CN112619697A

CN112619697A - Preparation method of composite AEI/CHA molecular sieve and prepared molecular sieve

Info

Publication number: CN112619697A
Application number: CN201910904845.6A
Authority: CN
Inventors: 丁佳佳; 刘红星; 陆贤; 赵昱; 管洪波
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: 2019-09-24
Filing date: 2019-09-24
Publication date: 2021-04-09
Anticipated expiration: 2039-09-24
Also published as: CN112619697B

Abstract

The invention discloses a preparation method of a composite AEI/CHA molecular sieve and the prepared composite AEI/CHA molecular sieve. The method adopts at least two CHA structure molecular sieves with defects as seed crystals, wherein the two CHA structure molecular sieves with defects are respectively a seed crystal I and a seed crystal II; the seed crystal I and the seed crystal II contain micropores, macropores and mesopores; wherein the proportion of the pore volume of the seed crystal I, macropores and mesopores in the total pore volume is 8-14%; the proportion of the pore volume of the seed crystal II, macropores and mesopores in the total pore volume is 15-35%. The composite AEI/CHA molecular sieve prepared by the method is used as a catalyst in a process of preparing low-carbon olefin from an oxygen-containing compound, and shows excellent low-carbon olefin selectivity, particularly higher propylene selectivity and longer service life of the catalyst.

Description

Preparation method of composite AEI/CHA molecular sieve and prepared molecular sieve

Technical Field

The invention relates to a preparation method of a composite AEI/CHA molecular sieve and the prepared molecular sieve.

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. Wherein the crystal structure of the SAPO-34 molecular sieve is a CHA type structure, the basic composition structural units of the SAPO-34 molecular sieve are double six-membered rings and CHA cages, the crystal structure of the SAPO-18 molecular sieve is an AEI structure, and the microporous pore channel structure of the molecular sieve is similar to the CHA structure. Among SAPO series of molecular sieves, SAPO-34 molecular sieve is widely used in modern petroleum processing industry because of its good thermal and hydrothermal stability, moderate acidity, high specific surface area and highly ordered microporous channels. 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 75 percent, and C is₅ ⁺The content of the components is small and almost no aromatic hydrocarbon is generated. The SAPO-18 molecular sieve has weaker surface acidity, and shows excellent catalytic performance and longer catalyst stability in the MTO process. SAPO-18 and SAPO-34 molecular sieves are compounded to form the eutectic SAPO molecular sieve which has the pore canals and the acidity of two crystal phase structures, and the eutectic molecular sieve is often used for catalytic reaction and shows a single ratioThe molecular sieve has better performance, and can effectively solve the problems of low catalytic activity and stability and the like of a single molecular sieve caused by single pore diameter. CN101076401A discloses a silicoaluminophosphate molecular sieve comprising intergrowth of CHA and AEI structures, which is mainly used for determining the ratio of AEI to CHA. CN103878018A discloses a preparation method of a small-crystal-grain SAPO-18/SAPO-34 eutectic molecular sieve, which has better activity selectivity and stability when applied to a reaction for preparing olefin from methanol. CN103833047A discloses an SAPO-5/SAPO-18/SAPO-34 symbiotic composite molecular sieve and a preparation method thereof, and the molecular sieve is applied to a catalyst for preparing low-carbon olefin from an oxygen-containing compound to show good catalytic activity, excellent propylene and butylene selectivity and longer service life.

