CN117902590A

CN117902590A - Method for preparing hierarchical pore molecular sieve by dynamic regulation

Info

Publication number: CN117902590A
Application number: CN202410094098.5A
Authority: CN
Inventors: 李晓峰; 张燕挺; 郭云鸦; 窦涛
Original assignee: Taiyuan Dacheng Environment And Energy Chemical Technology Co ltd; Taiyuan University of Technology
Current assignee: Taiyuan Dacheng Environment And Energy Chemical Technology Co ltd; Taiyuan University of Technology
Priority date: 2024-01-23
Filing date: 2024-01-23
Publication date: 2024-04-19

Abstract

The invention discloses a method for preparing a hierarchical pore molecular sieve by dynamic regulation, belonging to the technical field of catalyst preparation; burst nucleation is carried out by adopting the low temperature and ultra-low H ₂O/SiO₂ molar ratio; then, after the low temperature is finished, adding a water source, and synthesizing a solid phase crystallization mechanism and a liquid phase crystallization mechanism in a system by a two-step crystallization method for rapid growth under the conditions of high temperature and high H ₂O/SiO₂ molar ratio to prepare the multi-stage molecular sieve in a relay way; under the condition of not adding any mesoporous pore-forming agent, the invention only modulates the crystallization temperature of molecular sieve synthesis and H ₂O/SiO₂ mol ratio of a synthesis system, controls crystallization mechanism with dynamics, and the obtained molecular sieve has higher catalytic performance than the traditional method; and overcomes the defects of high cost, high roasting energy consumption, poor sample mesoporous penetrability, serious pollution of the pore-forming agent and the like of the mesoporous pore-forming agent which is required to be introduced in the traditional preparation process of the multistage pore molecular sieve.

Description

Method for preparing hierarchical pore molecular sieve by dynamic regulation

Technical Field

The invention belongs to the technical field of catalyst preparation, and relates to a method for preparing a hierarchical pore molecular sieve by dynamic regulation; in particular to a preparation method for preparing a multi-level pore molecular sieve under the condition of no mesoporous pore-forming agent.

Background

Molecular sieves are widely used as acid catalysts in various petrochemical and fine chemical processes, such as catalytic cracking, hydrocracking, isomerization, alkylation, catalytic oxidation, methanol conversion to olefins or gasoline, and the like, due to their unique pore structure, good shape selectivity, thermal stability, hydrothermal stability, and adjustable acidity. However, this results in a significant reduction in the catalytic performance of conventional molecular sieves due to the inherent micro-pore (typically less than 2 nm) internal diffusion of molecular sieves being greatly limited. Research has shown that in most catalytic reactions, particularly reactions in which macromolecules participate, the external active sites of the molecular sieve are fully utilized while the internal active sites are not highly utilized due to reactant control by internal diffusion (Chemical Society Reviews, 2015, 44 (24): 8877-8903). To solve the above problems, one of the most common solutions for researchers is to introduce mesopores into microporous molecular sieves to prepare multi-stage pore molecular sieves, so as to compensate for the difficulty of molecular sieve diffusion of reactants and products.

In the past twenty years, the methods for preparing the hierarchical pore molecular sieve mainly comprise a soft template agent method, a hard template agent method, a post-treatment method and the like. The soft template method is to add a surfactant into a synthesis system, the surfactant is expensive, and the method has the defect of possible toxicity and harm; the hard template method mainly comprises the steps of adding carbon black, carbon nano tubes and other materials into a synthesis system, wherein the hard template materials have low water solubility and low utilization rate in the synthesis process, and can also cause poor mesoporous connectivity of the prepared hierarchical pore molecular sieve; in addition, the post-treatment method damages the silicon-aluminum species in the molecular sieve framework through acid or alkali solution, and sites of the silicon-aluminum species from which the framework falls form intra-crystalline mesopores. However, this method is cumbersome in steps, and may produce a large amount of wastewater and decrease the yield of molecular sieves. Thus, how to synthesize a hierarchical pore molecular sieve in one step in green remains a great challenge.

Growth kinetics control is one of the usual strategies for green synthesis of hierarchical pore molecular sieves. Zhang Jiang (Jilin university paper, single crystal nano/multi-level pore ZSM-5 and Beta molecular sieve synthesis and catalysis performance research) indicates that the molecular sieve growth kinetics refers to the effective control of the diffusion rate agglomeration mode of atoms, clusters and nanoparticles by changing the parameter conditions of the raw material types, the template agent property and the consumption, the water amount and alkalinity of a system, the crystallization temperature and time, the seed crystal addition and the like in a synthesis system, and finally achieves the aim of controlling the nucleation and growth process of crystals. On one hand, the sectional crystallization is adopted to reduce the particle size of the molecular sieve product, so that the molecular sieve product is prepared into a multi-stage molecular sieve. For example, patent CN107055568 a proposes a method for synthesizing ZSM-5 molecular sieve at varying temperature, the prepared synthetic gel is crystallized for 10-20 hours at 80-110 ℃; then heating to 115-130 ℃ for crystallization for 10-40 hours, wherein the grain size distribution of the synthesized molecular sieve raw powder is narrow (0.9-1.1 mu m); patent CN104495869B provides a method for preparing small-grain ZSM-35 molecular sieve. The method comprises the following steps: uniformly mixing a silicon source, an aluminum source, an alkali source, a template agent and water to obtain a colloid solution, wherein the mole ratio of the components is as follows: siO ₂/Al₂O₃ =18.5-28.6, stencil/SiO ₂＝0.81-1.25、OH^-/SiO₂＝0.03-0.18、H₂O/SiO₂ =10-26; crystallizing the colloid solution at 15-80deg.C for 5-30 hr, and crystallizing at 150-200deg.C for 10-30 hr; the small-grain ZSM-35 molecular sieve is prepared after filtering, washing and drying. The preparation method uses cheap ethylenediamine as a template agent, and controls the crystallization process by adding seed crystal and dividing two-stage crystallization to synthesize the small-grain ZSM-35 molecular sieve, wherein the minimum grain size of the small-grain ZSM-35 molecular sieve can be about 0.5 mu m; patent CN104495869B proposes that the synthetic gel is pre-crystallized for 1-24 hours at 60-90 ℃, then pre-crystallized for 1-48 hours at 100-120 ℃, and finally crystallized for 24-192 hours at 150-200 ℃. The synthesized sample has inter-crystalline mesoporous and intra-crystalline mesoporous structures in addition to micropores with zeolite structures, wherein the primary nano-crystalline particle size is 40-500nm, and the secondary stacking particle size is 500nm-5 μm.

