本文選題：RP-3　切入點：生物油　出處：《中國科學院大學(中國科學院過程工程研究所)》2017年博士論文　論文類型：學位論文

【摘要】：生物油高溫氧化微觀機制的研究對于生物油的合理利用至關重要。由于生物油組成復雜,且其燃燒過程的溫度較高,目前缺乏對其燃燒中間產(chǎn)物的檢測方式。量子力學方法是研究燃燒過程時的一種常用理論方法。能對熱力學參數(shù)進行準確的計算,同時與恰當?shù)姆磻俾世碚摻Y合能得到燃燒的動力學性質。但因考慮電子相關,其計算成本高昂,可計算的體系規(guī)模在～100原子數(shù)量級,難以對復雜的生物油體系進行進行較為全面的描述。同時量子化學方法研究化學反應微觀機制通常需要對反應路徑進行預設,這對于復雜的生物油體系而言是一項困難的任務。ReaxFF是一種基于鍵級的反應分子力場,其與分子動力學結合的ReaxFF MD方法是一種可以對較大體系的化學反應進行描述的方法。該方法在每個模擬時間步用電負性平衡方法更新每個原子上的電荷,較好地考慮了極化作用;可以較好地重現(xiàn)密度泛函方法計算得出的反應勢能面。需要特別指出的是,ReaxFFMD方法是一種反應勢驅動的方法,無需預設反應路徑,這是其應用于復雜體系微觀化學反應機制研究的重要優(yōu)勢。ReaxFF MD已被應用于研究復雜體系的熱解、燃燒、爆炸、催化過程,并取得了一定的成果,對研究生物油這類復雜體系的化學反應具有一定潛力,也為研究生物油高溫氧化微觀機制提供了一種新的思路。本論文致力于探索利用ReaxFFMD模擬研究生物油高溫氧化反應機理的方法。為了摸索ReaxFF MD對復雜體系燃燒的模擬策略,作者對理論相對成熟的航空燃油RP-3替代燃料模型的高溫氧化過程進行了研究。作者在本論文中使用所在課題組自行研發(fā)的VARxMD分析工具對RP-3高溫氧化模擬過程中的反應物(燃料分子和02)主要產(chǎn)物(C2H4)和自由基(·CH3)隨溫度和時間的演化信息,并系統(tǒng)地對該過程中的化學反應進行了分析。ReaxFF MD模擬獲得的上述物種隨時間的演變在數(shù)量上與同樣條件下CHEMKIN模擬的結果處于同一數(shù)量級。VARxMD分析還獲得了詳細的物種結構信息和化學反應列表,進一步觀察模擬得到的反應路徑發(fā)現(xiàn)其形式和文獻的描述一致。通過統(tǒng)計燃料分子的第一個反應發(fā)現(xiàn),其反應類型主要分為分子內斷裂反應以及攫氫反應,且前者占主導;不同類型燃料分子引發(fā)反應的數(shù)量統(tǒng)計也定性展現(xiàn)了模擬條件下反應發(fā)生的難易程度。本論文對氧元素相關的反應進行了分析,發(fā)現(xiàn)氧分子主要與C1-C3分子發(fā)生反應,這可為簡化機理提供一定依據(jù)�；诜磻獧C理分析獲得了 RP-3四組分替代燃料模型高溫氧化過程中主要組分正癸烷的初始的化學反應網(wǎng)絡。本文構建了一個24組分生物油模型,并對其高溫氧化過程進行了 ReaxFFMD模擬研究。得到了燃料分子、氧分子、包括自由基在內的生物油高溫氧化初期的主要產(chǎn)物隨時間和溫度的演化趨勢。模擬得到的主要產(chǎn)物與文獻報道相符。獲得的燃料分子消耗動力學模型能夠預測長時間模擬的燃料消耗情況。揭示了生物油中5個代表性組分的初始反應網(wǎng)絡。生物油的氧化由攫氫反應或者均裂反應引發(fā),鏈傳播反應包括分子內氫轉移、攫氫反應和β斷裂反應。不飽和C—C鍵的氧化、苯酚自由基的縮環(huán)反應以及脫羰反應在該體系中較為常見。工作中觀察到的反應路徑與文獻較為符合。本文參考24組分生物油模型的化學種類以及比例和官能團數(shù)量信息,構建了 5個6組分生物油替代燃料模型。并用ReaxFF MD方法對所構建的替代模型和24組分模型進行了相同條件下的高溫氧化模擬。通過比較模型的元素組成,特別是對模擬替代模型和與24組分模型獲得的主要反應物和包括自由基的產(chǎn)物進行比較,對每個替代燃料模型進行了評價。分析發(fā)現(xiàn)5個替代燃料模型的元素比與24組分模型均較為接近。比較ReaxFF MD模擬的結果發(fā)現(xiàn),3號模型能較好的預測燃料和氧氣分子的演化趨勢;4號模型能較好地重現(xiàn)CH2O、C2H2O和·CH3的演化;2號模型能較好的重現(xiàn)CO的演化;5號模型能較好地重現(xiàn)H20的演化。本論文構建的24組分生物油模型對真實生物油的組成和化學結構多樣性有更好的表達。對RP-3的4組分替代模型和一個24組分生物油模型的高溫氧化過程進行ReaxFF MD模擬所獲得的結果展示了 一個用ReaxFF MD結合VARxMD分析研究生物油和航空燃油高溫氧化反應路徑的方法。利用ReaxFF MD模擬、以24組分生物油模型作為基準對所構建的生物油替代組分模型進行評價的方法也是一個新的嘗試。
[Abstract]:Study on high temperature oxidation mechanism of bio oil for the rational use of essential oil. The bio bio oil composition is complex, and the higher temperature of the combustion process, the lack of detection of the combustion intermediate product. Quantum mechanics method is a commonly used method of theory research on combustion process. The ability of accurate calculation of thermodynamic parameters at the same time, combined with the reaction rate theory can get appropriate dynamic properties of combustion. But because of considering the electron correlation, the computational cost is high, the scale can be calculated in the system to 100 atomic level, it is difficult for the bio oil system complex are comprehensively described. At the same time quantum chemical methods to study chemical reaction mechanism is usually the need for the reaction path selection, which for the bio oil complex system is a difficult task in.ReaxFF is a key level based on reaction Sub field, ReaxFF MD method combined with the molecular dynamics method is described for a large system of chemical reaction. The method in each simulation time step update charge on each atom with electronegativity balance method, better consider the polarization effect; reaction energy can well reproduce the density functional method the calculated surface. In particular, the ReaxFFMD method is the driving force of a reaction, there is no need to set the reaction path, this is an important advantage of.ReaxFF MD pyrolysis, it was applied to study the complex system of the micro chemical reaction mechanism has been applied to study the complex system of combustion, explosion, and catalytic process. Some results of this kind of complex chemical reaction system of bio oil has a certain potential, but also provides a new way for the research of bio oil oxidation mechanism. The paper induced Methods to explore the use of ReaxFFMD simulation on the reaction mechanism of bio oil oxidation. In order to explore the ReaxFF MD on the simulation strategy of complex system of