CN1287892C - Aluminium modified silica-gel adsorbent material and its preparing process - Google Patents

Abstract

The invention discloses a method for preparing an aluminum-modified silica gel adsorbent material, which comprises the following steps: (1) soaking inorganic fiber paper in water glass at room temperature, taking it out after 2-5 hours, and drying for 10-24 hours; (2) ) Formulate soluble aluminum salt into an aqueous solution, add weak acid to adjust the pH value of the solution to 0.5-2, heat up to 30-80°C, and under strong stirring, impregnate the above-mentioned inorganic fiber paper with the obtained solution, and generate on the surface of the inorganic fiber and its voids Co-precipitation reaction, full reaction for 12 to 24 hours; (3) Take out the reacted inorganic fiber paper, wash it with water until the pH is neutral, take it out and dry it, and use the temperature program to obtain the aluminum-modified silica gel adsorbent material. The aluminum-modified silica gel adsorbent material prepared by the above method has the advantages of large adsorption capacity, high dehumidification efficiency, low regeneration temperature, good heat resistance, high mechanical strength and long service life, and can be widely used in the production of dehumidification wheels manufacture.

Description

Aluminum modified silica gel adsorbent material and preparation method thereof

Technical field

The invention relates to a gas adsorbent technology, in particular to an aluminum-modified silica gel adsorbent material and a preparation method thereof.

Background technique

Adsorption gas purification technology has obvious advantages in low-grade energy utilization and environmental protection, and has become one of the sustainable development technologies. In the adsorption gas purification technology, the adsorption working fluid is the key to determine the performance of the adsorption system. There are more than a hundred kinds of adsorption working fluids and their combinations that have been developed, but they are selected based on the practicability of the adsorbent. The adsorbent in the dehumidifier is limited to highly hygroscopic substances such as lithium chloride, silica gel and molecular sieve; lithium chloride has good hygroscopicity and low regeneration temperature, but it is corrosive to surrounding metal equipment; molecular sieve is suitable for deep dehumidification with low dew point, but The regeneration temperature is high (above 250°C); the performance of silica gel is between the two, which is suitable for both conventional dehumidification (coarse pore silica gel) and low dew point deep dehumidification (fine pore silica gel), among which fine pore silica gel is suitable for making silica gel Dehumidification core, and the key to making silica gel dehumidification core is the organic combination of silica gel and inorganic fiber substrate; it can be made by bonding silica gel powder on inorganic fiber substrate with adhesive, but due to the powder and substrate The interface force between the two materials is weak, and the adhesion is poor. Repeated use at higher temperatures (above 150 ° C) is prone to powder falling, making the performance of the silica gel rotor unstable. At the same time, the use of adhesives will Partially block the substrate and silica gel channels, reducing the specific surface area of silica gel, thereby reducing the adsorption efficiency; the sol-gel method can also be used to impregnate sodium silicate on the inorganic fiber, and then react with acid to obtain silica gel precipitation deposited on the surface of the fiber and its In the void: due to factors such as the stability of the sol and the insolubility of the fiber in water, the amount of the adsorbent on the fiber is small, and it is difficult to form a high-concentration sol, so the amount of the sol attached to the inorganic fiber is small, and the silica gel produced is less , the dehumidification efficiency is low, and the adsorption efficiency of the dehumidification core is low. In order to overcome the shortcomings of these technologies, a "preparation method and application of nanoporous silica gel adsorbent material" is disclosed in the invention patent application with the patent application number 02149717.6. This adsorbent material is prepared by adding soluble calcium salt as a precipitant However, this technology also has the following deficiencies: (1) The adsorption performance needs to be improved; (2) The heat resistance performance needs to be strengthened; due to the weak heat resistance of silica gel, the dehumidification rotor core is kept at 80-150 ° C for a long time In the regenerative environment, phenomena such as melting, collapse, and blocked channels are prone to occur, thereby reducing the adsorption efficiency of the system; (3) The mechanical strength needs to be enhanced; due to the weak force between silica gel and ceramic fibers, the mechanical strength of the rotor material is poor. During the operation of the system, it is prone to pulverization and powder loss, which will affect its service life.

