1. Poisoning by Impurities Leading to Irreversible Deactivation
The catalytic performance relies on abundant active sites on the catalyst surface. In industrial production, raw materials inevitably contain trace harmful impurities such as sulfur, phosphorus and heavy metals. These impurities tend to adsorb on active centers, occupying reaction sites and chemically bonding with active components, thus causing permanent damage. Catalyst poisoning is mostly irreversible. With long-term operation, the number of effective active sites gradually decreases, leading to continuous performance decline and eventual complete failure of the catalyst.
2. Surface Carbon Deposition Blocking Micropores
In catalytic processes like petroleum refining and organic synthesis, side reactions such as cracking and polymerization occur alongside the main reactions, producing carbonaceous deposits. These deposits accumulate on the catalyst surface and internal micropores, covering active sites and blocking pore channels, which prevents reactants from contacting the catalyst. Light carbon deposition can be removed via high-temperature calcination and regeneration to restore catalytic performance. However, heavy and long-term deposition will cause permanent pore blockage, rendering the catalyst unrecyclable.
3.High-temperature aging damages the microstructure of the catalyst.
Most catalytic reactions proceed under high temperature, which is a major cause of catalyst aging. Sustained high temperature leads to carrier sintering and pore collapse. The original porous structure is damaged, resulting in a sharp drop in effective contact area. Meanwhile, active grains on the catalyst surface agglomerate and grow larger with reduced dispersion, greatly cutting down available active sites. Severe temperature fluctuations will also generate structural stress, causing cracking, pulverization and peeling and completely destroying the catalyst structure.
4.Unstable Operating Conditions Accelerating Wear and Performance Degradation
Fluctuations in working conditions greatly accelerate catalyst deterioration. Variations in system pressure and feed flow continuously impact and scour catalyst particles, causing abrasion, fragmentation and pulverization, which disrupt the stability of the reaction system. Unstable space velocity also triggers more side reactions and aggravates carbon deposition.
In practical production, stabilizing temperature, pressure and feed rate, as well as purifying raw materials strictly, are the core measures to slow down catalyst deactivation and extend its service life.