Selective Adsorptive Desulfurization with Alkaline-Earth Metal-Modified Zeolites in Oil in the Presence of Olefin.

Adsorptive desulfurization (ADS) was a hopeful method for deep desulfurization of oil in mild conditions. In this paper, based on the alkaline-earth (AE) metal-modified Y zeolite (AEY), synthesis, systematic characterization, ADS performance test, and analysis of related adsorption mechanisms were carried out. The crystal and pore structure of Y zeolite were not damaged after ion exchange of AE, while the amount of acid sites and the ratio of Lewis/Bronsted acid sites were both decreased. Although surface acid sites on zeolites were believed to be active sites for ADS, the performance test results showed that AEY adsorbents had rather good S adsorption capacity compared to NaY. Moreover, the S adsorption selectivity in the presence of hexene-1 in oil was also desirable for all AEY adsorbents. Based on these experimental results and previously proposed mechanisms for S-containing compound adsorption, a new adsorption mechanism was proposed for AEY, and this mechanism was further supported by the aid of DFT calculations. The good S-removal performance of AEY adsorbents as well as the new proposed adsorption mechanism may help people design and synthesize further improved S-compound adsorbents for ADS processes in an oil refinery.

A density functional theory study on the adsorption of different organic sulfides on boron nitride nanosheet.

The adsorption of methanethiol (MT), thiophene (T), benzothiophene (BT), dibenzothiophene (DBT) on hexagonal boron nitride (h-BN) has been investigated by the framework of the density functional theory (DFT) calculations in this work. The prefer adsorption sites and interfacial angles of different sulfur compounds on the surface of the h-BN are investigated and analyzed. The adsorption energy results indicated that the adsorption of MT (Ead ≈ -6 kcal mol-1), T (Ead ≈ -10 kcal mol-1), BT (Ead ≈ -15 kcal mol-1), and DBT (Ead ≈ -21 kcal mol-1) on monolayer h-BN is physical interaction, and the value of Ead on bilayer h-BN is more than that on monolayer h-BN 0.05%. Adsorptive conformations show that sulfides prefer to be adsorbed on center B atoms rather than N atoms. Meanwhile, thiophene and its analogues tend to be adsorbed parallel on h-BN plane. Energy decomposition, natural population analysis (NPA), and electrostatic potential (ESP) analysis used to better understand the nature of adsorption on h-BN. van der Waals force plays a dominant role in adsorption process. Due to the π-π interactions, T, BT, and DBT have larger van der Waals forces than MT and the value of adsorption energy is negative correlated to the number of benzene rings. These findings are helpful for deeper understanding the adsorptive desulfurization mechanism and help develop better adsorbents for desulfurization in the future.

Unraveling How the H2 Treatment Helps Improve the Performances of Cu and Ag Loaded Y Zeolites for Adsorptive Desulfurization.

This work seeks for a better understanding on how the gas treatment process affected the structure of metal loaded zeolite Y (MY, M = Ag, Cu) adsorbants and how the structural changes affected the performances of the adsorbents for adsorptive desulfurization. A series of characterization tools including solid-state nuclear magnetic resonance were employed. Compared to the N2 treatment, the H2 treatment on the MY adsorbents led to the reduction of the loaded M components to their metallic state and, consequently, brought several structural changes to the zeolitic framework. The structural changes brought by the H2 treatment can be accounted for the decreased Brönsted acidity over the Lewis acidity of the adsorbents and thus helped in improving their adsorption capacity. This paper provides new insights on how the zeolitic framework changes affected the sulfur adsorption capacity of MY, which is helpful for designing better adsorbents for sulfur removal from oil.