be 0.61mL / g. Weigh 23.50 g of molybdenum trioxide and slowly add it to 36 mL of 30 wt% hydrogen peroxide solution. Stir and react in an ice-water bath at 5 ± 5 °C for 60 min to form a clear orange-yellow peroxymolybdic acid precursor solution. To prepare an equal volume of molybdenum-containing impregnation solution that matches the absorbent pore volume of the carrier, calculate the amount of deionized water required based on the absorbent pore volume. First, add 90%–95% of this amount of deionized water and mix. Measure the pH of the solution at room temperature. If necessary, adjust the pH of the solution with 10 wt% dilute ammonia or 0.5 mol / L dilute nitric acid. Then, add a trace amount of deionized water to the target volume. Measure the pH of the final molybdenum-containing impregnation solution at room temperature. The pH is 1.8. The molybdenum-containing impregnation solution was added to the dried γ-Al₂O₃ extruded support in three equal-volume impregnation steps, with each addition being approximately one-third of the total volume of the molybdenum-containing impregnation solution. After each addition, the mixture was slowly stirred and impregnated for 3–5 minutes until the impregnation solution was largely absorbed by the support before the next addition was performed. After the three additions were completed, the mixture was allowed to stand and age at room temperature and atmospheric pressure for 25 minutes to allow molybdenum to preferentially deposit on the outer layer of the support particles. The impregnated sample was first dried at 60 °C for 1 hour and then at 110 °C for 3 hours to obtain a Mo-containing intermediate. After naturally cooling to room temperature, the water absorption pore volume of the Mo-containing intermediate was measured to be 0.48 mL / g. S2. Weigh 25.70g of nickel nitrate hexahydrate and 7.00g of citric acid, then calculate and prepare the nickel-containing complex impregnation solution. To prepare a nickel-containing complex impregnation solution with a volume 0.95 times the water absorption pore volume of the Mo-containing intermediate, calculate the amount of deionized water required based on the water absorption pore volume. First, mix 90%–95% of this amount of deionized water with 25.70g of nickel nitrate hexahydrate, then add 7.00g of citric acid, stir evenly, and measure the pH of the solution at room temperature. If necessary, adjust the pH of the solution with 10wt% dilute ammonia water. Then, add a trace amount of deionized water to the target volume. After measuring at room temperature, the final pH of the nickel-containing complex impregnation solution is 7.2. A nickel-containing complex impregnation solution was added to a Mo-containing intermediate using a near-equal-volume impregnation method. The volume of the nickel-containing complex impregnation solution was 0.95 times the actual water absorption pore volume of the Mo-containing intermediate. After mixing by rolling and stirring for 10 min, the mixture was allowed to stand and age for 30 min at normal pressure and room temperature, so that nickel was mainly distributed in the outer region enriched by molybdenum. The impregnated sample was first dried at 80℃ for 1 h, and then dried at 120℃ for 4 h to obtain a Ni-Mo-containing intermediate. After naturally cooling to room temperature, the water absorption pore volume of the Ni-Mo-containing intermediate was measured to be 0.37 mL / g. S3. Weigh 8.00g of ferric nitrate nonahydrate and 2.00g of malic acid, then calculate and prepare the iron-containing complex impregnation solution. To prepare an iron-containing complex impregnation solution with a volume 1.1 times the pore volume of the Ni-Mo intermediate, calculate the amount of deionized water required based on the pore volume. First, mix 90%–95% of this amount of deionized water with 8.00g of ferric nitrate nonahydrate, then add 2.00g of malic acid. After stirring evenly, measure the pH of the solution at room temperature. If necessary, adjust the pH of the solution with 10wt% dilute ammonia or 0.5mol / L dilute nitric acid. Then, add a trace amount of deionized water to the target volume. After measuring at room temperature, the final pH of the iron-containing complex impregnation solution is 3.5. The Ni-Mo intermediate was placed in a vacuum impregnation apparatus, and the vacuum was evacuated to -0.07 MPa and maintained for 3–5 min. Then, the above-mentioned iron-containing complex impregnation solution was added while maintaining the -0.07 MPa vacuum, and the vacuum was maintained for another 3–5 min. The pressure was then slowly restored to normal, and the sample was allowed to stand and age at room temperature for 45 min to allow the iron to be mainly distributed in the sub-outer to middle layer of the support. The resulting sample was then dried sequentially at 50 °C for 1 h, 60 °C for 2 h, 90 °C for 2 h, and 120 °C for 6 h, and then naturally cooled to room temperature to obtain the Ni-Mo-Fe primary sample. S4. The Ni-Mo-Fe primary sample obtained in step S3 is placed in a muffle furnace and calcined in stages under an air atmosphere: the temperature is raised from room temperature to 120°C at a rate of 1°C / min and held for 1 hour; then raised to 250°C at a rate of 1°C / min and held for 1 hour; then raised to 450°C at a rate of 2°C / min and held for 4 hours; and then naturally cooled to room temperature to obtain the radially gradient distributed Ni-Mo-Fe hydrogenation refining catalyst.

