Selection of Supports

The main criterion for selection of a GPC matrix is the fractionation range. Manufacturers of GPC media declare a fractionation range and avoid molar weight. These values are mostly obtained 

Additional chemical and mechanical stability of supports should be taken into consideration, as well as possible interactions between protein and matrix macromolecules. 

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Methanol is a major bulk chemical, and its global annual production exceeds 37 million tons. It is mainly used for the production of formaldehyde and methyl 6butyl ether (MTBE). Especially, formaldehyde is dominantly used for producing resins. At present, methanol and its decomposed derivatives can be oxidized to CO2 and H2O by the proper selection of supported noble metal catalysts such as palladium, platinum, and gold. 

In the propylene reaction with a 02-H2 mixture, the contact structure of Au NPs and the selection of support metal oxides are critical for producing propylene oxide (PO). 

Sucholeiki reviews the selection of supports for solid-phase organic synthesis. To address many of the problems presented above, we are seeing the use of a wide range of solid supports from the traditional Merrifield resin to newer composites, cellulose, silica, and others. This chapter presents the pros and cons of many of these potential supports, reviews modifications to enhance the solution-like behavior of the bound materials, and methods to increase the loading capacities. 

Selection of supports for solid-phase organic synthesis... 

Table 10.1 A selection of support materials and their key properties.

Yet, the activity and selectivity of supported Pd catalysts in the activation of carbon oxides strongly depends on the nature of all their active components. In a previous presentation of some of us it was reported that on well-purified silica (DAVISON G-59, mesoporous, Sg= 270 mVg) and in the absence of anionic or cationic promoters, Pd/Si02 catalysts obtained via ion exchange (I.E.) produced methanol with very high selectivity fi-om syn-gas. However, the catalytic activity was modest, almost that of Pd black [2]. 

The effects of oxidation - reduction cycles on the activity and selectivity of supported Rh catalysts were investigated using the hydrogenolysis of methylcyclopentane (MCP) as a test reaction. Prom the analysis of catalytic properties and reduction profiles it Is concluded that, on silica-supported catalysts, following the initial oxidation at 400 C successive reduction treatments at increasing temperatures cause a progressive reconstruction of the Rh particles. On y-alumina-supported catalysts the situation is more complex. The interaction of Rh with the support during the Initial oxidation makes a fraction of the Rh Inaccessible to the gas phase. Only after subsequent oxidation - reduction cycles do they behave like the silica-supported catalysts... 

The results suggest that it may be fhiitful to search for reactions for which supported metal clusters have catalytic properties superior to those of conventional supported metals. The important opportunity in catalysis may be to find reactions for which the activity or selectivity of supported metal clusters is superior to those of conventional supported metals. The high selectivity of Pt/LTL zeolite catalysts for paraffin dehydrocyclization, which is now exploited... 

Way, Noble and Bateman (49) review the historical development of immobilized liquid membranes and propose a number of structural and chemical guidelines for the selection of support materials. Structural factors to be considered include membrane geometry (to maximize surface area per unit volume), membrane thickness (<100 pm), porosity (>50 volume Z), mean pore size (<0.1)jm), pore size distribution (narrow) and tortuosity. The amount of liquid membrane phase available for transport In a membrane module Is proportional to membrane porosity, thickness and geometry. The length of the diffusion path, and therefore membrane productivity, is directly related to membrane thickness and tortuosity. The maximum operating pressure Is directly related to the minimum pore size and the ability of the liquid phase to wet the polymeric support material. Chemically the support must be Inert to all of the liquids which It encounters. Of course, final support selection also depends on the physical state of the mixture to be separated (liquid or gas), the chemical nature of the components to be separated (inert, ionic, polar, dispersive, etc.) as well as the operating conditions of the separation process (temperature and pressure). The discussions in this chapter by Way, Noble and Bateman should be applicable the development of immobilized or supported gas membranes (50). 

TEM images of Ir/Al203 and Ir/Fc203 are shown in Fig. 4. In the case of Ir/Al203, the deposited Ir was found to spread over the AI2O3 surface as a thin layer of approximately 5 nm thickness. Conversely, small clusters were deposited on the Fe203 surface. These results indicated that the selection of support greatly influences the surface structure of Ir deposited. 

Bconich J, Myers C, Pennline H, Luebke D (2(X)7) Experimental investigation of the permea-bUity and selectivity of supported ionic Uqtrid membranes for CO /He separation at temperatures up to 125°C. J Membr Sci 298 41 7... 

Support Paper. The selection of support paper is a very important part of the membrane development. This is often done in cooperation with the manufacturer of support paper. However, also here it must be realized that despite an extremely high growth of membrane filtration, the amount of support paper is very small compared to the usual manufacturing of paper. 

For hydrogenation of p-IBAP, supported Pd, Ni and Ru catalysts have been reported. However a comparative study of different types of catalysts has not been reported so far. Most of the earlier literature on this reaction is patented and there are only a few reports which deals with the catalytic aspects involved in the hydrogenation of p-IBAP (3-6). In this paper, experiments were performed to study the activity and selectivity of supported Ni and Ru... 

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