Phase change composite material as well as preparation method and application thereof

Abstract

The invention relates to the field of composite materials, and discloses a phase-change composite material and a preparation method and application thereof.The phase-change composite material comprises an inner core, a middle layer and an outermost layer, and the outer surface of the inner core is coated with the middle layer and the outermost layer; wherein the inner core is a phase change core material, the middle layer is a boehmite layer, and the outermost layer is an MFI zeolite molecular sieve. According to the phase-change composite material, boehmite is introduced to serve as a shell layer for coating a phase-change core material to prevent leakage of the core material, meanwhile, boehmite serves as an aluminum source for preparing an MFI zeolite molecular sieve through steam-assisted crystallization, nucleation sites are provided for in-situ growth of the zeolite molecular sieve, and the phase-change composite material has high thermal stability, good temperature control performance, high catalytic efficiency and high reusability.

Description

Technical Field

[0001] The present invention relates to the field of composite materials, and in particular to a phase change composite material and a preparation method and application thereof. Background Art

[0002] Catalytic cracking (FCC) reactions are often accompanied by strong heat absorption / release effects, which usually lead to uneven temperature distribution of the catalyst bed and local hot spots. In addition, in order to maximize production efficiency, the reaction system usually operates at a higher temperature. In this case, the hot spot temperature of the catalyst layer is close to the unstable range. A slight disturbance in the operating conditions will cause thermal runaway, deactivation, and other problems, leading to a series of problems such as changes in product distribution and reduced catalyst activity and life, which will further affect the economic benefits of industrial production. Therefore, efficient control of the catalyst bed temperature is crucial to the efficient and stable operation of the catalytic reaction device.

[0003] Phase change thermal storage material (PCM) is a type of functional material that can efficiently store or release thermal energy by changing its own material state at a constant temperature. Therefore, it is widely used in the field of energy storage and temperature regulation. According to the chemical composition of the material, PCM can generally be divided into organic PCM and inorganic PCM. Organic PCM covers a wide range, including paraffin, fatty acids and their eutectic mixtures, esters, sugars and sugar alcohols, and other organic compounds. However, their thermal conductivity is generally very low, and they are prone to leakage and volatilization during use. Compared with organic PCM, inorganic PCM often has a higher volumetric heat storage density, and its types mainly include hydrated salts, molten salts, metals and alloys. For salts, there are often inherent disadvantages such as large melt volume expansion, large supercooling, and easy phase separation, which greatly limit their practical application. Metals and alloys have good thermal stability and small volume change when melting, and are better energy storage materials. More importantly, their phase change temperature is consistent with the required temperature of the catalytic cracking reaction, and can be used as a functional component to control the local temperature of the catalyst bed. However, in order to prevent metals and alloys from leaking during the phase change process, they need to be encapsulated.

[0004] Zeolite molecular sieves, as a well-crystalline aluminum silicate, have the advantages of high thermal stability, high hydrothermal stability, and adjustable pore structure. They are widely used in industrial fields such as ion exchange, catalysis, and adsorption. In terms of catalytic applications, the special skeleton structure and rich micropore composition of zeolite molecular sieve ZSM-5 give it a high specific surface area, corrosion resistance, and cyclic stability, showing excellent application value. However, if you want to apply the phase change core material to the FCC process, you must consider how it is combined with the zeolite catalyst. Traditional physical mixing can easily lead to the energy storage area not being able to perform its functions well. Therefore, how to retain the high heat storage performance of the phase change core material after encapsulation, and how to achieve efficient assembly of zeolite active components and encapsulated energy storage components, improve the catalyst life, and apply it to the FCC field, are technical problems that need to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art that metal and alloy phase change heat storage materials are prone to leakage during the phase change process, the phase change performance is prone to deterioration after encapsulation, and how to fully apply the energy storage components to the field of catalytic cracking. A phase change composite material and its preparation method and application are provided. The phase change composite material introduces boehmite as a shell layer for coating a phase change core material to prevent the core material from leaking. At the same time, it serves as an aluminum source for steam-assisted crystallization to prepare MFI zeolite molecular sieves, providing nucleation sites for the in-situ growth of zeolite molecular sieves. The phase change composite material has high thermal stability, good temperature control, high catalytic efficiency and high reusability.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a phase change composite material, wherein the phase change composite material comprises an inner core, an intermediate layer coated on the outer surface of the inner core, and an outermost layer;

[0007] Among them, the inner core is a phase change core material, the middle layer is a boehmite layer, and the outermost layer is an MFI zeolite molecular sieve.

