A Novel Desulfurization Process for Fuel Oils Based on the Formation and Subsequent Precipitation of S-Alkylsulfonium Salts. 3. Denitrogenation Behavior of Light Oil Feedstocks

Abstract

The denitrogenation behavior of light oils, when occurring during a novel desulfurization process based on alkylation and a subsequent precipitation method, using the alkylating agents (CH3I and AgBF4), has been investigated. Denitrogenation results, obtained for three model nitrogen compounds (aniline, indole, and carbazole) in a xylene solution, were compared with the results for three light oils, of differing nitrogen, sulfur, and aromatic concentration. The nitrogen compounds in the light oils were found to be N-methylated by reaction with the alkylating agents, such that they were removed as precipitates under moderate conditions. By use of this process, the nitrogen contents of all of the light oils were reduced successfully to less than 20% of the corresponding feed concentration, thus demonstrating that the present process is satisfactory for the simultaneous denitrogenation of light oils combined with desulfurization. Although the denitrogenation of aniline and indole compounds from the light oils proceeded effectively, carbazoles and especially those having a large carbon number of alkyl substituents were difficult to be denitrogenized by the present process. This is because the electron density on the nitrogen atom decreases with increasing carbon number of the alkyl substituents on the molecule of the carbazoles.

Understanding Shale Oil Hydrotreatment with Composition Analysis Using Positive-Ion Mode Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

“…Their possible core structures are indole, carbazole, acridine, and their derivatives (see Figure e). Literature studies show that indole, carbazole, and their derivatives are difficult to be removed by HDN for their basicity lower than basic nitrogen species, such as quinoline. − Although acridine belongs to basic nitrogen species, hydrodeoxygenation (HDO) of N 1 O 1 (DBE of 12) may contribute to its high content in hydrotreated shale oil.…”

Nitrogen Removal from Oil: A Review

“…Nitrogen compounds are then precipitated as N-methylated tetrafluoroborates. Denitrogenation of light oils and vacuum gas oil was successfully achieved by this method (Table ), and it was accompanied by alkylation of sulfur and aromatics. , Studies with model compounds revealed that aniline, pyridine, quinoline, and carbazole were removed as precipitates of their corresponding methylated products, while indole and pyrrole were removed as insoluble polymerized materials. In addition, denitrogenation of basic nitrogen compounds and compounds containing alkyl substituents was more effective than that of nonbasic nitrogen compounds.…”

“…In addition, denitrogenation of basic nitrogen compounds and compounds containing alkyl substituents was more effective than that of nonbasic nitrogen compounds. This is because denitrogenation by this method depends on the electron density on the nitrogen atom, which is increased by alkyl substituents …”

“…N-Alkylation. Alkylation as a reaction has been investigated for denitrogenation of light oils 131 and vacuum gas oil. 132 The nitrogen compounds are methylated and then removed by precipitation.…”

“…This is because denitrogenation by this method depends on the electron density on the nitrogen atom, which is increased by alkyl substituents. 131 Bromoacetic acid (CH 2 BrCOOH) was also explored as a reagent for N-alkylation. Basic nitrogen compounds could be removed from crude oil by an alkylation denitrogenation method with bromoacetic acid.…”