Confined range type hydrogenation catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of diesel hydrogenation, and relates to a confinement type hydrogenation catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: carrying out alkylation surface modification on a microporous molecular sieve to obtain a silanized microporous molecular sieve; mixing the silanized microporous molecular sieve, ethanol, ammonia water and water to obtain a turbid liquid, adding tetraethoxysilane, dopamine, nickel salt and molybdenum salt into the turbid liquid, reacting for a certain time under the condition of microwave stirring, centrifugally separating, drying and roasting to obtain the nickel molybdenum / mesoporous silicon at molecular sieve confinement type hydrogenation catalyst with the core-shell structure. When the catalyst is used for diesel oil hydrogenation treatment, the hydrodesulfurization and denitrification activity and liquid yield of the catalyst are higher than those of a traditional diesel oil hydrogenation catalyst.

Description

Technical Field

[0001] The invention relates to the field of diesel hydrogenation catalysts, and in particular to a confined hydrogenation catalyst and a preparation method and application thereof. Technical Background

[0002] As the diesel quality standards implemented in my country become increasingly stringent, the market demand for high-quality clean diesel is growing year by year. Accelerating the upgrading of diesel quality and producing high-quality clean diesel is one of the key tasks of refining and chemical enterprises at present. The purpose of diesel hydrotreating to prepare clean diesel is to maximize desulfurization, denitrogenation, and aromatization and improve the cetane number. The most critical thing is to select targeted and efficient catalysts. At present, hydrodesulfurization, denitrogenation, and aromatization and improving the cetane number are achieved through the hydrorefining function and hydrocracking function in the catalyst respectively. The former uses metal catalysts to hydrogenate and saturate aromatics to generate cycloalkanes while desulfurizing and denitrogenating, and the latter uses acidic catalysts to open and crack cycloalkanes. At present, three processes are mainly used in industrial applications: single reactor bed filling two catalysts (single stage double agent), double reactors filling two catalysts (double stage double agent) or single reactor single catalyst filling (single stage single agent), but the disadvantages are obvious. In the first two processes, the catalyst and equipment costs are high, the process flow is complicated, and the hydrorefining function and hydrocracking function in the catalyst do not fully play a coordinated role at the microscopic scale. In the latter process, the acidic carrier (such as molecular sieve) and other carriers (such as alumina or carbon) in the catalyst are mixed disorderly, resulting in the disordered contact between the hydrofining function and the hydrocracking function in the catalyst at the microscopic scale, and the coordination between the two cannot be fully exerted. In addition, the above-mentioned catalysts are mechanically mixed with the acidic component carrier and other matrix carriers, which are overly exposed to the atmosphere of the reaction molecules, resulting in excessive cracking of the reaction molecules on the surface of the acidic carrier, loss of light components, reduced liquid yield, and loss of economic benefits. Therefore, the development of a multifunctional coupled catalyst that orderly connects the hydrofining and hydrocracking functions is particularly urgent.

[0003] The present invention uses a silanized microporous molecular sieve as a core, utilizes the repulsion effect of the alkyl modification group on the surface of the molecular sieve on inorganic salts, and uses tetraethyl orthosilicate and dopamine to coat a mesoporous carbon shell layer uniformly loaded with active components on the outer layer of the core, so as to obtain a confined hydrogenation catalyst with a core-shell structure. In the catalyst, the mesoporous carbon shell layer uniformly loaded with active components assumes a hydrorefining function, sulfur-containing and nitrogen-containing compounds in diesel undergo hydrodesulfurization reaction in the layer, and aromatic compounds undergo aromatic ring hydrogenation reaction in the layer, and the molecular sieve core assumes a hydrocracking function, and the alkane and cycloalkane compounds after desulfurization, denitrogenation and dearomatization transferred from the shell region undergo hydrocracking or hydroisomerization on the core, so that the hydrorefining and hydrocracking functional domains in the catalyst are clearly distinguished and orderly connected, and because the microporous molecular sieve is located at the core position, the contact frequency between the microporous molecular sieve and the alkane and cycloalkane compounds after desulfurization, denitrogenation and dearomatization transferred from the shell region is reduced, which is beneficial to inhibiting excessive cracking of such molecules and improving the diesel liquid yield. Summary of the invention

