溶胶-凝胶法制备铁酸盐超微粒子催化剂

采用溶胶－凝胶法制备了含Zn,Ni,Co的铁酸盐超微粒子催化剂，运用DTA－TG、IR、XRD以及BET比表面测试等手段对所制备的样品进行了表征。同时，考察了铁酸盐对二氧化碳选择性氧化乙苯制苯乙烯的催化性能。结果表明：制备的铁酸盐均为尖晶石型晶体，粒子的比表面积为31．9－36．3m^2/g，晶粒大小约为30－35nm，在由二氧化碳选择性氧化乙苯制苯乙烯的反应中表现出较好的催化活性。     

尖晶石型铁酸盐的制备和表征研究

本文采用空气氧化湿法制备尖晶石铁酸盐，得到最佳生成条件为：Ｒ－２ＯＨ＾－／（Ｍ＾２＋＋Ｆ２＋）≥１．０；Ｍ＾２＋／Ｆｅ＾２＋＝０．５摩尔比；氧化温度３４３－３５８Ｋ；氧化时间１０－２５小时。通过ＸＲＤ、ＴＰＲ和ＴＰＤ等方法对其进行表征，讨论了尖晶石型铁酸盐的氧化－还原活及其化学组成和结构的变化。     

尖晶石型铁酸盐的制备及表征研究

本文采用空气氧化的湿法制备了尖晶石型铁酸盐，得到最佳生成条件为：在空气流速为２００ｍｌ／ｍｉｎ和配料比Ｒ＝２ＯＨ－／（Ｍ２＋＋Ｆｅ２＋）≥１．０，Ｍ２＋／Ｆｅ２＋＝０．５（摩尔比）下氧化温度和时间分别为３４３－３５８Ｋ和１０－２５ｈ。使用ＸＲＤ、ＴＰＲ和ＴＰＤ等方法对所制备的铁酸盐进行了表征，研究了其结构特征及氧化－还原活性，并讨论了该活性与化学组成及结构的关系。     

CoFe2O4纳米微粒的制备及其催化性能

采用溶胶-凝胶法制备了铁酸钴纳米微粒催化剂，运用XRD、IR、TPR以及BET比表面测试等手段对所制备的样品进行了表征。研究了铁酸钴的结构和氧化还原性质，考察了铁酸钴对二氧化碳选择性氧化乙苯制苯乙烯的催化性能。结果表明：制备的铁酸钴微粒的比表面积为36.3m^2/g，晶粒大小约为30nm。在由二氧化碳选择性氧化乙苯制苯乙烯的反应中表现出较好的催化活性。     

铁酸盐MFe2O4的氢气还原热失重分析和氧缺位铁酸盐MFe2O4-δ的制备条件

使用程序升温（２９８－８４３Ｋ）和等温（５２３Ｋ、５７３Ｋ和６２３Ｋ）热失重分析研究了多种方法制备的尖晶石结构铁酸盐ＭＦｅ２Ｏ４（Ｍ＝Ｆｅ、Ｍｎ、Ｃｏ、Ｎｉ）的还原行为,讨论了铁酸盐的制备方法、粒径和比表面积对其还原性能的影响。根据程序升温过程中和等温还原下铁酸盐的失重量分别定量地测定了其活化速度和失氧速度,得出了制备氧缺位铁酸盐ＭＦｅ２Ｏ４－δ（０＜δ≤１）的最佳温度和时间。     

尖晶石型铁酸盐催化剂的担体效应考察

用共沉淀法和浸渍法制备了ZnFe_2O_4、ZnCrFeO_4以及它们在γ-Al_2O_3,TiO_2,SiO_2小球上的担载催化剂.用TPR.XRD.ESR,MBS,脉冲反应等技术对这些催化剂进行了考察.结果表明,载体的引入在不同程度上改变了催化剂的氧化还原性能.在不同的载体上形成尖晶石结构的趋势不同.铁酸盐尖晶石相无论是非载的还是担载的对于多次交替的氧化还原处理不敏感.然而氧化铁相则较不稳定,而且在不同载体上稳定性相差较大.加Cr组份有助于担体上形成正尖晶石相.在某些较难形成铁酸盐尖晶石相的担载催化剂中,其相的组成较为复杂.脉冲反应的结果表明,担载的单一正尖晶石铁酸盐以及γ-Al_2O_3上的氧化铁对丁烯氧化脱氢均有一定的活性,对于既含较多量正尖晶石铁酸盐又含一定量氧化铁的催化剂,其较好的催化性能暗示在这两相之间可能存在某种协同效应.     

废水中偏二甲肼在Ni/Fe催化剂上的催化分解研究

研究了Ni/Fe催化剂对废水中偏二甲肼臭氧化分解的催化作用,考察了组分含量、体系的pH值和偏二甲肼初始浓度对催化反应的影响.结果表明,Ni/Fe催化剂对水中偏二甲肼的臭氧化具有良好的催化活性.催化剂组分含量、体系的pH值和初始浓度对反应的影响程度不大.对催化剂的XRD表征结果表明,催化剂主要由尖晶石结构的铁酸盐和FeNi3合金相组成,催化剂的良好催化性能与催化剂中尖晶石结构的铁酸盐和FeNi3合金相的形成有关.     

