Separation of ionic liquid [Mmim][DMP] and glucose from enzymatic hydrolysis mixture of cellulose using alumina column chromatography

Pretreatment of cellulose with ionic liquids (ILs) can improve the efficiency of the hydrolysis by increasing the surface area of the substrates accessible to solvents and cellulases. However, the IL methods are facing challenges to separate the hydrolyzed sugar products as well as the renewable ILs from the complex hydrolysis mixtures. In this study, an alumina column chromatography (ACC) method was developed for the separation of hydrophilic IL N-methyl-N-methylimidazolium dimethyl phosphate ([Mmim][DMP]) and glucose, which was the main ingredient of the monosaccharide hydrolyzate. The processing parameters involved in ACC separation were investigated in detail. Our results showed that the recovery yields of [Mmim][DMP] and glucose can reach up to 93.38% and 90.14%, respectively, under the optimized parameters: the sampling ratio of 1:20 between the applied sample volume and the bed volume of the column; a gradient elution using methanol (100%, 150 ml) and then water (170 ml) as eluents with 1 ml/min flow rate. The recovered [Mmim][DMP] showed qualified property and was effective in a new hydrolysis reaction. In addition, scale-up ACC separations were successfully done with satisfied separation performance. The results indicated that the ACC is one of the available methods for the separation of ILs and monosaccharides from the hydrolysis mixtures.