Conversion under hydrogen of dichlorodifluoromethane over supported palladium catalysts

Journal Article · Sat May 01 00:00:00 EDT 1993 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1993.1115· OSTI ID:6217269

Coq, B; Figueras, F; Tournigant, D ^[1]; Cognion, J M ^[2]

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1. CNRS, Montpellier (France)
2. ATOCHEM, Pierre-Benite (France)

The conversion of difluorodichloromethane has been studied in the gas phase between 433 and 523 K at atmospheric pressure over Pd black and Pd supported on alumina, graphite, or AlF[sub 3]. In CF[sub 2]Cl[sub 2] hydrogenation, CH[sub 2]F[sub 2] and CH[sub 4] represented more than 95% of the products. The catalytic properties of Pd/AlF[sub 3] samples are unchanged with time, but Pd/graphite, Pd/Al[sub 2]O[sub 3], and Pd black suffered changes of activity and/or selectivity during the first few hours on stream. This was ascribed to the diffusion of halide species into the bulk of palladium, and transformation of Al[sub 2]O[sub 3] to AlF[sub 3]. At the steady state, the kinetics of CF[sub 2]Cl[sub 2] hydrogenation can be described either by a halogenation/dehalogenation of the Pd surface by CF[sub 2]Cl[sub 2] and H[sub 2], respectively, or by a classical Langmuir-Hinshelwood mechanism. It was concluded that at 453 K the interaction between the Pd surface and CF[sub 2]Cl[sub 2] or H[sub 2] is of the same order of magnitude. The CH[sub 2]F[sub 2]/CH[sub 4] selectivity ratio was the lowest on Pd/graphite and the highest on Pd/AlF[sub 3]. It is proposed that adsorbed, or absorbed, halide species are responsible for the loss of CH[sub 2]F[sub 2] selectivity. The high selectivity ratio on Pd/AlF [sub 3] is ascribed to a cooperative effect between Pd and AlF[sub 3]. 27 refs., 5 figs., 6 tabs.

• OSTI ID: 6217269
• Journal Information: Journal of Catalysis; (United States), Vol. 141:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CHLOROFLUOROCARBONS
HYDROGENATION
PALLADIUM
CATALYTIC EFFECTS
PALLADIUM COMPOUNDS
ALUMINIUM FLUORIDES
ALUMINIUM OXIDES
CATALYST SUPPORTS
CATALYSTS
CHEMICAL REACTION KINETICS
DEHALOGENATION
GRAPHITE
HALOGENATION
HETEROGENEOUS CATALYSIS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0400-1000 K
ALUMINIUM COMPOUNDS
CARBON
CATALYSIS
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTAL MINERALS
ELEMENTS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
KINETICS
METALS
MINERALS
NONMETALS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
REACTION KINETICS
TEMPERATURE RANGE
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties