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采用基于密度泛函的紧束缚模型（DFTB）和改进的反作用力场（ReaxFF）对全氟己酮的热分解机理进行反应分子动力学仿真研究,分析了热分解的初始反应路径、微观反应过程以及体系内气体的生成机理,探讨了温度对全氟己酮热分解的影响,建立了以仿真数据为基础的一级动力学方程并对热分解过程进行一级动力学评估。结果表明,全氟己酮热分解的起始反应为：全氟己酮→全氟异戊烷+一氧化碳,全氟己酮热分解的主要产物为一氧化碳、四氟甲烷、六氟丙烯、全氟异丁烯、十氟丁烷、全氟异戊烷及大量活性基团。经一级动力学评估得到指前因子和表观活化能分别为5.021 7×1014 s-1和1 771.96 kJ/mol。 相似文献
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《International Journal of Hydrogen Energy》2023,48(41):15695-15708
The attenuation of soot formation from polycyclic aromatic hydrocarbons during the fuel combustion process is important to human health and environmental pollution. This work studies the mechanism of inhibition soot formation process under electric field. The process of soot formation with the chemical bonding and physical stacking of PAHs nucleation was investigated under the influence of electric field by using ReaxFF molecular dynamics and density functional theory. MD simulation reveals that the electric field in 1 × 10−5–1 × 10−4 V/Å induces an alternation in dispersion and stacking of PAH cluster to inhibit the PAH nucleation. The electric field inhibits the dehydrogenation and C–C bond cracking of the initial PAH during chemical growth of PAHs. Due to instability of the 5–7 membered rings, there are fewer bonding sites for large graphite lamella growth. The elucidation of reaction enthalpy of dehydrogenation, dimer growth, and the binding energy of π-π stacking with different direction field, are explored using DFT. The computational work discloses the inhibition mechanism of electric field on PAH development. The characterization results obtained by scanning electron microscopy and the temperature-programmed oxidation shows the coke content and particle size can be reduced under the influence of electric field which validates the computational result. The scientific insights gained here is useful for understanding soot inhabitation phenomenon. 相似文献
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《International Journal of Hydrogen Energy》2020,45(56):32423-32432
Carbon deposition occurs when Dimethyl ether (DME) fuel is used for SOFC, leading to battery degradation. In order to study the effect of water addition on carbon deposition, this work used reactive force field molecular dynamics (Reaxff MD) to simulate the process of carbon deposition with or without water addition, and analyze its anti-carbon deposition mechanism on nickel-based anode.It is found that the number of carbon atoms on nickel can be effectively reduced by mixing water with fuel. As the H2O/DME ratio increases, there are fewer carbon atoms on the nickel anode. And there are two main ways for water molecules to resist carbon deposition. First is that the OH group generated by decomposition of water molecules at high temperature reacts with CH component to form aldehyde group, which reduces the formation of carbon deposition precursor. The other is that the increase of water molecules introduces more oxygen atoms into the system, and the carbon atoms formed by DME molecules combine with oxygen atoms to form CO, thus reducing carbon deposition. This study is helpful to promote the industrialization of DME as SOFC fuel. 相似文献
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《International Journal of Hydrogen Energy》2021,46(78):38854-38870
The pyrolysis and combustion mechanism of the hydrocarbon fuel has important scientific and practical significance. However, it is difficult to detect the whole intermediates and products using traditional methods, which brings trouble to the analysis of the reaction process. In this paper, the microscopic reaction mechanism and the main products of n-eicosane (C20H42) were simulated based on the reactive force field molecular dynamics (ReaxFF-MD). The effects of temperature (2000–3500 K) and oxygen on the initial decomposition, the distribution of main products, and the reactive pathways of C20H42 fuel were studied to determine its reaction mechanism. The initial decomposition of C20H42 was mainly initiated by small alkyl radicals in pyrolysis, and by the oxygen-containing radicals in combustion. The participation of oxygen had a greater effect on accelerating the decomposition reaction. The reactions involving oxygen of C20H42 initial decomposition accounted for 87.5% of the total reactions at 2000 K. Moreover, the detailed distribution and formation pathways of the main products of H2, C2H4, CH4, H2O, CO, and CO2 were depicted to construct the overall reaction mechanism of C20H42. •H radical formed from the composition of C2H4 was exactly consistent with the •H radical consumed by the generation of CH4 and H2 in the pyrolysis stage. The feasibility of the simulation method was verified by the result of thermal analysis. The results are helpful for further research on the reaction mechanism of hydrocarbon fuels. 相似文献
