稀土掺杂对氯化氢氧化制氯气CuO-CeO2-SiO2催化剂结构和性能的影响

采用模板法制备了CuO-CeO₂-SiO₂和稀土掺杂的CuO-Ce_0.9M_0.1O₂-SiO₂ (M=La, Pr, Nd)催化剂. 运用X射线衍射(XRD), N₂吸附-脱附, 透射电镜(TEM), 拉曼(Raman)光谱, X射线光电子能谱(XPS)和氢气-程序升温还原(H₂-TPR)等手段对催化剂的结构进行表征, 并考察稀土掺杂对氯化氢催化氧化制氯气性能的影响. 结果表明, 稀土掺杂进入CeO₂晶格中形成良好的固溶体结构, 获得更小的晶粒尺寸和更高的比表面积, 并且显著提高了固溶体的表面氧空位浓度. 稀土掺杂显著影响了催化剂的氯化氢催化氧化活性, 活性顺序为: CuOCe_0.9La_0.1O₂-SiO₂>CuO-Ce_0.9Nd_0.1O₂-SiO₂>CuO-Ce_0.9Pr_0.1O₂-SiO₂>CuO-CeO₂-SiO₂, 固溶体氧空位浓度的高低与氯化氢氧化活性直接相关. 通过与Ce_0.9M_0.1O₂-SiO₂催化剂的结构和性能的对比, 发现氧空位浓度的提高并不能增强在固溶体表面发生的氯化氢氧化反应. 动力学测试显示, 稀土掺杂后, 氧分子的吸附成为反应过程的决速步骤. 但在V(O₂):V(HCl)=1 条件下, 更高的氧空位浓度导致了固溶体更低的氯化氢氧化反应速率. 结合机理分析认为, CuO-Ce_0.9M_0.1O₂-SiO₂催化剂更高的氧空位浓度增强了固溶体表面的“氧溢流”, 加快了氯化氢氧化的整体反应速率, 这是CuO-Ce_0.9M_0.1O₂-SiO₂具备高活性的关键.     

KCl对Cu-K-La/γ-Al2O3催化剂上HCl氧化反应性能的影响

采用等体积浸渍法制备了Cu-K-La/γ-Al₂O₃催化剂,考察了KCl对该催化剂催化HCl氧化制Cl₂反应性能的影响. 当KCl的负载量为5 wt%时,Cu-K-La/γ-Al₂O₃催化剂表现出较好的催化活性和稳定性,可在较大的原料气空速变化范围内使用. 在0.1 MPa,360 ℃,空速450 L/（kg-cat·h）和HCl/O₂摩尔比为2：1的反应条件下,Cu-K-La/γ-Al₂O₃催化剂上HCl转化率在100 h内保持85%以上. 表征结果表明,Cu,K和La物种均高度分散于γ-Al₂O₃载体表面;一定量KCl的加入可降低Cu²⁺ → Cu⁺的还原温度,从而提高Cu²⁺活性中心的催化活性.     

天然粘土基催化剂的制备及HCl氧化制氯性能

分别以廉价易得的天然粘土为载体,制得CeCuK/高岭土、CeCuK/膨润土、CeCuK/活性白土催化剂,并进行了BET、XRD、Raman、H2-TPR、ICP、SEM等表征及HCl催化氧化性能研究。结果显示：CeCuK/活性白土具有较大的比表面积、孔容和平均孔径,活性组分CuO晶粒在活性白土载体上分散较好;在三种催化剂上CuO物种还原顺序为：CeCuK/活性白土 > CeCuK/膨润土>CeCuK/高岭土;CeCuK/活性白土表现出较好的催化性能,当反应温度为430 ℃,HCl的质量空速为1.53 h-1时,V(HCl):V(O2)=1:1,催化剂上HCl的反应能力为749 L?kg-1?h-1。     

天然粘土基催化剂的制备及HCl氧化制氯性能

分别以廉价易得的天然粘土为载体,制得CeCuK/高岭土、CeCuK/膨润土、CeCuK/活性白土催化剂,并进行了BET、XRD、Raman、H2-TPR、ICP、SEM等表征及HCl催化氧化性能研究.结果显示:CeCuK/活性白土具有较大的比表面积、孔容和平均孔径,活性组分CuO晶粒在活性白土载体上分散较好;在3种催化剂上CuO物种还原顺序为:CeCuK/活性白土CeCuK/膨润土CeCuK/高岭土;CeCuK/活性白土表现出较好的催化性能,当反应温度为430℃,HCl的质量空速为1.53 h-1时,V(HCl)∶V(O2)=1∶1,催化剂上HCl的反应能力为749 L·kg-1·h-1.     

