Hydroisomerization in liquid phase of a refinery naphtha stream over Pt-Ni/H-beta zeolite catalysts

Hydroisomerization in the liquid phase of a C7-C8 stream obtained by distillation of a refinery naphtha stream using bifunctional catalysts containing Pt and/or Ni, supported on beta zeolite was studied. Temperature-programmed reduction (TPR) and temperature-programmed desorption of ammonia (TPDA) were used to characterize bimetallic interactions and the acidity of beta-supported Pt and/or Ni catalysts. Test reactions were carried out at 90 bar and 290 degrees C in order to achieve liquid-phase conditions. The highest activity corresponded to the catalyst PtBETA. The addition of Pt led to a better catalytic performance at higher reaction times. Concerning the hydroisomerization products, the percentage of monobranched isomers decreased as Ni content in the catalyst increased, the contrary effect was noted for the multibranched ones. High conversion of aromatic compounds was reached. Only methylcyclopentane was obtained as a product during the hydrogenation of benzene, which implied that the presence of acid sites favoured cyclohexane isomerization to form methylcyclopentane. Finally, an increase in the research octane number was obtained with all the catalysts due to the high amount of iso-paraffins and naphthenic compounds present in the products. (c) 2007 Elsevier B.V. All rights reserved.