废催化剂中贵重金属回收的研究进展

对化工生产中广泛使用的铑、钯、铂等催化剂的回收工艺进行了介绍,并对各种回收工艺进行了评价。     

Selective Hydrogenation of Citral Over Noble Metals Intercalated Montmorillonite Catalysts

Surfactant stabilized platinum and ruthenium nano particles were intercalated into the interlamellar space of montmorillonite. The XRD patterns of the metal intercalated montmorillonite reveal that there was a significant swelling during the intercalation of surfactant stabilized metal particles without affecting the crystallinity of montmorillonite. The success of the synthesis of nano particles into montmorillonite catalysts was confirmed from the TEM micrographs of the catalytic materials. The TEM micrographs clearly indicated well dispersion of particles and the average diameter (in nm) of the intercalated metal particles were also determined. The catalytic activity and selectivity of these newly developed catalysts towards the selective hydrogenation of citral in liquid phase was found to be appreciable. The conversion levels were found to be 38% and 18% at 30 °C and increased to 61% and 46% at 100 °C over Pt-CTA-MM 2 and Ru-CTA-MM 2 catalysts respectively at 9 bar hydrogen pressure. The best selectivity towards geraniol and nerol was observed to be 61% over Pt-CTA-MM 2 among the catalysts studied. The effect of temperature, hydrogen pressure, amount of catalyst and time on stream on the conversion and selectivity towards geraniol and nerol were also discussed in detail.     

多相贵金属催化剂对芳香化合物催化加氢研究进展

综述了近年来多相贵金属催化剂对芳香化合物加氢的研究；揭示了负载型铂、钯、钌、铑以及二元金属催化剂各自在加氢反应中的特点，以及载体、助催化剂对其活性和选择性的重要作用；同时介绍了TCSM和Raney型贵金属催化剂的概况。     

负载型贵金属催化剂在甲醛完全催化氧化上应用的研究进展

甲醛是一种主要室内空气污染物之一,其对人体的健康造成很大的危害。催化氧化法是一种有效治理甲醛的方法。负载型贵金属催化剂因其在室温下就可以对甲醛具有很强的催化氧化能力,所以被认为是治理甲醛的最有前景的催化材料。因此,文章的目的是介绍贵金属催化剂在治理甲醛方面的研究进展。最后对负载型贵金属催化剂在甲醛催化氧化上的应用进行展望。     

Particle Size Effect on CH4 Oxidation Over Noble Metals: Comparison of Pt and Pd Catalysts

Intrinsic catalytic activities (TOF values) in CH₄ complete oxidation under lean conditions were estimated as a function of Pt and Pd particle sizes (d_m) for two series of Pt/Al₂O₃ and Pd/Al₂O₃ catalysts. Comparison of TOF ~ f(d_m) relationships revealed significant difference between Pt and Pd catalysts. For Pt catalyst TOF showed tendency to increase by 2–3 times with increasing particle size from 1 to ca 3 nm and remained constant, when Pt particles became larger than 3 nm. On the other hand, for Pd catalyst TOF increased almost linearly when particle size grew from 1 to 20 nm. These different tendencies were attributed to the different mechanisms of CH₄ oxidation over Pt and Pd catalysts: Langmuir–Hinshelwood and Mars-Van Krevelen respectively.     

贝壳粉负载TiO2对玫红酸的光降解催化反应

选择天然贝壳,经清洗、干燥、灼烧、研磨和过筛,制的天然贝壳粉.以TiCl<,4>溶液浸渍,经水解、过滤、清洗、干燥和灼烧,制的载有TiO<,2>的贝壳粉材料.以此种材料为催化剂,考察其对有色的玫红酸分解作用.对比实验表明,载有TiO<,2>的贝壳粉材料,对玫红酸有明显的降解作用.     

