不同温度制备生物炭的热解产物特征

Characterization of pyrolysis products in biochar prepared at different temperatures

本论文主要利用热解-气相色谱/质谱联用仪(Py-GC/MS)对不同温度制备生物炭的化学特征进行了研究,并探讨了制备温度对生物炭热解产物的影响。结果显示,不同温度制备的稻秆(RS)、玉米秆(CS)和松木(PW)生物炭的热解产物组成具有一定类似性。这些化合物均以芳烃和苯酚类化合物为主(55%~100%),另外还包含有呋喃类化合物(NA^31%)以及少量含氮化合物(NA^1.7%)等杂原子化合物,表明不同类型的生物炭具有较为类似的化学结构,均以芳香性结构组分以及连接在芳香结构上的烷基或含氧、氮等杂原子基团组成。然而不同温度制备生物炭的热解产物,其相对含量具有明显的差异。低温制备(≤350℃)的生物炭热解产物中检出较高含量的酚类化合物、呋喃类化合物和含氮化合物等,意味着生物炭中还保留了部分半纤维素、纤维素和木质素组织。随着制备温度的升高,热解产物中含氧、氮等杂原子的不稳定结构逐渐减少,相反,芳烃化合物的相对含量逐渐增加,表明生物炭逐步向缩合程度高的芳香化结构转变。此外,在相同制备温度条件下,3类生物炭的热解产物中可鉴定化合物的数量大小顺序为:RS>PW>CS。脂肪烃类化合物仅在RS中检出,而含硫化合物仅在PW中检出。这些结果表明,制备温度和原料均对生物炭的化学特征具有明显的影响,这对于生物炭的制备和应用等具有参考意义。

In this study,three types of biochar that had been produced at different temperatures were characterized by pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS)to investigate the influence of production temperature on their pyrolysis products.Results showed that pyrolysis products that were derived from biochar at different temperatures had some similarities.The product compounds were dominated by aromatic and phenolic moieties(55%–100%)with some other compounds,such as furans(NA–31%)and N-containing compounds(NA–1.7%),indicating the presence of aromatic components,linear or branched aliphatic chains,and/or oxygen-,nitrogen-containing units.The results also showed differences in product characteristics with different production temperatures.A certain amount of phenolic compounds,furans,and N-containing compounds were detected in the pyrolysis products of biochar that were prepared at low temperatures(?350℃),indicating that some hemicellulose,cellulose,and lignin tissues were retained in the biochar.With an increase in pyrolysis temperature,these labile O-and N-containing structures were gradually removed,while aromatic structures gradually increased.These changes indicated that aromatic structures of biochar reach a higher degree of condensation with increase in production temperature.Besides,the type of feedstock affected the pyrolysate composition of biochar as well.The number of identifiable pyrolysates in rice straw(RS)biochar was higher than in the other two types of biochar,ranging in the order of RS>pinewood(PW)>CS(corn straw).It was noted that the aliphatic hydrocarbons were present only in RS biochar and sulfur compounds were observed only in PW biochar.These results indicate that the production temperature and raw materials both have obvious effects on the chemical characteristics of biochar,which is of reference for its preparation and application.