钴掺杂OMS-2催化剂的制备及对邻二甲苯深度催化氧化的研究

发布时间：2018-04-28 17:02

本文选题：氧化还原沉淀法 + Co掺杂　；参考：《河北师范大学》2017年硕士论文

【摘要】：苯系污染物(如苯、甲苯及二甲苯等)属于挥发性有机污染物(VOCs,Volatile Organic Compounds)是空气中的主要污染物之一,其主要来源于化工原料的生产、汽车尾气的排放及家庭装修等,严重危害生态环境及人类的健康。催化燃烧法是治理VOCs的最佳方法之一,制备出高效的催化剂成为治理VOCs的关键。本论文以邻二甲苯为目标污染物,研制出一系列经过改进过后的低温高活性催化剂。实验结果如下:(1)利用乙酸钴、乙酸锰和高锰酸钾溶液发生反应,采用氧化还原沉淀法,制备出0.06Co-OMS-2-400(II型氧化锰八面体分子筛),简称XCo-OMS-2-Y-Z,其中X代表Co/Mn摩尔比,Y代表Co(CH3COO)_2溶液浓度,Z代表焙烧温度。并与浸渍法制备的0.06Co/OMS-2-400及空白样品OMS-2-400一一进行对比。催化邻二甲苯活性测试结果显示,0.06Co-OMS-2-400的T100(CO2的产率为100%时催化燃烧温度)为200℃,与浸渍法制备的催化剂0.06Co/OMS-2-400及空白样品OMS-2-400的T100相比分别降低了20℃和10℃;0.06Co-OMS-2-400的T20为130℃,比0.06Co/OMS-2-400及OMS-2-400的T20分别降低了45℃和36℃。可见氧化还原沉淀法掺杂钴有利于同时提高催化剂的高温及低温催化活性。XRD结构表征显示,两种制备方法制得的催化剂中Mn均以Mn O2形态存在,Co以Co3O4形态存在,但浸渍法制备的催化剂有Co3O4的特征吸收峰而氧化还原法制备的催化剂没有,经EDX测试,可知氧化还原沉淀法制得的催化剂是含有钴元素的,说明氧化还原沉淀法可能将钴物种分散在OMS-2晶格间隙中。BET测试表明0.06Co-OMS-2-400比表面积可达到129.452m~2/g,远远大于0.06Co/OMS-2-400(49.196m~2/g)和OMS-2(60.447m~2/g)的比表面积。SEM结果显示,0.06Co-OMS-2-400的形貌为规则的四方体颗粒,0.06Co/OMS-2-400的形貌为纳米颗粒堆积成的块状,OMS-2的形貌为大小不一的块状颗粒。H2-TPR测试表明,0.06Co-OMS-2-400的还原峰位置的温度最低可达到288℃,比OMS-2-400减低了38℃,0.06Co/OMS-2-400的低49℃。述结果表明,氧化还原沉淀法得到的钴掺杂OMS-2催化剂其催化活性提高可能是钴进入到OMS-2的晶格中,增大了Mn-O键间的距离使其比表面积最大而且0.06Co-OMS-2-400中的钴离子存在促进了Mn3+/Mn4+间的交换,有利于将邻二甲苯完全催化氧化成CO2和H2O。在催化氧化邻二甲苯的活性测试中0.06Co-OMS-2-0.7-400的T100为200℃,T20为130℃,催化活性最佳。(2)为了对氧化还原沉淀制备方法做进一步的研究,将钴锰摩尔比、乙酸钴溶液的浓度和焙烧温度进行改变,结果发现当钴锰摩尔比为0.06时、乙酸钴溶液的浓度为0.7mol/L、焙烧温度为400℃时,将钴物种高度分散到OMS-2的晶格中,能有效的活化晶格氧,明显提高催化剂的催化活性。在200℃时就能将邻二甲苯完全催化氧化。(3)当分别改变锰盐和钴盐的酸根(CH_3COO~-、NO_3~-、SO_4~(2-))时,XRD结果显示改变酸根后与未改变之前的晶型均为OMS-2。BET测试结果显示,当酸根为CH_3COO~-时,比表面积为129.452m~2/g;酸根为SO_4~(2-)时,比表面积为58.608m~2/g;酸根为NO_3~-时,比表面积为46.757m~2/g;XRD测试结果表明只有酸根为CH_3COO~-时,晶型明显且没有Co3O4的衍射峰;SEM结果显示反应物的酸根为乙酸根时制备的催化剂形为均匀分布的四方体颗粒。H2-TPR结果表明,乙酸盐制备的钴锰复合催化剂0.06Co-OMS-2-0.7-400的还原峰所在的温度最低。上述结果表明对于不同酸根的盐制备出的钴锰复合催化剂中,乙酸盐制备催化剂对催化活性的提高幅度最大。在200℃时就能将邻二甲苯完全催化氧化。
[Abstract]:Benzene, toluene and xylene, such as benzene, toluene and xylene, belong to one of the main pollutants in the air (VOCs, Volatile Organic Compounds), which are mainly derived from the production of chemical raw materials, emission of automobile exhaust and family decoration, which seriously harm the ecological environment and human health. The catalytic combustion method is the treatment of VOCs. One of the best methods is to prepare an efficient catalyst for the treatment of VOCs. In this paper, a series of modified low temperature and highly active catalysts have been developed with o-xylene as the target pollutant. The results are as follows: (1) the reaction of cobalt acetate, manganese acetate and Potassium Permanganate solution, and the oxidation reduction precipitation method, 0. are prepared. 06Co-OMS-2-400 (II type manganese oxide eight surface molecular sieve), referred to as XCo-OMS-2-Y-Z, which represents the Co/Mn mole ratio, Y represents the _2 solution concentration of Co (CH3COO), Z represents the calcination temperature. The catalytic combustion temperature of CO2 was 100% at 200 degrees C, decreased by 20 C and 10 C respectively compared with the T100 of the catalyst prepared by the impregnation method and the T100 of the blank sample OMS-2-400 respectively. The T20 of 0.06Co-OMS-2-400 was 130 degrees C, 45 and 36 centigrade, respectively, compared with T20 of 0.06Co/OMS-2-400 and OMS-2-400. The co doping of cobalt with the oxidation-reduction precipitation method can be seen. The structure characterization of high temperature and low temperature