TU Darmstadt / ULB / TUbiblio

How a Supported Metal Is Influenced by an Ionic Liquid: In-Depth Characterization of SCILL-Type Palladium Catalysts and Their Hydrogen Adsorption

Arras, Jürgen and Paki, Elisabeth and Roth, Christina and Radnik, Jörg and Lucas, Martin and Claus, Peter :
How a Supported Metal Is Influenced by an Ionic Liquid: In-Depth Characterization of SCILL-Type Palladium Catalysts and Their Hydrogen Adsorption.
[Online-Edition: http://dx.doi.org/10.1021/jp1016196]
In: The Journal of Physical Chemistry C, 114 (23) pp. 10520-10526.
[Article] , (2010)

Official URL: http://dx.doi.org/10.1021/jp1016196

Abstract

A novel approach to tremendously influence the gas adsorption behavior of heterogeneous metal catalysts consists of adding a small quantity of an ionic liquid during the catalyst synthesis yielding a supported catalyst with an ionic liquid layer (SCILL). Herein, SCILL-type catalysts derived from silica-supported palladium were characterized by means of ICP-OES, TPR, X-ray absorption spectroscopy (XANES/EXAFS), X-ray photoelectron spectroscopy (XPS), hydrogen pulse chemisorption, and differential scanning hydrogen adsorption calorimetry. EXAFS analysis of SCILL-type palladium catalysts did not indicate significant changes in the bulk properties of Pd compared to untreated Pd/SiO₂, the results are in good agreement with metallic Pd. XPS analysis revealed a more oxidized Pd surface if Pd/SiO₂ was treated with ionic liquids. In the case of [BMIM][N(CN)₂], Pd(II) species were present in part indicating a complexation of palladium by [N(CN)₂]⁻. Hydrogen uptakes determined by pulse chemisorption varied between 38 and 609 μmol gPd⁻¹ depending on the chosen IL, IL content, and temperature and were decreased in comparison to Pd/SiO₂ without IL. The initial heats of hydrogen adsorption were also affected in the presence of ionic liquids and were lowered compared to those of the untreated Pd/SiO₂. Mechanisms showing how the ionic liquids interact with the active palladium site are proposed and might be in summary interpreted as a ligand effect by the ionic liquid similar to the influence of second metals in bimetallic catalysts.

Item Type: Article
Erschienen: 2010
Creators: Arras, Jürgen and Paki, Elisabeth and Roth, Christina and Radnik, Jörg and Lucas, Martin and Claus, Peter
Title: How a Supported Metal Is Influenced by an Ionic Liquid: In-Depth Characterization of SCILL-Type Palladium Catalysts and Their Hydrogen Adsorption
Language: English
Abstract:

A novel approach to tremendously influence the gas adsorption behavior of heterogeneous metal catalysts consists of adding a small quantity of an ionic liquid during the catalyst synthesis yielding a supported catalyst with an ionic liquid layer (SCILL). Herein, SCILL-type catalysts derived from silica-supported palladium were characterized by means of ICP-OES, TPR, X-ray absorption spectroscopy (XANES/EXAFS), X-ray photoelectron spectroscopy (XPS), hydrogen pulse chemisorption, and differential scanning hydrogen adsorption calorimetry. EXAFS analysis of SCILL-type palladium catalysts did not indicate significant changes in the bulk properties of Pd compared to untreated Pd/SiO₂, the results are in good agreement with metallic Pd. XPS analysis revealed a more oxidized Pd surface if Pd/SiO₂ was treated with ionic liquids. In the case of [BMIM][N(CN)₂], Pd(II) species were present in part indicating a complexation of palladium by [N(CN)₂]⁻. Hydrogen uptakes determined by pulse chemisorption varied between 38 and 609 μmol gPd⁻¹ depending on the chosen IL, IL content, and temperature and were decreased in comparison to Pd/SiO₂ without IL. The initial heats of hydrogen adsorption were also affected in the presence of ionic liquids and were lowered compared to those of the untreated Pd/SiO₂. Mechanisms showing how the ionic liquids interact with the active palladium site are proposed and might be in summary interpreted as a ligand effect by the ionic liquid similar to the influence of second metals in bimetallic catalysts.

Journal or Publication Title: The Journal of Physical Chemistry C
Volume: 114
Number: 23
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Erneuerbare Energien
07 Fachbereich Chemie
07 Fachbereich Chemie > Fachgebiet Technische Chemie
07 Fachbereich Chemie > Fachgebiet Technische Chemie > Technische Chemie II
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 12 Sep 2011 05:30
Official URL: http://dx.doi.org/10.1021/jp1016196
Identification Number: doi:10.1021/jp1016196
Export:

Optionen (nur für Redakteure)

View Item View Item