本文關(guān)鍵詞： CO氧化 銅錳氧化物 釩 摻雜 OMS-2　出處：《河南師范大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

【摘要】：CO催化氧化是一個(gè)在室內(nèi)空氣凈化、氣體傳感器、CO_2激光器、汽車尾氣處理等方面有著廣泛應(yīng)用的重要反應(yīng)。盡管人們一直致力于CO催化氧化的貴金屬催化劑如:Au/TiO_2、Au/ZrO_2、Pt/SnO_2等的研究、但探索活性高、穩(wěn)定性好、成本低的非貴過渡金屬氧化物催化劑仍具有重要價(jià)值。本論文主要研究CuMnO_x和VMnO_x微納米結(jié)構(gòu)的制備、表征及其在CO催化氧化反應(yīng)中的性能,論文可分為三大部分。第一部分,以混合草酸鹽為前驅(qū)體采用一鍋熱解法合成了一系列銅錳氧化物催化劑,借助X射線衍射(XRD)、N_2物理吸附、掃描電子顯微鏡(SEM)、X射線光電子能譜(XPS)和程序升溫還原(TPR)等手段對(duì)催化劑進(jìn)行了表征,并探究了其在CO氧化反應(yīng)中的催化性能。為了進(jìn)一步改善銅錳氧化物的催化性能,我們還探討了老化時(shí)間、焙燒溫度等對(duì)其結(jié)構(gòu)、組成以及催化氧化CO性能的影響。實(shí)驗(yàn)結(jié)果表明,采用一鍋熱法制備的CuMnO_x催化劑能夠獲得較單一的尖晶石CuMn_2O_4相,且具有較大的比表面積和孔體積,能夠?yàn)榇呋疌O氧化反應(yīng)提供更多的Cu-O-Mn界面,故催化劑活性較高。提高焙燒溫度能提高CuMn_2O_4的結(jié)晶度,但是會(huì)相應(yīng)地降低CuMn_2O_4的比表面積和孔體積,使得暴露的Cu-O-Mn界面減少,從而導(dǎo)致CO氧化反應(yīng)活性降低。第二部分,采用三種不同方法合成了OMS-2,并通過浸漬法負(fù)載銅制備CuO/OMS-2催化劑,借助XRD、N_2物理吸附、XPS、TPR等表征方法探討了催化劑結(jié)構(gòu)與性能關(guān)系。實(shí)驗(yàn)結(jié)果表明,采用研磨法制備OMS-2比表面積大、能形成大量的吸附位,使得負(fù)載的氧化銅以高分散形式存在,能夠?yàn)镃O氧化反應(yīng)的進(jìn)行提高更多的Cu-O-Mn界面,故催化活性較高。而采用回流法和水熱法制備的OMS-2為針狀或纖維狀形貌、比表面積小,導(dǎo)致OMS-2表面存在大量聚集態(tài)氧化銅,所能獲得Cu-O-Mn界面大大減少,故催化活性顯著降低。第三部分,采用回流法制備了一系列不同釩源和不同釩錳比的V-OMS-2催化劑,詳細(xì)考察其在CO催化氧化反應(yīng)中的催化性能,并借助XRD、N_2物理吸附、Raman、XPS、TPR等譜學(xué)方法對(duì)催化劑進(jìn)行了表征。實(shí)驗(yàn)結(jié)果表明,以V_2O_5為釩源制備的V-OMS-2-O為納米棒狀結(jié)構(gòu)、比表面積大,而其它兩種釩源制備的樣品比表面積較小。另外,以V_2O_5為釩源制備的V-OMS-2-O表面晶格氧的活潑性和反應(yīng)性也明顯強(qiáng)于其它兩種釩源制備的催化劑,這使得V-OMS-2-V-O表現(xiàn)出更高的催化活性。摻雜少量的V(3%)能夠大幅度提高OMS-2的比表面積,且摻雜的V均以+5價(jià)離子形式替代Mn~(4+)進(jìn)入OMS-2的骨架結(jié)構(gòu)中,顯著改變了錳氧八面體位周圍O的配位環(huán)境,增加了表面晶格氧的活潑性和反應(yīng)性,因而能夠明顯改善OMS-2在CO氧化反應(yīng)中的催化活性。當(dāng)V摻雜量為3%時(shí),V-OMS-2-O的催化活性最高,100%CO轉(zhuǎn)化時(shí)反應(yīng)溫度降至50℃左右。過量的釩(6%)將導(dǎo)致OMS-2的孔道結(jié)構(gòu)破壞,釩在錳氧化物表面富積,嚴(yán)重影響錳氧化物表面晶格氧的活潑性和反應(yīng)性,導(dǎo)致催化劑活性降低。
[Abstract]:Co catalytic oxidation is a CO _ 2 laser with a gas sensor for indoor air purification. Automobile tail gas treatment has been widely used in many important reactions, although people have been dedicated to CO catalytic oxidation of noble metal catalysts such as: Au/ TiO2 / Au/ ZrO2. Pt/SnO_2 et al., but the exploration activity is high and the stability is good. Low-cost non-expensive transition metal oxide catalysts are still of great value. In this thesis, the preparation of CuMnO_x and VMnO_x microstructures is studied. In the first part, a series of copper-manganese oxide catalysts were synthesized by one-pot pyrolysis with mixed oxalate as precursor. Physical adsorption of N2 by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The catalysts were characterized by X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). In order to further improve the catalytic performance of Cu-Mn oxide, we also discussed the aging time, calcination temperature and so on. The