Question

The cyclization reaction of acetylene to benzene occurs at approximately 400°C and 4 atm. Gaseous acetylene is fed to the reactor at a rate of 20 L/min STP along with an equal amount of nitrogen. The stream exiting the reactor is at the same conditions as the reactor and has a volumetric flow rate of 21.4 L/min. This stream is sent to a condenser where it is cooled to 25°C (still at 4 atm), here only the benzene partially condenses. Assume that all gas streams can be treated ideally. a) Draw and label a flowchart for this system. b) Is this ideality assumption valid? Prove this. c)What is the reaction conversion? d) What is the flow rate of the benzene product stream from the condenser?

Answer 1

The reaction is 3C2H2 --à C6H6

Moles of Acetylene= PV/RT= 20*4/(0.0821*(400+273.15) =1.45 moles/min

Moles of nitrogen = 1.45 moles/min

Since all the Acetylene gets reacted, moles of Benzene= 1.45/3= 0.483 moles/min

Nitrogne does not participate in the reaction, moles of product= Benzene+ moles of Nitrogen= 0.483+1.45 =1.933 moles/min

Volume of this gas at 400 deg. c and 4 atm, V= nRT/P

1.933*0.0821*673.15/4=26.66 Lits/min but the given volume is onlyy 21.4 L/min suggesting at these conditions gas law is not valid.

Moles of product formed ( assumig gas law is valid)= 21.6*4/ (0.0821*673.15)= 1.563 moles/min

Nitrogen = 1.45 moles/min remaining is Benzene= 1.563-1.45=0.113 moles/min

Moles of C2H2 reacted= 0.113*3= 0.339 moles/min

Moles supplled= 1.45 moles/min

Conversion = 100*0.339/1.45=23.38%