生物柴油合成反应中KNO3/Al2O3催化剂的活性物种与失活研究

制备了KNO₃/Al₂O₃负载型固体碱催化剂，通过XRD、DRIFT、低温氮吸附、ICP和碱度滴定等手段对催化剂表面性质进行了表征，研究了其对大豆油与甲醇酯交换制备生物柴油的催化性能，剖析了在反应过程中该催化剂的催化本质以及失活原因。结果表明，高温焙烧后Al₂O₃表面KNO₃完全分解，形成了大量偏铝酸钾分散在载体表面；在酯交换反应时Al₂O₃表面的偏铝酸盐等活性组分不断溶出并参与反应，这是该催化剂表现出高活性的主要原因。在反应过程中生成的产物生物柴油和甘油对催化剂的活性有很大影响，其中，生物柴油与活性物种发生的皂化反应是造成催化剂失活的主要原因。

Active species and deactivation behavior of Al2O3 supported KNO3 catalyst in the synthesis of biodiesel via transesterification of soybean oil

Al₂O₃ supported KNO₃ (KNO₃/Al₂O₃) catalyst was prepared and characterized by XRD, DRIFT, nitrogen adsorption, ICP and basicity titration. The catalytic performance of KNO₃/Al₂O₃ in the transesterification of soybean oil with methanol for biodiesel production was investigated; especially, the nature of active species and deactivation behavior during the reaction was considered. The results illustrate that KNO₃ on the surface of Al₂O₃ is completely decomposed after calcination at 873 K, forming potassium aluminate. During the transesterification reaction, aluminate as the active species in KNO₃/Al₂O₃ is gradually dissolved out, which is responsible for the high catalytic activity of KNO₃/Al₂O₃. The biodiesel and glycerol products formed have a great influence on the catalyst activity and the catalyst deactivation is mainly ascribed to the saponification of biodiesel with the active species.