# Chapter 10 Self Test

## Moving Bed Reactors

The elementary irreversible gas phase catalytic reaction is to be carried out in a moving bed reactor at constant temperature. The reactor contains 5 kg. of catalyst. The feed is stoichiometric in A and B. The entering concentration of A is 0.2 mol/dm3. The catalyst decay law is zero order with kD = 0.2 s–1. What catalyst loading rate is necessary to achieve 40% conversion?

k = 1.0 dm6/(mol•kg. cat•s)

vo = 1 dm3/s

Hint 1 What are the mole balance and the rate law?

Hint 2 What is the equation for catalyst activity as a function of loading rate?

Hint 3 What is the differential equation that combines the mole balance, activity law and rate law?

Hint 4 What is the solution to the equation in Hint 3?

Hint 5 What conversion will be achieved for a catalyst feed rate of 0.5 kg/s?

Hint 6 Sketch the catalyst activity as a function of catalyst weight (i.e., distance) down the length such for a catalyst feed rate of 0.5 kg/s.

Hint 7 What is the maximum conversion that could be achieved (i.e. at infinite catalyst loading rate)?

Hint 8 At what catalyst loading rate (kg/s) will the catalyst activity be exactly zero at the exit of the reactor?

Hint 1. Mole balance and rate laws Back to Hints

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Hint 2. Equation for catalyst activity  Back to Hints

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Hint 3. Combine mole balance, rate law, decay law, and stoichiometry   (1)

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Hint 4. Solution to Hint 3. Back to Hints

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Hint 5. What is conversion Zero conversion. NONSENSE!

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Hint 6. Sketch a vs. W

Look at a vs. W Therefore  (2)

when therefore (3)

Rearranging Equation (1) and integrating Back to Hints

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Hint 9. Loading rate for which a is exactly zero at the exit of reaction. at a loading of 1 kg/s the catalyst activity will be exactly zero at the exit of the reactor.

What does an activity of zero mean? Can catalyst activity be less than zero?

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