On the other hand, the reduction of the water-to-silicon ratio of the synthesis system can reduce the particle size of the product, or can form a large amount of mesopores (CHEMICAL ENGINEERING Journal 291 (2016) 82-93). However, in the synthesis system with low water-silicon ratio in industrial production, the stirring of the synthetic gel is difficult, so that the heat transfer and mass transfer are not uniform easily, the crystallinity of the product is affected, and a large number of defect sites are formed. In molecular sieve supported catalysts, the number of defective sites can have some adverse effects, such as the formation of carbon deposits, leading to reduced catalyst life (chem. Soc. Rev., 2021, 50, 11156-11179). Therefore, the invention adopts a strategy of explosive nucleation under the conditions of low temperature and low water-silicon ratio and crystallization growth of high temperature and high water-silicon ratio to prepare the multi-level pore molecular sieve.

Disclosure of Invention

The invention overcomes the defects of the prior art and provides a method for preparing a hierarchical pore molecular sieve by dynamic regulation. So as to solve the problem of synthesizing the multi-level pore molecular sieve by the mesoporous pore-forming agent in the traditional synthesis system.

In order to achieve the above purpose, the invention is realized by the following technical scheme:

A method for preparing a multi-stage pore molecular sieve by dynamic regulation comprises the steps of mixing raw materials for preparing the molecular sieve, crystallizing at a low temperature range of 60-120 ℃ under the condition that the H ₂O/SiO₂ molar ratio is 1-3 to promote burst nucleation, then supplementing a water source, and rapidly growing at a high temperature range of 140-220 ℃ under the condition that the H ₂O/SiO₂ molar ratio is 15-50 to prepare the multi-stage pore molecular sieve.

Preferably, the low temperature range is 80℃to 100 ℃.

Preferably, the high temperature ranges from 140℃to 180 ℃.

More preferably, the corresponding molar ratio of H ₂O/SiO₂ in the high temperature range is 20-30.

The molecular sieve is a silicon-aluminum molecular sieve or a phosphorus-aluminum molecular sieve or a hetero-atom zeolite. Common silica-alumina molecular sieves, such as ZSM-5 molecular sieves, ZSM-11 molecular sieves, ZSM-12 molecular sieves, mordenite, Y molecular sieves, type A molecular sieves, beta molecular sieves, SSZ-13 molecular sieves, ZSM-48 molecular sieves, SSZ-39 molecular sieves, EU-1 molecular sieves, and MCM-22 molecular sieves; also included are phosphoaluminous molecular sieves, such as SAPO-31, SAPO-18, SAPO-34; in addition, hetero-atom zeolites such as TS-1 molecular sieves, TS-2 molecular sieves, ti-Beta molecular sieves, B-ZSM-5, fe-ZSM-5 molecular sieves, ga-ZSM-5 molecular sieves, and the like are included. The molecular sieve is preferably ZSM-5 molecular sieve, beta molecular sieve, EU-1 molecular sieve, MCM-22 molecular sieve and Silicalite-1 molecular sieve.

Preferably, the raw materials of the molecular sieve comprise a silicon source, an aluminum source, naOH and an organic template agent.

The silicon source is one of silica gel, silica sol, water glass, white carbon black, tetraethoxysilane and tetramethylsilicate. Among them, silica gel, white carbon black and ethyl orthosilicate are preferable.

The aluminum source synthesized by the molecular sieve comprises sodium metaaluminate, pseudo-boehmite, amorphous aluminum hydroxide and aluminum isopropoxide. Among them, sodium metaaluminate and pseudo-boehmite are preferable.

The organic template of molecular sieves is the most reported organic. The organic template for synthesizing ZSM-5 molecular sieve is tetrapropylammonium bromide, the organic template for synthesizing Beta molecular sieve is tetraethylammonium bromide, the organic template for synthesizing EU-1 molecular sieve is hexamethyldiammonium bromide, the organic template for synthesizing MCM-22 molecular sieve is hexamethyleneimine, the organic template for synthesizing TS-1 molecular sieve is tetrapropylammonium bromide, and the organic template for synthesizing Silicalite-1 molecular sieve is tetrapropylammonium bromide.

