CN114162833B - Thin-layer MCM-22 molecular sieve microsphere with microporous mesoporous structure, preparation and application - Google Patents

Thin-layer MCM-22 molecular sieve microsphere with microporous mesoporous structure, preparation and application Download PDF

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CN114162833B
CN114162833B CN202010954015.7A CN202010954015A CN114162833B CN 114162833 B CN114162833 B CN 114162833B CN 202010954015 A CN202010954015 A CN 202010954015A CN 114162833 B CN114162833 B CN 114162833B
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巩雁军
肖鹏
曹世伟
尚蕴山
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China University of Petroleum Beijing
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Abstract

The invention provides a thin-layer MCM-22 molecular sieve microsphere with a microporous mesoporous structure, and preparation and application thereof. The molecular sieve microsphere has the appearance of desert rose. The method comprises the following steps: preparing a main template agent, a second template agent and water into a solution A; preparing an aluminum source, naOH and water into a solution B; mixing the solution A, the solution B and a silicon source and aging to obtain mixed glue; the molar ratio of each component in the mixed glue meets the following conditions: siO (SiO) 2 /Al 2 O 3 ＝5‑200、OH ‑ /SiO 2 ＝0.005‑1、H 2 O/SiO 2 ＝5‑100、R 1 /SiO 2 ＝0.01‑1、R 2 /SiO 2 =0.005-0.5; and carrying out hydrothermal crystallization on the mixed glue, and then carrying out post-treatment to obtain the MCM-22 molecular sieve microsphere. In the liquid phase alkylation reaction of benzene and ethylene, the molecular sieve prepared by the method provided by the invention has higher benzene conversion rate and ethylene selectivity.

Description

Thin-layer MCM-22 molecular sieve microsphere with microporous mesoporous structure, preparation and application
Technical Field
The invention belongs to the field of chemical industry, and in particular relates to a thin-layer MCM-22 molecular sieve microsphere with a microporous mesoporous structure, and preparation and application thereof.
Background
Ethylbenzene is an important chemical feedstock, and despite the small amount of ethylbenzene present in crude oil, mass production is still dependent on the acid catalyzed reaction of benzene with ethylene. To date, a large number of laboratory and industrial production researches show that the MWW series molecular sieve represented by MCM-22 and the liquid phase benzene-ethylene alkylation process matched with the MWW series molecular sieve have the advantages of high ethylbenzene selectivity, long catalyst stable running time, low reaction temperature and capability of maintaining higher ethylene conversion rate under lower benzene mole ratio (2-5). Therefore, the development of a catalyst with high performance liquid phase alkylation reaction performance has been one of the hot spots of research for several years.
The MCM-22 molecular sieve mainly has three pore canal structures: the surface of the crystal has a bowl-shaped structure of a high-density semi-cage structure, (0.70 multiplied by 0.71 nm), the opening of the structure is a 12-membered ring, and the hole depth is 0.7nm; two-dimensional sinusoidal pore channels (0.4X0.59 nm) consisting of 10-membered rings in the unit cells; the layers are connected through a cage structure (0.71 multiplied by 1.81 nm), and the super-cage is communicated with six surrounding super-cages through a 10-membered ring window. The liquid phase alkylation reaction of styrene is mainly carried out in half-cups on the surface of the MCM-22 molecular sieve, so that more exposed half-cup structures are the most effective method for improving the accessibility of active sites of the molecular sieve. On the other hand, the reduction of the usage amount of the toxic template agent HMI or the substitution of the HMI template can effectively reduce the environmental pollution and accord with the development direction of green chemistry.
The MCM-22 molecular sieves currently in commercial use are typically on the order of microns, with platelets having a thickness of about 100nm, and too thick platelets have reduced outer surfaces, inhibiting accessibility of active sites in the half-cups and super-cages. Therefore, the thickness of the layer of the MCM-22 molecular sieve is thinned to increase the external surface area of the molecular sieve, the grain size is reduced, and the diffusion performance of the molecule is increased by maintaining proper micropore-mesopore structure characteristics in the molecular sieve structure, which are all approaches for effectively improving the accessibility of the active site of the catalyst per unit mass.
Patent CN201010264235 discloses a synthesis method of a small-grain MCM-22 molecular sieve, and although the grain size of the MCM-22 synthesized by the method is reduced to 100-500nm, the thickness of a sheet layer is 20-50nm, and the acid property, the morphology structure and the texture property of the MCM-22 are very little different from those of the traditional micron-sized MCM-22. The size of the molecular sieve is reduced to be extremely easy to wear and loss of nano particles (such as a fluidized bed), and the problems of difficult catalyst regeneration and the like exist.
Patent CN103803577B discloses a synthesis method of a small-grain ultrathin MCM-22 molecular sieve, wherein the thickness grain diameter of a sheet layer is 30-500nm, and the thickness is 2-10nm, but the method needs heavy water, and is difficult to realize large-scale production and application. All of the above reports aim to control the size or thickness of the MCM-22 platelets, but the MCM-22 platelets are not thoroughly dispersed, the platelets are easily bonded together, and Si-O-Si bonds are reformed during firing, which is detrimental to active site exposure. Thus, experimental and theoretical analysis indicate that the method of obtaining more half-cup structures per unit mass needs to meet two requirements, one of which is to control the layer thickness in the c-axis direction (half-cup opening direction) and reduce the stacking of hexagonal sheets. Secondly, stable three-dimensional structures are formed between the sheets through three-dimensional intersection, so that polycondensation between sheets in the roasting process can be avoided, thirdly, proper micropores and mesopore characteristics are maintained, so that the acid property is optimized, the diffusivity is improved, and meanwhile, the structural stability of the molecular sieve is maintained.
