Incipient-wetness impregnation

Typically, the IL and - if required - the catalyst complex are dissolved in a suitable organic solvent or water. The support is added, and the solvent is evajxtrated subsequently under mild vacuum conditions of a rotary evaporator to leave a thin layer of IL on the surface with the catalyst dissolved in the IL. The volumetric ratio between IL and total pore volume of the support is referred to as in vol% according to Eq. (4.1) 

In general, this type of catalyst preparation is a simple and fast approach to immobihze an IL onto a porous material, and various materials of Type A, B, and C have been prepared using this methodology. Depending on the size of the rotary evaporator, batches of SILP or SCILL materials between 10 g and 1 kg can be prepared. 

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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]. 

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. 

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. 

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. 

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. 

MCM-22 with Si/AM 5 was synthesized according to the method reported by Corma et al. [12]]. The physicochemical characteristics and the acidity of this MCM-22 sample are reported in a previous study [13], Platinum was introduced via three different ways ion exchange with a solution of Pt(NH3)4.Cl2 (sample E), incipient wetness impregnation with H2PtCl6.xH20 (I) and mechanical mixture with 0.45 wt.% Pt/Al203 (M). The Pt contents of all the samples are 1 wt.% with respect to the zeolite. 

Gallium was incorporated by incipient wetness impregnation of gallium nitrate, in three different amounts, namely ca. 2, 3 and 4 wt. %. The impregnated catalysts were calcined at 773K for four hours under dry air flow. 

To some extent the cobalt particles in Figure 2.1(c) seem to be distributed within the tubular structure of the multiwalled nanotubes. TEM analysis could not fully clarify if this is an artifact or if the particles are truly situated inside the hollow space of the tubes. However, Tavasoli et al.14 observed Co particles captured inside the tubes after incipient wetness impregnation. Thus, it can be assumed that this is the case here as well. 

Figure 3.10 XPS spectra in the range from 150 to 200 eV, showing the Zr 3d and Si 2s peaks of the 7.r02/Si02 catalysts after calcination at 700 °C. All XPS spectra have been corrected for electrical charging by positioning the Si 2s peak at 154 eV. The spectra labeled nitrate correspond to the catalysts prepared by incipient wetness impregnation with an aqueous solution of zirconium nitrate, and the spectrum labeled ethoxide to that prepared by contacting the support with a solution of zirconium ethoxide and acetic acid in ethanol. The latter preparation leads to a better Zr02 dispersion over the Si02 than the standard incipient wetness preparation does, as is evidenced by the high Zr 3d intensity of the bottom spectrum (adapted from Meijers et at, [33]).

Ethanol and methane steam reforming reactions were studied assuming that the exit composition of the ethanol reformer depends on the steam reforming of methane. The competition for the same active site for ethanol and methane reforming maximizes the H2 and C02 production and minimizes the CO formation Catalysts were prepared by incipient wet impregnation. 20 wt% Ni supported on ZnO exhibited better performance compared to that supported on La203, MgO and A1203... 

Catalysts were prepared by incipient wetness impregnation of commercial 56... 

Catalysts were prepared by incipient wetness impregnation of commercial supports using cobalt nitrate as a precursor. Metallic cobalt species were active centers in the ethanol steam reforming. Over 90% EtOH conversion achieved. Nature of support influences the type of byproduct formation. Ethylene, methane and CO are formed over Co supported on A1203, Si02 and MgO, respectively... 

Catalysts were prepared by incipient wetness impregnation of MgO from two different commercial sources using nitrate salts and Ni acetylacetonate. Ni/MgO exhibit better performance than Co/MgO in the SRE reaction because of the lower tendency of Ni to oxidize during the reaction. The catalyst also exhibit a stable performance during 630 h on-stream operation... 

Rh was loaded by incipient wetness impregnation. SRE reaction over these catalysts revealed that ethanol hydration is favorable over acidic or basic catalysts while dehydrogenation is favorable over redox catalysts. Among the catalysts, a 2%Rh/Ceo.8Zro.202 exhibited the best performance, may be due to strong Rh-support interaction... 

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