本文關(guān)鍵詞：新疆稀土鈣鈦礦應(yīng)用于機(jī)車尾氣凈化的密度泛函理論研究　出處：《新疆大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 稀土 稀土鈣鈦礦LaCoO_3 NO吸附 NO反應(yīng)機(jī)理 密度泛函理論

【摘要】：本文通過調(diào)研大量的文獻(xiàn)資料,收集了新疆地區(qū)主要的稀土產(chǎn)地的地質(zhì)資料及資源量數(shù)據(jù),證實確如文獻(xiàn)所載新疆擁有豐富的稀土資源。被譽(yù)為“工業(yè)維生素”的稀土因其特殊結(jié)構(gòu)延伸出較多的特性,而被廣泛應(yīng)用各個行業(yè),在環(huán)境治理方面它有著許多礦物材料無法媲美的優(yōu)勢。大氣污染問題一直是人們熱切關(guān)心地焦點(diǎn),近年來我國多數(shù)城市出現(xiàn)了大范圍的霧霾天氣。引發(fā)霧霾的原因很大程度上來源于數(shù)量日益增長的機(jī)動車所排放的機(jī)車尾氣構(gòu)成的大氣污染,治理機(jī)車尾氣已然成為了迫在眉睫的任務(wù)。依靠新疆豐富的稀土礦產(chǎn)資源來研究治理大氣污染的稀土鈣鈦礦催化劑不僅是地利,更是滿足當(dāng)前需求的天時。因此本文在考慮到上述亟待解決的問題以及擁有豐富物質(zhì)基礎(chǔ)的現(xiàn)實條件上,以新疆稀土為主要礦物原料制備成的稀土鈣鈦礦為研究對象,以密度泛函理論為核心理論而開發(fā)出來的計算模擬軟件——Materials Studio,為研究工具。首先,在軟件中建立了稀土鈣鈦礦LaCoO_3的晶體模型。隨后,采用軟件調(diào)查計算了它的晶體結(jié)構(gòu)參數(shù)和微觀電子性質(zhì)。在搞清楚了其基本性質(zhì)的基礎(chǔ)上,緊接著設(shè)計了有著“大氣污染中最大毒瘤”稱號的NO吸附在LaCoO_3(0 0 1)面兩種終端上的吸附構(gòu)型并計算了其被吸附在界面上時,受到了LaCoO_3中O、La和Co元素的電子怎樣的影響。最后確定了NO被稀土鈣鈦礦LaCoO_3氧化還原的反應(yīng)路徑,對計算出的結(jié)果進(jìn)行分析以探究NO與界面的反應(yīng)機(jī)理。以期計算的數(shù)據(jù)及分析成果能對制備出用于凈化機(jī)車尾氣的稀土鈣鈦礦催化劑提供一定的理論基礎(chǔ)并預(yù)測一定的實驗指導(dǎo)。主要結(jié)論由如下:(1)采用GGA-PBEsol-DN計算出的LaCoO_3的晶胞參數(shù)為a=5.453?,Co-O=1.933?,與實驗值最為接近,偏差僅為0.2%。能帶結(jié)構(gòu)圖、總態(tài)密度圖和分波態(tài)密度圖顯示出,能量在-6 eV~0 eV上時,LaCoO_3中的Co原子與O原子存在著劇烈的相互作用,反映出Co的3d態(tài)和O的2p態(tài)的共價特性。分析發(fā)現(xiàn)是由于Co原子是位于鈣鈦礦結(jié)構(gòu)中八面體中心上,這樣的結(jié)構(gòu)特點(diǎn)會使Co原子自己的3d電子軌道裂成t2g與eg軌道,其中的eg軌道與O的電子軌道相互作用改變了Co-O鍵的電子密度,致使LaCoO_3中Co-O的成鍵軌道和反鍵軌道受到影響從而引起了Co-O鍵的變化。最后,在能帶圖中最下端的兩部分也發(fā)現(xiàn)了La-5p與O-2s有相互共價作用,但是相對較弱。本章主要計算出了LaCoO_3的晶體結(jié)構(gòu)參數(shù),以及結(jié)構(gòu)中各原子的電子軌道的相互影響狀況。(2)模擬了NO在LaCoO_3的CoO_2和LaO終端的(0 0 1)面的吸附構(gòu)型并運(yùn)用了GGA-PBE的方法計算了NO的吸附性質(zhì)。從計算出的吸附能與Mulliken和Hirshfeid電荷構(gòu)成的數(shù)據(jù)表及各原子的分波態(tài)密度圖中,發(fā)現(xiàn)NO在CoO_2終端面上吸附的穩(wěn)定性強(qiáng)于LaO終端面,并且NO的N原子吸附在LaCoO_3的CoO_2終端的(0 0 1)面的Co上是吸附最穩(wěn)定的形式,并且分波態(tài)密度圖展示出LaCoO_3中原子Co對吸附NO效果極佳,源于Co擁有的3d電子軌道與NO擁有的p電子軌道出現(xiàn)了雜化的現(xiàn)象。綜合所有的結(jié)果來說,NO在LaCoO_3的CoO_2終端(0 0 1)面能被吸附形成多種較為穩(wěn)定的形式,證明LaCoO_3有對NO吸附有較為活躍的貢獻(xiàn)。(3)NO在稀土鈣鈦礦LaCoO_3的CoO_2終端(0 0 1)面上進(jìn)行反應(yīng)的分成兩種形式:其一是氧化的形式,最佳反應(yīng)路徑為O_2→O~*+O~*→NO+O~*→NO_2~*→NO_2+O~*→NO_3~*,影響產(chǎn)物NO_3~*形成速率的關(guān)鍵步驟是O_2的分解,這個步驟的完成需突破的能壘為10.96 eV,較大的能壘直接制約著產(chǎn)物的生成速率和反應(yīng)的進(jìn)行。其二還原的形式,最佳反應(yīng)路徑為NO+NO→NOON~*→N_2O~*→N_2O→O_2+N_2,產(chǎn)物N_2+O_2形成的速率控制步驟是N_2O的形成,這個過程需要克服的能壘分別是0.13 eV、1.27 eV和0.79 e V,這些數(shù)值表示反應(yīng)需要的最低能量相對較小。兩個結(jié)果進(jìn)行對比時發(fā)現(xiàn),NO的氧化需要的最低能量略大于NO還原所需要的最低能量,這意味著NO在LaCoO_3催化劑上反應(yīng)時還原較氧化易進(jìn)行,選擇性上還原強(qiáng)于氧化。
[Abstract]:In this paper, through a large number of research literature, geological data and data collection of the main resources of rare earth origin in Xinjiang, confirmed that the literature contained such as Xinjiang has rich rare earth resources. Known as the "industrial vitamin" rare earth because of its special structure extends more features, and is widely used in various industries, it there are many mineral materials can match the advantages in environmental governance. The air pollution problem has been the focus of concern, in recent years there has been a wide range of haze weather in China. Most of the city air pollution of locomotive vehicle exhaust caused by haze reason is largely due to the growing number of emissions constitute, management of locomotive exhaust has become an imminent task. Rare earth perovskite catalysts rely on Xinjiang's rich rare earth mineral resources on air pollution not only Place, it is meet the needs of the current day. Based on the consideration of the above problems to be solved and has rich material on the basis of the actual conditions, in Xinjiang rare earth rare earth perovskite prepared into main mineral raw materials as the research object, calculated by the density functional theory as the core theory and developed simulation software Materials Studio, as a research tool. First of all, in the software the