Upgrading the catalytic activity recovery capacity of a Ni–Mo/γ–Al2O3 catalyst via a modified remanufacturing process for residue hydrodesulfurization: Effect of acid leaching conditions and process sequence

Abstract

In this study, the improvement of catalytic activity recovery capacity of a modified catalyst remanufacturing process for Ni–Mo/γ–Al2O3 catalysts in residue hydrodesulfurization (RHDS) is evaluated by comparing it with our previous study. The enhancement of catalytic activity recovery is achieved by modifying the sequence and conditions of the acid leaching process in the catalyst remanufacturing process. The proposed improved process successfully restored the collapsed pore structure caused by contaminant deposition, a major deactivation factor identified in our previous study. The selective leaching of vanadium through the addition of ferric nitrate in the acid leaching process effectively addresses the issue of simultaneous removal of active species caused by excessive leaching. Consequently, the remanufactured catalyst exhibited an impressive catalytic activity recovery of 99% compared to the fresh catalyst at a reaction temperature of 395 °C, approaching a near-perfect state. Notably, the reducibility of the catalyst emerges as a key factor influencing catalytic activity recovery. The restored pore structure and selective removal of vanadium using ferric nitrate application increase the contact area between reactants and active precursors, enhancing reducibility and leading to a higher number of active sites. Additionally, a threshold effect is observed in the recovery of catalytic activity through improved specific surface area, where the enhancement of pore diameter resulting from vanadium removal on the exterior of catalyst surface becomes crucial. These findings contribute to advancing catalyst remanufacturing processes and understanding the factors influencing catalytic activity recovery.