CN108262003A - A kind of preparation method of diatom base hydration calcium silicate powder humidity adjusting material - Google Patents

Abstract

The present invention relates to inorganic functional powder field, specially a kind of preparation method of diatom base hydration calcium silicate powder humidity adjusting material.Using diatomite as natural mineral raw, make it that combination reaction occur with calcareous raw material and water in high temperature saturated steam, formed with hydrated calcium silicate powder humidity adjusting material as main component.Its key technology step includes：(1) by diatomite and calcareous raw material, dispensing mixing, the mixing water of addition siccative quality 20%~50% simultaneously continue to mix to substantially uniformity by a certain percentage；(2) reaction mixture carries out hydro-thermal reaction in 120~240 DEG C of saturated steam environment, and the time 2~for 24 hours；(3) it is moderately ground after the drying of gained sample, obtains diatom base hydration calcium silicate powder humidity adjusting material.Method provided by the present invention can obtain with hydrated calcium silicate powder body material as main component, can retain the abundant meso-hole structure of diatomite to a certain extent, and so as to assign the powder body material considerable moisture adsorption and releasing ability, humidity is excellent.

Description

A kind of preparation method of diatom-based calcium silicate hydrate powder humidity control material

technical field

The invention relates to the field of inorganic functional powders, in particular to a method for preparing a diatom-based calcium silicate hydrate powder humidity-conditioning material.

Background technique

In people's production and life, air conditioning equipment is usually used to maintain a comfortable temperature and humidity in the living environment, but there are disadvantages such as high equipment investment and high energy consumption. In addition, it is easy to cause indoor air quality problems and affect people's physical and mental health.

Humidity-regulating materials refer to materials that can sense changes in air temperature/humidity in the space they are in according to their own moisture absorption/release performance, and can automatically adjust the relative humidity of the air without consuming artificial energy. The preservation quality of items, more importantly, has far-reaching significance for reducing energy consumption and maintaining the ecological environment. It is generally believed that the small pores with a pore diameter of 2-50 nm have the most significant impact on the moisture absorption and desorption capacity of the humidity-conditioning material.

As an important part of cement concrete, calcium silicate hydrate (Calcium silicate hydrate, CSH) has an intrinsic microporous structure (pore diameter d<2nm, inside the crystal); Mesopores (pore diameter 2-50nm) and macropores (pore diameter above 50nm) also exist to varying degrees among the particles. Theoretically, building material products with calcium silicate hydrate as the main component should have considerable moisture absorption and desorption capacity, but the actual use of building material products such as cement concrete has not shown the expected humidity control performance. The reason is mainly because although the microporous structure in cement concrete and other building materials products is rich, the content of mesopores and macropores is low, and the pores are not connected to each other, resulting in the migration/diffusion of water molecules inside the product. It is difficult to achieve reversible adsorption/desorption of a large amount of water vapor, and it is impossible to obtain building material products with excellent humidity control performance.

Contents of the invention

In order to improve the humidity-controlling performance of calcium silicate hydrate CSH, the object of the present invention is to provide a preparation method of diatom-based calcium silicate hydrate powder humidity-conditioning material, which introduces more calcium silicate hydrate CSH Mesopores and macropores, the increase of mesopores helps to improve the reversible adsorption capacity of products for water vapor, while the macroporous structure can provide a fast channel for water molecules to enter and exit, and improve the environmental response speed of humidity-controlling materials.

Technical scheme of the present invention is:

A preparation method of a diatom-based calcium silicate hydrate powder humidity control material, comprising the following steps:

(1) Mix diatomite and calcareous raw materials in proportion, the ratio of calcareous raw materials to diatomite is between 0.45 and 0.99 in terms of molar ratio of calcium to silicon, and add 20% to 50% of dry material mass Add water and continue mixing until completely homogeneous;

(2) The reaction mixture is subjected to a hydrothermal reaction in a saturated water vapor environment at 120-240° C. for 2-24 hours;

(3) After the obtained sample is dried, it is ground to obtain a diatom-based calcium silicate hydrate powder humidity-conditioning material.

The preparation method of the diatom-based calcium silicate hydrate powder humidity-conditioning material adopts diatomite as the silicon raw material, the mass ratio percentage of _SiO2 in the diatomite is not less than 60%, and the specific surface area is not less than 60%. Less than 20m ² /g.

In the preparation method of the diatom-based calcium silicate hydrate powder humidity control material, the main component of the calcium raw material is calcium oxide CaO, calcium hydroxide Ca(OH) ₂ or a mixture of both.

