... cracked gas,ethylene, propylene, butylene, butadien The pore size of 3A molecular sieve is 3A . It does not absorb any molecular larger than ... 3A. It is an alkali metal alumino-silicate, the potassium form of the type A crystal structure ... sieve are replaced by potassium ions. Will absorb, in sequence of adsorption rate, helium, neon, nitrogen and water.Properties and ...