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.