有序介孔三氧化二锰负载PdPt合金:一种高效的甲烷催化燃烧催化剂（英文）

发布时间：2018-02-04 01:41

  本文关键词： 有序介孔三氧化二锰 PdPt合金纳米颗粒 负载贵金属催化剂 金属-载体强相互作用 甲烷燃烧　出处：《催化学报》2017年01期 　论文类型：期刊论文

【摘要】：甲烷作为一种清洁廉价的碳氢能源,广泛应用于运输业和其它工业领域.但是其本身是一种比二氧化碳导致全球变暖效应更强的温室气体,而且甲烷直接燃烧会产生其它污染物,比如一氧化碳、氮氧化物、未充分燃烧的碳氢化合物等.因此有必要开展有关甲烷催化燃烧的研究工作,以大幅度降低起燃温度,提高燃烧效率,有效地减少污染副产物的产生.由于具有较好的低温催化活性,Pd基催化剂常用于甲烷的催化燃烧.但是Pd基催化剂也存在一些亟需解决的问题,比如在催化燃烧过程中活性相结构不稳定.PdO通常被认为是碳氢化合物催化氧化中的活性相,但是在高温下PdO分解为Pd,导致催化活性下降.PdO遇到含水或硫的化合物时会生成惰性的Pd(OH)_2或稳定的硫化物,造成活性物种的流失,从而降低催化剂的性能.如果在材料中添加另一种贵金属Pt,使之与Pd一起形成贵金属合金,则可提高其低温催化燃烧的活性,增加Pd基催化剂的热稳定性以及抗水和抗硫能力.另一方面,过渡金属氧化物价格便宜,热稳定性以及抗硫性较好,也常作为甲烷燃烧的催化剂.其中三氧化二锰由于具有可变的氧化态以及较好的储氧能力受到了广泛关注.本课题组采用KIT-6作为硬模板,先合成具有有序介孔结构的Mn_2O_3(meso-Mn_2O_3)纳米催化剂,然后通过聚乙烯醇(PVA)保护的液相共还原法分别制备meso-Mn_2O_3担载Pd,Pt及PdPt合金的纳米催化剂(x(Pd_yPt)/meso-Mn_2O_3;x=(0.10-1.50)wt%;Pd/Pt摩尔比(y)=4.9-5.1).XRD结果表明,合成的meso-Mn_2O_3具有立方相晶体结构.其BET比表面积为106 m~2/g.由TEM照片可观察到粒径范围为2.1-2.8 nm的贵金属纳米颗粒均匀分散在meso-Mn_2O_3表面.通过XPS分析可知,结合能在529.6和531.2 eV的峰可分别归属于晶格氧(O_(latt))和表面吸附氧(O_(ads)).Pd~0和Pd~(2+)以及Pt~0和Pt~(2+)也均可通过曲线拟合后进行分峰确定.XPS定量分析结果表明,样品的O_(ads)/O_(latt)摩尔比有如下顺序: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),这与其催化活性的顺序一相致.该结果表明,高的吸附氧物种浓度有利于甲烷催化燃烧.负载Pd,Pt或Pd Pt以后的样品的表面吸附氧物种浓度显著提高,催化活性最好的1.41(Pd_(5.1)Pt)/meso-Mn_2O_3样品具有最高的吸附氧物种浓度.负载PdPt合金可有效提高催化剂对甲烷燃烧的催化活性.1.41(Pd_(5.1)Pt)/meso-Mn_2O_3催化剂的活性最好:在空速为20000 mL/(g×h)的条件下,甲烷燃烧的T_(10%),T_(50%)和T_(90%)分别为265,345和425 ℃.此外,还考察了引入一定量的SO_2,CO_2,H_2O和NO对甲烷在1.41(Pd_(5.1)Pt)/meso-Mn_2O_3催化剂上氧化反应的影响,发现引入少量的Pt可提高催化剂抗SO_2,CO_2和H_2O的能力,但是NO对甲烷燃烧的还原效应也不可忽视.基于催化剂物化性质的表征结果和活性数据,我们认为1.41(Pd_(5.1)Pt)/meso-Mn_2O_3优异的催化性能与其拥有高质量的三维有序多孔结构、高的吸附氧物种浓度、优良的低温还原性以及Pd-Pt合金与meso-Mn_2O_3载体之间的强相互作用有关.
[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.

【作者单位】： 绿色催化与分离北京市重点实验室
【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~~
【分类号】：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，

本文编号：1488941