Catalysts For Preparation Of Allyl Alcohol By Isomerization Of Propylene Oxide

The catalytic effect of basic lithium phosphate on the preparation of allyl alcohol by isomerization of propylene oxide was studied in this dissertation. The effects of preparation method and surface acidity and basicity on the catalytic properties were discussed. The changes of microstructure, phase components, surface properties and thermal properties of the catalysts before and after use were studied. The main content is as follows:1. Three methods were used to prepare basic lithium phosphate, of which the deposition-precipitation method using sodium phosphate as raw material and the mixing method was better. The effects of preparation conditions on the catalytic properties were studied. The properties of the catalysts using potassium as adjuvant and silica or silica gel as support were better. The pH value during preparation was adjusted to be 12 and the appropriate calcinations temperature was 320℃. The supporting ratio should be over 50%. The best temperature range for the isomerization reaction was (310 ~ 320)℃. After using 40h the conversion of the catalyst decreased from (60~70)% to 40% and two washing agents can be used to regenerate the catalysts in order to lengthen its life.2. The surface basicity of the catalyst was studied by TPD. The properties of the catalyst were different with different pH value and also there existed great difference between the TPD curves. The higher the pH value, the more the number of basic sites. The desorption kinetic parameters was measured for the catalyst with pH=12.3. The catalysts prepared by impregnating and mixing were characterized by IR, TG-DTA, XRD, BET and XPS, and the catalysts before and after use were compared. The active sites of the fresh catalyst was much more than that of the deactivated because after use the active sites were covered by the tar produced during the reaction; The crystal phases and the DTA curves of the catalysts calcined at different temperatures were different from that of the lithium phosphate agent and the DTA curves of the deactivated catalyst were also different; The BET surface area had great effect on the catalytic properties. Without appropriate surface area there won't be high catalytic properties and the surface area was lowered after deactivation. Distribution of pore size of the fresh catalyst was even and the pore is just appropriate for the isomerization of propylene oxide. Whereas the deactivated catalysts had more large pore of 12nm because pores fused during the isomerization reaction. The catalysts prepared by deposition-precipitation were of nanometer-grade. From TG-DTA, XPS and SEM-DTA data the cause of deactivation could...