However, both SAPO-18 and SAPO-34 molecular sieves are microporous, and the eutectic molecular sieve formed by the SAPO-18 and the SAPO-34 molecular sieves is also a microporous molecular sieve. The relatively long and narrow channels of the microporous molecular sieve present serious shape-selective limitation, which on one hand hinders the contact of raw material molecules with active centers inside the channels, and on the other hand limits the diffusion and mass transfer of reactants, intermediate transition products and final products, and the channels are easily blocked due to carbon deposit, so that the catalyst is inactivated, and the exertion of the catalytic performance is limited. 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, the hierarchical pore structure molecular sieve material has two pore channel systems of micropores and mesopores/macropores, so that the diffusion performance of the material can be greatly improved, the catalytic performance of the material is improved, and the material has good catalytic conversion performance in reactions involving macromolecules and reactions needing 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.); then, Danilina, chrysolel and the like take multifunctional long-chain organosilicon as a silicon source to respectively hydrothermally synthesize SAPO-5(Danilina N, Krum) with a hierarchical pore structureeich F, van Bokhoven J. journal of Catalysis,2010,272(1):37-43.) and SAPO-34 molecular sieves (Chenluo, Wangrun Wei, Ding et al. advanced school Chemicals, 2010; 31(9) 1693-; fan and the like can synthesize SAPO-11 molecular sieve with rich mesoporous structure under the conventional hydrothermal condition by adding long-chain organic phosphine as a mesoporous template (Fan Y, Xiao H, Shi G, et al. journal of Catalysis,2012,285(1): 251-259.); 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 addition, aiming at the condition of price change of the chemical raw material market, the MTO catalyst meeting the market situation is developed, so that the MTO catalyst with high ethylene yield is used when the ethylene price is high, and the MTO catalyst with high propylene yield is used when the propylene price is high, and the profit level of enterprises is improved to the maximum extent.

In summary, although the preparation of the hierarchical pore materials is a hot spot of research by many researchers at present, the existing methods for preparing the hierarchical pore SAPO molecular sieves have the disadvantages of complicated operation process, high cost and the like, and the structures of the molecular sieves are damaged while the mesoporous template is removed. In addition, aiming at the market demand of chemical raw materials, the development of the ethylene/propylene adjustable MTO catalyst is also an important method for improving the profit level of enterprise users. Therefore, the preparation cost is reduced, the operation procedure is simplified, and the development of a simple, efficient and controllable novel MTO molecular sieve preparation route has important practical significance.

Disclosure of Invention

The invention provides a preparation method and application of a composite AEI/CHA molecular sieve. The composite AEI/CHA molecular sieve prepared by the method is used as a catalyst in a process of preparing low-carbon olefin from an oxygen-containing compound, and shows excellent low-carbon olefin selectivity, particularly higher propylene selectivity and longer service life of the catalyst.

The invention provides a preparation method of a composite AEI/CHA molecular sieve, wherein at least two CHA structure molecular sieves with defects are adopted as seed crystals, and the two CHA structure molecular sieves with defects are respectively seed crystals I and seed crystals II; the seed crystal I and the seed crystal II contain micropores, macropores and mesopores; wherein the proportion of the pore volume of the seed crystal I, macropores and mesopores in the total pore volume is 8-14%; the proportion of the pore volume of the seed crystal II, macropores and mesopores in the total pore volume is 15-35%.

In the technical scheme, the mesoporous aperture of the seed crystal I is distributed in the range of 2-50 nanometers, and the macroporous aperture is distributed in the range of 50-200 nanometers; the mesoporous aperture of the seed crystal II is distributed in 2-50 nanometers, and the macroporous aperture is distributed in 300-800 nanometers.

In the technical scheme, the mass ratio of the seed crystal I to the seed crystal II is (15-40): (60-85), preferably (20-35): (65-80).

In the technical scheme, the seed crystal I is treated by an organic acidic modifier I at 30-48 ℃ for 3-5 hours.

In the technical scheme, the seed crystal II is treated by an organic acidic modifier II at 70-90 ℃ for 5-8 h to modify the CHA-structure molecular sieve.

In the technical scheme, when the seed crystal I is prepared, the concentration of the organic acid in the organic acid modifier I is 0.01-0.09 mol/L.

In the technical scheme, when the seed crystal I is prepared, the mass ratio of the organic acidic modifier I to the CHA structure molecular sieve dry base is (20-50): 1.

in the technical scheme, when the seed crystal II is prepared, the concentration of the organic acid in the organic acid modifier II is 0.10-0.30 mol/L.

