Evidence for a core-shell structure of hydrothermal carbon

Higgins, Luke; Brown, Andy; Harrington, John P.; Ross, Andrew B.; Kaulich, Burkhard; Mishra, Bhoopesh

doi:10.1016/j.carbon.2020.01.060

Cited by 45 publications

(24 citation statements)

References 46 publications

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“…Burst nucleation processes likely took place when the concentration of aromatic clusters reached the critical supersaturation point, the nuclei growing by diffusion to the surface of the chemical species present in the solution, eventually forming the spheroidal organic biomorphs (Sevilla and Fuertes, 2009a,b). According to the LaMer model (LaMer, 1952), the structure of these spheroidal organic biomorphs should be composed of an aromaticrich hydrophobic core and a hydrophilic surface containing a larger concentration of reactive oxygen-rich functional groups, as observed for hydrochars (Baccile et al, 2009;Sevilla and Fuertes, 2009a,b;Higgins et al, 2020). Yet, spatially resolved STXM investigations reveal that the spheroidal organic biomorphs produced here are quite homogeneous chemically, at least at the submicrometre scale, with rather equivalent concentrations of aromatic, ketone and amide groups inside their core and at their surface.…”

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confidence: 99%

Abiotic formation of organic biomorphs under diagenetic conditions

Criouet¹,

Viennet²,

Jacquemot³

et al. 2021

Geochem. Persp. Let.

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The most ancient fossil record contains fundamentally important information on both the diversity and disparity of ancient life. Yet this ancient record is not that easy to decode, due to difficulties mainly pertaining to the impact of the geological history. Thus, the convergence of multiple lines of evidence is seen as necessary to build a robust demonstration of the biogenicity of putative traces of life. Yet, we experimentally show here that abiotic organic cell-like microstructures meeting all the criteria of biogenicity may form in cherts under classical conditions of diagenesis. These organic biomorphs produced from a mixture of RNA and quartz in water exposed to temperature and pressure conditions (200°C, ∼15 bars) exhibit morphological, chemical and isotopic signatures typical of organic microfossils. The results of this study exemplify the pitfalls that Archean palaeontologists may encounter when searching for traces of life in ancient rocks.

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mentioning

confidence: 99%

Abiotic formation of organic biomorphs under diagenetic conditions

Criouet¹,

Viennet²,

Jacquemot³

et al. 2021

Geochem. Persp. Let.

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“…This is supported by a recent X-ray microscopy and spectroscopy study by our group on the surface properties of hydrothermal carbon, which also found that the surface was enriched in aromatic functionality compared with the bulk material. 18 3.2.3 Possible spectral distortion. Qualitative trends between the NEXAFS and XRS spectra clearly show the difference between the carbon chemical signature of the surface compared with the bulk.…”

Section: Comparison Of Nexafs and Xrs Spectroscopymentioning

confidence: 99%

“…Surface sensitivity is problematic since both hydrothermal and pyrolysis carbons have been shown to display different bulk to local-surface chemistry. 17,18 The use of soft X-rays in NEXAFS and XPS also results in difficult sample preparation and challenging high-vacuum sample environments, which render in situ studies impractical. 19 Herein, we present the case for X-ray Raman scattering (XRS) spectroscopy studies of bulk carbon chemistry in pyrolysis and HTC.…”

Section: Introductionmentioning

confidence: 99%

X-ray Raman scattering for bulk chemical and structural insight into green carbon

Higgins

Sahle

Balasubramanian

et al. 2020

Phys. Chem. Chem. Phys.

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“…They are formed of macromolecules with a maximum carbon composition of 65% [7][8][9]. Its chemical structure is rich in furans, carboxyl groups, ketones, and hydroxyl groups [10,11]. Furthermore, humins have a variety of components in smaller quantities, such as carbohydrates, peptidoglycans, and peptides derived from lignin [2].…”

Section: Introductionmentioning

confidence: 99%

Elucidating the thermal decomposition mechanism and pyrolysis characteristics of biorefinery-derived humins from sugarcane bagasse and rice husk

Gariboti

Macedo

et al. 2022

Bioenerg. Res.

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Biomass-derived humins produced in the biorefining of biomass represent an attractive feedstock for thermochemical processes and other carbon-derived platform chemicals. However, in most works, humins are merely a by-product that is not further analyzed. This work presents the purification and characterization of humins derived from sugarcane bagasse and rice husks (H-SCB and H-RH respectively), followed by the kinetic and thermodynamic analysis of its pyrolysis. Pyrolysis was examined via thermogravimetric analysis (TGA), and a global reaction model was adopted to address pyrolysis kinetics. To understand the pyrolysis process of humins and boost the quality of fit between the kinetic model and thermoanalytical data, the analyses were based on the Vyazovkin isoconversional method. The activation energy of H-SCB increased from 166.09 to 329.76 kJ mol -1 . In contrast, the activation energy of H-RH decreased from 163.31 to 84.99 kJ mol -1 . According to the results of the generalized master plot approach, the governing reaction mechanism shifted among order-based models, nucleation, and diffusion-controlled particle mechanisms. Derived thermodynamic properties showed that the heat absorbed helps the humins to achieve a more ordered state close to a conversion of 0.50. As far as we know, these findings are the first reported data on the forecast kinetic curves and pyrolysis mechanism of biorefinery-derived humins from sugarcane bagasse and rice husk, and these results will enable process design for the thermochemical conversion of these emerging materials to produce energy and other products.

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Evidence for a core-shell structure of hydrothermal carbon

Cited by 45 publications

References 46 publications

Abiotic formation of organic biomorphs under diagenetic conditions

Abiotic formation of organic biomorphs under diagenetic conditions

X-ray Raman scattering for bulk chemical and structural insight into green carbon

Elucidating the thermal decomposition mechanism and pyrolysis characteristics of biorefinery-derived humins from sugarcane bagasse and rice husk

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