Pyrolysis GC Research Articles

Physical and chemical characteristics of Maytenus rigida in different particle sizes using SEM/EDS, TG/DTA and pyrolysis GC–MS

Thermoanalytical techniques have been widely applied in the characterization of herbal medicines, providing data about the herbal products quality. The objective of this work was to use analytical techniques for the Maytenus rigida powder in different particle sizes characterization. The techniques used were scanning electron microscopy (SEM) with energy-dispersive spectroscopy, differential thermal analysis (DTA), Thermogravimetry (TG), using the model of Ozawa to evaluate the kinetic parameters and gas chromatography coupled to pyrolysis/mass spectrometry (PYR-GC/MS). Different particle morphologies and size were verified by SEM. The thermoanalytical techniques (TG and DTA) showed physical and chemical processes occurred. Different degradation profiles curves were obtained when the samples were exposed to the atmosphere of nitrogen and synthetic air. Kinetic data showed different activation energy values and the same reaction order to the studied samples. Through Ozawa kinetic parameters, it was possible to observe granulometries distinctions to the herbal medicine powder batches. Pyrolysis allowed to correlate TG decomposition data with the identification of its degradation products and showed two similar compounds among the samples at lower temperatures (250 °C) and at higher temperatures (600 °C). The fingerprint of the degradation components by PYR-GC–MS and the other analytical tools has been utilized as an alternative to the quality control of herbal medicine evaluation. Ea obtained by dynamic TG in air synthetic atmosphere was the parameter which better differentiate the samples.

Thermal and pyrolysis analysis of minerals reinforced intumescent fire retardant coating

Abstract This study presents the results of intumescent fire retardant coatings (IFRCs) developed to investigate the synergistic effects of mineral fillers (clay and wollastonite) based IFRC towards heat shielding, char expansion, morphology, composition, gaseous products and residual weight. The fire test has been performed to study the heat shielding effect of IFRCs on the substrate using UL-1709 standards. The results showed the synergistic effect of clay and wollastonite using 5 wt.% enhanced the fire protection, performance with recorded substrate temperature 113 °C after 1-h fire test. Field Emission Scanning Electron Microscopy (FESEM) and High-Resolution Transmission Electron Microscopy (HRTEM) showed the micrograph of compact char structure that increased char integrity due to the presence of inorganic fillers. X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) results showed the presence of boron phosphate, silicon phosphate oxide, aluminum borate in char that improved the thermal performance of IFRC up to 800 °C. X-Ray Photoelectron Spectroscopy (XPS) confirmed that 5 wt% (IFRC-5) of clay and wollastonite increased the carbon content up to 50.67%, lowering oxygen content to 27.73% in the char that enriched the fire resistance performance of the coating. Pyrolysis-Gas Chromatography-Mass Spectrometry (Pyrolysis GC–MS) confirmed that formulations IFRC-5 released less gaseous product concentration compared to IFRC-C and maximum reduction in gases was recorded from 3.4e +07 to 1.08e +07 . Thermogravimetric analysis (TGA) demonstrated in residual weight was increased to 46.45% for IFRC-5 which resulted in the high thermal stability of the coating.

Isoconversional thermal and pyrolytic GC–MS analysis of street samples of hashish

Thermal decomposition of hashish, a widely used illicit drug, was studied by isoconversional and pyrolytic GC–MS analysis. An accurate value of activation energy was determined by the B-1.92 method, which was used to determine degradation mechanism, impact of destruction by incineration of the drug on environment. The thermograms exhibited a weight loss of 11–19% from ambient to 463K due to moisture content. Major degradation occurred in the range 463–643K. The average activation energy was found to be ∼121kJmol−1 that suggested rapid volatilization of the material in the temperature range. The variation of activation energy with conversion suggested a multistep degradation of the samples. The mechanism of degradation was found to be a second order decomposition representing an exothermic chemical change. The residue at 1073K was analyzed by SEM-EDS and found to contain C, O, P, S, K, Mg, Ca, Al and Si to various extents; C and O were present in substantial amounts. Pyrolytic GC–MS analysis identified cannabidiol, limonene, β-caryophyllene and pyrolytic products of acetaminophen and dehydrophenacetin as the major decomposition products. This study shows that the incineration process does not completely destroy the drug, rather it throws large quantities of drug-related toxic substances into the environment. The pyrolysis GC–MS showed that the characteristic peak due to cannabidiol can be used as a signature of the drug in biological samples.

