Phase Equilibrium for Clathrate Hydrates Formed with Difluoromethane + either Cyclopentane or Tetra-n-butylammonium Bromide

This paper presents phase equilibrium data for the clathrate hydrates formed in two three-component systems a difluoromethane + cyclopentane + water system and a difluoromethane + tetra- n- butylammonium bromide + water system. The vapor + liquid + liquid + hydrate four-phase equilibrium in the former system was measured at pressures from 0.027 MPa to 1.544 MPa and at temperatures from 280.45 K to 299.75 K, while the vapor + liquid + hydrate three-phase equilibrium in the latter system was measured at pressures from 0.175 MPa to 1.215 MPa and temperatures from 286.45 K to 289.95 K. The pressure in the former four-phase equilibrium was found to be lower than that in the two-component difluoromethane + water system by an extent from 0.3 MPa to 0.9 MPa over the temperature range from 280.45 K to 294.1 K, the upper quadruple point for the two-component system. The three-phase equilibrium pressure of the difluoromethane + tetra- n- butylammonium bromide + water system has a strong temperature dependency such that, with an increase in the system temperature, it overtakes the three-phase equilibrium pressure of the two-component system, while the former is lower than the latter at temperatures below 289.4 K.