What are the factors influencing the ultra-long and stable operation of hydrogenation plants

Hydrogenation catalyst deactivation is one of the key factors affecting the long-cycle stable operation of fixed-bed hydrogenation units. The existing research results concluded that the main factors leading to the deactivation of hydrotreating catalysts include three aspects:

(i) Metal deposition covers the active center on the catalyst surface and destroys the active metal structure on the catalyst surface, leading to catalyst deactivation, while metal deposition leads to the reduction of catalyst specific surface area and pore size, and even blocks the catalyst micropores, which increases the diffusion resistance of macromolecules into the catalyst micropores;

(ii) Catalyst deactivation due to carbon accumulation on the catalyst surface, which mainly includes catalyst deactivation caused by the deposition of more polar compounds on the catalyst carrier and active center or blocking the catalyst pore channel leading to the reduction of catalyst activity;

(iii) Catalyst deactivation caused by aggregation of active metals on the catalyst itself and changes in the morphology of the active center. The first factor of catalyst deactivation is commonly found in heavy oil hydrogenation units, where metals such as Ni and V in the heavy oil feedstock are deposited on the catalyst surface as the hydrogenation reaction proceeds and form sulfides to cover the active center of the catalyst surface and block the catalyst pores, leading to catalyst deactivation; the second factor of catalyst deactivation occurs in all hydrogenation reactions, and the available research results suggest that carbon accumulation leads to catalyst deactivation. The third form of catalyst deactivation is less commonly encountered in industrial plants and occurs mainly in the research phase of catalysts. Catalysts used in industry generally do not exhibit significant active metal aggregation.

For the catalyst deactivation caused by metal deposition on the catalyst surface, the metal deposition deactivation of the main catalyst can be avoided by filling the upper part of the catalyst bed with demetallized catalyst or setting up a separate demetallized reactor to effectively remove the metal from the feedstock; catalyst carbon accumulation deactivation is the main cause of most hydrogenation main agent deactivation.