Papers by Keyword: Metal Dispersion

Abstract: We have reported the effect of support pretreatment with ammonia on Pd/SiO2 catalyst in this study. SiO2 was pretreated with ammonia water to increase the Pd dispersion before the preparation of Pd/SiO2 catalysts. The effect of support pretreatment with ammonia on Pd/SiO2 catalyst was investigated by XRD, FT-IR, N2-adsorption and FE-TEM. The Pd supported on pretreated SiO2 were characterized by XRD, CO-chemisorption and FE-TEM. The pretreatment of SiO2 with ammonia water lead to decrease of silanol groups (Si-OH) up to temperature 200 °C. This decline of silanol groups on the SiO2 affects highly dispersed Pd/SiO2 as 6.52 %. The result showed that the decrease of silanol group on the SiO2 was favorable for the Pd dispersion. It is reason that absence of the silanol groups contribute to the high metal reducibility.

Abstract: The purpose of this study is to present the effect of attracting-repelling force on the dispersion and particle size of palladium (Pd) between Pd and γ-Al₂O₃. The Pd supported on γ-Al₂O₃ catalyst were prepared by deposition-precipitation method with two different ways. From the CO-Chemisorption results, Pd/γ-Al₂O₃ (R2-FM) catalyst has the highest Pd dispersion of 43.16%. The results showed that particle size and distribution of Pd influenced by the surface charge state of γ-Al₂O₃ support, indicating relation of attracting-repelling force between Pd precursor and γ-Al₂O₃ surface.

Abstract: Pt catalysts have been researched and used for HI decomposition. Specifically, the effects of supports and reduction temperature on metal dispersion were investigated in this paper. Metal dispersion was high measured, in the order of Pt/Al₂O₃, Pt/ZrO₂, and Pt/SiO₂. HI conversion results coincided with the metal dispersion. With effect on reduction temperature, Pt dispersion was measured as 2.9 %, 26 %, and 60 % each 1173K, 973K, and 773 K. In addition, HI conversion presented 7.8%, 16.3%, and, 19.4% respectively. Consequently, Pt dispersion, influenced by supports and reduction temperature was considered to be crucial role in HI conversion.