(103c) Effects of Trace Amount of Noble Metal (Pd/Rh) on the Performance of Co-Clay Catalysts for Heavy Oil Upgrading

The increasing demand for lighter engine fuel and recent escalation of crude oil prices have stimulated research focused on the processing of comparatively cheaper heavy crude oils and the heavy residues. The main problem associated with heavy oil fractions is their high organic sulfur, nitrogen and metal content, which must be removed due to their toxicity and environmental impact. In addition, environmental regulations are becoming increasingly stringent with regards to sulfur content in fuels. Therefore, the need for more efficient hydortreating catalysts and process is growing. This communication reports the promotional effects of small amounts of Pd and Rh on the hydrodesulfurization (HDS) and hydrocracking (HC) activities of high porous saponite (HPS) supported Co catalysts. During catalyst preparation, HPS was first modified with the noble metal(s) using an incipient wetness impregnation technique followed by cobalt loading through an ion exchange method at 80 ºC. The catalysts were characterized by temperature-programmed reduction (TPR). Results showed that the reducibility of the catalysts was significantly improved due to the noble metal (Pd, Rh) promotional effects. Higher metal dispersion and hydrogen spillover effects were considered to be the main reasons for the increased reducibility of the catalysts. The activity of the catalysts was tested in a batch autoclave reactor using vacuum gas oil as feedstock. Both the HC and HDS activities of noble metal-promoted Co/HPS catalysts were found to be higher than that of plain Co/HPS catalysts. Furthermore, Rh displayed higher promotional effects as compared to Pd in both HC and HDS. This higher activity is consistent with the TPR results, which showed superior reducibility of the Rh promoted catalysts. A particular interesting finding of this study pertained to a synergic effects of bi-noble (Pd?Rh) metal promoted Co/HPS catalyst. It was observed that a trace amount of Rh and Pd exhibited a significant enhancement of the catalytic activity of Co/HPS. The activity of the bimetallic catalyst was comparable to that of the Rh promoted catalyst with higher Rh loading. It should be noted that this synergic effects was achieved with a lower overall noble metal content, which is crucial for the economic feasibility of the catalyst for industrial application. The coke deposition on the Pd?Rh promoted catalyst was also found be the lower than that of the plain and single noble metal promoted Co/HPS, which is a positive aspect for a longer catalyst lifetime. Therefore, this study revealed that trace amount of noble metal promoted Co/HPS catalyst holds great promise for hydrocracking and HDS of heavy oil.

Keywords: Heavy oil upgrading, Clay, Co, noble metals, bimetallic catalysts, TPR