Alcohol-to-jet kerosene hydrotreating: Impact of oxygenates on product properties

Abstract

A pilot plant study involving the production of fully formulated kerosene by mixed alcohol (ethanol, butanol, water) conversion and subsequent hydrotreating and distillation to evaluate compliance with synthetic jet fuel properties is described. A specific aim of the work was to determine whether hydrotreating using a reduced (non-sulphided) Ni/Al₂O₃ catalyst could process kerosene containing 0.75 wt.% oxygen from a low-severity operating mode of the alcohol conversion reactor. It was found that the hydrotreated kerosene contained sufficient aromatics to be fully formulated and that it complied with distillation and physical property requirements of ASTM D7566. The kerosene failed the jet fuel thermal oxidative stability test (JFTOT) even after four passes through the hydrotreater (220°C, 2 MPa, 0.5 h⁻¹, H₂-to-feed ratio of 375 normal m³ m⁻³) and still contained 0.48 wt.% oxygen. It was concluded that operating the alcohol conversion process in a way that it retained >0.5 wt.% oxygenates in the kerosene was not viable when paired with Ni/Al₂O₃ hydrotreating. The present study did not establish what the maximum acceptable oxygen content of the kerosene is to enable such a configuration for the alcohol-to-jet process.