In the technical scheme, when the seed crystal II is prepared, the mass ratio of the organic acidic modifier II to the CHA structure molecular sieve dry base is (20-50): 1.

in the technical scheme, the organic acidic modifier is at least one of oxalic acid and citric acid.

In the above technical scheme, the CHA structure molecular sieve with defects is derived from a step of modifying the CHA structure molecular sieve by post-treatment, and defect crystals with different pore channel structures can be obtained by controlling the treatment conditions. The CHA structured molecular sieve is a microporous CHA structured molecular sieve, and can be prepared by a conventional method or commercially available. The CHA structure molecular sieve can be a completely crystallized dry CHA structure molecular sieve containing a template agent, or a CHA structure molecular sieve obtained by roasting the molecular sieve at high temperature to remove the template agent.

In the technical scheme, the preparation method of the composite AEI/CHA molecular sieve comprises the following steps: and adding the seed crystal into gel prepared from a silicon source, an aluminum source, a phosphorus source, a template agent and water, and then crystallizing under a hydrothermal condition to prepare the composite AEI/CHA molecular sieve.

In the technical scheme, the aluminum source, the silicon source, the phosphorus source and the template agentAnd water with Al₂O₃：SiO₂：P₂O₅：R：H₂The molar ratio of O is 1: (0.05-1.5): (0.05-1.0): (1-8): (10 to 100), preferably 1: (0.2-1.2): (0.1-0.8): (2-6): (30-80); the total adding amount of the seed crystals I and II is 3-60% of the solid content of the gel, preferably 8-50% of the solid content of the gel, and in mass, R is a template agent.

In the above technical scheme, the aluminum source is at least one selected from pseudo-boehmite or alumina, the silicon source is at least one selected from silica white or silica sol, the phosphorus source is at least one selected from phosphoric acid and phosphorous acid, and the template agent is at least two selected from N, N-di-isopropylamine, tetraethyl ammonium hydroxide and triethylamine.

In the above technical solution, the crystallization conditions under the hydrothermal condition are as follows: the temperature is 150-230 ℃, preferably 170-200 ℃, and the time is 10-35 hours, preferably 15-30 hours.

In the above technical scheme, the method for preparing the CHA/AEI composite molecular sieve may further include at least one of the steps of washing, drying, and calcining the crystallized product according to actual needs. The washing, drying and roasting are conventional technical means in the field.

The second aspect of the invention provides a composite AEI/CHA molecular sieve prepared by the method, wherein the mass content ratio of AEI/CHA in the composite AEI/CHA molecular sieve is 95/5-60/40.

In the technical scheme, in the composite AEI/CHA molecular sieve, Al is contained₂O₃：P₂O₅：SiO₂In a molar ratio of 1: (0.2-0.8): (0.1-0.3).

In the technical scheme, the composite AEI/CHA molecular sieve has a micropore, mesopore and macropore structure; the diameter of the micropores is not more than 1 nanometer, preferably 0.3-0.5 nanometer; the diameter of the mesopores is distributed in 8-50 nanometers, preferably 10-30 nanometers; the diameter of the macropores is distributed in the range of 50-800 nm, preferably 80-400 nm.

In the technical scheme, the pore volume contributed by the micropores is 0.10-0.35 cm³A/g, preferably 0.18 to 0.25cm³Per gram; the pore volume contributed by the mesopores and the macropores is 0.05-0.40 cm³A/g, preferably 0.10 to 0.30 cm³Per gram.

In the technical scheme, the composite AEI/CHA molecular sieve is in a cubic crystal shape, and the crystal size is 0.1-2.0 microns.

The third aspect of the invention provides an application of the composite AEI/CHA molecular sieve in the reaction of preparing olefin from oxygen-containing compounds.

In the above technical scheme, the oxygen-containing compound is selected from methanol, ethanol, n-propanol, isopropanol and C_4-20At least one of alcohol, methyl ethyl ether, dimethyl ether, diethyl ether, diisopropyl ether, formaldehyde, dimethyl carbonate and dimethyl ketone, preferably methanol and/or dimethyl ether. The olefin comprises ethylene, propylene, or a combination thereof.

