NEWS OF THE WEEK
A NEW FEAT FOR GOLD CATALYSTS CATALYSIS: Gold-palladium
nanoparticles exclusively transform primary C–H bonds
DAVID J. WILLOCK/CARDIF F U
Gold-palladium nanoparticles (blue and yellow, depicted here on a carbon support) catalyze O2 oxidation of toluene to benzyl benzoate.
ANOPARTICLES MADE OF a gold-palladium
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alloy can selectively catalyze oxidation of the primary carbon-hydrogen bonds in toluene’s methyl group and related compounds, according to a study published by researchers at Cardiff University, in Wales (Science, DOI: 10.1126/science.1198458). The investigation may lead to new commercial catalytic processes that are less expensive and free from the acidic and chlorinated solvents used in some industrial reactions today. The study also provides new leads in the broad search for methods to efficiently transform raw materials such as methane into valuable products. The recent spike in gold-based catalysis research has uncovered a host of surprising findings showing that the generally inert precious metal can be a highly active
EUROPE’S DIOXIN SCARE WIDENS FOOD SAFETY: German eggs,
poultry, pork are under scrutiny for contamination
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Germany after regulators discovered that animal feed contaminated with the cancer-causing agent dioxin has passed into eggs, poultry, and pork. At the heart of the scandal is the German company Harles & Jentzsch, which supplied 3,000 tons of dioxin-contaminated fatty acids to animal feed companies. The fatty acids sold to the animal feed companies were intended for use in industrial processes, not as a nourishing ingredient for animal feed. In March 2010, the company measured amounts of dioxin in the fatty acids it was selling for animal feed at twice the allowable level. But agriculture authorities in Germany learned of NEWSCO M
A regulator in Germany examines eggs for dioxin.
FOOD SAFETY SCANDAL continues to rock
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catalyst when prepared in nanoparticulate form (C&EN, May 10, 2010, page 42). The Cardiff group, for example, which is led by Graham J. Hutchings, showed nearly two years ago that H2 and O2 can be combined directly to produce hydrogen peroxide on the surface of Au-Pd nanoparticles (C&EN, Feb. 23, 2009, page 8). The new study shows the particles to be versatile catalytically. By using a colloid immobilization method, the group, which also includes Lokesh Kesavan and coworkers at Cardiff and at Lehigh University, prepared a series of carbon- and TiO2-supported catalysts in the 2- to 5-nmdiameter range with a variety of Au-to-Pd ratios. They evaluated the catalysts’ facility to oxidize toluene with oxygen and found some that actively and selectively transformed the reactant’s primary C–H bonds under mild and solvent-free conditions. For example, several catalysts with a Au-to-Pd ratio of 1:1.85 produced mainly benzyl benzoate (>90% selectivity) and small amounts of benzyl alcohol, benzaldehyde, and benzoic acid. “This new example of selective oxidation of toluene by gold-palladium catalysts with molecular oxygen is another addition to the exciting story of catalysis by gold,” says Mayfair C. Kung, a catalysis specialist at Northwestern University. She adds that the results suggest the possibility that other supported bimetallic gold catalysts may one day be found capable of challenging catalytic feats, such as selectively activating linear alkanes at a terminal position.—MITCH JACOBY
the contamination problem only in December. On Jan. 10, the company filed for insolvency. In the past two weeks, millions of eggs from chickens that may have been given the contaminated feed were pulled off shelves in Germany, and some 5,000 farms across the country were closed for investigation. South Korea and China have blocked German poultry and meat products, and Japan is asking importers to report the arrival of German pork, poultry, and eggs. Stores in the U.K. have pulled from shelves products that may contain some of the tainted eggs. Levels of dioxin above legal limits have been found in a half-million eggs and several pigs, says Miriam Ewald, a spokeswoman for Germany’s Federal Institute for Risk Assessment. However, she says, there is no danger to public health. Although dioxins can cause cancer, problems arise only if they are consumed over a long period because the chemical collects in the body, she explains. Dioxins are aromatic, polyhalogenated compounds. The German Federal Ministry for Food, Agriculture & Consumer Protection has not reported which particular dioxins were present in the contaminated feed. German Agriculture Minister Ilse Aigner has called for stricter regulations on food safety across Europe and vowed that those responsible “will be held accountable.” The last dioxin scare in Europe was in 2008, when unacceptable levels of the contaminant were found in mozzarella cheese produced in Italy.—SARAH EVERTS
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