CN109422283B

CN109422283B - Preparation method of molecular sieve with hierarchical pore structure, prepared molecular sieve and application thereof

Info

Publication number: CN109422283B
Application number: CN201710784663.0A
Authority: CN
Inventors: 丁佳佳; 刘红星; 陆贤; 赵昱; 方敬东
Original assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Current assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Priority date: 2017-09-04
Filing date: 2017-09-04
Publication date: 2021-06-22
Anticipated expiration: 2037-09-04
Also published as: CN109422283A

Abstract

The invention relates to a preparation method of a molecular sieve with a hierarchical pore structure, the prepared molecular sieve and application thereof, and mainly solves the problems of complicated operation process, high cost and loss of a crystal molecular sieve containing defects in the synthesis process of adopting a mesoporous template agent. The invention better solves the problem by adopting the technical scheme that the molecular sieve with crystal defects is used as the seed crystal for hydrothermal crystallization, and can be used in the industrial production of the molecular sieve with the multilevel pore channel structure.

Description

Preparation method of molecular sieve with hierarchical pore structure, prepared molecular sieve and application thereof

Technical Field

The invention relates to a preparation method of a molecular sieve with a hierarchical pore structure, the prepared molecular sieve and application thereof.

Background

In 1984, united states of america united carbides (UCC) invented a silicoaluminophosphate molecular sieve (SAPO molecular sieve for short) with a pore size of about 0.4 nm. The SAPO molecular sieve is prepared from AlO₄、SiO₄And PO₄Crystal network structure composed of tetrahedrons, pore channels in the crystal being formed by Si⁴⁺Substituted P⁵⁺Or Al³⁺The resulting acidity can be either replaced with a metal to produce acidity. Among SAPO series of molecular sieves, SAPO-34 molecular sieve is widely applied to modern petroleum processing industry because of good thermal stability and hydrothermal stability, moderate acidity, high specific surface area and highly ordered microporous pore canalsIn industry. The molecular sieve is most attractive when applied to Methanol To Olefin (MTO) reaction, the conversion rate of methanol can reach 100 percent, the selectivity of ethylene and propylene can exceed 70 percent, and C is₅ ⁺The content of the components is small and almost no aromatic hydrocarbon is generated. However, the relatively narrow and long pore channels of the SAPO molecular sieve present severe shape-selective limitations, which on one hand hinder the contact of the raw material molecules with the active centers inside the pore channels, and on the other hand, can limit the diffusion and mass transfer of the reactants, intermediate transition products and final products, and is very easy to block the pore channels due to carbon deposit, thereby causing the inactivation of the catalyst and limiting the exertion of the catalytic performance.

In order to overcome the defects of a single microporous structure molecular sieve material, numerous researchers prepare a novel molecular sieve combining the advantages of various pore channels, namely a hierarchical pore structure molecular sieve. According to the structure type of the pore channel, the hierarchical pore molecular sieves can be divided into the following two types: one is a micropore-micropore composite molecular sieve formed by two-phase cocrystallization molecular sieves, and the material consists of two or more than two composite micropore pore canals; the other type is a mesoporous/macroporous-microporous composite molecular sieve, the material has a microporous channel system and a mesoporous/macroporous channel system, the diffusion performance of the material can be greatly improved, the catalytic performance of the material is improved, and the material shows good catalytic conversion performance in reactions involving macromolecules and reactions requiring rapid diffusion.

Therefore, a preparation method is proposed, which comprises adding a mesoporous template into a gel system and then carrying out hydrothermal synthesis. Choi et al reported that AlPO with mesoporous structure is synthesized by one-step hydrothermal synthesis by using silanized long-chain alkyl quaternary ammonium salt as template agent₄N-series molecular sieves (Choi M, Srivastava R, Ryoo R.chemical Communications, 2006; (42): 4380-4382.); subsequently, Danilina and chrysolel, etc. are hydrothermally synthesized into SAPO-5(Danilina N, Krumeich F, van Bokhovin J. journal of Catalysis,2010,272(1):37-43.) and SAPO-34 molecular sieve (Chenolol, Ronghui, Ding et al. advanced school chemistry, 2010; 31(9): 1693-); fan and the like can synthesize the product under the conventional hydrothermal condition by adding long-chain organic phosphine as a mesoporous template agentSAPO-11 molecular sieve rich in mesoporous structure (Fan Y, Xiao H, Shi G, et al. journal of Catalysis,2012,285(1): 251-; cui and others use polyethylene glycol (PEG) as a mesoporous template to synthesize SAPO-34 molecular sieve with a hierarchical pore structure under hydrothermal conditions, and the size of the mesopores can be changed by adjusting the amount of PEG (Cui Y, Zhang Q, He J, et al. Yang et al, taking silanized surfactant as mesoporous template, synthesize SAPO-34 of hierarchical pore structure under the microwave-assisted condition, the result shows that the introduction of microwave can not only effectively shorten the crystallization time (the crystallization process can be completed in 2 hours), but also the synthesized product has higher specific surface area and mesoporous pore volume (Yang S, Kim J, Chae H, et al, materials Research Bulletin, 2012; 47(11): 3888) 3892.). Although the SAPO-34 molecular sieve with a hierarchical pore structure can be prepared by introducing the mesoporous template into a synthesis system of the molecular sieve in the synthesis process, the suitable template is expensive, and the process of removing the template is difficult to control.

