Improvement of fuel properties via hydrogenation and ring opening : studies on tetralin/1,3-dimethyl-cyclohexane

Abstract

Due to environmental concerns, the reduction of aromatics in gasoline and diesel fuel is focused on many countries around the world. However, the decrease in aromatic contents via the hydrogenation process ended up with low octane number gasoline. Although, in the case of diesel fuel, the reduction of aromatics is closely related to an increase in cetance number, the saturation of aromatics using the conventional two-stage process might not be able to approach fuel requirements for the near future. Recently, the opening of the naphthenic ring was introduced as one of the promising reactions for both cetane and octane number improvement which depends on the positions of the cleavage of the C-C bond. In this work, the hydrogenation of tetralin on Pt/Al2O3, Pd/Al2O3, and Ni/Al2O3 catalysts in a gas phase reaction was investigated. It was found that the product selectivities depend on the intrinsic properties of the metal and the cis- to trans-decalin isomerization. A selective catalyst toward the cis-decalin product with low isomerization activity is more preferred to maximize cis-decalin, which facilitates ring opening products in subsequent processes. In addition, the ring opening of 1,3-dimethylcyclohexane (1,3-DMCH) was also carried out on Ir catalysts and promoted Ir catalysts with K or Ni. It is postulated that only the cleavage of the C-C bond at the unsubstituted poition of 1,3-DMCH is desired in order to yield high branched chain hydrocarbon products which are required for octane number improvement. It was found tha the addition of K or Ni altered the metal dispersion and metal-support interaction. Consequently, the product distribution can be modified using appropriate rations of Ir to K or Ir to Ni