本文關(guān)鍵詞：錳基氧化物制備及其選擇催化氧化氨性能研究　出處：《大連理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 錳基催化劑 NH_3-SCO 尿素 沉淀法

【摘要】：氨氣(ammonia, NH3)是一種典型的有毒工業(yè)廢氣,會(huì)對(duì)人體健康和生態(tài)環(huán)境產(chǎn)生嚴(yán)重的危害。因此,近年來對(duì)氨的控制和治理引起了人們的廣泛關(guān)注。目前存在的氨處理技術(shù)有很多,選擇性催化氧化法因其高效、快捷、無二次污染等特點(diǎn),成為了消除含氨廢氣的首選。貴金屬催化劑雖表現(xiàn)出良好的低溫活性,但價(jià)格昂貴、N2選擇性低；過渡金屬催化劑雖價(jià)格低廉,有很好的N2選擇性,但完全轉(zhuǎn)化溫度高,耗能大,不利于工業(yè)應(yīng)用。本論文通過采用不同合成方法制備錳基氧化物催化劑并測(cè)試其氨氧化活性,并通過考察催化劑結(jié)構(gòu)性質(zhì),研究結(jié)構(gòu)與活性間的關(guān)系。主要研究如下：1.采用沉淀法合成Mn-Ce復(fù)合氧化物催化劑并對(duì)其進(jìn)行氨選擇性催化氧化性能研究。實(shí)驗(yàn)發(fā)現(xiàn)：以n(urea)/n(Mn+Ce)=10:1的尿素作為沉淀劑,經(jīng)400℃焙燒得到的n(Mn):n(Ce)為4:1的Mn-Ce復(fù)合氧化物表現(xiàn)出較優(yōu)的氨氧化活性,在200℃即實(shí)現(xiàn)了氨的完全轉(zhuǎn)化。2.采用水熱沉淀法合成Mn-Ce復(fù)合氧化物催化劑并對(duì)其進(jìn)行氨選擇性催化氧化性能研究。實(shí)驗(yàn)發(fā)現(xiàn)：對(duì)沉淀過程中的錳源以及反應(yīng)溫度、壓力進(jìn)行調(diào)節(jié),可明顯影響催化劑的氨氧化性能。以Mn2+和MnO4-同時(shí)為錳源,在1408水熱條件下合成的Mn-Ce復(fù)合氧化物表現(xiàn)出更好的氨氧化活性,在180℃即能實(shí)現(xiàn)氨的完全轉(zhuǎn)化。結(jié)合表征結(jié)果發(fā)現(xiàn)：水熱沉淀法中引入KMnO4,可提高M(jìn)n-Ce復(fù)合氧化物的比表面積,促使Mn4+進(jìn)入Ce02立方螢石結(jié)構(gòu)中形成Mn-Ce-O固溶體,促進(jìn)氧的流動(dòng),從而提高催化劑的氧化還原能力,提高其氨氧化性能。3.采用水熱沉淀法合成純錳氧化物催化劑并對(duì)其進(jìn)行氨選擇性催化氧化性能研究。實(shí)驗(yàn)發(fā)現(xiàn)：水熱沉淀法合成的MnO2(UH)催化劑在170℃即可實(shí)現(xiàn)氨的完全轉(zhuǎn)化,N2選擇性為49%。并通過與水熱法合成的MnO2(H)催化劑以及商業(yè)Mn02進(jìn)行對(duì)比研究,結(jié)合XRD、BET、H2-TPR、SEM、XPS、NH3-TPD結(jié)果可知,合成過程中加入一定量的尿素可以對(duì)催化劑結(jié)構(gòu)進(jìn)行調(diào)變,使催化劑顆粒均勻分散且尺寸減小,并在保持α-MnO2晶相不變的情況下實(shí)現(xiàn)了催化劑形貌從納米棒到納米片的轉(zhuǎn)變,大量納米片又進(jìn)一步交叉聚集形成花狀的微粒小球,顯著提高了催化劑的比表面積,在其表面形成大量的吸附位點(diǎn)和氧空穴,促進(jìn)了污染物和分子態(tài)氧的吸附和活化,從而提高了催化劑的氨氧化活性。
[Abstract]:Ammonia ammonia (NH3) is a typical toxic industrial waste gas, which will cause serious harm to human health and ecological environment. In recent years, the control and treatment of ammonia has attracted wide attention. There are many ammonia treatment technologies, and selective catalytic oxidation process is characterized by its high efficiency, rapidity, no secondary pollution and so on. Noble metal catalysts showed good low temperature activity, but the selectivity of N2 was low. Although the transition metal catalyst has the advantages of low price and good N2 selectivity, the complete conversion temperature is high and the energy consumption is high. In this thesis, manganese based oxide catalysts were prepared by different synthesis methods and their ammonia oxidation activities were tested, and the structure and properties of the catalysts were investigated. The relationship between structure and activity was studied. The main results were as follows: 1. The Mn-Ce composite oxide catalyst was synthesized by precipitation method and its ammonia selective catalytic oxidation performance was studied. Urea of urea)/n(Mn Ce)=10:1 is used as precipitant. The Mn-Ce composite oxides calcined at 400 鈩，

本文編號(hào)：1420322