[0040] Example 2 A method for preparing a radially gradient-distributed P-Ni-Mo-Fe hydrorefining catalyst, the specific implementation method is basically the same as that in Example 1, the difference being: In step S2, a phosphorus-containing precursor (85wt% phosphoric acid solution) is introduced into the preparation of the nickel-containing complex impregnation solution. Specifically, 90%–95% of the required amount of deionized water is mixed with 25.7g of nickel nitrate hexahydrate and 1.15g of 85wt% phosphoric acid solution. Then, 7.00g of citric acid is added, and the mixture is stirred until homogeneous. The pH of the solution is measured at room temperature, and if necessary, 10wt% dilute ammonia is used to adjust the pH. A trace amount of deionized water is then added to the target volume. The final pH of the nickel-containing complex impregnation solution is approximately 7.2, measured at room temperature. After impregnation and drying, a P-Ni-Mo intermediate is obtained. In step S3, the preparation and introduction of the impregnation solution are the same as in Example 1, but the volume of the iron-containing complex impregnation solution is re-prepared to be 1.1 times the actual water absorption pore volume of the P-Ni-Mo intermediate obtained in Example 2.

[0041] Example 3 A method for preparing a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst, the specific implementation method is basically the same as that in Example 1, the difference being: In step S1, 19.00 g of molybdenum trioxide was weighed and slowly added to 30 mL of 30 wt% hydrogen peroxide solution. The same operation as in step S1 was followed to prepare an equal volume of molybdenum-containing impregnation solution that matched the water absorption pore volume of the carrier. The pH of the final molybdenum-containing impregnation solution was 2.2. After impregnation and drying, a Mo-containing intermediate was obtained. The preparation and introduction of the impregnation solution in subsequent steps S2 and S3 are the same as in Example 1, but the volume of the nickel complex impregnation solution is re-prepared to 0.95 times the actual water absorption pore volume of the Mo-containing intermediate obtained in Example 3, and the volume of the iron complex impregnation solution is re-prepared to 1.1 times the actual water absorption pore volume of the Ni-Mo intermediate obtained in Example 3.

[0042] Example 4 A method for preparing a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst, the specific implementation method is basically the same as that in Example 1, the difference being: To ensure the operability of the nickel-containing complex impregnation solution under high Ni loading conditions and to reduce local precipitation and surface accumulation caused by a single high-concentration impregnation, the nickel component was introduced in a two-step impregnation method. The first step was the same as step S2 in Example 1. The actual water absorption pore volume of the Ni-Mo one-step intermediate was measured to be 0.37 mL / g. The second impregnation step was then carried out: 17.10g of nickel nitrate hexahydrate and 4.67g of citric acid were weighed, and the nickel-containing complex impregnation solution was calculated and prepared. The nickel-containing complex impregnation solution was prepared in the same way as step S2, with a volume of 0.95 times the actual water absorption pore volume of the Ni-Mo one-step intermediate. The pH of the final nickel-containing complex impregnation solution was 7.0. The remaining operations were the same as step S2 in Example 1 to obtain the Ni-Mo intermediate. In step S3, the preparation and introduction of the impregnation solution are the same as in Example 1, but the volume of the iron-containing complex impregnation solution is re-prepared to 1.1 times the actual water absorption pore volume of the Ni-Mo intermediate obtained in Example 4, and finally a Ni-Mo-Fe hydrogenation refining catalyst with high Ni loading and radial gradient distribution is obtained.

