麦草NH_4OH-KOH蒸煮反应历程和动力学

Reaction Course and Kinetics in NH_4OH-KOH Pulping of Wheat Straw

在合适的蒸煮工艺条件下 ,研究了上海朱行麦草 NH4 OH-KOH法制浆的反应历程和反应动力学。结果表明 ,脱木素过程可分为从室温升温至 1 0 0°C的大量脱木素、1 0 0°C至 1 5 5°C下保温 45 min补充脱木素和 1 5 5°C下保温 45 min以后的残余脱木素 3个阶段 ,其中 65 %的木素溶解在大量脱木素阶段。动力学研究表明 ,脱木素反应对残余木素呈表观一级、对 OH-呈 0 .3 4级 ,反应的活化能为 2 9.75 k J/mol。脱木素速度方程为 -d Ldt=7.60 2× 1 0 2 exp(-3 5 77T ) Lc0 .34OH-。

The reaction course and kinetics in NH 4OH KOH pulping of Shanghai wheat straw were studied in pulping experiments carried out under constant and well defined conditions. The results showed that three distinct delignification phases occurred during this pulping process of wheat straw, namely, the initial delignification phase from the beginning of the cook to 100 °C , the bulk delignification phase from 100 °C to 155 °C kept 45 minutes and the residual delignification phase at 155 °C kept 45 minutes to the end of the cook. It is found that about 65% of the lignin is dissolved in the initial phase. The delignification during the initial delignification phase is found to be pseudo first order with respect to residual lignin and 0.34 with respect to residual alkali. The activation energy of the delignification reaction is 29.75 kJ/mol and rate equation of delignification is -d L d t =7.602×10 2exp(-3 577 T ) Lc 0.34 OH - for first delignification phase.