3D-printed molecular sieve catalysts, methods of making and using the same

Abstract

The present application relates to the field of molecular sieve catalyst, disclose a kind of 3D printing molecular sieve catalyst and its preparation method and application, the catalyst includes carrier and ZSM-5 molecular sieve with core-shell structure, the mass percentage content of ZSM-5 molecular sieve in the catalyst is 20-45%;The ZSM-5 molecular sieve includes core phase ZSM-5 molecular sieve and shell layer ZSM-5 molecular sieve.This 3D printing molecular sieve catalyst outer surface distribution has the ZSM-5 molecular sieve with core-shell structure, it is favorable to reduce the occurrence of molecular sieve outer surface side reaction, increase mesoporous volume, shorten reactant transmission path, improve the catalytic activity of catalyst.

Description

Technical Field

[0001] The present invention relates to the field of molecular sieve catalysts, and in particular to a 3D printed molecular sieve catalyst and a preparation method and application thereof. Background Art

[0002] The rapid growth of global chemical market demand has stimulated the vigorous development of catalytic cracking technology to increase the production of light olefins. In the 1970s, Mobil Corporation developed ZSM-5 molecular sieve, which has straight pores. and sinusoidal channels Molecular sieves are the most competitive solid acid catalysts due to their unique shape-selective catalytic effects and excellent thermal and hydrothermal stability. In practical applications, molecular sieve powders must be processed with a binder / matrix material into shaped catalysts such as microspheres, granules, or strips. The structure, composition, and catalytic performance of these shaped catalysts differ significantly from those of the original molecular sieve powder. Therefore, optimizing catalyst shaping methods to enhance the accessibility of the active sites of molecular sieve-based catalysts and improve reaction performance is a key issue in the research, development, and production of molecular sieve catalysts.

[0003] Processing solid powdered catalytic materials into structured catalysts with open pores (e.g., honeycomb ceramics) can effectively improve their mass and heat transfer capabilities. 3D printing, also known as additive manufacturing, involves curing a fluid ink with a certain degree of fluidity layer by layer based on a three-dimensional digital model file to achieve the formation of complex geometric shapes. Compared to traditional extrusion molding, 3D printing technology offers the advantages of high precision, multifunctional material integration, and digital / flexible design. To date, a variety of 3D-printed structured catalysts with molecular sieves as the main active component have shown great application potential in alkane catalytic cracking, ethylene oxidation, carbon monoxide oxidation, xylene isomerization, and α-pinene isomerization reactions. For example, Stuecker et al. (Industrial & Engineering Chemistry Research, 2005, 44, 302) prepared alternating stacked structured catalysts using extrusion-based 3D printing, which significantly improved the mass transfer efficiency of the carbon monoxide catalytic oxidation reaction while maintaining a low pressure drop. Currently, molecular sieves can be incorporated into the surface of 3D printed structured materials through secondary growth, surface deposition or coordination (X.Li, et al., Chemical Engineering Journal 2018, 333, 545; E. et.al, Applied Catalysis A: General 2019, 579, 75; C.Y. Chaparro-Garnica, et.al, ACS Applied Materials & Interfaces 2020, 12, 54573; A. Lind et.al, Materials & Design 2020, 187, 108377; X. Li, ACS Applied Energy Materials 2018, 1, 2740). However, the catalyst surface obtained by the above method directly exposes the ZSM-5 molecular sieve, which has a high density of external surface acidic sites. This makes side reactions such as hydrogen transfer and aromatization more likely to occur, exacerbating the formation of surface carbon. In addition, the microstructure of the molecular sieve is not conducive to the rapid diffusion of products such as light olefins.

[0004] In summary, existing methods for 3D-printed molecular sieve catalysts exhibit a high density of acidic sites on their outer surfaces, which can easily induce side reactions such as hydrogen transfer and aromatization, exacerbating carbon formation on the outer surface and failing to meet application requirements. Therefore, the development of core-shell 3D-printed catalysts with a weakly acidic passivation layer on the outer surface has application value. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems of high density of acidic sites on the outer surface and serious side reactions such as hydrogen transfer in the 3D printed molecular sieve catalyst prepared in the prior art, and to provide a 3D printed molecular sieve catalyst and its preparation method and application. The 3D printed molecular sieve catalyst has a ZSM-5 molecular sieve with a core-shell structure distributed on the outer surface. The composition of the core-shell structure and the molecular sieve is conducive to reducing the occurrence of side reactions on the outer surface of the molecular sieve, increasing the mesopore volume, shortening the reactant transmission path, and thus optimizing the product distribution. The preparation method of the catalyst is simple and the synthesis process has low equipment requirements.

[0006] In order to achieve the above object, the first aspect of the present invention provides a 3D printed molecular sieve catalyst, wherein the catalyst comprises a carrier and a ZSM-5 molecular sieve having a core-shell structure, and the mass percentage of the ZSM-5 molecular sieve in the catalyst is 20-45%;

[0007] The ZSM-5 molecular sieve includes a core phase ZSM-5 molecular sieve and a shell ZSM-5 molecular sieve. The core phase ZSM-5 molecular sieve is distributed on the outer surface of the carrier in the form of micron particle aggregates, and the average particle size of the micron particles is 1-5 microns.

[0008] The shell ZSM-5 molecular sieve covers the outer surface of the core phase ZSM-5 molecular sieve in the form of nanoparticles, and the average particle size of the nanoparticles is 50-300nm; the average thickness of the coating layer formed by the shell ZSM-5 molecular sieve is 50-400nm.

[0009] Preferably, the silicon to aluminum atomic molar ratio of the core phase ZSM-5 molecular sieve is 10-25, preferably 12-23.

[0010] Preferably, the silicon to aluminum atomic molar ratio of the shell ZSM-5 molecular sieve is 30-100, preferably 40-85.

[0011] A second aspect of the present invention provides a method for preparing a 3D printed molecular sieve catalyst, characterized in that the method comprises the following steps:

[0012] (1) providing an aluminosilicate photosensitive resin slurry containing aluminosilicate and a photosensitive resin, and then performing 3D printing to obtain an aluminosilicate ceramic body;

[0013] (2) sintering the aluminosilicate ceramic body to obtain an aluminosilicate ceramic carrier;

[0014] (3) crystallizing a crystallization mother solution containing a silicon source, an aluminum source, a template, an alkali source, and water to obtain a crystallization incubation solution;

[0015] (4) hydrothermally crystallizing the aluminosilicate ceramic support in a crystallization incubation solution, and then calcining a solid product obtained by the hydrothermal crystallization to obtain an intermediate product;

[0016] (5) The intermediate product is subjected to a desiliconization-recrystallization reaction in a composite alkaline solution, and calcined to obtain a 3D printed molecular sieve catalyst.

[0017] The third aspect of the present invention provides a 3D printed molecular sieve catalyst prepared by the preparation method described in the second aspect.

[0018] A fourth aspect of the present invention provides an application of the 3D printed molecular sieve catalyst described in the first aspect or the third aspect in a catalytic cracking reaction.

[0019] Through the above technical solution, the present invention has the following advantages:

[0020] (1) The 3D printed molecular sieve catalyst provided by the present invention comprises a ZSM-5 molecular sieve having a core-shell structure, wherein the shell ZSM-5 molecular sieve has a high silicon-aluminum ratio and the core phase ZSM-5 molecular sieve has a low silicon-aluminum ratio. This structure and composition are beneficial for reducing side reactions on the outer surface of the molecular sieve, increasing the mesopore volume, shortening the reactant transport path, improving the accessibility of the active center and the utilization rate of the acidic site of the molecular sieve, thereby improving the catalytic activity of the molecular sieve catalyst;

[0021] (2) The preparation method provided by the present invention can establish a model through three-dimensional software, and can customize complex three-dimensional structures suitable for different scenarios. It does not rely on molds and does not require complex post-processing of the carrier. The three-dimensional pore structure of the carrier is simple and controllable;

[0022] (3) In the present invention, preferably, the prepared molecular sieve catalyst is easy to separate and recover from the synthesis solution, and the synthesis process has low equipment requirements;

[0023] (4) In the present invention, preferably, the provided molecular sieve catalyst has high catalytic activity and the advantage of reducing bed pressure drop in the performance test of catalytic cracking reaction compared with traditional powder particle molecular sieve catalysts, and has application prospects in the field of catalytic cracking in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a cross-sectional view of the three-dimensional model test established in Example 1;

[0025] Figure 2 This is a photo of the 3D printed molecular sieve catalyst prepared in Example 1;

[0026] Figure 3 is the XRD pattern of the 3D printed molecular sieve catalyst prepared in Example 1;