[0004] The present invention proposes a confined hydrogenation catalyst and a preparation method and application thereof, which solves the problem of orderly connection between the hydrorefining and hydrocracking functions in a diesel hydrotreating catalyst and can effectively overcome the problem of low liquid yield caused by excessive cracking of reactant molecules.

[0005] The present invention provides a confined hydrogenation catalyst and a preparation method and application thereof, which are characterized by:

[0006] The preparation method comprises the following steps:

[0007] (1) Ultrasonic dispersion of microporous molecular sieve and silylating agent in toluene, microwave reaction for 2 to 6 hours, centrifugal separation, washing with anhydrous ethanol until there is no chloride ion, and drying to obtain silanized microporous molecular sieve;

[0008] (2) ultrasonically dispersing the silanized microporous molecular sieve in a mixture of ethanol, ammonia water and water, and stirring evenly to obtain a suspension;

[0009] (3) adding tetraethyl orthosilicate, dopamine, nickel salt and molybdenum salt to the suspension, stirring with microwave for 4 h to 24 h, centrifuging, drying and calcining;

[0010] (4) The powder obtained in the above step is stirred in a 20% hydrofluoric acid solution for 10 minutes, filtered to neutrality, dried, and calcined to obtain a nickel-molybdenum / mesoporous silicon@molecular sieve confined hydrogenation catalyst with a core-shell structure.

[0011] The microporous molecular sieve in step (1) is one of HY type molecular sieve, HBeta type molecular sieve or HZSM-5 type molecular sieve;

[0012] In the step (1), the silylating agent is one of trimethylsilyl chloride, tert-butyldimethylsilyl chloride, or di-tert-butyldichlorosilane;

[0013] In the step (1), the mass ratio of the microporous molecular sieve, the silylating agent, and toluene is 1:30:20;

[0014] The microwave reaction temperature in step (1) is 20-40°C;

[0015] In the step (2), the mass ratio of the silanized microporous molecular sieve, ethanol, ammonia water and water is 1:10:40:0.5;

[0016] In the step (3), the mass ratio of the silanized microporous molecular sieve, tetraethyl orthosilicate, and dopamine is 1: (0.1-0.6): (0.1-0.8);

[0017] In the step (3), the mass ratio of Ni to Mo is (2-4): (6-9);

[0018] In the step (3), the loading amount of Ni and Mo in the catalyst is 15% to 25%;

[0019] The microwave reaction temperature in step (3) is 20-40°C;

[0020] The calcination conditions in step (3) are calcination at 600-800° C. in nitrogen for 3-5 hours;

[0021] The calcination conditions in step (4) are calcination at 400-450° C. for 3-5 h in 10% H 2 S / N 2 ;

[0022] The basic principle of the present invention is: by means of the repulsion of inorganic salts by the alkyl modification groups on the surface of the molecular sieve, a mesoporous carbon shell layer uniformly loaded with active components is coated on the outer layer of the core by using tetraethyl orthosilicate and dopamine, so as to obtain a confined hydrogenation catalyst with a core-shell structure. In the catalyst, the mesoporous carbon shell layer uniformly loaded with active components assumes the function of hydrorefining, sulfur-containing and nitrogen-containing compounds in diesel undergo hydrodesulfurization reaction in this layer, and aromatic compounds undergo aromatic ring hydrogenation reaction in this layer. The molecular sieve core assumes the function of hydrocracking, and the alkane and cycloalkane compounds after desulfurization, denitrogenation and dearomatization transferred from the shell region undergo hydrocracking or hydroisomerization on the core, so that the functional domains of hydrorefining and hydrocracking in the catalyst are clearly distinguished and orderly connected, and because the microporous molecular sieve is located at the core position, the contact frequency between it and the alkane and cycloalkane compounds after desulfurization, denitrogenation and dearomatization transferred from the shell region is reduced, which is beneficial to inhibiting excessive cracking of such molecules and improving the diesel liquid yield.

