Introduction to the chemical principle of fumed silica

Chemical vapor deposition (CVD), also known as pyrolysis, dry or combustion. The raw materials are generally silicon tetrachloride, oxygen (or air) and hydrogen, which are formed by reaction at a high temperature. The reaction formula is: SiCl4 + 2H2 + O2 -> SiO2 + 4HCl. The air and hydrogen are respectively subjected to pressurization, separation, cooling and dehydration, silica gel drying, dust removal and filtration, and then sent to a synthetic hydrolysis furnace. After the silicon tetrachloride raw material is sent to the rectification column for rectification, it is heated and evaporated in an evaporator, and sent to the synthetic hydrolysis furnace by using the dried and filtered air as a carrier. After the silicon tetrachloride is gasified at a high temperature (flame temperature of 1000 to 1800 ° C), gas phase hydrolysis is carried out with a certain amount of hydrogen and oxygen (or air) at a high temperature of about 1800 ° C; the fumed silica particles formed at this time Very fine, forming aerosol with gas, not easy to capture, so it is first aggregated into larger particles in the concentrator, then collected by cyclone separator, then sent to the deacidification furnace, and the fumed silica is purged with nitrogen-containing air. To the PH value of 4 to 6, it is the finished product.

The particle size is small, so the specific surface area is large, the surface adsorption force is strong, the surface energy is large, the chemical purity is high, the dispersion performance is good, the thermal resistance, the resistance and the like have specific properties, and the superior stability, the reinforcing property, and the like Thickness and thixotropy are unique in many disciplines and fields and have an irreplaceable role. Nano-silica, commonly known as “ultra-fine white carbon black”, is widely used in various industries as an additive, catalyst carrier, petrochemical, decolorizing agent, matting agent, rubber reinforcing agent, plastic filling agent, ink thickener, metal softness. Polishing agent, insulating and insulating filler, advanced daily cosmetic filler and spraying materials, medicine, environmental protection and other fields. It also provides new material foundation and technical guarantee for the development of related industrial fields.