Modification, Zr-Embedding And Its Catalytic Properties Of Titanium Silicate TS-1for Ammoximation Of Cyclohexanone

The titanium-silicalite-1zeolite(TS-1) is an environmental friendly catalyst with goodperformance of catalytic oxidation,which can be applied to ammoximation ofcyclohexanone.Compared with the traditional complex route of hydroxylamine,TS-1makesammoximation process has the advantage of mild conditions (normal pressure and lowtemperature),high catalytic activity and without environment pollution. Because of themicropore size,TS-1has the disadvantage such as the serious internal diffusioneffect,difficulty of the exposure of catalytic active center to the reactants, buildup of theproduct molecule and carbon deposition in the pore, which cause eactivate easily. In thisproject,using TPAOH as the template,TS-1are synthesized with improved classical methodand further modified.The modificated samples are characterized by XRD、FT-IR、UV-vis、N2adsorptio-desorption and other methods.Using ammoximation of cyclohexanone asprobe reaction,effects of different modify methods on the catalytic performance are studied.In the first part of this thesis, hydrothermal modification of self-made TS-1zeolite arecarried out.Effect of modificate water, modificate time and modificate temperature on thestructrure of TS-1are investigated.The results show that after the hydrothermalmodification the surface acidity of TS-1zeolite changed slightly while no crystal structurechanged.Some of the surface Si lossed which causing the generation of slit pore.Because ofthe Si lossed, the active center of TS-1decreased,but with the help of the slit pore whichare in favor of diffusion, some of the lossed catalytic activity regained.Secondly,the self-made TS-1zeolite are modified by three different types of alkalisuch as TPAOH,NH3·H2O,and TEA.The results show that after modifiction,the surfaceatoms Si have lossed varying degree.The sample modified by inorganic alkali NH3·H2Ocaused the active center damaged,the catalytic activity reduced in result. Modified byorganic alkali TEA,which has poor thermal stability,led to the Si dissolution irreversiblyonly at the beginning of modification.As a result the active structure lossed and catalyticactivity reduced.The sample are modified by organic alkali TPAOH, which acts as templatereagent.Because of the corrosion of alkali, slit pore formed,at the beginning of themodification,which is propitious to the diffusion of the molecule. Scince TPAOH play therole of template,the dissolve Si and Ti are rearranged finally and as results the catalyticactivity are improved.Furtherly,TS-1are treated with template agent such as TMAOH,TEAOH,TPAOH and TBAOH.It is found that the lossed Ti change into TiO2and the catalyst activity decrease inthe sample modified by TMAOH.TEAOH can play a guiding role in the modification andmore stable Ti active site formed to make up the negative effect of Si loss.The samplestreated with TPAOH or TBAOH have more catalytic activity becsuse of the slit pore andmore stability Ti active site formed through rearrangement.Compared with the samplemodified after calcinations,TS-1treated with TBAOH before calcinations show lesscatalyst activity.for the decrase of active site and increase of TiO2.Finally,with the method of hydrothermal synthesis and template ion exchange, load Zris embedded in the TS-1and Zr-Si zeolites are synthesize.The results show that there is noactive of Zr-Si zeolite for ammoximation of cyclohexanone because the zirconium oxideincline to the invalid decomposition of hydrogen peroxide and the doped zirconium blocktitanium into zeolite.