| As the technologies for CO2 capture and sequestration and the clean hydrogen production from renewable energy become increasingly mature, converting the CO2 resource into chemicals via hydrogenation opens up an important research hotspot in the energy storage field. With a dual significant purpose of storing energy and mitigating the CO2 emission, hydrogenation of CO2 into methane or methanol paves a precedence developmental direction for the CO2 catalytic conversion. Among all the studies, the development of catalysts with high performance is crucial to the development of this technology. Hereby, the content of this dissertation is mainly focus on the following research aspects.(1) The supported Ru catalysts were prepared by a wet-impregnation method using rutile-TiO2 (r-TiO2) as the support. The influence of pretreatment temperature (3O0℃-800℃) on the activity and the structure of Ru/TiO2 catalyst were investigated in catalytic hydrogenation of CO2 to methane. It was found that the extent of encapsulation on the surface of Ru particles by TiOx layers increased with the pretreatment temperature increasing from 300℃ to 800 ℃. In addition, the trend of the extent of hydroxyl groups on the surface of TiO2 exhibited a volcano shape, with a maximum value at the catalyst pretreated at 600 ℃. Associated these changes with the activity, it could be concluded that the activity was dependent on both the extent of encapsulation of Ru particles by TiOx layers and the hydroxyl groups on the surface of TiOx Additionally, the mechanism of CO2 methanation was researched by in situ DRIFTS.(2) TiO2 modified Al2O3 binary oxide was prepared by a wet-impregnation method and used as the support for ruthenium catalyst. The effect of TiO2 content and TiO2-Al2O3 calcination temperature on catalytic performance of Ru/TiO2-Al2O3 catalyst in CO2 methanation reaction was investigated. It was found that the anatase TiO2 transformed to rutile TiO2 when the calcination temperature raised to 950℃. Since the similar crystal type and the high degree of lattice match between RuO2 and r-TiO2, r-TiO2 prevented the aggregation of RuO2 during calcining in air, more importantly, it effectively hindered the aggregation of Ru nano-particles during reduction in H2. Therefore, compared with Ru/Al2O3 catalyst, the activity of Ru/TiO2-Al2O3 catalyst was increased by 2.1 times in CO2 methanation reaction.(3) The effect of preparation methods, reduction temperatures and Pd loadings of Pd/ZnO/Al2O3 catalysts on the catalytic performance of CO2 hydrogenation to methanol was investigated. The results showed that the content of PdZn alloy varied dynamically by different preparation and pretreatment procedures, which eventually resulting in corresponding changes in methanol selectivity. Moreover, the results revealed that the smaller Pd particles formed with reducing the Pd loadings, which favored the formation of PdZn alloy phase and ZnOx modified·Pd species after reduction in H2, and hence led to the increase of methanol selectivity.(4) A series of modified Ni-Zn bimetallic catalysts were prepared by depositing different kinds of 4 wt% metals (Ir, Pt, Au, Cu, Ag) on the Ni-Zn-Al hydrotalcite and tested in the selective hydrogenation of acetylene. By comparison, the activity was enhanced significantly over the Au modified catalyst. Characterization by means of H2-TPR, XRD, SEM, and TEM revealed that doping Au in Ni-Zn bimetallic catalyst weakened the adsorption of acetylene and also hindered the coke deposition on the catalyst. |
PDF Full Text Request