Ethanol Evolves
New catalyst suggests additional uses for bio-ethanol
The right balance of zinc and zirconium oxides in this catalyst (purple block) converts ethanol to isobutene with few unwanted byproducts such as acetone and ethylene. Enlarge Image
Researchers from Pacific Northwest National Laboratory and Washington State University have developed a new catalyst that converts plant-based ethanol into renewable isobutene, which could be used to replace some petroleum-based products and expand ethanol’s usefulness beyond being a fuel additive. In an attempt to make hydrogen fuel from ethanol, the research team combined zinc oxide and zirconium oxide to improve on a conventional catalyst. Their experiments produced not only hydrogen but, for the first time, isobutene in a one-step reaction (because water is a co-reactant, it does not need to be purified first).
The team’s research showed that a catalyst made from just zinc oxide converted the ethanol mostly to acetone, and when it contained only zirconium oxide it converted ethanol mostly to ethylene. The isobutene occurred in useful amounts only when the catalyst contained both zinc and zirconium. With a 1:10 ratio of zinc to zirconium, the mixed oxide catalyst could turn more than 83% of the ethanol into isobutene. To better understand these results, the researchers used EMSL’s transmission electron microscopes to explore the chemistry microstructure. The team saw that the mixed oxide catalyst was made up of nanometer-sized crystalline particles.
The best-performing catalysts revealed zinc oxide distributed evenly over regions of zirconium oxide, and the worse-performing catalysts —including catalysts with a different zinc to zirconium ratio or physically mixed metal oxides—revealed regions of zinc oxide and regions of zirconium oxide. This suggested that the two metal oxides had to be close to each other to quickly convert the acetone intermediate into isobutene. Additional experiments and analysis enabled the researchers to optimize the chemical reactions that led to isobutene and limit degradation of the catalyst.
See a PNNL press release
about this research.
Reference: Sun J, K Zhu, F Gao, C Wang, J Liu, CHF Peden, and Y Wang. 2011. “Direct Conversion of Bio-ethanol to Isobutene on Nanosized ZnxZryOz Mixed Oxides with Balanced Acid-Base Sites.” Journal of the American Chemical Society, 133 (29):11096-11099, DOI: 10.1021/ja204235v (http://pubs.acs.org/doi/abs/10.1021/ja204235v).
Acknowledgement: This work was supported by the U.S. Department of Energy Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences and Geosciences.
Released: August 05, 2011
