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Carbon Dioxide Clathrate Hydrate Formation at Low Temperature E Carbon dioxide clathrate hydrate formation at low temperature E. Dartois, F. Langlet To cite this version: E. Dartois, F. Langlet. Carbon dioxide clathrate hydrate formation at low temperature: Diffusion- limited kinetics growth as monitored by FTIR. Astronomy and Astrophysics - A&A, EDP Sciences, 2021, 652, pp.A74. 10.1051/0004-6361/202140858. hal-03319738 HAL Id: hal-03319738 https://hal.archives-ouvertes.fr/hal-03319738 Submitted on 12 Aug 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. A&A 652, A74 (2021) https://doi.org/10.1051/0004-6361/202140858 Astronomy & © E. Dartois and F. Langlet 2021 Astrophysics Carbon dioxide clathrate hydrate formation at low temperature Diffusion-limited kinetics growth as monitored by FTIR E. Dartois1 and F. Langlet2 1 Institut des Sciences Moléculaires d’Orsay, UMR8214, CNRS, Université Paris-Saclay, 91405 Orsay, France e-mail: [email protected] 2 Institut d’Astrophysique Spatiale, UMR8617, CNRS, Université Paris-Saclay, 91405 Orsay, France Received 22 March 2021 / Accepted 31 May 2021 ABSTRACT Context. The formation and presence of clathrate hydrates could influence the composition and stability of planetary ices and comets; they are at the heart of the development of numerous complex planetary models, all of which include the necessary condition imposed by their stability curves, some of which include the cage occupancy or host–guest content and the hydration number, but fewer take into account the kinetics aspects. Aims. We measure the temperature-dependent-diffusion-controlled formation of the carbon dioxide clathrate hydrate in the 155–210 K range in order to establish the clathrate formation kinetics at low temperature. Methods. We exposed thin water ice films of a few microns in thickness deposited in a dedicated infrared transmitting closed cell to gaseous carbon dioxide maintained at a pressure of a few times the pressure at which carbon dioxide clathrate hydrate is thermodynam- ically stable. The time dependence of the clathrate formation was monitored with the recording of specific infrared vibrational modes of CO2 with a Fourier Transform InfraRed spectrometer. Results. These experiments clearly show a two-step clathrate formation, particularly at low temperature, within a relatively simple geometric configuration. We satisfactorily applied a model combining surface clathration followed by a bulk diffusion–relaxation growth process to the experiments and derived the temperature-dependent-diffusion coefficient for the bulk spreading of clathrate. The derived apparent activation energy corresponding to this temperature-dependent-diffusion coefficient in the considered tempera- −1 ture range is Ea = 24.7 ± 9.7 kJ mol . The kinetics parameters favour a possible carbon dioxide clathrate hydrate nucleation mainly in planets or satellites. Key words. infrared: planetary systems – planets and satellites: composition – comets: general – methods: laboratory: solid state – solid state: volatile – molecular processes 1. Introduction many models, principally on the basis of the stability curves for these inclusion compounds. During the evolution of the solar Clathrate hydrates are inclusion compounds that trap molecules nebula, the existence of clathrate hydrate, or rather its stabil- in a crystalline water ice network. For the two main structures, ity, depends on pressure and temperature. These thermodynamic these clathrate hydrates form water-based cages of different sizes properties represent a necessary but not sufficient condition. and of two types, a larger one (forming a hexagonal truncated In many bodies, in particular small bodies such as comets, or trapezohedron or hexadecahedron) and a smaller one (forming low-temperature objects orbiting at large distances, such as trans- a pentagonal dodecahedron), leading to the simplest clathrate Neptunian objects, including Kuiper Belt objects, the kinetics structures I and II, respectively. On Earth, the main interest for their formation becomes a primary driving factor to take into in clathrate hydrates is focused on methane clathrate hydrate, account in the modelling. either as a potential hydrocarbon resource (e.g. Jin et al. 2020; Carbon dioxide is a significant constituent of large to smaller Boswell et al. 2020) or for the problems caused by its ability icy bodies of the Solar System. The kinetics of carbon diox- to block pipelines in the petrol industry (e.g. Fink 2015) or its ide clathrate hydrate formation (Schmitt 1986; Schmitt et al. participation in climate change if natural fields are destabilised 2003; Circone et al. 2003; Genov et al. 2003) is a key ingredient (Riboulot et al. 2018). Carbon