HETEROGENEOUS TANDEM CATALYSIS CATALYSIS: Nanostructured layered material performs multistep reaction
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NOVEL TYPE of layered nanocrystal catalyst
that promises a new way to perform multistep, multicatalyst reactions could make industrial processes more efficient and environmentally friendly. University of California, Berkeley, chemistry professors Peidong Yang and Gabor A. Somorjai and their colleagues report the design of a class of nanocrystal catalysts that consist of two catalysts stacked on top of each other (Nat. Chem., DOI: 10.1038/nchem.1018). They show that the layered material can catalyze the industrially important multistep process of producing propanal from methanol and ethylene. The work has drawn praise from experts in the field, including catalysis expert R. Tom Baker of the University of Ottawa. “This clever design of nanostructured catalysts with interface control successfully realizes an important tandem reaction sequence,” Baker says. Catalyst makers often place heterogeneous metal catalysts on materials such as metal oxides to help increase their surface area. But as the researchers note, the interfaces between a metal and a metal oxide can also be key catalytic moieties in and of themselves. Consequently, scientists seek to harness the catalytic power of these interfaces. That, coupled with progress in nanostructure-assembling techniques, prompted the Berkeley group’s development of the new multilayered catalyst. Although a few tandem catalysts have been synthesized before, these have been for homogeneous catalytic systems. Compared with homogeneous systems,
however, heterogeneous catalysts are more stable and are easier to separate from products. To build their heterogeneous tandem catalyst, the Berkeley group deposited single layers of platinum nanocubes on top of a silica base. They then added a single layer of cerium oxide nanocubes to form an array of bilayered cubes 6–8 nm on a side. The interface between CeO2 and Pt catalyzed the decomposition of methanol to CO and H2. The Pt-SiO2 interface then catalyzed the reaction of CO and H2 with ethylene A CATALYST BUILT FOR TWO Two reactions to form propanal. that together yield propanal from methanol and This tandem reacethylene occur at the interfaces of a nanostructured tion produced layered catalyst. propanal even faster than the traditional method of starting with CO Active and H2 and using a interface for CeO2 CH3OH CH3OH Pt-SiO2 catalyst. decomposition “This is clearly Active an example where CO + 2H2 interface for + Pt the system is H2C CH2 hydroformylation greater than the sum of the parts,” CH3CH2CH says catalysis SiO2 O expert Christopher B. Murray of the University of Pennsylvania. He notes that the method has two strengths: Scientists can control the crystallographic orientation of the components by using cubic building blocks, and they can also control the spatial relationship of the components with layer-by-layer deposition. Both features allow fine-tuning of the catalyst’s reactivity. Even more promising, adds catalysis expert François-Xavier Felpin of the University of Bordeaux, in France, is the possibility, raised by this work, of “creating materials with unexpected and novel electronic properties.”—ELIZABETH WILSON
RENEWABLE CHEMICALS OPX collaborates with Dow for biobased acrylic acid Biobased chemicals start-up OPX Biotechnologies will partner with Dow Chemical to make acrylic acid from sugar at demonstration scale. In February, OPX said its pilot-scale process proved that acrylic acid could be produced commercially from corn sugar for 70 cents per lb, 5 cents cheaper than from petroleum. Now, OPX will work with Dow to prove the technical and economic viability of manufacturing and using biobased acrylic acid in an industrial setting. The deal allows OPX to concentrate on the first half of the production system:
making 3-hydroxypropionic acid (3HP) from sugar with its proprietary engineered microbes. “Then the partnership will leverage Dow’s abilities in catalytic chemical processes for 3HP dehydration to bioacrylic,” explains OPX CEO Charles R. Eggert. The Dow collaboration marks the first major corporate partnership for OPX, which was founded in 2007. A recent analysis of 83 renewables firms with technologies based on synthetic biology shows that partnerships with larger companies are an important indicator of dominance. “The Dow deal bumps OPX up in that
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category,” says Mark Bünger, research director at Lux Research, which developed the analysis. “In this burgeoning space, a lot of companies are going from relatively simple monomers to more high-value end products. For its part, Dow has made only a few alliances with outside firms for renewable chemicals technology. In March, it signed an agreement with algal-oil firm Solazyme to investigate use of the oil in biobased dielectric insulating fluids for transformers and other electrical applications.—MELODY BOMGARDNER
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