Patent CN1789126a discloses a method for synthesizing MCM-22 molecular sieves by using a diamine system, and diamine or a dual-template system synthesized molecular sieve is widely applied to various molecular sieve synthesis cases. The double template method can effectively integrate the functions of two templates, thereby achieving the modulation of the morphology, the particle size and the mesomicrostructure of the molecular sieve. Tempelman et al report a method for synthesizing nanocrystalline MCM-22 using a silicone TPOAC and HMI dual-template system, however, the regulation in these cases is mainly to reduce the crystal grain size of the MCM-22 molecular sieve from micron scale to nanometer scale, and does not involve the change of the layer thickness.
Patent CN102730711a discloses a preparation method of mesoporous MCM-22 molecular sieve, called post-treatment preparation method. The method comprises the steps of mixing an MCM-22 molecular sieve synthesized by a conventional hydrothermal method, adding organic amine and 0.1M NaOH solution, uniformly mixing, loading into a closed reaction kettle, reacting for 1-24 hours at 170 ℃ under autogenous pressure, cooling, filtering, washing, drying and roasting the product to obtain the mesoporous MCM-22 molecular sieve. The invention introduces the intragranular mesoporous into the MCM-22 structure to enable the intragranular ten-membered ring sinusoidal pore canal to be communicated with the inner part of the interlayer super cage, thereby improving the internal diffusion limit. In this case, post-treatment is required, the operation process is complicated, the reaction temperature is high, the time consumption is long, and the additional addition of the template causes resource waste and increases the cost, so that the method for synthesizing the mesoporous MCM-22 molecular sieve needs to be further improved.
Patent US5362697 discloses a synthesis method of a thin-layer MCM-56 molecular sieve first, but the crystal phase of the product is difficult to control, the crystal phase is easy to be converted into MCM-49, and the hydrothermal stability of the single-layer MWW molecular sieve is poor, so that the product is difficult to be applied to actual production.
In summary, a new synthesis system is designed, the usage amount of toxic template agents is reduced when the MCM-22 molecular sieve is prepared, the complex process of post-treatment is avoided, and the efficient green synthesis process is realized; meanwhile, the particle size is controlled or reduced, the thickness of the lamellar and the texture property of the molecular sieve are effectively regulated and controlled, more acid sites are exposed, the good hydrothermal stability and high crystallinity of the molecular sieve are maintained, and the catalytic activity of the molecular sieve is improved.
Disclosure of Invention
An object of the present invention is to provide a thin-layer MCM-22 molecular sieve microsphere having a microporous mesoporous structure; the microsphere is assembled by wafers with uniform layer thickness and wafer size in a certain mode, has a thin layer structure and has the characteristics of large specific surface area and mesoporous structure.
The invention also aims at providing a preparation method of the MCM-22 molecular sieve microsphere; the invention provides a new method for synthesizing MCM-22 microsphere with 'desert rose' morphology in situ by a one-step method double template.
It is a further object of the present invention to provide the use of the MCM-22 molecular sieve microspheres.
Aiming at the catalytic application characteristics of the MCM-22 molecular sieve, the invention aims at improving the synthesis efficiency of the molecular sieve and optimizing the physicochemical properties of the product. Firstly, the thickness of the layers in the c-axis direction (the opening direction of the half cup) of the MCM-22 molecular sieve is controlled, the stacking of hexagonal thin sheets is reduced, and a thin layer structure is controllably formed. And secondly, stable three-dimensional ordered aggregate structures are formed between the sheets through three-dimensional intersection, so that polycondensation among sheets is avoided, and the texture performance is regulated and controlled. Thirdly, the proper grain size of the molecular sieve is controlled, and the characteristics of micropores and mesopores are considered, so that the purposes of optimizing the acid property, improving the diffusivity and simultaneously maintaining the structural stability of the molecular sieve are achieved. Fourthly, the preparation is carried out under a high-concentration system so as to improve the yield of a single kettle and realize high-efficiency synthesis. Fifth, the molecular sieve catalytic process requiring a large external specific surface area in the alkylation reaction, hydrogenation reaction, and the like, is advantageous.
In order to achieve the above purpose, in one aspect, the present invention provides a method for preparing a thin-layer MCM-22 molecular sieve microsphere having a microporous mesoporous structure, wherein the method comprises the following steps:
the liquid preparation step comprises the following steps: preparing a main template agent, a second template agent and water into a solution A; preparing an aluminum source, an alkali source and water into a solution B;
mixing: mixing the solution A, the solution B and a silicon source and aging to obtain mixed glue; wherein the molar ratio of each component in the mixed glue meets the following conditions: siO (SiO) 2 /Al 2 O 3 ＝5-200、OH - /SiO 2 ＝0.005-1、H 2 O/SiO 2 ＝5-100、R 1 /SiO 2 ＝0.01-1、R 2 /SiO 2 =0.005-0.5; wherein R is 1 R is the main template agent 2 Is a second template agent;
and (3) crystallizing: and carrying out hydrothermal crystallization on the mixed glue, and then carrying out post-treatment to obtain the MCM-22 molecular sieve microsphere.
According to some embodiments of the invention, the master template is hexamethyleneimine.
According to some embodiments of the invention, the second templating agent is a double-headed quaternary ammonium salt or base.
According to some embodiments of the invention, wherein the double-headed quaternary ammonium salt has the formula X (H 2n+1 C n )(CH 3 ) 2 N + (CH 2 ) 6 N + (CH 3 ) 2 (C m H 2m+1 ) X, where n is an integer from 4 to 22, m is an integer from 4 to 12, and x= Cl, br, I, OH.
According to some embodiments of the invention, wherein the double-headed quaternary ammonium salt may have the formula Cl (H) 9 C 4 )(CH 3 ) 2 N + (CH 2 ) 6 N + (CH 3 ) 2 (C 4 H 9 ) Cl (abbreviated as Cl-C) 4-6-4 Where n=4, m=4, x=cl); cl (H) 37 C 18 )(CH 3 ) 2 N + (CH 2 ) 6 N + (CH 3 ) 2 (C 6 H 13 ) Cl (abbreviated as Cl-C) 18-6-6 Where n=18, m=6, x=cl); other double-headed quaternary ammonium salts are abbreviated as X-C in sequence 5-6-5 ，X-C 6-6-6 ，X-C 7-6-7 ，X-C 8-6-8 ，X-C 12-6-12 In the form of (a).
