Metal dispersion, calcination conditions effects

The effect of metal loading on the reducibility was examined with PdNaY (71). For samples calcined at 500°C, the TPR peak maximum shifts from 190 to 150°C the Pd loading increases from 2.0 to 6.7 wt%. This has been attributed to the formation of ion pairs in sodalite cages. The reduction conditions are important for the resultant metal dispersion. TEM and radial electron distribution (RED) evidence shows that reduction of Ir ions in an H2 flow results in much smaller Ir aggregates than reduction under static H2 (173). 

The present work deals with sintering of Ni/AbOa catalysts under reducing and steamreforming reaction conditions. The effects of preparation method (impregnation and coprecipitation), lanthanum oxide promoter, oxide phases developed after calcination, sintering temperature and atmosphere were studied in terms of the time evolution of metal dispersion, size distribution properties and kinetic parameters obtained from a GPLE model. 

Because of the cost of noble metal, the inetal loading should be low. and the inetal must be well dispersed to make the exposed metal surface as high as possible. Each type of metal complex, the conditions for ion exchange, the calcination procedure, and the reduction conditions have profound effects on the dispersion of the metal. 

It is concluded that copper-oxide catalyst system, particularly copper-lanthanide oxide catalyst system, show a high activity for CO hydrogenation. The effective condition of the catalyst is the homogeneous mixture of copper and oxide where a fine particle of the oxide dispersed homogeneously in the copper metal and the active eatalyst can be prepared from the mixed oxide of CueOgLnfNOj) and the homogeneous oxide mixture obtained from the calcination of the hydroxide coprecipitate. If the combined oxides were changed. 

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