Phase change composites, methods of making and using the same

Abstract

The application relates to the field of composite materials, and discloses a phase change composite material as well as a preparation method and application thereof. The phase change composite material comprises a core, an intermediate layer coated on the outer surface of the core and an outermost layer. The core is a phase change core material, the intermediate layer is a boehmite layer, and the outermost layer is an MFI zeolite molecular sieve. The phase change composite material introduces boehmite as a shell layer for coating the phase change core material, prevents leakage of the core material, simultaneously serves as an aluminum source for preparing the MFI zeolite molecular sieve through vapor-assisted crystallization, provides nucleation sites 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 application relates to the field of composite materials, in particular to a phase change composite material and a preparation method and application thereof. BACKGROUND

[0002] Catalytic cracking reaction (FCC) is often accompanied by strong endothermic / exothermic effect, which usually leads to uneven temperature distribution of catalyst bed, local hot spots and other problems. In addition, in order to maximize production efficiency, the reaction system is usually operated at a high temperature, and in this case the hot spot temperature of the catalyst layer is close to the unstable range, and a slight disturbance of the working condition will cause thermal runaway, deactivation and other problems, resulting in changes in product distribution, reduction of catalyst activity and service life, and a series of problems, which will further affect the economic benefits of industrial production. Therefore, efficient control of catalyst bed temperature is crucial for the efficient and stable operation of catalytic reaction devices.

[0003] Phase change material (PCM) is a kind of functional material that can store or release heat energy efficiently by changing its own state without changing temperature, so it is widely used in energy storage and temperature regulation fields. According to the chemical composition of the material, PCM can be generally divided into organic PCM and inorganic PCM. Organic PCM covers a wide range, including paraffin, fatty acid and eutectic mixture, ester, sugar and sugar alcohol, and other organic compounds. However, their thermal conductivity is generally low, and they are prone to leakage and volatilization during use. Compared with organic PCM, inorganic PCM often has higher volumetric heat storage density, and mainly includes hydrated salt, molten salt, metal and alloy. For salt, there are inherent shortcomings such as large molten volume expansion, large supercooling degree and easy phase separation, which greatly limit its practical application. Metals and alloys have good thermal stability and small volume change when melting, and are good energy storage materials. More importantly, their phase change temperature is consistent with the required temperature of catalytic cracking reaction, and they can be used as functional components to control the local temperature of the catalyst bed. However, in order to prevent the leakage of metals and alloys during phase change, they also need to be encapsulated.

[0004] As crystalline aluminosilicates with high thermal stability, high hydrothermal stability, adjustable pore structure and other advantages, zeolite molecular sieves are widely used in ion exchange, catalysis and adsorption and other industrial fields. In the aspect of catalytic application, the special framework structure and rich micropore composition of zeolite molecular sieve ZSM-5 make it have high specific surface area, corrosion resistance and cycle stability, and show excellent application value. However, in order to apply the phase change core material to the FCC process, the combination mode of the phase change core material and the zeolite catalyst must be considered, and the traditional physical mixing is easy to cause the energy storage area to not play a good role. Therefore, how to retain the high heat storage performance of the phase change core material after encapsulation, how to realize the efficient assembly of the active components of the zeolite and the energy storage components after encapsulation, improve the service life of the catalyst, and apply it to the FCC field are the technical problems to be solved at present. SUMMARY

[0005] The purpose of the present application is to overcome the problems of the prior art that the metal and alloy phase change heat storage materials are easy to leak in the phase change process, the phase change performance is easy to deteriorate after encapsulation, and how to fully apply the energy storage components to the field of catalytic cracking. A phase change composite material, a preparation method and application thereof are provided. The phase change composite material introduces boehmite as a shell layer for encapsulating the phase change core material, prevents the core material from leaking, and simultaneously serves as an aluminum source for preparing MFI zeolite molecular sieves by steam-assisted crystallization, thereby providing nucleation sites for in-situ growth of the 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 purpose, the first aspect of the present application provides a phase change composite material, wherein the phase change composite material comprises a core, an intermediate layer and an outermost layer which are encapsulated on the outer surface of the core.

