Catalytic upgrading of microalgal hydrothermal oil: Impact of algae species and catalyst for biofuel production

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Caractérisation de carburants alternatifs par chromatographie d'exclusion stérique et résonance magnétique nucléaire

Size Exclusion Chromatography and High Resolution and Solid State NMR analysis are combined to study hydroconversion products. In a first part, several catalysts were examined to produce biofuel from jatropha oil. By using an n-alcanes standards calibration for SEC, and high resolution NMR, fuel composition and structural identification were easily determined. These two analytical tools were also applied to characterisation of heavy molecular hydrocarbons from non conventional crude oils, liquid coals and derived products such as asphaltenes and pre-asphaltenes. Specific NMR pulse sequences were tested and applied to liquid or solid compounds for quantitatively determination of aromatic and aliphatic carbons.L'utilisation de ressources non conventionnelles dans des procédés catalytiques de production de carburants alternatifs nécessite une adaptation des techniques analytiques de caractérisation pour la compréhension. En effet, les molécules des ces ressources sont très diverses par leur nature chimique, très hétérogènes par leurs masses moléculaires et compositions chimiques et ont été peu étudiées par le passé La chromatographie d'exclusion stérique est ainsi employée et adaptée à l'analyse de produits de conversion d'huile végétale. L'adaptation du système de chromatographie, notamment par le choix des étalons de calibration, permet une identification aisée des molécules formées lors de la conversion d'huile de jatropha. La caractérisation multinucléaire par résonance magnétique nucléaire de ces mélanges complexes d'hydrocarbures permet l'identification structurale et l'analyse en composition de ces produits Ces deux techniques analytiques sont adaptées dans une seconde étude, à la valorisation de pétrole non conventionnel, de résidus pétroliers lourds et de liquéfiats de charbon en carburants alternatifs. Pour ces caractérisations, des séquences impulsionnelles RMN spécifiques sont testées et optimisées pour permettre une quantification structurale de la composition des milieux complexes. Ces séquences ont été appliquées à l'analyse de résidus sous vide et d'asphaltènes issus de coupes pétrolières en milieu liquide ainsi qu'à l'analyse d'asphaltènes et préasphaltènes issus de liquéfiat de charbon en milieu solide

Quantitative performance of forward fill/flush differential flow modulation for comprehensive two-dimensional gas chromatography

International audienceGC × GC is an advanced separation technique allowing to achieve quantitative and qualitative characterization of complex samples. In order to perform two-dimensional separation, the system must provide suitable peak modulation which will direct short impulses of first column flow towards the second column. Forward fill/ flush differential flow modulation is a cost effective and no cryogen requiring approach which allows modulation over a wide range of analytes with very different boiling points. However, optimization of the flow modulation process can be difficult to understand and quantification performance might be compromised if the parameters of the modulation process are not properly set. Modulated peak shape can be a good indication of the efficiency of the modulation process, however it is not sufficient to guarantee good quantification. Different average velocities in the beginning and the end of the thermally programmed GC run may cause different efficiency of the modulation process in various parts of the chromatogram. The purpose of this work is to investigate quantitative performance of the forward/fill flush modulation and delineate parameters that determine the effectiveness of the modulation process and its ability to properly reflect the quantitative composition of the investigated sample

