Flash Pyrolysis Gas Research Articles

N-Alkane bound biomarker fingerprints from asphaltenes in the bitumens of Eastern Dahomey Basin, Nigeria: Source and genetic implications

The asphaltene fractions of the bitumens of Eastern Dahomey Basin in Nigeria, were analyzed by flash pyrolysis-gas chromatography (Py-GC) method in order to unravel its geochemical history and properties. The distributions of the initial biomarkers of the original oils from the pyrolysates are related to the assessment of organic matter source, paleo-redox conditions and source environment during deposition. Also, it effectively establishes the genetic relationship of the bitumens. The n-alkane distributions in the pyrolysates reveal nC9-nC32n-alkanes, maximizing at nC14, isoprenoids-pristane (Pr) and phytane (Ph), and some n-alkene peaks. High peaks of low to medium-weight nC9-nC20n-alkanes and low peaks of nC21+n-alkanes characterize the distributions. These reveal that abundant algal organic matter with some terrigenous inputs contributed to the source rock of the bitumens. The high concentration of marine organic matter inputs to the source rock is further confirmed by the nC17/nC27 ratios which range from 5.39 to 19.82 and shows the predominance of nC17 alkanes. The general unimodal n-alkane distributions in the bitumens indicate derivation from similar organic matter types showing that they are genetically related. The anoxic to suboxic environmental conditions that prevailed during the deposition of the sediments is revealed by the isoprenoids, Pr/Ph ratios (0.72–1.28). Pristane/nC17 and Phytane/nC18 range from 0.16 to 0.33 and 0.22 to 0.56, revealing that the bitumens were from predominantly marine organic matter (type II kerogen) preserved in a reducing environment with no evidence of biodegradation. However, the Ph/nC18 ratio and the cross plot of Pr+Ph/nC17+nC18 allow the classification of the bitumens into two subfamilies/groups (A and B). The bitumen samples have low wax content as indicated by the degree of waxiness ranging from 0.21 to 0.38 which confirms low terrigenous input. Based on the carbon preference index (CPI: 0.92 to 1.55) and odd-even predominance (OEP: 0.70 to 1.36), it is concluded that the bitumens are immature to marginally mature.

Characterization of free and bound bitumen fractions in a thermal maturation shale sequence. Part 2: Structural evolution of kerogen and bitumen during shale oil generation, expulsion and retention

Knowledge of the formation and enrichment mechanisms of shale oil is essential to understanding its mobility and hence a critical aspect for evaluating shale oil exploration and production. Semi-open hydrous pyrolysis experiments were performed on an organic-rich shale to simulate the petroleum generation and expulsion processes of Type II kerogen. The residual rocks matured to different levels (Easy%Ro = 0.50–1.37) were thereafter treated with stepwise extraction to obtain free and bound bitumen fractions. This study focuses on the structural characteristics of kerogen, bitumen fractions, and expelled oil during shale maturation using Fourier transform infrared (FTIR) spectroscopy and quantitative flash pyrolysis–gas chromatography (Py–GC). The results reveal that the composition of expelled oils changes with increasing maturity, whereas an opposite trend in structural composition was observed for kerogen after significant oil expulsion from the shale occurs, beginning at Easy%Ro = 0.79. A notable change is that aliphatic carbon chains of kerogen became shorter and/or more branched while those of expelled oil appeared to be more aliphatic with longer carbon chains at this stage. However, the overall compositional structures of shale bitumen fractions, both in free and bound phases, show only slight changes within the oil window stage. The bound bitumen is generally enriched in oxygenated functional groups as compared to free bitumen, indicating that the bound bitumen is related mainly to the interaction between the mineral surface and the bitumen–kerogen matrix. During maturation, the cracking (including defunctionalization) and condensation of kerogen and bitumen fractions, as well as a compositional fractionation due to oil expulsion, are likely to be the main factors influencing the opposite trend observed in structural compositions between kerogen and expelled oil. These processes may control the quality and content of expelled oil and bitumen in a petroleum system. Nevertheless, kerogen, expelled oil and bitumen show a gradual trend of decarboxylation during shale maturation in general.

