The effect on the energy balance of a FCC unit after co-feeding the aqueous fraction of a bio-oil together with a vacuum gas oil (VGO) has been studied. The simulation program considers the interdependency relationship between the reaction and regeneration sections in the unit, where the heat of coke combustion has to sustain the energy requirements to preheat and vaporize the feedstock as well as the endothermic cracking reactions. The combustion of coke deposited on an equilibrium commercial FCC catalyst in cracking various bio-oil/VGO mixtures at 530 degrees C, with catalyst to oil relationships between 3 and 6 in a CREC Riser Simulator laboratory reactor, was investigated by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results showed that the heat from coke combustion is not enough to provide the energy needed in the unit when the amount of bio-oil in the feedstock is larger than 5 wt%, mainly due to the high content of water in the aqueous fraction of the bio-oil and to the lower heat of combustion of the coke formed in co-processing, as compared to the VGO alone.

Oxygenated model compounds representing typical components of bio-oils and a hydrocarbon hydrogen donor agent were used to study hydrogen transfer reactions between hydrocarbons and oxygenated compounds when coprocessed over acidic commercial fluid catalytic cracking (FCC) catalysts. Phenol, syringol, and trimethoxybenzene were each mixed with tetralin at 5 wt % individually in benzene as an inert solvent. The mixtures were reacted in a fluidized bed, batch CREC Riser Simulator laboratory reactor during 10 s contact time with a catalyst to oil relationship of 3 at 500 C degrees over a commercial equilibrium FCC catalyst, conditions being selected in order to simulate FCC bio-oil-vacuum gas oil coprocessing. Tetralin was also reacted alone at 5 wt % in benzene to gather background information. When tetralin was the only reactant, its conversion was 87%, the most important reactions being hydrogen transfer, as shown by the yield of naphthalene, and cracking. Alkylation and disproportionation were also observed to a lower extent. In the experiments with the mixtures, the oxygenated compounds converted completely and tetralin converted to less than half the conversion when pure. In these experiments, as compared to pure tetralin, the yield of gases and C-11+ hydrocarbons increased and the yield of coke decreased, showing the interaction between the hydrocarbon and the model oxygenated compound reactants. The index S-HT, which shows the selectivity to hydrogen transfer reactions from tetralin, increased significantly, to about 2 times, in the experiments with the mixtures. Moreover, coke from pure tetralin was shown to be qualitatively different from that in the experiments with the mixtures, where it was more condensed, thus confirming that the reaction pathways are dissimilar.