Unravelling Molecular Composition of Products from Cobalt Catalysed Fischer-Tropsch Reaction by Comprehensive Gas Chromatography: Methodology and Application

Abstract

Résumé -Élucider la composition moléculaire des produits obtenus par la réaction de FischerTropsch catalysée par le cobalt par chromatographie gazeuse bidimensionnelle : méthodologie et application -De nouvelles approches analytiques combinant différents types de méthodes chromatographiques telles que les chromatographies en phase gazeuse de basse résolution, de haute résolution et bi-dimensionnelle ont été mises en oeuvre pour améliorer la caractérisation moléculaire des produits de synthèse Fischer-Tropsch (FT). Particulièrement, la composition détaillée des oléfines et des oxygénés a été obtenue grâce à la résolution améliorée et la grande capacité de séparation fournies par la GC-2D. Une telle description de la totalité des effluents de la réaction de Fischer-Tropsch apporte des informations additionnelles qui peuvent être mises à profit pour améliorer la connaissance de la réaction. Ainsi, nous avons montré que les trois familles de produits (paraffines, oléfines et oxygénés) présentent leur propre distribution Anderson Schulz Flory (ASF). En dehors du méthane et de l'éthylène, la sélectivité de la réaction de Fischer-Tropsch a pu être décrite par des coefficients de croissance de chaîne spécifiques à chaque famille. Ces résultats peuvent permettent une meilleure compréhension du mécanisme réactionnel. Une hypothèse est proposée. Abstract -Unravelling Molecular Composition of Products from Cobalt Catalysed Fischer-Tropsch

Advanced fundamental modeling of the kinetics of Fischer–Tropsch synthesis

“…That evidently leads to three curves in a Schulz-Flory plot, as already shown, for example, by Bertoncini et al 43 Table 3 shows that the olefin readsorption was considered in the kinetic modeling, but Table 6, listing the values derived from the experimental data, reveals that the value of the single event frequency factor of olefin readsorption is very low compared to that of olefin formation. Figure 13 compares the rate coefficients and the rates of formation and readsorption of olefins.…”

Inhibiting effect of decanoic acid and its by-products on the transformation of n-hexadecane over a Pt/SiO2-Al2O3 catalyst

“…The Fischer-Tropsch waxes systematically contain oxygenated compounds [10]. Their detailed composition has also been carried out very recently using gas chromatography in two dimensions [10,15]. These compounds are the aliphatic alcohols, carboxylic acids, aldehydes and esters, with a typical overall weight content of a few percent [10].…”

“…Decanoic acid was chosen as a model molecule representative of the carboxylic acid and n-hexadecane as the model molecule representative of the long chain paraffin as reported in literature [15,22]. The decanoic acid and its oxygenated by-products (CO, CO 2 ) impact on the hydroconversion of n-hexadecane performed over a con- ventional Pt/silicated alumina hydrocracking catalyst was studied under typical hydrocracking conditions.…”

Quantitative carbon distribution analysis of hydrocarbons, alcohols and carboxylic acids in a Fischer-Tropsch product from a Co/TiO2 catalyst during gas phase pilot plant operation

“…Comprehensive two-dimensional chromatography (GCxGC) coupled with time-of-flight mass spectrometry has been used in many cases for the identification of trace components in FT products and sometimes quantification has also been given. Such examples show (i) the analysis of products from Co/Al 2 O 3 operated under slurry conditions demonstrating an Anderson-Schulz-Flory (ASF) plot of carbon distribution over the C 1 to C 20 range for paraffins, olefins and oxygenates (Bertoncini et al 2009); (ii) the quantification of 1-alcohols in liquid hydrocarbon from a Co/Al 2 O 3 catalyst (Silva et al 2011); (iii) the quantification of paraffins, olefins, aromatics and oxygenates in samples of oil made during high-temperature FT experiments (van der Westhuizen et al 2010); (iv) the quantification of paraffins, olefins, alcohols, aldehydes and carboxylic acids up to C 15 produced from a precipitated Fe catalyst in slurry operation (Grobler et al 2009); and (v) the simultaneous identification and quantification of alcohols and carboxylic acids, as their trimethylsilyl derivatives, in FT syn-crude and distilled products (Fernandes et al 2015). The use of supercritical fluid chromatography coupled with twodimensional gas chromatography-mass spectrometry for the separation and identification of saturated, unsaturated, aromatic and oxygenate species in hydrocarbon samples derived from a high-temperature FT reaction has also been demonstrated (Potgieter et al 2013), clearly indicating the diversity of class and number of organic compounds present in such products.…”

“…Additionally, aldehydes, ketones and ester can also be formed. There are numerous papers describing methods for analysis of the gas phase (Bertoncini et al 2009;Grobler et al 2009;Seomoon et al 2013;Pei et al 2015), aqueous phase (Anderson and White, 1994;Grobler et al 2009;Pei et al 2015;Ma et al 2019), liquid hydrocarbons and wax products (Bertoncini et al 2009;Grobler et al 2009;van der Westhuizen et al 2010;Silva et al 2011;Fernandes et al 2015;Pei et al 2015;Shafer et al 2019) but in general the quantitative distribution analysis of alcohols and carboxylic acids versus carbon chain length is difficult to achieve when these compounds are present at the low levels normally expected in a cobalt-catalysed FT product. This can be due to (i) the sensitivity of analytical methods at low oxygenate concentrations, (ii) the challenge of keeping high boiling point compounds in the vapour phase and then chromatographically separating a complex mixture of components when using on-line gas chromatography (GC) and (iii) the difficulty in obtaining an acceptable mass balance of all product phases when combining on-line and off-line analyses (Xiao et al 2017;Yang et al 2017).…”