A catalyst for selective hydrogenation of polycyclic aromatic hydrocarbons

Abstract

A catalyst for the selective hydrogenation of polycyclic aromatic hydrocarbons (PAHs) is provided, using alkali-modified alumina as a carrier, onto which an inorganic acid and an active component are loaded. The active component is distributed from the catalyst surface to a catalyst surface layer no thicker than one-third of the catalyst radius; the inorganic acid is loaded on the catalyst's outer surface. The addition of an inorganic acid to the catalyst of the present invention and loading of the inorganic acid on the catalyst's outer layer facilitates increasing the contact surface between the acid and the active metal, while also facilitating loading of the acid onto the active sites of the active metal, thereby fully utilizing the acid's ability to provide H protons. Pre-treating the carrier with an alkaline solution facilitates distribution of the active metal to the catalyst's outer surface, thereby reducing the catalyst's acidity. During the reaction, even if aromatic hydrocarbons diffuse into the carrier's interior, excessive hydrogenation will not occur, thereby achieving the goals of increasing the PAH hydrogenation activity and reducing the loss of monocyclic aromatic hydrocarbons.

Description

Technical Field

[0001] The present invention relates to the technical field of oil hydrogenation, and in particular to a polycyclic aromatic hydrocarbon selective hydrogenation catalyst. Background Art

[0002] The Beijing VIB diesel quality standard, which came into effect in December 2021, requires not only a sulfur content of less than 10µg / g in refined diesel but also a polycyclic aromatic hydrocarbon (PAH) content of less than 5%. Refiners need to reduce hydrogen consumption to lower costs when producing diesel. This requires hydrogenation catalysts with high PAH saturation activity and selectivity to prevent deep hydrogenation of PAHs into cycloalkanes.

[0003] CN201710709613.6 discloses a catalyst for the selective hydrogenation of polycyclic aromatic hydrocarbons, comprising: A) a non-acidic or weakly acidic porous support and a catalyst supported thereon; and B) at least two metal elements or compounds selected from Group VIII; wherein the metal elements or compounds are distributed on the support surface in a core-shell layer, with the core metal selected from a mixture of Ni and Fe, and the shell metal selected from a mixture of Pt and Pd. This catalyst uses precious metals as active components, which can improve the catalyst's polycyclic aromatic hydrocarbon hydrogenation saturation activity. However, the catalyst is expensive and has a low tolerance to sulfides, making it susceptible to poisoning and deactivation.

[0004] CN201710709621.0 discloses a method for the efficient and selective hydrogenation of polycyclic aromatic hydrocarbons, characterized by: a) a non-acidic or weakly acidic porous support and a catalyst supported thereon; b) at least two metal elements or compounds selected from VIII, IA, and IIA, wherein the metal elements or compounds are distributed in a core-shell layer on the support surface; the core metal is selected from at least one of Li, K, Mg, Ca, and Sr metals and their compounds; and the shell metal is selected from at least one of Pt, Pd, and Ir metals and their compounds. This catalyst uses a precious metal as an active component, which can improve its saturation activity for polycyclic aromatic hydrocarbon hydrogenation. However, the catalyst is expensive and has a low tolerance to sulfides, making it susceptible to poisoning and deactivation. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention discloses a polycyclic aromatic hydrocarbon selective hydrogenation catalyst and a preparation method thereof. The catalyst has high polycyclic aromatic hydrocarbon hydrogenation activity and low monocyclic aromatic hydrocarbon loss rate.

[0006] In the context of this specification, the pyridine adsorption infrared acid property characterization method is used to analyze the acid properties of the support and catalyst. The test conditions of the pyridine adsorption infrared acid property characterization method include: the sample is purified in a reaction tube at 500°C and 60mPa for 4 hours, cooled to room temperature, and vacuumed to 0.1mPa to adsorb pyridine, and the surface acid properties of the sample are measured.

