Support Effects in Nerol Hydrogenation over Pt/SiO 2 , Pt/H-Y and Pt/H-MCM-41 Catalysts
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Catalysis Letters Vol. 98, No. 4, December 2004 (Ó 2004)
Support effects in nerol hydrogenation over Pt/SiO2 , Pt/H-Y and Pt/H-MCM-41 catalysts Pa¨ivi Ma¨ki-Arvela1, Narendra Kumar1, Ivo Paseka2, Tapio Salmi1 and Dmitry Yu. Murzin1,* 1
Laboratory of Industrial Chemistry, Process Chemistry Centre, A˚bo Akademi University, FIN-20500 A˚ba/ Turku, Finland 2Institute of Inorganic Chemistry, Academy of Sciences of Czech Republic, Rez, Czech Republic
Received 9 June 2004; accepted 10 September 2004
Chemoselective hydrogenation of nerol was investigated over Pt/SiO2 , Pt/H-Y and Pt/H-MCM-41 catalysts. The initial total reaction rates decreased in following order:Pt/H-Y > Pt/SiO2 > Pt/H-MCM-41. Nerol hydrogenation was found to be an apparent structure sensitive reaction. The selectivities to citronellol at 30% conversion of nerol were 65%, 55% and 25% over Pt/SiO2 , Pt/HMCM-41 and Pt/H-Y, respectively. KEY WORDS: nerol, hydrogenation, kinetics, selectivity, Pt, H-MCM-41.
1. Introduction Nerol is an unsaturated alcohol, widely applied in perfumery industry. Annually 6000 tonnes of nerol and another alcohol geraniol and their esters as well as a product of nerol hydrogenation, citronellol and its esters are used for the synthesis of rose odour compounds [1]. Heterogeneous catalytic hydrogenation of nerol (A) has been very scarcely investigated [2,3]. Not only industrially, but also scientifically it is an interesting molecule, because besides hydrogenation it can undergo isomerization to an unsaturated aldehyde, citronellal (B) (figure 1) [3], which can in principle further be hydrogenated to 3,7-dimethyloctanal (F). The main hydrogenation products are citronellol (C) and 3,7dimethyloctanol (G). Additionally hydrocarbons can be formed by hydrogenolysis of nerol [3]. Citronellol is a valuable intermediate for the production of fragrances [1] and pheromones [4]. It can be synthesized by several methods, for instance catalytic hydrogenation starting from citral [5], citronellal [6,7], nerol [3] or geraniol [8], or hydrodealumination of the alumino-derivative of dihydromyrcene followed by oxidation and hydrolysis [9] or via treating an acyclic terpene with NaBH4 and AlCl3 with further hydration and oxidation with H2 O2 [10]. Furthermore C can be prepared via pyrolysis of pinane followed by hydration [11]. In the catalytic hydrogenation selectivities of over 95% have been achieved in citral hydrogenation over Ni/Al2 O3 catalyst in ethanol [5]. Over Rh black [12] and Ni/Cr2 O3 [13] the maximum selectivities to C in citral hydrogenation of 95% and 80%, have been respectively achieved, however, under diffusion limitations. Citral hydrogenation was very selective to C over a bimetallic *To whom correspondence should be addressed. E-mail: [email protected]
NiMo12 catalyst in 2-propanol [14]. Citronellal has been hydrogenated to citronellol with the selectivities up to 90% over Ru/TiO2 catalyst [6]. Very high selectivities for C (94%) have been reported in geraniol hydrogenation over pt/Y in toluene [8]. The only products were C and D.
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