In order to solve the above problems, the gas phase crystallization method is adopted by the Shiga service and the like to prepare a silicoaluminophosphate SAPO molecular sieve monolithic material with a hierarchical pore structure, and the material has higher catalytic activity in the MTO reaction compared with the conventional SAPO-34 molecular sieve (CN 102219237A; Yang H, Liu Z, Gao H, et al. journal of Materials Chemistry, 2010; 20(16): 3227-3231.). Recently, Jin et al uniformly mix and grind a silicon source, an aluminum source, a phosphorus source and morpholine, directly put the solid mixture into an oven, crystallize for 8-24 hours at 200 ℃ under the condition of no solvent, and wash, dry and bake the obtained product to obtain the SAPO-34 molecular sieve (Jin Y, Sun Q, Qi G, et al. Angewandte chemical International Edition, 2013; 125(35): 9342) with mesoporous structure, which also shows better catalytic performance in MTO reaction.

In summary, although the preparation of the hierarchical pore material is a hot spot of research by many researchers at present, the existing methods for preparing the hierarchical pore SAPO-34 molecular sieve have the disadvantages of complicated operation process, high cost and the like, and the structure of the molecular sieve is damaged while the mesoporous template is removed. Therefore, the preparation cost is reduced, the operation procedure is simplified, and the development of a simple and efficient preparation route of the hierarchical pore SAPO-34 molecular sieve has important practical significance. In addition, molecular sieves with defective crystals, which occur during the synthesis of SAPO-34 molecular sieves, are problematic from an economic standpoint if not discarded, and it is highly desirable to efficiently recover and reuse these discarded molecular sieves.

Disclosure of Invention

The invention provides a preparation method of a novel molecular sieve with a multilevel pore channel structure.

Specifically, the invention relates to a preparation method of a molecular sieve with a hierarchical pore structure, which comprises the step of performing hydrothermal crystallization by using the molecular sieve with crystal defects as seed crystals.

According to one aspect of the invention, the molecular sieve with crystal defects has a pore structure containing macropores and/or mesopores, wherein the proportion of the specific surface area of the macropores and/or the mesopores in the total specific surface area is not less than 10%, preferably 10-30%; the proportion of the macropore and/or mesopore volume in the total pore volume is not less than 15%, preferably 15-50%.

According to one aspect of the invention, in the molecular sieve with crystal defects, the pore diameter of macropores is distributed in a range of 100-2000 nm, and the pore diameter of mesopores is distributed in a range of 2-50 nm.

According to one aspect of the invention, the molecular sieve with crystal defects has a rough surface morphology and a large number of holes.

According to one aspect of the invention, the molecular sieve having crystal defects is derived from a molecular sieve that is not fully crystallized during synthesis.

According to one aspect of the invention, the molecular sieve is defined as having a relative crystallinity of 50 to 75% based on the molecular sieve having complete crystallization.

According to one aspect of the invention, the defect crystals originate from a step in which the molecular sieve, which is completely crystallized, is modified by a post-treatment.

According to one aspect of the invention, the post-treatment modification comprises the steps of contacting the fully crystallized molecular sieve with a modifier; the modifier is at least one selected from the group consisting of ammonia water, oxalic acid, citric acid, sodium carbonate, and tetraethylammonium hydroxide.

According to one aspect of the invention, the molecular sieve is selected from SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44, SAPO-47, SAPO-56, metal containing forms thereof, and mixtures thereof, preferably SAPO-34.

According to one aspect of the present invention, the method comprises the step of hydrothermally crystallizing a mixture of the seed crystal, a silicon source, a phosphorus source, an aluminum source, a templating agent, and water.

According to one aspect of the invention, the molar ratio of the aluminum source, the silicon source, the phosphorus source, the template agent and the water in the mixture is 1 (0.05-2): 0.05-1.5): 1-10): 10-200, preferably 1 (0.1-1.5): 0.2-1.2): 2-8): 30-150; the addition amount of the seed crystal is 1.5-20 wt% of the solid content, and preferably 3-15 wt%.

The invention also relates to the molecular sieve with the multilevel pore channel structure prepared by the preparation method.

According to one aspect of the invention, the molecular sieve with the hierarchical pore channel structure simultaneously has micropores, mesopores and macropores; wherein the aperture of the micropores is not more than 1 nanometer, the aperture of the mesopores is distributed in the range of 5-30 nanometers, and the aperture of the macropores is distributed in the range of 200-1500 nanometers; the pore volume of the micro-pores is 0.05-0.30 cm³The pore volume of the contribution of the mesopores is 0.10-0.40 cm³The pore volume of the macro pores is 0.10-0.60 cm³Per gram.

According to one aspect of the invention, the hierarchical porous structure molecular sieve is a hierarchical porous structure SAPO-34 molecular sieve.

The invention also relates to application of the molecular sieve with the multilevel pore structure prepared by the preparation method of the molecular sieve with the multilevel pore structure in the reaction of preparing olefin from oxygen-containing compounds.

