阅读说明：本技术 一种改性硅藻土基多孔相变材料的制备方法 (Preparation method of modified diatomite-based porous phase change material ) 是由 杨英英 赵玉刚 武卫东 凌沁宜 杨其国 任燕 杨果成 杨永飞 于 2021-09-30 设计创作，主要内容包括：本发明公开了一种改性硅藻土基多孔相变材料的制备方法,包括以下步骤：步骤1,对硅藻土进行酸改,按照盐酸：硅藻土为3:5向硅藻土中加入1～3mol/L的盐酸溶液,置于30～70℃的恒温水浴中反应30～90min,反应完成后洗涤、抽滤、干燥得到酸改硅藻土；步骤2,对酸改硅藻土进行盐改,酸改硅藻土与盐溶液按照1:5的质量比混合,在恒温水浴30～60℃下反应20～40min,待反应完成后静置,倒去上层清液,抽滤废液,干燥时间大于24h,即得改性硅藻土；步骤3,将改性硅藻土和相变材料通过真空吸附法进行混合,制备成改性硅藻土基多孔相变材料；本发明还公开了一种利用本发明的方法制备的改性硅藻土基多孔相变材料,该材料同时具备良好的储热和吸湿性能,可用于建筑领域,降低建筑的能源消耗。(The invention discloses a preparation method of a modified diatomite-based porous phase change material, which comprises the following steps: step 1, carrying out acid modification on diatomite according to the following hydrochloric acid: adding 1-3 mol/L hydrochloric acid solution into diatomite 3:5, placing the diatomite in a constant-temperature water bath at 30-70 ℃ for reaction for 30-90 min, and washing, filtering and drying the diatomite after the reaction is finished to obtain acid-modified diatomite; step 2, performing salt modification on the acid-modified diatomite, mixing the acid-modified diatomite and a salt solution according to a mass ratio of 1:5, reacting for 20-40 min in a constant-temperature water bath at 30-60 ℃, standing after the reaction is completed, pouring out supernatant, performing suction filtration on waste liquid, and drying for more than 24 hours to obtain modified diatomite; step 3, mixing the modified diatomite and the phase change material by a vacuum adsorption method to prepare a modified diatomite-based porous phase change material; the invention also discloses the modified diatomite-based porous phase change material prepared by the method, which has good heat storage and moisture absorption properties, can be used in the field of buildings and reduces the energy consumption of the buildings.)

1. The preparation method of the modified diatomite-based porous phase change material is characterized by comprising the following steps of:

step 1, carrying out acid modification on diatomite according to the following hydrochloric acid: adding 1-3 mol/L hydrochloric acid solution into diatomite according to the proportion of 3:5, placing the diatomite in a constant-temperature water bath at 30-70 ℃ for reaction for 30-90 min, and washing, filtering and drying the diatomite after the reaction is finished to obtain acid-modified diatomite;

step 2, performing salt modification on the acid-modified diatomite, mixing the acid-modified diatomite and a salt solution according to a mass ratio of 1:5, reacting for 20-40 min in a constant-temperature water bath at 30-60 ℃, standing after the reaction is completed, pouring out supernatant, performing suction filtration on waste liquid, and drying for more than 24 hours to obtain modified diatomite;

step 3, mixing the modified diatomite and the phase change material by a vacuum adsorption method to prepare a modified diatomite-based porous phase change material,

in the step 2, the salt solution comprises CaCl₂、MgCl₂And one or more of a NaCl solution.

2. The method for preparing the modified diatomite-based porous phase change material according to claim 1, wherein the method comprises the following steps:

in the step 1, the optimal acid-modifying condition of acid modification is that the concentration of hydrochloric acid is 1mol/L, the reaction temperature is 70 ℃, the reaction time is 60min, and the acid-soil ratio is 4: 1.

