Hydrodechlorination of 1,2-Dichloroethane on Platinum Catalysts: Insights from Reaction Kinetics Experiments, Density Functional Theory, and Microkinetic Modeling

Abstract

Catalytic hydrodechlorination is a promising strategy for treating industrial 1,2-dichloroethane wastes, for which Pt and Pt-based alloy catalysts are widely used. Here, we performed a detailed mechanistic study for 1,2-dichloroethane hydrodechlorination on Pt using a synergistic approach combining density functional theory (DFT) calculations, reaction kinetics experiments, and microkinetic modeling. Using planewave DFT calculations, we evaluated the reaction energy and activation energy barrier of each elementary step involved in the reaction network on Pt­(111). The calculated energetics were then incorporated into a comprehensive mean-field microkinetic model accounting for a total of 65 elementary steps. The model-predicted reaction rates were compared with the results from our reaction kinetics experiments on SiO2-supported Pt catalysts. Our results indicated that the hydrodechlorination of 1,2-dichloroethane on Pt(111) starts with a H-removal step; then, it proceeds through a sequence of alternating dechlorination and dehydrogenation steps until vinylidene (CH2C*) is formed; finally, CH2C* is hydrogenated to the final product, ethane, sequentially via vinyl (CH2CH*), ethylene, and ethyl (CH3CH2*) intermediates. After model parameter adjustments, we achieved good agreement between our theoretical model and experimental results; the adjustments to the calculated parameters are consistent with the typically anticipated coverage effects. Our study offers valuable mechanistic insights, which are useful for improving catalysts for this chemistry.

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

“…Previously, we examined the 1,2-DCA hydrodechlorination mechanism on pure Pt catalysts using a combination of reaction kinetics experiments, density functional theory (DFT) calculations, and mean-field microkinetic modeling. 37 We demonstrated that 1,2-DCA hydrodechlorination on pure Pt catalysts starts with a hydrogen-removal step and proceeds through the following reaction pathway (eq 1):…”

“…We previously demonstrated the success of this combined experimental and theoretical approach for the study of the same chemistry on pure Pt catalysts. 37 Using DFT calculations, we first studied the effect of Pt−Cu alloy composition on the binding properties of surface reaction intermediates. The reaction kinetics of surface elementary steps were then examined on Pt 1 Cu 3 (111), a Curich alloy model surface for the Pt−Cu catalysts used in our reaction kinetics experiments.…”

Freestanding 3D Ordered Hierarchical Porous Carbon Aerogel Cathodes for Efficient Electrocatalytic Dechlorination of 1,2-Dichloroethane to Ethylene

“…1,2-Dichloroethane (DCE) has found widespread applications as universal synthetic intermediates in organic chemistry owing to the inherent reactivity of carbon–chlorine bonds. , However, the excessive emissions of DCE with higher toxicity and lower biodegradability have made it classified as a priority pollutant in most countries. , Therefore, it is of great significance to develop efficient and applicable remediation strategies for the elimination of DCE. In our previous studies, we confirmed that dislodging DCE through electrochemical dechlorination is an economic and eco-friendly method to selectively produce ethylene, which is one of the most important feedstocks in petrochemical industries. − However, due to the stability of the C–Cl bond (327 kJ·mol –1 ) and the poor selectivity and Faradaic efficiency, the development and application of DCE dechlorination reaction have been limited .…”

“…■ INTRODUCTION 1,2-Dichloroethane (DCE) has found widespread applications as universal synthetic intermediates in organic chemistry owing to the inherent reactivity of carbon−chlorine bonds. 1,2 However, the excessive emissions of DCE with higher toxicity and lower biodegradability have made it classified as a priority pollutant in most countries. 3,4 Therefore, it is of great significance to develop efficient and applicable remediation strategies for the elimination of DCE.…”

Simultaneous Construction of Silica Nanotubes Loaded with Pd Nanoparticles for Catalytic Hydrodechlorination of Chlorophenols

“…The common catalysts used for HDC are supported noble metals, − for example, Pd, ,− Ru, and Rh, ,− while transition metals, such as Ni and Co, are effective for this reaction but require relatively critical reaction conditions. To achieve better performance, bimetallic alloy catalysts, for instance, PdAg, PtNi, NiFe, and PdNi, have also been studied, and their performances are usually dependent on the compositions of bimetallic alloys. , Among various catalysts, Pd has been recognized as efficient catalysts for HDC of various chlorophenols, which can be performed at atmospheric H 2 pressure and low temperatures.…”