A kind of method for preparing magnesia aerogel with bischofite as raw material

A bischofite and magnesium oxide technology, applied in the direction of magnesium oxide, can solve the problems of high toxicity of magnesium alkoxide, difficult process control, temperature and humidity sensitivity, etc., and achieve large raw material reserves, difficult synthesis, and good formability Effect

Active Publication Date: 2019-08-23
HUAIYIN INSTITUTE OF TECHNOLOGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] The invention provides a method for preparing magnesia airgel by using bischofite as a raw material. The invention effectively solves the problem that the existing magnesium alkoxide is used to prepare magnesia wet gel. The presence of magnesium alkoxide is very easy to hydrolyze and polycondense, and the process is not easy. Control; Magnesium alkoxide is highly toxic, expensive, and extremely sensitive to the temperature and humidity of the environment, and is not easy to synthesize and store.

Method used

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  • A kind of method for preparing magnesia aerogel with bischofite as raw material
  • A kind of method for preparing magnesia aerogel with bischofite as raw material

Examples

Experimental program
Comparison scheme
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Embodiment 1

[0039] Mix bischofite, distilled water, ethanol, and polyvinyl alcohol, stir for 20 minutes to obtain a transparent solution, then add propylene oxide to the solution and stir for 10 minutes to obtain a sol; The mass ratio of oxypropane is 1:10:10:0.05:2.

[0040]Seal the above sol for gelation, the gelation temperature is 30°C, and the gelation time is 2h to obtain a magnesium oxide wet gel, then soak and wash it with distilled water three times, each time for 2h, and finally in the normal pressure environment of 80°C Dry for 24 h to obtain MgO airgel. The density of the above magnesium oxide airgel is 0.15 g cm -3 , porosity 95.0%, BET specific surface area 200m 2 g -1 , the pore size distribution is 5~250nm, the compressive modulus is 1.7 MPa, and the thermal conductivity is 0.03 W m -1 k -1 .

Embodiment 2

[0042] Mix bischofite, distilled water, ethanol, and polymaleic anhydride, stir for 30 minutes to obtain a transparent solution, then add propylene oxide to the solution and stir for 5 minutes to obtain a sol; wherein bischofite, distilled water, ethanol, polymaleic anhydride The mass ratio of acid anhydride to propylene oxide is 1:1:5:0.05:4.

[0043] Seal the above sol for gelation, the gelation temperature is 70°C, and the gelation time is 20h to obtain a magnesium oxide wet gel, then soak and wash it with distilled water for four times, each time for 3h, and finally under the normal pressure of 80°C After drying for 24 h under ambient conditions, magnesium oxide airgel was obtained. The density of the above magnesium oxide airgel is 0.85 g cm -3 , the porosity is 71.6%, and the BET specific surface area is 50m 2 g -1 , the pore size distribution is 10~200nm, the compressive modulus is 30 MPa, and the thermal conductivity is 0.10W m -1 k -1 .

Embodiment 3

[0045] Mix bischofite, distilled water, isopropanol, and polymaleic anhydride, stir for 120 minutes to obtain a transparent solution, then add epichlorohydrin to the solution and stir for 60 minutes to obtain a sol; wherein bischofite, distilled water, isopropyl The mass ratio of alcohol, polymaleic anhydride and epichlorohydrin is 1:10:20:0.05:5.

[0046] Seal the above sol for gelation, the gelation temperature is 60°C, and the gelation time is 10h to obtain a magnesium oxide wet gel, then soak and wash with distilled water four times, each time for 3h, and finally vacuum freeze at -80°C After drying for 24 h, magnesium oxide airgel was obtained. The density of the above magnesium oxide airgel is 0.11 g cm -3 , porosity 96.3%, BET specific surface area 520m 2 g -1 , the pore size distribution is 5~210nm, the compressive modulus is 1.2 MPa, and the thermal conductivity is 0.027W m -1 k -1 .

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Abstract

The invention discloses a method for preparing magnesium oxide aerogel with bischofite as a material. The preparation method comprises the following steps: (1) bischofite, distilled water, alcohol solvent and water-soluble polymer are mixed and stirred for 5 to 120 minutes, so that a transparent solution is obtained, and an epoxy compound is then added into the solution and stirred for 5 to 60 minutes, so that a sol is obtained; (2) the prepared sol is sealed for gelation, the temperature of gelation is 20 DEG C to 95 DEG C, the time of gelation is 2 to 20 hours, and thereby a wet magnesium oxide gel is obtained; (3) the obtained wet magnesium oxide gel is immersed and washed with distilled water for not less than three times, and the usage of the distilled water is not less than the volume of the wet magnesium oxide gel; (4) after immersion and washing in step 3, the magnesium oxide gel is dried, and thereby the magnesium oxide aerogel is prepared. The method effectively solves the problem that magnesium alkoxide is extremely easy to hydrolytically polycondense and the process is not easy to control in the conventional preparation of wet magnesium oxide gel by utilizing the magnesium alkoxide and the problem that the magnesium alkoxide is highly toxic, expensive and extremely sensitive to the temperature and humidity of the environment, and is not easy to synthesize and store.

Description

technical field [0001] The invention relates to the technical field of preparation of nanoporous materials, in particular to a method for preparing magnesium oxide airgel by using bischofite as a raw material. Background technique [0002] There are many salt lakes in our country, and the brine of the salt lakes contains rich magnesium resources. Taking Chaerhan Salt Lake in Qinghai as an example, the magnesium chloride reserves are 1.65 billion tons, accounting for 74% of the national magnesium salt resources, and its bischofite (magnesium chloride hexahydrate, MgCl 2 •6H 2 O) is the magnesium raw material with the best quality (96%) and the largest output in the world. The development of the potash fertilizer industry has played a role in promoting the national agricultural production, but because every ton of potassium chloride extracted, 8-11 tons of magnesium chloride are discharged back to the salt lake, resulting in the local enrichment of magnesium salts in the sal...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01F5/02
Inventor 郭探云山朱秀芳高晓燕张加栋李彦兴李华举
Owner HUAIYIN INSTITUTE OF TECHNOLOGY
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