Preparation of Propanediol Isophthalate Polyester Capillary Chromatographic Column and Its Separation Performance and Thermal Stability in Coking Phenol Detection

Propanediol isophthalate polyester (polyester) was prepared by esterification and polymerization reactions using isophthalic acid and 1,2-propanediol as raw materials, and its microstructure was determined using Fourier transform infrared spectrometer, nuclear magnetic resonance spectrometer, and mass spectrometer. Polyester mentioned above was filled into a quartz capillary tube to prepare a capillary chromatographic column, whose separation performance for phenolic isomers in industrial coking phenol and high-purity 3,5-xylenol was investigated. Meanwhile, thermal stability of the self-made capillary chromatographic column was evaluated using a capacity factor curve. It was shown that the softening point of the synthesized polyester was 85℃, and the polymerization degree was about 7. When using the self-made capillary chromatographic column to detect industrial coking phenol, except for 2,4-xylenol and 2,5-xylenol, the resolutions of 9 components including phenol, 2,6-xylenol, o-cresol, m-cresol, p-cresol, p-ethylphenol, m-ethylphenol, 3,5-xylenol, and 3,4-xylenol were greater than 1.500, with RSDs (n=6) of the peak areas of the 9 components less than 6.0%, and the theoretical plate numbers for 3,5-xylenol reached 2 662 m⁻¹. When detecting high-purity 3,5-xylenol, the tailing of 3,5-xylenol did not affect the separation of nearby impurities such as m-ethylphenol and 3,4-xylenol, with the average resolution between 3,5-xylenol and m-ethylphenol of 3.917, and the average resolution between 3,5-xylenol and 3,4-xylenol of 10.026, and RSD (n=6) of the peak area of 3,5-xylenol was less than 1.0%. The capacity factor curve of the self-made capillary chromatographic column was drawn, and the highest operating temperature reached 225 ℃. After continuous using for 7 d at the highest operating temperature, there was no significant change in the capacity factor.