[0007] The core is a phase change core material, the intermediate layer is a boehmite layer, and the outermost layer is an MFI zeolite molecular sieve.

[0008] The second aspect of the present application provides a preparation method of the 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 agent and an optional aluminum source, and performing a heat treatment to obtain a dry gel precursor;

[0011] (3) mixing the dry gel precursor with the qualitative component and crystallizing.

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

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

[0014] Through the technical solution, the following beneficial effects are obtained:

[0015] (1) The phase change composite material provided by the present application introduces boehmite as a shell layer covering the phase change core material, preventing the core material from leaking, and simultaneously providing a nucleation site for the in-situ growth of zeolite molecular sieves as an aluminum source for the vapor-assisted crystallization of MFI 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 application grows zeolite catalysts for catalytic cracking reactions in-situ on the surface of the phase change core material through a vapor-assisted crystallization process. The operation is simple, the reaction conditions are mild, and the product parameters are controllable. The synthesized catalytic-thermal storage integrated material can be applied in the field of FCC catalytic cracking reactions.

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

[0018] Figure 1 is an SEM photo of the qualitative component obtained in Example 1;

[0019] Figure 2 is an SEM photo 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 an XRD spectrum of the phase change composite material obtained in Example 1. DETAILED DESCRIPTION

[0022] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The exact numerical values of the endpoints of the ranges and the separate points are not to be construed as being precise values by themselves, but are understood to be used in a merely illustrative sense. The ranges of numerical values include all values from and including the lower and upper numerical values of the range, as well as in the particular midpoint falling within the range. Any numerical value, however, can only be achieved with the exact numerical values by itself, but is understood to be used in a merely illustrative sense.

[0023] The first aspect of the present application provides a phase change composite material, wherein the phase change composite material comprises an inner core, an intermediate layer covering the outer surface of the inner core, and an outermost layer.

[0024] 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 provided by the application has a boehmite layer (AlOOH) coated on the phase change core material, and a zeolite molecular sieve is in-situ grown on the boehmite layer, so that the phase change composite has catalytic performance and energy storage performance, can improve the service life of a catalyst, ensure stable operation of a reactor, improve energy utilization efficiency, optimize a catalytic cracking process, and improve catalytic cracking efficiency.

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

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

[0028] In the application, the phase change core material described above is used. Since metals and alloys have the advantages of high energy storage density, small volume change during melting, good thermal stability, and high thermal conductivity, when the catalytic cracking reaction has a relatively high system temperature (generally higher than 500℃), only the phase change point of the metal and alloy core material can meet the requirement for the phase change point of the catalyst. The metal and alloy show good prospects in solving the problems of non-uniform bed temperature and heat dissipation in the catalytic reaction process.

[0029] According to the application, preferably, the particle size of the zeolite molecular sieve is 100-500 nm, for example, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, or 500 nm, or any range between any two of them, and preferably 200-400 nm. In the application, the particle size of the MFI zeolite molecular sieve in the outermost layer is observed by a scanning electron microscope. During the measurement process, the particle sizes of at least twenty zeolite molecular sieve grains are randomly selected and measured. In the application, the particle size has the conventional interpretation in the art, which refers to the size of a particle. If the particle is a spherical particle, it refers to the diameter of the sphere. If the particle is an irregular particle, it refers to the maximum straight-line distance in the particle.

[0030] According to the present invention, preferably, the mass percentage of the phase change core material, based on the total mass of the phase change composite material, is 5-70 wt%, for example, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 60 wt%, 70 wt%, or any range between the two, preferably 25-40 wt%. The mass percentage of the phase change core material is obtained by differential scanning calorimetry (DSC), measuring the phase change enthalpy of the phase change composite material and the phase change enthalpy of the pure alloy, respectively. The value of the mass percentage of the phase change core material is equal to 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 Si / Al molar ratio of the outermost MFI zeolite molecular sieve is in the range of 25-500, for example, 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 this invention, the Si / Al ratio of the outermost MFI zeolite molecular sieve is obtained by preparing a zeolite molecular sieve separately and determining the Si / Al ratio. 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 Si / Al ratio of the zeolite molecular sieve is determined by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0032] In this invention, the XRD diffraction pattern of the phase change composite material is used ( 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 topology. The zeolite molecular sieve with MFI structure is generated in situ grown on the surface of the phase change composite material.