3. The preparation method of the modified diatomite-based porous phase change material according to claim 1, wherein the preparation method comprises the following steps:

in the step 2, the optimal salt-modifying condition of the salt-modifying is 20 wt% of NaCl solution, the reaction temperature is 60 ℃, the reaction time is 30min, and the salt-soil ratio is 5: 1.

4. The preparation method of the modified diatomite-based porous phase change material according to claim 1, wherein the preparation method comprises the following steps:

in the step 3, the vacuum degree of the vacuum adsorption method is-0.08 MPa, the suction filtration time is 1h, and the vacuum adsorption method is heated and melted in a thermostatic water bath at 60 ℃.

5. The preparation method of the modified diatomite-based porous phase change material according to claim 2, wherein the preparation method comprises the following steps:

the optimal acid-modifying condition is determined based on the adsorption rate of the acid-modified diatomite to the phase change material, the condition when the adsorption rate is maximum is the optimal acid-modifying condition,

the calculation formula of the adsorption rate is as follows:

in the formula, m_pcmMass (kg) of the phase change material adsorbed)，m_diatomiteThe mass (kg) of the diatomite matrix, h_comThe phase change latent heat (kJ/kg), h of the composite phase change temperature and humidity regulating material_pcmIs the latent heat of phase change (kJ/kg) of the phase change material.

6. The method for preparing the modified diatomite-based porous phase change material according to claim 3, wherein:

the optimal salt modification condition is judged based on the phase change temperature and the phase change latent heat value of the modified diatomite-based porous phase change material, and the condition when the phase change temperature and the phase change latent heat value of the modified diatomite-based porous phase change material are optimal is the optimal salt modification condition.

7. A modified diatomite-based porous phase change material is characterized in that:

the modified diatomite-based porous phase change material is the modified diatomite-based porous phase change material as claimed in any one of claims 1-6.

Technical Field

The invention relates to the field of phase-change material preparation, in particular to a preparation method of a modified diatomite-based porous phase-change material.

Background

The phase change material has the characteristic of absorbing and releasing a large amount of energy through the change of its own phase state, and the temperature is substantially kept constant when the phase change occurs. The liquid phase-change material can be absorbed in pores by using a porous substance as a carrier to prepare the shaped phase-change material. Because the porous material has larger porosity and specific surface area, the heat storage capacity of the base material can be effectively improved by adsorbing and shaping the phase-change material.

The porous inorganic mineral humidity-controlling material in the moisture-absorbing material has the excellent properties of uniform permeability, high temperature resistance, corrosion resistance and the like. And the moisture absorption and release speed is high, the lag is small, the paint is nontoxic and harmless to human bodies and the environment, the production process is simple, the manufacturing cost is low, and the service life is long.

The composite material has heat storage and moisture absorption performances, can inhibit indoor temperature fluctuation caused by day and night temperature difference, plays roles in clipping peaks and delaying air conditioning load, reduces the demand of a building on electric energy, and simultaneously relieves the influence of outdoor environment humidity fluctuation on indoor environment relative humidity, thereby reducing building humidity load and air conditioning latent heat load.

Diatomite is a common porous material and is made of ancient timesRemains of diatom and mainly comprises amorphous SiO₂And contains a small amount of impurity Al₂O₃、Fe₂O₃、K₂O and various organic substances. Has the characteristics of looseness, porosity, small density, large specific surface area and the like, and the specific surface area is about 35-68 m²The water absorption rate can reach 1.4-4.2 times of the volume per se. The adsorption effect on water molecules is mainly capillary channel effect and surface chemical adsorption, and then surface physical adsorption. Therefore, the diatomite is a good carrier for adsorbing the phase change material, has excellent moisture absorption capacity and is a good porous humidity-controlling material.