铁酸盐MFe2O4的氢气还原热失重分析和氧缺位铁酸盐MFe2O4-δ的制备条件

使用程序升温(298-843K)和等温(523K、573K和623K)热失重分析研究了多种方法制备的尖晶石结构铁酸盐MFe₂O₄(M=Fe、 Mn、 Co、 Ni)的还原行为,讨论了铁酸盐的制备方法、粒径和比表面积对其还原性能的影响。根据程序升温过程中和等温还原下铁酸盐的失重量分别定量地测定了其活化速度和失氧速度,得出了制备氧缺位铁酸盐MFe₂O_4-δ(0<δ≤1)的最佳温度和时间。     

氟离子配位在氧化法制备高铁(Ⅵ)酸盐中的作用

氟离子配位在氧化法制备高铁(Ⅵ)酸盐中的作用;高铁(Ⅵ)酸盐;六氟合铁(Ⅲ)酸钾;次氯酸钠;稳定性     

Ni-Fe催化剂乙醇部分氧化制氢的研究

研究了Ni Fe催化剂对乙醇部分氧化制氢反应,系统地考察了不同O2/C2H5OH摩尔比及反应温度下催化剂的性能.发现Ni Fe催化剂对乙醇部分氧化制氢具有较好的催化活性,其中组成为Ni50Fe50催化剂最好,最佳的反应条件是O2/C2H5OH=1.0,T=573 K.XRD谱图表明催化剂主要由尖晶石结构的铁酸盐和FeNi3合金相组成. XPS结果说明,催化剂体相以还原态FeNi3合金相为主,表面以氧化态的铁酸盐为主.稳定性考察的结果表明,催化剂经40 h反应后,对氢的选择性明显下降,此时对应的FeNi3物相衍射峰强度也明显降低,表明催化剂对H2选择性的下降与FeNi3物相的转变有关.     

Deep Oxidation of Methane over Nano-Sized Ferrites with Spinel Structures

Ferrites with spinel structures as catalysts for the deep oxidation of methane have been studied by X-ray phase analysis and temperature programmed reduction. The most active catalysts are the nano-sized ferrites of cobalt and nickel, prepared by the decomposition of polynuclear complexes, with Al₂O₃ as carrier and with addition of a surface active agent to increase the thermal stability of the catalysts. At low temperatures (up to 450 °C), the effect of the size factor appears with the increase in specific catalytic activity of cobalt and nickel ferrites with decreasing of their particles. A correlation of the catalytic activity with the quantity and mobility (reactivity) of oxygen in the ferrites has been established.     

ZnFe2O4中阳离子分布对苯酚H2O2羟化制苯二酚催化活性的影响

具有尖晶石结构的铁酸盐是苯酚H2O2羟化合成苯二酚的有效催化剂.分别用共沉淀和水热法制备了ZnFe2O4,并用Mossbauer,XRD和ESR等方法予以表征.发现不同方法制备的ZnFe2O4中阳离子在四面体和八面体位置的分布不同,认为阳离子分布影响了催化活性.     

Effect of a structure-size factor on the catalytic properties of complex oxide compositions in the reaction of deep methane oxidation

The following catalysts for deep methane oxidation were studied using X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, temperature-programmed reduction with hydrogen, and temperature-programmed ammonia desorption: highly dispersed supported aluminum-manganese and cobalt-zirconium catalysts; bulk and supported nanosized spinel ferrites. It was found that structure-size factors in complex oxide nanocomposites are responsible for differences in the catalytic properties (activity and thermal stability). The efficiency of the supported ferrite and cobalt-zirconium catalysts depends on both the oxygen-catalyst bond strength and the acid properties of catalyst surfaces.     

Application of Nanosized Cu0.5Co0.5Fe2O4 Spinel Ferrite as a Nanocatalyst in the Synthesis of 14‐Aryl‐14H‐dibenzo[a,j]xanthene Derivatives under Solvent‐free Conditions

Copper and cobalt substituted spinel ferrites Cu_1‐xCo_xFe₂O₄ (0≤X≤1) have been synthesized by using hydrothermal method. The resultant spinel ferrites were systematically characterized by different techniques such as X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FT‐IR). It was indicated that all the resultant spinel ferrites obtained by the hydrothermal method had the single‐phase crystalline. The resultant spinel ferrites were employed in the synthesis of 14‐aryl‐14‐H‐dibenzo[a,j]xanthene derivatives. It was found that the nanocatalyst Cu_0.5Co_0.5Fe₂O₄ displays the best performance in the synthesis of 14‐aryl‐14H‐dibenzo[a,j]xanthenes. The catalyst was reused several times without significant loss of its activity for the preparation of desired product. In addition high yields of the products, solvent‐free conditions and reusability of the catalyst are other worthwhile advantages of the present study.     