[0033] In this invention, a boehmite layer is fully coated on the surface of the phase change core material to prevent core material leakage. The boehmite layer also provides an aluminum source for the crystallization and formation of zeolite molecular sieves. Zeolite molecular sieves, as highly crystalline aluminosilicates, possess advantages such as high thermal stability, high hydrothermal stability, and tunable pore structure, making them suitable for industrial applications such as ion exchange, catalysis, and adsorption. In catalytic applications, the MFI structure, especially the unique framework structure and abundant microporous composition of ZSM-5, gives it 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 includes:

[0035] (1) Mix aluminum hydroxide solution with phase change core material and carry out hydrothermal reaction to obtain qualitative components;

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

[0037] (3) mixing the dry gel precursor with a shape-determining component and crystallizing.

[0038] In the present application, the shape-determining component is prepared by coating the phase change core material with boehmite, and the zeolite molecular sieve is in-situ grown on the surface of the shape-determining component. The MFI-type zeolite molecular sieve is synthesized by using the steam-assisted crystallization (SAC) process, and the preparation process is simple, and the in-situ growth of the zeolite particles on the surface of the shape-determining component of the phase change material can be directly realized.

[0039] According to the present application, preferably, the mass concentration of the aluminum hydroxide solution is 0.2-20 g / L, for example, 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 between any two of them, preferably 0.5-5 g / L. In the present application, the preparation method of the aluminum hydroxide solution is not particularly limited, and preferably, the aluminum hydroxide is dissolved in water at a temperature of 25-120 ℃ to achieve uniform dissolution.

[0040] According to the present application, preferably, the mass ratio of the aluminum hydroxide to the phase change core material is 0.002-10:1, for example, 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 any two of them, preferably 0.04-1:1, and more preferably 0.04-0.5:1. The addition of the aluminum hydroxide and the phase change core material in the above mass ratio can fully coat the phase change core material with the aluminum hydroxide, and avoid the leakage of the core material. An excessively thick shell layer will result in a low core material loading rate, and further result in a low or even poor phase change performance.

[0041] According to the present application, preferably, the phase change core material is at least one selected from the group consisting of Al-Si alloy, Zn-Mg alloy, Mg-Si alloy, Al-Fe alloy, elemental tin, elemental magnesium and elemental aluminum, and preferably at least one selected from the group consisting of Al-Si alloy, elemental tin and elemental aluminum. In the present application, the phase change core material is an alloy and / or metal capable of forming a corresponding hydroxide in hot water, and the formed hydroxide and the aluminum hydroxide together form a coating for the phase change core material, avoiding the leakage of the phase change core material.

[0042] According to the present application, preferably, the particle size of the phase change core material particles is 2-10 μm, preferably 5-7 μm. In the present application, 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 meeting the particle size limit can be prepared by grinding. In the present application, the particle size of the phase change core material particles is tested by scanning electron microscopy (SEM). During the measurement, the particle sizes of twenty phase change core material particles are randomly measured and averaged.

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

[0044] In the present application, preferably, the pH value of the aluminum hydroxide solution is adjusted by adding ammonia water. The amount of ammonia water added is not particularly limited, as long as the pH value of the aluminum hydroxide solution meets the range of 6-11.

[0045] According to the present application, preferably, the conditions of the hydrothermal reaction include: the phase change core material mixing temperature is 40-100℃, for example 40℃, 50℃, 60℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, or any range between any two of them, preferably 70-100℃; the reaction time is 0.5-6h, preferably 1-3h. In the present application, under the above conditions, the hydrothermal reaction realizes full coverage 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 application, preferably, after the hydrothermal reaction, pre-precipitation is optionally performed, and the conditions of the pre-precipitation include: the reaction temperature is 40-80℃, preferably 50-70℃; the reaction time is 0-24h, preferably 0-6h.

