發(fā)布時間：2018-02-04 01:41

  本文關(guān)鍵詞： 有序介孔三氧化二錳 PdPt合金納米顆粒 負(fù)載貴金屬催化劑 金屬-載體強相互作用 甲烷燃燒　出處：《催化學(xué)報》2017年01期 　論文類型：期刊論文

【摘要】：甲烷作為一種清潔廉價的碳?xì)淠茉?廣泛應(yīng)用于運輸業(yè)和其它工業(yè)領(lǐng)域.但是其本身是一種比二氧化碳導(dǎo)致全球變暖效應(yīng)更強的溫室氣體,而且甲烷直接燃燒會產(chǎn)生其它污染物,比如一氧化碳、氮氧化物、未充分燃燒的碳?xì)浠衔锏?因此有必要開展有關(guān)甲烷催化燃燒的研究工作,以大幅度降低起燃溫度,提高燃燒效率,有效地減少污染副產(chǎn)物的產(chǎn)生.由于具有較好的低溫催化活性,Pd基催化劑常用于甲烷的催化燃燒.但是Pd基催化劑也存在一些亟需解決的問題,比如在催化燃燒過程中活性相結(jié)構(gòu)不穩(wěn)定.PdO通常被認(rèn)為是碳?xì)浠衔锎呋趸械幕钚韵?但是在高溫下PdO分解為Pd,導(dǎo)致催化活性下降.PdO遇到含水或硫的化合物時會生成惰性的Pd(OH)_2或穩(wěn)定的硫化物,造成活性物種的流失,從而降低催化劑的性能.如果在材料中添加另一種貴金屬Pt,使之與Pd一起形成貴金屬合金,則可提高其低溫催化燃燒的活性,增加Pd基催化劑的熱穩(wěn)定性以及抗水和抗硫能力.另一方面,過渡金屬氧化物價格便宜,熱穩(wěn)定性以及抗硫性較好,也常作為甲烷燃燒的催化劑.其中三氧化二錳由于具有可變的氧化態(tài)以及較好的儲氧能力受到了廣泛關(guān)注.本課題組采用KIT-6作為硬模板,先合成具有有序介孔結(jié)構(gòu)的Mn_2O_3(meso-Mn_2O_3)納米催化劑,然后通過聚乙烯醇(PVA)保護的液相共還原法分別制備meso-Mn_2O_3擔(dān)載Pd,Pt及PdPt合金的納米催化劑(x(Pd_yPt)/meso-Mn_2O_3;x=(0.10-1.50)wt%;Pd/Pt摩爾比(y)=4.9-5.1).XRD結(jié)果表明,合成的meso-Mn_2O_3具有立方相晶體結(jié)構(gòu).其BET比表面積為106 m~2/g.由TEM照片可觀察到粒徑范圍為2.1-2.8 nm的貴金屬納米顆粒均勻分散在meso-Mn_2O_3表面.通過XPS分析可知,結(jié)合能在529.6和531.2 eV的峰可分別歸屬于晶格氧(O_(latt))和表面吸附氧(O_(ads)).Pd~0和Pd~(2+)以及Pt~0和Pt~(2+)也均可通過曲線擬合后進行分峰確定.XPS定量分析結(jié)果表明,樣品的O_(ads)/O_(latt)摩爾比有如下順序:1.41(Pd_(5.1)Pt)/meso-Mn_2O_3(0.77)1.40Pd/meso-Mn_2O_3(0.69)0.72(Pd_(5.1)Pt)/meso-Mn_2O_3(0.65)1.42Pt/meso-Mn_2O_3(0.63)0.07(Pd4.9Pt)/meso-Mn_2O_3(0.53)0.07(Pd_(4.9)Pt)/bulk-Mn_2O_3(0.52)meso-Mn_2O_3(0.45),這與其催化活性的順序一相致.該結(jié)果表明,高的吸附氧物種濃度有利于甲烷催化燃燒.負(fù)載Pd,Pt或Pd Pt以后的樣品的表面吸附氧物種濃度顯著提高,催化活性最好的1.41(Pd_(5.1)Pt)/meso-Mn_2O_3樣品具有最高的吸附氧物種濃度.負(fù)載PdPt合金可有效提高催化劑對甲烷燃燒的催化活性.1.41(Pd_(5.1)Pt)/meso-Mn_2O_3催化劑的活性最好:在空速為20000 mL/(g×h)的條件下,甲烷燃燒的T_(10%),T_(50%)和T_(90%)分別為265,345和425 ℃.此外,還考察了引入一定量的SO_2,CO_2,H_2O和NO對甲烷在1.41(Pd_(5.1)Pt)/meso-Mn_2O_3催化劑上氧化反應(yīng)的影響,發(fā)現(xiàn)引入少量的Pt可提高催化劑抗SO_2,CO_2和H_2O的能力,但是NO對甲烷燃燒的還原效應(yīng)也不可忽視.基于催化劑物化性質(zhì)的表征結(jié)果和活性數(shù)據(jù),我們認(rèn)為1.41(Pd_(5.1)Pt)/meso-Mn_2O_3優(yōu)異的催化性能與其擁有高質(zhì)量的三維有序多孔結(jié)構(gòu)、高的吸附氧物種濃度、優(yōu)良的低溫還原性以及Pd-Pt合金與meso-Mn_2O_3載體之間的強相互作用有關(guān).
[Abstract]:Methane is a kind of clean and cheap hydrocarbons are widely used in transportation and other industrial fields. But it is a ratio of carbon dioxide greenhouse gases that cause global warming effect, and methane combustion will produce other pollutants, such as carbon monoxide, nitrogen oxides, incompletely combusted hydrocarbons. So the research work necessary to carry out the catalytic combustion of methane, to greatly reduce the ignition temperature, improve combustion efficiency, effectively reduce pollution byproducts. Because it has better catalytic activity, Pd based catalyst used in methane combustion. But Pd catalyst also has some problems to be solved, such as activity in catalytic combustion in the process of phase structure of unstable.PdO is generally considered to be the catalytic oxidation of hydrocarbons in the active phase, but at high temperatures PdO decomposed into Pd, to urge The activity of.PdO decreased when water or sulfur compounds encountered will generate inert Pd (OH) _2 or stable sulfides, resulting in the loss of the active species, thereby reducing the performance of the catalyst. If you add another noble metal Pt in the material, which together form a noble metal alloy and Pd, can improve the low temperature the catalytic combustion activity, increase the thermal stability of Pd based catalyst and anti water and anti sulfur ability. On the other hand, transition metal oxides, cheap price, good thermal stability and sulfur resistance, is often used as a catalyst for methane combustion. The three