Question

Styrene is made from ethylbenzene and is a monomer for making plastics. Styrene and ethylbenzene are relatively difficult to separate due to similarities in boiling points. A 100 mol/min solution of 15% styrene in ethylbenzene is fed to a flash drum operated at 125°C, where is undergoes phase equilibrium separation, partially vaporizing the liquid. The exit liquid ends up with a composition of 20% styrene and the balance ethylbenzene; the exit vapor composition is unknown. a) Draw and fully label a flow chart of this process. b) What is the total pressure for the system if there are just these two components? c) Write the equations needed to solve for the liquid and vapor exit flow rates.

Answer 1

Kd = styeren in ethyl benzene/ styrene on glycol = 0.19

100 g   ethylene glycol

ethyl benznen mass = ( 73/100) x 120 = 87.6 g

styrene mass = ( 25 /100) x 120 = 30 g

Now   let m be mass of styrene passed to glycol layer.

then mass in ethyl benzene = 30 - m.

Hence Kd = 0.19 = ( 30-m) / ( 87.6) /   ( m/100)

0.19 = ( 100/87.6)    x ( 30-m / m )

0.16644 m= 30-m

m = 25.72 g

thus mass transferred to glycol layer is 25.72 grams