Alumina-based catalyst support

Alumina-based catalyst supports Other Applications of Aluminas in Catalysis Future Work... 

Sodium alumiaate is widely used in the preparation of alumina-based catalysts. Aluminosilicate [1327-36-2] can be prepared by impregnating siHca gel with alumiaa obtained from sodium alumiaate and aluminum sulfate (41,42). Reaction of sodium alumiaate with siHca or siHcates has produced porous crystalline alumiaosiHcates which are useful as adsorbents and catalyst support materials, ie, molecular sieves (qv) (43,44). 

A recent comparative investigation of the NO + CO reaction shows a significant rate enhancement in the formation of N2 on Ce0.98Pda02O2 8 prepared via a combustion synthesis method in comparison with conventional Pd-based catalysts supported on alumina... 

An alumina-based catalyst will be bound, for the purpose of mechanical strength, with carbon. The alumina-carbon mixture is essentially a composite support for adsorbing the Pt precursor. If it is desired that all metal go onto the alumina phase, which type of carbon (oxidized or unoxidized) and what type of Pt complex should be used and why A sketch of the surface potential vs. pH for alumina and the carbon binder will help. 

Upon discovery of this mechanism, new catalysts have been developed, now presenting alkylidene ligands in the metal coordination sphere, such as [(=SiO) Ta(=CH Bu)Np2 and [(=SiO)Mo(=NAr)(=CH Bu)Np] [43, 88]. Table 11.4 presents results obtained with several catalysts prepared by SOMC. Although [(=SiO) Ta(CH3)3Cp (=SiOSi=)] is not active in alkane metathesis (the tantalum site would not be as electrophilic as required) [18], results obtained with [(=SiO)Mo(=NAr) (=CH Bu)Np] show that ancillary ligands are not always detrimental to catalytic activity this species is as good a catalyst as tantalum hydrides. Tungsten hydrides supported on alumina or siHca-alumina are the best systems reported so far for alkane metathesis. The major difference among Ta, Mo and W catalysts is the selectivity to methane, which is 0.1% for Mo and less than 3% for W-based catalysts supported on alumina, whereas it is at least 9.5% for tantalum catalysts. This... 

The ATR of glycerol has also been examined over Pt- and Rh-based catalysts supported on alumina foams [298]. High selectivity to H2 can be achieved by adjusting the fuel-to-air and fuel-to-steam feed ratios, and also the catalyst formulation. The addition of ceria to AI2O3 provides a catalyst vhich shows high fuel conversion and high selectivity to H2. 

During n-paraffin reforming over Pt-based catalysts, supported on chlorided alumina, methane is produced on the metal function (3). Only a very small amount of methane is produced by a carbocation mechanism on acid sites of the... 

Nafta reforming and alkane dehydrogenation processes are directly connected on platinum alumina based catalysts. The stability and selectivity requirements for industrial purposes induced the addition of a second metal like Sn, Ge or Re. In fact, these promoters coupled to other acidity controllers added on the support enhanced the catalytic efficiency [1-3]... 

Various solid state reactions are involved in the process. In addition to those governing sintering, catalyst-support interactions may alter the nature and catalytic activity of the solid and may stabilise or destabilise the solid towards sintering. Thus, for example, the formation of nickel aluminate, NiAlgO, is well established in steam reforming catalysts [21,22], and this compound is catalytically inactive. However, its presence may affect the thermal stability of the solid [23], as is the case in cobalt-molybdenum and nickel-molybdenum based catalysts supported on alumina and used for hydro-treating [24]. 

Preferential oxidation (PROX) catalysts were prepared by washcoating of alumina suspensions with PVA and acetic acid [61]. The stainless-steel reactor contained heat exchangers at the inlet and outlet and the stacks were sealed with graphite seals. Temperature was measured with a thermocouple at the reactor outlet. Noble metal-based catalysts supported on alumina were tested. The influence of the temperature, space velocity and O2/CO ratio and the effect of water were studied. The CO content could be reduced from ca 1% to 10 ppm. The authors recommended a dual-stage PROX reactor in order to minimize the hydrogen loss. 

In this paper, we describe methods for the preparation of single or binary inorganic oxide aerogels that could be used as carriers for high performance supported Pd automotive catalysts. Indeed we have shown that alumina - based aerogel supported palladium catalysts were very active in propane oxidation [2]. Here we present the catalytic performances, in the reaction CO + NO -1- O2, of palladium catalysts supported on some of the prepared aerogels and compare their performances with those of Pd or Pt-Rh catalysts supported on a commercial alumina. 

Early reports on this reaction were focused on iron oxide-based catalysts, supported on different supports alumina, zeolite, and active carbon, among others. Later, hydrotalcite-like compounds, and the topical V-Mg-0 catalysts were explored. Park and his group, one of the most active in this field, first reported the use of zirconia as a catalyst, " and later on that of ceria-zirconia-based catalysts and vanadium-antimony oxide-based catalysts. Publications up to 2007 have been subject of several reviews. Therefore, the most relevant feamres will be revised hereinafter, as well as more recent publications, and the reader is invited to get further details in the aforementioned reviews. 

The use of cerium on Ru-based catalysts supported on alumina and activated carbon increased selectivity to unsaturated alcohols in the hydrogenation of crotonaldehyde (in the gas phase) and citral (in the liquid phase with isopropanol as solvent). However, the observed activities were very low. 

Nitrogen-doped CNTs have also been reported recently by Pham-Huu and coworkers as an efficient metal-free catalyst in the partial oxidation of H2S into elemental sulfur [139]. Such reaction is mostly catalyzed by iron-based catalysts supported on different carriers such as silica, alumina, or silicon carbide [140,141]. The optimization process was further conducted... 

The most common HDS catalyst consists of 2- to 3-nm-wide, singlelayered MoS nanoparticles, promoted with cobalt or nickel and supported on alumina. Only the edges of the S-Mo-S layers are known to be active. Sophisticated surface science studies have shown that even in such a well-defined nanostructure, two different types of active sites are present. In the reformation step, the Pt-Re-alumina-based catalyst catalyzes dehydrogenation and isomerization reactions. High octane gasoline must be rich in aromatics and branched chain paraffins, and this is achieved by subjecting crude gasoline to these reactions. 

From nitrogen physisorption measurements of the nitrate prepared gamma alumina based catalyst it is clear that only very limited BET surface area loss occurred upon the treatments carried out (figure 2). As a result one could already cautiously rule out sintering of the support as a decisive cause... 

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