Coke Aging and Its Incidence on Catalyst Regeneration

The effects of a sweeping treatment on the activity recovery, coke content, H/C ratio, and kinetics of coke combustion have been studied in the coke deposited on an HZSM-5 zeolite. The reaction test studied is the transformation of acetone into hydrocarbons at 400 °C, and the gases used in the sweeping are He, H<INF>2</INF>, and steam. Aside from the partial elimination of coke, which occurs with all these gases, each one has a different effect. Thus, sweeping with H<INF>2</INF> causes catalyst rejuvenation. Sweeping with He promotes coke aging and a reduction in the H/C ratio. Steam is efficient for coke elimination but causes dealumination. The combustion of the remaining coke is disfavored (the activation energy is increased, and the kinetic constant is decreased) by the sweeping treatment that decreases the H/C ratio of the coke.