[0008] A second aspect of the present invention provides a method for preparing a phase change composite material, wherein the preparation method comprises:

[0009] (1) mixing an aluminum hydroxide solution with a phase change core material and performing a hydrothermal reaction to obtain a qualitative component;

[0010] (2) preparing a precursor solution containing a silicon source, a template and an optional aluminum source, and performing a heat treatment to obtain a dry glue precursor;

[0011] (3) Mixing and crystallizing the dry glue precursor and the qualitative components.

[0012] The third aspect of the present invention provides a phase change composite material prepared by the preparation method described in the second aspect.

[0013] The fourth aspect of the present invention provides an application of the phase change composite material described in the first aspect or the third aspect in a petroleum catalytic cracking reaction.

[0014] Through the above technical solution, the beneficial effects obtained are as follows:

[0015] (1) The phase change composite material provided by the present invention introduces boehmite as a shell layer covering the phase change core material to prevent the core material from leaking, and at the same time serves as an aluminum source for steam-assisted crystallization to prepare MFI zeolite molecular sieves, providing nucleation sites for the in-situ growth of zeolite molecular sieves. The phase change composite material has both high thermal conductivity and high thermal stability;

[0016] (2) The preparation method of the phase change composite material provided by the present invention uses a steam-assisted crystallization process to in-situ grow a zeolite catalyst for catalytic cracking reaction on the surface of the phase change core material. The operation is simple, the reaction conditions are mild, and the product parameters are controllable. The synthesized catalytic-energy storage integrated material can be applied to the field of FCC catalytic cracking reactions.

[0017] (3) In the present invention, the phase change composite material can realize efficient loading of catalytically active components on the surface of the phase change heat storage component, effectively avoid thermal deactivation of the catalytically active components during catalytic cracking, realize effective temperature control of the reaction system, and greatly improve the life of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a SEM photograph of the qualitative components obtained in Example 1;

[0019] Figure 2 is a SEM photograph of the phase change composite material obtained in Example 1;

[0020] Figure 3 is a partial enlarged view of the phase change composite material obtained in Example 1;

[0021] Figure 4 is the XRD spectrum of the phase change composite material obtained in Example 1. DETAILED DESCRIPTION

[0022] The endpoints and any values ​​of the ranges disclosed in this article 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 endpoint values ​​of each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0023] The first aspect of the present invention provides a phase change composite material, wherein the phase change composite material comprises an inner core, an intermediate layer coated on the outer surface of the inner core, and an outermost layer;

[0024] Among them, the inner core is a phase change core material, the middle layer is a boehmite layer, and the outermost layer is an MFI zeolite molecular sieve.

[0025] The phase change composite material provided by the present invention has a boehmite layer (AlOOH) coated on the outside of the phase change core material, and a zeolite molecular sieve is in-situ grown outside the boehmite layer. It has both catalytic performance and energy storage performance, can increase the life of the catalyst, ensure the stable operation of the reactor and improve the energy utilization efficiency, optimize the catalytic cracking process and improve the catalytic cracking efficiency.

[0026] According to the present invention, preferably, the phase change core material is selected from at least one of Al-Si alloy, Zn-Mg alloy, Mg-Si alloy, Al-Fe alloy, elemental tin, elemental magnesium and elemental aluminum.

[0027] In the present invention, when the phase change core material is an alloy material, the mass percentage of the alloy components is not particularly limited, as long as the purpose of the present invention can be achieved. For example, the mass percentage of Si in Al-Si alloy is 12-30wt%, preferably 12-20wt%. The mass percentage of Mg in Zn-Mg alloy is 15-48wt%.

[0028] In the present invention, the above-mentioned phase change core material is used. Since metals and alloys have the advantages of high energy storage density, small volume change when melting, good thermal stability and high thermal conductivity, when the catalytic cracking reaction has a high system temperature (generally higher than 500°C), only the phase change point of metal and alloy core materials can meet the requirements for the phase change point of the catalyst. Metals and alloys show good prospects in solving the problems of uneven bed temperature and heat energy dissipation in the catalytic reaction process.