The porous phase change material prepared by taking the diatomite as the matrix has heat storage and moisture absorption performances, is an excellent building material, can reduce the building energy consumption, achieves the building energy-saving effect, and has great practical application potential and value. The adsorption characteristics of diatomaceous earth are closely related to its pore structure (physical structure and chemical structure), generally the larger the specific surface area the greater the adsorption capacity; the larger the pore size, the greater the diffusion rate of the adsorbate in the pore size, which is more favorable for achieving adsorption equilibrium. However, metal oxide and organic impurities still exist on the surface of the diatomite, and the existence of the impurities changes the chemical properties of the surface of the diatomite. The chemical activity of the diatomite is reduced because the impurities occupy the active sites on the surface of the diatomite. Therefore, the diatomite needs to be modified to improve the porosity and adsorption rate.

At present, some diatomite modification related technologies exist, but only the moisture absorption performance of diatomite is considered in the modification process, and the adsorption capacity and the heat storage performance of the diatomite on a phase change material are not considered.

Disclosure of Invention

The present invention is made to solve the above problems, and an object of the present invention is to provide a method for preparing a modified diatomite-based porous phase change material.

The invention provides a preparation method of a modified diatomite-based porous phase change material, which is characterized by comprising the following steps:

step 1, carrying out acid modification on diatomite according to the following hydrochloric acid: adding 1-3 mol/L hydrochloric acid solution into diatomite according to the proportion of 3:5, placing the diatomite in a constant-temperature water bath at 30-70 ℃ for reaction for 30-90 min, and washing, filtering and drying the diatomite after the reaction is finished to obtain the acid-modified diatomite.

And 2, performing salt modification on the acid-modified diatomite, mixing the acid-modified diatomite and a salt solution according to a mass ratio of 1:5, reacting for 20-40 min in a constant-temperature water bath at 30-60 ℃, standing after the reaction is completed, pouring out a supernatant, performing suction filtration on waste liquid, and drying for more than 24 hours to obtain the modified diatomite.

And 3, mixing the modified diatomite and the phase change material by a vacuum adsorption method to prepare the modified diatomite-based porous phase change material.

Wherein in step 2, the salt solution comprises CaCl₂、MgCl₂And one or more of a NaCl solution.

In the preparation method of the modified diatomite-based porous phase change material provided by the invention, the modified diatomite-based porous phase change material also has the following characteristics: in the step 1, the optimal acid-modifying condition of acid modification is that the concentration of hydrochloric acid is 1mol/L, the reaction temperature is 70 ℃, the reaction time is 60min, and the acid-soil ratio is 4: 1.

In the preparation method of the modified diatomite-based porous phase change material provided by the invention, the modified diatomite-based porous phase change material also has the following characteristics: wherein in the step 2, the optimal salt-modifying condition of the salt-modifying is 20 wt% of NaCl solution, the reaction temperature is 60 ℃, the reaction time is 30min, and the salt-soil ratio is 5: 1.

In the preparation method of the modified diatomite-based porous phase change material provided by the invention, the modified diatomite-based porous phase change material also has the following characteristics: wherein, in the step 3, the vacuum degree of the vacuum adsorption method is-0.08 MPa, the suction filtration time is 1h, and the heating and melting are carried out in a thermostatic water bath at 60 ℃.

In the preparation method of the modified diatomite-based porous phase change material provided by the invention, the modified diatomite-based porous phase change material also has the following characteristics: the optimal acid-modifying condition is determined based on the adsorption rate of the acid-modified diatomite to the phase change material, the condition when the adsorption rate is maximum is the optimal acid-modifying condition,

the calculation formula of the adsorption rate is as follows:

in the formula, m_pcmMass (kg) of the phase change material adsorbed, m_diatomiteThe mass (kg) of the diatomite matrix, h_comThe phase change latent heat (kJ/kg), h of the composite phase change temperature and humidity regulating material_pcmIs the latent heat of phase change (kJ/kg) of the phase change material.

