氮吸附法分析生物质焦孔隙结构

Porosity of biomass chars studied by using nitrogen adsorption method

采用氮吸附法对4种生物质焦(稻壳、树叶、玉米秆、棉花秆)的孔隙结构进行测量,结果表明,不同种类焦样的比表面积和孔径分布有明显差别,树叶的比表面积最大,为242.21 m2.g-1,玉米秆的比表面积最小,为0.81 m2.g-1。850℃时,稻壳、树叶、玉米秆焦样的孔径分布曲线在微孔和中孔范围各有一个分布峰,而棉花秆焦样的孔径分布曲线只在中孔范围内出现一个分布峰。热解温度是影响孔隙结构的一个重要因素,在高温条件下,同步热解得到的焦样的比表面积较大,微孔较多。在本研究中,600℃、850℃的稻壳焦样和850℃的树叶焦样具有较大的比表面积,比较适合做吸附剂。

Porosities of 4 biomass chars of rice hull, tree leaf, cornstalk and cotton stem were studied using the N2 adsorption method. The special surface area （SSA） and pore size distribution were obtained for the samples. The resuits showed that there were significant differences in SSA and pore size distribution among the biomass chars. The largest SSA was 242.21 m^2·g^-1 , while the smallest 0.81 m^2·g^-1. At the pyrolysis temperature of 850℃, the pore size distributions of rice hull, tree leaf and cornstalk char peaked in the micropore and the mesopore ranges. In contrast, the cotton stalk char had only one peak in the mesopore range. The pyrolysis temperature considerably affected the porosity. Synchronous heating resulted in larger SSA and more fine pores than asynchronous condition. In this study, it was found that chars obtained at 600℃ or 850℃ for rice hull and 850℃ for tree leaves had the largest SSA. Therefore, they were considered more suitable to be used as adsorbents.