Ni phosphide catalysts on Al2O3-zeolite prepared by phosphidation for methyl palmitate hydroconversion

Abstract

BACKGROUND

One-stage hydroconversion of fatty-acid based feedstocks is a promising way to obtain high-quality fuels. This process is based on hydrodeoxygenation, isomerization and hydrocracking reactions. In this work, Ni₂P/Al₂O₃-zeolite catalysts were synthesized and tested in hydroconversion of a model compound – methyl palmitate.

RESULTS

Ni₂P catalysts were prepared by in situ phosphidation of metallic Ni/Al₂O₃-zeolite precursors by PPh₃. Mixtures of zeolite (30 wt%) and boehmite were peptized and extruded to obtain the support granules. SAPO-11, ZSM-5, ZSM-22, ZSM-23 and ZSM-12 were used as a zeolite component. The catalysts and supports were characterized by a range of physicochemical methods: chemical analysis (ICP-AES), low-temperature N₂ adsorption, H₂-temperature programmed reduction, NH₃-temperature programmed desorption, Fourier transform infrared spectroscopy of adsorbed CO, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and ²⁷Al and ³¹P magic angle spinning nuclear magnetic resonance. The catalysts were studied in methyl palmitate hydroconversion (one-stage hydrodeoxygenation-isomerization-hydrocracking) in a continuous-flow fixed bed reactor at 290–340 °C, 2 MPa, H₂/feed = 600 Ncm³/cm³ and LHSV = 5.3 h⁻¹. SAPO-11 containing sample showed high selectivity to C15 and C16 iso-alkanes (63%, at 340 °C), and all ZSM-containing samples showed high selectivity to cracked C5–C9 products (55–100%, at 340 °C) with varying amounts of iso-alkanes (31–57%, at 340 °C).

CONCLUSION

The results show that by choosing the zeolite component of the catalyst it is possible to finely tune product quality in the range from low-temperature diesel fuel to jet fuel or gasoline. © 2024 Society of Chemical Industry (SCI).