Caractérisation des espèces métalliques présentes dans les asphaltènes. : Étude de leurs interactions dans les coupes pétrolières lourdes appliquée à l’hydrodémétallation

The presence of heteroatoms and metals in heavy fractions of crude oil can lead to the deactivation of hydrotreating and hydrocracking catalysts. The metals that are most difficult to remove from their matrix are concentrated in asphaltenes. The aim of this thesis work is to gain a better understanding of the metals contained in asphaltenes and their chemical environment in order to optimize the refining process.Separation techniques such as Gel Permeation Chromatography (GPC), High Performance Thin Layer Chromatography (HPTLC) which has been developed and solid/liquid separation have been combined with elemental analysis techniques such as Inductively Coupled Plasma High Resolution Mass Spectrometry (ICP MS) or Ion Cyclotron Resonance Molecular Mass Spectrometry (ICR MS) for the characterization of heavy crude oil fractions. In a first part, the hydrodynamic volume profiles of species containing vanadium and sulphur were determined by GPC preceded by solid/liquid extraction followed by on-line detection by ICP-MS and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). It appears that the larger the size of the aggregates, the more aliphatic the compounds are. However, despite the coupling of two separation techniques, the vanadium porphyrins contained in the large aggregates could not be characterised because they were inaccessible during ionisation.Similar analyses were then carried out but this time by HPTLC which allows separation of the oil samples by polarity. HPTLC was thus coupled to a solid-liquid separation followed by an elemental and molecular analysis. A method of separation by HPTLC in a single migration step has been developed. This method made it possible to isolate free porphyrins from aggregated porphyrins. However, the vanadium-containing molecules in the fractions that remained at the deposition point could not be ionised by Matrix Assisted Laser Desorption Ionisation (MALDI)-FT-ICR-MS.Finally, a method was developed based on doping with silver. It appears that spiking a sample of asphaltene with silver can disaggregate some of the vanadium contained in the larger aggregates. Subsequently this method could allow much more detailed analysis of the compounds present in this fraction.La présence d'hétéroatomes et de métaux dans les fractions lourdes du pétrole brut peut entraîner la désactivation des catalyseurs d'hydrotraitement et d'hydrocraquage. Les métaux les plus difficile à éliminer de leur matrice sont concentrés dans les asphaltènes. Ces travaux de thèse visent à obtenir une meilleure connaissance des métaux contenues dans les asphaltènes et de leur environnement chimique afin d’optimiser le processus de raffinage.Des techniques de séparation telles que la Gel Permeation Chromatography (GPC), l’High Performance Thin Layer Chromatography (HPTLC) qui a été developpée et la séparation solide/liquide ont été combinées à des techniques d'analyse élémentaires telles que l’Inductively Coupled Plasma High Resolution Mass Spectrometry (ICP MS) ou la spectrométrie de masse moléculaire à résonance cyclotronique ionique pour la caractérisation des fractions lourdes du pétrole brut. Dans une première partie, les profils de volume hydrodynamique des espèces qui contiennent du vanadium et du soufre, ont été déterminés par GPC précédés d’une extraction solide/liquide suivis d’une détection en ligne par ICP-MS et par Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). Il apparait que plus la taille des agrégats est importante, plus les composés sont aliphatiques. Cependant malgré le couplage de deux techniques de séparation, les porphyrines de vanadium contenues dans les agrégats de grandes tailles n’ont pas pu être caractérisé car inaccessibles lors de l’ionisation.Ensuite des analyses similaires ont été menées mais cette fois-ci par HPTLC qui permet une séparation des échantillons pétroliers par polarité. L’HPTLC a ainsi été couplée à une séparation solide liquide suivie d’une analyse élémentaire et moléculaire. Une méthode de séparation par HPTLC en une seule étape de migration a été développée. Cette méthode a permis d’isoler les porphyrines libres de celles agrégées. Cependant les molécules contenant le vanadium dans les fractions qui sont restées au point de dépôt n’ont pas pu être ionisées par Matrix Assisted Laser Desorption Ionisation (MALDI)-FT-ICR-MS.Pour finir, une méthode a été développée à base de dopage avec de l’argent. Il apparait que doper un échantillon d’asphaltène avec de l’argent permet de désagréger une partie du vanadium contenu dans les agrégats de grandes tailles. Par la suite cette méthode pourrait permettre une analyse beaucoup plus poussée des composés présents dans cette fraction

