N1 Class Species Research Articles

Characterization of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particles (PM2.5) in the North China Plain using positive-ion atmospheric pressure photoionization (APPI) coupled with fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS)

Many aromatic compounds, including 16 types of U.S. EPA priority PAHs, exist in substituted or unsubstituted forms and have high toxicities. Aromatic compounds in aerosols collected in the North China Plain (NCP) were characterized by GC-MS and atmospheric pressure photoionization (APPI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). The concentrations of the 16 types of PAHs in the collected samples ranged from 277.0 to 876.8 ng/m3, which were higher than those collected in other regions and countries. Previous studies reported that only 27 wt% of aromatic compounds could be eluted using the GC system and demonstrated that APPI FT-ICR MS is a useful method for identifying large-molecular aromatics. In this study, two samples collected from the NCP were successfully characterized by APPI FT-ICR MS. In the APPI + mode, 231 and 228 CH formulas (containing only C and H and having a double bond equivalent (DBE) of 4 or greater) were identified, accounting for 10% of the numerical fraction and more than 40% of the intensity fraction. The FT-ICR data revealed that condensed PAHs with 6–8 aromatic rings had relatively high abundances and that a series of PAH homologs (alkylated PAHs) with identical DBE values ranging from 4 to 30 were present. Furthermore, heteroatom groups were also identified as significant components of the aromatic fractions. The O1, O2, N1, NO2, and S1 class species with DBE values of 3–34 and carbon numbers of 11–42 were identified by APPI FT-ICR MS. The heteroatom PAHs had DBE values and carbon number distributions similar to regular PAHs. The aromatic fractions determined in this work provide useful data for future quantitative analyses of aromatic compounds with high toxicities and our findings will help improve the current understanding of PAH compositions in the northern China. However, further research is needed to determine the abundances and toxicities of various apparent or substituted PAHs outside of the 16 types identified by the U.S. EPA as priority PAH compounds, which have been extensively researched.

Distribution of nitrogen and oxygen compounds in shale oil distillates and their catalytic cracking performance

The positive- and negative-ion electrospray ionization (ESI) coupled with Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) was employed to identify the chemical composition of heteroatomic compounds in four distillates of Fushun shale oil, and their catalytic cracking performance was investigated. There are nine classes of basic nitrogen compounds (BNCs) and eleven classes of non-basic heteroatomic compounds (NBHCs) in the different distillates. The dominant BNCs are mainly basic N1 class species. The dominant NBHCs are mainly acidic O2 and O1 class species in the 300–350 °C, 350–400 °C, and 400–450 °C distillates, while the neutral N1, N1O1 and N2 compounds become relatively abundant in the > 450 °C fraction. The basic N1 compounds and acidic O1 and O2 compounds are separated into different distillates by the degree of alkylation (different carbon number) but not by aromaticity (different double-bond equivalent values). The basic N1O1 and N2 class species and neutral N1 and N2 class species are separated into different distillates by the degrees of both alkylation and aromaticity. After the catalytic cracking of Fushun shale oil, the classes of BNCs in the liquid products remain unchanged, while the classes and relative abundances of NBHCs vary significantly.

Occurrence forms and molecular structural characteristics of the organic nitrogen in lignite

The occurrence forms of organic nitrogen in Xianfeng lignite (XL), Xiaolongtan lignite (XLT) and Shengli lignite (SL) as well as their extraction residues were characterized by X-ray photoelectron spectroscopy (XPS). The results show that the content distributions of organic nitrogen in the three extraction residues are different, but all are mainly dominated by pyrrolic nitrogen. The NaOH-catalyzed supercritical methanolysis of lignite extraction residues at 300°C was then investigated, which indicates that the yields of petroleum ether soluble portions from supercritical methanolysis of extraction residues derived from XL, XLT and SL are 46.0%, 43.8%, and 47.6%, respectively. The characterization of nitrogen-containing compounds (NCCs) in petroleum ether soluble portions by Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS) indicates that NCCs are mainly composed of N1, N1O1-N1O5, N2, N2O1-N2O4, N3O2 and N5O2-N5O4 class species. The molecular structural characteristics of NCCs were speculated according to the distributions of double bond equivalent values and carbon numbers, which shows that most of NCCs contain oxygen-functional groups like hydroxyl and carboxyl groups, and the nitrogen atoms are mainly present in aromatic structures (mainly 1–3 aromatic rings) in the forms of pyrrolic, pyridinic and amino groups. The cleavage of C-O bridged bonds in lignite is an important pathway for producing NCCs.