According to some embodiments of the invention, wherein the aluminum source is selected from the group consisting of sodium aluminate, aluminum nitrate, aluminum chloride, aluminum sulfate, aluminum oxide, aluminum hydroxide, and aluminum oxide monohydrate.
It will be appreciated that the scope of the invention also includes equivalent alternatives to the above-described solutions, for example, boehmite and pseudo-boehmite may be substituted for alumina monohydrate.
According to some embodiments of the invention, the alkali source is selected from one or more of sodium hydroxide, lithium hydroxide and potassium hydroxide.
According to some embodiments of the invention, the silicon source is selected from the group consisting of white carbon black, silica sol, coarse pore silica gel, sodium silicate, silica gel, silicic acid, tetraethyl orthosilicate, and water glass.
According to some embodiments of the invention, the molar ratio of the components in the mixed gel in the mixing step satisfies the following conditions: siO (SiO) 2 /Al 2 O 3 ＝15-100、OH - /SiO 2 ＝0.1-0.4、H 2 O/SiO 2 ＝15-50、R 1 /SiO 2 ＝0.05-0.4、R 2 /SiO 2 ＝0.005-0.2。
According to some embodiments of the invention, wherein R in the mixing step 1 And R is 2 The molar ratio of (2) to (20).
According to the present inventionSome embodiments of the invention, wherein R in the mixing step 1 And R is 2 The molar ratio of (2) is 5-20.
According to some embodiments of the invention, wherein the aging temperature is 20-100 ℃.
According to some embodiments of the invention, the aging temperature is 40-80 ℃.
According to some embodiments of the invention, the aging time is 2-12 hours.
According to some embodiments of the invention, the aging time is 2-10 hours.
According to some embodiments of the invention, the crystallization temperature is 120-180 ℃.
According to some embodiments of the invention, the crystallization temperature is 130-160 ℃.
According to some embodiments of the invention, the crystallization time is 3-15d.
According to some embodiments of the invention, the crystallization time is 4-10d.
According to some embodiments of the invention, the crystallizing step comprises placing the mixed gum in a container and performing hydrothermal crystallization under conditions that the container rotates at a speed of 10-120 r/min.
According to some embodiments of the invention, the crystallizing step comprises placing the mixed gum in a container and performing hydrothermal crystallization under conditions that the container rotates at a speed of 30-60 r/min.
According to some embodiments of the invention, the crystallization step comprises transferring the mixed glue into a crystallization kettle, placing the mixed glue into a rotary oven, setting the rotation speed to be 10-120r/min, and performing hydrothermal crystallization at 120-180 ℃.
According to some embodiments of the invention, the container is rotatable about a horizontal axis.
According to some embodiments of the invention, the post-treatment of the crystallization step comprises washing, separating and drying the product obtained after the hydrothermal crystallization to obtain the MCM-22 molecular sieve microspheres.
It will be appreciated that any combination of the above embodiments is possible without conflict.
On the other hand, the invention also provides the thin-layer MCM-22 molecular sieve microsphere with the microporous mesoporous structure, which is prepared by the method.
According to some embodiments of the invention, the MCM-22 molecular sieve microspheres have a microsphere diameter of 1-2 μm.
According to some embodiments of the invention, wherein the MCM-22 molecular sieve microspheres have a micropore volume of 0.10 to 0.18cm 3 ·g -1 Mesoporous volume of 0.45-0.77cm 3 ·g -1 。
According to some embodiments of the invention, the MCM-22 molecular sieve microspheres are aggregates of a "desert rose" morphology.
According to some embodiments of the invention, the MCM-22 molecular sieve microspheres are formed from a stack of uniformly ordered, inter-interlaced platelets.
According to some embodiments of the invention, the sheets are assembled in a spiral fashion.
According to some embodiments of the invention, the thickness of the sheet is 5nm to 55nm.
According to some embodiments of the invention, the sheet is formed by orderly stacking 2-22 hexagonal sheets. According to some embodiments of the invention, wherein the thickness of the individual flakes is 2.5nm.
According to some embodiments of the invention, the individual lamellae have a side length of 100-200nm.
The lamellar thickness of the MCM-22 molecular sieve microsphere is related to the hydrophobic chains of the double-headed quaternary ammonium salt, long hydrophobic chains result in thicker lamellar, and short hydrophobic chains result in thinner lamellar.
The thickness of the molecular sieve slice layer of the invention is reasonably modulated (5-50 nm).
The size of the molecular sieve flaky crystal is 100-200nm, three-dimensional uniform microsphere particles are formed between the flaky layers through cross assembly, the particle size is 1-2 mu m, and slit mesoporous characteristics such as dislocation and the like are formed between the flaky layers.
Thus, the invention provides that the MCM-22 molecular sieve is a lamellar spheroidal aggregate structural morphology with intra-crystalline micropores-mesopores.
In yet another aspect, the invention also provides the use of the MCM-22 molecular sieve microspheres in catalytic alkylation reactions, cracking reactions, disproportionation reactions, isomerization reactions, and epoxidation reactions.
In still another aspect, the present invention provides a method for liquid phase alkylation of styrene, wherein the method comprises reacting benzene and ethylene as raw materials with the MCM-22 molecular sieve microspheres of the present invention as a catalyst to produce ethylbenzene.
According to some embodiments of the invention, wherein the reaction conditions include: the molar ratio of benzene to ethylene is 2-6, the reaction temperature is 150-300 ℃, and the ethylene airspeed is 0.5-5h -1 The pressure is 3-4MPa.
