Propylene oxide is an important bulk chemical that is used primarily in the production of polyurethane plastics.
Currently, propylene oxide is usually made from propylene (propene) in a process that uses chlorine as an oxidizing agent. This results in undesired byproducts as well as toxic chlorinated organic compounds. Existing alternative routes are mostly complicated and uneconomical.
The development of an environmentally friendly propylene oxide synthesis with oxygen as the oxidizing agent is high on the wish list. Japanese researchers have now developed a new catalyst that brings this goal closer. As the scientists working with Masatake Haruta report in the journal Angewandte Chemie, the catalyst is based on gold clusters and a special titanium-containing support.
In the oxidation of propylene (propene, CH3–CH=CH2) to propylene oxide (propene oxide), an oxygen atom is formally inserted into the double bond. This forms a ring containing two carbon atoms and one oxygen atom. Using oxygen as the oxidizing agent had not been considered before because the oxygen molecule (O2) can only be split into individual oxygen atoms with the input of a large amount of energy. Furthermore, propylene preferentially reacts with atomic oxygen to form acrolein and not the desired propylene oxide. A suitable catalyst is eagerly sought, and has come to be viewed as the “holy grail” of catalyst research. There have been a number of catalytic developments that have been not quite satisfactory.
Building upon prior work, Haruta and his team have been able to achieve a further step. Their new catalyst consists of gold clusters, which are less than 2 nm in size, deposited on a special titanium-containing silicalite support. “It is important that the gold used is not in the form of nanoparticles, but is in clusters,” emphasizes Haruta. Although these two terms are often used interchangeably in the literature, there are important differences. Gold clusters are explicitly defined, structurally uniform nanoscopic structures, whereas gold nanoparticles are particles with size in the nanometer range that have neither uniform size nor structure. “Our gold clusters are able to convert oxygen and water into hydroperoxide species, which are transferred onto neighboring titanium centers,” explains Haruta. “The resulting titanium hydroperoxide species (Ti–OOH) are the actual reaction partners for the propylene, which is converted to propylene oxide.”
“The yields and selectivities we have achieved so far are inadequate for an industrial process,” says Haruta, “however, our catalyst is another important milestone on the way to an environmentally friendly synthesis for propylene oxide.”
Author: Masatake Haruta, Tokyo Metropolitan University (Japan), mailto:email@example.com
Title: Propene Epoxidation with Dioxygen Catalyzed by Gold Clusters
Angewandte Chemie International Edition 2009, 48, No. 42, 7862–7866, doi: 10.1002/anie.200903011
Masatake Haruta | Angewandte Chemie
Show me your leaves - Health check for urban trees
12.12.2017 | Gesellschaft für Ökologie e.V.
Liver Cancer: Lipid Synthesis Promotes Tumor Formation
12.12.2017 | Universität Basel
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
12.12.2017 | Physics and Astronomy
12.12.2017 | Earth Sciences
12.12.2017 | Power and Electrical Engineering