A composite desiccant and preparation method thereof

Abstract

The present invention discloses a composite desiccant and a preparation method thereof, and belongs to the field of desiccant preparation. The composite desiccant comprises modified silica gel and activated carbon in a mass ratio of (7 to 15): (1 to 5). The present application not only has an excellent moisture absorption rate, but also can absorb odors, and is easy to shape so as to have a wider application space by compounding the modified silica gel and activated carbon. Specifically, the modified silica gel prepared by the present application has an excellent microporous structure. After being treated with an organic acid solution, it can play a certain role in cleaning and expanding the micropores, thereby making it have a high specific surface area, and can load more activated carbon, synergistically, and achieve a better adsorption effect; in addition, the modified silica gel of the present application has a larger number of hydroxyl groups and a high internal structure stability, which can not only significantly improve its adsorption performance, but also is not easy to deform, deteriorate or penetrate out of the packaging bag after absorbing water to affect the product, and the recycling and reuse process is simple.

Description

Technical Field

[0001] The invention relates to the field of desiccant preparation, and in particular to a composite desiccant and a preparation method thereof. Background Art

[0002] Desiccant, also called adsorbent, is used in moisture-proof and mildew-proof aspects to play a drying role. According to the adsorption method and reaction products, it is divided into physical adsorption desiccant and chemical adsorption desiccant. Physical adsorption desiccant includes silica gel, alumina gel, molecular sieve, activated carbon, bone charcoal, charcoal, mineral desiccant, or activated clay, etc. Its drying principle is to physically adsorb water molecules in its own structure. At present, the most common desiccant in China is porous silica gel. Silica gel is also known as silica gel. The main component is silicon dioxide. It belongs to amorphous silicon material. It is a highly active adsorption material and one of the common porous materials. It is mainly used as a desiccant and an adsorbent in column chromatography and thin layer chromatography. However, silica gel itself has poor selectivity and adsorption capacity, which limits its application. Most silica has a tetrahedral structure, in which each silicon atom is surrounded by four oxygen atoms. Due to different preparation methods, the microporous structure of different types of silica gel is different. The prior art introduces other groups through bonding reactions or surface modification methods to improve its adsorption. For example, in a prior art method for modifying silica gel by alkylation, a methoxy-type silane reagent is used as a silica gel modifier to graft functional groups onto the surface of silica gel. The modified silica gel has a higher adsorption capacity for benzoic acid than ordinary silica gel before modification. Although the technology discloses that silica gel modification can improve its adsorption capacity for benzoic acid, it is easily affected by environmental humidity. Molecular sieve desiccants are also used in the prior art. In addition to adsorbing water vapor, it can also adsorb other gases, but the total saturated moisture absorption rate is not high, below 18%.

[0003] The pharmaceutical industry has extremely stringent requirements on the humidity of packaging materials. The characteristics of pharmaceuticals determine the requirements for packaging materials. In particular, oxygen and moisture in the air can easily cause chemical reactions such as oxidation and hydrolysis of the product, causing the active ingredients to deteriorate. Therefore, it is extremely important to develop a desiccant that is less affected by the environment, has high stability, has excellent moisture absorption effect, and is not prone to expansion after moisture absorption, and meets the requirements of the pharmaceutical health care, biological reagent, and food industries. Summary of the invention

[0004] Based on this, in order to solve the problems in the prior art that the desiccant is greatly affected by the environment, has low stability, poor moisture absorption effect and is prone to expansion after moisture absorption, the present invention provides a composite desiccant and a preparation method thereof, and the specific technical scheme is as follows:

[0005] A composite desiccant, comprising modified silica gel and activated carbon in a mass ratio of (7-15): (1-5); wherein the preparation method of the modified silica gel comprises the following steps:

[0006] Methyltrimethoxysilane is added to solvent 1 and dissolved to obtain mixture A;

[0007] Tetraethyl silicate was added to solvent 2 and dissolved to obtain mixture B;

[0008] The mixture B is added to the mixture A, and a proper amount of water is added to perform a hydrolysis reaction, and then a proper amount of an organic acid solution is added, and the mixture is stirred evenly, and then subjected to a standing treatment, a first drying treatment, and a grinding treatment to obtain a mixture C;

[0009] The mixture C is added to the barium chloride solution, and treated for 15 h to 20 h at a stirring rate of 150 r / min to 200 r / min and a temperature of 28° C. to 35° C., and after a second drying treatment, a modified silica gel is obtained.

