玉米秸秆生物炭制备及结构特性分析

Preparation biochar of corn stover and structural characteristics analysis

关键词:  玉米秸秆, 生物炭, 限氧裂解, 结构

Key words:  corn stover, biochars, oxygen-limited pyrolysis, structure

摘要:

为了高效、经济、环保地解决华北平原地区玉米秸秆处置问题并寻求有效途径,该研究以玉米秸秆为原料,采用限氧裂解法在不同温度(200、300、400、500 ℃)下制备生物炭,并对生物炭的热解动力学、结构形貌、元素组成、比表面积、孔径分布、官能团等理化特征进行了分析表征。结果表明:不同裂解温度制备的生物炭具有不同的差热曲线,其官能团的组成也存在差异,这表明了样品中不同生物质的热解反应过程。随着热解温度的升高,生物炭产率、氢和氧含量下降,同时H/C和(O+N)/C比值也降低,而碳和氮含量却升高,说明生物炭芳香性增强,亲水性和极性减弱,性质趋于稳定。生物炭热重曲线和差热曲线分为三个过程,热解温度高时失重比例低,曲线趋向平缓。生物炭的比表面积、微孔比表面积、中孔体积和微孔体积随着热解温度的升高而增大,但最可几孔径却减小,吸附能力增强。综上所述,400 ℃的温度制备生物炭,其产率相对较高、结构最稳定、吸附性能最佳,有助于最大程序的利用农业废弃物资源、降低耗能,提高农产品附加值。

Abstract:

Biochar is rich in carbon, which can reduce carbon emissions greatly by carbon sequestration, and play a significant role in controlling the diffusion of pollutants and promoting plant growth. Biochar, as a by-product of a variety of agricultural waste, such as corn stove, can increase the added value of agricultural products and increase agricultural income. To resolve the problem of the processing and utilization of corn stalk in North China in a high efficient, economic and environment-friendly way, in this study, a series of biochars were made from corn stove under different temperatures(200, 300, 400, 500 ℃)using oxygen-limited pyrolysis method. The pyrolysis kinetics, structure, morphology, element composition, specific surface area, pore dimeter distribution and surface functional groups were analyzed thoroughly and systematically by according methods, respectively. The results showed the biochars prepared under different pyrolysis temperatures possessed differential pyrolysis kinetics and distinct surface functional groups, which meant the pyrolysis process of different biomasses. With the heating-up process of pyrolysis, the yield, contents of nitrogen and carbon decreased, but the hydrogen and oxygen increased; meanwhile, the ratios of H/C and(O+N)/C decreased, which meant the decreasing of hydrophilicity and polarity and the increasing of aromaticity and stability. Thermogravimetric curve and differential thermal curve included three processes respectively. When the pyrolysis temperature was high, the weight loss ratio was low and the curve tended to be gentle. The specific surface area, micropore specific surface, medium pore volume, micropore volume increased with the elevation of pyrolysis temperature, but the most probable aperture decreased; moreover, adsorption capacity enhanced. In conclusion, the biochars could be prepared under 400 ℃ with a relative high yield and the most stable structure and the best adsorption performance could be obtained