Zn/Al复合氧化物催化生物柴油酯交换反应

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。

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

Zn_((1-x)) Alx(OH)_2]~(x+) (CO3)_(x/n)~(2-), 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.