A method to quantify C 1 –C 5 hydrocarbon gases by kerogen primary cracking using pyrolysis gas chromatography

Liao, Yuhong; Zheng, Yijun; Pan, Yinhua; Sun, Yongge; Geng, Ansong

doi:10.1016/j.orggeochem.2014.12.009

Cited by 19 publications

(17 citation statements)

References 18 publications

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“…The repeatability of the response values of the internal standard shows that the relative standard deviation (RSD) is only 5.23% (n = 60), indicating excellent instrument performance. Our recent work (Liao et al, 2015), using a CDS-5150 pyroprobe connected to a GC-FID showed that there is a good linear relationship between peak area of C 1 -C 5 hydrocarbon gases and kerogen sample weight. Table 2 also suggests that the relative standard deviations of normalized yields of C 7 -C 27 n-alk-1-ene/n-alkane doublets for various carbon numbers by Py-GC and THM-GC from asphaltenes, and Py-GC from AH asphaltene, are in the range of 0.98-3.33%, 2.26-6.07% and 2.62-7.51%, respectively.…”

Section: Py-gc and Thm-gc Analysesmentioning

confidence: 99%

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

Pan

Liao

Zheng

2015

Organic Geochemistry

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Section: Py-gc and Thm-gc Analysesmentioning

confidence: 99%

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

Pan

Liao

Zheng

2015

Organic Geochemistry

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“…Previous sequential pyrolysis of kerogen in a Py-GC system at 650, 800, 900, and 1000 °C for 10 s shows that the C 1 −C 5 gaseous hydrocarbons can be released almost completely from this kerogen after pyrolysis at 800 °C. 11 For the quantitative Py-GC analysis of gaseous hydrocarbons, the temperature of the pyrolysis probe was first raised to 250 °C and held for 2 min in a nitrogen flow to remove any moisture and low-molecular-weight organic molecules adsorbed on the platinum wire loop and then ramped to 800 °C at a rate of 5000 °C/s and held at the final temperature for 10 s. The pyrolysis products were introduced into the GC injector via a transfer line, both of which were kept at a constant temperature of 245 °C. The GC was operated under the same conditions as for the analysis of hydrocarbons gases from GTCS pyrolysis described above, except that polystyrene was used as the external standard.…”

Section: Samples and Experimental Methodsmentioning

confidence: 99%

“…13 For quantitation purposes, a polymer of simple molecular structure such as poly-(p-tert-butylstyrene) is often used in Py-GC analysis as either an internal 13,21 or external standard. 11 In the work by Eglinton et al, 12 the loss of C 6 + aliphatic structure from kerogen during thermal maturation was quantified by Py-GC. Liao et al 11 proposed an instantaneous pyrolysis method based on Py-GC using polystyrene as an external standard to quantify C 1 −C 5 gaseous hydrocarbons released from different types of kerogens.…”

Section: Introductionmentioning

confidence: 99%

“…11 In the work by Eglinton et al, 12 the loss of C 6 + aliphatic structure from kerogen during thermal maturation was quantified by Py-GC. Liao et al 11 proposed an instantaneous pyrolysis method based on Py-GC using polystyrene as an external standard to quantify C 1 −C 5 gaseous hydrocarbons released from different types of kerogens. For the quantification of C 1 −C 5 hydrocarbons, the deviation coefficients were found to be much lower when polystyrene was used as an external than as an internal standard, mainly because the gaseous products such as methane, ethene, and propylene from the decomposition of polystyrene (if used as an internal standard) can coelute and interfere with the target gaseous hydrocarbons.…”

Section: Introductionmentioning

confidence: 99%

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Relationship between Hydrocarbon Gas Generation and Kerogen Structural Evolution Revealed by Closed System Pyrolysis and Quantitative Py-GC Analysis of a Type II Kerogen

