High temperature characterization of Y-zeolite loaded with chlorobenzene

Due to their widespread use in many industrial sectors, low solubility in water and their bioaccumulation tendency, Volatile Organic Compounds (VOCs) are hazardous organic chemicals commonly present in water. Among this class of pollutants, chlorobenzene (CB) is included as benzene (i.e., BTEX species) halogenated compound. Therefore, due to its toxic effects on both human health and environmental systems, the removal of CB from water is a primary issue. Recently, it has been highlighted that organophylic and hydrophobic zeolites are efficient as sorbent materials and completely regenerable without showing remarkable changes in adsorption capacity and structural properties. Nowadays, these zeolites features, combined with their high thermal stability, are exploited in regeneration processes through thermal treatment in order to reuse regenerated zeolites in new adsorption processes (Rodeghero et al., 2016). Therefore, the aim of the project is to investigate the desorption process of chlorobenzene (purchased by Sigma Aldrich with a purity of 99.8%) Y (HSZ-390HUA code; 200 SiO2/Al2O3 ratio) system to: 1) determine the desorption temperature of extraframework content; 2) characterize the structural modifications induced by high temperature treatment and 3) highlight the temperature effects on the interactions between organic molecules and framework oxygen atoms. With this purpose, Y-CB sample was prepared and characterized by chromatographic (via Headspace Solid Phase Microextraction-GC) and thermal (TG and DTA) analysis. Desorption process was constantly monitored, through synchrotron X-ray powder diffraction, at the high resolution Beamline ID22 (ESRF, Grenoble) from room temperature to 590°C with a heating rate of 8°C/min. Rietveld refinements showed that chlorobenzene molecules are desorbed at about 210°C. These results are in good agreement with thermal analysis, which suggest that all the extraframework (H2O and CB molecules) content is completely released between 190 and 210°C. Hence, the detected desorption temperature reveals an acceleration of desorption kinetics compared to that reported on a patent previously published (Vignola et al., 2008). Moreover, structural refinements highlighted that both only slight memory effects in terms of structural deformations are registered in 12MR channel geometry after regeneration process and the reactivated zeolite regain the unit-cell parameters of the bare material almost perfectly. Furthermore, any significant crystallinity loss is observed. Based on these results, the High Silica Y zeolite is potentially reusable in a new adsorption/desorption cycle. Rodeghero, E., Martucci, A., Cruciani, G., Bagatin, R., Sarti, E., Bosi, V., Pasti, L. (2016): Kinetics and dynamic behaviour of toluene desorption from ZSM-5 using in situ high-temperature Synchrotron X-ray diffraction and chromatographic techniques. Catalysis Today, 277, 118-125. Vignola, R. (2008): WO 2009/000429 A1, Eni S.p.A