氧化物负载磷钨酸催化甘露醇脱水反应的研究

Dehydration of Mannitol Catalyzed by Oxide Supported Phosphotungstic Acid

分别以SiO_(2),TiO_(2),ZrO_(2)和Al_(2)O_(3)为载体,采用浸渍法负载Keggin型磷钨酸,制备了一系列不同负载量的催化剂。通过红外光谱(FT-IR)、X射线衍射(XRD)、扫描电镜(SEM)和程序升温脱附(NH3-TPD)等表征手段分析催化剂。在无溶剂、减压条件下,使用制得的催化剂,研究了催化剂催化甘露醇脱水反应的性能,考察了催化剂载体种类、磷钨酸负载量、反应时间、反应温度和催化剂用量对甘露醇转化率和脱水产物的影响。结果表明,以30%PW/SiO_(2)为催化剂,催化反应性能较好,较佳的工艺条件是催化剂与甘露醇质量比为0.03,反应温度为170℃,反应时间为2 h,反应体系真空度为0.09 MPa,在此条件下甘露醇的转化率为100.0%,2,5-脱水山梨醇收率为55.7%,1,4-脱水甘露醇收率为9.7%,异甘露醇收率为25.9%,副产物收率为8.5%。

A series of supported catalysts with different loading amounts were prepared by impregnating Keggin-type phosphotungstic acid onto SiO_(2),TiO_(2),ZrO_(2),and Al_(2)O_(3) carriers.Characterization methods such as infrared spectroscopy(FT-IR),X-ray diffraction(XRD),scanning electron microscopy(SEM),and temperature programmed desorption(NH_(3)-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/SiO_(2) 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%.