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•Obtainment of oils from pyrolysis of degraded silica-polyethyleneimine CO2sorbent.•Optimisation of GC–MS for quantitation of pyrazine and five alkylpyrazines in PEI oils.•Comparison with HPLC-DAD showed 63 % equivalence in individual concentration values.•GC–MS and HPLC-DAD methods provided equivalent values of total pyrazine pyrolysis yields.

Modern mass spectrometry techniques produce a wealth of spectral data, and although this is an advantage in terms of the richness of the information available, the volume and complexity of data can prevent a thorough interpretation to reach useful conclusions. Application of molecular formula prediction (MFP) to produce annotated lists of ions that have been filtered by their elemental composition and considering structural double bond equivalence are widely used on high resolving power mass spectrometry datasets. However, this has not been applied to secondary ion mass spectrometry data. Here, we apply this data interpretation approach to 3D OrbiSIMS datasets, testing it for a series of increasingly complex samples. In an organic on inorganic sample, we successfully annotated the organic contaminant overlayer separately from the substrate. In a more challenging purely organic human serum sample we filtered out both proteins and lipids based on elemental compositions, 226 different lipids were identified and validated using existing databases, and we assigned amino acid sequences of abundant serum proteins including albumin, fibronectin, and transferrin. Finally, we tested the approach on depth profile data from layered carbonaceous engine deposits and annotated previously unidentified lubricating oil species. Application of an unsupervised machine learning method on filtered ions after performing MFP from this sample uniquely separated depth profiles of species, which were not observed when performing the method on the entire dataset. Overall, the chemical filtering approach using MFP has great potential in enabling full interpretation of complex 3D OrbiSIMS datasets from a plethora of material types.

Internal combustion engines are used heavily in diverse applications worldwide. Achieving the most efficient operation is key to improving air quality as society moves to a decarbonized energy system. Insoluble deposits that form within internal combustion engine components including fuel injectors and filters negatively impact CO2and pollutant emissions. Understanding the composition, origins, and formation mechanisms of these complex materials will be key to their mitigation however, previous attempts only afforded nondiagnostic chemical assignments and limited knowledge toward this. Here, we uncover the identity and spatial distribution of molecular species from a gasoline direct injector, diesel injector, and filter deposit in situusing a new hyphenation of secondary ion mass spectrometry and the state-of-the-art Orbitrap mass analyzer (3D OrbiSIMS) and elemental analysis. Through a high mass resolving power and tandem MS we unambiguously uncovered the identity, distribution, and origin of species including alkylbenzyl sulfonates and provide evidence of deposit formation mechanisms including formation of longer chain sulfonates at the gasoline deposit’s surface as well as aromatization to form polycyclic aromatic hydrocarbons up to C66H20, which were prevalent in the lower depth of this deposit. Inorganic salts contributed significantly to the diesel injector deposit throughout its depth, suggesting contamination over multiple fueling cycles. Findings will enable several strategies to mitigate these insoluble materials such as implementing stricter worldwide fuel specifications, modifying additives with adverse reactivity, and synthesizing new fuel additives to solubilize deposits in the engine, thereby leading to less polluting vehicles.

Carbon (C) rich grassland soils may offer an additional C store, utilising tools such as biocharIdentification of practical, economic, social and legislative challenges for scaled adoption of biochar in grasslandsKey question: will enhanced C storage in grasslands soils cause a loss in additional ecosystem services?

In this study, pyrolysis experiments were conducted with a saturate-rich Tertiary source rock-derived oil from the South China Sea basin using a fixed-volume pressure vessel at temperatures from 350 to 425 °C for 24 h (0.92–1.85% Easy R0) to investigate pressure effects up to 900 bar on the generation and stable carbon isotopic fractionation of light hydrocarbons in the C6–C7range. The results demonstrate that the pressure retards oil cracking to light hydrocarbons, but the retardation depends on the thermal evolution. In the peak oil to early wet gas stage (350 and 373 °C, 0.92–1.15% Easy R0), the light hydrocarbon generation is low but it is still suppressed by increasing pressure. In the late stages of the wet gas window (390, 405, and 425 °C, 1.35–1.85% Easy R0), the light hydrocarbon generation is suppressed significantly from 200 to 470 bar, followed by promotion and promotion-suppression as pressure is increased up to 900 bar. Meanwhile, the distributions of branched alkanes, cycloalkanes, and aromatic hydrocarbons are pressure-dependent. The medium to high pressures result in increasing Mango K1values and toluene/n-C7ratios and decreasing n-C7/methylcyclohexane ratios, suggesting that pressure benefits the occurrence of cyclization and aromatization during oil cracking, probably involving bimolecular reaction pathways. Preferential aromatization and isomerization with increasing pressure lead to significant carbon isotopic fractionations of aromatic hydrocarbons and branched alkanes as up to 4‰ and 2‰, respectively. However, stable carbon isotopic compositions of cycloalkanes show almost no fractionation under pressurized cracking. Therefore, caution must be taken with respect to the application of light hydrocarbon-derived parameters in deep petroleum reservoirs usually at high temperatures and pressures. The carbon isotopes of branched alkanes and aromatic hydrocarbons could be potential measures to identify the pressure effects, while carbon isotopes of cycloalkanes could be an effective index for oil–oil/oil–source correlations.