More preferably, the NaOH/SiO ₂ molar ratio is in the range of 0.05-0.5, wherein the NaOH/SiO ₂ molar ratio is preferably in the range of 0.1-0.3; the molar ratio of R/SiO ₂ is in the range of 0.01-0.2, wherein R represents an organic template agent; siO ₂/Al₂O₃ molar ratio is more than or equal to 30, preferably 30-100.

More preferably, a seed crystal is further included, and the seed crystal is added in an amount of 0 to 10% by mass of the silicon source, and preferably 0 to 5% by mass.

The form of the seed crystal may be a solid seed crystal or a seed crystal solution. The solid seed crystal can be the seed crystal without the template agent removed by high-temperature roasting, or the seed crystal without the template agent removed by high-temperature roasting. Among them, solid seed crystals from which the template is removed by high-temperature calcination are preferable.

The seed crystal is preferably a homogenous seed crystal consistent with the crystalline form of the product.

The catalyst prepared by the molecular sieve can be used for preparing olefin from methanol, preparing propylene from methanol, xylene isomerization, preparing p-diethylbenzene from ethylbenzene ethylation, trimethylbenzene isomerization, methylation of naphthalene, catalytic cracking, preparing BTX from catalytic diesel hydrocracking, preparing ethylbenzene from benzene and ethylene by alkylation, preparing propylene from toluene and methanol by alkylation, toluene disproportionation, cyclohexanone oxime, preparing propylene from propane dehydrogenation, beckmann rearrangement reaction and the like. Among them, xylene isomerization, catalytic diesel hydrocracking to produce BTX and benzene, cyclohexanone oximation and ethylene alkylation to produce ethylbenzene, propane dehydrogenation to produce propylene, beckmann rearrangement reaction, and the like are preferable.

Compared with the prior art, the invention has the following beneficial effects:

(1) Under the condition of not adding mesoporous pore-forming agent, the invention successfully prepares a plurality of multi-level porous molecular sieve structures by adjusting the crystallization temperature of molecular sieve synthesis and the molar ratio of gel H ₂O/SiO₂. The method does not need to add mesoporous pore-forming agent in a synthesis system, thereby reducing the preparation cost of the multi-level pore molecular sieve and being more environment-friendly; meanwhile, the mesoporous template agent is not required to be removed at high temperature in the later stage, so that the energy consumption is greatly reduced. The method adopts a two-step crystallization method, firstly, burst nucleation is carried out under the conditions of low temperature and ultra-low H ₂O/SiO₂ molar ratio, then water source is added after the low temperature is finished, and the multi-stage molecular sieve is prepared by rapid growth under the conditions of high temperature and high H ₂O/SiO₂ molar ratio.

(2) The multistage pore molecular sieve has good penetration performance, so that the diffusion performance of reactants and products is improved. Therefore, the hierarchical porous molecular sieve catalyst prepared by the method has high activity and low side reaction in the corresponding catalytic reaction.

(3) The method combines two crystallization mechanisms of solid phase conversion and liquid phase conversion in the preparation process of the molecular sieve, overcomes the defect of a single mechanism, and the prepared hierarchical pore molecular sieve product has relatively perfect crystallization and few defect sites. However, in the catalytic reaction process, the molecular sieve defect site is easy to generate carbon deposition and other problems in the long-period operation process, so that the stability of the molecular sieve is reduced. Therefore, the molecular sieve catalyst prepared by the method has good stability.

Drawings

FIG. 1 is an XRD spectrum of a hierarchical pore ZSM-5 molecular sieve prepared in comparative example 1 and examples 1-2. From the figure, the ZSM-5 molecular sieve sample prepared by the method has a pure-phase MFI topological structure and good crystallinity.

FIG. 2 is an SEM image of a multi-stage pore ZSM-5 molecular sieve prepared according to comparative example 1 and example 1-2. As can be seen from the figure, the ZSM-5 molecular sieve sample prepared by the method has small particle size compared with the sample prepared by the traditional method.

FIG. 3 is the external specific surface area data of the multistage pore ZSM-5 molecular sieves prepared in comparative example 1 and examples 1-2. As can be seen from the figure, the ZSM-5 molecular sieve sample prepared by the method has a large outer surface area compared with the sample prepared by the traditional method.

FIG. 4 is an XRD spectrum of a hierarchical pore EU-1 molecular sieve prepared in comparative example 2 and examples 3-4. As can be seen from the figure, the EU-1 molecular sieve sample prepared by the method has a pure-phase EUO topological structure and good crystallinity.

FIG. 5 is an SEM image of a hierarchical pore EU-1 molecular sieve prepared according to comparative example 2 and examples 3-4. As can be seen from the figure, the EU-1 molecular sieve sample prepared by the method has smaller particle size than the sample prepared by the traditional method.

FIG. 6 is the external specific surface area data of the hierarchical pore EU-1 molecular sieves prepared in comparative example 2 and examples 3-4. As can be seen from the figure, the EU-1 molecular sieve sample prepared by the method has a large outer surface area compared with the sample prepared by the traditional method.

FIG. 7 is an XRD spectrum of the hierarchical pore Beta molecular sieves prepared in comparative example 3 and examples 5-6. As can be seen from the figure, the Beta molecular sieve sample prepared by the method has a BEA topological structure of a pure phase and has good crystallinity.

FIG. 8 is an SEM image of a hierarchical pore Beta molecular sieve prepared according to comparative example 3 and examples 5-6. As can be seen from the figure, the Beta molecular sieve sample prepared by the method has smaller particle size than the sample prepared by the traditional method.

