Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a Y-Y composite molecular sieve with a core-shell structure and a preparation method thereof.
The invention provides a Y-Y composite molecular sieve with a core-shell structure, wherein the specific surface area of the Y-Y composite molecular sieve is 800-1000 m 2/g, the external specific surface area is 100-200 m 2/g, the grain size of an outer surface shell layer is 100-300 nm, and the pore volume is 0.35-0.46 cm 3/g.
The invention provides a preparation method of a Y-Y composite molecular sieve with a core-shell structure, which comprises the following steps:
(1) Mixing an aluminum source, a silicon source, sodium hydroxide and water, stirring, and aging to prepare a guiding agent;
(2) Mixing an aluminum source, sodium hydroxide and water, then mixing with an SSY molecular sieve, and stirring to obtain a mixture I; mixing a silicon source with water to obtain a mixture II; mixing the mixture II with the mixture I, and stirring to obtain mixed gel;
(3) Mixing the guiding agent prepared in the step (1) with the mixed gel prepared in the step (2), stirring, and crystallizing to obtain the Y-Y type molecular sieve with a core-shell structure.
In the method of the invention, the aluminum source, the silicon source, the sodium hydroxide and the water in the step (1) are fed according to the following molar ratio: al 2O3:Na2O:SiO2:H2 O=1:20.0-35.0:8.6-32.5:323.1-650.0, preferably Al 2O3:Na2O:SiO2:H2 O=1:24.3-33.9:10.0-25.6:359.5-600.3.
In the method of the invention, in the step (1), the stirring time is 30-120 min. The aging temperature is 20-50 ℃, preferably 20-40 ℃; the aging time is 3 to 24 hours, preferably 5 to 20 hours.
In the method of the invention, in the step (2), the aluminum source, sodium hydroxide, a silicon source and water are fed according to the following molar ratio: al 2O3:Na2O:SiO2:H2 O=1:24.3-40.3:4.5-12.9:266-563, preferably 1:27.1-36.8:6.5-10.9:298-533. Wherein, in the mixture II, the molar ratio of the silicon source to the water is SiO 2:H2 O=1:13.2-33.6.
In the method, the aluminum sources in the step (1) and the step (2) are respectively and independently selected from one or more of aluminum sources such as aluminum chloride, aluminum sulfate, sodium metaaluminate, aluminum hydroxide and the like; the silicon sources in the step (1) and the step (2) are respectively and independently selected from one or more of water glass, silica sol, white carbon black and other silicon sources.
In the method, in the step (2), the SSY molecular sieve is a modified molecular sieve obtained by dealuminating and silicon supplementing the Y molecular sieve by ammonium fluosilicate. The specific surface area of the SSY molecular sieve is 650-850 m 2/g, and the pore volume is 0.30-0.50 cm 3/g. The mass content of sodium oxide contained is less than 2.5% based on the total mass of the SSY molecular sieve.
In the method of the invention, in the step (2), based on the mass of SiO 2 in the obtained mixed gel, the addition amount of the SSY molecular sieve accounts for 8.5-35.7%, preferably 15.3-28.4% of the mass of SiO 2.
In the process according to the invention, in step (2), the stirring time after mixing of mixture II with mixture I is generally from 30 to 60 minutes, until the mixture assumes a milky gel state.
In the method of the invention, in the step (3), the mass of the added guiding agent is 4.5-25% of the mass of the mixed gel obtained in the step (2), and preferably 10-20%.
In the method of the present invention, in the step (3), the crystallization temperature is 80 to 150 ℃, preferably 90 to 120 ℃, and the crystallization time is 12 to 36 hours, preferably 16 to 28 hours.
In the process of the present invention, in step (3), after the crystallization reaction is completed, the Y-Y type molecular sieve product may be separated by any conventionally known separation means. Examples of the separation method include a method of filtering, washing and drying the obtained mixture. Here, the filtering, washing and drying may be performed in any manner conventionally known in the art. As a specific example, as the filtration, for example, the obtained product mixture may be simply suction-filtered. The washing may be performed using deionized water and/or ethanol, for example. The drying temperature may be, for example, 100 to 150 ℃, and the drying time may be, for example, 24 to 48 hours. The drying may be performed under normal pressure or under reduced pressure.
The invention provides an application of a Y-Y composite molecular sieve with a core-shell structure.
The Y-Y composite molecular sieve with the core-shell structure is used in a hydrocracking catalyst.
Compared with the prior art, the invention has the following advantages:
The core-shell structure Y-Y type molecular sieve has good hydrothermal stability, keeps good morphology and pore structure after being subjected to high-temperature hydrothermal treatment, can be used for preparing a hydrocracking catalyst carrier, and is beneficial to improving the yields of heavy naphtha and aviation kerosene.
