Analytic Setup for Multicomponent High‐Pressure Phase Equilibria via Dual Online Gas Chromatography

Abstract

A high-pressure analytic phase equilibria setup, capable of operation at 150°C and 30 MPa, was developed. The variable-volume view cell contains two heightadjustable samplers enabling simultaneous sampling from two phases. Concurrent analysis of both samples was performed with dual online gas chromatography (GC). The GC comprises two inlets, four columns, two switch valves, and three detectors, arranged in parallel pathways. Quantitative detector calibrations were used. The setup was validated by sampling from a one-phase ternary of known composition, and comparison with binary and ternary literature data. The setup produces accurate phase composition data for supercritical systems and is wellsuited to handle mixture constituents ranging from volatile gases to mid-length hydrocarbons.

Analytic High‐Pressure Phase Equilibria. Part II: Gas Chromatography and Sampling Method Development

“…Pressure is measured with an ONEhalf20 melt transmitter. Refer to Fourie et al 9 for more detail on the apparatus. The materials listed in Tab.…”

“… GC configuration: (BV) ball valve; (C 1 , C 2 ) DB‐1, l = 30 m, ø = 0.53 mm, film = 1.5 µm; (C 3 ) HP‐PLOT/Q, l = 15 m, ø = 0.53 mm, film = 40 µm; (C 4 ) HP‐PLOT/Q, l = 30 m, ø = 0.53 mm, film = 40 µm; (EPC) carrier gas control; (HB) heated valve box; (R) ROLSI™; (SSL) split‐splitless inlet; (TT) transfer tubing; (V) 4‐port valve; broken lines: temperature‐controlled regions [a], [b], and [c]; reproduced from 9. …”

“…This approach enables concurrent liquid‐ and vapor‐phase analysis for mixture species ranging from light gases to mid‐length hydrocarbons. Method parameters are tabulated in Fourie et al 9. Split and septum purge flow affect the success of this GC method: The effective split ratio is dependent on split vent flow (Fig.…”

“…Different functional groups, isomerism, and solute‐solute interactions have been investigated as factors affecting system behavior 7, 8. Within this project, an analytic apparatus to measure multicomponent high‐pressure phase equilibria via online gas chromatography (GC) was developed 9. This apparatus is currently used to study ternary mixtures comprising CO 2 and the solutes n ‐dodecane ( n C 12 ), 3,7‐dimethyl‐1‐octanol (37DM1O), and 1‐decanol (C 10 OH).…”

“…The objective of this paper is threefold. Firstly, the experimental procedure from Fourie et al 9 is expanded with an emphasis on the sampling procedure and optimum sample size. Secondly, online GC analysis is covered in detail.…”