State of the Science: Making Plastics from Biomass, Not Fossil Fuels

Researchers review advances in catalysts that turn bioethanol into valuable chemicals

(May 2014)

Plastic bottles, traditionally made from fossil fuels, could be created from biomass, according to an invited review by scientists at Washington State University and Pacific Northwest National Laboratory. Enlarge Image.

Results: Ethanol from garbage and other sources could replace fossil fuels in manufacturing plastics, rubber, and other chemicals if scientists can gain the needed knowledge of catalysis, according to scientists at Pacific Northwest National Laboratory (PNNL) and Washington State University (WSU). In their invited article, Dr. Yong Wang and Dr. Junming Sun review the current state of understanding on converting ethanol into a host of other chemicals. They also identify future research directions, including one-step ethanol conversions.

Wang and Sun were asked to write the article, which appears in ACS Catalysis, because of their applied research, including their one-step process for upgrading ethanol to isobutene. Wang has a joint appointment with PNNL and WSU. At PNNL, he is an Associate Director at the Institute for Integrated Catalysis; at WSU, he is the Voiland Distinguished Professor. Sun completed a postdoctoral fellowship at PNNL and is now a research professor at WSU.

Why It Matters: Renewable fuel requirements are increasing the availability and decreasing the cost of ethanol, with the production in the United States expected to reach more than 30 billion gallons in 2017. With only 15 to 16 billion gallons needed for fuel blending, the additional alcohol could be used to produce plastic water bottles, carpet backing, and thousands of other products. This study provides a detailed summary of the research to date, giving scientists a needed overview.

"We need to debottleneck the process, from lignocellulose to the end products," said Wang.

Methods: In the article, the team reviewed the progress made on deconstructing ethanol to provide hydrogen for use in proton exchange membrane fuel cells. Ethanol is of interest because of its easy-to-use form, nontoxicity, and high hydrogen content. Highly stable and selective catalysts, based on cobalt and other earth-abundant metals, appear promising for hydrogen production. Yet, efficiency and deactivation issues remain.

The team also discussed the production of light olefins, which can be used in building alkenes, alkanes, and aromatics, longer chained or ring-structured hydrocarbons. For example, producing the light olefin, i.e., ethylene, using gamma aluminum oxide is a commercial success; however, the reaction requires high temperatures when water is present. Mixed metal oxides with balanced acid-base pairs can enable direct production of 1-butanol and 1,3-butadiene from ethanol. However, questions remain, including the formatting of key intermediates, which inhibit the effective conversion of ethanol.

"Olefins are exciting because they are a nice platform molecule that can be further converted to other chemicals," said Wang. "Essentially, the potential is great, but if you look at the current status, a significant amount of research is needed before commercialization."

What's Next? The researchers are continuing to better understand the catalysts and the reaction mechanisms involved, including the influence of impurities introduced with the bioethanol. They are also looking at the coupling thermochemical conversions to biological processes that produce the ethanol.

Acknowledgments:

Sponsor: U.S. Department of Energy Office of Science's Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division

Research Area: Chemical Sciences

Research Team: Junming Sun, Washington State University; Yong Wang, Washington State University and Pacific Northwest National Laboratory

Reference: Sun, J, and Y Wang. 2014. "Recent Advances in Catalytic Conversion of Ethanol to Chemicals." ACS Catalysis 4, 1078-1090. DOI: 10.1021/cs4011343