oxidation two manganese oxidation state due to having variable and better oxygen storage capacity by wide attention. The research group using KIT-6 as hard template, the first synthesis of ordered mesoporous structure of Mn_2O_3 (meso-Mn_2O_3) nano catalyst, followed by polyvinyl alcohol (PVA) protection liquid CO original method for preparation of me respectively. So-Mn_2O_3 supported Pd nano catalyst Pt and PdPt alloy (x (Pd_yPt) /meso-Mn_2O_3; x= (0.10-1.50) wt%; Molby Pd/Pt (y) =4.9-5.1).XRD results showed that the synthesis of meso-Mn_2O_3 has a crystal structure of cubic phase. The BET surface area is 106 m~2/g. by TEM photos can be observed for your size 2.1-2.8 metal nanoparticles nm uniformly dispersed on the surface of meso-Mn_2O_3. Through XPS analysis, the binding energy which can be attributed to lattice oxygen in 529.6 and 531.2 eV peak (O_ (latt)) and the surface adsorbed oxygen (O_ (ads).Pd~0) and Pd~ (2+ and Pt~0) and Pt~ (2+) can also be through curve fitting after peak.XPS quantitative analysis results show that the samples of O_ (ads) /O_ (latt) Molby has the following order: 1.41 (Pd_ (5.1) Pt (0.77) /meso-Mn_2O_3 (0.69) 1.40Pd/meso-Mn_2O_3 (0.72) Pd_ (5.1) Pt) /meso-Mn_2O_3 (0.65) 1.42Pt/meso-Mn_2O_3 (0.63) and 0.07 (Pd4.9Pt) /meso-Mn_2O _3 (0.53) 0.07 (Pd_ (4.9) Pt) /bulk-Mn_2O_3 (0.52) meso-Mn_2O_3 (0.45), and its catalytic activity of this sequence. The results show that the phase induced, high concentration of adsorbed oxygen species for the catalytic combustion of methane. The load of Pd, the surface oxygen species concentrations of Pt or Pd after Pt samples significantly, the best catalytic activity (1.41 Pd_ (5.1) Pt) /meso-Mn_2O_3 sample has the highest concentration of adsorbed oxygen species. Can effectively improve the catalytic activity of.1.41 catalyst for methane combustion load of PdPt alloy (Pd_ (5.1) Pt) /meso-Mn_2O_3 catalyst activity most good: the speed is 20000 mL/ (G * h). Under the condition of methane combustion T_ (10%), T_ (50%) and T_ (90%) were 265345 and 425 degrees. In addition, was investigated by introducing a certain amount of SO_2, CO_2, H_2O and NO on methane in 1.41 (Pd_ (5.1) Pt) effects on /meso-Mn_2O_3 catalyst oxidation, found that the introduction of a small amount of Pt can improve the catalyst Anti SO_2 ability of CO_2 and H_2O, but NO on the reduction effect of methane combustion can not be ignored. The characterization results of catalyst properties and activity based on the data, we believe that the 1.41 (Pd_ (5.1) Pt) a three-dimensional ordered porous structure and excellent catalytic properties of /meso-Mn_2O_3 with high quality, high concentration of adsorbed oxygen species the excellent low temperature reduction and strong interaction between Pd-Pt alloy and meso-Mn_2O_3 carrier.

【作者單位】： 綠色催化與分離北京市重點實驗室
【基金】：supported by the Ph.D. Program Foundation of Ministry of Education of China (20131103110002) the NNSF of China (21377008) National High Technology Research and Development Program (863 Program, 2015AA034603) Foundation on the Creative Research Team Con-struction Promotion Project of Beijing Municipal Institutions Scientific Research Base Construction-Science and Technology Creation Plat-form-National Materials Research Base Construction~~
【分類號】：O643.36
【正文快照】： 1.Introduction Methane is widely considered to be the cleanest available hydrocarbon energy source for transportation and industrial applications[1].Methane itself,however,is a greenhouse gas,with a global warming effect 21 23 times greater than that o，

本文編號：1488941