[0047] According to the present application, in the precursor solution, the molar ratio of the silicon source (calculated as SiO2), the aluminum source (calculated as Al), the template agent, water and the 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 application, the template agent is a common template agent required for the preparation of MFI zeolite molecular sieve. Preferably, the template agent is tetrapropylammonium hydroxide and / or tetrapropylammonium bromide, preferably tetrapropylammonium hydroxide.

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

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

[0051] According to the present application, the preparation method of the precursor solution is not limited, and the silicon source, the template agent and the aluminum source are mixed uniformly. Preferably, the preparation of the precursor solution comprises: mixing time of 1-6h, mixing temperature of 20-60℃. Preferably, the precursor solution is prepared under stirring, and the stirring rate is not particularly limited.

[0052] According to the present application, preferably, the heat treatment conditions comprise: heat treatment temperature of 70-120℃, for example 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, or any range between any two of them, preferably 80-100℃; heat treatment time of 4-12h, for example 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, or any range between any two of them, preferably 6-10h. In the present application, the dry gel precursor is obtained by heat treatment under the above conditions, which is used for subsequent mixing with the qualitative component for crystallization.

[0053] In the present application, preferably, the process further comprises drying and sufficiently grinding the heat treatment product to obtain the dry gel precursor in powder form. The dry gel precursor is ground into powder and mixed uniformly 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. Avoiding directly adding the qualitative component to the precursor solution, the generated zeolite molecular sieve and the encapsulated core material exist independently, and cannot be coated on the surface of the qualitative component.

[0054] According to the present application, preferably, in step (3), the mass ratio of the dry gel precursor to the qualitative component is 0.05-10:1, for example, 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 any two of them, preferably 0.5-2:1. The dry gel precursor is mixed with the qualitative component in the above-mentioned ratio, and then subjected to a crystallization reaction, so that the MFI structure zeolite molecular sieve is in-situ grown on the surface of the qualitative component, which can further fully coat the qualitative component. The synthesis process is simple in operation, mild in conditions, and controllable in parameters.

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

[0056] In the present application, the equipment for the crystallization is not particularly limited, as long as it can perform the reaction under the above-mentioned crystallization conditions, and a person skilled in the art can select as needed. According to a preferred embodiment of the present application, the hydrothermal reaction is performed in a reaction kettle.

[0057] In the present application, preferably, after the crystallization is completed, the reaction kettle is cooled (preferably to room temperature) and then opened. The preferred embodiment avoids the safety hazard of opening the kettle when there is autogenous pressure in the kettle due to the crystallization reaction at high temperature.

[0058] According to the present application, preferably, step (3) further includes the steps of washing, drying and calcining the crystallization product. In the present application, the washing method is a conventional washing method in the art, and the washing method and the washing solvent are not particularly limited, and preferably, the crystallization product can be washed with deionized water.

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

[0060] According to the present application, preferably, the calcination conditions include: the calcination temperature is 450-800℃, preferably 500-700℃; the calcination time is 4-12h, preferably 6-10h.

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

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

[0063] According to the present application, preferably, the conditions of the catalytic cracking reaction include: reaction temperature of 450-600℃; reaction time of 50-240s; and catalyst to oil ratio of 1-5. In the present application, the catalyst to oil ratio refers to the mass ratio of the amount of catalyst circulating to the total amount of feedstock.

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

[0065] In the present application, the use of the above phase change composite material can effectively avoid thermal deactivation of the catalytic component during the catalytic cracking process, and greatly improve the service life.

[0066] The present application 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 application are commercially available.

[0067] Example 1

[0068] (1) Preparation of the shape-fixing component, according to M 氢氧化铝 : M 相变芯材 : M 水 = 0.5:10:400 by mass ratio, first complete the dissolution of aluminum hydroxide at a temperature of 90℃, and then add ammonia water to adjust the pH value to 7, keep 90℃, then add Al-12wt%Si alloy powder to stir fully and carry out hydrothermal reaction for 2.5h, then further stir at a temperature of 60℃ for 1h for pre-precipitation to achieve full coating of boehmite.

