Abstract:

A kind of high viscosity poly alpha-olefin (PAO) as base oil was characterized by time of flight mass spectrometry, and infrared spectrum to investigate the structure of the sample and the fractions after distillation, as well as carbon number distributions and double bond types. The mass spectrometry results show that poly 1-decene with degrees of polymerization of 2-21 is the main component in the PAO sample; the strongest peak is attributed to the pentamer of 1-decene. Both single olefin and alkane can be observed in PAO with different degrees of polymerization. The coupled twin peaks of olefin and hydrogen with the same carbon number as vinylidene are observed by nuclear magnetic resonance 1H spectrum, indicating the existence of trace olefin bond at terminal position. The olefin peaks are much stronger after vacuum distillation, demonstrating the occurrence of thermal cracking. The FT-IR indicates that the olefin bound in PAO sample is the vinylidene double bond type, which proves that the remained double bound and newly produced double bound after hydro-saturation of PAO are terminal position double bound, not the internal olefin.

Key words: FD-TOF MS, mass spectrometry, nuclear magnetic resonance, infrared spectrum, PAO, 1-decene, base oil