银改性磷钨酸催化制备生物柴油工艺研究

Preparation of Biodiesel Using Silver-Modified Phosphotungstic Acid as Catalyst

本文以硝酸银和磷钨酸为原料制备了系列银改性磷钨酸催化剂AgxH3-xPW12O40(x=2、3,x表示AgNO3与磷钨酸的物质的量之比),并利用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)、热重量分析-导数热重量分析(TGA-DTG)和固体核磁共振结合探针分子(^31P-TMPO MAS-NMR)技术对它们的结构、稳定性及酸性进行了表征;同时考察了甲醇/大豆油的物质的量之比、催化剂用量、反应温度和反应时间等因素对磷钨酸银催化酯交换反应的影响.研究结果表明,Ag2HPW12O40催化剂具有最好的催化酯交换反应活性和重复使用性能,其结构中的Brφnsted酸中心与Lewis酸中心之间的协同效应是使其具有高催化性能的原因.以Ag2HPW12O40为催化剂,在甲醇/大豆油的物质的量之比为32/1、催化剂用量为6 wt.%、反应温度为150℃、反应时间为20h条件下,生物柴油产率可达96.4%.

A series of silver-modified phosphotungstic acid catalysts AgxH3-xPW12O40(x=1,2,3)were synthesized by incorporating silver nitrate into phosphotungstic acid.The structure,stability and acidity of the catalysts synthesized were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),thermal gravimetric analysisderivative thermogravimetric analysis(TGA-DTG)and ^31P-TMPO magic-angle spinning nuclear magnetic resonance(31P-TMPO MAS-NMR)spectroscopy.The effects of various reaction parameters,such as methanol/oil molar ratio,amount of catalyst,reaction time,and reaction temperature on the catalytic transesterification of soybean oil and methanol with Ag2 HPWi2 O40 were investigated.The results demonstrated that Ag2 HPWi2 O40 had the best catalytic activity,superior biodiesel yield and excellent durability.The high catalytic activity of the catalyst was attributed to Brφnsted-Lewis acid synergy.With 6 wt.%Ag2 HPW12O40 ca)talyst,the yield of biodiesel reached 96.4%with a methanol/soybean oil molar ratio of 32/1,a reaction temperature of 150℃and a reaction time of 20 h.