Preparation of supports

Salts of neodecanoic acid have been used in the preparation of supported catalysts, such as silver neodecanoate for the preparation of ethylene oxide catalysts (119), and the nickel soap in the preparation of a hydrogenation catalyst (120). Metal neodecanoates, such as magnesium, lead, calcium, and zinc, are used to improve the adherence of plasticized poly(vinyl butyral) sheet to safety glass in car windshields (121). Platinum complexes using neodecanoic acid have been studied for antitumor activity (122). Neodecanoic acid and its esters are used in cosmetics as emoUients, emulsifiers, and solubilizers (77,123,124). Zinc or copper salts of neoacids are used as preservatives for wood (125). 

In the present report the opportunity of use of the sol-gel process for preparation of supports for chromatography is considered by three ways ... 

CFPs are (disappointingly underscored) ideal supports for the preparation of supported M° nanostructured catalysts to be employed under liquid phase conditions. 

The goal of this work was to develop a support independent synthetic technique for the preparation of supported metal catalysts. There were three criteria that had to be simultaneously achieved ... 

Recent Advances in the Preparation of Supported Catalysts Containing Metal Particles of Tailored Sizes... 

Activated carbon supported palladium catalysts have been widely used in organic chemical synthesis (1). A comprehensive review surveys the research and development work on preparation of supported palladium catalysts covering... 

Campelo JM, Luna D, Luque R, Marinas JM, Romero AA (2009) Sustainable preparation of supported metal nanoparticles and their applications in catalysis. ChemSusChem 2 18—45... 

Jacinto, M.J., Landers, R. and Rossi, L.M. (2009) Preparation of supported Pt(0) nanopartides as efficient recyclable catalysts for hydrogenation of alkenes... 

In the last few years remarkable progress has been made in the preparation of supported metal catalysts. Entirely new methods have been developed, comprising precipitation of the metal as an insoluble salt or hydroxide on the support under controlled conditions, or loading the support with the metal by means of ion exchange. A feature of catalysts prepared according to the former method (I, 2) is that, after reduction, they have a high metal content (50% by weight, or more), while the metal crystals are still small (20-40 A) and distributed very uniformly over the support. The latter approach yields catalysts with metal crystallites of approximately 10 A however, the metal content is rather low [about 2% (3-5)]. 

In many cases, the comparison of a reaction accelerated by microwave irradiation has been made with the same reaction in an oil bath at the same bulk temperature. Unfortunately, there have been quite a few reports in the chemical literature that have not been conducted with such proper control of conditions and consequently a fair comparison is not possible. Nevertheless, using this MW approach, the problems associated with waste disposal of solvents that are used several fold in chemical reactions, and excess usage of chemicals are avoided or minimized. The discussion pertaining to the preparation of supported reagents or catalysts has not been included in this chapter because numerous review articles are available on this theme [14—22],... 

The microwave technique has also been found to be a potential method for the preparation of the catalysts containing highly dispersed metal compounds on high-porosity materials. The process is based on thermal dispersion of active species, facilitated by microwave energy, into the internal pore surface of a microporous support. Dealuminated Y zeolite-supported CuO and CuCl sorbents were prepared by this method and used for S02 removal and industrial gas separation, respectively [5], The results demonstrated the effective preparation of supported sorbents by micro-wave heating. The method was simple, fast, and energy-efficient, because the synthesis of both sorbents required a much lower temperature and much less time compared with conventional thermal dispersion. 

An alternative approach for the preparation of supported metal catalysts is based on the use of a microwave-generated plasma [27]. Several new materials prepared by this method are unlikely to be obtained by other methods. It is accepted that use of a microwave plasma results in a unique mechanism, because of the generation of a nonthermodynamic equilibrium in discharges during catalytic reactions. This can lead to significant changes in the activity and selectivity of the catalyst. 

Kraum, M., and Baems, M. 1999. Fischer-Tropsch synthesis The influence of various cobalt compounds applied in the preparation of supported cobalt catalysts on their performance. Appl. Catal. A Gen. 186 189-200. 

Another study on the preparation of supported oxides illustrates how SIMS can be used to follow the decomposition of catalyst precursors during calcination. We discuss the formation of zirconium dioxide from zirconium ethoxide on a silica support [15], Zr02 is catalytically active for a number of reactions such as isosynthesis, methanol synthesis, and catalytic cracking, but is also of considerable interest as a barrier against diffusion of catalytically active metals such as rhodium or cobalt into alumina supports at elevated temperatures. 

