Characterization Of Sulfur-Containing Compounds In Petroleum Based On Multidimensional Mass Spectrometry And Application In Hydrodesulfurization

Sulfur-containing compounds in petroleum are a hot research topic.On the one hand,sulfur oxides can seriously harm human health and reduce engine life.On the other hand,with the increasing sources of petroleum,the content and complexity of sulfur-containing compounds in petroleum become higher and higher.Hydrotreating,as one of the main desulfurization processes,is faced with the key problem of reducing hydrotreating efficiency.The comprehensive characterization of sulfur-containing compounds in crude oil or petroleum products is of great significance for refining process,catalyst design and optimization of petroleum molecular management.This work aims to establish a new method for structural characterization of sulfur-containing compounds in petroleum based on multi-dimensional mass spectrometry(ultra-high resolution mass spectrometry and ion mobility mass spectrometry),and explore the changes of molecular composition and structure during hydrodesulfurization.Firstly,the direct ionization method of sulfur-containing compounds based on atmospheric pressure chemical ionization was developed,and the precise molecular composition of the compounds was determined by ultra-high resolution mass spectrometry.Ion-mobility mass spectrometry was introduced to separate and analyze the isomers,and the full width at half maximum was used to describe the structural diversity of sulfur-containing compounds before and after the reaction.The analysis results of Dagang diesel oil showed that the full width at half maximum of benzothiophene series sulfur-containing compounds increased,indicating that hydrodesulfurization reaction increased the diversity of its isomers,while the dibenzothiophene series remained basically unchanged.The results of catalytic diesel analysis with different catalyst particle sizes showed that the full width at half maximum of benzothiophene series sulfurcontaining compounds decreased with the increase of catalyst particle size,indicating that the catalyst size has different effects on the diversity of isomers.Then,ion mobility separation combined with collision-induced dissociation was used to distinguish and identify the long and short alkyl side chain substitutions of sulfurcontaining compounds.The isomer separation of sulfur-containing compounds was carried out by ion mobility mass spectrometry.Then the fragmentation map was obtained by collision-induced dissociation,and the alkyl substitutions were analyzed.The analysis results of Dagang diesel oil showed that the relative content of benzothiophene series replaced by short alkyl side chain increased after hydrodesulfurization,indicating that it showed low reactivity during hydrodesulfurization process.The results of catalytic diesel analysis with different catalyst particle sizes showed that the relative content of benzothiophene series replaced by multi-short alkyl side chain increased with the increase of catalyst particle size,indicating that catalyst size has an effect on the reactivity of different structural compounds.Finally,based on the measured collision cross section data of sulfur-containing compounds,theoretical calculation and experimental data were compared to further confirm the heterogeneity of substituent framework and position.The comparison results of Dagang diesel oil not only further inferred the possible structure,but also confirmed the multi-short alkyl chain substitution structure,which is more difficult to remove sulfurcontaining compounds.In this paper,ultra-high resolution mass spectrometry,ion mobility mass spectrometry and theoretical calculation were used to characterize sulfur compounds in petroleum.The analysis of sulfur-containing compounds is extended from molecular composition to structural characterization,and its side chain substitution is analyzed in detail.The results of structural characterization of sulfur-containing compounds in hydrodesulfurization oil revealed the relationship between structure and reactivity,which has important guiding significance for catalyst design and optimization and upgrading of hydrodesulfurization technology.