Kinetics of autocatalytic acid hydrolysis of cellulose with crystalline and amorphous fractions
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The acid hydrolysis of cellulose with crystalline and amorphous fractions is analyzed on the basis of autocatalytic model with a positive feedback of acid production from the degraded biopolymer. In the condition of low acid rate production compared with hydrolysis rate, both fraction of cellulose decrease exponentially with linear and cubic time dependence, and the normalized number of scissions per cellulose chain follows a sigmoid behavior with reaction time. The model predicts that self generated acidic compounds from cellulose accelerate the degradation of the biopolymer. However, if the acidic compounds produced are volatile species, then their release under low pressure will reduce the global rate of degradation of cellulose toward its intrinsic rate value determined by the residual acid catalyst present in the starting material.
KeywordsCellulose Depolymerization Acid hydrolysis Ageing Autocatalytic kinetics
MHG thanks FAPESP and CNPq for the financial support of this study. This work is also within the scope of INCT-Catálise Research Center in Brazil. Special acknowledge is given to Dr. Paolo Calvini, Ministero Beni Culturali, Genova, Italy, for his very useful, detailed comments and suggestions on this work.
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