5,291 research outputs found
Synthesis and characterization of ultrahigh crystalline TiO2 nanotubes
No full textUltrahigh crystalline TiO2 nanotubes were synthesized by hydrogen peroxide treatment of very low crystalline titania nanotubes (TINT-as prepared), which were prepared with synthesized TiO2 nanoparticles by hydrothermal methods in an aqueous NaOH solution. Thus, prepared ultrahigh crystalline TiO2 nanotubes (TINT-H2O2) showed comparable crystallinity with high crystalline TiO2 nanoparticles. The details of nanotubular structures were elucidated by high resolution-transmission electron microscopy (HR-TEM), field emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis in transmission electron microscopy (TEM-EDX), X-ray diffraction (XRD), photoluminescence (PL), and BET surface area. TINT-H2O2 was found to be a multiwalled anatase phase only with an average outer diameter of similar to 8 nm and an inner diameter of similar to 5 nm and grown along the [001] direction to 500-700 nm long with an interlayer fringe distance of ca. 0.78 nm. The photocatalytic activity of TINT-H2O2 was about 2-fold higher than those of TINT-as prepared, synthesized TiO2 nanoparticles, and TiO2-P25 (Degussa) in the photocatalytic oxidation of trimethylamine gas under UV irradiation
DEACTIVATION CHARACTERISTICS IN N-HEPTANE REFORMING REACTION CATALYZED OVER SMALL PT, IR AND PT-IR BIMETALLIC CLUSTERS IN NAY
No full textThe deactivation characteristics of highly dispersed (about 1 nm) Pt, Ir and Pt-Ir bimetallic clusters in NaY were studied by hydrogen chemisorption, coke analysis and temperature programmed oxidation of used catalyst in n-heptane reforming reaction. As the Ir content was increased, the amount of coke decreased. Most of coke was located around the metal cluster and this coke decreased the selectivity of dehydrocyclization in n-heptane reaction. The higher activity and more improved activity maintenance of Pt-Ir/NaY bimetallic catalysts than those of Pt/NaY are related to the less amount of coke formation
Characterization and catalytic properties of Pt, Ir, Pt-Ir clusters entrapped in NaY for reforming reaction
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Comparison of platinum-iridium bimetallic catalysts supported on γ-alumina and HY-zeolite in n-hexane reforming reaction
No full textThe characteristics and activity, selectivity and stability of Pt-Ir bimetallic catalysts supported on gamma-Al2O3 and HY-zeolite were examined using hydrogen chemisorption on catalysts calcined at different temperatures as well as by catalyst performance for n-hexane reforming at 573-773 K and atmospheric pressure. All the catalysts used in this study were prepared by impregnation. The Pt-Ir/HY and Pt-Ir/Al2O3 calcined at 773 k did not exhibit severe oxidative agglomeration, in contrast to monometallic iridium catalysts, and their activity and selectivity in n-hexane reforming were quite different from those of monometallic platinum or iridium catalysts. The catalysts supported on HY-zeolite showed high activity for isomerization while gamma-Al2O3-supported catalysts had high activity for dehydrocyclization. Deactivation with reaction time was much more pronounced on HY-zeolite-supported catalysts. Pt-Ir catalysts supported on Al2O3 and HY showed high selectivity and activity to high-octane value hydrocarbons when the both metals were present in equal amount, 0.5 wt.-%. Especially the HY-zeolite-supported Pt-Ir bimetallic catalyst showed a good performance for producing high-octane hydrocarbons containing less amounts of aromatic compounds. It may be concluded that the nature of the support greatly affected the catalytic properties of Pt-Ir bimetallic catalysts for n-hexane reforming
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