(166a) Fossil and Bio Carbon Story in FCC Co-Refining

Fossil and bio carbon story in FCC co-refining

Nicolas Thegarid, Gabriella Fogassy, Frédéric Meunier, Yves Schuurman, Claude Mirodatos*

Ircelyon, CNRS-UCBL, 2 Avenue Albert Einstein, 69626 Villeurbanne, France.

claude.mirodatos@ircelyon.univ-lyon1.fr

Introduction. In order to meet the international binding renewable energy targets by 2020 (10% share in all forms of transportation fuels) [1], a realistic alternative to the first generation bio-fuels is to produce hybrid bio- and fossil fuels by co-refining biomass pyrolysis oil with crude oil fractions in a conventional oil refinery [2, 3]. However, co-refining leads to significant changes in products quality, such as higher gasoline aromaticity and coke deposits [4]. A detailed understanding is therefore necessary on how the oxygenated moieties affect the FCC mechanism and how both fossil and renewable carbon is dispatched among the FCC products (essentially in the gasoline and in the coke produced during the cracking and burned during the regeneration steps). In this study, up-graded pyrolysis bio-oils (hydrodeoxygenated, HDO or catalytic, CPO) are added to crude oil distillates (VGO or long residue) and the quality of the produced "hybrid" FCC fuels is analyzed and compared, focusing on coke generation and nature as a signature of the cracking process.

Experimentals. The various types of coke deposited during the cracking step were analysed by TPO, thermogravimetry under flowing air, DRIFT, TEM and ¹³C-CP-MAS NMR. The coke occupancy in the porous volume was measured by BET/BJH nitrogen adsorption.

Results and conclusion. From pore volume changes upon co-refining and from coke analysis, the rate of coke deposition was found significantly higher (about two fold) in the presence of oxygenates in the feed, either from HDO or CPO oils, and still much higher when processing a pure HDO bio-oil. It was found in addition that the amount and nature of the deposited coke depends strongly on the composition of the reacting feed (either VGO alone, or a mixture VGO/upgraded bio oil, or the pure bio-oil). From TEM and BET-BJH analyses, the coke deposits from the VGO cracking are essentially graphitic and located inside or close to the Y zeolite microstructures, without affecting much their pore volume, while extra framework deposits, essentially amorphous, are formed in the meso/macroporous structure after bio-oil degradation/condensation. From NMR and DRIFT analysis, the coke formed from the oxygen containing bio-molecules is found to present more highly condensed aromatic rings than the coke formed from the feed hydrocarbons. From the radio carbon analysis for a typical co-processing experiment (ca. 9% of added bio-oils to VGO feed), it comes that the bio-carbon contained in the HDO-oil is concentrated mainly in the gas fraction (11%) and in the coke fraction (16%) while the targeted liquid product, gasoline, contains only around 7% of bio-carbon [5].

By acounting for the above results and others not presented here, a general mechanistic scheme is proposed where the lignin polymeric fragments of the added bio-oils are cracked into smaller methoxy phenols in the extra-framework space, leading also to a specific amorphous coke deposition. The latter tends to block the mesopores when fed at high concentration. In turn, the graphitic coke deposition arising from the hydrocarbons cracking essentially in the zeolite micropores is not significantly affected by the co-presence of oxygenated molecules.

These important and original findings can be considered as strong guide-lines to adapt the FCC catalysts design to future co-refining operating conditions.

References:

1. http://ec.europa.eu/energy/renewables/targets_eu.htm

2. F. de Miguel Mercader, J.A. Hogendoorn, S.R.A. Kersten, N.W.J. Way, C.J. Schaverien, M.J. Groeneveld, Appl. Catal. A, 96, 57-66 (2010).

3. Y. Schuurman, G. Fogassy, C. Mirodatos. Tomorrow's biofuels: hybrid bio-gasoline by co-processing in FCC units in "The Role of Catalysis for the Sustainable Production of Bio-fuels and Bio-chemicals", Eds Triantafyllidis, Stöcker and Lappas, Elsevier, 2013, 321–349.

4. G. Fogassy, N. Thegarid, Y. Schuurman and C. Mirodatos. From biomass to bio-gasoline by FCC co-processing: effect of feed composition and catalyst structure on product quality. Energy & Environmental Sci. 4 (2011) 5068-5076.

5. G. Fogassy, N. Thegarid, Y. Schuurman and C. Mirodatos The fate of bio-carbon in FCC co-processing products. Green Chem., 14 (2012) 1367-1371