Double impregnation method

Recently, Soria et al. [109] also investigated the effect of synthesis method on the WGS activity of Au/Fc203 catalysts. They prepared catalysts by deposition-precipitation method, liquid phase reductive depositions and double impregnation method. Among the various catalysts, the catalyst synthesized by deposition-precipitation method exhibits higher CO conversion. 

Au/Ce-Ti-O materials have been scarcely used in catalysis [1-5]. In the few available reports on the synthesis of this kind of materials, the Ce-Ti-O supports were synthesized by a sol-gel method [1,2,4,5] or by incipient wetness impregnation of aqrreorrs solution of cerimn nitrate on titania [3]. In these works, Au was loaded by Deposition-Precipitation [1-5]. We have previously synthesised Ce-Ti-O supports with different Ce/Ti molar ratios by solvothermolysis [6]. In the preserrt work, Ce-Ti-O supports, with higher Ce contents, were loaded with Au by a double impregnation method (DIM) [7], characterised by several techniques and tested for CO oxidatioa To the best of our knowledge, this is the first report with the combination of the solvothermal method for Ce-Ti-O synthesis with the DIM approaeh for gold loading. 

Ce02, Ti02 and Ce-Ti-O supports with different Ce/Ti molar ratios were synthesized by solvothermolysis. The combination of titania with ceria produced a nanostmctured architecture, evidencing the strong influence of Ti on the support structure. The materials obtained were mainly amorphous, with some crystalline nuclei. Addition of Ce to titania strongly increases the surface area and oxygen content of samples. Au was loaded by a double impregnation method onto the supports. The differences between samples obtained in CO oxidation can be explained based on the Au nanoparticle size. 

The double padding method makes it possible to work with a very stable stock solution of the dye containing no alkali whatsoever. The cloth is first padded with the dye solution and then dried, after which it is impregnated with alkali and salt. It then passes into a steaming chamber where the dyestuff is fixed, and finally washed off. The sequence of operations is illustrated diagrammatically in Fig. 22.7. There are other permutations of the sequence of events in continuous ranges but, with the exception... 

The cocatalyst, a combination of Cr and one other metal component, was loaded onto the as-prepared GaN ZnO by a co-impregnation method. In a typical preparation, the co-impregnation was performed by suspending 0.3-0.4 g of the photocatalyst powder in an aqueous solution containing an appropriate amount of Cr (N03)3 9H20 and the nitrate or chloride of the paired metal. The solution was then evaporated to dryness over a water bath followed by calcination in air at 623 K for 1 h. In the case of Ni or Ni-Cr cocatalysts, the impregnated catalyst was reduced by exposure to H2 (20 kPa) at 573 K for 2 h and then oxidized by exposure to O2 (10 kPa) at 473 K for 1 h in a closed gas circulation system to produce an Ni/NiO (core/shell) double structure [48]. 

Impregnation of reactive species into a host polymer provides a method for polymer modification via a chemical reaction. TTiis work has been extended by showing that photolysis of W(CO)6 in polyethylene (PE) can lead to isomerization of the C=C double bonds, an interesting variation of Wrighton s work on catalytic alkene isomerization [40]. The method can be used to prepare iso-merized PE because the W(CO)e can be removed entirely after the isomerisation has taken place [5,41]. Ultraviolet photolysis of Fe(CO)5 in PE under a pressure of H2 leads to reduction of up to 80% of the C=C bonds [41], while photolysis under an atmosphere of O2 generates an oxide, most probably Fe203, within the PE matrix [41]. 

Reference may be made here to a procedure for separating mixtures of mono-olefinic fatty acids and for subsequently determining the structure of the components [11]. This method utilises two-dimensional TLC on silica gel, impregnated with paraffin and silver nitrate a similar procedure is described in [225]. A scheme for determination of the position and configuration of the double bonds in polyolefinic acids [170] depends on partial hydrogenation with hydrazine, separation of the reduction products through argentation-TLC and determination of... 

Detection is most simple when the compounds of interest are naturally colored or fluorescent or absorb ultraviolet (UV) light. However, application of a location or visualization reagent by spraying or dipping is usually required to produce color or fluorescence for most compounds. Absorption of UV light is common for many compounds, e.g., aromatics and those with conjugated double bonds. This leads to a simple, rather universal detection method on layers impregnated with a fluorescence indicator (fluorescence quench detection). 

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