Catalysis Science & Technology Blog

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

Compared to homogeneous catalysts, heterogeneous catalysts used in hydrosilylation reactions are quite rare. In this HOT article, the catalytic activity and recyclability of PtO₂ is examined for the hydrosilylation of n-octene with heptamethyltrisiloxane.

Compared to the usual homogeneous catalysts PtO₂ dissolves only to a small degree after reaction with silane. The un-reacted solid catalyst is then easily separated from the reaction mixture by simple decantation or filtration and so can be used for subsequent runs. The observation of an induction period in every cycle indicates that the active species is formed in situ before the reaction can take place and new material has to dissolve for each run.

The active species is formed by reduction of PtO₂ with the silane and is soluble in the reaction mixture. The solubility behavior together with the high activity allows a ‘‘self-dosing’’ of the catalyst—leading to little waste of precious metal in contrast to other ‘‘homogeneous’’ (i.e. better soluble) Pt-based catalysts making it potentially useful for industrial applications.

Read more for FREE throughout 2012 at:

PtO₂ as a “self-dosing” hydrosilylation catalyst
Sophie Putzien, Eckhart Louis, Oskar Nuyken and Fritz E. Kühn
Catal. Sci. Technol., 2012, Advance Article
DOI: 10.1039/C2CY00367H