Potential approach for fractionating oxygenated aromatic compounds from renewable resources

Various oxygenated aromatic compounds (OACs) could be obtained from renewab le resources if separations were available to fractionate the complex mixtu res. We examined adsorption for the fractionation of OACs into (i) acids, ( ii) phenols, (iii) alcohols, and (iv) compounds lacking hydrogen-bond donat ing ability. Specifically, we studied adsorption from a nonpolar solvent on to a neutral acrylic ester sorbent. The acid, 3-phenylpropionic acid, exist s in hexane as monomers and self-associated (e.g., dimeric) species. Phenom enological evidence indicates that monomers can adsorb but that adsorption competes with solution-phase dimerization. Previous studies indicate that p henols and alcohols adsorb through a hydrogen-bonding mechanism, while OACs lacking hydrogen-bond donating ability (i.e. aldehydes, ketones, esters, a nd ethers) adsorb weakly. Isotherms show that these four classes of OACs ad sorb with significantly different affinities. Desorption is achieved by exp loiting deprotonation reactions in an aqueous desorption phase and that the acids and phenols can be selectively desorbed based on differences in thei r pK(a)'s. A potential approach for fractionating renewable OACs is conside red.