In the technical scheme, when the composite AEI/CHA molecular sieve is adopted in the reaction for preparing olefin from oxygen-containing compound, the reaction temperature is 200-700 ℃, and the weight hourly space velocity is 1-1000 hours^-1The pressure is 0.5 kPa-5 MPa.

The method is based on defect site-oriented synthesis of the composite AEI/CHA molecular sieve in the defect crystal, and has the following advantages:

(1) the novel composite AEI/CHA molecular sieve is prepared by adopting the seed crystal I and the seed crystal II with different defects, and the operation process is simple and easy to implement;

(2) the technology for preparing olefin from methanol is developed to present, the yield of diene (ethylene + propylene) is generally 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 composite AEI/CHA molecular sieve prepared by the method is used as a catalyst active component 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 1 percent, can also obviously improve the reaction stability of the catalyst by more than 10 percent, and obtains better technical effect.

(3) The price of the chemical raw material market is constantly changing, and an MTO catalyst meeting the market situation is developed, so that the MTO catalyst with high ethylene yield is used when the ethylene price is high, and the MTO catalyst with high propylene yield is used when the propylene price is high, and the profit level of an enterprise can be improved to the maximum extent.

Drawings

Fig. 1 is an XRD spectrum and an SEM photograph of a defect crystal prepared [ example 2 ];

fig. 2 is an XRD spectrum and an SEM photograph of the composite type molecular sieve prepared [ example 4 ];

fig. 3 is an XRD spectrum and an SEM photograph of the molecular sieve prepared [ comparative example 1 ];

fig. 4 is an XRD spectrum and an SEM photograph of the composite type molecular sieve prepared [ comparative example 2 ].

Detailed Description

As one embodiment of the present invention, it should be noted that the scope of the present invention is not limited by these specific embodiments, but is defined by the claims.

In the present invention, the pore volume, also referred to as pore volume, means the volume of pores per unit mass of the molecular sieve.

In the present invention, the molecular sieve (referred to as a single crystal) has a crystal morphology of a sponge structure, particularly a primary crystal morphology of a sponge structure, when observed with a Scanning Electron Microscope (SEM). Here, the crystal morphology refers to an external shape that a single molecular sieve crystal exhibits in an observation field of the scanning electron microscope. In addition, the term "native" refers to a structure that the molecular sieve objectively and directly assumes after production, and does not mean a structure that the molecular sieve assumes after production and after artificial treatment.

In the invention, XRD data is measured by adopting an X-ray diffractometer of German Bruker AXS D8Advance type 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 and the pore size distribution of the molecular sieve; the mercury intrusion data and the pore size distribution are measured by a Thermo full-automatic mercury intrusion instrument and are used for representing the pore size of the macropore of the molecular sieveDistributing; 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 technical solution of the present invention is further illustrated by the following specific examples.

[ example 1 ]

CHA molecular sieves containing only micropores are prepared.

With silica sol (30% by weight SiO)₂) Pseudo-boehmite (70 wt% Al)₂O₃) And phosphoric acid (85 wt% H)₃PO₄) Respectively as Si, Al and P sources, triethylamine NEt₃As a template agent, according to SiO₂：Al₂O₃：P₂O₅：NEt₃：H₂O1.0: 1.0: 0.6: 3: 50, aging the mixed gel in a water bath kettle at 15 ℃ for 18 hours, then transferring the gel into a reaction kettle to crystallize at 200 ℃ for 48 hours, and after crystallization is finished, cooling, filtering, washing, drying and roasting the crystallized product to obtain the CHA molecular sieve marked as A.

XRD characterization results show that the synthesized molecular sieve has the characteristic diffraction peak of the CHA molecular sieve, and the synthesized product is the pure CHA molecular sieve; SEM pictures show that the prepared CHA molecular sieve is a cubic crystal with smooth crystal surface.

The micropore volume of A is 0.25cm³The pore diameter of the micropores is distributed in the range of 0.3 to 0.5 nm.

From the above characterization results, it can be demonstrated that the conventional microporous CHA molecular sieve with high crystallinity is prepared.

