Question

State the significant difference between catalyst deactivation by coking and sulfur poisoning.

Answer 1

Catalysts are the chemical substance that alters (increase or decrease) the rate of chemical reaction. It helps in gaining equilibrium and opens a different route of chemical reactions between reactants and products.

When a chemical, mechanical or thermal process deactivates catalytic activity, it is known as Catalytic deactivation. Several mechanisms of catalytic deactivation are poisoning, fouling, coking, sintering, phase transformation, attrition and crushing etc.

Significant difference between Coking and Sulfur poisoning are-

Coking	Sulfur Poisoning
It blocks catalytic pores by physically depositing (belonging from fluid phase) carbonaceous material on the catalytic surface. It is a mechanical type mechanism. Coking is done on Metal oxide (carbonaceous materials), Metal Catalyst, Zeolite and sulfur catalyst. Example- Cracking reaction lead to coke formation.	It blocks site of catalytic reaction by strong chemisorption of species at catalytic site. It is a chemical type mechanism. It brings changes in electronic and geometrical structures. Apart from sulfur it includes metals from group V, VIA, VIIA and other heavy metals and molecules. Example- Sulfur is used as poison during synthesis of methane using Ni catalyst. Poisons- H2S, S