In the preparation method of the modified diatomite-based porous phase change material provided by the invention, the modified diatomite-based porous phase change material also has the following characteristics: the optimal salt-modifying condition is judged based on the phase-change temperature and the phase-change potential heat value of the modified diatomite-based porous phase-change material, and the condition when the phase-change temperature and the phase-change potential heat value of the modified diatomite-based porous phase-change material are optimal is the optimal salt-modifying condition.

The invention also provides a modified diatomite-based porous phase change material, which is characterized in that: the modified diatomite-based porous phase change material is prepared by the preparation method of the modified diatomite-based porous phase change material.

Action and Effect of the invention

According to the preparation method of the modified diatomite-based porous phase change material, firstly, the diatomite is subjected to acid modification according to the following steps of hydrochloric acid: adding 1-3 mol/L hydrochloric acid solution into diatomite according to the proportion of 3:5, placing the diatomite in a constant-temperature water bath at 30-70 ℃ for reaction for 30-90 min, and washing, filtering and drying the diatomite after the reaction is finished to obtain acid-modified diatomite; secondly, performing salt modification on the acid-modified diatomite, mixing the acid-modified diatomite and a salt solution according to a mass ratio of 1:5, reacting for 20-40 min at the temperature of 30-60 ℃ in a constant-temperature water bath, standing after the reaction is finished, pouring out supernatant, performing suction filtration on waste liquid, and drying for more than 24 hours to obtain the modified diatomite; and finally, mixing the modified diatomite and the phase change material by a vacuum adsorption method to prepare the modified diatomite-based porous phase change material. The acid modification process removes impurities on the surface of the diatomite and in the pores, enlarges the porosity, improves the adsorption performance of the diatomite, and improves the moisture absorption performance of the diatomite. Meanwhile, the diatomite base material with high adsorption performance and high moisture absorption performance is prepared under the optimal acid modification condition and the optimal salt modification condition. The whole preparation method is simple, the used raw materials are non-toxic and harmless, and the obtained modified diatomite-based phase change moisture absorption material has high adsorption rate on the phase change material and good moisture absorption effect, and is suitable for the field of building energy conservation.

Drawings

FIG. 1 is a flow chart of a method for preparing a modified diatomite-based porous phase change material according to an embodiment of the present invention;

FIG. 2 is a DSC thermogram of the acid-modified diatomite-based composite phase change material under different acid-modification conditions in the example of the present invention;

FIG. 3 is a graph of the saturated moisture absorption of modified diatomaceous earth in examples of the present invention;

FIG. 4 is a FT-IR plot of the infrared spectrum of modified diatomaceous earth in an example of the present invention;

FIG. 5 is an SEM image of unmodified diatomaceous earth in an example of the present invention;

fig. 6 is an SEM image of modified diatomaceous earth in an example of the present invention.

Detailed Description

In order to make the technical means, creation features, achievement purposes and effects of the present invention easy to understand, the following embodiments specifically describe the preparation method of the modified diatomite-based porous phase change material in combination with the accompanying drawings.

In this embodiment, a preparation method of a modified diatomite-based porous phase change material is provided.

Fig. 1 is a flow chart of a preparation method of the modified diatomite-based porous phase change material in the embodiment of the invention.

As shown in fig. 1, the preparation method of the modified diatomite-based porous phase change material according to the embodiment includes the following steps:

step S1, the diatomaceous earth was acid-modified, 50g of diatomaceous earth was weighed into a beaker, and the orthogonal acid-modification test was performed according to the test protocol set forth in table 1. Adding hydrochloric acid solution according to the acid-soil ratio in the table 1, placing the mixture in a constant-temperature water bath for reaction, taking out a sample after the reaction is finished, and repeatedly washing the sample in an ultrasonic cleaning instrument by using deionized water until the filtrate is neutral. And (3) placing the neutral kieselguhr into a vacuum filtration bottle for filtration, and drying the sample in a hot air drying box at 60 ℃ after the filtration is finished to obtain the acid-modified kieselguhr under different acid-modified conditions.

Table 1 shows the diatomaceous earth acid correction cross-over test protocol in this example.

