合成低聚甘油M/ZrO_(2)催化剂的制备及性能

Preparation and properties of M/ZrO_(2)catalysts for synthesis of oligoglycerol

采用共沉淀法分别将Na^(+)、K^(+)、Ca^(2+)、Sr^(2+)、Ba^(2+)掺杂到ZrO_(2)中,制得了Na/ZrO_(2)、K/ZrO_(2)、Ca/ZrO_(2)、Sr/ZrO_(2)、Ba/ZrO_(2)催化剂,并将其用于合成低聚甘油。通过XRD、Raman、CO_(2)-TPD考察了不同金属离子掺杂对催化剂结构及其表面碱量的影响。采用GC和ICP考察了催化剂的活性和稳定性。结果表明,Na/ZrO_(2)和K/ZrO_(2)为单斜相,Ba/ZrO_(2)为四方相,Ca/ZrO_(2)和Sr/ZrO_(2)为立方相,且各催化剂表现出不同的碱性位点。5种催化剂中,Ca/ZrO_(2)表现出最佳的稳定性,Ca^(2+)浸出量(质量分数)为0.003%,催化剂用量减半并循环使用4次后,甘油转化率保持在22%以上,催化剂回收率在95%以上。在Ca/ZrO_(2)为1.0 g、甘油100 g、反应温度270℃、反应24 h的条件下,低聚甘油产率为73.05%,选择性为100%。

Individual Na/ZrO_(2),K/ZrO_(2),Ca/ZrO_(2),Sr/ZrO_(2) and Ba/ZrO_(2) were obtained by co-precipitation of Na^(+),K^(+),Ca^(2+),Sr^(2+),and Ba^(2+)with ZrO_(2) respectively,and then used as catalysts for the oligoglycerol synthesis.The effects of different metal ion doping on the catalyst structure and its surface base amount were investigated by XRD,Raman,and CO_(2)-TPD,while the activity and stability of the catalyst were further investigated by GC and ICP.The results showed that Na/ZrO_(2) and K/ZrO_(2) were monoclinic phases,Ba/ZrO_(2) was tetragonal phase,Ca/ZrO_(2) and Sr/ZrO_(2) were cubic phases,and each catalyst showed different basic sites.Among the five catalysts,Ca/ZrO_(2) showed the best stability with Ca^(2+)leaching amount(mass fraction)of 0.003%.Moreover,with the catalyst dosage halved and recycled 4 times,the glycerol conversion rate still remained above 22%and the catalyst recovery rate was above 95%.Under the conditions of Ca/ZrO_(2)1.0 g,glycerol 100 g,reaction temperature 270°C,reaction time 24 h,the yield and the selectivity of oligoglycerol were 73.05%and 100%respectively.