15 – experimental determination of pure component and mixture properties


Textbook Examples:

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15.01          Vapor Space Correction in Static VLE Measurement (p.608)


15.02         Static VLE without Degassing (p. 612)


Additional Problems:

P14.01       Vapor Pressure from Transpiration
Calculate the vapor pressure of n-dodecane at 60°C from transpiration method experiments. An inert carrier gas (helium) stream of 1 × 10−4 mol/min is saturated with the heavy boiling component n-dodecane in a gas saturator at a pressure of 1 atm and a temperature of 60°C. The evaporated n-dodecane is recovered from the gas stream in a cooling trap. The experiment is run for 2.5 hours. The captured mass of hydrocarbon in the trap is determined to be 5.81 mg.


15.2         Composition Error in Synthetic Static VLE Measurement
Two components are injected into a static VLE cell using piston pumps.
Derive an expression for the mean composition error as function of composition and mean injection volume error. The volume errors of the pumps can be described as the sum of an absolute and relative error. Typical errors are ΔVabs = 2 × 10−3 cm3 and ΔVrel = 5 × 10−4 cm3. The total injected volume is 25 cm3.


15.3        Limiting Activity Coefficient from GLC Retention Time
In a gas chromatographic experiment, the net retention time of acetone on a column with 1.2 g of eicosane (C20H42) as stationary phase was found to be 40.5 seconds. The oven temperature was 60°C, and the flow rate of the carrier gas helium was 5 cm3/min at column conditions. Calculate the activity coefficient at infinite dilution of acetone in eicosane using the virial equation of state for the calculation of the fugacity coefficient of acetone at saturation pressure. The second virial coefficient of acetone at 60°C is −1263 cm3/mol. Further required property values can be found in Appendix A.


15.4 Limiting Separation Factor in an Extractive Solvent from GLC Retention Times
A gas chromatographic column is prepared with N-methylpyrrolidone (NMP) as stationary phase, which is a common solvent for extractive distillation (see Chapter 11). Then the netto retention times for benzene and methylcyclohexane at 80 ∘C and constant flow rate of the carrier gas are measured. The measured values are 93.1 seconds for benzene and 18.3 seconds for methylcyclohexane. Determine the separation factor of benzene and methylcyclohexane at infinite dilution in NMP.