Scientists from Massachusetts Institute of Technology (MIT) developed a new technology for refining allowing for separation of feedstock into fractions at the molecular level without thermal reactions. This innovation will help to reduce energy consumption in refining by 90%. The project was partially funded by ExxonMobil within the MIT Energy Initiative.
Modern oil refining requires significant energy: the process of separating the feedstock into such fractions as gasoline, diesel fuel and fuel oil accounts for about 1% of global energy consumption and about 6% of global CO₂ emissions. The major part of this energy is spent to assure the heating required to separate the components by their boiling points.
MIT engineers proposed an alternative is the form of molecular “sieving” of oil through a specialized membrane. In the article published in Science journal, the authors of this development, Zakari P. Smith, the associate professor of the MIT chemical engineering department, and Tehun Li, currently the associate professor of Sungkyunkwan University (South Korea), characterized this method as filtration on the atomic level.
Certain attempts to create membranes for hydrocarbons separation already took place earlier, and the developers focused on polymers with internal (PIM), such as PIM-1 material. However, while assuring quick passage of molecules, these membranes turned out to be prone to swelling when interacting with organic compounds, and that worsened their filtering capabilities.
In search for a more stable material, the MIT researchers turned to membranes used in water desalinization technology based on reverse osmosis method (in 1970s this technology provided for dramatic decrease of energy consumption in this sphere). Polyamide film formed on the border between water and organic solvent (e.g., hexane) is the key element in such membranes. The dissolved in water hydrophilic monomer MPD (meta-phenylenediamine) reacts with hydrophobic monomer TMC (trimesoyl chloride) from the organic layer forming a polyamide structure MPD-TMC. To adapt this membrane to the refining conditions, the scientists modified its chemical structure: changed the amide bond to a more rigid hydrophobic imine bond and added triptycene monomer — a stable molecule facilitating formation of pores of the required size.
Testing of the new membrane demonstrated its high efficiency. When filtering the mix of toluene and triisopropylbenzene (TIPB) the toluene concentration grew 20 times. Other mixes close to industrial mixes (such as naphtha, kerosine and diesel fuel) in terms of their composition were also tested successfully. The developers believe that such membranes may be used in cascade: first, for separating crude oil into light and heavy fractions, and then — for precise separation of target components. Due to the fact that interfacial polymerization technology is applied in industry already, the new membrane may be quickly scaled up and implemented for the existing production processes.
