Catalisadores Ru/xZnO-Al2O3 na hidrogenação parcial do benzeno

Abstract

Benzene has been associated with an increase in diseases such as leukemia and it can also cause irreversible chromosomal modifications and damage to life. The cyclohexene is an intermediate for nylon and other fine chemical products and it can be generated through partial benzene hydrogenation, which is an alternative application for this toxic compound. However, from the thermodynamic point of view, the total benzene hydrogenation to cyclohexane is much more favorable than its partial hydrogenation to cyclohexene. Based in this context, this work aims at the preparation, characterization and evaluation of Ru/xZnO-Al2O3 catalysts in the partial benzene hydrogenation reaction using a batch reactor. The ZnAl mixed oxides were synthesized by co-precipitation of their respective salts. The catalysts were prepared by dry impregnation of RuCl3.6H2O and the samples received the following nomenclatures: RuAl, Ru5ZnAl, Ru10ZnAl, Ru20ZnAl, Ru50ZnAl, Ru90ZnAl and RuZn. Textural analysis, X-ray fluorescence, X-ray diffraction, X-ray phoelectron, temperature programmed reduction and H2 chemisorption techniques were used to characterize the catalysts. Partial benzene hydrogenation was carried out in a PARR reactor Instruments. The order of activity for the reaction with pure benzene was as follows: Ru10ZnAl >>> Ru5ZnAl > Ru20ZnAl > RuAl >> Ru90ZnAl = Ru50ZnAl = RuZn. Over the studied catalysts, Ru10ZnAl presented lower particle size (8 nm) and higher surface area (297 m².g-1) and these factors most likely have favoured ruthenium high dispersion on the catalyst surface. In addition, through the TPR analysis, there was a partial ZnO reduction on this catalyst. Tests conducted with addition of solvents using Ru10ZnAl catalyst showed lower activities than the ones containing only benzene