[0043] Example 5 A method for preparing a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst, the specific implementation method is basically the same as that in Example 1, the difference being: To ensure the operability of the iron-containing complex impregnation solution under high Fe loading conditions and to reduce local precipitation and surface accumulation caused by a single high-concentration impregnation, the iron component is introduced in a two-step impregnation method. The first step is the same as step S3 in Example 1. The actual water absorption pore volume of the Ni-Mo-Fe one-step intermediate is measured to be 0.32 mL / g. The second impregnation step was then carried out: 16.00g of ferric nitrate nonahydrate was weighed, and 4.00g of malic acid was added. Then, the iron-containing complex impregnation solution was calculated and prepared. The iron-containing complex impregnation solution containing 1.1 times the actual water absorption pore volume of the Ni-Mo-Fe one-step intermediate was prepared according to the same operation as in step S3. The pH of the final iron-containing complex impregnation solution was 3.5. The same vacuum impregnation treatment was then performed to obtain the Ni-Mo-Fe primary sample.

[0044] Example 6 A method for preparing a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst, the specific implementation method is basically the same as that in Example 1, the difference being: In step S1, 12.80 g of molybdenum trioxide was weighed and slowly added to 19.6 mL of 30 wt% hydrogen peroxide solution. The final molybdenum-containing impregnation solution had a pH of 2.0. The remaining steps of S1 were the same as in Example 1. In step S2, 11.30g of nickel nitrate hexahydrate and 3.08g of citric acid were weighed. The final nickel-containing complex impregnation solution had a pH of 7.0. The remaining steps in S2 were the same as in Example 1. In step S3, 1.80g of ferric nitrate nonahydrate and 0.45g of malic acid were weighed. The final iron-containing complex impregnation solution had a pH of 3.5. The remaining steps in S3 were the same as in Example 1.

[0045] Example 7 A method for preparing a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst, the specific implementation method is basically the same as that in Example 1, the difference being: In step S1, Mo is introduced by a multi-stage molybdenum-containing impregnation method; the first step is the same as in Example 1, and the actual water absorption pore volume of the Mo-containing one-step intermediate is measured to be 0.48 mL / g; The second step, molybdenum impregnation, was then carried out: 14.70 g of molybdenum trioxide was weighed and slowly added to 22.5 mL of 30 wt% hydrogen peroxide solution. The same procedure as in step S1 was followed to prepare an equal volume of molybdenum impregnation solution matching the pore volume of the Mo-containing one-step intermediate. The pH of the final molybdenum impregnation solution was 2.2. The remaining S1 procedure was the same as in Example 1. The actual pore volume of the obtained Mo-containing two-step intermediate was 0.41 mL / g. In step S2, Ni is introduced by a multi-stage nickel-containing impregnation method; the first step is the same as in Example 1, but the volume of the impregnation liquid is determined based on the actual water absorption pore volume of the two-step intermediate containing Mo obtained in S1; the remaining operations in S2 are the same as in Example 1, and the actual water absorption pore volume of the one-step intermediate containing Ni-Mo is measured to be 0.37 mL / g. A second nickel-containing impregnation was then performed: 34.50 g of nickel nitrate hexahydrate was weighed and 9.39 g of citric acid was added, resulting in a final nickel-containing impregnation solution with a pH of 7.0; the remaining S2 operations were the same as in Example 1, and the actual water absorption pore volume of the obtained Ni-Mo two-step intermediate was determined to be 0.31 mL / g. In step S3, Fe is introduced by a stepwise iron-containing impregnation method. The first step is the same as in Example 1, but the volume of the impregnation liquid is determined based on the actual water absorption pore volume of the Ni-Mo two-step intermediate obtained in S2. The remaining operations in S3 are the same as in Example 1, and the actual water absorption pore volume of the obtained Ni-Mo-Fe one-step intermediate is measured to be 0.28 mL / g. A second iron-containing impregnation was then performed: 37.24g of ferric nitrate nonahydrate was weighed and 9.31g of malic acid was added, resulting in an iron-containing impregnation solution with a pH of 3.5; the remaining S3 operations were the same as in Example 1, yielding a Ni-Mo-Fe primary sample.

