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Monitoring Transport Phenomena of Paramagnetic Metal-Ion Complexes Inside Catalyst Bodies with Magnetic Resonance Imaging

Authors

  • Jaap A. Bergwerff Dr.,

    1. Inorganic Chemistry and Catalysis Group, Department of Chemistry, Faculty of Science, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands, Fax: (+31) 30-251-1027
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  • Anna A. Lysova Dr.,

    1. International Tomography Center SB Ras, 3A Institutskaya Street, Novosibirsk 630090, Russia
    2. Boreskov Institute of Catalysis Sb RAS, 5 Ak. Lavrent'eva Prospekt, Novosibirsk 630090, Russia
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  • Leticia Espinosa-Alonso,

    1. Inorganic Chemistry and Catalysis Group, Department of Chemistry, Faculty of Science, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands, Fax: (+31) 30-251-1027
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  • Igor V. Koptyug Prof. Dr.,

    1. International Tomography Center SB Ras, 3A Institutskaya Street, Novosibirsk 630090, Russia
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  • Bert M. Weckhuysen Prof. Dr.

    1. Inorganic Chemistry and Catalysis Group, Department of Chemistry, Faculty of Science, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands, Fax: (+31) 30-251-1027
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Abstract

An indirect magnetic resonance imaging (MRI) method has been developed to determine in a noninvasive manner the distribution of paramagnetic Co2+ complexes inside Co/Al2O3 catalyst extrudates after impregnation with Co2+/citrate solutions of different pH and citrate concentrations. UV/Vis/NIR microspectroscopic measurements were carried out simultaneously to obtain complementary information on the nature of the Co2+ complexes. In this way, it could be confirmed that the actual distribution of Co2+ inside the extrudates could be derived from the MRI images. By combining these space- and time-resolved techniques, information was obtained on both the strength and the mode of interaction between [Co(H2O)6]2+ and different Co2+ citrate complexes with the Al2O3 support. Complexation of Co2+ by citrate was found to lead to a stronger interaction of Co with the support surface and formation of an eggshell distribution of Co2+ complexes after impregnation. By addition of free citrate and by changing the pH of the impregnation solution, it was possible to obtain the rather uncommon egg-yolk and egg-white distributions of Co2+ inside the extrudates after impregnation. In other words, by carefully altering the chemical composition and pH of the impregnation solution, the macrodistribution of Co2+ complexes inside catalyst extrudates could be fine-tuned from eggshell over egg white and egg yolk to uniform.

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