Special Sites at Noble and Late Transition Metal Catalysts

An overview of recent advancements in density functional theory modeling of particularly reactive sites at noble and late transition metal surfaces is given. Such special sites include sites at the flat surfaces of thin metal films, sites at stepped surfaces, sites at the metal/oxide interface boundary for oxide-supported metal clusters, and sites at the perimeter of oxide islands grown on metal surfaces. The Newns–Anderson model of the electronic interaction underlying chemisorption is described. This provides the grounds for introducing the Hammer–N?rskov d-band model that correlates changes in the energy center of the valence d-band density of states at the surface sites with their ability to form chemisorption bonds. A reactivity change described by this model is characterized as an electronic structure effect. Br?nsted plots of energy barriers versus reaction energies are discussed from the surface reaction perspective and are used to analyze the trends in the calculated changes. Deviations in the relation between energy barriers and reaction energies in Br?nsted plots are identified as due to atomic structure effects. The reactivity change from pure Pd surfaces to Pd thin films supported on MgO can be assigned to an electronic effect. Likewise for the reactivity change from flat Au surfaces, over Au thin films to Au edges and the Au/MgO interface boundary. The reactivity enhancement at atomic step sites is of both electronic and atomic structure nature for NO dissociation at Ru, Rh and Pd surfaces. The enhancement of the CO oxidation reactivity when moving from a CO+O coadsorption structure on Pt(111) to the PtO₂ oxide island edges supported by Pt(111) is, however, identified as mainly an atomic structure effect. As such, it is linked to the occurrence of favorable pathways at the oxide island edges and is occurring despite of stronger adsorbate binding of the oxygen within the oxide edge, i.e. despite of an opposing electronic effect. As a final topic, a discussion is given of the accuracy of density functional theory in conjunction with surface reactions; adsorption, desorption, diffusion, and dissociation. Energy barriers are concluded to be more robust with respect to changes in the exchange-correlation functional than are molecular bond and adsorption energies.     

铜阳极泥中硒及贵金属的提取

针对生产电解铜产品中端副产物铜阳极泥的元素组成和含量情况,讨论了其中金、银、铂、钯、硒等稀贵元素的提取方法。工艺过程火法、湿法结合,扬长避短,节能降耗。实践表明,生产的安全性、环保性以及稀贵元素的回收率都较高。     

聚苯二胺与贵金属纳米复合物的研究进展

基于国内外最新的研究文献和本课题组的研究成果,系统论述了贵金属与聚苯二胺如聚邻苯二胺、聚间苯二胺、聚对苯二胺的纳米复合物的制备方法及其优异的电导性能和电催化性能。指出通过电沉积技术、自组装技术、化学氧化还原复合法及原位聚合原位还原复合法可以获得具有多功能性的聚苯二胺／金属纳米复合物,其电导率较基体聚苯二胺最高可提高1000倍,该复合物修饰电极的电还原催化电流较金属裸露电极最高可提高70倍。聚苯二胺／金属纳米复合物在电催化、修饰电极、二次电池等领域展现出诱人的应用前景。     

贵金属加氢脱芳催化剂的复合氧化物载体的研究进展

催化剂载体是加氢脱芳（HDA）研究的重要内容,20世纪80年代以来,复合载体受到了极大的关注。综述了近年来贵金属深度加氢脱芳催化剂载体（负载贵金属Pd和Pt）的研究进展。主要介绍了含Al2O3、TiO2及SiO2的复合氧化物载体的催化剂在芳烃加氢过程中表现出的加氢活性和抗硫性。无论从催化剂的催化活性,还是抗硫性能方面比较,复合氧化物载体的催化剂都表现出良好的性能,尤其是三元复合氧化物载体的催化剂,比其他更加稳定,具有更好的催化性能。     

Noble Metals as a Source of Continuous Scattering in Fluoride Glasses

Submicrometer scattering centers in fluorozirconate glasses were analyzed in an analytical electron microscope. Spherical platinum particles were found most frequently; other morphologies and noble metals such as gold, rhodium, and iridium were also observed.     

贵金属催化剂制备条件对氧化性能的影响

采用浸渍法制备了贵金属负载型催化剂,考察了载体脱氧、负载方法、贵金属种类及还原途径等制备因素对双甘膦催化氧化合成草甘膦的影响.结果表明:活性炭载体表面用不同脱氧前处理剂处理,其催化效果相差很大;采用浸渍法对贵金属进行负载,干浸法与湿浸法相比,干浸法更佳.贵金属铂和钯均能有效提高催化性能,其中铂炭催化剂的催化活性更高;对3种还原方法进行了比较,采用液气串联还原途径时,催化剂效果最佳;最终得到在90℃、0.34 Mpa反应条件下,用Pt/AC催化剂,草甘膦产品纯度达97.6%,收率达75.4%.     

Activity and Selectivity Control in Reductive Amination of Butyraldehyde over Noble Metal Catalysts

Approaches to control selectivity and activity in the catalytic reductive amination of butyraldehyde with ammonia over carbon supported noble metal catalysts (Ru, Rh, Pd, and Pt) were explored. Detailed analysis of the reaction network shows that the Schiff base N-[butylidene]butan-1-amine is the most prominent initial product and, only after nearly all butyraldehyde had been converted to N-[butylidene]butan-1-amine, amines are detected in the product mixture. From this intermediate, good hydrogenolysis catalysts (Ru, Rh) produce mostly butylamine, while catalysts less active in hydrogenolysis (Pd, Pt) lead to the hydrogenation of N-[butylidene]butan-1-amine to mostly dibutylamine.     

