Abstract:

The pyrolysis characteristics of oil sand at different heating rate was investigated by using a thermogravimetric analyzer. The results showed that the mass loss of oil sand sample contained four processes: desorption, low temperature pyrolysis, main pyrolysis and char condensation. The evolution order of CO₂, CO, C₂H₆, CH₄ and H₂ was determined via the micro fixed bed reactor coupled with mass spectra analyzer, and the corresponding initial releasing temperature were 155, 178, 146, 174 and 354℃, respectively. The composition and chemical structure parameters of liquid and solid products in different temperature ranges were studied by NMR spectroscopy and IR spectrometry. The results showed that the principle reaction before 350℃ was desorption of light oil, in which the aromatic carbon ratio amounted to 7.92% including the breaking of carboxylic and alkyl side chains. The oil sand pyrolysis process mainly occurred in the temperature range of 350—520℃. The aromatic carbon ratio of the obtained pyrolysis oil was 23.51%. By using Coats-Redfern method, the corresponding activation energy of low temperature pyrolysis and main pyrolysis process were 27.63 and 90.30 kJ·mol^-1, respectively, indicating that the activation energy of ring-opening and cracking reaction was higher than that of desorption of oil sand, decomposition of carboxyl and breaking of the weak bonds.

Key words: oil sand, pyrolysis, gas evolution order, NMR and IR analysis, pyrolysis mechanism

摘要：

在热重分析仪中考察了不同升温速率下油砂的热解特性,结果表明:油砂样品失重过程分为少量气体脱附、低温热解、主要热解、半焦缩聚4个阶段。通过微型固定床与在线质谱耦合测得的气体释放顺序为CO₂、CO、C₂H₆、CH₄和H₂,所对应的初释温度分别为155、178、146、174、354℃。结合核磁和红外对不同温度段液固产物的化学结构进行分析,发现350℃前主要是油砂中轻质油脱附,还包括羧基和烷基侧链的断裂,轻质油品中芳碳率达7.92%;350～520℃之间为油砂的主要热解阶段,油砂油结构中芳碳率为23.51%。据Coats-Redfern法计算得到油砂低温热解和主要热解段的活化能分别为27.63和90.30 kJ·mol^-1,说明开环与裂解反应所需活化能大于油砂油脱附、羧基分解和弱键断裂反应的活化能,揭示了分段热解机理。

关键词: 油砂, 热重分析, 气体逸出顺序, 核磁和红外分析, 热解机理