本文選題：二氧化鈰　切入點(diǎn)：氧空位　出處：《大連理工大學(xué)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：二氧化鈰作為催化劑和催化劑載體,廣泛應(yīng)用于可再生能源生產(chǎn)、環(huán)境污染治理以及精細(xì)化學(xué)品合成等領(lǐng)域。二氧化鈰優(yōu)異的催化性能歸因于其獨(dú)特的氧化還原性和適宜的酸堿性,而這些性質(zhì)通常與其結(jié)構(gòu)中氧空位的性質(zhì)密切相關(guān)。本論文通過形貌選擇合成、控制還原和金屬離子摻雜等方法實現(xiàn)了二氧化鈰中氧空位性質(zhì)的調(diào)變,并探索了缺陷二氧化鈰作為一種多功能催化劑在氧化縮合反應(yīng)以及Prins縮合-水解等串聯(lián)反應(yīng)中的應(yīng)用,系統(tǒng)地研究了氧空位濃度變化對催化劑氧化還原性以及酸堿性的影響,建立了氧空位濃度變化與催化性能之間的關(guān)系。主要研究結(jié)果如下:通過形貌控制,制備出了棒狀、立方體和八面體三種不同形貌的CeO_2催化劑。Raman光譜顯示,這三種形貌的CeO_2上的氧空位濃度不同,其中棒狀CeO_2催化劑上氧空位濃度最高。制備出的二氧化鈰能催化串聯(lián)反應(yīng)苯甲醇與苯胺串聯(lián)氧化縮合制備亞胺類化合物(N-苯亞甲基苯胺)。該反應(yīng)首先需要將苯甲醇氧化為苯甲醛,繼而與苯胺發(fā)生縮合生成產(chǎn)物。反應(yīng)過程中,催化劑的氧空位濃度和氧化還原性至關(guān)重要。二氧化鈰作為一種氧化-堿催化雙功能催化劑,能有效催化苯甲醇與苯乙酮氧化-Aldol縮合制備α,β-不飽和酮(查爾酮)。通過原位屏蔽和動力學(xué)實驗,確證該串聯(lián)反應(yīng)中苯甲醇的氧化發(fā)生在CeO_2的氧化還原位點(diǎn)上,而苯甲醛與苯乙酮之間的Aldol縮合反應(yīng)發(fā)生在CeO_2的堿位點(diǎn)上,其中堿位點(diǎn)上發(fā)生的Aldol縮合是反應(yīng)的決速步。通過Raman光譜和CO_2-TPD表征發(fā)現(xiàn),棒狀CeO_2催化劑上氧空位濃度和堿位點(diǎn)濃度最高,在苯甲醇與苯乙酮的氧化-Aldol縮合反應(yīng)中表現(xiàn)出最佳的催化活性。二氧化鈰還可作為一種氧空位誘導(dǎo)的耐水Lewis酸催化劑,催化異丁烯與HCHO水溶液間的Prins縮合-水解反應(yīng)。通過形貌選擇合成和控制還原溫度,對二氧化鈰氧空位濃度進(jìn)行調(diào)變。通過Raman光譜、NH3-TPD、31P-NMR和吡啶紅外等表征對催化劑氧空位濃度和酸性質(zhì)進(jìn)行表征,發(fā)現(xiàn)二氧化鈰氧空位誘導(dǎo)的酸位點(diǎn)主要為弱的Lewis酸,且二氧化鈰中氧空位濃度越高,催化劑的Lewis酸位點(diǎn)濃度越高,Prins縮合-水解反應(yīng)活性越高。通過Al、Zr、Eu、Pr和La等金屬離子的摻雜,實現(xiàn)了對CeO_2氧空位濃度的調(diào)變。HAADF-TEM、吡啶吸附紅外、Raman光譜表征表明,Pr的摻雜產(chǎn)生了更多的氧空位,使得催化劑Lewis酸濃度增加。Pr高度分散的摻雜CeO_2能高效催化異丁烯與HCHO水溶液之間的Prins縮合-水解反應(yīng)。應(yīng)用DFT對Prins縮合-水解反應(yīng)過程中兩種底物分子的吸附進(jìn)行計算,確證HCHO的吸附活化是該反應(yīng)的關(guān)鍵步驟,Pr的摻雜增強(qiáng)了 HCHO在催化劑表面Ce-O位上的吸附活化。
[Abstract]:As catalyst and catalyst carrier, cerium oxide is widely used in renewable energy production. The excellent catalytic performance of cerium oxide is attributed to its unique redox and suitable acidity and alkalinity. These properties are usually closely related to the properties of oxygen vacancies in the structure. In this paper, the properties of oxygen vacancies in cerium oxide have been adjusted by means of morphology selective synthesis, controlled reduction and doping of metal ions. The applications of defective cerium oxide as a multifunctional catalyst in the oxidative condensation reaction and the series reaction such as Prins condensation and hydrolysis were investigated. The effects of the oxygen vacancy concentration on the redox and acidity and alkalinity of the catalyst were systematically studied. The relationship between oxygen vacancy concentration and catalytic performance was established. The main results are as follows: by controlling the morphology, three kinds of CeO_2 catalysts with different morphologies, such as rod, cube and octahedron, were prepared. The oxygen vacancy concentrations on the three morphologies of CeO_2 are different, The prepared cerium oxide catalyst can catalyze the series reaction of benzyl alcohol and aniline in series to produce imines, N-phenylene methylaniline. Alcohol is oxidized to benzaldehyde, In the process of reaction, the oxygen vacancy concentration and redox activity of the catalyst are very important. Cerium oxide is a bifunctional oxidation-alkali catalyst. 偽, 尾 -unsaturated ketone was prepared by condensation of benzyl alcohol with acetophenone. The in situ shielding and kinetic experiments confirmed that the oxidation of benzyl alcohol occurred at the redox site of CeO_2. The Aldol condensation reaction between benzaldehyde and acetophenone occurs on the base site of CeO_2, in which the Aldol condensation at the base site is the fast step of the reaction. The oxygen vacancy concentration and base site concentration on the rod-like CeO_2 catalyst are the highest, showing the best catalytic activity in the oxide-Aldol condensation reaction of benzyl alcohol with acetophenone. Cerium oxide can also be used as a water-tolerant Lewis acid catalyst induced by oxygen vacancy. Catalytic Prins condensation and hydrolysis between isobutene and HCHO aqueous solution. The oxygen vacancy concentration and acid properties of the catalyst were characterized by Raman spectra, NH _ 3-TPDN _ 3P-NMR and pyridine infrared spectra. It was found that the acid sites induced by cerium oxide oxygen vacancies were mainly weak Lewis acids. The higher the concentration of oxygen vacancy in cerium oxide is, the higher the concentration of Lewis acid sites in the catalyst is. The modulation of oxygen vacancy concentration of CeO_2. HAADF-TEM has been realized. The IR spectra of pyridine adsorption show that more oxygen vacancies are produced by the doping of pr. Doping CeO_2, which makes the concentration of catalyst Lewis acid increase. Pr highly dispersed, can efficiently catalyze the Prins condensation hydrolysis reaction between isobutene and HCHO aqueous solution. The adsorption of two kinds of substrate molecules in the process of Prins condensation and hydrolysis is calculated by DFT. It is confirmed that the adsorption and activation of HCHO is a key step of the reaction. The doping of pr enhances the adsorption and activation of HCHO on the surface of Ce-O on the catalyst surface.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：O643.36;TQ133.3

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本文編號：1579158