综合利用稻壳制备木糖、电容炭与硅酸钙晶须

利用酸水解稻壳中的半纤维素制备木糖, 并将糖渣经过炭化后分离出碳和硅, 碳采用稀碱溶液活化改性制备电容炭, 硅采用水热法合成了硅酸钙晶须, 从而使稻壳所有组分得到充分利用. 采用循环伏安(CV)和恒流充放电(GCD)研究了电容炭的电化学性能. 通过X射线衍射(XRD)和扫描电子显微镜(SEM)对所得硅酸钙晶须的结构和形貌进行了表征. 实验结果表明, 稻壳酸水解的最优条件为硫酸浓度7%(质量分数)、 固液比(g/mL)为1:8、 反应时间为2.0 h, 在该条件下, 一次水解、 二次水解和三次水解的木糖收率(Y₁/Y₂/Y₃)和浓度(质量分数, C₁/C₂/C₃)都能达到最大值, Y₁=98.5%, C₁=3.6%; Y₂=85.4%, C₂=6.3%; Y₃=76.6%, C₃=9.0%. 采用15 mL 8%(质量分数) NaOH稀碱溶液活化改性制得的电容炭(AC/15)比电容值为77.32 F/g, 而且具有较好的倍率性和循环稳定性; 硅酸钙晶须为扫帚状针钠钙石晶须.

Comprehensive Utilization of Rice Husk to Prepare Xylose,Capacitance Carbon and Calcium Silicate Whiskers†

Hemicellulose of rice husk was used to prepare xylose by acid catalytic hydrolysis. The xylose cinder was carbonized and separated into C and Si. C was activated into capacitance carbon by activated modification, and Si was used to synthesize calcium silicate whiskers by hydrothermal method. Thus, all the components of rice husk were utilized comprehensively. The electrochemical performance of the capacitance carbon was studied by cyclic voltammeter(CV) and galvanostatic charge-discharge(GCD) tests. The structure and morphology of the calcium silicate whiskers were studied by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The results show that the xylose yields(Y₁/Y₂/Y₃) and contents(mass fraction, C₁/C₂/C₃) of the first, the second and the third hydrolysis can achieve Y₁=98.5%, C₁=3.6%, Y₂=85.4%, C₂=6.3% and Y₃=76.6%, C₃=9.0% under the optimized conditions, which are 7%(mass fraction) sulfuric acid, 1:8 solid-to-liquid ratio(g/mL), 2.0 h reaction time. The capacitance carbon prepared by activated modification with 15 mL 8% NaOH solution(AC/15) has the specific capacitance of 77.32 F/g, and a better double rate and cyclic stability.