Heterogeneous catalytic oxidation of phenol by in situ generated hydrogen peroxide applying novel catalytic membrane reactors O. Osegueda a,b,c , A. Dafinov a,b,⇑ , J. Llorca d , F. Medina a,b , J. Sueiras a,b a Chemical Engineering Department, Rovira i Virgili University, Av. Països Catalans 26, Tarragona 43007, Spain b EMas-Research Center on Engineering of Materials and Micro/nanoSystems, Campus Sescelades, Tarragona 43007, Spain c Central American University ‘‘José Simeón Cañas’’, Blvd. Los Próceres, Antiguo Cuscatlán, El Salvador d Institute of Energy Technologies and Centre for Research in NanoEngineering, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain highlights  Selective deposition of active phase on the reaction zone.  Formation of nanometer sized palladium particles.  High selectivity to hydrogen peroxide in the H 2 oxidation.  Efficiently use of in situ generated hydrogen peroxide.  Role of the hydrogen in the Pd deactivation process. graphical abstract CMR H2 flow Support -H H2 Water + dissolved O2 Pd Pd H2 O2 -H -H H2O air -H H2O2 -H -H -H O2 -H H2O2 •HO article info Article history: Received 23 May 2014 Received in revised form 18 September 2014 Accepted 19 September 2014 Available online 7 October 2014 Keywords: Hydrogen peroxide generation Catalytic membrane reactor Sputtered palladium nanoparticles Phenol oxidation Palladium nanoparticle deactivation abstract This work presents a novel method for oxidation of organic matter in water solutions based on catalytic membrane reactors. The oxidant, hydrogen peroxide, is generated directly in the bulk of the liquid inves- tigated. Commercial symmetric alumina hollow fibers have been used as a starting material thereafter introducing the active phases. It has been proven that two different catalysts are necessary in order to complete the overall reaction, as well as to generate hydrogen peroxide and a heterogeneous Fenton pro- cess. Palladium has been used for the hydrogen peroxide generation and a second active phase, transi- tional metal oxides or homogeneous Fe 2+ , has been used for the hydroxyl radical generation. An additional method for specific Pd loading to the reaction zone based on sputtering technique has been developed. All prepared catalytic membrane reactors (CMRs) are capable of generating hydrogen perox- ide in amounts comparable to CMRs reported in the literature. The catalytic membrane reactors prepared by Pd impregnation show very high activity and stability in phenol oxidation reaching 40% of the gener- ated H 2 O 2 usage in the oxidation reaction. Despite the very high activity of the catalytic membrane reac- tors obtained by Pd sputtering in H 2 O 2 production they suffer very fast deactivation. Specific reactivation including a calcination step has been found to be appropriate for the recovery of their activity. Additional experiments give new insights for better understanding of Pd deactivation especially when the metal particles are of nanometer sizes. Ó 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cej.2014.09.064 1385-8947/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: Chemical Engineering Department, Rovira i Virgili University, Av. Països Catalans 26, Tarragona 43007, Spain. Tel.: +34 977558112; fax: +34 977559621. E-mail address: anton.dafinov@urv.cat (A. Dafinov). Chemical Engineering Journal 262 (2015) 344–355 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej