Impregnation to Incipient Wetness

In order to attempt to solve the problem of gold sintering because of the presence of chloride, impregnation with gold salts free of chlorides was 

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At this point we have an aluminum type sepiolite which shows mild acidity and could be used as a component for FCC catalysts. Then, we have checked if the aluminium containing sepiolite can also passivate vanadium. To do that, two FCC catalysts containing 20% of a REHY zeolite in either 80% of a 23 wt% A1203 containing silica-alumina, or 80% of aluminic sepiolite were prepared. Both samples where impregnated to incipient wetness with a V naphthenate/xylene mixture (15), in order to introduce 6000 ppm of vanadium. Both samples were steam deactivated... 

After calcination, palladium sulfate was deposited by impregnation to incipient wetness with an acidic solution of PdS04 2H20 (Alfa products) in water. An additional amount of sulfuric acid was added to the solution to aid the palladium sulfate dissolution. The amount of sulfuric acid in the solution was adjusted to obtain a S042YPd2+ ratio of 10 in the catalyst. Catalysts were dried and stored in air at 350 K. 

In impregnation the pores of the support are filled with a solution of the gold precursor. Where just the needful volume is used, the method is impregnation to incipient wetness, but sometimes an excess of solution is used and the solvent removed by evaporation, so that concentrated solution finally resides in the pores (Sections 4.2.1 and 4.3.1). In these methods, the metal dispersion ultimately obtained depends critically on the conditions of drying.1... 

We will try to separate as far as possible the procedures of preparation from the chemical reactions that occur during these preparations. For instance in the case of impregnation to incipient wetness, both the metal ions and the counter-ions are deposited on the support, but the speciation of the metal-containing ions may vary with the pH of the solution in contact with the support, and the way in which they interact with the support will also depend on the PZC of the support. 

An example is shown in Table 44 [613]. A typical Cr/silica-titania catalyst was impregnated to incipient wetness with concentrated, aqueous solutions of the nitrate salts of the alkaline earth metals. Then ammonium hydroxide was added to precipitate the alkaline metal hydroxide within and around the pore structure of the catalyst. After a few hours of aqueous alkaline aging, the catalyst was washed and dried. 

Cylindrical y-Al203 pellets (PV 1.1 ml/g, SA 200 m /g) of 3 mm diameter and height were impregnated to incipient wetness with different 0.5 M Co, 1 M Mo solutions. Catalysts prepared from these solutions would contain 14 wt% MoOa and 4 wt% CoO after calcination. Phosphoric acid and citric acid were added to the solutions to study the influence of these complexing agents on the speciation of Co- and Mo-complexes inside the pellets after impregnation. Solution (CoMoP(O.l)) contained phosphate at a concentration of 0.1 M. Another solution (CoMoP(0.3)CA(0.2) contained 0.3 M phosphate and 0.2 M citric acid. 

Several methods are available for preparing supported metal catalysts. Commonly used methods include impregnation to incipient wetness, deposition-precipitation (DP), coprecipitation, and deposition/immobilization of colloidal metals. A useful description of such techniques is reported for gold catalysts [43]. 

Fixation of nickel ions in alumina supports impregnated to incipient wetness... 

Fixation of nickel ions to the inner surface of y- and a-alumina support bodies, impregnated to incipient wetness, takes place to a considerable extent, especially at elevated tenq>erature. In y-alumina fixation proceeds to completeness upon generating hydroxyl ions by in situ hydrolysis of urea or nitrite. The gases released are discharged smoothly, without expelling liquid from the pore system. This procedure leads to an improved reducibiUty compared to catalysts prepared by ordinary impregnation and successive drying. With a-alumina the surface area iq>pears to restrict the amount of nickel that can be anchored. 

The catalyst was prepared by impregnating y-alumina (Alon) to incipient wetness using an aqueous solution of (PtClg). After impregnation, the powder was dried, and calcined in air at 773 K (500°C) for 2 h. The infrared disc was prepared by compressing 0.08 g of the catalyst powder at 58 840 N. The properties of the catalyst disc are listed in Table I. 

TS-1 (mesoporosity 20nm, 0.3-1.2 xm size), carbon black pearls 700 (Carbot Corp., average particle diameter =18 nm (ASTM D-3249)) were impregnated by the incipient wetness method with a clear solution of TPAOH, water, and ethanol. After evaporation of ethanol, the carbon particles were impregnated with 20% excess (relative to incipient wetness) of a mixture of TEOT and TEOS. Aging for a minimum of 3 h at room temperature and heating at 453 K for 72 h yielded the solid product, which was isolated, and the carbon black was removed by controlled combustion in air at 523 K for 8 h. 