[0069] (2) Preparation of the dry gel precursor, tetraethyl orthosilicate (TEOS, calculated as silicon dioxide), tetrapropylammonium hydroxide (TPAOH), water, and sodium aluminate are mixed according to N TEOS : N TPAOH : N 水 : N 偏铝酸钠中的Al = 1:0.2:40:0.04, mix all raw materials, stir at 30℃ for 2h, and further heat treat at a temperature of 85℃ for 9h until the dry gel precursor is formed.

[0070] (3) After the dry gel precursor is fully ground, the prepared dry gel powder and the shape-fixing component are mixed according to M 干胶粉末 : M 定形组分= 1.25:1 were mixed and moved into the reactor for dry gel conversion, and crystallized at 150℃ for 72h. After the reactor was cooled to room temperature, the product was sequentially subjected to centrifugation, washing, drying, and calcination at 600℃ for 7h to obtain the phase change composite material.

[0071] Figure 1 is the SEM photo of the qualitative component obtained in Example 1, which shows that the prepared qualitative component is fully coated. Figure 1 Figure 2 is the SEM photo of the phase change composite material obtained in Example 1. Figure 3 is the partial enlarged view of the phase change composite material obtained in Example 1, which shows that the surface of the prepared phase change composite material is composed of many granular ZSM-5 zeolites. Figure 2 3 Figure 4 , it can be seen that the material has obvious diffraction peaks at 2θ = 7.9°, 8.8°, 23.1°, 23.9°, 24.4°, indicating a typical MFI topology structure, and the outermost layer is ZSM-5 zeolite, further indicating that the Al-12wt%Si@Al2O3@ZSM-5 phase change composite material is successfully constructed.

[0072] Example 2

[0073] (1) Preparation of the shaped component, according to M 氢氧化铝 : M 相变芯材 : M 水 = 2:30:500 by mass ratio, first complete aluminum hydroxide dissolution at a temperature of 87℃, and then add ammonia water to adjust the pH value to 9, and then add tin powder to stir thoroughly for hydrothermal reaction for 1.5h, and then further stir at a temperature of 57℃ for 2.5h to achieve full coating of boehmite.

[0074] (2) Preparation of the dry gel precursor, according to N TEOS : N TPAOH : N 水 : N 偏铝酸钠中的Al = 1:0.18:45:0.03, mix all raw materials, stir at 35℃ for 4h, and further heat treat at a temperature of 95℃ for 6.5h until the dry gel precursor is formed.

[0075] (3) After the dry gel precursor is fully ground, mix the prepared dry gel powder with the shaped component according to M 干胶粉末 : M 定形组分 = 1:1, and move into the reactor for dry gel conversion, and crystallize at 155℃ for 68h. After the reactor is cooled to room temperature, the product is sequentially subjected to centrifugation, washing, drying, and calcination at 500℃ for 8h to obtain the tin powder@Al2O3@ZSM-5 phase change composite material.​​​

[0076] Example 3

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

[0078] (2) Preparation of the dry gel precursor, according to N TEOS :N TPAOH :N 水 :N 偏铝酸钠中的Al = 1:0.3:30:0.015, mix all raw materials, stir at 55°C for 2 h, and further heat treat at a temperature of 82°C for 9.5 h until the dry gel precursor is formed.

[0079] (3) After the dry gel precursor is fully ground, mix the prepared dry gel powder with the shape-fixing component according to M 干胶粉末 :M 定形组分 = 1.75:1 and move into the reaction kettle for dry gel conversion, and crystallize at 165°C for 64 h. After the reaction kettle is cooled to room temperature, the product is sequentially subjected to centrifugation, washing, drying, and calcination at 700°C for 6 h to obtain the Al powder@Al2O3@ZSM-5 phase change composite material.

[0080] Example 4

[0081] According to the method of Example 1, except that the mass of the dry gel precursor in step (3) is adjusted so that the mass ratio of the dry gel precursor to the shape-fixing component is 5:1, and other conditions are the same as in Example 1, an Al-12wt%Si@Al2O3@ZSM-5 phase change composite material is prepared.