[ example 2 ]

Preparing the CHA structure molecular sieve with crystal defects, namely the seed crystal I.

The starting material was taken from conventional CHA molecular sieve a containing only micropores, prepared as per [ example 1 ].

Weighing 30g of molecular sieve A, placing the molecular sieve A into 0.05mol/L citric acid solution, wherein the dosage of the citric acid solution is 1L, stirring for 4 hours at 40 ℃, filtering, washing and drying to obtain a product B.

The XRD pattern of B is shown in figure 1, and the molecular sieve has the characteristic diffraction peak of CHA molecular sieve.

B, as shown in FIG. 1, the molecular sieve crystals have a distinct pore structure and a large number of defects.

The pore diameter of the micropores of the B is distributed in the range of 0.3-0.5 nm, the pore diameter of the mesopores is distributed in the range of 15-30 nm, and the pore diameter of the macropores is distributed in the range of 80-150 nm.

The pore volume contributed by the micropores was 0.24cm³The pore volume of the macro-mesopore contribution is 0.03cm³(ii) in terms of/g. Therefore, the proportion of the pore volume of the macro-mesopores to the total pore volume was 11%.

According to the characterization results, the prepared CHA molecular sieve with the hierarchical pore channel structure and the crystal defects can be proved.

[ example 3 ]

Preparing the CHA structure molecular sieve with crystal defects, namely the seed crystal II.

Weighing 30g of molecular sieve A, placing the molecular sieve A into 0.2mol/L citric acid solution, wherein the dosage of the citric acid solution is 0.9L, stirring for 6 hours at 80 ℃, filtering, washing and drying to obtain a product C.

The XRD spectrum of C is similar to that of B, and the molecular sieve has the characteristic diffraction peak of CHA molecular sieve.

The SEM photograph of C is similar to that of B, the crystal of the molecular sieve has obvious pore structure, and the crystal of the molecular sieve has a plurality 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 20-40 nm, and the aperture of the macropores is distributed in the range of 200-500 nm.

The pore volume contributed by the micropores was 0.20cm³The pore volume of the macro-mesopore contribution is 0.08cm³(ii) in terms of/g. Therefore, the proportion of the pore volume of the macro-mesopores to the total pore volume is 29%.

[ example 4 ]

Preparation of composite AEI/CHA molecular sieves

With silica sol (30% by weight SiO)₂) Pseudo-boehmite (70 wt% Al)₂O₃) And phosphoric acid (85 wt% H)₃PO₄) Respectively as silicon source, aluminium source and phosphorus source, N, N-diisopropylethylamine as template agent, according to SiO₂：Al₂O₃：P₂O₅：C₈H₁₉N：H₂O ═ 0.6: 1.0: 0.9: 1.6: 55, and finally adding the seed crystal I and the seed crystal II which are prepared according to the methods of example 2 and example 3, wherein the total addition amount of the seed crystal is 10 percent of the solid content, and the mass ratio of the seed crystal I to the seed crystal II is 25: 75. after addition of seed I and seed II, the mixture was crystallized at 180 ℃ for 24 hours. 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 composite AEI/CHA molecular sieve, which is marked as D.

The XRD spectrum of D is shown in figure 2, and as can be seen from figure 2, the synthesized molecular sieve has the characteristic diffraction peak of the CHA/AEI molecular sieve, which indicates that the synthesized product is a composite molecular sieve, and the XRD quantitative method can be used for knowing that the percentage content of the AEI structure molecular sieve in the composite molecular sieve is 93 percent and the percentage content of the CHA molecular sieve is 7 percent.

D, as shown in FIG. 2, the molecular sieve is cubic, and a large number of holes are visible in the crystal.

D, 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 8-30 nm, and the pore diameter of the macropores is distributed in the range of 80-300 nm; the pore volume contributed by the micropores was 0.20cm³(ii)/g, pore volume contributed by mesopores of 0.08cm³Per g, pore volume contributed by macropores of 0.13cm³/g。

According to XRD pattern, SEM photograph, N₂The results of physical adsorption and mercury intrusion characterization are sufficient to prove that the prepared multi-level pore structure composite type AEI/CHA molecular sieve with the cubic morphology of a spongy structure is prepared, wherein the ratio of AEI/CHA is 93/7.