Characterization of metal species of asphaltenes and their interactions in heavy oil cuts applied to hydrodemetallation

La présence d'hétéroatomes et de métaux dans les fractions lourdes du pétrole brut peut entraîner la désactivation des catalyseurs d'hydrotraitement et d'hydrocraquage. Les métaux les plus difficile à éliminer de leur matrice sont concentrés dans les asphaltènes. Ces travaux de thèse visent à obtenir une meilleure connaissance des métaux contenues dans les asphaltènes et de leur environnement chimique afin d’optimiser le processus de raffinage.Des techniques de séparation telles que la Gel Permeation Chromatography (GPC), l’High Performance Thin Layer Chromatography (HPTLC) qui a été developpée et la séparation solide/liquide ont été combinées à des techniques d'analyse élémentaires telles que l’Inductively Coupled Plasma High Resolution Mass Spectrometry (ICP MS) ou la spectrométrie de masse moléculaire à résonance cyclotronique ionique pour la caractérisation des fractions lourdes du pétrole brut. Dans une première partie, les profils de volume hydrodynamique des espèces qui contiennent du vanadium et du soufre, ont été déterminés par GPC précédés d’une extraction solide/liquide suivis d’une détection en ligne par ICP-MS et par Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). Il apparait que plus la taille des agrégats est importante, plus les composés sont aliphatiques. Cependant malgré le couplage de deux techniques de séparation, les porphyrines de vanadium contenues dans les agrégats de grandes tailles n’ont pas pu être caractérisé car inaccessibles lors de l’ionisation.Ensuite des analyses similaires ont été menées mais cette fois-ci par HPTLC qui permet une séparation des échantillons pétroliers par polarité. L’HPTLC a ainsi été couplée à une séparation solide liquide suivie d’une analyse élémentaire et moléculaire. Une méthode de séparation par HPTLC en une seule étape de migration a été développée. Cette méthode a permis d’isoler les porphyrines libres de celles agrégées. Cependant les molécules contenant le vanadium dans les fractions qui sont restées au point de dépôt n’ont pas pu être ionisées par Matrix Assisted Laser Desorption Ionisation (MALDI)-FT-ICR-MS.Pour finir, une méthode a été développée à base de dopage avec de l’argent. Il apparait que doper un échantillon d’asphaltène avec de l’argent permet de désagréger une partie du vanadium contenu dans les agrégats de grandes tailles. Par la suite cette méthode pourrait permettre une analyse beaucoup plus poussée des composés présents dans cette fraction.The presence of heteroatoms and metals in heavy fractions of crude oil can lead to the deactivation of hydrotreating and hydrocracking catalysts. The metals that are most difficult to remove from their matrix are concentrated in asphaltenes. The aim of this thesis work is to gain a better understanding of the metals contained in asphaltenes and their chemical environment in order to optimize the refining process.Separation techniques such as Gel Permeation Chromatography (GPC), High Performance Thin Layer Chromatography (HPTLC) which has been developed and solid/liquid separation have been combined with elemental analysis techniques such as Inductively Coupled Plasma High Resolution Mass Spectrometry (ICP MS) or Ion Cyclotron Resonance Molecular Mass Spectrometry (ICR MS) for the characterization of heavy crude oil fractions. In a first part, the hydrodynamic volume profiles of species containing vanadium and sulphur were determined by GPC preceded by solid/liquid extraction followed by on-line detection by ICP-MS and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). It appears that the larger the size of the aggregates, the more aliphatic the compounds are. However, despite the coupling of two separation techniques, the vanadium porphyrins contained in the large aggregates could not be characterised because they were inaccessible during ionisation.Similar analyses were then carried out but this time by HPTLC which allows separation of the oil samples by polarity. HPTLC was thus coupled to a solid-liquid separation followed by an elemental and molecular analysis. A method of separation by HPTLC in a single migration step has been developed. This method made it possible to isolate free porphyrins from aggregated porphyrins. However, the vanadium-containing molecules in the fractions that remained at the deposition point could not be ionised by Matrix Assisted Laser Desorption Ionisation (MALDI)-FT-ICR-MS.Finally, a method was developed based on doping with silver. It appears that spiking a sample of asphaltene with silver can disaggregate some of the vanadium contained in the larger aggregates. Subsequently this method could allow much more detailed analysis of the compounds present in this fraction

Chemical Characterization Using Different Analytical Techniques to Understand Processes: The Case of the Paraffinic Base Oil Production Line