非晶态ZrO_2镶嵌的超细CeO_2催化HCl氧化

采用不同方法制备了铈锆复合氧化物催化剂用于催化HCl氧化反应。自发沉积策略制备的CeO_2@ZrO_2催化剂中,超细CeO_2纳米粒子均匀的镶嵌于非晶态ZrO_2中。CeO_2粒子显著的"尺寸效应"使得该催化剂具有更高的Ce~(3+)和氧空位浓度,而较高的Ce~(3+)和氧空位浓度使得催化剂具有优异的低温氧化还原性能和储释氧能力。催化性能测试表明,CeO_2@ZrO_2催化剂展现出最好的催化活性(1.90 gCl2·gcat~(-1)·h~(-1)),同时CeO_2粒子周围非晶态的ZrO_2阻碍CeO_2的高温烧结,提高了该催化剂的稳定性。     

载体焙烧温度对RuO_2/TiO_2催化HCl氧化性能的影响

以不同温度焙烧TiO(OH)_2得到的TiO_2为载体,采用湿法浸渍法制备RuO_2/TiO_2-C(C=450、550、650及750℃)催化剂,利用XRD、N_2吸附-脱附、TEM和H_2-TPR等表征手段研究催化剂的物理化学性质,并对其在HCl氧化反应中的催化性能进行考察.结果表明:载体焙烧温度对催化剂的结构与活性有显著影响.随着载体焙烧温度(≤650℃)的升高,RuO_2与TiO_2之间的晶面匹配度逐渐变高,促进了RuO_2在TiO_2表面的分散,其中RuO_2/TiO_2-650催化剂表现出最优的催化性能.而当载体焙烧温度过高时,RuO_2/TiO_2-750催化剂的反应活性大大下降,可能是由于过高的焙烧温度导致载体出现严重的烧结团聚现象,以及RuO_2与TiO_2之间过强的相互作用,阻碍了HCl氧化反应的进行.此外,减小RuO_2的粒径可以促进HCl氧化活性的提升.动力学结果显示,催化剂表面的HCl氧化反应主要受O_2分压的影响,表明O_2从催化剂表面的解离吸附为决速步骤.     

非晶态ZrO2镶嵌的超细CeO2催化HCl氧化

采用不同方法制备了铈锆复合氧化物催化剂用于催化HCl氧化反应。自发沉积策略制备的CeO₂@ZrO₂催化剂中,超细CeO₂纳米粒子均匀的镶嵌于非晶态ZrO₂中。CeO₂粒子显著的“尺寸效应”使得该催化剂具有更高的Ce³⁺和氧空位浓度,而较高的Ce³⁺和氧空位浓度使得催化剂具有优异的低温氧化还原性能和储释氧能力。催化性能测试表明,CeO₂@ZrO₂催化剂展现出最好的催化活性（1.90 g_Cl2·g_cat^-1·h^-1）,同时CeO₂粒子周围非晶态的ZrO₂阻碍CeO₂的高温烧结,提高了该催化剂的稳定性。     

铈基复合氧化物的结构及其对HCl催化氧化性能的影响

采用氨水共沉淀法制备了一系列铈基复合氧化物(Ce0.9M0.1O2,M=Cu、Cr、Zr、Ti、La),借助XRD、Raman、N2吸附-脱附、ESEM和H2-TPR等手段对复合氧化物的结构进行了表征,并考察了其在HCl催化氧化制Cl2过程中的性能.结果显示:Cu、Cr和Zr掺杂能显著减小复合氧化物晶粒尺寸,提高复合氧化物的比表面积和孔容,并提供更多的低温可还原氧物种.而La和Ti的掺杂可以获得较大的表面氧空位浓度以及增加高温可还原氧物种数目.复合氧化物结构和表面性质的变化显著影响了其HCl催化氧化活性,在430℃下铈基复合氧化物催化剂活性顺序为:Ce0.9Cu0.1O2Ce0.9Cr0.1O2Ce0.9Zr0.1O2Ce0.9Ti0.1O2Ce O2Ce0.9La0.1O2,低温可还原氧物种数目直接与催化剂活性有关.反应动力学测试显示催化剂低温可还原氧物种有利于HCl在催化剂表面的吸附和活化,而催化剂表面的氧空位可以促进氧分子的吸附和活化.     

