‘If the catalyst pore size is small in comparison with the mean free path, collisions with the pore wall controls the process’. The diffusivity under this condition is called ‘Knudsen diffusivity’, which is affected by the_____________________?

Related Mcqs:

1. Effective diffusivity (DE) in a catalyst pellet is related to molecular diffusivity (DN) and Knudsen diffusivity (DK) as_________________?

   A. DE = DM + DK
   B. 1/DE = 1/DN + DK
   C. DE = DM . DE
   D. DE = DN/DE

2. Effectiveness factor E. of a catalyst pellet is defined as, E = (actual rate within pore of the catalyst)/(rate if not snowed by pore diffusion), Effectiveness factor for a first order reaction is given by (where, T = Thiele modulus) ___________________?

   A. tan hT/T
   B. tan T/T
   C. tan hT/tan T
   D. None of these

3. A spherical porous catalyst particle of radius R is subjected to reactant A which reacts to form B by a zero order surface reaction A → B. Film mass transfer resistance is negligible and pore diffusion of A is rate controlling. The effectiveness factor of the catalyst is reported as 7/8. Which of the following statement is true?

   A. Inner catalyst core of radius R/8 does not participate in reaction
   B. Inner catalyst core of radius R/2 does not participate in reaction
   C. Inner catalyst core of radius 7R/8 does not participate in reaction
   D. Effectiveness factor for a zero order reaction cannot be 7/8 as it must always be 1

4. If the pore diffusion controls in a catalytic reaction, the apparent activation energy Ea is equal to___________________?

   A. The intrinsic activation energy E
   B. (E + ED) where ED is activation due to diffusion
   C. (E + ED)/2
   D. ED/2

5. Brunauer, Emmet and Teller (BET) equation is used to determine the specific surface area of a porous particle but not the pore volume & the porosity of the catalyst bed. Which of the following postulates is not used to derive BET equation ?

   A. Langmuir’s assumption applies to every adsorbed layer
   B. There is no dynamic equilibrium between successive layer
   C. The adsorbed layer may be polymolecular in thickness and the heat of adsorption in each layer
   (except the first one) is involved in each of the evaporation process
   D. None of these

6. Following isothermal kinetic data are obtained in a basket type of mixed flow reactor for a porous catalyst. Determine the role of pore diffusion and external mass transfer processes ?

   A. Strong pore diffusion control and mass transfer not controlling
   B. Both pore diffusion and mass transfer not controlling
   C. Both pore diffusion and mass transfer controlling
   D. Mass transfer controlling

7. Bulk diffusion in catalyst pore _______________ with increase in pressure?

   A. Increases
   B. Decreases
   C. Remains unchanged
   D. Increases exponentially

8. If Thiele modulus is ________________, then the pore diffusion resistance in a catalyst may be considered as negligible?

   A. 0
   B. ∞
   C. < 0.5
   D. > 0.5

9. Knudsen diffusion is directly proportional to _____________________?

   A. T
   B. √T
   C. 1/√T
   D. T2

10. A catalyst is said to be a negative catalyst, if it ___________________?

    A. Retards the rate of reaction
    B. Reduces the value of equilibrium constant
    C. Does not initiate the reaction
    D. All A., B. and C.