Catalysts incipient wetness with

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. 

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. 

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. 

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... 

The much more stable MIL-lOO(Cr) lattice can also be impregnated with Pd(acac)2 via incipient wetness impregnation the loaded catalyst is active for the hydrogenation of styrene and the hydrogenation of acetylene and acetylene-ethene mixtures to ethane [58]. MIL-lOl(Cr) has been loaded with Pd using a complex multistep procedure involving an addition of ethylene diamine on the open Cr sites of the framework. The Pd-loaded MIL-lOl(Cr) is an active heterogeneous Heck catalyst for the reaction of acrylic acid with iodobenzene [73]. 

Figure 2 schematically presents a synthetic strategy for the preparation of the structured catalyst with ME-derived palladium nanoparticles. After the particles formation in a reverse ME [23], the hydrocarbon is evaporated and methanol is added to dissolve a surfactant and flocculate nanoparticles, which are subsequently isolated by centrifugation. Flocculated nanoparticles are redispersed in water by ultrasound giving macroscopically homogeneous solution. This can be used for the incipient wetness impregnation of the support. By varying a water-to-surfactant ratio in the initial ME, catalysts with size-controlled monodispersed nanoparticles may be obtained. 

More information on the nature of active sites was obtained using some model catalysts obtained by incipient wetness impregnation of a commercial silica (Si-1803 with surface area = 300 nP g ). A preliminary test performed using the support (Table 39.6) showed a very low selectivity to MDB, with the preferential formation 2-EMP, indicating that acid sites alone are not able to promote the cyclization of the intermediate. 

Catalysts - A commercial Raney nickel (RNi-C) and a laboratory Raney nickel (RNi-L) were used in this study. RNi-C was supplied in an aqueous suspension (pH < 10.5, A1 < 7 wt %, particle size 0.012-0.128 mm). Prior to the activity test, RNi-C catalyst (2 g wet, 1.4 g dry, aqueous suspension) was washed three times with ethanol (20 ml) and twice with cyclohexane (CH) (20 mL) in order to remove water from the catalyst. RCN was then exchanged for the cyclohexane and the catalyst sample was introduced into the reactor as a suspension in the substrate. RNi-L catalyst was prepared from a 50 % Ni-50 % A1 alloy (0.045-0.1 mm in size) by treatment with NaOH which dissolved most of the Al. This catalyst was stored in passivated and dried form. Prior to the activity test, the catalyst (0.3 g) was treated in H2 at 250 °C for 2 h and then introduced to the reactor under CH. Raney cobalt (RCo), a commercial product, was treated likewise. Alumina supported Ru, Rh, Pd and Pt catalysts (powder) containing 5 wt. % of metal were purchased from Engelhard in reduced form. Prior to the activity test, catalyst (1.5 g) was treated in H2 at 250 °C for 2 h and then introduced to the reactor under solvent. 10 % Ni and 10 % Co/y-Al203 (200 m2/g) catalysts were prepared by incipient wetness impregnation using nitrate precursors. After drying the samples were calcined and reduced at 500 °C for 2 h and were then introduced to the reactor under CH. 

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. 

Mo/HZSM-5 catalysts (3 wt% Mo nominal loading) were prepared by incipient wetness impregnation with an aqueous solution of ammonium heptamolybdate (Merck), drying at 100°C, and calcination at 500°C for 6 h. 

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