Catalysis Science & Technology Blog

As well as eutrophication, excess nitrates in water can also cause serious side-effects in humans including increased rates of cancer and blue-baby disease. Legislation dictates the amount of nitrate that agricultural waste water can contain, specifically 50, 0.1 and 0.5 ppm for NO₃, NO₂ and NH₄⁺, respectively. The need to treat water to remove nitrates is an important challenge for catalysis.

This Hot Article from Jacinto Sa and Noelia Barrabe et al. investigates nitrate reduction using the bimetallic catalysts Pt–Cu and Pd–Cu. The team were able to use in situ high-energy resolution fluorescence detection (HERFD) X-ray absorption spectroscopy (XAS) to study the oxidation state of copper, which is in a redox cycle with hydrogen and the unwanted nitrates.

As all articles in Catalysis Science & Technology are free to access for the duration of 2012, you can look at the teams results in more detail by downloading their hot article.

The oxidation state of copper in bimetallic (Pt–Cu, Pd–Cu) catalysts during water denitration
Jacinto Sá, Noelia Barrabés, Evgeny Kleymenov, Chen Lin, Karin Föttinger, Olga V. Safonova, Jakub Szlachetko, Jeroen A. van Bokhoven, Maarten Nachtegaal, Atsushi Urakawa, Gastón A. Crespo and Günther Rupprechter
Catal. Sci. Technol., 2012, Advance Article
DOI: 10.1039/C2CY00461E

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One of the obstacles in using H₂ as an energy source is generating H₂ gas and while the photocatalysis of water has been widely studied, catalysts which operate under visible light have been rather under-utilised.

Su Su Khine Ma, Kazuhiko Maeda and Kazunari Domen have developed a ZrO₂-modified tantalum oxynitride photocatalyst which operates at wavelengths > 420 nm and in their Hot article discuss a range of preparations using different Zr precursors under different conditions. All articles in Catalysis Science & Technology are free to access for the duration of 2012 so you can see full details of their investigation and the factors that affect H₂ evolution by downloading their full paper.

Modification of TaON with ZrO2 to improve photocatalytic hydrogen evolution activity under visible light: influence of preparation conditions on activity
Su Su Khine Ma, Kazuhiko Maeda and Kazunari Domen
Catal. Sci. Technol., 2012, Advance Article
DOI: 10.1039/C2CY00499B

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ZSM-5 is a crystalline zeolite structure used in the petroleum industry as a heterogeneous catalyst for hydrocarbon isomerization reactions. Modification of the microporous structure is being investigated to improve the catalytic potential of the zeolites, alkaline treatment can desilicate the structure and introduce interconnected mesopores. However a consequence of this is the production of extra-framework aluminium and amorphous alumina, which can realuminate on the external surface and affect pore direction.

Acid washing after alkali leaching aims to restore the original framework composition and can enhance the micropore volume, mesoporous surface area, and crystallinity. The effects of these modifications to the ZSM-5 structure undoubtedly affect the catalytic properties as the alkali and acid treatments alter the porosity and composition of the catalyst.

This Hot article by Javier Perez-Ramirez et al. at ETH Zurich aims to de-couple the effects of porosity and composition using the alkylation of toluene (and cyclohexylbenzene) with benzyl alcohol as a model reaction. Alkaline-treated ZSM-5 zeolites are prepared with and without subsequent acid treatment and their catalytic properties determined, the separate effects of porosity and composition are then examined with some very insightful results.

Decoupling porosity and compositional effects on desilicated ZSM-5 zeolites for optimal alkylation performance
Maria Milina, Sharon Mitchell, Zair Domínguez Trinidad, Danny Verboekend and Javier Pérez-Ramírez
Catal. Sci. Technol., 2012, Advance Article
DOI: 10.1039/C2CY00456A

All articles are free to access in Catalysis Science & Technology for the duration of 2012, you can also keep up to date with latest news in catalysis by liking us on facbook, following us on twitter and signing up to our e-alert service.

Other articles which may of interest from the Pérez-Ramírez group include:

Design of hierarchical zeolite catalysts by desilication
Danny Verboekend and Javier Pérez-Ramírez
Catal. Sci. Technol., 2011, 1, 879-890
DOI: 10.1039/C1CY00150G, Minireview

Mesoporous ZSM-22 zeolite obtained by desilication: peculiarities associated with crystal morphology and aluminium distribution
Danny Verboekend, André M. Chabaneix, Karine Thomas, Jean-Pierre Gilson and Javier Pérez-Ramírez
CrystEngComm, 2011, 13, 3408-3416
DOI: 10.1039/C0CE00966K, Paper

Hierarchical zeolites: enhanced utilisation of microporous crystals in catalysis by advances in materials design
Javier Pérez-Ramírez, Claus H. Christensen, Kresten Egeblad, Christina H. Christensen and Johan C. Groen
Chem. Soc. Rev., 2008, 37, 2530-2542
DOI: 10.1039/B809030K, Critical Review

High-quality semiconductor supported Au particles have been successfully made using a simple seeded growth approach. The two Au catalysts produced have shown enhanced photocatalytic performance in the reduction of 4-nitropheno. Read on in the recent free-to-access Hot Article:

Synthesis of high-quality I–III–VI semiconductor supported Au particles and their catalytic performance
Xiao Wang, Dapeng Liu, Shuyan Song and Hongjie Zhang
Catal. Sci. Technol., 2012, DOI: 10.1039/C2CY00372D

Dieter Vogt and co-workers have shown that using water as co-solvent in rhodium-catalysed aldehyde hydrogenation under hydroformylation conditions enhances both rate and selectivity towards primary alcohols. Find out more about this cheap and cheerful advance in their recent Hot Article:

“On-water” rhodium-catalysed hydroformylation for the production of linear alcohols
Olivier Diebolt, Christian Müller and Dieter Vogt
Catal. Sci. Technol., 2012, DOI: 10.1039/C2CY00450J

Also of interest – further recent research from the Vogt group:

Recent advances in the recycling of homogeneous catalysts using membrane separation
Michèle Janssen, Christian Müller and Dieter Vogt
Green Chem., 2011, 13, 2247-2257
DOI: 10.1039/C1GC15264E, Critical Review
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C–H activation of 2,4,6-triphenylphosphinine: unprecedented formation of cyclometalated [(PC)Ir(III)] and [(PC)Rh(III)] complexes
Leen E. E. Broeckx, Martin Lutz, Dieter Vogt and Christian Müller
Chem. Commun., 2011, 47, 2003-2005
DOI: 10.1039/C0CC04660D, Communication

Molecular weight enlargement—a molecular approach to continuous homogeneous catalysis
Michèle Janssen, Christian Müller and Dieter Vogt
Dalton Trans., 2010, 39, 8403-8411
DOI: 10.1039/C0DT00175A, Perspective
From themed issue Bridging the gap in catalysis via multidisciplinary approaches