Preparation And Catalytic Properties Of Carbonyl Sulfide Hydrogenation Catalysts

Coal is the main source of energy in our country. Due to high efficiency and low pollution, Integrated Gasification Combined Power Generation (IGCC) technology has become the one of the most promising clean coal power generation technology, in which gas desulfurization is the key point. The organic sulfur gas (mainly carbonyl sulfide, COS) removal is relatively difficult. Because of high precision removal of gaseous organic sulfur, simple operation, low investment in equipment, and the H2 source in coal gas can be used directly without the additional gas source, hydrodesulphurization (HDS) is the effective means for COS removal. The exploitation of high efficiency catalysts for the HDS of COS becomes an interesting task.In recent years, the development of nano-technology has brought new opportunities for catalyst research, and the excellent catalytic properties of nanometer materials is effected by parameters such as nanocrystalline exposed, shape and the surface defects. Based on the background of the subject, the main aim of our work is focused on the shape-control synthesis of nanocrystals and their properties as unsupported catalysts for COS hydrogenation. The contents are as follows:(1) Shape-control synthesis of cerium oxide nanocrystals and its performance for COS removal. CeO2 nanocrystals with different shape of nanopolyhedra and one dimensional nanorods have been obtained through hydrothermal route by controlling the reaction parameters. Compared with commercial grade CeO2, the COS conversion over the as-prepared products in strong reduction atmosphere is investigated. Results show that CeO2 nanopolyhedra can keep higher activity and stability for a long time than CeO2 nanorods and commercial CeO2. The COS removal mechanism of CeO2 nanopolyhedra under different temperatures has been discussed.(2) Shape-control synthesis of cobalt oxide nanocrystals and its performance for COS removal. CO3O4 nanocrystals, i.e. nanorods and nanopolyhedra, have been synthesized by a facile ethylene glycol route. After in situ presulfidation, the HDS activity of COS is conducted on these unsupported catalysts with unchanged morphology. Under the same reaction condition, the catalytic activity of the nanorods is more than four times of the nanopolyhedra at low temperature of 200℃. By the help of TEM,BET,XRF,H2-TPR technologies, it is found that the catalytic properties of the as-made nanocrystals are dependent on the nature of their surface, exposed facets, and the crystal plane of Co3O4 plays an important role in determining its degree and easiness of presulfidation and consequently HDS performance for COS.In addition, considering palladium is one of the most active components in hydrogenation reaction, we further study the performance of Pd-supported catalysts for the HDS of COS. Adopting the above-mentioned CeO2 nanopolyhedra and several carbon materials as supports, including coconut active carbon (AC), high surface active carbon (SAC) and carbon nanotubes (CNTs), the activities of Pd/CeO2 and Pd/C catalysts for the hydrogenation of COS are determined. It is clear that Pd/CeO2 is superior to CeO2 itself, and the activity order of Pd/C is as follows:Pd/CNTs>Pd/SAC>Pd/AC under the same reaction condition, so the nature of support is a crucial factor for the COS hydrodesulphurization.