Application of direct analysis in real time (DART) and direct inlet probe (DIP-APCI) mass spectrometry in the context of industrial sample analysis

In today’s industry, quick and reliable analytical methods play an important role for quality control. On that account, two emerging techniques, namely direct inlet probe-atmospheric pressure chemical ionization (DIP-APCI) and direct analysis in real time (DART) mass spectrometry, are particularly promising. In case of a DIP-APCI source, small amounts of solid or liquid samples can be studied without sample pre-treatment. A similar system is the DART ion source. In addition to the analysis of solid and liquid samples without pre-separation, this ion source offers the possibility to scan the surface of a sample. A method for industrial sample analysis focusing on the study of delamination of coatings from a panel was developed using DIP-APCI-Q-TOF-MS and DART-Q-TOF-MS, respectively. Comparative studies based on the conventional pyrolysis–GC–MS were carried out.

Study of historical Chinese lacquer culture and technology – Analysis of Chinese Qin-Han dynasty lacquerware

Abstract A Chinese Qin-Han dynasty lacquerware was analyzed by cross-section, field emission scanning electron microscope with energy dispersive X-ray spectrometry (EDX), strontium isotope ratios ( 87 Sr/ 86 Sr), carbon-14 age determination, and pyrolysis-gas chromatography–mass spectrometry. The carbon-14 analysis results showed that the wood base was from a Zelkova schneideriana tree grown in the Yangtze River area about 2300 years ago, and the film was sap collected from lacquer tree about 2200–2250 years ago. The 87 Sr/ 86 Sr isotope ratio was 0.71146 consistent with that of the Chinese mainland (> 0.71). Pyrolysis GC–MS detected 3-heptylphenol and 3-pentadecylphenol in the mass chromatograms at m/z = 108, and palmitic acid and stearic acid were detected at m/z = 60, suggesting that the sap collected from Toxicodendron vernicifluum tree and that many additives had been added. The cross-section and EDX revealed the coating technique and pigment species of lacquerware. Based on these results, the Chinese Qin-Han Dynasty lacquer culture is discussed.

Selective Synthesis of Phenolic Compounds from Alkali Lignin in a Mixture of Sub- and Supercritical Fluids: Catalysis by CO2

A successful selective liquefaction of lignin has been demonstrated in the presence of a H2O–CO2 mixture at 300 °C, yielding 40–50 wt % organic phenolic phase. The effect of the temperature at a constant pressure and short residence time on the selectivity and yield of phenolic products from the hydrothermal reforming of alkali lignin in a mixture of sub- and supercritical fluids (H2O mixed with CO2 or N2) has been investigated. Dependent upon the processing conditions, the lignin samples produced a homologous series of phenols, such as guaiacol, homovanillic acid, quaiacyl carbonyls, guaiacyl dimers, phenol, and cresol. Gas chromatography–mass spectrometry (GC–MS), total organic carbon (TOC), and pyrolysis–GC–MS (Py–GC–MS) were used for chemical analysis of the organic liquid and solid phases. The results from GC–MS analysis of the liquid organic phases demonstrated the trend of increasing the amounts of major guaiacol products with the temperature. The thermal carbon analysis (TCA) showed a significant ...

LC fractionation followed by pyrolysis GC–MS for the in-depth study of aroma compounds formed during tobacco combustion

Analytical pyrolysis combined with gas chromatography–mass spectrometry (Py-GC–MS) is an effective technique for studying combustion processes such as cigarette smoking. Direct pyrolysis of tobacco leaf results in a very complex mixture of organic compounds containing volatile, semi-volatile and non-volatile compounds. Consequently, detecting and identifying the main tobacco aroma compounds and their formation pathways are very difficult.An innovative workflow that can elucidate the aroma compounds formed during the combustion of tobacco is presented. The workflow consists of LC fractionation of a tobacco leaf extract, recombination of fractions in a fraction omission approach and Py-GC–MS. Using multivariate statistical data analysis, the fractions that contribute most to the formation of typical cigarette smoke aromas could be identified. In addition, GC–MS analysis of derivatized LC fractions could be used to identify the precursors of these aroma compounds.The analytical approach is suitable to correlate the effect of different classes of compounds in tobacco to the typical aroma compounds in cigarette smoke.