Contents of invention

The purpose of the present invention is to overcome the disadvantages of the prior art, and provide an aluminum-modified silica gel adsorbent material with superior properties such as large adsorption capacity, low regeneration temperature, good heat resistance, and high mechanical strength.

Another object of the present invention is to provide a method for preparing the above-mentioned aluminum-modified silica gel adsorbent material.

The object of the present invention is achieved through the following technical solutions: the preparation method of the aluminum modified silica gel adsorbent material comprises the following steps——

(1) Soak the inorganic fiber paper in water glass at room temperature, take it out after 2-5 hours, and dry it for 10-24 hours;

(2) Prepare the soluble aluminum salt into an aqueous solution, add weak acid to adjust the pH value of the solution to 0.5-2, raise the temperature to 30-80°C, and under strong stirring, impregnate the above-mentioned inorganic fiber paper with the obtained solution, and place it on the surface of the inorganic fiber and its voids. A co-precipitation reaction occurs in the medium, and the reaction is sufficient for 12 to 24 hours;

(3) Take out the reacted inorganic fiber paper, wash it with clean water until the pH is neutral, take it out and dry it, and process it by temperature programming to obtain an aluminum-modified silica gel adsorbent material.

In the step (1), the modulus of water glass is 2.0～3.5, and the concentration is 10～40% (percentage by weight); the selection of modulus of water glass is based on the premise of not blocking the honeycomb channel when impregnating the honeycomb dehumidification core, and the concentration of the water glass The selection is based on the amount of glue on the base material as much as possible; the inventor has found through repeated tests that the modulus of water glass is 2.8 to 3.5, and when the weight percentage concentration of water glass is 20 to 35%, the obtained silica gel dehumidification core has the best performance. Good appearance and good adsorption performance.

In the step (2), the soluble aluminum salt is aluminum chloride, aluminum nitrate, aluminum sulfate, etc., and its concentration is 5% to 25% (percentage by weight); if the concentration of aluminum salt is too low, it is not conducive to deposition, and if it is too high, the deposition will not It is uniform, and the proportioning concentration with better effect proved by experiments is 10-25% (percentage by weight).

The pH value of the solution in the step (2) is preferably 1 to 1.8; when selecting an acid to adjust the pH value of the salt solution, the corrosiveness of the acid solution to the core (such as high-concentration acid, strong acid) must be considered, and the pH value in the system must also be considered. The range of change (the pH value fluctuates as little as possible), it is advisable to use low-concentration weak acids (such as acetic acid, lactic acid, gluconic acid, etc.) to adjust the pH value, so that the generated porous material has uniform pore size and narrow distribution.

The temperature in the step (2) is preferably 40-60°C; if the temperature is too low, the reaction rate is slow, which is not conducive to production, and if the temperature is too high, the corrosion effect on the impregnation equipment and adsorbent material will be enhanced. More importantly, the reaction temperature It is closely related to the adsorption performance of the adsorbent material.

Stirring speed in the step (2) is based on the premise that the concentration of the reaction system is uniform, especially the pH value of the solution needs to be adjusted, because as the reaction continues, the pH value of the solution continues to rise, so it is necessary to constantly add acid solution to Maintain the pH of the solution in a constant range.

The temperature-programmed treatment in the step (3) is to slowly heat up at 200-300° C., and cool naturally, repeat 2-3 times, then slowly heat up to 450-550° C., keep warm for 1-3 hours, and then cool naturally; The temperature programming process is adopted to remove moisture and volatile impurities in the core, and to reduce the shrinkage rate of the gel as much as possible during the formation of the Si-O-Si (or Si-O-Al) network, to avoid Cracks are generated due to stress concentration in the internal area of the material, reducing the brittleness of the material.

The present invention adopts the method of impregnating and co-precipitating, adopts processes such as impregnating water glass and aluminum salt in sequence, and adjusting the pH value of the solution, heating up, and a strong stirring bar, so that a large amount of the generated aluminum-modified silica gel is deposited on the voids and surfaces of the inorganic fibers, and then After forming and sintering, the aluminum-modified silica gel adsorbent material with high adsorption capacity, low regeneration temperature, good heat resistance and mechanical strength is synthesized; the prepared adsorbent material can be applied to adsorption gas dehumidification and drying Or in the dehumidification core device in the adsorption refrigeration air conditioner.