The invention has the beneficial effects that: the method is based on the defect site orientation synthesis of the molecular sieve with the multi-stage pore channel structure in the defect crystal, and has the following advantages: 1. expensive mesoporous template agent is not needed in the synthesis process, so that the cost can be effectively saved; 2. the operation process is simple, is similar to the synthesis process of the conventional molecular sieve, and only needs to replace the common crystal seeds with the defective crystal seeds; 3. the source of the seed crystal is wide, and the seed crystal can be a molecular sieve which is not completely crystallized or a molecular sieve which is completely crystallized. 4. From an economic point of view, the loss of the abandoned molecular sieve with crystal defects in the synthesis process is effectively limited.

In addition, the technology for preparing olefin from methanol is developed to date, the yield of diene (ethylene and propylene) reaches 80-83%, and on the basis, if the yield is improved by 0.5%, the economic benefit is very considerable for a ten-thousand-ton device. The SAPO-34 molecular sieve with the multi-stage pore structure prepared by the method is used as the active component of the catalyst in the process of preparing olefin from oxygen-containing compounds, shows good catalytic performance, can improve the yield of diene (ethylene and propylene) by more than 2 percent, can also obviously improve the reaction stability of the catalyst by more than 10 percent, and obtains better technical effect.

Drawings

Fig. 1 is XRD patterns of SAPO-34 molecular sieve A, F, K prepared in example 1, example 6 and comparative example 1. Wherein A and K are SAPO-34 molecular sieves only containing micropores, and F is a multi-stage pore SAPO-34 molecular sieve simultaneously having micropores, mesopores and macropores. As can be seen, molecular sieves A, F, K all have the characteristic diffraction peak of SAPO-34 molecular sieve.

Figure 2 is an SEM photograph of a conventional SAPO-34 molecular sieve containing only micropores prepared [ example 1 ]. As can be seen from the figure, the conventional molecular sieve has a regular cubic shape and a compact and smooth surface.

FIG. 3 is an SEM photograph of a defective crystal prepared in example 2, in which a large number of pores are formed on the surface of the crystal.

FIG. 4 is N of a defective crystal produced [ example 2 ]₂Adsorption-desorption isotherms and pore size distributions. As can be seen from the figure, N₂The adsorption and desorption isotherms have an obvious hysteresis loop in the high-pressure zone.

Fig. 5 is a mercury intrusion pore size distribution of the defect crystals prepared [ example 2 ]. As can be seen from the figure, the pore diameter of the macropores of the molecular sieve is concentrated near 1000 nanometers.

Figure 6 is an SEM photograph of a multi-stage pore SAPO-34 molecular sieve with micropores, mesopores, and macropores prepared [ example 6 ]. As can be seen from the figure, the molecular sieve with the multilevel pore channel structure is cubic, and a large number of holes are formed on the surface.

FIG. 7 is a diagram of N of a hierarchical SAPO-34 molecular sieve with micropores, mesopores, and macropores prepared [ example 6 ]₂Adsorption-desorption isotherms and pore size distributions. As can be seen from the figure, N₂The adsorption and desorption isotherm has an obvious hysteresis loop in a high-pressure region, and the mesoporous aperture is concentrated near 12 nanometers.

FIG. 8 is the mercury intrusion pore size distribution of a multi-stage pore SAPO-34 molecular sieve with micropores, mesopores, and macropores prepared [ example 6 ]. As can be seen from the figure, the macropore aperture of the molecular sieve is concentrated near 500 nm.

Detailed Description

The invention is described in detail below with reference to the drawings, but it is to be noted that the scope of the invention is not limited thereto, but is defined by the appended claims.

All publications, patent applications, patents, and other references mentioned in this specification are herein incorporated by reference in their entirety. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present specification, including definitions, will control.

When the specification concludes with claims with the heading "known to those skilled in the art", "prior art", or the like, to derive materials, methods, or steps, etc., it is intended that the subject matter so derived encompass those conventionally used in the art at the time of filing this application, but also those that are not currently in use, but would become known in the art to be suitable for a similar purpose.

It should be particularly noted that two or more aspects (or embodiments) disclosed in the context of the present specification may be combined with each other at will, and thus form part of the original disclosure of the specification, and also fall within the scope of the present invention.

The invention relates to a preparation method of a molecular sieve with a hierarchical pore structure, which comprises the step of performing hydrothermal crystallization by taking the molecular sieve with crystal defects as a seed crystal.

According to one aspect of the invention, the molecular sieve with crystal defects has a pore structure which contains macropores and/or mesopores besides micropores, wherein the proportion of the specific surface area of the macropores and/or the mesopores in the total specific surface area is not less than 10%, preferably 10-30%; the proportion of the macropore and/or mesopore volume in the total pore volume is not less than 15%, preferably 15-50%. The pore diameter of the micropores is less than 2 nanometers; the pore diameter of the macropores is larger than 50 nanometers, and the macropores are preferably distributed in 100-2000 nanometers; the pore diameter of the mesopores is distributed in the range of 2-50 nm. The molecular sieve with the crystal defects has rough crystal surface appearance and a large number of holes.

