Kinetic Model of the Dehydrogenation of Methylcyclohexane over Monometallic and Bimetallic Pt Catalysts

Abstract

Various kinetic models were developed for methylcyclohexane (MCH) dehydrogenation over supported Pt catalysts. The best fitting mechanistic model is of the non-Langmuirian/noncompetitive Horiuti-Polanyi type. In this model, the Horiuti-Polanyi aromatic hydrogenation mechanism, which assumes an atomic hydrogen addition to aromatics on the catalyst surface, is applied in reverse to MCH dehydrogenation. The model also assumes that hydrogen and MCH molecules adsorb noncompetitively on two different types of sites to accommodate the observed near zero-order dependence of reaction rate on MCH and the negative order dependence upon hydrogen. To account for the increase in the hydrogen inhibition effect with pressure, a non-Langmuirian adsorption isotherm is adopted, which assumes a nonlinear dependency between the adsorption equilibrium constant for hydrogen and the system pressure. The reversible and irreversible deactivation kinetics are satisfactorily included in the kinetic model.

Dehydrogenation of methylcyclohexane to toluene over partially reduced Mo–SiO2 catalysts

“…Due to the high intrinsic hydrogenation/dehydrogenation activity, the conventional Pt-based catalysts are currently used for the methylcyclohexane dehydrogenation, such as Pt/Al 2 O 3 , Pt/V 2 O 5 , Pt/Y 2 O 3 and Pt-Re/Al 2 O 3 [8][9][10][11][12][13][14][15][16][17][18]. But the scarcity and the high cost of the noble metals prompted researchers to find alternatives, and thus, various transition metals have recently been tested in cycloalkanes dehydrogenation such as Ni, Cu, Sn [19][20][21][22].…”

Associative Adsorption Kinetics: A Novel Kinetic Model for the Dehydrogenation of Methylcyclohexane

“…Re/Al 2 O 3 catalyst, Pal et al[30] found a value of 56.4 kJ mol -1 on the same catalyst as that of Jothimurugesan et al[25], Tsakiris[19] reported apparent activation energy values in the range of 44.1 - 60.0 kJ mol -1 for his Pt over α-and γ-alumina catalysts and for 0.3 wt% Pt/α-Al 2 O 3 and 1.0 wt% Pt/-Al 2 O 3 , activation energies were 45.7 and 49.8 kJ mol -1 , respectively, Alhumaidan et al[20] used a value of 55.4 kJ mol -1 as the activation energy for the kinetic study of all of his commercial and in-house Pt/Al 2 O 3 catalysts, and Usman et al[7] have found activation energies of 50.2 for their work on 1.0 wt% Pt/θ-Al 2 O 3 .…”

Macrokinetic effects in perhydro-N-ethylcarbazole dehydrogenation and H2productivity optimization by using egg-shell catalysts

“…The above mentioned storage density does not take into account the total system volume (e.g. [21][22][23] More recently, polycyclic LOHCs with a nitrogen heteroatom have been proposed with the N-functionality causing much milder dehydrogenation conditions. The search for suitable LOHC compounds and mixtures thereof is 60 continued, since some of the components (e.g.…”