| In recent years the rapidly increasing price of crude oil and the growing scarcity of sweet crudes have caused refiners to process heavier feedstocks containing significant quantities of undesirable materials of high carbon-to-hydrogen ratio and with sulfur, nitrogen and heavy metals bound in complex compounds such as asphaltenes. Naphtha and heavier cuts of these crudes all must be hydrotreated to remove these elements, which are environmentally unacceptable and are also catalyst poisons for subsequent processes. This treatment also reduces the carbon-to-hydrogen ratio of the oil.; Information concerning the morphology and behavior of active components on commercially aged catalyst, the effects of regeneration conditions on activity, and insights into the nature of coke and contaminant metal deposits could lead to improved catalysts and operating conditions, yielding significant economic returns. Spent Ni-Mo/Al(,2)O(,3) hydrotreating catalyst from a commerical hydrotreater was examined using TGA, SEM, STEM, XPS and a microreactor. Information concerning intraparticle distributions of active components, characteristics of the coke and metal deposits, and catalytic activity for fresh, spent and regenerated catalyst was used to draw general conclusions concerning hydrotreating catalyst deactivation.; It was found that catalytic activity was reduced and the nature of the hydrogenation function was altered due to bulk migration and agglomeration of molybdenum. This process was found to be accelerated by high-temperature regeneration. Results also indicated that iron deposits might catalyze formation of coke. Tentative generalizations and suggestions on improved reactor operation are presented. |
