Newswise – Ethylene is sometimes called the most important chemical in the petrochemical industry because it serves as a raw material for a large number of everyday products. It is used in the production of antifreeze, vinyl, synthetic rubber, foam insulation and all types of plastics.
Currently, ethylene is produced through an energy- and resource-intensive process called steam cracking, where extremes of temperature and pressure produce ethylene from crude oil in the presence of steam—and in the process, release tons of carbon dioxide into the atmosphere. Another way ethylene can be produced is through a process called oxidative coupling of methane (OCM). It has the potential to be a greener alternative to steam cracking, but until recently, the amount of ethylene it yields did not make the process economically viable.
„Until now, the catalytic yield is less than 30 percent, which means passing methane and oxygen through the catalyst and getting ethylene on the other side,” says Bar Mosvitsky Liss, a postdoctoral research associate in the Department of Chemistry. and biomolecular engineering at Lehigh University's PC Rosin College of Engineering and Applied Sciences. „Studies that simulated an entire industrial process using OCM showed that the technology does not become profitable until single-pass yields reach 30 to 35 percent.”
OCM is now one step closer to leaving the lab and entering the real world. For the first time, researchers from North Carolina State University (NCSU) and Lehigh University, along with researchers from the Guangzhou Institute of Energy Conversion and East China University of Science and Technology, have developed an OCM catalyst with greater than 30 percent Ethylene is produced. Paper A report detailing their progress was recently published Natural communication.
Collaboration was held under the leadership Fanxing Li, Alcoa Professor of Engineering at NCSU. His group developed a class of core-shell Li2CO3-coated mixed rare earth oxides as catalysts for the oxidative coupling of methane using a chemical looping scheme. This resulted in a single-pass yield of up to 30.6 percent.
„The idea of the chemical loop is that instead of co-feeding methane and oxygen into the chamber with the catalyst, you do it sequentially,” says Mosevitzky Lis, one of the study's co-authors. „Over time, you lose oxygen from the catalyst and it becomes useless. With chemical looping, you start with methane, then switch to oxygen, then switch to methane, and the oxygen continues to re-oxidize the catalyst, thereby replenishing its capacity to supply oxygen to the reaction.
Mosevitzky led Lis and his team at Lehigh Israel waxG. Whitney Snyder Professor and Director of Chemical and Biomolecular Engineering running Molecular Spectroscopy and Catalysis Research Lab– Did the nature of the catalyst.
“Our expertise lies with on the site „Surface characterization,” says Mosewitzki Lis, means we characterize the surface of catalysts as the reaction proceeds. We use a wide range of physical and chemical techniques to understand the changes that occur on the surface of catalysts as catalysts run and how these changes make for good catalysts.
The catalyst is formed from a mixed oxide core covered with lithium carbonate, and it is the interaction between the core and the shell during the chemical cycle that accounts for the high yield. The results suggest that, for the first time, upgrading methane—found in natural gas and biogas—to ethylene will be within industrial reach.
„OCM is cheaper and more efficient when it comes to energy and emissions,” he says. “Plus, instead of using crude oil, you're using methane that typically comes from natural gas, but in the future could be made from biogas and the electrochemical reduction of carbon dioxide. Once ethylene is available, it can be converted into a myriad of products used around the world.
The next step is to determine the suitability of the catalyst for industrial-scale production, while trying to further increase the yield. However, it marks a milestone to have finally developed a system that has been an unfulfilled promise since the 1980s.
„The subtlety of the setting and the dynamics that happen, it's almost like art,” Mosvitsky tells Liz. „Both the core and the shell of the catalyst undergo very intense processes, creating all kinds of interesting things on the surface. It's beautiful.”
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