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Study On The New Hydrogenation Catalysts For The Production Of Hydrogen Peroxide Through Anthraquinone Route

Posted on:2005-12-21Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y J HouFull Text:PDF
GTID:1101360122982262Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
Hydrogen peroxide is a very important industrial product used in many fields. Since it is only converted into water after reaction, it belongs to one of the green chemicals. It has been attracting more and more attention under the viewpoint of sustainable development. By far, it has mainly been produced by anthraquinone (AQ) route in which the hydrogenation catalyst is the main cost of its production. Currently, Raney Ni and supported Pd are mainly used in the hydrogenation of anthraquinone. Considering the shortage in the resource of precious metals and the protection of the environment, it is of great importance to find more active and non-precious metal catalysts to replace Pd and Raney Ni. In the present work, several series of Ni and Ni-B amorphous alloy catalysts, either supported or unsupported, were produced by borohydride or hydrazine reduction methods, characterized by ICP, BET, DSC, XRD, XPS, TEM and H2-TPD etc., and studied in the hydrogenation of 2-ethylanthraquinone. Among all the catalysts prepared, the activity of 2-ethylanthraquinone hydrogenation reaction follows the order: 0.25%Pd/(-Al2O3>La-doped Ni-B>Mo-doped Ni-B>Cr-doped Ni-B>Ce-doped Ni-B>Raney Ni>NiH/SiO2>Ni-B-La/γ-Al2O3>NiN/SiO2>Ni-B>NiLaN/(-Al2O3>NiN/(-Al2O3>Ni-B/γ-Al2O3>Ni-B/SiO2>NiH/(-Al2O3 (all catalysts denote the ones with optimal Ni loadings for supported catalysts or optimal amounts of dopants for the doped Ni-B catalysts).The results of H2-chemisorption and H2-TPD over Ni powders, Raney Ni, Ni-B and Ni-B-La amorphous alloy catalysts showed that there were two types of adsorbing sites for hydrogen, a weak adsorbing site and a strong adsorbing site, existing on the surfaces of these catalysts, while only strong adsorbing site existed on the surface of Ni-B-La catalysts. The reaction results, in combination with H2-TPD results, showed that the hydrogen desorbed from the strong adsorbing site might be active for the hydrogenation of 2-ethylanthraquinone to form 2-ethylanthrahydroquinone. La, Ce, Cr and Mo were studied as dopants for the Ni-B amorphous alloy catalysts. The results of activities and characterizations showed that with the addition of La, Ce, Cr and Mo, both the extents of H2-chemisorption and H2-TPD areas first increased markedly and then decreased. The hydrogenation activities of these series of catalysts also showed the same trend. The effects of La, Ce, Cr and Mo were all attributed to its dispersion of Ni particles, resulting in the formation of more surface Ni centers. However, much higher dopant contents might result the coverage of surface Ni centers. After heat treatment at higher temperatures, the amorphous structures of all these Ni-B catalysts were destroyed, the active centers decreased, and therefore the activities decreased.Two series of supported Ni-B amorphous catalysts, Ni-B /γ-Al2O3 and Ni-B/SiO2 were also studied. For the series of Ni-B/γ-Al2O3 catalysts, it was found that Ni species were dispersed by γ-Al2O3, while optimal Ni loadings were needed to achieve the maximum activity. This might be ascribed to the following reasons: first, γ-Al2O3 increased the dispersion of the surface Ni, resulting in the formation of more active centers and hence higher activities; however, higher loadings might block the pores in γ-Al2O3. For the series of Ni-B/SiO2 catalysts, it was found that with the increase of the active component loadings, both the extents of H2-chemisorption and the activities continually increased in the studied ranges. This might be due to the higher pore volume and wider pore diameters of SiO2 than γ-Al2O3.A series of amorphous Ni-B/γ-Al2O3 catalysts with different La loadings were characterized and studied in the hydrogenation of anthraquinone. In comparison with the catalyst without La loadings, the presence of proper amounts of lanthanum species in the supported amorphous alloy catalysts leaded to more active centers, higher extents of H2 chemisorption, the shift of H2 desorption peaks to lower temperatures, the enhancement of thermal stability as wel...
Keywords/Search Tags:hydrogen peroxide, 2-ethylanthraquinone, hydrazine, potassium borohydride, hydrogenation, Ni-B amorphous alloy, Ni-B/γ-Al2O3, Ni-B/SiO2, La, Ce, Cr, Mo
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