Liquid-phase hydrogenation kinetics of aromatic hydrocarbon mixtures

The liquid-phase hydrogenation kinetics of one multiaromatic mixture and five binary aromatic mixtures of toluene, ethylbenzene, xylenes, and mesitylene were determined in a semibatch reactor operating at a pressure of 40 bar and a temperature of 125 degrees C. Commercial preactivated catalyst particles of nickel-alumina were used in the experiments. In mixtures, the aromatic compounds reacted in queues so that the most reactive components started to react immediately while the least reactive components did not react until the most reactive components had been hydrogenated completely. This type of reactivity decreased with the increasing number of substituents, i.e. in the order monosubstituted > disubstituted > trisubstituted. The relative positions of the substituents affected the reaction rate so that the reactivity decreased in the order ortho > para > meta. The queue effect was described with a kinetic model based on the rapid adsorption of aromatic compounds and hydrogen and sequential addition of hydrogen to the aromatic nucleus, the first hydrogen addition step being rate determining. The kinetic parameters were estimated from a heterogeneous reactor model with nonlinear regression analysis. The kinetic model was able to describe hydrogenation kinetics of the binary aromatic mixtures.