过渡金属复合氧化物的气敏性能及催化性能研究

发布时间：2018-01-07 16:24

本文关键词：过渡金属复合氧化物的气敏性能及催化性能研究　出处：《山东大学》2017年博士论文　论文类型：学位论文

【摘要】：本论文基于过渡金属氧化物独特的物理化学性质,分别研究了几类过渡金属复合氧化物对低浓度有害气体的敏感性能以及对机动车尾气中部分污染物(CO、NO、碳烟)的催化氧化性能。研究了不同元素添加对金属氧化物气敏或催化性能的影响,并找出了最佳添加元素、添加元素的最佳比例或添加方式。利用XRD、BET、SEM、TEM、FTIR、H2-TPR等多种方法对系列材料的晶相结构、微观形貌、表面性质和氧化还原能力等进行了表征。在此基础上,结合气敏和催化反应的实验结果,探讨了引入不同元素对过渡金属氧化物复合材料改性的构效关系。论文的主要研究内容如下:(1)采用共沉淀法合成了具有不同铝含量的类水滑石基镍铝复合氧化物NixAl(O)(x = 1～4)。考察了铝的引入对氧化镍材料气敏性能和催化性能的影响,分别找出了两类反应中铝元素最佳的掺杂比例,对铝的添加所起的作用进行了讨论。实验结果表明,与同法制备的NiO相比,适量比例的A1203的加入显著提高了材料对2-氯乙醇的气敏性能。其中,镍铝比例为3/1的样品性能最好,在160℃,该样品对2-氯乙醇具有良好的选择性和稳定性,对20 ppm的2-氯乙醇最高响应值达到6.8;另外,发现适当比例的A1203与NiO复合在一定程度上也改善了 NiO对CO的催化氧化性能。其中镍铝比例为2/1的样品具有最好的催化性能,其催化氧化CO的半转化温度(T50)为190℃,C02完全转化温度为340℃(比纯NiO的降低了 100℃左右)。表明A1元素的适量添加能提高材料的气敏性能和较低温度的催化活性。(2)采用溶胶凝胶法合成了具有不同锰含量的钙钛矿型复合氧化物La0.7Ba0.3Fe1-xMnxO3(x = 0～0.6)。考察了 Mn的掺杂对材料气敏性能和催化性能的影响,分别找出了这两类反应中Mn元素的最佳掺杂比例,对Mn的添加所起的作用进行了讨论。实验结果表明,Mn的适量掺杂可以提高材料对NH3的响应。在制备的系列材料中,Mn掺杂量为x = 0.1的样品性能最好,该样品在140℃对500 ppm氨气的响应值接近5.0,明显高于不含锰的样品;另外,发现锰的掺杂可以在较低温度促进NO氧化反应的进行,并且使得材料储存吸附NOx的温度由500℃降至400℃左右。在制备的系列材料中,Mn掺杂量为x = 0.6的样品催化氧化NO性能最好,其N02的最高转化率可达40.1%,对应的温度为365℃(比Mn0.0的低了 20℃)。表明Mn的适量替代能提高材料的气敏性能和低温催化活性。(3)利用CTAB辅助溶胶凝胶法制备了不同过渡金属(Co、Mn、Fe和Cu)掺杂的镧锡烧绿石型复合氧化物。考察了不同过渡金属掺杂对复合氧化物催化碳烟燃烧性能的影响,找出了掺杂效果最好的过渡金属元素,对过渡金属掺杂所起的作用进行了讨论。实验结果表明,富氧气氛下,少量过渡金属掺杂提高了烧绿石催化碳烟燃烧的活性和选择性,这与氧空位浓度的增加以及氧化还原能力的提高有关。其中Co掺杂样品具有较好的催化性能,起燃温度(T10)为379℃,二氧化碳的选择性超过97%;NOx气氛存在可以进一步提升催化剂氧化去除碳烟的性能。利用等温反应和碳烟厌氧滴定实验分别进行了反应动力学分析和活性氧浓度的测定,并计算出富氧气氛下催化反应的转化频率(TOF),其中Co掺杂样品的TOF值最大,基于转化频率(TOF)的活性顺序与程序升温氧化(TPO)法得到的起燃性能的结果基本一致。(4)用溶胶凝胶法和浸渍法分别制备了铯添加的镧钴钙钛矿型复合氧化物。考察了碱金属Cs的不同添加方式(Cs负载和Cs掺杂)对LaCo03复合氧化物催化去除碳烟和NOx储存能力的影响,找出了添加过渡金属元素铯的较好方式,对不同的铯添加方式所起的作用进行了讨论。实验结果表明,富氧气氛下,以掺杂方式引入Cs提高了 LaCo03复合氧化物催化碳烟燃烧的活性,Cs负载样品以及未添加Cs样品的半转化温度T50分别为472℃、436℃,而Cs掺杂样品降低为425℃;NOx气氛存在可以进一步提升催化剂氧化去除碳烟的活性。另外,在测试样品中,Cs掺杂样品还具有最大的NOx储存能力。表明Cs掺杂后提高了材料的催化碳烟燃烧性能和NOx储存能力。
[Abstract]:The unique physical and chemical properties of transition metal oxide based on sensitivity of several kinds of transition metal oxides harmful gases of low concentration were studied and some pollutants in vehicle exhaust (CO, NO, soot) catalytic oxidation performance of different elements. Effects on the metal oxide gas sensing or catalytic performance, and find the best add elements, optimum proportion of added elements or add. Using XRD, BET, SEM, TEM, FTIR, H2-TPR and other methods on the morphology of series of crystalline structure, surface properties, and redox ability were investigated. On the basis of experimental results, combining the gas sensor and the catalytic reaction, this paper discusses different elements of transition metal oxide composites. The structure-activity relationship of the main contents of this dissertation are as follows: (1) using the co precipitation method combined with different aluminum content Hydrotalcite based nickel aluminum composite oxide NixAl weight (O) (x = 1 ~ 4) was studied. The impact of the introduction of aluminum nickel oxide gas sensitive material properties and catalytic properties, are found in Al doping ratio of two types of reactions in the best play of the role of the addition of aluminium discussion. The experimental results show that compared with the NiO prepared by adding proper amount, ratio of A1203 significantly improved the gas sensing properties of 2- chlorethanol materials. Among them, the ratio of nickel aluminum sample 3/1 has a better performance, at 160 degrees, the sample has good selectivity and stability of 2- chlorethanol. 