Studies On Epoxidation Catalytic Performance Over Supported Phosphomolybdate Base Mixed Oxide

Olefin epoxidation reaction is the primary method for the preparation of epoxy compounds,which are widely used as intermediates in fine chemicals and pharmaceutical industries.Sodium phosphomolybdates and transition metal Me(Co、Mn、Fe)modified salts having keggin-type structure were loaded on MCM-41(M)and Ti-MCM-41(TM(0.2))mesoporous molecular sieve,then calcined at 500℃,to obtain NPMO/M,NPMO/TM(0.2)and NPMMeO/TM(0.2)samples.Their catalytic performances were investigated in the epoxidation reaction of cyclohexene using H2O2 as oxygen source.The catalysts were characterized by XRD,UV,N2 adsorption-desorption,XPS and H2-TPR.The results showed that phosphomolybdates were decomposed after calcination,ones loaded on TM(0.2)were decomposed more fully.After mixed oxides NPMO were supported,the catalytic performance and utilization of hydrogen peroxide were obviously improved,which due to the improvement of reduction performance of MoO3,catalytic performance can be further improved by amorphous Ti species in the TM(0.2).Compare to NPMO/TM(0.2),catalytic performance of NPMMeO/TM(0.2)were improved dramaticlly.The descending order of epoxycyclohexane yield is NPMCoO/TM(0.2)>NPMMnO/TM(0.2)>NPMFeO/TM(0.2)>NPMO/TM(0.2).The optimum preparation methods of NaPMoMeO/TM(0.2)(Me=Co,Mn)are 30%NPMCo1O/TM(0.2)-500 and 30%NPMMn1.50/TM(0.2)-500.Used 30%NPMCo1O/TM(0.2)-500 as catalyst,optimum reaction conditions:catalyst 0.1g,cyclohexene 20mmol,H2O2 30mmol(30wt%),reaction time 4 hours,reaction temperature 60℃,conversion of cyclohexene and selectivity of epoxycyclohexane reached 60.82%and 73.30%respectively.