The preparation method of the described diatom-based calcium silicate hydrate powder humidity-conditioning material, the main mineral component of the diatom-based calcium silicate hydrate powder humidity-conditioning material is semi-crystalline calcium silicate hydrate CSH (B) , and the content of mesopores with a size of 2-50 nm is not less than 0.06 cm ³ /g.

Advantage of the present invention and beneficial effect are:

(1) The preparation method provided by the present invention can use diatomite as a raw material to obtain calcium silicate hydrate powder with developed mesoporous structure, and the hydration product retains the pore structure characteristics of diatomite raw material to a large extent, Therefore, more pores, especially mesopores of 3-50 nm, are introduced into the calcium silicate hydrate, which is beneficial to the improvement of the moisture absorption and desorption capacity of the calcium silicate hydrate.

(2) The preparation method provided by the present invention uses diatomite as the siliceous raw material, and does not have high requirements on the purity and specific surface area of diatomite. And building materials products with high economic value. Therefore, diatomite resources can be rationally used to increase the economic value of diatomite, which is beneficial to the development and utilization of low-grade diatomite natural mineral deposits, and has certain reference value for the research and development of functional building materials.

(3) The technical advantages of the preparation method provided by the present invention include: raw materials are cheap and easy to obtain; the preparation method is simple to operate, and the production efficiency is high; value.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) pattern of diatom-based calcium silicate hydrate powder obtained by different raw material ratios. In the figure, the abscissa 2θ is the diffraction angle (°), and the ordinate Intensity is the intensity (a.u.).

Figure 2-Figure 3 is the microstructure of diatom-based calcium silicate hydrate powder obtained at different hydration reaction temperatures; among them, Figure 2 is a scanning electron microscope (SEM) photo, (a) 120 ° C, (b) 160 ° C , (c) 200°C, (d) 240°C; Figure 3 shows the pore size distribution characteristics (BET method), the abscissa Pore width is the pore width (nm), the ordinate Pore surface area is the pore specific surface area (m ² ·g ^{- 1} ). The molar ratio of calcium to silicon in the reaction raw materials is controlled to be 0.59, and the hydrothermal reaction time is 4 hours.

Figure 4-Figure 5 is the microstructure of diatom-based calcium silicate hydrate powder obtained at different hydration reaction times; wherein, Figure 4 is a scanning electron microscope (SEM) photo, (a) 2h, (b) 4h, ( c) 6h, (d) 8h; Figure 5 shows the pore size distribution characteristics (BET method), the abscissa Pore width is the pore width (nm), and the ordinate Pore surface area is the pore specific surface area (m ² ·g ^-1 ). The molar ratio of calcium to silicon in the reaction raw materials is controlled to be 0.59, and the hydrothermal reaction temperature is 200°C.

Figure 6(a)-Figure 6(b) shows the consistency relationship between the moisture absorption and desorption capacity of diatom-based calcium silicate hydrate powder obtained under different hydrothermal reaction conditions and the mesopore content; among them, (a) at different temperatures Under reaction for 4 hours, abscissa T is temperature (°C), ordinate (left) Moisture desorption rate is moisture release rate (%), ordinate (right) Pore volume (3～50nm) is pore specific volume (cm ³ g ^-1 ); (b) different reaction times at 200°C, abscissa T is temperature (°C), ordinate (left) Moisture desorption rate is moisture release rate (%), ordinate (right) Pore volume (3～50nm ) is the pore specific volume (cm ³ ·g ^-1 ).

Detailed ways

In the specific implementation process, the present invention uses diatomite with rich, regular and orderly pore structure as natural raw material, and makes it react with calcareous raw material and water in high-temperature saturated water vapor to form hydrated silicic acid Calcium is the main component of the powder humidity control material. The powder material can retain the mesoporous structure characteristics of diatomite to a certain extent, thus endowing the powder material with considerable moisture absorption and release capacity, and excellent humidity control performance. The method specifically includes the following steps:

(1) Mix diatomite and calcareous raw materials according to a certain proportion, add mixing water with a dry weight of 20% to 50% and continue mixing until completely uniform;

(2) The reaction mixture is subjected to a hydrothermal reaction in a saturated water vapor environment at 120-240° C. for 2-24 hours;

(3) The obtained sample is moderately ground after drying to obtain a diatom-based calcium silicate hydrate powder humidity control material.

