Alumina supported platinum catalyst

In addition to this work on charcoal- and silica-supported catalysts and on evaporated platinum films, a number of studies have been made on alumina-supported platinum catalysts (e.g., 111-114, 81,115) in which the aim has been the study of reactions at the platinum alone. In these cases, one cannot automatically dismiss the possibility of participation of the alumina support (i.e., of dual function behavior of the catalyst) because it is known that alumina may have acidic properties, particularly when retained halogen is present. In general terms, there is no immediate answer to this problem because the nature of this sort of catalyst wall be much dependent on the details of catalyst history, preparation, and use. However, there can be little doubt that in many experimental studies using plati-num/alumina, and in which the assumption has been made that the alumina support is inert, this assumption is essentially valid. For instance, one may note the inert alumina used by Davis and Venuto (111) and the justification provided by Gault et al. (116) for the inertness of the alumina used in a substantial body of previous work irrespective of whether the catalyst was... 

Gopalan, U., Hydrodenitrogenation of Pyridine over Alumina Supported Platinum Catalyst. Master of Applied Science Thesis. University of Otawa, Chemical Engineering. 1998, p. 69. 

Shabaker, J. W. Davda, R. R. Huber, G. W. Cortright, R. D. Dumesic, J. A., Aqueous-phase reforming of methanol and ethylene glycol over alumina-supported platinum catalysts. Journal of Catalysis 2003, 215, 344. 

We describe in some detail the techniques of nuclear magnetic resonance which are used for studying alumina-supported platinum catalysts. In particular, we describe the spin-echo technique from which the Pt lineshape can be obtained. We also discuss spin echo double resonance between surface Pt and chemisorbed molecules and show how the NMR resonance of the surface Pt can be separately studied. We present examples of experimental data and discuss their interpretation. 

Figure 4 in Ref. 216, reproduced on the right, displays Pt 4d5/2 XPS spectra from calcined alumina-supported platinum catalysts, pure (Pt/A) and doped with lanthanum (Pt/A-L), cerium... 

Promotion and deactivation of unsupported and alumina-supported platinum catalysts were studied in the selective oxidation of 1-phenyl-ethanol to acetophenone, as a model reaction. The oxidation was performed with atmospheric air in an aqueous alkaline solution. The oxidation state of the catalyst was followed by measuring the open circuit potential of the slurry during reaction. It is proposed that the primary reason for deactivation is the destructive adsorption of alcohol substrate on the platinum surface at the very beginning of the reaction, leading to irreversibly adsorbed species. Over-oxidation of Pt active sites occurs after a substantial reduction in the number of free sites. Deactivation could be efficiently suppressed by partial blocking of surface platinum atoms with a submonolayer of bismuth promoter. At optimum Bi/Ptj ratio the yield increased from 18 to 99 %. 

In the gas-phase, benzene shows a single line,77 78 and can yield useful information regarding the diffusion/transport properties. Benzene trapped within pores in glasses and silica gels too yields results, about pore size and adsorbed versus liquid-phase conditions.79 Chemisorption on alumina-supported platinum catalysts leads to disclosure as to how and where the benzene molecules are located, via FT NMR.80... 

C. F. Tlrendl, G. A. Mills and C. Dybowski, Platinum-proton coupling in the NMR spectrum of benzene on an alumina-supported platinum catalyst.. Phys. Chem., 1992, 96(12), 5045-5048. 

For efficient raw material utilization as well as for fuel conservation (e.g., methane), discharge controls integral with the process absorbers have obvious advantages. Nitric oxide and nitrogen dioxide may be reduced by ammonia using alumina-supported platinum catalysts without the need to consume the residual oxygen first [54] (Eqs. 11.50 and 11.51). 

The discussion in this section pertains to alumina-supported platinum catalysts. The work by C.P. Poole and D.S. Maciver provides an extensive review of chromia-alumina catalysts... 

The key role of dehydrogenation catalysts is to accelerate the main reaction while controlling other reactions. Unmodified alumina-supported platinum catalysts are highly active but are not selective to dehydrogenation. Various by-products, as indicated in Figs. 5 and 6, can also form. In addition, the catalyst rapidly deactivates because of fouling by heavy carbonaceous materials. Therefore, the properties of platinum and the alumina support need to be modified to suppress the formation of by-products and to increase catalytic stability. 

Aben, P.C. van der Eijk, H. and Oelderik, J.M. "The characterization of the metal surface of alumina-supported platinum catalysts by temperature-programmed desorption of chemisorbed hydrogen." In Hightower, J.W., ed. Proceedings of the Fifth International Congress on Catalysis. Vol. 1. Amsterdam North-Holland 1973 p. 717-726. 

Using carbon-13 labelled hydrocarbons it was pointed out that two Bond Shift (BS) mechanisms are taking place on inert alumina supported platinum catalysts. 

The study of the oxidation of ammonia to nitrogen and water at low temperature has become more and more important in recent years due to agricultural and industrial waste streams. Noble metals (Pt, Ir) are suitable for the selective, low temperature oxidation of ammonia to nitrogen and water. Alumina supported platinum catalysts are promising in the conversion of gaseous ammonia to N2 and H2O. They possess a high activity and selectivity in N2 formation.I l However, these catalysts are susceptible to rapid deactivation due to irreversible adsorption of reaction intermediates such as NHx species. 

Shelimov, B.N., Lambert, J.-F., Che, M., Didillon, B. (1999). Initial Steps of the Alumina-Supported Platinum Catalyst Preparation a Molecular Study by i spt NMR, UV-Visible, EXAFS and Raman Spectroscopy. Journal of Catalysis, Vol.185, No.2, (July 1999), pp. 462-478, ISSN 0021-9517... 

The present work was undertaken to examine this possibility by trying a new method of low-temperature catalyst preparation. The method studied involves the adsorption of metal precursors on supports and the reduction by sodium tetrahydroborate solution for the preparation of supported platinum catalysts. The adsorption and reduction of platinum precursors are carried out at room temperature and the highest temperature during the preparation is 390 K for the removal of solvent. The activities of the catalysts prepared were examined for liquid-phase hydrogenation of cinnamaldehyde under mild conditions. Our attention was directed to not only total activity but also selectivity to cinnamyl alcohol, since it is difficult for platinum to hydrogenate the C=0 bond of this a, -unsaturated aldehyde compared to the C=C bond [2]. We examined the dependence of the catalytic activity and selectivity on preparation variables including metal precursor species, support materials and reduction conditions. In addition, the prepared catalysts were characterized by several techniques to clarify their catalytic features. The activity of the alumina-supported platinum catalyst prepared by the present method was briefly reported in a recent communication [3]. 

Singh, J. and van Bokhoven, J. (2010). Structure of alumina supported platinum catalysts of different particle size during CO oxidation using in situ IR and HERFD XAS, Catal. Today, 155, pp. 199-205. 

Sarkany J, Gonzalez RD. Support and dispersion effects on silica- and alumina-supported platinum catalysts II. Effect on the CO-O2 reaction. Appl Catal. 1983 5 85. 

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