Preparation Of Interparticle Porosity Dominated Hierarchical Porous TS-1 For Epoxidation Of Styrene

Epoxides is not only a fine chemical but also an important organic synthesis intermediate for production of perfume,epoxy resins,plasticizers,drugs,sweeteners,etc.From the perspective of green chemistry,the direct epoxidation of olefins has been regarded as a promising and viable alternative to the conventional processes.However,due to the relatively active C=C double bonds in olefin,the epoxidation of olefins produces a variety of by-products faced with a low conversion rate,poor selectivity and many other issues.Therefore,it is of great theoretical and practical value to develop and design a new type and highly efficient catalyst,especially heterogeneous catalyst.Among heterogeneous catalysts,Titanium Silicalite-1?TS-1?zeolite has drawn great attention,because of their excellent catalytic activity in oxidation of various organic molecules.Indeed,the inherent microporous structure of TS-1 zeolite strongly restrains the diffusion of bulky reactants and products,which brings undesired effects during the catalytic reaction.In order to improve the catalytic performance of TS-1,the use of mesoporous structure has been envisaged as a solution to solve the limitation of the micropore structure without changing the excellent properties of the TS-1 zeolite.However,Ti-containing mesoporous molecular sieves do not show the required high stability Therefore,the synthesis of a hierarchical TS-1 zeolite with high stability has been a very high application prospects for the epoxides of olefins.In this work,a convenient and easily large-scale production to construct intercrystal porosity dominated hierarchical porous TS-1?marked as IPD-mesoTS-1?based on sufficiently small TS-1 nanolized crystals was designed.The thesis work is as follows:?1?The IPD-mesoTS-1 was synthesized by using TEOS and Na₂SiO₃·5H₂O,C₁₂H₂₈O₄Ti as silicon and titanium sources,respectively,Series of IPD-mesoTS-1?Si/Ti ratios=46.7,28.0,17.5,13.2,10.0?were synthesized.The samples were characterized by a variety of techniques including:N₂ adsorption/desorption,PXRD,SEM,EDS.The results showed that the samples were all interparticle porosity dominated hierarchical porous TS-1 with the MFI topology,based on sufficiently small TS-1 nanolized crystals.Simultaneously,the catalytic performances for epoxidation of styrene catalyzed by IPD-mesoTS-1 were systematically evaluated.The results revealed the various parameters,such as various Si/Ti,oxidants and reaction temperature,played important roles in controlling the epoxidation.It was found that IPD-mesoTS-1?e?had the highest catalytic activity in the optimal reaction conditions.?2?In order to improve the catalytic activity of IPD-mesoTS-1,series of Co supported on IPD-mesoTS-1 catalysts?Co/IPD-mesoTS-1?were prepared in situ.The samples were characterized by a variety of techniques including:N₂ adsorption/desorption,PXRD,SEM,EDS.The results indicated that the Co nanoparticles were not aggregated but highly dispersed on the IPD-mesoTS-1.Simultaneously the catalytic performances for epoxidation of styrene were systematically evaluated.The as-prepared Co/IPD-mesoTS-1 showed high catalytic activities for epoxidation of styrene.In addition,various parameters,such as Co loading,solvents,oxidants,reaction temperature and reaction time,played important roles in controlling the epoxidation.