Thermal treatment effects on the Ru/CeO_2 catalysts performance for partial hydrogenation of benzene

摘要

The aim of this work is to study the effect of the preparation conditions of Ru/CeO_2 catalyst (calcination temperature and/or reduction) over the performance in the partial hydrogenation of benzene reaction in the presence of TiCl_3. The catalysts were prepared through chlorinated precursors by incipient wetness impregnation method. The reaction occurred in three-phase reactional medium in presence of water at 373 K and 5.0 MPa. Temperature programmed reduction (TPR) profiles of calcinated catalysts indicate the presence of oxidated ruthenium. X-ray photoelectron spectroscopy (XPS) analysis confirms this supposition, showing that the ruthenium appears in the form of RuO_2 for the sample calcinated at 673 K, while for the reduced solid at 773 K, the Ru appears in the metallic state. However, the calcination step followed or not by reduction, strongly hinders the catalytic performance. In its turn, the direct reduction leads to a more active Ru/CeO_2 catalysts, as well as higher cyclohexene yields throughout all the reaction.