"Desiccant" isn't one product — the three main options adsorb moisture through different mechanisms and suit different humidity ranges and applications.
Silica Gel
Silica gel is the most widely used general-purpose desiccant, with high moisture-adsorption capacity across a broad relative-humidity range and low cost. It's the default choice for packaging, instrument cases, and general drying where a broad operating range matters more than adsorbing to extremely low residual moisture levels.
See our guide to blue vs white silica gel, or the product pages for Silica Gel Blue and Silica Gel White.
Activated Alumina
Activated alumina has a more open pore structure than silica gel and holds up better at higher temperatures, which makes it a common choice for compressed-air drying, catalyst support applications, and fluoride/arsenic adsorption in water treatment. It's also readily regenerated (reactivated by heating to drive off adsorbed moisture) for reuse in continuous-cycle drying systems.
See Activated Alumina (IS 9700-1981).
Zeolite (Molecular Sieve)
Zeolite's crystalline pore structure adsorbs by molecular size, which lets it pull moisture down to very low residual levels — useful where "dry" needs to mean genuinely dry, such as natural gas dehydration, refrigerant drying, and double-glazing spacer bars. It performs better than silica gel at low relative humidity, where silica gel's capacity drops off.
See Zeolite (Powder).
Which One Should You Choose?
For general packaging and moderate-humidity drying, silica gel is the simplest and most economical choice. For higher-temperature or regenerable-cycle drying, activated alumina is usually the better fit. Where you need to reach very low residual moisture — gas drying, refrigerants, insulated glazing — zeolite is the specialist choice.