Synthesize、 Characterization And Catalysis Performance Of CuO/CeO₂ And Ion Embed-Leached CuO/CeO₂ Catalysts

CuO/CeO₂ shows the high catalytic performance in many reactions. The catalytic property is associated closely with its composition and structure which are depended on the preparation process. In this thesis, CuO/CeO₂ samples were prepared by incipient wet impregnation from CeO₂ which as the supporter, and the ion embed-leached type CuO/CeO₂ catalysts, which were leached in the ammonia, were prepared by which copper is easy to complex in the ammonia. The as-prepared CuO/CeO₂ and ion embed-leached type CuO/CeO₂ catalysts were tested for water-gas shift reaction in a fixed bed reactor and characterized by XRD、SEM、BET and TPR,Effect of the preparation conditions and NH₃·H₂O leaching on the structure and catalytic properties of as-prepared CuO/CeO₂ and embed/leached CuO/CeO₂ catalysts for water-gas shift reaction were studied.For the 12% CuO/CeO₂ catalysts, the dispersion of the active component copper was higher on the surface of CeO₂, and the microcrystal was more, but the crystallization was poorer, and both the specific surface area and the pore volume were larger, but average pore diameter was smaller, which resulting in easy reduction and good activity; The CuO/CeO₂ catalysts prepared at copper loadings more than 12% had lower specific surface area and smaller pore volume and the grain size increased gradually, and there were CuO single crystals,which was hard to reduced and had poor catalytic activity. The best loading of copper is 12%. The CuO/CeO₂ catalysts prepared at the calcinations temperature below 650℃had higher specific surface area and larger pore volume and a highly dispersed of CuO on the surface of CeO₂, which was easy to reduced and had good activity. When the calcinations temperature was above 750℃, it lead to the dramatically decreasing of specific surface area, pore volume and the dispersion of CuO on the surface of CeO₂ was deteriorated, which due to the agglomeration of CuO crystals, and reduction temperature was relative higher, and had poor catalytic activity.The crystallinity variation law and phase composition of samples which were leached in the amnion weren’t changed and the grain size of samples was always increased after leached in the amnion. When CuO loadings was less than 12%, specific surface area and pore volume of samples were reduced after leached in the amnion. Therefore, the oxygen vacancies on the surface of CeO₂ combine with the number of Cu active sites were decreased, activity of leached samples was lower than not leached samples. When CuO loadings were more than 12%, specific surface area and pore volume of leached samples were also decreased. However, the extent of decreasing were less than CuO loadings≤12%, because the CuO crystals was leached and more actives were exposed on the surface of CuO/CeO₂ catalysts. Therefore, the activities of catalysts had a decrease or even rise a bit. Catalytic activities of leached samples were lower than not leached samples at different calcinations temperature.