According to one aspect of the invention, the molecular sieve having crystal defects may be derived from a molecular sieve that is not fully crystallized during synthesis. The molecular sieve which is not completely crystallized means that the molecular sieve is formed, but the crystal is not completely crystallized. Complete crystallization means that the molecular sieve is crystallized, and the size, the morphology and the relative crystallinity of the molecular sieve crystal cannot be changed even if the crystallization time is prolonged. Compared with the molecular sieve with complete crystallization, the relative crystallinity of the molecular sieve without complete crystallization is 50-75%. Therefore, the molecular sieve with complete crystallization is defined as the molecular sieve with complete crystallization, and the relative crystallinity of the molecular sieve is 50-75%.

According to one aspect of the invention, the molecular sieve having crystal defects may also be derived from a step of modifying a molecular sieve that is completely crystallized by post-treatment. The post-treatment modification comprises the step of contacting the fully crystallized molecular sieve with a modifier. The modifier is at least one selected from the group consisting of ammonia water, oxalic acid, citric acid, sodium carbonate, and tetrapropylammonium hydroxide. The step of contacting the modifier with the crystallization-completed molecular sieve may be performed in a manner well known in the art, such as by contacting an aqueous solution containing the modifier with the crystallization-completed molecular sieve. Generally, the concentration of the modifier in the aqueous solution is 0.05-0.5 mol/l, and the mass ratio of the modifier-containing aqueous solution to the completely crystallized molecular sieve dry basis is (25-70): 1. The contact temperature is 50-90 ℃ and the contact time is 6-24 hours.

According to one aspect of the invention, the crystal-defect molecular sieve that is seeded is selected from the group consisting of crystal-defect SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44, SAPO-47, SAPO-56, metal-containing forms thereof, and mixtures thereof, preferably a crystal-defect SAPO-34 molecular sieve. Correspondingly, the multi-stage pore structure molecular sieve is selected from the group consisting of multi-stage pore structure SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44, SAPO-47, SAPO-56, metal containing forms thereof, and mixtures thereof, preferably a multi-stage pore structure SAPO-34 molecular sieve.

According to one aspect of the invention, the method for synthesizing the molecular sieve with the hierarchical pore channel structure by taking the molecular sieve with the crystal defects as the seed crystal comprises the step of carrying out hydrothermal crystallization on a mixture of the seed crystal, a silicon source, a phosphorus source, an aluminum source, a template and water. The molecular sieve with crystal defects can be the molecular sieve without removing the template agent or the molecular sieve after removing the template agent by roasting; preferably, the defect seeds employed are template-removing. In the mixture, the molar ratio of the aluminum source, the silicon source, the phosphorus source, the template agent and the water is 1 (0.05-2): 0.05-1.5): 1-10): 10-200, preferably 1 (0.1-1.5): 0.2-1.2): 2-8): 30-150; the addition amount of the seed crystal is 1.5-20 wt% of the solid content, and preferably 3-15 wt%. The silicon source is at least one selected from the group consisting of tetraethoxysilane, white carbon black or silica sol, the phosphorus source is at least one selected from the group consisting of phosphoric acid, phosphate or phosphorous acid, and the aluminum source is at least one selected from the group consisting of aluminum isopropoxide, pseudo-boehmite or alumina. The template agent is at least one selected from the group consisting of tetraethylammonium hydroxide, triethylamine, diethylamine or morpholine. The hydrothermal crystallization temperature is 150-250 ℃, preferably 170-210 ℃. The hydrothermal crystallization time is 3 to 50 hours, preferably 10 to 35 hours. The method further comprises the steps of washing, drying and calcining the product of the hydrothermal crystallization, which may be performed in a manner well known in the art.

According to one aspect of the invention, the molecular sieve with the hierarchical pore channel structure simultaneously has micropores, mesopores and macropores; wherein the aperture of the micropores is not more than 1 nanometer, the aperture of the mesopores is distributed in the range of 5-30 nanometers, and the aperture of the macropores is distributed in the range of 200-1500 nanometers; the pore volume of the micro-pores is 0.05-0.30 cm³The pore volume of the contribution of the mesopores is 0.10-0.40 cm³The pore volume of the macro pores is 0.10-0.60 cm³Per gram. The multi-stage pore structure molecular sieve is selected from the group consisting of multi-stage pore structure SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44, SAPO-47, SAPO-56, metal containing forms thereof, and mixtures thereof, preferably a multi-stage pore structure SAPO-34 molecular sieve.

The oxygen-containing compound is selected from methanol, ethanol, n-propanol, isopropanol, C_4-20Alcohol, methyl ethyl ether, dimethyl ether, diethyl ether, diisopropyl ether, formaldehyde, dimethyl carbonate, dimethyl ketone, preferably methanol or dimethyl ether. The olefin comprises ethylene, propylene, or a combination thereof.

The temperature used to convert the oxygenate to light olefins can vary widely depending, at least in part, on the catalyst, the portion of the catalyst mixture in which the catalyst is regenerated, and the reactor configuration and reactor design. Although these methods are not limited by temperature, best results are achieved if the method is controlled to a temperature of 200 to 700 ℃, desirably 250 to 600 ℃, and most desirably 300 to 500 ℃. Lower temperatures generally result in lower reaction rates and the rate of production of the desired light olefin product is significantly slower. However, when the temperature is above 700 ℃, the process also does not produce optimal amounts of light olefin products, and the rate of coke and light saturates formation on the catalyst becomes too fast.