catalytic activity.XRD showed that Mn existed in the form of Mn O2 in the two preparation methods, and Co was in the form of Co3O4, but the catalyst prepared by the impregnation method had the characteristic absorption peak of Co3O4 and the catalyst prepared by the oxidation reduction method was not. It was known that oxidation was also obtained by EDX test. The catalyst obtained by the original precipitation method contains cobalt, indicating that the redox precipitation method may disperse cobalt species in the gap of OMS-2 lattice and.BET test shows that the specific surface area of 0.06Co-OMS-2-400 can reach 129.452m~2/g, which is far greater than the specific surface area.SEM results of 0.06Co/OMS-2-400 (49.196m~2/g) and OMS-2 (60.447m~2/g), 0.06Co-OMS-2-. 400 of the tetrapo particles with regular morphology, the morphology of the 0.06Co/OMS-2-400 is the bulk of the nanoparticles. The.H2-TPR test of the bulk particles of the OMS-2 shows that the temperature of the peak position of the 0.06Co-OMS-2-400 can be lowest to 288, 38 and 49 lower than that of OMS-2-400. The catalytic activity of cobalt doped OMS-2 catalyst obtained by oxidation-reduction precipitation method may be that cobalt enters into the lattice of OMS-2, increases the distance between Mn-O bonds and makes its specific surface area maximum and the cobalt ion in 0.06Co-OMS-2-400 promotes the exchange of Mn3+/Mn4+, which is beneficial to the complete catalytic oxidation of xylene into CO2 and H2O.. In the activity test of catalytic oxidation of o-xylene, the T100 of 0.06Co-OMS-2-0.7-400 was 200 c and T20 was 130 C, and the catalytic activity was the best. (2) in order to further study the preparation method of redox precipitation, the cobalt and manganese molar ratio, cobalt acetate solution concentration and calcination temperature were modified. The results showed that cobalt acetate solution was 0.06 when the molar ratio of cobalt and manganese was 0.06. When the concentration of the liquid is 0.7mol/L and the calcination temperature is 400 C, the cobalt species is highly dispersed in the lattice of OMS-2, and the lattice oxygen can be activated effectively. The catalytic activity of the catalyst is obviously improved. (3) when the acid roots of manganese and cobalt salt (CH_3COO~-, NO_3~-, SO_4~ (2-)) are changed respectively, the result of XRD shows a significant result. The OMS-2.BET test results show that the specific surface area is 129.452m~2/g when acid root is CH_3COO~- and the specific surface area is 58.608m~2/g when acid root is SO_4~ (2-); when acid root is NO_3~-, the specific surface area is 46.757m~2/g; XRD test results show that only when acid root is CH_3COO~-, the crystal shape is obvious and no Co. The diffraction peaks of 3O4 show that the SEM results show that the catalyst of the acid root of the reactant is the uniform distribution of the tetrasquare particle.H2-TPR, and the result shows that the temperature of the reduction peak of the cobalt manganese compound catalyst 0.06Co-OMS-2-0.7-400 is the lowest. The results show that the cobalt manganese compound prepared from the salt of different acid roots is found. In the catalyst, the catalyst prepared by acetic acid has the largest catalytic activity. At 200 degrees C, the catalytic oxidation of o-xylene can be completely catalyzed.

【学位授予单位】：河北师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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