Pyrolysis GC–MS for the rapid environmental forensic screening of contaminated brownfield soil

An abandoned chemical plant in Asturias (Spain) was studied using a multi-faceted molecular fingerprinting approach, demonstrating that it is possible to: (1) carefully unravel tangled evidence resulting from multiple pollution sources, and (2) recognize major contaminants largely ignored by conventional analyses. This methodology employed a battery of GC–MS analyses of liquid chromatographic fractions of soil extracts, plus the pyrolysis products of the soil extract’s asphaltene fraction and the whole soil itself. In this example, coal tar distillation and the subsequent production of naphthalene, phenols and polymer resins are responsible for most of the soil contamination. Styrene, naphthalene, indene and their methylated derivatives and dimers (most notably naphthyl–methylnaphthalene) are particularly abundant and/or distinctive. It is remarkable that most of the contaminants were detected simply by pyrolysis GC–MS, demonstrating its effectiveness for rapid environmental forensic screening of organic contamination. Commonly used environmental analytical approaches would likely have overlooked the predominant pollutants at this site. This could lead to serious shortcomings in remediation planning and implementation. The novel methodology presented herein appears practical and applicable to complex contaminated brownfield sites around the world.

Geochemical characteristics of crude oils, their asphaltene and related organic matter source inputs from Fula oilfields in the Muglad Basin, Sudan

Bulk geochemical characteristics of crude oils, coupled with geochemical analyses of reservoir oil asphaltenes from Fula oilfields in the Muglad Basin, have provided information on source organic matter input, depositional environment and the correlation between these crude oils and their potential source rocks in the basin. Only one oil family is present within the Fula oilfields as indicated by biomarker and non-biomarker parameters. The Fula oils are characterized by moderate API gravity, low sulphur and moderate trace metal (Ni, V) contents, and high wax contents. This suggested that the oils were generated from source rock that was deposited in a principally lacustrine environment. This is supported by bulk geochemical characteristics and biomarker compositions. A variety of biomarker–specific parameters obtained from n-alkanes, regular isoprenoids, terpanes and steranes indicate that the Fula oils were generated predominantly from algae-derived organic matter that was deposited in a lacustrine environment which then experienced a slight seawater influence under suboxic to relatively anoxic conditions. These oils were generated from source rock with a wide range of thermal maturity ranging from early to peak oil window. The biomarker characteristics of these oils are consistent with those of the early Cretaceous Abu Gabra shales. The oil-source rock relationship is also demonstrated by similarities in the structural moieties of the Fula oil asphaltene and the Abu Gabra shale kerogens. The Pyrolysis GC of the analyzed Fula oil asphaltene indicates that the oils were derived from Type I-algal organic matter, consistent with paraffinic high wax oils.

Sustainable polysaccharide-based biomaterial recovered from waste aerobic granular sludge as a surface coating material

To evaluate the possibility of utilizing polysaccharide-based biomaterial recovered from aerobic granular sludge as a coating material, the morphology, molecular weight distribution and chemical composition of the recovered biomaterial were investigated by atomic force microscopy, size exclusion chromatography and pyrolysis–GC–MS to have a better understanding of the properties of the biomaterial. The biomaterial recovered from aerobic granular sludge demonstrates chain-like structure. The molecular weight of 1/3 of the biomaterial is higher than 70kDa. It is amphiphilic due to containing polysaccharides as a major fraction and lipids as a minor fraction. The biomaterial easily forms a film on a hydrophilic surface (e.g. paper), and functions as a water resistant barrier. Biomaterial recovery from waste aerobic granular sludge in biological wastewater treatment process provides a new resource of sustainable materials.

