Magnetic Properties of Porous Iron Oxides and their Application as Desulfurization Sorbents

This work focused on the study of porous iron oxides and on applying them as a desulfurization sorbent. The advantages of this sorbent material are gaining high sulfur sorption capacity at a low working temperature with a cheaper price. To achieve this goal, the research was broken down into three sections: (1) material synthesis and magnetic study; (2) the study on the desulfurization process; (3) high sulfur sorption capacity sorbent and condition optimization. In the first section, the different phased iron oxides with different porous structure were synthesized by the improved inversed micelle sol-gel method. The mesoporous maghemite and magnetite were carefully studied by an 57Fe spin-echo nuclear magnetic resonance (NMR) and a magnetometer. From those magnetic studies, the phases of iron oxides were identified. In addition, the crystalline structure, morphology and the porosity of the structures were characterized using X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), and N2 sorption techniques. The process parameters are also very important to improve the sulfur sorption capacity. According to the experimental data, the pressure on the sorbent during the desulfurization process greatly improves the sorption efficiency. The sorption capacity would be increased more than 3 times compared with the same sorbent without pressure. All those detailed analyses and discussion are presented in the second section. Porous hydrous ferric oxide is carefully studied as a good desulfurization sorbent in the third section. The fresh sorbent and the deactivate materials are characterized by XRD, high resolution TEM, SEM, and N2 sorption techniques. Without the pressure, the sulfur sorption capacity of porous hydrous ferric oxide can be reached up to 58.5 under 50 sccm at 300 oC, which is more than 4 times higher than the commercial sample and about 50% higher than mesoporous Co3O4. Based on the comparison of the material characterization, the high sorption capacity is probably due to the combination effect of physical and chemical sorption.