Transformation of Cyanobacterial Biomolecules by Iron Oxides During Flash Pyrolysis: Implications for Mars Life-Detection Missions.

Answering the question of whether life ever existed on Mars is a key goal of both NASA's and ESA's imminent Mars rover missions. The obfuscatory effects of oxidizing salts, such as perchlorates and sulfates, on organic matter during thermal decomposition analysis techniques are well established. Less well studied are the transformative effects of iron oxides and (oxy)hydroxides, which are present in great abundances in the martian regolith. We examined the products of flash pyrolysis-gas chromatography-mass spectrometry (a technique analogous to the thermal techniques employed by past, current, and future landed Mars missions) which form when the cyanobacteria Arthrospira platensis are heated in the presence of a variety of Mars-relevant iron-bearing minerals. We found that iron oxides/(oxy)hydroxides have transformative effects on the pyrolytic products of cyanobacterial biomolecules. Both the abundance and variety of molecular species detected were decreased as iron substrates transformed biomolecules, by both oxidative and reductive processes, into lower fidelity alkanes, aromatic and aryl-bonded hydrocarbons. Despite the loss of fidelity, a suite that contains mid-length alkanes and polyaromatic hydrocarbons and/or aryl-bonded molecules in iron-rich samples subjected to pyrolysis may allude to the transformation of cyanobacterially derived mid-long chain length fatty acids (particularly unsaturated fatty acids) originally present in the sample. Hematite was found to be the iron oxide with the lowest transformation potential, and because this iron oxide has a high affinity for codeposition of organic matter and preservation over geological timescales, sampling at Mars should target sediments/strata that have undergone a diagenetic history encouraging the dehydration, dihydroxylation, and oxidation of more reactive iron-bearing phases to hematite by looking for (mineralogical) evidence of the activity of oxidizing, acidic/neutral, and either hot or long-lived fluids.

Flammability Characterization of a Polysulfide Based Ramjet Fuel

ABSTRACT This research program seeks to understand how the proportions of the fuel ingredients affect the ignition and decomposition characteristics of a novel solid ramjet fuel. The approach involves an ingredient mixture study that varies the proportions of three fuel components over a 10% range: epoxy cured polysulfide polymer, sulfur, and a perfluoropolyether. The primary objective of this work is to demonstrate the manipulation of the lower flammability limit and the thermal desorption species of the various formulations as a direct result of the doping fractions of sulfur and perfluoropolyether. Laboratory experiments include closed cup flash point testing and pyrolysis gas chromatography mass spectroscopy. The results show that, for the conditions investigated, both sulfur and perfluoropolyether act to decrease the lower flammability limit when added to polysulfide fuel. Low ignition temperature species including hydrogen sulfide are desorbed from sulfur-doped formulations. The mole fractions of diluent species decrease with the addition of either sulfur or perfluoropolyether. These experiments isolate the fundamental fuel properties by decoupling fuel behavior from combustor operating parameters such as geometry, chamber pressure, air temperature, and flux. Understanding relationships between the controlling mechanisms of solid fuel ramjet performance and fundamental fuel properties can aid in design prior to static firings.

Assessment of oil potentials for humic coals on the basis of flash Py-GC, Rock-Eval and confined pyrolysis experiments

Confined pyrolysis experiments (gold capsules), quantitative flash pyrolysis-gas chromatography (Py-GC) and Rock-Eval analysis were performed on ten coals from the Junggar Basin and seven coals from the Kuqa Depression, Tarim Basin, northwestern China. The maximum yields of liquid components in confined pyrolysis experimnets (MCPΣC8+), which reflect oil potentials, have close correlations with the yields of n-alkanes + n-alkenes (FPΣn-C7+) in flash Py-GC, but have poor correlations with Rock-Eval QI ((S1 + S2)/TOC) values. Thus, oil potentials of coals can be better predicted on the basis of FPΣn-C7+ yields from flash Py-GC analysis. Coals with FPΣn-C7+ yield >10.4 mg/g TOC can generate MCPΣC8+ yield >∼22.5 mg/g TOC or oil yield >∼40 mg/g TOC in confined pyrolysis or in natural systems and are effective oil source rocks. Although both Py-GC and Rock-Eval are open systems, the yields of total liquid components (FPΣC7+) obtained from flash Py-GC have poor correlations with, and are substantially lower than, Rock-Eval QI. In contrast, FPΣC7+ values have much better correlations with oil potentials (MCPΣC8+). Coals with higher oil potentials (MCPΣC8+) generate higher amounts of liquid components detected in flash Py-GC (FPΣC7+) than those with lower oil potentials but similar Rock-Eval QI. The correlations for parameters with gas to oil ratios (GOR) in confined pyrolysis are increasingly better in the sequence of Rock-Eval QI, H/C atomic ratios, MCPΣC8+, FPΣn-C7+ and FPΣn-C7+/ΣC7+ ratios. GOR of petroleum generated from coals within oil generative window can be reasonably predicted on the basis of FPΣn-C7+/ΣC7+ ratio from flash Py-GC analysis.

