The second-order decomposition reaction A B+2C
is carried out in a tubular reactor packed with catalyst pellets 0.4 cm in diameter. The reaction is internal-diffusion-limited. Pure A enters the reactor at a superficial velocity of 3 m/s, a temperature of 250°C, and a pressure of 500 kPa. Experiments carried out on smaller pellets where surface reaction is limiting yielded a specific reaction rate of 0.05 m6/mol g cat s. Calculate the length of bed necessary to achieve 80% conversion. Critique the numerical answer.
Additional information:
Effective diffusivity: 2.66 × 10-8 m2/s
Ineffective diffusivity: 0.00 m2/s
Bed porosity: 0.4
Pellet density: 2 × 106 g/m3
Internal surface area: 400 m2/g