Among them, diatomite is used as the natural siliceous raw material, the mass percentage of SiO ₂ in diatomite is not less than 60% (preferably 70% to 90%), and the specific surface area is not less than 20m ² /g (preferably 50～100m ² /g). The calcium raw material used is calcium oxide CaO, calcium hydroxide Ca(OH) ₂ or a mixture of the two, and the ratio of the calcium raw material to diatomite in the raw material mixture is between 0.45 and 0.99 in terms of molar ratio. The main mineral component of the calcium silicate hydrate powder material is semi-crystalline calcium silicate hydrate CSH (B), and the content of mesopores with a size of 2-50nm is not less than 0.06cm ³ /g (preferably 0.10- 0.30 cm ³ /g).

The present invention is further described below in conjunction with embodiment, but content of the invention is not limited to described embodiment:

Example 1

In this example, diatomite is produced in Changbai, Jilin, with a SiO ₂ content of 61.38% by mass and a specific surface area of 65 m ² /g. Using diatomite as raw material, the specific process and technical parameters of the diatom-based calcium silicate hydrate powder humidity-conditioning material are:

(1) Mix diatomaceous earth and calcium hydroxide according to the calcium-silicon molar ratio of 0.45, add mixing water with a dry weight of 20% and continue mixing until completely uniform;

(2) The reaction mixture is subjected to a hydrothermal reaction for 4 hours in a saturated water vapor environment at 200°C;

(3) The obtained sample is moderately ground after drying to obtain a diatom-based calcium silicate hydrate powder humidity control material.

The X-ray diffraction (XRD) results of the calcium silicate hydrate powder obtained by the hydrothermal reaction are shown in Figure 1, and the analysis shows that the reaction product in the powder is mainly semi-crystalline calcium silicate hydrate CSH (B).

The humidity control performance test shows that the 24h moisture absorption of the powder in an environment with a relative humidity of 75% after drying (105°C) reaches 8.32% (mass percentage), and then the 24h moisture release in an environment with a relative humidity of 33% On the other hand, it was 2.87%, and the moisture absorption/release ability was good.

Example 2

In this example, the diatom-based calcium silicate hydrate powder humidity-conditioning material was prepared according to the steps of Example 1, the difference is that calcium oxide is used as the calcium raw material in step (1), and the calcium-silicon molar ratio is adjusted to 1.0; other operating steps and conditions are the same. The X-ray diffraction (XRD) results of the calcium silicate hydrate powder obtained by the hydrothermal reaction are shown in Figure 1. The analysis shows that the reaction product in the powder is mainly semi-crystalline calcium silicate hydrate CSH (B), but there is hydrogen Calcium oxide diffraction peaks remain, indicating excess calcium oxide in the raw material. The humidity control performance test shows that the 24h moisture absorption of the powder in an environment with a relative humidity of 75% after drying (105°C) reaches 6.56% (mass percentage), and then the 24h moisture release in an environment with a relative humidity of 33% It is 2.11%, and the moisture absorption/release ability is good.

Example 3

In this example, the diatom-based calcium silicate hydrate powder humidity-conditioning material was prepared according to the steps of Example 1, the difference being that the hydrothermal reaction conditions in step (2) were adjusted to 120°C and 4h; other operating steps and Same conditions. The scanning electron microscope (SEM) microscopic morphology of the calcium silicate hydrate powder obtained by the hydrothermal reaction is shown in Figure 2(a), indicating that the hydration product is calcium silicate hydrate with poor crystallinity, and the reaction is incomplete. Nitrogen adsorption experiments show that the calcium silicate hydrate powder has a pore content of 0.012cm ³ /g in the range of 2-50nm pore diameter, and the humidity control performance test shows that the powder is dried (105°C) and placed at a relative humidity of 75 The 24h moisture absorption in the % environment reaches 5.31% (mass percentage), and then the 24h moisture release in the environment with a relative humidity of 33% is 1.15%, and the moisture absorption/release capacity is general.

Example 4

In this example, the diatom-based calcium silicate hydrate powder humidity-conditioning material was prepared according to the steps in Example 3, the difference being that the hydrothermal reaction conditions in step (2) were adjusted to 120°C and 24h; other operating steps and Same conditions. The humidity control performance test shows that the 24h moisture absorption of the powder in an environment with a relative humidity of 75% after drying (105°C) reaches 8.45% (mass percentage), and then the 24h moisture release in an environment with a relative humidity of 33% On the other hand, it was 3.23%, and the moisture absorption/release ability was good.