Research results show that the SSY molecular sieve treated by ammonium fluosilicate is used as a nuclear phase molecular sieve, the nuclear phase molecular sieve is subjected to a hole expanding process, the surface of the nuclear phase molecular sieve is rich in silicon to form Si-O-Al bonds, surrounding silica-alumina gel is attracted to aggregate in the process of synthesizing a shell layer molecular sieve to form a primary structural unit, so that the shell phase Y-shaped molecular sieve is obtained, the outer surface area of the molecular sieve is effectively improved, the diffusion path of reactant molecules in the shell layer structure can be greatly shortened, and the smooth pore channel structure of the nuclear phase Y-shaped molecular sieve is beneficial to improving the diffusion efficiency of reactants and products.
Detailed Description
The following examples further illustrate the preparation of the present invention, but are not intended to limit the invention.
In the present invention, XRD was measured by X-ray diffractometer of D/Max-2500 of RIGAKU Co., japan; n2 adsorption-desorption characterization was measured in ASAP 2420, MICROMERITICS, U.S.A.; SEM was a JEM-2100 (HR) type transmission electron microscope manufactured by JEOL corporation, japan.
Example 1
(1) Adding sodium metaaluminate, sodium hydroxide, sodium silicate and deionized water into a container according to the mole ratio of Al 2O3:Na2O:SiO2:H2 O=1:28.9:18.7:532, stirring for 60min to a uniform state, sealing, placing at a constant temperature of 25 ℃ for aging for 14h, and taking out for later use to prepare a guiding agent;
(2) Dissolving sodium metaaluminate and sodium hydroxide with deionized water, then adding an SSY molecular sieve (the specific surface area of the SSY molecular sieve is 750.9m 2/g, the pore volume is 0.37cm 3/g, and the mass content of sodium oxide contained in the SSY molecular sieve is 1.81 percent based on the total mass of the SSY molecular sieve), and stirring at a high speed until the mixture is in a uniform state to obtain a mixture I; diluting water glass with an aqueous solution to obtain a mixture II; wherein, in the total system, the molar ratio of sodium metaaluminate, sodium hydroxide, water glass and water is Al 2O3:Na2O:SiO2:H2 O=1:32.5:8.6:445, siO 2:H2 O=1:20.8 in the mixture II is poured into the mixture I, and the mixture is stirred at high speed for 45min until the mixture is in a milky gel state, thus obtaining mixed gel; based on the mass of SiO 2 in the obtained mixed gel, the addition amount of the SSY molecular sieve accounts for 18.9wt% of the mass of SiO 2;
(3) Adding the guiding agent prepared in the step (1) into the mixed gel prepared in the step (2), wherein the mass of the added guiding agent is 15% of the mass of the mixed gel prepared in the step (2), stirring for 60min, filling into a reaction kettle for sealing, placing at 100 ℃ for crystallization for 24h, filtering the product in the reaction kettle, and drying at 100 ℃ for 30h to obtain the final product. The SEM photograph of the obtained product is shown in fig. 1, and is a core-shell structure Y-Y type molecular sieve, and the XRD pattern of the obtained product is shown in fig. 7, and is a crystalline phase of the Y type molecular sieve.
The SEM photograph of the product obtained by the hydrothermal treatment at 500 ℃ for 1h is shown in figure 9, the SEM photograph of the product obtained by the hydrothermal treatment at 600 ℃ for 1h is shown in figure 10, and the appearance of the product after the hydrothermal treatment is basically unchanged.
Example 2
(1) Adding sodium metaaluminate, sodium hydroxide, silica sol and water into a container according to the mole ratio of Al 2O3:Na2O:SiO2:H2 O=1:25.9:18.7:532, stirring for 60min to a uniform state, sealing, placing at a constant temperature of 35 ℃ for aging for 8h, and taking out for later use to prepare a guiding agent;
(2) Dissolving sodium metaaluminate and sodium hydroxide with deionized water, then adding an SSY molecular sieve (the specific surface area of the SSY molecular sieve is 820.4m 2/g, the pore volume is 0.38cm 3/g, and the mass content of sodium oxide contained is 2.05% based on the total mass of the SSY molecular sieve), and stirring at a high speed until the mixture is in a uniform state to obtain a mixture I; diluting the silica sol with an aqueous solution to obtain a mixture II; wherein, in the total system, the molar ratio of sodium metaaluminate, sodium hydroxide, silica sol and water is Al 2O3:Na2O:SiO2:H2 O=1:34.8:10.5:435, siO 2:H2 O=1:15.8 in the mixture II is poured into the mixture I, and the mixture is stirred at high speed for 60min until the mixture is in a milky gel state, thus obtaining mixed gel; based on the mass of SiO 2 in the obtained mixed gel, the addition amount of the SSY molecular sieve accounts for 25.9wt% of the mass of SiO 2;
(3) Adding the guiding agent prepared in the step (1) into the mixed gel, wherein the mass of the added guiding agent is 12% of the mass of the mixed gel prepared in the step (2), stirring for 60min, filling into a reaction kettle for sealing, placing at 100 ℃ for crystallization for 24h, filtering the product in the reaction kettle, and drying at 100 ℃ for 28h to obtain the final product. The SEM photograph of the obtained product is shown in figure 2, and is a core-shell structure Y-Y type molecular sieve.
