Effect of Modification of Cu+-13X Zeolite by Lanthanum on Dynamic Competitive Adsorption of 3-Methylthiophene and Benzothiophene

Abstract

The zeolite sorbents Cu + -13X and La/Cu + -13X were prepared by the ion-exchange method. Dynamic adsorption of 3-methylthiophene and benzothiophene on fixed beds of the adsorbents was studied. It was found that introducing a rare-earth element into 13X zeolite increases its adsorption capacity and selectivity for sulfur compounds and reduces adsorption competition. The effect of the adsorbent bed height, feed rate, and liquid phase/adsorbent contact time was studied. The best results are obtained for adsorbent bed height 14 cm, feed rate 14 mL/h, and liquid phase/adsorbent contact time 30 minutes.Rare-earth elements have a special 4f electron shell configuration and a large atomic radius, very readily give up outer 6s electrons, and are characterized by some special physical and chemical properties. When combined with other metal ions, rare-earth ions can display unexpected functional properties [1][2][3][4].Although hydrodesulfurization is a major technology for removing sulfur compounds from fuels, it is a very complicated process to obtain ultra-low sulfur fuels. New technologies have been proposed for production of such fuels: adsorption desulfurization, biodesulfurization, extraction of sulfur compounds by ionic liquids, desulfurization by complex formation [5][6][7][8]. References 9 and 10 report on an efficient and environmentally friendly technology for deep desulfurization of fuels for fuel cells.Adsorption desulfurization on zeolites is widely studied, but when the large molecules of sulfur compounds participate in adsorption, zeolites are ineffective due to their small cage size. The authors of [11][12][13] introduced La 3+ ions into the zeolite. On the one hand, the binding strength between aluminum and oxygen atoms is increased, so more aluminum and consequently more acid sites are retained in the zeolite. On the other hand, the La 3+ ions increase the proton number, create additional acid sites, prevent loss of aluminum, and improve the stability and catalytic activity of the zeolite.