Kinetics of oil generation from brackish-lacustrine source rocks in the southern Bohai Sea, East China

Oil generation (C14+ hydrocarbons) of three Type II kerogen samples isolated from brackish-lacustrine mudstones from Palaeogene strata (Ed3, Es1, Es3) in the southern Bohai Sea was simulated by closed-system gold tube experiments. In addition, a series of complementary analyses (Rock-Eval pyrolysis, total organic carbon, vitrinite reflectance, trace element, X-ray diffraction and flash pyrolysis-gas chromatography–mass spectrometry) were also performed to identify the bulk geochemistry, palaeo-environment and chemical composition of the kerogen. The aim of this study was to achieve a better understanding of the kinetics of oil generation from lacustrine source rocks in the southern Bohai Sea. The results show that the three samples are Type II source rocks deposited in similar palaeo-environments (hot and arid climates, anoxic conditions, and brackish water in shallow to semi-deep lakes) with consequent similarity in the chemical compositions of their kerogens. The organic matter inputs are predominantly composed of lacustrine microalgae, with a relatively small contribution from land plants. The activation energies of oil generation from these samples show a range of 44–52 kcal/mol, with a frequency factor varying from 1.116 × 1014 to 1.274 × 1014 s−1. Due to the similar palaeo-environments and chemical composition, samples in this study exhibit strong consistencies in kinetic parameters. Transformation ratio (TR) evolution curves of oil generation from the three samples, calculated under a linear heating rate (3 K/Ma), exhibit a slight difference, which varies within 4 °C at a given TR. Due to the great similarities of the three kinetic models, an average kinetic model for the Type II brackish-lacustrine source rocks in the southern Bohai Sea was established. This model integrates the characteristics of the three kinetic models and is still dominated by activation energy of 52 kcal/mol. The geological temperature of the oil generation phase for the average model in the southern Bohai Sea is from 92 to 137 °C.

Experimental and dynamics simulation studies of the molecular modeling and reactivity of the Yaojie oil shale kerogen

In this study, the chemical structural parameters of a kerogen from Yaojie oil shale were identified and investigated by using experimental data obtained from solid-state 13C nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, flash pyrolysis–gas chromatography–mass spectrometry, and Fourier transform infrared spectroscopy. Twelve constitutional isomers of the Yaojie 2D models with different grids and their corresponding 3D models were constructed by the combination of molecular simulation methods and multiple testing techniques. Finally, a reasonable 3D model of Yaojie kerogen was determined by a series of anneal dynamics simulations and geometry optimization calculations. From the results obtained by Mulliken population analysis and electron density analysis, the π–π conjugation effect among the aromatic ring structures is significantly impacted by the heteroatoms, leading to the accumulation of electrons on heteroatoms. Meanwhile, sulfur, oxygen, and nitrogen in the heterocyclic structures exhibited higher electronic charge density and considerably more reactivity compared with those of other atoms. Moreover, the molecular orbitals of HOMO and LUMO were calculated to examine the properties of chemical reaction of kerogen. The HOMO–LUMO energy gap indicated that the Yaojie kerogen exhibited higher reactivities compared to Type Ⅰ kerogen.