[0029] According to the present invention, preferably, the particle size of the zeolite molecular sieve is 100-500nm, such as 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, or any range between the two, preferably 200-400nm. In the present invention, the particle size of the outermost MFI zeolite molecular sieve is observed by scanning electron microscopy, and during the measurement process, the particle size of at least 20 zeolite molecular sieve crystal grains is randomly taken for measurement. The particle size described in the present invention has the conventional interpretation of this area, referring to the particle size, if it is a spherical particle, it refers to the diameter of the sphere, and if it is an irregular particle, it refers to the largest linear distance in the particle.

[0030] According to the present invention, preferably, based on the total mass of the phase change composite material, the mass percentage of the phase change core material is 5-70wt%, such as 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 60wt%, 70wt%, or any range between the two, preferably 25-40wt%. The mass percentage of the phase change core material is obtained by differential scanning calorimetry (DSC) testing, and the phase change enthalpy of the phase change composite material and the phase change enthalpy of the pure alloy are measured respectively, and the mass percentage of the phase change core material = the ratio of the phase change enthalpy of the phase change composite material to the phase change enthalpy of the pure alloy.

[0031] According to the present invention, preferably, the silicon-aluminum ratio (Si / Al molar ratio) of the outermost MFI zeolite molecular sieve is in the range of 25-500, such as 25, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, or any range between the two, preferably 50-100. In the present invention, the silicon-aluminum ratio of the outermost MFI zeolite molecular sieve is obtained by separately preparing the zeolite molecular sieve and measuring the silicon-aluminum ratio, and the preparation method and raw material feed ratio of the separately prepared zeolite molecular sieve are the same as those of the outermost MFI zeolite molecular sieve. The silicon-aluminum ratio of the zeolite molecular sieve is determined by inductively coupled plasma emission spectroscopy (ICP-AES).

[0032] In the present invention, the XRD diffraction pattern of the phase change composite material ( Figure 4 ) It can be seen that the material has obvious diffraction peaks at 2θ=7.9°, 8.8°, 23.1°, 23.9°, and 24.4°, indicating that it has a typical MFI topological structure, and the zeolite molecular sieve with MFI structure is in situ grown on the surface of the phase change composite material.

[0033] In the present invention, a layer of boehmite is fully coated on the surface of the phase change core material to prevent the core material from leaking. The boehmite layer also provides an aluminum source for the crystallization of zeolite molecular sieves. Zeolite molecular sieves, as aluminosilicates with good crystallinity, have the advantages of high thermal stability, high hydrothermal stability, and adjustable pore structure, and are used in industrial fields such as ion exchange, catalysis, and adsorption. In terms of catalytic applications, the MFI structure, especially the special skeleton structure of ZSM-5 itself and the rich micropore composition, make it have a high specific surface area, corrosion resistance, and cycle stability.

[0034] A second aspect of the present invention provides a method for preparing a phase change composite material, wherein the preparation method comprises:

[0035] (1) mixing an aluminum hydroxide solution with a phase change core material and performing a hydrothermal reaction to obtain a qualitative component;

[0036] (2) preparing a precursor solution containing a silicon source, a template and an optional aluminum source, and performing a heat treatment to obtain a dry glue precursor;

[0037] (3) Mixing and crystallizing the dry glue precursor and the qualitative components.

[0038] In the present invention, boehmite is used to wrap the phase change core material to obtain a qualitative component, and a zeolite molecular sieve is in situ grown on the surface of the qualitative component. The MFI zeolite molecular sieve is synthesized by a steam assisted crystallization (SAC) process. The preparation process is simple and can directly realize the in situ growth of zeolite particles on the surface of the phase change material qualitative component.

[0039] According to the present invention, preferably, the mass concentration of the aluminum hydroxide solution is 0.2-20 g / L, such as 0.2 g / L, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 5 g / L, 10 g / L, 15 g / L, 20 g / L, or any range therebetween, preferably 0.5-5 g / L. In the present invention, the preparation method of the aluminum hydroxide solution is not particularly limited. In order to make the aluminum hydroxide uniformly dissolved, preferably, the aluminum hydroxide is dissolved in water at a temperature of 25-120°C.

