Chemical History with a Nuclear Microprobe

A nuclear microprobe cannot give direct information on the chemical state of an element, but the spatial distribution of elements in a specimen is often determined by the chemical history of the sample. Fuel cells and minerals are examples of complex systems whose elemental distributions are determined by past chemical history. The distribution of catalyst in used fuel cell electrodes provides direct information on the chemical stability of dispersed catalysts under operating conditions. We have used spatially resolved Rutherford backscattering to measure the migration of platinum and vanadium from intermetallic catalysts and to determine their suitability for use under the extreme operating conditions found in phosphoric acid fuel cells. Geologic materials are complex, heterogeneous samples with small mineral grains. The trace element distribution within the individual mineral grains and between different mineral phases is sensitive to the details of the mineral formation and history. The spatial resolution and sub-100-ppm sensitivity available with a nuclear microprobe open up several new classes of experiments to the geochemist. Geochemistry and electrochemistry are two areas proving particularly fruitful for application of the nuclear microprobe

Tuning porosity and activity of microporous polymer network organocatalysts by co-polymerisation

Microporous polymer networks based on binaphthyl phosphoric acids are suitable heterogeneous asymmetric organocatalysts. Herein we show that the porous characteristics of such networks can be fine-tuned by co-polymerisation. This enables us to investigate the influence of the surface area and porosity in microporous networks on their catalytic performance. In this case, the activity of the polymers in an asymmetric hydrogenation reaction is increased by the use of polymers with higher surface areas.EC/FP7/278593/EU/Organic Zeolites/ORGZEODFG, EXC 314, Unifying Concepts in Catalysi

Редокс-свойства гетерометаллических кластерных соединений осмия

Электрохимическими методами изучены редокс-свойства гетерометаллических четырехъядерных анионных [Os3Fe(μ-H)(CO)13]–, [Os3Co(CO)13]– и нейтральных Cp*MOs3(CO)10(μ-H) (μ-Cl) (M = Rh, Ir) кластеров в ацетонитриле и дихлорметане на платиновом, стеклоуглеродном и ртутном капельном электродах. Показано, что в результате редокс-превращений всех изученных гетерометаллических кластеров происходит элиминирование M-содержащих (М = Fe, Co, Rh, Ir) фрагментов и образование гомометаллических трехъядерных кластеров осмия, участвующих в дальнейших электрохимических реакция

Catalizadores heterogéneos utilizados para la obtención de biodiesel

El ahorro energético y el cuidado medioambiental son de gran importancia en todos los países, debido a estos aspectos se ha desarrollado la búsqueda de combustibles alternos para sustituir los provenientes defuentes fósiles. En este artículo se presenta información relacionada con los diferentes catalizadores utilizados para la producción de biodiesel, mencionando su clasificación química y física, también se citan las propiedades químicas y las características morfológicas que los hacen ser una opción apropiada para utilizarlos en la reacción de transesterificación, la cual está implicada en la producción de biodiesel. Además, se resalta la importancia de los catalizadores heterogéneos por sus características de baja contaminación al medio ambiente, su capacidad de ser reutilizados y porque pueden separarse fácilmente del producto

Infra-red studies of the surface acidity of oxides and zeolites using adsorbed probe molecular

The use of infrared spectroscopy to probe the surface acidity of oxides and molecular sieves is reviewed. The experimental requirements and the type and nature of probe molecules available are also discussed. Special emphasis is given to the criteria that have to be met to arrive at a characterization of the solid that is useful for its catalytic application

Heterogeneous Solid-Liquid Catalysis Of N-glycosylation By Natural Phosphate Doped With Potassium Iodide

Theone-step synthesis of several ?-D-ribonucleosides was performed in good yields under reflux in HMDS. Keywords: N-Glycosylation D-ribonucleosides,Natural phosphate doped with Potassium iodide KI (NP/KI), heterogeneous solid-liquid catalysi

Consolidators and survivors: formal self help and self-help homebuilders in South Africa

