Ultra-Deep Oxidative Desulfurization of Fuel with H2O2 Catalyzed by Mesoporous Silica-Supported Molybdenum Oxide Modified by Ce

A mesoporous silica-supported molybdenum oxide catalyst with a cerium(Ce) modifier was prepared by in situ synthesis and used in a hydrogen peroxide (H2O2) system for the desulfurization of dibenzothiophene (DBT), benzothiophene (BT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) fuel oils. The catalytic performance of the catalyst was studied. The catalyst was characterized by Fourier Transform Infra-Red (FT-IR), X-ray diffraction (XRD), Brunner−Emmet−Teller (BET), and X-ray Photoelectron Spectroscopy (XPS). The influences of m(catalyst)/m(fuel oil), v(H2O2)/v(fuel oil), reaction temperature, and reaction time were investigated. The catalyst had excellent catalytic oxidation desulfurization performance under moderate operational conditions. The catalytic performance was in the order DBT > 4,6-DMDBT > BT. The kinetic analysis results showed that the reaction was a pseudo first-order kinetics process and the apparent activation energies of DBT, BT, and 4,6-DMDBT were 46.67 kJ/mol, 56.23 kJ/mol, and 55.54 kJ/mol, respectively. The reaction products of DBT, BT, and 4,6-DMDBT were DBTO2, BTO2, and 4,6-DMDBTO2, respectively. The recycling experiments indicated that DBT, BT, and 4,6-DMDBT removal could still reach levels of 94.0%, 63.0%, and 77.9% after five cycles.

Mathematical modeling of arsenic(V) adsorption onto iron oxyhydroxides in an adsorption-submerged membrane hybrid system

The adsorption of arsenic (V), As(V), on two porous iron oxyhydroxide-based adsorbents, namely, micro-sized tetravalent manganese feroxyhyte (μTMF) and granular ferric hydroxide (μGFH), applied in a submerged microfiltration membrane hybrid system has been investigated and modeled. Batch adsorption tests were carried out to determine adsorption equilibrium and kinetics parameters of As(V) in a bench-scale slurry reactor setup. A mathematical model has been developed to describe the kinetic data as well as to predict the As(V) breakthrough curves in the hybrid system based on the homogeneous surface diffusion model (HSDM) and the corresponding solute mass balance equation. The kinetic parameters describing the mass transfer resistance due to intraparticle surface diffusion (D_s) involved in the HSDM was determined. The fitted D_s values for the smaller (1-63 μm) and larger (1-250 μm) diameter particles of μGFH and μTMF were estimated to be 1.09 × 10^-18 m²/s and 1.53 × 10^-16 m²/s, and 2.26 × 10^-18 m²/s and 1.01 × 10^-16 m²/s, respectively. The estimated values of mass transfer coefficient/ kinetic parameters are then applied in the developed model to predict the As(V) concentration profiles in the effluent of the hybrid membrane system. The predicted results were compared with experimental data for As(V) removal and showed an excellent agreement. After validation at varying adsorbent doses and membrane fluxes, the developed mathematical model was used to predict the influence of different operation conditions on As(V) effluent concentration profile. The model simulations also exhibit that the hybrid system benefits from increasing the amount of adsorbent initially dosed and from decreasing the membrane flux (increasing the contact time).

Adsorption desulfurization performance and adsorption-diffusion study of B2O3 modified Ag-CeOx/TiO2-SiO2

In this work, the adsorption desulfurization performance and adsorption diffusion study of B₂O₃ modified Ag-CeO_x/TiO₂-SiO₂ adsorbent were investigated. The adsorption desulfurization performance was studied by batch and fixed bed tests. The homogeneous surface diffusion model (HSDM) was employed to investigate the adsorption and diffusion behavior of 4,6-dimethyldibenzothiophene (4,6-DMDBT) in diesel. It was found that the addition of B₂O₃ promotes the dispersion of CeO_x species and then further facilitates the dispersion and oxidation of Ag species resulting in higher adsorption desulfurization activity. Ag species are in state of Ag, Ag₂O and Ag₂O₂, among which, Ag₂O and Ag₂O₂ are found to be the active centers. The kinetics of adsorption desulfurization of model diesel fuel was investigated to provide guiding significance for the prediction of breakthrough curves of fixed-bed adsorption columns. The batch kinetic experiment modeled by HSDM model indicates that surface diffusion controls the main rate. The surface diffusion coefficient D_s determined by batch adsorption experiments is independent of operation conditions, which can be used to directly predict the breakthrough behavior in fixed bed adsorption. The modified HSDM model is proposed to describe the breakthrough behavior. Results indicate that the breakthrough time is affected by bed height, flowrate and influent concentration.