Palm oil hydrodeoxygenation into green diesel over NiO/NbOPO4 catalyst: A novel approach of synthesizing NbOPO4 from NbCl5

Green diesel is an emerging alternative fuel that could be produced from a series of biomass conversion, of which is catalytic hydrodeoxygenation. Herein, we aimed to study the effect of pH and calcination temperature on the preparation of NiO/NbOPO4 catalyst for hydrodeoxygenation of palm oil into green diesel. The catalyst was prepared through a sol-gel method at pH 2, 4, 6, and 8, respectively. Subsequently, the calcination was carried out on the catalyst at a variation of temperature (600, 700, and 800 °C). The green diesel was produced using a hydrothermal autoclave reactor at 250 °C with a pressure of 3.5 MPa for 5 h. X-ray diffraction analysis confirmed the formation of NiO/NbOPO4, where the crystallinity index reached 77%. Morphological, elemental content, and functional group analyses, altogether revealed that the prepared catalyst had nano-size distribution along with various sets of Nb-P bonds. The hydrodeoxygenation using NiO/NbOPO4 catalyst, prepared at pH 8 and 800 °C calcination temperature, succesfully removed the oxygen content of saturated and unsaturated fatty acids from the palm oil with a yield as high as 85.747%. Gas chromatography-mass spectroscopy on the produced green diesel using NiO/NbOPO4 catalyst with 8% nickel loading showed the dominance of C12-C15 fraction (97.07%), which is mostly occupied by C15 (pentadecane) molecules (58.14%). Last but not least, we propose NiO/NbOPO4 as a very promising catalyst for industrial-scale green diesel production.