The Study Of Transesterification Reaction Using Polyoxometalates As Catalyst

Fatty acid methyl ester (FAME) are generally classified as biodiesel fuels which a reproduced by a catalytic transesterification of fats and oils, waste flying oils with alcohol most of methanol. Because of having proper viscosity, boiling point, a high cetane number, nontoxic and bio-degrade, fatty acid methyl esters derived from oils by transesterification recently have gradually become a new alternative diesel fuel. So many researchers have tried their best to find the friendly environmental heterogeneous catalysts with high activity and selectivity, can act at lower temperature and be used several times, and have little corrosion and pollution to equipments and air.In this thesis, we synthesize and characterize 12-tungstophosphoric acid, zirconiumdodecatungstophosphate, aluminiumdodecatungstophosphate, zincdodecatu -ngstophosphate, and the catalytic activity of these catalysts was studied by transesterification of waste frying oil with methanol.1. A solid acid 12-tungstophosphoric acid was synthesized and the catalytic activity was studied by transesterification of waste frying oil with methanol and esterification of long-chain palmitic acid with methanol in a heterogeneous system. The reaction conditions including methanol/oil (acid) molar ratio, reaction time, reaction temperature, catalyst dosage and introduction of co-solvent were studied to value how they affected the conversions. The results showed that, for 12-tungstophosphoric acid catalyst, the appreciate conditions were: methanol/oil mole ratio70:l, catalyst amount 0.1 mmol, reaction time 14 h, reaction temperature 65℃, and the highest conversion could reach 87 % under the above conditions. From the esterification reaction, it can be seen that the esterifictaion of FFAs is completed.2. A solid catalyst zirconiumdodecatungstophosphate was synthesized and characterized by FTIR, XRD, elemental analysis, TEM, Hammett acid strength (Ho), NH3-TPD and FTIR pyridine adsorption spectroscopy. The catalytic activity of the catalyst was studied by transesterification of waste cooking oil (WCO) with methanol. The conversion of the WCO can reach 97 % with methanol to oil molar ratio 20:1, at 65℃for 12 h. The catalyst was recycled and reused with negligible loss in activity.3. A solid catalyst aluminiumdodecatungstophosphate and zincdodecatungstophosphate were synthesized and characterized by FTIR, XRD, elemental analysis, TEM, Hammett acid strength (Ho), NH3-TPD and FTIR pyridine adsorption spectroscopy. The catalytic activities of the two catalysts were studied by transesterification of waste cooking oil (WCO) with methanol. The conversion of the WCO can reach 92 % with methanol to oil molar ratio 34:1, at 65℃for 12 h when using aluminiumdodecatungstophosphate as catalyst, and the conversion of the WCO can reach 92 % with methanol to oil molar ratio 28:1, at 65℃for 12 h when using zincdodecatungstophosphate as catalyst. The two catalysts were both recycled and reused with negligible loss in activity.