In summary, the invention provides a thin-layer MCM-22 molecular sieve microsphere with a microporous mesoporous structure, and preparation and application thereof. The molecular sieve microsphere has the following advantages:
the MCM-22 molecular sieve of the invention has regular microsphere morphology, which comprises crystals with adjustable lamellar thickness (5-50 nm), and the lamellar layers are formed by cross assembly.
The molecular sieve has mesoporous structure characteristic and thin crystal structure characteristic, and has uniform particle size of 1-2 mu m.
The novel morphological characteristics of the MCM-22 molecular sieve prepared by the invention greatly enrich mesoporous characteristics, the mesoporous volume is improved by nearly one time compared with that of the MCM-22 molecular sieve synthesized by a single template, the total pore volume is improved by about 60%, the external specific surface area is increased by more than one time, more interlayer half cups are exposed, and meanwhile, the micropore structure is maintained, namely, the original micropores are rarely reduced (still within 0.10-0.18 cm) 3 /g). This is advantageous in that the molecular sieve improves its reactivity (high activity, high selectivity) and high stability.
The MCM-22 molecular sieve synthesized by the invention has simple synthesis method, and avoids the complicated process of post-treatment; the addition of the second template reduces the usage amount of toxic HMI template agent, saves cost, optimizes the synthesis system and the preparation process, and simultaneously, the molecular sieve can be synthesized under a high-concentration system, and has higher yield.
In the liquid phase alkylation reaction of benzene and ethylene, compared with the traditional MCM-22 molecular sieve, the molecular sieve prepared by the method provided by the invention has higher benzene conversion rate and ethylene selectivity.
The MCM-22 molecular sieve prepared by the method has good quality and wide application prospect. Of course, the molecular sieve can also realize alkylation reaction of other aromatic hydrocarbon with corresponding alcohol and olefin, and has potential application in catalytic reaction processes of catalytic cracking, disproportionation, isomerization, epoxidation and the like.
Drawings
FIG. 1 shows XRD patterns of the products of examples 1 to 10 (b-k) and comparative example 1 (a) according to the present invention. It can be seen that the addition of the second template agent does not affect the structure of the MCM-22 molecular sieve, and is a pure phase MCM-22 molecular sieve.
FIG. 2 is an SEM image of examples 1-10 (b-k) wherein a is an SEM image of comparative example 1; as can be seen from the figure, the sample synthesized by the single template system of comparative example 1 is a conventional irregular stack of sheets with a certain amount of dispersed hexagonal flakes present; adding a second template agent, wherein the morphology of the molecular sieve is changed into microsphere particles which are stacked in a staggered way, and the particle size is 1-2 mu m; examples 1,2,5,6,8 and 10 used shorter hydrophobic chains (n.ltoreq.7) and yielded thinner sheets of microsphere particles; examples 3,4,7 and 9 used longer hydrophobic chains (n.gtoreq.8) and resulted in thicker sheets of microsphere particles.
FIG. 3 is a TEM image of comparative example 1 and examples 1-10; as can be seen from the figure, the thickness of the single sheet in comparative example 1 was around 50 nm; examples 1,2,5,6,8 and 10 (b, c, f, g, i, k) have a c-axis thickness of 5 to 20nm; in examples 3,4,7 and 9 (d, e, h, j), the thickness of the individual sheets was about 20-55nm.
FIG. 4 shows a second template Br-C 6-6-6 And Cl-C 18-6-6 Is a NMR chart of (2).
Detailed Description
The following detailed description of the invention and the advantages achieved by the embodiments are intended to help the reader to better understand the nature and features of the invention, and are not intended to limit the scope of the invention.
And (3) synthesizing a second template agent:
Cl-C 18-6-6 is synthesized by the following steps:
(1) Adding chlorooctadecane into a mixed solution of acetonitrile and toluene of tetramethyl hexamethylenediamine (wherein the molar ratio of the chlorooctadecane to the tetramethyl hexamethylenediamine is 1:1) to react for 12 hours at 50 ℃, and then drying for 24 hours in a fume hood to obtain (H) 37 C 18 )(CH 3 ) 2 N + (CH 2 ) 6 N + (CH 3 ) 2 Cl。
(2) Then (H) 37 C 18 )(CH 3 ) 2 N + (CH 2 ) 6 N + (CH 3 ) 2 Cl was reacted with chloro-n-hexane at 90℃for 8 hours (wherein (H) 37 C 18 )(CH 3 ) 2 N + (CH 2 ) 6 N + (CH 3 ) 2 The molar ratio of Cl to chloro-n-hexane is 1: 1) Then, the mixture was recrystallized from acetone, and the resultant was dried in a fume hood for 48 hours to obtain Cl (H) 37 C 18 )(CH 3 ) 2 N + (CH 2 ) 6 N + (CH 3 ) 2 (C 6 H 12 ) Cl, abbreviated as Cl-C 18-6-6 . (NMR figure see FIG. 4)
For the synthesis of other templates, e.g. Br-C 6-6-6 (NMR figure see FIG. 4) Synthesis procedure with Cl-C 18-6-6 Similarly, only the chlorooctadecane in step (1) was replaced with bromo-n-hexane and the chloro-n-hexane in step (2) was replaced with bromo-n-hexane.