The action mechanism of the present invention is: immerse the inorganic fiber paper containing sodium silicate in a soluble aluminum salt solution with a certain acidity, due to the Al ³⁺ modification, the Al atoms in the tetrahedron partially replace the Si atoms, due to [AlO ₄ ] ^5- has more negative charges than [SiO ₄ ] ^4- , which makes the corner top O have a greater force on the proton of OH, forming a stronger hydrogen bond, that is, Al ³⁺ has a stronger affinity for water molecules , easy to adsorb more water molecules; on the other hand, due to Al ³⁺ modification, it significantly affects the network structure formed by silica particles in the sol-gel process, and increases the specific surface area and pore volume of the aluminum-modified adsorbent material. Increase the active adsorption site, thereby improving the adsorption performance of the adsorbent material; at the same time, due to the formation of Al-O-Si bonds on the surface of the aluminum-modified adsorbent material, it not only enhances the supporting force of the pore skeleton, but also improves the heat resistance of the material , and enhance the interaction between the adsorbent and the inorganic fiber, improve the mechanical strength of the material.

Compared with the prior art, the present invention has the following advantages and effects: (1) large adsorption capacity and high dehumidification efficiency; (2) low regeneration temperature (equal to silica gel); (3) good heat resistance, high mechanical strength, Long service life; experiments have proved that the performance of the aluminum-modified silica gel adsorbent material prepared by the method of the present invention is significantly better than that of the same type of silica gel products (the nanopore silica gel adsorbent material disclosed in the invention patent application with the patent application number 02149717.6), The aluminum-modified silica gel adsorbent material can increase the adsorption capacity by 12.0%-25.0%, enhance the heat resistance, increase the mechanical strength by 35.0-74.0%, and increase the service life by 1-2 times.

Description of drawings

Figure 1 is a comparison chart of adsorption performance of different adsorbents at 298K.

Fig. 2 is a graph of thermal weight loss of different adsorbents at a temperature of 298K to 973K.

Figure 3 is a comparison chart of the mechanical strength of different adsorbents.

Figure 4 is a schematic diagram of the pore size distribution of different adsorbents.

Figure 5 is a schematic diagram of the specific surface area and pore volume of different adsorbents.

Detailed ways

After several years of development, the inventor has many successful examples; in order to better illustrate that the present invention has not only increased the dehumidification capacity, improved the adsorption performance, but also improved the heat resistance and mechanical strength of the material, thereby improving the use of the material. Life, three embodiments of the present invention are listed below and their technical performance indicators are compared with the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

The inventive method comprises the following specific steps: (1) at room temperature, in a 250L circular plastic container, add 100L of water, then add 80Kg of water glass with a modulus of 3.0, stir evenly, and heat-roll the molded glass of inorganic fiber paper Put the honeycomb core (300mm×150mm) into it and soak it for 3 hours, make it fully soaked, take it out and dry it in the air, then dry it at 60°C for 18 hours, and cool it to room temperature; (2) Weigh 30Kg of crystalline sulfuric acid Dissolve aluminum in 120L of water, add acetic acid to adjust the pH value of the solution to 1.0, raise the temperature to 50°C, immerse the above-mentioned honeycomb core in it under strong stirring, and strictly control the reaction under the condition that the pH value of the solution is 1.0 (with As the reaction continues, the pH value of the solution increases, and it is necessary to add acid solution from time to time, the same below), take it out after 12 hours, rinse with water, dry in the air, and then dry it in an oven at 60°C for 24 hours, and cool to room temperature ; (3) Place the rotating core in an intelligent constant temperature sintering furnace, first slowly heat up at 200-300°C, and cool naturally, repeat 2-3 times, then slowly heat up to 450°C, keep it warm for 3 hours, and then cool naturally to A desiccant rotor core containing an aluminum-modified silica gel adsorbent was obtained at room temperature.