crystal model of rare earth perovskite LaCoO_3 is established. Then, using the software to investigate its crystal structure parameters and micro electronic properties were calculated. The clear basis of its basic properties, followed by the design of a "cancer" in the title of the air pollution adsorption of NO on LaCoO_3 (001) surface adsorption configuration two terminal and the calculation of the adsorbed on the interface by LaCoO_3, O, La and Co of electronic elements. The how After determining the reaction path of the oxidation of NO rare earth perovskite LaCoO_3 reduction, the reaction mechanism of the calculated results were analyzed to explore the NO and interface. The data and analysis results in order to calculate the prepared for rare earth perovskite catalysts for purification of vehicle tail gas to provide a theoretical basis and experimental guidance. The main prediction the conclusion is as follows: (1) the cell parameters calculated by using GGA-PBEsol-DN LaCoO_3 a=5.453?, Co-O=1.933?, and most close to the experimental value, deviation is only 0.2%. band structure, total density of state and partial density map shows that the energy in the -6 eV~0 eV, LaCoO_3 Co with the O atoms and the interaction exists severe, reflecting the characteristics of the 2p covalent 3D state and O Co. The analysis found that due to the Co atom is located in the center of the perovskite structure with eight sides, so the structure characteristics of the Co atom 3D electronic track their split into t2g and eg orbitals, electron orbit eg orbital and O where the interaction changes the electron density of Co-O bond, resulting in LaCoO_3 Co-O bonding and antibonding orbitals affected to cause changes in the Co-O bond. Finally, in the two part to the bottom in the band diagram the La-5p and O-2s have also found each other but relatively weak covalent interaction. This chapter mainly calculated the crystal structure parameters of LaCoO_3, the mutual influence of electronic and atomic structure in orbit. (2) simulated NO in CoO_2 and LaO terminal of the LaCoO_3 (001) surface configuration and use the method of GGA-PBE adsorption properties of the NO were calculated. The calculated adsorption energy of Mulliken and Hirshfeid and charge the data table and each atom of the PDOS map, found that the stability of NO adsorption on CoO_2 end face is stronger than the LaO and NO terminal. The adsorption of N atoms in the CoO_2 terminal of the LaCoO_3 (001) Co surface is the most stable adsorption form, and partial density of states shows atom Co LaCoO_3 on adsorption of NO effect is excellent, P orbits of 3D orbits and NO derived from Co have appeared with hybrid phenomenon. All the results for NO in the CoO_2 terminal LaCoO_3 (001) surface can be absorbed to form a variety of relatively stable form, have proved that LaCoO_3 adsorption of NO have more active contributions. (3) the CoO_2 terminal NO in rare earth perovskite LaCoO_3 (001) surface reactions were divided into two forms: one is the oxidized forms, the optimum path for the O_2 - O~*+O~* - NO+O~* - NO_2~* - NO_2+O~* - NO_3~*, product NO_3~* is the key step in the formation rate of O_2 decomposition, this step need to break the barrier of 10.96 eV, high energy barrier directly restricts the product Generation rate and reaction. The reduction of the form, the best reaction path for the NO+NO - NOON~* - N_2O~* - N_2O - O_2+N_2, the rate controlling step is the formation of the N_2O product of N_2+O_2 formation, this process needs to overcome the energy barrier are 0.13 eV, 1.27 eV and 0.79 e V, the value that the minimum energy reaction the relatively small. Compared two results, the lowest energy minimum energy of NO oxidation than NO reduction required, which means that the NO reaction on LaCoO_3 catalyst. The oxidation reduction is easy, is stronger than the original selective oxidation.