[0082] Example 5

[0083] According to the method of Example 1, except that the mass of the phase change core material is adjusted so that the mass ratio of aluminum hydroxide to the phase change core material is 2:1, and other conditions are the same as in Example 1, an Al-12wt%Si@Al2O3@ZSM-5 phase change composite material is prepared.

[0084] Example 6

[0085] (1) Preparation of the shape-fixing component, according to M 氢氧化铝 :M 相变芯材 :M 水= 5:80:1500 mass ratio, first complete aluminum hydroxide dissolution at a temperature of 75°C, and then add ammonia water to adjust the pH value to 7.5, and then add Zn-48wt% Mg alloy powder to stir and hydrothermal reaction for 2h, and then further stir the pre-precipitate at a temperature of 65°C for 5.5h to achieve full 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 = 1:0.35:40:0.05 molar ratio, stirring at 45°C for 3h, and further heat treatment at a temperature of 80°C for 10h until the dry gel precursor is formed.

[0087] (3) After the dry gel precursor is fully ground, the prepared dry gel powder is mixed with the shaping component according to M 干胶粉末 : M 定形组分 = 0.5:1 ratio and moved into the reaction kettle for dry gel conversion, and crystallization at 170°C for 36h. After the reaction kettle is cooled to room temperature, the product is sequentially subjected to centrifugation, washing, drying, and calcination at 560°C for 7.5h to obtain the Zn-48wt% Mg@Al2O3@ZSM-5 phase change composite material.

[0088] Comparative Example 1

[0089] Prepared according to the method of Example 1, except that step (1) does not coat boehmite, and the dry gel precursor is directly mixed with Al-12wt% Si alloy powder for crystallization, and other conditions are the same as in Example 1, to obtain an Al-12wt% Si@Al2O3 / ZSM-5 composite material.

[0090] Test Example

[0091] The test results of the zeolite molecular sieve particle size, phase change core material particle size, mass percentage content of the phase change core material, and the molar ratio of silicon to aluminum 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-reaction device. The conditions of the catalytic cracking reaction include: the amount of phase change composite material is 2.67g, the reaction temperature is 580°C, the reaction time is 70s, the catalyst to oil ratio is 1.70, and the feed flow rate is 0.0225g / s. The raw material is light diesel oil (mainly composed of alkane compounds, mainly including straight-chain alkanes and naphthenes), and the catalytic cracking reaction results are shown in Table 2.

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

[0096] The phase change point is the phase change point of the phase change composite, measured by a differential scanning calorimeter (DSC).

[0097] Table 2

[0098]

[0099]

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

[0101] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and belong to the protection scope of the present application.

Claims

1. A method for preparing a phase change composite material, characterized in that, The preparation method includes: (1) Mix aluminum hydroxide solution with phase change core material and carry out hydrothermal reaction to obtain qualitative components; (2) Prepare a precursor solution containing a silicon source, a template agent and an optional aluminum source, and perform heat treatment to obtain a dry glue precursor; (3) The dry gel precursor is mixed with the qualitative component and crystallized to obtain a phase change composite material with MFI zeolite molecular sieve as the outermost layer; Step (3) also includes washing, drying and calcining the crystallized product; 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; The mass ratio of aluminum hydroxide to phase change core material is 0.002-10:

1.

2. The preparation method according to claim 1, wherein, The mass concentration of the aluminum hydroxide solution is 0.2-20 g / L.

3. The preparation method according to claim 2, wherein, The mass concentration of the aluminum hydroxide solution is 0.5-5 g / L.

4. The preparation method according to claim 1, wherein, The mass ratio of aluminum hydroxide to phase change core material is 0.04-1:

1.

5. The preparation method according to claim 1, wherein, The particle size of the phase change core material particles is 2-10 μm.

6. The preparation method according to claim 5, wherein, The particle size of the phase change core material particles is 5-7 μm.

