## Self Assessment Quiz

Q4.1. A vessel contains pure gas A initially at atmospheric pressure and temperature  in which  the isothermal gas phase reaction  A↔B ↔C takes place. The velocity constants k1= 0.002 /min and k2 = 0.001/ min.

(a) Estimate the composition of a batch 6.5 hours after start. (b) What would be the result if CSTR of 6.5 h residence time were employed.

Q4.2. The Chlorination of pure benzene is carried out in a CSTR at 550C. And 30% conversion is required. Monochloro and dichloro benzene alone were produced. The reaction are irreversible and pseudo first order since the liquid is saturated in chlorine. The rate equation are below:

rB = 0.4CB kmol/cum.hr

rD = 0.4CM kmol/cum.hr

What is the CSTR volume required to produce 4.5 kmol/hr of monochloro benzene. Sourced from Fogler

Q4.3 Reactions taking place during ammonia oxidation are shown below:

4NH3 + 5O2 = 4NO + 6H2O

4NH3 + 3O2 = 2N2 + 6H2O

2NO + O2 = 2 NO2

4NH3 + 6NO = 5N2 + 6H2O

2NO = N2 + O2

N2 + 2O2 = 2NO2

Q4.3.1. Find the number of independent reactions

Q4.3.2. Set up design equations for a PFR and CSTR.

Q4.4..A reaction A <=> B <=> C is carried out in (a) CSTR and (b) PFR. Determine the variation of composition with respect to system parameters.

Q4.5. A reaction A<=>B and A<=>C is carried out in (a) CSTR and (b) PFR. Determine the variation of composition with respect to system parameters.

Q4.6. Benzene is to be chlorinated in the liquid phase in a CSTR; operation is at steady state. Liquid benzene is added continuously and liquid and gaseous products are recovered continuously. Reaction is carried out at 55C. All reactions are second order and irreversible. Sourced from J.M.Smith

B + C = MB + HCL

MB + C = DB + HCL

DB + C = TB = HCL

Assume that chlorine in liquid is constant so that a pseudo homogenous first order rate constant can be defined. Data suggests that the ratio of these rate constant are typically K1/K3 = 8.0 and K2/K3 = 30.0

Determine the composition of the medium in terms of system parameters. What is the composition if a benzene/chlorine ratio of 1.4 is employed? Assume Cl2 completely consumed.

Q4.7. A product B is to be product from reagent A which also reacts to form worthless product. The instantaneous yield of B (φ) was found to depend on conversion of A as follows:

Φ = 0.6 + 2x - 5x2

The reaction is to be terminated when φ reaches 0.5 as it is uneconomical to proceed further to higher conversion which leads to lower yield. Sourced from Denbigh

Calculate overall yield if reaction is carried out in a) batch reactor b) in a single stirred tank

Q4.8. The reaction above is carried out in two stirred tanks in series. What conversion in the effluent from tank 1 would lead to highest overall yield and what is that overall yield.

Q4.9. If is effluent from the above plant is to correspond to 50 percent conversion what is the highest overall yield which would be obtained and what arrangement would produce it?

Q4.10. The following liquid phase triangular reversible reaction network A<=>B<=>C<=>A is to be handled in a CSTR operating at steady state. Feed to the reactor is 10 mol/s of pure A. All reactions are instantaneous. The equilibrium constant at 50 deg C for rxn 1  A=>B is 1.0, for reaction  rxn 2

B =>C is 2.0, and for the reaction  rxn 3 C =>A is 0.5.

The heat of the reaction ∆H1* is 10000 cal/mol, ∆H2* is 10000 cal/mol and ∆H3* is -20000 cal/mol. All heats of reaction are temperature independent. Specific heat of reaction mixture is 1000 cal/lit.deg C, molar density 50 mol/lit and feed temperature is 25 deg C.

Q4.10.1. Set up the stoichiometric table for this multiple reaction network and obtain conversion in terms of system parameters.

Q4.10.2. It is proposed to operate the reactor at 50 deg C and at steady state. Specify the molar flow of components A, B, C at reactor outlet and the heat load to be handled to achieve this reactor operation.

Q4.10.3.Organic oxidations are among the very important commercial processes. Cite one industrially important example giving reasons for the choice of catalyst and the reactor system employed.

Q4.11. Polymerisation reaction in CSTR

An ideal CSTR is used for the homogeneous polymerization of a monomer M. The volumetric flow rate is Q. The reactor volume is V and density of reaction solution is invariant with composition. The feed concentration is MO.

The polymer product is produced by an initiation step and is followed by consecutive series of propagation reactions. The initiation step is given as

M  =>   P1     (initiation); ri = kiM

Where P1 is the activated monomer product and P2 => Pn are polymers containing monomer units. The rate equation for this initiation reaction is first order in M with k1 as the rate constant. The propagation reactions are given as

 P1 + M => P2 Pn + M =>Pn+1              where Rp = kp  Pn M

Where the function rn is given by second order expression with rate constant Kp (Same for all steps)

Q4.11.1. Show that Pn can be given as and monomer conversion X can be given as  Q4.11.2. If the rate constant ki = 10-2/s; kP = 100 ml/gmol.s and MO = 1.0 gmol/1 apply in a certain situation determine monomer conversion and trimer (P3) outlet

concentration for a mean residence time  500 second. Comment on your results.

Q4.11.3. Cite two examples of industrially important polymerization reactions indicating the monomer used and polymer produced. Comment on the reactor system used for your indicated industrial proces