David E. Sherwood

Effect of diffusion on resid hydrodesulfurization activity

Abstract The HDS reaction of vacuum resid is strongly influenced by intrapellet diffusion. The incorporation of macroporosity in the >25 nm pore diameter range is beneficial to the initial resid HDS activity of a resid hydrotreating catalyst with a mesopore mode in the range from 5 to 15 nm. The primary function of the macropore is to provide access to the mesopore structure. The resid HDS activity is related to the catalytic metals in the desired mesopore structure, and the rate determining step for HDS reaction of vacuum resid is the diffusion in the mesopore region. Restriction of HDS activity due to diffusion effects can be alleviated by decreasing the pellet diameter and choosing the optimum mesopore and macropore diameters and volumes.