Incipient wetness method

Gomez-Sainero et al. (11) reported X-ray photoelectron spectroscopy results on their Pd/C catalysts prepared by an incipient wetness method. XPS showed that Pd° (metallic) and Pdn+ (electron-deficient) species are present on the catalyst surface and the properties depend on the reduction temperature and nature of the palladium precursor. With this understanding of the dual sites nature of Pd, it is believed that organic species S and A are chemisorbed on to Pdn+ (SI) and H2 is chemisorbed dissociatively on to Pd°(S2) in a noncompetitive manner. In the catalytic cycle, quasi-equilibrium ( ) was assumed for adsorption of reactants, SM and hydrogen in liquid phase and the product A (12). Applying Horiuti s concept of rate determining step (13,14), the surface reaction between the adsorbed SM on site SI and adsorbed hydrogen on S2 is the key step in the rate equation. 

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. 

Incipient wetness method. For every 1 g of SBA-15, varying amounts of titanium isopropoxide in 10 g of ethanol were used for impregnation. The titanium concentration in the solution varies from 0.05 to 5 M, depending on the desired titanium loading. The impregnated material was dried and calcined at 723 K for 5 h. 0.6-36 (XPS) Pore size = 4.2-5.1 nm, specific surface area = 690-997 m2/g, volume = 0.81-1.17 cm3/g (27)... 

The same groups also reported on a 64-fold ceramic block reactor and a ceramic monolithic reactor for the screening of up to 250 catalysts in parallel (Figure 3.41). The catalyst array was prepared via an incipient wetness method by combination of different amounts of Pt, Zr and V on the alumina walls of the monolith by means of an automatic liquid handler. Gas samples from each channel of the monolith were analyzed sequentially by a quadrupole mass spectrometer by moving a capillary sampling line into the channels with the help of a three-dimensional positioning system [69],... 

Preparation of Pt-TiOx/Pd membranes. It was also desirable to prepare metalloceramic membranes in which the catalytic activity of the ceramic phase was enhanced through the addition of a noble metal. The very low surface area of the titania films prepared as described above made them difficult to impregnate with adequate dispersion by traditional incipient wetness techniques. Instead, finely ground titania (>200 mesh) was impregnated with platinum via the incipient wetness method with a chloroplatinic acid solution. This powder was then sprinkled onto the surface of a freshly dipped membrane, which was dried and heat treated as described. These materials were activated before use at 350°C in hydrogen for three hours. 

Figure 13 Immobilisation via the anion Incipient wetness method...

Highly Lewis-acidic chloroaluminate ionic liquids (ILs) are well known to be both versatile solvents and effective catalysts for Friedel-Crafts reactions [1,2]. Tailoring the physical and chemical properties of the ILs to the needs of a specific reaction allows for a high diversity of applications [3,4]. We could show that immobilising these ILs on inorganic supports yields very active catalysts for alkylation reactions. The immobilisation of ionic liquids leads to novel Lewis-acidic catalysts (NLACs). The methods presented include the method of incipient wetness (method 1, further on called NLAC I), which has been introduced in detail by Hoelderich et al. f5], but focus of this presentation lies on the methods 2 (NLAC II) and 3 (NLAC III). 

Akins et al. successfully immobilized polyoxometaloeuropates [(Eu2PWio038)4(W30s (H20)2(0H)4)] inside the channels of MCM-41 mesoporous molecular sieve material by means of the incipient wetness method. For proper host-guest interactions, amine groups were introduced into the system as a result of an aminosilylation procedure. The photoluminescent behavior of the composite at room temperature indicates a characteristic trivalent europium emission pattern corresponding to Dq transitions. Such a composite might represent a new material with potential applications as a photoluminescent device or phosphor [85]. 

Method 1 Classical incipient wetness method [19] of the calcined support with stoichiometric amount ofZnO and Fc203 (1 1) ratio at 10% w/wofthe support. 

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. 

Alumina-supported cobalt catalysts were prepared by the incipient wetness method. After calcination at 500°C for 24 h, the catalysts were reduced in II2 by heating them linearly to... 

Nickel was deposited by impregnation of zeolite powders using the incipient wetness method with a 3% wt solution of Ni(NOj)2 bH O (Baker Analyzed). The solids were dried at 100°C in air for 24 hours and calcined in flowing air (2.4 1 ) at 500°C for 2 hours the nickel content of all samples was 2.5% wt. Before reaction the catalysts were prereduced in flowing hydrogen (2.01/h) at 500°C for 2 hours. 

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 second way to prepare Pd/C catalyst is the incipient wetness method. Typically, 0.5 ml of palladium chloride solution (containing 0.05 g of palladium) is slowly added in several steps to 1 g of active carbon. Between each addition, the active carbon is carefully mfaced. The catalyst is then dried (helium, 4 h, 130°C) and reduced (hydrogen, 1 h, 150°C). The impregnation volume of palladium salt solution is kept at a constant value, typically lower than the porous volume of the support. Such catalysts are called IW catalysts. 

---