Effects of Microwave Irradiation on the Structure of Zinc Oxide Sorbents for High Temperature Coal Gas Desulfurization

To investigate the effects of microwave irradiation on the structure properties of ZnO sorbents, fractal dimensions and desulfurization kinetics of sorbents prepared by microwave and conventional heating respectively have been studied in the present paper. The performances for desulfurization were tested in a fixed-bed reactor, and the sorbents were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Fractal dimensions were calculated based on the Frenkel-Halsey-Hill theory, and desulfurization kinetics of sorbents was acquired by the equivalent grain model. The analysis date revealed that the fractal dimensions and sulfur capacity of sorbents prepared by microwave heating are 2.744 and 10.77%, while those of the sorbents prepared by conventional heating are 2.719 and 8.633%. Desulfurization kinetics studies presented that the apparent chemical reaction activation energy and the diffusion activation energy of sorbents heated by the microwave method are 6.756 kJ.mol(-1) and 17.57 kJ.mol(-1), and those of sorbents heated by the conventional method are 7.980 kJ.mol(-1) and 23.09 kJ.mol(-1). The consequences interpret that microwave irradiation leads ZnO sorbents to form an abundant three-dimensional pore structure and an irregular surface which facilitate gas transfer in the desulfurization process. Hence, the reaction between 112S gas and ZnO more readily proceeds for sorbents heated by microwave.