Impregnation techniques

Porosity and Pore Size. The support porosity is the volume of the support occupied by void space and usually is described in units of cm /g. This value represents the maximum amount of Hquid that may be absorbed into the pore stmcture, which is an especially important consideration for deposition of metal salts or other active materials on the support surface by Hquid impregnation techniques. The concentration of active material to be used in the impregnating solution is deterrnined by the support porosity and the desired level of active material loading on the catalyst. If the porosity is too low, inefficient use of the support material and reactor volume may result. If the porosity is too high, the support body may not contain sufficient soHd material to provide the strength necessary to survive catalyst manufacture and handling. 

Prior to functionalization the carbon nanomaterials were washed in concentrated nitric acid (65% Fisher Scientific) for 8 h using a Soxhlet device in order to remove catalyst residues of the nanomaterial synthesis as well as to create anchor sites (surface oxides) for the Co on the surface of the nanomaterials. After acid treatment the feedstock was treated overnight with a sodium hydrogen carbonate solution (Gruessing) for neutralization reasons. For the functionalization of the support media with cobalt particles, a wet impregnation technique was applied. For this purpose 10 g of the respective nanomaterial and 10 g of cobalt(II)-nitrate hexahydrate (Co(N03)2-6 H20, Fluka) were suspended in ethanol (11) and stirred for 24 h. Thereafter, the suspension was filtered via a water jet pump and finally entirely dried using a high-vacuum pump (5 mbar). 

A direct comparison of the productivities of the Co/nanomaterials and a typical Co catalyst23 (promoted Co/Ru-alumina catalyst) is presented in Table 2.3. Bearing in mind that the nanocatalysts are unpromoted systems and that only a simple wetness impregnation technique was employed for catalyst production, the obtained activities are quite promising, especially in the case of the Co/MW catalyst. 

The present paper focuses on the interactions between iron and titania for samples prepared via the thermal decomposition of iron pentacarbonyl. (The results of ammonia synthesis studies over these samples have been reported elsewhere (4).) Since it has been reported that standard impregnation techniques cannot be used to prepare highly dispersed iron on titania (4), the use of iron carbonyl decomposition provides a potentially important catalyst preparation route. Studies of the decomposition process as a function of temperature are pertinent to the genesis of such Fe/Ti02 catalysts. For example, these studies are necessary to determine the state and dispersion of iron after the various activation or pretreatment steps. Moreover, such studies are required to understand the catalytic and adsorptive properties of these materials after partial decomposition, complete decarbonylation or hydrogen reduction. In short, Mossbauer spectroscopy was used in this study to monitor the state of iron in catalysts prepared by the decomposition of iron carbonyl. Complementary information about the amount of carbon monoxide associated with iron was provided by volumetric measurements. 

Table HI lists the THF solubilities of Illinois 6 obtained as a function of catalyst and method of impregnation. As shown in these dat2 the impregnation by the wet impregnation technique did little in terms of changes in THF solubility.

The pristine MCM-48 silica phase has been synthesized by standard procedures described elsewhere [1]. Wet impregnation technique was used (1.6 molar aqueous solutions of cobalt(II) nitrate (Co(N03)2 6H20) and iron(III) nitrate (Fe(N03)3-9H20) with a ratio of lCo 2Fe) to introduce cobalt iron oxides into the mesoporous MCM-48 molecular sieve. After impregnation the material was calcined at 575° C for 6 hours, followed by a calcination at 600° C for 72 hours (product A) or at 650° C for 72 hours (product B), respectively. 

Impregnation with the solution of the compound of a poisoning element [Sn, Pb, Bi, P etc.) is considered as the most general way to poison nickel catalysts. However, upon using conventional impregnation techniques the optimal selective poisoning of the supported or skeletal catalysts cannot be guarantecu[4]. 

Enhanced imaging of several dairy products has been demonstrated through the application of a relatively elaborate preparative technique in combination with a cold-field emission scanning electron microscope (FESEM) [86], The preparative methods include a metal-impregnation technique, termed tannin-ferrocyanide-osmium (TA-F-O, Figure 21), which was adapted from Hirano et al. [87]. 

In order to visualize the process of non-wetting fluid injection Wood s metal Porosimetry was used [11-16], Wood s metal Impregnation technique is based on the same principles as Mercury Porosimetry, i.e., an immiscible,... 

Unsupported particulates, like their powder counterparts, contain active sites without the addition of other catalytic species. Synthetic zeolites and Si02-Al203 catalysts used for cracking heavy oils to gasolines are catalytic due to their acid sites. They are produced by chemical reactions between the various components but can be found in nature. These materials are often modified by chemical techniques such as ion exchange however, the impregnation techniques typical of dispersed catalysts are not used. Promoters can be added to enhance performance. 

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