本文選題：NH_3選擇性催化還原　切入點：鈰基催化劑　出處：《南京理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：氮氧化物(NO_x)是大氣污染的主要污染源之一。鈰基催化劑在選擇性催化還原NO_x展現(xiàn)了良好的性能。然而在水汽和SO_2存在的情況下其脫硝活性嚴(yán)重地受到了抑制。本文采用沉淀法制備PS-NCLS、Cu-Ce(S)等鈰基催化劑。分別通過SO_2預(yù)處理和加入硫酸鹽前驅(qū)體兩種方法對催化劑進(jìn)行硫元素?fù)诫s改性以提高其抗水抗硫性能。采用X射線衍射(XRD)、透射電鏡(TEM)、X射線光電子能譜(XPS)、程序升溫脫附(TPD)、傅里葉變換紅外(FTIR)、原位漫反射紅外(in situ DRIFTS)、熱重(TG)等分析測試方法對催化劑的結(jié)構(gòu)和形貌、反應(yīng)機(jī)理和改性的作用等進(jìn)行了研究。在固定床反應(yīng)器測試了催化劑的脫硝活性及抗水抗硫性能。對于PS-NCLS催化劑,La~(3+)摻雜進(jìn)CeO_2螢石晶格中導(dǎo)致了晶胞的膨脹,產(chǎn)生了更多的晶格缺陷并提升了晶格氧的流動性。Ni~(2+)在催化劑表面富集,形成了新的Lewis酸性位。硫酸化處理增加了催化劑中Ce~(3+)和化學(xué)吸附氧的比例,并提升了晶格氧的流動性。通過硫酸化處理,催化劑保留了多數(shù)Lewis酸性位并生成了新的Bronsted酸性位。提出了縮核模型來解釋催化劑的硫酸化過程。此外,原位漫反射紅外實驗證實了硫酸化處理后催化劑上NH_3-SCR反應(yīng)主要遵循L-H機(jī)理。硫酸化處理后的PS-NCLS催化劑在水汽和SO_2共存條件下保留了良好的NO吸附性,并增加了 NH_3的吸附性。這些結(jié)果闡述了Ni和La的引入以及硫酸化處理對催化劑的脫硝活性和抗水抗硫性能的提升具有重要的作用。對于Cu-Ce(S)催化劑,隨著Cu摻雜量的增加,Cu-Ce固溶體中摻雜的Cu~(2+)趨于飽和,CuO相開始出現(xiàn)并分散在催化劑表面。較低的Cu摻雜量具有較高的Ce~(3+)比例,導(dǎo)致了催化劑較強的Lewis酸性�；瘜W(xué)吸附氧的比例隨著Cu摻雜量的增加而增加。Cu-Ce(S)催化劑中的SO_4~(2-)增強了催化劑的Bronsted酸性。在水汽和SO_2共存情況下,催化劑表面出現(xiàn)了亞硫酸銨鹽和硫酸銨鹽的沉積,而摻雜的Cu抑制了銨鹽的沉積現(xiàn)象。3%Cu-Ce(S)催化劑比CeO_2催化劑具有更寬的溫度窗口、更好的的中低溫脫硝活性和抗水抗硫性能。
[Abstract]:No _ x) is one of the main pollution sources of air pollution. Cerium based catalyst shows good performance in selective catalytic reduction of NO_x. However, the denitrification activity is severely inhibited in the presence of water vapor and SO_2. Cerium-based catalysts such as PS-NCLS- Cu-CeS-) were prepared by precipitation method. The catalysts were modified by SO_2 pretreatment and sulphate precursor respectively in order to improve their water resistance and sulfur resistance. X-ray diffraction (XRD) and permeation were used to improve the water resistance and sulfur resistance of the catalysts. The structure and morphology of the catalyst were studied by means of X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), Fourier transform infrared spectroscopy (FTIR), in situ diffuse reflectance infrared spectroscopy (DIR) in situ, thermogravimetry (TG), etc. The mechanism of the reaction and the effect of modification were studied. The denitrification activity and water resistance to sulfur of the catalyst were tested in a fixed bed reactor. For the PS-NCLS catalyst, Lajian3) doping into the CeO_2 fluorite lattice resulted in the expansion of the unit cell. More lattice defects were produced and the mobility of lattice oxygen was enhanced. Ni2) was enriched on the surface of the catalyst to form a new acidic site of Lewis. Sulfation treatment increased the ratio of Ce~(3) and chemisorbed oxygen in the catalyst. The mobility of lattice oxygen was enhanced. Through sulfation treatment, the catalyst retained most of the acidic sites of Lewis and formed a new acidic site of Bronsted. A shrinking nucleation model was proposed to explain the sulfation process of the catalyst. In situ diffuse reflectance infrared (DIR) experiments confirmed that the NH_3-SCR reaction on the sulfated catalyst mainly followed the L-H mechanism. The sulfated PS-NCLS catalyst retained good no adsorption under the condition of coexistence of water vapor and SO_2. The results show that the introduction of Ni and La and the sulfation treatment play an important role in the denitrification activity of the catalyst and the improvement of water resistance to sulfur. With the increase of Cu doping amount, the Cu~(2 doped in Cu-Ce solid solution tends to appear in saturated CuO phase and disperse on the surface of the catalyst. The lower Cu doping content has a higher Ce~(3) ratio. The ratio of chemisorbed oxygen to oxygen increased with the increase of Cu doping content. The SO4C _ 2) enhanced the Bronsted acidity of the catalyst. Under the condition of the coexistence of water vapor and SO_2, the acidity of the catalyst was enhanced. The deposition of ammonium sulfite and ammonium sulfate appeared on the surface of the catalyst, while Cu doping inhibited the deposition of ammonium salt. 3Cu-CeS) catalyst had wider temperature window, better denitrification activity and water resistance to sulfur than CeO_2 catalyst.
【學(xué)位授予單位】：南京理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O643.36;X701

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