Preparing Of Molding MAO And Study On Synthesis Of Polyether With Narrow Molecular Distribution

This paper was focused on moldling of catalyst and reaction kinetics of ethoxylation with n-octanol and ethylene oxide(EO).Firstly, upon the foundation of correlative research, the optimal process parameters of synthesis of Mg/Al Hydrotalcite(HT),which was pre-body of catalyst, was obtained by studying the influence of NaOH/(Mg+Al), NaOH/Na₂CO₃, crystallization time and dropping ratio on structure of HT hydrotalcite, this process was proved to be high stable and repeatable. Secondly, the dried HT was pressed into cylinder (?4×5mm) under different pressure after blending with starch and then calcined at 500℃, which gave to a novel catalyst known as particle of Mg/Al complex oxide(MAO). The particle of MAO possessed distinct activity of ethoxylation. The results revealed the best process was10%(m) starch and 200 MPa pressure. At last, the other conditions of process for the synthesis of n- octanol polyether catalyzed by particle of MAO were studied in details, A group of optimal process parameters, such as temperature at 160+-5℃,catalyst amount at 0.5%,pressure at 0.4Mpa was got. The products of ethoxylation were colorless and content of by-products were less than 5%, and EO unit distribution index reached to more than 80%. What is more, the used catalyst could be washed by H₂O, chloroform, H₂O and dried in oven, its catalysis activity had no obvious change after four times, furthermore, the quality of the product (n-octanol polyether) was not worse than that by the non- molding catalyst. The other research in this paper was about reaction kinetics of ethoxylation of n-octanol catalyzed by powder MAO.Firstly, the reaction stage fitted to the kinetics equation was found by the plot of Conversion—Time. The reaction was supposed as first order reaction for EO. The plot of lnP-t was obtained at the stage referred above. Then, a linear fit was made for the plot, whose slope was the reaction rate constant (k) and intercept was lnPo according to the kinetics equation. At the same time, the correctness of the assumption was validated. Further more, the reaction rate constant (k) at various temperature was obtained. Andthe plot of Ink—— was given by the Arrhenius equation. After the linear fit, theactivation energy was figured out to be 60.2 KJ/mol with powder MAO. (in identicalcondition, 50.2 KJ/mol with KOH)The result indicated that the ethoxylation reaction over the MAO was a little moredifficult to occur than over KOH, and the reaction rate of the former was a littleslower than the latter.