Synthesis of large pore carbon-alumina supported catalysts for hydrodemetallization

摘要

This study is carried out to synthesize a supported hydrodemetallization (HDM) catalysts. The supports are prepared by mixing peptized alumina with activated carbon. The compositions of the supports (0-75 % activated carbon in alumina), the stepwise drying, and the calcination under the moderate flow of air in a rotating furnace produced supports with large pore volume, which respectively enhanced the metal storage capacity and minimized diffusion limitations of large hydrocarbon molecules (i.e., asphaltene). The presence of carbon in support also helped in reducing coke and metal depositions on pore-mouth and catalytic sites. The optimum textural and mechanical properties of the support are obtained when the carbon-alumina weight ratio is 1:1. The catalysts are synthesized by impregnating the support extrudates with low content of Mo active metal with or without Co or Fe as a promoters metals. FeMo supported catalyst showed better synergy than the CoMo and NiMo catalysts. The FeMo supported catalyst composition (10-75 wt% carbon) indicated best HDM results for an optimum pore diameter. The activity and the stability of the catalysts were evaluated using residual oil and heavy crude oil (Ku crude), which respectively have metal content (Ni and V) of 212 ppm and 567 ppm. The catalyst contains mesomacro-pores along with bimodal-type pore structure and has textural properties such as an average pore diameter of 5-1000 nm, a total pore volume of 0.3-1.5 ml/g, and moderate surface area of 50-200 m(2)/g.