[0027] Figure 4 This is a scanning electron microscope image of the catalyst prepared in Example 1 before the growth of the ZSM-5 molecular sieve shell;

[0028] Figure 5 This is a scanning electron microscope image of the 3D printed molecular sieve catalyst prepared in Example 1 at a magnification of 50K times;

[0029] Figure 6 is a transmission electron microscopy image of the 3D printed molecular sieve catalyst prepared in Example 1;

[0030] Figure 7 is the isothermal adsorption curve of the 3D printed molecular sieve catalyst prepared in Example 1;

[0031] Figure 8 is the pore distribution curve of the 3D printed molecular sieve catalyst prepared in Example 1;

[0032] Figure 9 is a scanning electron microscope image of the catalyst prepared in Comparative Example 1;

[0033] Figure 10 This is a scanning electron microscope image of the catalyst prepared in Comparative Example 2. DETAILED DESCRIPTION

[0034] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0035] A first aspect of the present invention provides a 3D printed molecular sieve catalyst, wherein the catalyst comprises a carrier and a ZSM-5 molecular sieve having a core-shell structure, and the mass percentage of the ZSM-5 molecular sieve in the catalyst is 20-45%;

[0036] The ZSM-5 molecular sieve includes a core phase ZSM-5 molecular sieve and a shell ZSM-5 molecular sieve. The core phase ZSM-5 molecular sieve is distributed on the outer surface of the carrier in the form of micron particle aggregates, and the average particle size of the micron particles is 1-5 microns.

[0037] The shell ZSM-5 molecular sieve covers the outer surface of the core phase ZSM-5 molecular sieve in the form of nanoparticles, and the average particle size of the nanoparticles is 50-300nm; the average thickness of the coating layer formed by the shell ZSM-5 molecular sieve is 50-400nm.

[0038] The 3D-printed molecular sieve catalyst provided by the present invention comprises a ZSM-5 molecular sieve with a core-shell structure and a carrier. The carrier has good regularity, the molecular sieve mass percentage in the 3D molecular sieve catalyst is high, the structural precision is high, and the ZSM-5 molecular sieve is directly exposed to the outer surface of the carrier through in-situ growth, which has the advantage of high accessibility of the active center.

[0039] In the present invention, the core phase ZSM-5 molecular sieve refers to the micron-sized ZSM-5 molecular sieve grown on the outer surface of the carrier, such as Figure 4 As shown, the particle size of the core phase ZSM-5 molecular sieve is in the micron order. The shell ZSM-5 molecular sieve refers to a nano ZSM-5 molecular sieve grown on the outer surface of the core phase molecular sieve by desiliconization and recrystallization, and the particle size of the shell ZSM-5 molecular sieve is in the nanometer order. In the present invention, the core phase molecular sieve and the shell molecular sieve can be distinguished by transmission electron microscopy.

[0040] According to the present invention, preferably, the mass percentage of ZSM-5 molecular sieve in the catalyst is 30-43%. In the present invention, the mass percentage of molecular sieve in the molecular sieve catalyst is expressed by relative crystallinity, with reference to ASTMD3906-03 standard method, with commercial molecular sieve crystallinity of 100% tested (Tianjin Nanhua Catalyst Co., Ltd., Nankai University Catalyst Plant Na type ZSM-5 molecular sieve, silicon-aluminum ratio 25). Test instrument: D5005 X-ray diffractometer of Siemens, Germany. Test conditions: Cu target, Kα radiation, solid detector, tube voltage 40kV, tube current 40mA, step scan, step width 0.02°, prefabrication time 2s, scanning range 5°-70°.

[0041] According to the present invention, preferably, the weight percentage of the carrier in the catalyst is 55-80%, preferably 57-70%. In the present invention, the weight percentage of the carrier in the catalyst is determined by grinding the entire catalyst and then testing the crystallinity, with the crystallinity representing the weight percentage of the molecular sieve in the catalyst, where the weight percentage of the carrier = 100% - the weight percentage of the molecular sieve.

[0042] In the present invention, the composition of the carrier comprises silica and alumina, and the ratio of silica to alumina in the carrier is not particularly limited. Preferably, the carrier is obtained by a 3D printing method, and the composition of the carrier satisfies the 3D printing conditions. The 3D printing process is described in detail in the preparation method section. During the process of forming the core-shell structure of the ZSM-5 molecular sieve on the carrier surface, crystallization and desiliconization-recrystallization reactions occur, causing the ratio of silica to alumina in the carrier to change. Therefore, the composition of the carrier is not excessively limited.

[0043] In the present invention, the carrier is a carrier obtained by 3D printing, and the range of selection for the specific structure of the carrier is relatively wide. Preferably, the carrier has a multi-pore self-supporting three-dimensional structure, and further preferably has a self-supporting three-dimensional structure with parallel radial and axial interconnected pore structures.

[0044] According to the present invention, preferably, in the core phase ZSM-5 molecular sieve, the average particle size of micron particles is 1.5-4.5 microns. In the present invention, the average particle size of the core phase ZSM-5 molecular sieve micron particles is tested in an electron microscope (Hitachi Hitachi scanning electron microscope, S-4800), and by Nano Measurer software, the average value obtained by randomly measuring the grain size of 20 molecular sieve micron particles is obtained. In the measuring process, the size for a molecular sieve micron particle is the straight-line distance obtained by connecting the two most distant endpoints on the particle in the electron micrograph.

[0045] According to the present invention, preferably, the average particle size of the nanoparticles in the shell ZSM-5 molecular sieve is 70-280 nm. In the present invention, the average particle size of the nanoparticles is tested in a transmission electron microscope, and the average value of the grain size of 20 molecular sieve nanoparticles is obtained by randomly measuring the grain size of 20 molecular sieve nanoparticles using Nano Measurer software. During the measurement process, the size of a molecular sieve nanoparticle is the straight-line distance obtained by connecting the two most distant endpoints on the particle in the electron microscopic image.

[0046] According to the present invention, different morphologies of the core phase and the shell are observed by transmission electron microscopy. The core phase ZSM-5 molecular sieve presents a hexagonal stack with a smooth outer surface, and the shell ZSM-5 molecular sieve presents a rough and porous nanocrystalline aggregate. Preferably, the average thickness of the coating formed by the shell ZSM-5 molecular sieve is 100-300nm. The average thickness is the average value obtained by randomly measuring the shell thickness at 20 locations in the transmission electron microscope image.

[0047] According to the present invention, preferably, the silicon-aluminum atomic molar ratio of the core-phase ZSM-5 molecular sieve is 10-25, preferably 12-23. In the present invention, the silicon-aluminum atomic molar ratio of the core-phase ZSM-5 molecular sieve grown on the outer surface of the catalyst support is tested by XPS, and the silicon-aluminum atomic molar ratio of the core-phase ZSM-5 molecular sieve is the silicon-aluminum atomic molar ratio measured when the shell layer is not grown.

[0048] According to the present invention, preferably, the silicon to aluminum atomic molar ratio of the shell ZSM-5 molecular sieve is 30-100, preferably 40-85. In the present invention, the surface chemical composition of the catalyst can be tested by XPS, and the surface Si / Al ratio can be calculated by the XPS signal to obtain the silicon and aluminum content of the outermost shell ZSM-5 molecular sieve of the catalyst.

[0049] In the present invention, the silicon to aluminum atomic molar ratio is the molar ratio of Si / Al.

[0050] In the present invention, preferably, the shell ZSM-5 molecular sieve of the 3D molecular sieve catalyst has a high silicon-aluminum ratio, and the core phase ZSM-5 has a low silicon-aluminum ratio, which has the advantages of reducing side reactions on the outer surface of the molecular sieve, increasing the mesopore volume, shortening the reactant transport path, and improving the accessibility of the active center and the utilization rate of the molecular sieve acid site.

[0051] According to the present invention, preferably, the catalyst has micropores and mesopores. In the present invention, the catalyst has a multi-level pore structure of mesopores and micropores, which is beneficial to improving the catalytic activity of the catalyst.

[0052] According to the present invention, preferably, the micropore volume of the catalyst is 0.03-0.08 cm 3 / g, preferably 0.04-0.07cm 3 / g.

[0053] According to the present invention, preferably, the mesopore volume of the catalyst is 0.08-0.15 cm 3 / g, preferably 0.1-0.13cm 3 / g.

[0054] In the present invention, the micropore volume and mesopore volume of the molecular sieve catalyst were measured using a low-temperature nitrogen adsorption capacity method using a Micromeritics ASAP2400 static nitrogen adsorption instrument. The test conditions were as follows: the sample was vacuum degassed at 1.33 Pa and 300°C for 4 hours, then exposed to liquid nitrogen at 77 K for isothermal adsorption and desorption. The adsorption and desorption isotherms were measured, and the micropore volume and mesopore volume were calculated using the BET equation.