FIG. 9 is the external specific surface area data of the hierarchical pore Beta molecular sieves prepared in comparative example 3 and examples 5-6. As can be seen from the figure, the Beta molecular sieve sample prepared by the method has a large outer surface area compared with the sample prepared by the traditional method.

FIG. 10 is an XRD spectrum of a hierarchical pore MCM-22 molecular sieve prepared in comparative example 4 and examples 7-8. As can be seen from the figure, the MCM-22 molecular sieve sample prepared by the method has a pure-phase MWW topological structure and has good crystallinity.

FIG. 11 is an SEM image of a hierarchical pore MCM-22 molecular sieve prepared according to comparative example 4 and examples 7-8. As can be seen from the figure, the MCM-22 molecular sieve sample prepared by the method has smaller particle size than the sample prepared by the traditional method.

Figure 12 is an external specific surface area data for hierarchical pore MCM-22 molecular sieves prepared in comparative example 4 and examples 7-8. As can be seen from the figure, the MCM-22 molecular sieve sample prepared by the method has a large outer surface area compared with the sample prepared by the traditional method.

FIG. 13 is an XRD spectrum of the hierarchical pore TS-1 molecular sieve prepared in comparative example 5 and examples 9-10. The figure shows that the TS-1 molecular sieve sample prepared by the method has a pure-phase MFI topological structure and good crystallinity.

FIG. 14 is an SEM image of a hierarchical pore TS-1 molecular sieve prepared according to comparative example 5 and examples 9-10. As can be seen from the figure, the TS-1 molecular sieve sample prepared by the method has smaller particle size than the sample prepared by the traditional method.

FIG. 15 is the external specific surface area data of the hierarchical pore TS-1 molecular sieves prepared in comparative example 5 and examples 9-10. As can be seen from the figure, the TS-1 molecular sieve sample prepared by the method has a large outer surface area compared with the sample prepared by the traditional method.

FIG. 16 is a graph of conversion data for the hierarchical pore TS-1 molecular sieves prepared in comparative example 5 and examples 9-10.

FIG. 17 is a graph of selectivity data for the hierarchical pore TS-1 molecular sieves prepared in comparative example 5 and examples 9-10.

FIG. 18 is an XRD spectrum of a hierarchical pore Silicalite-1 molecular sieve prepared in comparative example 6 and examples 11-12. As can be seen from the figure, the Silicalite-1 molecular sieve prepared by the method has a pure-phase MFI topological structure and good crystallinity.

FIG. 19 is an SEM image of a hierarchical pore Silicalite-1 molecular sieve prepared according to comparative example 6 and examples 11-12. As can be seen from the figure, the Silicalite-1 molecular sieve sample prepared by the method has smaller particle size than the sample prepared by the traditional method.

FIG. 20 is the external specific surface area data of the hierarchical pore Silicalite-1 molecular sieves prepared in comparative example 6 and examples 11-12. As can be seen from the figure, the Silicalite-1 molecular sieve sample prepared by the method has a large outer surface area compared with the sample prepared by the traditional method.

FIG. 21 is a graph showing Beckmann rearrangement conversion performance data for the hierarchical pore Silicalite-1 molecular sieves prepared in comparative example 6 and examples 11-12.

FIG. 22 is Beckmann rearrangement selection performance data for the hierarchical pore Silicalite-1 molecular sieves prepared in comparative example 6 and examples 11-12.

FIG. 23 is propane dehydrogenation conversion data for the hierarchical pore Silicalite-1 molecular sieves prepared in comparative example 6 and examples 11-12.

FIG. 24 is propane dehydrogenation selectivity data for the hierarchical pore Silicalite-1 molecular sieves prepared in comparative example 6 and examples 11-12.

Detailed Description

In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the invention is further described in detail by combining the embodiments and the drawings. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. The following describes the technical scheme of the present invention in detail with reference to examples and drawings, but the scope of protection is not limited thereto.

Example 1

A method for preparing a multistage hole ZSM-5 molecular sieve by dynamic regulation comprises the following steps: sodium hydroxide is added into water, then tetrapropylammonium bromide (TPABr) and sodium metaaluminate are added, stirring is carried out for 5min, and silica gel is added, at the moment, the molar ratio SiO ₂: 0.033 Al₂O₃: 0.1NaOH: 0.15 TPABr :1H₂ O of the initial gel is crystallized for 1d at the low temperature of 100 ℃. After the low-temperature crystallization is finished, opening the reaction kettle to supplement deionized water, crystallizing 1d at the high temperature of 180 ℃ with the molar ratio of SiO ₂: 0.033Al₂O₃: 0.1NaOH : 0.15 TPABr :30H₂ O in the system, quenching, drying and roasting after the crystallization is finished to obtain the ZSM-5 molecular sieve, which is denoted as Z-1.

Example 2

A method for preparing a multistage hole ZSM-5 molecular sieve by dynamic regulation comprises the following steps: sodium hydroxide was added to water, followed by tetrapropylammonium bromide (TPABr) and pseudo-boehmite, stirred for 5min, and silica gel was added, at which time the molar ratio of the initial gel, siO ₂: 0.01Al₂O₃: 0.1NaOH: 0.15TPABr :2H₂ O, was crystallized at 100℃for 1d. After the low-temperature crystallization is finished, the reaction kettle is opened to be supplemented with deionized water, so that the mol ratio of SiO ₂: 0.01Al₂O₃: 0.1NaOH: 0.15TPABr: 20H₂ O in the system is 1d after the crystallization is finished, and the ZSM-5 molecular sieve is obtained through quenching, drying and roasting after the crystallization is finished and is marked as Z-2.

