On Preparation And Catalytic Properties Of Solid Superacid Catalyst SO₄^2-/TiO₂/MAS-5

Solid superacid is a novel kind of green catalytic material.Compared with the tranditional liquid-acid catalyst,it has many advantages,such as mild reaction condition,high selectivity,easy separation,low corrosion to appliance,high recycle performance.Therefore,the development and application of solid superacid have got more and more attention in recent years.Up to now,solid superacid has not been applied in industry,on account of the limited catalytic activity,which is caused by small specific surface area and total acids,and the limited life of catalyst,which is caused by easy loss of SO42-and inactivation on catalyst surface.However,oxide-supported solid superacid can relieve those problems effectively,especially,the modified solid superacid,which uses mesoporous molecular sieve as carrier.It can provide larger specific surface area,enhance selectivity and lower the reaction temperature.This thesis aimed at unitizing self-prepared MAS-5 mesoporous molecular sieve with silicate to aluminium ratio of 30 as carrier to load Ti02 by sol-gel method and SO42-by impregnation technique to prepare solid superacid SO42-/TiO2/MAS-5.The prepared catalyst was used for the kinetic study of PMA esterification reaction of acetic acid with PM.The main contents are listed as follows:(1)The hydrothermal synthesis method was adoped to prepare MAS-5 mesoporous molecular sieves with different silica alumina ratios.The BET characterization results indicated that the MAS-5 with the silica alumina ratio of 30 is the best choise for doping TiO2.(2)Comparing with traditional method of aging at low temperature to support TiO2,the catalyst,which was prepared by sol-gel technique had a higher catalytic activity.PMA esterification reaction was conducted to explore the optimum systhesis conditions for catalyst of SO42-/TiO2/MAS-5.The catalyst recycled experiments indicted the optimized catalyst exhibited good recycled performance.(3)The mesoporous molecular sieve MAS-5,the support TiO2/MAS-5 and the catalyst SO42-/TiO2/MAS-5 were characterized and analyzed by BET,SEM,TEM,TGA,and XRD.(4)In the batch reaction stirring apparatus,SO42-/TiO2/MAS-5 was used as catalyst to carry out the kinetic study of PMA esterification reaction of acetic acid with PM.The effects of reaction temperature,catalyst concentration and molar ratio of HAc and PM on PMA esterification reaction were explored after eliminating the effect of external diffusion.A pseudo-homogeneous kinetic model was established and the kinetic parameters were determined by the experimental values.The conversion of PM calculated from the proposed rate model excellently coincided with the experimental value.