[0055] A second aspect of the present invention provides a method for preparing a 3D printed molecular sieve catalyst, wherein the method comprises the following steps:

[0056] (1) providing an aluminosilicate photosensitive resin slurry containing aluminosilicate and a photosensitive resin, and then performing 3D printing to obtain an aluminosilicate ceramic body;

[0057] (2) sintering the aluminosilicate ceramic body to obtain an aluminosilicate ceramic carrier;

[0058] (3) crystallizing a crystallization mother solution containing a silicon source, an aluminum source, a template, an alkali source, and water to obtain a crystallization incubation solution;

[0059] (4) hydrothermally crystallizing the aluminosilicate ceramic support in a crystallization incubation solution, and then calcining a solid product obtained by the hydrothermal crystallization to obtain an intermediate product;

[0060] (5) The intermediate product is subjected to a desiliconization-recrystallization reaction in a composite alkaline solution, and calcined to obtain a 3D printed molecular sieve catalyst.

[0061] In the present invention, the aluminosilicate ceramic carrier is hydrothermally crystallized in a crystallization incubation solution, and a molecular sieve with good dispersibility and high catalytic activity can be obtained on the aluminosilicate ceramic carrier. The preparation process is simple and a complex three-dimensional structure can be formed without relying on a mold. The prepared molecular sieve catalyst has high structural precision, a high molecular sieve content in the catalyst, and high catalytic activity.

[0062] In the present invention, preferably, the aluminosilicate photosensitive resin slurry in step (1) can be obtained by mixing aluminosilicate and a photosensitive resin. The mixing method is not particularly limited. According to a preferred embodiment of the present invention, the mixing can be achieved by ball milling, with a ball milling speed of 250-500 rpm, preferably 280-450 rpm, and a ball milling time of 3-18 hours, preferably 5-15 hours.

[0063] According to the present invention, the aluminosilicate preferably comprises a silicon-based powder and an auxiliary powder, wherein the weight percentage of the silicon-based powder on a dry basis is 35-65%, preferably 45-60%, and the weight percentage of the auxiliary powder on a dry basis is 35-65%, preferably 40-55%. Using this preferred composition of the aluminosilicate further facilitates the sintering of the support material, achieving both structural stability and chemical activity under hydrothermal conditions.

[0064] In the present invention, the aluminosilicate has the conventional meaning in the art. Aluminosilicate is a class of substances including commonly used mineral soils, whose main components are aluminum oxide and silicon dioxide. The molecular formula can be expressed as xAl2O3·ySiO2, wherein the ratio of aluminum oxide to silicon dioxide is not constant.

[0065] In the present invention, the particle size of the aluminosilicate is not particularly limited; it can be large particles or small powders, as long as the aluminosilicate is uniformly distributed in the carrier. If larger particles are used, their uniformity is preferably further improved by subsequent ball milling. Preferably, the aluminosilicate has a particle size D90 in the range of 0.5-100 μm.

[0066] In the present invention, preferably, the above-mentioned silicon-based powder is mixed with an auxiliary powder to obtain aluminosilicate, and the silicon-based powder can be used as a silicon source for growing molecular sieves on a carrier in the subsequent preparation process. When the amount of the silicon-based powder added is too much, the silicon dissolution degree of the carrier after calcination during the hydrothermal crystallization process is too high, and the in-situ molecular sieve growth reaction rate on the carrier surface is too high, making the carrier structure unstable and collapsing, and no longer maintaining the original self-supporting structure. When the amount of silicon-based powder added is insufficient, the silicon dissolution of the carrier after calcination during the hydrothermal crystallization process is limited, resulting in an in-situ molecular sieve growth reaction rate on the carrier surface that is too low, resulting in a low molecular sieve content in the catalyst finally obtained, which cannot meet the requirements of the catalytic reaction.

[0067] In the present invention, there is no particular limitation on the particle sizes of the silicon-based powder and the auxiliary powder. It is preferred that the particle size of the aluminosilicate obtained after mixing meets the above-mentioned particle size requirements.

[0068] According to the present invention, the silicon-based powder can be conventional silicon-based powder in the art, and those skilled in the art can make an adaptive selection according to needs. Preferably, the silicon-based powder is selected from at least one of silicon dioxide, white carbon black and diatomaceous earth.

[0069] According to the present invention, there is no particular limitation on the auxiliary powder, as long as it is chemically inert under hydrothermal conditions to maintain the stability of the self-supporting structure. Preferably, the auxiliary powder is selected from at least one of kaolin, metakaolin, bentonite, and montmorillonite.

[0070] According to the present invention, the range of selection for the amount of the aluminosilicate and the photosensitive resin is relatively wide, so as to ensure that the 3D printing process proceeds smoothly. Preferably, the mass ratio of the aluminosilicate to the photosensitive resin is 0.5-1:1, for example, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, and any range between any two values, preferably 0.6-0.9:1.

[0071] According to the present invention, the specific composition of the photosensitive resin can be selected from a wide range and can be selected according to conventional techniques in the art. Preferably, the raw materials of the photosensitive resin include, by weight, 1-5% photoinitiator, 30-65% prepolymer, and 30-65% monomer. More preferably, the raw materials include, by weight, 1.5-4% photoinitiator, 35-60% prepolymer, and 37-62% monomer. Using the photosensitive resin composed of the above raw materials for 3D printing results in fast curing speed and high production efficiency.

[0072] In the present invention, the photoinitiator can be a conventional photoinitiator in the art. Preferably, the photoinitiator is selected from at least one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (photoinitiator TPO), phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator 819) and isopropylthioxanthone (ITX).

[0073] In the present invention, the prepolymer may be a conventional acrylate prepolymer in the art. Preferably, the prepolymer is an epoxy acrylate prepolymer and / or a polyurethane acrylate prepolymer.

[0074] In the present invention, the monomer may be a conventional monomer in the art. Preferably, the monomer is selected from at least one of 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA) and trimethylolpropane triacrylate (TMPTA).

[0075] In this invention, an aluminosilicate ceramic green body is prepared using 3D printing. Modeling software is used to design the three-dimensional structure, and then aluminosilicate photosensitive resin slurry is poured into the material tank of a DLP light-curing printer for printing. This produces the aluminosilicate ceramic green body. "Aluminosilicate ceramic green body" is a general term for all of the green bodies prepared. Printing allows for customized, complex three-dimensional structures suitable for various scenarios, without the need for molds or complex post-processing of the substrate. The three-dimensional pore structure of the substrate is simple and controllable.

[0076] In the present invention, preferably, modeling software is used for three-dimensional structure design, and the modeling software is selected from SolidWorks, 3DMAX, AutoCAD or Materialise Magics.

[0077] According to the present invention, preferably, the conditions for 3D printing include: the light curing exposure power is 0.5-5mW / cm 2 The exposure time of the first layer is 15-30s, the exposure time of other layers is 5-15s, and the thickness of a single layer of light curing is 20-100μm.

[0078] In the present invention, preferably, the obtained aluminosilicate ceramic body is also cleaned after printing. There is no special limitation on the cleaning conditions, and those skilled in the art can make appropriate selections. According to a preferred embodiment of the present invention, anhydrous ethanol is used for sufficient cleaning.

[0079] The present invention does not particularly limit the size and structural shape of the aluminosilicate ceramic body. Those skilled in the art can make appropriate selections based on the specific application scenarios of the catalyst produced. The present invention subsequently provides a specific preferred embodiment for use in a catalytic cracking catalyst, but the present invention is not limited thereto.

[0080] In the present invention, the aluminosilicate ceramic body provides a skeleton for the molecular sieve catalyst. The body has a multi-porous structure and forms an aluminosilicate ceramic carrier after sintering, so that the molecular sieve seeds in the crystallization incubation solution can grow rapidly on the carrier, thereby increasing the mass percentage of the molecular sieve (preferably ZSM-5) in the prepared molecular sieve catalyst.

[0081] According to the present invention, preferably, the aluminosilicate ceramic carrier has a multi-porous self-supporting three-dimensional structure. The present invention has no special limitation on the multi-porous self-supporting three-dimensional structure, which has the conventional interpretation in this field. Specifically, the "self-supporting" means that the aluminosilicate ceramic carrier has its own strength and rigidity, and can maintain its shape and stability without external support. The "multi-porous" means that the main frame of the aluminosilicate ceramic carrier has a multi-porous structure. There is no special limitation on the distribution of the pores, and it can be appropriately selected according to the specific catalyst application scenario. The distribution of the pores can be uniform, symmetrical, or uneven and asymmetrical. In order to further improve the application effect of the catalyst in catalytic cracking reactions, it is further preferred that the aluminosilicate ceramic carrier is a self-supporting three-dimensional structure with parallel radial and axial interconnected pore structures. The specific pore structure is as follows Figure 1 and Figure 2 shown.