Example 3

Preparation of a hierarchical pore EU-1 molecular sieve by kinetic regulation: sodium hydroxide was added to water, followed by hexamethyldiammonium bromide (HMBr) and sodium metaaluminate, stirred for 5min, and further silica gel and 5% seed crystals (mass fraction relative to the silicon source) were added, at which time the molar ratio of the initial gel, siO ₂: 0.033Al₂O₃: 0.3NaOH: 0.05 HMBr : 2H₂ O, was crystallized at 100 ℃ for 1d. After the low-temperature crystallization is finished, the reaction kettle is opened to be supplemented with deionized water, so that the molar ratio of SiO ₂: 0.033 Al₂O₃: 0.3NaOH: 0.05 HMBr : 25H₂ O in the system is enabled to be high-temperature 170 ℃ for 2d of crystallization, and EU-1 molecular sieve is obtained after quenching, drying and roasting after the crystallization is finished, and is marked as E-1.

Example 4

Preparation of a hierarchical pore EU-1 molecular sieve by kinetic regulation: sodium hydroxide was added to water, followed by hexamethyldiammonium bromide (HMBr) and sodium metaaluminate, stirred for 5min, and then silica gel and 1% seed crystals (mass fraction relative to the silicon source) were added, at which time the molar ratio of the initial gel, siO ₂: 0.033Al₂O₃: 0.3NaOH: 0.05 HMBr: 3H₂ O, was crystallized at 100 ℃ for 1d. After the low-temperature crystallization is finished, the reaction kettle is opened to be supplemented with deionized water, so that the molar ratio of SiO ₂: 0.033 Al₂O₃: 0.3NaOH: 0.05 HMBr :20H₂ O in the system is enabled to be crystallized for 2d at the high temperature of 180 ℃, and the EU-1 molecular sieve is obtained through quenching, drying and roasting after the crystallization is finished and is marked as E-2.

Example 5

Preparing a hierarchical pore Beta molecular sieve by dynamic regulation: sodium hydroxide was added to water, followed by tetraethylammonium bromide (TEAbr) and pseudoboehmite, stirred for 5min, and further silica gel and 1% seed crystals (mass fraction relative to the silicon source) were added, at which time the molar ratio of the initial gel was SiO ₂: 0.033 Al₂O₃: 0.2NaOH: 0.1TEABr : 1 H₂ O and crystallized at 100℃for 1d. After the low-temperature crystallization is finished, the reaction kettle is opened to be supplemented with deionized water, so that the molar ratio of SiO ₂: 0.033 Al₂O₃: 0.2NaOH: 0.1 TEABr : 30 H₂ O in the system is 1d after the crystallization is finished, and the Beta molecular sieve is obtained through quenching, drying and roasting after the crystallization is finished and is marked as B-1.

Example 6

Preparing a hierarchical pore Beta molecular sieve by dynamic regulation: sodium hydroxide was added to water, followed by tetraethylammonium bromide (TEAbr) and pseudoboehmite, stirred for 5min, and further silica gel and 2% seed crystals (mass fraction relative to the silicon source) were added, at which time the molar ratio of the initial gel was SiO ₂: 0.01 Al₂O₃: 0.2NaOH : 0.15 TEABr : 2H₂ O and crystallized at 100℃for 1d. After the low-temperature crystallization is finished, the reaction kettle is opened to be supplemented with deionized water, so that the molar ratio of SiO ₂: 0.01 Al₂O₃: 0.2NaOH: 0.15TEABr :25H₂ O in the system is 1d after the crystallization is finished, and the Beta molecular sieve is obtained through quenching, drying and roasting after the crystallization is finished and is marked as B-2.

Example 7

Preparing a hierarchical pore MCM-22 molecular sieve by dynamic regulation: sodium hydroxide was added to water, followed by Hexamethyleneimine (HMI) and pseudo-boehmite, stirred for 5min, and further silica gel was added, at which time the molar ratio of the initial gel was SiO ₂: 0.033 Al₂O₃: 0.25NaOH ：0.15 HMI :1 H₂ O, crystallized at 90 ℃ for 1d. After the low-temperature crystallization is finished, the reaction kettle is opened to be supplemented with deionized water, so that the molar ratio of SiO ₂: 0.033Al₂O₃: 0.25NaOH ：0.15 HMI: 20H₂ O in the system is 1d after the crystallization is finished, and the MCM-22 molecular sieve is obtained through quenching, drying and roasting after the crystallization is finished and is marked as M-1.

Example 8

Preparing a hierarchical pore MCM-22 molecular sieve by dynamic regulation: sodium hydroxide was added to water, followed by Hexamethyleneimine (HMI) and pseudo-boehmite, stirred for 5min, and further silica gel was added, at which time the molar ratio of the initial gel was SiO ₂: 0.033Al₂O₃: 0.25NaOH ：0.15 HMI :2H₂ O, crystallized at 100 ℃ at 1d. After the low-temperature crystallization is finished, the reaction kettle is opened to be supplemented with deionized water, so that the molar ratio of SiO ₂: 0.033Al₂O₃: 0.25NaOH ：0.15 HMI : 25H₂ O in the system is 1d after the crystallization is finished, and the MCM-22 molecular sieve is obtained through quenching, drying and roasting after the crystallization is finished and is marked as M-2.