Light olefins will be formed over a wide range of pressures, although not necessarily in optimum amounts, including, but not limited to, pressures of 0.1kPa to 5MPa, desirably pressures of 5kPa to 1MPa, and most desirably pressures of 20kPa to 500 kPa. Pressures outside the above pressure ranges may also be used and are not excluded from the scope of the present invention. Lower and higher pressures can adversely affect selectivity, conversion, coke formation, and/or reaction rate; however, light olefins are still produced and therefore these pressure ranges are considered part of the present invention.

The weight space velocity WHSV for the oxygenate conversion reaction is desirably high enough to maintain the catalyst in a fluidizable state under the reaction conditions and in the reactor's structure and design. Generally, WHSV is in the range of l to 5000hr^-1Preferably 2 to 3000hr^-1More preferably 5 to 1500hr^-1。

During the conversion of oxygenates to olefins, carbonaceous deposits accumulate on the catalyst used to promote the conversion reaction. In some cases, the accumulation of these carbonaceous deposits can result in a decrease in the catalytic ability of the oxygenate feed to light olefin conversion. In this case, the catalyst loses part of its activity. The catalyst is considered to be completely deactivated when the catalyst is no longer capable of converting the oxygenate to olefin product. As an optional step in the oxygenate to olefin reaction, a portion of the catalyst is withdrawn from the reactor and at least a portion of the catalyst withdrawn from the reactor is regenerated in a regeneration unit. By regeneration, it is meant that the carbonaceous deposits are at least partially removed from the catalyst. The regenerated catalyst, which may or may not be cooled, is then returned to the reactor. Desirably, the amount of the portion of the catalyst withdrawn for regeneration is 0.1 to 99% of the amount of the catalyst exiting the reactor. More desirably, the extraction is from 0.2 to 50%, most desirably from 0.5 to 5%.

The catalyst may be regenerated in any process, batch, continuous, semi-continuous, or a combination thereof. Continuous catalyst regeneration is a desirable process. Desirably, the catalyst is regenerated to a level of 0.01 to 15 wt% of the amount of carbon deposit. The regeneration temperature of the catalyst should be 250 to 750 ℃, and is desirably 500 to 700 ℃.

In the method, XRD data is measured by adopting a German Bruker AXS D8 advanced type X-ray diffractometer and is used for representing the crystal structure of the molecular sieve and calculating the relative crystallinity; n is a radical of₂The adsorption-desorption data are measured by an American Mack ASAP-2020 adsorption instrument and are used for measuring the specific surface area, the pore volume, the pore size distribution of mesopores and micropores of the molecular sieve; mercury intrusion data and pore size distribution are measured by a Thermo full-automatic mercury intrusion instrument and are used for representing the macroporous pore size distribution of the molecular sieve; SEM pictures were obtained from a field emission scanning electron microscope, FEI Quanta200F, the netherlands, and used to characterize the morphology of the molecular sieves.

The invention is further illustrated by the following specific examples.

[ example 1 ]

Preparing the SAPO-34 molecular sieve only containing micropores.

With silica sol (30% by weight SiO)₂) Pseudo-boehmite (70 wt% Al)₂O₃) And phosphoric acid (85 wt% H)₃PO₄) Respectively, silicon, aluminum and phosphorus sources, triethylamine NEt₃As a template agent, according to SiO₂：Al₂O₃：P₂O₅：NEt₃：H₂O1.0: 1.0: 0.6: 3: 50, and crystallizing the mixture at 200 ℃ for 48 hours. And after crystallization is finished, cooling, filtering and washing the crystallized product, and drying at 120 ℃ for 6 hours to obtain the conventional SAPO-34 molecular sieve only containing micropores, which is marked as A.

A ofThe XRD spectrum is shown in figure 1, and as can be seen from figure 1, the synthesized molecular sieve has the characteristic diffraction peak of the SAPO-34 molecular sieve, and the 2 theta is 9.5^o、15.9^o、20.5^o、26^oAnd 31^oDiffraction peaks appear indicating that the synthesized product is a clean SAPO-34 molecular sieve with relative crystallinity defined as 100%.

The SEM photograph of A is shown in FIG. 2, the surface is quite smooth, the appearance is regular cube, and the size of the product is 3-5 μm.

The micropore volume of A is 0.28cm³The pore diameter of the micropores is 0.3-0.5 nm.

According to SEM photograph, N₂As a result of physical adsorption, it was confirmed that the conventional microporous molecular sieve was prepared.

[ example 2 ]

SAPO-34 molecular sieve seeds with crystal defects are prepared.

The starting material was taken from conventional SAPO-34 molecular sieve a prepared according to [ example 1 ] containing only micropores.

Weighing 30g of molecular sieve A, placing the molecular sieve A into 0.05M citric acid solution, wherein the dosage of the citric acid solution is 0.9L, stirring the solution for 10 hours at 75 ℃, and filtering, washing and drying the solution to obtain a product B.

The XRD pattern of B is similar to that of A, and the relative crystallinity is 85%.

B, as shown in FIG. 3, the surface of the molecular sieve has obvious pore structure, and the molecular sieve crystal has a large number of defects.

