| Abstrakt: |
In this research, the thermochemistry of the hydrolysis process of cellulose samples with different crystallinity has been studied. Calorimetric methods were used to determine the combustion enthalpies of cellulose samples and enthalpies their interaction with water. As a result, the standard formation enthalpies of dry and wet cellulose samples were calculated. In addition, the standard formation enthalpy of glucose solution formed after hydrolysis of wet cellulose substrates was found. Based on the obtained thermodynamic characteristics, the standard enthalpy of the cellulose hydrolysis reaction was obtained. It has been established that the hydrolysis reaction is endothermic when the cellulose crystallinity (X) is above 50%. Thus, the hydrolysis process of cellulose with increased crystallinity is possible only if the entropy of hydrolysis exceeds the enthalpy of the endothermic hydrolysis reaction. Elevated temperature increases the contribution of the entropy factor to the negative Gibbs potential and promotes the hydrolysis of highly crystalline cellulose. On the other hand, the hydrolysis process of amorphized cellulose samples having X below 50% is exothermic and can occur spontaneously even without the contribution of the entropy factor to the Gibbs potential of this reaction. [ABSTRACT FROM AUTHOR] |