Simultaneous investigation into the yields of 22 pyrolysis gases from coal and biomass in a small-scale fluidized bed reactor

Flash pyrolysis gas yields from bituminous coal and torrefied biomass have been investigated in the temperature range between 873 and 1273K for 22 different gas species simultaneously. Recording a larger number of species gives a more detailed insight into pyrolysis of solid fuels than it is provided by other studies in literature, where typically smaller numbers of species are tracked. As processes utilizing biomass are designed for lower process temperatures, literature data for biomass pyrolysis are scarce in the temperature range between 1023 and 1273K. This work, aiming at investigating potential fuels for pulverized solid fuel combustion, approximates pyrolysis conditions in the ignition zone of actual power plant boilers, where possible.Thus, based on results of a literature review, an experiment was designed using a small-scale fluidized bed reactor (FBR) to simultaneously analyze the pyrolysis gas yields for 22 species and to close the temperature gap found for biomass. Small batches of pulverized torrefied biomass from poplar wood and pulverized Colombian bituminous coal (Mina Norte) were rapidly pyrolyzed in the reactor. The two fuels were chosen as exemplary conventional and alternative energy sources for pulverized fuel fired power plants. Experiments have been carried out under atmospheric pressure in pure nitrogen atmosphere.Product gas analysis was carried out by Fourier transform infrared spectroscopy (FTIR) including two different sampling techniques. As a novelty, offline measurements have been used exclusively to improve the gas species selection procedure and reliability of detection. In case of offline measurements, the gas flow to the FTIR gas cell is stopped and the gas is enclosed in the cell allowing longer scan times of the captured gas mixture and thereby enlarging the signal-to-noise ratio (SNR). In succession, regular measurements with continuous flow (online) were performed for the simultaneous quantitative analysis of total pyrolysis yields for 22 selected gas species.Obtained pyrolysis yields show good agreement with available literature data. The larger number of investigated species provides an extended data set also covering minor pyrolysis species, for which quantitative data are scarce. Additionally, trends in the gas yields for biomass agree well with those found by other authors outside the mentioned temperature gap between 1023 and 1273K.

Effect of biodegradation on the molecular composition and structure of asphaltenes: Clues from quantitative Py–GC and THM–GC

There is an on-going debate about whether asphaltenes can be anaerobically biodegraded in reservoir rocks due to their complex macromolecular structure. In this study, asphaltenes were precipitated from a sequence of bitumens at various degrees of biodegradation. The compositions of alkyl moieties within the asphaltene molecular structure were characterized by on-line flash pyrolysis–gas chromatography (Py–GC), on-line thermally assisted hydrolysis and methylation using tetramethylammonium hydroxide (THM–GC), and Py–GC combined with alkaline hydrolysis. The results indicate that alkyl moieties bonded to asphaltene macromolecules are dominated by linear structures with chain lengths up to C27, mainly bonded through C–C and ether (thioether) bonds but less so through ester and hydrogen bonds. Furthermore, most n-fatty acids and linear aliphatic alcohols bonded to asphaltene structure by ester and hydrogen bonds were altered at slight–moderate biodegradation stages, while linear alkyl moieties attached to the asphaltene core through C–C and ether (thioether) bonds were likely altered at heavy–severe biodegradation stages. This indicates that the linear alkyl moieties bonded to the asphaltene structure by hydrogen and ester bonds are more susceptible to biodegradation than those bonded to the asphaltene core through stronger covalent bonds such as C–C and ether (thioether) bonds. Furthermore, variations in the chemical compositions and molecular structure of asphaltenes during biodegradation may not only be attributed to the alteration of linear alkyl moieties, but also the replacement of linear alkyl moieties bonded to the asphaltene structure by hydrogen and ester bonds with other biodegradation products.

