ExxonMobil Corp., in collaboration with Spain’s Instituto de Tecnologia Quimica (ITQ), has discovered a “potentially revolutionary” material that may sharply reduce the amount of energy and emissions associated with producing ethylene.
Depending on the application, the new material’s use, in conjunction with other novel separation processes, may result in up to a 25% reduction in the energy needed for ethylene separation and the associated carbon dioxide emissions. The research was published in the peer-reviewed journal Science.
Researchers said the new material, composed of a uniquely structured silica zeolite, could be used in gas separation processes, such as recovering ethylene from ethane, with an unprecedented degree of selectivity at ambient temperature.
The new material may provide insights into the design of additional materials to be used as adsorbents or membranes in various gas separation applications associated with chemical manufacturing.
Zeolites are porous materials frequently used as adsorbents and catalysts in chemical processes.
“Cryogenic distillation, the current commercial-scale process used for ethylene separation, is an energy-intensive process,” said Vice President Vijay Swarup, who handles research and development at the ExxonMobil Research and Engineering Co. “If advanced to commercial scale, use of this new material could significantly reduce the amount of energy and emissions associated with ethylene production.”
Ethylene, a key feedstock for many chemicals and polymers, during production requires cryogenic separation from ethane, which is energy-consuming. In theory, pure silica zeolites should be well suited to separate olefins from paraffins.
Finding more efficient solutions to produce ethylene is considered paramount as world demand grows for auto parts, housing materials, electronics and other products made from plastics and other petrochemicals.
Chemical plants now account for about 8% of global energy demand and about 15% of the projected growth in demand to 2040. Chemical manufacturers have evaluated alternatives to cryogenic distillation, including adsorbents and separation processes, but many technologies are hindered by an inability to regenerate when they are exposed to contaminants, according to ExxonMobil.
The patented material, ITQ-55, is able to selectively adsorb ethylene over ethane because of its flexible pore structure, researchers said. Built from heart-shaped cages interconnected by flexible elongated pore openings, the material allows the flatter ethylene molecules to be diffused, as opposed to the more cylindrical-shaped ethane molecules. The new material acts as a “flexible molecular sieve,” according to researchers.
“ITQ-55 is a very interesting material whose unique combination of pore dimension, topology, flexibility and chemical composition results in a highly stable and inert material that is able to adsorb ethylene and filter out ethane,” said ITQ’s Avelino Corma, who co-authored the research. Additional research still has to be done before the material may be considered for larger-scale demonstration and commercialization. Research is planned on incorporating the material into a membrane and developing additional materials for gas separation.
“Our ultimate goal of actually replacing cryogenic distillation is a long-term challenge that will require many more years of research and testing, in and out of the lab,” said ExxonMobil’s Gary Casty, section head for catalysis at the research arm. “Our next steps will focus on better understanding the full potential of this new zeolite material.”
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