Effect of alkaline and autohydrolysis processes on the purity of obtained hemicelluloses from corn stalks

► Hemicelluloses were extracted from corn stalks using autohydrolysis and alkaline processes. ► Optimal extraction conditions for maximum solubilization of hemicelluloses with minor undesirable compounds were determined. ► Lignin removal from hydrolysate was studied as purification step. ► Hemicellulose obtained by alkaline extraction showed the best physicochemical properties and higher yield. A study of the potential of autohydrolysis and alkaline extraction processes from corn stalks was performed for high purity hemicellulose extraction. The influence of process parameters on the purity of obtained hemicelluloses was analyzed. An experimental design was developed for the autohydrolysis treatments to determine the optimal conditions to solubilize the hemicelluloses with lowest content in contaminants. On the other hand, alkaline extraction, including raw material pretreatment (dewaxing and delignification step) was carried out analyzing the effectiveness of this processes for maximum pure hemicellulose recovery. The maximum yield (54% of the raw material hemicelluloses) and the best physicochemical properties (highest hemicellulose content free of lignin) were obtained with these pretreatments in alkaline extraction. Moreover, the effect of lignin removal by sulfuric acid from the autohydrolysis liquors before hemicellulose precipitation was studied. This purification step has allowed to obtain lignin-free autohydrolysis hemicellulose but with the presence of sulfur as predominant contaminant.