We are interested in designing a process to manufacture styrene from ethylbenzene $($EB$).$ The

following significant reactions take place.

Ethylbenzene $$ Styrene $+$ Hydrogen $(5)$

Ethylbenzene $->$ Benzene $+$ Ethylene $(6)$ Ethylbenzene $+$ Hydrogen $->$ Toluene $+$ Methane $(7)$

The primary reaction is typically equilibrium limited$.$ The reaction is carried out in the presence of steam as an inert. The reaction temperature is $875$ K and the pressure is $0\mathrm{.}9$ bar.

Reaction kinetic and thermodynamic Keq $=$

data is given below:

ystyreneyhydrogenP $(8)$

ln $($Keq $)$ fB

fT

$=$

$==$

yethylbenzene

$15\mathrm{.}540814852\mathrm{.}6(9)$

T

$0\mathrm{.}333$S $0\mathrm{.}215$S$2+2\mathrm{.}547$S$3(10)$

$0\mathrm{.}084$S $0\mathrm{.}264$S$2+2\mathrm{.}638$S$3(11)$

where Keq is the equilibrium constant for the first reaction, T is reaction temperature in K$,$ P is reactor pressure in bar, yi is mol fraction of species i$,$ S is selectivity towards styrene, fB is mol of benzene produced per mol of styrene and fT is mol of toluene produced per mol of styrene. We are interested in producing $120$ kmol$/$h of polymer$-$grade styrene monomer $(99\mathrm{.}95\%$ purity$).$ Raw material ethylbenzene contains small impurities of benzene $(1\%$ of EB$)$ and Toluene $(1\%$ of EB$).$ For this system,

$($a$)$ Draw level $2$ process flowsheet. You will need to justify elements of the flowsheet with the help of level $2$ design decisions.

$($b$)$ Draw level $3$ process flowsheet. You will need to justify elements of the flowsheet with the help of level $3$ design decisions.

$($c$)$ The two key design variables are reactor conversion $($x$)$ and steam to aromatics ratio $($M$)$ at the reactor inlet. Perform relevant level $2$ and level $3$ material balances to compute inlet and outlet flows for the process. Assess profitability of the design using level $2$ economic potential. Consider x $=0\mathrm{.}6$ and M $=10.$

$($d$)$ As the main reaction is equilibrium limited$,$ we cannot arbitrarily select conversion and expect that it will be less than the equilibrium conversion. However, we can check if the selected conversion is feasible or not. Using the material flows computed earlier, check if the selected conversion is thermodynamically feasible or not.

$3$

Q $5.$

Cumene $($isopropyl benzene$)$ is an important petrochemical as it is a raw material for the production of phenol. Cumene is manufactured by reaction of benzene and propylene. Unfor$-$ tunately, cumene can get alkylated further to produce undesired p$-$diisopropyl benzene which has only fuel value. In order to selectively get cumene, excess benzene is used in the reactor. The following gas phase exothermic reactions are of interest $($temperature around $350-450$ C$,$ pressure $25$ bar$).$

Benzene $+$ propylene $->$ Cumene $(12)$ Cumene $+$ propylene $->$ p $$ diisopropylbenzene $(13)$

You are tasked to explore economic feasibility of this process. Consider that the desired production rate for cumene is $100$ kmol$/$h$.$ Benzene feed is pure, however, propylene feed has $5\%$ propane as impurity. Consider that the reactor propylene conversion is $0\mathrm{.}8.$ Mol fraction of propylene in purge can be taken as $0\mathrm{.}1.$ Ratio of benzene to propylene at the reactor inlet is $2.$ For this process,

$($a$)$ Develop level $2$ and level $3$ flowsheets for the process. You are required to discuss pros and cons of the relevant decisions leading to these flowsheets with respect to this process.

$($b$)$ Perform appropriate material balance and compute level $2$ economic potential. You can use the following data for calculations.

You can use the following data for calculations.You can use the following data for calculations.