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Location and Surface Species of Fluid Catalytic Cracking Catalyst Contaminants: Implications for Alleviating Catalyst Deactivation

Etim, U. J., Wu, Pingping, Bai, Peng, Xing, Wei, Ullah, Rooh, Subhan, Fazle, Yan, Zifeng
Energy & Fuels 2016 v.30 no.12 pp. 10371-10382
aluminum oxide, carbon, catalysts, catalytic cracking, micropores, nickel, oxidation, steam, synergism, vanadium
The deposition of appreciable amounts of metal poisons and carbon poses serious problems to the refiner during fluid catalytic cracking (FCC) unit operation. To check the effects of these contaminants on the catalyst, an in-depth understanding of their locations and existing states becomes necessary. In this work, the location and nature of vanadium, nickel, and coke species on the FCC catalyst were investigated. Detailed analyses of catalyst samples, including industrial equilibrium catalysts (E-cats), were accomplished using a variety of characterization techniques. It was found that nickel and vanadium concentrated mainly in meso- and micropores of the FCC catalyst, respectively. On the surface of E-cats, vanadium exists mainly in +4 and +5 oxidation states, while nickel is present as NiO, NiAl₂O₄, and surface nickel hydrosilicates and as NiO and NiAl₂O₄ in the bulk. The formation of a large amount of NiAl₂O₄ on the alumina support by nickel indicates its preferential location in the alumina component of the FCC catalyst. When co-existing, a synergic effect between vanadium and nickel is likely. On the other hand, coke distributed within the catalyst pore spaces, exhibiting different behaviors in different catalysts as a result of the effects of the metals and steam treatment. The coke deposits consist of a layer of graphitized carbon with both hydrocarbon and aromatic carbon species. Results obtained in this study provide insights into the nature of contaminants of FCC catalysts and could help in the rational design of catalysts to alleviate the metal poisons during catalytic cracking.