Optimizing Pretreatment Process Conditions Using Lewis Acid Catalyst for Higher Crystallinity of α-Cellulose

The development of an environmentally benign process for extraction of valued chemicals by catalytic hydrolysis of cellulose is considered as one of the key technologies for making complete usage of cellulosic biomacromolecules in near future. Present research deals with the application of Lewis acid of iron(III) chloride (FeCl3) based catalytic hydrolysis system which is capable of enhancing the crystallinity index of alpha-cellulose relatively at lower reaction temperature using moderate to dilute mineral acid. Process parameters were optimized by 2-Level Factorial Central Composite Design (CCD) approach to obtain microcrystalline cellulose (MCC) from alpha-cellulose. Process variables such as temperature (x(1)), hydrolyzing time (x(2)) and concentration of FeCl3 catalyst solution in HCl (2.5 M) acid were studied. Responses selected were yield (y(1)) and percentage crystallinity (y(2)) of the finally procured MCC sample. Regression analysis was accomplished to develop significant models. Analysis of Variance (ANOVA) showed that temperature was the most persuasive aspect for hydrolyzing the amorphous segments of cellulose. Under optimum condition, percentage yield and percentage crystallinity obtained were 83.21 +/- 0.23 and 86.98 +/- 0.32 respectively. The results elucidated that, catalytic effect of FeCl3 salt in presence of mineral acid can considerably increase the crystallinity of alpha-cellulose up to a certain extent by selective hydrolysis of amorphous domain while keeping the crystalline region almost unaltered.