[ example 5 ]

Preparation of composite AEI/CHA molecular sieves

Similarly [ example 4 ], except that the seed crystal I and the seed crystal II are used to remove the template after calcination, the product is designated as E.

The XRD spectrum of E is similar to that of FIG. 2, and the percentage of AEI molecular sieve in the composite molecular sieve is 91% and the percentage of CHA molecular sieve is 9% by using XRD quantification method. .

E, the SEM photograph is similar to that of FIG. 2, the molecular sieve is cubic, and a large number of holes are visible in the crystal.

E, 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 100-250 nm; the pore volume contributed by the micropores was 0.18cm³(ii)/g, pore volume contributed by mesopores of 0.10cm³Per g, pore volume contributed by macropores of 0.15cm³/g。

According to XRD pattern, SEM photograph, N₂The results of physical adsorption and mercury intrusion characterization are sufficient to prove that the prepared multi-level pore structure composite type AEI/CHA molecular sieve with the cubic morphology of a spongy structure is prepared, wherein the ratio of AEI/CHA is 91/9.

[ example 6 ]

Preparation of composite AEI/CHA molecular sieves

As in example 4, except that the amount of defect crystals added was 20% of the solid content, the resulting product was designated as F.

The XRD spectrum of F is similar to that of FIG. 2, and the percentage of AEI molecular sieve in the composite molecular sieve is 85% and the percentage of CHA molecular sieve is 15% by using XRD quantitative method.

The SEM photograph of F is similar to that of FIG. 2, the molecular sieve is cubic, and a large number of holes are visible in the crystal.

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 20-30 nm, and the pore diameter of the macropores is distributed in the range of 120-300 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 0.13cm³/g。

According to XRD pattern, SEM photograph, N₂The results of physical adsorption and mercury pressure characterization are enough to prove that the prepared multi-level pore structure composite AEI/CH with spongy morphologyMolecular sieve A, wherein the ratio AEI/CHA is 85/15.

[ example 7 ]

Preparation of composite AEI/CHA molecular sieves

As in example 4, except that the amount of defect crystals added was 40% of the solid content, the resulting product was designated G.

The XRD spectrum of G is similar to that of FIG. 2, and it can be seen by the method of XRD quantification that the percentage of AEI molecular sieve in the composite molecular sieve is 68% and the percentage of CHA molecular sieve is 32%.

The SEM photograph of G is similar to that of FIG. 2, the molecular sieve is cubic, and a large number of holes are visible in the crystal.

The aperture of the G micropores is distributed in the range of 0.3-0.5 nm, the aperture of the mesopores is distributed in the range of 10-30 nm, and the aperture of the macropores is distributed in the range of 100-400 nm; the pore volume contributed by the micropores was 0.19cm³(ii)/g, pore volume contributed by mesopores of 0.13cm³Per g, pore volume contributed by macropores of 0.16cm³/g。

According to XRD pattern, SEM photograph, N₂The results of physical adsorption and mercury intrusion characterization are sufficient to demonstrate that the prepared multi-stage pore structure composite type AEI/CHA molecular sieve with sponge-like morphology is prepared, wherein the ratio of AEI/CHA is 68/32.

[ example 8 ]

Preparation of composite AEI/CHA molecular sieves

The same as [ example 4 ], except that the mass ratio of the seed crystal I to the seed crystal II is 32: 68 and the resulting product is designated as H.

The XRD spectrum of H is similar to that of FIG. 2, and the percentage of AEI molecular sieve in the composite molecular sieve is 92% and the percentage of CHA molecular sieve is 8% by using XRD quantitative method.

The SEM photograph of H is similar to that of FIG. 2, the molecular sieve is cubic, and a large number of holes are visible in the crystal.

