The So <sub> 4 </ Sub> <sup> 2 - </ Sup> / Tio <sub> 2 </ Sub>-al-mcm-41 Molecular Sieve Solid Superacid Catalyst Preparation And Its Catalytic Performance Studies

Solid superacid ,which not only has the advantages of good catalitical activity, broad catalytical range, no corrosion to devices,non-pollution itself and producing no pollution to environment, but also has the merits of being renewable ,and being able to be used repeatedly, can be separated easily ,reduce production costs and save resources greatly.It is considered a new green catalyst having wide application prospects in industry and becomes one of new universal concerned catalytic materials,being used in petrochemical industry , industry of fine chemicals,organic synthesis and so on..Especially for the type of solid superacid SO₄^2-/MxOy,it is easy to preparate and its thermal stability is good.With the getting involved of more and more researchers of the Occident ,the study of solid superacid has become a hotspot in industry catalyst field since 1990s.Inspite of its wide prospects , the solid superacid SO₄^2-/M_xO_y is only researched in laboratory and reported in literature,but diffcult to be industrilized.This is mainly because of the following two aspects:on the one hand,being reduced of sulphor element of high valence , being solvated and lost of acid radical SO₄^2- , coking of catalyst on the surface and poisoning of catalystresult in the catalyst deactivity;on the other hand,with the catalyst application it has been found that while the catalyst has higher acid strength ,its total acid content is relatively smaller than liquid acid,furthermore , its specific surface area is small as well.all those the above have limit its catalical activity in reaction and appilication in industry.Mesoporous molecular sieves have been a research focus in the community of material science and chemistry since it was discovered ten years ago due to it s important potential applications in the large molecule chemistry and the related processing technologies.In this paper, the accelerator of catalyst SO₄^2-/M_xO_y was kept unchanged,and the carrier was modificated by using mesoporous molecular sieve Al-MCM-41due to its particular excellence:high specific surface area large and controllable pore diameter and so on.This paper researched its classification and synthesis methods including the selection of the inorganic precursors,usage and removal of the templates.Accordingly ,the preparation,catalytic performance and application of the solid superacid SO₄^2-/TiO₂-Al-MCM-41 were systematically reseached including the organic synthesis of buty1 valerate, pyrazines and alkylpyrazines, ethoxy quinoline, as well as their reaction mechanisms.The achieved research results of modification for SO₄^2-/M_xO_y by mesoporous molecular sieve Al-MCM-41 as carrier have provided a new way and base,and are of both theoretical and practical significance in further studying on solid superacid .Al-MCM-41 mesoporous material was prepared using tetraethy1 orthosilicate (TEOS) as the silica source,cetyltrimethy1 ammonium bromide (CTAB) as the structure-directing agent, aluminium sulfate as aluminium source.Then, using Al-MCM-41 as carrier,titanium (â…£)sulfate the titanium source, and sulfuric acid(0.5mol/L) as impregnating solution, SO₄^2-/TiC₂-Al-MCM-41 solid superacid was prepared.Both of them were charaterized by XRD,SEM,TEM,IR,N2 adsorption-deadsorption,ammett indicator method and so on.The results showed that the mesoporous molecular sieve with good ordered pore structure as MCM-41 was obtained with the aluminum ion successfully incorporated in the framework of it, that the sample SO₄^2-/TiO₂-Al-MCM-41 retained the mesoporous structure and its BET specific surface area was 700.12m²/g,its acidic strength was less than -14.52. When the calcination temperature was 550℃and concentration of sulfuric acid was 0.5 mol/L,the good molecular sieve solid superacid can be obtained.In this paper,the new solid superacid catalyst was applied to carry out experiments inorder to study the performance and application of it.Among them,there were esterification reaction,cyclization reaction by water-elimination of alcohol,cyclization reaction by ammonia-elimination of diamine, etc.Piperazine, alkylpyrazine, diethyene oxide and ethoxy quinoline were obtained successfully in fixe-bed reactor.The results show that SO₄^2-/TiO₂-Al-MCM-41 solid superacid have high catalytic activity with increasing in specific surface area and total acid content,and that the solid superacid is fit for the fixed-bed and the flow-bed catalytic methodology, and that the solid superacid SO₄^2-/TiO₂-Al-MCM-41 make the fixed-bed catalytic methodology better by being used directly because of its porous and loose structure without being made into spherical granule.Therefore,it has a bright prospect in industrial application.