Preparation incipient wetness

Catalysts were prepared incipient wetness impregnation. Daiichi RSC-H zirconia (100% monoclinic, pellets 0 3 mm) and Degussa 7701 titania (mainly rutile, ca. 85%, pellets 0 4.5 mm), specified to be >97% and >99% chemically pure, respectively, were treated at 850°C and 700°C, respectively, in air for 16 h to obtain a stable specific surface area of about 20 mVg for both supports and pore volumes of about 0.25 and 0.15 ml/g. 

Catalyst preparation Incipient wetness Impregnation with solution of HgPdCl., aging (20 h), drying in vacuum (50-70 C) and reduotion ln hydrogen (250 °C). 

A 20 wt% of Co/TiOa was prepared by the incipient wetness impregnation. A designed amoimt of cobalt nitrate [Co(N03) 6H20] was dissolved in deionized water and then impregnated onto TiOj containing various ratios of rutileianatase obtained from above. The catalyst precursor was dried at 110°C for 12 h and calcined in air at 500°C for 4 h. 

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. 

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. 

Catalysts were prepared on various supports. One example was a Calgon 120% CTC coconut carbon. The impregnation volume of metal solution was calculated using the measured incipient wetness of the support 0.85 cc liquid per gram of carbon for the... 

It was prepared by incipient wetness impregnation using Co(N03)2, 6H20, 99.9%, as cobalt precursor. Silica Aerosil 380 was purchased from Degussa. The sample was then dried at 573 K (300°C) and subsequently calcined at 773 K (500°C) under synthetic air. The quantity of cobalt introduced was 2wt.%. 

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. 

The catalysts used throughout the research were 2.5 % Rh/Si02 catalysts prepared by incipient wetness. Grace Catalysts supplied the catalyst supports and the catalysts were prepared by Johnson Matthey. 

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. 

The method of metal introduction should significantly affect the degree of proximity between the Pt and acidic sites, hence the catalytic properties. In a previous study, the behavior of Pt/MCM-22 samples in n-hexane transformation was explored by Martins et al. [11]. In this study the same reaction was used in order to evaluate the influence of the mode of Pt introduction. Three 1 wt.% Pt/MCM-22 samples were prepared, differing by the mode of platinum introduction ion exchange, incipient wetness impregnation or mechanical mixture of the zeolite with Pt/Al203. 

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