combustion, high temperature oxidation process of aviation fuel RP-3 theory is relatively mature alternative fuel model is studied. The author's research group used a self-developed VARxMD analysis tool to simulate the reaction process the oxidation of RP-3 in this paper (fuel molecules and 02) main products (C2H4) and free radical (- CH3) evolution with temperature and time, and the system of chemical reaction in the process was analyzed by.ReaxFF MD simulation of the species obtained with the simulation of CHEMKIN and under the same conditions of time the evolution in the number of the results in the analysis of the same magnitude.VARxMD also obtained the species structure information and a detailed list of chemical reactions, the reaction path simulation for further observation The size form and literature described above. Through the first reaction of fuel molecules found in statistics, the reaction types are divided into intramolecular cleavage reactions and hydrogen abstraction reaction, and the former is dominant; counting the number of different types of fuel molecule reactions also shows the difficulty of qualitative reaction under simulated conditions. This the response to oxygen was analyzed, found mainly oxygen molecules react with C1-C3 molecules, which can provide a certain basis for the simplification of the mechanism. The reaction mechanism analysis of chemical reaction network RP-3 four component model of high temperature oxidation of alternative fuels in the process of the main points based on the initial set of n-decane. This paper constructs a the 24 component of bio oil model, and the high temperature oxidation process are studied using ReaxFFMD simulation. The fuel molecules, molecular oxygen, bio oil oxidation, including free radicals The main product of the early evolution trend with time and temperature. The main products are simulated with the reported consistent fuel consumption. The consumption of molecular kinetic model is able to predict long time simulation of fuel. Reveals the bio oil from 5 representative components of the initial reaction network. The oxidation of bio oil by hydrogen abstraction reaction or homolytic reaction initiation, chain propagation reaction including intramolecular hydrogen transfer, hydrogen abstraction reaction and beta scission reaction. Oxidation of unsaturated C - C bond, ring contraction reaction of phenol radical and decarbonylation reaction in this system is more common. The reaction path and observed in the literature work is consistent with this paper. The 24 component of bio oil model chemical species and the proportion and the number of functional groups, constructed 5 6 components of bio oil alternative fuel model. Using ReaxFF MD method to replace the built model and 24 component model. The high temperature oxidation under the same conditions. By comparing the simulation model of elements, especially the comparison of the main reaction products of simulation model and 24 component replacement model and include free radicals, for each alternative fuel model was evaluated. The analysis found 5 alternative fuel elements than the model with 24 component models are more close to the ReaxFF MD. The simulation results show that 3 models can better predict the evolution trend of fuel and oxygen molecules; 4 model can reproduce the evolution of CH2O, C2H2O and CH3; 2 of the CO model can evolve better; the evolution of 5 model to reproduce the H20. This paper constructs 24 component model of bio oil composition has better chemical structure and diversity of the true expression of bio oil. The RP-3 4 component substitution model and a 24 component of bio oil model of high temperature oxidation process The ReaxFF MD simulation results show that a ReaxFF MD combined with VARxMD analysis of bio oil and aviation fuel oxidation reaction path. By using ReaxFF MD simulation method, as the base of bio oil substitute group constructed model to evaluate 24 components of bio oil model is a new try.

【學位授予單位】：中國科學院大學(中國科學院過程工程研究所)
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TE667

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