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 10-23 nm, and the aperture of the macropores is distributed in the range of 100-350 nm; the pore volume contributed by the micropores was 0.21cm³(ii)/g, pore volume contributed by mesopores of 0.06cm³Per g, pore volume contributed by macropores of 0.10cm³/g。

According to XRD patternSpectrum, SEM photograph, N₂The results of physical adsorption and mercury intrusion characterization are sufficient to demonstrate that the prepared multi-stage pore structure composite type AEI/CHA molecular sieve with sponge-like morphology is prepared, wherein the ratio of AEI/CHA is 68/32.

Comparative example 1

As in example 4, except that no seed crystals were added during the synthesis, the resulting product was designated as I.

The XRD spectrum of I is shown in figure 3, which shows that the synthesized molecular sieve has the characteristic diffraction peak of the molecular sieve with AEI structure.

The SEM photograph of I is shown in FIG. 3, and it can be seen that the crystals of the molecular sieve are cubic, the grain size is 1-2 μm, and the surface is smooth.

I the aperture of the micropores is distributed in the range of 0.3-0.5 nm, and the pore volume contributed by the micropores is 0.23cm³And/g, no obvious mesopore and macropore pore size distribution.

According to XRD spectrogram, SEM photograph and N₂The physical adsorption characterization result proves that the prepared molecular sieve is a cubic AEI molecular sieve only containing micropores.

Comparative example 2

The same as [ example 5 ] except that defect free CHA seeds prepared [ example 1 ] were added during the synthesis, the resulting product is denoted J.

The XRD spectrum of J is shown in figure 4, and it can be seen from figure 4 that the synthesized molecular sieve has the characteristic diffraction peak of the AEI/CHA molecular sieve, which indicates that the synthesized product is a composite molecular sieve, and the XRD quantitative method can be used to know that the percentage content of the AEI structure molecular sieve in the composite molecular sieve is 92% and the percentage content of the CHA molecular sieve is 8%.

The SEM photograph of J is shown in FIG. 4, and it can be seen that the crystal of the molecular sieve is cubic, the grain size is 0.5-1 μm, and the surface of the molecular sieve crystal is smooth.

The aperture of the J micropores is distributed in the range of 0.3-0.5 nm, and no meso/macroporous distribution is formed. The pore volume contributed by the micropores was 0.23cm³/g。

According to XRD spectrogram, SEM photograph and N₂The results of the physical adsorption characterization are sufficient to demonstrate that the prepared cubic complexesA combination AEI/CHA molecular sieve.

[ example 9 ]

The molecular sieves obtained in examples 4 to 8 and comparative examples 1 to 2 were tabletted to prepare catalysts for the reaction of producing olefins from methanol. 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. As can be seen from Table 1, when the composite molecular sieve of the invention is used in MTO reaction, diene yield can be obviously improved, and the catalyst has better stability.

TABLE 1

Note: in the present invention, the yield of each product is by mass.

[ example 10 ]

Tabletting the molecular sieve D obtained in example 4, crushing to 40-60 meshes, and evaluating the catalytic performance of MTO by using a fixed bed reactor, wherein the used process conditions are as follows: the loading of the catalyst was 0.3g, and the catalyst was activated by introducing nitrogen at 500 ℃ for 2.0 hours and then cooled to 400 ℃. The methanol is carried by nitrogen, the flow rate of the nitrogen is 15mL/min, and the weight space velocity of the methanol is 2.0h^-1And analyzing the obtained product by gas chromatography, wherein the service life of the catalyst is 900min, the yield of the diene is 89.54%, the yield of ethylene is 54.37%, and the yield of propylene is 35.17%.

Claims

1. A preparation method of a composite AEI/CHA molecular sieve adopts at least two molecular sieves with a defective CHA structure as seed crystals, wherein the two molecular sieves with the defective CHA structure are respectively a seed crystal I and a seed crystal II; the seed crystal I and the seed crystal II contain micropores, macropores and mesopores; wherein the proportion of the pore volume of the seed crystal I, macropores and mesopores in the total pore volume is 8-14%; the proportion of the pore volume of the seed crystal II, macropores and mesopores in the total pore volume is 15-35%.