experimental results show that the single spinel CuMn_2O_4 phase can be obtained from the CuMnO_x catalyst prepared by one-pot thermal method. And it has a large specific surface area and pore volume, which can provide more Cu-O-Mn interface for the catalytic CO oxidation reaction. Therefore, the activity of the catalyst is high. The crystallinity of CuMn_2O_4 can be increased by increasing the calcination temperature, but the specific surface area and pore volume of CuMn_2O_4 will be reduced accordingly. The exposed Cu-O-Mn interface was reduced, which resulted in the decrease of CO oxidation activity. In the second part, three different methods were used to synthesize OMS-2. The CuO/OMS-2 catalyst was prepared by impregnation method supported on copper. TPR and other characterization methods were used to investigate the relationship between the structure and performance of the catalyst. The experimental results showed that the preparation of OMS-2 by grinding method had large specific surface area and formed a large number of adsorption sites. The supported copper oxide exists in the form of high dispersion, which can improve the Cu-O-Mn interface for CO oxidation. Therefore, the catalytic activity is higher. However, the OMS-2 prepared by reflux method and hydrothermal method is acicular or fibrous, and the specific surface area is small, resulting in a large number of aggregate copper oxide on the surface of OMS-2. In the third part, a series of V-OMS-2 catalysts with different vanadium sources and different vanadium / manganese ratios were prepared by reflux method. Its catalytic performance in CO catalytic oxidation reaction was investigated in detail, and Raman XPS was obtained by means of XRDX / N2 physical adsorption. The catalyst was characterized by TPR and the experimental results showed that V-OMS-2-O with V _ S _ 2O _ 5 as vanadium source had a large specific surface area. However, the specific surface area of the samples prepared by the other two vanadium sources is smaller. The surface lattice oxygen activity and reactivity of V-OMS-2-O prepared by V _ 2O _ 5 as vanadium source were also stronger than those of the other two kinds of vanadium catalysts. This makes V-OMS-2-V-O exhibit higher catalytic activity. Doping a small amount of V _ (3) can greatly improve the specific surface area of OMS-2. Moreover, the doped V was substituted for Mn~(4 in the form of 5 valence ions, which changed the coordination environment of O around the octahedron of MNO. The activity and reactivity of surface lattice oxygen were increased, and the catalytic activity of OMS-2 in CO oxidation reaction was improved obviously when the amount of V doping was 3. The maximum catalytic activity of V-OMS-2-O is about 50 鈩，

本文編號(hào)：1442780