Adsorption Desulfurization on a Nanocrystalline NaY Zeolite Synthesized Using Carbon Nanotube Templated Growth

Abstract

FAU-type (NaY) zeolite nanocrystals have been synthesized through crystallization of gel in a mesoporous system of carbon nanotubes (CNTs) with an internal diameter of 20–30 nm. Investigation using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM) shows that the nanocrystals possess the typical nanosized zeolite structural characteristics, which are different from those of microsized zeolites. Desulfurization of various model fuels containing about 500 ţg/g sulfur was studied over the synthesized nanosized NaY with a liquid hourly space velocity of 7.5 hr−1 at ambient conditions. The sulfur adsorption capacity was 7.2, 1.7, 6.7, 6.9, and 6.5 mg(S)/g adsorbent for thiophene, tetrahydrothiophene (THT), dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT), and 4,6-dimethyldibenzo-thiophene (4,6-DMDBT), respectively. The charges on the S atom in thiophene, THT, DBT, 4-DMDBT, and 4,6-DMDBT, calculated using density functional theory (DFT), were −0.159, −0.298, −0.211, −0.188, and −0.214, respectively, implying that the S-M bond between the adsorption sites and these sulfides is much weaker than other bonds (maybe due to π complexation).