A confined hydrogenation catalyst, a preparation method and application thereof

Abstract

The present application belongs to the technical field of diesel hydrogenation, and relates to a limited domain type hydrogenation catalyst and a preparation method and application thereof. The preparation steps are as follows: microporous molecular sieves are subjected to alkyl surface modification to obtain silanized microporous molecular sieves; the silanized microporous molecular sieves, ethanol, ammonia water and water are mixed to obtain a suspension, tetraethyl orthosilicate, dopamine, a nickel salt and a molybdenum salt are added to the suspension, and under microwave stirring conditions, the reaction is carried out for a certain time, centrifugal separation, drying and calcination are carried out, and a nickel-molybdenum / mesoporous silica@molecular sieve limited domain type hydrogenation catalyst with a core-shell structure is obtained. When the catalyst is used for diesel hydrogenation treatment, the hydrogenation desulfurization and denitrification activity and liquid yield are higher than those of a conventional diesel hydrogenation catalyst.

Description

Technical Field

[0001] This invention relates to the field of diesel hydrogenation catalysts, specifically to a confined hydrogenation catalyst, its preparation method, and its application. Technical Background

[0002] With increasingly stringent diesel quality standards implemented in my country, 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 currently one of the key tasks for refining and chemical enterprises. The purpose of diesel hydrotreating to produce clean diesel is to maximize desulfurization, denitrification, and aromatics removal, and to increase the cetane number. The most crucial aspect is the selection of a targeted and efficient catalyst. Currently, hydrodesulfurization, denitrification, and aromatics removal, and increasing the cetane number are achieved through the hydrorefining function and hydrocracking function of the catalyst, respectively. The former utilizes a metal catalyst to hydrogenate aromatics to saturate and generate cycloalkanes while simultaneously removing sulfur and nitrogen, while the latter utilizes an acidic catalyst to perform ring-opening cracking of cycloalkanes. Currently, industrial applications mainly employ three processes: single-reactor layered loading of two catalysts (single-stage dual-agent), dual-reactor layered loading of two catalysts (dual-stage dual-agent), or single-reactor single-catalyst loading (single-stage single-agent). However, all three have significant drawbacks. The first two processes involve high catalyst and equipment costs, complex process flows, and the hydrorefining and hydrocracking functions of the catalyst do not fully leverage their coordinated effects at the microscopic scale. In the latter process, the acidic support (e.g., molecular sieve) and other supports (e.g., alumina or carbon) in the catalyst are disorderedly mixed, resulting in disordered contact between the hydrorefining and hydrocracking functions at the microscale, failing to fully leverage their synergistic effects. Furthermore, in the aforementioned catalysts, due to the mechanical mixing of the acidic component support with other matrix supports, the excessive exposure of the reactant molecules to the reactive molecular atmosphere leads to excessive cracking of the reactants on the acidic support surface, resulting in the loss of light components, reduced liquid yield, and diminished economic benefits. Therefore, the development of multifunctional coupled catalysts that orderly integrate hydrorefining and hydrocracking functions is particularly urgent.

[0003] This invention uses a silanized microporous molecular sieve as the core, leveraging the repulsion effect of alkyl modification groups on the molecular sieve surface on inorganic salts. A mesoporous carbon shell layer with uniformly loaded active components is coated around the core using tetraethyl orthosilicate and dopamine, resulting in a confined hydrogenation catalyst with a core-shell structure. In this catalyst, the uniformly loaded mesoporous carbon shell layer performs the hydrorefining function, where sulfur and nitrogen-containing compounds in diesel fuel undergo hydrodesulfurization, and aromatic compounds undergo aromatic ring hydrogenation. The molecular sieve core performs the hydrocracking function. Alkanes and cycloalkanes after desulfurization, denitrification, and dearomatization, transferred from the shell region, undergo hydrocracking or hydroisomerization on the core. This clearly distinguishes and orderly connects the hydrorefining and hydrocracking functional regions within the catalyst. Furthermore, because the microporous molecular sieve is located at the core, the frequency of contact between it and the alkanes and cycloalkanes after desulfurization, denitrification, and dearomatization transferred from the shell region is reduced, which helps to suppress excessive cracking of these molecules and improve diesel fuel yield. Summary of the Invention

