doctoralThesis
Estudo experimental e teórico da dessulfurização adsortiva de diesel real usando materiais mesoporosos de alta eficiência
Fecha
2020-08-28Registro en:
SALES, Rafael Viana. Estudo experimental e teórico da dessulfurização adsortiva de diesel real usando materiais mesoporosos de alta eficiência. 2020. 149f. Tese (Doutorado em Química) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2020.
Autor
Sales, Rafael Viana
Resumen
The burning of fossil fuels emits sulfur oxides (SOx), which negatively affect human health and
the environment, in addition to being highly undesirable by oil refineries. Researchers have
sought to develop alternative methods to conventional technology, hydrodesulfurization (HDS),
which is an expensive and ineffective method for removing heavy sulfur molecules. Thus, in
this work, the mesoporous silicas MCM-41 and SBA-15 were synthesized and modified with
metallic cations Ni2+ and Ag+ for application in adsorptive desulfurization of real diesel fuel.
MCM-41 was obtained from green silica (amorphous silica MPI), from beach sand, and
commercial silica. The pure and modified adsorbents were characterized by X-ray
diffractometry (XRD), N2 adsorption-desorption isotherms, high-resolution scanning electron
microscopy by field emission (SEM-FEG), scanning transmission electron microscopy
(STEM), high-resolution transmission electron microscopy (HRTEM) and X-ray excited
photoelectron spectroscopy (XPS). These techniques were important for the elucidation of
materials of the type MCM-41 and SBA-15. The results of the SEM-FEG and STEM
micrographs coupled with X-ray spectroscopy by dispersive energy (EDX) showed a uniform
dispersion of Ag nanoparticles on the supports. Molecular dynamics simulation, using the
DFT/ONIOM method, and XPS data revealed that the adsorption of aromatic sulfur compounds
by AgMCM-41 is controlled by the interactions between the sulfur atoms and the silver
species. The best fit of the experimental data to the kinetic model of pseudo-second order and
to the Langmuir equilibrium model is an indication that chemisorption mechanisms, especially
-41 and AgSBA15 adsorbents, under the conditions studied, which is in agreement with the theoretical study
and the XPS results. The maximum adsorptive capacities for AgMCM-41 obtained from
sustainable silica and for AgSBA-15 were 31.25 mg g-1 -1, respectively. The
pure and silver modified supports showed a satisfactory regeneration rate, after 5 recycling
steps, using a chloroform/hexane/acetone solution.