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2008
ACL
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S.Habib, F.Launay, S.Laforge, J.D.Comparot, A.C.Faust, Y.Millot, T.Onfroy, V.Montouillout, P.Magnoux, J.L.Paillaud, A.Gédéon, 'High catalytic cracking activity of Al-MCM-41 type materials prepared from ZSM-5 zeolite crystals and fumed silica', Appl. Catal. A-Gen. 344 61-69 (2008) doi:10.1016/j.apcata.2008.04.001
Two series of mesoporous aluminosilicate materials of the Al-MCM-41 type have been prepared from pre-formed ZSM-5 crystals. The synthesis involved the alkaline attack of the zeolite alone (M(-)/x samples) or in the presence of an external silicon source (e.g. fumed silica, M(S)/x samples) followed by a conventional 48 h hydrothermal treatment (100°C) with cetyltrimethylammonium chloride as the structure directing agent. The effect of sodium hydroxide concentration (0.8 x 3 M) on the properties of the final materials was investigated by powder XRD, nitrogen sorption, pyridine sorption (IRFT), SEM, TEM, MAS and 2D MQ-MAS 27Al NMR. It was shown that the addition of fumed silica to the synthesis gel results in the improvement of the structuration of the mesopore network. The stability of M(-)/x and M(S)/x materials towards boiling water (5 days) as well as their activity in the acid-catalysed transformation of methycyclohexane at 350°C were compared to that of ZSM- 5, Al-MCM-41 and of a ZSM-5/Al-MCM-41 mechanical mixture. Because of the existence of a 2-fold pore system with zeolite domains, M(S)/0.8 and M(S)/1.9 composites are more efficient catalysts than amorphous Al-MCM-41 and a mechanical mixture of Al-MCM-41 and ZSM-5. The best combination in terms of hydrothermal stability and catalytic activity was found for the M(S)/1.9 sample.
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