73. Kumar, Sandeep; Gupta, Rajesh; Lee, Y. Y.; Gupta, Ram B.. Cellulose pretreatment in subcritical water: Effect of temperature on molecular structure and enzymatic reactivity. Bioresource Technology (2010), 101(4), 1337-1347.
Microcryst. cellulose (MCC) was pretreated with subcrit. water in a continuous flow reactor for enhancing its enzymic reactivity with cellulase enzyme. Cellulose/water suspension was mixed with subcrit. (i.e., pressurized and heated) water and then fed into the reactor maintained at a const. temp. and pressure. After the reaction, product was immediately cooled in a double-pipe heat exchanger. The solid portion of the product (i.e., treated MCC) was sepd. and tested for mol. structure and enzymic reactivity. Expts. were conducted at temps. ranging from 200 to 315 C, at 27.6 MPa, and for 3.4-6.2 s reaction times. The treated MCC was characterized for d.p. (DPv) by viscosimetry, and crystallinity by X-ray diffraction (XRD). In addn., differential scanning calorimetry and SEM (SEM) analyses were carried out to study any transformation in the cellulose structure. As expected, DPv of cellulose steadily decreased with increase in the pretreatment temp., with a rapid drop occurring above 300 C. On the other hand, XRD anal. did not show any decrease in crystallinity upon pretreatment but, partial transformation of celluloses I-II structure was noticed in the MCC treated at 300 C. Development of surface cracks and trenches were obsd. in the SEM images for all the treated samples. Enzymic reactivity was increased after the treatment at 300 C.