Chemical reaction engineering quiz 2019

CHEMICAL REACTION ENGINEERING QUIZ

Q. 1 The elementary liquid-phase irreversible reactions

take place in an isothermal ideal CSTR (Continuous-Stirred Tank Reactor). Pure A is fed to the reactor at a concentration of 2 mol/Liter. For the residence time that maximizes the exit concentration of B, the percentage yield of B, defined is..........(rounded off to the nearest integer).

Q. 2. For a first order reaction in a porous spherical catalyst pellet, diffusional effects are most likely to lower the observed rate of reaction for

slow reaction in a pellet of small diameter
slow reaction in a pellet of large diameter
fast reaction in a pellet of small diameter
fast reaction in a pellet of large diameter

Q. 3 The desired liquid-phase reaction

is accompanied by an undesired side reaction

Four isothermal reactor schemes (CSTR: ideal Continuous-Stirred Tank Reactor; PFR: ideal Plug Flow Reactor) for processing equal molar feed rates of D and E are shown in figure. Each scheme is designed for the same conversion. The scheme that gives the most favorable product distribution is:

Q. 4 Consider two non-interacting tanks-in-series as shown in figure. Water enters TANK 1 and q cm³ / s and drains down to TANK 2 by gravity at a rate k√h₁ (cm³ / s). Similarly, water drains from TANK 2 by gravity at a rate of k√h₂ (cm³ / s) where h₁ and h₂ represent levels of TANK 1 and TANK 2, respectively (see figure). Drain valve constant k = 4 cm^2.5 / s and crosssectional areas of the two tanks are A₁ = A₂ = 28 cm²

At steady state operation, the water inlet flow rate is q_ss = 16cm³ / s . The transfer function relating the deviation variables h₂ (cm) to flow rate q (cm^3
0
1
1.5
2

Q. 5 The elementary, irreversible, liquid-phase, parallel reactions 2A → D and 2A → U, take place in an isothermal non-ideal reactor. The C-curve measured in a tracer experiment is shown in the figure, where C(t) is the concentration of the tracer in g / m³ at the reactor exit at time t (in min).

The rate constants are k₁ = 0.2 Litre (mol min) and k₂ = 0.3 Litre (mol min). Pure A is fed to the reactor at a concentration of 2 mol/Liter. Using the segregated model, the percentage conversion in the reactor is................(rounded off to the nearest integer).

Q. 6 The elementary irreversible gas-phase reaction A → B + C is carried out adiabatically in an ideal CSTR (Continuous-Stirred Tank Reactor) operating at 10 atm. Pure A enters the CSTR at a flow rate of 10 mol/s and a temperature of 450 K. Assume A, B and C to be ideal gases. The specific heat capacity at constant pressure ( C_pi ) and heat of formation
(H_i⁰), of component i(i = A,B,C) are:
C_PA = 30 J / (mol K),C_PB = 10 J / (mol K),C_Pc = 20 J / (mol K)
H_A⁰ = -90 kJ / mol,H_B⁰ = -54 kJ / mol, H_C⁰ = -45 kJ / mol
The reaction rate constant where E = 31.4 kJ / mol and universal gas constant R = 0.082 L atm/(mol K) = 8.314 J/(mol K). The shaft work may be neglected in the analysis, and specific heat capacities do not vary with temperature. All heats of formation are referenced to 273 K. The reactor volume (in Liters) for 75% conversion is____________(rounded off to the nearest integer).

Q. 7 Consider the reactor-separator-recycle process operating under steady state conditions as shown in the figure. The reactor is an ideal Continuous-Stirred Tank Reactor (CSTR), where the reaction A + B → C occurs. Assume that there is no impurity in the product and recycle streams. Other relevant information are provided in the figure. The mole fraction of B (x_B) in the reactor that minimizes the recycle rate is.........................(rounded off to two decimal places).

Q. 8 A first-order irreversible liquid phase reaction A → B (k = 0.1 min^-1) is earned out under isothermal, steady state conditions in the following reactor arrangement comprising an ideal CSTR (Continuous-Stirred Tank Reactor) and two ideal PFRs (Plug Flow Reactors). From the information in the figure, the volume of the CSTR (in Liters) is ...............................(rounded off to the nearest integer).