Carbon Supported Pd Nanocrystals as High Efficient Catalyst for Regioselective Hydrogenation of p -Phenylphenol to p -Cy
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Carbon Supported Pd Nanocrystals as High Efficient Catalyst for Regioselective Hydrogenation of p-Phenylphenol to p-Cyclohexylphenol Chengyun Liu • Lianhai Lu • Zeming Rong • Changhai Liang • Yue Wang • Qingping Qu
Received: 19 December 2011 / Accepted: 11 September 2012 / Published online: 25 September 2012 Ó Springer Science+Business Media New York 2012
Abstract A series of Pd based nanocrystals were used to catalyze regioselective hydrogenation of p-phenylphenol (p-PP) to p-cyclohexylphenol (p-CP). The polar solvents such as THF, methanol and ethanol offered much higher selectivity to p-CP than nonpolar solvent. Concerning the effect of supports, the active carbon supported Pd nanocrystals show the best performance probably due to its hydrophobicity and high surface area. The best result with high selectivity (89.1 %) was obtained by using Pd/active carbon as catalyst when p-PP was 100 % converted. Keywords Regioselective hydrogenation Support effect Pd nanocrystal p-Phenylphenol p-Cyclohexylphenol
1 Introduction p-Cyclohexylphenol (p-CP), a very important fine chemical, has been widely used in the production of antioxidants of elastomers, liquid crystal monomers, high pressure lubricates and automatic transmission fluids [1, 2]. Several methods such as the Friedel–Crafts alkylation of phenol with cyclohexanol or cyclohexene using acidic catalyst and the hydrogenation of p-phenylphenol (p-PP) have been
Electronic supplementary material The online version of this article (doi:10.1007/s10562-012-0906-1) contains supplementary material, which is available to authorized users. C. Liu L. Lu Z. Rong (&) C. Liang Y. Wang Q. Qu (&) State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, China e-mail: [email protected] Q. Qu e-mail: [email protected]
most studied to produce p-CP [3, 4]. For the Friedel–Crafts alkylation, the major products were o-cyclohexylphenol, p-cyclohexylphenol, cyclohexyl phenyl ether and some polyalkylated phenols. However, the existence of hydroxyl group in phenol favors the formation of o-cyclohexylphenol (o-CP) and reduces the selectivity to p-CP in the product mixture. On the other hand, catalytic hydrogenation is a more environmentally benign approach that is a promising route to produce p-CP. Especially, the heterogeneous catalytic hydrogenations which the catalysts can be recyclable used have been extensively studied to hydrogenate bicyclic aromatics. Smith et al. [5] obtained essentially pure cyclohexylphenyl intermediates in the halfhydrogenation of diphenylmethane and 1, 1-diphenylethane. Similarly, a minimum of 90 % phenylcyclohexylacetic acid was formed from diphenylacetic acid over Adams platinum oxide. Gates and coworkers [6, 7] studied the hydrogenation kinetics of biphenyl over sulfided CoOMoO3/c-Al2O3. Lu et al. [8] studied the selective hydrogenation of single benzene ring in biphenyl by using skeletal Ni and obtained the yield of 99.4 %. Furthermore, dilute aqueous alkaline solutions [9] and supercritical carbon dioxide [10] h
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