Sintering is the most common irreversible deactivation phenomenon of industrial catalysts under high-temperature conditions, widely occurring in chemical units such as catalytic cracking, flue gas denitrification and hydrogenation reactors. Unlike carbon deposition and catalyst poisoning, which can be restored via regeneration, sintering causes permanent structural damage to catalysts that cannot be repaired, requiring full replacement. It is a key factor shortening unit operation cycles and raising production costs.
Most industrial catalysts are supported catalysts whose catalytic activity originates from nano-sized metal particles dispersed on the carrier surface. The reaction efficiency relies heavily on the large specific surface area and abundant active sites provided by tiny metal particles. Under operating conditions including continuous overtemperature, long-term high-temperature service, or high temperature coupled with water vapor, the stability of metal particles drops drastically. Fine metal particles migrate, collide and fuse on the carrier surface, resulting in continuous particle growth and severe agglomeration.
Along with metal particle agglomeration, catalyst carriers degrade simultaneously. Common porous carriers like alumina and molecular sieves suffer pore collapse and crystal phase transformation under extreme high temperatures. Their porous structure is destroyed and specific surface area declines sharply, losing the function to disperse and immobilize active metals. Enlarged metal particles and damaged carrier structures drastically reduce active sites and catalytic performance, lowering unit reaction conversion rates and increasing energy consumption.
Major triggers of catalyst sintering include sudden temperature runaway, local overtemperature, sharp temperature fluctuations and excessive water vapor in the reaction system. As an irreversible deactivation mode, sintering cannot be recovered through conventional processes such as coke burning, purging or regeneration, making it a troublesome catalyst failure in industrial production.
Stable operating conditions serve as the core principle to prevent catalyst sintering. Operators must strictly control reaction temperatures to avoid overtemperature and temperature runaway, minimize temperature fluctuations, and limit water vapor concentration in the system. Meanwhile, optimizing carrier structures and adding rare earth additives can immobilize surface metal particles and restrain particle migration and agglomeration. These methods effectively improve the high-temperature stability of catalysts, extend service life and ensure long-term stable operation of production units.