Structural characterization of suberan isolated from river birch (Betula nigra) bark

Suberan is a biopolymer located in the periderm (cork) of above ground parts of plants or the endoderm of roots. It acts as a protective barrier between plants and the environment and is commonly associated with another suberinic biopolymer, suberin. The structure of suberan has not been suggested, but is believed to have structural components similar to suberin. With the use of destructive and non-destructive techniques, including Fourier transform infrared (FTIR) spectroscopy, flash pyrolysis–gas chromatography–mass spectrometry (py–GC–MS), one and two-dimensional high-resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR) spectroscopy, the structure of suberan from the Betula nigra bark, is now described. Based on data obtained from B. nigra bark, the non-saponifiable residue, considered to be suberan, is a polymethylenic biopolymer with alkyl chain length consisting mainly of 22 carbons, which is consistent with previous degradative studies. Furthermore, esters, acids and primary alcohols were also observed in suberan, which contribute to a glyceryl structural entity. The long-chain polymethylenic structures demonstrate a high degree of crystallinity, providing a primary structural difference between suberan and suberin.

Petrology and structural studies in liquefaction reactions of Late Permian coals from Southern China

Three coals from South China, having high contents of vitrinite, liptinite, hydrogen, volatile matter, and high H/C atomic ratios, were subjected to liquefaction in tubing-bomb microreactors at 430°C for 1h with tetralin, hydrogen, and iron sulfate catalyst. The optical characteristics of the liquefaction residues were studied by white-light and fluorescence microscopy. A comparative study on the chemical structural features of the raw coals and their respective liquefaction residues was conducted by Fourier transform infrared spectroscopy (FTIR) and flash pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The liquefaction conversions were in the range of 79.0–87.1% (daf basis) under the conditions used. The optical examination of the liquefaction residues indicated that all of the liptinite and most of the vitrinite have reacted. For Dahebian coal, the observed liquefaction conversion was greater than the total vitrinite and liptinite content, indicating that some of the inertinite macerals must have participated in the reaction. Anisotropic semicoke was observed in the residue. Both FTIR and Py-GC/MS techniques showed that aliphatic groups, oxygen-containing functional groups, alkylbenzenes, and alkylphenol have reacted in liquefaction. C2-naphthalene and C3-naphthalene are main constitutions in residues.

Lepidodendron dawsonii: functional groups and pyrolysates of compression and fossilized-cuticle (Late Asturian, Canada)

Lepidodendron dawsonii BELL 1938 is an endemic species of Late Asturian age in the Canadian Sydney Coalfield, with conspicuous elongate leaf cushions. The study specimen, 35 cm long and 10 cm wide, represents a dichotomous bough from the tree crown in which the inner part of one side is black and compression-preserved, whereas the one in contact with the entombing rock matrix is dark-amber in colour and fossilized-cuticle preserved. Only stomatal pits and cuticular details are preserved. Comparison of these preservation states, based on Fourier transform infrared (FTIR) spectrometry, and flash pyrolysis gas chromatography mass spectroscopy (Py-GC/MS), demonstrate sufficient differences in chemistry to be able to link the two preservation states with differing pathways of organic matter transformation (diagenesis). The aliphatic-hydrocarbon chains of the cuticles are comparatively shorter and more branched than the longer chains of the compressions. Py-GC/MS results support the presence of hydrocarbon markers of plant cuticles. The high abundances of C1 and -C2 alkylphenols and C1 and -C2 alkylbenzenes in pyrolysates are likely derived from maturing lignin or lignin-like biomacromolecules. We suggest comparison of L. dawsonii’s cuticles with Lepidodendron coal macerals in Chinese Permian Leping coal, and with suberinite.

Infra red spectroscopy, flash pyrolysis, thermally assisted hydrolysis and methylation (THM) in the presence of tetramethylammonium hydroxide (TMAH) of cultured and sediment-derived Lingulodinium polyedrum (Dinoflagellata) cyst walls

The macromolecular composition of dinoflagellate cyst walls is poorly understood and is usually referred to as ‘sporopollenin-like’. We have carried out micro-Fourier transform infra red (micro-FTIR) analysis of chemically untreated sediment-derived and enzymatically and chemically purified culture-derived Lingulodinium polyedrum cyst walls, which suggests an aliphatic polymer rich in C O bonds and relatively poor in CH 2 and CH 3 groups, and which is much closer to cellulose than to sporopollenin or algaenan. This is in agreement with flash pyrolysis–gas chromatography–mass spectrometry (py–GC–MS), with and without tetramethylammonium hydroxide (TMAH) of purified culture derived cyst walls, which indicated an oxygen-rich polymer without normal or isoprenoid carbon chains. The results support a strongly cross-linked carbohydrate-based polymer and as such confirm earlier hypotheses that the cysts were unlike algaenan or sporopollenin, contrasting with the suggestion that the cyst walls were highly aromatic and contained tocopherol as a major monomeric building block.

