稀土改性固体超强酸催化制备生物柴油的研究

Study on the preparation of biodiesel with rare earth modified solid superacid catalysts

以SO42-/ZrO2为母体,引入稀土元素La、Ce对其进行改性,制备出一系列稀土固体超强酸催化剂,用X射线衍射、红外光谱和BET手段表征了催化剂的物化性能。研究了催化剂合成生物柴油的催化性能,系统考察了n(甲醇):n(脂肪酸甘油三酯)、催化剂用量、反应温度、反应时间等因素对生物柴油产率的影响。结果表明:稀土的引入使活性四方相ZrO2更加稳定;催化剂中形成了固体超强酸结构,且改性后酸强度增大,催化剂活性中心数目增加。SO42-/ZrO2-La2O3的催化活性较高,n(甲醇)∶n(脂肪酸甘油三酯)=10∶1、m(催化剂)∶m(原料油)=4∶100、反应温度250℃、反应时间9 h,此时甲酯的产率可达到73.46%。该催化剂活性较高,重复使用3次后生物柴油产率仍在60%之上。

A series of rare earth solid superacid catalyst were prepared from SO2-4/ZrO2 catalyst precursor composition,and modified by the introduction of rare earth elements.The catalysts were characterized by means of FTIR,XRD and BET.Various reaction parameters,such as the molar ratio of methanol to waste oils,amount of catalyst,reaction temperature,reaction time and other factors influencing the synthesis were discussed and the optimum conditions were established.An analysis of XRD patterns revealed that the incorporation of rare earth into tetragonal zirconiacan stabilize the compound,and it can be seen from the FTIR spectra that superacid structures were formed in the catalysts and the acidity was strengthened remarkably and the activated centre of the catalyst was increasesed.The experimental results indicated that SO4^2-/ZrO2-La2O3 has a higher activity and the optimum reaction conditions obtain as follows：10∶1 of molar ratio of methanol to waste oils,catalyst dosage 4% of oil mass used,250 ℃of reaction temperature,9 hours of reaction time.The yield of the biodiesel can reach 73.46%.The catalyst can be used repeatedly and the yield of the biodiesel can be more than 60% after the catalyst is used for three times.