Methodology and Application of Soft Ionization Techniques for Petroleum Molecular Characterization by Mass Spectrometry

Author:Ma Su Tian

Supervisor:zhou ya song shi quan


Degree Year:2018





The contradiction between the poor supply of crude oil and the strict demand for products has become increasingly prominent.For the refining companies in the existing relatively mature processes,equipment and catalysts conditions,optimizing the refining production process is the most effective way to achieve maximum efficiency.Molecular refining advocates considering the refining process at the molecular level.The technological approach to molecular refining is molecular management,which need to understand and interfere the refining process from the perspective of molecular composition and transformation.The basis of molecular management techniques is the accurate molecular composition of petroleum.In this paper,mass spectrometry analysis techniques of the weak-polar compounds,especially the non-polar saturaed hydrocarbons in the petroleum fractions,are optimized.(1)The gas chromatography field ionization time-of flight mass spectrometry(GC/FI TOF MS)instrument parameters are investigated and optimized.The relative intensity of the light components of coking diesel is enhanced.The lowest detected carbon number is eight,which is consistent with the gas chromatography flame ionization detector(GC/FID)results.The separation method for saturated and aromatic hydrocabons of coking diesel is established.The analysis results of GC/FI TOF MS are calibrated by the ASTM standard methods,then the molecular composition of diesels and heavy distillate fractions can be obtained.(2)Ruthenium ion catalyzed oxidation(RICO)combined with negative electrospary ionization Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS)is used to cheracterization the molecular composition of lubricant base oils.The saturated hydrocarbons are converted into alcohols,which can be ionized by the negative ESI.Compared to the conventional GC/FI TOF MS,there is no fragment ions,heavy boiling point fractions which can not be vaporized by GC can also be analyzed.The carbon number distribution is consistent with the simulated distillation data.The relative abundance of different saturated hydrocarbons are closer to the ASTM data,and the hydrogen to carbon ratio is closed to the elemental analysis data.In general,RICO/ESI FT-ICR MS can be used as a quantitative analysis method for the lubricant base oils.(3)When the NH4+is added into the sample solution,HC,S1 and S2 compounds can be ionized by positive ESI.NH4+ESI has stong selectivity for the polar compound.The M+and[M+H]+produced by atmospheric presure photoionization(APPI)make the analysis more complicated.Therefore,positive ESI with ammonium formate ass a ionization promoter can be used as a supplementary method for the analysis of weak polar compounds.(4)Negative ion atmospheric presure chemical ionization(NI-APCI)combined with GC/MS is introduced for the direct analysis of phenolic compounds in coal tars.Phenolic compounds can be selectively ionized from the complex hydrocarbon matrix,which enable the direct analysis of phenolic compounds in coal tar.Monohydroxyl phenolic molecules were ionized to[M-H]-and[M-H+O]-,while dihydroxy phenolic molecules were ionized to[M-H]-,[M-2H]-,and[M-2H+O]-.The technique is potential for phenolic compounds analysis in other samples.