微波加热烟杆制备微孔活性炭的研究

Study on Preparation of Micropore Activated Carbons from Tobacco Stems Impregnated with Zinc Chloride by Microwave Heating

研究了微波加热烟杆氯化锌活化法制备微孔活性炭的新工艺。采用正交试验研究了氯化锌浓度、浸渍时间、微波功率和活化时间对活性炭得率和吸附性能的影响。最佳工艺条件为ZnCl2浓度25%,浸渍时间36h,微波功率为700W,加热时间为16 min时,所制备的活性炭的碘吸附值为1059.32 mg/g,亚甲基蓝吸附值为21 mL/0.1g,得率为32.90%。该工艺将常规加热方法的预热、干燥、炭化和活化简化为一个过程,所需要加热时间仅为传统方法的1/13,产品活性炭的亚甲基蓝吸附值为国家一级品标准的2.33倍。同时测定了该活性炭的氮吸附等温线,通过BET法计算了活性炭的比表面积,并通过H-K方程、D-A方程和密度函数理论(DFT)表征了活性炭的孔结构。结果表明:该活性炭为微孔型,BET比表面积为1214m2/g,总孔容为0.7387 mL/g,微孔占总孔容74.03%,中孔占24.54%,大孔占1.43%。

A novel method of preparing micropore activated carbons from tobacco stems impregnated with zinc chloride by microwave heating was studied. The effects of impregnating time, concentration of zinc chloride solution, microwave power and heating time on the yield and adsorption properties of activated carbons were systematically studied via orthogonal experiments. The optimum conditions were as follows： concentration of zinc chloride solution 25% and impregnating time 36 hours, microwave power 700 watts, heating time 16 minutes. Under above conditions, the yield of the activated carbons was 32.90% . The methylene blue adsorption reached 21 mL/0.1 g, and the iodine number was 1059.32 mg/g. The microwave heating method can complete conventional processing of pre-heating, drying, carbonization and activating in one stage. The heating time was only 1/13 times as fast as that of the conventional process. The methylene blue adsorption was 2.33 times of that the first grade product specified in the National Standard. Furthermore, the activated carbons prepared at optimum conditions were tested by nitrogen adsorption at 77 K. The specific surface area of activated carbons was 1214 m^2/g by BET method. The porous structures of the activated carbons were investigated by Horvath-Kawazoe equations, Dubinin-Astakhov equations and Density Functional Theory. It was shown that the activated carbon was microporous with 0. 7387 mL/g total pore volume, of which 74.03% was micropore volume, 24.54% was mesopore volume and 1,43% was macropore volume.