7. The preparation method according to claim 1, wherein, The pH value of the aluminum hydroxide solution is 6-11; And / or, the conditions for the hydrothermal reaction include: a phase change core material mixing temperature of 40-100℃; and a reaction time of 0.5-6h.

8. The preparation method according to claim 7, wherein, The pH value of the aluminum hydroxide solution is 7-9; And / or, the conditions for the hydrothermal reaction include: a phase change core material mixing temperature of 70-100℃; and a reaction time of 1-3 h.

9. The preparation method according to claim 1, wherein, The hydrothermal reaction is followed by optional pre-precipitation, wherein the pre-precipitation conditions include: a reaction temperature of 40-80℃ and a reaction time of 1-24 h.

10. The preparation method according to claim 9, wherein, The pre-precipitation conditions include: a reaction temperature of 50-70℃ and a reaction time of 1-6h.

11. The preparation method according to claim 1, 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:templating agent:water:aluminum source is 1:(0.05-0.5):(10-120):(0-0.1).

12. The preparation method according to claim 11, 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:templating agent:water:aluminum source is 1:(0.15-0.35):(25-50):(0.015-0.065).

13. The preparation method according to claim 11, wherein, The template agent is tetrapropylammonium hydroxide and / or tetrapropylammonium bromide; And / or, the silicon source is selected from at least one of tetraethyl orthosilicate, water glass, and silica sol; And / or, the aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum chloride, and aluminum isopropoxide.

14. The preparation method according to claim 13, wherein, The template agent is tetrapropylammonium hydroxide.

15. The preparation method according to claim 1, wherein, The preparation of the precursor solution includes: mixing time of 1-6 hours and mixing temperature of 20-60℃.

16. The preparation method according to claim 1, wherein, The heat treatment conditions include: a heat treatment temperature of 70-120℃ and a heat treatment time of 4-12h.

17. The preparation method according to claim 16, wherein, The heat treatment conditions include: a heat treatment temperature of 80-100℃ and a heat treatment time of 6-10h.

18. The preparation method according to claim 1, wherein, In step (3), the mass ratio of the dry gel precursor to the qualitative component is 0.05-10:

1.

19. The preparation method according to claim 18, wherein, In step (3), the mass ratio of the dry gel precursor to the qualitative component is 0.5-2:

1.

20. The preparation method according to claim 1, wherein, The crystallization conditions include: a crystallization temperature of 120-190℃ and a crystallization time of 24-96 h.

21. The preparation method according to claim 20, wherein, The crystallization conditions include: a crystallization temperature of 150-180℃ and a crystallization time of 48-72 h.

22. The preparation method according to claim 1, wherein, The calcination conditions include: a calcination temperature of 450-800℃ and a calcination time of 4-12 hours.

23. The preparation method according to claim 22, wherein, The calcination conditions include: a calcination temperature of 500-700℃ and a calcination time of 6-10 hours.

24. The phase change composite material prepared by the preparation method according to any one of claims 1-23.

25. The phase change composite material according to claim 24, wherein, The zeolite molecular sieve in the phase change composite material has a particle size of 100-500 nm.

26. The phase change composite material according to claim 25, wherein, The zeolite molecular sieve in the phase change composite material has a particle size of 200-400 nm.

27. The phase change composite material according to claim 24, wherein, The phase change core material has a mass percentage of 5-70 wt% based on the total mass of the phase change composite material.

28. The phase change composite material according to claim 27, wherein, The phase change core material has a mass percentage of 25-40 wt% based on the total mass of the phase change composite material.

29. The phase change composite material according to claim 24, wherein, The Si / Al molar ratio of the zeolite molecular sieve in the phase change composite material is 25-500.

30. The phase change composite material according to claim 29, wherein, The Si / Al molar ratio of the zeolite molecular sieve in the phase change composite material is 50-100.

31. The application of the phase change composite material prepared by the preparation method according to any one of claims 1-23 in petroleum catalytic cracking reaction.

32. The application according to claim 31, wherein, The conditions for the catalytic cracking reaction include: a reaction temperature of 450-600℃; a reaction time of 50-240s; and a catalyst-to-oil ratio of 1-5.

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