负载型烯土复合氧化物燃烧催化剂的失活研究

本文探讨了负载型稀土复合氧化燃烧催化剂在使用过程中失活的主要特征，通过ＸＲＤ，ＴＥＭ，ＢＥＴ比表面测定及不同使用期的活性测定，证实催化剂在使用后的４－８个月内，烧结是失活的主因；因ＸＰＳ谱显示硫中毒积累性，以ＳＯ＾２－４形式沉积于催化剂表面，构成了燃烧催化剂后期失活的主要因素，由于催化燃烧反应在较高的温度进行，并充分供氧，所以积炭引起失活的可能性较小，这可以从孔容数据和一些电镜照片中得到证实。     

氟里昂12(CCl2F2)燃烧分解催化剂性能的研究

本文对贵金属、氧化物和复合氧化物体系催化剂上氟里昂_(12)(F_(12))燃烧分解反应进行了活性评价和稳定性研究.结果表明:TiO_2,ZrO_2/TiO_2催化剂对氟里昂_(12)燃烧分解反应具有良好的低温催化活性和较好的稳定性,ZrO_2/TiO_2催化剂具有一定的臭氧-催化氧化活性     

Ag—Mn,Ag—Co和Ag—Ce复合氧化物上CO,丙酮和吡啶的催化燃烧

本文考察了Ａｎ－Ｍｎ，Ａｇ－Ｃｏ和Ａｇ－Ｃｅ复合氧化物上ＣＯ，丙酮和吡啶的催化氧化性能，结果表明，双组分Ａｇ－Ｍｎ／Ａｌ２Ｏ３和Ａｇ－Ｃｏ／Ａｌ２Ｏ３催化剂的氧化活性均高于单组分Ａｇ／Ａｌ２Ｏ３．在Ａｇ－Ｃｅ／Ａｌ２Ｏ３催化剂上，ＣＯ氧化反应的速率言程可用ｒ＝ｋＰｏ２＾ｍＰＣＯ来表示，随着催化剂中氧化铈含量的增加，对氧的反应级数明显下降。     

氟里昂12（CC12F2）燃烧分解催化剂性能的研究

本文对贵金属、氧化物和复合氧化物体系催化剂上氟里昂１２（Ｆ１２）燃烧分解反应进行了活性谰价和稳定性研究。结果表明：ＴｉＯ２,ＺｒＯ２／ＴｉＯ２催化剂对氟里昂１２燃烧分解反应具有良好的低温催化活性和较好的稳定性,ＺｒＯ２／ＴｉＯ２催化剂具有一定的臭氧－催化氧化活性。     

La2O3—ZrO2缺陷萤石型燃烧催化剂的制备

缺陷萤石型Ｌａ２Ｏ３－ＺｒＯ２固溶体的催化燃烧活性受制备条件的影响,本文通过对其共沉淀前体的表面结构和热分解过程的分析,发现共沸蒸馏的办法可以有效地控制前体表面羟基的缩合过程,减少团聚,保持前体中金属离子均匀分散,为生成缺陷有序的烧结石型的Ｌａ２Ｚｒ２Ｏ７复氧化物提供了可能。复合氧化物固溶体的表面阳离子配置情况与样品的催化氧化性能密切相关,软团聚前体的烧结产物对甲烷燃烧反应具有更高的催化活性。     

负载型稀土复合氧化物燃烧催化剂的失活研究

本文探讨了负载型稀土复合氧化物燃烧催化剂在使用过程中失活的主要特征.通过XRD,TEM,BET比表面测定及不同使用期的活性测定.证实催化剂在使用后的4—8个月内,烧结是失活的主因;而XPS谱显示硫中毒有积累性,以SO_4~(2-)形式沉积于催化剂表面,构成了燃烧催化剂后期失活的主要因素.由于催化燃烧反应在较高的温度下进行,并充分供氧,所以积炭引起失活的可能性较小,这可以从孔容数据和一些电镜照片中得到证实.     