[0007] In order to achieve the above technical objectives, the technical solutions of the present invention are as follows:

[0008] The technical purpose of the first aspect of the present invention is to provide a polycyclic aromatic hydrocarbon selective hydrogenation catalyst, which uses alkali-modified alumina as a carrier, on which an inorganic acid and an active component are loaded, wherein the active components are Group VIB metal sulfide and Group VIII metal sulfide; based on the total weight of the catalyst, the alkali accounts for 0.1-5.0%, preferably 0.3-3.0%; the inorganic acid accounts for 1-12wt%, preferably 1.5-8wt%, more preferably 2-6wt%; the Group VIB metal sulfide accounts for 10-30%, preferably 15-28%, and the Group VIII metal sulfide accounts for 2-10%, preferably 4-8%; the active component is distributed from the catalyst surface to the catalyst surface layer not more than 1 / 3 of the catalyst radius thickness; the inorganic acid is loaded on the outer surface of the catalyst.

[0009] Furthermore, the Br acid content of the alkali-modified alumina is 0.01-0.04 mmol / g, and the L acid content is 0.01-0.1 mmol / g; the Br acid content of the catalyst is 0.05-0.2 mmol / g, and the L acid content is 0.3-1.0 mmol / g.

[0010] Furthermore, the base is selected from at least one of sodium hydroxide, potassium hydroxide and ammonia.

[0011] Furthermore, the inorganic acid is selected from at least one of phosphoric acid, boric acid, hydrofluoric acid, hydrochloric acid and sulfuric acid.

[0012] Furthermore, the inorganic acid loaded on the outer surface of the catalyst is loaded on a Group VIB metal sulfide, and / or loaded on a Group VIII metal sulfide, and / or loaded on an alumina carrier.

[0013] Furthermore, the active component is preferably distributed from the catalyst surface to a catalyst surface layer not greater than 1 / 4 of the catalyst radius thickness, more preferably not greater than 1 / 5 of the catalyst radius thickness of the catalyst surface layer. The concentration distribution of the active metal component in the radial direction of the catalyst can be measured using an electron probe. In the technical solution of the present invention, having an active component distribution means that from the outside to the inside in the radial direction of the catalyst particle, when the active component content is reduced to less than 30% of the content of the component in the outermost layer of the catalyst particle, it is considered that there is no active component distribution from the current catalyst layer to the catalyst center, and there is an active component distribution from the catalyst layer to the catalyst surface. The determination of the active component content in a certain catalyst layer is to randomly select 10 points in the catalyst layer of the same radius as the catalyst, use an electron probe to determine the element content, and perform arithmetic averaging on the measured values.

[0014] It should be understood by those skilled in the art that, for spherical catalysts, the radius is easy to determine, while for cylindrical, strip-shaped and other special-shaped catalysts, the catalyst radius referred to in the present invention refers to the radius of the circumscribed circle of the catalyst cross section.

[0015] Furthermore, the Group VIB metal sulfide is molybdenum sulfide and / or tungsten sulfide, and the Group VIII metal sulfide is nickel sulfide and / or cobalt sulfide.

[0016] The technical purpose of the second aspect of the present invention is to provide a method for preparing the above-mentioned polycyclic aromatic hydrocarbon selective hydrogenation catalyst, comprising the following steps:

[0017] (1) impregnating an alumina support with an alkaline solution and drying the alumina support to obtain a pretreated support;

[0018] (2) impregnating the pretreated support of step (1) with an impregnation solution containing a Group VIB metal salt and a Group VIII metal salt, wherein the volume of the impregnation solution is less than 70% of the saturated water absorption capacity of the alumina support, and performing drying and sulfurization treatment to obtain a catalyst precursor;

[0019] (3) Impregnating the catalyst precursor of step (2) with an inorganic acid solution, and drying in an inert atmosphere to obtain the polycyclic aromatic hydrocarbon selective hydrogenation catalyst.

[0020] Furthermore, the alkaline solution in step (1) is selected from at least one of sodium hydroxide, potassium hydroxide and ammonia solution, and the solute concentration in the solution is 0.01 g / mL-0.1 g / mL.

[0021] Furthermore, preferably, the volume of the alkaline solution is 70%-110%, preferably 80%-100%, of the saturated water absorption capacity of the alumina support.

[0022] Furthermore, the drying temperature in step (1) is 90-200° C., and the drying time is 3-6 hours.

