A sustainable design of ZnO-based adsorbent for robust H2S uptake and secondary utilization as hydrogenation catalyst

Low sulfur capacity and low regeneration performance are the long-time problems in the industrial application of ZnO-based adsorbents for ambient H2S removal. However, no efficient approach has been reported up to now to simultaneously solve these two problems. With the increasingly stringent environmental regulations in China, a robust but sustainable ZnO-based adsorbent is strongly desired. Herein, we constructed such an adsorbent for the first time by introducing cobalt species into ZnO/SiO2 to form a heterostructured ZnO-Co3O4/SiO2 nanocomposite. For comparison, Co doped ZnO/SiO2 and Zn doped Co3O4/SiO2 were also fabricated. According to the breakthrough tests with initial H2S partial pressure of 57 Pa, the heterostructured ZnO-Co3O4/SiO2 adsorbent exhibited highest sulfur capacity of 188.4 mg S/g sorbent at breakthrough level of 1%, the corresponded partition coefficient (at 0.57 Pa, 303 K) was 10.3 mol. kg(-1). Pa-1. The introduced Co species not only improved the dispersion of ZnO nanograins, but also served as active sites for reacting and oxidizing H2S molecular. It also found that the formed ZnO-Co3O4 heterostructure could boost the hydroxylation of H2O, which provided an alkali environment for H2S dissociation. More meaningfully, this exhausted sorbent could be secondarily utilized as catalyst for carbonyl sulfide (COS) hydrogenation and exhibited 100% COS conversion even at a temperature lower than 200 degrees C, which was almost 3.3 times the conversion achieved by a commercial Co-Mo/Al2O3 catalyst (30%). This study will provide a new idea for rational design of metal oxide-based adsorbents to avoid causing secondary pollution by the spend adsorbents.