Catalysts by impregnation

Ronning, Holmen, and coworkers—Ce doping of Cu/Zn/Al catalysts improves stability. Ronning et al,339 explored the impact of ceria addition to Cu/ZnO catalysts. Catalysts were prepared by co-precipitation of Cu, Zn, and Al from their corresponding nitrates. Ceria was incorporated into the catalyst by impregnation of cerium nitrate either before or after calcination (6 hours at 350 °C or 400 °C). The chemical compositions of the resulting catalysts are reported in Table 62. 

Platinum carbonylate anion clusters like [Pt3(CO)6] can be obtained by alkaline reduction of [PtCh] in a CO atmosphere. From [Pt3(CO)s] other higher nuclear-ity anions can be obtained. In this context, several examples have been reported in which this type of anionic cluster is used in the preparation of catalysts by impregnation or exchange methods. Salts of [Pt3 (CO)6 ] (n = 3, 5) have been used to prepare, by impregnation, dispersed platinum on ZnO and MgO [49] and, by ion exchange methods, to prepare Pt3 /C electrodes for the electrocatalytic oxidation of methanol [50]. A salt of [Pti2(CO)24] has recently been used to prepare... 

Janicke et al. [63] applied a sol-gel-type deposition technique by filling micro channels with aluminum hydroxide solution, which was dried and caldned at 550 °C thereafter. Platinum was introduced as catalyst by impregnation on the coating up to three times, resulting in different loadings of the precious metal. 

The preparation of alumina supported catalysts by impregnation with a solution containing metallic ions may give rise to precursor-support interactions of different types. Evidence of the formation of certain species can help to understand reaction mechanisms. 

Abstract Rice straw was catalytically gasified over nickel catalysts supported on kieselguhr. This has been done by varying the content of alkali carbonate, lithium metal (3-20wt%) and various sodium compounds. In the case which alkali metal carbonates were separately added with nickel catalyst, conversion to gas was increased in the following order of Li< Cs< Kalkali metals were used to as co-catalyst by impregnation method, gas formation was increased in the following order Cs< tC a< Li. These results showed same aspects with TPR patterns. 

The pH of the solution can be critical in the impregnation process. In the preparation of Rh/Ti02 catalysts by impregnating titania with aqueous solutions of rhodium chloride it was found that at low pH the interaction between the salt and the support surface takes place in several steps. Initially the oxide particles become more positively charged and, thus, adsorb the anionic species such as RhCl4 . After adsorption, these anions are more firmly anchored to the support by the displacement of one or more chloro ligands by OH groups on the titania... 

Metal promoters were loaded on the commercial Ni/Al203 catalyst by impregnation. The addition of a small amount of promoter metal to 20wt% Ni/Al203 catalyst increased the H2 production only at higher temperatures, around 800 °C, and the H2 production was in the order Ni-Zn > Ni-Fe > Ni-Cr > unpromoted > Ni-Cu. 

The catalyst used in this study was a copper chromite doped with barium (YPl). The other solids were prepared from that catalyst by impregnation with alkaline salts from Prolabo (LiNOj, KOH, CsNOs). After impregnation, the catalysts were dried in a sand-bath (120°C), and then calcinated at 350°C for 4 hours under a dry air stream. 

Two precipitated silicas, varying in surface area and pore volume, were obtained from W. R. Grace and converted into catalysts by impregnation of 0.4 Cr atom nm-2 followed by activation at 700 °C. These catalysts were tested for polymerization activity under the usual slurry conditions, and the results are summarized in Table 32. The JC-a values of the polymers were extremely high, indicating high levels of LCB. 

More recently. Mayoral and coworkers [34] prepared Ti(IV)/Si02 catalysts by impregnating silica with Ti(0-i-Pr)4 then heating at 140 °C in vacuo. Under these conditions the catalyst retained (presumably one per titanium) isopropoxy groups. It was shown to be an excellent catalyst for epoxidations with TBHP, giving smooth conversions with a variety of olefins at room temperature (Table 1). 

Scheme 5.6-1 Preparation of supported Lewis acidic chloroaluminate ionic liquids catalysts by impregnation with [BMIM][(AICl3)jfCl] (top), by grafting of l-(triethoxysilylpropyl)-3-methylimidazolium chloride followed by AICI3 addition (middle), and by sol-gel formation followed byAICis addition (bottom) [73].

Scheme 6-2 Production of supported metal catalysts by impregnation...

Reference [2] also indicates that the most economic route to vinyl acetate, when acetic acid is available, is to convert the raw materials to product in the vapor phase over a palladium catalyst. We therefore asked our research chemists to develop a catalyst suitable for the operation. They found a suitable catalyst by impregnating a silica base with 2% palladium along with some other proprietary chemicals. The chemists performed numerous experiments with the catalyst and found that it is quite selective towards vinyl acetate and quite active as measured in its space time yield (STY, grams of vinyl acetate/hr per liter of catalyst). The only significant side reaction we could notice is the combustion of ethylene to carbon dioxide and water... 

Gates group has extensively used Au(CH3)2(acac) for the preparation of gold catalysts by impregnation of various supports in dried pentane or hexane MgO... 

I C Production of Supported Catalysts by Impregnation and (Viscous) Drying... 

Scheme 9. BP preparation of fluid-bed catalysts by impregnation of a fluidizable support... 

---