[0082] According to the present invention, preferably, the method further comprises, before the sintering, pyrolyzing the aluminosilicate ceramic body to remove organic matter in the body, and the pyrolysis conditions include: temperature of 350-550°C and time of 5-15h; preferably, the pyrolysis conditions include: temperature of 380-520°C and time of 6-13h.

[0083] In the present invention, those skilled in the art can adjust the heating rate of the pyrolysis process as needed. Preferably, the heating rate of the pyrolysis process is 0.1-5°C / min, preferably 0.5-2°C / min.

[0084] According to the present invention, preferably, the sintering conditions in step (2) include: a temperature of 1100-1300° C. for 5-20 hours. Further preferably, the sintering conditions in step (2) include: a temperature of 1150-1250° C. for 8-16 hours.

[0085] In the present invention, the aluminosilicate ceramic body is sintered in step (2). Those skilled in the art can adjust the heating rate of the sintering process as needed. Preferably, the heating rate is 0.1-10°C / min, preferably 0.5-5°C / min.

[0086] According to the present invention, preferably, in the crystallization mother solution, the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the alkali source is calculated as alkali metal oxide X2O, and the molar ratio of SiO2:Al2O3:template:X2O:H2O is 1:(0.018-0.027):(0.18-0.27):(0.22-0.33):(65-100), preferably 1:(0.02-0.025):(0.2-0.25):(0.24-0.31):(70-90).

[0087] In the present invention, preferably, the above silicon source, aluminum source and template are used to provide molecular sieve seeds for the crystallization mother solution, which helps to accelerate the growth rate of the molecular sieve on the aluminosilicate ceramic carrier and shorten the crystallization time of the molecular sieve.

[0088] According to the present invention, preferably, the silicon source can be a conventional silicon source in the art, and those skilled in the art can make an adaptive selection according to needs, preferably silica sol and / or tetraethyl orthosilicate.

[0089] According to the present invention, preferably, the aluminum source can be a conventional aluminum source in the art, and those skilled in the art can make an adaptive selection as needed, preferably selected from at least one of aluminum sulfate, aluminum isopropoxide and aluminum trichloride.

[0090] In the present invention, the template agent has a wide range of options and can be selected according to the specific type of molecular sieve to be synthesized. Preferably, the template agent is an organic amine microporous template agent known to those skilled in the art for use in preparing ZSM-5, preferably tetrapropylammonium hydroxide and / or tetrapropylammonium bromide.

[0091] In the present invention, the alkali source is a conventional alkali source in the art, and those skilled in the art can adaptably select it as needed. It is preferably sodium hydroxide and / or potassium hydroxide.

[0092] In the present invention, the crystallization mother liquor is alkaline, with a pH of 9-12, preferably 10-11. When the pH of the crystallization mother liquor is less than 9, an alkali source needs to be added to bring the pH of the crystallization mother liquor to 9-12. Placing the carrier in the crystallization mother liquor within the above pH range and carrying out the crystallization reaction can increase the solubility of the silicon-aluminum raw material, shorten the induction period, and increase the crystallization rate.

[0093] According to the present invention, preferably, the crystallization conditions in step (3) include: a crystallization temperature of 155-185° C., preferably 165-180° C., and a crystallization time of 3-10 h, preferably 4-9 h.

[0094] In the present invention, the range of reaction equipment for crystallization and hydrothermal crystallization is relatively wide, and those skilled in the art can make an adaptive selection as needed, preferably in a crystallization kettle. In the present invention, it is preferred that after the crystallization and / or hydrothermal crystallization is completed, the crystallization kettle is cooled (preferably to room temperature) and then opened. This preferred embodiment avoids the safety hazard of opening the kettle due to the self-generated pressure in the kettle caused by the crystallization reaction at high temperature.

[0095] In the present invention, preferably, the crystallization mother liquor is crystallized under the above conditions to obtain a crystallization incubation liquid, which can further improve the crystallinity of the prepared molecular sieve catalyst. The crystallization incubation liquid contains molecular sieve seeds. From the perspective of crystal growth kinetics, the use of the incubation liquid can significantly shorten the crystal nucleation period (nucleation period) on the carrier surface, thereby accelerating the molecular sieve crystallization process on the carrier surface.

[0096] According to the present invention, preferably, in step (4), the mass ratio of the aluminosilicate ceramic support to the crystallization incubation solution is 1:5-12, for example, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, and any range between any two values, preferably 1:6.5-10. This preferred embodiment is more conducive to matching the silicon species dissolution rate of the support itself and the crystallization rate of the surface molecular sieve, thereby obtaining a crystallized product that takes into account both crystallinity and self-supporting structural strength.

[0097] According to the present invention, preferably, the conditions for the hydrothermal crystallization include: a crystallization temperature of 155-185° C., preferably 165-180° C., and a crystallization time of 12-40 h, preferably 15-35 h.

[0098] In the present invention, preferably, the method further comprises: post-treating the solid product obtained by hydrothermal crystallization, wherein the post-treating comprises washing and drying. The washing can be performed using conventional methods and conditions in the art. According to some preferred embodiments of the present invention, the washing can be performed using deionized water.

[0099] In the present invention, drying can be carried out using conventional methods and conditions in the art. According to some preferred embodiments of the present invention, drying can be carried out in an oven under the following drying conditions: drying at 60-120° C. for 2-10 hours.

[0100] According to the present invention, there are no particular restrictions on the calcination conditions, as long as the template in the solid product can be removed. Preferably, the calcination conditions include: a temperature of 500-600°C for 4-8 hours. There are no particular restrictions on the calcination equipment. Preferably, the calcination can be performed in a muffle furnace.

[0101] According to the present invention, preferably, in step (5), the composite alkali solution comprises an alkali metal hydroxide and a microporous template. The composite alkali solution is prepared by dissolving the alkali metal hydroxide and the microporous template in water. The desiliconization-recrystallization reaction using the composite alkali solution can form a ZSM-5 molecular sieve having a core-shell structure on the surface of the support.

[0102] In the present invention, the alkali metal hydroxide is an alkali metal hydroxide known to those skilled in the art and can be used to prepare ZSM-5, preferably sodium hydroxide and / or potassium hydroxide.

[0103] In the present invention, the microporous template agent is an organic amine microporous template agent known to those skilled in the art and can be used to prepare ZSM-5, and preferably can be tetrapropylammonium hydroxide and / or tetrapropylammonium bromide.

[0104] According to the present invention, preferably, the molar concentration of the alkali metal in the composite alkali solution in step (5) is 0.3-0.5 mol / L, preferably 0.34-0.46 mol / L; the molar concentration of the microporous template agent is 0.4-0.6 mol / L, preferably 0.44-0.56 mol / L.

[0105] In the present invention, preferably, a composite alkali solution having the above-mentioned concentration ratio is used for desiliconization-recrystallization reaction, which can form a ZSM-5 molecular sieve with a specific core-shell structure on the surface of the carrier. If the molar concentration of the alkali metal is too high, the degree of desiliconization is too high, and the microporous structure of the molecular sieve is severely damaged. If the molar concentration is too low, the degree of desiliconization is too low, and sufficient silicon source species cannot be provided for subsequent recrystallization, and a shell structure cannot be obtained. If the molar concentration of the microporous template agent is too high, the shell ZSM-5 molecular sieve will be difficult to form a porous structure and increase the cost. If the molar concentration of the microporous template agent is too low, the recrystallization rate is too low, and it is not easy to obtain a complete shell structure.

[0106] According to the present invention, preferably, in step (5), the mass ratio of the intermediate product to the composite alkali solution is 1:3-8, preferably 1:4-7, based on their respective total masses. The intermediate product and the composite alkali solution undergo a desiliconization-recrystallization reaction at the above mass ratio, and silicon in the core phase ZSM-5 molecular sieve can be quickly removed, and a shell ZSM-5 molecular sieve coating layer of nanoparticles grows on the surface of the core phase ZSM-5 molecular sieve.

[0107] According to the present invention, preferably, the desiliconization-recrystallization conditions include: a crystallization temperature of 155-185°C, preferably 165-180°C, and a crystallization time of 15-50 hours, preferably 20-40 hours. Carrying out the desiliconization-recrystallization reaction under the above conditions is conducive to the formation of a stable ZSM-5 molecular sieve with a multi-level porous core-shell structure on the support surface, thereby improving the catalytic activity of the catalyst.

