Pt AI2O3 catalyst

A simple example of using preadsorbed hydrogen as reductant was the preparation of a homodispersed Pt/ AI2O3 catalyst with increasing particle sizes prepared by platinum returning to the parent Pt/Al203 catalyst saturated with irreversibly chemisorbed hydrogen [20]. 

PS-19c The dehydrogenation of methylcyclohexane (M) to produce toluene (T) was carried out over a 0.3% PT/AI2O3 catalyst in a differential c lytic reactor, The reaction is carried out in the presence of hydrogen (H,) to avoid coking [./. Phys. Ckem., 64, 1559 (I960)]. 

The occurrence of a third mechanism, C, was suggested by a number of results that could be explained by none of the above mechanisms A and B, especially those involving the rupture of methyl-substituted C-C bonds, that is, the formation of n-hexane from methylcyclopentane on 10% Pt/AI2O3 catalysts at high temperature (86), n-hexane from trans-1,2-dimethylcyclobutane on metal films (89), n-heptane and 3-methylhexane from 1,2-dimethylcyclopentane, and methylhexanes from 1,3-dimethylcyclopentane on 10% Pt/Al2O3 at relatively low temperature (94). 

Pt/ AI2O3 Catalysts Conditions of Preparation and Metal Dispersion... 

Figure 2. Catalytic wet oxidtion of phenol at 423K and 1.4MPa (A unca yzed reaction, reaction with 3g metal-free AI2O3, reaction with 3g lwt% Pt/ AI2O3 catalyst).

Table S-43 Naphtha reforming with 0.6 % Pt /AI2O3 catalyst deactivation and regeneration [T35]...

The catalytic dehydrogenation of cyclohexane in an FAU-type zeolite-membrane reactor packed with a 1 wt.% Pt/ AI2O3 catalyst has been studied by Jeong et al. [247,248]. The conversion of cyclohexane in the membrane reactor is... 

Characteristics of the MetaUic Phase of Pt/ AI2O3 and Na-Dop>ed Pt/ AI2O3 Catalysts for Light Paraffins Dehydrogenation. Chemical Engineering Journal, V0I.II8, No.3, (May 2006), pp. 161-166, ISSN 1385-8947... 

Dulaurent, O. Bianchi, D. Adsorption isobars for CO on a Pt/ AI2O3 catalyst at high temperatures using FTIR spectroscopy isosteric heat of adsorption and adsorption model. Appl. Catal. A General 2000,196,271-280... 

Janicke, M.T., Kestenbaum, H., Hagendorf, U., Schiith, F., Fichtner, M. Schubert, K. (2000). The Controlled Oxidation of Hydrogen from an Explosive Mixture of Gases Using a Microstructured Reactor/Heat Exchanger and Pt/ AI2O3 Catalyst. Journal of Catalysis, Vol. 191,282-293. 

Rc-Pt [Re2Pl(CO)i2] 197 K-AI2O3 Catalyst characterization (IR. XPS. TPR, chemisorption) Catalyst characterization (EXAFS. chemisorption) and methylcyclohe.xane dehydrogenation 203 204... 

We measured the dispersion of Pt (impregnated from a chloroplatinic acid precursor, calcined at 450 C and reduced at 500 C) on a series of Nd203-loaded silica-aluminas (Fig. 8). We find, unexpectedly, that dispersion increases with increasing rare earth oxide loading up to about 18% Nd203, where it plateaus at between 40 and 50%, compared to 10% with unmodified Si-Al. This compares with dispersions of -60-80% measured on similarly Pt-loaded transitional AI2O3 catalysts. Transmission electron micrographs confirmed the decrease in particle size with rare earth content on Si-Al. 

G. Jacobs, T. K. Das, P. M. Patterson, J. Li, L. Sanchez and B. H. Davis, Fischer-Tropsch synthesis XAFS XAFS studies of the effect of water on a Pt-promoted C0/AI2O3 catalyst, Appl. Catal. A, 2003, 247, 335-343. 

Figure 4 STEM images of a 5% wt Pt on Y-AI2O3 catalyst (a) Bright field, (b) low angle annular detector, (c) high angle annular detector.

As an aside, we should mention that the same principles apply to the formation of bimetallic clusters on a support. In the case of Pt-Re on AI2O3 it has been shown that hydroxylation of the surface favors the ability of Re ions to migrate toward the Pt nuclei and thus the formation of alloy particles, whereas fixing the Re ions onto a dehydroxylated alumina surface creates mainly separated Re particles. As catalytic activity and selectivity of the bimetallic particles differ vastly from those of a physical mixture of monometallic particles, the catalytic performance of the reduced catalyst depends significantly on the protocol used during its formation. The bimetallic Pt-Re catalysts have been identified by comparison with preparations in which gaseous Re carbonyl was decomposed on conventionally prepared Pt/Al203 catalysts. ... 

Co and Fe catalysts have also been studied for the partial oxidation of methane to synthesis gas. Their potential relies on the fact that Co and Fe have higher melting and vaporizing points than Ni. Lower performances were mostly observed, however, which is probably related to the higher activity of CoO and FC2O3 for the complete oxidation of methane [121, 132, 133]. The recognized order of reactivity for partial oxidation is in fact Ni Co > Fe. However, it was observed that the performance of Co improves when a promoter is added. An extensive study of the catalytic partial oxidation of methane over CO/AI2O3 catalysts with different metals (0.1 wt% of Ni, Pt,... 

Figure 13.19 Sketch of the reduction mechanism for a Pt—Ba/y-AI2O3 catalyst upon regeneration with H2.

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 Pt particle size after reduction for the Pt/K-Al2C>3 catalyst is smaller than for the Pt/Cl-AI2O3 catalyst (coordination number Npt-pt 6.5 vs. 8.8). The Pt/K-Al203 sample shows a larger decrease of the Pt-Pt coordination distance after evacuation at 473 K (Pt/K-Al203 2.75 to 2.68 A Pt/Cl-Al203 2.76 to 2.73 A). The evacuation treatment leads for both catalysts to a decrease in the Pt-Pt coordination number and an increase in the Pt-0 coordination number (see Table 1 and Table 2). 

As noted above, these are typical petroleum-reforming catalysts [9a, b, 18, 19]. EUROPT-3 is 0.3% Pt AI2O3, and EUROPT-4 contains in addition 0.3% Re. Their surface areas are about 185m2g I, their N2 pore volumes about 0.5 cm3 g-1, and both contain about 1% Cl [18]. 

Fig. 5.9. Total activity (conversion per mg/cat) as a function of catalyst composition, in reactions of neohexane on Pt-Re/ AI2O3 catalysts.

---