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

[0005] This invention proposes a confined hydrogenation catalyst, its preparation method, and its application, characterized in that:

[0006] The preparation method includes the following steps:

[0007] (1) The microporous molecular sieve and silylating reagent were ultrasonically dispersed in toluene, microwaved for 2-6 hours, centrifuged, washed with anhydrous ethanol until no chloride ions were present, and dried to obtain silylated microporous molecular sieve.

[0008] (2) The silanized microporous molecular sieve is ultrasonically dispersed in a mixture of ethanol, ammonia and water, and stirred evenly to obtain a suspension;

[0009] (3) Add tetraethyl orthosilicate, dopamine, nickel salt and molybdenum salt to the suspension, stir in microwave for 4h to 24h, centrifuge, dry and calcinate;

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

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

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

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

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

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

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

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

[0018] In step (3), the loading 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℃ in nitrogen for 3-5 hours;

[0021] The calcination conditions in step (4) are calcination at 400-450℃ for 3-5 hours in 10% H2S / N2;

[0022] The basic principle of this invention is as follows: Utilizing the repulsive effect of alkyl-modified groups on the surface of a molecular sieve on inorganic salts, a mesoporous carbon shell layer uniformly loaded with active components is coated with tetraethyl orthosilicate and dopamine on the outer layer of the core, resulting in a confined hydrogenation catalyst with a core-shell structure. In this catalyst, the uniformly loaded mesoporous carbon shell layer of active components performs the hydrorefining function. Sulfur and nitrogen-containing compounds in diesel fuel undergo hydrodesulfurization reactions in this layer, while aromatic compounds undergo aromatic ring hydrogenation reactions. The molecular sieve core performs the hydrocracking function. Alkanes and cycloalkanes after desulfurization, denitrification, and dearomatization, transferred from the shell region, undergo hydrocracking or hydroisomerization on the core. This results in a clear distinction and orderly connection between the hydrorefining and hydrocracking functional regions in the catalyst. Furthermore, because the microporous molecular sieve is located at the core, the frequency of contact between it and the alkanes and cycloalkanes after desulfurization, denitrification, and dearomatization transferred from the shell region is reduced, which helps to suppress excessive cracking of these molecules and improve diesel fuel yield.

[0023] Compared with existing technologies, the confined hydrotreating catalyst provided by this invention isolates and orderly connects the hydrorefining and hydrocracking functions in separate regions. Using this catalyst in diesel hydrotreating reactions facilitates the stepwise but highly efficient hydrogenation of sulfur- and nitrogen-containing molecules and aromatic molecules in diesel fuel on the catalyst. It also helps to further elucidate the transport mechanism of probe molecules and the reaction relay mechanism in different functional regions, and promotes a deeper understanding of the structure-activity relationship between the catalyst's microstructure and the macroscopic performance of hydrotreating. Furthermore, the catalyst can avoid over-cracking caused by exposure or aggregation of acidic supports, which is beneficial for improving the liquid yield of diesel fuel after hydrotreating and enhancing economic efficiency. Attached Figure Description

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

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] Confined hydrogenation catalysts are prepared by the following method:

[0028] (1) Mix 1.0g HZSM-5 molecular sieve, 30g trimethylchlorosilane and 20g toluene evenly, microwave at 30℃ for 4h, filter, wash with anhydrous ethanol until no chloride ions are present, and dry at 100℃ to obtain silanized molecular sieve.

