NiAl <inf>2</inf> O <inf>4</inf> spinel-type catalysts for deoxygenation of palm oil to green diesel

Abstract

© 2018 Elsevier B.V. NiAl 2 O 4 spinel-type catalyst was successfully prepared by an incipient wetness impregnation method accompanied with high-temperature calcination at 1273 K for 10 h. The effect of reduction temperatures (773, 923, and 1073 K) on the catalytic activity for palm oil deoxygenations to green diesel was investigated at 573 K and 5 MPa in a trickle bed reactor. The XRD and XANES analyses confirmed the formation of metallic Ni after pre-reduction, which exhibited a variation of reduction degree at different temperatures. The TEM analysis revealed the formation of large particle size of the catalysts reduced at higher temperature. The highest product yield (94.3%) was achieved for the NiAl 2 O 4 reduced at 923 K. Interestingly, the spinel-type catalyst was highly stable for 24 h on-stream, while the fast degradation was found over a reference catalyst, Ni supported on γ-Al 2 O 3 . The decarbonylation and/or decarboxylation (DCO/DCO 2 ) reactions were dominant over the hydrodeoxygenation (HDO) pathway over all the catalysts. The high performance of NiAl 2 O 4 spinel-type catalyst could be attributed to the characteristic feature of the well-dispersed metallic Ni species with highly stable spinel structure.