[0023] Furthermore, the volume of the impregnation solution in step (2) is preferably 5-55% of the saturated water absorption capacity of the alumina support, and more preferably 25%-50%.

[0024] In the impregnation process of step (2), due to the high active metal content, it is not possible to ensure that the active metal is completely dissolved when the volume of the impregnation solution is low. Therefore, the active metal can be loaded onto the carrier by impregnation in batches multiple times. Each impregnation is carried out according to the agreed volume of impregnation solution. After each impregnation, it is dried and calcined before the next impregnation. This ensures that the active components are distributed in the agreed catalyst layer. The calcination conditions are: temperature of 300-500°C and time of 3-6 hours.

[0025] Furthermore, in step (2), the impregnation solution containing the Group VIB metal salt is a phosphate or ammonium salt solution of the Group VIB metal, and its preparation method is well known to those skilled in the art. The Group VIB metal is preferably Mo and / or W.

[0026] Furthermore, in step (2), the impregnation solution containing a Group VIII metal salt is a nitrate, acetate, or sulfate solution of a Group VIII metal, and its preparation method is well known to those skilled in the art. The Group VIII metal is Ni and / or Co.

[0027] Furthermore, the drying conditions shown in step (2) are: drying temperature 90-200° C., and drying time 3-6 hours.

[0028] Furthermore, the vulcanization treatment in step (2) is dry vulcanization or wet vulcanization. The dry vulcanizing agent is hydrogen sulfide, and the wet vulcanizing agent is one or two of carbon disulfide, dimethyl disulfide, methyl sulfide, and n-butyl sulfide; the vulcanization pressure is 3.2-6.4 MPa, the vulcanization temperature is 250-400°C, and the vulcanization time is 4-12 hours.

[0029] Furthermore, the inorganic acid in step (3) is selected from at least one of phosphoric acid, boric acid, hydrofluoric acid, hydrochloric acid, and sulfuric acid. The concentration of the inorganic acid solution is 0.01 g / mL to 0.1 g / mL.

[0030] Furthermore, the volume of the inorganic acid solution in step (3) is 10%-40%, preferably 10-30%, of the saturated water absorption of the catalyst precursor prepared in step (1).

[0031] Furthermore, the inert atmosphere in step (3) is one or more of N2 and an inert gas; the drying temperature in step (3) is 20-90°C, and the drying time is 4-16 hours.

[0032] Furthermore, when the alkaline solution, active component and inorganic acid are impregnated with an impregnation solution lower than the saturated water absorption capacity of the carrier, appropriate operations should be taken to ensure that the catalyst surface is in contact with the impregnation solution as evenly as possible, such as using an impregnation method in a rotating drum or a spray impregnation method.

[0033] The technical purpose of the third aspect of the present invention is to provide a method for hydrogenation saturation reaction of polycyclic aromatic hydrocarbons in oil products, wherein the oil products are contacted with the above-mentioned catalyst or the catalyst prepared by the above-mentioned preparation method for reaction.

[0034] Furthermore, the process conditions for the polycyclic aromatic hydrocarbon hydrogenation saturation reaction are as follows: pressure 1.0~12.0MPa, preferably 6.0~10.0MPa, wherein the hydrogen partial pressure accounts for 50%~90% of the total pressure; volume space velocity 0.1~10.0h -1 , preferably 0.5~3.0h-1 ; Reaction temperature 200~400℃, preferably 330~380℃; Hydrogen to oil volume ratio 10:1~1000:1, preferably 100:1~800:1.

[0035] Furthermore, the oil product is diesel, coker diesel, straight-run diesel, vacuum gas oil, catalytic cracking gas oil or thermal cracking gas oil.

[0036] Compared with the prior art, the catalyst of the present invention has the following advantages:

[0037] (1) Inorganic acid is added to the catalyst of the present invention, and the inorganic acid is loaded on the outer layer of the catalyst instead of being mixed with the carrier or loaded into the carrier. On the one hand, it is beneficial to increase the contact surface between the acid and the active metal, and at the same time, it is beneficial to load the acid on the active site of the active metal, giving full play to the ability of the acid to provide H protons, and improving the hydrogenation activity of the catalyst; on the other hand, the acid will corrode the surface of the catalyst, increase the specific surface area and pore size of the catalyst, and improve the polycyclic aromatic hydrocarbon hydrogenation saturation activity of the catalyst.

