Deep adsorption desulfurization of liquid petroleum gas by copper-modified bentonite

Abstract

The removal of sulfur compounds from liquid petroleum gas (LPG) was investigated using a fixed-bed flow sorption system. Copper-modified bentonite adsorbents significantly enhanced the desulfurization of LPG. Several factors that influence desulfurization, including the copper loading, the baking temperature, the valence state and the type of anion used, were investigated. The adsorbents were characterized by nitrogen adsorption, X-ray diffraction, inductively coupled plasma-atomic emission spectrometry, thermogravimetric analysis, Raman spectrometry and FTIR spectrometry. Optimum desulfurization with Cu(II)-modified bentonite adsorbents was obtained at a loading of 15 wt% Cu²⁺ and a calcination temperature of 150 °C. The Cu(I)-modified bentonite adsorbents were shown to be better than the Cu(II)-modified bentonite adsorbents in removing sulfur compounds from LPG; the anion used had no significant influence on the desulfurization ability of the Cu(II)-modified bentonite adsorbents. FTIR analyses showed that the surface Lewis acid sites contributed to the desulfurization process. The sulfur compounds were adsorbed over Cu(I)- and Cu(II)-modified bentonite by a direct sulfur–adsorbent interaction.