Study of Bimetallic Catalyst Pd-Ni for Styrene Hydrogenation

CAROLINA BETTI; J.M. BADANO; M.J. MACCARRONE; C.R. LEDERHOS; NICOLÁS CARRARA; CARLOS VERA; D. LIPRANDI; F. COLOMA-PASCUAL; M.E. QUIROGA

Kazan

Congreso; 12th European Congress on Catalysis - EuropaCat-XII; 2015

Gasoline and BTX(Benzene, toluene and xylenes) streams coming from the cracking of petroleummust be purified in order to minimize the concentration of diolefins,responsible of gums formations. The widespread method of purification is the selectivehydrogenation of vinyllic bond, keeping the aromatic rings unaltered. Thesestreams can have up to 1000 ppm of sulfur compounds, among them thiophene isone of the most common ones , being these sulfur compounds the main causeof the loss of activity of metal catalysts in several refinery processes. Theobjective of this work is to evaluate the influence of the order ofimpregnation of Pd and Ni in bimetallic catalysts on the activity and sulfurresistance during styrene partial hydrogenation.The effect of the sequence of impregnation was evaluated for a series ofbimetallic Pd?Ni catalysts. The properties assessed were the catalytic activityand the sulfur resistance during the selective hydrogenation of styrene. TheXPS results point to the presence of different Pd0, Pdd- and Pdd+OxClyspecies. The presence of Pdd- species wouldindicate the formation of a metallic bond or a Pd?Ni alloy. The order of totalconversion of styrene in the absence of sulfur was: PdNi@Pd>NiPd. After the poisoning with thiophenethe order changed to: Pd>PdNi@NiPd. Bimetallic PdNi catalyst turned out to be theleast sulfur resistant, this is likely due to the exposed Ni0 thatpromotes a strong adsorption of thiophene and thus an enhanced blocking ofactive sites. The higher sulfur resistance of NiPd than Pd catalyst could berelated to the high surface Cl/Al ratio, indicating that Pdd+species prevent the adsorption of thiophene bymeans of steric effect and/or an electronic effect