Coprocessing Bio-oils in Fluid Catalytic Cracking: Hydrogen Transfer from Hydrocarbons to Oxygenated Compounds

Model oxygenated compounds of bio-oils (ethyl acetate, acetic acid, furfural, and methylcyclopentenolone) and a hydrogen donor hydrocarbon (tetralin) were used to study the hydrogen transfer reactions between hydrocarbons and oxygenated compounds when co-fed in the fluid catalytic cracking (FCC) process. The conversion experiments of pure compounds and their mixtures were carried out in a CREC Riser Simulator fluidized bed laboratory reactor at 500 °C over a commercial equilibrium FCC catalyst, reaction times being from 3 to 12 s with a catalyst/oil ratio of 3. Model compounds were reacted individually and taking part of mixtures with tetralin, each of them with a concentration of 5 wt %, using benzene as an inert solvent. The conversion profiles of the reactants and the corresponding product distributions showed that oxygenated compounds compete strongly with the hydrocarbons for the acid sites available on the catalyst surface. The oxygenated compounds convert similarly when reacted pure or in coprocessing, while tetralin decreased its conversion when coprocessed. Hydrogen provided by tetralin is transferred to the oxygenated compounds in coprocessing by means of hydrogen transfer reactions, as shown by changes in product distributions. The index SHT was defined to quantify the magnitude of hydrogen transfer, which increased as a function of reaction time in coprocessing.