Characterization of heteroatom class species in asphaltenes from medium/low temperature coal tar

ABSTRACT The classes, structures, and distributions of heteroatom compounds in asphaltenes from medium/low temperature coal tar (LCT) were characterized by using positive-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The NX, S1OX, S2OX, SX, S1N1OX, OX, N1OX, N2OX, N3OX, S1NX, and S2NX class species were identified in LCT asphaltenes. The O1 class species were the most abundant species of the total heteroatom class species, of which structures were likely furan derivatives or ketone oxides. There were mainly N1 class species of the basic nitrides, and the structures were likely pyridine derivatives with DBE of 16 − 25. The S1 class species were predominant of the sulfur-containing compounds, of which structures were likely thiophene derivatives or thioether derivatives with low degree of condensation. Nitrogen oxides of LCT asphaltenes mainly belong to N1O1 class species composed of 4 − 8 aromatic rings with a keto group and a pyridine ring. The sulfur oxides were mainly S1O1 class species consisted of 5 − 8 aromatic rings with a thiophene sulfoxide ring. The oxygen and sulfur heteroatoms in LCT were mainly concentrated in asphaltenes, which were mainly high-condensation compounds. The N1 class species in LCT asphaltenes have a higher degree of condensation, which occupied only smaller proportion in LCT.

Molecular characterization of polar heteroatom species in oilsands bitumen-derived vacuum residue fractions by Fourier transform ion cyclotron resonance mass spectrometry

A Canadian in situ oilsands bitumen-derived vacuum residue (VR) was subjected to supercritical fluid extraction and fractionation (SFEF) into 13 extractable fractions and an unextractable end-cut and characterized by positive- and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results of negative-ion ESI FT-ICR MS showed that the N1 class species was the most abundant and the multifunctional group compounds, such as N1O1, N1O2, N1S1, N1S2, and N2 class species became abundant as the SFEF fraction became heavier. In positive-ion ESI mode, the relative abundance of N1 class species decreased gradually in the heavy SFEF fractions while that of multifunctional group compounds increased. The relative abundance of N4V1O1 increased dramatically in heavy fractions and the end-cut. The distributions of polar heteroatom species of VR derived from oilsands bitumen were similar with those of VR derived from the Venezuela Orinoco extra heavy oil.

Compositional Characterization of Expelled and Residual Oils in the Source Rocks from Oil Generation-Expulsion Thermal Simulation Experiments.

Petroleum generation–expulsion thermal simulation experiments on a low-maturity type I source rock were carried out. The composition of hydrocarbons and heteroatom-containing compounds in both expelled and residual oils was characterized by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and gas chromatography-mass spectrometry. A thorough analysis of fractionation effects was presented between expelled and residual oils. The oil composition strongly depended on the pyrolysis temperature. A significant difference in the molecular composition was found between expelled and residual oils at various pyrolysis temperatures. The difference in maturity for expelled and residual oils could be revealed clearly by the difference in the molecular composition of heteroatom-containing compounds. Carboxylic acids in the residual oil cracked quickly with the pyrolysis temperature above 350 °C (% Ro = 1.0) but part of them would survive if they were expelled out of the source rock timely. The variations between the relative abundance of oxygen compounds and nitrogen compounds indicated that the thermostability of oxygen-containing nitrogen compounds was lower than that of neutral nitrogen compounds. The variation trends in double bond equivalents and carbon number distributions of O1, O2, and N1 class species were similar. The aromaticity of heteroatom-containing polar species increased with maturity.

Geochemical assessment of oils from the Mero Field, Santos Basin, Brazil

Three crude oils recovered from three different wells of the Mero Field in the pre-salt of the Santos Basin were selected for detailed geochemical analysis. The samples were analyzed using a 7.2 T LTQ FT-ICR MS instrument by negative electrospray ionization (–ESI), focusing on the polar compounds, i.e., nitrogen-, sulfur-, and oxygen-containing compounds (NSO). Additionally, a combination of traditional geochemical methods including GC-FID, GC-MS, and carbon isotopic composition (whole oil and n-alkanes) were used to assess the samples. Through this work, it was demonstrated that –ESI FT-ICR MS is a reliable method for assessing crude oil composition and providing information about the origin and thermal maturity of the samples. Results showed that the dominant heteroatom classes are N1, O2, N1O1, and O1. Due to the similarity of double bound equivalent (DBE), which means number of unsaturation present in an organic molecule, and carbon number distributions for the N1 class species it is possible to suggest that Mero's filling history had an oil charge representing the peak of the oil window (0.7–0.9 %Ro) and that the oils were generated by a source rock deposited in a lacustrine environment.

