香兰素热稳定性及热分解过程机理研究

Study on Thermal Stability and Thermal Decomposition Mechanism of Vanillin

香兰素主要以愈创木酚-乙醛酸法合成,其粗品需要在较高温度下连续进行长时间的精馏纯化。长时间受热易导致香兰素的热分解,进而影响产品质量及收率。对香兰素的热稳定性及热分解机理进行了系统研究,综合运用高效液相色谱(HPLC)、X-射线粉末衍射(XRD)、综合热分析(TGDSC)以及气相色谱-质谱联用(GC-MS)等方法,研究香兰素在130~150℃下加热24 h过程中的纯度及其热分解产物。结果表明,在加热过程中,香兰素的晶型没有发生变化;随着加热温度的升高和加热时间的延长,香兰素热分解比例增加。在150℃加热24 h后,香兰素的热分解比例达到5%。在加热24 h后的香兰素样品中,香兰酸的含量明显增多。

Vanillin is mainly synthesized by guaiacol-glyoxylic acid method.In the distillation and purification stage,crude vanillin needs to be operated continuously at high temperature for a long time.Thermal decomposition of vanillin can be easily caused by long time heat exposure,thus affecting the quality and yield of the product.The thermal stability and thermal decomposition mechanism of vanillin were systematically studied in this paper.The purity and thermal decomposition products of vanillin in the process of heating at 130-150℃for 24 h,and were studied by high performance liquid chromatography(HPLC),X-ray powder diffraction(XRD),thermogravimetery and differential scanning calorimetery(TGDSC),and gas chromatography-mass spectrometer(GC-MS).Results showed that crystal morphology transformation was not observed during the heating process.With the increase of heating temperature and heating time,the proportion of vanillin thermal decomposition increased.After heated at 150℃for 24 h,the thermal decomposition ratio of vanillin reached 5%.After heated for 24 h,the content of vanillin acid increased obviously.