Catalyst Converts Bio-based Ethanol into Environmentally Friendly Plastics

Researchers at the Washington State University have developed a catalyst to efficiently convert bio-ethanol into isobutene a widely used industrial chemical.

Bio-ethanol is obtained from fermentation of a number of natural products, either crops like corn, grown specifically for its production, or from waste plant material like leaves and stems, often from food production. Ethanol has long been converted to ethene, but of more interest to both industry and research is its conversion to other alkenes, and in turn to other more valuable products. The chemical of choice for this research was isobutene. Its basic polymer is the rubber polyisobutene. It has a number of other important uses, such as for fuel additives, for food, and as a feedstock for other compounds too.

As the threat of climate change looms closer, and in light of the recent Paris summit, green approaches to chemistry are welcome. Catalysis not only provides an alternative source of isobutene to cracking naptha from oil, but it is also a useful, if not essential, component of all Green Chemistry as it greatly lowers the energy cost of the process. The reaction occurs via a cascade route, ethanol being converted to acetone, then to isobutene. Existing catalysts accelerated this reaction, but with a number of unfortunate side effects – notably catalysis of side reactions, waste production and degradation of the catalyst.

This new catalyst, based on zinc, zirconium and oxygen, produces isobutene with unprecedented efficiency ~88.9%, and with very high catalyst stability. The researchers also worked out how this catalyst works, which could easily lead to the production of catalysts for related processes. Already patented, it is clearly a significant development for Green Chemistry and a step away from the use of oil for chemicals.

Photo: Flickr, Ed Uthman