4) Four identical stirred tank reactors are connected in series as shown in the

Question

4) Four identical stirred tank reactors are connected in series as shown in the attached diagram. Pure liquid Benzene is fed to the first reactor at a rate of 100 kmol h and the partially reacted Benzene cascades down the reactor train. Each reactor is fitted with internal cooling coils. control the energy release and produces a gaseous effluent stream of Hydrogen Chloride gas as well as the liquid product stream. Each reactor receives a measured supply of gaseous Chlorine to The reactions taking place in the reactor set are The percentage conversions appropriate to each reactor are, 30 mol% of the Benzene in the reactor feed reacts to give Monochlorobenzene, 10 mol% of the Monochlorobenzene in the reactor feed reacts to give Dichlorobenzene and 5 mol % of the Dichlorobenzene in the reactor feed reacts to give Trichlorobenzene. Calculate a) The Composítion (mol fractions of theliquid leaving the fourth reactor b) The Chlorine requirement for each reactor c) The total mass of Hydrogen Chloride liberated in the reactor series

Explanation / Answer

given 100 kmoles/hr enters the 1st reactor. The reaction is C6H6+ Cl2------->C6H5Cl+ HCl

1mole of Benzene requires 1 mole of chlorine.

100 kmoles/hr of benzene requires 100 kmoles/hr of chlorine.

but 30% conversion of chlorine takes place. Monochloro benzene formed = 30kmoles/hr , HCl formed =30 kmoles/hr. chlorine remaining = 100-30= 70 kmoles/hr

moles of monochloro benzene entering the second reactor= 30 kmoles/hr,   the reaction is C6H5Cl+ Cl2 ---->C6H4Cl2+ HCl, moles of Cl2 to be supplied= 30 kmoles/hr,

but 10% conversion of monochlorobenzene takes place, Dichlorobenzene formed =30*10/100= 3 kmoles/hr, HCl formed = 3 kmoles/hr, Cl2 remaining = 30-3= 27 kmoles/hr, monochlorobenzene remaining = 30-3= 27 moles/hr

Dichlorobenzene entering the second reactor= 3 kmoles/hr, Cl2 to be supplied as per the reaction. C6H4Cl2 + Cl2 ------->C6H3Cl3 + HCl= 3 kmoles/hr

Trichlorobenzene formed = 3*1/100= 0.3 kmoles/hr, moles of HCl formed =0.3 kmoles/hr, moles of Cl2 remaining = 3-0.3= 2.7 kmoles/hr, moles of Dichlorobenzene remaining = 3-0.3= 2.7 kmoles/hr

Liquid products : Benzene remaining   that enters the 4th reactor= 70 kmoles/hr, Monochlorobenzene= 30-3= 27 kmoles/hr, dichlorobenzene= 2.7 kmoles/hr and trichlorobenzene= 0.3 kmoles/hr

total moles of liquid products= 70+27+2.7+0.3= 100 kmoles/hr

Composition of liquid product : benzene = 70/100=0.7, Monochlorobenzene= 27/100=0.27, Dichlorobenzene= 2.7/100 =0.027, Trichlorobenzene= 0.3/100 =0.003

moles of chlorine supplied = 100 kmoles/hr (1st reactor)+ 30 kmoles/hr (2nd reactor)+ 3 kmoles/hr ( 3rd reactor)= 133 kmoles/hr

Moles of Hcl formed = 30 kmoles/hr (1st reactor)+ 3 kmoles/hr (2nd reactor)+ 0.3 kmoles/hr (3rd reactor)= 33.3 kmoles/hr

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