Speciation of Basic Nitrogen Compounds in Gas Oils and Vacuum Gas Oils by Derivatization with BF 3 prior to NMR Analysis
Résumé
Nitrogen-containing compounds, present in gas oils (GO) or vacuum gas oils (VGO) cuts, affect many of the important petroleum processes such as hydrocracking and hydrotreating due to their nucleophilic character. Thus, hydrodenitrogenation catalysts and processes (HDN) are well studied and detailed knowledge of the type and concentration of N-compounds present in hydrocarbons cuts is required to optimize these HDN processes. Basic Nitrogen compounds, which can inhibit the acidic sites of the catalyst, are mainly pyridine derivatives (6-membered-ring nitrogen compounds) and despite the use of very resolutive methods, their characterization especially in VGO is still limited. In this work, we are presenting a very original and innovative analytical methodology to characterize the basic nitrogen species which are present in hydrocarbons cuts. This methodology is based on a chemical derivatization of the nitrogen compounds by the Lewis acid BF3 prior to a NMR characterization. Indeed, once derivatized, nitrogen species form BF3-adduct which have specific responses in 19F NMR analysis. By exploiting the data of 19F, 1H, 1H-19F HMBC and 19F DOSY NMR experiments of derivatized hydrocarbons cuts, it is possible to have very specific information about the initial nitrogen species and especially about the close environment of the nitrogen atom. We have demonstrate that this information is independent from the size of the molecule and thus, the methodology is applicable to many hydrocarbons cuts. This is particularly interesting on VGO cuts since, to our knowledge, no analytical method is able to reach such detail in chemical functions determination.
Domaines
Physique [physics]
Origine : Fichiers produits par l'(les) auteur(s)
