Characterization of ZSM-5 modified with niobium pentoxide: the study of thiophene adsorption

Abstract

Adsorventes ZSM-5 impregnados com Nb 2 O 5 foram aplicados na remoção de enxofre sob a forma de tiofeno, substância refratária de difícil remoção dos combustíveis líquidos. Para tanto, foi preparado um combustível modelo contendo iso-octano contaminado com tiofeno nas concentrações de 877,5 a 1155 ppmw. As amostras foram caracterizadas por difratometria de raios X (XRD), espectroscopias no infravermelho (FTIR) e Raman (FT-Raman) por transformada de Fourier para confirmação dos adsorventes obtidos, sendo priorizado o estudo de adsorção com aquele contendo 5% de pentóxido de nióbio, que apresentou uma maior capacidade de remoção de tiofeno. Os melhores resultados de adsorção foram alcançados a 353 K, sendo observado um maior tempo para atingir o equilíbrio. Sob essas condições, o melhor ajuste cinético foi alcançado utilizando a equação de pseudo-segunda ordem, evidenciando o domínio do fenômeno de quimissorção. Por outro lado, sob menores temperaturas, o modelo de difusão apresentou uma melhor aproximação dos resultados experimentais. O aumento da temperatura também favoreceu os processos espontâneos.ZSM-5 adsorbents impregnated with Nb 2 O 5 were applied in the sulfur removal in the form of thiophene, refractory substance of difficult removal of liquid fuels. For this purpose, a model fuel containing iso-octane contaminated with thiophene in concentrations of 877.5 to 1155 ppmw was prepared. The samples were characterized by X-ray diffractometry (XRD), Fourier transform infrared (FTIR) and Fourier transform-Raman (FT-Raman) spectroscopies for confirmation of the adsorbents, being prioritized the adsorption study with that containing 5 wt.% of niobium pentoxide, because it showed a greater capacity for removal of thiophene. The best results of adsorption were achieved at 353 K, a longer time to reach equilibrium was observed. Under these conditions, the best kinetic fitting was achieved using the equation of pseudo-second order, demonstrating the domain of the phenomenon of chemisorption. While under lower temperatures, the diffusion model presented a better approximation of the experimental results. Also, the increasing of temperature did enhance spontaneous processes.

Adsorption of sulfur compound utilizing rice husk ash modified with niobium

“…Similar results obtained in previous studies using ZSM-5 as a support [37] and the loss in adsorption capacity may be associated with the monolayer excess of niobium oxide in the support [58].…”

“…In the study of the thiophene adsorption on ZSM-5 modified with niobium [37] the PSOE was also the one that best approached the experimental data, which provides evidence of the participation of niobium directly in the thiophene adsorption. According to theoretical studies Soscún et al [63] and Garcia e Lercher [64] interaction with silanol groups may also be formed with the sulfur atom, with the formation of weak hydrogen bonds corresponding to van der Waals complexes.…”

“…A multilinearity in IPDE fitting indicates there may be more than one step in the diffusion in this type Table 6 Kinetic parameters of IPDE for the thiophene adsorption by the Nb (5) of material. Furthermore, in previous work [37] the IPDE applied to the adsorption of thiophene in ZSM-5 modified with niobium showed a greater number of lines. This may indicate that in the Nb(5)RHAI adsorbent system the diffusion phenomenon occurs more simply in a smaller number of steps, and this could be related to the greater particle size of Nb(5)RHAI or the absence of microporosity in the RHA.…”

“…For example, the theoretical and experimental study of titanium oxide in the adsorption of thiophene demonstrated relatively weak and selective interactions between thiophene molecules and the metal oxide [36]. In previous work of our research group [37], it was observed that the adsorbents prepared from ZSM-5 had their adsorption capacity of thiophene potentialized when this material is impregnated with niobium pentoxide. According to Hüger et al [38], elemental sulfur has a significant interaction with metallic niobium.…”

Uso do grafeno e nióbio na prática médica: uma revisão narrativa de literatura

“…A fixação biológica não é alcançada quando a estabilidade a longo prazo não é garantida. Sob essa perspectiva, os ensaios in vivo e in vitro demonstraram que a presença do óxido de nióbio potencializou as propriedades osteoestimuladora do biovidro (Cavalcanti et al, 2013). Assim, além de biocompatível, ele passou a ser também bioativo, favorecendo a regeneração do tecido ósseo.…”