Example 9

Preparing a hierarchical pore TS-1 molecular sieve by dynamic regulation: ethyl orthosilicate was added to tetrapropylammonium bromide, followed by tetraethyl titanate, and after stirring for 30min, ethanol was distilled off at 60℃for 3 h. After the alcohol removal is finished, water is added to make the molar ratio of the whole gel system be SiO ₂: 0.02TiO₂: 0.2TPABr :3H₂ O, and the gel system is crystallized for 1d at a low temperature of 100 ℃. After the low-temperature crystallization is finished, the reaction kettle is started to be supplemented with deionized water, so that the molar ratio of SiO ₂: 0.02TiO₂: 0.2TPABr :10H₂ O in the system is crystallized for 3d at 170 ℃, and the TS-1 molecular sieve is obtained after quenching, drying and roasting after the crystallization is finished and is marked as T-1.

Example 10

Preparing a hierarchical pore TS-1 molecular sieve by dynamic regulation: ethyl orthosilicate was added to tetrapropylammonium bromide, followed by tetraethyl titanate, and after stirring for 30min, ethanol was distilled off at 60℃for 3 h. After the alcohol removal is finished, water is added to make the molar ratio of the whole gel system be SiO ₂: 0.02 TiO₂:0.2 TPABr :2H₂ O, and the gel system is crystallized for 1d at a low temperature of 100 ℃. After the low-temperature crystallization is finished, the reaction kettle is started to be supplemented with deionized water, so that the molar ratio of SiO ₂: 0.02 TiO₂: 0.2TPABr : 30H₂ O in the system is crystallized for 3d at 170 ℃, and the TS-1 molecular sieve is obtained after quenching, drying and roasting after the crystallization is finished and is marked as T-2.

Example 11

Preparation of hierarchical pore Silicalite-1 molecular sieves by kinetic control: sodium hydroxide was added to water, followed by silica gel, sodium metaaluminate, tetrapropylammonium bromide and mixing. At this time, the molar ratio of the initial gel was SiO ₂: 0.033 Al₂O₃: 0.25NaOH ：0.15 TPABr :1 H₂ O, and the initial gel was crystallized at a low temperature of 90℃to 1 d. After the low-temperature crystallization is finished, the reaction kettle is opened to be supplemented with deionized water, so that the molar ratio of SiO ₂: 0.033 Al₂O₃: 0.25NaOH ：0.15 TPABr :25 H₂ O in the system is 3d at 170 ℃, and the Silicalite-1 molecular sieve is obtained after quenching, drying and roasting after the crystallization is finished and is marked as S-1.

Example 12

Preparation of hierarchical pore Silicalite-1 molecular sieves by kinetic control: sodium hydroxide was added to water, followed by silica gel, sodium metaaluminate, tetrapropylammonium bromide and mixing. At this time, the molar ratio of the initial gel was SiO ₂: 0.033 Al₂O₃: 0.25NaOH ：0.15TPABr :2H₂ O, which was crystallized at 90℃for 1d. After the low-temperature crystallization is finished, the reaction kettle is opened to be supplemented with deionized water, so that the molar ratio of SiO ₂: 0.033 Al₂O₃: 0.25NaOH ：0.15TPABr :40H₂ O in the system is 3d at 170 ℃, and the Silicalite-1 molecular sieve is obtained after quenching, drying and roasting after the crystallization is finished and is marked as S-2.

Comparative example 1

Preparation of a traditional ZSM-5 molecular sieve: sodium hydroxide was added to water followed by tetrapropylammonium bromide (TPABr) and sodium metaaluminate, stirred for 5min, and silica gel was added at which time the molar ratio of the initial gel, siO ₂: 0.033 Al₂O₃:0.1NaOH: 0.2 TPABr :30 H₂ O. Crystallizing at 180 ℃ for 1d, quenching, drying and roasting after crystallization to obtain the ZSM-5 molecular sieve, which is denoted as Z-0.

Comparative example 2

Preparation of conventional EU-1 molecular sieves: sodium hydroxide was added to water followed by hexamethyldiammonium bromide (HMBr) and sodium metaaluminate, stirred for 5min, and then silica gel and 5% seed crystals (mass fraction relative to the silicon source) were added, at which time the molar ratio of the initial gel, siO ₂: 0.033Al₂O₃: 0.3NaOH: 0.05 HMBr: 30H₂ O. Crystallizing at 170 ℃ for 2d, quenching, drying and roasting after crystallization to obtain EU-1 molecular sieve, which is designated as E-0.

Comparative example 3

Preparation of traditional Beta molecular sieves: sodium hydroxide was added to water, followed by tetraethylammonium bromide (TEAbr) and pseudoboehmite, stirred for 5min, and then silica gel and 1% seed crystals (mass fraction relative to the silicon source) were added, at which time the molar ratio of the initial gel, siO ₂: 0.033Al₂O₃: 0.2NaOH: 0.1TEABr: 30H₂ O. Crystallizing at 140 deg.C for 2d, quenching, drying and calcining to obtain Beta molecular sieve, which is designated as B-0.