[0046] Comparative Example 1 A method for preparing a Ni-Mo-Fe hydrorefining catalyst differs from Example 1 in that: a conventional co-impregnation method is used to simultaneously introduce a molybdenum precursor, a nickel precursor, and an iron precursor into the same impregnation solution. The molybdenum precursor is ammonium heptamolybdate, the nickel precursor is nickel nitrate hexahydrate, and the iron precursor is iron nitrate nonahydrate. The pH of the system is adjusted to 3.8 using 0.5 mol / L dilute nitric acid / 10 wt% dilute ammonia. The catalyst is then impregnated into a pre-dried support in equal volumes. After impregnation, the catalyst is dried at 120°C for 6 hours and then subjected to the same segmented calcination operation as in Example 1 to obtain the Ni-Mo-Fe hydrorefining catalyst.

[0047] Comparative Example 2 A method for preparing a Ni-Mo-Fe hydrorefining catalyst is described, with the specific implementation method being the same as in Example 1, except that: in step S3, the reduced pressure suction treatment is not performed, and the catalyst is directly dried at 120°C for 6 hours after impregnation. The remaining steps are the same, and the Ni-Mo-Fe hydrorefining catalyst is obtained.

[0048] Comparative Example 3 A method for preparing a Ni-Mo hydrorefining catalyst, the specific implementation method is the same as in Example 1, except that the iron-containing complex impregnation treatment in step S3 is not performed, and the Ni-Mo hydrorefining catalyst is obtained.

[0049] Comparative Example 4 A method for preparing a Ni-Mo-Fe hydrorefining catalyst is described, with the specific implementation method being the same as in Example 1, except that the order of metal introduction is changed to Fe first, then Mo, and then Ni. Specifically, the support is first treated with an iron-containing complex impregnation solution with a pH of approximately 3.5 and then dried, followed by treatment with a peroxymolybdic acid impregnation solution with a pH of approximately 1.8, and finally treatment with a nickel-containing impregnation solution with a pH of approximately 7.2. The remaining conditions are the same as in Example 1, and the Ni-Mo-Fe hydrorefining catalyst is obtained.

[0050] Performance testing I. ICP Determination of Hydrorefining Catalysts The hydrorefining catalysts obtained in Examples 1-7 and Comparative Examples 1-4 were subjected to ICP determination, and the results are shown in Table 1.

[0051] Table 1. ICP Measurement Results

[0052] II. XRD and Scanning Electron Microscopy Tests like Figure 1 and Figure 2 The characterization results shown indicate that Figure 1No characteristic diffraction peaks of Ni, Mo, and Fe oxides were observed in the XRD pattern, and the presence of these elements was confirmed by SEM-EDS, indicating that the active components are highly dispersed on the γ-Al₂O₃ support surface and have not formed large crystalline phases, which is conducive to exposing more active sites. Meanwhile, Figure 2 SEM-EDS cross-sectional analysis showed that the active components Ni, Mo, and Fe exhibited a distinct radial distribution. Ni and Mo were concentrated in the outer layer (shell) of the catalyst, while Fe was distributed in the sub-outer layer region. The core was mainly a porous γ-Al2O3 support, and the distribution regions of Ni and Mo highly overlapped.

[0053] III. Performance Evaluation of Styrene Tar Hydrorefining The catalysts prepared in Examples 1-7 and Comparative Examples 1-4 were used to evaluate the performance of styrene tar hydrorefining. The evaluation was conducted in a fixed-bed continuous reactor. The composition of styrene tar raw material is as follows: 2.2 wt% styrene, 2.5 wt% α-methylstyrene, 68.1 wt% dimers and oligomers, and the remainder is other high-boiling aromatic hydrocarbons. Other specific raw material information is shown in Table 2.

[0054] Table 2 Properties of styrene tar

[0055] The steps for applying the hydrorefining catalyst in the hydrorefining of styrene tar are as follows: (1) 80 mL of hydrorefining catalyst was packed into a fixed-bed reactor. After purging with nitrogen for 1 h, the system pressure was switched to hydrogen and stabilized to 2.5 MPa. Then, pre-sulfurized oil containing 3.0 wt% dimethyl disulfide as solvent, with toluene as the solvent, was introduced for pre-sulfurization at a liquid hourly space velocity of 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 300 Nm. 3 / m 3 The pre-sulfurization process is as follows: hold at 100℃ for 2 hours, hold at 180℃ for 2 hours, hold at 250℃ for 2 hours, and hold at 330℃ for 5 hours. After pre-sulfurization, a sulfurized catalyst is obtained. (2) After pre-sulfurization, styrene tar feedstock is introduced into the hydrogenation refining reaction under a hydrogen atmosphere at a temperature of 340°C, a pressure of 6.0 MPa, and a liquid hourly space velocity of 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 500 Nm 3 / m 3 .

