Vapor-Liquid equilibria of the systems 1-octanol/nitrogen and 1-octanol/oxygen at pressures from 3 to 9 MPa and temperatures up to 613 K – Measured in a microcapillary with Raman spectroscopy

Abstract

Vapor-liquid equilibria (VLE) of the binary systems 1-octanol/nitrogen and 1-octanol/oxygen were investigated at engine-relevant temperatures (T=303to613K for 1-octanol/nitrogen; T=303to493K for 1-octanol/oxygen) and pressures (p=3to9MPa). In order to acquire vapor–liquid equilibrium data, the pressurized fuel (1-octanol) and gas (nitrogen or oxygen) are mixed in a T-junction, where a Taylor flow of alternating liquid-phase and vapor-phase segments is formed. This segmented flow passes into a microcapillary that is inserted in a steal heating block, in which the equilibrium compositions of both phases are measured by in situ Raman spectroscopy. The measured Raman signal ratios are correlated to mole fractions by a calibration, performed in the unsaturated vapor and liquid phase regimes. The obtained VLE data agree well with the few available literature data points. The VLE compositions calculated by the Peng-Robinson equation of state (PR-EoS) and perturbed-chain statistical associating fluid theory (PC-SAFT) were furthermore compared to the here obtained experimental data. Both models show good agreement as indicated by the absolute average deviations (AAD), that are at maximum 9.5 % for the saturated vapor phase and 4.2 % for the saturated liquid phase.