Modified and ion exchanged clinoptilolite for the adsorptive removal of sulfur compounds in a model fuel: New adsorbents for desulfurization

摘要

In this research, modified and ion exchanged natural clinoptilolite (CZ) were prepared for adsorptive desulfurization of refractory dibenzothiophene (DBT) and 4,6-dimethyl dibenzothiophene (4,6-DMDBT) sulfur compounds in a model fuel. For this purpose, H-form (H-CZ) and mesopore (meso-CZ) clinoptilolite were prepared and then ion exchanged with Cu+ and Ni2+ cations. The raw and treated samples were characterized by Xray diffraction (XRD), X-ray fluorescence (XRF), FTIR spectroscopy and N-2 adsorption-desorption (BET) analysis. The obtained surface areas of CZ, H-CZ and meso-CZ were 19.6, 249.71 and 194.65m(2)/g, and their obtained total pore volumes were 0.0644, 0.1869 and 0.2404 cm(3)/g, respectively. In Ni2+- and Cu+-exchanged adsorbents due to presence of d-electrons, sulfur compounds interact with the cations through pi-complexation which resulted in significant increase adsorption capacity of ion exchanged samples, compared to parent samples. The experimental data were analyzed using Langmuir, Freundlich, Langmuir-Freundlich (L-F) and Dubinin-Radushkevich (D-R) isotherms. For adsorption of DBT onto all adsorbents, L-F was the best-fitting isotherm to the experimental data. Due to high surface area and mesopore volume, large pore width, higher ion exchange compared to Ni-meso-CZ, and also formation of pi-complexation between sulfur atom and Cu+ cation, Cu-meso-CZ gives the best results for removal of DBT (28.12 mg DBT/g adsorbent) based on L-F isotherm. In addition, the effect of solvent and sulfur compound on adsorption capacity of adsorbents and regeneration of them were investigated by thermal method.