2- chlorethanol highest response to the 20 ppm value reached 6.8; in addition, find the proper proportion of A1203 and NiO compound to a certain extent, but also improved the catalytic oxidation performance of NiO to CO. The ratio of nickel aluminum 2/1 sample has the best catalytic performance, the conversion of semi temperature catalytic oxidation of CO (T50) for 19 0 degrees, C02 completely changed the temperature of 340 DEG (than the pure NiO reduced about 100 DEG C). The results indicated that A1 element added can improve the gas sensing properties of materials and low temperature catalytic activity. (2) perovskite type oxides La0.7Ba0.3Fe1-xMnxO3 with different manganese contents were synthesized by sol gel method (x = 0 ~ 0.6). The effects of Mn doping on the gas sensitive properties and catalytic properties, respectively, to find out the best doping ratio of Mn elements of these two types of reactions, on the addition of Mn process are discussed. The experimental results show that Mn doping can improve the response of materials NH3 in the series of materials in the preparation of Mn doped sample performance of x = 0.1 is the best, the samples of 140 degrees in response to 500 ppm ammonia value close to 5, significantly higher than that of Mn containing samples; in addition, the Mn doping can be found at low temperature to promote the oxidation of NO For, and makes the material storage and NOx adsorption temperature from 500 degrees to 400 degrees Celsius. In the series of materials in the preparation of Mn doped samples of NO catalytic oxidation performance of x = 0.6 is the best, the highest conversion rate of up to 40.1% N02, corresponding to the temperature of 365 DEG (20 lower than Mn0.0 C). Instead of Mn shows that proper can improve the gas sensitive properties of materials and low temperature catalytic activity. (3) different transition metal prepared by CTAB assisted sol-gel method (Co, Mn, Fe and Cu) lanthanum tin doped pyrochlore type complex oxides. The effects of different transition metal doping effect on Combustion properties of composite catalytic soot, the transition metal doping effect is the best, the transition metal doping effect is discussed. The experimental results show that the oxygen enriched atmosphere, a small amount of transition metal doping improves the pyrochlore catalytic soot combustion activity and selectivity, The oxygen vacancy concentration increases and the redox ability. The Co doped sample has good catalytic performance, ignition temperature (T10) of 379 DEG C, the selectivity of CO2 over 97%; the atmosphere of NOx performance can further enhance the catalytic oxidation of soot were determined. The reaction kinetics and activity analysis oxygen concentration using isothermal reaction and soot anaerobic titration experiment, and calculate the transformation frequency of catalytic reaction of oxygen enriched atmosphere (TOF), the Co doped samples the maximum TOF values, based on the transformation frequency (TOF) activity sequence and temperature programmed oxidation (TPO) method to obtain the ignition performance results are basically the same. (4) by sol-gel method and impregnation method were used to prepare the lanthanum cobalt perovskite type composite oxides prepared by adding cesium. The effects of different ways of adding alkali metal Cs (Cs load and Cs doped) of LaCo03 composite oxide The influence of catalytic removal of soot and NOx storage capacity, find out the better way of adding transition metal elements casium, adding the role of different CS are discussed. The experimental results show that the oxygen enriched atmosphere, the introduction of Cs to improve the way of doping LaCo03 composite oxide catalyst for soot combustion activity, Cs load samples and samples without the addition of Cs semi transformation temperature T50 were 472 C, 436 C, and Cs doped samples is reduced to 425 DEG C; NOx atmosphere can further enhance the catalytic oxidation of soot removal activity. In addition, in the test sample, the Cs doped sample has the largest storage capacity of NOx showed that the Cs doped. After improving the catalytic soot combustion of materials and performance of NOx storage capacity.

【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36;X734.2

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