RECENTLY PUBLISHED WORK ON EUROPT-1, A 6-PERCENT PT/SIO2 REFERENCE CATALYST

EUROPT-1 is a 6% Pt/SiO2 catalyst which has been thoroughly characterised with respect to its composition, structure, chemisorption behaviour and catalytic properties. Extensive further work on this catalyst has been published and this is now reviewed. Debye function analysis of X-ray diffraction spectra suggest platinum particles to be cubooctahedral, although preliminary extended X-ray absorption fine structure results do not accord with this model. Further isotherms for carbon monoxide, hydrogen and oxygen chemisorption have been reported and enthalpies of adsorption for the last two gases measured. Limited results on structure-insensitive reactions such as exchange of methane with deuterium and alkene hydrogenation are available. Methane homologation as well as skeletal reactions of alkanes in the presence of hydrogen represent structure-sensitive reactions. Some further work on ethane, propane and n-butane is reported; detailed results on n-hexane and methylcyclopentane include changes in rates and selectivities as a function of hydrogen and hydrocarbon pressure. They are interpreted in terms of availability of surface hydrogen and hydrogen effects on the formation of carbonaceous deposits of various degree of dehydrogenation. Effects of sintering have also been studied, and active centres for various reactions have been tentatively suggested. On the whole, EUROPT-1 shows behaviour which is characteristic of platinum catalysts containing small platinum particles but in some limited respects it shows unusual and unexpected properties. Reactions of some oxygenated compounds are described briefly. Catalytic properties of EUROPT-1 can be modified by metals, oxides, sulphur and nitrogen; treatment with cinchonidine converts it into an enantioselective catalyst for the hydrogenation of methyl pyruvate. Finally the importance of selecting appropriate reference supported metal catalyst(s) is stressed and the future role for EUROPT-1 as a possible candidate is pointed out; results must however be compared under carefully defined conditions if they are to have real value.