One-pot neutron imaging of surface phenomena, swelling and diffusion during methane absorption in ethanol and n-decane under high pressure

Abstract

We report a powerful method for capturing the time-resolved concentration profiles, liquid swelling and surface phenomena during the absorption of methane (CH 4) in still liquid ethanol (C 2 D 6 O) and n-decane (n-C 10 D 22) and at high spatial resolution (pixel size 21.07 μm) using neutron imaging. Absorption of supercritical methane was followed at two temperatures and two pressures of methane, namely 7.0, 37.8˚C and 80, 120 bar. Fick's second law, which was used in the liquid-fixed coordinates, enabled for an adequate parameterization of the observed concentration profiles and liquid levels using simple analytical expressions. For both studied liquids, anomalously slow diffusion was observed in the initial stage of the absorption experiment. This was ascribed to the slow formation of the surface excess on the interface, time constant ranged 130-275 s. The axial symmetry of the cell allowed for the tomographic reconstructions of the profiles of the menisci. Based on these profiles, contact angle and surface tension were evaluated using the Young-Laplace equation. Overall, neutron imaging made it possible to capture time-and space-resolved information from which the methane concentration, liquid level and meniscus shape under high-pressure conditions inside a cylindrical titanium vessel were quantitatively derived. Multiple characteristics of ethanol, a methane hydrate inhibitor, and n-decane, a model constituent of crude oil, were thus measured for the first time under industrially relevant conditions in a one-pot experiment.

Absorption of pressurized methane in normal and supercooled p-xylene revealed via high-resolution neutron imaging

“…Composition revealed using neutron imaging. Liquids were maintained at a constant temperature and exposed to a methane pressure step at the zero time in cylindrical cells 44 . Since the cells were axially symmetric (inner diameter 9.0 ± 0.1 mm), the onion-peeling algorithm 51 was used to provide the tomographic reconstructions at the central plane of the sample.…”

“…The experimental setup was described in our previous study 44 and consisted of a pair of equivalent axially symmetric titanium measuring cells from which one was used for this study were placed in a duralumin block maintained at a constant temperature to within ± 0.2 °C using a Julabo F12-MA water circulator, the temperature was measured using a platinum resistance thermometer (Greissinger GMH 3710), the setup was placed in a duralumin box purged with nitrogen to avoid moisture condensation on the outer parts of the measuring setup. The cells were rinsed with acetone, vacuumed (< 0.01 Pa, Leybold D4B), and twice washed with the fresh sample liquid prior to the filling.…”

“…For the evaluation of the data from the first two respective series, ten data points were provided as an average of 10 images having the respective time stamp of the average time of the respective 10 images; for the latter series, the entire 50 images were averaged into a single data point having the time stamp of the average of the 50 images. The experimental setup was described in our previous study 44 and consisted of a pair of equivalent axially symmetric titanium measuring cells from which one was used for this study were placed in a duralumin block maintained at a constant temperature to within ± 0.2 °C using a Julabo F12-MA water circulator, the temperature was measured using a platinum resistance thermometer (Greissinger GMH 3710), the setup was placed in a duralumin box purged with nitrogen to avoid moisture condensation on the outer parts of the measuring setup. The cells were rinsed with acetone, vacuumed (< 0.01 Pa, Leybold D4B), and twice washed with the fresh sample liquid prior to the filling.…”

“…For instance, Raman spectroscopy and Nuclear Magnetic Resonance were used for studies on the formation of natural gas hydrate under relevant conditions 42 , 43 . As we show in this study, our non-tactile one-pot neutron imaging method 44 is applicable for studying systems involving supercooled liquids exposed to pressurized gases.…”

Sorption of vapors in methanol soaked and in thermally annealed Matrimid® films

“…While transient sorption of volatile compounds in liquids appears governed by Fick's second law, 43,56,57 rubbery polymers frequently show concentration dependence of diffusivity, [58][59][60][61][62] and glassy polymers commonly show anomalous diffusion. 58,59,61,[63][64][65][66][67][68][69][70][71] Since the anomalous sorption kinetics involves multiple phenomena, such as viscoelastic relaxation and concentration dependence of diffusivity, their quantitative parameterization remains demanding and not unified.…”