Liquid-phase hydrogenation kinetics of isooctenes on Ni/Al2O3

kinetics of the hydrogenation of isooctenes [2,4,4-trimethyl-1-pentene (TMP-1), and 2,4,4-trimethyl-2-pentene (TMP-2)] to isooctane (2,2,4-trimethylpentane) was studied on a commercial Ni/Al2O3 catalyst in a three-phase reactor. Experiments showed that nickel is a highly active catalyst for the reactions. In addition to the hydrogenation reactions, slow isomerization occurred between TMP-1 and TMP-2. Kinetic equations were derived based on the Horiuti-Polanyi mechanism, involving a half-hydrogenated surface intermediate and rate limitation in the first hydrogen addition. Isomerization was assumed to take place via the partly hydrogenated intermediate, since no isomerization products were observed in the absence of hydrogen. The dynamic reactor model consisted of material balances for the gas and liquid phases, as well as for the porous catalyst particles. The estimated activation energies for the hydrogenation of TMP-1 and TMP-2 were 34 and 49 kJ/mol, respectively. The model described the experimentally recorded data accurately.