The role of prehydrolysis refining in obtaining microcrystalline cellulose: case of biodamage wood from Picea abies, Larix sibirica and Populus tremula species

Abstract

The ability of grinding equipment in the production of microcrystalline cellulose (MCC) to separate plant polymers into fibers, grind and develop certain properties in them can be used if it is impossible to minimize the concentration of acid. To obtain microcrystalline cellulose, samples (N = 6) of dry wood Picea abies (L.) H.KARST., Larix sibirica LEDEB., Populus tremula L. species were used. The samples were cooked in a laboratory autoclave, prehydrolysis grinding was carried out in a centrifugal grinding machine at a fibrous mass concentration of 6% and varying the degree of grinding from 15 to 85 degrees of Schopper Riegler (°SR). Chemical treatment of cellulose samples with different degrees of grinding was carried out with varying hydrolysis temperatures from 80 to 100 °C, hydrochloric acid concentrations from 54.75 to 91.25 g/l, and hydrolytic degradation time from 60 to 120 minutes. The dependences of the degree of polymerization (R2 = 0.93) and the degree of crystallinity (R2 = 0.99) on these factors are approximated by second-order regression equations and visualized as three-dimensional response surfaces. The optimal values of the hydrolysis variables are: hydrochloric acid concentration – 54.75 g/l, hydrolytic degradation time – 60 min, hydrolysis temperature – 80 °C, grinding degree – 85 °C. The degree of grinding of the fibrous mass has the greatest influence on the quantitative values of the degree of polymerization and the degree of crystallinity, the lowest is the temperature of hydrolysis. With an increase in the degree of grinding, a significant 2.7-fold decrease in the degree of polymerization occurs in MCC samples from P. abies and P. tremula wood. An increase in the degree of crystallinity (17%) and bulk density (20%) is observed to a greater extent in MCC samples from P. abies and L. sibirica wood. The use of prehydrolysis milling of cellulose in the process of obtaining MCC reduces the cost of chemical treatment by 1.7 times.