Special Issue "Heterogeneous Catalysis"

Guest Editor
Dr. Eric Guibal
Ecole des Mines d'Alčs, Laboratoire Génie de l'Environnement Industriel, 6 Avenue de Clavières, F-30319 Alès, Cedex, France
E-Mail:
Interests: treatment of wastewaters (metals, dyes); adsorption & biosorption process; liquid/liquid extraction processes; coagulation & flocculation; catalytic processes; synthesis of new materials based on biopolymers (physical and chemical modifications)

Dear Colleagues,

Heterogeneous catalysis is key step in the synthesis pathway of a number of products in fields as diverse as petrochemicals, pharmaceuticals, fine chemicals but also in environmental applications;. The specific properties brought to the reaction by the supports open the route to enhanced efficiency, selectivity in synthesis, and improved competitiveness. This special issue of molecules dedicated to Heterogeneous Catalysis calls for both fundamental and applied contributions in this field of growing academic and industrial interests. Special attention will be paid to the characterization of materials (surface properties, diffusion characteristics), the identification of mechanisms and limiting steps, and the contribution of support properties to the orientation/selectivity of catalytic reactions. A special attention will be paid to original supports (based on renewable resources).

Dr. Eric Guibal
Guest Editor

Submission

• heterogeneous catalysis
• support characterization
• surface properties
• porosity
• kinetics
• governing rate
• selectivity
• reaction pathways
• modeling
• alternative supports

Manuscript ID: Molecules-heterocat-20090911-Sanchez-es
Type of Paper: Review
Title: Microheterogeneous Catalysis
Author: F. Sanchez; E-Mail: gcjrv@us.es
Abstract: Starting from the fundamental equation of the kinetics in condensed phases, the Brönsted equation, the equations of catalysis and electrocatalysis are obtained. Using this approach, the data corresponding to microheterogeneous catalytic processes are rationalized. These data correspond to non-saturable catalysts (receptors) such as micelles and polymers, as well as saturable one (e. g. cyclodextrins and related systems). The situation when one of the reactants is in an excited state is also examined.

Manuscript ID: Molecules-heterocat-200915-Kiparissides-gr
Type of Paper: Article
Title: Modeling and Simulation of Gas- and Slurry-Phase Olefin Polymerization Industrial Reactors Over Heterogeneous Ziegler-Natta Catalysts
Authors: V. Kanellopoulos, V. Touloupides and C. Kiparissides
Abstract: A comprehensive dynamic model accounting for the multi-scale phenomena taking place in continuous heterogeneous catalytic gas- and slurry-phase ethylene polymerization processes is developed. From the numerical solution of the proposed integrated model, the temporal-spatial evolution of the morphological (i.e., particle size distribution, PSD) and molecular (i.e., molecular weight distribution, MWD) polymer properties in catalytic polymerization gas- and slurry-phase reactors can be predicted. In particular, the polymer molecular properties are determined by employing a generalized multi-site, Ziegler-Natta kinetic scheme. To determine the growth of a single catalyst/polymer particle, the random pore polymeric flow model (RPPFM) is utilized. The RPPFM is solved together with a dynamic particle population balance equation to calculate the dynamic evolution of PSD in the reactors. Extensive numerical simulations are carried out to conduct a comparative study on the operation of industrial-scale catalytic, gas- and slurry-phase olefin polymerization reactors.

Manuscript ID: Molecules-heterocat-20090929-Avgouropoulos-gr
Title: A review of preferential CO oxidation reaction over CuO-CeO₂ catalysts
Author: George Avgouropoulos
Affiliation: Foundation for Research and Technology-Hellas (FORTH), Institute of Chemical, Engineering and High Temperature Chemical Processes (ICE-HT), P.O. Box 1414, GR, 26504 Patras, Greece; E-mail: geoavg@iceht.forth.gr
Abstract: Optimum operation of Low Temperature Polymer Electrolyte Membrane Fuel Cells (LT-PEMFCs) with hydrogen-rich gas mixture obtained from liquid hydrocarbon or alcohol fuels requires complete CO removal, in order to avoid poisoning of anode electrocatalysts and degradation of the cell performance. Although, the water-gas shift reaction provides primary CO conversion, an additional CO removal step is necessary due to thermodynamic limitations. Among the currently available methods, the preferential catalytic CO oxidation process, also known as PROX reaction, is the most studied and preferable one. Non-precious metal-based catalysts, mainly CuO-CeO₂ catalysts, have been proposed as one of the best PROX candidates. These catalysts are able to operate in a temperature range of 100-200°C with almost ideal selectivity. They are also very stable under reaction conditions and can tolerate high concentrations of CO₂ and H₂O. Compared to the Pt group-based catalysts, they exhibit superior activity and selectivity. Compared to the gold catalysts, they are less active, but much more selective and stable. This article reviews the advances achieved in the development of CuO-CeO₂ catalysts for purification of hydrogen via PROX reaction.

