Continuous selective deoxygenation of palm oil for renewable diesel production over Ni catalysts supported on Al ₂O ₃ and La ₂O ₃–Al ₂O ₃†

Abstract

The present study provides, for the first time in the literature, a comparative assessment of the catalytic performance of Ni catalysts supported on γ-Al ₂O ₃ and γ-Al ₂O ₃ modified with La ₂O ₃, in a continuous flow trickle bed reactor, for the selective deoxygenation of palm oil. The catalysts were prepared via the wet impregnation method and were characterized, after calcination and/or reduction, by N ₂ adsorption/desorption, XRD, NH ₃-TPD, CO ₂-TPD, H ₂-TPR, H ₂-TPD, XPS and TEM, and after the time-on-stream tests, by TGA, TPO, Raman and TEM. Catalytic experiments were performed between 300–400 °C, at a constant pressure (30 bar) and different LHSV (1.2–3.6 h ⁻¹). The results show that the incorporation of La ₂O ₃ in the Al ₂O ₃ support increased the Ni surface atomic concentration (XPS), affected the nature and abundance of surface basicity (CO ₂-TPD), and despite leading to a drop in surface acidity (NH ₃-TPD), the Ni/LaAl catalyst presented a larger population of medium-strength acid sites. These characteristics helped promote the SDO process and prevented extended cracking and the formation of coke. Thus, higher triglyceride conversions and n-C ₁₅ to n-C ₁₈ hydrocarbon yields were achieved with the Ni/LaAl at lower reaction temperatures. Moreover, the Ni/LaAl catalyst was considerably more stable during 20 h of time-on-stream. Examination of the spent catalysts revealed that both carbon deposition and degree of graphitization of the surface coke, as well as, the extent of sintering were lower on the Ni/LaAl catalyst, explaining its excellent performance during time-on-stream.

Abstract

Highly selective and stable Ni supported on La ₂O ₃–Al ₂O ₃ catalyst on the deCO/deCO ₂ reaction paths for the production of renewable diesel.