International audienceMineral base oils are used to produce commercial lubricants and are obtained from refining vacuum residue. Lubricants are used to reduce friction in industry devices, so their viscosity is a key characteristic that needs to be optimized throughout the process. The purpose of this study is to show how global chemical characterization of samples from the base oil production chain can facilitate a better understanding of the molecular impacts of processing and their effect on macroscopic properties like viscosity. Eight different samples were characterized by different analytical techniques, including liquid chromatography and mass spectrometry techniques, to understand their chemical evolution through the different process units at the molecular level. Furthermore, a statistical treatment allowed for the identification of parameters that influence viscosity, mainly sulfur and polyaromatics content. This study demonstrates the importance and effectiveness of cross-checking results from different complementary analytical techniques to acquire valuable data on lubricating oil base samples

Speciation of Metals in Asphaltenes by High-Performance Thin-Layer Chromatography and Laser Ablation Inductively Coupled Plasma-Mass Spectrometry

International audienceAsphaltenes are considered to be the most problematic components of heavy oils because they can self-aggregate which leads to precipitation and causes various problems during oil recovery, transportation, and refining. The contribution of the porphyrins present in asphaltenes to the aggregation was previously studied by gel permeation chromatography inductively coupled plasma-mass spectrometry (GPC-ICP MS). The molecular weight of asphaltene aggregates was shown to be increased by free metal-containing porphyrins (corresponding to the lower molecular weight fraction) interacting with the aggregate’s surfaces by weak forces. The characterization of free porphyrins within the asphaltenes is therefore for the understanding of the mechanism of the aggregation, coprecipitation, and demetalation processes. Here, we developed a method for the separation of free porphyrins from asphaltenes on the basis of their polarity using high-performance thin-layer chromatography (HPTLC). This technique, using disposable plates, is particularly well suited for asphaltene analysis since it eliminates the risk of clogging typical of column chromatography. Cellulose plates were used in this study. The lower polarity of their hydroxyl groups limit the irreversible adsorption and improves the detection limit by the ICP-MS. Two well-separated peaks were obtained from purified asphaltene (Asphaltene 2017; Asphaltene Characterization Interlaboratory Study for PetroPhase 2017. In Proceedings of the 18th International Conference on Pretroleum Phase Behavior and Fouling, Le Havre, France, June 11–15, 2017; Total, the University of Pau, and the University of Rouen-Normandy: Le Havre, France, 2017.) and its corresponding whole crude oil and C5 and C7 fractions. The distribution of vanadium due to migration was determined by laser ablation (LA) ICP MS. The eluted fraction contained the free porphyrins, whereas the major fraction did not migrate and corresponded to trapped porphyrins. A comparison with the signal obtained by UV densitometry allowed the ratio between the inorganic and organic material to be measured

Speciation of Metals in Asphaltenes by High-Performance Thin-Layer Chromatography and Solid–Liquid Extraction Hyphenated with Elemental and Molecular Identification

International audienceAsphaltenes are among the most challenging components in petroleum processing because they contain high amounts of heteroatoms (i.e., S, N, O, V, and Ni) thought to be responsible for strong aggregation tendencies, precipitation, and fouling problems. The role of vanadium- and nickel-containing petroleum compounds (i.e., petroporphyrins) in aggregation and fouling is not completely understood because asphaltene composition and structure is still a subject of debate in the petroleum chemistry community. Characterization of asphaltenes, namely, molecular analysis that employs no chromatographic separation, often fails to reveal their comprehensive composition. The work herein presents asphaltene fractionation by (1) solid/liquid extraction, which allows for separation of single-core (“island”) and multicore (“archipelago”) structural motifs and by (2) high-performance thin layer chromatography (HPTLC) with cellulose as the stationary phase and DCM/MeOH as the eluent, which facilitates access to petroporphyrins. Characterization is performed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and matrix-assisted laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI FT-ICR MS). The results demonstrate that even with multiple separation steps, a large quantity of vanadyl porphyrins remains inaccessible for molecular analysis by MALDI FT-ICR MS, which raises the question of what portion of a complex sample of asphaltene can be revealed by ultrahigh resolution mass spectrometry. Furthermore, the results show that easily accessible porphyrins migrate with the solvent front in HPTLC. Thus, HPTLC can be used to isolate and identify “free” porphyrins not locked into asphaltene aggregates; however, further development of separation methods is required to access the most difficult and problematic asphaltene fractions, which do not migrate and impose analytical challenges due to their stronger aggregation tendency