Investigation of the pyrolysis mechanisms of cellobiose in the presence of a polysiloxane

Treatment of cellulose yarns by a polysiloxane followed by a fast pyrolysis step gave carbon fibres exhibiting strong enhancement of their mechanical resistance. To account for the beneficial effect of the polysiloxane, an investigation of the pyrolysis mechanisms was performed on a model system based on cellobiose and a polysiloxane resin. A chemical interaction between cellobiose and the resin (e.g. grafting of siloxane fragments onto the cellobiose) was established by using various physicochemical analysis techniques: nuclear magnetic resonance (NMR), photoelectron spectrometry (XPS), electronic paramagnetic resonance (EPR), Flash pyrolysis–gas chromatography–mass spectrometry (FP/GC/MS) and IR.

Analysis of organic matter by flash pyrolysis-gas chromatography–mass spectrometry in the presence of Na-smectite: When clay minerals lead to identical molecular signature

Different studies have already pointed out the influence of clays during the analysis of pure organic compounds (especially alkanols, alkanoic acids) as well as macromolecules (humic acids) by flash pyrolysis-gas chromatography–mass spectrometry (PyGC–MS). Especially, the occurrence of clay minerals favors the generation of aromatic units such as alkylbenzenes and polycyclic aromatic hydrocarbons. So as to better identify the nature of the organic compounds which are sensitive to the presence of clays during flash pyrolysis, a humic acid mixed in variable proportions of a Na-homoionic clay was tested. The smectite/humic acid mixtures containing from 10% to 100% humic acid allowed us to identify the progressive disappearance or appearance of specific compounds after PyGC–MS. n-Alk-1-enes disappear when the clay proportion is higher than 67%. For higher contents of Na-smectite, n-alkanes become less and less abundant with a preferential consumption of high molecular weight n-alkanes, whereas the aromatic hydrocarbon proportion increases. Moreover, the distribution of each aromatic hydrocarbon family (alkylbenzenes and alkylnaphthalenes) has been investigated. The pyrogram of pure humic acid exhibits a specific distribution of alkylbenzenes and alkylnaphthalenes reflecting the structure of the organic macromolecule. With the increase in clay proportion, these distributions are modified and lead to other distributions with a preferential predominance of thermally stable isomers. Pyrograms of humic acid and undecanoic acid in the presence of 90% of Na-smectite are similar, especially concerning alkylbenzene and alkylnaphthalene distributions. Therefore, clays (Na-smectite in our experiments) in high proportion modify initial organic products by recombination reactions and lead to the generation of new compounds of very similar distribution, whatever the nature of the initial organic matter. Such results underline the very important catalytic properties of clay minerals on functionalized organic matter during flash pyrolysis.

Pyrolysates of raw vitrinites and their residues after CS2-NMP solvent extraction and its significance for petroleum geology

Binary solvent (CS2-NMP) has extreme high extraction ability to coals, and it can extract most bitumens out of coals and vitrinites. And large amount of messages on side chains and their distribution character in vitrinites should be acquired through flash pyrolysis before and after binary solvent (CS2-NMP) extraction. A few low maturated coals have been selected and vitrinites are handpicked from coals. Then vitrinites have been extracted using different solvents in the order of polarity. Flash pyrolysis-Gas Chromatography/Mass spectrum has been applied to samples. The result shows that CS2-NMP is efficient for the extraction of vitirnites, giving much higher extraction yield than common solvents. Production ratio of liquid hydrocarbons in pyrolysates of vitrinites extracted with CS2-NMP is lower than that of raw vitrinites. And relative ratio of each component in pyrolysates has changed apparently. Production ratio of aliphatic hydrocarbons, especially those long chain aliphatics have decreased much after mixed solvent extraction. It shows that bitumens extracted with CS2-NMP have largely contributed to pyrolysates, especially those aliphatics in pyrolysates.

