Effects Of Introducing Rare Earth La On The Structure And Properties Of SO₄～(2-)-modified Pillared Clay Solid Acid Catalysts

Four La-containing sulfated Zr-pillared clay solid acids(SO42-/LaZr-CLR; SO427La-Zr-CLR; SO42-/Zr-La-CLR; SO42-/Zr(c)-La-CLR)with rectorites as matrix were prepared by utilizing different methods for La introduction. The catalytic activity of four kinds of catalysts was investigated by taking esterification of HAc with n-BuOH as probing reaction. XRD, DTA, TGA, nitrogen adsorption/desorption NHj-TPD and Py-IR techniques were used for characterization and the effects of different introduction methods for La on the structure and properties of the resulting catalysts were investigated .The experimental results show that:The preferable preparation conditions for sulfated La-Zr pillared rectorite solid acids (SO42-/LaZr-CLR) are: n(La)/n(Zr)=0.15 in pillaring agent; n(Zr)/m(Na-R) =3.5mmol/g; m(SO42-) /m(clay)=30%; calcinations temperature 600C,under which the conversion rate of HAc was high as 96.74% and decreased only 4.68% after 4 regeneration cycles.The preferable synthesis conditions of n-butyl acetate over SO42-/LaZr-CLR are : utilizing benzene as distill water solvent; n(Hac) : n(n-BuOH) = 1:1.2; w(SO42-/LaZr-CLR)=6.4%;reaction time is 2h;reaction temperature 120C.The methods of introducing La have a remarkable effect on the structure and properties of the resulting catalysts. Thermal stability and regularity for the layer structure of resulting catalysts are significantly improved either by exchanging Na-rectorite with LaCl3 solution followed by pillaring with Zr pillaring agent (SO42-/'La-Zr-CLR )or by utilizing La-Zr bipillaring agent .In addition, the employment of these two preparation methods leads to a more uniform pore size distribution, a larger specific surface area and an improvement in the amount and intensity of Lewis acid .By either pillaring with Zr pillaring agent followed by exchanging Zr-CLR with LaCl3 solution(SO42-/Zr-La-CLR)or exchanging calcined Zr-CLR with LaCl3 (SO42- /Zr(c)-La-CLR) ,the regularity for the layer structure and the amount, intensity of Lewis acid of resulting catalysts decreased .Three kinds of catalysts prepared from utilizing different methods of introducing La show different catalytic activity. In the esterification of HAc with n-BuOH, theSO427La-Zr-CLR sample show the best activity i.e. a conversion of HAc as high as 97.65%, and good stability i.e. the fourth use of this catalyst revealed only 3.83 percentage point decrease in the conversion of HAc. SO427Zr-La-CLR and SO42-/Zr(c)-La-CLR show relatively low catalytic activity.