Chlorofluorocarbon dechlorination on Pd(111): effect of chlorine stoichiometry

Catalytic Hydrodechlorination of Tetrachloroethylene over Pd/TiO2 Minimonoliths

“…Heterogeneous CHD has been reported in liquid , and gas phase reactions, involving aliphatic, olefinic, and aromatic reactants. − Pd, Pt, Rh, and Ni on several supports are suitable catalysts for this reaction. Notwithstanding, Pd appears to be the most active metal at lower operating temperatures. , In most works, 0.5 wt % Pd over Al 2 O 3 , SiO 2 , carbon, and TiO 2 supports has been used. ,,, More recently 0.8 wt % Pd/TiO 2 was found to be more active. , There have been several attempts at kinetic modeling ,, and pseudo-first-order kinetics for the CHD has been mainly postulated. ,, In the development of hydrodechlorination models reported so far, the authors have worked with catalysts having high affinity to hydrogen and organochlorinated compounds. The mechanisms have been described by Langmuir−Hinshelwood, ,,, where two possibilities are considered: chemisorption of hydrogen and organochlorinated compounds on the same active sites or on different active sites.…”

“…Dissociative or molecular adsorption depends on the type of organochlorinated compound. In the case of olefinic compounds as TTCE, the rate limiting step has been mainly linked with C−Cl scission . In general, kinetic studies have been performed with different catalysts, organochlorinated compounds, and reaction conditions.…”

Direct Observation of Extremely Low Temperature Catalytic Dehydrochlorination of 1,1,1-Trichloroethane over Platinum

“…However, although copper surfaces are effective for low-temperature C−Cl dissociation, they have little relevance to catalytic dechlorination processes because copper binds the liberated chlorine too strongly to regenerate active sites and complete the catalytic cycle. , Indeed, alloying with platinum (or palladium) is necessary to generate practical group IB dehalogenation catalysts. Furthermore, although a few studies have explored the influence of halogen substitution on the surface reactivity, surprisingly the only investigation of complex (>C 1 ) 1,1,1-substituted haloalkanes to date is that of chlorofluorocarbons on Pd{111} …”

Neutral Organic Radical Formation by Chemisorption on Metal Surfaces

“…This second component (low binding energy component, Cl–Ag) is small in 1 /Ag but dominates for 1 /Cu. In the three cases, the high-energy component Cl–C can be attributed to Cl atoms involved in a covalent Cl–C bond in 1 . − The lower binding energy contribution Cl–Ag, on the contrary, is most likely related to Cl atoms directly interacting with the metallic surface arising from C–Cl bond dissociations in 1 . ,,, (See section 2.1 of the SI for further details.) By comparing Cl 2p of 1 /Au, 1 /Ag, and 1 /Cu, it is evidenced that the interaction of 1 with Au does not alter its molecular structure, whereas C–Cl bond cleavage occurs on Ag (22%) to a lesser extent and on Cu (59%) to a major extent.…”

“…32−37 The lower binding energy contribution Cl−Ag, on the contrary, is most likely related to Cl atoms directly interacting with the metallic surface arising from C−Cl bond dissociations in 1. 32,33,35,38 (See section 2.1 of the SI for further details.) By comparing Cl 2p of 1/Au, 1/Ag, and 1/Cu, it is evidenced that the interaction of 1 with Au does not alter its molecular structure, whereas C−Cl bond cleavage occurs on Ag (22%) to a lesser extent and on Cu (59%) to a major extent.…”