The microwave-assisted chemical process is environmentally friendly and energy-saving. In this study, microwave irradiation was applied to enhance the hot coal gas desulfurization process with modified semi-coke-supported Fe 2 O 3 as the sorbent. The results indicate that the sorbent with 20% Fe 2 O 3 shows the greatest breakthrough sulfur capacity (9.0%) at 500 °C in the simulated coal gas. Besides Fe 1−x S, sulfur was also produced during the desulfurization process. The deactivation model could be used to simulate the adsorption behavior of the sorbents for H 2 S. The activation energies of the sulfidation reaction by microwave and conventional techniques are 26.9 and 27.8 kJ mol −1 , respectively. The sorbents adsorbing H 2 S under microwave irradiation show much larger initial rate constants (308−2071 m 3 min −1 kg −1 ) for the sulfidation reaction. In comparison to the conventional technique, microwave desulfurization generally results in much better performance of H 2 S removal and leads to less negative effects on the pore structure of the sorbent. The improvement of desulfurization properties may be attributed to the roles of microwave irradiation (enhanced mass transfer kinetics and intensified ion diffusions). Additionally, the adverse influence of H 2 , CO, and CO 2 on the sulfur capacity of the sorbents under microwave irradiation is not significant when the adsorption time varies from 0 to 120 min.
Ordered mesoporous MCM-41 (two-dimensional (2D) hexagonal pore arrangement) and MCM-48 (threedimensional (3D) cubic channel arrangement) with similar pore sizes and surface areas were selected for comparison when used as support for Zn-based sorbents for hot coal gas desulfurization. Compared to that of Zn/M48 (MCM-48-supported desulfurizer), the adsorption capacity of Zn/M41 (MCM-41-supported sorbent) increases by 24.4−56.3%. The initial reaction rate constants of Zn/ M41 are 1−13 times greater than those of Zn/M48. These are correlated to the structural features of sorbents. Zn/M41 has a large wall thickness of the framework, suggesting higher thermal stability. Furthermore, the sorbent particles and ZnO grains in Zn/M41 are both smaller in size, which facilitates contact between H 2 S and ZnO. Additionally, Zn/M41 possesses a large surface area and pore volume, beneficial for the diffusion of H 2 S through sorbents. The analysis of the atmospheric effects reveals that there is a stronger synergistic effect of CO and H 2 on desulfurization over Zn/M41.
Zn‐based MCM‐41 supporter sorbents were prepared using the microwave in‐situ oxidation method. Other sorbents were heated using a conventional heating method to contrast the performance for H2S removal. The sorbents were tested at 500°C in fixed reactor and dried simulated Texaco coal gas was employed for the sulphurized atmosphere. The results show that sorbents prepared by microwave oxidation had a better toleration for the adsorption of H2S. A 13.2% improvement occurred in the sulphur capacity of the sorbents heated by the microwave method. XRD, SEM with EDS‐element mapping, TEM, N2 adsorption, and XPS were used to characterize the properties of the sorbents. Due to the selective heating of the microwave and the superiority of the in‐situ oxidation method, the sorbents heated by microwave exhibited more appropriate structures for sulphurization. Meanwhile, the even heating environment supplied by the microwave resulted in a more uniform distribution of the active component. The microwave also had an effect on the chemical bond and reduced the binding energy of the active component, which enhanced the reactivity between the H2S and the sorbents. The preferable features generated by microwave in‐situ oxidation accelerate the replacement of S to O, and therefore the Zn‐based MCM‐41 sorbents prepared by the microwave method have an increased capability for H2S removal in high temperature coal gas.
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