[0040] According to the present invention, preferably, the mass ratio of the aluminum hydroxide to the phase change core material is 0.002-10:1, such as 0.002:1, 0.005:1, 0.01:1, 0.02:1, 0.04:1, 0.08:1, 0.1:1, 0.2:1, 0.4:1, 0.5:1, 0.6:1, 0.8:1, 1:1, 1.5:1, 2:1, 4:1, 6:1, 8:1, 10:1, or any range between the two, preferably 0.04-1:1, more preferably 0.04-0.5:1. Adding aluminum hydroxide and phase change core material according to the above mass ratio can make aluminum hydroxide fully wrap the phase change core material to avoid leakage of the core material. Too thick shell coating will cause the core material loading rate to be too low, which will lead to low or even poor phase change performance.

[0041] According to the present invention, preferably, the phase change core material is selected from at least one of Al-Si alloy, Zn-Mg alloy, Mg-Si alloy, Al-Fe alloy, elemental tin, elemental magnesium and elemental aluminum, preferably selected from at least one of Al-Si alloy, elemental tin and elemental aluminum. In the present invention, the phase change core material is an alloy and / or metal that can form corresponding hydroxides in hot water, and the formed hydroxides and aluminum hydroxide together wrap the phase change core material to prevent leakage of the phase change core material.

[0042] According to the present invention, preferably, the particle size of the phase change core material particles is 2-10μm, preferably 5-7μm. In the present invention, the phase change core material particles can be commercially available or prepared by existing methods. When the particle size of the phase change core material particles does not meet the above range, the phase change core material particles that meet the particle size limit can be prepared by grinding. In the present invention, the particle size of the phase change core material particles is obtained by scanning electron microscopy (SEM) testing. During the measurement process, the particle sizes of twenty phase change core material particles are randomly measured and the average value is taken.

[0043] According to the present invention, preferably, the pH value of the aluminum hydroxide solution is 6-11, preferably 7-9. In the present invention, adjusting the pH value of the aluminum hydroxide solution can fully encapsulate the core material while retaining a high phase change performance.

[0044] In the present invention, preferably, the pH value of the aluminum hydroxide solution is adjusted by using ammonia water, and the amount of the ammonia water added is not particularly limited, so that the pH value of the aluminum hydroxide solution satisfies the range of 6-11.

[0045] According to the present invention, preferably, the conditions of the hydrothermal reaction include: the mixing temperature of the phase change core material is 40-100°C, such as 40°C, 50°C, 60°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or any range between the two, preferably 70-100°C; the reaction time is 0.5-6h, preferably 1-3h. In the present invention, the hydrothermal reaction is carried out under the above conditions, and aluminum hydroxide achieves sufficient coating of boehmite (AlOOH) on the surface of the phase change core material, which can prevent the leakage of the phase change core material, and at the same time can provide part of the aluminum source for the subsequent crystallization process, and provide nucleation sites for the in-situ growth of zeolite molecular sieve particles.

[0046] According to the present invention, preferably, the hydrothermal reaction further comprises optional pre-precipitation, and the conditions of the pre-precipitation include: reaction temperature of 40-80°C, preferably 50-70°C; reaction time of 0-24h, preferably 0-6h.

[0047] According to the present invention, preferably, in the precursor solution, the silicon source is calculated as SiO2, the aluminum source is calculated as Al, and the molar ratio of silicon source: template: water: aluminum source is 1:(0.05-0.5):(10-120):(0-0.1), preferably 1:(0.15-0.35):(25-50):(0.015-0.065).

[0048] According to the present invention, the template agent is a conventional template agent required for preparing MFI zeolite molecular sieves. Preferably, the template agent is tetrapropylammonium hydroxide and / or tetrapropylammonium bromide, preferably tetrapropylammonium hydroxide.

[0049] According to the present invention, the type of the silicon source is not particularly limited, and those skilled in the art can select a conventional silicon source required for preparing MFI zeolite molecular sieves. Preferably, the silicon source is selected from at least one of ethyl orthosilicate, water glass and silica sol.

[0050] In the present invention, aluminum hydroxide can provide part of the aluminum source, and an additional aluminum source needs to be added to form a zeolite molecular sieve. According to the present invention, the type of the aluminum source is not particularly limited, and those skilled in the art can select a conventional aluminum source required for preparing the MFI zeolite molecular sieve. Preferably, the aluminum source is selected from at least one of sodium metaaluminate, aluminum sulfate, aluminum nitrate, aluminum chloride and aluminum isopropoxide.