Example 5

In this example, the diatom-based calcium silicate hydrate powder humidity-conditioning material was obtained according to the steps of Example 1, the difference being that the ratio of raw materials in step (1) was 0.83 in terms of calcium-silicon molar ratio; other operating steps Same as condition. The scanning electron microscope (SEM) microscopic morphology of the calcium silicate hydrate powder obtained by the hydrothermal reaction is shown in Figure 2(b), indicating that the hydration product is semi-crystalline calcium silicate hydrate CSH (B), and fragmented crystals aggregate into group. Nitrogen adsorption experiments show that the calcium silicate hydrate powder has a pore content of 0.114cm ³ /g in the range of 2-50nm pore size, which is significantly higher than the powder samples obtained at other reaction temperatures and the same reaction time, as shown in Figure 3. The humidity control performance test shows that the 24h moisture absorption of the powder in an environment with a relative humidity of 75% after drying (105°C) reaches 8.76% (mass percentage), and then the 24h moisture release in an environment with a relative humidity of 33% On the other hand, it was 3.32%, and the moisture absorption/release ability was good.

Example 6

In this example, the diatom-based calcium silicate hydrate powder humidity-conditioning material was prepared according to the steps of Example 5, the difference being that the hydrothermal reaction conditions in step (2) were adjusted to 240°C and 4h; other operating steps and Same conditions. The scanning electron microscope (SEM) microscopic morphology of the calcium silicate hydrate powder obtained by the hydrothermal reaction is shown in Figure 2(c), which shows that the hydration product is crystalline calcium silicate hydrate tobermullite, and the crystals are aggregated into agglomerates. Nitrogen adsorption experiments show that the calcium silicate hydrate powder has a pore content of 0.062 cm ³ /g in the range of 2-50 nm pore diameter. The humidity control performance test shows that the 24h moisture absorption of the powder in an environment with a relative humidity of 75% after drying (105°C) reaches 4.93% (mass percentage), and then the 24h moisture release in an environment with a relative humidity of 33% On the other hand, it was 1.84%, and the moisture absorption/release ability was good.

Example 7

In this example, the diatom-based calcium silicate hydrate powder humidity-conditioning material was prepared according to the steps of Example 5, the difference being that the hydrothermal reaction conditions in step (2) were adjusted to 200°C and 2h; other operating steps and Same conditions. The scanning electron microscope (SEM) microscopic morphology of the calcium silicate hydrate powder obtained by the hydrothermal reaction is shown in Figure 4(a), indicating that the hydration product is semi-crystalline calcium silicate hydrate CSH (B), but the hydration reaction is not completely. Nitrogen adsorption experiments show that the calcium silicate hydrate powder has a pore content of 0.031cm ³ /g in the range of 2-50nm pore diameter, which is significantly higher than the powder samples obtained at other reaction temperatures and the same reaction time, as shown in Figure 5. The humidity control performance test shows that the 24h moisture absorption of the powder in an environment with a relative humidity of 75% after drying (105°C) reaches 7.11% (mass percentage), and then the 24h moisture release in an environment with a relative humidity of 33% It was 1.57%, and the moisture absorption/release ability was good.

Example 8

In this example, diatomite is produced in Changbai, Jilin, with a SiO ₂ content of 85.61% by mass and a specific surface area of 22 m ² /g. Using diatomite as raw material, the specific process and technical parameters of the diatom-based calcium silicate hydrate powder humidity-conditioning material are:

(1) Mix diatomite and calcium hydroxide according to the calcium-silicon molar ratio of 0.83, add mixing water with 50% dry weight and continue mixing until completely uniform;

(2) The reaction mixture is subjected to a hydrothermal reaction for 4 hours in a saturated water vapor environment at 200°C;

(3) The obtained sample is moderately ground after drying to obtain a diatom-based calcium silicate hydrate powder humidity-conditioning material

The water humidity control performance test shows that after the powder is dried (105°C) and placed in an environment with a relative humidity of 75% for 24 hours, the moisture absorption reaches 4.25% (mass percentage), and then transferred to an environment with a relative humidity of 33% for 24 hours to dehumidify The amount is 1.40%, and the moisture absorption/release ability is better.

As shown in Figure 2(a)-(d), it can be seen from the scanning electron microscope (SEM) photos of different hydration reaction temperatures that under the same reaction time of 4h, with the increase of hydrothermal temperature, the reaction product gradually changes from The amorphous gel (Fig. 2a) transformed into semi-crystalline (Fig. 2b) and then transformed into crystalline (Fig. 2c, 2d). Comparing the moisture absorption and desorption properties of the corresponding samples, it is found that the calcium silicate hydrate product CSH (B) obtained at a lower temperature is more beneficial to the improvement of the moisture absorption and desorption capacity of the samples.

