Chemists make molecules with less mess

In a step toward more environmentally benign chemistry, researchers have designed

a new catalyst that reduces pollution from a commercially important, century-old

chemical reaction.

Chemists use the reaction, called the Baeyer-Villiger oxidation, to make classes

of molecules called esters and lactones. These, in turn, go into polymers,

pharmaceuticals, and fragrances.

In the new work, chemists found a way to substitute hydrogen peroxide for the

waste-producing acids now used in Baeyer-Villiger oxidation. In its current form,

the reaction produces a molecule of waste, also an acid, with each product

molecule, says Avelino Corma of the Institute of Chemical Technology at the

Polytechnic University of Valencia in Spain.

Not so for the hydrogen peroxide approach, which produces only water as a by-

product in this reaction, says Corma. To work efficiently, however, this modified

reaction requires a catalyst. Until now, potential catalysts have fallen short.

Some have led to a variety of products, rather than the one desired molecule.

Other catalysts end up dissolving in the reaction solution and are difficult to

separate from the product.

In the July 26 Nature, Corma and other researchers from Valencia and Universal Oil

Products, a chemical company in Des Plaines, Ill., present a solution to these

problems. The researchers made zeolite crystals with tin atoms built into the many

channels within the crystals. These tin-zeolite catalysts produced the desired

esters and lactones from the Baeyer-Villiger oxidation when the researchers

substituted hydrogen peroxide for the typical acid ingredient. What’s more, the

researchers report, the crystal doesn’t dissolve and can be easily filtered from a

solution and reused.

Universal Oil Products is now trying to scale up the researchers’ laboratory-scale

variation on the Baeyer-Villiger oxidation reaction, says Corma.

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