TABLE 1 Diatom acid Quadrature test protocol

And adsorbing the phase-change material in pores of the acid-modified diatomite under different acid-modified conditions to obtain the acid-modified diatomite-based composite phase-change material under different acid-modified conditions. Firstly, 10g of phase change material is added into a beaker, heated, melted and stirred for 30min in a constant temperature water bath at 60 ℃. Meanwhile, drying the acid-modified diatomite in a filter flask, wherein the mass ratio of the diatomite to the phase change material is 1:2, and placing the filter flask on a heat collection type magnetic stirrer, and keeping the heating temperature at 60 ℃; opening a vacuum pump, directing the pressure to-0.08 MPa, extracting air and moisture in the material, and keeping for 1 h; after vacuum, opening a valve of the separating funnel to enable the molten phase-change material to slowly flow into the bottle, and stirring; and keeping the heating temperature at 60 ℃, continuously stirring for 1h, filtering out unadsorbed phase-change materials to obtain the acid-modified diatomite-based composite phase-change materials under different acid-modified conditions, and drying in a hot air drying oven at 40 ℃ for 12 h.

Fig. 2 is a Differential Scanning Calorimetry (DSC) thermogram image of the acid-modified diatomite-based composite phase change material under different acid-modification conditions in this example.

Testing the phase change latent heat of the kieselguhr before and after acid modification and the acid-modified kieselguhr-based composite phase change material under different acid modification conditions by using a differential scanning calorimeter, wherein the temperature range is-20-70 ℃, the temperature rise and fall rate is 8.0K/min, and the test atmosphere is N₂. And analyzing the thermal analysis curve at the selected temperature range of 0-60 ℃ to obtain the latent heat of phase change of different composite materials.

The adsorption rate of the acid-modified diatomite-based porous phase-change material is converted after the phase-change latent heat value is measured, and the calculation formula is as follows:

analyzing the influence of different modification conditions on the adsorption effect of the diatomite: the concentration of hydrochloric acid is more than the reaction temperature, the acid leaching time is more than the acid-soil ratio. The optimal modification conditions are as follows: the concentration of hydrochloric acid is 1mol/L, the reaction temperature is 70 ℃, the acid leaching time is 60min, and the acid-soil ratio is 4: 1.

Step S2, the acid-modified diatomite is subjected to salt modification, and a salt solution is CaCl₂、MgCl₂And NaCl to prepare a 20 wt% solution, mixing the acid-modified diatomite and the salt solution under the optimal acid modification condition according to the mass ratio of 1:5, and reacting for 30min by keeping a constant-temperature water bath at 60 ℃. Standing after the reaction is finished, pouring out supernatant, carrying out suction filtration on the residual waste liquid, and drying the diatomite in a hot air drying oven at 80 ℃ for 24 hours to obtain the modified diatomite under different salt modification conditions.

The phase change material is adsorbed to modified diatomite under different salt modification conditions to prepare the modified diatomite-based porous phase change material under different salt modification conditions, a DSC instrument is utilized to test the modified diatomite-based porous phase change material under different salt modification conditions, and the test result shows that the influence of 20 wt% NaCl modification on the phase change temperature and the phase change latent heat of the modified diatomite-based porous phase change material is small, so that NaCl is the best salt modification material among three inorganic salts, and finally NaCl is used for carrying out salt modification on the acid modified diatomite to obtain the modified diatomite.

And step S3, mixing the modified diatomite and the phase-change material through a vacuum adsorption method to prepare the modified diatomite-based porous phase-change material.

The vacuum degree of the vacuum adsorption method is-0.08 MPa, the suction filtration time is 1h, and the mixture is heated and melted in a constant-temperature water bath at 60 ℃.

FIG. 3 is a graph showing the saturated moisture absorption of modified diatomaceous earth in examples of the present invention.