【學(xué)位授予單位】：新疆大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：X734.2

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 傅太宇;李葆華;董曉燕;許龍;;我國稀土礦床分布、分類及特征分析[J];河南科技;2015年14期

2 錢方兵;王麗;沈建宇;符嬌鸞;吳可永;陳瀟;;納米鈣鈦礦型ABO_x(A=La、Y;B=Mn、Co、Ni)的制備、表征及其對NO+CO的催化活性[J];稀土;2014年03期

3 吳一丁;羅翔;;我國稀土產(chǎn)業(yè)沿價值鏈“逆向”發(fā)展的解析——基于經(jīng)營績效視角[J];江西理工大學(xué)學(xué)報;2014年02期

4 李光燦;王枝梅;施川;康贏利;余旦;余高奇;;LaCoO_3超細(xì)粒子的模板法制備及光催化性能研究[J];稀土;2013年04期

5 張一波;王德強(qiáng);王靜;陳去非;張震東;潘喜強(qiáng);苗珍珍;張彬;武志堅;楊向光;;BiMnO_3鈣鈦石上低溫NH_3選擇性催化還原NO[J];催化學(xué)報;2012年09期

6 夏學(xué)惠;袁家忠;郗國慶;閻飛;韓彬;;塔里木地臺北緣內(nèi)生磷礦預(yù)測及資源遠(yuǎn)景評價[J];化工礦產(chǎn)地質(zhì);2009年03期

7 徐光憲;;強(qiáng)烈呼吁國家建立稀土戰(zhàn)略元素儲備制度[J];中國高新區(qū);2009年08期

8 張永明;劉鐘馨;孫中亮;張武元;張德拉;;稀土鈣鈦礦型過氧化氫分解催化劑研究[J];中國稀土學(xué)報;2007年03期

9 朱洪元;張元;周丹紅;關(guān)靜;包信和;;Mo/MCM-22分子篩碳化鉬活性中心結(jié)構(gòu)及甲烷活化機(jī)理的密度泛函理論研究[J];催化學(xué)報;2007年02期

10 冉銳,吳曉東,翁端;稀土鈣鈦礦催化劑制備方法的研究進(jìn)展[J];稀土;2004年05期

相關(guān)碩士學(xué)位論文 前1條

1 林尚康;西昆侖贊坎鐵礦區(qū)英安斑巖地球化學(xué)特征及U-Pb年代學(xué)研究[D];昆明理工大學(xué);2015年

，

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