from first principles PP-I-1

OY-III-3Unusually Active Nanostructured Ni Catalysts with Low Metal Coveragefor Chlorobenzene HydrodechlorinationKavalerskaya N.E., Rostovchshikova T.N., Lokteva E.S., Golubina E.V., Maslakov K.I.Lomonosov Moscow State University, Department of Chemistry, Moscow, Russian.kavalerskaya@gmail.comMetal particle size and metal-support interaction are of the great importance in heterogeneouscatalysis. When an isolated metal cluster is placed on the support, it could result in the electricfield appearance in between. It represents an additional variable of state which, like pressureor temperature, can alter chemical equilibrium. Usually it is manifested in reagents andpruducts chemisorption parameters during surface reactions. Both the nature of a support andmetal distribution influence on the strength of such interaction. Laser electrodispersion (LED)technique was successfully used for preparation of nanostructured catalysts containing highlyuniform (about 2 nm) metal particles, and the particle size is constant in the wide range ofmetal loadings. In this work, LED prepared Ni catalysts on conductive and non-conductivesupports (Sibunit and Al 2 O 3 ) with different metal loadings (from 0,25 of monolayer to severallayers, where 1 monolayer is 0.001 wt% on Sibunit and 0.005 wt% on Al 2 O 3 ) were tested inthe hydrodechlorination of chlorobenzene at 50-350 o C in the gas-phase flow type system. Thesimilar samples prepared by wet impregnation were used for comparison. Catalysts wereexamined by HR TEM, XPS and adsorption methods.It was demonstrated by XPS that at low coverages, Ni in LED samples is presentedpredominantly in more oxidized forms than at higher contents which are close to monolayer.This dependence is more prominent for alumina supported samples, than for Sibunitsupported ones. Catalytic activity of Ni on these supports is different as well. For Ni/γ-Al 2 O 3 ,extremal dependence of catalytic activity on Ni loading with maximum at 0,001 wt% wasobserved (2,9•10 4 Mol/Mol (Ni)•h), that is comparable with the values for Pd. The activity ofNi/Sibunit significantly grows with the decrease of Ni loading (4,9•10 4 mol/mol (Ni)•h at0,001 wt% Ni). Such unusual activity at the Ni loadings of about one monolayer could beexplained in terms of charge transfer between the closely situated Ni particles or between Niparticle and support.This work was supported by RFBR (№ 10-03-00372, 11-03-00403) and Leading ScientificSchools grant НШ-2724.2012.3. Results were obtained with the help of SRCCU“Nanochemistry and Nanomaterials” of Lomonosov Moscow State University.96