Example 1
Adding main template HMI (R) into 20g deionized water 1 ) And a second template Cl-C 4-6-4 (R 2 ) Preparing solution A; naAlO of 2 Dissolving NaOH in 40g deionized water, and mixingAnd (5) placing the mixture into a solution B. Slowly adding the solution A into the solution B, stirring, adding silica sol, and aging at 60 ℃ for 5 hours to obtain mixed glue, wherein the mole ratio of the mixed glue is as follows: siO (SiO) 2 /Al 2 O 3 ＝30、OH - /SiO 2 ＝0.2、H 2 O/SiO 2 ＝30、R 1 /SiO 2 ＝0.2、R 2 /SiO 2 =0.02. The mixed glue is moved into a crystallization kettle, placed into a rotary oven, set at a rotation speed of 60r/min, and subjected to hydrothermal crystallization at 150 ℃ for 7d. And then washing, separating and drying to obtain the MCM-22 microsphere molecular sieve. The XRD pattern of the synthesized catalyst is shown as b in figure 1, and is a pure phase MCM-22 molecular sieve. SEM image, as shown in FIG. 2 b, shows the particle size of the MCM-22 microsphere was 2. Mu.m. In the TEM image, as shown in b of FIG. 3, the thickness of the sheet in the c-axis direction is 5-10nm. The texture properties are shown in Table 2, and the external specific surface area is 143m 2 ·g -1 The total control pore volume is 0.76cm 3 ·g -1 Mesoporous volume of 0.65cm 3 ·g -1 The micropore volume is 0.14cm 3 ·g -1 . The reaction data are shown in Table 1.
Example 2
Adding main template HMI (R) into 20g deionized water 1 ) And a second templating agent Br-C 6-6-6 (R 2 ) Preparing solution A; naAlO of 2 KOH, in 34g deionized water to prepare solution B. Dropwise adding the solution A into the solution B, stirring, adding coarse pore silica gel, and aging for 5 hours at 60 ℃ to obtain mixed gel, wherein the molar ratio of the mixed gel is as follows: siO (SiO) 2 /Al 2 O 3 ＝35、OH - /SiO 2 ＝0.15、H 2 O/SiO 2 ＝27、R 1 /SiO 2 ＝0.2、R 2 /SiO 2 =0.015. The mixed glue is moved into a crystallization kettle, placed into a rotary oven, set at a rotation speed of 60r/min, and subjected to hydrothermal crystallization at 150 ℃ for 7d. And then washing, separating and drying to obtain the MCM-22 microsphere molecular sieve. The XRD pattern of the synthesized catalyst is shown as c in figure 1, and is a pure phase MCM-22 molecular sieve. SEM image, as shown in FIG. 2c, shows the particle size of the MCM-22 microsphere was 2. Mu.m. In the TEM image, as shown in c of FIG. 3, the thickness of the sheet in the c-axis direction is 5-20nm. The texture properties are shown in Table 2, and the external specific surface area is 212m 2 ·g -1 The total pore volume is 0.92cm 3 ·g -1 Mesoporous volume of 0.77cm 3 ·g -1 The micropore volume is 0.15cm 3 ·g -1 . The reaction data are shown in Table 1.
Example 3
Adding main template HMI (R) into 20g deionized water 1 ) And a second templating agent HO-C 8-6-8 (R 2 ) Preparing solution A; aluminum nitrate, naOH and 30g deionized water were dissolved to prepare a solution B. Dropwise adding the solution A into the solution B, stirring, adding silica gel, and aging for 5 hours at 60 ℃ to obtain mixed gel, wherein the molar ratio of the mixed gel is as follows: siO (SiO) 2 /Al 2 O 3 ＝30、OH - /SiO 2 ＝0.25、H 2 O/SiO 2 ＝25、R 1 /SiO 2 ＝0.2、R 2 /SiO 2 =0.02. The mixed glue is moved into a crystallization kettle, placed into a rotary oven, set at a rotation speed of 60r/min, and subjected to hydrothermal crystallization at 150 ℃ for 7d. And then washing, separating and drying to obtain the three-dimensional MCM-22 microsphere molecular sieve. The XRD pattern of the synthesized catalyst is shown as d in figure 1, and is a pure phase MCM-22 molecular sieve. SEM image, as shown in FIG. 2 d, shows the particle size of the MCM-22 microsphere was 2. Mu.m. The TEM image shows that the thickness of the c-axis layer is 20-40nm as shown in d of FIG. 3. The texture properties are shown in Table 2, and the external specific surface area is 159m 2 ·g -1 The total pore volume is 0.65cm 3 ·g -1 Mesoporous volume of 0.51cm 3 ·g -1 The micropore volume is 0.15cm 3 ·g -1 . The reaction data are shown in Table 1.
Example 4
Adding main template HMI (R) into 20g deionized water 1 ) And a second template Cl-C 18-6-6 (R 2 ) Preparing solution A; alumina monohydrate, naOH, and dissolved in 20g deionized water were prepared as solution B. Dropwise adding the solution A into the solution B, stirring, adding sodium silicate, and aging for 5 hours at 60 ℃ to obtain mixed glue, wherein the molar ratio of the mixed glue is as follows: siO (SiO) 2 /Al 2 O 3 ＝25、OH - /SiO 2 ＝0.25、H 2 O/SiO 2 ＝20、R 1 /SiO 2 ＝0.2、R 2 /SiO 2 =0.02. The mixed glue is moved into a crystallization kettle, placed into a rotary oven, set at a rotation speed of 60r/min, and subjected to hydrothermal crystallization at 150 ℃ for 7d. And then washing, separating and drying to obtain the MCM-22 microsphere molecular sieve. The XRD pattern of the synthesized catalyst is shown as e in figure 1, and is a pure phase MCM-22 molecular sieve. SEM pictures, as shown in FIG. 2 e, showed that the MCM-22 microsphere had a particle size of 2. Mu.m. As shown in e of FIG. 3, the thickness of the sheet in the c-axis direction was 20-55nm in TEM image. The texture properties are shown in Table 2, and the external specific surface area is 117m 2 ·g -1 The total pore volume is 0.61cm 3 ·g -1 Mesoporous volume of 0.45cm 3 ·g -1 The micropore volume is 0.16cm 3 ·g -1 . The reaction data are shown in Table 1.