In this study, a C9+fraction of saturate-rich Tertiary source rock-derived oil from the South China Sea basin was pyrolyzed in normal and supercritical water using a 25 mL vessel at a range of temperature from 350 to 425 °C for 24 h, to probe pressure effects up to 900 bar on gas yields and their stable carbon isotopic compositions during thermal cracking. Pressure generally retards oil cracking, as evidenced by reduced gas yields, but the trends depend upon the level of thermal evolution. In the early stages of cracking (350 and 373 °C, equivalent vitrinite reflectance of < ∼1.1% R0), the suppression effect increases with pressure from 200 to 900 bar, but it is most marked between 200 and 470 bar. At the later stages in the wet gas window (390, 405, and 425 °C, equivalent vitrinite reflectance of >1.3% R0), pressure still has a strong suppression effect from 200 to 470 bar, which then levels off or is reversed as the pressure is increased further to 750 and 900 bar. Interestingly, the stable carbon isotopic composition of the generated methane becomes enriched in 13C as the pressure increases from 200 to 900 bar. A maximum fractionation effect of ∼3‰ is observed over this pressure range. Due to pressure retardation, the isotopically heaviest methane signature does not coincide with the maximum gas yield, contrary to what might be expected. In contrast, pressure has little effect on ethane, propane, and butane carbon isotope ratios, which show a maximum variation of ∼1‰. The results suggest that the rates of methane-forming reactions affected by pressure control methane carbon isotope fractionation. Based on distinctive carbon isotope patterns of methane and wet gases from pressurized oil cracking, a conceptual model using “natural gas plot” is constructed to identify pressure effect on in situ oil cracking providing other factors excluded. The transition in going from dry conditions to normal and supercritical water does not have a significant effect on oil-cracking reactions as evidenced by gold bag hydrous and anhydrous pyrolysis results at the same temperatures as used in the pressure vessel.

Mg Ni mixed metal oxide photocathodes have been prepared by a mixed NiCl2/MgCl2sol–gel process. The MgO/NiO electrodes have been extensively characterized using physical and electrochemical methods. Dye-sensitized solar cells have been prepared from these films, and the higher concentrations of MgO improved the photovoltage of these devices; however, there was a notable drop in photocurrent with increasing Mg2+. Charge extraction and XPS experiments revealed that the cause of this was a positive shift in the energy of the valence band, which decreased the driving force for electron transfer from the NiO film to the dye and, therefore, the photocurrent. In addition, increasing concentrations of MgO increases the volume of pores between 0.500 and 0.050 μm, while reducing pore volumes in the mesopore range (less than 0.050 μm) and lowering BET surface area from approximately 41 down to 30 m2g–1. A MgO concentration of 5% was found to strike a balance between the increased photovoltage and decreased photocurrent, possessing a BET surface area of 35 m2g–1and a large pore volume in both the meso- and macropore range, which lead to a higher overall power conversion efficiency than NiO alone.

Fly-ash derived zeolites have recently -received great attention as cheaper adsorbents to remove heavy metals from water since they can be synthesized from a waste product. In this study, we evaluated the single- and multi-cation adsorption efficiencies of fly-ash derived NaP1 for the removal of zinc (Zn), copper (Cu) and lead (Pb). We also determined precipitation and leaching from NaP1 during the adsorption. Results showed that the uptake capacities for Zn (34 mg/g) and Pb (192 mg/g) were higher than other fly-ash derived NaP1 and adsorbents such as clinoptilolite and activated carbon. The Cu uptake was estimated ~ 14.6 mg/g. Pb2+> Cu2+> Zn2+is the order for the metal cation selectivity of NaP1. Langmuir adsorption isotherm and pseudo-second order kinetic model fitted best for all elements. The metal uptake occurred in 15 min. Diffusion of hydrated metals through microporous channels is the rate-determining step.