Example 2

The inventive method comprises the following specific steps: (1) at room temperature, in a 250L circular plastic container, add 100L of water, then add 100Kg of water glass with a modulus of 3.5, stir evenly, and heat-roll the inorganic fiber paper Honeycomb core (5300mm×150mm) was soaked in it for 5 hours to make it fully soaked, took it out to dry, then dried at 60°C for 24 hours, cooled to room temperature; (2) Weighed 40Kg crystalline aluminum chloride to dissolve In 120L of water, heat up to 60°C, under strong stirring, immerse the above honeycomb core in it, add lactic acid to adjust the pH value of the solution to 1.5, take it out after 18 hours of reaction, rinse with clean water and dry it, and then put it in an oven Dry at low temperature at 60°C for 24 hours, and cool to room temperature; (3) Place the rotor in an intelligent constant temperature sintering furnace, first slowly heat up at 200-300°C, and cool naturally, repeat 2-3 times, and then slowly heat up to 500°C ℃, heat preservation for 2 hours, and then naturally cooled to room temperature to obtain a desiccant core containing aluminum-modified silica gel adsorbent.

Example 3

The inventive method comprises the following specific steps: (1) at room temperature, in a 250L circular plastic container, add 100L of water, then add 100Kg of water glass with a modulus of 2.8, stir evenly, and heat-roll the inorganic fiber paper The honeycomb rotor (300mm×150mm) was soaked in it for 2 hours to make it fully soaked, took it out to dry, then dried at 60°C for 12 hours, and cooled to room temperature; (2) Weighed 45Kg of crystalline aluminum nitrate and dissolved it in 120L Add gluconic acid to adjust the pH value of the solution to 1.8, raise the temperature to 40°C, immerse the above-mentioned honeycomb core in it under vigorous stirring, rinse it with clean water until the pH is neutral after 24 hours, take it out and dry it, and then place it in the Dry in an oven at 60°C for 24 hours, and cool to room temperature; (3) Place the rotor in an intelligent constant temperature sintering furnace, first slowly heat up at 200-300°C, and cool naturally, repeat 2-3 times, and then slowly Raise the temperature to 550° C., keep it warm for 1 hour, and then naturally cool to room temperature to obtain a dehumidification rotor core made of an aluminum-containing modified silica gel adsorbent material.

The performance test was carried out on the adsorbent material prepared by the above examples. In order to compare the effects more directly, the aluminum-modified silica gel adsorbent material of the present invention was compared with the invention patent application (hereinafter referred to as "the prior application") with the patent application number 02149717.6 ) were compared with the nanoporous silica gel (hereinafter referred to as "silica gel") adsorbent material. Fig. 1 is the comparison of adsorption properties of different adsorbents at 298K. As can be seen from Fig. 1, the adsorption properties of the aluminum-modified silica gel adsorbents obtained by the method of the present invention are higher than those of the silica gel generated by the prior application technology under the same conditions. up to 12.0-25.0%, and the adsorption performance of the aluminum-modified silica gel obtained in Example 2 is the best (the saturated adsorption capacity reaches 148.8 g·m ^-2 ).

Figure 2 shows the thermal weight loss curves of different adsorbents at the temperature of 298K～973K. The weight loss is divided into two stages: 25～150℃ and 150～700℃. Adsorption performance, as can be seen from the first stage, aluminum-modified silica gel is the same as silica gel, and the desorption temperature is equivalent, but the adsorption performance is obviously higher than silica gel; and the weight loss of the second stage is shown as M-OH (M=Si, Al) Condensation dehydration between them reflects the heat resistance of the material. From the weight loss percentage of the second stage, it can be seen that the order of sample weight loss is: silica gel>Example 1≈Example 2>Example 3. It shows that the heat resistance of the aluminum-modified silica gel adsorbent is better than that of silica gel, and the more the modified aluminum ion content is, the better the heat resistance is (Example 3).

The mechanical strength comparison of different adsorbents is shown in Figure 3. It can be seen from Figure 3 that the fracture length of aluminum-modified silica gel is better than that of silica gel, with an increase of 35.0-74.0%, and the mechanical strength of Example 2 is the best.