Example 5
Adding main template HMI (R) into 20g deionized water 1 ) And a second template Cl-C 6-6-6 (R 2 ) Preparing solution A; aluminum chloride, naOH and 30g deionized water were dissolved to prepare a solution B. Dropwise adding the solution A into the solution B, stirring, adding coarse pore silica gel, and aging for 5 hours at 60 ℃ to obtain mixed gel, wherein the molar ratio of the mixed gel is as follows: siO (SiO) 2 /Al 2 O 3 ＝30、OH - /SiO 2 ＝0.25、H 2 O/SiO 2 ＝25、R 1 /SiO 2 ＝0.2、R 2 /SiO 2 =0.05. The mixed glue is moved into a crystallization kettle, placed into a rotary oven, set at a rotation speed of 60r/min, and subjected to hydrothermal crystallization at 150 ℃ for 8 days. And then washing, separating and drying to obtain the MCM-22 microsphere molecular sieve. The XRD pattern of the synthesized catalyst is shown as f in figure 1, and is a pure phase MCM-22 molecular sieve. SEM image, as shown in FIG. 2 f, shows the particle size of the MCM-22 microsphere was 2. Mu.m. In the TEM image, as shown in f of FIG. 3, the thickness of the sheet in the c-axis direction is 5-10nm. The texture properties are shown in Table 2, and the external specific surface area is 161m 2 ·g -1 The total pore volume is 0.68cm 3 ·g -1 Mesoporous volume of 0.56cm 3 ·g -1 The micropore volume is 0.12cm 3 ·g -1 . The reaction data are shown in Table 1.
Example 6
Adding the master mold to 20g deionized waterPlate agent HMI (R) 1 ) And a second templating agent HO-C 7-6-7 (R 2 ) Preparing solution A; naAlO of 2 LiOH was dissolved in 10g deionized water to prepare solution B. Dropwise adding the solution A into the solution B, stirring, adding white carbon black, and aging for 4 hours at 80 ℃ to obtain mixed glue, wherein the molar ratio of the mixed glue is as follows: siO (SiO) 2 /Al 2 O 3 ＝25、OH - /SiO 2 ＝0.15、H 2 O/SiO 2 ＝15、R 1 /SiO 2 ＝0.2、R 2 /SiO 2 =0.1. The mixed glue is moved into a crystallization kettle, placed into a rotary oven, set at a rotation speed of 60r/min, and subjected to hydrothermal crystallization at 150 ℃ for 7d. And then washing, separating and drying to obtain the MCM-22 microsphere molecular sieve. The XRD pattern of the synthesized catalyst is shown as g in figure 1, and is a pure phase MCM-22 molecular sieve. SEM pictures, as shown in FIG. 2 g, showed that MCM-22 microsphere had a particle size of 2. Mu.m. TEM image, as shown in g of FIG. 3, the thickness of the sheet in the c-axis direction is 7.5-10nm. The texture properties are shown in Table 2, and the external specific surface area is 163m 2 ·g -1 The total pore volume is 0.67cm 3 ·g -1 Mesoporous volume of 0.53cm 3 ·g -1 The micropore volume is 0.13cm 3 ·g -1 . The reaction data are shown in Table 1.
Example 7
Adding main template HMI (R) into 20g deionized water 1 ) And a second templating agent HO-C 12-6-12 (R 2 ) Preparing solution A; aluminum sulfate, naOH and 30g deionized water were dissolved to prepare a solution B. Dropwise adding the solution A into the solution B, stirring, adding white carbon black, and aging for 5 hours at 70 ℃ to obtain mixed glue, wherein the molar ratio of the mixed glue is as follows: siO (SiO) 2 /Al 2 O 3 ＝25、OH - /SiO 2 ＝0.20、H 2 O/SiO 2 ＝25、R 1 /SiO 2 ＝0.2、R 2 /SiO 2 =0.02. The mixed glue is moved into a crystallization kettle, placed into a rotary oven, set at a rotation speed of 50r/min, and subjected to hydrothermal crystallization at 150 ℃ for 8 days. And then washing, separating and drying to obtain the MCM-22 microsphere molecular sieve. The XRD pattern of the synthesized catalyst is shown as h in figure 1, and is a pure phase MCM-22 molecular sieve. SEM image, as shown in FIG. 2h, of particle size of MCM-22 microsphereThe dimensions were 2. Mu.m. TEM image shows that the thickness of the c-axis layer is 20-50nm as shown in h of FIG. 3. The texture properties are shown in Table 2, and the external specific surface area is 136m 2 ·g -1 The total pore volume is 0.58cm 3 ·g -1 Mesoporous volume of 0.41cm 3 ·g -1 The micropore volume is 0.17cm 3 ·g -1 . The reaction data are shown in Table 1.
Example 8
Adding main template HMI (R) into 20g deionized water 1 ) And a second template Cl-C 6-6-6 (R 2 ) Preparing solution A; alumina, naOH, and 40g deionized water were dissolved to prepare solution B. Dropwise adding the solution A into the solution B, stirring, adding water glass, and aging for 5 hours at 60 ℃ to obtain mixed glue, wherein the molar ratio of the mixed glue is as follows: siO (SiO) 2 /Al 2 O 3 ＝20、OH - /SiO 2 ＝0.2、H 2 O/SiO 2 ＝30、R 1 /SiO 2 ＝0.15、R 2 /SiO 2 =0.005. The mixed glue is moved into a crystallization kettle, placed into a rotary oven, set at a rotation speed of 30r/min, and subjected to hydrothermal crystallization at 150 ℃ for 7d. And then washing, separating and drying to obtain the MCM-22 microsphere molecular sieve. The XRD pattern of the synthesized catalyst is shown as i in figure 1 and is a pure phase MCM-22 molecular sieve. SEM pictures, as shown in FIG. 2 i, showed that the MCM-22 microsphere had a particle size of 2. Mu.m. In the TEM image, as shown in i of FIG. 3, the thickness of the sheet in the c-axis direction is 5-10nm. The texture properties are shown in Table 2, and the external specific surface area is 133m 2 ·g -1 The total pore volume is 0.59cm 3 ·g -1 Mesoporous volume of 0.42cm 3 ·g -1 The micropore volume is 0.16cm 3 ·g -1 . The reaction data are shown in Table 1.