In addition, the catalyst preparation method plays an important role sol immobilization appears superior to incipient wetness or impregnation methods. Gold sol immobilization occurs via citrate reduction of HAuCU, yielding a narrow par-... 

When the Co-POM was impregnated by incipient wetness onto immodified silica [95] or embedded in a siliea matrix or attached electrostatically to NHs -silica [96,97], no splitting of the absorption oecurred (Figure 3). Recently, the formation of coordination bond was found for the sandwich-type polyanion, [(PW9034)2Co4 (H20)2] °", supported on NH2-silica [134]. 

AAA-alumina (75% Si02/25% AI2O3 aluminosilicate gel provided by Davison) was used without further pretreatment. Benzene solutions of either vanadyl porphyrin (5, 10, 15, 20-tetraphenyl-21H, 23H-porphine vanadium oxide) or vanadyl naphthenate were impregnated by incipient wetness onto the EuY or the gel to generate a loading of 1.0 wt % vanadium. Vanadyl naphthenate has been widely utilized as a model V-contaminant and metalloporphyrins have been identified as metallic species in crude oil (29-30). The solvent was removed under... 

Most of the published methods for preparing gold catalysts in small research quantities are unlikely to prove suitable for commercial applications.1 Complete removal of precious metal from the liquid phase is desirable when using solution methods deposition-precipitation (DP) techniques, whilst producing highly active catalysts, also consume large quantities of water and the cost of treatment of wastewater is an expensive additional process. Other preparation methods such as appropriate modifications of impregnation via incipient wetness techniques are more likely to be suitable for commercial production if they lead to reproducible, stable... 

Supports and Catalysts. The preparation of the supports used in this study was discussed in detail elsewhere. The two phosphate supports, A O AIPO and 4MgO lSA O 10A1P0 were co-precipi-tated using the necessary nitrate salts, phosphoric acid, and ammonium hydroxide at a fixed pH (.] ) Niobia was precipitated by adding ammonium hydroxide to a methanolic solution of niobium chloride (8). The niobia-silica support was prepared by impregnating SiO (Davison 952) to incipient wetness with a hexane solution of niobium ethoxide. The sample was then dried and calcined to obtain a homogeneous surface phase oxide (9). 

Mn(N03)2 4H20 (Merck, P.A.) was slowly added to the supports to give solids with a content of about 6 wt.% Mn. The solids were subsequently dried at 393 K for 16 h and calcined at 773 K for 4 h in a muffle. A series of acid and alkali-modified silica-supported manganese oxide catalysts was also prepared. The silica support was first treated with acid (H2SO4 or citric acid) or alkali (Na or Cs) in a way similar to the one for the bulk manganese oxides, and then impregnated by incipient wetness with an aqueous solution of manganese, dried at 393 K for 16 h and calcined at 773 K for 4 h. 

The Carbon Black Pearls labeled BP 2000 was supplied by Cabot Corp. 10 g of carbon black pearls (BP-2000) was dried in an oven at 110 °C overnight. In a 200-mL flask, 17.2 g of 40 % tetrabutylammonium hydroxide, 2.5 g of I BO and 15.1 g of ethanol was stirred to obtain a homogeneous solution. The dried carbon black was impregnated with this solution to incipient wetness. After evaporation of ethanol at room temperature for 12 h, carbon particles were impregnated with 19.3 g of tetraethyl orthosilicate. This mixture was left at ambient conditions to hydrolyze overnight. The hydrothermal synthesis was performed in a Teflon-lined autoclave at 180 °C for 72 h. Then the autoclave was cooled, a solid product was filtered and washed with distilled water. Calcination was carried out in a muffle oven at 550 °C for 18 h [86],... 

The Pt/SiO2 catalysts were prepared by impregnation of the silica support with chloroplatinic acid to incipient wetness, followed by vacuum drying, calcination in air to 300°C, and reduction in pure H2 at 425°C. 

With the ZSM-5/TMP zeolite prepared using the method 2 the presence of much broader mesopore distribution indicates that nucleation starts within the interparticle voids of aggregates of carbon black. As carbon black was impregnated with TEOS to approximately 20 % excess (compared to incipient wetness), standard zeolite crystals were formed and encapsulated the carbon matrix. The mesopore volume of the sample ZSM-5/IMP is larger than in the case of ZSM-5/10 and it attains 0.193 cm /g (Table 2). The mesopore size distribution of this sample is broader in comparison with that of the samples prepared by the secondary templating (Fig. 4). Therefore, we can assume that small clusters formed from a few carbon black particles were operative as mesopore template. 

The syntheses of Ni and Ni-Cu supported catalysts were carried out by impregnation of the supports to incipient wetness with aqueous solutions of nickel or nickel and copper as previously described [5-11]. Bulk nickel was... 

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