Delignification Kinetics Study on the Tetrahydrofurfuryl Alcohol/HCl Pulping of Rice Straw

Abstract

In this study, the delignification kinetics of tetrahydrofurfuryl alcohol (THFA)/HCl pulping of rice straw was investigated. In the atmospheric pressure pulping, two phases of different delignification rates were observed which were closely related to the amount of HCl and temperature. Equations for the transition time of these two phases at various temperatures and catalyst dosages were derived. For optimal cooking control, the transition time of these two phases can be calculated. The cooking showed very low activation energies, which, in phase I and phase II, were only 26.5 kJ and. 32.2 kJ mol -1 , respectively. At phase I pulping, delignification was the main reaction with minimal dissolution of carbohydrate fractions. Consequently, the yield loss was low. In phase II, however, when the residual lignin content was less than about 5%, the dissolution of the carbohydrate was greater than the lignin removal, causing a marked reduction in pulp yield. Comparisons of K L /K C (ratio of delignification rate and rate of carbohydrate dissolution) and ΔL/ΔC (ratio of lignin removed and carbohydrate dissolved during pulping) values in phases I and II were made. Results showed that both values were greater in phase I, and both values reached their maxima at 120 °C and catalyst dosage of 0.020 mol L -1 .

Hansen Solubility Parameters: A Tool for Solvent Selection for Organosolv Delignification

“…Among the delignification processes, the organosolv process is particularly interesting because of the possibility of recovery and recycling the solvents. In organosolv processes it is still possible to add catalyst (acidic or basic) and apply high pressures (subcritical and/or supercritical fluid conditions) to optimize the reaction conditions. , …”

“…In organosolv processes it is still possible to add catalyst (acidic or basic) and apply high pressures (subcritical and/or supercritical fluid conditions) to optimize the reaction conditions. 9,11 Therefore, for organosolv processes, the dissolution of the lignin fragments plays an essential role to the delignification efficiency. In this context, Solubility Parameters can provide valuable information on the mechanisms underlining the solubility of lignin, thus enabling the rational choice of the best solvent composition for the extraction of lignin.…”

Microwave-Assisted Urea-Based-Hydrotropic Pretreatment of Rice Straw: Experimental Data and Mechanistic Kinetic Models

“…Lignocellulose pretreatment selectivity could be observed from the ratio of solubilization rate constant of lignin to the one of cellulose (k l /k 2 ). 66 The higher the ratio, the more the lignin solubilized than the cellulose which results in higher process selectivity. A ratio of (k l /k 2 ) as high as 15.3 was obtained from the application of tetrahydrofurfuryl alcohol (THFA) over the presence of 0.02 M of HCl for rice straw lignin removal conducted at 120 °C and 120 min of solubilization reaction, 66 while the ratio of (k l /k 2 ) found in this work is 14.76 from the mechanistic model with assumption of the absence of lignin condensation.…”

“…66 The higher the ratio, the more the lignin solubilized than the cellulose which results in higher process selectivity. A ratio of (k l /k 2 ) as high as 15.3 was obtained from the application of tetrahydrofurfuryl alcohol (THFA) over the presence of 0.02 M of HCl for rice straw lignin removal conducted at 120 °C and 120 min of solubilization reaction, 66 while the ratio of (k l /k 2 ) found in this work is 14.76 from the mechanistic model with assumption of the absence of lignin condensation. The lower (k l /k 2 ) ratio found in this work might be due to the microwave-assisted hydrotropic pretreatment which was conducted in lower system temperature, that is, 90 °C and the application of different chemicals.…”

Kinetics Models of Lignin Isolation from Rice Husk Using Alkaline Hydrogen Peroxide

“…Guolin et al [12] studied the pulping kinetics of wheat straw using an aqueous caustic potashammonia process. Ho et al [13] studied the delignification kinetics of rice straw using tetrahydrofurfuryl alcohol with HCl. Kim and Holtzapple [14] studied the delignification kinetics of corn stover using lime pretreatment.…”