Mechanistic Study of 1,2-Dichloroethane Hydrodechlorination on Cu-Rich Pt–Cu Alloys: Combining Reaction Kinetics Experiments with DFT Calculations and Microkinetic Modeling

Abstract

Cu-rich Pt−Cu bimetallic catalysts are among the most promising candidates for actively catalyzing the hydrodechlorination of 1,2-dichloroethane (1,2-DCA) toward ethylene production. Combining reaction kinetics experiments with density functional theory (DFT) calculations and mean-field microkinetic modeling, we present a systematic mechanistic study for 1,2-DCA hydrodechlorination on Cu-rich Pt−Cu alloy catalysts. Our DFT (PBE+(TS+SCS)) results suggest that increasing Cu content in the Pt−Cu alloy destabilizes C 2 -species adsorption while stabilizing the binding of atomic chlorine. The reaction energetics of all the elementary steps in the 1,2-DCA reaction network were calculated on a Pt 1 Cu 3 (111) model surface. The DFT results were then used to construct a microkinetic model, and the model-predicted reaction rates were compared with our reaction kinetics experimental results on a Cu-rich SiO 2 -supported Pt−Cu alloy catalyst through a parameter estimation procedure. Both the reaction kinetics experiments and the microkinetic model after parameter adjustments yielded 100% selectivity to ethylene. The microkinetic model pointed to a reaction pathway involving two sequential chlorineremoval steps on the Pt−Cu alloy catalyst, a mechanism distinct from the one previously identified on pure Pt/SiO 2 catalysts, which involved an initial hydrogen-removal step. Adjustments to the DFT-derived parameters indicate the possible formation of chlorineinduced Cu-enriched surface sites during 1,2-DCA hydrodechlorination conditions, sites that are more active than those encountered in the bulk Pt 1 Cu 3 (111) alloy surface. Our study offers valuable initial insights on the 1,2-DCA hydrodechlorination reaction mechanism and the nature of the active sites on PtCu bimetallic catalysts.

Highly Efficient ZIF-67-Derived PtCo Alloy–CN Interface for Low-Temperature Aqueous-Phase Fischer–Tropsch Synthesis

“…The bimetallic alloys with an FCC crystal structure in the general form of an A 3 B (L1 2 )-type alloy structure, having 75:25 compositions of A and B metals, respectively, are considered here in DFT studies. Similar A 3 B (L1 2 )-type bimetallic alloy models have been previously used to understand the catalytic reaction mechanism and trend studies for bimetallic alloys in different studies by Norskov et al, − Mavrikakis et al, − Studt et al, − Bligaard et al, , and Zhu et al Moreover, in some of our previous studies, similar A 3 B alloy models have been used for in silico bimetallic catalyst screening. , …”

Industrial Chlorinated Organic Removal with Elimination of Secondary Pollution: A Perspective

“…Chlorophenols reduced to phenol by Pd/Fe nanoparticles follow the reaction rates of 4-chlorophenol > 2,4-dichlorophenol > 2,4,6-trichlorophenol because the energy barrier of the first cracked C–Cl was increased by the vicinal chlorination . A similar phenomenon with chloroethanes was also observed, that is, a dechlorination barrier following 1,2-dichloroethane > chloroethane > chloroethylene . The pH value of the reaction environment also significantly influences the efficiency of dechlorination hydrogenation, especially for the bimetallic Pd catalysts.…”

“…57 A similar phenomenon with chloroethanes was also observed, that is, a dechlorination barrier following 1,2-dichloroethane > chloroethane > chloroethylene. 58 The pH value of the reaction environment also significantly influences the efficiency of dechlorination hydrogenation, especially for the bimetallic Pd catalysts. The dislodgement of Pd islets is caused by surface erosion in acidic pH; contrarily, surface passivation by hydroxide precipitation of additional metals, including Fe, Cu, and Ag, will also occur in an alkaline environment.…”