Study of Bimetallic Catalyst Pd-Ni for Styrene Hydrogenation

CAROLINA P. BETTI; JUAN M. BADANO; MARÍA JULIANA MACCARRONE; CECILIA R. LEDERHOS; NICOLÁS CARRARA; CARLOS R. VERA; DOMINGO LIPRANDI; FERNANDO COLOMA-PASCUAL; MÓNICA E. QUIROGA

Kazan

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

Gasoline and BTX (Benzene, toluene and xylenes) streams coming from the cracking of petroleum must be purified in order to minimize the concentration of diolefins, responsible of gums formations. The widespread method of purification is the selective hydrogenation of vinyllic bond, keeping the aromatic rings unaltered. These streams can have up to 1000 ppm of sulfur compounds, among them thiophene is one of the most common ones [1,2], being these sulfur compounds the main cause of the loss of activity of metal catalysts in several refinery processes. The objective of this work is to evaluate the influence of the order of impregnation of Pd and Ni in bimetallic catalysts on the activity and sulfur resistance during styrene partial hydrogenation. The effect of the sequence of impregnation was evaluated for a series of bimetallic PdNi catalysts. The properties assessed were the catalytic activity and the sulfur resistance during the selective hydrogenation of styrene. The XPS results point to the presence of different Pd0, Pd- and Pd+OxCly species. The presence of Pd- species would indicate the formation of a metallic bond or a Pd?Ni alloy. The order of total conversion of styrene in the absence of sulfur was: PdNiPd>NiPd. After the poisoning with thiophene the order changed to: Pd>PdNiNiPd. Bimetallic PdNi catalyst turned out to be the least sulfur resistant, this is likely due to the exposed Ni0 that promotes a strong adsorption of thiophene and thus an enhanced blocking of active sites. The higher sulfur resistance of NiPd than Pd catalyst could be related to the high surface Cl/Al ratio, indicating that Pd+species prevent the adsorption of thiophene by means of steric effect and/or an electronic effect.