[0010] Furthermore, the composite desiccant further comprises a binder, and the added amount of the binder accounts for 1% to 12% of the mass of the composite desiccant.

[0011] Furthermore, the adhesive is at least one of carboxymethyl cellulose, epoxy resin, polyurethane, waxberry gum, acrylate, polyether urea and chloroprene rubber.

[0012] Furthermore, the volume ratio of methyltrimethoxysilane to solvent one is (1-3):(5-8).

[0013] Furthermore, the volume ratio of tetraethyl silicate to solvent 2 is (1-3):(5-8).

[0014] Furthermore, the temperature of the hydrolysis reaction is 45°C to 65°C, and the time is 1h to 3h.

[0015] Furthermore, the organic acid is at least one of acetic acid, p-toluenesulfonic acid and dodecylbenzenesulfonic acid.

[0016] Furthermore, the concentration of the organic acid solution is 1 mol / L to 5 mol / L.

[0017] Furthermore, the mass percentage concentration of the barium chloride solution is 0.2 mol / L to 0.5 mol / L.

[0018] In addition, the present invention also provides a method for preparing a composite desiccant, the preparation method comprising the following steps:

[0019] After the modified silica gel and activated carbon are mixed according to the mass ratio, a binder is added, water is added, the mixture is heated to 65°C to 70°C, and stirred for 45min to 60min to obtain a slurry;

[0020] The slurry is dried at 90°C to 120°C, and after crushing, a mud material with a moisture content of 15% to 30% is obtained, and then the mud material is extruded to obtain a molded desiccant;

[0021] The molded desiccant is placed in a drying device, and the drying device is heated to 500°C to 580°C at a heating rate of 5°C / min to 15°C / min, and dried at 500°C to 580°C for 3h to 5h to obtain a composite desiccant.

[0022] In the above scheme, by compounding modified silica gel and activated carbon, it not only has excellent moisture absorption rate, but also can absorb odor, and is easy to shape, so that it has a wider range of applications. Specifically, the modified silica gel prepared by the present application has an excellent microporous structure. After being treated with an organic acid solution, it can play a certain role in cleaning and expanding the micropores, thereby making it have a high specific surface area and can load more activated carbon, which synergistically achieves a better adsorption effect; in addition, the modified silica gel of the present application has a larger number of hydroxyl groups and a high internal structural stability, which can not only significantly improve its adsorption performance, but also is not easy to deform, deteriorate or penetrate out of the packaging bag after absorbing water to affect the product, and the recycling and reuse process is simple. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0025] A composite desiccant in one embodiment of the present invention comprises modified silica gel and activated carbon in a mass ratio of (7-15):(1-5); wherein the preparation method of the modified silica gel comprises the following steps:

[0026] Methyltrimethoxysilane is added to solvent 1 and dissolved to obtain mixture A;

[0027] Tetraethyl silicate was added to solvent 2 and dissolved to obtain mixture B;

[0028] The mixture B is added to the mixture A, and a proper amount of water is added to perform a hydrolysis reaction, and then a proper amount of an organic acid solution is added, and the mixture is stirred evenly, and then subjected to a standing treatment, a first drying treatment, and a grinding treatment to obtain a mixture C;

[0029] The mixture C is added to the barium chloride solution, and treated for 15 h to 20 h at a stirring rate of 150 r / min to 200 r / min and a temperature of 28° C. to 35° C., and after a second drying treatment, a modified silica gel is obtained.

[0030] In one embodiment, the composite desiccant further includes a binder, and the added amount of the binder accounts for 1% to 12% of the mass of the composite desiccant.

[0031] In one embodiment, the adhesive is at least one of carboxymethyl cellulose, epoxy resin, polyurethane, bayberry gum, acrylate, polyether urea and chloroprene rubber.

[0032] In one embodiment, the volume ratio of methyltrimethoxysilane to solvent one is (1-3):(5-8).

[0033] In one embodiment, the volume ratio of tetraethyl silicate to solvent 2 is (1-3):(5-8).

[0034] In one embodiment, the solvent one and the solvent two are both methanol.

[0035] In one embodiment, the hydrolysis reaction is carried out at a temperature of 45°C to 65°C and for a time of 1 h to 3 h.

