不同温度下小麦秸秆生物炭的制备及表征

Biochar Made from Wheat Straw:Preparation and Characterization

以小麦秸秆作为生物质原材料,在200、400、600℃温度条件下,采用限氧控温裂解法制备生物炭。采用热重分析、元素分析、红外光谱分析、比表面积分析和扫描电镜分析表征各物质结构特征,并分析不同制备方法对其元素组成、表面结构、表面性质的影响。结果显示:热重、红外光谱分析结果显示小麦秸秆在热解温度升高到350℃时失重率最大,为33.73%,秸秆的热解过程发生化学键的断裂及脂肪性烷基链的消失;小麦秸秆焚烧物的产率、灰分分别为12%、64.78%,灰分较大;生物炭随着碳化温度的升高,其产率降低,灰分含量增大;随着热解温度升高,生物炭逐渐成为"富炭颗粒",其极性降低,芳香性增大,疏水性增强;电镜扫描分析显示随着炭化温度升高,生物炭孔壁逐渐变薄,内部孔结构逐渐增大,甚至出现大量微孔。

In this paper, a laboratory experiment on preparation of biochar from wheat straw was described in terms of the preparation method of limited oxygen pyrolysis under different temperatures and the characterization of biochar by means of thermo gravimetric （TG）, elemental analysis, infrared spectrum （FFIR）, specific surface area analysis and scanning electron microscopy （SEM）. Analysis of TG-DTG and FTIR spectroscopy showed that the weight-loss rate of wheat straw rose to a maximum of 33.73% when the pyrolytic temperature at 350 ℃, during which the chemical bond was breaking and fatty alkyl chains faded away, and the straw ash yield was 12%, ash content accounted for 64.78%; as the pyrolytic temperature went up the biochar turned into a kind of ＂carbon-rich particles＂, and its aromaticities （H/C ratio） and hydrophobicity （O/C ratio） were enhanced dramatically, while the polarity [（O ＋N）/C] decreased sharply. In addition, the SEM revealed the hole-wall of biochar got thinner gradually with the increasing of pyrolytic temperature; furthermore, the internal pore structure of biochar enlarged gradually, and then a large number of micropores within the biochar appeared.