Preparation Of Supported SAPO-34 Zeolite Catalysts For The Application In Complete Oxidation Of Toluene

Preparation of supported SAPO-34 zeolite catalysts for theapplication in complete oxidation of tolueneVolatile organic compounds like toluene are a class of common air pollutants,which can bring serious risks to public health and ecological environment.Therefore,it is of great significance to develop effective way for elimination of toluene in air.Catalytic oxidation is believed to be a very,effective method and has been extensively studied.Supported noble metals and transition metal oxides have been widely used as active catalysts for complete oxidation of toluene.Research results suggested that the composition,structure,surface properties and preparation methods of the catalyst can significantly affect their catalytic performance.Recently,it was reported that supported noble metals?such as Pt?catalysts prepared by using molecular sieves such as Beta and ZSM-5 as supports have shown excellent catalytic activity for toluene oxidation.Considering the diversity of molecular sieve structure and composition,it is expected that such supports materials may have very broad application prospects in the field of catalytic oxidation and are worthy of further exploration and research.SAPO-34 with CHA topological structure has excellent structure stability and moderate acidity.It has been successfully used in selective catalytic reduction?SCR?of NO_x and methanol-to-olefin?MTO?reactions.In this thesis,we make a attempt to use this kind of zeolite as a supports to prepare several kinds of supported noble metal and transition metal oxides catalysts,and to investigate their catalytic performance in toluene oxidation.Different factors,such as the Si/Al ratio of supports,metal types and loading amounts,preparation methods and so on,have been investigated.The main research contents and conclusions are as follows:?1?Using a modified impregnation method,preparation of a series of Pt-supported SAPO-34 catalysts were prepared by introducing a polyvinylpyrrolidone?PVP?dispersant into an alcohol system.Compared with the catalyst prepared by the conventional impregnation method,Pt-SAPO-34?P_??showed higher catalytic activity,and a 95%conversion of toluene can be acteved at 181°C.Characterization results revealed that the Pt nanoparticles in Pt-SAPO-34?P_??have better dispersity,smaller particle size and higher Pt⁰/Pt²⁺ratio.In addition,the chemical features of zeolites like Si/Al ratio could also influence the activities of the catalysts.Among them the catalyst with Si/Al ratio of 0.4 exhibit a relatively high catalytic activity.It can be seen that the introduction of PVP into the alcohol system is beneficial to the high dispersion and reduction of Pt species on the surface of SAPO-34.The acidity of SAPO-34 support could affect the interaction between Pt species and the support,thus change the dispersion state of Pt speices,and eventually affecting the performance of the catalyst.?2?A series of SAPO-34 supported transition metal?Mn and Co?catalysts were prepared by impregnation method.Their catalytic properties,for toluene oxidation,were investigated.The effects of metal types,loading and space velocities on the catalytic performance of the catalysts were also studied.The results showed that 9.4%CoO_x/SAPO-34?0.4?and 10%MnO_x/SAPO-34?0.4?exhibited relatively high catalytic activity,and the conversion of toluene reached 90%at 304°C and 352°C,respectively.Combined with some characterization results,it can be proposed that changing the loading and the Si/Al ratio of the support can change the amount of oxygen adsorbed on the surface,and adjust the redox performance of the catalysts.For both CoO_x/SAPO-34 and MnO_x/SAPO-34 catalysts,there is a certain synergistic effect between the redox ability of CoO_x and MnO_x and the acidity of SAPO-34,which should play determinative role in enhancing the high catalytic activity of the catalysts.