Comparative example 4

Preparation of a traditional MCM-22 molecular sieve: sodium hydroxide was added to water followed by Hexamethyleneimine (HMI) and pseudoboehmite, stirred for 5min, and then silica gel was added, at which time the molar ratio of the initial gel was SiO ₂: 0.033Al₂O₃: 0.25NaOH: 0.30 HMI: 30 H₂ O. Crystallizing at 180 ℃ for 1d, quenching, drying and roasting after crystallization to obtain the MCM-22 molecular sieve, which is designated as M-0.

Comparative example 5

Preparation of a traditional TS-1 molecular sieve: ethyl orthosilicate was added to tetrapropylammonium bromide, followed by tetraethyl titanate, and after stirring for 30 minutes, ethanol was distilled off at 60℃for 3 hours. After the alcohol removal is finished, adding water to make the molar ratio of the whole gel system be SiO ₂: 0.02TiO₂:0.2TPABr :10 H₂ O, crystallizing for 3d at the high temperature of 170 ℃, quenching, drying and roasting after the crystallization is finished to obtain the TS-1 molecular sieve, which is marked as T-0.

Comparative example 6

Preparation of a traditional Silicalite-1 molecular sieve: sodium hydroxide was added to water, followed by silica gel, sodium metaaluminate, tetrapropylammonium bromide and mixing. At this time, the molar ratio of the initial gel is SiO ₂: 0.033 Al₂O₃: 0.25NaOH ：0.15 TPABr :25 H₂ O, which is crystallized at a high temperature of 170 ℃ for 3 days, and the Silicalite-1 molecular sieve is obtained by quenching, drying and roasting after the crystallization is finished, and is designated as S-0.

In order to verify the catalytic performance of the molecular sieve prepared in the invention, various characteristic reactions are selected as specific application examples, and the specific reactions are as follows:

Catalyst Performance test example 1

And (3) testing the ethylbenzene deethylation isomerization catalytic performance of the ZSM-5 molecular sieve. The reaction raw materials comprise 7.0% of ethylbenzene and 93.0% of m-xylene by mass. Before the catalytic performance test, a molecular sieve sample is loaded with 0.05% of noble metal Pt to prepare the ethylbenzene deethylation isomerization catalyst containing an acid center and a metal center. The comparative example 1 and the examples 1 to 2 were subjected to the catalytic performance test, and the specific results are shown in Table 1.

Conditions for catalyst performance test: the reaction temperature is 370 ℃; the reaction pressure is 0.8 MPa; airspeed = 8.0 h ^-1; the molar ratio of hydrogen to hydrocarbon was 2.0, and after 24, 24 h, the liquid reaction product was analyzed by gas chromatograph. The catalytic performance parameters are ethylbenzene conversion X _EB and isomerization activity S _PX, which are defined as follows: in the formula of X _EB=（1-w_EB/w_EB,0）×100 %,S_PX=w_PX/w_ΣX multiplied by 100%, w _EB,w_PX and w _ΣX respectively represent the mass fractions of ethylbenzene, paraxylene and total xylene in the liquid product, and w _EB,0 represents the mass fraction of ethylbenzene in the raw oil.

As can be seen from table 1: the ethylbenzene conversion of the synthetic samples of this example 1 was higher than that of comparative example 1.

Catalyst Performance test example 2

EU-1 molecular sieves preparation catalysts were used for catalytic performance testing of xylene isomerization. To verify the catalytic performance of xylene isomerization prepared in examples 3-4 (the catalyst evaluation method referred to X.F. Li et al Chinese Journal of CHEMICAL ENGINEERING (2016) 1577-1583), samples were tested for catalytic performance using 15.0% ethylbenzene and 85.0% meta-xylene as reaction materials, and the results are shown in Table 2.

Conditions for catalyst performance test: the reaction temperature is 360 ℃; the reaction pressure is 0.5 MPa; airspeed = 4.5 h ^-1; the molar ratio of hydrogen to hydrocarbon was 2.0, and after reaction 3 h, the liquid reaction product was analyzed by gas chromatograph. The catalytic performance parameter has isomerization activity. S _PX=w_PX/w_ΣX×100 %,w_PX and w _ΣX represent the mass fractions of para-xylene and total xylenes, respectively, in the liquid product.

Catalyst Performance test example 3

Beta molecular sieve preparation catalyst is used for the catalytic performance test of the liquid phase alkylation of benzene and ethylene. To demonstrate the catalytic performance of the synthetic hierarchical pore Beta molecular sieves of the present invention, benzene was reacted with ethylene alkylation as a probe, wherein the catalytic data for the comparative example 3 sample, the example 5 sample, and the example 6 sample are shown in Table 3. ( The reaction conditions are as follows: the reaction temperature is 250 ℃; the reaction pressure was 3 MPa; airspeed = 13.3 h ^-1; the ratio of benzene=4.16, after reaction 6 h, a sample was taken and analyzed by gas chromatograph. Where ethylbenzene selectivity = ethylbenzene content in the hydrocarbonated liquid/(benzene content in the 100-hydrocarbonated liquid) ×100%. )