Example 9
Adding main template HMI (R) into 20g deionized water 1 ) And a second template Cl-C 18-6-6 (R 2 ) Preparing solution A; aluminum hydroxide, naOH and 40g of deionized water were dissolved to prepare a solution B. Dropwise adding the solution A into the solution B, stirring, adding tetraethoxysilane, and aging for 5 hours at 60 ℃ to obtain mixed glue, wherein the molar ratio of the mixed glue is as follows: siO (SiO) 2 /Al 2 O 3 ＝30、OH - /SiO 2 ＝0.25、H 2 O/SiO 2 ＝30、R 1 /SiO 2 ＝0.3、R 2 /SiO 2 =0.02. The mixed glue is moved into a crystallization kettle, placed into a rotary oven, set to a rotation speed of 60r/min, and subjected to hydrothermal crystallization at 130 ℃ for 9d. And then washing, separating and drying to obtain the MCM-22 microsphere molecular sieve. The XRD pattern of the synthesized catalyst is shown as j in figure 1 and is a pure phase MCM-22 molecular sieve. SEM image, as shown in FIG. 2, j, shows that the MCM-22 microsphere has a particle size of 2. Mu.m. In the TEM image, as shown in j of FIG. 3, the thickness of the sheet in the c-axis direction is 20 to 50nm. The texture properties are shown in Table 2, and the external specific surface area is 146m 2 ·g -1 The total pore volume is 0.79cm 3 ·g -1 Mesoporous volume of 0.61cm 3 ·g -1 The micropore volume is 0.18cm 3 ·g -1 . The reaction data are shown in Table 1.
Example 10
Adding main template HMI (R) into 20g deionized water 1 ) And a second template Cl-C 6-6-6 (R 2 ) Preparing solution A; naAlO of 2 KOH, dissolved in 20g deionized water to prepare solution B. Dropwise adding the solution A into the solution B, stirring, adding white carbon black, and aging for 5 hours at 60 ℃ to obtain mixed rubber, wherein the molar ratio of the mixed rubber is as follows: siO (SiO) 2 /Al 2 O 3 ＝30、OH - /SiO 2 ＝0.3、H 2 O/SiO 2 ＝20、R 1 /SiO 2 ＝0.1、R 2 /SiO 2 =0.03. The mixed glue is moved into a crystallization kettle, placed into a rotary oven, set to a rotation speed of 60r/min, and subjected to hydrothermal crystallization at 140 ℃ for 7d. And then washing, separating and drying to obtain the MCM-22 microsphere molecular sieve. The XRD pattern of the synthesized catalyst is shown as k in figure 1 and is a pure phase MCM-22 molecular sieve. SEM image, as shown in FIG. 2, k, shows the particle size of the MCM-22 microsphere was 2. Mu.m. In the TEM image, as shown in k of FIG. 3, the thickness of the sheet in the c-axis direction is 5-15nm. The texture properties are shown in Table 2, and the external specific surface area is 166m 2 ·g -1 The total pore volume is 0.66cm 3 ·g -1 Mesoporous volume of 0.56cm 3 ·g -1 The micropore volume is 0.10cm 3 ·g -1 . Number of reactionsAs shown in table 1.
Comparative example 1
For comparison. According to the traditional MCM-22 synthesis method, a single template is used for synthesizing the MCM-22 molecular sieve. The synthesis steps are as follows: into 20g deionized water, main template agent HMI (R) 1 ) Preparing solution A; naAlO of 2 NaOH was dissolved in 40g of deionized water to prepare solution B. Dropwise adding the solution A into the solution B, stirring, adding silica sol, and aging for 5 hours at 60 ℃ to obtain mixed glue, wherein the molar ratio of the mixed glue is as follows: siO (SiO) 2 /Al 2 O 3 ＝30、OH - /SiO 2 ＝0.2、H 2 O/SiO 2 ＝30、R 1 /SiO 2 =0.4. The mixed glue is moved into a crystallization kettle, placed into a rotary oven, set at a rotation speed of 60r/min, and subjected to hydrothermal crystallization at 150 ℃ for 7d. And then washing, separating and drying to obtain the MCM-22 molecular sieve. The XRD pattern of the synthesized catalyst is shown as a of figure 1, and is a pure phase MCM-22 molecular sieve. SEM image, as shown in FIG. 2 a, the MCM-22 molecular sieve is a dispersed hexagonal flake. As shown in FIG. 3 a, the thickness of the sheet in the c-axis direction was about 50nm in TEM image. The texture properties are shown in Table 2, and the external specific surface area is 66m 2 ·g -1 The total pore volume is 0.57cm 3 ·g -1 Mesoporous volume of 0.37cm 3 ·g -1 The micropore volume is 0.21cm 3 ·g -1 . The reaction data are shown in Table 1.
Test example 1
Accurately weighing 1g of 20-40 mesh molecular sieve catalyst particles, mixing with equal volume of quartz sand, placing in a fixed bed reactor, setting the reaction temperature at 210 ℃, and setting the mass space velocity for 3h -1 The reaction pressure was 3.5MPa, benzene/alkene ratio=2.6. After the air tightness of the reaction is checked to be normal, opening a benzene feed valve for pressure preparation; after the reaction temperature is reached, ethylene feeding is started, a liquid sample is collected, the components of the sample are analyzed by gas chromatography, and the product composition within 12-24 hours before the reaction is calculated. From the results of the liquid phase alkylation reaction, thinner MCM-22 microsphere particles (examples 1,2,5,6,8 and 10 (b, c, f, g, i, k)) increased ethylbenzene production by about 6% over the conventional MCM-22 catalyst (comparative example 1), and improved stability of the reactionGood. Therefore, the thinner lamellar thickness can expose more half cup structures, and the reaction molecule ethylene and benzene are more accessible and enter the reaction place, thereby improving the reaction performance.
