abstracts - Институт катализа им. Г.К. Борескова

OP-III-13MOLECULAR MECHANISM OF 1,2-DICHLOROETHANE DECHLORINATIONOVER Cu AND Cu-Pt CATALYSTS. DENSITY FUNCTIONAL THEORY STUDYAvdeev V.I., Kovalchuk V.I. 1 , Zhidomirov G.M., Julie L. d’Itri 1Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia1 Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USAE-mail: via@catalysis.nsk.suIntroductionCatalysts based on bimetallic compounds may dramatically change both activity andselectivity, as compared to the individual metals, by creating new reaction pathways [1]. Themost impressive example of enhanced catalytic behavior as a result of alloying is the reactionof hydrogen-assisted 1,2-dichloroethane dechlorination.CH 2 Cl-CH 2 Cl + H 2 → CH 2 =CH 2 + 2HClIt has been found that Cu catalyzes this reaction with 100% selectivity to C 2 H 4 , but thecatalytic activity is extremely low [2]. However, alloying Cu with Pt results in catalystshighly selective toward C 2 H 4 , when the ratio of Cu/Pt exceeds 3 with the activity compared tothat of pure Pt [3]. Even though several hypotheses have been put forth [4], the reason of highactivity and ethylene selectivity of Cu-Pt catalysts is still poorly understood and the details ofthe mechanism of the 1,2-dichloroethane (1,2-DCE) dechlorination have not been elucidated.Thus, the present investigation is a theoretical analysis of the reaction pathways of the 1,2-DCE dechlorination to ethylene over Cu 20 and Cu 8 Pt 2 clusters that model active sites (AS) ofmono-Cu and bi-metallic Pt-Cu catalysts, respectively [models AS(Cu) and AS(Pt-Cu)].The calculations were performed within the Density Functional Theory (DFT) approachwith a GAUSSIAN_03 software package on Seaborg Supercomputer of National EnergyResearch Scientific Computing Center (USA) under contract No. DE-AC03-76SF00098.Becke three-parameter exchange functional (Becke3) within the gradient corrections and theLee-Yang-Parr (LYP) correlation functional were used (approximation Becke3LYP/CEP-31G/6-31G*).ResultsFor both AS(Cu) and AS(Pt-Cu) models the calculations predict two differentmechanisms of the 1,2-DCE dechlorination to ethylene (Figures 1 and 2). The firstmechanism corresponds to synchronous elimination of two chlorine atoms from 1,2-DCE inone elementary step. Ethylene evolves into the gas phase without the intermediate adsorption(direct mechanism). The other mechanism consists of three consecutive steps (step-by-step338