Acid hydrolysis of cellulose. part i. experimental kinetic analysis

Abstract

The main objective of this investigation is to obtain experimental data for the sulfuric acid hydrolysis of cotton and mechanically pretreated cotton fibres. These data indicate that some glycosidic bonds of cellulose have very high accessibility to catalytic ions. It was also shown that milling increases the accessibility of some glycosidic bonds of cellulose and decreases the volume of the crystalline regions of cotton. From the glucose yield versus time data, it was found that the effect of milling on the rate of cellulose depolymerization depends on the reactivity and accessibility of the glycon rings of cellulose. It was also found that at 1OO°C, the rate of cellulose depolymerization was not affected by the extraction of cotton wax and this was related to a rolling up process of cotton wax caused by melting. The kinetic constants of glucose degradation and cellobiose hydrolysis have been determined for the stochastic simulation of cellulose depolymerization which is the subject of the second part of this work.

The Electronic Nature of the 1,4‐β‐Glycosidic Bond and Its Chemical Environment: DFT Insights into Cellulose Chemistry

“…Taking the free energy cost of generating structure 10 into account, we thus find that the overall barrier for the hydrolysis of cellobiose through the transition states TS( 10 → 18 ) and TS( 18 → 21 ) amounts to 30.6 and 30.7 kcal mol −1 , respectively. Experimental studies obtained similar results by kinetic analyses: 32.3 kcal mol −1 (cellobiose, 90–135°, sulfuric acid 0.05–0.10 N)55 and 31.7 kcal mol −1 (cellobiose, 117‐165°, sulfuric acid 0.03 N) 56…”

“…Experimental studies obtained similar results by kinetic analyses: 32.3 kcal mol À1 (cellobiose, 90-1358, sulfuric acid 0.05-0.10 N) [55] and 31.7 kcal mol À1 (cellobiose, 117-1658, sulfuric acid 0.03 N). [56] We have also estimated, in an analogous manner, the reaction free energy of the hydrolysis of cellobiose in aqueous solution that yields a-glucose and b-glucose (see the Supporting Information for details). By using a suitable thermodynamic cycle in combination with BB1K/6-31 + + GA C H T U N G T R E N N U N G (d,p) calculations and the SMD solvation model, the overall reaction is found to be exergonic by À2.7 kcal mol À1 .…”

“…This value is consistent with experimental results. [55,56] This article sheds light on the electronic nature of the 1,4b-glycosidic bond and its chemical environment. To understand the fundamental bonding concepts based on DFT computations, natural bond orbital (NBO) analysis was performed.…”

Kinetic Studies of Acid Hydrolysis of Food Waste-Derived Saccharides

“…Additional studies, based on Saeman's empirical model, have been carried out by Fagan et al 14 and others [15][16][17][18][19][20] . Glucose units in cellulose are bonded by β (1 -4) glycosidic linkages, which are oriented equatorially unlike the axially oriented α (1 -4) glycosidic linkages between D-glucopyranose units in starch.…”

Conversion of Polysaccharides to Sugar Alcohols: A Modeling Approach Based on Oligosaccharides

“…The main feature of a Monte Carlo simulation is its estimative and goal-oriented nature as compared to a full-edged Markov chain simulation. A Monte Carlo algorithm might be used to implement a Markov chain model to make it more tractable regarding computation cost and feasibility [16,17,[19][20][21]. The third common method of kinetic modeling is based on deterministic view in which the population balance of species is used directly in formulating the reaction kinetics [22][23][24][25].…”