ExxonMobil reduces energy required for production of ethylene
Scientists at ExxonMobil and Spain's Instituto de Tecnologia Quimica have developed a new material capable of separating ethylene from ethane - known as cryogenic distillation - at room temperature, potentially reducing the energy required for the process by a quarter. The researchers used ITQ-55, a silica zeolite with a heart-shaped structure, which acted like a chemical sieve, for the ethylene molecules. The teams said more work is needed to fully understand the potential of the zeolite material.
Scientists from ExxonMobil and the Instituto de Tecnologia Quimica (ITQ) in Valencia, Spain, have discovered a new material that could significantly reduce the amount of energy and emissions associated with the production of ethylene. Depending on the application, use of the new material in conjunction with other novel separation processes could result in up to a 25% reduction in both the energy needed for ethylene separation, as well as associated carbon dioxide emissions.

Ethylene is a critical component in producing chemicals and plastics. Finding alternative, low-energy technologies to separate ethylene from ethane has been a longstanding challenge due to their similar properties. While chemical manufacturers have evaluated a number of alternatives to cryogenic distillation, including new adsorbents and separation processes, many of these technologies are hindered by low selectivity and an inability to regenerate when exposed to contaminants.

The researchers found that the new material, composed of a uniquely-structured silica zeolite, can be used in gas separation processes (such as the recovery of ethylene from ethane) with an unprecedented degree of selectivity at ambient temperature. The material could provide insights into the design of additional materials to be used as adsorbents or membranes in a variety of gas separation applications associated with chemical manufacturing. Zeolites are porous materials frequently used as adsorbents and catalysts in chemical processes.

The patented material, ITQ-55, is able to selectively adsorb ethylene over ethane as a result of its flexible pore structure. Built from heart-shaped cages interconnected by flexible elongated pore openings, the material allows the diffusion of the flatter ethylene molecules as opposed to the more cylindrical-shaped ethane molecules. The new material acts as a flexible molecular sieve.

Additional research must be conducted before the material can be considered for larger-scale demonstration and commercialisation. Fundamental research will continue focusing on incorporating the material into a membrane and developing additional novel 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 Gary Casty, section head for catalysis at ExxonMobil Research and Engineering Co. “Our next steps will focus on better understanding the full potential of this new zeolite material.”

Chemical plants account for about 8% of global energy demand and about 15% of the projected growth in demand to 2040. As global populations and living standards continue to rise, demand for auto parts, housing materials, electronics and other products made from plastics and other petrochemicals will continue to grow. Improving industrial efficiency is part of ExxonMobil’s mission to meet the world’s growing need for energy while minimising environmental impacts.