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GATE 2026 CH – Question 17

Chemical Reaction Engineering · Heterogeneous catalysis, diffusion effects and catalyst deactivation · 1 mark · Multiple choice

An irreversible chemical reaction occurs on a porous catalyst. All the pores are of same size. In strong pore diffusion regime, the observed activation energy is 120 kJ mol$^{-1}$. The activation energy of diffusion is 10 kJ mol$^{-1}$. Assuming Arrhenius temperature dependency for both reaction and diffusion, which one of the following is the true activation energy (in kJ mol$^{-1}$) of the reaction?

  1. 65
  2. 110
  3. 130
  4. 230

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Correct answer: (D) 230

Explanation

In the strong pore diffusion regime the observed rate constant varies as $\sqrt{k D_e}$, so the observed activation energy is the average $E_{obs} = \frac{E_{true} + E_D}{2}$. Then $E_{true} = 2 \times 120 - 10 = 230$ kJ mol$^{-1}$.