Application Of Ion Mobility-time-of-flight Mass Spectrometry In Characterization Of VGO

Petroleum resources have become increasingly scarce and inferior since 1990s.The processing of heavy oil has become the focus of petroleum refining researchers in recent years.As the increase of proven recoverable reserves of natural gas,the utilization of coal and natural gas resources has also attracted the attention of researchers.The current main approach of liquid hydrocarbon synthesis is to first convert coal or natural gas to CO and H₂,and then to synthesize through the Fisher-Tropsch reaction,but study of the products is still lacking.The current molecular characterization technology of vacuum gas oil(VGO)is mainly based on gas chromatography,which is limited by the boiling point sample.Most methods can only characterize low-boiling petroleum components.In order to expand the range of molecular characterization,ultra-high-resolution mass spectrometry represented by FT-ICR MS has been used in petroleum engineering to achieve an in-depth understanding of petroleum composition in the dimension of sample molecular mass.In this paper,we explored the application of ion mobility-time-of-flight mass spectrometry(IMS-TOF MS)in the characterization of VGO.By combining ion mobility time-of-flight mass spectrometry(IMS-TOF MS)with column chromatography separation technology,molecular characterization methods for aromatics and heteroatom compounds in vacuum gas oil fractions of both petroleum and F-T synthetic oils were developed,including the molecular characterization of nitrides and aromatic hydrocarbons in vacuum wax oils from different sources,and the qualitative analysis of the molecular composition of oxides in F-T wax oil.In the first and second parts of the paper,by combined column chromatography separation technology and IMS-TOF MS,electrospray ionization source(ESI)and atmospheric pressure photoinduced ionization source(APPI)were used to analyze basic nitrides and aromatic hydrocarbon relatively.It was shown that the basic nitrogen compounds and aromatic hydrocarbons in VGO samples can be characterized at the molecular level by using ESI source and APPI source,and the structure difference of aromatic hydrocarbons in aromatic and resin fractions can be observed by combining with column chromatography,improving the depth of data analysis.The third part of the paper studied the application of atmospheric pressure solid probe(ASAP)in petroleum VGO,and compared the result with ESI and APPI results.It was indicated that the ASAP ionization source had a good ionization ablity for both aromatic hydrocarbons and heteroatom compounds.The information obtained by the ASAP source is similar with the result of APPI ionization source,but compounds with higher molecular masses had higher response on ASAP ionization source.The number of mass spectrometry peaks in its measurement results is higher than that of the APPI source.The fourth part of the paper analyzed the aromatic and resins of Fischer-Tropsch vacuum gas oil(F-T VGO).By combining column chromatography separation technology with IMS-TOF MS,we tried to study a high boiling range F-T oil which is difficult to analyze by GC or GC-MS.The characterization result using ESI ionization source and ASAP ionization source indicated that the distribution of aromatic hydrocarbons and various types of oxides are both discontinuous and uneven,which was significantlydifference from the molecular composition of petroleum based samples.It is also proposed that combining ASAP technology with a high-resolution quality analyzer is a promising characterization method in the analysis of FT synthesis products.