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采用ReaxFF动力学方法模拟了非交联固化单环苯并噁嗪树脂在不同温度下的热解特性。模拟结果表明,N桥键的断裂是热解的主要引发反应,H_2,H_2O和大分子碳团簇是热解的主要产物。随着反应温度升高,H_2的数量急剧增加,而H_2O的数量反而降低,高温有利于促进相对分子质量较大的碳团簇的形成,还观察到了CO,NH_3,N_2和HCN等小分子产物。用ReaxFF动力学方法模拟所得的气体产物以及含类似石墨烯结构的碳团簇与实际实验结果一致,ReaxFF动力学模拟方法可以作为一种研究苯并噁嗪树脂高温热解反应的有效途径。 相似文献
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采用ReaxFF反应分子动力学模拟添加不同膨胀阻燃体系的聚丙烯（PP）的热解过程,从分子水平探究嵌段共聚物（PAPO-MP）与共混（PAPP/MPP）2种状态下阻燃体系的热解反应机制。结果表明,模拟热重曲线与实验结果误差低于2.1%;加入膨胀阻燃体系后,反应活化能从200.16kJ/mol分别降至154.64kJ/mol(PAPO-MP)和159.14 kJ/mol(PAPP/MPP),说明阻燃剂优先反应从而保护基材;气体小分子数量分别减少10%(PAPO-MP)和17.5%(PAPP/MPP),P—O—P结构可以促进大分子团聚物生成,从而降低有毒有害气体生成及提高残炭质量;添加PAPO-MP比添加PAPP/MPP的体系势能平均降低11.6×103 kcal/mol,因此添加嵌段共聚物材料稳定性更优。 相似文献
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Yinbin Wang Senjun Yao Wei Wang Chenglong Qiu Jing Zhang Shengwei Deng Hong Dong Chuan Wu Jianguo Wang 《中国化学工程学报》2021,29(3):94-102
Styrene-butadiene rubber (SBR) is widely used in tires in the automotive segment and vulcanization using sulfur is a common process to enhance its mechanical properties. However, the addition of sulfur as the cross-linking agent usually results in impurities in pyrolysis products during rubber recycling, and thus the desulfurization during tire pyrolysis attracts much attention. In this work, the pyrolysis of vulcanized SBR is studied in detail with the help of ReaxFF molecular dynamics simulation. A series of crosslinked SBR models were built with different sulfur contents and densities. The following ReaxFF MD simulations were performed to show products distributions at different pyrolysis conditions. The simulation results show that sulfur products distribution is mainly controlled by sulfur contents and temperatures. The reaction mechanism is proposed based on the analysis of sulfur products conversion pathway, where most sulfur atoms are bonded with hydrocarbon radicals and the rest transfer to H2S. High sulfur contents tend to the formation of elemental sulfur intermediate, and temperature increase facilitates the release of H2S. 相似文献
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ReaxFF反应力场在冲击起爆、爆轰等问题中的应用多围绕常规含能材料。利用增加了长程修正项Elg的ReaxFF/lg反应力场对梯恩梯/萘（TNT/C10H8）共晶初始高温热分解进行模拟,并通过TNT单晶比较了C10H8对共晶整体反应特征的影响,利用指数函数及反应速率方程拟合得到共晶初级吸热反应和次级放热反应的活化能分别为35.7 kcal/mol和56.1 kcal/mol. 初级吸热反应的活化能与TNT单晶基本相同,而次级放热反应的活化能则远远高于TNT单晶,并且同温度条件下共晶次级反应放热量小于TNT单晶。拟合得到的反应物的衰减速率表明,C10H8的加入将抑制共晶内TNT的分解。产物识别分析显示初始产物为NO2、NO和HONO,并且通过NO2和TNT—NO2,NO和TNT—NO,HONO和TNT—HONO分布数量的比较论证了固相共晶和TNT单晶的初始反应路径为双分子反应机制。共晶热分解最终主要产物为N2,H2O,CO2和CO. 并且由于共晶内C10H8分子C—C键断裂所需的能量高于C—H键断裂所需的能量,C10H8分子的初始热分解路径为C—H键断裂,并且形成的H原子将促进共晶内H2O的产率高于TNT单晶内H2O的产率。 相似文献
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Dandan Jiang Yan Wang Ming Zhang Jinli Zhang Wei Li You Han 《International Journal of Hydrogen Energy》2017,42(15):9667-9678
The degradation mechanism of benzo[a]pyrene (BaP), a representative component of coking wastewater, and the pathway for the production of H2 and CO in supercritical water have been investigated via ReaxFF reactive molecular dynamics simulations. The BaP molecules in the SCWG, SCWPO and SCWO systems show different degradation pathways. The maximum H2 yield is obtained at the oxygen ratio of 0.2. There are three routes for the generation of H2 molecules and production from H radical-rich water is the main route. CO molecules are formed by the CC bond breakage and CO bond breakage in the reforming fragments. There is a time delay between the fuel gas generation reaction and the side reactions due to the change of the instantaneous concentrations of H2 and CO, providing a possible pathway to increase the amount of the produced fuel gases by designing a suitable reactor and recovering the gas fuel in time. Finally, kinetic behaviors of coking wastewater have been analyzed. 相似文献