Separation of phenolic compounds with modified adsorption resin from aqueous phase products of hydrothermal liquefaction of rice straw

Abstract

Hydrothermal liquefaction can be used to convert rice straw into an aqueous phase product that contains valuable phenolic compounds. In experiments, commercial adsorption resin XAD-4 was modified by a benzene ring - α,α'-dichloro-p-xylene (DCX) - in order to separate the phenolic compounds from the aqueous phase product; and, the optimal conditions for separation were explored. The results showed that, after modification of the resin, its adsorption capacity improved by 50%, due to increases in surface area, pore volume and micropore volume. The selectivity of the resin increased when the benzene ring was introduced as the ring formed hydrogen bonds with the compounds. The optimal conditions for separation were desorption agent of 40%, 45% and 55% ethanol solution, a flow rate of 2.5-5 mL/min, and a ratio of the sample volume to the column volume was 1:1. The total content of phenolic compounds in aqueous solution increased from 18% to 78% after separation.

Keywords: Adsorption resin; Hydrothermal liquefaction; Modification; Straw.