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Ordered Mesoporous Pd/Silica-Carbon as a Highly Active Heterogeneous Catalyst for Coupling Reaction of Chlorobenzene in Aqueous Media
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
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2009 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, no 12, 4541-4550 p.Article in journal (Refereed) Published
Abstract [en]

Heterogeneous palladium catalysts, which are supported on ordered mesoporous silica-carbon nanocomposites, have been applied in water-mediated coupling reactions of chlorobenzene without assistance of any phase-transfer catalysts. Characterization by XRD, TEM, N2 sorption, FT-IR, TG, XPS, and H2 chemisorption techniques reveals the highly ordered mesostructure, high surface areas (?345 m2/ g), large pore volumes (?0.46 cm3/g), uniform mesopore sizes (?6.3 nm), hybrid silicate and carbonaceous compositions, and a high dispersion of palladium nanoparticles (about 3 nm) in the mesopores. The catalyst exhibits a high yield for trans-stilbene (?60%) in the Heck coupling reaction of chlorobenzene and styrene at 100 ‹C and for biphenyl (46%) in the Ullmann coupling reaction of chlorobenzene at 30 ‹C, using water as a solvent. When substituted aryl chlorides (hydroxyl, methoxyl, and methyl) are involved in the Ullmann reaction, the yields of symmetrical substituted biphenyl are also higher than 44% (this value reaches 86% for the coupling reaction of 4-chlorophenol) at a low temperature of 30 ‹C. This heterogeneous catalyst is stable, which shows negligible metal leaching, and can be reused more than 20 times. For comparison, the catalytic activities for Pd catalysts supported on pure mesoporous polymeric, carbonaceous, and silicate frameworks are also investigated. The results clearly indicate that the pore wall nature shows great influence on the dispersion of metallic Pd species and, in turn, the catalytic performance.

 

Place, publisher, year, edition, pages
2009. Vol. 131, no 12, 4541-4550 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:su:diva-36709DOI: 10.1021/ja808481gISI: 000264792900067OAI: oai:DiVA.org:su-36709DiVA: diva2:289993
Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12Bibliographically approved
In thesis
1. EM study of Mesoporous Crystals, Hollow Spheres and Intergrowth Tungsten Bronzes
Open this publication in new window or tab >>EM study of Mesoporous Crystals, Hollow Spheres and Intergrowth Tungsten Bronzes
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Research subject
Structural Chemistry
Identifiers
urn:nbn:se:su:diva-36942 (URN)
Presentation
2010-02-01, K247, Svante Arrheniusväg 16c, Stockholm, 14:00 (English)
Opponent
Supervisors
Available from: 2010-06-29 Created: 2010-02-01 Last updated: 2010-06-29Bibliographically approved
2. Characterizing cavity containing materials using electron microscopy: A study of metal oxides, mesoporous crystals and porous material containing nanosized metal-particles
Open this publication in new window or tab >>Characterizing cavity containing materials using electron microscopy: A study of metal oxides, mesoporous crystals and porous material containing nanosized metal-particles
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns the characterization of novel materials by utilizing electron microscopy techniques. The examined materials contain cavities with certain attributes that enables desired properties for applications such as gas separation, catalysis and fuel cells. The specimens concerned herein belong to the following groups of materials: Metal oxides in the Sb-W-Mo-O system; ordered mesoporous silicas and carbons; hollow spheres containing Au-nanoparticles; zeolite LTA incorporated with mesopores; metal organic frameworks doped with nickel.

With scanning electron microscopy (SEM) and transmission electron microscopy (TEM) you get vast possibilities within the field of characterization. This thesis utilizes conventional electron microscopy techniques such as imaging, energy-dispersive spectroscopy and electron diffraction as well as reconstruction techniques, such as exit-wave reconstruction, electron tomography and electron crystallography. Furthermore, the sample preparation technique cross-section polishing has been used in conjunction with low voltage SEM studies.

The scientific approach is to gain knowledge of nano-sized cavities in materials, in particular their shape, size and content. The cavities often have irregularities that originates from the synthesis procedure. In order to refine the synthesis and to understand the properties of the material it is required to carefully examine the local variations. Therefore average characterization techniques such as crystallography needs to be combined with local examination techniques such as tomography. However, some of the materials are troublesome to investigate since they to some extent bring limitations to or gets easily damaged by the applied characterization technique. For the development of novel materials it is essential to find means of overcoming also these obstacles.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University, 2011. 84 p.
Keyword
Electron microscopy
National Category
Inorganic Chemistry Materials Chemistry
Research subject
Structural Chemistry
Identifiers
urn:nbn:se:su:diva-64164 (URN)978-91-7447-247-9 (ISBN)
Public defence
2012-01-20, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:15 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 6: Submitted.Available from: 2011-12-15 Created: 2011-11-11 Last updated: 2012-03-26Bibliographically approved

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