[0038] (2) The present invention uses an alkaline solution to pretreat the carrier and then load the active components. On the one hand, the alkaline solution can weaken the acidic properties of the carrier surface, which is conducive to the distribution of active metals to the outer surface of the catalyst; on the other hand, the alkalinity inside the carrier can weaken the acidity of the catalyst. During the reaction, even if the aromatic hydrocarbons diffuse into the interior of the carrier, excessive hydrogenation reaction will not occur, which can achieve the purpose of improving the hydrogenation activity of polycyclic aromatic hydrocarbons and reducing the loss of monocyclic aromatic hydrocarbons.

[0039] (3) The active metal is impregnated onto the support in a manner lower than the saturated water absorption of the support, so that as much active metal as possible is distributed within a certain thickness of the catalyst surface. This can improve the hydrogenation saturation activity of polycyclic active metals and prevent the diffusion of polycyclic metals into the catalyst, which causes the polycyclic aromatic hydrocarbons to be hydrogenated into monocyclic aromatic hydrocarbons and then further hydrogenated to saturate.

[0040] (4) After the catalyst is prepared, it is treated with inorganic acid to improve the surface acid properties of the catalyst and enhance the hydrogenation capacity.

[0041] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0042] The following non-limiting examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0043] In the context of this specification, the acid properties of the catalyst are analyzed by the pyridine adsorption infrared acid property characterization method. The test conditions of the pyridine adsorption infrared acid property characterization method include: the sample is purified in a reaction tube at 500°C and 60mPa for 4 hours, cooled to room temperature, and vacuumed to 0.1mPa to adsorb pyridine, and the surface acid properties of the sample are measured.

[0044] In the technical solution of the present invention, "active component distribution" means that, when the active component content decreases to less than 30% of the content of the component in the outermost layer of the catalyst particle, the active component is considered to be absent from the current catalyst layer to the center of the catalyst, but to be present from the current catalyst layer to the catalyst surface. The active component content in a catalyst layer is determined by measuring the elemental content using an electron probe at 10 randomly selected points within the catalyst layer of the same radius, and the measured values ​​are arithmetic averaged.

[0045] Example 1

[0046] (1) The alumina support was impregnated with 0.04 g / mL sodium hydroxide solution by equal volume impregnation method, and then dried at 150 °C for 4 hours to obtain a pretreated support;

[0047] (2) An impregnation solution containing ammonium heptamolybdate and nickel nitrate was prepared according to 50% of the saturated water absorption capacity of the alumina carrier, and the pretreated carrier was impregnated by the rotating drum impregnation method. After impregnation, it was dried at 110°C for 3 hours, and then sulfurized with hydrogen containing 1.5% H2S. The sulfurization temperature was 330°C, the sulfurization pressure was 3.2 MPa, and the sulfurization time was 5 hours. Then, it was cooled to room temperature in a N2 atmosphere to obtain catalyst precursor B.

[0048] (3) According to 20% of the saturated water absorption of catalyst precursor B, a corresponding volume of 0.02 g / mL phosphoric acid solution was taken as the impregnation liquid, and the catalyst precursor B prepared in step (2) was impregnated by spray impregnation. Then, the catalyst precursor B was dried at 80°C in a nitrogen atmosphere for 5 h to obtain catalyst C-1.

[0049] The weight percentages of the components in catalyst C-1 are: MoS2 20%, NiS 4.2%, phosphoric acid 4.0%, sodium hydroxide 1.0%, and the rest is alumina support.

[0050] Example 2

[0051] (1) The alumina support was impregnated with 0.05 g / mL sodium hydroxide solution by equal volume impregnation method, and then dried at 130 °C for 4 hours to obtain a pretreated support;

[0052] (2) An impregnation solution containing ammonium heptamolybdate and nickel nitrate was prepared according to 58% of the saturated water absorption capacity of the alumina carrier, and the pretreated carrier was impregnated by the rotating drum impregnation method. After impregnation, it was dried at 120°C for 3 hours, and then sulfurized with hydrogen containing 1.5% H2S. The sulfurization temperature was 360°C, the sulfurization pressure was 3.2 MPa, and the sulfurization time was 6 hours. Then, it was cooled to room temperature in a N2 atmosphere to obtain catalyst precursor B.

