Abstract:

Pyrolysis-gas-chromatography/mass spectrometry (Py-GC/MS) was employed to investigate the thermal cracking evolution and thermochemical conversion pathways of the main carbon and oxygen-containing functional groups contained in sewage sludge under different pyrolysis temperatures. The results show that sewage sludge mainly contain carbon-carbon double bonds (C=C), carboxyl groups (—COOH), hydroxyl groups (—OH), aldehyde groups (—CHO) and benzene (π-π^*). Pyrolysis temperature has an evident influence on the functional groups evolution. At the stage of the pyrolysis with a temperature lower than 350℃, the increased temperature results in the largest decrease of —COOH content, which is approximately 33%. In the mid-temperature thermal cracking stage (350-550℃), the production of C=C, —OH, —CHO, and π-π^* in pyrolysis product increased significantly, while —COOH show a decreasing trend, but its mass ratio is still the highest. The benzene becomes the main functional groups when the pyrolysis temperature higher than 550℃. In the high temperature pyrolysis stage (>550℃), due to aliphatic hydrocarbon molecules. The chemical activity is enhanced, mainly due to aromatization polycondensation reaction such as dehydration, decarboxylation, decarbonylation and aldol condensation. In the range of pyrolysis temperature study, carbon-carbon double bonds, aldehyde groups and hydroxyl groups content are lower, but show obvious pyrolysis rules. Further, combining the pyrolysis rules of each functional group, the possible path of the pyrolysis evolution of carbon and oxygen-containing functional groups in sludge is proposed.

Key words: sewage sludge, pyrolysis, carbon-containing functional, oxygen-containing functional, Py-GC/MS, reaction pathways

摘要：

基于裂解-气相色谱/质谱联用技术（Py-GC/MS），分析了污泥中主要含碳和含氧官能团在不同温度条件下的热解演变规律和热化学转化路径。结果表明，污泥中主要含碳和含氧官能团为碳碳双键（C=C）、羧基（COOH）、羟基（—OH）、醛基（—CHO）和苯环（π-π^*）。温度对官能团裂解演变的影响较大，低温热解阶段（＜350℃），温度升高导致产物中—COOH含量降幅最大，约降低33%；中温热解阶段（350～550℃），产物中C=C、—OH、—CHO和π-π^*生成量显著增加，而—COOH呈下降趋势，但其所占质量比仍最高；在高温热解阶段（>550℃），由于脂肪烃分子化学活性增强，主要发生以脱水、脱羧、脱羰和羟醛缩合等为主的芳香化缩聚反应，同时由于污泥中的蛋白质、纤维素等大分子热解使得π-π^*成为产物中主要官能团。根据各个官能团热解演变规律，提出了污泥含碳、含氧官能团热解演变反应路径。

关键词: 污泥, 热解, 含碳官能团, 含氧官能团, Py-GC/MS, 反应路径