Sulfur removal from model fuel by Zn impregnated retorted shale and with assistance of design of experiments

Effect of Hydroxylation and Carboxylation on the Catalytic Activity of Fe2O3/Graphene for Oxidative Desulfurization and Denitration

Iron-based particles loaded on porous carbon materials have attracted extensive attention as catalysts for denitration and desulfurization reactions. However, the carbon support of a high-temperature denitration catalyst is inevitably oxidized in the presence of H2O and O2. The mechanism of denitration catalyst oxidation and its influence on the catalytic reaction remain to be further explored. Fe2O3-loaded graphene models with carbon vacancy (Gdef), hydroxyl (HyG), and carboxyl (CyG) were constructed to investigate the effects of hydroxylation and carboxylation on the catalytic activity of Fe2O3/graphene for oxidative desulfurization and denitration by using density functional theory (DFT) calculations. According to the analysis of structural properties and adsorption energy, the adsorption process of Fe2O3 on HyG and CyG was observed to have proceeded more favorably than that on Gdef. The density-of-states (DOS) results also affirmed that HyG and CyG promote the electron delocalization of Fe2O3 around the Fermi level, enhancing the chemical activity of Fe2O3. Moreover, adsorption energy analysis indicates that hydroxylation and carboxylation enhanced the adsorption of SO2 and H2O2 on Fe2O3/graphene while also maintaining preferable adsorption stability of NO. Furthermore, mechanistic research explains that adsorbed H2O2 on HyG and CyG directly oxidizes NO and SO2 into HNO2 and H2SO4 following a one-step reaction. The results provide a fundamental understanding of the oxidized catalyst on catalytic denitration and desulfurization reactions.

Influence of modifications on the deep desulfurization behavior of NaY and Na13X zeolites in gasoline

NaY and Na13X zeolites were modified by different modification manners including H⁺ modification, metal ion modification (Cu²⁺, Ni²⁺, or Ce³⁺), and H⁺ modification followed by metal ion modification to investigate their deep desulfurization behavior in gasoline. The sorbents were characterized by X-ray diffraction, FTIR of chemisorbed pyridine, N₂ adsorption, and scanning electron microscope (SEM). The desulfurization performance of these sorbents was evaluated in model gasoline containing thiophene and cyclohexane with thiophene concentration of 500 mg/L, and the results were analyzed to investigate the effect of preparation methods on adsorption desulfurization behavior. The result indicates that H⁺ modification or metal ion modification could all improve the desulfurization performance of both NaY and Na13X zeolites, except for Na13X modified by Cu²⁺ and Ni²⁺. For Cu²⁺ or Ni²⁺ ion exchanging, the crystal structure of Na13X would be destroyed, resulting in a much lower desulfurization efficiency than that of the parent Na13X. The desulfurization efficiency of sorbents prepared via H⁺ modification followed by metal ion modification is higher than that of sorbents prepared by single H⁺ modification or single metal ion modification, because the former is more conducive to improve the content of metal elements on the sorbents than the latter. In addition, the increase of the specific surface area and pore volume of the sorbents would directly lead to the improvement of desulfurization performance of the sorbents. Compared with Na13X, the H⁺ modification on NaY zeolite can significantly enhance the desulfurization performance of the sorbents. Among those prepared sorbents, the CuHY has the highest desulfurization efficiency. The influence of thiophene concentration (100-1000 mg/L) on desulfurization efficiency of CuHY sorbent was evaluated. The results indicate that the desulfurization efficiency of CuHY sorbent is nearly 100% at room temperature, when the thiophene concentration is lower than 300 mg/L. Moreover, its desulfurization behavior could be described by Langmuir isothermal equation. Graphic abstract .