發(fā)布時(shí)間：2018-03-26 14:40

  本文選題：負(fù)載型銅基催化劑　切入點(diǎn)：CuO-CeO_2　出處：《山東大學(xué)》2017年碩士論文

【摘要】：CO是一種易燃易爆,對(duì)人體有害的氣體分子污染物。因此必須消除人體周圍環(huán)境中的CO。目前,人們普遍認(rèn)為催化氧化技術(shù)是消除CO氣體污染物的有效方法,由于其高效節(jié)能的特點(diǎn)。常用于催化CO氧化反應(yīng)的催化劑主要有貴金屬催化劑和銅基催化劑。貴金屬催化劑低溫下就具有很高的催化活性,但由于價(jià)格昂貴、儲(chǔ)量稀少以及穩(wěn)定性較差等缺點(diǎn)限制了其在實(shí)際生產(chǎn)中的應(yīng)用。而銅基催化劑催化活性雖遠(yuǎn)不及貴金屬催化劑,但其價(jià)格低廉、穩(wěn)定性較好,依然受到人們的關(guān)注。CeO_2是一種重要的稀土催化氧化物,具有較強(qiáng)的儲(chǔ)放氧能力,因此常被選作催化劑的載體。尤其是在CuO-CeO_2復(fù)合催化劑中,銅物種與CeO_2之間較強(qiáng)的協(xié)同作用可以有效提高催化劑的催化性能,因此具有較好的應(yīng)用前景。本論文系統(tǒng)研究了負(fù)載型銅基復(fù)合催化劑催化CO氧化反應(yīng)的性能,探究了銅的負(fù)載量對(duì)CuO-CeO_2納米片催化劑反應(yīng)活性的影響,詳細(xì)指認(rèn)了催化反應(yīng)的活性物種。同時(shí)還將CuO-CeO_2同時(shí)負(fù)載在其他功能材料上制備得到三相催化劑,考察其結(jié)構(gòu)與活性之間的關(guān)系。并通過一系列表征技術(shù),包括XRD、TEM/HRTEM、Raman、BET、H_2-TPR、XAFS 及in-situ DRIFTS,對(duì)催化劑的物相結(jié)構(gòu)和催化性能進(jìn)行了詳細(xì)的表征。主要研究內(nèi)容如下:1.選用二維結(jié)構(gòu)的超薄CeO_2納米片作為載體,通過沉積沉淀法制備了一系列不同負(fù)載量的CuO-CeO_2納米片催化劑,并對(duì)其催化CO氧化性能進(jìn)行了測試。結(jié)果發(fā)現(xiàn)5CuCe樣品催化活性最好,可能是由于其表面含有較多的CuO活性物種。隨著負(fù)載量進(jìn)一步增加到10 wt.%,10CuCe樣品表現(xiàn)出了最差的活性,可能是由于表面生成了惰性的體相CuO物種,與XRD及H_2-TPR表征結(jié)果一致。根據(jù)in-situ DRIFTS測試結(jié)果,證明Cu~+物種是CO吸附的活性位點(diǎn),而它主要來自于表面高分散CuO_x簇的還原。從而表明了表面高分散的CuO_x簇是活性物種,而不是具有強(qiáng)相互作用的Cu-[O_x]-Ce結(jié)構(gòu),同時(shí)體相CuO物種對(duì)催化反應(yīng)的進(jìn)行有一定的抑制作用。2.選用形貌規(guī)則的SiO_2微球作為載體,采用分步法制備了一系列CeO_2包覆量不同和銅負(fù)載量不等的Cu-SiO_2@CeO_2復(fù)合催化劑,考察了不同CeO_2包覆量和銅負(fù)載量對(duì)催化性能的影響。結(jié)果表明CeO_2包覆量和銅負(fù)載量對(duì)活性影響較大,其中5Cu-SiO_2@50CeO_2樣品性能最好。并對(duì)活性最優(yōu)的5Cu-SiO_2@50CeO_2催化劑進(jìn)行了 24 h的高溫穩(wěn)定性測試,在溫度為600℃、空速為1448,000 mL·gcat~(-1)·h~(-1)的條件下,樣品的活性沒有任何下降的趨勢,穩(wěn)定性明顯優(yōu)于采用一步共浸漬法制備的5Cu25Ce-SiO_2催化劑。
[Abstract]:Co is a kind of combustible and explosive gas molecular pollutant harmful to human body. Therefore, it is necessary to eliminate CO. at present, it is generally accepted that catalytic oxidation technology is an effective method to eliminate CO gas pollutants. Because of its characteristics of high efficiency and energy saving, the catalysts used to catalyze CO oxidation are mainly noble metal catalysts and copper based catalysts. The noble metal catalysts have high catalytic activity at low temperature, but because of the high price, The shortage of reserves and poor stability limit its application in practical production. Although the catalytic activity of copper based catalyst is far less than that of precious metal catalyst, its price is low and its stability is good. CeOS _ 2 is an important rare earth catalytic oxide with strong oxygen storage and discharge ability, so it is often selected as the support of catalyst, especially in CuO-CeO_2 composite catalyst. The strong synergistic action between copper species and CeO_2 can effectively improve the catalytic performance of the catalyst, so it has a good prospect of application. In this paper, the catalytic performance of supported copper based composite catalyst for CO oxidation was systematically studied. The effect of copper loading on the catalytic activity of CuO-CeO_2 nanoparticles was investigated, and the active species of catalytic reaction were identified in detail. At the same time, three phase catalysts were prepared by loading CuO-CeO_2 on other functional materials at the same time. The relationship between its structure and activity was investigated and characterized by a series of techniques. The phase structure and catalytic performance of the catalyst were characterized in detail, including XRDX / TM / HRTEMN Raman-Bet / H2-TPR-XAFS and in-situ DRIFTS. The main contents of the study are as follows: 1. The ultrathin CeO_2 nanoparticles with two-dimensional structure were selected as the support. A series of CuO-CeO_2 nanocrystalline catalysts with different loading amounts were prepared by deposition precipitation method, and their catalytic activity for CO oxidation was tested. The results showed that 5CuCe samples had the best catalytic activity. It may be that there are more active species of CuO on the surface. As the loading amount increases to 10 wt. the sample of 10CuCe exhibits the worst activity, which may be due to the formation of inert CuO species on the surface. According to the results of in-situ DRIFTS test, it was proved that Cu ~ species are active sites for CO adsorption, and they mainly come from the reduction of highly dispersed CuO_x clusters on the surface, which indicates that the highly dispersed CuO_x clusters on the surface are active species. Instead of Cu- [Ox] -Ce structure with strong interaction, the CuO species in bulk phase have some inhibition on the catalytic reaction. 2. SiO_2 microspheres with regular morphology are selected as the carrier. A series of Cu-SiO_2@CeO_2 composite catalysts with different CeO_2 coating and copper loading were prepared by step method. The effects of different CeO_2 coating and copper loading on the catalytic performance were investigated. The results showed that CeO_2 coating and copper loading had great influence on the catalytic activity. The performance of 5Cu-SiO_2@50CeO_2 sample was the best, and the stability of the 5Cu-SiO_2@50CeO_2 catalyst with the best activity was tested for 24 h. Under the conditions of 600 鈩，

本文編號(hào)：1668282