Study of Adsorptive Denitrogenation of Diesel Fuel over Mesoporous Molecular Sieves Based on Breakthrough Curves

Abstract

Adsorptive denitrogenation of model fuel and commercial diesel containing organic nitrogen compounds was studied over three typical mesoporous molecular sieves (Ti-HMS, HMS, and MCM-41) in a fixed-bed adsorption system at ambient pressure. The adsorbents were characterized by X-ray diffraction, UV–visible spectroscopy, transmission electron microscopy, N2 physical adsorption–desorption, and temperature-programmed NH3 desorption techniques. The adsorption capacities for various compounds (pyridine, quinoline, pyrrole, and indole) were examined and compared on the basis of the breakthrough curves, which provided insight into the adsorption behaviors over the different adsorbents. It is shown that the breakthrough time is shortened at increased temperature and liquid hourly space velocity (LHSV). The adsorption performance of HMS and Ti-HMS depends dominantly on the acid–base interaction. In addition, the polarity of the adsorbate is another factor that influences the adsorption capacity. The introduction of Ti improves the acidity of Ti-HMS, which thus exhibits a higher adsorption capacity than HMS, as confirmed by UV–visible spectroscopy and temperature-programmed NH3 desorption. The adsorption performance of nonacidic MCM-41 depends principally on the molecular weight of the adsorbate. For commercial diesel, the adsorption competition between sulfur and nitrogen compounds influences the adsorption of total nitrogen.