[0051] According to the present invention, the preparation method of the precursor solution is not limited, in order to make the silicon source, template and aluminum source fully mixed and uniform. Preferably, the preparation of the precursor solution includes: mixing time 1-6h, mixing temperature is 20-60°C. Preferably, the precursor solution is prepared under stirring conditions, and the stirring rate of the stirring is not particularly limited.

[0052] According to the present invention, preferably, the heat treatment conditions include: the heat treatment temperature is 70-120°C, such as 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, or any range between the two, preferably 80-100°C; the heat treatment time is 4-12h, such as 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, or any range between the two, preferably 6-10h. In the present invention, heat treatment is carried out under the above conditions to obtain a dry glue precursor, which is used for subsequent mixing with qualitative components for crystallization.

[0053] In the present invention, preferably, the process of drying and fully grinding the heat-treated product to obtain a powdered dry glue precursor is also included. The dry glue precursor is ground into powder and mixed evenly with the qualitative component, so that the zeolite molecular sieve can be grown in situ on the surface of the qualitative component during the crystallization reaction. Avoid directly adding the qualitative component to the precursor solution, so that the generated zeolite molecular sieve exists independently from the encapsulated core material and cannot be coated on the surface of the qualitative component.

[0054] According to the present invention, preferably, in step (3), the mass ratio of the dry gel precursor to the qualitative component is 0.05-10:1, such as 0.05:1, 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or any range between the two, preferably 0.5-2:1. The dry gel precursor and the qualitative component are uniformly mixed according to the above ratio, and then a zeolite molecular sieve with an MFI structure is in situ grown on the surface of the qualitative component through a crystallization reaction, so that the qualitative component can be further fully coated. The synthesis process is simple to operate, the conditions are mild, and the parameters are controllable.

[0055] According to the present invention, preferably, the crystallization conditions include: a crystallization temperature of 120-190°C, for example, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, or any range therebetween, preferably 150-180°C; a crystallization time of 24-96h, for example, 24h, 30h, 36h, 42h, 48h, 54h, 60h, 66h, 72h, 78h, 84h, 90h, 96h, or any range therebetween, preferably 48-72h.

[0056] In the present invention, there is no particular limitation on the crystallization equipment, as long as it can react under the above crystallization conditions, and those skilled in the art can select it as needed. According to a preferred embodiment of the present invention, the hydrothermal reaction is carried out in a reactor.

[0057] In the present invention, after the crystallization is completed, the reactor is preferably opened after the temperature is lowered (preferably to room temperature). This preferred embodiment avoids the safety hazard when opening the reactor due to the self-generated pressure in the reactor caused by the crystallization reaction at high temperature.

[0058] According to the present invention, preferably, step (3) further comprises the steps of washing, drying and calcining the crystallized product. In the present invention, the washing method is a conventional washing method in the art, and there is no particular limitation on the washing method and the washing solvent. Preferably, the crystallized product can be washed with deionized water.

[0059] In the present invention, the drying method and drying conditions are not particularly limited, and those skilled in the art can select conventional drying methods and drying conditions.

[0060] According to the present invention, preferably, the calcination conditions include: a calcination temperature of 450-800° C., preferably 500-700° C.; and a calcination time of 4-12 h, preferably 6-10 h.

[0061] The third aspect of the present invention provides a phase change composite material prepared by the preparation method described in the second aspect.

[0062] The fourth aspect of the present invention provides an application of the phase change composite material described in the first aspect or the third aspect in a petroleum catalytic cracking reaction.

[0063] According to the present invention, preferably, the conditions of the catalytic cracking reaction include: reaction temperature of 450-600°C; reaction time of 50-240s; catalyst-oil ratio of 1-5. In the present invention, the catalyst-oil ratio refers to the mass ratio of the catalyst circulation amount to the total feed amount.

[0064] In the present invention, the equipment for the catalytic cracking reaction is not particularly limited, and those skilled in the art can adaptively select suitable catalytic cracking reaction equipment, and the feed flow rate of the reaction raw materials can be adaptively adjusted according to the catalytic cracking reaction equipment, for example, the feed flow rate in a micro-reactor is 0.01-0.04 g / s.

[0065] In the present invention, the use of the above phase change composite material can effectively prevent the catalytic component from thermal deactivation during the catalytic cracking process and greatly increase its lifespan.

[0066] 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 used in the present invention are all commercially available.