Example 3
(1) Adding sodium metaaluminate, sodium hydroxide, white carbon black and water into a container according to the mole ratio of Al 2O3:Na2O:SiO2:H2 O=1:32.9:24.7:489, stirring for 60min to a uniform state, sealing, placing at a constant temperature of 20 ℃ for aging for 20h, and taking out for later use to prepare a guiding agent;
(2) Dissolving sodium metaaluminate and sodium hydroxide with deionized water, then adding an SSY molecular sieve (the specific surface area of the SSY molecular sieve is 783.2m 2/g, the pore volume is 0.37cm 3/g, and the mass content of sodium oxide contained is 1.79% based on the total mass of the SSY molecular sieve), and stirring at a high speed until the mixture is in a uniform state to obtain a mixture I; diluting white carbon black with an aqueous solution to obtain a mixture II; in the total system, the molar ratio of sodium metaaluminate to sodium hydroxide to white carbon black to water is Al 2O3:Na2O:SiO2:H2 O=1:35.8:6.5:435, siO 2:H2 O=1:32.8 in the mixture II is poured into the mixture I, and the mixture is stirred at a high speed for 90min until the mixture is in a milky gel state, so that mixed gel is obtained; taking the mass of SiO 2 in the obtained mixed gel as a reference, wherein the addition amount of the SSY molecular sieve accounts for 15.6wt% of the mass of SiO 2;
(3) And (3) adding the guiding agent prepared in the step (1) into the obtained mixed gel, wherein the mass of the added guiding agent is 18% of the mass of the mixed gel obtained in the step (2), stirring for 90min, filling into a reaction kettle for sealing, placing at 90 ℃ for crystallization for 28h, filtering the product in the reaction kettle, and drying at 100 ℃ for 32h to obtain the final product.
Example 4
(1) Adding sodium metaaluminate, sodium hydroxide, water glass and water into a container according to the mole ratio of Al 2O3:Na2O:SiO2:H2 O=1:27.3:24.7:363.5, stirring for 60min to a uniform state, sealing, placing at a constant temperature of 20 ℃ for aging for 20h, and taking out for later use to prepare a guiding agent;
(2) Dissolving sodium metaaluminate and sodium hydroxide with deionized water, then adding an SSY molecular sieve (the specific surface area of the SSY molecular sieve is 803.5m 2/g, the pore volume is 0.39cm 3/g, and the mass content of sodium oxide contained is 2.11 percent based on the total mass of the SSY molecular sieve), and stirring at a high speed until the mixture is in a uniform state to obtain a mixture I; diluting water glass with an aqueous solution to obtain a mixture II; wherein, in the total system, the molar ratio of sodium metaaluminate, sodium hydroxide, water glass and water is Al 2O3:Na2O:SiO2:H2 O=1:27.8:6.9:335, siO 2:H2 O=1:16.8 in the mixture II is poured into the mixture I, and the mixture is stirred at high speed for 60min until the mixture is in a milky gel state, thus obtaining mixed gel; taking the mass of SiO 2 in the obtained mixed gel as a reference, wherein the addition amount of the SSY molecular sieve accounts for 15.9wt% of the mass of SiO 2;
(3) Adding the guiding agent prepared in the step (1) into the mixed gel, wherein the mass of the added guiding agent is 10% of the mass of the mixed gel prepared in the step (2), stirring for 90min, filling into a reaction kettle for sealing, placing at 120 ℃ for crystallization for 16h, filtering the product in the reaction kettle, and drying at 100 ℃ for 25h to obtain the final product.
