(85d) Catalytic Hydrotreating of Tall Oils into Renewable Feedstocks for Petrochemical Processes

The interest for bio-based fuels and chemicals is increasing due to the major concerns over greenhouse gas (GHG) emissions result from fossil based fuels.¹ Importantly, the sustainable production of bio-based chemicals, mainly platform chemicals seems to be more promising for the future than the production of biofuels. However, there are number of criteria should be taken into account for developing a sustainable chemical industry; in which selection of an economically viable feedstock is prime important.² Tall oil, derived as a by-product from Kraft-pulping is a potential candidate as an economically viable starting material, and upon catalytic upgrading it can be converted into a more suitable feedstock for a bio-based chemical industry.³

This research approach discusses the catalytic upgrading (hydrotreatment) of tall oils such as crude tall oil (CTO), distilled tall oil (DTO) and tall oil fatty acids (TOFA) on a commercial NiMo catalyst. Hydrotreating experiments were conducted in a continuous, down flow; fixed bed reactor at different process conditions (WHSV 1-3h^-1, Pressure 5 MPa and Temperature 300 - 450 ^oC). After the stabilization period (6 h.), the liquid samples were collected and separated into organic and aqueous phases. The detailed product distribution from the organic phase, conversions of major components (fatty acids, resin acids and sterols) of tall oils, and degree of deoxygenation was calculated using various analytical techniques.

This study reported that upon upgrading tall oils mainly produced paraffins, cycloalkanes and aromatics. Paraffins were the major groups of products obtained from tall oils at different process conditions. Lower temperatures (< 400 ^oC) were found to be more favorable for the production of paraffins, and at most favorable conditions (WHSV= 1 and 2 h^-1, T= 325-375 ^oC) TOFA was found to give maximum yield of paraffins (85-90 wt %). Maximum (100 %) degree of deoxygenation and conversion of fatty and resin acids was achieved from TOFA and DTO under the tested conditions. However, with CTO, tested conditions were inadequate to achieve 100 % degree of oxygenation and conversion.

This study also discusses the chemical compositions of naphtha range feeds obtained from tall oils under different process conditions, will be addressed in the talk in comparison with state-of-the-art refinery naphtha feeds. The talk will also address boiling point distribution and C/H ratio of various product streams obtained from tall oils upon upgrading. Most importantly, the talk will discuss the success criteria of catalytic hydrotreating of tall oils for steam cracking. 

References

1.  Abhari, R.; Tomlinson, H.L.;  Roth, E.G. Biorenewable naphtha, USA, 2009
2. Brent, H. S. Conversion of Biorenewable Feedstocks: New Challenges in Heterogeneous Catalysis Ind. Eng. Chem. Res. 2010, 49, 10212–10217
3. Coll, R.; Udas, S.; Jacoby, W.A.  Conversion of the Rosin Acid Fraction of Crude Tall Oil into Fuels and Chemicals. energy&fuels 2001, 15, 1166-1172