Influence of Resins on Crystallization and Gelation of Waxy Oils

In the present work, we employed model oil systems to examine the effects of resins upon the gelation and crystallization of waxy oils. Two types of waxes were explored, namely, n-tetracosane (wax A) and a commercial wax with a melting temperature of 52–54 °C (wax B). The resins were extracted from a deoiled asphalt from Venezuelan residue by the saturates, aromatics, resins, and asphaltenes fractionation method. The results from negative-ion electrospray ionization Fourier transform ion cyclotron resonance-mass spectrometry suggest that resins consist of one to four fused benzenes rings or one to two fused naphthalene rings constructed by N1, N1O1, N1S1, N1O1S1, N1O2, O1, O1S1, and O2 class species containing stacking aromatic rings. For both types of waxes examined, adding resins to the waxy oils suppresses wax precipitation and modifies the morphology of wax crystals, which collectively leads to lower gelation temperature and lower yield stress. Up to 7 °C of reduction in gelation temperature, 60% of r...

Combined Hydrotreating and Fluid Catalytic Cracking Processing for the Conversion of Inferior Coker Gas Oil: Effect on Nitrogen Compounds and Condensed Aromatics

Inferior coker gas oil (ICGO) derived from Venezuelan vacuum residue delayed coking is difficult to process using fluid catalytic cracking (FCC) or hydrocracking (HDC). The high content of nitrogen and condensed aromatics leads to major coking and readily deactivates the acid catalyst. In this work, a sequence of hydrotreating (HDT) and FCC processing is used to effectively convert ICGO to a high-value light oil product. The results show a higher overall conversion and a significant increase in the yield of gasoline compared to FCC processing. Molecular level characterization of the nitrogen compounds and condensed aromatics before and after HDT confirms that the nitrogen content and the 2+-ring aromatic content decreased, whereas the single-ring aromatics increased. The nitrogen compounds were mainly N1, N1O1, N1O2, and N1S1 class species in basic nitrogen and N1, N1O1, N1O2, N2, and N2O1 class species in non-basic nitrogen. Moreover, the double bond equivalent of these species shifted to lower values. T...

Transformation of nitrogen-containing compounds in atmospheric residue by hydrotreating

Atmospheric residue from Saudi Arabia light crude oil was subjected to the hydrotreating process in a continuous fixed-bed reactor with hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) catalysts. The detailed molecular composition of the polar heteroatom species in the feedstock and products was determined by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) combined with other analytical methods. The ESI FT-ICR MS analysis indicates that the N1 class species have the highest relative abundance. In the hydrotreating process, small neutral N1 class species with high aromaticity and short side chains showed the highest relative abundance and were defined as easily removable compounds. High aromaticity and small molecule basic N1 compounds exhibited higher catalytic activity towards hydrogenation. The N1S1 class species were converted to the N1 class species, or even hydrocarbons, by the preferential removal of the sulfur atoms. Most of the N1O1 class species were difficult to remove, because of their stable chemical structure.

The transformation of basic nitrogen compounds in coker gas oil during catalytic cracking

ABSTRACTTwo narrow fractions distilled from Liaohe coker gas oil were used for the research. The distribution of basic nitrogen compounds in feedstocks and their liquid products were characterized by ESI FT-ICR MS. The results showed that N1 class species were the most predominant in both feedstocks and products. The catalytic cracking progress reduced the relative abundance of all class species, except for the N1 and N1S1 class species. Although the N1 class species had longer side chains and higher condensation in the heavier feedstock, the distribution of N1 class species became similar in the two liquid products.

Structure and Composition Changes of Nitrogen Compounds during the Catalytic Cracking Process and Their Deactivating Effect on Catalysts

The comprehensive structure and composition changes of the nitrogen compounds during the catalytic cracking processes of coker gas oil and vacuum residue are investigated using electrospray ionization combined with Fourier transform ion cyclotron resonance mass spectrometry. These experiments were conducted over different cracking materials under the reaction temperatures of 500/520 °C, the weight hourly space velocity of 18 h–1, and the catalyst/oil ratio of 5. The results show that the diffusion resistance in the micropores of the zeolite is the key factor affecting the interaction between the nitrogen compounds and the acid sites. The basic N1 and N2 class species with double bond equivalence (DBE) values smaller than 10 can easily diffuse into the micropores of the zeolite and are preferentially adsorbed onto the acid sites. These adsorbed nitrogen compounds generally conduct condensation reactions and hydrogen transfer reactions to form coke deposited on the cracking catalysts. The basic N1 and N2 cl...