Example 5
(1) Adding sodium metaaluminate, sodium hydroxide, silica sol and water into a container according to the mole ratio of Al 2O3:Na2O:SiO2:H2 O=1:20.9:18.7:532, stirring for 60min to a uniform state, sealing, placing at a constant temperature of 40 ℃ for aging for 8h, and taking out for later use to prepare a guiding agent;
(2) Dissolving sodium metaaluminate and sodium hydroxide with deionized water, then adding an SSY molecular sieve (the specific surface area of the SSY molecular sieve is 723.1m 2/g, the pore volume is 0.35cm 3/g, and the mass content of sodium oxide contained is 1.65% based on the total mass of the SSY molecular sieve), and stirring at a high speed until the mixture is in a uniform state to obtain a mixture I; diluting the silica sol with an aqueous solution to obtain a mixture II; wherein, in the total system, the molar ratio of sodium metaaluminate, sodium hydroxide, silica sol and water is Al 2O3:Na2O:SiO2:H2 O=1:30.8:9.5:335, siO 2:H2 O=1:18.8 in the mixture II is poured into the mixture I, and the mixture is stirred at high speed for 60min until the mixture is in a milky gel state, thus obtaining mixed gel; taking the mass of SiO 2 in the obtained mixed gel as a reference, wherein the addition amount of the SSY molecular sieve accounts for 28.4wt% of the mass of SiO 2;
(3) Adding the guiding agent prepared in the step (1) into the mixed gel, wherein the mass of the added guiding agent is 10% of the mass of the mixed gel prepared in the step (2), stirring for 90min, filling into a reaction kettle for sealing, placing at 120 ℃ for crystallization for 18h, filtering the product in the reaction kettle, and drying at 100 ℃ for 30h to obtain the final product.
Comparative example 1
The guiding agent was prepared according to the formulation and procedure of example 1. Meanwhile, materials are added according to the material proportion of the embodiment 1, SSY molecular sieves are not added in the process, and other preparation steps are identical to the embodiment 1. The SEM photograph of the obtained product is shown in fig. 3.
Comparative example 2
The guiding agent was prepared according to the formulation and procedure of example 1. Meanwhile, materials are added according to the material proportion of the embodiment 1, the SSY molecular sieve added in the process accounts for 5.3 weight percent of the mass of SiO 2, and other preparation steps are consistent with the embodiment 1. The SEM photograph of the obtained product is shown in fig. 4.
Comparative example 3
The guiding agent was prepared according to the formulation and procedure of example 1. Meanwhile, materials are added according to the material proportion of the embodiment 1, the SSY molecular sieve added in the process accounts for 40 weight percent of the mass of SiO 2, and other preparation steps are consistent with the embodiment 1. As shown in FIG. 5, the SEM photograph of the obtained product shows that the shell phase molecular sieve is not uniformly wrapped on the outer surface of the core phase molecular sieve, and is in a dispersed state.
Comparative example 4
The materials were added in the material proportions of example 1, the director aging temperature was 60℃and the aging time was 12 hours, the other preparation steps being identical to example 1. An SEM photograph of the obtained product is shown in fig. 6.
Comparative example 5
The material ratios were varied according to the experimental conditions of example 1.
(1) Adding sodium metaaluminate, sodium hydroxide, sodium silicate and water into a container according to the mole ratio of Al 2O3:Na2O:SiO2:H2 O=1:10.9:40.7:532, stirring for 60min to a uniform state, sealing, placing at a constant temperature of 25 ℃ for aging for 14h, and taking out for later use to prepare a guiding agent;
(2) Dissolving sodium metaaluminate and sodium hydroxide with deionized water, then adding an SSY molecular sieve (the specific surface area of the SSY molecular sieve is 750.9m 2/g, the pore volume is 0.37cm 3/g, and the mass content of sodium oxide contained in the SSY molecular sieve is 1.81 percent based on the total mass of the SSY molecular sieve), and stirring at a high speed until the mixture is in a uniform state to obtain a mixture I; diluting water glass with an aqueous solution to obtain a mixture II; wherein, in the total system, the molar ratio of sodium metaaluminate, sodium hydroxide, water glass and water is Al 2O3:Na2O:SiO2:H2 O=1:32.5:8.6:445, siO 2:H2 O=1:20.8 in the mixture II is poured into the mixture I, and the mixture is stirred at high speed for 45min until the mixture is in a milky gel state, thus obtaining mixed gel; based on the mass of SiO 2 in the obtained mixed gel, the addition amount of the SSY molecular sieve accounts for 18.9wt% of the mass of SiO 2;
(3) Adding the guiding agent prepared in the step (1) into the obtained mixed gel, wherein the mass of the added guiding agent is 15% of the mass of the mixed gel prepared in the step (2), stirring for 60min, filling into a reaction kettle for sealing, placing at 100 ℃ for crystallization for 24h, filtering the product in the reaction kettle, and drying at 100 ℃ for 30h to obtain the final product. The XRD pattern of the obtained product is shown in figure 8, and the molecular sieve synthesized under the condition has a hetero-phase P molecular sieve XRD peak, namely a P molecular sieve hetero-phase.
