The conversion of biomass into organic products is expected to be a core technology for the future sustainable society. However, published studies show that the energy costs and environmental impact of making organic products from biomass are often worse than making those products from fossil fuels. The problematic step in converting biomass is removing water. If the ecological and energetic costs for the separation of water and organic products cannot be reduced, it will be difficult for organic products to be more environmentally friendly and cheaper than fossil-based products. We propose a new method for separating organic products from water: switchable high pressure water (HPSW). HPSW is a process that combines two well-known phenomena: CO2 Expansion of liquids (CXL) and CO2-Switchable water (SW). HPSW takes advantage of changing the polarity of organic liquids when the CO is high2 Pressures and the repulsive amine-solute interactions that occur when SW amines are exposed to CO2both contribute to the removal of the organic matter from water. Any process alone can cause some organics to separate from water, but individually they are not effective at removing hydrophilic organic solutes. We hypothesized that when performed simultaneously, CXL and SW would act synergistically and promote more efficient and cleaner separations. For test mixtures of acetone and water, we have shown that several amino ionogens can promote phase separation of acetone from water at lower pressures than CXL alone. 2,6,10-Trimethyl-2,6,10-triazaundecane (TMTAD) was one of the best amines tested, which reduced the separation pressure to 3 bar CO2 compared to 30 bar without ionogen. In addition, 93% of the initial TMTAD added to the mixture was recovered using reverse osmosis (RO). If HPSW can reduce the energy consumption of separations, the current separation problems of the biomass conversion sector could be overcome.

Graphic Summary: Reversible High Pressure Water: An Alternative Method for Separating Organic Products from Water

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