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Nitrogen is a significant element that constitutes ambient organic aerosol. Individual N-containing organic molecules are known to have both natural and anthropogenic sources and implicated in a wide-ranging health and environmental effects. Yet, unlike carbon (C), the total quantity of aerosol organic nitrogen (ON) remains largely unquantified, hindering a quantitative understanding of their major sources and impacts. Here, for the first time, aerosol ON is quantified in hundreds of aerosol filter samples collected from sites of varying urban influence in China using our recently developed method that permits simple, and yet sensitive, simultaneous detection of inorganic and organic nitrogen. Annual average ON concentration was in the range of 0.4-1.4 μg N m-3, representing 17-31% of aerosol total nitrogen. Monte Carlo simulations constrained by paired ON and organic carbon (OC) measurements suggest N-containing organic molecules contributed typically 37-50%, with a 95% confidence interval of [12%, 94%], to ambient organic aerosols. Source apportionment analysis reveals that biomass burning and secondary formation are dominant ON sources, accounting for 21-24% and ~30% of ON, respectively. Primary biological aerosol is also a significant source of ON (7-18%), with its contribution more prominent in non-urban atmospheres. The revelation of the large presence of nitrogenous molecules in atmospheric aerosols implies their role in carbon chemistry has likely been under-appreciated in the past. This new compositional insight, we anticipate, would bring forth a breakthrough in our ability to describe and model organic aerosols and to rethink the focus of studying and modeling OA.

The collision cross-section (CCS) values of ions determined by ion mobility-mass spectrometry (IM-MS) can be used to deduce the shape and size of the ions. For each compound, as well as its isomer or tautomer, a unique arrival time peak was obtained in extracted ion mobility (EIM) spectra, which corresponded to a specific CCS value. However, the generation of solvated ions by electrospray ionization (ESI) increases the number of mobility peaks, which makes the EIM spectra difficult to interpret. In this study, solvent clusters formed by acetonitrile and methanol around 1,8-naphthalic anhydride (1,8-NA) cations ([C

Molecular characterization of sulfur-containing compounds in petroleum is of great significance for not only the oil refining but also geochemical application. One practical approach for the charac...

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.

Contrast experiments of fluid catalytic cracking (FCC) were conducted in a technical pilot scale riser FCC apparatus. The results showed that the use of a low-temperature regenerated catalyst and high ratio of catalyst to oil (CTO) improved the initial contact between the catalyst and feedstock. Thermal cracking was inhibited and catalytic cracking was promoted in the FCC riser, which were favorable for increasing the conversion and generation of desirable products. A modified FCC process was proposed and numerical simulation were used in the selection of the equipment structure for mixing cold and hot regenerated-catalyst streams to achieve optimal contact between the catalyst and the feedstock. A commercial unit was revamped based on the experimental results to test the modified FCC process. Results from industrial practice showed that product distributions under optimal conditions of low-temperature contact and high ratio of catalyst to oil in the modified FCC process were superior to those from routin...

The influences of the boiling point and fractional composition of coker gas oil (CGO) on the fluid catalytic cracking performance were investigated. Nitrogen compounds and condensed aromatics in CGO were identified by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and gas chromatography-mass spectrometry (GC-MS), respectively, and their effects were studied systematically. The result shows that the catalytic cracking performance of CGO does not correspond to the boiling point of narrow fractions but rather to the basic nitrogen compounds and condensed aromatics that have high molecular weight and/or high condensation tendencies adversely. On the basis of these results, a divisional fluid catalytic cracking (DFCC) process was proposed where a separate reaction zone was added to reduce the contents and effects of the adverse compounds in CGO during catalytic cracking. The simulation experiments of the DFCC process show that improved conversion and enhance...

The coking phenomenon of coker gas oil (CGO) feedstock during fluid catalytic cracking (FCC) using a commercial equilibrium catalyst was investigated. Different types of coke formed via coker gas oil (CGO) catalytic cracking were also analyzed. The coke formed was composed of adsorption coke (Cad), dehydrogenation condensation coke (Cdh), and hydrogen transfer coke (Cht). Cad, derived from nitrogen compounds, adsorbed on the acid sites of the catalyst and accounted for 37 wt % of the total coking content under conventional reaction conditions. Cdh was formed by the dehydrogenation condensation of polycyclic aromatic hydrocarbons and accounted for about 43 wt % of the total coking content. The coking content of Cht was greatly determined by the degree of the secondary reaction. Coke selectivity can be decreased and Cht yield can be controlled by simultaneously increasing the reaction temperature and shortening the reaction time.