[0029] (2) 1.0 g of silylated ZSM-5 molecular sieve was dispersed in a mixture of 10 ml anhydrous ethanol and 40 ml water and stirred at room temperature for 20 min. 0.5 ml ammonia water was added dropwise and stirred for 10 min. Then 0.5 ml tetraethyl orthosilicate, 0.6 g dopamine, 0.34 g nickel acetate and 0.38 g ammonium molybdate were added and microwaved for 12 h. After centrifugation, the powder was dried at 60 °C and calcined at 800 °C in N2 for 4 h. The resulting powder was stirred in a 20% hydrofluoric acid solution for 10 min, filtered until neutral, 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] Confined hydrogenation catalysts are prepared by the following method:

[0032] (1) Mix 1.0g HY molecular sieve, 30g trimethylchlorosilane and 20g toluene evenly, microwave at 30℃ for 4h, filter, wash with anhydrous ethanol until no chloride ions are present, and dry at 100℃ to obtain silanized molecular sieve.

[0033] (2) 1.0 g of silylated ZSM-5 molecular sieve was dispersed in a mixture of 10 ml anhydrous ethanol and 40 ml water and stirred at room temperature for 20 min. 0.5 ml ammonia water was added dropwise and stirred for 10 min. Then 0.5 ml tetraethyl orthosilicate, 0.6 g dopamine, 0.34 g nickel acetate and 0.38 g ammonium molybdate were added and microwaved for 12 h. After centrifugation, the powder was dried at 60 °C and calcined at 800 °C in N2 for 4 h. The resulting powder was stirred in a 20% hydrofluoric acid solution for 10 min, filtered until neutral, 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] Confined hydrogenation catalysts are prepared by the following method:

[0036] (1) Mix 1.0g HBeta molecular sieve, 30g trimethylchlorosilane and 20g toluene evenly, microwave at 30℃ for 4h, filter, wash with anhydrous ethanol until no chloride ions are present, and dry at 100℃ to obtain silanized molecular sieve.

[0037] (2) 1.0 g of silylated ZSM-5 molecular sieve was dispersed in a mixture of 10 ml anhydrous ethanol and 40 ml water and stirred at room temperature for 20 min. 0.5 ml ammonia water was added dropwise and stirred for 10 min. Then 0.5 ml tetraethyl orthosilicate, 0.6 g dopamine, 0.34 g nickel acetate and 0.38 g ammonium molybdate were added and microwaved for 12 h. After centrifugation, the powder was dried at 60 °C and calcined at 800 °C in N2 for 4 h. The resulting powder was stirred in a 20% hydrofluoric acid solution for 10 min, filtered until neutral, 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] Confined hydrogenation catalysts are prepared by the following method:

[0040] (1) Mix 1.0g HY molecular sieve, 30g trimethylchlorosilane and 20g toluene evenly, microwave at 30℃ for 4h, filter, wash with anhydrous ethanol until no chloride ions are present, and dry at 100℃ to obtain silanized molecular sieve.

[0041] (2) 1.0 g of silylated ZSM-5 molecular sieve was dispersed in a mixture of 10 ml anhydrous ethanol and 40 ml water and stirred at room temperature for 20 min. 0.5 ml ammonia water was added dropwise and stirred for 10 min. Then 0.5 ml tetraethyl orthosilicate, 0.6 g dopamine, 0.31 g nickel acetate and 0.43 g ammonium molybdate were added and microwaved for 12 h. After centrifugation, the powder was dried at 60 °C and calcined at 700 °C in N2 for 4 h. The resulting powder was stirred in a 20% hydrofluoric acid solution for 10 min, filtered until neutral, 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] Confined hydrogenation catalysts are prepared by the following method:

[0044] (1) Mix 1.0g HUSY molecular sieve, 30g trimethylchlorosilane and 20g toluene evenly, microwave at 30℃ for 4h, filter, wash with anhydrous ethanol until no chloride ions are present, and dry at 100℃ to obtain silanized molecular sieve.