[0108] In the present invention, preferably, the method further comprises: post-treating the solid product obtained by desiliconization and recrystallization, wherein the post-treating comprises washing and drying. The washing can be performed using conventional methods and conditions in the art. According to some preferred embodiments of the present invention, the washing can be performed using deionized water.

[0109] In the present invention, drying can be carried out using conventional methods and conditions in the art. According to some preferred embodiments of the present invention, drying can be carried out in an oven under the following drying conditions: drying at 60-120° C. for 2-10 hours.

[0110] In the present invention, the calcination conditions are not particularly limited, as long as the template in the solid product can be removed. Preferably, the calcination conditions include: a temperature of 500-600°C for 4-8 hours. The calcination equipment is not particularly limited; preferably, the calcination can be performed in a muffle furnace.

[0111] The third aspect of the present invention provides a 3D printed molecular sieve catalyst prepared by the preparation method described in the second aspect.

[0112] The fourth aspect of the present invention provides an application of the 3D printed molecular sieve catalyst described in the first aspect or the third aspect in a catalytic cracking reaction.

[0113] In the present invention, the 3D-printed molecular sieve catalyst is preferably pretreated before being used in a catalytic cracking reaction. This preferably includes exchanging the 3D-printed molecular sieve catalyst with ammonia to obtain an ammonia-type catalyst, followed by washing, drying, and calcining the ammonia-type catalyst to obtain a hydrogen-type catalyst for catalytic cracking experiments. Those skilled in the art can adapt and adjust these pretreatment conditions as needed.

[0114] In the present invention, preferably, the reaction conditions of the catalytic cracking reaction are: reaction pressure of 0.09-0.3 MPa, reaction temperature of 550-680°C, raw material feed weight space velocity of 50-100h -1 .

[0115] In the present invention, there is no particular limitation on the reaction apparatus for the catalytic cracking reaction, and those skilled in the art can make an appropriate selection based on the application scenario of the molecular sieve catalyst. According to a preferred embodiment of the present invention, the catalytic cracking reaction can be carried out in a fixed bed reactor.

[0116] In the present invention, the prepared molecular sieve catalyst has high catalytic activity and the advantage of reducing bed pressure drop, and can be widely used in catalytic cracking reactions.

[0117] According to a particularly preferred embodiment of the present invention, a method for preparing a 3D printed molecular sieve catalyst comprises the following steps:

[0118] (1) providing an aluminosilicate photosensitive resin slurry containing aluminosilicate and a photosensitive resin, and then performing 3D printing to obtain an aluminosilicate ceramic body;

[0119] (2) sintering the aluminosilicate ceramic body to obtain an aluminosilicate ceramic carrier;

[0120] (3) crystallizing a crystallization mother solution containing a silicon source, an aluminum source, a template, an alkali source, and water, wherein the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, the alkali source is calculated as X2O, and the molar ratio of SiO2:Al2O3:template:X2O:H2O is 1:(0.02-0.025):(0.2-0.25):(0.24-0.31):(70-90), and the crystallization conditions include: a crystallization temperature of 165-180°C and a crystallization time of 4-9 hours; obtaining a crystallization incubation solution;

[0121] (4) hydrothermally crystallizing the aluminosilicate ceramic support in a crystallization incubation solution, and then calcining a solid product obtained by the hydrothermal crystallization to obtain an intermediate product;

[0122] (5) subjecting the intermediate product to a desiliconization-recrystallization reaction in a composite alkali solution, wherein the mass ratio of the intermediate product to the composite alkali solution is 1:4-7 based on the total mass of each, and the desiliconization-recrystallization reaction is completed, and the 3D printed molecular sieve catalyst is obtained after calcination;

[0123] The composite alkali solution includes an alkali metal hydroxide and a microporous template agent, wherein the alkali metal hydroxide is sodium hydroxide and / or potassium hydroxide, and the alkali metal molar concentration is 0.34-0.46 mol / L; the microporous template agent is tetrapropylammonium hydroxide and / or tetrapropylammonium bromide, and the microporous template agent molar concentration is 0.44-0.56 mol / L.

[0124] The present invention will be described in detail below through examples and comparative examples. In the following examples and comparative examples, unless otherwise specified, the reagents and materials used can be obtained commercially, and the room temperature is 25°C;

[0125] The ball milling was carried out using a Juchuang environmental protection vertical planetary ball mill (model JC-QM-0.4);

[0126] The three-dimensional model is established by Solidworks software;

[0127] The 3D printing was completed by a sinking DLP-3D printer (model SU136A or SU-100A) produced by Foshan Guanglei Intelligent Manufacturing Co., Ltd. (light source wavelength: 405 nm).

[0128] The test methods and test conditions for the molecular sieve mass percentage, surface morphology, average particle size and pore structure of the molecular sieve catalyst are described in the aforementioned specification and will not be repeated here.

[0129] Example 1

[0130] (1) Preparation of aluminosilicate ceramic body:

[0131] (1-1) Diatomaceous earth is used as a silicon-based powder and metakaolin is used as an auxiliary powder. The mass fraction of the silicon-based powder is 60% (on a dry basis) and the mass fraction of the auxiliary powder is 40% (on a dry basis) to obtain an aluminosilicate. The D90 particle size of the aluminosilicate is 5.8 μm.

[0132] (1-2) 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) is used as a photoinitiator, polyurethane acrylate prepolymer is used as a prepolymer, and 1,6-hexanediol diacrylate (HDDA) is used as a monomer. The mixture is mixed at a ratio of 4% of photoinitiator, 35% of prepolymer, and 61% of monomer to obtain a photosensitive resin;

[0133] (1-3) mixing aluminosilicate and photosensitive resin in a mass ratio of 0.65:1, and thoroughly ball milling them in a ball mill for 14 h (rotation speed 280 rpm) to obtain aluminosilicate photosensitive resin slurry;

[0134] (1-4) Perform three-dimensional structure design, import the three-dimensional model file into the 3D printing equipment, pour the aluminosilicate photosensitive resin slurry into the DLP light-curing printer material tank for printing, and the printing parameters are: exposure power 1mW / cm 2 , exposure time 10s (first layer exposure time is 20s); after printing is completed, the obtained aluminosilicate ceramic body is placed in anhydrous ethanol for thorough cleaning.

[0135] (2) The formed aluminosilicate ceramic body is dried, pyrolyzed and sintered. The specific pyrolysis and sintering conditions are: heating from room temperature to 450°C at a rate of 0.5°C / min and maintaining for 8 hours; heating from 450°C to 1200°C at a rate of 3°C / min and maintaining for 15 hours to obtain an aluminosilicate ceramic carrier. The aluminosilicate ceramic carrier has the same Figure 1 A similar multi-porous self-supporting three-dimensional structure is a cylinder composed of strips arranged in a horizontal and vertical staggered manner. Its cross-sectional diameter is 1.27 cm, the height is 1.18 cm, and the spacing between different strips on the same horizontal plane is 0.06 cm.

[0136] (3) Silica sol (40 wt% SiO2, Grace Ludox AS40) and aluminum sulfate (99 wt%, Innochem) were used as silicon source and aluminum source, respectively, and tetrapropylammonium hydroxide (TPAOH, 25 wt%, Innochem) was used as template. The silicon source, aluminum source, template and sodium hydroxide were added to water and mixed to obtain a crystallization mother solution, wherein the molar ratio of each raw material, i.e., SiO2:Al2O3:template:X2O:H2O, was 1:0.022:0.22:0.28:81. The above mixture was crystallized at 170°C for 6 hours to obtain a crystallization incubation solution.

[0137] (4) The aluminosilicate ceramic support was placed in a crystallization incubation solution, wherein the mass ratio of support to crystallization incubation solution was 1:7.5, and the support-incubation solution mixture was hydrothermally crystallized at 165°C for 35 hours. After the hydrothermal crystallization, the hydrothermal crystallized product was cooled, separated, washed, dried at 100°C for 4 hours, and calcined at 550°C for 4 hours to obtain an intermediate product.

[0138] (5) Sodium hydroxide and tetrapropylammonium hydroxide were dissolved in water and mixed to obtain a composite alkali solution, wherein the molar concentration of sodium hydroxide was 0.4 mol / L and the molar concentration of tetrapropylammonium hydroxide was 0.5 mol / L. The intermediate product was placed in the composite alkali solution, wherein the mass ratio of the intermediate product to the composite alkali solution was 1:5, and a desiliconization-recrystallization reaction was carried out in a hydrothermal reactor at 170°C for 24 hours. After the reaction, the product was cooled, separated, washed, dried at 100°C for 4 hours, and calcined at 550°C for 4 hours to obtain a 3D printed molecular sieve catalyst.

