不同热解温度下生物质废弃物制备的生物质炭组成及结构特征

以玉米秸秆、树枝和树叶3种生物质废弃物为原料,分别采用差热/热重分析(TG/DTG)、红外光谱(FT-IR)、Boehm滴定及X射线衍射(XRD)方法考察热解温度为350,550,750℃时制备的生物质炭结构及组成特征.结果表明:玉米秸秆原料的热稳定性最低,热解过程中质量损失最大,其次是树枝和树叶;玉米秸秆原料的XRD谱弥散程度最大,构成炭的微晶层数相对较少;不同原料在相同温度制备的生物质炭,其单位质量含有的表面官能团种类和总量相近,但pH值差别较大,其中玉米秸秆制成的生物质炭pH最大;随着温度的升高,相同原料制备生物质炭的芳香化程度增加,表面官能团总量减少,pH值升高,纤维素和半纤维素特征峰消失,结构趋于石墨微晶.

Structure and Composition Characteristics of Biochars Derivedfrom Biomass Wastes at Different Pyrolysis Temperatures

Biomass charcoals were made from 3 kinds of biomass wastes, maize straw, branches and leaves trees at 350,550,750 ℃, respectively. The
 structure and composition characteristics of biomass charcoals were characterised by thermogravimetric analysis, FT IR analysis, Boehm titration and X-ray diffraction analysis. The results show that maize straw has the lowest thermal stability and the highest mass loss, followed by those of the branches and leaves. Compared with branches and leaves, maize straw has the greatest dispersion degree in X ray diffraction with a less layer number of microcrystalline. The total quantity of surface functional groups in biomass charcoals made from different feedstocks at the same temperature is similar, the pH value has larger differences and biochars derived from maize straw have the highest pH value. Results of characterization of biochars derived from the same feedstock show that with the increase of pyrolysis temperature, the aromatization degree of biochars increases; the content of surface functional groups decreases; pH value increases; the characteristic peaks of cellulose and hemicellulose disappear; the structure of biomass charcoals tends to graphite crystallite structure.