In catalytic dehydrogenation of hydrocarbons the catalyst activity decays with use because of carbon deposition on the active surfaces. Let us study this process in a specific system.

A gaseous feed (10% C₄, H₁₀, - 90% inerts, π = 1 atm, T = 555°C) flows (τ' = 1.1 kg · hr/m³) through a packed bed of alumina-chromia catalyst. The butane decomposes by a first-order reaction

Examination of the 0.55-mm pellets shows the same extent of carbon deposition at the entrance and the exit of the reactor, suggesting concentration independent deactivation. Develop rate equations for reaction and deactivation. This problem was devised from the information given by Kunugita et al., J. Chem. Eng. (Japan), 2, 75 (1969).

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C4H10 C4H8 carbon other gases and the behavior with time is as follows: 0 1 2 3 45 0.89 0.78 0.63 0.47 0.34 0.26 t, hr XA