稀土-过渡金属复合氧化物催化剂用于汽车尾气净化研究

以不含贵金属的稀土 过渡族金属四元复合氧化物为催化剂 ,模拟汽车尾气的组成含量 ,运用连续流动式反应器 ,研究了四元复合氧化物La0 5Sr0 5Ni1 -xCuxO3系列 (x =0—1 0 )对CO和NOx 的催化氧化还原消除活性及其在消除反应条件的抗硫中毒能力 .实验结果表明 ,钙钛矿型四元复合氧化物催化剂La0 5Sr0 5Ni0 5Cu0 5O3对CO和NOx 的氧化还原消除都具有较高的活性 ;脉冲中毒实验指出 ,当反应温度≥ 3 0 0℃ ,SO2 在催化剂中的脉冲积累含量为 1 2 2× 1 0 - 2 mmol时 ,该复合氧化物仍表现出良好的抗硫毒性能 ,它对CO的氧化消除活性并未因体系中SO2 的存在而受到影响     

负载型La0.8Sr0.2MnO3催化剂对油烟燃烧的催化作用

采用浸渍法制备Ld0.8Sr0.2MnO3负载型纳米催化剂,用X-射线衍射仪(XRD),扫描电镜(SEM)对催化剂负载层的表面形态、晶相结构和粒径大小进行了表征．并考察了催化剂对油烟低温燃烧的催化活性,以及不同负载量和不同浸渍时间对催化活性的影响．结果显示,催化剂经700℃焙烧后形成了钙钛矿La0.8Sr0.2MnO3纳米晶粒,催化剂对油烟催化燃烧具有较好的低温高活性．     

低浓CH4催化燃烧的研究

制备了陶瓷蜂窝结构贵金属和金属氧化物催化剂,研究了CH_4的氧化活性,其中金属Pd催化剂具有最佳的活性,使用Pd催化剂测定了低浓CH_4燃烧的若干基本参数,获得若干基础性的结果。     

Redox reactions of iron and manganese oxides in complex systems

• Mechanisms of redox reactions of Fe- and Mn-oxides were discussed. • Oxidative reactions of Mn- and Fe-oxides in complex systems were reviewed. • Reductive reaction of Fe(II)/iron oxides in complex systems was examined. • Future research on examining the redox reactivity in complex systems was suggested. Conspectus Redox reactions of Fe- and Mn-oxides play important roles in the fate and transformation of many contaminants in natural environments. Due to experimental and analytical challenges associated with complex environments, there has been a limited understanding of the reaction kinetics and mechanisms in actual environmental systems, and most of the studies so far have only focused on simple model systems. To bridge the gap between simple model systems and complex environmental systems, it is necessary to increase the complexity of model systems and examine both the involved interaction mechanisms and how the interactions affected contaminant transformation. In this Account, we primarily focused on (1) the oxidative reactivity of Mn- and Fe-oxides and (2) the reductive reactivity of Fe(II)/iron oxides in complex model systems toward contaminant degradation. The effects of common metal ions such as Mn²⁺ , Ca²⁺, Ni²⁺, Cr³⁺ and Cu²⁺, ligands such as small anionic ligands and natural organic matter (NOM), and second metal oxides such as Al, Si and Ti oxides on the redox reactivity of the systems are briefly summarized.     