Chemical equilibrium studies have predicted that elemental sulfur (S0) could play a crucial role in mercury mobility in salt marsh sediments. This prompted us to consider the occurrence of S0 in conjunction with the degree of contamination in sediments of a coastal wetland (Pialassa Baiona, Italy) impacted by inputs of mercury derived from past industrial activity. The distribution of S0, total Hg, soluble sulfates and acid-soluble sulfides was studied in five sediment cores collected in two ponds of the lagoon. Sulfides, sulfates and S0 exhibited vertical profiles typical of salt marsh systems, with concentrations declining with depth. Mercury enrichment (2–23 mg kg−1) was detected at the surface strata where the highest concentrations of sulfides and S0 were found (up to 1.70 and 0.9 g kg−1, respectively). The effect of elevated levels of sulfides and elemental sulfur on the fate of mercury in the lagoon is discussed.

The aim of this investigation is to ascertain whether the mode of action of melamine in flexible polyurethane (PU) involves condensed phase chemistry in terms of promoting char formation. A combination of in situ1H NMR analysis, solid state 13C NMR characterization of chars prepared ex situ, and normal TGA and DSC has been employed. Solid state 13C NMR indicates that there is no major discernible difference in the structure of the dichloromethane‐insoluble chars prepared with and without melamine, the remaining polyol only accounting for 20–25 % of the total carbon at 350 °C, but still being quite mobile. However, in situ1H NMR provides definitive evidence that melamine acts in the condensed phase in terms of promoting the formation of rigid char which forms in more significant quantity by 450 °C. No increase in the residue yields is observed by TGA upon melamine addition, probably due to a combination of the small sample size and open sample holder in relation to the in situ1H NMR analysis which also involves fairly slow heating.© 2000 Society of Chemical Industry

Neuere Anwendungen von hochauflösenden Lösungs- und Festkörper-NMR-Techniken auf fossile Brennstoffe und ihre Derivate werden vorgestellt mit der Betonung auf Quantifizierung der aromatischen, aliphatischen und heteroaromatischen Gruppen. Methoden der Editierung von 13C-NMR-Spektren, die separate Spektren für C, CH, CH2 und CH3-Gruppen liefern, sind bei löslichen Materialien ausreichend quantitativ. Zweidimensionale Methoden helfen bei der Signalzuordnung der 1H- und 13C-NMR-Spektren von Destillaten. Zwar liegen einige Berichte über Untersuchungen von Heteroatomumgebungen mit 17O-, 14N-, 15N- und 33S-NMR vor, doch hat sich die Derivatisierung mit Gruppen, die einen empfindlicheren Kern als Meßsonde besitzen (1H, 13C, 10F, 29Si), als erfolgreich zur Abschätzung der Konzentration acider OH-, NH- und SH-Gruppen in aus Kohle entstandenen Flüssigkeiten und in Erdölrückständen erwiesen. Die Analyse von Kohle und ähnlichen Materialien mit Hilfe der Festkörper-13C-NMR-Spektroskopie ist oft nur halbquantitativ, da nicht alle Kohlenstoffatome mit der Cross-Polarisations-Technik beobachtet werden.

The characteristics of the ligands in inclusion complexes formed from stearic, palmitic, oleic, linoleic, linolenic and docosahexaenoic acids, glycerol monooleate (GMO), glycerol monopalmitate (GMP) and lysophosphatidylcholine (LPC) have been studied by13C NMR in dry and hydrated forms of the complexes, with13C labels being used for the car☐yl and C-1(3) glycerol carbons in stearic acid and GMO, respectively.13C NMR provides definitive proof that V-amylose inclusion complexes have been formed with the mono-car☐ylic fatty acids of varying degrees of unsaturation, GMO, GMP and LPC. The chemical shift of the mid-chain methylenes in stearic acid moves about 1.5 ppm upfield upon complexation with the1H rotating frame relaxation times becoming identical for the lipid and amylose. With the exception of docosahexaenoic acid, the mid-chain methylenes inside the V-helical segments have essentially the same chemical shift for all the other unsaturated fatty acids and lipids investigated. The cross-polarisation dynamics for the car☐yl and glycerol groups in stearic acid and GMO, respectively, have indicated that these bulky polar groups occupy highly mobile conformations in the hydrated complexes which must lie outside the V-helical segments adjacent to the amorphous domains.