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

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(2)O(3) and γ-Al(2)O(3) modified with La(2)O(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(2)O(3) in the Al(2)O(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.