Dehydration of Mannitol Catalyzed by Oxide Supported Phosphotungstic Acid
A series of supported catalysts with different loading amounts were prepared by impregnating Keggin-type phosphotungstic acid onto SiO2,TiO2,ZrO2,and Al2O3 carriers.Characterization methods such as infrared spectroscopy(FT-IR),X-ray diffraction(XRD),scanning electron microscopy(SEM),and temperature programmed desorption(NH3-TPD)were used to analyze the catalyst.The performance of the prepared catalysts in the dehydration of mannitol was studied under solvent-free and depressurized conditions.The effects of catalyst carrier type,phosphotungstic acid loading,reaction time,reaction temperature,and catalyst dosage on the conversion of mannitol and dehydration products were investigated.The results showed that the 30%PW/SiO2 catalyst exhibited superior catalytic performance.The optimal process conditions were a catalyst to mannitol mass ratio of 0.03,a reaction temperature of 170℃,a reaction time of 2 h,and a vacuum degree of 0.09 MPa.Under these conditions,the conversion of mannitol was 100.0%,the yield of 2,5-sorbitan was 55.7%,the yield of 1,4-mannitan was 9.7%,the yield of isomannide was 25.9%,and the yield of other components was 8.5%.
dehydration of mannitolcatalystsupported phosphotungstic acidreaction conditionsmetal oxides
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