Oxygen dissolved in liquid solvents may present problems during use of the solvents.

(a) Using the Peng-Robinson equation and the techniques introduced in problem 15.27, estimate the solubility of oxygen in n-hexane at an oxygen partial pressure of 0.21 bar.

(b) From the above results, estimate the Henry’s law constant.

Data from Problem 15.27

For the gas/solvent systems below, we refer to the “gas” as the low molecular weight component. Experimental solubilities of light gases in liquid hydrocarbons are tabulated below. The partial pressure of the light gas is 1.013 bar partial pressure. Do the following for each assigned system.

Estimate the partial pressure of the liquid hydrocarbon by calculating the pure component vapor pressure via the Peng-Robinson equation, and by subsequently applying Raoult’s law for that component.

Estimate the total pressure and vapor composition using the results of step (a).

Use the Peng-Robinson equation with k_ij = 0 to calculate the vapor and liquid compositions that result in 1.013 bar partial pressure of the light gas and compare the pressure and gas phase composition with steps (a) and (b).

Henry’s law asserts that f^{^}_i = h_ix_i , when x_i is near zero, and hi is the Henry’s law constant. Calculate the Henry’s law constant from the calculations of part (c).

Calculate the solubility expected at 2 bar partial pressure of light gas by using Henry’s law as well as by the Peng-Robinson equation and comment on the results.

Transcribed Image Text:

Gas (1) Methane (ii) Methane (iii) Methane (iv) Methane Methane Liquid Cyclohexane Carbon tetrachloride Benzene n-hexane n-hexane T (°C) 25 25 25 25 25 Xgas 2.83 E-3 2.86 E-3 2.07 E-3 3.15 E-3 4.24 E-3 Source a a a b с