Molybdenum and Tungsten Phosphides in Hydrodesulfurization and Hydrodenitrogenation of Petroleum Compounds

Abstract

Published data on hydrodesulfurization and hydrodenitrogenation of model petroleum compounds in the presence of molybdenum and tungsten phosphides are analyzed. The majority of papers in which these catalysts are compared to traditional sulfide catalysts demonstrate higher activity of the phosphide catalysts. The influence exerted on the activity of phosphide catalysts in these processes by the feed composition (presence of sulfur- and nitrogen-containing compounds), catalyst synthesis conditions and active phase content, reaction conditions, and promoter is described. When performing the synthesis at high temperatures or using large amounts of the active phase deposited onto an Al-containing support, the catalyst activity can decrease owing to the formation of AlPO₄. The promotion of molybdenum and tungsten phosphides with nickel or cobalt enhances the catalyst activity. The major cause of phosphide deactivation is the presence of nitrogen-containing compounds in the feed, whereas the presence of sulfur-containing compounds, on the contrary, in most cases leads to an increase in the catalyst activity owing to the formation of the phosphosulfide phase.