Oxidative regeneration of deactivated binderless 5A molecular sieves for the adsorption–separation of normal hydrocarbons

Abstract

The deactivation of binderless 5A molecular sieves for the adsorption–separation of normal hydrocarbons was investigated on a fixed-bed adsorber. The deactivated molecular sieves were regenerated by removing the coke deposited through oxidation under various conditions. They showed lower surface area, smaller pore volume, and larger pore diameter than the fresh sample because certain passages of small pore in the molecular sieves were blocked by the coke deposited. With the increase of the coke content in the molecular sieves, the deactivation rate decreased gradually. With the increase of oxidation temperature from 582 K to 787 K, the coke removal efficiency was elevated from 64% to 100%. At 787 K, the coke deposited in the molecular sieves was completely removed and the adsorption activity of the molecular sieves was recovered; however, the surface area and pore volume of the regenerated molecular sieves could not be restored to the original values of the fresh samples. Under 685–884 K, the removal of coke from the binderless 5A molecular sieves by the oxidative treatment could be expressed with a macrokinetic formula: ln( C 0/ C) = 0.013exp(−28122.1/ T) ( po 2) 0.32 t.