Catalyst deactivation during the hydrotreatment of high aliphatic and low sulfur atmospheric residue

Hydrotreatment of high aliphatic and low sulfur atmospheric residue (Residue A) over a combination of demetallation and desulfurization catalysts caused greater catalyst deactivation than low aliphatic and high sulfur residue (Residue B). Since the catalytic dissociative reaction of the aliphatic group was initiated by the adsorption of the residue on the alumina support of the desulfurization catalyst, olefins produced by acid sites on the alumina are probably responsible for the catalyst deactivation through the deposition of coke. Use of an amorphous silica-alumina with stronger acid sites than alumina as the catalyst support for the desulfurization catalyst reduced the reaction temperature necessary for the desired conversion (WAT) by 20degreesC compared to the alumina support catalyst at 1500 h after the beginning of the reaction. However, catalyst deactivation of the catalyst supported on silica-alumina was significantly faster than of the catalyst supported on alumina. Feeding a mixture of Residue A (60 vol%) and Residue B (40 vol%) into the desulfurization process decreased catalyst deactivation of the combination of conventional catalysts supported on alumina. Although sulfur compounds in Residue B are important to reduce coke formation during the hydrotreatment of atmospheric residue, effective hydrotreatment of Residue A with long aliphatic chains was not achieved with the present catalyst combination.