In various catalytic reaction processes, carbon deposition and coking constitute major causes of catalyst activity decline and shortened operation cycle of process units. Continuous reactions including thermal cracking of feedstock components, polymerization of unsaturated hydrocarbons, and dehydrogenation-condensation of intermediate products generate carbonaceous deposits on the catalyst surface and inside pore channels. These deposits cover active sites and block microporous structures, leading to notable deterioration in catalyst selectivity and reaction efficiency. In practical production, carbon deposition and coking can be effectively restrained via process optimization, catalyst modification, feedstock pretreatment and routine operation maintenance.
Adjustment of process parameters serves as the core measure for coking control. Excessively high reaction temperature intensifies deep cracking and condensation of feed materials, acting as the primary trigger for carbon deposition. The reaction temperature range must be strictly controlled during production to eliminate local overheating. Appropriately raising the dosage ratio of hydrogen and steam enables in-situ consumption of hydrocarbon fragments and intermediate oily substances prone to converting into solid coke through steam gasification and hydrogenation saturation reactions. Meanwhile, stable space velocity and system pressure prevent prolonged retention of materials inside catalyst pores, thereby reducing carbonaceous deposits from the perspective of reaction conditions.
Modifying intrinsic catalyst properties fundamentally improves its anti-coking performance. Doping rare earth metals and oxide additives optimizes the distribution of acid-base sites on the catalyst surface and raises the content of surface active oxygen, accelerating oxidative decomposition of carbonaceous substances. Adopting a hierarchical pore structure for the carrier speeds up material transport into and out of pores, cuts the residence time of reactants and products within pore channels, and restrains macromolecule condensation coking and accumulated carbon deposition.
Feedstock pretreatment and regular regeneration maintenance are equally important. Pre-removal of high-boiling components such as colloids and polycyclic aromatic hydrocarbons from raw materials cuts down the precursors for carbon deposition at the source. Inert gas full purging is required during unit startup, shutdown and working condition switching to avoid residual feedstock forming coke and carbon deposits under high temperature. Besides, regular low-temperature controlled carbon burning regeneration gently removes carbonaceous sediments on the catalyst surface and internal pores, which efficiently restores catalytic activity, slows down deactivation rate and ensures long-term stable and high-efficiency operation of catalytic units.