Stepwise structural characterization of hydrocarbon compounds and polar components during atmospheric residue hydrotreatment

A continuous fixed-bed micro-reactor was adopted to conduct a hydrotreatment experiment on the atmospheric residue obtained from Saudi Arabia. The feedstock and hydrotreated liquid products were subjected to high-temperature gas chromatography to undertake simulated distillation analysis, and to gel permeation chromatography to carry out molecular size investigations. 1H NMR and element analysis were carried out to derive structural parameters. Positive- and negative-ion electrospray ionization Fourier transform-ion cyclotron resonance mass spectrometry was combined with other analytical means to explore the stepwise structural characterization of polar components (especially the nitrogen (N)-containing compounds) when passing through beds filled with different catalysts during the hydrotreatment process. According to the different numbers of nitrogen, oxygen, and sulfur atoms, N-containing compounds could be divided into Nx, NxOy, and NxSy class species. The results indicated that hydrotreatment process led to more concentrated distribution of hydrocarbon molecules in the products. The heteroatoms, which accounted for the largest proportion in the feedstock and liquid products, were N1 class species. During the hydrotreatment process, the relative abundance of N1, N2, N1O1, N1O2, and N1S1 class species changed significantly with the progress of hydrotreatment process, however the conversion regularity varied among heteroatomic compounds.

Transformation of Nitrogen Compounds through Hydrotreatment of Saudi Arabia Atmospheric Residue and Supercritical Fluid Extraction Subfractions

Atmospheric residue (AR) from Saudi Arabia (SZAR) was subjected to supercritical fluid extraction fractionation (SFEF) and four extractable subfractions (SFEF-1–4) and an unextractable end-cut were obtained. SZAR and SFEF-1–4 were subjected to hydrotreatment (HDT) in a continuous mini fixed-bed reactor. Three commercial catalysts were used to remove the impurity in the feedstock. The composition and structural transformation of nitrogen (N)-containing compounds were investigated. Electrospray ionization (ESI) Fourier transform–ion cyclotron resonance mass spectrometry (FT-ICR MS) was used for molecular characterization of N-containing compounds of SZAR, extractable SFEF subfractions, and HDT products. Results showed that N1 class species with high aromaticity and/or low carbon number exhibited higher catalytic hydrogenation reactivity. N1 class species with lower aromaticity were removed regardless of chain length.

Retardation effect of nitrogen compounds and condensed aromatics on shale oil catalytic cracking processing and their characterization.

Untreated shale oil, shale oil treated with HCl aqueous solution and shale oil treated with HCl and furfural were used to do comparative experiments in fixed bed reactors. Nitrogen compounds and condensed aromatics extracted by HCl and furfural were characterized by electrospray ionization Fourier transform cyclotron resonance mass spectrometry and gas chromatography and mass spectrometry, respectively. Compared with untreated shale oil, the conversion and yield of liquid products increased considerably after removing basic nitrogen compounds by HCl extraction. Furthermore, after removing nitrogen compounds and condensed aromatics by both HCl and furfural, the conversion and yield of liquid products further increased. In addition, N1 class species are predominant in both basic and non-basic nitrogen compounds, and they are probably indole, carbazole, cycloalkyl-carbazole, pyridine and cycloalkyl-pyridine. As for the condensed aromatics, most of them possess aromatic rings with two to three rings and zero to four carbon atom.

Molecular Characterization of Dissolved Organic Matter and Its Subfractions in Refinery Process Water by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Dissolved organic matter (DOM) in oil refinery process water was fractionated by XAD-8 resin techniques into four subfractions: hydrophobic acid (HOA), hydrophobic base (HOB), hydrophobic neutral (HON), and hydrophilic substance (HIS) fractions. Negative and positive electrospray ion (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to characterize the composition of DOM and its subfractions. Compounds with multi-oxygen atoms were found to be predominant in DOM by either negative or positive ESI analysis, which are similar in composition to most other treated water samples. The DOM in the HOA fraction had a similar molecular composition to that of raw process water by negative ESI analysis. The DOM in the HOB fraction had a low molecular weight (MW) when analyzed by positive ESI, and basic nitrogen compounds, such as N1 class species, were found to be predominant. The DOM in the HON fraction was predominantly O2 class species. The DOM in the HIS fraction had a relative...