High solubility of Victorian brown coal in ‘distillable’ ionic liquid DIMCARB

Ionic liquids formed by association of carbon dioxide (CO2) with low molecular weight secondary amines to form carbamate salts (e.g. N,N-dimethylammonium N′,N′-dimethylcarbamates, or DIMCARB) as solvents have been identified as ‘distillable’ as they reform their volatile precursor components upon heating at relatively low temperature and, thus, can be recovered by condensation. DIMCARB was selected for the solubilisation of a number of Victorian brown coals including Loy Yang coal, a dark, a medium light and a light lithotype and a Yallourn woody coal. The coal was mixed with DIMCARB at a mass ratio of 1:20 for 24 h at room temperature. The soluble product was recovered by centrifugation followed by acid washing to remove residual DIMCARB. The solubilisation yields achieved were between 10% and 63% in the order of woody coal < dark lithotype < medium light lithotype < Loy Yang < light lithotype. The soluble and non-soluble products were characterised by FTIR, NMR and pyrolysis GC–MS. Results revealed a positive correlation between the solubility and aliphatic content in the coals. Polycyclic aliphatic and aromatic compounds, specifically the triterpenoid group, were selectively dissolved by DIMCARB.

Characterization of additives of PVAc and acrylic waterborne dispersions and paints by analytical pyrolysis–GC–MS and pyrolysis–silylation–GC–MS

Commercial formulations of poly(vinyl acetate) (PVAc) and acrylic dispersions and paints commonly used by artists include a number of additives such as surfactants, coalescing agents, defoamers and thickeners, which are designed for improving shelf-life, as well as chemical and physical properties of the resulting product. Recent studies have shown that additives present in paints play an important role in the alteration processes undergone by the painting during ageing and further in cleaning tasks planed in conservation interventions. However, the identification of additives is a difficult task due to the elusive character of these substances present at low concentration in the paint.In this context, a four-step approach is proposed that includes analysis of paint samples together with analysis of their water extracted products by pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) and pyrolysis–silylation–gas chromatography–mass spectrometry (Py–silylation–GC–MS). This analytical strategy enables a better characterization of common additives present in commercial PVAc and acrylic paints and dispersions. In particular, the analysis of water soluble extracts, which are mainly composed by paint additives, avoids the interference of the major polymer pyrolizates. Experimental conditions concerning sample preparation and instrumental working conditions of both Py–GC techniques are optimized.Both acrylic and PVAc paints presented poly(ethylene oxide) (POE) type fragments dominating the background of their pyrograms, especially when derivatized by means of hexamethyldisilazane (HMDS). For the first time, additives such as alkyl sulfate and alkyl ether sulfate with C10 and C12 alkyl chains, poly(ethoxylate) fatty alcohol and octylphenyl poly(ethoxylate) surfactants were identified, as well as polyvinyl alcohol (PVOH) protective colloids, hydrophobically modified ethoxylated urethane (HEUR) thickeners an defoamers. Their major fragments and corresponding mass spectra are discussed.

Structural elucidation of inhomogeneous lignins from bamboo

A better understanding of the inhomogeneous molecular structure of lignin from bamboo is a prerequisite for promoting the “biorefinery” technologies of the bamboo feedstock. A mild and successive method for fractionating native lignin from bamboo species was proposed in the present study. The molecular structure and structural inhomogeneity of the isolated lignin polymers were comprehensively investigated by elemental analysis, carbohydrate analysis, state-of-the-art NMR and analytical pyrolysis techniques (quantitative 13C NMR, 13C-DEPT 135 NMR, 2D-HSQC NMR, 31P NMR, and pyrolysis–GC–MS). The results showed that the proposed method is effective for extracting lignin from bamboo. NMR results showed that syringyl (S) was the predominant unit in bamboo lignin over guaiacyl (G) and p-hydroxyphenyl (H) units. In addition, the lignin was associated with p-coumarates and ferulates via ester and ether bonds, respectively. Moreover, various substructures, such as β-O-4, β-β, β-5, β-1, and α,β-diaryl ether linkages, were identified and quantified by NMR techniques. Based on the results obtained, a proposed schematic diagram of structural heterogeneity of the lignin polymers extracted from the bamboo is presented. In short, well-defined inhomogeneous structures of native lignin from bamboo will facilitate further applications of bamboo in current biorefineries.