Figure 4 shows the pore size distribution of different adsorbents. It can be seen from Figure 4 that aluminum-modified silica gel (including silica gel) has a pore size in the range of 0.3 to 8 nm. Huge adsorption capacity, while the presence of modified Al ³⁺ has little effect on the micropore diameter in the surface structure of the adsorbent, while the mesopore diameter increases significantly.

Figure 5 shows the specific surface area and pore volume of different adsorbents. From the intrinsic state (silica gel) to the modified Al ³⁺ accounted for 5.530wt% (Example 2), the specific surface area increased sharply from 347.4m ² ·g ^-1 to 472.1m ² ·g ^-1 , an increase of 35.90%; similarly, the pore volume of the adsorbent also increases significantly; from silica gel to Example 2, the change in pore volume increases from 0.2690cm ³ ·g ^-1 to 0.4765cm ³ ·g ^-1 , the increase is as high as 47.65%. Obviously, the modification of aluminum ions increases the specific surface area and pore volume of silica gel, indicating that the modification of aluminum ions significantly affects the formation of the network structure in the sol-gel process of the system.

In summary, the performance parameters of the aluminum-modified silica gel adsorbent prepared by the method of the present invention are significantly better than those of the same type of adsorbent, with large adsorption capacity, low regeneration temperature (<150°C), good heat resistance, and mechanical strength. High advantages, can be widely used in the production of desiccant rotors.

Claims (10)

1, a kind of preparation method of aluminum modified silica gel adsorbent material, it is characterized in that comprising the steps: (1) Soak the inorganic fiber paper in water glass at room temperature, take it out after 2-5 hours, and dry it for 10-24 hours; (2) Prepare the soluble aluminum salt into an aqueous solution, add weak acid to adjust the pH value of the solution to 0.5-2, raise the temperature to 30-80°C, and under strong stirring, impregnate the above-mentioned inorganic fiber paper with the obtained solution, and place it on the surface of the inorganic fiber and its voids. A co-precipitation reaction occurs in the medium, and the reaction is sufficient for 12 to 24 hours; (3) Take out the reacted inorganic fiber paper, wash it with clean water until the pH is neutral, take it out and dry it, and process it by temperature programming to obtain an aluminum-modified silica gel adsorbent material. 2. The method for preparing an aluminum-modified silica gel adsorbent material according to claim 1, characterized in that: in the step (1), the modulus of water glass is 2.0-3.5, and the concentration is 10-40%. 3. The method for preparing an aluminum-modified silica gel adsorbent material according to claim 1, wherein the soluble aluminum salt in the step (2) is aluminum chloride, aluminum nitrate, or aluminum sulfate. 4. The preparation method of aluminum-modified silica gel adsorbent material according to claim 1, characterized in that: the concentration of soluble aluminum salt in the step (2) is 5%-25%. 5. The method for preparing an aluminum-modified silica gel adsorbent material according to claim 1, characterized in that the pH value of the solution in the step (2) is 1-1.8. 6. The method for preparing an aluminum-modified silica gel adsorbent material according to claim 1, wherein the weak acid in step (2) is acetic acid, lactic acid, or gluconic acid. 7. The preparation method of aluminum-modified silica gel adsorbent material according to claim 1, characterized in that: the heating temperature in the step (2) is 40-60°C. 8. The method for preparing an aluminum-modified silica gel adsorbent material according to claim 1, wherein acid solution is added during the stirring process of the step (2) to maintain the pH value of the solution within a constant range. 9. The method for preparing an aluminum-modified silica gel adsorbent material according to claim 1, characterized in that: in the step (3), the temperature-programmed treatment is to slowly raise the temperature at 200-300°C, then cool naturally, and repeat 2-3 times, then slowly raise the temperature to 450-550°C, keep it warm for 1-3 hours, and then cool naturally. 10. An aluminum-modified silica gel adsorbent material prepared according to the method for preparing an aluminum-modified silica gel adsorbent material according to any one of claims 1-9.

Images