Table 1 properties of the synthesized molecular sieves of each of the examples and comparative examples
Sample of |
Specific surface area, m 2/g |
External specific surface area, m 2/g |
Pore volume, cm 3/g |
Grain size of outer surface shell layer, nm |
Example 1 |
845.3 |
168.6 |
0.44 |
150 |
Example 2 |
843.2 |
157.4 |
0.43 |
200 |
Example 3 |
839.8 |
153.8 |
0.43 |
180 |
Example 4 |
815.9 |
134.2 |
0.42 |
240 |
Example 5 |
810.3 |
133.9 |
0.42 |
250 |
Comparative example 1 |
413.2 |
—— |
0.17 |
Amorphous state |
Comparative example 2 |
801.3 |
—— |
0.33 |
Amorphous state |
Comparative example 3 |
861.2 |
—— |
0.38 |
Amorphous state |
Comparative example 4 |
618.9 |
—— |
0.24 |
Amorphous state |
Comparative example 5 |
741.3 |
—— |
0.31 |
With P molecular sieve impurity phase |
Table 2 properties of the synthetic molecular sieves of examples and comparative examples after hydrothermal treatment
The application of the core-shell structure Y-Y composite molecular sieve in the hydrocracking catalyst:
the pretreatment process of the core-shell structure Y-Y composite molecular sieve comprises the following steps: preparing 1.5mol/L ammonium nitrate solution, wherein the liquid-solid ratio is 1g/10ml, and carrying out ammonium exchange treatment on the Y-Y composite molecular sieve at 80 ℃ for 1.0h each time, and exchanging for 2 times to obtain the NH 4 Y-Y molecular sieve. Carrying out hydrothermal treatment on the NH 4 Y-Y molecular sieve, wherein the hydrothermal treatment temperature is 600 ℃, the hydrothermal treatment time is 1 hour, and the pressure is controlled to be 0.1MPa, so as to obtain the SY-Y molecular sieve. And (3) carrying out acid treatment on the SY-Y molecular sieve, preparing 1.0mol/L nitric acid solution, wherein the solid-liquid ratio is 1:10, and stirring for 1 hour at 90 ℃ to obtain the pretreated Y-Y molecular sieve.
The preparation method of the catalyst comprises the following steps: uniformly mixing the Y-Y type molecular sieve obtained in the pretreated examples 1-5 and the SSY molecular sieve used in the example 1 of the invention with aluminum oxide, molybdenum oxide and nickel nitrate, uniformly rolling the powder under the action of an adhesive to prepare a hydrocracking catalyst, drying at 120 ℃ for 24 hours, putting into a muffle furnace, roasting at 500 ℃ for 3 hours to obtain the hydrocracking catalyst 1-6 respectively, wherein the catalyst comprises the following components: y molecular sieve (35 wt%), molybdenum oxide (18 wt%), nickel oxide (2 wt%), aluminum oxide (balance).
Catalyst evaluation conditions: the hydrocracking catalyst was presulfided and then placed in a 200mL small hydrocracking apparatus. The properties of the raw oil used in the experiment are shown in Table 3, and the evaluation process conditions are as follows: the pressure is 15.7MP, the liquid hourly space velocity (R1/R2) is 1.0/1.5h -1, the hydrogen-oil volume ratio is 1500:1, and the conversion rate is 75wt%. The comparative results of the catalyst reaction performance are shown in Table 4. The raw oil sequentially passes through two beds of a hydrofining catalyst and a hydrocracking catalyst, and the organic nitrogen content of the raw oil in the hydrofining catalyst bed needs to be controlled to be less than 5ppm.
TABLE 3 Properties of raw oil
TABLE 4 catalyst product distribution
As can be seen from Table 4, when the conversion rate of the hydrocracking reaction is controlled to be the same, the reaction temperature is obviously lower than that of the catalyst prepared by adopting the nuclear phase Y-type molecular sieve in the embodiment, and the reaction temperature is 7-11 ℃ lower, which indicates that the catalyst prepared by taking the Y-Y composite molecular sieve of the invention as a cracking component has higher reaction activity. In the product distribution, the yield of heavy naphtha (65-177 ℃) and the yield of aviation kerosene (177-260 ℃) obtained by adopting the catalyst are obviously higher than those of the catalyst prepared by adopting the SSY molecular sieve. The modified Y-Y composite molecular sieve prepared by the method has better reactivity and selectivity performance of target products.