Gas chromatography vacuum ultraviolet spectroscopy: A review

RMN+ECI2D+ALL:CLO:CGEInternational audienceAccelerated technological progress and increased complexity of interrogated matrices imposes a demand for fast, powerful, and resolutive analysis techniques. Gas chromatography has been for a long time a ‘go‐to’ technique for the analysis of mixtures of volatile and semi‐volatile compounds. Coupling of the several dimensions of gas chromatography separation has allowed to access a realm of improved separations in the terms of increased separation power and detection sensitivity. Especially comprehensive separations offer an insight into detailed sample composition for complex samples. Combining these advanced separation techniques with an informative detection system such as vacuum ultraviolet spectroscopy is therefore of great interest. Almost all molecules absorb the vacuum ultraviolet radiation and have distinct spectral features with compound classes exhibiting spectral signature similarities. Spectral information can be ‘filtered’ to extract the response in the most informative spectral ranges. Developed algorithms allow spectral mixture estimation of coeluting species. Vacuum ultraviolet detector follows Beer–Lambert law, with the possibility of calibrationless quantitation. The purpose of this article is to provide an overview of the features and specificities of gas chromatography–vacuum ultraviolet spectroscopy coupling which has gained interest since the recent introduction of a commercial vacuum ultraviolet detector. Potentials and limitations, relevant theoretical considerations, recent advances and applications are explored

Advanced data pre−processing for Comprehensive two−dimensional Gas Chromatography with Vacuum Ultraviolet Spectroscopy detection

International audienceComprehensive two−dimensional Gas Chromatography with Vacuum Ultraviolet detection (GC×GC/VUV) results in sizable data for which noise and baseline drift ought to be corrected. As GC×GC/VUV signal is acquired from multiple channels, these pre−processing steps have to be applied to data from all channels while being robust and rather fast with respect to significant size of the GC×GC/VUV data. In this study, we describe advanced GC×GC/VUV data pre−processing techniques for noise and baseline correction that are not available in commercial softwares. Noise reduction was performed on both the spectral and the time dimension. For baseline correction, a morphological approach based on iterated convolutions and rectifier operations is proposed. On the spectral dimension, much less noisy and reliable spectra are obtained. From a quantitative point of view, mentioned pre−processing steps significantly improve signal to noise ratio for analyte detection and hence improve their limit of detection (circa 6 times in this study). These pre−processing methods were integrated into plug im! platform (https://www.plugim.fr/)

Quantitative analysis of hydrocarbons in gas oils by two-dimensional comprehensive gas chromatography with vacuum ultraviolet detection.

International audienceGas oils (GOs) analysis is essential for production process control, in order to meet quality standards, to render these products safer for the environment, and to support research for alternative fuels. GOs quantitative analysis can be commonly achieved by employing two-dimensional comprehensive gas chromatography with flame ionization detection (GC × GC-FID) in combination with identification templates. However, in order to perform quantification for families which coelute in GC × GC analysis (e.g., naphthenes/olefins or polynaphthenes/monoaromatics), prefractionation of gas oil before GC × GC analysis is necessary. Recent introduction of the vacuum ultraviolet (VUV) detector has offered new possibilities in GOs analysis, as this detector can discern between the majority of hydrocarbon families thus possibly rendering the gas oil prefractionation unnecessary. Additionally, it can perform quantification according to Beer–Lambert’s law provided that VUV relative response factors (RRFs) are known. The purpose of this work is to report, for the first time, VUV RRFs for numerous hydrocarbons in GOs (∼160) according to their family and their carbon number, permitting to perform their direct quantification without the necessity of GO prefractionation. VUV RRFs were measured by using a GC × GC-VUV/FID dual detection setup in which FID was employed as a quantitative reference. In order to obtain VUV RRFs representative for any gas oil, a set of 14 GOs with different origins was employed. Both VUV RRFs averaged in the 125–240 nm range and spectral VUV RRFs (reference spectra) were obtained. It was demonstrated that VUV RRFs were similar between employed GOs allowing their universal use. Obtained RRFs were used to perform hydrocarbons quantification for a light cycle oil (LCO) by GC × GC-VUV, with olefins and naphthenes being quantified through spectral decomposition. Good comparability with results obtained by prefractionation was observed demonstrating the great interest of the GC × GC-VUV approach for the detailed and rapid analysis of hydrocarbons in gas oils

Effect of H 2 S on the mechanisms of naphthene ring opening and isomerization over Ir/NaY: A comparative study of decalin, perhydroindan and butylcyclohexane hydroconversions

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