Bio-oils are the product of biomass upgrading processes such as fast pyrolysis and reductive catalytic fractionation. These liquids can be converted into value-added feedstocks, yet separating them remains difficult due to limitations of traditional thermal methods. We utilize a spirocyclic polytriazole (DUCKY-9) membrane to separate simple and synthetic bio-oil mixtures via pressure-driven permeation. Steady-state permeation tests evaluated its ability to separate a larger phenolic compound (guaiacol). Although present in low concentration, guaiacol preferentially permeated and became enriched in the product stream. Its transport was found to be strongly coupled with methanol flux, allowing guaiacol to permeate “uphill” against its concentration gradient. Sorption isotherm measurements were used to identify the origin of this coupling behavior. This phenomenon suggests a promising route for dilute compound recovery using osmotically assisted reverse osmosis (OARO), offering a low-energy approach to bio-oil processing.
In parallel, we introduce DUCKY-11, a truly self-crosslinkable polytriazole designed for hydrocarbon separations. Its crosslinked network forms solely with time spent in the casting solution (no additives, heating, or UV treatment required). Using toluene and triisopropylbenzene (TIPB) separation as a benchmark, along with a model crude-oil mixture separation, we tested the membrane by systematically varying the degree of crosslinking. Measurements of permeance, selectivity, and polymer solubility revealed tunable separation performance.
These studies illustrate how tuning membrane chemistry and transport properties can enable efficient separation of complex liquid mixtures across a wide range of chemical processes.