Application of the three-reactor hydrogenation process in the recycling utilization of waste lubricating oil and study on the catalyst deactivation mechanism

In the recycling of waste lubricating oil, the rapid deactivation of catalysts during the hydrotreating process limits their industrial application. In this paper, a three-reactor process is proposed for the refining of waste lubricating oil, which is compared with the conventional two-reactor process. Experimental results reveal that the three-reactor technique demonstrates enhanced performance in hydrodesulfurization (HDS), hydrodechlorination (HDCl), hydrodenitrogenation (HDN), hydro-decolorization, and demetallization, effectively doubling the service life of the catalysts. Characterization of the deactivated catalysts identifies carbon deposition, silicon (Si) poisoning, and boron (B) poisoning as the primary factors contributing to catalyst deactivation. The presence of a protective agent (the second catalyst) within the three-reactor process effectively removes Si and B, thereby mitigating the Si and B poisoning of the primary hydrogenation catalyst, and extending the catalyst's lifespan. This approach offers a viable solution to the challenge of frequent catalyst deactivation encountered during the high-value utilization of waste lubricating oils, thereby providing an effective pathway for overcoming this issue in the chemical industry.