Incipient wetness method, oxidation

Mixed oxide samples were prepared by the co-precipitation from aquatic solutions of the cations ([Ce(IV)] = 0.1 M) by adding equal volume of 1 M NHj solution under controlled conditions. Further calcium cerium mixed oxide samples were prepared by the incipient wetness method, for comparison. The solid phase was heated to dryness, in an oven at 250 C. Samples of magnesium cerium and calcium cerium mixed oxide prepared by co-precipitation were subsequently calcined at 400, 600 and 800 "C. 

Mixed calcium cerium oxide samples were also prepared by the incipient wetness method. Experimental data from both nitrogen isotherm analysis and FTIR spectra indicate the presence of calcium cerium mbced oxide and pure calcium and cerium oxide phases, thus reinforcing the idea that for the precipitation experiments, mixed phases are indeed prepared. 

Cerium was added to the support by two different procedures, both based in the incipient wetness method. In the first procedure, zirconium hydroxide was impregnated with aqueous cerium (IV) nitrate in order to get 1 % wt of cerium in the support (support A). The second procedure consisted of calcining the hydroxide at 700 C for 4 h to obtain the oxide and then impregnation with the same cerium solution (support B). In both cases the incipient wetness technique was used to impregnate the solid. Zirconium oxide with no cerium added was prepared by calcining the hydroxide at 700 C. 

The cerium oxide was incorporated by the conventional incipient wetness method from an CeCNOals nHzO aqueous solution, at 40°C and 30 mmHg. Promoter-modified alumina samples were dried at 120°C for 2 hours and calcined in air at 700°C for 4 hours to decompose the nitrate to oxide. 

The catalysts were prepared by impregnating Ca(OH)2 with aqueous solution of NaOH applying the incipient wetness method. After impregnation the samples were dried and calcined in CO2 free air at 973 K. Other alkaline earth oxides (Analar) were also used for activity measurements. X-ray diffraction studies were carried out in a Phillips instrument using a Guinier camera applying crystal reflected monochromatic CuK a radiation. IR spectra were recorded by a Perkin-Elmer FTIR 1710 spectrometer. The samples were dried for 1 Oh at 383 K prior to preparing the pellets. The catalytic experiments were carried out in a quartz made reactor, details of the reactor operation and product analysis have been described elswhere [8]. 

The Cr catalysts were prepared by the incipient-wetness method with chromium(VI)oxide (CrOj) (UCB) onto alumina and silica. The chromium loading was 0.2 wt%. Silica and alumina were prepared by the sol-gel method starting from respectively TEOS and Al(iP)3 and H2O, followed by titration. The obtained gels were dried, calcined and crushed. Details about the preparation method and the characteristics of the materials were published elsewhere [13,14] (TEOS = tetraethyl orthosilicate, Al(iP)j = aluminium triisopropoxide). 

Oxidation of native starch by incipient wetness method... 

XPS measurements are illustrated in Fig. 4. In order to get more accurate results the peak area sensitivity factors are used instead of peak height sensitivity factors. The results indicate that there is no threshold existing in the sample series prepared by incipient wetness method with aqueous solution of nitrate. The dispersion state of ferric ions on alumina is complicated with increasing the Fe loading. The formation of "clusters" or crystallites of iron oxide with a broad size distribution and the solubility of ferric ions into the support lattice produce a changeable XPS response with increasing Fe loadings. In a word, a... 

The more common methods for preparing supported oxide catalysts involve the dispersion of the active species or its precursor onto the surface of a preformed support. This has been accomplished using procedures referred to as equilibrium adsorption, incipient wetness or dry impregnation.9,20... 

A series of V205/Ti02 catalysts were prepared by coprecipitation, grafting, incipient wetness and dry impregnation. It was found that there were three types of vanadium species present on each of these catalysts with the relative amounts of each dependent on the method used for the preparation. >20 It was proposed that all three species are involved in the catalytic oxidation of o-xylene to phthalic anhydride (Eqn. 10.15), a reaction for which supported... 

Obviously, the number of [Me(NH3) ] complexes adsorbed depends both on the concentration of the acidic sites and on the nature of the X anion. Hence, solutions of ammonia complexes of metal hydroxides and oxidized carbon supports (Cox) are used to prepare catalysts via adsorption [12,24,64,65,114,117-120]. Equilibrium (7) is significantly shifted to the left in the case of the adsorption of metal salts, [Me(NH3) ]Xz (X = Cr,NOj), due to releasing strong acids HX. Eor this reason, the most frequently used method for supporting these salts is incipient wetness impregnation [41,42,121-127]. The completeness of the adsorption processes usually is not stated in this case, which makes it difficult to classify the prepared Me/C specimens as impregnated or adsorbed catalysts. 

Methane and ethane have been photooxidised to the corresponding aldehydes using a solid-supported vanadium oxide catalyst, V205/S102-IW (incipient wetness) at elevated temperatures.Both processes are highly sensitive to reaction temperature and to the method by which the catalyst is prepared. 

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