低分子量有机化合物对MnO_2和土壤氧化锰的还原溶解作用

为考察土壤锰氧化物的还原溶解行为,本文选取常见的根系分泌的8种有机酸(抗坏血酸、香草酸、柠檬酸、草酸、酒石酸、水杨酸、半胱氨酸和邻苯二甲酸)和1种酚类化合物(邻苯二酚),人工合成的Mn O2和5种富含氧化锰的土壤(广东徐闻的砖红壤、海南澄迈的砖红壤、云南昆明的砖红壤、浙江嵊县的红壤和江苏南京的黄棕壤),研究了有机化合物对氧化锰的还原溶解作用.结果表明,较低p H和较高温度有利于有机化合物对Mn O2的还原溶解.在p H 4.5—5.5和温度5—45℃范围内,不同有机化合物还原溶解Mn O2能力的大小顺序为:邻苯二酚半胱氨酸抗坏血酸香草酸柠檬酸草酸≈酒石酸水杨酸≈邻苯二甲酸.邻苯二酚、半胱氨酸和抗坏血酸对土壤中氧化锰也有较强的还原溶解能力.当5种土壤比较时,徐闻砖红壤中还原溶解出的锰量最高,其次为昆明砖红壤,嵊县红壤中还原溶解出的锰量最小.当有还原性有机化合物存在时徐闻砖红壤、昆明砖红壤和澄迈砖红壤中的氧化锰容易发生还原溶解反应,增加土壤中可溶态和交换态Mn2+的含量,并可能对植物产生锰毒害.     

Amorphous oxides of manganese as new sorbents of strontium ions

Samples with the best adsorption properties are selected as a result of investigations conducted on synthesis of manganese-dioxide-based materials and study of their physicochemical properties. Materials were selected on the basis of their low cost and the simplicity of their production technology. In the laboratory the synthesis and analyses of materials was carried out for selected samples. The sorption of a series of elements is studied for a more detailed investigation of materials obtained. The results obtained will promote the synthesis of materials with improved adsorption properties with the aim of their application for purification of water from strontium. It is shown that the most promising way for amendment of manganese oxide is modification of this material using acid-resistant oxides. These oxides are also less expensive than existing sorbents for strontium.     

Amorphous oxides of manganese as new sorbents of strontium ions

Samples with the best adsorption properties are selected as a result of investigations conducted on synthesis of manganese-dioxide-based materials and study of their physicochemical properties. Materials were selected on the basis of their low cost and the simplicity of their production technology. In the laboratory the synthesis and analyses of materials was carried out for selected samples. The sorption of a series of elements is studied for a more detailed investigation of materials obtained. The results obtained will promote the synthesis of materials with improved adsorption properties with the aim of their application for purification of water from strontium. It is shown that the most promising way for amendment of manganese oxide is modification of this material using acid-resistant oxides. These oxides are also less expensive than existing sorbents for strontium.     

Al2O3负载Pd催化剂对溴氯代乙酸的催化加氢脱卤研究

分别以氧化铝、氧化硅和多壁碳纳米管为载体,采用沉淀-沉积法制备负载型Pd催化剂.采用透射电镜(TEM)、X射线衍射(XRD)、电感耦合等离子体发射光谱(ICP-AES)、X射线光电子能谱(XPS)等手段对材料进行表征,并对溴氯代乙酸(BCAA)的液相催化加氢脱卤反应进行了研究.结果表明,由于Pd/Al_2O_3催化剂具有较高的等电点,因此相对于Pd/CNT、Pd/SiO_2在BCAA的加氢脱卤反应中具有更高的活性.以Pd/Al_2O_3为目标催化剂,对BCAA的加氢脱卤展开研究,发现催化活性随Pd的负载量的增加而提高.当反应物的初始浓度为0. 1 mmol·L~(-1),pH值为5.6,Pd(1.39)/Al_2O_3用量为25 mg·L~(-1)时,BCAA在20 min时可以实现完全脱溴并在反应2 h后脱氯达60.5%.另外,pH的升高不利于脱卤反应的进行.当反应物的浓度从0. 05 mmol·L~(-1)提高到0.4 mmol·L~(-1)时,反应初活性从1.55 mmol·L~(-1) min~(-1) gCat~(-1)提高到8.37 mmol·L~(-1) min~(-1) gCat~(-1).进一步通过拟合Langumir-Hinshelwood模型,相关系数达到0.97,说明BCAA的加氢脱卤是吸附控制机制.催化过程中溴氯代乙酸的脱溴和脱氯具有协同作用,反应最终生成乙酸.     

