Byung-Gwon Lee

Phase equilibria of CFC alternative refrigerant mixtures : 1,1,1,2,3,3,3-Heptafluoropropane (HFC-227ea) + difluoromethane (HFC-32), + 1,1,1,2-tetrafluoroethane (HFC-134a), and + 1, 1-difluoroethane (HFC-152a)

Isothermal vapor–liquid equilibria were measured for the binary systems difluoromethane (HFC-32)+1,1,1,2,3,3,3-heptafluoropropane (HFC-22ea) and 1,1-difluoroethane (HFC-152a)+1,1,1,2,3,3,3-heptafluoropropane at 283.15 and 303.15 K and 1,1,1,2-tetrafluoroethane (HFC-134a)+1,1,1,2,3,3,3-heptafluoropropane at 303.15 and 323.15 K in an apparatus in which both phases were recirculated. The experimental data were correlated with the Peng–Robinson equation of state using the Wong–Sandler mixing rules. Azeotropic behavior has not been found in any of the three mixtures.

Vapor–Liquid Equilibria of CFC Alternative Refrigerant Mixtures: Trifluoromethane (HFC-23)+Difluoromethane (HFC-32), Trifluoromethane (HFC-23)+Pentafluoroethane (HFC-125), and Pentafluoroethane (HFC-125)+1,1-Difluoroethane (HFC-152a)

Isothermal vapor–liquid equilibria for three binary mixtures of CFC alternative refrigerants were determined in an equilibrium apparatus in which both phases were continuously recirculated. The pressures and vapor and liquid compositions were measured for the binary systems trifluoromethane (HFC-23)+difluoromethane (HFC-32) and trifluoromethane (HFC-23)+pentafluoroethane (HFC-125) at 283.15 and 293.15 K and pentafluoroethane (HFC-125)+1,1-difluoroethane (HFC-152a) at 293.15 K. The experimental data were correlated with the Peng–Robinson–Stryjek–Vera equation of state using the Huron–Vidal original mixing rule. Calculated results with this equation showed good agreement with the experimental data.

METHYLFORMATE FORMATION FROM METHANOL AND CO ON CU/ZNO CATALYSTS

The reaction mechanism for the methylformate formation on Cu/ZnO catalysts from methanol and CO was investigated by the labeling study with13C methanol. It was found that methylformate could be formed through two parallel reaction routes, i.e., methanol-formaldehyde reaction and carbonylation of methanol depending upon the catalyst composition as well as the reaction conditions. The major reaction route on the high ZnO-contcnt catalyst (Cu/ZnO=30/70) was found to be the methanol-formaldehyde reaction, and changed to the carbonylation reaction with the increase ol CO partial pressure. On the other hand, the major reaction route on the high Cu-content catalyst (Cu/ZnO=80/20) remained as methanol-formaldehyde reaction even under the high CO pressure.

Synthesis of HFC-134a by isomerization and hydrogenation

For the preparation of HFC-134a, the isomerization of CFC-114 and the hydrogenation of CFC-114a were investigated. Both reactions were catalyzed by AlC3 and supported Pd catalysts, respectively. For the comparison purpose, the isomerization of CFC-113 was carried out also. With virgin AICI3 catalyst, both isomerization reactions proceeded after a certain induction period probably because the catalyst needed the activation by the halogen exchange. The catalyst deactivated gradually with the time on stream. However, the deactivation rate could be reduced by removing impurities from the reactants. Isomerization rate of CFC-114 was much slower than that of CFC-113. Palladium supported on carbon catalyzed the hydrogenation reaction quite selectively while the selectivity declined when the support was replaced with different supports. The catalytic activity and selectivity to desired products increased in the following order. Pd/kieselguhr Pd/silica-alumina ≅Pd/silica gel Pd/TiO2Pd/Al2O3Pd/C