[0053] (3) According to 30% of the saturated water absorption of catalyst precursor B, a corresponding volume of 0.03 g / mL boric acid solution was taken as the impregnation liquid, and the catalyst precursor B prepared in step (2) was impregnated by spray impregnation, and then dried at 80 ° C for 5 h in a nitrogen atmosphere to obtain catalyst C-2.

[0054] The weight percentages of the components in catalyst C-2 are: MoS2 18.6%, NiS 4.2%, boric acid 3.0%, sodium hydroxide 0.8%, and the rest is alumina support.

[0055] Example 3

[0056] (1) The alumina support was impregnated with 0.03 g / mL potassium hydroxide solution by equal volume impregnation method, and then dried at 130 °C for 4 hours to obtain a pretreated support;

[0057] (2) An impregnation solution containing ammonium heptamolybdate and cobalt nitrate was prepared according to 69% of the saturated water absorption capacity of the alumina carrier, and the pretreated carrier was impregnated by the rotating drum impregnation method. After impregnation, it was dried at 120°C for 3 hours, and then sulfurized with hydrogen containing 1.5% H2S. The sulfurization temperature was 360°C, the sulfurization pressure was 6.0 MPa, and the sulfurization time was 4 hours. Then, it was cooled to room temperature in a N2 atmosphere to obtain catalyst precursor B.

[0058] (3) According to 30% of the saturated water absorption of catalyst precursor B, a corresponding volume of 0.03 g / mL hydrofluoric acid solution was taken as the impregnation liquid, and the catalyst precursor B prepared in step (2) was impregnated by the rotating drum impregnation method, and then dried at 80°C in a nitrogen atmosphere for 5 h to obtain catalyst C-3.

[0059] The weight percentages of the components in catalyst C-3 are: MoS2 19.7%, CoS 4.6%, hydrofluoric acid 3.2%, potassium hydroxide 1.2%, and the rest is alumina support.

[0060] Example 4

[0061] (1) The alumina support was impregnated with 0.05 g / mL sodium hydroxide solution by equal volume impregnation method, and then dried at 120 ° C for 4 hours to obtain a pretreated support;

[0062] (2) The active component is impregnated by secondary impregnation: according to the agreed active metal content, half of the active metal is taken, and an impregnation solution containing ammonium heptamolybdate and cobalt nitrate is prepared according to 25% of the saturated water absorption of the alumina carrier. The pretreated carrier is impregnated by spray impregnation, dried at 120°C for 3 hours, and calcined at 320°C for 3 hours. The remaining active metal is prepared into a solution according to 25% of the saturated water absorption of the alumina carrier, spray impregnation, dried at 120°C for 3 hours, and then sulfided with hydrogen containing 1.5% H2S. The sulfidation temperature is 380°C, the sulfidation pressure is 4.8 MPa, and the sulfidation time is 6 hours. Then, the catalyst precursor B is obtained by cooling to room temperature in a N2 atmosphere.

[0063] (3) According to 20% of the saturated water absorption of catalyst precursor B, a corresponding volume of 0.05 g / mL boric acid solution was taken as the impregnation liquid, and the catalyst precursor B prepared in step (2) was impregnated by spray impregnation, and then dried at 80°C in a nitrogen atmosphere for 5 h to obtain catalyst C-4.

[0064] The weight percentages of the components in catalyst C-4 are: MoS2 22.5%, CoS 4.6%, boric acid 3.2%, sodium hydroxide 0.5%, and the rest is alumina support.