[0023] Compared with the prior art, the confined hydrogenation catalyst provided by the present invention isolates the hydrorefining function and the hydrocracking function in different regions but connects them in an orderly manner. The use of the catalyst for diesel hydrotreating reaction is conducive to the hydrogenation reaction of sulfur-containing and nitrogen-containing molecules and aromatic molecules in diesel on the catalyst in a step-by-step but highly connected manner, and is conducive to further revealing the transmission mechanism of probe molecules and the reaction relay mechanism in different functional areas, and is conducive to a deep understanding of the structure-activity relationship between the catalyst microstructure and the macroscopic performance of hydrogenation. The catalyst can also avoid the excessive cracking phenomenon caused by the exposure or agglomeration of the acidic carrier, which is conducive to improving the liquid yield after diesel hydrotreating and improving the economic benefit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope image of catalyst 2 prepared in Example 2. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1

[0027] The confined hydrogenation catalyst is prepared by the following method:

[0028] (1) 1.0 g HZSM-5 molecular sieve, 30 g trimethylsilyl chloride and 20 g toluene were mixed evenly, subjected to microwave reaction at 30° C. for 4 h, filtered, washed with anhydrous ethanol until there was no chloride ion, and dried at 100° C. to obtain a silanized molecular sieve.

[0029] (2) Disperse 1.0 g of silylated ZSM-5 molecular sieve in a mixture of 10 ml of anhydrous ethanol and 40 ml of water, and stir at room temperature for 20 min. Add 0.5 ml of ammonia water and stir for 10 min. Add 0.5 ml of ethyl orthosilicate, 0.6 g of dopamine, 0.34 g of nickel acetate and 0.38 g of ammonium molybdate, and stir in a microwave for 12 h. Centrifuge, dry at 60 ° C, and calcine at 800 ° C in N2 for 4 h. The obtained powder is stirred in 20% hydrofluoric acid solution for 10 min, filtered to neutrality, dried at 100 ° C, and calcined at 450 ° C in 10% H2S / N2 for 5 h to obtain a confined hydrogenation catalyst.

[0030] Example 2

[0031] The confined hydrogenation catalyst is prepared by the following method:

[0032] (1) 1.0 g HY molecular sieve, 30 g trimethylsilyl chloride and 20 g toluene were mixed evenly, subjected to microwave reaction at 30° C. for 4 h, filtered, washed with anhydrous ethanol until there was no chloride ion, and dried at 100° C. to obtain a silanized molecular sieve.

[0033] (2) Disperse 1.0 g of silylated ZSM-5 molecular sieve in a mixture of 10 ml of anhydrous ethanol and 40 ml of water, and stir at room temperature for 20 min. Add 0.5 ml of ammonia water and stir for 10 min. Add 0.5 ml of ethyl orthosilicate, 0.6 g of dopamine, 0.34 g of nickel acetate and 0.38 g of ammonium molybdate, and stir in a microwave for 12 h. Centrifuge, dry at 60 ° C, and calcine at 800 ° C in N2 for 4 h. The obtained powder is stirred in 20% hydrofluoric acid solution for 10 min, filtered to neutrality, dried at 100 ° C, and calcined at 450 ° C in 10% H2S / N2 for 5 h to obtain a confined hydrogenation catalyst.

[0034] Example 3

[0035] The confined hydrogenation catalyst is prepared by the following method:

[0036] (1) 1.0 g of HBeta molecular sieve, 30 g of trimethylsilyl chloride and 20 g of toluene were mixed evenly, subjected to microwave reaction at 30° C. for 4 h, filtered, washed with anhydrous ethanol until there was no chloride ion, and dried at 100° C. to obtain a silanized molecular sieve.

