负载型固体碱催化制备生物柴油重复性能比较

Repetitive performance comparison of supported solid base as catalyst for biodiesel synthesis

采用共沉淀、浸渍及焙烧的方法制备了Ca O/Mg-Al-O及Ca O/Zn-Al-O固体碱催化剂;采用共沉淀、焙烧及研磨的方法制备了KF/Mg-Al-O及KF/Ca-Al-O固体碱催化剂。采用醇洗、干燥及焙烧的方法对使用过的催化剂进行活化处理后用于下一次实验。以蓖麻油和甲醇的酯交换反应为活性评价反应,考察了催化剂重复使用次数对催化剂活性的影响。应用Hammett指示剂滴定法、XRD技术对新催化剂及使用后经活化处理的催化剂进行了表征,并对催化过程中碱溶解流失和析出的甘油量、总甘油量进行了测定。结果表明:Ca O/Mg-Al-O、Ca O/Zn-Al-O、KF/Mg-Al-O和KF/Ca-Al-O固体碱催化剂第一次使用催化活性很好,第二次使用催化活性较差;新催化剂的碱量均比使用过的催化剂的碱量高得多;新催化剂的晶体结构和使用过的催化剂的晶体结构差别很小;新催化剂的碱溶解流失均比较大,且生成的甘油量均较多。

The CaO/Mg - A1 - O and CaO/Zn - A1 - 0 solid base catalysts were prepared by co - precipi- tation, impregnation and calcination, and the KF/Mg- A1 -O and KF/Ca -A1 -O solid base catalysts were prepared by co - precipitation, calcination and grinding. Activation treatment of used catalyst was conducted by alcohol washing, drying and calcination for the next experiment. The effects of repetitive utilization times of catalyst on catalyst activity were investigated with transesterifieation of castor oil and methanol as a model reaction. The new catalyst and catalyst activated after using were characterized by Hammett indicator titration and XRD technology, and loss of alkali dissolution, precipitated glycerol and total glycerol were measured in the catalytic process. The results showed that the two types of solid base catalysts had good catalytic activity for the first time, and poor catalytic activity for the second time. The base amount of the new catalyst was much higher than that of the used catalyst. The crystal structures of new catalyst and used catalyst had little difference. The new catalyst had larger loss of alkali dissolution, and generated more zlvcerol.