Study On The Preparation And Catalytic Performance Of Purely Siliceous Molecular Sieve Supported DMAP Catalyst

4-dimethylaminopyridine?DMAP?as a superior nucleophilic catalyst has been widely used in acylation,silylation,tritylation,ester rearrangement,polymerization,Darkin-West reaction,Baylis-Hillman reaction,sulfonamides synthesis and CO₂ fixation.Although DMAP possesses many advantages such as low catalyst loading,great solubility,mild reaction conditions,excellent catalytic activity,the main drawback of homogeneous DMAP is the difficulty in recovery and recycling.Therefore,many researchers have paied attention to develop organic or inorganic carriers supported DMAP.In order to criuvment the use of dangerous chemical,two supported DMAP catalysts?MCM-41-DMAP,MCM-41-DMAP^e?have been prepared via the N-alkylation of 4-methylaminopyridine?MAP?and N-alkylation of N¹,N²-dimethyl-N¹-?4-pyridyl?-1,2-ethyenediamine?DMEAP?with?-chloropropylated MCM-41 molecular sieve under mild conditions.The effect of reaction variables on immobilization process was investigated in detail.And the resulting supported DMAP was used to catalyze the acylation of vitamin E with acetic anhydride to produce vitamin E acetate?VEA?,respectively.The supporeted DMAP was prepared by the reaction of MAP or DMEAP with?-chloropropylated MCM-41.?-chloropropylated MCM-41?MCM-41-Cl?was prepared via the reaction of MCM-41 molecular sieve with 3-chloropropyltrimethoxysilane?CPTMS?.On the one hand,the N-alkylation of MAP with resulting?-chloropropylated MCM-41 was promoted by potassium iodide?KI?to prepare supported DMAP?MCM-41-DMAP?.Experimental result indicated that the highest amount of DMAP immobilized as 1.75 mmol/g was obtained in o-xylene solution under the following conditions:MCM-41/MAP mass ratio of 5:1,KI/MAP mole ratio of 2:1,K₂CO₃/MAP mole ratio of 2:1,stirring intensity of 500 rpm,reaction temperature of 130°C,reaction time of 21 h.On the other hand,another supported DMAP?MCM-41-DMAP^e?was prepared by the N-alkylation of DMEAP with?-chloropropylated MCM-41.Result revealed that the highest amount of DMAP immobilized as 0.9 mmol/g was obtained in DMSO solution under following conditions:MCM-41/DMEAP mass ratio of 9:1,stirring intensity of 600 rpm,reaction temperature of 140°C,reaction time of 18 h.Meanwhile,the resulting catalysts were analysized via FT-IR,TG/DTG,BET;and characterization result confirmed that DMAP was successfully immobilized to MCM-41 surface.Furthermore,the immobilized DMAP was used to catalyze the acylation of vitamin E with acetic anhydride to produce vitamin E acetate?VEA?,respectively.And the optimal condition was investigated in detail.Result indicated that the both two catalysts have great potential for the acetylation of vitamin E to produce vitamin E acetate.The catalytic acetylation of vitamin E over MCM-41-DMAP could proceed to 80%in toluene under the following condition:acetic anhydride/vitamin E mole ratio of 3:1,catalyst loading of 100 mg,reaction temperature of 50°C,stirring intensity of 500 rpm,reaction time of 12 h.On the other hand,the catalytic acetylation of vitamin E over MCM-41-DMAP^e could proceed to 90%in toluene under the following conditions:acetic anhydride/vitamin E mole ratio of3:1,catalyst loading of 100 mg,reaction temperature of 50°C,stirring intensity of 400 rpm,reaction time of 12 h.Meanwhile,the both two catalysts indicated high stability,which could be recycled 10 times and could retain initial catalytic activity.