稀土掺杂过渡金属型汽车尾气净化催化剂的制备及其性能研究

【作者】 王红霞；

【导师】 黄可龙；

【作者基本信息】 中南大学 ， 应用化学， 2002， 硕士

【摘要】 本研究采用浸渍法，分别以γ-Al₂O₃和堇青石、泡沫镍为载体，以硝酸铜、亚硝酸锰和亚硝酸铈及氯化钯为原料，制备了一系列载体相同，活性成分不同和活性成分一定时，载体不同的汽车尾气净化催化剂样品。并且以CO-NO为探针反应，考察了浸渍时间、负载量、活化温度、反应温度及气体组成等因素对催化剂活性的影响。在本课题的实验研究中，本人重点进行了以下几项工作。（1） 在本研究中，首先建立了汽车尾气催化净化剂性能测试系统。模拟汽车尾气的成分，采用气相色谱分析法来检测催化剂的活性。（2） 主要采用浸渍法制备了一系列催化剂。首先考察了以Y—Al₂O₃为载体，分别以氧化物CuO、MnO_x、Cu-Ce-O（x）、Mn-Ce-O（x）及Cu-Mn-Ce-O（x）为活性成分的样品，研究了制备工艺对其催化活性的影响。考察了浸渍时间、负载量、活化温度、反应温度和气体组成等因素对催化剂性能的影响。从而选择最佳的实验条件。研究表明，对Cu-Ce-O（x）催化剂的最佳活化温度为700℃左右，浸渍时间一般控制在2.5h，催化剂的负载量以铜的原子百分含量计算为Cu/（Cu+Ce）=15，CO转化率为50％时的反应温度为90℃(2，Cu-Mn-Ce-O（x）催化剂来说，最佳浸渍时间为2.0h，组成为Cu：Mn：Ce=9：8：3催化活性最好。当活化温度为500℃左右，在反应温度为80℃时，催化剂对CO的最高转化率为85％左右，说明该催化剂具有较好的低温活性。并且我们还研究了氧化铈在催化剂中的作用。催化剂中添加铈后可以提高CO+O₂的低温反应性能以及CO+NO的高温反应性能，CeO₂的存在能阻止催化剂中CuMn₂O₄相的生成。（3） 以NK₃-NO为探针反应，考察了催化剂的抗SO₂中毒性能。实验表明，Cu-Mn-Ce-O（x）催化剂在3％的SO₂／空气中强制中毒后，对CO的转化率仍达到80％左右，说明该催化剂具有较好的抗硫中毒性能。然而，Mn-Ce-O（x）催化剂经过硫化中毒后催化活性下降。（4） 考察了不同载体下催化剂的活性。主要以活性氧化铝、堇青石和泡沫镍为研究对象，以CuO、CuO-Pd、MnO_x及MnO_x-Pd为活性成分，研究载体不同时催化剂对CO的催化转化活性及载体的耐高温强度。发现泡沫镍催化剂具有与堇青石催化剂相似的活性，但在高温下容易破碎，说明以泡沫镍为载体的催化剂的耐热性能差，还不能达到汽车尾气净化器的性能要求，但堇青石和γ·Al₂O₃都是良好的催化剂载体。更多还原

【Abstract】 A new type of catalytic materials of purification of automobile exhaust has been studied. The catalysts were made from CuO, MnOx, CeC>2 or their complex oxides such as bimetallic oxide catalyst Cu-Ce-O(x) with Cu(NOs)2, Mn(NC>3)2 and Ce(NO3)3 as initial materials. The catalysts were synthesized by impregnation method with its properties characterized through XRD and BET techniques, and its performance was tested with CO-NO and NHs-NO as probe molecules.The factors affecting their catalytic activities, such as impregnation period, global metal content on y -A^Os, calculations temperature and the period of calculations et al. have been investigated. Its catalytic activity was tested in a fixed-bed reactor by exposing the sample to the atmosphere of simulating automobile exhaust. The variation of the gas determined by gas chromatography. The main work carried out in the research is as followings.Firstly, I set up the testing system for automobile exhaust purification.Secondly, a series of samples were prepared by impregnation method. I initially investigated the effect of different preparing process on the activities of the catalysts by comparing the activity of different samples. The results showed that, to Cu-Ce-O(x) sample, 2h of the impregnation period, and the calcinations temperature was 700 癈, atom percent Cu/(Cu+Ce) =15 was controlled, the conversion of CO to COi by NO on the catalyst reached the maximum. As for Cu-Mn-Ce-O(x)/ Y -A^Os sample, when Cu:Mn;Ce=9:8:3 was controlled, calculations temperature was 500 癈 , the conversion of CO oxidation by NO was over 85% under the condition of 80癈 of reaction tempereture. Morever, the influence of CeO2 addition was also studied.Thirdly, the ability of the catalysts of resisting to SO2-poisoning was studied by exposing the Mn-Ce-O(x) and Cu-Mn-Ce-O(x) to the 160mL/min S02/air respectively for 16h at 500℃, then their activities for conversion of CO oxidation by NO .The conversion of NO reduction over the sulfated catalyst is somewhat higher than that over the fresh catalyst except that the optimum temperature increased about 100癈. Also at the optimum process for the experiment, the selective catalytic oxidation of CO by NO was 76% and the conversion of NO reduction was over 80% by NHj.What’s more, we studied the effect of carriers on the activities. The samples were prepared on different carriers such as Y -A^Os, honeycomb cordierite and foam nic]4e respectively. Although they have similar activity, foam nickel wasn’t a suitable carrier because it became breakable at high calculations temperature.更多还原