The specific evaluation of the reaction mainly uses two indexes of benzene conversion rate XB and ethylbenzene selectivity SEB to reflect the reaction activity of the catalyst. The specific operation is as follows:
Figure BDA0002677984280000121
Figure BDA0002677984280000122
TABLE 1 liquid phase alkylation reaction results for examples 1-10
Reaction temperature/. Degree.C Ethylene space velocity h -1 Benzene conversion/% Ethylbenzene selectivity/%
Example 1 210 3 31.5 93.4
Example 2 210 3 33.4 92.5
Example 3 210 3 27.3 89.5
Example 4 210 3 26.8 90.5
Example 5 210 3 31.2 92.6
Example 6 210 3 30.6 92.3
Example 7 210 3 29.5 93.6
Example 8 210 3 32.7 92.3
Example 9 210 3 27.3 90.6
Example 10 210 3 32.1 92.7
Comparative example 1 210 3 26.7 87.6
TABLE 2 texture Properties of MCM-22 molecular sieve samples
Figure BDA0002677984280000131
a A BET method; b the t-Plot method; c p/p 0 volume absorption=0.9999.

Claims (13)

1. A method for preparing a thin-layer MCM-22 molecular sieve microsphere with a microporous mesoporous structure, wherein the method comprises the following steps:
the liquid preparation step comprises the following steps: preparing a main template agent, a second template agent and water into a solution A; preparing an aluminum source, an alkali source and water into a solution B; the main template agent is hexamethyleneAn imine; the second template agent is double-headed quaternary ammonium salt; the molecular formula of the double-headed quaternary ammonium salt is X (H) 2n+1 C n ) (CH 3 ) 2 N + (CH 2 ) 6 N + (CH 3 ) 2 (C m H 2m+1 ) X, wherein n is an integer from 4 to 22, m is an integer from 4 to 12, x= Cl, br, I, OH;
mixing: mixing the solution A, the solution B and a silicon source and aging to obtain mixed glue; wherein the molar ratio of each component in the mixed glue meets the following conditions: siO (SiO) 2 /Al 2 O 3 ＝5-200、OH - /SiO 2 ＝0.005-1、H 2 O/SiO 2 ＝5-100、R 1 /SiO 2 ＝0.01-1、R 2 /SiO 2 =0.005-0.5; wherein R is 1 R is the main template agent 2 Is a second template agent; r is R 1 And R is 2 The molar ratio of (2) to (20); the aging temperature is 40-80 ℃; the aging time is 2-10 h;
and (3) crystallizing: carrying out hydrothermal crystallization on the mixed glue, and then carrying out post-treatment to obtain the MCM-22 molecular sieve microspheres; the crystallization temperature is 120-180 ℃; the crystallization time is 3-15d.
2. The method of claim 1, wherein SiO 2 /Al 2 O 3 ＝15-100、OH - /SiO 2 ＝0.1-0.4、H 2 O/SiO 2 ＝15-50、R 1 /SiO 2 ＝0.05-0.4、R 2 /SiO 2 ＝0.005-0.2。
3. The method of claim 1, wherein R 1 And R is 2 The molar ratio of (2) is 5-20.
4. The method of claim 1, wherein the aluminum source is selected from one or more of sodium aluminate, aluminum nitrate, aluminum chloride, aluminum sulfate, aluminum oxide, aluminum hydroxide, and aluminum oxide monohydrate; the alkali source is selected from one or a combination of more of sodium hydroxide, lithium hydroxide and potassium hydroxide; the silicon source is selected from one or more of white carbon black, silica sol, coarse pore silica gel, sodium silicate, silica gel, silicic acid, tetraethoxysilane and water glass.
5. The method of claim 1, wherein the crystallization temperature is 130-160 ℃; the crystallization time is 4-10d.
6. The method of claim 1, wherein the crystallizing step comprises placing the mixed gum in a container and performing hydrothermal crystallization under conditions that the container rotates at a speed of 10-120 r/min.
7. The method of claim 6, wherein the container rotates about a horizontal axis.
8. The method of claim 6, wherein the crystallizing step comprises placing the mixed glue in a container and rotating the container at a speed of 30-60 r/min.
9. A method according to claim 1, wherein the post-treatment of the crystallization step comprises washing, separating and drying the product obtained after hydrothermal crystallization to obtain the MCM-22 molecular sieve microspheres.
10. The thin-layer MCM-22 molecular sieve microsphere with a microporous mesoporous structure prepared by the method according to any one of claims 1-9; the diameter of the microsphere is 1-2 mu m; the micropore volume is 0.10-0.18cm 3 ·g -1 Mesoporous volume of 0.45-0.77 and 0.77cm 3 ·g -1 The method comprises the steps of carrying out a first treatment on the surface of the The MCM-22 molecular sieve microspheres are formed by stacking uniformly and regularly staggered lamellar layers; the thickness of the sheet layer is 5nm-55 nm; each sheet layer is formed by orderly stacking 2-22 hexagonal sheets.
11. Use of MCM-22 molecular sieve microspheres according to claim 10 for catalyzing alkylation reactions, cracking reactions, disproportionation reactions, isomerisation reactions and epoxidation reactions.
12. A liquid phase alkylation process for styrene, wherein the process comprises reacting benzene and ethylene as raw materials with MCM-22 molecular sieve microspheres of claim 10 as a catalyst to produce ethylbenzene.
13. The liquid phase alkylation of styrene process of claim 12, wherein the reaction conditions comprise: the molar ratio of benzene to ethylene is 2-6, the reaction temperature is 150-300 ℃, and the ethylene airspeed is 0.5-5h -1 The pressure is 3-4MPa.
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