Characterization of basic heteroatom-containing organic compounds in liquefaction residue from Shenmu–Fugu subbituminous coal by positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Extracts of liquefaction residue from Shenmu–Fugu subbituminous coal (LRSFSBC) were obtained by sequential extraction with petroleum ether, methanol, and carbon disulfide. They were analyzed using a Fourier transform infrared (FTIR) spectrometer and a positive-ion (PI) electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI FT-ICR MS). In total, 65.37% of LRSFSBC was extracted. Aromatic C=C, C=O, and CO were identified in the extracts by FTIR analysis. Nitrogen, oxygen, and sulfur forms of LRSFSBC and the inextractable portion were characterized using X-ray photoelectron spectrometry. A series of basic N1, N2, N1O1, N1O2, N2S2, and N2O5S1 class species were identified in the extracts using ESI FT-ICR MS in PI mode. The ring plus double bond equivalents of the extracts ranges from 1–47, but is mainly below 23. In LRSFSBC some compounds are enwrapped into “capsules”, which are formed from different species associated with each other by hydrogen bonds, π–π interaction, and/or π–hydrogen bonds.

Characterization of nitrogen compounds in coker gas oil by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and Fourier transform infrared spectroscopy.

In this study, the classes and structures of nitrogen species in coker gas oil (CGO) are characterized by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) combined with Fourier transform infrared (FT-IR) spectroscopy. The results demonstrate that the m/z of basic and non-basic nitrogen compounds ranges from 180 to 560 and from 200 to 460, respectively. Six basic nitrogen compounds, N1 (a molecule contains one nitrogen atom, similarly hereinafter), N1O1, N1O1S1, N1O2, N1S1, and N2, are identified by their positive-ion mass spectra, and four non-basic nitrogen compounds, N1, N1O1, N1S1, and N2, are characterized by their negative-ion mass spectra. Among these nitrogen compounds, the N1 class species are the most predominant. Combined with the data of ESI FT-ICR MS and FT-IR, the basic N1 class species are likely pyridines, naphthenic pyridines, quinolines, and benzoquinolines. The most non-basic N1 class species are derivatives of benzocarbazole. The N2 class species are likely amphoteric molecules with pyridine and pyrrole core structures.

Polycyclic Aromatic Hydrocarbons (PAHs) in Ambient Aerosols from Beijing: Characterization of Low Volatile PAHs by Positive-Ion Atmospheric Pressure Photoionization (APPI) Coupled with Fourier Transform Ion Cyclotron Resonance

Aromatic fractions derived from aerosol samples were characterized by gas chromatography and mass spectrometry (GC-MS), high temperature simulated distillation (SIMDIS), and positive-ion atmospheric pressure photoionization (APPI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), respectively. It was found that about 27 wt % compounds in aromatic fractions could not be eluted from a GC column and some large molecule PAHs were neglected in GC-MS analysis. APPI FT-ICR MS was proven to be a powerful approach for characterizing the molecular composition of aromatics, especially for the large molecular species. An aromatic sample from Beijing urban aerosol was successfully characterized by APPI FT-ICR MS. Results showed that most abundant aromatic compounds in PM2.5 (particles with aerodynamic diameter ≤ 2.5 μm) were highly condensed hydrocarbons with 4-8 aromatic rings and their homologues with very short alkyl chains. Furthermore, heteroatom-containing hydrocarbons were found as the significant components of the aromatic fractions: O1, O2, N1, and S1 class species with 10-28 DBEs (double bond equivalents) and 14-38 carbon numbers were identified by APPI FT-ICR MS. The heteroatom PAHs had similar DBEs and carbon number distribution as regular PAHs.

Characterization of Basic Nitrogen-Containing Compounds in the Products of Lube Base Oil Processing by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

The distribution of basic nitrogen-containing compounds in three vacuum gas oils (VGOs) with different boiling ranges and their dewaxed oils from the lube base oil refining unit of a refinery were characterized by positive-ion electrospray ionization (ESI) Fourier transform-ion cyclotron resonance mass spectrometry (FTICR MS). It turned out that the composition of basic nitrogen compounds in the samples varied significantly in DBE and carbon number, and the dominant basic N-containing compounds in these oil samples were N1 class species. N1O1, N1O2, and N2 class species with much lower relative abundance were also identified. The composition of basic nitrogen compounds in VGOs and dewaxed VGOs were correlated with increased boiling point and varied in DBE and carbon numbers. The comparison of the analytical results between VGOs and dewaxed VGOs indicated that more basic N-containing compounds in VGO with low carbon number and small molecular weight tend to be removed by solvent refining in lube base oil processing.