[0065] Example 5

[0066] (1) The alumina support was impregnated with 0.05 g / mL potassium hydroxide solution by equal volume impregnation method, and then dried at 120 °C for 4 hours to obtain a pretreated support;

[0067] (2) An impregnation solution containing ammonium metatungstate and cobalt nitrate was prepared according to 50% of the saturated water absorption capacity of the alumina carrier, and the pretreated carrier was impregnated by the rotating drum impregnation method. After impregnation, it was dried at 120°C for 3 hours, and then sulfurized with hydrogen containing 1.5% H2S. The sulfurization temperature was 380°C, the sulfurization pressure was 4.8 MPa, and the sulfurization time was 6 hours. Then, it was cooled to room temperature in a N2 atmosphere to obtain catalyst precursor B.

[0068] (3) According to 30% of the saturated water absorption of catalyst precursor B, a corresponding volume of 0.05 g / mL phosphoric acid solution was taken as the impregnation liquid, and the catalyst precursor B prepared in step (2) was impregnated by spray impregnation. Then, the catalyst was dried at 80°C in a nitrogen atmosphere for 5 h to obtain catalyst C-5.

[0069] The weight percentages of the components in catalyst C-5 are: WS2 is 23.5%, CoS is 4.6%, phosphoric acid is 3.8%, potassium hydroxide is 0.5%, and the rest is alumina support.

[0070] Example 6

[0071] (1) The alumina support was impregnated with 0.05 g / mL sodium hydroxide solution by equal volume impregnation method, and then dried at 120 °C for 4 hours to obtain a pretreated support;

[0072] (2) An impregnation solution containing ammonium metatungstate and nickel nitrate was prepared according to 50% of the saturated water absorption capacity of the alumina carrier, and the pretreated carrier was impregnated by the rotating drum impregnation method. After impregnation, it was dried at 120°C for 3 hours, and then sulfurized with hydrogen containing 1.5% H2S. The sulfurization temperature was 360°C, the sulfurization pressure was 4.8 MPa, and the sulfurization time was 6 hours. Then, it was cooled to room temperature in a N2 atmosphere to obtain catalyst precursor B.

[0073] (3) According to 30% of the saturated water absorption of catalyst precursor B, a corresponding volume of 0.05 g / mL boric acid solution was taken as the impregnation liquid, and the catalyst precursor B prepared in step (2) was impregnated by spray impregnation. Then, the catalyst was dried at 80°C in a nitrogen atmosphere for 5 h to obtain catalyst C-6.

[0074] The weight percentages of the components in catalyst C-6 are: WS2 is 22.5%, NiS is 4.6%, boric acid is 3.2%, sodium hydroxide is 0.5%, and the rest is alumina support.

[0075] Comparative Example 1

[0076] Except that the active component was impregnated in an equal volume impregnation manner in step (2), the other operations were the same as in Example 1 to obtain a comparative catalyst DC-1.

[0077] The weight percentages of the components in the comparative catalyst DC-1 are: MoS2 20%, NiS 4.2%, phosphoric acid 4.0%, sodium hydroxide 1.0%, and the rest is alumina support.

[0078] Comparative Example 2

[0079] The catalyst was prepared by performing only steps (2) and (3) without impregnating the support with an alkaline solution in step (1). The specific conditions were the same as those in (2) and (3) of Example 1, and a comparative catalyst DC-2 was obtained.

[0080] The weight percentages of the components in the comparative catalyst DC-2 are: MoS2 is 20%, NiS is 4.2%, phosphoric acid is 4.0%, and the rest is alumina support.

[0081] Comparative Example 3

[0082] Without performing the treatment in step (3), the operation procedures of steps (1) and (2) were the same as those in Example 1 to obtain comparative catalyst DC-3.

[0083] The weight percentages of the components in the comparative catalyst DC-3 are: MoS2 is 20%, NiS is 4.2%, sodium hydroxide is 1.0%, and the rest is alumina support.

[0084] Comparative Example 4

[0085] The equal volume impregnation method was adopted, with alumina as the carrier, impregnated with the impregnation solution of ammonium heptamolybdate and nickel nitrate, dried at 110°C for 3 hours, and then sulfurized with hydrogen containing 1.5% H2S. The sulfurization temperature was 330°C, the sulfurization pressure was 3.2MPa, and the sulfurization time was 5h. Then, it was cooled to room temperature in a N2 atmosphere to obtain the comparative catalyst DC-4.

