Deep adsorptive desulfurization over ion-exchanged zeolites: Individual and simultaneous effect of aromatic and nitrogen compounds

Abstract

The presence of aromatics and nitrogen compounds in petroleum fuel has a strong inhibiting impact on deep adsorptive desulfurization (ADS). This work aimed to clarify the individual and simultaneous effect of these compounds on ADS of the most refractory sulfur-containing polyaromatic compounds (dibenzothiophene and 4,6-dimethyldibenzothiophene) over Na–Y, Ni–Y, La–Y, Ce–Y and Ni–Ce–Y zeolites in a fixed bed system at ambient conditions. Polyaromatics (naphthalene) and nitrogen (quinoline and indole) compounds caused a marked decrease in the sulfur adsorption capacity, while the nitrogen compounds decreased the sulfur adsorption capacity more than naphthalene. The negative electrostatic potential of compounds might play an important role in the adsorptive selectivity on the pre-reduced Ni–Y zeolite. The results show that the adsorption sites of aromatics and nitrogen compounds on the adsorbents are the same as for the sulfur compounds. This competitive adsorption was very strong especially for the metal that enhanced π-complexation interaction. The reduced Ni2+ introduced into Na–Y zeolite increased resistance to aromatics and nitrogen compounds on ADS. For the spent adsorbent, the regeneration efficiency, in terms of the desorption amount, depended on the similarity of the polarity of the solvent (hexane and toluene) and adsorbate, where a high temperature and low flow rate of solvent favored the extraction of adsorbates leading to an increased regeneration efficiency. This study provides an insight into the interactions among these three kinds of components and adsorbents, which is useful for further development of the ADS process.