[0036] In one embodiment, the organic acid is at least one of acetic acid, p-toluenesulfonic acid and dodecylbenzenesulfonic acid.

[0037] In one embodiment, the concentration of the organic acid solution is 1 mol / L to 5 mol / L.

[0038] In one embodiment, the static treatment time is 1 hour to 3 hours.

[0039] In one embodiment, the temperature of the first drying treatment is 65° C. to 75° C., and the time is 8 h to 10 h.

[0040] In one embodiment, the added amount of the mixture C is (1 g to 3 g) / 10 mL.

[0041] In one embodiment, the mass percentage concentration of the barium chloride solution is 0.2 mol / L to 0.5 mol / L.

[0042] In one embodiment, the temperature of the second drying treatment is 95° C. to 100° C., and the time is 5 h to 8 h.

[0043] In addition, the present invention also provides a method for preparing a composite desiccant, the preparation method comprising the following steps:

[0044] After the modified silica gel and activated carbon are mixed according to the mass ratio, a binder is added, water is added, the mixture is heated to 65°C to 70°C, and stirred for 45min to 60min to obtain a slurry;

[0045] The slurry is dried at 90°C to 120°C, and after crushing, a mud material with a moisture content of 15% to 30% is obtained, and then the mud material is extruded to obtain a molded desiccant;

[0046] The molded desiccant is placed in a drying device, and the drying device is heated to 500°C to 580°C at a heating rate of 5°C / min to 15°C / min, and dried at 500°C to 580°C for 3h to 5h to obtain a composite desiccant.

[0047] In one embodiment, the solid content of the slurry is 15% to 30%.

[0048] The present application combines modified silica gel and activated carbon, which not only has excellent moisture absorption rate, but also can absorb odors, and is easy to shape, so that it has a wider range of applications. Specifically, the modified silica gel prepared by the present application has an excellent microporous structure. After being treated with an organic acid solution, it can play a certain role in cleaning and expanding the micropores, thereby making it have a high specific surface area and can load more activated carbon, which has a synergistic effect and has a better adsorption effect; in addition, the modified silica gel of the present application has a larger number of hydroxyl groups, which can significantly improve its adsorption performance, and the recycling and reuse process is simple.

[0049] The embodiments of the present invention will be described in detail below with reference to specific examples.

[0050] Embodiment 1:

[0051] A method for preparing a composite desiccant comprises the following steps:

[0052] Methyltrimethoxysilane in a volume ratio of 3:8 was added to methanol to dissolve, thereby obtaining a mixture A; tetraethyl silicate in a volume ratio of 3:7 was added to methanol to dissolve, thereby obtaining a mixture B; the mixture B was added to the mixture A, and an appropriate amount of water was added, and a hydrolysis reaction was carried out at a temperature of 55° C. for 2 hours, and then acetic acid with a mass percentage concentration of 3 mol / L was added, and after being stirred evenly, the mixture was allowed to stand for 1 hour, dried at 65° C. for 8 hours, and ground to obtain a mixture C;

[0053] The mixture C was added to a barium chloride solution with a mass percentage concentration of 0.2 mol / L at an addition amount of 3 g / 10 mL, and treated for 15 h at a stirring rate of 200 r / min and a temperature of 35° C., and dried at 95° C. for 8 h to obtain a modified silica gel;

[0054] Modified silica gel and activated carbon were mixed at a mass ratio of 15:3, and then 10% of carboxymethyl cellulose, which accounted for the mass of the composite desiccant, was added, and water was added, heated to 65° C., and stirred for 55 minutes to obtain a slurry with a solid content of 23%;

[0055] The slurry is dried at 90° C., crushed to obtain a mud material with a moisture content of 15%, and then the mud material is extruded to obtain a molded desiccant;

[0056] The molded desiccant is placed in a drying device, and the drying device is heated to 550° C. at a heating rate of 10° C. / min, and dried at 550° C. for 3 hours to obtain a composite desiccant.

