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|Title:||Stereoselective cascade hydrogenation of 4-tert-butylphenol and p-cresol over Zr-zeolite beta-supported rhodium||Authors:||Nie, Y.
van Bekkum, H.
|Issue Date:||15-Feb-2007||Citation:||Nie, Y., Jaenicke, S., van Bekkum, H., Chuah, G.-K. (2007-02-15). Stereoselective cascade hydrogenation of 4-tert-butylphenol and p-cresol over Zr-zeolite beta-supported rhodium. Journal of Catalysis 246 (1) : 223-231. ScholarBank@NUS Repository. https://doi.org/10.1016/j.jcat.2006.12.008||Abstract:||The hydrogenation of 4-tert-butylphenol and p-cresol was investigated over Zr-beta-supported rhodium catalysts. By designing a suitable bifunctional catalyst, the intermediate, 4-alkylcyclohexanone, formed by metal-catalyzed hydrogenation of 4-alkylphenol, could be reduced via the highly stereoselective Meerwein-Ponndorf-Verley reduction over zirconium Lewis acid sites. Thus, in the presence of 2-propanol as solvent and MPV reductant, a high stereoselectivity to cis-4-alkylcyclohexanol was observed. Over 0.5% Rh/Zr-beta, 4-tert-butylphenol, and p-cresol were hydrogenated to the cis-alcohols with 95 and 89% stereoselectivity, respectively. A higher metal loading or the use of solvents such as hexane or tert-butanol led to a lower stereoselectivity, as metal-catalyzed hydrogenation predominated. Similarly, the cis:trans alcohol ratio was lower for rhodium supported on zirconia or Al-beta. Compared with rhodium, palladium was less active in the hydrogenation of the 4-alkylphenols, requiring a higher hydrogen pressure and temperature. A two-step cascade reaction mechanism is proposed for the conversion of 4-alkylphenols to cis-4-alkylcyclohexanols. © 2006 Elsevier Inc. All rights reserved.||Source Title:||Journal of Catalysis||URI:||http://scholarbank.nus.edu.sg/handle/10635/77053||ISSN:||00219517||DOI:||10.1016/j.jcat.2006.12.008|
|Appears in Collections:||Staff Publications|
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