本文選題：NO + 低溫催化還原　； 參考：《浙江工業(yè)大學(xué)》2015年碩士論文

【摘要】：氮氧化物(nitrogen oxides)是大氣污染物中主要的有害成分,主要包含NO,NO2,N2O等,它們是造成光化學(xué)煙霧和酸雨的一個(gè)重要原因。降解氮氧化物有許多行之有效的方法,其中催化還原技術(shù)是現(xiàn)階段發(fā)展較為成熟的方法之一,而又以NH3-SCR法最先開始工業(yè)化。但是NH3是一種危害性氣體,在使用中易造成安全事故,對(duì)設(shè)備要求較高,而且無法應(yīng)用到移動(dòng)源的氮氧化物處理中。因此H2-SCR逐漸開始走入人們視線,且貴金屬催化劑在低溫情況下展現(xiàn)了較好的催化還原能力。我們課題組制備的組合型Pt催化劑其制備過程簡(jiǎn)單,可重復(fù)性高,有其獨(dú)特的方法優(yōu)勢(shì):(1)Pt前驅(qū)體在高壓H2環(huán)境中還原,能充分地還原Pt。(2)碳酸丙二醇酯(PC)作為分散劑兼穩(wěn)定劑,無毒無害,性質(zhì)穩(wěn)定,得到的Pt納米溶液能長(zhǎng)時(shí)間保持穩(wěn)定狀態(tài)。(3)高分散的Pt納米顆粒再吸附到載體避免了直擊浸漬法攪拌不均勻的缺陷,使得活性組分分散性更高。(4)直接吸附法全過程無氯。通過該法制備得到的催化劑在鄰氯硝基苯加氫反應(yīng)、VOCs催化氧化方面已經(jīng)證實(shí)了有非常好的催化效果,并且貴金屬催化劑對(duì)H2-SCR反應(yīng)有很好的低溫催化效果,因此將該方法制備的Pt基催化劑用于H2-SCR反應(yīng),探究其在還原NO方面的催化特性,并討論了催化性能與催化劑結(jié)構(gòu)性質(zhì)的內(nèi)在聯(lián)系。論文主要按照以下幾個(gè)方面展開:一、Pt/Ti O2催化劑催化還原NO性能研究以Ti O2為載體,采用直接吸附法將制備得到的Pt納米顆粒吸附到Ti O2載體上,從而制備出Pt/Ti O2催化劑(Pt/Ti O2-AS),并以NO還原反應(yīng)為探針反應(yīng),研究其催化效果。結(jié)果表明:組合型Pt/Ti O2催化劑在6%O2體積分?jǐn)?shù)、H2/NO摩爾比為7、空速為120000 ml·g-1·h-1時(shí)具有較高的NO轉(zhuǎn)化率,在低溫70℃時(shí)轉(zhuǎn)化率最高能達(dá)到80%,且在50-220℃的范圍內(nèi)都能保持較高活性。同樣制備條件下,其他載體和其他活性組分未能表現(xiàn)出更高活性。為探討載體酸堿性對(duì)反應(yīng)的影響,通過添加K2SO4、KOH等助劑來改變催化劑表面的酸性位。實(shí)驗(yàn)證明,保持催化劑上的酸性位更有利于NO還原反應(yīng),而添加堿性助劑不利于該反應(yīng)。二、Pt/Si O2催化劑上催化還原NO性能研究Si O2具有極大的比表面積,更有利于活性組分的分布,且酸性載體更利于NO還原反應(yīng),因此選用Si O2作為載體,對(duì)比了直接吸附法和傳統(tǒng)浸漬法制備得到的催化劑在H2-SCR反應(yīng)的催化能力,進(jìn)而得出直接吸附法的優(yōu)勢(shì)所在。結(jié)果表明:Si O2載體在溫度低至58℃時(shí)轉(zhuǎn)化率就能達(dá)到80%,展現(xiàn)了較高的低溫催化活性。結(jié)合各種表征結(jié)果得出Pt/Si O2-AS催化劑表面上Pt更多以Pt0形式存在,并且碳酸丙二醇酯(PC)作為分散劑,使制得的Pt納米顆粒均一穩(wěn)定,Pt物種主要以還原態(tài)的Pt均勻穩(wěn)定地分散在載體表面,能更好地與反應(yīng)物接觸,顯示出良好的低溫催化能力。
[Abstract]:Nitrogen oxides are the main harmful components of atmospheric pollutants, including no _ (no _ 2) _ (2) N _ (2) O and so on. They are an important cause of photochemical smog and acid rain. There are many effective methods for the degradation of nitrogen oxides, among which catalytic reduction is one of the more mature methods at present, and the NH _ 3-SCR method is the first to begin industrialization. However, NH _ 3 is a dangerous gas, which can easily cause safety accidents in use, require high equipment, and can not be applied to the nitrogen oxide treatment of moving sources. Therefore, H2-SCR gradually began to be seen, and the noble metal catalyst showed good catalytic reduction ability at low temperature. The composite Pt catalyst prepared by our group has the advantages of simple preparation process and high repeatability. It has its unique advantages in reducing the Pt precursor in high pressure H 2 environment, and can fully reduce Pt.2) propanediol carbonate (PC) as both dispersant and stabilizer. The Pt nanoparticles with high dispersion can be adsorbed to the carrier for a long time to avoid the defect of non-uniform stirring by direct impact impregnation. The dispersivity of the active component is higher. 4) the whole process of direct adsorption is chlorine free. The catalyst prepared by this method has been proved to have a very good catalytic effect in the catalytic oxidation of o-chloronitrobenzene in the presence of VOCs, and the noble metal catalyst has a good catalytic effect at low temperature for the H2-SCR reaction. Therefore, the Pt-based catalyst prepared by this method was used in the H2-SCR reaction to investigate its catalytic properties in the reduction of no, and the intrinsic relationship between the catalytic performance and the structural properties of the catalyst was discussed. The main contents are as follows: firstly, the catalytic reduction of no on Pt / TIO _ 2 catalyst was studied. The Pt nanoparticles were adsorbed on TIO _ 2 carrier by direct adsorption method. The catalytic effect of Pt / TIO _ 2 catalyst was studied by using no reduction reaction as probe reaction. The results show that the combined PTT / TIO _ 2 catalyst has a high no conversion when the molar ratio of H _ 2 / no is 7 and the space velocity is 120000 ml g ~ (-1) h ~ (-1). The highest conversion of no can be reached at 70 鈩，

本文編號(hào)：2026347