Design Of Catalytic-Activitives-Centered Polyoxometalates And Research Of Catalytic Properties

Nowadays,heterogeneous catalysis has played a critical role in esterification and direct oxidative esterification.Heteropolyacids?HPAs?are strong Br?nsted acids and have been widely used as homogeneous or heterogeneous acid catalysts for esterification and direct oxidative esterification.The main results of this work are as follows:1.This chapter has designed acid-base bi-functional heterogeneous catalyst with mesoporous HPA/Ti/chitosan and applied it into esterification reaction.The results showed that the immobilized catalysts of HPA/Ti/chitosan in catalytic active site H3PW12O40 basic structure did not change,which is because the hydrogen bonding interaction can make H3PW12O40 evenly dispersed well on the surface of chitosan.In acid catalytic esterification reaction,the optimum reaction conditions are as follows: reaction temperature stays at 65 oC,alcoholic acid mole ratio at 15:1,catalyst dosage of 5 wt %,7 h and esterification reaction of the conversion rate is as high as 97.3%,after repeated five times to achieve the good condition-conversion from the original 97.3% to 97.3%,only with 3.1% lower.That fact showed that the immobilized catalysts of HPA/Ti/chitosan remains high catalytic activity.2.This chapter expounds a functional acid catalyst-H₂PW/Fe TPP,when the catalysts are used in the esterification reaction,with the reaction conditions for reaction temperature keeping at 65 oC,alcohol acid mol ratio of 15:1,catalyst for 7 wt %,after 7 h's reaction,conversion rate was 91.3%.In addition,its hydrophobic could be repeatedly used to reduce the cost of raw materials.3.As for H₂PW/Fe TPP porphyrin structure of function,it has a very good oxidation function.That is to say,catalyst showed high catalytic effect after it was applied to the oxidation of alcohols acidification reaction.Results show that when the reaction condition is: the catalyst of 250 wt%,45 oC reaction temperature,reaction time is 8 h,the n-butyl alcohol reached its maximum of conversion rate and yield rate-100% and 76.4%.After repeated six times,the experimental catalytic effect had no obvious change.4.Through the experiment,we elaborated a multi-functional acid catalyst-H₂PMo/Fe TPP.On the surface of this kind of catalyst,there are both oxidation group and acid group,making the reaction contains the oxidation reaction as well as esterification reaction at the same time.In reaction conditions as follows: the catalyst 300 wt%,45 oC reaction temperature,reaction time for 7 h,under the condition of the n-butyl alcohol reached its maximum of conversion rate and yield rate-100% and 69.4%.In addition,its hydrophobic could be repeatedly used to reduce the cost of raw materials.