KINETICS AND MECHANISM OF TOLUENE HYDRODEALKYLATION ON NICKEL/ALUMINA CATALYST

The use of 6% Ni/Al2O3 catalyst for the hydrodealkylation of toluene (THD) using the pulse technique at differential reactor conditions has been investigated. The hydrodealkylation selectivity (or the selectivity to benzene production) was optimum at 593 K showing some hydrogenation of the aromatic ring at lower temperatures and favoring hydrocracking at higher temperatures. Activation energy was found to be 97.9 kJ.mol(-1). Reaction rates at low conversion runs were interpreted both by empirical power equation of the type r = KPTm P-H(n) and by Langmuir-Hinshelwood type equations, determining the corresponding parameters. A good fit to the experimental results was obtained with the empirical equation (m = 0.65; n = 0.16) and the L-H equation of the form: r = 4.104 P-T P-H(1/2)/ (1+0.037P(T) + 0.0086P(H)(1/2))(2) A reaction sequence is presented for the rate determining surface reaction suggesting sequential reactant absorption at a common catalytic site for toluene and atomic hydrogen.