Question: A feed mixture containing 50 wt% n-heptane and 50 wt% methyl cyclohexane (MCH) is to be separated by liquid-liquid extraction into one product containing 92.5 wt% methylcyclohexane and another containing 7.5 wt% methylcyclo- hexane. Aniline will be used as the solvent. (a) What is the minimum number of theoretical stages necessary to effect this separation?

A feed mixture containing 50 wt% n-heptane and 50 wt% methyl cyclohexane (MCH) is to be separated by liquid-liquid extraction into one product containing 92.5 wt% methylcyclohexane and another containing 7.5 wt% methylcyclo- hexane. Aniline will be used as the solvent. (a) What is the minimum number of theoretical stages necessary to effect this separation? (b) What is the minimum extract reflux ratio? (c) If the reflux ratio is 7.0, how many theoretical contacts will be required? Liquid-liquid equilibrium data for the system n-heptane-methyl cyclohexane-aniline at 25°C and at 1 atm (101 kPa) Hydrocarbon Layer Solvent Layer Welght percent MCH, solvent- free basis Pounds aniline/ pound solvent- free mixture Weight percent MCH, solvent- free basis Pounds aniline/ pound solvent- free mixture 0.0 9.9 20.2 23.9 36.9 44.5 50.5 66.0 74.6 79.7 82.1 93.9 100.0 0.0799 0.0836 0.087 0.0894 0.094 0.0952 0.0989 0.1062 0.1111 0.1135 0.116 0.1272 0.135 0.0 11.8 33.8 37.0 50.6 60.0 67.3 76.7 84.3 88.8 90.4 96.2 100.0 15.12 13.72 11.5 11.34 9.98 9.0 8.09 6.83 6.45 6.0 5.9 5.17 4.92