Cation Incorporated Hydrotalcites And Their Application In Yhe Synthesis Of Isophorone

The mixed oxide catalyst which prepared by hydrotalcite has high BET surface, high activity and selectivity, etc... Many scholars of home and abroad give their interests in recent years. The mixed oxide catalyst was widely used on many reactions, such as, cyclization, dehydration and condensation, etc...This article has emphatically studied the use of the hydrotalcite in acetone adol condensation reaction, studied the relation of the activity and the isophorone selectivity.Hydrotalcite of Mg Al was prepared by a new method, the influence of the Mg/Al ratio, particle size and supporter on the activity of the catalyst has been investigated. The results show that, the catalyst with the Mg/Al ratio is 2, the particle size is 20-30 month, add 30%wt (dry catalyst) of diatomite has the high activity (18%) and high isophorone selectivity (79%).Cation-incorporated hydrotalcites were prepared by the same method. The cation include:Zn,Cr,La,Cu and Na. According the microreactor test, the catalysts of the La-doped and Cu-doped have higher isophorone selectivity (about 90%); the catalysts of the Cr-doped and Zn-doped have higher acetone conversion (above 30%). The two cation-incorporated hydrotalcites were successfully prepared in this article. According the microreactor test, all of the catalysts have the similar acetone conversion (about 30%) and isophorone selectivity (about 60%).In order to study the influence of the catalyst structure on its active, XRD,BET,SEM and TPD were obtained. All of the catalysts (except La-doped) showed the characteristic diffraction lines typical for an HT compound, proving the formation of hydrotalcite-like structure. In the mixed oxide issued from lanthanum containing HT, a small amount of La2O2CO3 phase was obtained. The morphology of HT and HTc samples were investigated by SEM, It is observed that our synthesis results in HT-like materials with a sheet-like morphology, The sheets produced by our synthesis have an irregular, ill-defined shape and display an open "lettuce head" type. After calcined the sheets did roll up into a spherical shape. The basic sites of the catalysts are different depending on the alkaline metal considered. In the acetone condensation, the strength of the basic sites of the catalysts plays an important role. Both on the initial stage and steady stage, the selectivity of IP depends on the strength of the basic site. The acetone oligomerization can only be achieved over strong basic sites. The presence of more strong basic sites were helpful to the high selectivity of IP. But for the relation of conversion and basic sites, it can be seen that the initial acetone conversion rate corresponding to the overall basic sites number,but the steady acetone conversion rate corresponding to the weak basic sites density.