[0139] Figure 1 This is a cross-sectional view of the three-dimensional model test established in Example 1. The three-dimensional structure design is performed using modeling software, and the structural shape of the molecular sieve catalyst can be selected according to actual needs. Figure 2 This is a photo of the 3D-printed molecular sieve catalyst prepared in Example 1. The molecular sieve catalyst obtained by 3D printing achieves high-precision, digital design of the molecular sieve catalyst and has better regularity.

[0140] The XRD spectrum of the catalyst prepared in Example 1 is as follows: Figure 3 As shown, from Figure 3 It can be seen that the synthesized 3D printed molecular sieve catalyst has the characteristic diffraction peak of ZSM-5 molecular sieve, with an obvious five-finger diffraction peak at 22.0-25.0°, and the mass percentage of ZSM-5 is 36%.

[0141] Figure 4 This is a scanning electron microscope image of the catalyst prepared in Example 1 before the shell ZSM-5 molecular sieve is grown. It can be seen from the image that the core phase molecular sieve grows on the outermost surface of the catalyst and exists in the form of micron particle aggregates. The grain size of 20 molecular sieve micron particles was randomly measured, and the average particle size was calculated to be 3.5 microns.

[0142] Figure 5 This is a scanning electron microscope image of the 3D printed molecular sieve catalyst obtained in Example 1 at a magnification of 50K times, and Figure 4 By comparison, the growth of the shell ZSM-5 molecular sieve can be clearly seen.

[0143] Figure 6 This is a transmission electron microscopy image of the 3D printed molecular sieve catalyst prepared in Example 1. Shell ZSM-5 molecular sieve and core ZSM-5 molecular sieve with different morphologies can be observed. The shell ZSM-5 molecular sieve is distributed on the outer surface of the core ZSM-5 molecular sieve and exists in the form of nanoparticle aggregates. The grain size of 20 molecular sieve nanoparticles was randomly measured, and the average particle size was 90 nm. The average thickness of the coating layer formed by the shell ZSM-5 molecular sieve was 200 nm. Figure 6The right side is an enlarged view of the square area circled on the left. By enlarging, the unique lattice stripes of ZSM-5 molecular sieve can be observed, and it can be seen that the shell is formed by ZSM-5 molecular sieve.

[0144] Figure 7 is the isothermal adsorption curve of the 3D printed molecular sieve catalyst prepared in Example 1, Figure 8 is the pore distribution curve of the 3D printed molecular sieve catalyst prepared in Example 1, as shown in FIG. Figure 7 、 Figure 8 As shown in the figure, a hysteresis loop can be observed in the adsorption isotherm of the 3D printed molecular sieve catalyst, and the presence of mesopores in the sample can be observed from the pore size distribution curve, of which the micropore volume is 0.05 cm 3 / g, and the mesopore volume is 0.12cm 3 / g.

[0145] Example 2

[0146] (1) Preparation of aluminosilicate ceramic body:

[0147] (1-1) Diatomaceous earth is used as a silicon-based powder and metakaolin is used as an auxiliary powder. The mass fraction of the silicon-based powder is 60% (on a dry basis) and the mass fraction of the auxiliary powder is 40% (on a dry basis) to obtain an aluminosilicate. The D90 particle size of the aluminosilicate is 5 μm.

[0148] (1-2) 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) is used as a photoinitiator, polyurethane acrylate prepolymer is used as a prepolymer, and 1,6-hexanediol diacrylate (HDDA) is used as a monomer. The mixture is mixed at a ratio of 4% of photoinitiator, 35% of prepolymer, and 61% of monomer to obtain a photosensitive resin;

[0149] (1-3) mixing aluminosilicate and photosensitive resin in a mass ratio of 0.65:1, and thoroughly ball milling them in a ball mill for 14 h (rotation speed 280 rpm) to obtain aluminosilicate photosensitive resin slurry;

[0150] (1-4) Perform three-dimensional structure design, import the three-dimensional model file into the 3D printing equipment, perform 3D printing according to the three-dimensional model of Example 1, pour the aluminosilicate photosensitive resin slurry into the DLP light-curing printer material tank for printing, and the printing parameters are: exposure power 1mW / cm 2 , exposure time 10s (first layer exposure time is 20s); after printing is completed, the obtained aluminosilicate ceramic body is placed in anhydrous ethanol for thorough cleaning.

[0151] (2) The formed aluminosilicate ceramic body is dried, pyrolyzed, and sintered. The specific pyrolysis and sintering conditions are as follows: heating from room temperature to 450°C at a heating rate of 0.5°C / min and maintaining for 8 hours; heating from 450°C to 1200°C at a heating rate of 3°C / min and maintaining for 15 hours to obtain an aluminosilicate ceramic carrier.

[0152] (3) Silica sol (40 wt% SiO2, Qingdao Junqiang New Materials Co., Ltd.) and aluminum sulfate (99 wt%, Innochem) were used as silicon source and aluminum source, respectively, and tetrapropylammonium hydroxide (TPAOH, 25 wt%, Innochem) was used as template. The silicon source, aluminum source, template and sodium hydroxide were added to water and mixed to obtain a crystallization mother liquor, wherein the molar ratio of each raw material, i.e., SiO2:Al2O3:template:X2O:H2O, was 1:0.021:0.21:0.26:74. The above mixture was crystallized at 165°C for 9 hours to obtain a crystallization incubation solution.

[0153] (4) The aluminosilicate ceramic support was placed in a crystallization incubation solution, wherein the mass ratio of support to crystallization incubation solution was 1:6.8, and the support-incubation solution mixture was hydrothermally crystallized at 170°C for 32 hours. After the hydrothermal crystallization, the hydrothermal crystallized product was cooled, separated, washed, dried at 100°C for 4 hours, and calcined at 550°C for 5 hours to obtain an intermediate product.

[0154] (5) Sodium hydroxide and tetrapropylammonium hydroxide were dissolved in water and mixed to obtain a composite alkali solution, wherein the molar concentration of sodium hydroxide was 0.36 mol / L and the molar concentration of tetrapropylammonium hydroxide was 0.46 mol / L. The intermediate product was placed in the composite alkali solution, wherein the mass ratio of the intermediate product to the composite alkali solution was 1:4.2, and a desiliconization-recrystallization reaction was carried out in a hydrothermal reactor at 170°C for 32 hours. After the reaction, the product was cooled, separated, washed, dried at 100°C for 4 hours, and calcined at 550°C for 5 hours to obtain a 3D printed molecular sieve catalyst.

[0155] Example 3

[0156] (1) Preparation of aluminosilicate ceramic body:

[0157] (1-1) Diatomaceous earth is used as a silicon-based powder and metakaolin is used as an auxiliary powder. The mass fraction of the silicon-based powder is 65% (on a dry basis) and the mass fraction of the auxiliary powder is 35% (on a dry basis) to obtain an aluminosilicate. The D90 particle size of the aluminosilicate is 10 μm.

[0158] (1-2) 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) is used as a photoinitiator, polyurethane acrylate prepolymer is used as a prepolymer, and 1,6-hexanediol diacrylate (HDDA) is used as a monomer. The mixture is mixed at a ratio of 4% of photoinitiator, 35% of prepolymer, and 61% of monomer to obtain a photosensitive resin;

[0159] (1-3) mixing aluminosilicate and photosensitive resin in a mass ratio of 0.65:1, and thoroughly ball milling them in a ball mill for 14 h (rotation speed 280 rpm) to obtain aluminosilicate photosensitive resin slurry;

[0160] (1-4) Perform three-dimensional structure design, import the three-dimensional model file into the 3D printing equipment, perform 3D printing according to the three-dimensional model of Example 1, pour the aluminosilicate photosensitive resin slurry into the DLP light-curing printer material tank for printing, and the printing parameters are: exposure power 1mW / cm 2 , exposure time 10s (first layer exposure time is 20s); after printing is completed, the obtained aluminosilicate ceramic body is placed in anhydrous ethanol for thorough cleaning.

[0161] (2) The formed aluminosilicate ceramic body is dried, pyrolyzed, and sintered. The specific pyrolysis and sintering conditions are as follows: heating from room temperature to 450°C at a heating rate of 0.5°C / min and maintaining for 8 hours; heating from 450°C to 1200°C at a heating rate of 3°C / min and maintaining for 15 hours to obtain an aluminosilicate ceramic carrier.

