Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Phys Chem Chem Phys. 2019 Jan 2;21(2):813-832. doi: 10.1039/c8cp06097e.
With the rise in production of natural gas, there is increased interest in homogeneous partial oxidation (POX) to convert methane to syngas (CO + H2), ethene (C2H4) and acetylene (C2H2). In POX, polycyclic aromatic hydrocarbons (PAH) are important undesired byproducts. To improve the productivity of such POX processes, it is necessary to have an accurate chemical mechanism for methane-rich combustion including PAH. A new mechanism was created to capture the chemistry from C0 to C12, incorporating new information derived from recent quantum chemistry calculations, with help from the Reaction Mechanism Generator (RMG) software. For better estimation of kinetics and thermochemistry of aromatic species, including reactions through carbene intermediates, new reaction families and additional data from quantum chemistry calculations were added to RMG-database. Many of the rate coefficients in the new mechanism are significantly pressure-dependent at POX conditions. The new mechanism was validated against electron-ionization molecular beam mass spectrometry (EI-MBMS) data from a high-temperature flow reactor reported by Kohler et al. In this work quantification of additional species from those experiments is reported including phenylacetylene (C8H6), indene (C9H8), naphthalene (C10H8) and acenaphthylene (C12H8) at many temperatures for several feed compositions. Comparison of the experimental species concentration data and the new kinetic model is satisfactory; the new mechanism is generally more accurate than other published mechanisms. Moreover, because the new mechanism is composed of elementary chemical reaction steps instead of global fitted kinetics, pathway analysis of species could be investigated step-by-step to understand PAH formation. For methane-rich combustion, the most important routes to key aromatics are propargyl recombination for benzene, reactions of the propargyl radical with the phenyl radical for indene, and hydrogen abstraction acetylene addition (HACA) for naphthalene.
随着天然气产量的增加，人们对甲烷的均相部分氧化（POX）产生了浓厚的兴趣，以期将其转化为合成气（CO+H2）、乙烯（C2H4）和乙炔（C2H2）。在 POX 中，多环芳烃（PAH）是重要的不期望的副产物。为了提高此类 POX 工艺的生产力，有必要建立一个包含 PAH 的富甲烷燃烧的准确化学反应机理。新机制是为了捕捉从 C0 到 C12 的化学变化，将最近量子化学计算得出的新信息融入其中，并借助反应机理生成器（RMG）软件的帮助。为了更好地估计芳香族物质的动力学和热化学，包括通过卡宾中间体的反应，RMG 数据库中增加了新的反应族和来自量子化学计算的数据。新机制中的许多速率系数在 POX 条件下对压力有很大的依赖性。该新机制是通过与 Kohler 等人在高温流动反应器中进行的电子离子化分子束质谱（EI-MBMS）数据进行验证的。在这项工作中，报告了来自那些实验的其他物种的定量结果，包括苯乙炔（C8H6）、茚（C9H8）、萘（C10H8）和苊烯（C12H8）在多种温度下和几种进料组成下的浓度数据。实验物种浓度数据与新动力学模型的比较是令人满意的；新机制通常比其他已发表的机制更准确。此外，由于新机制由基本的化学反应步骤组成，而不是全局拟合的动力学，因此可以逐步进行物种的途径分析，以了解 PAH 的形成。对于富甲烷燃烧，关键芳香族化合物的最重要途径是苯的丙炔基重组，茚的丙炔基自由基与苯基自由基的反应，以及萘的氢提取乙炔加成（HACA）。