Fe-Mn/AC催化湿式过氧化氢氧化间甲酚

采用等体积浸渍法制备了一种新型Fe-Mn/AC催化剂,应用于催化湿式过氧化氢氧化(CWPO)间甲酚废水.通过SEM和XRF表征了其表面形态结构和元素组成,通过穆斯堡尔谱分析了催化剂中铁离子的存在形态,结果表明,新型Fe-Mn/AC催化剂中的铁以二价铁、三价铁以及四氧化三铁的形式存在.通过正交实验考察了CWPO降解间甲酚的影响因素,结果表明,各因素对间甲酚转化率影响的大小顺序依次为:底物初始p H值反应温度反应时间催化剂投加量.通过正交实验得到CWPO降解间甲酚的最佳反应条件.当间甲酚浓度为100 mg·L-1、反应温度为40℃、反应时间为40 min、催化剂投加量为0.6 g·L-1及底物初始p H值为3时,间甲酚转化率为99.8%,TOC去除率为28.3%.气相色谱/质谱联用没有检测到中间产物,气相色谱检测到CWPO降解间甲酚中间产物主要为乙酸和丙酸.     

碳纳米管负载Pd基催化剂对水中2,4-二氯酚的催化加氢脱氯

对多壁碳纳米管(MWNTs)进行掺氮得到含氮的多壁碳纳米管N-MWNTs,分别以MWNTs和N-MWNTs为载体,采用浸渍法合成了催化剂Pd/MWNTs和Pd/N-MWNTs.使用透射电镜(TEM)、电感耦合等离子体发射光谱仪(ICP)、X射线衍射仪(XRD)、元素分析仪等对催化剂进行了表征,并对2,4-二氯酚(2,4-DCP)的液相催化加氢脱氯反应进行了研究.结果表明,Pd/N-MWNTs对2,4-DCP具有更高的催化活性;该反应体系的催化反应过程不受传质阻力的影响;2,4-DCP在催化剂上的加氢脱氯行为符合Langmuir-Hinshelwood模型,即2,4-DCP的还原脱氯受表面吸附所控制.     

Chemistry and adsorption-desorption properties of manganese oxides deposited in Forehill Water Treatment Plant,Grampian, Scotland

Manganese oxide coatings on sand particles within filtration beds from a water treatment plant in Grampian, Scotland were examined to determine their control on metal mobility. This study first sought to characterise the oxides, notably their mineralogy and metal content, to provide a foundation for studies on the adsorption of dissolved metals from the treated water by the oxides. The oxides were examined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and analysed by flame atomic absorption spectrophotometry (AAS). These techniques showed the oxide coatings were amorphous but uniformly distributed over each sand grain. The oxides were selectively removed from the sand grains prior to analysis by AAS using a hydroxylamine hydrochloride selective leaching method. The compositional range of the extracts was 100–150 mg L⁻¹ Mn; 30–55 mg L⁻¹ Fe; 17–56 mg L⁻¹ Ca; 4.6–7.0 mg L⁻¹ Ni; 4.6–6.8 mg L⁻¹ Zn and 1.3–5.7 mg L⁻¹ Mg. When these results are expressed as mg of metal per mg of Mn, the metal content of the oxides is remarkably uniform: 0.25–0.37 mg Fe; 0.14–0.35 mg Ca; 0.035–0.042 mg Ni; 0.035–0.040 mg Zn; 0.01–0.04 mg Mg. The greatest metal concentrations were consistently found in the upper 3 cm of the filtration bed, and these decrease with increasing depth. After the beds are cleaned a more uniform distribution of metals occurs throughout the bed. The metals taken up by the manganese coating are retained over a wide pH range with the exception of Ca and Mg which desorb to a significant extent. The percentage of calcium and magnesium lost from the coating ranges from 30–94%, the amount being dependent on the final pH of the solution. The presence of manganese oxide in the filtration beds appears to be advantageous in terms of removal of transition metals from the treated water.