Catalysis Science & Technology Blog

Heterogeneous catalysts in the powerful Suzuki–Miyaura reaction for forming C–C bonds are still struggling to rival homogeneous ones in terms of catalytic activity, despite being more reusable and easier to recover. But now, scientists from China have made an inorganic-supported palladium catalyst that is soluble in organic solvent for the first time.

The homogenised zirconium phosphate supported catalysts can be used at room temperature and removed from the reaction mixture using solid/liquid separation.

By bridging the shortcomings of both heterogeneous and homogeneous catalysts, the team have produced a borderline class of catalyst, which can easily be extended to other metal systems.

Read the Catalysis Science & Technology article now…
Homogenization of inorganic material-supported palladium catalysts in Suzuki coupling reaction at room temperature
Yueyue Ma, Xuebing Ma, Qiang Wang and Jinqin Zhou

Karen Wilson and Adam Lee from Cardiff University discuss the recent development of heterogeneous catalysts for synthesising biodiesel.

Biodiesel is synthesised from triglycerides and free fatty acids that have been extracted from plant oil seeds (such as rapeseed, palm, soybean), animal fats, and algae. Transesterification and esterification of triglycerides and free fatty acids, respectively, using simple acid or base catalysis produces the resultant biodiesel alkyl ester.

Soluble base or acid catalyts can create problems such as reactor corrosion and you also have the added task of having to remove the catalyst from the product which can be somewhat energy intensive (thereby lessening the green-ness of the fuel). It would seem that heterogeneous catalysis is the way forward, providing a more efficient process and also enabling greater purity of the glycerol by-product .

As Wilson and Lee set out in their Perspective article, several considerations should be made when designing solid acid and base catalysts: acid or base strength, tuneable surface polarity, and pore architecture.

To find out the effects these catalytic properties have, download the article now for free…

Rational design of heterogeneous catalysts for biodiesel synthesis
Karen Wilson and Adam F. Lee

Epoxides are used in the production of a wide range of compounds including resins, perfumes and polyethers among many others. The commercial synthesis of epoxides uses olefins, either through the chlorohydrin process or the hydroperoxide process. This Hot Article from Professor Bert Weckhuysen et al. details a mechanistic study on cyclohexene epoxidation with cyclohexyl hydroperoxide, the team performed the reaction over titanium grafted mesoporous silica.

Two competing reactions appear to occur, one producing the epoxide and the other yielding
cyclohexanone. As all articles are free to access in Catalysis Science & Technology for the duration of 2012 you can download this article now to see the proposed mechanistic pathways.

Mechanistic insights in the olefin epoxidation with cyclohexyl hydroperoxide
Bart P. C. Hereijgers, Rudy F. Parton and Bert M. Weckhuysen
Catal. Sci. Technol., 2012, Advance Article
DOI: 10.1039/C2CY00455K, Paper

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Catalytic hydrogen transfer (CTH) reactions have been around for a while and provide an alternative to traditional hydrogenation, where H₂ gas is applied under high pressure. Hydrogen donors include alcohols or formate salts while acceptors are unsaturated organic compounds, ketones, olefins and nitroaromatics among others. Ruthenium complexes are some of the most active homogeneous catalysts for CTH and a wide range have been developed over the last 40 years.

This Hot Article from Judith Toubiana and Yoel Sasson (The Hebrew University of Jerusalem) details their investigation into the mechanism of CTH between alcohols and ketones using RuCl₂(PPh₃)₃, the pair have made a remarkable discovery regarding the actual active species in the reaction……and it isn’t the ruthenium complex.

As all Catalysis Science & Technology articles are free to access for the duration of 2012 you can download the paper now to find out what has been discovered and how.

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The true catalyst in hydrogen transfer reactions with alcohol donors in the presence of RuCl2(PPh3)3 is ruthenium(0) nanoparticles
Judith Toubiana and Yoel Sasson
Catal. Sci. Technol., 2012, Advance Article
DOI: 10.1039/C2CY00514J, Paper

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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