Deactivation kinetics for poisoning

or petroleum feed containing trace impurities such as sulfur, the poisoning reaction can be written as

The rate of deactivation is given as

The C p is the concentration of poison in feed. The ‘m' and ‘q' are respective orders.

The rate of removal of poison from the reactant by catalyst sites is proportional to the number of sites that are not poisoned (C_to - C_ps) and concentration of poisons in the gas phase, C_p. The C_ps is the concentration of poisoned sites and C_to is the total number of fresh sites initially available. Then rate of removal of poison is equal to rate of formation of poisoned site and is given as

(4)

Dividing throughout by C_to and if ‘f' is the fraction of the total number of the sites that have been poisoned then equation (4) can be written as

(5)

The fraction of sites available for adsorption (1-f) is essentially the activity a (t). Then equation (5) becomes

Determination of deactivation kinetic parameters

Case 1: Consider a reaction in a mixed reactor under constant flow condition. Let independent deactivation occurs. Assume the main reaction to be 1^st order and the deactivation reaction to be also in first order in activity ‘a'

Then

Reaction rate

(6)

Deactivation rate

(7)

Integrating equation (7)

	. a0 is initial activity

......................

Substituting expression for rate from equation (6)