[0056] Test method: The obtained sulfided catalyst was tested after 120 hours of continuous operation, and the results are shown in Table 3.

[0057] ① The qualitative and quantitative analysis of styrene and α-methylstyrene products was performed using GC and GC-MS; ② Bromine value of product: determined according to SH / T0630, unit is gBr / 100g oil.

[0058] ③ Operating pressure drop: The operating pressure drop during the reaction process is recorded online by the device.

[0059] ④ Catalyst coke content: Characterized by TG-DSC, the weight loss was calculated by programmed temperature rise oxidation under air atmosphere. The test temperature range was 20℃~800℃, and the heating rate was 20℃ / min.

[0060] Table 3 Performance Evaluation of Hydrorefining

[0061] The above results indicate that the present invention, through a programmed preparation method of "acidic Mo outer layer pre-deposition—near-neutral Ni outer layer anchoring—weak acid complexed Fe vacuum absorption into the middle layer," combined with segmented drying and curing and segmented calcination, can optimize the spatial distribution of active components in the support particles. Benefiting from this structural feature, Ni and Mo preferentially accumulate in the outer layer of the particles, which is beneficial for the rapid hydrogenation stabilization of highly active unsaturated components in styrene tar, thereby reducing the bromine value of the product and inhibiting polymerization and coking. The introduction of Fe components and its subsequent spatial distribution optimization are beneficial for improving the local interfacial environment and operational stability of the catalyst. For Example 2 containing P, based on the radial gradient distribution structure constructed in this invention, the introduction of a small amount of phosphorus is beneficial for adjusting the anchoring and dispersion state of Ni and Mo species, and to a certain extent promotes the formation of the hydrogenation-refined active phase, thus exhibiting higher styrene and α-methylstyrene conversion rates and lower product bromine values. However, the introduction of P may also affect the acidity and pore environment of the support surface, enhancing the residence and conversion of some heavy unsaturated components on the catalyst surface, thereby leading to a slight increase in catalyst coking.

[0062] In contrast, Comparative Example 1, using a one-pot co-impregnation method, allowed Ni, Mo, and Fe to coexist disorderly within the particles, making it difficult to form a clear outer Ni-Mo synergistic enrichment structure. This resulted in highly active unsaturated components being preferentially stabilized on the outer layer of the particles in a timely manner, leading to increased polymerization and coking. This manifested as lower conversion rates, higher bromine values ​​in the products, faster increases in bed pressure drop, and a significant increase in coke buildup. Comparative Example 2, without depressurization suction treatment, allowed Fe to remain more readily on the outermost layer of the particles, making it difficult for Fe to exert its regulatory effect on the inner environment of the shell. This also weakened the rational stratification of active components. The distribution of active components leads to a decrease in catalyst stability. Comparative Example 3, which did not introduce Fe, still achieved a certain degree of Ni-Mo outer layer enrichment, but lacked further regulation of the local interfacial environment and operational stability within the particles. Therefore, its overall performance was significantly lower than that of the embodiments of this invention. In Comparative Example 4, due to the altered metal introduction order, the initially introduced Fe was easily disturbed during subsequent Mo and Ni impregnation processes, making it difficult to form an effective combination with the outer Ni-Mo shell. This resulted in an imbalance in the spatial distribution of active components, thus affecting the rapid stabilization effect of the highly active unsaturated components. In summary, the active component spatial distribution regulation strategy proposed in this invention is beneficial for improving the activity, anti-coking ability, and operational stability during the hydrorefining of styrene tar.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present application in any way. Although the present application discloses the preferred embodiment as described above, it is not intended to limit the present application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of the present application using the disclosed technical content are equivalent to equivalent implementation cases. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst, comprising an active component and a support, characterized in that, The Ni-Mo-Fe hydrorefining catalyst comprises, by mass percentage, 10–25 wt% MoO3, 2–10 wt% NiO, and 0.2–6 wt% Fe2O3, with the remainder being the support; and Ni and Mo in MoO3 and NiO are enriched in the outer layer of the support, while Fe in Fe2O3 is enriched in the sub-outer to middle layer of the support. The average concentration of Ni in the outer region of the catalyst is 1.2 to 3.0 times its overall average concentration, and the average concentration of Mo in the outer shell region is 1.1 to 2.5 times its overall average concentration; wherein, the overall average concentration refers to the average value obtained by dividing the total molar amount of elements in the catalyst particles by the total volume of the catalyst particles.