超临界CO2中醇类的分子氧氧化*

本文以催化剂体系为主线,介绍了超临界二氧化碳中以分子氧代替化学计量氧化剂的醇类清洁氧化技术的研究进展。分析了所研究的催化剂体系的催化性能,主要有钯、铂、钌、金等金属催化剂以及杂多酸催化剂体系;介绍了超临界二氧化碳体系中相行为的影响。指出超临界二氧化碳中醇类清洁氧化技术的研究才刚刚起步,其中高效催化剂体系的开发是超临界二氧化碳中醇类清洁氧化技术能否工业化的关键。     

铁锆复合氧化物催化甲醇与CO2直接合成 DMC反应性能

采用溶胶-凝胶法制备的铁锆复合氧化物催化甲醇与CO2直接合成碳酸二甲酯（DMC）反应,其催化活性远高于氧化铁和氧化锆,当铁锆摩尔比为5：1时,其催化活性是氧化锆的2倍。利用XRD、XPS、IR、TPD和N2物理吸附-脱附等技术对催化剂进行了表征。结果表明,氧化铁主要以六方晶相的α-Fe2O3形式存在,氧化锆主要以四方晶相存在,铁锆之间发生了相互作用,使铁锆复合氧化物表面L酸增强和少量B酸产生。L酸的增强和B酸的产生是催化剂催化活性增加的主要原因,并对催化剂的催化作用机理进行了探讨。     

Evaluation of the catalytic effect of ZnO as a secondary phase in the Ni0.5Zn0.5Fe2O4 system and of the stirring mechanism on biodiesel production reaction

In search of efficient ways to produce biodiesel under environmentally friendly conditions, catalytic reactions have been explored with emphasis on replacing homogeneous by heterogeneous catalysis with the use of new catalyst types, such as the spinel ferrites, which are described as a viable option, since they are stable, highly active, inexpensive, reusable, and allow the easy recovery of the reaction medium through the application of magnetic fields. In this context, the present work proposes to contribute to the consolidation of the catalytic viability of the Ni_0.5Zn_0.5Fe₂O₄ system obtained by combustion reaction, because although previous studies indicate the catalytic effectiveness of this system in polyphasic form, the present work seeks as differential to evaluate the influence of the secondary phases and magnetization of the Ni-Zn system in the conversion to biodiesel, and for this purpose, it aims to evaluate the catalytic effect of ZnO formed as secondary phase and obtained concomitantly in the Ni-Zn ferrite synthesis, besides evaluating the effect of the stirring mechanism used in biodiesel production reaction by the ethyl transesterification of soybean oil. The synthesized Ni-Zn ferrites and ZnO sample were characterized by X-ray diffraction (XRD), nitrogen adsorption textural analysis (BET), particle size distribution, and then, tested in two reactor types, one with magnetic stirring, and another of mechanical stirring, to observe the magnetization effect of the material, and the characterization of the obtained biodiesels by gas chromatography (GC) and acidity index. The performed catalytic tests showed that the Ni-Zn ferrites promoted excellent ester conversions with values near and above 94%, thus confirming that although ZnO also promotes good ester conversion (83.9%), the catalytic effectiveness of the Ni-Zn ferrite is evident and independent of secondary phases. Moreover, the catalytic tests performed in the magnetic stirring reactor using the Ni-Zn ferrites as catalysts made it possible to realize that their magnetic properties may be interference in the catalytic effectiveness, being this, a more determining factor than the surface characteristics.     

A novel magnetic silica supported spinel ferrites NiFe2O4 catalyst for heterogeneous Fenton-like oxidation of rhodamine B

As the heterogeneous Fenton-like catalyst, a series of spinel ferrites magnetic nanoparticles NiFe₂O₄ and NiFe₂O₄@SiO₂ catalysts were synthesized and were applied into the oxidation of rhodamine B, which exhibited the good catalytic performance and strong magnetic separation after reaction.     

Oxidative dehydrogenation of ethylbenzene with carbon dioxide over zeolite-supported iron oxide catalysts

Oxidative dehydrogenation of ethylbenzene with carbon dioxide was carried out over ZSM-5 zeolite-supported iron oxide catalysts. In the presence of carbon dioxide, ethylbenzene was predominantly converted into styrene by oxidation. It was found that carbon dioxide in this reaction plays a role as a soft oxidant to greatly improve catalytic activity. An active phase for the dehydrogenation with carbon dioxide was suggested as rather reduced and isolated magnetite-like phase having oxygen deficiency in zeolite matrix.     

Fe-Containing Intermetallic Compounds As Catalysts of Methane Conversion with Carbon Dioxide

Systems based on iron and aluminum were studied in methane conversion with carbon dioxide. The systems were prepared by the method of self-propagating high-temperature synthesis. Massive iron did not exhibit noticeable catalytic activity in methane conversion with carbon dioxide. The deactivation of iron-containing intermetallic compounds was shown to occur because of the formation of the FeC and FeO phases, which screened the active centers of the catalyst surface. The suggestion was made that the active center of the dissociative adsorption of methane was the γ-Fe phase, which existed at the working temperature of methane conversion with carbon dioxide.