Preparation, characterization, and hydrogenation activity of new Rh0–MCM-41 catalysts prepared from as-synthesized MCM-41 and RhCl3 - 21/02/18
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Abstract |
Impregnation of as-synthesized MCM-41 silica by ethanolic solutions of rhodium(III) chloride was tested as an alternative to its introduction into the synthesis gel to get, after calcination and reduction by H2, highly dispersed metal(0) nanoparticles throughout the mesopores network. Rh(III) and Rh(0)–based solids thus obtained were analyzed by infrared spectroscopy, elemental analysis, transmission electron microscopy, N2 sorption, and X-ray diffraction. Materials with 1.6 wt % of rhodium could be obtained as a result of CTA+/Rh3+ exchange. The determining role of CTA+ was emphasized through blank experiments. In a second series of materials, ethanol was also exploited for its ability to reduce Rh(III). All Rh(0)-based solids were tested as catalysts in the hydrogenation of styrene under mild temperature and pressure conditions. Catalysis performances of the most efficient sample (reduced by H2) were further compared with those of a very similar material prepared by the introduction of Rh(III) directly into the synthesis gel of MCM-41 silica. Better cis selectivities in the hydrogenation of disubstituted arene derivatives were achieved with materials issued from the new preparation method.
Le texte complet de cet article est disponible en PDF.Graphical abstract |
Ammonium template facilitates incorporation of Rh(III) in the as-synthesized MCM-41 in ethanol, thus affording, after an ex situ reduction step, catalytically active dispersions of Rh(0) with a high cis selectivity in the hydrogenation of disubstituted arenes.
Highlights |
• | The role of cetyltrimethylammonium in the uptake process of rhodium(III) was clearly demonstrated in ethanol. |
• | Relationship between surfactant removal and rhodium incorporated was tested at different nominal molar Si/Rh ratios. |
• | Ethanol can also be used as a reducing agent provided that the reaction is carried out ex-situ. |
• | Differences were highlighted between the materials prepared according to this new path and that of direct hydrothermal synthesis. |
• | Resulting materials lead to a better selectivity in cis hydrogenated compounds compared to samples prepared by DHT. |
Keywords : MCM-41, Rhodium, Template-ion exchange, Ethanol, Hydrogenation
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