Raw data of gas hydrate equilibria and PXRD measurements in system C3H8/CH4 – H2O – Urea
The raw data from the measurements of the gas hydrate equilibrium conditions in the methane/propane-water-urea system are given in the “Hydrate equilibrium (C3H8+CH4-Urea-H2O)” archive. A model gas mixture of 4.34% C3H8 + 95.66% CH4 (mol%) was used as a hydrate-forming gas. A total of 39 equilibrium points have been measured. For each of them there is a separate .xlsx file in the archive with columns of numerical values of the following parameters measured by sensors of GHA350 autoclave: time, temperature (°C), gauge pressure (bar), stirrer speed (rpm). The file name represents the sample under study and the point number. For example, the file name “30% Urea_point 24” corresponds to the raw data obtained from measurements of the 24th equilibrium point (numbering from Table 1 of data paper ) for a 30 mass% aqueous solution of urea. Cells D1:H3 of each file (except for 0% Urea sample) display numerical values of the masses and concentrations of urea and water in the aqueous phase. The raw data presented in the archive “PXRD analysis (C3H8+CH4-Urea-H2O)” are related to the powder X-ray diffraction study of the phase composition of gas hydrate samples synthesized from urea aqueous solutions. Diffractograms were recorded for 5 samples. Two of them were recorded for the samples obtained from 20 mass% aqueous urea solution (samples 1 and 2). For samples 1 and 2, the pressure of the hydrate-forming gas during the synthesis was 1.5 and 6 MPa, respectively. Two diffractograms were acquired for the samples obtained from 40 mass% urea solution (samples 3 and 4). For samples 3 and 4, the gas pressure during hydrate synthesis was 1.5 and 6 MPa, respectively. One diffractogram was obtained for a frozen 40 mass% urea solution (sample 5) without methane/propane hydrates. For each sample, a separate file containing numerical values of 2θ (degree) and signal intensity (a.u.) is provided. The raw data is linked to the papers:  Yinghua Gong, Rais I. Mendgaziev, Wei Hu, Yingzhou Li, Zhi Li, Andrey S. Stoporev, Andrey Yu. Manakov, Vladimir A. Vinokurov, Tianduo Li, Anton P. Semenov (2022) Urea as a Green Thermodynamic Inhibitor of sII Gas Hydrates // Chemical Engineering Journal, 429, 132386 DOI: 10.1016/j.cej.2021.132386  Anton P. Semenov, Yinghua Gong, Rais I. Mendgaziev, Andrey S. Stoporev, Vladimir A. Vinokurov, Tianduo Li (2023) Dataset for the phase equilibria and PXRD studies of urea as a green thermodynamic inhibitor of sII gas hydrates // Data in Brief, in Press
Steps to reproduce
I. Determination of gas hydrate equilibrium pressure and temperature from “Hydrate equilibrium (C3H8+CH4-Urea-H2O)” archive. To extract the equilibrium point (P, T) from a single experimental pressure-temperature trajectory as follows: 1) Convert gauge pressure (bar) to absolute pressure (bar) by adding 1 to all gauge pressure values in the “Pressure (bar)” column. 2) Plot the experimental P(T) trajectory (the absolute pressure column is from step 1, and the temperature is from the “Temperature (ｰC) Bath” column). 3) Approximate the segments of the experimental P(T) trajectory before and after the endpoint of gas hydrate dissociation at a ramp heating (0.1 K/h) with linear functions. 4) The intersection of two linear functions is the endpoint of the gas hydrate dissociation with equilibrium pressure and temperature. 5) Convert the obtained values of the hydrate equilibrium temperature (°C) to (K), and the hydrate equilibrium pressure (bar) to (MPa). II. Determination of phase composition of gas hydrate samples from “PXRD analysis (C3H8+CH4-Urea-H2O)” archive. 1) Plot intensity as a function of 2θ (degree). 2) The peaks in the diffractogram correspond to the signals of the phases including sII methane/propane hydrate, hexagonal ice Ih and solid urea (tetragonal P421m phase I), which can be confirmed by comparison with literature and reference data.