engleski

Experimental and Theoretical Study of Ni/Al2O3 Deactivation

A quantitative assessment of the effect of the internal mass transport on a catalytic system involving chemical poisoning is based on solving a set of coupled partial differential equations describing the reactant and product activity profile within the catalyst particle. It is convenient to describe the results by a pellet effectiveness factor for the main reaction which depends upon time, intraparticle position, diffusional and reaction parameters. Based on kinetics of gas phase benzene hydrogenation to cyclohexane, catalyst poisoning and pore diffusion time-dependent effectiveness behaviour of a Ni/Al2O3 catalyst pellet was simulated. Deactivation measurements were carried out in an isothermal fixed-bed reactor at hydrogen partial pressure of 99.82 kPa, benzene partial pressure of 7.55 kPa, thiophene partial pressure 0.032 kPa and the reaction temperatures ranging from 403 to 473 K. The calculated time-dependent effectiveness factor as a function of Thiele modulus has been compared with the experimental observation for commercial catalyst pellet. In general, a satisfactory degree of correlation between theoretical prediction and experimental results was found when benzene hydrogenation was represented by power-law kinetic equation. Some criticism may be made on results when Hougen-Watson kinetic model for benzene hydrogenation is used.

Catalyst deactivation; Mass transport; Effectiveness factor

nije evidentirano