Hydrogenation and Deactivation Kinetics in the Liquid-Phase Hydrogenation of Isooctenes on Pt/Al₂O₃

Abstract

Isooctenes (2,4,4-trimethyl-1-pentene, TMP-1, and 2,4,4-trimethyl-2-pentene, TMP-2) were hydrogenated to isooctane (2,2,4-trimethylpentane) using a commercial Pt/Al 2 O 3 catalyst in a three-phase laboratory-scale reactor. The terminal double bond in TMP-1 was hydrogenated substantially faster than the internal double bond in TMP-2, and double bond isomerization was found to be of no importance. Furthermore, strong catalyst deactivation through the formation of carbonaceous deposits was observed under the applied reaction conditions. Kinetic models, which were formulated on the basis of the Horiuti-Polanyi mechanism, described the experimental data accurately and with physically reasonable parameter values (E a 49 kJ/mol for TMP-1 and 65 kJ/mol for TMP-2). Catalyst deactivation was successfully described with the first-order equation, in which the deactivation constant was dependent on the alkene-to-hydrogen ratio. Features in which the studied Pt catalyst deviates from Ni and Co include higher activation energies, stronger hydrogen adsorption, and more severe catalyst deactivation.

Temperature Programmed Hydrogenation of Toluene

“…Lylykangas et al [17,18] observed deactivation in liquid-phase hydrogenation of isooctenes with the same Ni, Co and Pt catalysts as used in our study. The Ni catalyst lost 20%, the Co catalyst 45% and the Pt catalyst over 80% of its initial activity during 30 h runs.…”

“…Details of these measurements can be found elsewhere [17,18]. For the nickel, platinum and iridium catalysts the calculation of apparent TOF was based on irreversible hydrogen uptake at 30°C.…”

Catalytic activity of the VIII Group metals in the hydrogenation and isomerization of α- and β-pinenes

“…The powdered carbon support Sibunit with the following texture characteristics was used: S sp /m 2 g -1 (based on Ar adsorption) 480 V pore /cm 3 g -1 (based on moisture content) 0.7 D pore /nm (based on N 2 adsorption) [30][31][32][33][34][35] Sibunit was preliminarily activated by the treatment with a 5% solution of HNO 3 at 100°C for 4 h to change the composi tion and amount of oxygen containing groups on the carbon material surface. The supported catalysts 0.9% Rh/C, 1.5% Ru/C, 1.0% Pt/C, 1.0% Pd/C, 4.0% Pd/С, and 1.0% Ir/C were prepared by the precipitation of the corresponding metal hydroxide on the carbon support according to previously de scribed procedures.…”

Effects of the activation method on the performance of base metal catalysts prepared by wet impregnation for toluene hydrogenation in liquid phase

“…The deactivation of catalysts on liquid phase hydrogenation reactions has been studied, but there is still no consensus about its causes. Lylykangas et al [38] studied Ni, Co and Pt catalysts employed in the hydrogenation of isooctenes in liquid phase. The authors observed a deactivation of these solids, which was attributed to the formation of carbonaceous species.…”