Ruthenium catalyst

Catalyst deactivation
Catalyst deactivation refers to the phenomenon that the catalyst loses its activity due to various factors during use. The reasons for the deactivation of the noble metal catalyst are generally classified into three categories: poisoning, sintering and heat deactivation, coking and clogging.
Inactivation caused by poisoning
(1) Temporary poisoning (reversible poisoning): When the poison is adsorbed or combined on the active center, the bond strength generated is relatively weak. The poison can be removed by appropriate methods to restore the activity of the catalyst without affecting the properties of the catalyst. It is called reversible poisoning or temporary poisoning.
(2) Permanent poisoning (irreversible poisoning): The poison interacts with the active component of the catalyst to form a strong chemical bond. It is difficult to remove the poison by a general method to restore the activity of the catalyst. This poisoning is called irreversible poisoning or permanent poisoning.
(3) Selective poisoning: Catalytic poisoning may lose the catalytic ability to a certain reaction, but still have catalytic activity for other reactions. This phenomenon is called selective poisoning. In a series of reactions, if the poison only poisons the active site that causes the subsequent reaction, the reaction can be left in the intermediate stage to obtain a high yield of intermediate product.
Inactivation caused by coking and clogging
The carbonaceous deposits on the surface of the catalyst are referred to as coking. Coking can occur almost in the heterogeneous catalytic reaction process using organic materials as a raw material and solid as a catalyst. Since the carbonaceous material and/or other substances are deposited in the pores of the catalyst, the pore size is reduced (or the pores are reduced), so that the reactant molecules cannot diffuse into the pores. This phenomenon is called clogging. Usually carbonaceous deposits can be removed by vaporization with hydrogen or hydrogen, so coking inactivation is a reversible process. 3
Sintering and heat deactivation
Sintering and thermal deactivation of the catalyst refers to changes in the structure and properties of the catalyst caused by high temperatures. In addition to causing sintering of the catalyst, high temperatures may cause other changes, including: chemical composition and phase composition changes, semi-melting, grain growth, active components are embedded in the carrier, and the active components are formed by volatile substances or Sublimation of substances can be lost.