Adsorption Desulfurization Performance and Adsorption-Diffusion Study of B2O3 Modified Ag-CeOxTiO2-SiO2

Meiqin Zheng^1*

¹ Fujian Province University Key Laboratory of Green Energy and Environment Catalysis, College of Chemistry and Materials, Ningde Normal University, Ningde, Fujian 352100, China

* Correspondence author E-mail: 15280002581@163.com.

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) ¹ were 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 activity². Ag species are in a state of Ag, Ag₂O and Ag₂O₂, among which, Ag₂O and Ag₂O₂ were found to be the active centers^2,3.

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.

Simultaneously, a 2D porous media CFD model is developed for a fixed bed adsorber to remove the 4,6-dimethyldibenzothiophene (4,6-DMDBT) from diesel. The CFD simulation results demonstrated that porous media CFD model can describe successfully the adsorption mass transfer process for removal of 4,6-DMDBT from diesel. The mass transfer rate increased with increasing feed concentration at the beginning due to the higher driving force at higher feed concentration, conversely, the lower mass transfer rate was obtained at higher feed concentration after a period of adsorption time because of the decrease in the saturation time at the fixed bed column entrance gradually at higher feed concentration.

Key words: adsorption desulfurization; B₂O₃; diffusion; HSDM; CFD.

REFERENCES

1. Zheng M, Xu C, Hu H, Ye Z, Chen X. A modified homogeneous surface diffusion model for the fixed-bed adsorption of 4,6-DMDBT on Ag–CeO_x/TiO₂–SiO₂. RSC Adv. 2016;6(114):112899-112907.
2. Zheng M, Hu H, Ye Z, Huang Q, Chen X. Adsorption desulfurization performance and adsorption-diffusion study of B2O3 modified Ag-CeOx/TiO2-SiO2. J. Hazard. Mater. 2019/01/15/ 2019;362:424-435.
3. Xu C, Zheng M, Chen K, Hu H, Chen X. CeO_x Doping on a TiO₂-SiO₂ Supporter Enhances Ag Based Adsorptive Desulfurization for Diesel. J. Fuel. Chem. Techno. 2016;44(8):943-953.