Speciation of Basic Nitrogen Compounds in Gas Oils and Vacuum Gas Oils by Derivatization with BF3 Prior to NMR Analysis

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. Basic nitrogen compounds, which can inhibit the acidic sites of the catalysts, are mainly pyridine derivatives (6-membered-ring nitrogen compounds), and despite the use of highly resolutive methods, their characterization, especially in VGO, is still limited. Herein, we propose a new promising methodology, coupling the derivatization with BF3 of nonprotogenic nitrogen species and the use of NMR analysis. By crossing information from F-19, H-1, H-1-F-19 HMBC and F-19 DOSY, it is possible to determine the close environment of the nitrogen atom of the most nucleophilic nitrogen impurities in GO or in VGO cuts, independently of the sizes of the molecules. This approach allows the characterization and comparison of fingerprints of basic nitrogen impurities in charges or effluents.