[0086] The weight percentages of the components in the comparative catalyst DC-4 are: MoS2 is 20%, NiS is 4.2%, and the rest is alumina support.

[0087] Comparative Example 5

[0088] An impregnation solution containing ammonium heptamolybdate and nickel nitrate was prepared according to 50% of the saturated water absorption capacity of the alumina carrier. The pretreated carrier was impregnated by the rotating drum impregnation method. After impregnation, it was dried at 110°C for 3 hours and then sulfurized with hydrogen containing 1.5% H2S. The sulfurization temperature was 330°C, the sulfurization pressure was 3.2 MPa, and the sulfurization time was 5 hours. Then, the temperature was cooled to room temperature in a N2 atmosphere to obtain a comparative catalyst DC-5.

[0089] The weight percentages of the components in the comparative catalyst DC-5 are: MoS2 is 20%, NiS is 4.2%, and the rest is alumina support.

[0090] The acid properties and active metal distribution (ratio of radial thickness of active component to catalyst radius) of the catalysts C-1 to C-6 prepared in the above examples and the catalysts DC-1 to DC-5 prepared in the comparative examples were analyzed. The analysis results are shown in Table 1.

[0091] Table 1.

[0092]

[0093] Example 7

[0094] This example illustrates the hydrogenation performance of the catalyst provided by the present invention for diesel polycyclic aromatic hydrocarbons.

[0095] The raw oil used for evaluation is a diesel raw material provided by a refinery of Sinopec. Its main properties are as follows: distillation range 200-380℃, sulfur content of 1.5wt%, nitrogen content of 580μg / g, monocyclic aromatic hydrocarbon content of 20%, and polycyclic aromatic hydrocarbon content of 30%. A 200mL fixed-bed hydrogenation device was used to evaluate the reaction performance of catalysts C-1 to C-6 and comparative examples DC-1 to DC-5. Catalysts C-1 to C-6 and comparative examples DC-1 and DC-5 do not require pre-sulfurization treatment. The evaluation reaction conditions are: operating pressure 7.0MPa, reaction temperature 365℃, hydrogen / oil volume ratio 500:1, and volume space velocity of 1.5h -1 The evaluation results are shown in Table 2. The ratio of monocyclic aromatic hydrocarbon saturation rate to polycyclic aromatic hydrocarbon saturation rate is used to characterize the polycyclic aromatic hydrocarbon saturation selectivity of the catalyst. The smaller the ratio, the higher the selectivity.

[0096] Table 2.

[0097]

[0098] As can be seen from Table 2, the polycyclic aromatic hydrocarbon hydrogenation and saturation catalyst of the present invention has very high polycyclic aromatic hydrocarbon hydrogenation and saturation activity and selectivity.

Claims

1. A catalyst for selective hydrogenation of polycyclic aromatic hydrocarbons, characterized in that The invention uses alkali-modified alumina as a carrier, on which an inorganic acid and an active component are loaded, wherein the active components are Group VIB metal sulfide and Group VIII metal sulfide. Based on the total weight of the catalyst, the alkali accounts for 0.1-5.0%, the inorganic acid accounts for 1-12wt%, the Group VIB metal sulfide accounts for 10-30%, and the Group VIII metal sulfide accounts for 2-10%. The catalyst has a Br acid content of 0.05-0.2 mmol / g and a L acid content of 0.3-1.0 mmol / g. The active component is distributed from the catalyst surface to a catalyst surface layer no thicker than 1 / 3 of the catalyst radius. The inorganic acid is loaded on the outer surface of the catalyst. The distribution of active components refers to the distribution from the outside to the inside of the catalyst particle in the radial direction. When the content of the active component drops to less than 30% of the content of the component in the outermost layer of the catalyst particle, it is considered that there is no active component distribution from the current catalyst layer to the center of the catalyst, but there is an active component distribution from the catalyst layer to the catalyst surface; the determination of the active component content in a certain catalyst layer is to randomly select 10 points in the catalyst layer with the same radius of the catalyst, use an electron probe to determine the element content, and perform arithmetic averaging on the measured values.