Manuscript ID: Molecules-heterocat-20091001-Hajek-cz
Type of Paper: Review
Title: Microwave-Enhanced Heterogeneous Catalysis
Author: M. Hajek, E-mail: hajek@icpf.cas.cz
Abstract: The review is focused on the effects of microwave irradiation on heterogeneous catalytic systems. Presented results show significant increase in reaction rates and product selectivity enhancement under microwave conditions as compared to convenmtional heating methods. The most probable explanation to understand the mechanism of microwave effects on chemical catalytic reactions is presented. Particular emphasis is placed on the investigation of the application of microwave heating to a range of heterogeneous catalytic systems both in gas and liquid phase. It is explained what are microwave effects and possibility of their utilization in organic synthetic reactions. Special attention is paid to the microwave effects like fast heating, volumetric heating, superheating, selective heating and simultaneous cooling. Definition of microwave effects is provided and experimental arrangement is briefly described.

Manuscript ID: Molecules-heterocat-20091116-Abramovic-yu
Type of Paper: Article
Title: Photocatalytic Degradation of Mecoprop and Clopyralid in Aqueous Suspension of Nanostructured N-Doped TiO₂
Authors: D. Šojić ¹, V. Despotović ¹, B. Abramović ¹, N. Todorova ², T. Vaimakis ³ and C. Trapalis ²
Affiliations: ¹ Faculty of Science, Department of Chemistry, Trg D. Obradovića 3, 21000 Novi Sad, Serbia; E-Mail: biljana.abramovic@dh.uns.ac.rs
² Laboratory of Nanocomposite and Nanofunctional Materials, IMS, NCSR Demokritos, Athens 153 10, Greece
³ University of Ioannina, Department of Chemistry, 45110, Ioannina, Greece
Abstract: The work describes a study of the oxidation power of N-doped and undoped anatase TiO₂, as well as TiO₂ Degussa P25 suspensions for photocatalytic degradation of herbicides RS-2-(4-chloro-o-tolyloxy)propionic acid (mecoprop) and 3,6-dichloropyridine-2-carboxylic acid (clopyralid) using visible and UV light. Undoped nanostructured TiO₂ powder in the form of anatase was prepared by sol–gel route. The synthesized TiO₂, as well as TiO₂ Degussa P25 powder, were modified with urea to introduce nitrogen into the structure. N-doped TiO₂ appeared to be somewhat more efficient than the starting undoped TiO₂ (anatase) powder when visible light was used for mecoprop degradation. N-doped TiO₂ Degussa P25 was also slightly more efficient than TiO₂ Degussa P25. However, under the same experimental conditions, no degradation of clopyralid was observed in the presence of any of the mentioned catalysts. When the kinetics of mecoprop degradation was studied using UV light, more efficient were the undoped powders, while in the case of clopyralid, N-doped TiO₂ Degussa P25 powder was most efficient, which is probably a consequence of the difference in the molecular structure of the two herbicides.

Manuscript ID: Molecules-heterocat-20091201-Guidotti-it
Type of Paper: Review
Title: Design and use of nanostructured single-site heterogeneous catalysts for the selective transformation of fine chemicals
Authors: V. Dal Santo, F. Liguori, C. Pirovano, M. Guidotti
Abstract: Nanostructured single-site heterogeneous catalysts possess the advantages of classical solid catalysts, in terms of easy recover and recycling, together with a defined tailored chemical and steric environment around the catalytically active metal site. The use of inorganic oxide supports with selected shape and pore topology at nanometric level may have a relevant impact on the regio- and stereochemistry of the catalytic reaction. Analogously, by choosing the optimal preparation techniques to obtain spatially isolated and well-characterised active sites, it is possible to achieve performances that are comparable to (or, in the most favourable cases, better than) those obtained over homogeneous systems. Such class of catalysts is therefore particularly suitable to be applied in the transformation of highly-functionalised fine chemicals and some relevant examples where high chemo-, regio- and stereoselectivity are crucial will be described.

Title: Immobilized versus free Oxazaborolidine in Enantioselective Reduction of Acetophenone.
Authors: Jeremy H. Yune, Françoise Quignard, Karine Molvinger
Affiliation: Institut Charles Gerhardt, UMR 5253 CNRS/ENSCM/UM2/UM1, Matériaux Avancés pour la Catalyse et la Santé, «MACS»-8, rue de l’Ecole Normale, 34296 Montpellier cedex 5, France; E-mail: karine.molvinger@enscm.fr (K.M.)
Abstract: Chiral 1,3,2-oxazaborolidines are highly effective homogeneous catalysts for the enantioselective reduction of ketones to chiral secondary alcohols by borane. Besides, these chiral ligands have been widely used during the synthesis of various pharmaceutical compounds. Nevertheless, since separation of the alcohol product from the chiral amino alcohol (catalyst precursor) can be difficult, heterogeneisation of the ligand would allow combining both the advantages of homogeneous and heterogeneous catalysis. The main goal of this article is to study how the anchoring of oxazaborolidines on a solid support may modify the enantioselective properties of this supported oxazaborolidine. The chiral ligand has been immobilised on mesoporous silica via the boron or via the nitrogen substituent. In this paper, we will describe several strategies of immobilization in terms of synthesis and related catalytic properties.