Aromatization of organic matter induced by the presence of clays during flash pyrolysis-gas chromatography–mass spectrometry (PyGC–MS): A major analytical artifact

The macromolecular characterization of fossil or recent organic matter in soils and sediments is frequently carried out using flash pyrolysis-gas chromatography—mass spectrometry (PyGC–MS). Such analyses providing information on the organic matter structure and reactivity, can be applied on isolated organic materials or on raw samples. Nevertheless, working on pure organic material implies heavy and time-consuming pre-treatments (humic substance isolation, mineral removal by acids), which can induce molecular alteration of the initial organic matter. On the contrary, PyGC–MS analysis on raw sample avoids heavy preparation. However, previous studies have shown that mineral matrixes and especially clay can induce analytical artifacts. The aim of this study is to test clay influences during the flash pyrolysis of pure organic compounds, which can be generated during pyrolysis of natural macromolecules and humic acid. Moreover, flash pyrolysis was carried out with and without a methylation derivative so as to evaluate its ability to limit clay effects. Pyrolysis of Na-smectite/model compounds mixtures indicates that clays intensify recombination reactions. For instance, in the presence of Na-smectite, aromatization increases as a function of the organic compound polarity. Especially, alkyl-benzenes and polycyclic aromatic hydrocarbons are generated during pyrolysis of alkanol, alkanal and especially alkanoic acid. The pyrolysis of humic acid in the presence of clays was also carried out and reveals that clays significantly affect initial molecular distribution especially by intense aromatization. Moreover, the aromatization degree is dependant on the nature of the clay, Na-smectite exhibiting the most intense influence on the molecular signature. Whatever the nature of the organic matter (model compounds or humic acid), the thermally assisted hydrolysis and methylation allows to limit clay interactions and seems a promising way of raw sediments and soils investigation.

Flash pyrolysis – a rapid method for screening bacterial species for the presence of bacteriohopanepolyols

Flash pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) was applied to freeze dried cells of eleven bacterial species. Six species known to synthesise bacteriohopanepolyols (BHPs) were found to produce easily identifiable C 27–C 35 hopenes and hopanes upon flash pyrolysis. These compounds could not be observed in the pyrolysis products of five species, two of which are known not to produce BHPs. In the search for BHP-containing bacteria this rapid screening approach prevents unnecessary time-consuming laboratory work to characterise species that would produce negative results.

Synthesis and characterization of saturated and unsaturated polysulfide polymers and their thermal degradation processes investigated by flash pyrolysis–gas chromatography/mass spectrometry

AbstractThe synthesis of polysulfide polymers with unsaturated and saturated units in the backbone and their characterization by Fourier transform infrared, NMR, gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry are reported. This is the first report on an analysis of the thermal degradation of an unsaturated polysulfide polymer [poly(2‐butene sulfide)] carried out by pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). A unique phenomenon of exothermic degradation has been detected by differential thermal analysis and has been attributed to the energetics of the unsaturated polysulfide linkage during degradation. The thermal degradation products studied by Py–GC/MS indicate that the formation of sulfur‐containing products is more favored than the formation of non‐sulfur‐containing products. Furthermore, a comparative study of the thermal degradation of unsaturated and saturated polysulfide polymers has been conducted with thermogravimetry and Py–GC/MS analyses. These analyses have shown that the mechanisms of degradation of these polymers are different, and the lower number of pyrolysis products indicates a selective cleavage of the polymer during degradation in the saturated polysulfide polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 638–649, 2005

The Preservation of Invertebrates in 16th‐Century Cesspits at St Saviourgate, York*

The taphonomy of invertebrates from 16th‐century cesspits at St Saviourgate, York, was investigated. Earthworms, fly larvae and puparia are preserved through replication in calcium phosphate, a process facilitated by acidic cesspit pore water and by the presence of abundant organic matter, bones and shells. Features preserved by mineralization include muscles, blood vessels and setae. Non‐mineralized invertebrate remains include puparia and beetles. Py–GC/MS (flash pyrolysis–gas chromatography/mass spectrometry) revealed a very high level of preservation of structural biomolecules, with all the protein and chitin markers that are evident in the living forms still being detectable in the divalent remains.