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Discovery on Liquid Alkanes can Benefit Petroleum Industry

Yang Zhang (Credit: NPRE Illinois)

The latest finding from a group of scientists, headed by Yang Zhang, assistant professor of Nuclear, Plasma, and Radiological Engineering and Beckman Institute for Advanced Science and Technology, has contradicted a theory that has been the norm for more than eight decades and holds major promise for the petroleum industry.

The research results revealed that products such as gasoline and crude oil could be transported across the nation 30 times faster in the near future, and the time taken to fill a tank can be reduced from minutes to just seconds.

Zhang’s team used high flux neutron sources at Oak Ridge National Laboratory (ORNL) and the National Institute of Standards and Technology (NIST) over the past year to record the molecular movement of alkanes, which is a key component of natural gas and petroleum. The team studied that the thickness of liquid alkanes can be reduced significantly, enabling a considerable increase in the rate of flow of the substance.

Alkane is basically a chain of carbon atoms. By changing one carbon atom in the backbone of an alkane molecule, we can make it flow 30 times faster.

Yang Zhang, Assistant Professor, Beckman Institute for Advanced Science and Technology

The discovery was made by Zhang, his graduate students Ke Yang, Zhikun Cai, and Abhishek Jaiswal, and collaborators Dr. Madhusudan Tyagi at NIST and Jeffrey S. Moore, Interim Director of the Beckman Institute and HHMI Professor of Chemistry at Illinois, and contradicts a popular theory that was formed in the late 1940s by Walter Kauzmann and Henry Eyring, professors from Princeton University.

The Princeton University professors had stated that near their melting points, all alkanes have a universal viscosity. The theory has been cited more than 3,000 times, says Zhang.

However, the team discovered a quite distinct odd-even effect of the liquid alkane dynamics. Almost all introductory organic chemistry textbooks teach the odd-even effect in solid alkanes i.e., due to the difference in the periodic packing of even- and odd-numbered alkane solids, odd-even variation of their melting points and densities are formed. However, as there are no periodic structures in liquids, such an effect was unexpected in liquid alkanes.

We would have thought that no structural memory may carry over from the solids to the liquids, but clearly, the cooler liquid already has the origins of the odd-even effect built into its diffusion!

Professor Martin Gruebele, the James R. Eiszner Chair Professor in Chemistry

“The classical Kauzmann-Eyring theory of molecular viscous flow is over simplified,” Zhang said. “It seems some chemistry textbooks may need revisions.”

The team had the benefit of super high-resolution (at the nano-meter, 1 billionth of a meter) and super high-speed (at the pico-second, 1 trillionth of a second) “video cameras” that used neutrons to make video recordings of the molecules. “A neutron ‘microscope’ is the major breakthrough in materials research and we use it to look at everything. There are things we’ve never seen before,” Zhang said.

The study, titled ‘Dynamic Odd-Even Effect in Liquid n-Alkanes near Their Melting Points,’ has been reported in the German publication, Angewandte Chemie International Edition, which is a leading chemistry journal in the world. This new discovery is fundamental to understanding and improving a variety of chemical processes, including heat transfer, lubrication and diffusion through porous media.

Zhang started work on the study after he was selected for an American Chemical Society Petroleum Research Fund Doctoral New Investigator Award, in fall 2015. Ke Yang, who graduated in summer 2016 and is currently working at the Dow Chemical Company is the first author of the research paper.


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