The data in the Figs. 9.1,9.2 and 9.4 nicely illustrate the complementarity of XPS and SIMS and the possibilities that thin film oxide supports offer for surface investigations. Owing to the conducting properties of the support, charging is virtually absent and typical single crystal techniques such as monochromatic XPS and static SIMS can be applied to their full potential to answer questions on the preparation of supported catalysts. 

B. Kraeutler, A.J. Bard, Heterogeneous photocatalytic preparation of supported catalysts. Photodeposition of platinum on titanium dioxide powder and other substrates, /. Am. Chem. Soc. 100 (1978) 4317-4318. 

Although much remains to be done in the study of macroporous monoliths, recent achievements open new vistas for the preparation of supports and separation media with exactly tailored properties. The experimental work done so far... 

J. D. Grunwaldt, C. Kiener, C. Wogerbauer, and A. Baiker, Preparation of supported gold catalysts for low-temperature CO oxidation via size-controlled gold colloids, J. Catal. 181(2), 223—232 (1999). 

Q. Xin, Preparation of supported RRu/C electrocatalyst for direct methanol fuel cells, Electrochim. Acta 50, 2371-2376 (2005). 

Our efforts in this area of catalysis began in 1980. Our initial emphasis was on the preparation of supported phase transfer catalysts. We later became interested in the chemistry of anioni-cally activated alumina(25) and the reactivity of metal carbonyl anions prepared under these conditions. A brief description of our work in the preparation of these materials and their synthetic applications follows. 

Ommen, J. G. van, K. Hoving, H. Bosch, A. J. van Hengstum and P. J. Gellings. 1983. The preparation of supported oxide catalysts by adsorption of metal acetylacetonates, M(AcAc)n on different supports. Z. Phys. Chemie Neue Folge 134 99-106. 

The use of hetero-metallic (MM )carbonyl complexes as precursors can lead to the preparation of supported catalysts having weU-defined bimetallic entities in which the intimate contact between M and M remains in the final catalyst and the atomic ratio M/M of the aggregates is that of the bimetallic carbonyl precursor used. This is illustrated in Figure 8.1, in which the definite interaction of the MjM (CO) complex with the functional group (F) of a surface (S) produces a new anchored surface species. This new surface species could evolve with an appropriate treatment producing tailored bimetallic particles. 

On the other hand, hi- or multi-metallic supported systems have been attracting considerable interest in research into heterogeneous catalysis as a possible way to modulate the catalytic properties of the individual monometalUc counterparts [12, 13]. These catalysts usually show new catalytic properties that are ascribed to geometric and/or electronic effects between the metalUc components. Of special interest is the preparation of supported bimetallic catalysts using metal carbonyls as precursors, since the milder conditions used, when compared with conventional methods, can render catalysts with homogeneous bimetallic entities of a size and composition not usually achieved when conventional salts are employed as precursors. The use of these catalysts as models can lead to elucidation of the relationships between the structure and catalytic behavior of bimetalUc catalysts. 

Figure 8.2 Open routes for the preparation of supported bimetallic particles from carbonyl species generated on the surface of a support from an initial M L metal precursor.

The exceptional renewed interest in supported gold catalysts leads us to mention here a few recent examples of the formation of in situ gold carbonyl species from supported gold that can be related to the preparation of supported Au nanoclusters [53-55]. On the other hand, bimetallic carbonyl cluster salts of [Au4Fe4(CO)i,5] and [AuFe4(CO)i,5] have been used recently in the preparation of Au/Fe0,t/Ti02 catalysts for the total oxidation of dichlorobenzene and toluene [56]. 

Sections 8.3.1-8.3.3 present the use of iron, mthenium and osmium carbonyls, respectively, in the preparation of supported catalysts. Over non-inert supports, besides the characteristics of carbonyl compounds, the reactivity of the surface and that of the specific element, mainly related with its redox properties, will be covered for each metal. 

Fe(CO)s and Fe3(CO)i2 are the most frequently used carbonyl iron complexes in the preparation of supported catalysts Fe2(CO)g is not soluble in hydrocarbon... 

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