Dual coke deactivation pathways during the catalytic cracking of raw bio-oil and vacuum gasoil in FCC conditions

Abstract

Coke deposition pathways have been studied during the fluid catalytic cracking of bio-oil, vacuum gasoil (VGO) and a blend of the previous two (80wt% VGO and 20wt% bio-oil), under realistic riser conditions of the fluid catalytic cracking (FCC) unit, using a commercial catalyst at 500°C and contact times of 1.5–10s. Amount and composition of soluble and insoluble coke in dichloromethane have been analyzed using a set of techniques (TPO, FTIR, 13C NMR, XPS, Raman, GC–MS and MALDI-TOF MS, among others). The relationship of coke deposition with its composition and the reaction medium has allowed us to set two pathways of coke formation: (i) heavy hydrocarbon pathway tend to form ordered polycondensed aromatic nanostructures; whereas (ii) oxygenate pathway tend to form a lighter fraction of coke containing oxygen, less ordered and more aliphatic coke. A synergy between the two pathways have been verified due to the lower coke deposition of the blend compared to the individual components, and this has been explained in terms of (i) attenuation of the heavy hydrocarbon pathway caused by the steam contained or originated from the bio-oil, and (ii) the hydride transfer from hydrocarbons to the precursors of the oxygenate pathway.