Catalytic behavior of biosorbents supported in zeolites

The catalytic oxidation of 1,2-dichlorobenzene at 350 oC was investigated over a robust biosorption system consisting of a bacterial biofilm supported on NaY or NaX zeolites. The batch method has been employed using chromium concentrations in solution ranging from 50 to 250 mgCr/L. The results showed that the maximum removal efficiency was 20% for Cr in both systems based in NaY or NaX. The bacterial biofilm, Arthrobacter viscosus, supported on the zeolite reduces Cr(VI) to Cr(III). The Cr(III) is retained in the zeolite by ion exchange. The new biosorvents catalysts were characterized by spectroscopic methods (FTIR and ICP-AES), surface analysis (DRX) and thermal analysis (TGA). The various techniques of characterization used show that this biosorption process does not modify the morphology and structure of the FAUzeolites. These catalysts, Cr/FAU, prepared through this new procedure present good activity and selectivity for dichlorobenzene oxidation in wet air. The Cr50-Y was selected as the most active, selective and stable catalyst for oxidation of 1,2 dichlorobenzene in wet air.Fundação para a Ciência e a Tecnologia (FCT)Departamento de Ciências da Terra of Universidade do MinhoAgence de l’Environnement et de la Maîtrise de l’Energie (ADEME) and the Région Poitou-Charente

Oxidation catalysts prepared from biosorbents supported on zeolites

The catalytic oxidation of 1,2-dichlorobenzene was investigated over NaYand NaX zeolites, loaded with chromiumthrough the action of a robust biosorption system consisting of a bacterial biofilm supported on the zeolites. The results of biosorption showed that the maximum metal removal efficiencywas 20%, in both systems based on NaYorNaX, starting fromsolutions with chromium(VI) concentrations ranging from 50 to 250 mgCr/L. The bacterial biofilm, Arthrobacter viscosus, supported on the zeolite reduces Cr(VI) to Cr(III). The Cr(III) is retained in the zeolite by ion exchange. The new catalysts were characterized by spectroscopic methods (FTIR ), chemical analyses (ICP-AES), surface analysis (XRD) and thermal analysis (TGA). The various techniques of characterization show that this biosorption process does not modify the morphology and structure of the FAUzeolites. These catalysts,Cr/FAU, prepared through this newprocedure present good activity and selectivity for dichlorobenzene oxidation in wet air at 350 ºC. The Cr50-Y was selected as the most active, selective and stable catalyst for oxidation of 1,2-dichlorobenzene in wet air.Departamento de Ciências da Terra of Universidade do Minho; Fundação para a Ciência e a Tecnologia (FCT) ; Agence de l’Environnement et de la Maîtrise de l’Energie (ADEME); Région Poitou-Charentes

Catalytic oxidation of VOCs on NaX zeolite: Mixture effect with isopropanol and o-xylene

International audienceCatalytic oxidation of isopropanol and o-xylene alone as well as in mixture was investigated over basic NaX zeolite. Experiments were carried out in wet air (11,000 ppm of water) and at a high gas hourly space velocity (GHSV) of 18,000 h(-1). Results show an inhibiting effect of the o-xylene on the isopropanol destruction whereas the isopropanol has no effect on the o-xylene destruction. Adsorption experiments as well as molecular modelling seem to demonstrate that this inhibiting effect of o-xylene is due to the adsorption of this aromatic VOCs near the apertures of the NaX supercages limiting the access of isopropanol to the basic active sites of this zeolite. Furthermore, the concentration of o-xylene influences the formation of secondary products (propene, coke) resulting from the isopropanol transformation. (C) 2010 Elsevier B.V. All rights reserve

Direct evidence of the role of dispersed ceria on the activation of oxygen in NaX zeolite by coupling the O-17/O-16 isotopic exchange and O-17 solid-state NMR

International audienceThe possibility to understand the phenomena of oxygen diffusion in the solids may be decisive to explain the role of framework oxygen atoms in a catalytic mechanism or in catalyst regeneration steps. In this work, two highly efficient characterization techniques have been associated: the O-17/O-16 isotopic exchange and the O-17 high field solid-state NMR spectroscopy. This combination leads to a powerful tool to investigate the interaction between gaseous dioxygen molecule and lattice oxygen atoms. Here, it permits to demonstrate the enhancement of the participation of zeolitic oxygen atoms in the exchange with the gas phase when ceria is simply mixed with Na