[0067] Example 1

[0068] (1) Preparation of the shaping component, according to M 氢氧化铝 :M 相变芯材 :M 水 =0.5:10:400 by mass ratio, first dissolve aluminum hydroxide at 90°C, add ammonia water to adjust the pH value to 7, maintain 90°C, then add Al-12wt% Si alloy powder and stir well to carry out hydrothermal reaction for 2.5h, then further stir for 1h at 60°C for pre-precipitation to achieve sufficient coating of boehmite.

[0069] (2) Preparation of dry glue precursor: tetraethyl orthosilicate (TEOS, in terms of silicon dioxide), tetrapropylammonium hydroxide (TPAOH), water, sodium aluminate, and TEOS :N TPAOH :N 水 :N 偏铝酸钠中的Al All the raw materials were mixed in a molar ratio of 1:0.2:40:0.04, stirred at 30° C. for 2 h, and further heat treated at 85° C. for 9 h until a dry glue precursor was formed.

[0070] (3) After the dry glue precursor is fully ground, the prepared dry glue powder and the shaping component are mixed according to M 干胶粉末 :M 定形组分=1.25:1 ratio and transferred into a reactor for dry gel conversion, and crystallized at 150°C for 72h. When the reactor was cooled to room temperature, the product was centrifuged, washed, dried, and calcined at 600°C for 7h to obtain a phase change composite material.

[0071] Figure 1 is a SEM photo of the qualitative components obtained in Example 1. Figure 1 It can be seen that the prepared shaping component is fully coated; Figure 2 is a SEM photograph of the phase change composite material obtained in Example 1; Figure 3 is a partial enlarged view of the phase change composite material obtained in Example 1; Figure 2 , 3 It can be seen that the surface of the prepared phase change composite material is composed of many granular ZSM-5 zeolites; in addition, from the XRD diffraction pattern ( Figure 4 ) It can be seen that the material has obvious diffraction peaks at 2θ=7.9°, 8.8°, 23.1°, 23.9°, and 24.4°, indicating that it has a typical MFI topological structure and the outermost layer is ZSM-5 molecular sieve, further indicating that the Al-12wt%Si@Al2O3@ZSM-5 phase change composite material has been successfully constructed.

[0072] Example 2

[0073] (1) Preparation of the shaping component, according to M 氢氧化铝 :M 相变芯材 :M 水 =2:30:500 by mass ratio, first dissolve aluminum hydroxide at 87°C, add ammonia water to adjust the pH value to 9, then add tin powder and stir well to carry out hydrothermal reaction for 1.5h, then further stir and pre-precipitate at 57°C for 2.5h to achieve sufficient coating of boehmite.

[0074] (2) Preparation of dry gel precursor, according to N TEOS :N TPAOH :N 水 :N 偏铝酸钠中的Al All the raw materials were mixed in a molar ratio of 1:0.18:45:0.03, stirred at 35° C. for 4 h, and further heat treated at 95° C. for 6.5 h until a dry glue precursor was formed.

[0075] (3) After the dry glue precursor is fully ground, the prepared dry glue powder and the shaping component are mixed according to M 干胶粉末 :M 定形组分 =1:1 ratio and transferred into the reactor for dry gel conversion, and crystallized at 155°C for 68h. When the reactor was cooled to room temperature, the product was centrifuged, washed, dried, and calcined at 500°C for 8h to obtain the tin powder @ Al2O3 @ ZSM-5 phase change composite material.

[0076] Example 3

[0077] (1) Preparation of the shaping component, according to M 氢氧化铝 :M 相变芯材 :M 水 =10:50:800 by mass ratio, first dissolve aluminum hydroxide at 70°C, add ammonia water to adjust the pH value to 8, then add Al powder and stir the hydrothermal reaction for 2.75h, then further stir at 52°C for pre-precipitation for 4h to achieve sufficient coating of boehmite.

[0078] (2) Preparation of dry gel precursor according to N TEOS :N TPAOH :N 水 :N 偏铝酸钠中的Al All the raw materials were mixed in a molar ratio of 1:0.3:30:0.015, stirred at 55° C. for 2 h, and further heat treated at 82° C. for 9.5 h until a dry glue precursor was formed.

[0079] (3) After the dry glue precursor is fully ground, the prepared dry glue powder and the shaping component are mixed according to M 干胶粉末 :M 定形组分 =1.75:1 ratio and transferred into a reactor for dry gel conversion, and crystallized at 165°C for 64h. When the reactor was cooled to room temperature, the product was centrifuged, washed, dried, and calcined at 700°C for 6h to obtain Al powder @Al2O3@ZSM-5 phase change composite material.

