Journal of Molecular Catalysis A: Chemical 204–205 (2003) 747–754 Modifier effects on Pt/C, Pd/C, and Raney-Ni catalysts in multiphase catalytic hydrogenation systems Pietro Tundo ∗ , Alvise Perosa, Sergei Zinovyev Dipartimento di Scienze Ambientali, Università Ca’ Foscari, Consorzio Interuniversitario Nazionale “La Chimica per l’Ambiente”, Dorsoduro 2137, 30123 Venezia, Italy Received 7 October 2002; received in revised form 22 January 2003; accepted 3 February 2003 Dedicated to Professor Renato Ugo on the occasion of his 65th birthday Abstract In the presence of a catalyst modifier (an onium salt, an amine, or a polyethylene glycol (PEG)), in a biphasic aqueous–organic mixture, the activity and the selectivity of hydrogenation reactions conducted using catalysts such as Pt/C, Pd/C or Raney-Ni, can change significantly. Hydrodehalogenation of haloaromatics, reduction of functional groups on the aromatic ring and of the aromatic ring itself, benzyl group hydrogenolysis, can be conducted under mild conditions, with high rates and interesting regio-, chemo- or stereoselectivities. The modifier coats the catalyst, thereby forming an interfacial film, wherein the reactions take place. This film partitions the catalyst at the aqueous–organic interface and influences the outcome of the reactions by mediating the substrate–catalyst interactions. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Catalytic hydrodechlorination; Catalyst modifier; Phase-transfer; Multiphase; Aliquat ® 336 1. Introduction Catalytic hydrogenolysis of aromatic halides repre- sents a viable, low-cost, and green methodology with an environmental value since it can be applied for the degradation of hazardous halogenated organic sub- stances, such as polychlorinated benzenes, phenols, Cl–C3 halocarbons, and of more toxic PCB, pesti- cides, dioxins, etc. This methodology is a promising detoxification tool for a number of environmental ob- jects, such as contaminated soils, municipal waste in- cinerator fly-ashes, hazardous organochlorine wastes, etc. There are a number of examples in the literature [1–10] that exemplify applications of the catalytic hy- ∗ Corresponding author. Fax: +39-041-2348620. E-mail address: tundop@unive.it (P. Tundo). drodehalogenation (HDX), in particular, hydrodechlo- rination (HDCl), and point at the advantages of the cat- alytic reductive treatment before combustion for waste disposal. As a rule, supported palladium [1–12] is the most active catalyst for the HDCl reaction, especially for the exhaustive dechlorination of polychlorinated substrates, which are known to be the harder to re- duce as the number of chlorine atoms present on the aromatic ring grows. There are examples using supported Ni catalysts as well [13–16], and other metals, such as Pt, Ru, Rh, etc. However, for HDCl with H 2 in most cases high pressures and/or tem- peratures are required in both gas- and liquid-phase systems. Herein, we report the use of catalyst modifiers in multiphase catalytic systems, which allow to 1381-1169/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S1381-1169(03)00360-1