TiO2／ACF的制备及光催化降解四氯乙烯性能

以钛酸四丁酯为前驱物，活性炭纤维（ACF）为载体，蔗糖为胶粘剂，采用真空吸附水解的方法制得了TiO2／ACF催化剂．采用BET、XRD、SEM等手段对其物理化学特性进行表征，以四氯乙烯光降解反应为探针反应，考察了TiO2／ACF催化剂的光催化降解性能、实验结果表明，采用真空吸附水解法可以将TiO2很好地负载到活性炭纤维表面上、通过优化条件制备的TiO2／ACF催化剂在光照2h条件下，可以将水中溶解量的四氯乙烯降解90％以上．催化剂可以多次循环使用，光催化反应活性不变．     

Electrocatalytic Performance of Palladium Dendrites Deposited on Titania Nanotubes for Formic Acid Oxidation

Pd catalyst with dendritic morphology was synthesized on ordered and uniformly distributed titania nanotubes (TNT/Ti), and bare Ti by a simple electrochemical deposition process. The influence of support morphology was studied in relation to Pd deposition and its electro catalytic oxidation of formic acid. The structural property of Pd dendrites was characterized by scanning electron microscopy and X‐ray diffraction. The electrochemical study showed the activity and durability of Pd/TNT/Ti catalyst for formic acid oxidation was enhanced compared to Pd/Ti electro catalyst. The synergetic contribution from TNT/Ti as support for Pd and its enhanced catalytic activity is discussed.     

Variation in In-Plane Stress during Densification and Crystallization of Titania Gel Coatings Deposited on Different Substrate Surfaces

Titania gel films were prepared from a coating solution with a starting mole ratio of Ti(OC₃H₇ⁱ)₄:H₂O:HNO₃:C₂H₅OH=1:1:0.2:30 on Si(100) wafers by spin coating, with and without sol–gel-derived, fired silica, and titania underlayers. In situ measurement was conducted on the in-plane stress in the titania gel films during heating up to 500°C at 5°C/min. Basically, for all the gel films, the in-plane, tensile stress increases once with increasing temperature, and then decreases around the temperature of crystallization. The increase in stress was thought to result from the capillary pressure due to solvent evaporation and from the densification of the coatings. The reduction in stress around the temperature of crystallization was ascribed to the accelerated atomic diffusion in the coatings and to the difference in thermal expansion coefficient between the coatings and the Si wafer. However, when the stress–temperature curves were examined more in detail, differences were found in the variation in stress, depending on the underlayers. Then, the question of how the underlayers could induce the crystallization and relax the strain in the coatings was discussed.     

LaMnO3 Perovskite Supported Noble Metal Catalysts for the Total Oxidation of Methane

Two series of LaMnO₃ supported noble metal (Pt, Pd, Rh) catalysts prepared by the citrate method and calcined in air at 600 and 800 °C, respectively, were investigated. The catalysts resulting from method A were prepared by simultaneous incorporation of the noble metals during perovskite preparation and those following method B were generated by impregnation of the calcined perovskites with the noble metal compounds. The noble metals form solid solutions with the perovskite lattice. Reduction of the catalysts with hydrogen prior to the catalytic reaction led to a significant enhancement of the catalytic activity. During the catalytic reaction, the noble metal clusters are partially transformed to highly dispersed noble metal oxides or nonstoichiometric noble metal oxide phases, which are the catalytically active phases for the total oxidation of methane. The best results were obtained with the Pd containing catalysts prepared by method B.     

Low Temperature Steam Reforming of Ethanol Over Supported Noble Metal Catalysts

The catalytic activity of M/Al₂O₃ catalysts for the reaction of steam reforming of ethanol has been investigated in the temperature range of 300–450 °C. It has been found that the catalytic performance varies in the order of Pt > Pd > Rh > Ru, with Pt exhibiting high activity and selectivity toward hydrogen production, as well as long term stability at low temperatures. It is shown that the reaction occurs in a bifunctional manner, with the participation of both the dispersed metallic phase and the support. Ethanol interacts strongly with the Al₂O₃ carrier, promoting mainly ethanol dehydration, while in the presence of Pt, catalytic activity is shifted toward lower temperatures. Ethanol decomposition and dehydrogenation reactions dominate at low temperatures, while reforming, water-gas shift and methanation contribute significantly to product distribution.     

Enhanced Ability of Nanostructured Titania Film to Assist Photodegradation of Rhodamine B in Water Through Natural Aging

Gradually but significantly improved abilities of titania films with various nanofeatures and crystal structures to assist photodegradation of trace rhodamine B in water were observed when the films were subjected to natural aging. The so-called natural aging behavior can be attributed to the gradual increase in the surface hydroxyl groups that are beneficial to the photocatalytic reaction.