Liquid-phase thiophene adsorption on MCM-22 zeolite and activated carbon
CADONI, ENZO;FERINO, ITALO
2008-01-01
Abstract
The liquid-phase adsorption of thiophene from thiophene/iso-octane and toluene-rich thiophene/toluene/iso-octane solutions has been investigated in batch conditions at room temperature and atmospheric pressure on MCM-22 zeolite and activated carbon. The adsorption of toluene from toluene/iso-octane solutions has also been investigated on both the adsorbents. These were characterised by X-ray diffraction, nitrogen physisorption, scanning electron microscopy and adsorption microcalorimetry of ammonia. Both MCM-22 and activated carbon were able to adsorb thiophene and toluene from the corresponding single-adsorptive iso-octane solutions. MCM-22 appeared superior to activated carbon for the adsorption of thiophene from toluene-rich thiophene/toluene/iso-octane mixtures. The adsorption data for MCM-22 were correlated with the acid sites and silanol groups concentrations, as determined by microcalorimetric experiments. No such correlation was found for activated carbon. Apparently, on MCM-22 thiophene adsorption occurs first on the acid sites until they are saturated and then continues on the silanol groups. Toluene adsorption also occurs on the acid sites of MCM-22 until saturation, but no further adsorption by interaction of toluene with the silanol groups takes place. GC/MS investigation of the nature of the organosulphur material retained by the adsorbent revealed that the tiophene adsorbed on MCM-22 undergoes transformation into heavy products. Besides thiophene trimers and tetramers, these include other compounds formed by two and three thiophenic rings linked by alkyl groups, as well as a rather high molecular weight product where a trimer is linked to thiophenic ring by a cyclohexadienic ring. Reaction pathways leading to these products have been tentatively outlined. (C) 2007 Elsevier Inc. All rights reserved.Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.