Incipient wetness technique

A 5 wt.% CoOx/Ti02 catalyst was prepared via an incipient wetness technique in which an aqueous solution of Co(N03)2 6H20 (Aldrich, 99.999%) was impregnated onto a shaped Ti02 (Milleimium Chemicals, commercially designated as DT51D, 30/40 mesh), as described in detail elsewhere [6]. Other supported metal oxide catalysts, such as FeOx, CuO, and NiOx, were obtained in a fashion similar to that used for preparing the CoO, catalyst. 

The catalysts were prepared by impregnation of Si02 with an aqueous solution of H2PtCI6 and the appropriate promoting metal salts, using the incipient wetness technique. Si02, type M from Chemische Werke Uetikon, Switzerland, was used (20-35 mesh (ASTM), BET surface area 470 m2/g, pore volume 0,38 ml/g, composition 41,9% Si, 860 ppm Ca, 150 ppm Mg, <200 ppm Na, <200 ppm Al, <200 ppm Ti, <150 ppm Fe, 50 ppm S, 50 ppm Cl). The presence of Ca and... 

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. 

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... 

The usual preparation of supported micrycrystalline samples by the incipient wetness technique involves the impregnation of a support, e.g., silica gel or alumina, with a solution of a metal salt to form a thick slurry that is subsequently dried and sometimes heat-treated. 

The most direct evidence for the development of metallic platinum and PtSn alloy, by reduction of a catalyst prepared by the incipient wetness technique on low area Degussa alumina (110 irf/g) / was presented by Davis, et al. (11). Their conclusions were based on detailed XRD patterns, recorded in situ at elevated temperatures under flowing hydrogen. With 0.68% platinum samples containing tin, only Pt/Sn alloy diffraction lines were observed. 

This phenomenon has also been observed for catalysts prepared using an aqueous route (182). Both the iron and cobalt promoters led to an increase in selectivity. The iron-promoted catalyst was characterized by an increase in activity, but the cobalt-promoted catalyst was characterized by a decrease in activity. The decrease in activity of the cobalt-doped catalyst was attributed to the formation of VOPO4 in the final catalyst. The VOPO4 is formed by the oxidation of V0HP04 1 H20 during the introduction of the promoters in the incipient wetness technique. A similar effect was reported for catalysts doped with indium and tetraethy-lorthosilicate (TEOS) (181). The improved performance was observed only with both promoters in the catalyst. It was proposed that the... 

Experimental Procedure. FCC catalysts employing the submicron zeolite structure were used in this study. These catalysts were synthesized, spray-dried into 60 /tm pellets and impregnated with the metals by the incipient wetness technique at CREC-UWO. 

In a much earlier patent, the removal of organics from exhaust gases by oxidation over a supported uranium oxide catalyst was reported by Hofer and Anderson [39]. The catalyst was 4% U3O8 supported on alumina spheres. The authors used the incipient wetness technique to impregnate alumina with uranyl nitrate solution. In this case the catalyst precursors were calcined at 700°C for 3 h to decompose the uranium salt. The use of other uranium compounds as starting materials was mentioned and these included uranyl acetate, uranium ammonium carbonate and uranyl chloride. The alumina-supported catalyst had a surface area of ca 400m g and further added components, such as copper, chromium and iron, were highlighted as efficient additives to increase activity. 

Supported metal catalyst were prepared by the incipient wetness techniques. SiOn. supported Ni and other metal catalysts (10wt%) were used for both CO, methanation and CH4 decomposition. Catalytic activity to COj methanation and the decomposition of methane were performed with a pair of conventional fixed bed micro flow reactors at an atmospheric pressure connected in series, of which temperature controlled separately. 

The Nb205 support (BET area = 65 m /g) was obtained by calcination of niobic acid (CBMM, HY 340/AD 929) in air at 773 K for 2 h. A commercial y-A]203 from Harshaw (A1 3996, BET area 200 m /g) was employed as support to Pt/Al203 reference catalyst. The monometallic and the bimetallic catalysts were prepared by incipient wetness technique, following a procedure described elsewhere [4]. The platinum and tin content were 1% wt/wt on mono and bimetallic catalysts. 

On the other hand, cerium has been shown to be an effective oxygen reservoir, enhancing the activity of many oxidation catalysts. Due to this property, cerium oxide is also considered to potentially enhance the thioresistance of the catatysts. This aspect is of great practical importance, since the use of palladium catalysts is hindered by the poisonous effect of sulphur compoimds, often present in off gases. Most works dealing with ceria-zirconia catalysts have been carried out with catalysts prepared by coprecipitation methods, whereas in this work an ahemative procedure, based on the incipient wetness technique is used to incorporate ceria to the zirconia support. The aim is to maintain the advantages of zirconia supports, especially the thermal stability. 

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. 

ZrO was obtained from ZrCl via hydrolysis and subsequent precipitation with aqueous ammonia. The precipitate was washed and dried at 110°C. Sulphate ions were introduced (to a level of ca 3 wt%) by impregnation with a solution of ammonium sulphate (incipient wetness technique), followed by drying first at... 

