$1\mathrm{.}22.$ Distillation sequence for a wide$-$boiling mixture.

The effluent from the reactor of a toluene hydrodealkylation process of the type stated in Exercise $1\mathrm{.}17.$ is as

follows:

The reactor effluent at $1265F$ and $500$ psia is to be separated into four products: $($a$)$ a gaseous mixture rich

in hydrogen and methane; $($b$)$ a benzene$-$rich product of high purity; $($c$)$ a toluene$-$rich mixture of low purity

that is recycled to the reactor; and $($c$)$ a biphenyl by$-$product of high purity. Using the heuristics of $1\mathrm{.}8{\mathrm{.}2}_{?},$

determine one or two favorable sequences. A sequence can contain one single$-$stage partial condenser in

place of one multistage distillation column.