The aperture of the micropores of the B is distributed in the range of 0.3-0.5 nm, no obvious mesoporous aperture is distributed, and the aperture of the macropores is distributed in the range of 800-1200 nm.

The pore volume contributed by the micropores was 0.23cm³The pore volume of the macro-mesopore contribution is 0.20cm³(ii) in terms of/g. Therefore, the proportion of the pore volume of the macro-mesopores to the total pore volume was 47%.

The proportion of the large-mesoporous specific surface area to the total specific surface area was 25%.

According to SEM photograph, N₂The results of physical adsorption and mercury intrusion characterization can prove that the prepared multi-level pore channel junction with crystal defectsForming a molecular sieve.

[ example 3 ]

SAPO-34 molecular sieve seeds with crystal defects are prepared.

The preparation method is the same as example 2, except that the used raw materials are conventional microporous SAPO-34 molecular sieves for industrial production, and a product C is obtained after filtration, washing and drying.

The XRD pattern of C is similar to that of A, and the relative crystallinity is 82%.

The SEM photograph of C is similar to that of FIG. 3, the surface of the molecular sieve has obvious pore structure, and the molecular sieve crystal has a large number of defects.

The aperture of the micropores of the C is distributed in the range of 0.3-0.5 nm, the aperture of the mesopores is distributed in the range of 20nm, and the aperture of the macropores is distributed in the range of 750-1150 nm.

The pore volume contributed by the micropores was 0.25cm³The pore volume of the macro-meso pore contribution is 0.22cm³(ii) in terms of/g. Therefore, the proportion of the pore volume of the macro-mesopores to the total pore volume was 47%.

According to SEM photograph, N₂The results of physical adsorption and mercury intrusion characterization can prove that the prepared molecular sieve with the multilevel pore channel structure has crystal defects.

[ example 4 ]

SAPO-34 molecular sieve seeds with crystal defects are prepared.

The preparation method is the same as example 2, except that the solution is oxalic acid solution, the concentration is 0.03M, the reaction temperature and the reaction time are respectively 80 ℃ and 15 hours, and the product D is obtained after filtration, washing and drying.

The XRD pattern of D is similar to a in fig. 1, with a relative crystallinity of 80%.

D, similar to the SEM picture of FIG. 3, the surface of the molecular sieve has obvious pore structures, and the molecular sieve crystal has a large number of defects.

The aperture of the micropores of D is distributed in the range of 0.3-0.5 nm, no obvious mesoporous aperture is distributed, and the aperture of the macropores is distributed in the range of 750-1150 nm.

The pore volume contributed by the micropores was 0.22cm³The pore volume of the macro-mesopore contribution is 0.18cm³(ii) in terms of/g. Therefore, the proportion of the pore volume of the macro-mesopores to the total pore volume was 45%.

The proportion of the large-mesoporous specific surface area to the total specific surface area was 20%.

[ example 5 ]

SAPO-34 molecular sieve seeds with crystal defects are prepared.

The preparation method is the same as example 2, except that the solution is tetraethylammonium hydroxide solution, the concentration is 0.10M, the reaction temperature and the reaction time are 70 ℃ and 8 hours respectively, and the product E is obtained after filtration, washing and drying.

The XRD pattern of E is similar to a in fig. 1, with a relative crystallinity of 85%.

E, SEM photograph is similar to that of figure 3, the surface of the molecular sieve has obvious pore structure, and the molecular sieve crystal has a large number of defects.

The aperture of the micropores of E is distributed in the range of 0.3-0.5 nm, no obvious mesoporous aperture is distributed, and the aperture of the macropores is distributed in the range of 500-800 nm.

The pore volume contributed by the micropores was 0.28cm³Pore volume of 0.25 cm/g, large-mesopore contribution³(ii) in terms of/g. Therefore, the proportion of the pore volume of the macro-mesopores to the total pore volume was 47%.

[ example 6 ]

Preparation of multi-stage pore canal SAPO-34 molecular sieve simultaneously containing micropores, mesopores and macropores

With silica sol (30% by weight SiO)₂) Pseudo-boehmite (70 wt% Al)₂O₃) And phosphoric acid (85 wt% H)₃PO₄) Respectively, silicon, aluminum and phosphorus sources, triethylamine NEt₃And tetraethylammonium hydroxide TEAOH as a template agent according to SiO₂：Al₂O₃：P₂O₅：NEt₃：TEAOH：H₂O1.0: 1.0: 0.6: 2.0: 1.0: 50, and finally adding the defect crystal B prepared by the method [ example 2 ], wherein the addition amount of the crystal is 10% of the solid content, and after the addition of the crystal, crystallizing the mixture at 200 ℃. And after crystallization is finished, cooling, filtering and washing the crystallized product, drying at 120 ℃ for 6 hours, and roasting at 550 ℃ for 5 hours to obtain the multi-stage pore channel SAPO-34 molecular sieve simultaneously containing micropores, mesopores and macropores, and recording the molecular sieve as F.

The XRD spectrum of F is shown in figure 1, and as can be seen from figure 1, the synthesized molecular sieve has the characteristic diffraction peak of the SAPO-34 molecular sieve, which indicates that the synthesized product is the pure SAPO-34 molecular sieve.

The SEM photograph of F is shown in FIG. 6, the crystals of the molecular sieve are cubic, but the surface of the molecular sieve has a more obvious pore structure.

