摘要
以油酸和甲醇为原料,采用浓硫酸、固体酸SO42-/TiO2-SiO2或油酸的自催化作用进行催化,研究了油酸和甲醇酯化合成生物柴油过程的催化反应动力学。通过测定不同反应温度、不同催化剂浓度和不同甲醇/油酸摩尔比条件下油酸的转化率,回归得到了酯化反应动力学参数。研究结果表明,酯化反应及其逆反应均为二级反应。不同催化反应下的正逆反应活化能分别为33.8和13.9 kJ.mol-1(浓硫酸催化)、37.1和18.5 kJ.mol-1(SO42-/TiO2-SiO2催化)或49.1和31.1 kJ.mol-1(油酸自催化作用)。以上述过程中得到的反应动力学方程分别计算了油酸的转化值,与实验值吻合很好。由上述结果可知,浓硫酸具有最高催化活性,要在相同反应时间内得到相同油酸转化率时需要的反应温度最低。油酸自催化反应速率慢,在相同的反应时间内,高温反应时才可使油酸的转化率与浓硫酸低温催化作用下的油酸转化率相同。SO42-/TiO2-SiO2催化活性介于浓硫酸与油酸自催化之间,由于具有稳定好、分离简单和无腐蚀等优点,也适合作为酯化反应的催化剂。
The kinetics of the esterification of oleic acid with methanol were studied by using different catalysts such as concentrated sulfuric acid and SO42-/TiO2-SiO2, or auto-catalyzed by the oleic acid. The parameters in the esterification kinetic were determined by measuring the conversion of oleic acid under the conditions of different reaction temperatures, different loadings of catalyst and different molar ratios of methanol/oleic acid. The results showed that both the esterification （forward reaction） and the hydrolysis of oleic acid methyl ester （inverse reaction） were the second-order reaction. The activation energy of the forward and inverse reaction for different catalytic conditions were 33. 8 and 13. 9 kJ/mol （catalyzed by concentrated sulfuric acid）, 37. 1 and 18. 5 kJ/mol （catalyzed by SO4^2-/TiO2-SiO2） or 49. 1 and 31. 1 kJ/mol （auto-catalyzed by oleic acid）. The conversions of oleic acid calculated from the obtained kinetic equations were in agreement with the experimental data. From above results, it could be known that the catalytic activity of the concentrated sulfuric acid was the highest, and the lowest reaction temperature was required to obtain the same conversion of oleic acid at the same reaction time. The oleic acid autocatalysis exhibited a slow reaction rate. In order to obtain the same conversion of oleic acid on this condition or using the concentrated sulfuric acid as catalyst, it required a higher reaction temperature. The catalytic activity of SO4^2-/ TiO2-SiO2 was between the concentrated sulfuric acid and SO4^2-/TiO2-SiO2, it could be regarded as a suitable catalyst for the esterification due to it has several advantages such as good stability, easily separation and no-corrosion.
出处
《化学反应工程与工艺》
CAS
CSCD
北大核心
2009年第3期250-255,共6页
Chemical Reaction Engineering and Technology
关键词
油酸
酯化反应
酸催化
生物柴油
动力学
oleic acid
esterification
acid catalysis
biodiesel
kinetics
