SEPARATION OF FATTY-ACID METHYL-ESTERS FROM TALL OIL BY SELECTIVE ADSORPTION

Fatty acid methyl esters (FAME) and resin acids (RA) were separated fr om tall oil by selective adsorption. Commercial nonmodified molecular sieve 13X was used as adsorbent. The adsorption isotherms of fatty aci ds (FA), FAME, and RA on molecular sieve 13X at 25 degrees C were dete rmined using various solvents. The solvents were methanol, ethanol, is opropanol, acetone, benzene, hexane, isooctane, petroleum ether (40-60 degrees C), and petroleum naphtha (80-180 degrees C). With each solve nt, FA and RA were adsorbed to a greater extent than FAME. Adsorption isotherms for RA and FAME in binary adsorption systems were also deter mined using petroleum ether, petroleum naphtha, benzene, and isopropan ol. For each component in the binary adsorption, the equilibrium amoun ts are lower than the values for pure component adsorption. The adsorp tion of FAME decreased in the presence of RA markedly in petroleum eth er and petroleum naphtha. This fact may be the indication of the pheno menon of selective adsorption. Separation was accomplished by adding a solution of esterified tall oil in solvents used in the binary adsorp tion systems, through a column packed with molecular sieve 13X. With p etroleum naphtha, FAME and RA were recovered in yields of 93 and 94%, respectively, from esterified tall oil. Petroleum naphtha gave the bes t results. The effects of particle size of adsorbent and flow rate of solvent on the efficiency of the separation were also investigated in fixed-bed column studies. The particle size-of adsorbent did not appar ently alter the results, Changes in the particle size should not signi ficantly change the number of available adsorption sites in a micropor ous molecular sieve.