A Systematic Study on the Effect of Desilication of Clinoptilolite Zeolite on its Deep-Desulfurization Characteristics

Natural clinoptilolite zeolite (CLP) in its original or metal ion- exchanged form (Ni2+) is a weak adsorbent for relatively large thiophene derivative molecules like benzothiophene (BT) and di-benzothiophene (DBT), due to its rather restricted micro-channel structure. A novelty of this work is that upon desilication treatments, it is possible to enhance the adsorption behavior of Ni2+-exchanged CLP for such large sulfur- containing molecules. A natural CLP zeolite has been desilicated using NaOH solutions in a concentration range of 0.2-2.0 M. The resulting powders have been subjected to XRF, XRD, FTIR, nitrogen adsorption/desorption, TEM and TGA analyses. The adsorption isotherms for the removal of thiophene (TP), BT, DBT and iso-propyl mercaptan (IPM) have been obtained experimentally at 20 °C from simulated liquid fuels using iso-octane as solvent. The sample treated with 1.5 M NaOH solution showed the most significant enhancement in adsorptive properties. The selectivity order is IPM TP BT DBT. Regenerability tests show a quasi constant adsorption capacity after the first cycle. The observed phenomena have been thoroughly discussed based on the physico-chemical analyses of the samples.