Cu/S102 catalysts were prepared by the ion-exchange technique [13,14], A 6.44 vt% Cu/Si02 catalyst was obtained from an aqueous solution of 0,2 mol Cu(N03)2/l at pH 11. Cu/MgO and Cu/-f-Al20a catalysts were prepared by Impregnation (incipient wetness technique). The catalysts were dried at 120 C for 12 hours, calcined at 400 °C for 12 hours and finally sieved (250 - 400 pm). The Cu loading was measured by X-ray fluorescence (XRF). The Cu surface area was measured by the decomposition of N20 at 90 °C (pulse method), assuming a stoichiometric factor (N20/Cu) of 0.5 and a specific atom density of 1.46 x 10 1 toma/mz 115). The total surface area (BET) was determined by N2 adsorption at - 195 G [16]. Table 1 shows a summary of the catalyst properties. 

The Supported Sr-promoted La203 catalysts with different Sr/La ( 0.0, 0.03, 0.3, 2.0, 10.0) ratios and with Sr-La203 loading of 16 1.5 wt% were prepared by impregnating 22-30 mesh size particles of commercial low surface area porous, inert catalyst carrier ( SA-5205 obtained from Norton Co., USA) by the active catalyst mass. The impregnation of mixed nitrates of Sr and La from their aqueous solution on the support particles was done by the incipient wetness technique. The resulting supported catalyst mass was dried at 90°C for 16 h and then calcined in static air at 950°C for 4 h. 

Supported nickel catalysts are widely used for hydrogenation reactions. The most common supports are silica and activated carbon, however several studies have shown that clays are rather more effective in maintaining high metal surface area and can impart useful selectivity to the catalyst.18 Deposition of nickel(II) by the incipient wetness technique [in which the volume of nickel(II) solution used is equal to the pore volume of the clay and then dried] followed by H2 reduction was found to be the most effective method of generating a high dispersion of metal particles (< 10 nm in size) within the clay. 

Gadolinium-doped ceria (CGO) substrates are prepared from nitrate salt precursors by either coprecipitation or glycine-nitrate combustion techniques. Pt, Rh, orNi is loaded onto the CGO using the incipient wetness technique. Typical weight loadings are 1 wt% or less for Pt and Rh and up to 10... 

A similar Rh complex, [HRh(CO)(PPh3)3], immobilized onto AC and CNTs (ends-opened) by an incipient wetness technique was tested as a catalyst for propene hydroformylation [70]. Activity assay of the catalysts showed that the CNT-supported Rh complex displayed not only high activity for propene conversion but also excellent regioselectivity to the butyraldehyde product. Under the experimental conditions used, the molar ratio of normal to branched aldehydes reached 12 to 13 at a TOP of 0.12 s corresponding to a propene conversion of 32%. To understand the excellent catalytic behavior of the CNT-supported catalyst, an ends-unopened CNT was also used as support and its catalytic properties tested In this particular case, propene conversion and the nii ratio reached only 17.2% (corresponding to a TOP of 0.06 s ) and 6.0, respectively. On the basis of this result, the authors concluded that the high propene conversion and excellent regioselectivity demonstrated by ends-opened CNT-supported catalyst was due mainly to the confinement effect induced by the presence of a Rh-phosphine complex in the inner surface of the tubular nanochannels of CNT [70]. 

Similarly, Pt catalysts supported on carbon aerogels were used in the combustion reaction of toluene, o-xylene, and m-xylene [41,67]. Carbon aerogels were obtained by carbonization of an organic aerogel at 773 and 1273 K. Both samples were mesoporous, and their microporosity was equally accessible to N2 and CO2 at 77 and 273 K, respectively. Pt was deposited on both carbon aerogels by an incipient wetness technique using an aqueous solution of [Pt(NH3)4]Cl2. The supported catalysts thus obtained were pretreated in different atmospheres to obtain different mean Pt particle sizes. 

A Pt-doped carbon xerogel containing 10 wt% Pt was prepared by an incipient wetness technique [88]. The mean particle size was around 2 nm. The activity of the catalyst for methanol electrooxidation was higher in alkaline than in acid solution. In addition, the Pt surface slowly developed more favorable sites during cycling in alkaline solution. Pt supported on carbon xerogel showed better performance in the methanol electrooxidation than another Pt catalyst supported on Vulcan XC-72R with the same metal content. The large mesoporous surface... 

For bimetallic Ni-M catalysts, the support was co-impregnated with an aqueous solution of appropriate composition of the two metal salts (NiXa and MXn) by using the incipient wetness technique. It was then dried at 333K under vacuum, in the presence of molecular sieves. In order to obtain the desired total metal loading the procedure was repeated two or three times. The salts which were used are given in Table 1. 

Catalyst preparation All the catalysts were prepared on Aerosil 200 using an incipient wetness technique. Different series of platinum catalysts were synthesized Pt-Cu catalysts with a varying Cu/Pt atomic ratio and a total metal loading of 5.0wt%, a series of promoted 5wt% PtX catalysts (X=promoter... 

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