Assessing Compositional Changes of Nitrogen Compounds during Hydrotreating of Typical Diesel Range Gas Oils Using a Novel Preconcentration Technique Coupled with Gas Chromatography and Atomic Emission Detection

Abstract

This paper describes the identification of nitrogen-containing compounds in a typical feed for diesel oil hydrotreating and how their individual concentrations change upon hydrotreating over a conventional sulfided CoMo/Al2O3 catalyst at commercial conditions. A preconcentration procedure followed by gas chromatographic (GC) analysis utilizing a highly sensitive nitrogen-specific detector (atomic emission detector) allowed the quantitative analysis of individual nitrogen-containing compounds (N compounds) at levels as low as 0.05 μg N/mL. The nitrogen compounds in the feed and products were identified by comparison with reference compounds as well as by high-resolution GC/mass spectrometric characterization. The relative reactivities of individual compounds in the diesel fuel feed were determined and the most refractory compounds identified. Alkyl-substituted carbazoles were found to be the major compound class in the feed and to be among the least reactive N compounds in the feed. Just as in the case of alkyldibenzothiophene hydrodesulfurization, carbazoles having alkyl substituents at positions adjacent to the nitrogen atom were found to be the least reactive N compounds in the diesel fuel feed for hydrodenitrogenation.

Denitrogenation of Transportation Fuels by Zeolites at Ambient Temperature and Pressure

“…[1][2][3][4][5] Denitrogenation and desulfurization are accomplished commercially by hydrotreating using catalysts in reactors under high temperature and pressure. Denitrogenation is considerably more difficult than desulfurization because the organonitrogen compounds are much less reactive than the organosulfur compounds.…”

“…Denitrogenation is considerably more difficult than desulfurization because the organonitrogen compounds are much less reactive than the organosulfur compounds. [1][2][3][4][5] In this work, we show that denitrogenation can be achieved effectively by using a zeolite sorbent that removes the nitrogen-containing molecules by selective adsorption at ambient temperature and pressure. The sorbent can remove nitrogen from a commercial diesel fuel that contains 83 parts per million by weight (ppmw) nitrogen to well below 0.1 ppmw nitrogen at a sorbent capacity of 43 cm 3 diesel per gram of sorbent.…”

“…[1][2][3] In addition, it becomes increasingly important to process heavy, low-quality stocks and the anticipated syncrudes, both are rich in highly refractory nitrogen compounds. Denitrogenation and desulfurization are coupled and are performed simultaneously in catalytic hydrotreating, which is an integral part of oil refining.…”

“…The reactivities of the organonitrogen compounds are significantly lower than that of the corresponding organosulfur compounds. [1][2][3][4][5] For example, the alkyl-substituted carbazoles (i.e., pyrrole sandwiched between two benzene rings, the most abundant nitrogen compounds) appear to react at rates about 1/10 as fast as those of alkyl-dibenzothiophenes of comparable structures. [2] Thus, it is considerably more difficult to remove organonitrogen compounds than organosulfur compounds.…”

Efficient concurrent removal of sulfur and nitrogen contents from complex oil mixtures by using polyoxometalate-based composite materials

“…[1][2][3] The sulfur and nitrogen compounds are common contaminants in gasoline, diesel and jet fuels, which can lead to the formation of SOx and NOx exhaust gases with known environmental consequences (e.g. acid rain etc.).…”