HCl存在下CeO2基催化剂上乙烷氧化脱氢制乙烯

报道了一种HCl存在时温和条件下的乙烷氧化脱氢制乙烯催化转化新途径. 研究发现,在多种金属氧化物催化剂中,CeO₂呈现最佳乙烯生成的催化性能. 与纳米粒子相比,具有棒状和立方体状形貌的CeO₂纳米晶具有较高的乙烷转化率和乙烯选择性. 以MnO_x修饰CeO₂可进一步提高催化性能. 在8 wt% MnO_x-CeO₂催化剂上,723K反应2 h时乙烷转化率和乙烯选择性分别为94%和69%. 该催化剂性能稳定,反应100 h乙烯收率可保持在65%-70%. HCl的存在对乙烯的选择性生成起着至关重要的作用,一部分乙烯来自于氯乙烷的脱HCl反应.     

Zn-Al共掺杂La2O3催化剂在甲烷氧化偶联中的性能

采用柠檬酸溶胶凝胶法制备了Zn掺杂和Zn-Al共掺杂的La_2O_3催化剂,运用原位表征技术研究了该催化剂在甲烷氧化偶联(OCM)反应中的构效关系。原位XRD表征结果发现,La_2O_3晶体在高温下沿c轴发生热膨胀。H2-TPR结果显示,La_2O_3基催化剂中含有两种类型的氧物种,即强结合氧和弱结合氧;XPS结果表明,强结合氧归属于为O-。Zn掺杂的La_2O_3催化剂在高温下形成更多的氧空位,能活化氧气产生更多的强结合氧,因而在OCM反应中表现出较好的催化性能。Al的共掺杂能促进Zn在La_2O_3中的分散,进一步增加强结合氧数量,提升OCM反应C2+烃的选择性。     

Influence of preparation methods on CuO-CeO2 catalysts in the preferential oxidation of CO in excess hydrogen

Influence of three different preparation methods, i.e. impregnation, coprecipitation, and inverse coprecipitation, on the preferential oxidation of CO in excess hydrogen （PROX） over CuO-CeO2 catalysts has been investigated and CuO-CeO2 catalysts are characterized using BET, XPS, XRD, UV Raman, and TPR techniques. The results show that the catalysts prepared by coprecipitation have smaller particle sizes, well-dispersed CuOx species, more oxygen vacancies, and are more active in the PROX than those prepared by the other methods. However. the inverse coprecipitation depresses the catalytic performance of CuO-CeO2 catalysts and causes the growth of CuO-CeO2 because of different pH value in the precipitation process.     

Low-temperature CO oxidation over CuO-CeO2/SiO2 catalysts：Effect of CeO2 content and carrier porosity

The effects of CeO2 contents and silica carder porosity with their pore diameters ranging from 5.2 nm to 12.5 nm of CuO-CeO2/SiO2 catalysts in CO oxidation were investigated. The catalysts were characterized by N2 adsorption/desorption at low temperature, X-ray diffraction (XRD), temperature-programmed reduction by H2 (H2-TPR), oxygen temperature programmed desorption (O2-TPD) and X-ray photoelectron spectroscopy (XPS). The results suggested that, the ceria content and the porosity of SiO2 carder possessed great impacts on the structures and catalytic performances of CuO-CeO2/SiO2 catalysts. When appropriate content of CeO2(Ce content ≤8 wt%) was added, the catalytic activity was greatly enhanced. In the catalyst supported on silica carrier with larger pore diameter, higher dispersion of CuO was observed, better agglomeration-resistant capacity was displayed and more lattice oxygen could be found, thus the CuO-CeO2 supported on Si-1 showed higher catalytic activity for low-temperature CO oxidation.     

Influence of rare-earth metal doping on the catalytic performance of CuO-CeO2 for the preferential oxidation of CO in excess hydrogen

Doping of different rare-earth metals （Pr, Nd, Y and La） had an evident influence on the catalytic performance of CuO-CeO2 for the preferential oxidation （PROX） of CO in excess hydrogen. As for Pr, the doping enhanced the catalytic activity of CuO-CeO2 for PROX. For example, the CO conversion over the above catalyst for PROX was higher than 99% at 120 °C. Especially, the doping of Pr widened the temperature window by 20 °C over CuO-CeO2 with 99% CO conversion. For Nd, Y, and La, the doping depressed the catalytic activity of CuO-CeO2 for PROX. However, the doping of transition metals markedly improved the selectivity of CuO-CeO2 for PROX.     

