Oxidative catalytic desulfurization of 4,6-DMDBT from model fuel by activated carbons: the key role of the surface chemistry
Commercial nanoporous activated carbons were examined as non-metal catalysts for the desulfurization of 4,6-dimethyldibenzothiophene (4,6-DMDBT) from model fuel solvent under ambient conditions. Both theirs adsorptive and catalytic desulfurization capability were investigated, while the addition of hydrogen peroxide as well as of various experimental parameters were also evaluated. The best performing commercial activate carbon was further chemically treated with two different acids (HNO3 or H2SO4) in order to examine if the structural or the surface chemistry features play the most crucial role. The catalysts were characterized by Fourier transform infrared spectroscopy (FT-IR), N2 adsorption-desorption, potentiometric titration, Boehm titration and EDX. The formation of products as a result of the catalytic ability of carbons were determined spectroscopically (UV-Vis) and chromatographically (GC). The used carbons presented a micro or micro-mesoporous structure and different surface chemistry. Oxidative desulfurization experiments revealed that the textural and structural features weren’t the determinant factors, while their surface chemistry played a crucial role. Additionally, their surface modification by oxidation had a positive impact on the catalytic activity, leading to an enhanced oxidation extend of 4,6-DMDBT and a 100 % desulfurization performance. The density of the acidic surface functional groups per surface area was found as the key feature for both adsorptive and catalytic desulfurization capability of the porous activated carbons.