Organic geochemical and petrographic characteristics of Neogene organic-rich sediments from the onshore West Baram Delta Province, Sarawak Basin: Implications for source rocks and hydrocarbon generation potential

The Neogene succession of the onshore petroleum prolific West Baram Province of North-West Borneo contains organic-rich sediments particularly within Sarawak Basin. Bulk and quantitative pyrolysis results, coupled with organic petrographic characteristics of Neogene organic-rich sediments have enabled investigation of the source rock characteristics and evaluation of the hydrocarbon generation potential. The results were used to assess the quantity of organic matter, kerogen composition, thermal maturity and type of petroleum that could possibly be generated from these Neogene sediments.The total organic carbon (TOC) contents of the Neogene sediments range between 1.06 and 11.11 wt. % and Hydrogen Index (HI) values are largely below 105 mg HC/g TOC, suggesting that the sediments are organically rich and contain gas-prone Type III kerogen. This kerogen type is supported by the abundant terrestrial materials (i.e., vitrinite phytoclasts, spores and pollen), low atomic hydrogen-to-carbon atomic (H/C) ratio and high abundance of aromatic hydrocarbons in Pyrolysis GC pyrograms and would likely generate mainly condensate and gas. The analysed samples have vitrinite reflectance in the range of 0.39–0.48 %Ro and pyrolysis Tmax in the range of 401–434 °C which indicate that these Neogene sediments contain immature to very early-mature organic matter. This implies that these onshore sediments have not been buried to a sufficient depth, however the offshore stratigraphic equivalent of these sediments are known to have been buried to deeper depth and could therefore act as an effective petroleum source rock in particular for natural gas.

Evaluating reaction pathways of hydrothermal abiotic organic synthesis at elevated temperatures and pressures using carbon isotopes

Experiments were performed to better understand the role of environmental factors on reaction pathways and corresponding carbon isotope fractionations during abiotic hydrothermal synthesis of organic compounds using piston cylinder apparatus at 750°C and 5.5kbars. Chemical compositions of experimental products and corresponding carbon isotopic values were obtained by a Pyrolysis–GC–MS–IRMS system. Alkanes (methane and ethane), straight-chain saturated alcohols (ethanol and n-butanol) and monocarboxylic acids (formic and acetic acids) were generated with ethanol being the only organic compound with higher δ13C than CO2. CO was not detected in experimental products owing to the favorable water–gas shift reaction under high water pressure conditions. The pattern of δ13C values of CO2, carboxylic acids and alkanes are consistent with their equilibrium isotope relationships: CO2>carboxylic acids>alkanes, but the magnitude of the fractionation among them is higher than predicted isotope equilibrium values. In particular, the isotopic fractionation between CO2 and CH4 remained constant at ∼31‰, indicating a kinetic effect during CO2 reduction processes. No “isotope reversal” of δ13C values for alkanes or carboxylic acids was observed, which indicates a different reaction pathway than what is typically observed during Fischer–Tropsch synthesis under gas phase conditions. Under constraints imposed in experiments, the anomalous 13C isotope enrichment in ethanol suggests that hydroxymethylene is the organic intermediate, and that the generation of other organic compounds enriched in 12C were facilitated by subsequent Rayleigh fractionation of hydroxymethylene reacting with H2 and/or H2O. Carbon isotope fractionation data obtained in this study are instrumental in assessing the controlling factors on abiotic formation of organic compounds in hydrothermal systems. Knowledge on how environmental conditions affect reaction pathways of abiotic synthesis of organic compounds is critical for understanding deep subsurface ecosystems and the origin of organic compounds on Mars and other planets.

