Efficient separation and extraction of guaiacol and its derivatives from bio-oils based on a heterogeneous extraction technique

Abstract

To fully utilized the high value-added phenolic compounds in biomass pyrolysis bio-oils, a heterogeneous extraction method was developed in this study to separate 4-ethylguaiacol, guaiacol, and eugenol from bio-oil one by one. Based on the high selectivity of coordination intermediates generated between Ca²⁺ and phenolic compounds with hydroxyl and methoxy groups towards the parent phenol, the reaction intermediate between each of 4-ethylguaiacol, guaiacol, eugenol and Ca²⁺ was used as the extracting agents. Influencing parameters investigated were the sequence of extracting three phenolic compounds from the model bio-oil, the optimal extraction conditions, and the Ca²⁺ distribution in the original extracting agents at the end of the reaction. The optimal extraction sequence was determined to be 4-ethylguaiacol, eugenol and guaiacol through the evaluation of multiple experiments changing their addition sequence. Under the conditions of 25 °C reaction temperature, 45 min reaction time, and pH value of 7, the extraction efficiency of 4-ethylguaiacol, eugenol and guaiacol from bio-oil reached 60.6 %, 46.1 % and 60.7 %, respectively. Meanwhile, the purity of these three phenolic compounds achieved 62.4 %, 90.0 % and 89.0 %.