[0162] (3) Silica sol (40 wt% SiO2, Qingdao Junqiang New Materials Co., Ltd.) and aluminum sulfate (99 wt%, Innochem) were used as silicon source and aluminum source, respectively, and tetrapropylammonium hydroxide (TPAOH, 25 wt%, Innochem) was used as template. The silicon source, aluminum source, template and potassium hydroxide were added to water and mixed to obtain a crystallization mother liquor, wherein the molar ratio of each raw material, i.e., SiO2:Al2O3:template:X2O:H2O, was 1:0.024:0.24:0.29:86. The above mixture was crystallized at 175°C for 4 hours to obtain a crystallization incubation solution.

[0163] (4) The aluminosilicate ceramic support was placed in a crystallization incubation solution, wherein the mass ratio of support to crystallization incubation solution was 1:9.5, and the mixture of support and crystallization incubation solution was hydrothermally crystallized at 175°C for 30 hours. After the hydrothermal crystallization, the hydrothermal crystallized product was cooled, separated, washed, dried at 100°C for 4 hours, and calcined at 550°C for 5 hours to obtain an intermediate product.

[0164] (5) Potassium hydroxide and tetrapropylammonium hydroxide were dissolved in water and mixed to obtain a composite alkali solution, wherein the molar concentration of potassium hydroxide was 0.44 mol / L and the molar concentration of tetrapropylammonium hydroxide was 0.53 mol / L. The intermediate product was placed in the composite alkali solution, wherein the mass ratio of the intermediate product to the composite alkali solution was 1:6.7. The desiliconization-recrystallization reaction was carried out in a hydrothermal reactor at 175°C for 35 hours. After the reaction, the product was cooled, separated, washed, dried at 100°C for 4 hours, and calcined at 550°C for 5 hours to obtain a 3D printed molecular sieve catalyst.

[0165] Example 4

[0166] A core-shell structured 3D printed molecular sieve catalyst was prepared according to the method of Example 1, except that in step (3), the raw materials in the crystallization mother liquor were mixed according to the molar ratio of SiO2:Al2O3:template:X2O:H2O=1:0.018:0.18:0.23:65 to prepare a 3D printed molecular sieve catalyst sample.

[0167] Example 5

[0168] A 3D printed molecular sieve catalyst was prepared according to the method of Example 1, except that in step (5), the molar concentration of the alkali metal in the composite alkali solution was 0.49 mol / L, and the molar concentration of the microporous template was 0.59 mol / L, to prepare a 3D printed molecular sieve catalyst sample.

[0169] Example 6

[0170] A 3D printed molecular sieve catalyst was prepared according to the method of Example 1, except that in step (5), the mass ratio of the intermediate product to the composite alkali solution was 1:3.5, and a 3D printed molecular sieve catalyst sample was prepared.

[0171] Comparative Example 1

[0172] A 3D printed molecular sieve catalyst was prepared according to the method of Example 1, except that no alkali metal hydroxide was added to the composite alkaline solution in step (5), and a 3D printed molecular sieve catalyst sample was prepared.

[0173] The SEM image of the sample of Comparative Example 1 is as follows: Figure 9 As shown, from Figure 9 It can be seen that due to the lack of alkali metal hydroxide, the core-phase ZSM-5 molecular sieve did not undergo subsequent desiliconization-recrystallization reaction, so the core-shell structure was not formed on the surface of the 3D printed carrier, and only the core-phase ZSM-5 molecular sieve was distributed on the outer surface of the 3D printed catalyst.

[0174] Comparative Example 2

[0175] The 3D-printed molecular sieve catalyst was prepared according to the method of Example 1, except that no microporous template was added to the composite alkali solution in step (5), to obtain a 3D-printed molecular sieve catalyst sample. The SEM image of the sample of Comparative Example 2 is shown in Figure 10 Figure 10 As can be seen from the SEM image in

[0176] Comparative Example 3

[0177] The hydrogen-type ZSM-5 powder was tabletted to prepare 40-60 mesh molecular sieve particles, and the hydrogen-type ZSM-5 powder was 35% by mass of commercial hydrogen-type molecular sieve + 65% of quartz sand, which was directly used for evaluation of catalytic cracking of alkane molecules. Except for the difference in catalyst, the other reaction evaluation conditions were the same as in Example 1.

[0178] Test Example 1

[0179] The mass percentage of ZSM-5 molecular sieve, the average particle size of microparticles, the Si / Al atomic ratio of core-phase molecular sieve, the average particle size of nanoparticles, the Si / Al atomic ratio of shell layer molecular sieve, the shell layer thickness, the micropore volume, and the mesopore volume of the 3D-printed molecular sieve catalyst prepared in the examples and comparative examples are shown in Table 1.

[0180] Table 1 Properties of the molecular sieve catalyst samples prepared in the examples and comparative examples

[0181]

[0182]

[0183] As can be seen from Table 1, the shell layer of the 3D-printed molecular sieve catalyst prepared in the examples has a high Si / Al atomic ratio of ZSM-5 molecular sieve, and the core-phase ZSM-5 molecular sieve has a low Si / Al atomic ratio. This structure and composition are beneficial to reducing the side reactions on the outer surface of the molecular sieve, increasing the mesopore volume, shortening the transport path of the reactants, and optimizing the product distribution.

[0184] Test Example 2

[0185] Catalytic activity test of the 3D-printed molecular sieve catalyst with core-shell structure.

[0186] First, the prepared 3D-printed molecular sieve catalyst was placed in an aqueous ammonium sulfate solution (catalyst: ammonium sulfate mass ratio = 2:1) and stirred at 80°C for 2 hours for ion exchange, for a total of 2 times, to obtain an ammonia-type catalyst. Subsequently, the ammonia-type catalyst was washed, dried, and calcined at 550°C for 4 hours to obtain a hydrogen-type catalyst for catalytic cracking experiments.​

[0187] The pretreated 3D printed molecular sieve catalyst was placed in a fixed bed reactor with a reaction pressure of 0.95 MPa, reaction temperatures of 500 °C and 550 °C, and a feed weight hourly space velocity (WHSV) of 8 h -1 The catalyst-to-oil ratio was 3 (mass ratio of catalyst to total feed). After the reaction, the liquid phase was collected in a cold bath, and the gaseous product was collected by drainage gas collection. The liquid product was analyzed for composition using an Agilent 7890B (HP-PONA column) chromatograph, and the gaseous product was analyzed for composition using an Agilent 6890 chromatograph.

[0188] The n-octane conversion rate was calculated according to the following formula: n-octane conversion rate = 1-(mass of n-octane in liquid product / mass of n-octane raw material) × 100%;

[0189] Propylene selectivity = propylene yield / n-octane conversion, propylene yield = propylene output / n-octane raw material mass × 100%. The results are shown in Table 2.

[0190] Table 2 Conversion rates of samples obtained from various examples and comparative examples in the catalytic cracking reaction of n-octane

[0191]

[0192] As can be seen from Table 2, the catalytic cracking reaction using the 3D printed molecular sieve catalysts prepared in Examples 1-6 has a significantly higher conversion rate than that of Comparative Examples 1-2 under the same reaction conditions, and has a better cracking effect on hydrocarbon molecules.

[0193] When the catalyst of Comparative Example 3 was used to carry out catalytic cracking reaction, the conversion rate was also significantly lower than that of the embodiment under the same reaction conditions.

[0194] Compared with traditional molecular sieve powder, the 3D printed ZSM-5 molecular sieve catalyst prepared by the present invention is easy to separate and recover from the synthesis solution, the synthesis process has low equipment requirements, and has high catalytic activity. Therefore, the present invention has good application prospects.

[0195] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present invention and fall within the scope of protection of the present invention.

Claims

1. A 3D printed molecular sieve catalyst, characterized in that: The catalyst comprises a carrier and a ZSM-5 molecular sieve having a core-shell structure, wherein the mass percentage of the ZSM-5 molecular sieve in the catalyst is 20-45%; The ZSM-5 molecular sieve includes a core phase ZSM-5 molecular sieve and a shell ZSM-5 molecular sieve. The core phase ZSM-5 molecular sieve is distributed on the outer surface of the carrier in the form of micron particle aggregates, and the average particle size of the micron particles is 1-5 microns. The shell ZSM-5 molecular sieve is covered on the outer surface of the core phase ZSM-5 molecular sieve in the form of nanoparticles, and the average particle size of the nanoparticles is 50-300 nm; the average thickness of the coating layer formed by the shell ZSM-5 molecular sieve is 50-400 nm; The carrier has a multi-porous self-supporting three-dimensional structure; The silicon-aluminum atomic molar ratio of the core phase ZSM-5 molecular sieve is 10-25; The silicon to aluminum atomic molar ratio of the shell ZSM-5 molecular sieve is 30-100; The catalyst has micropores and mesopores; The micropore volume of the catalyst is 0.03-0.08 cm 3 / g; The mesopore volume of the catalyst is 0.08-0.15 cm 3 / g.

