Note Equilibrium data of (tetrahydropyran + hydrogen sulphide) and (tetrahydropyran + methane) clathrate hydrates q Amir H. Mohammadi ⇑ , Dominique Richon MINES ParisTech, CEP/TEP – Centre Énergétique et Procédés, 35 Rue Saint Honoré, 77305 Fontainebleau, France Thermodynamics Research Unit, School of Chemical Engineering, University of KwaZulu-Natal, Howard College Campus, King George V Avenue, Durban 4041, South Africa article info Article history: Available online 8 January 2012 Keywords: Gas hydrate Hydrogen sulphide Methane Tetrahydropyran Experimental data abstract Presented here are experimental hydrate dissociation pressures for the (hydrogen sulphide + tetrahydro- pyran + water) and (methane + tetrahydropyran + water) systems over the temperature ranges of (293.5 to 305.0) K and (294.2 to 301.0) K, respectively. An isochoric pressure-search method was used to gener- ate the experimental results. The hydrate dissociation data for the (methane + tetrahydropyran + water) system are compared with the literature data and the acceptable agreement (±0.2 K at given pressures) confirms the reliability of the experimental method used in this work. To study the hydrate promotion effects of tetrahydropyran, the experimental results for both systems measured are compared with the corresponding experimental data in the absence of tetrahydropyran reported in the literature. It is shown that this promotion effect is remarkable. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Gas hydrates (or clathrate hydrates) are crystalline solids in which water molecules form hydrogen-bonded cage like structures, encapsulating the small molecule(s) like methane, hydrogen sul- phide etc. [1]. Gas hydrates are known to form generally three typ- ical crystal structures: structure I (sI), structure II (sII), and structure H(sH), where each structure is composed of a certain number of cavities [1]. The formation of structure H and also structure II of some heavy molecules requires the presence of large and small guest molecules [1]. Large molecules occupy large cavities while small molecule(s) (called help gas) can fill the remaining cavities [1]. It has been reported that tetrahydropyran forms structure II of clathrate hydrates with a gas like methane, carbon dioxide and methylfluoride [2–4]. In addition, clathrate hydrates of the (pro- pane + tetrahydropyran + water) system have also been reported [5]. However, the information on other gases is limited. To the best of our knowledge, there is no information on clathrate hydrate for- mation of tetrahydropyran with hydrogen sulphide. In this communication, we report gas hydrate dissociation data for the (hydrogen sulphide + tetrahydropyran + water) and (meth- ane + tetrahydropyran + water) systems within the (293.5 to 305.0) K and (294.2 to 301.0) K temperature ranges, respectively. The experimental results were generated using an isochoric pressure-search method [6–10]. As gas hydrate dissociation data for the (methane + tetrahydropyran + water) system have already been reported in the literature [2], therefore, we first generated and report experimental data for the latter system and compare them with the literature data [2] to confirm the reliability of the experimental method used in our work. We then report hydrate dissociation data for the (hydrogen sulphide + tetrahydropy- ran + water) system. To study the hydrate promotion effects of tetrahydropyran, the experimental values for the systems studied are finally compared with some selected experimental data from the literature for the (methane + water) [8,11,12] and (hydrogen sulphide + water) [6,13–15] systems. 2. Experimental 2.1. Chemicals Reported in table 1 are the purities and suppliers of the chem- icals used in this work. 2.2. Experimental apparatus Briefly, the main part of the apparatus is a cylindrical vessel made of Hastelloy, which can withstand pressures up to 20 MPa. The volume of the vessel is approximately 30 cm 3 . A stirrer in- stalled in the vessel was used to agitate the fluid(s) and hydrate crystals. Two platinum resistance thermometers (Pt100) inserted into the vessel were used to measure temperature and check for equality of temperatures within temperature measurement 0021-9614/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.jct.2011.12.038 q Paper for gas hydrate initiative. ⇑ Corresponding author. Tel.: +33 1 64 69 49 70; fax: +33 1 64 69 49 68. E-mail address: amir-hossein.mohammadi@mines-paristech.fr (A.H. Mohammadi). J. Chem. Thermodynamics 48 (2012) 36–38 Contents lists available at SciVerse ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct