The Structure-Activity Relationship Of Tin-Zinc Oxide Supported Gold Catalyst In The Carbon Monoxid Oxidation Reaction

In this thesis,there are two independent components: based on CO oxidation of gold-based series of catalyst 'structure-effect relationship' research and application of propylene epoxidation of molybdenum series of catalysts preliminary study.CO has been an important source of air pollution.For a long time,researchers have been working tirelessly for the purpose of finding efficient CO catalytic oxidation catalysts.As a new type of catalyst,gold-loaded metals or non-metal oxides have been attracting attention.For the long research people get that the structure of the gold and the characteristics of the carrier play a crucial role in the performance of the catalyst.In all the research systems,a consensus conclusion is obtained that the oxygen vacancy content in the carrier is very important for the performance of the catalyst The effects of Fe₂O₃,CeO2,ZnO2,Al2O3,CuO,TiO₂,Co₃O₄,SnO₂ and so on have been studied.Zinc tin oxide?Zn₂SnO₄?is a kind of perovskite compound,it has a high proton conductivity,rich oxygen vacancies,mainly used in solar cells,gas sensors,photocatalyst,etc.There has been no relevant work reported Zn₂SnO₄ as a carrier-supported for gold-catalyzed CO oxidation.Whether Zn₂SnO₄ is a good carrier,how its structure effect the size and structure of Au,what kind of relationship between Au/Zn₂SnO₄ structure and activity,etc.,are not know.In this paper,the structure-activity relationship of Au/Zn₂SnO₄ catalyst was studied.In this work,0.7 wt% Gold was supported on a new type of oxide carrier-Zn-Sn composite oxide?Zn₂SnO₄?by deposition precipitation method.The texture of the carrier could be composed of alkali?N₂H₄·x H₂O?and metal ion(Zn²⁺)ratio between 4/1,8/1 and 16/1.It has been found that the catalyst exhibited the highest activity when N₂H₄·xH₂O/Zn²⁺ = 8/1,and decreased to near pure Zn₂SnO₄ carrier when N₂H₄·xH₂O/Zn²⁺ = 16/1.We used the characterization techniques such as nitrogen adsorption and desorption,X-ray diffraction?XRD?,transmission electron microscopy?TEM?,high angle dark field scanning transmission electron microscopy?HAADF-STEM?,X-ray photoelectron spectroscopy?XPS?,X-ray absorption fine structure spectrum?XAFS?and hydrogen process temperature reduction?H2-TPR?.?Pore volume and pore size distribution?of the carrier oxides were found to be critical for the particle size of gold,thus determining the activity of Au-Zn₂SnO₄ catalyst.Propylene oxide is an important basic organic chemical raw material.The second work of this paper was focuses on the development of a new catalyst to let the reaction process from the multi-step into propylene from the direct production of propylene oxide through molecular oxygen.MoO₃/SiO₂ has a higher ability to catalyze epoxidation of propylene.It has also been shown that the biodegradation of propylene in Bi-P-Mo-based system follows the mechanism of free radical reaction.SiO₂ supported TiO₂ catalyst exhibits good PO yield and the selectivity,We have made a preliminary study on the preparation method of catalyst and the effect of the addition of additives on the morphology of the catalyst.The results show that the modification of the additive K+ has a very large effect on the morphology of MoO₃-SiO₂.The order of addition K+ was diffrernt made MoO₃ showed a different morphology,and first addition of K+ the MoO₃ finally exhibited spherical,and later addition of K+ the MoO₃ was finally acicular.The modification of Na+ had little effect on the morphology of MoO₃-TiO₂,and there was no significant difference.In addition,other methods such as hydrothermal synthesis and Sol-Gel synthesis were used to prepare Mo-based and Ti-based catalysts.The crystallinity of MoO₃-SiO₂ catalyst prepared by sol-gel method was better than that of impregnation method.XRD showed that Mo was present in the form of an oxidized state in the catalyst.