F, the pore diameter of the micropores is distributed in the range of 0.3-0.5 nm, the pore diameter of the mesopores is distributed in the range of 10-20 nm, and the pore diameter of the macropores is distributed in the range of 300-500 nm; the pore volume contributed by the micropores was 0.21cm³(ii)/g, pore volume contributed by mesopores of 0.13cm³Per g, pore volume contributed by macropores of 0.12cm³/g。

According to SEM photograph, N₂The results of physical adsorption and mercury intrusion characterization are enough to prove that the prepared hierarchical pore channel SAPO-34 molecular sieve simultaneously containing micropores, mesopores and macropores.

[ example 7 ]

As in example 6, except that the defective crystal used was crystal C prepared by the method described in example 3, the template was removed by firing, and the product was designated G.

The XRD pattern of G is similar to F in fig. 1.

The SEM photograph of G is similar to that of FIG. 6, and the surface of the molecular sieve has a more obvious pore structure.

G, the pore diameter of the micropores is distributed in the range of 0.3-0.5 nm, the pore diameter of the mesopores is distributed in the range of 10-20 nm, and the pore diameter of the macropores is distributed in the range of 300-500 nm; the pore volume contributed by the micropores was 0.20cm³(ii)/g, pore volume contributed by mesopores of 0.15cm³Per g, pore volume contributed by macropores of 0.13cm³/g。

[ example 8 ]

As in [ example 6 ], except that the defective crystal used was the crystal D prepared by the method of [ example 4 ], the obtained product was designated as H.

The XRD pattern of H is similar to F in fig. 1.

The SEM photograph of H is similar to that of FIG. 6, and the molecular sieve has a more obvious pore structure on its surface.

The aperture of the H micropores is distributed in the range of 0.3-0.5 nm, the aperture of the mesopores is distributed in the range of 8-18 nm, and the aperture of the macropores is distributed in the range of 200-600 nm; the pore volume contributed by the micropores was 0.21cm³(ii)/g, pore volume contributed by mesopores of 0.12cm³Per g, pore volume contributed by macropores of 0.15cm³/g。

[ example 9 ]

As in [ example 6 ], except that the defective crystal used was the crystal E prepared by the method of [ example 5 ], the obtained product was designated as I.

The XRD pattern of I is similar to F in FIG. 1.

The SEM photograph of I is similar to that of FIG. 6, and the molecular sieve surface has a more obvious pore structure.

I, the pore diameter of the micropores is distributed in the range of 0.3-0.5 nm, the pore diameter of the mesopores is distributed in the range of 15-25 nm, and the pore diameter of the macropores is distributed in the range of 250-600 nm; the pore volume contributed by the micropores was 0.15cm³(ii)/g, pore volume contributed by mesopores of 0.18cm³Per g, pore volume contributed by macropores of 0.12cm³/g。

[ example 10 ]

As in example 6, except that the defect crystals used were incompletely crystallized molecular sieves. The preparation method of the defect crystal comprises the following steps: with silica sol (30% by weight SiO)₂) Pseudo-boehmite (70 wt% Al)₂O₃) And phosphoric acid (85 wt% H)₃PO₄) Respectively, silicon, aluminum and phosphorus sources, triethylamine NEt₃As a template agent, according to SiO₂：Al₂O₃：P₂O₅：NEt₃：H₂O1.0: 1.0: 0.6: 3: 50, and crystallizing the mixture at 200 ℃ for 10 hours. After crystallization is finished, cooling, filtering, washing, drying and roasting the crystallized product to obtain the defect crystal for molecular sieve synthesis, wherein the relative crystallinity of the defect crystal is 60%.

The pore diameter of micropores of the obtained defect crystal is distributed in the range of 0.3-0.5 nm, the pore diameter of mesopores is distributed in the range of 10-35 nm, and the pore diameter of macropores is distributed in the range of 300-800 nm. The pore volume contributed by the micropores was 0.18cm³The pore volume of the macro-mesopore contribution is 0.10cm³(ii) in terms of/g. Therefore, the proportion of the large-mesopore volume to the total pore volume was 36%. The proportion of the large-mesoporous specific surface area to the total specific surface area was 15%.

Synthesis of molecular sieves prepared according to the method of [ example 6 ], the product obtained is J.

The XRD pattern of J is similar to F in fig. 1.

The SEM photograph of J is similar to that of FIG. 6, and the molecular sieve has a more obvious pore structure on its surface.

The aperture of the J micropores is distributed in the range of 0.3-0.5 nm, the aperture of the mesopores is distributed in the range of 15-30 nm, and the aperture of the macropores is distributed in the range of 200-600 nm; the pore volume contributed by the micropores was 0.22cm³(ii)/g, pore volume contributed by mesopores of 0.15cm³Per g, pore volume contributed by macropores of 0.10cm³/g。

[ examples 11 to 15 ]

The SAPO-34 molecular sieve obtained in example 6-10 was tableted to prepare a catalyst for a methanol to olefin reaction. A fixed bed catalytic reaction device is adopted, a reactor is a stainless steel tube, and the used process conditions are considered as follows: the loading of the catalyst is 2.0g, the reaction temperature is 460 ℃, and the weight space velocity is 3h^-1The pressure was 0.1MPa, and the evaluation results are shown in Table 1. It can be seen that when the multi-stage pore channel SAPO-34 molecular sieve containing micropores, mesopores and macropores is used in the MTO reaction, the diene yield can be obviously improved, and the catalyst has better stability.