African Studies Seminar series. Paper presented October, 1984It is widely acknowledged that self-help procedures produce housing (Harms, 1982), but there are differing perspectives on the contexts and motives leading to the emergence of the self-help housing phenomenon; and the significance of self-help housing action in the lives of the actors themselves (Martin, 1984). The first issue has been the focus of sustained debate elsewhere (Burgess, 1978; 1982; Harms, 1976; 1982; Lea, 1979; Turner, 1978; 1982), but the second has remained largely the domain of the supporters of self-help housing strategies. This discussion is a first attempt at focusing critical scrutiny on the impact of self-help housing among those who are most intimately involved in it, the self-help homebuilders. This is not a clear-cut task, because the existing self-help literature provides few leads. The bulk of critical work focusing on self-help is a response to the glowing descriptions of self-help enterprise that emerged from the pens of fieldworkers in the squatter settlements of Latin America (Burgess, 1978). Most of this criticism places the self-help squatter phenomenon within a class-based framework of domination and subjection. Here, the group is the unit of analysis, and self-help action is seen to be the collective response to structural poverty. We find this analysis useful, but somewhat unsatisfactory in the context of our own research. Firstly, having worked among self-help homebuilders, it is apparent, to us that self help means different thing to different people. Whatever the overarching principle behind the emergence of self help, it is clear that every self-help scheme incorporates winners and losers, opportunists and unwilling co-optees, developers and survivors (Martin, 1984). Secondly, self-help housing and squatting are by no means synonymous in South Africa. Around South African cities, controlled, state-sanctioned self-help has emerged in the wake of ailing mass housing schemes. Self-helpers in this situation are not squatters, but may be relocatees, refugees from chronic overcrowding elsewhere, or even speculators keen to grab new residential possibilities. All enter the self-help arena with different chances of making out, some determined by entry, and others by contextual and personal factors beyond this

Recent Advances in Heterogeneous Frustrated Lewis Pair: Synthesis, Characterization, and Catalysi

Frustrated Lewis pair (FLP) in heterogeneous chemistry have garnered tremendous attention in recent years owing to their diverse structural designs and outstanding activation ability for small molecules. The ability to tailor the structure of FLP enables precise control over their reactivity and selectivity, paving the way for the creation of catalysts for specific reactions. This review offers an in‐depth examination of the design, characterization, and application of FLP within heterogeneous systems over the past few years. The current challenges in developing solid FLP catalysts are discussed. Furthermore, future potential advancements are explored, considering how emerging technologies and innovative approaches could enhance the design, advance characterization, and application of FLP in heterogeneous chemistry. Through this detailed overview, it is aimed to provide valuable insights into the evolving landscape of FLP research and its implications for the future applications in catalysis

Synthesis and characterisation of carbon supported gold catalysts prepared by ion-exchange

Includes abstract.Includes bibliographical references (leaves 86-97).Gold has been previously overlooked as a catalyst, mainly because the metal has been regarded as catalytically inert, and was tested as large aggregates, and not as nanocrystallites. Large crystallites of gold do not exhibit significant catalytic activity, and if they do, their activity is small compared with platinum group metals. The recent interest in gold as a catalyst has been fuelled by the development of processes to deposit gold on a catalyst support as nano-crystallites (Prati and Martra, 1999). Gold catalysts with nano-crystallites on selected supports have been shown to exhibit high activity for mainly redox reactions (Gluhoi, 2005; Hutchings, 2005). These catalysts have recently been attracting attention as they can be used at near ambient conditions, which allows for cheaper and more environmentally friendly processes. Glucose yielding gluconic acid is an industrially important reaction (Biella et aI., 2002). Gluconic acid and its salts are used as water-soluble cleansing agents or as additives in food and beverages which makes these products important in industrial applications (Kirk-Othmer, 1995). Industrially, the aerobic oxidation of glucose is an enzyme catalysed process. However, due to the low productivity of the glucose fermentation process, the development of a chemical route is of interest. Gold catalysis provides a promising alternative route which can be applied at mild conditions

Photocatalytic Activity: Experimental Features to Report in Heterogeneous Photocatalysis

Heterogeneous photocatalysis is a prominent area of research with major applications in solar energy conversion, air pollution mitigation, and removal of contaminants from water. A large number of scientific papers related to the photocatalysis field and its environmental applications are published in different journals specializing in materials and nanomaterials. However, many problems exist in the conception of papers by authors unfamiliar with standard characterization methods of photocatalysts as well as with the procedures needed to determine photocatalytic activities based on the determination of “apparent quantum efficiencies” within a wavelength interval or “apparent quantum yields” in the case of using monochromatic light. In this regard, an astonishing number of recent research articles include claims of highly efficient (photo)catalysts or similar terms about materials with superior or enhanced efficiency for a given reaction without proper experimental support. Consequently, the comparison of the efficiencies of photocatalysts may result as being meaningless, especially when reports are only based on expressions determining (1) a reaction rate per weight of catalyst or its surface area, (2) quantum efficiencies or quantum yields, and (3) turnover frequencies or turnover numbers. Herein, we summarize the standards needed for reporting valuable data in photocatalysis and highlight some common discrepancies found in the literature. This work should inform researchers interested in reporting photocatalysis projects about the correct procedures for collecting experimental data and properly characterizing the materials by providing examples and key supporting literature