[0045] (2) 1.0 g of silylated ZSM-5 molecular sieve was dispersed in a mixture of 10 ml anhydrous ethanol and 40 ml water and stirred at room temperature for 20 min. 0.5 ml ammonia water was added dropwise and stirred for 10 min. Then 0.5 ml tetraethyl orthosilicate, 0.6 g dopamine, 0.31 g nickel acetate and 0.43 g ammonium molybdate were added and microwaved for 12 h. After centrifugation, the powder was dried at 60 °C and calcined in N2 at 800 °C for 4 h. The resulting powder was stirred in a 20% hydrofluoric acid solution for 10 min, filtered until neutral, dried at 100 °C, and calcined in 10% H2S / N2 at 450 °C 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 type molecular sieve and mesoporous carbon are carefully ground and mixed evenly in an agate mortar to obtain a carrier.

[0049] (2) Using the equal volume impregnation method, the weighed nickel acetate solution and ammonium molybdate were added dropwise to the carrier. After impregnation, the carrier was left overnight, preliminarily dried under infrared lamp, dried at 120℃ for 3 hours, calcined at 500℃ in air for 4 hours, and then calcined at 450℃ in 10% H2S / N2 for 4 hours to obtain the control catalyst.

[0050] Example 7

[0051] This embodiment evaluates catalyst 2, catalyst 5, and the reference standard provided in the above embodiments using a 100mL small-scale batch reactor. 1.4g of catalyst was charged into the reactor, and the temperature was gradually increased to 300℃ under a hydrogen atmosphere. The feedstock was straight-run diesel and catalytic diesel at a mass ratio of 1:1, with a sulfur content of 3200μg / g and a nitrogen content of 410μg / g. The reaction conditions were: reaction pressure 4.0MPa, reaction temperature 300℃, and reaction time 72h. The comparative evaluation results of catalyst 2, catalyst 5, and the reference standard are shown in Table 1. As can be seen from Table 1, the catalysts provided by this invention exhibit higher desulfurization and denitrogenation activities than the reference catalysts, and the liquid yield is improved.

[0052] Table 1. Properties and hydrogenation performance of catalysts 2, 5, and reference standards.

[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 are as follows: (1) Disperse the microporous molecular sieve and silanizing reagent in toluene by ultrasonication, react with microwave for 2-6 hours, separate by centrifugation, wash with anhydrous ethanol until no chloride ions are present, and dry to obtain silanized microporous molecular sieve; (2) The silanized microporous molecular sieve is ultrasonically dispersed in a mixture of ethanol, ammonia and water, and stirred evenly to obtain a suspension; (3) Add tetraethyl orthosilicate, dopamine, nickel salt and molybdenum salt to the suspension, stir in microwave for 4h to 24h, centrifuge, dry and calcinate; (4) The powder obtained in the above steps is stirred in a 20% hydrofluoric acid solution for 10 min, filtered until neutral, dried, and calcined to obtain a confined hydrogenation catalyst. In step (1), the microporous molecular sieve is one of HY type molecular sieve, HBeta type molecular sieve or HZSM-5 type molecular sieve; In step (1), the silylating agent is one of trimethylchlorosilane, tert-butyldimethylchlorosilane, or di-tert-butyldichlorosilane; In step (1), the mass ratio of microporous molecular sieve, silanizing reagent, and toluene is 1:30:20; The microwave reaction temperature in step (1) is 20–40°C; In step (2), the mass ratio of silanized microporous molecular sieve, ethanol, ammonia and water is 1:10:40:0.5; In step (3), the mass ratio of silanized microporous molecular sieve, tetraethyl orthosilicate, and dopamine is 1:(0.1-0.6):(0.1-0.8). In step (3), the mass ratio of Ni to Mo is (2-4):(6-9); In step (3), the loading 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℃ in nitrogen for 3-5 hours; The calcination conditions in step (4) are calcination at 400-450°C for 3-5 hours in 10% H2S / N2.

2. The confined hydrogenation catalyst prepared by the method of claim 1.

3. The application of the confined hydrotreating catalyst according to claim 2 in diesel hydrotreating reaction, characterized in that, The hydrogenation reaction conditions are: reaction temperature 260℃~360℃, hydrogen pressure 2MPa~6MPa.

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