[0080] Example 4

[0081] The method of Example 1 was used to prepare the Al-12wt% Si@Al2O3@ZSM-5 phase change composite material, except that the mass of the dry gel precursor in step (3) was adjusted so that the mass ratio of the dry gel precursor to the qualitative component was 5:1. Other conditions were the same as those of Example 1, and an Al-12wt% Si@Al2O3@ZSM-5 phase change composite material was obtained.

[0082] Example 5

[0083] The method of Example 1 was used for preparation, except that the mass of the phase change core material was adjusted so that the mass ratio of aluminum hydroxide to the phase change core material was 2:1. Other conditions were the same as those of Example 1, and an Al-12wt% Si@Al2O3@ZSM-5 phase change composite material was obtained.

[0084] Example 6

[0085] (1) Preparation of the shaping component, according to M 氢氧化铝 :M 相变芯材 :M 水=5:80:1500 by mass ratio, first dissolve aluminum hydroxide at 75°C, add ammonia water to adjust the pH value to 7.5, then add Zn-48wt% Mg alloy powder and stir the hydrothermal reaction for 2h, then further stir the pre-precipitation at 65°C for 5.5h to achieve sufficient coating of boehmite.

[0086] (2) Preparation of dry gel precursor according to N TEOS :N TPAOH :N 水 :N 偏铝酸钠中的Al All the raw materials were mixed in a molar ratio of 1:0.35:40:0.05, stirred at 45° C. for 3 h, and further heat treated at 80° C. for 10 h until a dry glue precursor was formed.

[0087] (3) After the dry glue precursor is fully ground, the prepared dry glue powder and the shaping component are mixed according to M 干胶粉末 :M 定形组分 =0.5:1 ratio and transferred into a reactor for dry gel conversion, and crystallized at 170°C for 36h. When the reactor was cooled to room temperature, the product was centrifuged, washed, dried, and calcined at 560°C for 7.5h to obtain a Zn-48wt%Mg@Al2O3@ZSM-5 phase change composite material.

[0088] Comparative Example 1

[0089] The preparation was carried out according to the method of Example 1, except that in step (1), no boehmite coating was performed, and the dry gel precursor was directly mixed with the Al-12wt% Si alloy powder for crystallization. Other conditions were the same as in Example 1 to obtain an Al-12wt% Si@Al2O3 / ZSM-5 composite material.

[0090] Test Case

[0091] The test results of the zeolite molecular sieve particle size, the phase change core material particle size, the mass percentage of the phase change core material and the silicon-aluminum molar ratio of the zeolite molecular sieve of the phase change composite material are shown in Table 1.

[0092] Table 1

[0093]

[0094] The prepared phase change composite material is used for petroleum catalytic cracking reaction, and the catalytic cracking reaction is carried out in a micro reactor. The conditions of the catalytic cracking reaction include: the amount of phase change composite material is 2.67g, the reaction temperature is 580℃; the reaction time is 70s, the agent-oil ratio is 1.70, and the feed flow rate is 0.0225g / s. The raw material is light diesel (the main component is alkane compounds, mainly including straight-chain alkanes and cycloalkanes), and the catalytic cracking reaction results are shown in Table 2.

[0095] The melting enthalpy is the melting enthalpy of the phase change composite material, which is measured by differential scanning calorimetry (DSC);

[0096] The phase transition point is the phase transition point of the phase change composite material, which is measured by differential scanning calorimetry (DSC).

[0097] Table 2

[0098]

[0099]

[0100] It can be seen from the results of Table 1 and Table 2 that the phase change materials of the embodiments of the present invention are used for petroleum catalytic cracking reactions, and the conversion rate of the reactant light diesel is higher, the melting enthalpy of the phase change composite material is higher, and it has a better energy storage-catalytic effect. The phase change composite materials of Examples 1 and 3 have higher melting enthalpy and phase change point, and the conversion rate of light diesel is high, which can effectively avoid thermal deactivation of the catalytic component during the catalytic cracking process. Example 2 uses elemental tin as the phase change core material, which has a low phase change point and can be applied to low-temperature catalytic cracking reactions to obtain a higher light diesel conversion rate.