dioxide clathrate hydrate is of in any discussion about clathrate formation. Kinetics experi- interest for fundamental research on Earth, or for its potential ments have been performed on clathrates using, for example, use in greenhouse gas sequestration (Duc et al. 2007; House et al. neutron diffraction experiments monitoring the ice structural 2006). change towards clathrate formation (Falenty et al. 2013; Henning In a planetary or astrophysical context, clathrate hydrates et al. 2000), or more classical, Pressure, Volume, Temperature are considered because they can retain volatile molecules at (PVT) experiments (Falenty et al. 2013) in the 272–185 K range. pressures higher than the pure compound that would otherwise These experiments are mostly based on the polydisperse distri- sublimate under most astrophysical conditions, and/or influence bution of ice spheres, with peak size distributions generally in the geophysics of large bodies (e.g. Fortes & Choukroun 2010; the 20–200 microns range. The interpretation of these data is Choukroun et al. 2010; Bollengier et al. 2013). The existence of performed using a modified so-called Johnson–Mehl–Avrami– clathrate hydrates in Solar System bodies has been explored in Kolmogorov (JMAK) phenomenological model and knowledge A74, page 1 of7 Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A&A 652, A74 (2021) of the size distribution of ice particles. The duration of the neu- Table 1. Summary of experiments. tron diffraction experiments is often limited to typically tens of hours because of the availability of diffraction beam lines TP P (a) Duration Thickness shifts, which can limit the temperature range explored. Indeed, exp eq (K) (mbar) (mbar) h/(days) (µm) as the diffusion coefficient generally follows an Arrhenius equa- tion, it evolves exponentially with temperature and going to 155 20 9.32 430(18) 2.6 ± 0.4 lower temperatures becomes a difficult issue, requiring long- 165 60 23.5 2820(118) 3.6 ± 0.5 duration experiments. In this article, we develop an alternative 170 120 37.3 1260(53) 0.7 ± 0.1 experimental approach based on the direct measurement, in 177.5 200 71.7 1778(74) 5.0 ± 0.7 transmittance, of the infrared signature of the caged molecules 185 400 128.6 1595(66) 5.0 ± 0.7 within a controlled thin ice film structure. This approach allows 190 700 186.5 1196(50) 6.5 ± 1.0 us to extend the measurements to lower temperatures (down 200 1200 365.0 379(16) 5.1 ± 0.7 to 155K) at which the kinetics are measured. The article is 205 1600 498.0 1080(45) 20 ± 3 organised as follows: in the following section, we describe the 207.5 1700 588.4 254(11) 4.9 ± 0.7 kinetics experiments performed and the two-step diffusion and 210 2000 678.7 162(7) 3.0 ± 0.5 nucleation model adjusted to the data. We then discuss the results, derive the kinetics and apparent activation energy of Notes. (a)From Miller & Smythe(1979) and Falabella(1975). the low-temperature carbon dioxide clathration, and discuss their astrophysical implications. hydrate was confirmed. A close-up on the ν1 + ν3 and 2ν2 + ν3 (alternatively named ν1 + ν3 Fermi resonances 1 and 2) is shown. These combination modes were selected to follow the evolution 2. Experiments of the process of clathration, because the gas phase absorptions CO2 was purchased from Air liquide. The initial purity is N25 are not fully saturated during pressurisation, and the caged CO2 (99.999%). The experimental setup consists in a gold-coated infrared signature can be observed within the comb of the rovi- copper cell, thermally coupled to a liquid N2-transfer cold finger brational transitions, as shown in Fig.1. In addition to the cell − placed in a high-vacuum, evacuated cryostat (P < 10 7 mbar). temperature diode measurement, the gas phase CO2 tempera- Infrared transmitting zinc selenide windows of 4 mm in thick- ture can also be monitored via the observed comb. We modelled ness facing each other with some space in between, are sealed the gas phase spectrum using the HITRAN database (Kochanov with indium gaskets, and allow the spectrometer beam to record et al. 2016) for a 200 µm path length, a CO2 pressure of 60 mbar, clathrate hydrate spectra in transmittance. A soldered stainless and a gas temperature of 165K, and convolved using the transfer steel injection tube brazed to the lower part of the cell allows the function of the spectrometer. The result is shown in the lower entry or evacuation of gas. A description of such a cell can be trace in Fig.1, which also confirms the gas thermalisation. found in Dartois et al.(2010) for example. The cell was modified to limit the distance between the two ZnSe windows to a space of the order of 200 µm, which is sufficiently small to allow us to 3.
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