Analysis of a POE Refrigeration Oil for Its Chemical Composition and Molecular Structures

FTIR and GC-MS in hyphenation were applied to the analysis of an imported POE refrigeration oil (abbr. as oil A) for its chemical composition and molecular structures of the constituents. As shown by the FTIR spectrum, oil A is an ester of pentaerythritol and acyclic carboxylic acid with complete esterification. It was found in the TIC chromatogram of GC-MS, that there are 5 main components in the oil. By applying the ester exchange technique, pentaerythritol was replaced by methyl alcohol. It was deduced from the GC-MS spectra obtained after trans-esterification that oil A is the product of esterification of pentaerythritol with ethylhexanoic acid and azelaic acid. Under complete esterification, 6 products will be produced, among which 2 products are isomers. This is the reason that only 5 signal peaks were found in the chromatogram. The above result was verified by synthesis of a simulated oil A through esterification of pentaerythritol with azelaic acid in laboratory.