低温水热预处理对高蛋白小球藻N分布和藻渣热解特性的影响

利用水热釜研究了低温水热预处理过程中高蛋白小球藻的水热降解特性，考察了125-200℃各相产物产率、元素组成、能量回收率和关键元素C、N的分布规律。结果表明，大量的C、N元素富集在水相中，且提高温度（>175℃）有利于脱氨反应进而提高水相中NH₃的相对含量。随着预处理温度升高，N在油相产物中分布逐渐增加且在175℃后快速增加；固相产率及能量回收率逐渐降低，但同时其N/C和O/C也降低，表明水热预处理是一个提质过程。借助FT-IR、XPS、TG-FTIR-MS和Py-GC-MS对比分析了原料和藻渣的官能团结构和热降解特性。结果表明，水热预处理过程改变了C、N不同官能团的相对含量，与原料相比，藻渣中C-C相对含量增加，而C-N、C-O等相对含量降低；除了蛋白质-N和季胺类-N，预处理后藻渣中出现了少量吡啶-N。固体藻渣官能团组分含量和结构变化降低了热失重过程NH₃和HCN的释放、及快速热解产物中含N杂环化合物的含量。

Effects of low-temperature hydrothermal pretreatment of high-protein Chlorella sp.on N distribution and thermal degradation of solid residue

Decomposition behavior of Chlorella sp. during low-temperature hydrothermal pretreatment (HTP) were studied. Distribution of various product yields, element components, energy recovery ratio and key elements (i.e., C and N) along with temperature (125-200℃) were investigated. The results show that amounts of C and N are enriched into aqueous phase, and high content of NH₃-N is detected due to deamination reaction above 175℃. During the HTP process, N distribution in oil product first increases gradually and then rapidly increases above 175℃. During the whole low-temperature HTP process, the yield and energy recovery ratio of solid residue decreases continuously. The N/C and O/C ratio of the solid residue also decreases, indicating HPT would promote property of the solid residue. The functional structure and thermal-degradation of Chlorella sp. and its solid residue are then comparatively examined by various techniques including FT-IR, XPS, TG-FTIR-MS and Py-GC/MS. The results show that functional structure of the solid residue is distinguished from that of the raw sample. The relative content of C-C bond increases while that of C-N and C-O bonds decreases. In addition to protein-N and quaternary-N, a low fraction of pyridine-N is also detected in the solid residue. Compared with these from raw material, less NH₃ and HCN are released from solid residue, and less N-containing heterocyclic compounds are generated during rapid pyrolysis.