本文選題：Fe-ZSM-5　切入點(diǎn)：NO　出處：《太原理工大學(xué)》2017年碩士論文

【摘要】：隨著現(xiàn)代工業(yè)的迅速發(fā)展和機(jī)動(dòng)車保有量的日益增加,工業(yè)廢氣和機(jī)動(dòng)車尾氣引起的環(huán)境問題日益嚴(yán)重,由此產(chǎn)生的NOx作為大氣污染的主要成分,其日益增加的排放量人們的正常生活和身心健康都產(chǎn)生的嚴(yán)重的影響,引起的環(huán)境問題也嚴(yán)重阻礙經(jīng)濟(jì)的發(fā)展與人民的生活水平。目前工業(yè)上主要使用V_2O_5-MoO_3/TiO_2和V_2O_5-WO_3/TiO_2催化劑以NH_3為還原劑脫除NOx,但由于V_2O_5容易隨尾氣排放到大氣中,其自身的生物毒性會(huì)威脅生態(tài)系統(tǒng)和人類健康。近年來,由于堿金屬氧化物、過渡金屬氧化物等活性中心分子篩催化劑的不斷開發(fā)和革新,NOx直接分解反應(yīng)的效率得到一定程度的提高并且成本大大降低,加之該技術(shù)工藝過程簡(jiǎn)單,沒有二次污染物的副作用,經(jīng)濟(jì)性好,再次受到研究者的重點(diǎn)關(guān)注�；谏鲜鏊悸�,本文通過密度泛函理論,利用Materials Studio6.0軟件的DMol3模塊,對(duì)18T Fe-ZSM-5簇模型表面兩個(gè)NO分子先后吸附和相應(yīng)的直接分解機(jī)理進(jìn)行研究。得到以下主要結(jié)論:(1)第一個(gè)NO分子在Fe-ZSM-5表面可以形成四種穩(wěn)定的吸附構(gòu)型,均放出熱量,為穩(wěn)定的化學(xué)吸附。穩(wěn)定性順序?yàn)?NO分子N端吸附于Fe位最穩(wěn)定,NO分子的N原子和O原子同時(shí)吸附于Fe-ZSM-5次之,O端吸附于Fe-ZSM-5的穩(wěn)定性最差。其中三種為NO分子在Fe原子的不同吸附方式,而另一種吸附實(shí)質(zhì)上為NO與晶格氧反應(yīng)生成NO_2并吸附于Fe原子。NO分子吸附后均被活化,且吸附反應(yīng)活性與Fe-ZSM-5模型的Fukui函數(shù)預(yù)測(cè)相一致。(2)以第一個(gè)NO分子四種不同穩(wěn)定吸附態(tài)分別作為起始反應(yīng)點(diǎn),第二個(gè)NO分子的吸附為反應(yīng)初始步驟,以N_2O中間產(chǎn)物為關(guān)鍵反應(yīng)中間體,N_2和O_2為目標(biāo)產(chǎn)物,以窮舉法對(duì)可能發(fā)生的催化分解過程進(jìn)行研究,并通過過渡態(tài)搜索和頻率驗(yàn)證分析方法進(jìn)行確認(rèn),得到四種NO在Fe-ZSM-5模型表面直接分解機(jī)理。四種分解機(jī)理均可生成氣態(tài)N_2和O_2,同時(shí)底物Fe-ZSM-5模型在反應(yīng)后恢復(fù)初始狀態(tài)可繼續(xù)進(jìn)行催化,從而完成催化劑的循環(huán)。在得到的四種反應(yīng)路徑中,當(dāng)NO分子N原子和O原子同時(shí)吸附于Fe-ZSM-5后的反應(yīng)路徑能壘最低,且反應(yīng)步驟較少。整個(gè)路徑可描述為NO(g)→NO(ads)→NO(ads)+NO(ads)→OONN(ads)→O_2(ads)+N_2(ads)→O_2(ads)+N_2(g)→O_2(g)+N_2(g),反應(yīng)熱為-43.74 kcal/mol,控速步驟為OONN(ads)的生成即NO(ads)+NO(ads)→OONN(ads),其能壘為25.73kcal/mol。
[Abstract]:With the rapid development of modern industry and the increasing number of motor vehicles, the environmental problems caused by industrial exhaust gas and motor vehicle exhaust gas are becoming more and more serious. The resulting NOx is the main component of air pollution.Its increasing emissions of people's normal life and physical and mental health have a serious impact, resulting in environmental problems also seriously hinder the economic development and people's living standards.At present, V_2O_5-MoO_3/TiO_2 and V_2O_5-WO_3/TiO_2 catalysts are mainly used to remove no _ x with NH_3 as reducing agent in industry. However, because V_2O_5 is easy to be discharged into the atmosphere with tail gas, its own biological toxicity will threaten ecosystem and human health.In recent years, the efficiency of direct decomposition of no _ x has been greatly improved and the cost has been greatly reduced due to the continuous development and innovation of active center molecular sieve catalysts such as alkali metal oxide and transition metal oxide.In addition, the process of this technology is simple, no side effects of secondary pollutants, and good economy.Based on the above idea, the adsorption and direct decomposition mechanism of two no molecules on the surface of 18T Fe-ZSM-5 cluster model were studied by using density functional theory and DMol3 module of Materials Studio6.0 software.The main conclusions are as follows: (1) the first no molecule can form four stable adsorption configurations on the surface of Fe-ZSM-5, all of which give off heat and are chemically stable.The order of stability is as follows: the N and O atoms of N end adsorbed on Fe site and O atom simultaneously adsorbed on Fe-ZSM-5 and then O terminal adsorbed on Fe-ZSM-5 are the least stable.Three of them are different adsorption modes of no molecules at Fe atoms, while the other is that no reacts with lattice oxygen to form NO_2 and then adsorbs on Fe atoms. No molecules are activated after adsorption.The adsorption activity of the first no molecule is consistent with the Fukui function prediction of the Fe-ZSM-5 model, and the four different stable adsorption states of the first no molecule are taken as the starting reaction points respectively, and the adsorption of the second no molecule is the initial step of the reaction.Taking the intermediate products of Ns _ 2O as the key reaction intermediates, N _ S _ 2 and O _ s _ 2 as the target products, the possible catalytic decomposition process was studied by exhaustive method, and confirmed by transition state search and frequency verification analysis.The direct decomposition mechanism of four kinds of no on the surface of Fe-ZSM-5 model was obtained.All four decomposition mechanisms can produce gaseous Ns _ 2 and O _ 2s, while the substrate Fe-ZSM-5 model can continue to catalyze after the initial state is restored, thus completing the cycle of the catalyst.Among the four reaction pathways obtained, the lowest barrier of the reaction path was obtained when N and O atoms were adsorbed on Fe-ZSM-5 simultaneously, and the reaction steps were less.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：X701;O643.3

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