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|Title:||Zr-zeolite beta: A new heterogeneous catalyst system for the highly selective cascade transformation of citral to (±)-menthol|
|Authors:||Nie, Y. |
|Citation:||Nie, Y., Jaenicke, S., Chuah, G.-K. (2009-02-09). Zr-zeolite beta: A new heterogeneous catalyst system for the highly selective cascade transformation of citral to (±)-menthol. Chemistry - A European Journal 15 (8) : 1991-1999. ScholarBank@NUS Repository.|
|Abstract:||The transformation of citral to menthols involves hydrogénation steps as well as cyclisation of the intermediate, citronellal. The ability of Zrzeolite beta to catalyse the cyclisation with high diastereoselectivity to (±)-isopulegol is the critical step in this cascade transformation. Bifunctional catalysts containing nickel or rhodium supported on Zr-zeolite beta gave menthols in yields of 87-89 % and an excellent diastereoselectivity of 94% for the desired (±)-menthol. Dual catalyst systems of Zr-zeolite beta and nano-dispersed Ni on an MCM-41 support were equally effective and have the added advantage that the rates of the acid and hydrogenation-catalysed steps can be independently varied. By applying a pressure ramp of 0.2-2 MPa, the yield of menthols could be increased to 95 %, with 94 % diastereoselectivity for (±)-menthol. The low initial pressure minimises the rates of competing hydrogenation reactions to byproducts such as citronellol and 3,7-dimethyloctanol. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.|
|Source Title:||Chemistry - A European Journal|
|Appears in Collections:||Staff Publications|
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