Raw data of gas hydrate equilibrium measurements for CH4 – MeOH – MgCl2 – H2O system and ice freezing point determination of aqueous MeOH and MgCl2 solutions
The raw data of the temperature and pressure measurements of the three-phase equilibrium (vapor – aqueous solution – gas hydrate) in the system methane – methanol – magnesium chloride – water is collected in the archive “Gas hydrate equilibrium (CH4-MeOH-MgCl2-H2O)”. A total of 164 equilibrium points have been measured. This includes the methane – water system (no inhibitors). For each of them there is a separate .xlsx file in the archive with columns of numerical values of the following parameters measured: time (column A), temperature setpoint (°C, column B), temperature in the autoclave (°C, column C), temperature of the coolant (°C, column D), gauge pressure (bar, column E), stirrer speed (rpm, column F), and stirrer torque (N·cm, column K). The file name specifies the number of the equilibrium point and the feed composition of the aqueous solution sample (in mass%). For example, the file "point 21_10.01% MeOH" consists of the raw data for the 21st equilibrium point (numbering from Table 1 of the data paper ) for aqueous methanol solution with alcohol concentration of 10.01 mass%. The raw data from the determination of ice freezing temperatures of methanol and magnesium chloride aqueous solutions at ambient pressure can be found in the "Ice freezing points (MeOH-MgCl2-H2O)" archive. There are files for 53 ice freezing point measurements. The file name indicates the number of the measurement and the concentration of the solute (methanol (MeOH) or magnesium chloride (MgCl2)) or a mixture of them in mass% in aqueous solution. The numbers correspond to Table 10 of the co-submitted data paper . Each .xlsx file has a column with the recorded temperatures of the sample at the specified time (one T value per two seconds). The raw data is linked to the papers:  Anton P. Semenov, Rais I. Mendgaziev, Vladimir A. Istomin, Daria V. Sergeeva, Vladimir A. Vinokurov, Andrey S. Stoporev (2023) Searching for synergy between alcohol and salt to produce more potent and environmentally benign gas hydrate inhibitors // Renewable and Sustainable Energy Reviews, RSER-D-23-01186.  Anton P. Semenov, Rais I. Mendgaziev, Andrey S. Stoporev (2023) Data on searching for synergy between alcohol and salt to produce more potent and environmentally benign gas hydrate inhibitors // Data in Brief, submitted.
Steps to reproduce
I. Determination of methane hydrate equilibrium pressure and temperature from “Gas hydrate equilibrium (CH4-MeOH-MgCl2-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 E. 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 C). 3a) In the case of the ramp heating technique (0.1 K/h or 0.5 K/h), approximate the segments of the P-T trajectory before and after the endpoint of gas hydrate dissociation at a slow ramp heating stage (0.1 K/h or 0.5 K/h) with two linear functions. 3b) In the case of the step heating technique, it is necessary to average the temperature and pressure over 50 adjacent readings (1 reading every 2 seconds) for the end of each temperature step (at constant coolant temperature, column D) before and after the endpoint of gas hydrate dissociation. Then approximate the obtained average values of temperature and pressure before and after the endpoint of gas hydrate dissociation with two linear functions. 4) Find the intersection of the two linear approximating equations. The equilibrium point of methane hydrate dissociation at defined pressure and temperature values is the intersection of two linear functions. 5) Convert the obtained values of the hydrate equilibrium temperature (°C) to (K), and the hydrate equilibrium pressure (bar) to (MPa). II. Determination of ice freezing temperatures of aqueous methanol and magnesium chloride solutions from the “Ice freezing points (MeOH-MgCl2-H2O)” archive. 1) Plot the sample temperature (“T, °C” column C) as a function of time. 2) The ice freezing point can be determined from the plotted experimental curve as the T value at the plateau (or maximum) after the temperature spike corresponding to the onset of ice crystallization in the supercooled aqueous solution under intensive stirring (600 rpm). 3) Convert the obtained value of the ice freezing temperature (°C) to (K).