Catalyst Performance test example 4

The MCM-22 molecular sieve prepared catalyst is used for the catalytic performance test of the liquid phase alkylation of benzene and ethylene. To demonstrate the catalytic performance of the inventive synthetic hierarchical pore MCM-22 molecular sieves, benzene was reacted with ethylene alkylation as a probe, wherein the catalytic data for the comparative example 4 sample, the example 7 sample, and the example 8 sample are shown in table 4. ( The reaction conditions are as follows: the reaction temperature is 250 ℃; the reaction pressure was 3 MPa; airspeed = 13.3 h ^-1; the ratio of benzene=4.16, after reaction 6 h, a sample was taken and analyzed by gas chromatograph. Where ethylbenzene selectivity = ethylbenzene content in the hydrocarbonated liquid/(benzene content in the 100-hydrocarbonated liquid) ×100%. )

Catalyst Performance test example 5

The catalytic performance of the TS-1 molecular sieve in the invention is tested by cyclohexanone ammoximation. The reaction temperature is 76 ℃, tertiary butanol is used as a solvent, the volume ratio of tertiary butanol to cyclohexanone is 3.4:1, and cyclohexanone: ammonia gas: hydrogen peroxide=1:2.3:1.05 (molar ratio), whereas the catalyst is used in an amount of 1.8% (mass fraction). The catalytic properties mainly comprise the conversion rate of cyclohexanone and the selectivity of cyclohexanone oxime, and specific calculation and evaluation are referred to in industrial catalysis 2018,26 (5) 83-88. The catalytic data of the comparative example 5 sample, the example 9 sample and the example 10 sample are shown in FIGS. 16 and 17.

Catalyst Performance test example 6

The catalytic performance of the Silicalite-1 molecular sieve of the present invention was tested using a gas phase Beckmann rearrangement reaction. First activated for 1 hour at 350 ℃ and then lowered to 300 ℃. A toluene solution of 5wt% cyclohexanone oxime was used as the reaction feed, at a space velocity of 5h ^-1. Catalytic properties mainly include conversion and selectivity. Among them, the vapor phase beckmann rearrangement catalytic data of comparative example 6, example 11 and example 12 are shown in fig. 21 and 22.

Catalyst Performance test example 7

In addition, propane dehydrogenation reactions can be used to test the catalytic performance of Silicalite-1 molecular sieves of the present invention. Before the catalytic performance evaluation, the Silicalite-1 molecular sieve was subjected to an equal volume impregnation, supporting Pt (0.5%) and Sn (1.0%). After the catalyst loading was completed, the temperature was raised to 600 ℃ and the reaction was started after 3h purges. The conditions for catalytic evaluation were normal pressure, the reaction temperature was 600℃and the space velocity of propane was 3h ^-1. Propane dehydrogenation catalytic data for comparative example 6, example 11 and example 12 are shown in fig. 23 and 24.

While the invention has been described in detail in connection with specific preferred embodiments thereof, it is not to be construed as limited thereto, but rather as a result of a simple deduction or substitution by a person having ordinary skill in the art to which the invention pertains without departing from the scope of the invention defined by the appended claims.

Claims

1. A method for preparing a multi-stage pore molecular sieve by dynamic regulation is characterized in that raw materials for preparing the molecular sieve are mixed, the mixture is crystallized at a low temperature of 60-120 ℃ under the condition that the molar ratio of H ₂O/SiO₂ is 1-3 to promote burst nucleation, then water sources are added, and the mixture is rapidly grown at a high temperature of 140-220 ℃ under the condition that the molar ratio of H ₂O/SiO₂ is 15-50 to prepare the multi-stage pore molecular sieve.

2. The method for preparing the hierarchical pore molecular sieve according to claim 1, wherein the low temperature is 80-100 ℃.

3. The method for preparing the hierarchical pore molecular sieve according to claim 2, wherein the high temperature is 140-180 ℃.

4. A method for preparing a hierarchical pore molecular sieve according to claim 3, wherein the corresponding molar ratio of H ₂O/SiO₂ at high temperature ranges is 20-30.

5. The method for preparing the hierarchical pore molecular sieve according to claim 1, wherein the molecular sieve is a silicon aluminum molecular sieve or a phosphorus aluminum molecular sieve or a hetero atom zeolite.

6. The method for preparing the hierarchical pore molecular sieve according to claim 1, wherein the raw materials of the molecular sieve comprise a silicon source, an aluminum source, naOH and an organic template agent.

7. The method for preparing the hierarchical pore molecular sieve according to claim 6, wherein the silicon source is one of silica gel, silica sol, water glass, white carbon black, ethyl orthosilicate and methyl orthosilicate.

8. The method for preparing the hierarchical pore molecular sieve according to claim 6, wherein the organic template for synthesizing the ZSM-5 molecular sieve is tetrapropylammonium bromide, the organic template for synthesizing the Beta molecular sieve is tetraethylammonium bromide, the organic template for synthesizing the EU-1 molecular sieve is hexamethyldiammonium bromide, the organic template for synthesizing the MCM-22 molecular sieve is hexamethyleneimine, the organic template for synthesizing the TS-1 molecular sieve is tetrapropylammonium bromide, and the organic template for synthesizing the Silicalite-1 molecular sieve is tetrapropylammonium bromide.

9. The method for preparing the hierarchical pore molecular sieve according to claim 6, wherein the molar ratio of NaOH/SiO ₂ is in the range of 0.05-0.5; the molar ratio of R/SiO ₂ is in the range of 0.01-0.2, wherein R represents an organic template agent; siO ₂/Al₂O₃ mol ratio is more than or equal to 30.

10. The method for preparing the hierarchical pore molecular sieve according to claim 6, further comprising seed crystals, wherein the addition amount of the seed crystals is 0-10% of the mass fraction of the silicon source.