- Hydrogenation of alkyl-anthraquinone over hydrophobically functionalized Pd/SBA-15 catalysts
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Organosilane-functionalized mesoporous silica SBA-15 was prepared by the co-condensation method and then applied as a support of Pd catalysts for hydrogenation of 2-alkyl-anthraquinone (AQ, alkyl = ethyl, tert-butyl and amyl). The as-prepared Pd catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, N2 adsorption-desorption, zeta potential, water contact angles measurement and transmission electron microscopy. By extending the pre-hydrolysis time of the silica source, the content of functional groups in the catalysts slightly increases. However, there is an initial increase in zeta potential and water contact angles up to a maximum at 2 h, followed by a decrease as the pre-hydrolysis time was further prolonged. The hydrophobicity created by organic functionalization has positive effects on AQ hydrogenation. The catalyst with the highest hydrophobicity exhibits the highest catalytic activity, with increments of 33.3%, 60.0% and 150.0% for hydrogenation of ethyl-, tert-butyl- and amyl-anthraquinone compared with the unfunctionalized one.
- Wang, Li,Zhang, Yue,Ma, Qingqing,Pan, Zhiyong,Zong, Baoning
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- Highly dispersed Pd nanoparticles supported on γ-Al2O3 modified by minimal 3-aminopropyltriethoxysilane as effective catalysts for 2-ethyl-anthraquinone hydrogenation
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Faced with the problems of poor activity and inferior selectivity, highly dispersed Pd catalysts pre-modified by minimal 3-aminopropyltriethoxysilane (APTES) were prepared via impregnation reduction method. The amount of APTES was adjusted according to molar ratios of the APTES to Pd (APTES/Pd). The catalytic hydrogenation efficiency exhibited a volcano-shape trend with the amount of APTES. Grafting of suitable amount of APTES improved the dispersion of the Pd, increased the weak acid content of the γ-Al2O3 and regulated the reducibility of the catalysts. The catalyst having APTES/Pd = 2 with 0.192 wt% Pd showed the highest catalytic activity and selectivity, with 100 % in the selectivity and the improvement of 27.3 % in the hydrogenation efficiency and 104.8 % in the H2O2 productivity compared with the commercial catalyst (0.298 wt%). Furthermore, the APTES aggregated with the amount of APTES, which provided intense anchoring sites for the Pd and resulted in the increase in larger palladium nanoparticles.
- Li, Wenqian,Wang, Fuming,Zhang, Xubin,Sun, Mingshuai,Hu, Jiaqi,Zhai, Yi,Lv, Huihui,Lv, Guojun
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- The role of alkali modifiers (Li, Na, K, Cs) in activity of 2%Pd/Al 2O3 catalysts for 2-ethyl-9,10-anthraquione hydrogenation
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Present research concentrates on the role of alkali modifiers (Li, Na, K, Cs) in activity of 2%Pd/Al2O3 catalyst for 2-ethyl-9,10-anthraquinone (eAQ) hydrogenation. The catalysts with various content of alkali modifier (Me/Pd molar ratio ranges from 0.5 up to 4, Me-alkali metal) were prepared by impregnation of pre-reduced 2%Pd/Al2O 3 catalyst with appropriate alkali metal carbonates. The XPS, EDS and TEM measurements show that alkali promoters are introduced into alumina matrix. The microcalorimertic experiments of CO adsorption prove the interaction of CO with catalysts leading to stronger bonding of carbon monoxide by alkali doped catalysts. The presence of alkali promoters in Pd/Al2O3 catalyst plays an essential role in the whole eAQ hydrogenation process. The nature of alkali promoter and its content (Me/Pd atomic ratio) in catalyst are of importance. As the alkalinity of promoter increases going from Li to Cs all the effects caused by their presence become stronger. In the presence of alkali doped catalysts the content of 2-ethyloxoanthrone (OXO, isomer of 2-ethyl-9,10-anthrahydroquinone) formed is higher than that on un-doped 2%Pd/Al2O3. On the other hand, reactions in the "deep hydrogenation" stage comprising the formation of 2-ethyl-5,6,7,8- tetrahydro-9,10-anthraquinone (H4eAQ) and the transformation of OXO to 2-ethylanthrone and other degradation products are remarkably inhibited. In particular, the formation of 2-ethylanthrone via hydrogenolysis of OXO isomer is strongly suppressed. The Cs-doped catalyst exhibits the highest activity to OXO among all the catalysts tested whereas the ability of Cs-doped catalysts to the formation of anthrone is most effectively inhibited. The role of alkali modifiers is considered to be associated with stronger interactions between the catalyst and quinone reagents, and in particular OXO isomer. Moreover, in the reagent adsorption the centres of support nearby the palladium particles may also participate by affecting the mode of reagents adsorption.
- Kosydar,Drelinkiewicz,Lalik,Gurgul
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experimental part
p. 121 - 131
(2012/04/10)
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- Liquid Phase Catalytic Hydrogenation of 2-Ethyl-9,10-Anthraquinone to 2-Ethyl-5,6,7,8-Tetrahydro-9,10-Anthraquinone. I. Introductory Experiments
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It was found that during 2-ethyl-9,10-anthraquinone (eAQ) hydrogenation at the presence of Pd/silica-alumina catalyst, at first 2-ethyl-9,10-dihydroxyanthracene (eAQH2) was formed with high selectivity.In the further process, eAQH2 was hydrogenated and 2-ethyl-5,6,7,8-tetrahydro-9,10-dihydroxyanthracene (H4eAQH2) as a main product was formed.A part of eAQH2 was hydrogenated to the other products denoted as "degradation products".At room temperature the rate of hydrogenation was influenced by the hydrogen diffusion within catalyst pores.At the presence of this limitations, selectivity of H4eAQH2 formation depended on initial eAQ concentration, catalyst amount and temperature.
- Drelinkiewicz, Alicja
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p. 219 - 230
(2007/10/02)
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