Rhodium impregnation

Cavallaro et al. [156] reported that rhodium impregnated on y-alumina is highly suitable for SRE. The catalyst stability was investigated with and without oxygen. 

Filter paper impregnated with dicarbonyl(benz-2,l,3-thiadiazole)rhodium chloride gives characteristic colorations with the aminophenol isomers after fixation and can be used as an indicator paper (99). 

Figure 4.30. AFM images of rhodium particles deposited by spin-coating impregnation on flat Si02 on a Si(lOO) substrate particle, after reduction in hydrogen. [Adapted from...

Reaction conditions aUcenerCOrEL = 1 1 1, T = 100 °C, 0.2 wt% Rh metal loading, silica 100 p = 10 bar for guanidinium and norbos-Cs, p = 5 bar for sulfoxantphos ionic liquid used for impregnation [BMIM][PF6] a) molar ligand to metal ratio b) ratio of ionic liquid volume to support pore volume c) mol aldehyde per mol rhodium per hour d) ratio between linear and branched aldehyde e) support loaded with ionic liquid only. 

Routinely used X-ray sources are Mg Ka (1253.6 eV) and A1 Ka (1486.3 eV). In XPS one measures the intensity of photoelectrons N(E) as a function of their kinetic energy. The XPS spectrum, however, is usually a plot of N(E) versus Ek, or, more often, versus the binding energy Eb. Figure 3.3 shows the XPS spectrum of an alumina-supported rhodium catalyst, prepared by impregnating the support with... 

In the example of Fig. 7.15 [43j rhodium particles have been deposited by spin coat impregnation of a Si02/Si substrate with an aqueous solution of rhodium trichloride. After drying, the particles were reduced in hydrogen. The images show samples prepared at three different rotation speeds in the spin coating process, but with concentrations adjusted such that each sample contains about the same amount of rhodium atoms. The particles prepared at high rotation speeds are smaller, which... 

An alternative strategy for catalyst immobilisation uses ion-pair interactions between ionic catalyst complexes and polymeric ion exchange resins. Since all the rhodium complexes in the catalytic methanol carbonylation cycle are anionic, this is an attractive candidate for ionic attachment. In 1981, Drago et al. described the effective immobilisation of the rhodium catalyst on polymeric supports based on methylated polyvinylpyridines [48]. The activity was reported to be equal to the homogeneous system at 120 °C with minimal leaching of the supported catalyst. The ionically bound complex [Rh(CO)2l2] was identified by infrared spectroscopic analysis of the impregnated resin. 

An immediate extension of SAPC and SILC was the continuous-flow analogue performed by Eehrmann and co-workers, called supported ionic hquid phase (SILP). The catalyst was prepared by impregnation of the rhodium precursor,... 

The first fixed-bed application of a supported ionic liquid-phase catalyst was hydroformylation of propylene, with the reactants concentrated in the gas phase (265). The catalyst was a rhodium-sulfoxantphos complex in two ionic liquids on a silica support. The supported ionic liquid phase catalysts were conveniently prepared by impregnation of a silica gel with Rh(acac)(CO) and ligands in a mixture of methanol and ionic liquids, [BMIMJPFg and [BMIM][h-C8Hi70S03], under an argon atmosphere. 

Additional evidence of that hypothesis is given In Tables 4 and 5. The catalysts prepared with carbonyl clusters in n-hexane medium must avoid the MgO hydrolysis. The selectivity patterns for such catalysts show notable differences in comparison with the aqueous Impregnated type catalysts. The carvotanacetone formation is largely diminished and the stereospecificity to axial-equatorial carvomenthol is totaly inhibited. However in Rhodium silica supported catalysts the selectivity to carvotanacetone practically does not change. The effects in stereospecifity towards the carvomenthol product may be due to a small silica hydrolysis effect. 

Catalysts prepared by the wash-coating method were first used to check the reproduction of the measured values. For this reason, six elementary metal salts (platinum, zirconium, molybdenum, nickel, silver, and rhodium) were dissolved and impregnated onto a titer-plate. The catalysts were pre-reduced inside the reactor with 5% hydrogen in 95% nitrogen at 250 °C. The results were recorded first before the pre-reduction and then after the pre-reduction. The repeated measurements indicated good reproducibility in both cases. The conversion of methane with the rhodium catalyst is better after the pre-reduction. Methane conversion after 18 h runtime was still stable. 

The amount of wash coat which was deposited in the testing reactors was in the same range, between 14 and 17 mg, for the rhodium, platinum and palladium samples tested. The platinum sample was calcined after impregnation at a lower temperature of 450 °C, all other samples at 800 °C. The reason for this will be explained below. The content of the active noble metal was around 5 wt.%. All noble metal-containing samples were laboratory-made catalysts. A commercial a-alumina-based catalyst containing 14 wt.% Ni was added for comparison, as nickel catalysts are applied in industrial steam reforming [52],... 

Metallic monoliths made of both rhodium ([HCR 1]) and FeCrAlloy (72.6% Fe, 22% Cr and 4.8% Al ([HCR 3]) carrying micro channels of 120 pm x 130 pm cross-section at various length (5 and 20 mm) were applied. The monoliths were prepared of micro structured foils by electron beam welding. After bonding, the FeCrAlloy was oxidized in air at 1 000 °C for 4 h to form an a-alumina layer, which was verified by XRD. Its thickness was determined as < 10 pm by SEM/EDX. The alumina layer was impregnated with rhodium chloride and alternatively with a nickel salt solution. The catalyst loading with nickel (30 mg) was much higher than that with rhodium (1 mg) (see Table 2.4). The amount of rhodium on the catalyst surface was determined as 3% by XPS. 

The rhodium monolith showed a lower hydrogen selectivity of 50% at the same temperature and residence time. For the FeCrAlloy monolith impregnated with nickel, full conversion was achieved at 900 °C, but at a lower hydrogen yield [55],... 

The beneficial effect of the rhodium catalyst was proved by experiments at a reactor which was coated only with alumina. However, full conversion was also achieved at 1 000 °C, but along with inferior selectivity. Decreasing the residence time was beneficial for both conversion and hydrogen selectivity at the reactor impregnated with rhodium. This was explained by a temperature increase due to an increased rate of the combustion reaction, which in turn propagated the reforming reactions. 

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