[0037] (2) Disperse 1.0 g of silylated ZSM-5 molecular sieve in a mixture of 10 ml of anhydrous ethanol and 40 ml of water, and stir at room temperature for 20 min. Add 0.5 ml of ammonia water and stir for 10 min. Add 0.5 ml of ethyl orthosilicate, 0.6 g of dopamine, 0.34 g of nickel acetate and 0.38 g of ammonium molybdate, and stir in a microwave for 12 h. Centrifuge, dry at 60 ° C, and calcine at 800 ° C in N2 for 4 h. The obtained powder is stirred in 20% hydrofluoric acid solution for 10 min, filtered to neutrality, dried at 100 ° C, and calcined at 450 ° C in 10% H2S / N2 for 5 h to obtain a confined hydrogenation catalyst.

[0038] Example 4

[0039] The confined hydrogenation catalyst is prepared by the following method:

[0040] (1) 1.0 g HY molecular sieve, 30 g trimethylsilyl chloride and 20 g toluene were mixed evenly, subjected to microwave reaction at 30° C. for 4 h, filtered, washed with anhydrous ethanol until there was no chloride ion, and dried at 100° C. to obtain a silanized molecular sieve.

[0041] (2) Disperse 1.0 g of silylated ZSM-5 molecular sieve in a mixture of 10 ml of anhydrous ethanol and 40 ml of water, and stir at room temperature for 20 min. Add 0.5 ml of ammonia water and stir for 10 min. Add 0.5 ml of ethyl orthosilicate, 0.6 g of dopamine, 0.31 g of nickel acetate and 0.43 g of ammonium molybdate, and stir in a microwave for 12 h. Centrifuge, dry at 60 ° C, and calcine at 700 ° C in N2 for 4 h. The obtained powder is stirred in a 20% hydrofluoric acid solution for 10 min, filtered to neutrality, dried at 100 ° C, and calcined at 450 ° C in 10% H2S / N2 for 4 h to obtain a confined hydrogenation catalyst.

[0042] Example 5

[0043] The confined hydrogenation catalyst is prepared by the following method:

[0044] (1) 1.0 g HUSY molecular sieve, 30 g trimethylsilyl chloride and 20 g toluene were mixed evenly, subjected to microwave reaction at 30° C. for 4 h, filtered, washed with anhydrous ethanol until there was no chloride ion, and dried at 100° C. to obtain a silanized molecular sieve.

[0045] (2) Disperse 1.0 g of silylated ZSM-5 molecular sieve in a mixture of 10 ml of anhydrous ethanol and 40 ml of water, and stir at room temperature for 20 min. Add 0.5 ml of ammonia water and stir for 10 min. Add 0.5 ml of ethyl orthosilicate, 0.6 g of dopamine, 0.31 g of nickel acetate and 0.43 g of ammonium molybdate, and stir in a microwave for 12 h. Centrifuge, dry at 60 ° C, and calcine at 800 ° C in N2 for 4 h. The obtained powder is stirred in a 20% hydrofluoric acid solution for 10 min, filtered to neutrality, dried at 100 ° C, and calcined at 450 ° C in 10% H2S / N2 for 5 h to obtain a confined hydrogenation catalyst.

[0046] Example 6

[0047] The control catalyst was prepared by the following method:

[0048] (1) The HY molecular sieve and the mesoporous carbon were carefully ground in an agate mortar and mixed evenly to obtain a carrier.

[0049] (2) Using the equal volume impregnation method, weighed nickel acetate solution and ammonium molybdate were respectively added dropwise onto the carrier, left overnight after impregnation, initially dried under an infrared lamp, then dried at 120°C for 3 h, calcined at 500°C in air for 4 h, and then calcined at 450°C in 10% H2S / N2 for 4 h to obtain a control catalyst.

