H2S-Selective Catalytic Oxidation: Catalysts and Processes

The most widely used catalysts and processes for H2S-selective catalytic oxidation are overviewed in this review. Two kinds of catalysts have been investigated intensively: carbon-based catalysts (active carbon catalyst, carbon nanotube catalyst, and carbon nanofiber catalyst), metal oxide-based catalysts (metal oxide catalyst, oxide-supported catalyst, and clay-supported catalyst). Among them, carbon-based catalysts are utilized mainly in discontinuous processes at relatively low temperatures, whereas metal oxide catalysts are the most widely used in practice. However, the reaction temperature is relatively high. Fortunately, a MgAlVO catalyst derived from LDH materials and intercalated clay-supported catalysts exhibit excellent catalytic activities at relatively lower temperatures. According to various studies, the catalytic behaviors mainly obey the Mars–van Krevelen mechanism; however, the catalyst deactivation mechanism differs, depending on the catalyst. In practice, the mobil direct oxidation process (MODOP), super-Claus and Euro-Claus processes were developed for H2S-selective catalytic oxidation. Nevertheless, MODOP has to proceed under water-free conditions. The super-Claus process can operate in up to 30% water content. The Euro-Claus process is a modified version of the super-Claus process, which was developed to eliminate recovery losses of escaped SO2.