Chemical Engineering

A vapor-recirculation apparatus was used to determine the
vapor-liquid  equllibrlum  conditions of the carbon
tetrafluoride-chlorotrifluoromethane system at a
temperature of 199.80, K over the full composition range,
covering a  pressure range of 1.544-15.272  bar.
Liquld-phase activlty coefficients were  calculated from the
experlmental data by  using a modlfled Redllch-Kwong
equation of state to describe vapor-phase nonidealities.
The actlvity coefficients were  correlated with the Wllson
equation, thus permitting the calculation of the equllibrlum condition at the temperaturainvestigated

Vapor-liquid equilibrium data were determined by the vapor recirculation technique
for  the trifluoromethane-trifluorochloromethane  binary at  31.9, -0.1 , -55.1,  and
-100.05'F  over the full range of composition.  The compositions of the maximum-
pressure (minimum-boiling)  azeotrope  exhibited by this system are 0.656,  0.630,
0.579, and 0.533 mol fraction CHFg, respectively, at pressures of 400.6, 247.1, 90.47,
and 31.32 psia, respectively.  The heats of vaporization of the azeotropes computed
primarily  from the equilibrium  data, are 3639, 4723, 5845, and 6363 Btu/lb mol,
respectively.  liquid-phase activity coefficients were calculated from the experimental
data under the assumption that  the Redlich-Kwong equation of  state gave an ade-
quate description of the vapor phase.  Subsequently, the Wilson  equation was flt to
these activity Coefficients, and a correlation was developed which permits the vapor-
liquid equilibria to be computed for any temperature between 32 and -100°F

Eighteen commercial lipase preparations, either immobilized or crude enzyme powders, were screened for the transesterification of wood sterols. The reactions were carried out in a solvent-free system, at the optimum temperature of the enzyme preparations as reproted by the manufacturer and at the pressure of 2 mbar, with 5 or 10% in weight of the enzyme relative to the wood sterol content of the reacting mixture. Methyl esters of sunflower fatty acids were used as transesterifying agent. Of all the enzymes assayed, only Lipase TL from Pseudomonas stutzeri PL-836 (Meito Sangyo) exhibited any significant transesterifying capacity, 85 and 95% of conversion after 2 and 8 h of reaction, respectively, when 10% in weight of enzyme was used.