title: Hydrodechlorination of Tetrachloromethane over Palladium Catalysts Supported on Mixed MgF₂-MgO Carriers.
abstract: Pd/MgO, Pd/MgF₂ and Pd/MgO-MgF₂ catalysts were investigated in the reaction of CCl₄ hydrodechlorination. All the catalysts deactivated in time on stream, but the degree of deactivation varied from catalyst to catalyst. The MgF₂-supported palladium with relatively large metal particles appeared the best catalyst, characterized by good activity and selectivity to C₂-C₅ hydrocarbons. Investigation of post-reaction catalyst samples allowed to find several details associated with the working state of hydrodechlorination catalysts. The role of support acidity was quite complex. On the one hand, a definite, although not very high Lewis acidity of MgF₂ is beneficial for shaping high activity of palladium catalysts. The MgO-MgF₂ support characterized by stronger Lewis acidity than MgF₂ contributes to very good catalytic activity for a relatively long reaction period (~5 h) but subsequent neutralization of stronger acid centers (by coking) eliminates them from the catalyst. On the other hand, the role of acidity evolution, which takes place when basic supports (like MgO) are chlorided during HdCl reactions, is difficult to assess because different events associated with distribution of chlorided support species, leading to partial or even full blocking of the surface of palladium, which plays the role of active component in HdCl reactions.
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw 01-224, Poland. mbonarowska@ichf.edu.pl.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Bonarowska
authors.affiliation: Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, Poznań 61-614, Poland. emawoj@amu.edu.pl.
authors.forename: Maria
authors.initials: M
authors.lastname: Wojciechowska
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw 01-224, Poland. mzielinski@ichf.edu.pl.
authors.forename: Maciej
authors.initials: M
authors.lastname: Zieliński
authors.affiliation: Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, Poznań 61-614, Poland. angelika.kiderys@gmail.com.
authors.forename: Angelika
authors.initials: A
authors.lastname: Kiderys
authors.affiliation: Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, Poznań 61-614, Poland. mardok@amu.edu.pl.
authors.forename: Michał
authors.initials: M
authors.lastname: Zieliński
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, Warsaw 00-664, Poland. piotrw@ch.pw.edu.pl.
authors.forename: Piotr
authors.initials: P
authors.lastname: Winiarek
authors.affiliation: Faculty of Mathematics and Natural Sciences, School of Science, Cardinal Stefan Wyszyński University, Wóycickiego 1/3, Warsaw 01-938, Poland. z.karpinski@uksw.edu.pl.
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Karpiński
mesh_terms: D002384:Catalysis; D002713:Chlorine / Q000737:chemistry*; D002725:Chloroform / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D058116:Lewis Acids / Q000737:chemistry; D017616:Magnesium Compounds / Q000737:chemistry*; D008277:Magnesium Oxide / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D058116:Lewis Acids; D017616:Magnesium Compounds; D008277:Magnesium Oxide; D002713:Chlorine; C031288:magnesium fluoride; D010165:Palladium; D002725:Chloroform; D005459:Fluorides
keywords: CCl4 hydrodechlorination; Lewis acidity; MgF2; MgO; MgO-MgF2; palladium; supports