[0101] 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, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A phase change composite material, characterized in that: The phase change composite material comprises an inner core, an intermediate layer and an outermost layer coated on the outer surface of the inner core; Among them, the inner core is a phase change core material, the middle layer is a boehmite layer, and the outermost layer is an MFI zeolite molecular sieve.

2. The composite material according to claim 1, wherein The phase change core material is selected from at least one of Al-Si alloy, Zn-Mg alloy, Mg-Si alloy, Al-Fe alloy, elemental tin, elemental magnesium and elemental aluminum; Preferably, the particle size of the zeolite molecular sieve is 100-500 nm, preferably 200-400 nm; Preferably, based on the total mass of the phase change composite material, the mass percentage of the phase change core material is 5-70wt%, preferably 25-40wt%; Preferably, the silicon-aluminum ratio of the zeolite molecular sieve is 25-500, preferably 50-100.

3. A method for preparing a phase change composite material, characterized in that: The preparation method comprises: (1) mixing an aluminum hydroxide solution with a phase change core material and performing a hydrothermal reaction to obtain a qualitative component; (2) preparing a precursor solution containing a silicon source, a template and an optional aluminum source, and performing a heat treatment to obtain a dry glue precursor; (3) Mixing and crystallizing the dry glue precursor and the qualitative components.

4. The preparation method according to claim 3, wherein The mass concentration of the aluminum hydroxide solution is 0.2-20 g / L, preferably 0.5-5 g / L; Preferably, the mass ratio of the aluminum hydroxide to the phase change core material is 0.002-10:1, preferably 0.04-1:1; Preferably, the phase change core material is selected from at least one of Al-Si alloy, Zn-Mg alloy, Mg-Si alloy, Al-Fe alloy, elemental tin, elemental magnesium and elemental aluminum; Preferably, the particle size of the phase change core material particles is 2-10 μm, preferably 5-7 μm.

5. The preparation method according to claim 3 or 4, wherein The pH value of the aluminum hydroxide solution is 6-11, preferably 7-9; Preferably, the conditions of the hydrothermal reaction include: the phase change core material mixing temperature is 40-100°C, preferably 70-100°C; the reaction time is 0.5-6h, preferably 1-3h; Preferably, the hydrothermal reaction further comprises optional pre-precipitation, and the conditions of the pre-precipitation include: reaction temperature of 40-80° C., preferably 50-70° C.; reaction time of 0-24 h, preferably 0-6 h.

6. The preparation method according to any one of claims 3 to 5, wherein: In the precursor solution, the silicon source is calculated as SiO2, the aluminum source is calculated as Al, and the molar ratio of silicon source: template: water: aluminum source is 1: (0.05-0.5): (10-120): (0-0.1), preferably 1: (0.15-0.35): (25-50): (0.015-0.065); Preferably, the template is tetrapropylammonium hydroxide and / or tetrapropylammonium bromide, preferably tetrapropylammonium hydroxide; Preferably, the silicon source is selected from at least one of tetraethyl orthosilicate, water glass and silica sol; Preferably, the aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum chloride and aluminum isopropoxide.

7. The preparation method according to any one of claims 3 to 6, wherein: The preparation of the precursor solution includes: a mixing time of 1-6 hours and a mixing temperature of 20-60° C.; Preferably, the heat treatment conditions include: heat treatment temperature of 70-120°C, preferably 80-100°C; heat treatment time of 4-12h, preferably 6-10h.

8. The preparation method according to any one of claims 3 to 7, wherein: In step (3), the mass ratio of the dry gel precursor to the qualitative component is 0.05-10:1, preferably 0.5-2:1; Preferably, the crystallization conditions include: a crystallization temperature of 120-190° C., preferably 150-180° C.; a crystallization time of 24-96 h, preferably 48-72 h; Preferably, step (3) further comprises the steps of washing, drying and calcining the crystallized product; Preferably, the calcination conditions include: a calcination temperature of 450-800° C., preferably 500-700° C.; and a calcination time of 4-12 h, preferably 6-10 h.

9. The phase change composite material obtained by the preparation method according to any one of claims 3 to 8.

10. Use of the phase change composite material according to any one of claims 1 to 2 and 9 in petroleum catalytic cracking reaction; Preferably, the conditions of the catalytic cracking reaction include: The reaction temperature is 450-600°C; the reaction time is 50-240s; The agent-oil ratio is 1-5.

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