Research on the scope of application of silica gel desiccant

In production and life, silica gel can be used to dry N2, air, hydrogen, natural gas [1] and so on. According to acid and alkali, desiccant can be divided into: acid desiccant, alkaline desiccant and neutral desiccant [2]. Silica gel appears to be a neutral dryer that seems to dry NH3, HCl, SO2, etc. However, from the principle point of view, silica gel is composed of three-dimensional intermolecular dehydration of orthosilicic acid molecules, the main body is SiO2, and the surface is rich in hydroxyl groups (see Figure 1). The reason why silica gel can absorb water is that the silicon hydroxyl group on the surface of silica gel can form intermolecular hydrogen bonds with water molecules, so it can adsorb water and thus play a drying role. The color-changing silica gel contains cobalt ions, and after the adsorption water reaches saturation, the cobalt ions in the color-changing silica gel become hydrated cobalt ions, so that the blue silica gel becomes pink. After heating the pink silica gel at 200℃ for a period of time, the hydrogen bond between the silica gel and water molecules breaks, and the discolored silica gel will turn blue again, so that the structure diagram of the silicic acid and silica gel can be reused as shown in Figure 1. So, since the surface of silica gel is rich in hydroxyl groups, the surface of silica gel may also form intermolecular hydrogen bonds with NH3 and HCl, etc., and there may be no way to act as a desiccant of NH3 and HCl, and there is no relevant report in the existing literature. So what were the results? This subject has done the following experimental research.