Unique selectivity in the hydrodechlorination of 2,4-dichlorophenol over hematite-supported Au

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• 作者：Santiago Gó ; mez-Quero¹ ; Fernando Cá ; rdenas-Lizana² ; Mark A. Keane ; ^{M.A.Keane@hw.ac.uk}
• 关键词：Chlorophenol(s) ; Selective hydrodechlorination ; Au/Fe2O3 ; 2 ; 4-Dichlorophenol ; Inductive effects
• 刊名：Journal of Catalysis
• 出版年：2013
• 出版时间：July, 2013
• 年：2013
• 卷：303
• 期：Complete
• 页码：41-49
• 全文大小：1152 K

文摘

The gas-phase hydrodechlorination of 2,4-dichlorophenol (at 423 K) has been studied over Au/Fe₂O₃ prepared by deposition-precipitation. Support and catalyst were characterised by TPR, XRD, H₂ chemisorption/TPD, BET area/porosity and TEM/SEM measurements. Fe₂O₃ was reduced to Fe₃O₄ and Fe following TPR to 673 K and 1273 K, respectively; inclusion of Au lowered (by 200 K) support reduction temperature. TPR of Au/Fe₂O₃ to 423 K generated quasi-spherical Au particles (mean size = 2.6 nm) that promoted hydrogenolysis of ortho-Cl, generating 4-chlorophenol via a stepwise mechanism. We attribute this unprecedented selectivity to reactant interaction through -OH at electron-deficient Au sites, rendering ortho-Cl susceptible to attack. Solvent effects are demonstrated for a range of carriers where conversion of aqueous 2,4-DCP delivered the highest rate (1 ¡Á 10^?3 mol_Cl h^?1 ), equivalent to that achieved with Ni/SiO₂ at 573 K. Selectivity in the cleavage of sterically constrained Cl in mono-, di- and tri-chlorophenols is also demonstrated.