[0057] Embodiment 2:

[0058] A method for preparing a composite desiccant comprises the following steps:

[0059] Methyltrimethoxysilane in a volume ratio of 3:8 was added to methanol to dissolve, thereby obtaining a mixture A; tetraethyl silicate in a volume ratio of 3:7 was added to methanol to dissolve, thereby obtaining a mixture B; the mixture B was added to the mixture A, and an appropriate amount of water was added, and a hydrolysis reaction was carried out at a temperature of 65° C. for 2 hours, and then acetic acid with a mass percentage concentration of 3 mol / L was added, and after being stirred evenly, the mixture was allowed to stand for 2 hours, dried at 70° C. for 8 hours, and ground to obtain a mixture C;

[0060] The mixture C was added to a barium chloride solution with a mass percentage concentration of 0.2 mol / L at an addition amount of 3 g / 10 mL, and treated for 15 h at a stirring rate of 200 r / min and a temperature of 35° C., and dried at 95° C. for 8 h to obtain a modified silica gel;

[0061] Modified silica gel and activated carbon are mixed at a mass ratio of 15:4, and then 10% of carboxymethyl cellulose, which accounts for the mass of the composite desiccant, is added, and water is added, heated to 70° C., and stirred for 60 minutes to obtain a slurry with a solid content of 20%;

[0062] The slurry is dried at 100° C., crushed to obtain a mud material with a moisture content of 15%, and then the mud material is extruded to obtain a molded desiccant;

[0063] The molded desiccant is placed in a drying device, and the drying device is heated to 550° C. at a heating rate of 10° C. / min, and dried at 550° C. for 3 hours to obtain a composite desiccant.

[0064] Embodiment 3:

[0065] A method for preparing a composite desiccant comprises the following steps:

[0066] Methyltrimethoxysilane in a volume ratio of 3:8 was added to methanol to dissolve, thereby obtaining a mixture A; tetraethyl silicate in a volume ratio of 3:7 was added to methanol to dissolve, thereby obtaining a mixture B; the mixture B was added to the mixture A, and an appropriate amount of water was added, and a hydrolysis reaction was carried out at a temperature of 65° C. for 2 hours, and then acetic acid with a mass percentage concentration of 3 mol / L was added, and after being stirred evenly, the mixture was allowed to stand for 2 hours, dried at 75° C. for 9 hours, and ground to obtain a mixture C;

[0067] The mixture C was added to a barium chloride solution with a mass percentage concentration of 0.2 mol / L at an addition amount of 3 g / 10 mL, and treated for 15 h at a stirring rate of 200 r / min and a temperature of 35° C., and dried at 98° C. for 8 h to obtain a modified silica gel;

[0068] Modified silica gel and activated carbon were mixed at a mass ratio of 15:5, and then 10% of carboxymethyl cellulose, which accounted for the mass of the composite desiccant, was added, and water was added, heated to 70° C., and stirred for 60 minutes to obtain a slurry with a solid content of 22%;

[0069] The slurry is dried at 100° C., crushed to obtain a mud material with a moisture content of 15%, and then the mud material is extruded to obtain a molded desiccant;

[0070] The molded desiccant is placed in a drying device, and the drying device is heated to 550° C. at a heating rate of 10° C. / min, and dried at 550° C. for 3 hours to obtain a composite desiccant.

[0071] Comparative Example 1:

[0072] The difference between Comparative Example 1 and Example 3 is that the silica gel in Comparative Example 1 is not modified, that is, the silica gel is directly mixed with the activated carbon, and the rest is the same as Example 3.

[0073] Comparative Example 2:

[0074] The difference between Comparative Example 2 and Example 3 is that acetic acid is not added when preparing the modified silica gel in Comparative Example 2, and the rest is the same as Example 3.

[0075] Comparative Example 3:

[0076] The difference between Comparative Example 3 and Example 3 is that barium chloride is not added when preparing the modified silica gel in Comparative Example 3, and the rest is the same as Example 3.

[0077] Comparative Example 4:

[0078] Comparative Example 4 uses a single modified silica gel prepared in the same manner as in Example 3 as a desiccant.

[0079] Comparative Example 5:

[0080] Comparative Example 5 uses conventional silica gel as a desiccant.

[0081] Comparative Example 6:

[0082] Comparative Example 6 uses the same single activated carbon as Example 3 as the desiccant.

[0083] The performance tests of the composite desiccant samples prepared in Examples 1 to 3 and the comparative samples in Comparative Examples 1 to 6 were performed as follows:

[0084] Moisture absorption: Place the sample under 20%, 50% and 90% conditions for 48 hours, take it out and weigh it quickly. Test three times and take the average of the moisture absorption calculated from the three tests.

