Kinetic Study of Soda Pulping from Kenaf Stalk

In this study, the kinetic of Soda pulping from bast, core and whole stem of kenaf (cultivar 7615) was evaluated. The Klason and acid soluble lignin content based on oven dry weight (O.D.) were found to be 17.2% and 3% for the core fibers, and 8.5% and 3.85% for bast fibers, respectively. For Soda pulping from bast, core and whole stem Cooking conditions was alkaline charge 40 g/L (as NaOH based on O.D. fiber), liquor to wood ratio 20/1, cooking maximum temperature from 140 to 170 °C (based on raw material) and the cooking time from 0 to 1500 min. (based on maximum temperature and raw material). The results indicated that delignification in kenaf bast and core fibers were completed during three phases and activation energy required for delignification in final phase were 85.89 kJ/mol and 94.53 kJ/mol for the bast and core, respectively. Rate constant of delignification in final phase for core in temperatures of 155, 160, and 170°C were 3910-4, 70×10-4 and 93×10-4 (min-1), and for the bast in temperatures of 140, 145, 150, and 155 °C, were 30×10-4, 41×10-4, 53×10-4, and 73×10-4 (min-1), respectively. Temperature of 155°C was chosen for pulping for whole stem because in this temperature, second and third phases are observable in both of the bast and core.