2. The radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst according to claim 1, characterized in that, The support is γ-Al₂O₃ or η / γ composite alumina, and the specific surface area of ​​the support is 120–300 m². 2 / g, with a water absorption pore volume of 0.35~0.90mL / g and an average pore size of 6~20nm.

3. The radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst according to claim 1, characterized in that, The active ingredients contain, in terms of oxide content, 0.01 to 4 wt% P2O5 by mass percentage.

4. A method for preparing a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst according to any one of claims 1-3, characterized in that, Includes the following steps: S1. The carrier is pre-dried; the pre-dried carrier is first impregnated with a molybdenum-containing impregnation solution with a pH of 0.8 to 2.5, so that molybdenum is preferentially deposited in the outer layer of the carrier particles, and then dried to obtain a Mo-containing intermediate. S2. The Mo-containing intermediate obtained in step S1 is impregnated a second time with a nickel-containing complex impregnation solution with a pH of 6.0 to 8.5, so that nickel is mainly distributed in the outer region enriched by molybdenum. After drying, a Ni-Mo-containing intermediate is obtained. S3. The Ni-Mo intermediate obtained in step S2 is impregnated for the third time with an iron-containing complex impregnation solution with a pH of 2.5 to 4.5, and then subjected to vacuum aspiration treatment and normal pressure aging treatment in sequence, so that the iron is mainly distributed in the sub-outer layer to the middle layer region of the carrier particles. The sample is dried in stages to obtain the Ni-Mo-Fe primary sample. S4. The Ni-Mo-Fe primary sample obtained in step S3 is subjected to segmented calcination to obtain the radially gradient distributed Ni-Mo-Fe hydrogenation refining catalyst.

5. The method for preparing the radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst according to claim 4, characterized in that, The pH of the molybdenum-containing impregnation solution in step S1 is 1.0 to 2.2; the molybdenum precursor used in the molybdenum-containing impregnation solution is selected from any one or more of ammonium heptamolybdate, ammonium parmolybdate, ammonium metamolybdate, molybdic acid, and molybdenum trioxide.

6. The method for preparing the radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst according to claim 4, characterized in that, The pH of the nickel-containing complex impregnation solution in step S2 is 6.8 to 7.2; the nickel precursor used in the nickel-containing complex impregnation solution is selected from any one or more of nickel nitrate, nickel acetate and nickel carbonate.

7. The method for preparing the radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst according to claim 4, characterized in that, The pH of the iron-containing complex impregnation solution in step S3 is 3.2 to 3.8; the iron precursor used in the iron-containing complex impregnation solution is selected from any one or more of ferric nitrate, ferric citrate, ferric oxalate and ferric acetylacetone.

8. The method for preparing the radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst according to claim 4, characterized in that, The vacuum degree of the depressurization inhalation treatment in step S3 is -0.04 to -0.09 MPa, and the holding time is 3 to 20 minutes; the time for the atmospheric pressure aging treatment is 20 to 120 minutes.

9. The application of a radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst according to any one of claims 1-3 in the hydrorefining of styrene tar.

10. The application of the radially gradient-distributed Ni-Mo-Fe hydrorefining catalyst according to claim 9, characterized in that, The steps for applying the Ni-Mo-Fe hydrorefining catalyst in the hydrorefining of styrene tar are as follows: (1) The Ni-Mo-Fe hydrorefining catalyst is packed into the reactor and a sulfiding agent is introduced for pre-sulfidation treatment to obtain a sulfidated catalyst; (2) After pre-sulfurization, styrene tar feedstock is introduced into the hydrogenation refining reaction under a hydrogen atmosphere. The reaction temperature is 260-400℃, the reaction pressure is 1.0-12.0MPa, and the liquid hourly space velocity is 0.1-5.0h. -1 The hydrogen-to-oil volume ratio is 50–2000 Nm³. 3 / m 3 .

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