Geochemical and petrographic characterisation of organic matter from the Upper Cretaceous Fika shale succession in the Chad (Bornu) Basin, northeastern Nigeria: Origin and hydrocarbon generation potential

The Upper Cretaceous Fika shales in the Chad (Bornu) Basin, northeastern Nigeria were analysed to evaluate the origin of the organic matter and the hydrocarbon generation potential. This study is based on geochemical analyses (total organic carbon (TOC) content, pyrolysis (SRA), pyrolysis gas chromatography (Py–GC), bitumen extraction and biomarker distributions) and kerogen analysis of organic matter by microscopy. The present-day TOC contents range between 0.50 and 2.37 wt.% and Hydrogen Index (HI) values are largely below 200 mg HC/g TOC, suggesting that the shales are organically lean and contain Type III and Type IV kerogens. This is evidenced by palynofacies investigation whereby the kerogen is characterised by large amounts of non-fluorescent amorphous organic matter (AOM) and phytoclasts. Pyrolysis GC analysis proved that all the investigated Fika shale samples contain Type III kerogen that produces mainly gaseous hydrocarbons. The Fika shales have high gas-generation potential due to a combination of kerogen type and thermal maturity. The Fika shales have vitrinite reflectance and Tmax values in the range of 0.70–1.34% and 430–465 °C, respectively, indicating early to late oil-window maturity, thus higher maturity levels have affected the HI of the samples and the hydrocarbon generation potential, decreasing both. The higher thermal maturity level is attributed to the presence of volcanic intrusives, which occur as diorite sills at numerous horizons in the Fika Formation.

Source rock characteristics of the Lower Cretaceous Abu Gabra Formation in the Muglad Basin, Sudan, and its relevance to oil generation studies

Organic-rich shale and claystone are present within the Lower Cretaceous Abu Gabra Formation of the Muglad Basin, representing excellent oil source rocks. The source rock potential of Abu Gabra organic-rich whole rock samples from two oilfields in the Muglad Basin was investigated using bulk and quantitative pyrolysis techniques. The analytical program included TOC, pyrolysis (SRA), pyrolysis GC, bulk kinetics, elemental analysis and kerogen microscopy. The results were used to characterize the kerogen composition and type of petroleum generated from these Abu Gabra organic-rich sediments to clarify the structural variability of the organic matter in the Abu Gabra source rock. The investigated Abu Gabra organic-rich sediments proved to contain excellent quality lacustrine kerogens. The samples have moderate to high hydrogen index (HI) values (267–837 mg HC/g rock), consistent with predominantly oil-prone Types I and II kerogen with a minor contribution of Type II–III kerogens. This is supported by the abundant liptinitic materials (i.e., lipid-rich structured algae, structureless (amorphous) alginite, and sporinite) and high atomic hydrogen-to-carbon (H/C) ratio. However, pyrolysis GC analysis proved that all the investigated Abu Gabra samples contain homogeneous Type I kerogen that produces mainly waxy oil.Bulk Kinetic experiments on these samples indicate that the source rock facies derived from a homogenous organic matter, spans an extremely narrow distribution of activation energy (Ea) ranges from 49 kcal/mol to 51 kcal/mol. The magnitude order of frequency factors (A) also show a narrow distribution range from 1012 to 1013/s. Based on the discrete simulated model using 3.3 °C/My heating rate, the average of predicted geological temperature is 0.73% Ro where the peak generation of 0.85% Ro, thus shows a typical characteristic of Type I Kerogen.

Pyrolysis GC–MS as a novel analysis technique to determine the biochemical composition of microalgae

The biochemical composition of microalgae is a major factor in the feasibility of microalgae biofuel systems. Currently full compositional analysis entails tedious, costly and time consuming analysis methods. In the current research, an attempt has been made to use Analytical Pyrolysis Gas Chromatography Mass Spectrometry (Py–GC–MS) to determine the biochemical composition of microalgae. By identifying pyrolysis marker compounds of each main biochemical component of microalgae, the composition of algae samples could be estimated. This was aided by performing Py–GC–MS of a model protein, carbohydrate and lipid. Indole was shown to be a decomposition product from the protein fraction and its levels were consistent with the changing protein content. The lipid content of the microalgae could be estimated from the presence of alkanes and the carbohydrate fraction by the presence of 1,2-cyclopentanedione, 3-methyl-. A total of 26 different microalgae and cyanobacteria strains were investigated for their protein, carbohydrate and lipid levels using established analysis techniques. The biochemical compositions are compared to the results from the novel technique using Py–GC–MS and are shown to correspond well; R2 values were found to be 0.6–0.9. The results suggest that Py–GC–MS can be used as a rapid test for studying levels and changes in biochemical composition of different algae using one fast technique with minimal sample preparation.