2. The polycyclic aromatic hydrocarbon selective hydrogenation catalyst according to claim 1, characterized in that Based on the total weight of the catalyst, the base accounts for 0.3-3.0%; the inorganic acid accounts for 1.5-8wt%.

3. The polycyclic aromatic hydrocarbon selective hydrogenation catalyst according to claim 2, characterized in that Based on the total weight of the catalyst, the inorganic acid accounts for 2-6 wt%.

4. The polycyclic aromatic hydrocarbon selective hydrogenation catalyst according to claim 1, characterized in that Based on the total weight of the catalyst, the Group VIB metal sulfide accounts for 15-28%, and the Group VIII metal sulfide accounts for 4-8%.

5. The polycyclic aromatic hydrocarbon selective hydrogenation catalyst according to claim 1, characterized in that The B acid content of the alkali-modified alumina is 0.01-0.04 mmol / g, and the L acid content is 0.01-0.1 mmol / g.

6. The polycyclic aromatic hydrocarbon selective hydrogenation catalyst according to claim 1, characterized in that The alkali is selected from at least one of sodium hydroxide, potassium hydroxide and ammonia.

7. The polycyclic aromatic hydrocarbon selective hydrogenation catalyst according to claim 1, characterized in that The inorganic acid is selected from at least one of phosphoric acid, boric acid, hydrofluoric acid, hydrochloric acid and sulfuric acid.

8. The polycyclic aromatic hydrocarbon selective hydrogenation catalyst according to claim 1, characterized in that The Group VIB metal sulfide is molybdenum sulfide and / or tungsten sulfide, and the Group VIII metal sulfide is nickel sulfide and / or cobalt sulfide.

9. The method for preparing the polycyclic aromatic hydrocarbon selective hydrogenation catalyst according to any one of claims 1 to 8, comprising the following steps: (1) impregnating an alumina support with an alkaline solution and drying the alumina support to obtain a pretreated support; (2) impregnating the pretreated support of step (1) with an impregnation solution containing a Group VIB metal salt and a Group VIII metal salt, wherein the volume of the impregnation solution is less than 70% of the saturated water absorption capacity of the alumina support, and performing drying and sulfurization treatment to obtain a catalyst precursor; (3) Impregnating the catalyst precursor of step (2) with an inorganic acid solution, and drying in an inert atmosphere to obtain the polycyclic aromatic hydrocarbon selective hydrogenation catalyst.

10. The preparation method according to claim 9, characterized in that The alkaline solution in step (1) is selected from at least one of sodium hydroxide, potassium hydroxide and ammonia solution, and the solute concentration in the alkaline solution is 0.01 g / mL-0.1 g / mL.

11. The preparation method according to claim 9, characterized in that The volume of the alkaline solution is 70%-110% of the saturated water absorption capacity of the alumina support.

12. The preparation method according to claim 9, characterized in that The volume of the impregnation solution in step (2) is 5-55% of the saturated water absorption capacity of the alumina support.

13. The preparation method according to claim 9, characterized in that The inorganic acid in step (3) is selected from at least one of phosphoric acid, boric acid, hydrofluoric acid, hydrochloric acid and sulfuric acid, and the concentration of the inorganic acid solution is 0.01 g / mL-0.1 g / mL.

14. The preparation method according to claim 9, characterized in that The volume of the inorganic acid solution used in step (3) is 10%-40% of the saturated water absorption of the catalyst precursor prepared in step (1).

15. A method for hydrogenation saturation of polycyclic aromatic hydrocarbons in oil products, comprising contacting the oil product with the catalyst according to claim 1 or the catalyst prepared by the preparation method according to claim 9 for reaction.

16. The method according to claim 15, characterized in that The process conditions for the polycyclic aromatic hydrocarbon hydrogenation saturation reaction are as follows: pressure 1.0~12.0MPa, wherein the hydrogen partial pressure accounts for 50%~90% of the total pressure; volume space velocity 0.1~10.0h -1 , reaction temperature 200~400℃, hydrogen-oil volume ratio 10:1~1000:

1.

17. The method according to claim 15, characterized in that The oil product is diesel, vacuum gas oil, catalytic cracking gas oil or thermal cracking gas oil.

Images