Alumina-supported rhodium catalyst

Oh, S.H. (1990) Effects of cerium addition on the CO-NO reaction kinetics over alumina-supported rhodium catalysts, J. Catal. 124, 477. 

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... 

Fuentes, S., and Figueras, F., The influence of particle size on the catalytic properties of alumina-supported rhodium catalysts. /. Catal. 61, 443 (1980). 

Ferreira-Aparicio P, Femandez-Garcia M, Guerrero-Ruiz A, Rodriguez-Ramos I (2000) Evaluation of the role of the metal-support interfacial centers in the dry reforming of methane on alumina-supported rhodium catalysts. J Catal 190 2%-308... 

Preparation of Alumina-Supported Rhodium Model Catalysts... 

The stepwise mechanism was also shown later to be valid over supported platinum (55), and palladium 56, 56a) catalysts, as well as over alumina-supported rhodium (57). 

A very active elemental rhodium is obtained by reduction of rhodium chloride with sodium borohydride [27]. Supported rhodium catalysts, usually 5% on carbon or alumina, are especially suited for hydrogenation of aromatic systems [iTj. A mixture of rhodium oxide and platinum oxide was also used for this purpose and proved better than platinum oxide alone [i5, 39]. Unsaturated halides containing vinylic halogens are reduced at the double bond without hydrogenolysis of the halogen [40]. 

Furthermore, it was clearly shown that noble metals, rhodium in particular, play an active role in promoting the OSC of the support [1,3-6,31]. It was shown for example that only Rh can really promote OSC on alumina catalysts [32,33]. Nevertheless the situation changes when ceria is added to alumina. A comparative study of alumina and ceria-alumina supported bimetallic catalysts [32,33] demonstrated the differences between those systems. Ceria-alumina catalysts were shown to have higher OSC values which do not depend on the composition of the bimetallic (Fig. 7.3). 

Another ion exchange procedure involves the interaction of a metal acetylacetonate (acac) with an oxide support. Virtually all acetylacetonate complexes, except those of rhodium and ruthenium, react with the coordinatively unsaturated surface sites of 7 alumina to produce stable catalyst precursors. On thermal treatment and reduction these give alumina supported metal catalysts having relatively high dispersions. 38 Acetylacetonate complexes which are stable in the presence of acid or base such as Pd(acac)2, Pt(acac)2 and Co(acac)3, react only with the Lewis acid, Al" 3 sites, on the alumina. Complexes which decompose in base but not in acid react not only with the Al 3 sites but also with the surface hydroxy groups. Complexes that are sensitive to acid but not to base react only slightly, if at all, with the hydroxy groups on the surface. It appears that this is the reason the rhodium and ruthenium complexes fail to adsorb on an alumina surface. 38... 

Rupprechter G, Hayek K, Hofmeister H (1998) Electron microscopy of thin film model catalysts Activation of alumina supported rhodium nanoparticles. J Catal 173 409... 

Literature on the use of promoters is voluminous, and all claim enhancement of semi-hydrogenation selectivity. One of the more successful commercial catalysts for ethyne conversion to ethene, uses a silver promoted alumina-supported palladium catalyst [23]. Other promoting metals have been used, including rhodium and gold [24,25], copper [26-28], zinc (shown to inhibit oligomerization) [29-... 

Conditions cited for Rh on alumina hydrogenation of MDA are much less severe, 117 °C and 760 kPA (110 psi) (26). With 550 kPa (80 psi) ammonia partial pressure present ia the hydrogenation of twice-distilled MDA employing 2-propanol solvent at 121°C and 1.3 MPa (190 psi) total pressure, the supported Rh catalyst could be extensively reused (27). Medium pressure (3.9 MPa = 566 psi) and temperature (80°C) hydrogenation usiag iridium yields low trans trans isomer MDCHA (28). Improved selectivity to aUcychc diamine from MDA has been claimed (29) for alumina-supported iridium and rhodium by iatroduciag the tertiary amines l,4-diazabicyclo[2.2.2]octane [280-57-9] and quiaucHdine [100-76-5]. 

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