Comparative example 1

The SAPO-34 molecular sieve A obtained in example 1 was tableted to prepare a catalyst for a methanol to olefin reaction. A fixed bed catalytic reaction device is adopted, a reactor is a stainless steel tube, and the used process conditions are considered as follows: the loading of the catalyst is 2.0g, the reaction temperature is 460 ℃, and the weight space velocity is 3h^-1The pressure was 0.1MPa, and the evaluation results are shown in Table 1.

TABLE 1

Claims

1. A preparation method of a molecular sieve with a hierarchical pore structure comprises the step of performing hydrothermal crystallization by taking a molecular sieve with crystal defects as a seed crystal; wherein the molecular sieve with crystal defects is obtained by modifying a completely crystallized molecular sieve through post-treatment; the post-treatment modification comprises the step of contacting the completely crystallized molecular sieve with a modifier; the modifier is selected from at least one of ammonia water, oxalic acid, citric acid, sodium carbonate and tetraethyl ammonium hydroxide;

the molecular sieve with the crystal defects has a pore structure containing macropores and/or mesopores, and the proportion of the specific surface area of the macropores and/or the mesopores in the total specific surface area is not less than 10%; the proportion of the pore volume of macropores and/or mesopores in the total pore volume is not less than 15%;

the temperature of the hydrothermal crystallization is 150-250 ℃, and the time of the hydrothermal crystallization is 3-50 hours;

the molecular sieve with the hierarchical pore structure simultaneously has micropores, mesopores and macropores; wherein the aperture of the micropores is not more than 1 nanometer, the aperture of the mesopores is distributed in the range of 5-30 nanometers, and the aperture of the macropores is distributed in the range of 200-1500 nanometers; the pore volume of the micro-pores is 0.05-0.30 cm³The pore volume of the contribution of the mesopores is 0.10-0.40 cm³The pore volume of the macro pores is 0.10-0.60 cm³Per gram.

2. The preparation method of the molecular sieve with the hierarchical pore structure according to claim 1, wherein the proportion of the specific surface area of macropores and/or mesopores of the molecular sieve with the crystal defects in the total specific surface area is 10-30%; the proportion of the macropore and/or mesopore volume in the total pore volume is 15-50%.

3. The method for preparing the molecular sieve with the hierarchical pore structure according to claim 1, wherein the molecular sieve with the crystal defects has macropores with a pore size of 100-2000 nm and mesopores with a pore size of 2-50 nm.

4. The method for preparing the molecular sieve with the hierarchical pore structure according to claim 1, wherein the molecular sieve with the crystal defects has a rough surface appearance and a large number of pores.

5. The method of claim 1, wherein the molecular sieve is at least one selected from the group consisting of SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44, SAPO-47, and SAPO-56.

6. The method of claim 5, wherein the molecular sieve is selected from SAPO-34.

7. The method of claim 1, wherein the method comprises the step of hydrothermally crystallizing a mixture of the seed crystal, the silicon source, the phosphorus source, the aluminum source, the template agent and water.

8. The method for preparing the molecular sieve with the hierarchical pore structure as set forth in claim 7, wherein the molar ratio of the aluminum source, the silicon source, the phosphorus source, the template agent and the water in the mixture is 1 (0.05-2): 0.05-1.5): 1-10): 10-200, and the amount of the seed crystal added is 1.5-20 wt% of the solid content.

9. The method for preparing the molecular sieve with the hierarchical pore structure as set forth in claim 8, wherein the molar ratio of the aluminum source, the silicon source, the phosphorus source, the template agent and the water in the mixture is 1 (0.1-1.5): 0.2-1.2): 2-8): 30-150.

10. The method for preparing the molecular sieve with the multilevel pore channel structure according to claim 8, wherein the addition amount of the seed crystal is 3-15 wt% of the solid content.

11. The molecular sieve with a hierarchical pore structure prepared by the preparation method of the molecular sieve with a hierarchical pore structure as claimed in any one of claims 1 to 10.

12. According to claim 11The molecular sieve with the multilevel pore channel structure is characterized in that the molecular sieve with the multilevel pore channel structure simultaneously has micropores, mesopores and macropores; wherein the aperture of the micropores is not more than 1 nanometer, the aperture of the mesopores is distributed in the range of 5-30 nanometers, and the aperture of the macropores is distributed in the range of 200-1500 nanometers; the pore volume of the micro-pores is 0.05-0.30 cm³The pore volume of the contribution of the mesopores is 0.10-0.40 cm³The pore volume of the macro pores is 0.10-0.60 cm³Per gram.

13. The hierarchical porous molecular sieve of claim 12, wherein the hierarchical porous molecular sieve is a hierarchical porous SAPO-34 molecular sieve.

14. The application of the molecular sieve with the multilevel pore structure prepared by the preparation method of the molecular sieve with the multilevel pore structure of any one of claims 1 to 10 in the reaction of preparing olefin from oxygen-containing compounds.