The Influence of Pretreatment on the Metal Function of a Commercial Pt–Re/Al2O3Catalyst

Segregation of Pt and Re During CO2 Reforming of CH4

“…The temperature of reduction for this catalyst is approximately 65°C higher than for the PCZ catalyst but still significantly lower than the Re catalyst. The temperature of reduction agrees with the temperature (300°C) previously reported for a Pt-Re/Al 2 O 3 with 0.3 wt% Pt and 0.3 wt% Re [43]. Although the amount of hydrogen consumed during the reduction of the bimetallic catalyst is less than the sum of the hydrogen consumption for the individual Pt and Re catalysts, it is still greater than the amount required for complete reduction of the Pt and Re.…”

“…Also, the amount of hydrogen consumed is less than the amount consumed for the Pt catalyst even though the loading of Re is four times greater. TPR studies of 0.3 wt% Re supported on Al 2 O 3 have shown that Re reduction occurs between 500°C and 600°C, and that only 55% of the Re is reduced from the Re +7 state to metallic Re [43]. The temperature of reduction for the catalyst in this study is shifted to lower temperatures compared to the one reported in the literature.…”

XPS study of oxidation of rhenium metal on ?-Al2O3 support

“…Botman et al [25] showed that hydrogenolysis activity of the Re/γ -Al 2 O 3 catalyst decreased significantly after calcination in air at 450 • C. In contrast, Rochester and co-workers [8] found for Re/Al 2 O 3 that oxidation treatments at 550 • C had little effect on activity and selectivity for heptane-H 2 reactions. Prestvik et al [20] and earlier Isaacs and Petersen [26] found that the reduction temperature of Re in Re/Al 2 O 3 catalysts is influenced by the temperature of calcination/oxidation pretreatment. Chądzyński and Kubicka [18] established the increased resistance of the oxidized Re/γ -Al 2 O 3 catalyst with low Re content to rereduction by hydrogen.…”

“…Supported rhenium catalysts have been tested for hydrocarbon conversion craking [4][5][6], hydrogenation of benzene [6,7], n-heptane reforming [8], and recently as promising catalysts for methane [9] and ethane [10] aromatization and also for ammonia synthesis [11]. Catalytic hydrocarbon reactions are always accompanied by the catalyst deactivation, which results from the sintering of the catalyst, Re/Al 2 O 3 catalyst above 300 • C leads to segregation of Pt and Re oxide [15,20,21] and as a consequence causes important changes in the catalytic behavior of the system. XANES and TPR studies of a Pt-Re/Al 2 O 3 catalyst subjected to oxychlorination also showed that redispersion of both active components into their single, monometallic oxides occurs [22,23].…”

Study of Pt and Rh based supported catalysts modified with tetrabutyltin for the selective hydrogenation of 4-methoxyacetophenone

“…The hydrogen uptake for the calcined Rh/SiO 2 sample was 6.68 cm 3 /g sample , which corresponded to the reduction of ca. 95% of Rh(III), whereas the H 2 consumption of 3.51 cm 3 /g sample and the two peaks for Pt/SiO 2 could be assigned to the reduction of PtO 2 and Pt species interacting more strongly with the support [14]. Figure 2 shows the scheme of the probable reaction routes and products in the hydrogenation of 4-methoxyacetophenone.…”