Method for rapidly preparing hydrophobic silica aerogel through subcritical drying of methanol

Abstract

The invention relates to a method for rapidly preparing hydrophobic silica aerogel through subcritical drying of methanol. The method comprises the steps of (1) sufficiently hydrolyzing silicate ester and ethoxysilane proportioning solution in a methanol environment under the action of an acid catalyst; (2) adding an alkali catalyst, and then, enabling near-neutral or alkali gel to form wet gel; or after obtaining the near-neutral or alkali gel, compounding the near-neutral or alkali gel and inorganic fibers to prepare a gel-fiber composite, and aging; and after aging, placing the gel-fiber composite into a methanol extracting device, and drying; and (3) heating and increasing the pressure until being up to the subcritical state of methanol, separating and extracting methanol in pores of dried hydrophobic silica aerogel, cooling, releasing the pressure and standing to obtain the hydrophobic silica aerogel. A solvent replacement link is omitted in the method, so that the time is saved, and the energy cost is reduced; the drying temperature is 180-200 DEG C, the pressure is 5-6MPa, and the energy consumption is greatly reduced; and methanol provides parts of hydrophobic groups for a body, and a proper amount of methylethoxysilane is introduced to a silicon source, so that the hydrophobicity of the hydrophobic silica aerogel is ensured.

Description

technical field [0001] The invention relates to the field of airgel production, in particular to a method for rapidly preparing hydrophobic silica airgel by using methanol subcritical drying and an airgel product prepared by the method. Background technique [0002] Airgel is known as one of the ten most potential new materials in the future. Because of its porosity as high as 95%, thermal conductivity and density as low as 0.01W / m. It has unparalleled advantages in noise reduction and sound insulation, and will definitely contribute to energy conservation and emission reduction in the future. [0003] Airgel was invented by Professor Kistler of Stanford University in 1931, using water glass as a silicon source, and aerogel was prepared by sol-gel process, but the process is complicated and has not been applied. [0004] In the 1960s, Nicolaon et al. used silicon alkoxide as a precursor to prepare wet gel by sol-gel process, and then made it by supercritical drying (SCFD) p...

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Problems solved by technology

However, the critical temperature and pressure of methanol are 240°C and 7.95MPa respectively. To make the whole system fully reach the supercritical state of methanol, the heating source will be close to 300°C, and the pressure will be close to 20MPa, which will cause the following problems: 1) high cost energy consumption; 2) huge potential safety hazard; 3) long preparation time

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