Influence of pH values in the preparation of CuO-CeO2 on its catalytic performance for the preferential oxidation of CO in excess hydrogen

CuO-CeO2 catalyst prepared with co-precipitation showed high catalytic performance for the preferential oxidation of CO in excess hydrogen (PROX). Influence of pH values in the preparation of CuO-CeO2 on its catalytic performance was investigated in this work. The CuO-CeO2 catalyst prepared at pH = 13.03 had the smallest particle size (5.4 nm), the largest surface areas (138 m2/g) and the highest activity with CO conversion of 99.6% at 130 ℃. The CuO-CeO2 catalyst was characterized using BET, XRD and TPR techniques. The results showed that when the pH value of the mixed solution containing Cu and Ce species was properly adjusted, both the adsorption layers and diffusion layers of the formed colloidal particles in hydroxide precursor of CuO-CeO2 were modified, resulting in the better catalytic performance for PROX on the final CuO-CeO2 catalyst.     

A simple and efficient synthesis of 2-substituted benzothiazoles catalyzed by H_2O_2/HCl

A simple and efficient procedure for the synthesis of substituted benzothiazoles through condensation of 2-aminothiophenol with aromatic aldehydes in the presence of H_2O_2/HCl system in ethanol at room temperature is described.The target compounds have been characterized by ~1H NMR,~(13)C NMR,IR and MS.Short reaction time,easy and quick isolation of the products,and excellent yields are the main advantages of this procedure.     

High performance CuO-CeO2 catalysts for selective oxidation of CO in excess hydrogen： Effect of hydrothermal preparation conditions

High performance CuO-CeO₂ catalysts for selective oxidation of CO in excess hydrogen were prepared by a hydrothermal method under different preparation conditions and evaluated for catalytic activities and selectivities. By changing the n_CTAB/n_Ce ratio and hydrothermal aging time, the catalytic activity of the CuO-CeO₂ catalysts increased and the operating temperature window, in which the CO conversion was higher than 99%, was widened. XRD results showed no peaks of CuO_x species and Cu-Ce-O solid solution were observed. On the other hand, Cu⁺ species in the CuO-CeO₂ catalysts, which was associated with a strong interaction between copper oxide clusters and cerium oxide and could be favorable for improving the selective oxidation performance of CO in excess H₂, were detected by H₂-TPR and XPS techniques.     

三维有序大孔SnO2基固溶体用于有效燃烧碳烟颗粒

柴油车尾气排放的碳烟颗粒对人类的生存环境和身体健康带来了严重危害.催化燃烧是消除碳烟颗粒污染的有效途径.碳烟颗粒催化燃烧是固-固-气相反应,因此催化剂本身具有活泼的氧中心且其能与碳烟颗粒有效接触是提高反应效率的关键因素.为改善碳烟颗粒与催化剂的接触,设计制备三维有序大孔(3DOM)催化剂,使碳烟颗粒可以进入催化剂孔道内部,增加其与催化剂的有效接触,是提高反应活性的有效途径.此外,在催化剂晶格中掺杂其它金属离子形成固溶体结构,可提高其氧化还原性能,也可有效提高其碳烟燃烧活性.SnO2富含活泼的表面缺位氧和可还原的晶格氧,且其熔点高达1630 oC,具有良好的热稳定性,被广泛用于制备气体传感、电化学和催化等材料.在过去的6年中,本课题组在SnO2催化化学领域做了大量系统的工作,将SnO2基催化材料用于多种环保和能源反应.发现通过其它阳离子Fe3+,Cr3+,Ta5+,Ce4+和Nb5+等的掺杂,替换晶格中部分Sn4+形成金红石型SnO2固溶体结构,可显著提高催化剂氧物种的流动性、活性和本身的热稳定性.本文采用胶体晶体模板法制备出了Ce4+,Mn3+和Cu2+离子掺杂的SnO2三维有序大孔固溶体催化剂用于松散接触条件下的碳烟催化燃烧.采用SEM,TEM,XRD,STEM-mapping,O2-TPD和XPS等手段对催化剂进行表征,研究其碳烟催化燃烧性能.SEM和TEM结果表明已成功合成三维有序大孔结构样品.XRD,Raman和STEM-mapping结果表明,Ce4+,Mn3+和Cu2+离子均进入四方金红石型SnO2晶格形成固溶体结构.另外,Raman,H2-TPR,XPS和O2-TPD等结果发现上述离子掺杂三维大孔SnO2后,催化剂表面形成了更活泼、丰富的氧物种,有利于碳烟颗粒燃烧.其中3DOM-Cu1Sn9催化剂具有最丰富的活泼氧中心,因此表现出最高的活性.