Oil-generation characteristics of Mesozoic syn-rift Madbi source rock in the Masila Basin, Eastern Yemen: New insights from kerogen pyrolysis and bulk kinetic modelling

Organic-rich shale layer is present within the syn-rift Madbi Formation of the Masila Basin, representing excellent oil source rock. Twenty-five representative immature to very early-mature source rock samples from the Upper Jurassic Madbi shale sequences were investigated using bulk and quantitative pyrolysis techniques. The analytical program included TOC, pyrolysis (SRA), pyrolysis GC, bulk kinetics, and kerogen microscopy. The results were used to characterize the kerogen composition and type of petroleum generated during thermal maturation from Madbi source rock and to clarify the variability of the organic matter and their effect on the timing of petroleum generation.Pyrolysis data identified two major organic facies with different petroleum generation characteristics; Type II kerogen with HI values of >400 mg HC/g TOC; Type II/III facies with HI values <400 mg HC/g TOC. This is supported by the abundant liptinitic materials (i.e., alginite, structureless (amorphous), and spores). Pyrolysis GC analysis on extracted rock samples show a dominance of a marine aliphatic-rich organic matter with variable contributions from transported terrestrial organic matter and proved to produce mainly paraffinic–naphthenic–aromatic oils with low wax contents.Bulk kinetic analysis on Madbi shale samples indicate that the Type II facies mostly derived from a homogenous organic matter, spans relatively narrow distribution of activation energy (50–54 kcal/mol) and predicted petroleum formation temperature is very different, with onset (TR 10%) temperatures of ∼125 °C (geological Tmax ∼138 °C). In contrast, the Type II/III facies reveals a relatively broad distribution of activation energies (40 kcal/mol to 62 kcal/mol) that are directly related to the heterogeneity in the organic matter, onset (TR 10%) temperatures of ∼106 °C (geological Tmax ∼139 °C). The bulk kinetic analysis also suggested that the peak generation temperatures (geological Tmax) are variable and ranging from 135 °C to 142 °C, reaching a significant transformation ratio (∼50% TR). Therefore, the Madbi source rock potential could have be generated and expelled mature oils in the Masila Basin.

Evaluation of the thermal and environmental stability of switchgrass biochars by Py–GC–MS

Flash pyrolysis GC–MS (Py–GC–MS) was applied to the characterisation of 35 biochars synthesised from switchgrass with a bench scale reactor at different temperatures (400–700°C) and residence times (1–20min). Py–GC–MS data were compared with the molar hydrogen to carbon ratios (H/C) taken as an index of the charring intensity along with other parameters. O/C ratios and biochar yields were directly correlated with H/C ratios, while ash, total carbon and pH were inversely correlated. A weak inverse correlation was found between polycyclic aromatic hydrocarbon (PAH) concentrations and H/C. The intensity and variety of pyrolysis products in the pyrograms decreased with decreasing H/C ratios, so that pyrograms of highly carbonised biochars (H/C<0.4) were principally characterised by benzene, pyrrole, toluene, C2–benzenes, benzonitrile, benzofuran, naphthalene, diphenyl, phenanthrene. These compounds were taken as representative of a highly carbonised, but thermally labile portion of biochar. Their relative abundance (% charred) with respect to pyrolysis products representative of weakly charred lignocelluloses was linearly correlated with H/C (R=−0.93). Good correlations were found between specific pyrolysis product ratios and H/C ratios. Four selected biochars were mixed with soil and subjected to short respiration rate experiments (220 days). Biochars with a moderate (H/C∼0.6) and high (H/C∼0.4) degree of carbonisation produced different pyrograms, but exhibited the same degradation rates, with a much lower conversion into CO2 than the weakly carbonised sample (H/C∼1.5) characterised by a high proportion of hemicellulose/cellulose markers in the pyrolysate.