Desulfurization and regeneration performance of Co doped ZnO/SiO₂ composite desulfurizer at room temperature

Coal is the main source of energy, but it is also the main source of pollution. The clean transformation and efficient utilization of coal is a national strategic demand, and the desulfurization and purification of coal gas essence is the key link in the efficient and clean utilization of coal. ZnO is widely used in industry as a medium temperature desulfurizer, which is often used for fine desulfurization. It has more thermodynamic advantages at low temperature and can achieve superfine desulfurization, but its activity is very low due to the restriction of kinetics. At the same time, the regeneration performance of zinc oxide desulfurizer is not ideal either for medium temperature or normal low temperature. So far, there is no renewable and recycled desulfurizer of zinc oxide in industry, so the solid waste generated makes it face great environmental pressure. Based on this background, the influence of metal Co doping on the desulfurization and regeneration performance of zinc oxide at room temperature was investigated. Series of Co doped ZnO/SiO₂ composites with different doping contents were prepared by a sol-gel method, and the effect of Co doping on the desulfurization and regeneration performance of ZnO/SiO₂ adsorbents was studied in detail. The results indicated that Co is doped into ZnO in the form of Co²⁺, Co doping not only results in an increase of the specific surface area of adsorbents, but also increases the concentrations of lattice defects on the ZnO surface. The latter promotes the dissociation of H₂S owing to its improvement on surface basicity. Both of the mentioned above are responsible for the enhanced performance. And the breakthrough sulfur capacity reaches the highest of 143 mg/g when the doping amount is 3%, 1.6 times than that of ZnO/SiO₂ adsorbent. It is also found that although Co doping, to some extent, inhibits the formation of sulfate during the regeneration of ZnO adsorbents, their generation cannot be fully avoided. The sulfate will reduce the surface alkalinity of desulfurizer, and lead to a sharp decrease in the specific surface area of desulfurizer, so that the working sulfur capacity of desulfurizer after regeneration decreases significantly. It is still a great challenge to obtain a recyclable desulfurizer of zinc oxide at room temperature.