Zheng

Liao

2020

Energy Fuels

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Kerogen can release both liquid and gaseous hydrocarbons during thermal maturation. In this study, the maturation and hydrocarbon generation of a low-maturity type II kerogen were simulated via temperature-programmed gold tube closed system (GTCS) pyrolysis at two different heating rates. In addition to the yields of C 1 −C 5 gaseous hydrocarbons, H/C atomic ratios and δ 13 C values were also obtained on the kerogen residues from GTCS pyrolyses. The remaining C 1 −C 5 gaseous hydrocarbon and C 6 + liquid hydrocarbon generation potentials in both the original kerogen and the kerogen residues of various thermal maturities were determined by quantitative flash pyrolysis-gas chromatography (Py-GC) and were used to estimate the loss of aliphatic carbons in artificially matured kerogens compared with that in the original kerogen. The yields of C 1 −C 5 gaseous hydrocarbons from GTCS pyrolysis were compared with the lost amount of C 1 −C 5 gaseous hydrocarbon potentials within the kerogen structure at the same maturities. The results indicate that the H/C atomic ratios of kerogen residues decreased and the δ 13 C values of kerogen residues became progressively heavier (i.e., being enriched in 13 C) with increasing maturity in the oil generation window (OGW) but with δ 13 C becoming slightly lighter above the calculated R o (Calcd R o , namely, Easy R o or equivalent vitrinite reflectance) of 2.5%. It is worth noting that, in the OGW, the yields of C 1 −C 5 gaseous hydrocarbons from GTCS pyrolyses were significantly lower than the amounts of lost C 1 −C 5 potentials indicated by Py-GC. We speculate that hydrocarbon gases generated in OGW may either be partially adsorbed within kerogen and dissolved in oil or participate in the thermal degradation of kerogen during GTCS pyrolyses, resulting in lower yields of C 1 −C 5 gaseous hydrocarbons than the decrease in kerogen C 1 −C 5 potentials. The Py-GC results of kerogen residues also show that the rates of loss for C 1 , C 2 , and C 3 hydrocarbons are about 92%, 98%, and 99%, respectively, at 1.3% Calcd R o . This indicates that most of the C 2 + alkyl side chains can be cleaved from the kerogen structure within OGW. In comparison, at a Calcd R o of 1.3%, the formation rate of methane (C 1 ) from GTCS pyrolysis of kerogen at a heating rate of 2 °C/h only amounted to about 32%. The results from this study appear to suggest that, in GTCS pyrolysis, most C 1 generated from type II kerogen at the overmature stage cannot be attributed to primary kerogen cracking but to gradual secondary cracking of hydrocarbons with high molecular weights.

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“…Unlike alkanes, the thermal evolution of aromatic hydrocarbons approaches the end of disproportionation. As a result, the polycondensation reactions are dominant, and the cracking reactions are limited during the thermal evolution (Killops et al, 1998;Killops & Killops, 2005;Liao et al, 2015).…”

Section: Chemical Reaction Mechanismsmentioning

confidence: 99%

Pyrolytic Gaseous Hydrocarbon Generation and the Kinetics of Carbon Isotope Fractionation in Representative Model Compounds With Different Chemical Structures

Xue

et al. 2019

Geochem Geophys Geosyst

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Five model compounds with representative chemical structures were selected for use in simulation experiments of pyrolytic gas production. The gas production and isotopic fractionation characteristics were observed and analyzed. Then, the factors affecting carbon isotope fractionation during natural gas generation were discussed, and a fractionation model was established and calibrated. We concluded that the final hydrocarbon gas (C1–5) yield of octadecane, octadecylamine, octadecanoic acid, decahydronaphthalene, and 9‐phenylanthracene decreased in turn with the effective hydrogen content. Compared with linear alkanes or alkyl compounds, cycloalkanes have higher thermal stability and generate gas later. The variation in the carbon isotopic composition of natural gas is primarily controlled by the following three factors: (a) the thermal evolution of organic matter results in a gradually heavier isotopic composition for the main gas production stage. (b) Gas inherits the isotopic composition of its parent material, and this effect is evident when the chemical structure and gas generation mechanism between parent materials are similar. (c) The structure of organic matter determines the reaction mechanism of gas generation, which has a significant influence on the range and trend of carbon isotope fractionation in the process of methane generation. An improved chemical kinetic model can accurately characterize carbon isotope fractionation during gas generation.

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A method to quantify C 1 –C 5 hydrocarbon gases by kerogen primary cracking using pyrolysis gas chromatography

Cited by 19 publications

References 18 publications

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

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

Relationship between Hydrocarbon Gas Generation and Kerogen Structural Evolution Revealed by Closed System Pyrolysis and Quantitative Py-GC Analysis of a Type II Kerogen

Pyrolytic Gaseous Hydrocarbon Generation and the Kinetics of Carbon Isotope Fractionation in Representative Model Compounds With Different Chemical Structures

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