2. The catalyst according to claim 1, wherein The mass percentage of ZSM-5 molecular sieve in the catalyst is 30-43%.

3. The catalyst according to claim 1, wherein The carrier is a self-supporting three-dimensional structure with parallel radial and axial interconnected pore structures.

4. The catalyst according to claim 1, wherein In the core phase ZSM-5 molecular sieve, the average particle size of the micron particles is 1.5-4.5 microns.

5. The catalyst according to claim 1, wherein In the shell ZSM-5 molecular sieve, the average particle size of the nanoparticles is 70-280 nm. The catalyst according to claim 1 , wherein The average thickness of the coating layer formed by the shell ZSM-5 molecular sieve is 100-300 nm.

7. The catalyst according to claim 1, wherein The silicon-aluminum atomic molar ratio of the core phase ZSM-5 molecular sieve is 12-23.

8. The catalyst according to claim 1, wherein The silicon-aluminum atomic molar ratio of the shell ZSM-5 molecular sieve is 40-85.

9. The catalyst according to claim 1, wherein The micropore volume of the catalyst is 0.04-0.07 cm 3 / g.

10. The catalyst according to claim 1, wherein The mesopore volume of the catalyst is 0.1-0.13 cm 3 / g.

11. A method for preparing a 3D printed molecular sieve catalyst according to any one of claims 1 to 10, characterized in that: The method comprises the following steps: (1) providing an aluminosilicate photosensitive resin slurry containing aluminosilicate and a photosensitive resin, and then performing 3D printing to obtain an aluminosilicate ceramic body; (2) sintering the aluminosilicate ceramic body to obtain an aluminosilicate ceramic carrier; (3) crystallizing a crystallization mother solution containing a silicon source, an aluminum source, a template, an alkali source, and water to obtain a crystallization incubation solution; (4) hydrothermally crystallizing the aluminosilicate ceramic support in a crystallization incubation solution, and then calcining the solid product obtained by the hydrothermal crystallization to obtain an intermediate product; (5) The intermediate product is subjected to a desiliconization-recrystallization reaction in a composite alkaline solution, and calcined to obtain a 3D printed molecular sieve catalyst.

12. The method according to claim 11, wherein The aluminosilicate comprises silicon-based powder and auxiliary powder. The mass percentage of the silicon-based powder calculated on a dry basis is 35-65%, and the mass percentage of the auxiliary powder calculated on a dry basis is 35-65%.

13. The method according to claim 12, wherein: The aluminosilicate comprises silicon-based powder and auxiliary powder. The mass percentage of the silicon-based powder calculated on a dry basis is 45-60%, and the mass percentage of the auxiliary powder calculated on a dry basis is 40-55%.

14. The method according to claim 12, wherein: The silicon-based powder is selected from at least one of silicon dioxide, white carbon black and diatomaceous earth.

15. The method according to claim 12, wherein: The auxiliary powder is selected from at least one of kaolin, metakaolin, bentonite and montmorillonite.

16. The method according to claim 11 or 12, wherein: The mass ratio of the aluminosilicate to the photosensitive resin is 0.5-1:

1.

17. The method according to claim 16, wherein The mass ratio of the aluminosilicate to the photosensitive resin is 0.6-0.9:

1.

18. The method according to claim 11, wherein The raw materials of the photosensitive resin include, by mass percentage, 1-5% of photoinitiator, 30-65% of prepolymer, and 30-65% of monomer.

19. The method according to claim 18, wherein The raw materials of the photosensitive resin include, by mass percentage, 1.5-4% of photoinitiator, 35-60% of prepolymer, and 37-62% of monomer.

20. The method according to claim 18, wherein The photoinitiator is selected from at least one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and isopropylthioxanthone.

21. The method according to claim 18, wherein The prepolymer is an epoxy acrylate prepolymer and / or a polyurethane acrylate prepolymer.

22. The method according to claim 18, wherein The monomer is at least one selected from 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and trimethylolpropane triacrylate.

23. The method according to claim 11, wherein The conditions for 3D printing include: light curing exposure power of 0.5-5mW / cm 2 The exposure time of the first layer is 15-30s, the exposure time of other layers is 5-15s, and the thickness of a single layer of light curing is 20-100μm.

24. The method according to claim 11, wherein The aluminosilicate ceramic carrier has a multi-porous self-supporting three-dimensional structure.

25. The method according to claim 24, wherein The aluminosilicate ceramic carrier is a self-supporting three-dimensional structure with parallel radial and axial interconnected pore structures.

26. The method according to claim 11, wherein The sintering conditions in step (2) include: a temperature of 1100-1300° C. and a sintering time of 5-20 hours.

27. The method according to claim 11, wherein The method further comprises pyrolyzing the aluminosilicate ceramic body before sintering, wherein the pyrolysis conditions include: a temperature of 350-550° C. and a time of 5-15 hours.

28. The method according to claim 11, wherein In the crystallization mother solution, the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the alkali source is calculated as X2O. The molar ratio of SiO2:Al2O3:template:X2O:H2O is 1:(0.018-0.027):(0.18-0.27):(0.22-0.33):(65-100).

29. The method according to claim 28, wherein In the crystallization mother solution, the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, and the alkali source is calculated as X2O. The molar ratio of SiO2:Al2O3:template:X2O:H2O is 1:(0.02-0.025):(0.2-0.25):(0.24-0.31):(70-90).

30. The method according to claim 11, wherein The silicon source is silica sol and / or tetraethyl orthosilicate; the aluminum source is selected from at least one of aluminum sulfate, aluminum isopropoxide and aluminum trichloride; and the template is an organic amine microporous template for preparing ZSM-5.

31. The method according to claim 11, wherein The alkali source is sodium hydroxide and / or potassium hydroxide.

32. The method according to claim 11, wherein The crystallization conditions in step (3) include: a crystallization temperature of 155-185° C. and a crystallization time of 3-10 h.

33. The method according to claim 32, wherein The crystallization conditions in step (3) include: a crystallization temperature of 165-180° C. and a crystallization time of 4-9 h.

34. The method according to claim 11, wherein In step (4), the mass ratio of the aluminosilicate ceramic carrier to the crystallization incubation solution is 1:5-12 based on their respective total masses.

35. The method according to claim 34, wherein In step (4), the mass ratio of the aluminosilicate ceramic carrier to the crystallization incubation solution is 1:6.5-10 based on their respective total masses.

36. The method of claim 11, wherein: The conditions for the hydrothermal crystallization include: a crystallization temperature of 155-185° C. and a crystallization time of 12-40 hours.

37. The method according to claim 36, wherein The conditions for the hydrothermal crystallization include: a crystallization temperature of 165-180° C. and a crystallization time of 15-35 hours.

38. The method of claim 11, wherein The calcination conditions include: a temperature of 500-600° C. and a time of 4-8 hours.

39. The method according to claim 11, wherein In step (5), the composite alkali solution includes alkali metal hydroxide and a microporous template.

40. The method of claim 39, wherein The alkali metal hydroxide is sodium hydroxide and / or potassium hydroxide; the microporous template agent is tetrapropylammonium hydroxide and / or tetrapropylammonium bromide.

41. The method of claim 39, wherein The molar concentration of the alkali metal in the composite alkali solution is 0.3-0.5 mol / L; the molar concentration of the microporous template agent is 0.4-0.6 mol / L.

42. The method according to claim 41, wherein The molar concentration of the alkali metal in the composite alkali solution is 0.34-0.46 mol / L; the molar concentration of the microporous template agent is 0.44-0.56 mol / L.

43. The method of claim 11, wherein In step (5), the mass ratio of the intermediate product to the composite alkali solution is 1:3-8 based on their respective total masses.

44. The method according to claim 43, wherein In step (5), the mass ratio of the intermediate product to the composite alkali solution is 1:4-7 based on their respective total masses.

45. The method of claim 11, wherein The desilication-recrystallization conditions include: reaction temperature of 155-185° C., and reaction time of 15-50 h.

46. ​​The method of claim 45, wherein The desiliconization-recrystallization conditions include: reaction temperature of 165-180° C., and reaction time of 20-40 h.

47. The method of claim 11, wherein In step (5), the calcination conditions include: temperature of 500-600°C and time of 4-8h.

48. Use of the 3D printed molecular sieve catalyst according to any one of claims 1 to 10 in a catalytic cracking reaction.

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