Supports reduction temperature effect

Figure 3.7 Effect of the reduction temperature on the performance of the catalyst supported on nanotunneled mesoporous H-CNF.

Pt promotion has been also investigated with other support materials. For example, Schanke et al. studied the influence of small amounts of Pt (0.4 wt%), on the reducibility of Co/Si02 and C0/AI2O3 catalysts containing 9 wt% Co, and observed that the presence of Pt decreased in all cases the reduction temperature of C03O4, although the effect was more pronounced for... 

The term SMSl was introduced by Tauster et al. (S.J. Tauster, S.C. Funk, R.L. Garten, J. Am. Chem. Soc. 1978, 100, 170) to denote the effect responsible for the drastic decrease in CO and H2 chemisorption on titania-supported metals after increasing the reduction temperature from 200 to 500°C. More details on this effect can be found in a review paper of Hadjiivanov and Klissurski (K.I. Hadjiivanov, D.G. Klissurski, Chem. Soc. Rev., 1996, 25, 61). 

The initial reaction rate values show the effect of metal support interaction, the extent of reduction and method of preparation. For alumina supported sample the increase in reduction temperature, and an increase in the degree of reduction, results in a fourfold increase in initial... 

Rolek et al tried to distinguish between viscosity, temperature and composition in their influence on the effects of molybdenum disulphide dispersions in oils. They used a series of white oils, mineral oils, and the same mineral oils with some polar additives removed. The results were not entirely clear, but they supported Tsuya s findings (see below) on the effect of viscosity. However, they also seemed to indicate a more specific effect of temperature and the presence of polar additives. It seemed that there was a specific inhibiting effect of polar additives in suppressing any friction reduction by the molybdenum disulphide. In addition they identified a temperature effect distinct from its effect on viscosity, and suggested that this might be related to a transition temperature, possibly associated with desorption of polar compounds. 

In a recent review work (117) on the chemical and nano-structural characterization of NM/CeO catalysts, a detailed study of the H interaction with a Pt/CeO catalyst reduced at temperatures ranging fh)m 473 K to 773 K is reported. The experimental techniques used in this work were TPD-MS and Isotopic Transient Kinetics (ITK) of the H2/D2 exchange at 298 K. The catalyst sample was carefully selected in order to minimise the Pt and support sintering effects in the investigated range of reduction temperatures. Likewise, a chlorine-free metal precursor, [Pt(NH3)4](OH)2, was used in the preparation of the catalyst. 

Nanostructural Features of Metal-Support Interaction Effects in NM/Ce(M)02, Catalysts. Their Evolution with Reduction Temperature. 

When considering metal-support interaction effects, the whole set of Electron Microscopy data presented in the previous section point out some important differences between the behaviour of noble metal catalysts supported on ceria and that of titania-supported catalysts. Much higher reduction temperatures are required in the case of ceria-type supports to observe nanostructural features similar to those described for the so called SMS I efTect. 

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