Study on the adsorption behavior of glycerin from fatty acid methyl esters by a tertiary amine-type anion exchange resin

A weakly basic anion exchange resin with hydroxylated tertiary amine groups was successfully synthesized and used for the first time in an adsorption study for glycerin in fatty acid methyl esters (FAME). A kinetic study of glycerin adsorption on the resin demonstrated that the resin exhibited a rapid initial adsorption behavior, and the correlation coefficients (r(2)(2)) of the pseudo-second order reaction model were all greater than 0.98, which indicated the existence of hydrogen bonds through sharing electrons between glycerin and active sites on the resin. The whole process of glycerin adsorption onto the resin was a combination mechanism involving hydrogen bond sorption and intraparticle diffusion. The thermodynamic experiments showed that the glycerin adsorption onto the resin was a spontaneous exothermic process accompanied with a gradual decrease in entropy. In addition to intraparticle diffusion, the adsorption behaviors of the resin for glycerin also involved hydrogen bond forces between the -OH in the glycerin molecule and N atom in the -N(CH3)(2) group, glycerin intermolecular hydrogen bond attraction, the dipole bond forces between glycerin and the -N(CH3)(2) group (90.96%) in the resin, and the dipole bond forces between glycerin and several of the -N(CH3)(3+) groups (9.04%) in the resin. (C) 2018 Elsevier B.V. All rights reserved.