2. The method of claim 1, wherein: the seed crystal I is treated by an organic acidic modifier I at the temperature of 30-48 ℃ for 3-5 hours; and treating the modified CHA structure molecular sieve for 5-8 h at 70-90 ℃ by adopting an organic acidic modifier II as the seed crystal II.

3. The production method according to claim 1 or 2, characterized in that: when the seed crystal I is prepared, the concentration of organic acid in the organic acid modifier I is 0.01-0.09 mol/L; when the seed crystal II is prepared, the concentration of the organic acid in the organic acid modifier II is 0.10-0.30 mol/L.

4. The production method according to claim 1 or 3, characterized in that: when the seed crystal I is prepared, the mass ratio of the organic acidic modifier I to the CHA structure molecular sieve dry base is (20-50): 1; when the seed crystal II is prepared, the mass ratio of the organic acidic modifier II to the CHA structure molecular sieve dry base is (20-50): 1.

5. the production method according to claim 1 or 4, characterized in that: the organic acidic modifier is at least one of oxalic acid and citric acid.

6. The method of claim 1, wherein: the mass ratio of the seed crystal I to the seed crystal II is (15-40): (60-85), preferably (20-35): (65-80).

7. According to any one of claims 1 to 6; the preparation method is characterized by comprising the following steps: the preparation method of the composite AEI/CHA molecular sieve comprises the following steps: and adding the seed crystal into gel prepared from a silicon source, an aluminum source, a phosphorus source, a template agent and water, and then crystallizing under a hydrothermal condition to prepare the composite AEI/CHA molecular sieve.

8. The method of claim 7, wherein: the aluminum source, the silicon source, the phosphorus source, the template agent and the water are mixed by Al₂O₃：SiO₂：P₂O₅：R：H₂The molar ratio of O is 1: (0.05-1.5): (0.05-1.0): (1-8): (10 to 100), preferably 1: (0.2-1.2): (0.1-0.8): (2-6): (30-80); the total adding amount of the seed crystals I and II is 3-60% of the solid content of the gel, preferably 8-50% of the solid content of the gel, and in mass, R is a template agent.

9. The method of claim 7, wherein: the aluminum source is selected from at least one of pseudo-boehmite or alumina, the silicon source is selected from at least one of white carbon black or silica sol, the phosphorus source is selected from at least one of phosphoric acid and phosphorous acid, and the template agent is selected from at least two of N, N-diisoethylpropylamine, tetraethylammonium hydroxide and triethylamine.

10. The method of claim 7, wherein: the conditions for crystallization under the hydrothermal condition are as follows: the temperature is 150-230 ℃, preferably 170-200 ℃, and the time is 10-35 hours, preferably 15-30 hours.

11. A composite AEI/CHA molecular sieve prepared by the method of any one of claims 1 to 10, wherein the AEI/CHA molecular sieve has an AEI/CHA mass content ratio of 95/5 to 60/40.

12. The molecular sieve of claim 11, characterized in that: the composite AEI/CHA molecular sieve has a micropore, mesopore and macropore structure; the diameter of the micropores is not more than 1 nanometer, preferably 0.3-0.5 nanometer; the diameter of the mesopores is distributed in 8-50 nanometers, preferably 10-30 nanometers; the diameter of the macropores is distributed in the range of 50-800 nanometers, preferably 80-400 nanometers;

the pore volume contributed by the micropores is 0.10-0.35 cm³A/g, preferably 0.18 to 0.25cm³Per gram; the pore volume contributed by the mesopores and the macropores is 0.05-0.40 cm³A/g, preferably 0.10 to 0.30 cm³Per gram.

13. The molecular sieve of claim 11, characterized in that: the composite AEI/CHA molecular sieve is in a cubic crystal shape, and the crystal size is 0.1-2.0 microns.

14. The use of the AEI/CHA composite molecular sieve of any one of claims 11 to 13 in an oxygenate to olefin reaction.