[0085] Water resistance test: 100 intact samples were immersed in water for 96 hours at 25°C and 90% humidity, and the intact rate of the particles was calculated (intact rate of particles = number of intact particles / 100*100%).

[0086] The odor absorption adopts a subjective evaluation method. The odorous product and the corresponding sample / comparison sample are placed in a sealed space respectively, that is, the odorous product 1 and the sample of Example 1 are placed in a sealed space, the odorous product 2 and the sample of Example 2 are placed in a sealed space, and so on. After 24 hours, the odor judges make a subjective preliminary evaluation on whether the odor is absorbed.

[0087] The results are shown in Table 1 below.

[0088] Table 1: Moisture absorption, water resistance test and odor absorption

[0089]

[0090]

[0091] From the data analysis of Table 1, it can be seen that the present application can play a significant role in water absorption through the compounding of modified silica gel and activated carbon, and also has excellent odor absorption. From the comparison between Comparative Example 1 and Example 3, it can be seen that the silica gel in Comparative Example 1 has not been modified, and the added reagents of the modified treatments of Comparative Examples 2 to 3 are different, so that the final water absorption is worse than that of Example 3, indicating that the modified silicon prepared in the present application has a certain promoting effect on the absorption. The difference between Comparative Example 4 and Example 3 is that a single modified silica gel is used as a desiccant in Comparative Example 4, and the water absorption is slightly worse than that of Example 3, but the odor absorption is significantly worse than that of Example 3, indicating that the addition of activated carbon can obviously play a role in absorbing odor. It can be seen from the data of Comparative Examples 5 and Comparative Examples 6 that the present application uses a compound of modified silica gel and activated carbon, which can take into account the absorption of water and odor, and has a wider application value.

[0092] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A composite desiccant, characterized in that: The composite desiccant comprises modified silica gel and activated carbon in a mass ratio of (7-15): (1-5); The preparation method of the modified silica gel comprises the following steps: Methyltrimethoxysilane is added to solvent 1 and dissolved to obtain mixture A; Tetraethyl silicate was added to solvent 2 and dissolved to obtain mixture B; Add the mixture B to the mixture A, add an appropriate amount of water, perform a hydrolysis reaction at a temperature of 45° C. to 65° C. for 1 h to 3 h, then add an appropriate amount of an organic acid solution, stir evenly, and then perform a standing treatment, a first drying treatment, and a grinding treatment to obtain a mixture C; The mixture C is added to the barium chloride solution, and treated for 15 h to 20 h at a stirring rate of 150 r / min to 200 r / min and a temperature of 28° C. to 35° C., and after a second drying treatment, a modified silica gel is obtained; Wherein, the organic acid is at least one of acetic acid, p-toluenesulfonic acid and dodecylbenzenesulfonic acid; The preparation method of the composite desiccant comprises the following steps: After the modified silica gel and activated carbon are mixed according to the mass ratio, a binder is added, water is added, the mixture is heated to 65°C to 70°C, and stirred for 45min to 60min to obtain a slurry; The slurry is dried at 90°C to 120°C, and after crushing, a mud material with a moisture content of 15% to 30% is obtained, and then the mud material is extruded to obtain a molded desiccant; The molded desiccant is placed in a drying device, and the drying device is heated to 500°C~580°C at a heating rate of 5°C / min~15°C / min, and dried at 500°C~580°C for 3h~5h to obtain a composite desiccant.

2. The composite desiccant according to claim 1, characterized in that: The composite desiccant further comprises a binder, and the added amount of the binder accounts for 1% to 12% of the mass of the composite desiccant.

3. The composite desiccant according to claim 2, characterized in that: The adhesive is at least one of carboxymethyl cellulose, epoxy resin, polyurethane, waxberry gum, acrylate, polyether urea and chloroprene rubber.

4. The composite desiccant according to claim 1, characterized in that: The volume ratio of methyltrimethoxysilane to solvent one is (1~3):(5~8).

5. The composite desiccant according to claim 1, characterized in that: The volume ratio of tetraethyl silicate to solvent 2 is (1-3):(5-8).

6. The composite desiccant according to claim 5, characterized in that: The concentration of the organic acid solution is 1 mol / L to 5 mol / L.

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