As can be seen from the figure, the saturated moisture absorption rate of the modified diatomaceous earth tends to increase rapidly after about 70% relative humidity, and the main reason is that the NaCl molecular structure is relatively stable and is not easily combined with water molecules to form hydrates, but after the diatomaceous earth adsorbs moisture in the air, NaCl ions are dissolved in the adsorbed water, changing the water vapor partial pressure of water adsorbed by the diatomaceous earth, and thus the saturated moisture absorption rate of the modified diatomaceous earth tends to increase rapidly when the saturated vapor pressure of the environment is greater than the vapor pressure of the saturated NaCl salt solution.

FIG. 4 is a FT-IR plot of the infrared spectrum of modified diatomaceous earth in an example of the invention.

The FT-IR diagram of infrared spectrum mainly utilizes the different absorption degrees of the infrared light with different wavelengths of the sample to be detected so as to analyze the structural composition of the substance, and reveals whether chemical reaction occurs in the acid modification and salt modification processes. As can be seen from FIG. 4, in the characteristic absorption curve of the infrared spectrum of the acid-modified diatomite, except for the change of the intensity of the peak value and the slight shift of the position, the peak shape is basically consistent with that of the unmodified diatomite, which indicates that the SiO in the diatomite is not destroyed by the hydrochloric acid modification₂Chemical structure of the crystal. The modified diatomite is 3431.54cm^-1The main reason why the characteristic absorption peak is not seen is that after the modification of inorganic salt NaCl, the metal cation M⁺(Na⁺、Mg2⁺、Ca2⁺… …) can activate hydroxyl groups bound by hydrogen bonds on the surface of diatomite and release H⁺Leading to the increase of the electronegativity of the surface of the diatomite and Na passing⁺Hydrogen bonding, indicating that NaCl has successfully modified the diatomaceous earth.

Fig. 5 is an SEM image of unmodified diatomaceous earth in an example of the present invention.

Fig. 6 is an SEM image of modified diatomaceous earth in an example of the present invention.

It can be seen that the debris on the surface of the acid modified diatomite is obviously reduced, the porous structure is dredged, the opening number of micropores is increased, the pore diameter is increased, and the specific surface area is increased. Fig. 6 is an SEM microstructure of the modified diatomaceous earth, and compared with fig. 5, the modified diatomaceous earth has a cleaner surface, substantially no impurities blocking the pores, a clear pore structure, and a larger porosity and specific surface area.

Effects and effects of the embodiments

According to the preparation method of the modified diatomite-based porous phase change material, according to the embodiment, firstly, diatomite is modified by acid according to the following hydrochloric acid: adding 1-3 mol/L hydrochloric acid solution into diatomite according to the proportion of 3:5, placing the diatomite in a constant-temperature water bath at 30-70 ℃ for reaction for 30-90 min, and washing, filtering and drying the diatomite after the reaction is finished to obtain acid-modified diatomite; secondly, performing salt modification on the acid-modified diatomite, mixing the acid-modified diatomite and a salt solution according to a mass ratio of 1:5, reacting for 20-40 min at the temperature of 30-60 ℃ in a constant-temperature water bath, standing after the reaction is finished, pouring out supernatant, performing suction filtration on waste liquid, and drying for more than 24 hours to obtain the modified diatomite; and finally, mixing the modified diatomite and the phase change material by a vacuum adsorption method to prepare the modified diatomite-based porous phase change material. The acid modification process removes impurities on the surface of the diatomite and in the pores, enlarges the porosity, improves the adsorption performance of the diatomite, and improves the moisture absorption performance of the diatomite. Meanwhile, the diatomite base material with high adsorption performance and high moisture absorption performance is prepared under the optimal acid modification condition and the optimal salt modification condition. The whole preparation method in the embodiment is simple, the used raw materials are non-toxic and harmless, and the obtained modified diatomite-based phase change moisture absorption material has high adsorption rate on the phase change material and good moisture absorption effect, and is suitable for the field of building energy conservation.