Silica gel and molecular sieve are two different materials with significant differences in composition, structure, properties and application areas.
Types & Composition & Structure
Silica gel:
Including white silica gel, blue silica gel, orange silica gel, WS type silica gel, H type silica gel, etc., among which blue and orange gel silica are indicative. When adsorbed with water, blue silica gel beads will change from blue to red, and orange silica gel beads will change from orange to green. The main component of silica gel is hydrate of silicon dioxide, with a porous mesh structure inside, irregular pore distribution, and different pore sizes, which belongs to an amorphous structure.
Molecular sieve:
The type includes 3A molecular sieve, 4A molecular sieve, 5Amolecular sieve, 13X molecular sieve, 13X HP molecular sieve, 13X APG molecular sieve, lithium molecular sieve, carbon molecular sieve. Zeolite molecular sieve is a kind of aluminosilicate microporous crystal, which has a uniform pore size and extremely high specific surface area, and belongs to a microporous material.
Adsorption Performance
Silica gel bead mainly uses the principles of physical adsorption and chemical adsorption, and has a strong adsorption capacity for polar molecules. It is especially suitable for dehumidification in dry environments. The adsorption capacity increases significantly with the increase of relative humidity, but the adsorption capacity for low-humidity gases is weak. Its adsorption process is reversible and can be regenerated by heating (such as 120°C). Molecular sieves, on the other hand, selectively adsorb molecules according to the size and shape of molecules, and only adsorb molecules smaller than the pore size of the molecular sieve. For small polar molecules and unsaturated molecules, it has selective adsorption performance and maintains high adsorption capacity under low humidity and high temperature conditions. Its adsorption selectivity is much higher than that of silica gel, and the regeneration temperature is usually higher.
Application Field
Silica gel desiccant is widely used in chemical, electronic, mechanical manufacturing, pharmaceutical and other industries and in daily life. For example, its high specific surface area and mechanical strength are used as a carrier of catalysts; it absorbs moisture in a closed environment to prevent instruments and equipment from rusting, as well as packaging for clothing, shoes and bags, food, medicine, furniture and electronic products.
Molecular sieve adsorbents are widely used in petroleum, chemical, electronic, pharmaceutical, new energy, environmental protection, gas separation, air purification, metallurgy, fertilizer and other industries. Such as being used for drying gases and liquids (drying of air, natural gas, petroleum cracking gas, methanol, ethanol, ethylene and propylene); being used for producing oxygen and nitrogen in pressure swing adsorption devices; and being used for adsorbing water, carbon dioxide and hydrogen sulfide gases.
