煤快速裂解过程脂肪烃的组成及生成机制

Aliphatic Hydrocarbons from Fast Pyrolysis of Coal and Its Forming Mechanism

研究煤快速裂解过程脂肪烃的组成与生成行为是优化煤炭分级热解气化工艺的关键。本研究借助快速裂解仪联用气相色谱-飞行时间质谱考察了一种淄博烟煤的快速裂解行为,深入分析了裂解产物脂肪烃的组成,进而依据实验结果推测了产物生成机理。结果显示快速裂解过程共有60种脂肪烃类化合物生成,主要包括直链烷烃、支链烷烃、直链烯烃、支链烯烃以及少量环烷烃、取代环烷烃、环烯烃以及二烯烃和炔烃。脂肪烃类碳数分布于C_3-C_(16)之间,并且主要以C_(10)以下为主。由于快速裂解的热流密度较大,使得煤中芳环外侧链同时发生多处断键反应。裂解一次产物进一步发生取代、加成和环化等二次反应是裂解产物中低碳烯烃、支链和环烷烃类生成的主要原因。此外,C_(13)脂肪烃含量较高表明原煤中含有大量26个碳的烷基侧链。

Investigation on the aliphatic species and its form mechanism during fast pyrolysis process is of great important for optimizing cascade of pyrolysis and gasification process to produce aliphatic-rich gaseous products. The work conducted a fast pyrolysis experiment of a bituminous coal on a fast pyrolyzer coupled with on-line gas chromatography-time of flight mass spectrometer. The aliphatic species in pyrolysate were deeply analyzed and the probable mechanism was speculated. The results showed that sixty kinds of aliphatic species were identified and they were mainly normal alkanes, branched alkanes, normal alkenes, and branched alkenes. These aliphatic species distributed from C3 to C16 and aliphatic species with carbon numbers less than ten were the most abundant. Due to high heat density on the coal sample during fast pyrolysis process, cracking of alkyl side chains outside aromatic clusters in coal occurred at several different place simultaneously. Furthermore, there existed a great number of C13 aliphatic species indicating that C26alkyl side chains in coal were abundant.