磷钨酸催化法制备红麻秆芯炭微球的研究

Study on the preparation of hydrochar microspheres from kenaf core using phosphotungstic acid as catalyst

【目的】寻求环境友好的固体酸催化剂,以在温和的水热炭化条件下实现农林副产物的高附加值转化。【方法】以红麻秆芯为原料,考察了磷钨酸用量、水解条件、炭化温度和炭化时间对红麻秆芯水热炭化效果的影响,对水热炭的得率、表面官能团、元素组成及形貌特征进行表征,并对磷钨酸催化剂的回收再利用特性进行研究。【结果】将添加质量分数10%磷钨酸水溶液的红麻秆芯原料在900 W超声波细胞破碎机中预处理15 min后,经由180℃水解4h制得的水解液在相同温度下进一步水热炭化6h,制备获得的水热炭微球形貌较规整且得率最高。经乙醚萃取分离的磷钨酸,在重复循环使用4次后仍保持较高的催化活性。【结论】磷钨酸可以在低温下直接用于木质纤维原料的催化水热炭化制备形貌单一的炭微球,且可以进行4次的循环回收再利用。

[Objective] This study selected environmental friendly solid acid catalyst to achieve high val- ue-added conversion of agricultural and forestry by-products via a benign hydrothermal carbonization （HTC） approach. [Method] Facile hydrolysis of kenaf core followed by low-temperature hydrothermal car- bonization of its hydrolysate using phosphotungstic acid as catalyst was carried out for the first time to pre- pare biomass-based carbon microspheres. The effects of phosphotungstic acid concentration, hydrolysis con- ditions,hydrothermal carbonization temperature and holding time on yield, characteristics of surface func- tional groups,elemental composition and micro-morphology of the prepared hydrochar microspheres were investigated. [Result] The maximum yield of hydrochar with regular spherical microstructure was obtained when the kenaf core was treated with a consecutive combination process of 15 min ultrasound-assisted pre- hydrolysis at 180 ~C for 4 h followed by further 6 h HTC in the presence of 10% phosphotungstic acid. Phosphotungstic acid extracted with diethyl ether had good catalytic activity after 4 times recycling. [Con- clusion] Phosphotungstic acid was an effective solid acid catalyst for direct catalytic hydrothermal carboni- zation of lignocellulosic biomass for generation of hydrochar microspheres under low temperature. The phosphotungstic acid catalyst can be readily recovered by ether for 4 times.