(246f) Fractionation of Guayule Resin Using Supercritical CO2

Guayule (Parthenium argentatum A. Gray) is a desert shrub and a key alternative source of natural rubber. Guayule rubber can be extracted from the dried shrub using solvent

extraction, or from freshly-harvested shrub using aqueous (latex) extraction. Resin, a viscous liquid mixture of low-molecular-weight rubber and secondary plant metabolites, and bagasse are the residues from guayule rubber extraction. Techno-economic analysis has shown the value-added use of these co-products substantially impacts the rubber production cost.

Resin contains terpenes, sesquiterpenes, triterpenoids, and fatty acids with potential commercial application in the food, bio-insecticide, adhesive, and pharmaceutical industries. Fractionating guayule resin is a crucial step for any value-added use. The complexity and range of polarity of molecules in guayule resin the evaluation of many extraction methods.

In this study, supercritical CO₂, with and without co-solvents, was used to fractionate guayule resin to increase the solubilizing power for the desired compounds and the solvent diffusivity. This technique is faster, more selective, and better controlled for recovery of high-value thermolabile compounds than conventional liquid solvent fractionation and vacuum distillation methods. The effect of operating parameters, such as pressure, temperature, residence time, CO₂ flowrate, and co-solvent ratio have been investigated on the fractionation yield and selectivity of each compound group. Results from the fractionation experiments will ultimately be combined with models of fractionation process costs and fraction utility tests to identify the most efficient processing pathways for guayule resin utilization.