industrial chemical reaction operations involve the use of a metal catalyst finely persed over and within a porous substrate material, e.g. activated carbon. Given that a chemical reaction utilising a porous catalyst must undergo several key mass transport processes, outline and briefly describe the series of seven steps that must occur for successful reaction. Provide a suitable diagram. [10 marks] What is meant by the term 'Knudsen' diffusion? [3 marks] The hydrodesulphurisation reaction of thiophene (C4H4S) with hydrogen is typically conducted in a catalytic packed bed reactor at 650K and 35 bar(a). Given the properties of the catalytic bed are: Specific surface area, obtained from BET measurement, S=180m2g1 Particle density p=1400kgm3 Particle porosity =0.40 Tortuosity factor =2.0 The bulk diffusion coefficient for thiophene as a bulk gas is 5.2106m2s1 at 600K and 35bar(a). Calculate: i. The mean pore radius (r,m) of the catalyst particle. [3 marks] ii. The Knudsen diffusion coefficient (DK,m2s1) for thiophene in a straight cylindrical pore using the correlation; DK=97r(RMMT)0.5 where T is absolute temperature and RMM is relative molecular mass. [2 marks] iii. The effective diffusivity within the catalyst particle. [4 marks] iv. Which is the more dominant diffusional process, bulk or Knudsen? Give a brief explanation for your answer. [3 marks]