[0050] Example 7

[0051] This embodiment evaluates the catalyst 2, catalyst 5 and reference substance provided in the above embodiment, and the device used is a 100mL small kettle evaluation device. 1.4g of catalyst was loaded into the reactor, and the temperature was gradually raised to 300°C under a hydrogen atmosphere. The feedstock oil is a 1:1 mass ratio of straight-run diesel to catalytic diesel, wherein the sulfur content is 3200μg / g and the nitrogen content is 410μg / g. The reaction conditions are: reaction pressure 4.0MPa, reaction temperature 300°C, and reaction time 72h. The comparative evaluation results of catalyst 2, catalyst 5 and reference substance are shown in Table 1. As can be seen from Table 1, the desulfurization and denitrification activities of the catalyst provided by the present invention are higher than those of the reference catalyst, and the liquid yield is improved.

[0052] Table 1 Properties and hydrogenation performance of catalyst 2, catalyst 5 and reference

[0053] catalyst <![CDATA[Specific surface area (m 2 / g)]]> Pore ​​volume (ml / g) Desulfurization rate Denitrification rate Liquid yield Catalyst 2 225 0.42 85.6 83.2 97.4 Catalyst 5 268 0.53 89.1 84.5 96.1 Reference 253 0.49 82.4 79.4 94.3

Claims

1. A method for preparing a confined hydrogenation catalyst, characterized in that: The steps include: (1) Ultrasonic dispersion of microporous molecular sieve and silylating agent in toluene, microwave reaction for 2 to 6 hours, centrifugal separation, washing with anhydrous ethanol until there is no chloride ion, and drying to obtain silanized microporous molecular sieve; (2) ultrasonically dispersing the silanized microporous molecular sieve in a mixture of ethanol, ammonia water and water, and stirring evenly to obtain a suspension; (3) adding tetraethyl orthosilicate, dopamine, nickel salt and molybdenum salt to the suspension, stirring with microwave for 4 h to 24 h, centrifuging, drying and calcining; (4) The powder obtained in the above step is stirred in a 20% hydrofluoric acid solution for 10 minutes, filtered to neutrality, dried, and calcined to obtain a nickel-molybdenum / mesoporous silicon@molecular sieve confined hydrogenation catalyst with a core-shell structure. The microporous molecular sieve in step (1) is one of HY type molecular sieve, HBeta type molecular sieve or HZSM-5 type molecular sieve; In the step (1), the silylating agent is one of trimethylsilyl chloride, tert-butyldimethylsilyl chloride, or di-tert-butyldichlorosilane; In the step (1), the mass ratio of the microporous molecular sieve, the silylating agent, and toluene is 1:30:20; The microwave reaction temperature in step (1) is 20-40°C; In the step (2), the mass ratio of the silanized microporous molecular sieve, ethanol, ammonia water and water is 1:10:40:0.5; In the step (3), the mass ratio of the silanized microporous molecular sieve, tetraethyl orthosilicate, and dopamine is 1: (0.1-0.6): (0.1-0.8); In the step (3), the mass ratio of Ni to Mo is (2-4): (6-9); In the step (3), the loading amount of Ni and Mo in the catalyst is 15% to 25%; The microwave reaction temperature in step (3) is 20-40°C; The calcination conditions in step (3) are calcination at 600-800° C. in nitrogen for 3-5 hours; The calcination conditions in step (4) are calcination at 400-450° C. in 10% H 2 S / N 2 for 3-5 hours.

2. A catalyst prepared by the method for preparing a confined hydrogenation catalyst according to claim 1.

3. The catalyst prepared by the method for preparing a confined hydrogenation catalyst according to claim 1, characterized in that: With microporous molecular sieve as the core, nickel-molybdenum oxide is evenly dispersed in the shell of mesoporous silica.

4. The catalyst prepared by the method for preparing a confined hydrogenation catalyst according to claim 1, characterized in that: The hydrogenation reaction conditions are: reaction temperature 260°C to 360°C, hydrogen pressure 2MPa to 6MPa.

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