Zn/Al复合氧化物催化生物柴油酯交换反应

Transesterification of Rapeseed Oil over Zn/Al Catalyst for Production of Biodiesel

共沉淀法煅烧制备的Zn/Al复合氧化物可有效催化生物柴油酯交换反应。采用XRD、AAS、BET分别表征催化剂及其前驱体Zn/Al类水滑石,结果显示,前驱体为单一类水滑石结构(LDH),前驱体在400℃煅烧8 h后所得复合氧化物中Al充分分散于ZnO晶格中。用菜籽油-甲醇酯交换反应评价所得催化剂的催化活性,结果表明,在200℃,醇油物质量比为24∶1,搅拌转速为400 r/min,体系压力2.5 MPa,催化剂用量为菜籽油油重的1.4%条件下,反应90 min后,菜籽油转化率达到80%以上,证明Zn/Al复合氧化物在较低醇油比条件下也具有较高的酯交换催化活性。同时考察了FFA和水分对催化剂的影响,结果表明,当FFA含量低于油重的6%,水含量低于油重的10%时,油脂转化率仍在80%以上。

[Zn（1-x） Alx（OH）2]x＋（CO3）x/n2-,a hydrotalcite-like compound with Zn/Al=4 and a effective catalyst for transesterification to produce biodiesel,was synthesised via the conventional coprecipitation method.XRD,AAS,BET were used to characterize the precipitate.The XRD results indicated that it was a pure and stable hydrotalcite-like structure.The precursor was calcined at 400 ℃ for 8 h to obtain the catalyst in which the Al was highly dispersed inside the ZnO crystalline.Transesterification activity measurement with rapeseed oil obtained an oil conversion of 80% in 90 min under the conditions of 200 ℃,2.5 MPa,24∶1 molar ratio of methanol to rapeseed oil and 1.4%（wt） of catalyst amount.The results show that the obtained catalyst is an effective catalyst for the transesterification reaction.Effects of FFA and water content on the catalyst activity have been also researched.