Assessing the potential of crude tall oil for the production of green-base chemicals: an experimental and kinetic modeling study

Crude tall oil (CTO) is a cost-competitive biomaterial available from the Kraft pulping process that contains approximately 50% fatty acids, 30% resin acids and 20% neutral polycyclic oxygenated species such as sterols. Although CTO differs drastically from conventional fossil-derived feedstocks, it proves to be an interesting drop-in alternative to produce renewable base chemicals. The proposed two-step process in which, first, CTO is converted into a highly paraffinic/naphthenic feedstock through hydrodeoxygenation (HDO) over a NiMo catalyst, followed by steam cracking, produces up to 34 wt % of ethylene, 15 wt % of propylene and 5 wt % of 1,3-butadiene. A dedicated kinetic model was developed for HDO-CTO steam cracking containing over 500 species to further optimize its industrial potential. Reaction path analysis shows that the HDO severity must be optimized to remove all oxygen but dehydrogenation should be avoided so that valuable light olefins and aromatic production are maximized instead of low va...