Coke deactivation during catalytic coal oils hydrotreatment
A 0.013 m by 0.5 m trickle-bed reactor equipped with automatic temperature, pressure and flow controls, and adequate safety monitoring system has been used to study catalyst coking deactivation during hydrotreating coal-derived liquids. Two feedstocks were used: EDS and SRC-I oils. The Shell 324 NiMo/Al/sub 2/O/sub 3/ catalyst was used and was presulfided before reactor startup. The nominal operational conditions were: temperature, 400 C; pressure, 13.9 MPa; liquid volume space time, 2.50 hours; and hydrogen-to-oil feed ratio, 1780 std. m/sup 3/H/sub 2//m/sup 3/ oil. The used catalysts were separated into five sections, 0.1 meter each, extensively extracted with pyridine, and dried in a vacuum oven. These catalysts were characterized in terms of coke content, surface area, pore volume, pore size distribution and pellet carbon profile. The product oils were routinely analyzed for hydrogen and nitrogen contents which were referred to catalyst activities in this study. The catalyst decayed rapidly during its 1-153 hours on stream when the SRC-I oil was hydrotreated. This rapid catalyst activity decay was found to be parallel to coke content in the catalyst. Based on this observation, a parallel fouling model was developed to represent the experimental results: coke profiles with time both within catalyst pellets and reactor beds; most frequent pore size, and hydrogenation and hydrodenitrogenation activities as functions of coke content. The better catalyst, in terms of higher activity and longer life, for hydrotreating the SRC oil is the one that has lower diffusional restrictions which can be achieved by increasing the pore size and/or reducing the pellet size, but preferably both.
- OSTI ID:
- 6291293
- Country of Publication:
- United States
- Language:
- English
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