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GATE 2025 CH – Question 20

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

Choose the CORRECT ordering of the diameter $d$ of the different types of pores in a solid catalyst.

  1. $d_{Micro-pore} < d_{Macro-pore} < d_{Meso-pore}$
  2. $d_{Macro-pore} < d_{Meso-pore} < d_{Micro-pore}$
  3. $d_{Meso-pore} < d_{Micro-pore} < d_{Macro-pore}$
  4. $d_{Micro-pore} < d_{Meso-pore} < d_{Macro-pore}$

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Correct answer: (D) $d_{Micro-pore} < d_{Meso-pore} < d_{Macro-pore}$

Explanation

By the IUPAC classification, micropores are narrower than 2 nm, mesopores are 2 to 50 nm and macropores are wider than 50 nm. So micro < meso < macro.