As shown in Figure 3, from the analysis results of the pore structure of the samples obtained at different temperatures for 4 h, it can be seen that with the increase of the reaction temperature, the peak area of the pore distribution at the position of 3-20 nm in the sample increases first and then decreases, and at 200 °C The peak of the pore distribution under the condition is the most obvious. At the same time, the test shows that the moisture absorption/release rate of the corresponding sample is also the largest, that is, the humidity control ability of the diatom-based calcium silicate hydrate powder is directly related to the mesoporous content of the sample.

As shown in Figure 4(a)-(d), it can be seen from the scanning electron microscope (SEM) photos of different hydration reaction times that when the reaction temperature is the same as 200 °C, with the prolongation of the hydrothermal time, the reaction products gradually From semi-crystalline (Fig. 2a) to crystalline (Fig. 2b, 2c, 2d); as the hydrothermal reaction proceeds, the crystal size of the product gradually increases, and the stacking structure between each other becomes tighter. Comparing the moisture absorption and desorption properties of the corresponding samples, it is found that the hydrothermal reaction time at 200°C and higher temperatures should not be too long, otherwise it may have a certain impact on the moisture absorption and desorption capabilities of the samples.

As shown in Figure 5, from the pore structure analysis results of samples obtained at different reaction times at 200 °C, it can be seen that with the prolongation of the reaction time, the peak area of the pore distribution at the position of 3-20 nm in the sample first increases and then decreases, and at 4 h The peak of the pore distribution under the condition is the most obvious. At the same time, the test shows that the moisture absorption/release rate of the corresponding sample is also the largest, that is, the humidity control ability of the diatom-based calcium silicate hydrate powder is directly related to the mesoporous content of the sample.

As shown in Figure 6(a) and (b), further analysis and calculation of the structure-properties of diatom-based calcium silicate hydrate moisture-conditioning powder shows that the moisture absorption and desorption capacity of diatom-based calcium silicate hydrate is related to the The pore content is directly related, and the consistency of the change law is good when the hydrothermal reaction temperature and time are adjusted.

The results of the examples show that the preparation method of the calcium silicate hydrate powder with remarkable humidity control performance of the present invention uses diatomite as the natural siliceous raw material, and utilizes diatomite and calcium oxide, calcium hydroxide and other calcium raw materials Calcium silicate hydrate with appropriate crystallinity and rich mesoporous structure can be obtained through the hydrothermal combination reaction, which can show considerable water vapor adsorption/desorption or moisture absorption and desorption capacity when the ambient humidity changes. The method provided by the present invention can obtain the powder material with calcium silicate hydrate as the main component, which can retain the rich mesoporous structure of diatomite to a certain extent, thereby endowing the powder material with considerable moisture absorption and desorption capacity, adjusting Excellent wet performance.

Claims (4)

1. a kind of preparation method of diatom base hydration calcium silicate powder humidity adjusting material, which is characterized in that include the following steps：

(1) by diatomite and calcareous raw material dispensing mixing in proportion, calcareous raw material and diatomaceous ratio are in terms of calcium silicon mol ratio Between 0.45~0.99, add in the mixing water of siccative quality 20%~50% and continue to mix to substantially uniformity；

(2) reaction mixture carries out hydro-thermal reaction in 120~240 DEG C of saturated steam environment, and the time 2~for 24 hours；

(3) after the drying of gained sample, grinding obtains diatom base hydration calcium silicate powder humidity adjusting material.

2. the preparation method of diatom base hydration calcium silicate powder humidity adjusting material according to claim 1, which is characterized in that adopt It is siliceous raw material with diatomite, SiO in diatomite₂Quality than percentage composition not less than 60%, specific surface area is not less than 20m²/ g。

3. the preparation method of diatom base hydration calcium silicate powder humidity adjusting material according to claim 1, which is characterized in that calcium The main component of matter raw material is calcium oxide CaO, calcium hydroxide Ca (OH)₂Or both mixture.

4. the preparation method of diatom base hydration calcium silicate powder humidity adjusting material according to claim 1, which is characterized in that silicon The main mineral constituent of algae base hydration calcium silicate powder humidity adjusting material is hemicrystalline hydrated calcium silicate CSH (B), and 2~50nm The mesoporous content of size is not less than 0.06cm³/g。