Controllable Preparation And Catalytic Application Of Highly Dispersed Au And Ru Catalysts

Supported noble metal catalysts play an important and irreplaceable role in the fields of modern chemical energy conversion,high-value chemical manufacturing and environmental protection technology.Au and Ru nanoparticles,especially nano-Au nanoparticles,are hot spots in the field of noble metal catalysis.Controlling and stabilizing their particle size is the most difficult thing in the preparation process of catalysts,and greatly determines their catalytic performance.The strong interaction between metal and support has an important impact on controlling and stabilizing the particle size of Au and Ru and improving their catalytic performance.It is an important consideration in the optimization process of catalyst preparation.In order to prepare Au and Ru catalysts with nano-good catalytic performance,a series of Au and Ru nanaoparticles,based on the design idea of adjusting the strong interaction between metal and support（SMSI）,were prepared and characterized through the strategies of adjusting the crystal form of support,modifying transition metal oxide and optimizing the preparation method,and then taking the representative trinitrostyrene selective hydrogenation,CO oxidation and one-step oxidative esterification of methacrylaldehyde as model reactions.The catalytic performance of this series of catalysts was investigated,and meanwhile their structure and properties of the catalysts were characterized by TEM,XRD,TG/DSC,H₂-TPR,O₂-TPD,EPR and FT-IR.The main research results are as follows:（1）A series of Ru/TiO₂ catalysts,used the TiO₂ support with different crystal structures,were prepared by impregnation method,and their selective hydrogenation catalytic properties were investigated.The results show that due to the strong interaction between Ru and TiO₂ support（SMSI）,the prepared Ru/TiO₂ catalyst has good selectivity for the selective hydrogenation of trinitrostyrene.The Ru/TiO₂ catalyst,prepared by sol-gel method,has a mixed crystal structure of rutile and anatase,and its conversion and selectivity in the selective hydrogenation of trinitrostyrene are higher than those of Ru/TiO₂ catalyst supported by pure rutile and anatase TiO₂.The catalytic performance of Ru catalyst supported on commercial TiO₂,which has a higher specific surface area and mixed crystal structure,is better than that of Ru/TiO₂ prepared by sol-gel method.It is further verified that the mixed crystal structure of TiO₂,higher specific surface area and corresponding pore volume could promote the catalytic performance of selective hydrogenation of trinitrostyrene.（2）The optimized transition metal oxides Mg O and TiO₂ were used to modify the surface of Al₂O₃ support,and the preparation method of optimized catalyst was explored to improve the strong interaction between Au nano-particles and support,stabilize Au nano-particles and improve their catalytic performance.The results show that compared with Au/Al₂O₃ catalyst,the prepared Au/Mg O-La₂O₃/Al₂O₃ gold nano-particles has more active lattice oxygen on the surface,has higher activity for CO oxidation reaction,and shows relatively good reaction stability in dry co reaction feed gas.This may be due to the reaction of active lattice oxygen O^2-with a small amount of water vapor in the feed gas and the formation of more surface hydroxyl groups at the interface between Au and the support.However,in the dry reaction atmosphere,the catalyst is also inactivated due to the formation of some carbonate species that are not easy to desorb,such as-COOH,HCO₃^-and CO₃^2-,which occupy or cover the active sites of Au nanoparticles.（3）In order to further verify the strong interaction between Au nano-particles and the preferred transition metal oxide modified Al₂O₃ support,a series of Au nano-particles were tested for the reaction of one-step oxidative esterification of methacrylaldehyde（MAL）to methyl methacrylate（MMA）,and the synergistic catalysis between Au nano-particles and the support was investigated.Compared with Au/Al₂O₃ catalyst,the prepared Au/Mg O-TiO₂/Al₂O_3,Au/Mg O-Zn O/Al₂O₃ and other gold catalysts contain more active lattice oxygen species on the surface,and have a higher conversion of MAL and higher product selectivity of MMA,and its reaction cycle stability is also improved,which can be attributed to the improve the SMSI interaction between Au nano-particles and the support,and thus preparing and maintaining more small Au nano-particles to a certain extent.In addition,if we do not load Au nano-particles,MAL could only be converted a little,but no MMA is generated,which further indicates that the strong SMSI effect between Au nano-particles and the support is necessary,and meanwhile shows a significant synergistic catalysis.