Catalytic upgrading of distilled tall oil (DTO) in a trickle- Bed reactor: An investigation of catalyst deactivation mechanism

The deactivation behavior of commercial NiMo and CoMo catalysts during the hydrodeoxygenation of distilled tall oil in a trickle- bed reactor was studied. Carbon and sulfur analysis results showed that the amount of coke decreased with increasing contact time and temperature at a given H2 pressure. The decrease in amount of coke at higher temperature could be attributed to the hydrogenation of coke deposited on the catalyst to stable products. The coke removal by hydrogenation was significant at > 375°C. At < 375°C, polymerization of heavy molecules dominated over the hydrogenation of coke precursors, which in turn increased the coke formation. The sulfur analysis results of the spent catalysts showed that leaching out of sulfur from the catalyst is minimal during the first 6 hr of run. However, the sulfur leaching would be a major concern during long run reactions. Thus, coke formation, H2O inhibition, metal impurities in the feed, and sulfur leaching out from the catalyst surface were the contributing factors for the deactivation mechanism.