Pyrolysis GC Research Articles

Modeling and tracing of polycarbonate (PC) degradation in soil microcosm with a PC microplastics quantification method based on pyrolysis GC–MS

Understanding the migration and transformation of polycarbonate (PC) plastic wastes in the natural environment is crucial for assessing their environmental impact and bioremediation. In this study, PC plastic degradation was modeled and traced in soil microcosm by investigating physiochemical properties changes of PC, the formation of microplastics, and changes in soil microbial communities. Notably, PC microplastics quantification method was also successfully devised by pyrolysis gas chromatography mass spectrometry and also applied herein. Through gel permeation chromatography analysis, the molecular weight of the naturally aged PC film obviously reduced, whereas no change for unaged ones. After 12 months of soil burial, the surface corrosion and holes formation were emerged on the surfaces of both PC films in the non-sterilized soil harboring indigenous microorganisms by scanning electron microscope. The worsened thermal stability of both PC films in non-sterilized soil was demonstrated by thermogravimetric analysis. Meanwhile, the presence of increased hydroxyl group absorption and decreased carbonyl peak highlighted molecular chain breakage in both PC films by Fourier transform infrared spectroscopy. In particular, all the changes were more significant in aged PC than unaged ones. Furthermore, the increase of quantified PC microplastics on the surface of PC film in the non-sterilized soil accompanied the decreasing of microbial diversity and the enrichment of potential functional microorganisms. These findings revealed that the combination of natural aging and indigenous microbes exhibited a noticeable performance in PC plastics degradation in soil microcosm, providing new insights into the degradation mechanism of PC plastic wastes in the natural environment.

Organic compounds in aquatic sediments analyzed by pyrolysis–GC–MS with tetramethylammonium hydroxide (TMAH) and alkaline CuO oxidation methods

Thermally assisted hydrolysis and methylation with tetramethylammonium hydroxide (TMAH) can analyze various organic compounds, e.g., lignin phenols, fatty acids, sterols, etc., thus, suitable for profiling organic matter in sediments. Although the method uses pyrofoils with different reaction temperatures, changes in the yield of organic compounds in sediment samples at different temperatures are unclear and requires clarification. This study characterizes the compounds released during the TMAH reaction by testing the effect of reaction temperatures and comparing the results with a conventional method (alkaline CuO oxidation). The reaction temperatures (315 °C, 358 °C, 445 °C, 500 °C, 590 °C, and 670 °C) effects via thermochemolysis with TMAH using a Curie point pyrolyzer–GC–MS instrument (TMAH method) on lignin phenols, alkanoic acids, cutin acids, alcohols, sterols, and phytol in marine (offshore California) and lake (Lake Baikal) sediments were determined. Comparison between two different sediment locations provided a variety of compounds derived from marine and terrestrial environments. Lower temperatures (≤ 358 °C) were suitable for n-C14–C18 alkanoic acids, unsaturated n-C16:1 and C18:1 acids, cutin acids, n-C16–C28 alcohols, sterols, and phytol, whereas higher temperatures (from 445 °C to 500 °C or 590 °C) were appropriate for lignin phenols, n-C20–C30 alkanoic acids, ω-hydroxyalkanoic acids, and n-alkanedioic acids. However, relatively high concentrations determined under high temperature conditions may be due to the apparent high concentrations obtained by the decomposition of the internal standard (n-C19 alkanoic acid). Vertical distribution of lignin phenols, alkanoic acids, and cutin acids collected from lake sediments using the TMAH method at 358 °C and 590 °C were compared with those obtained by alkaline CuO oxidation (CuO method). Significant linear relationships were observed for lignin phenols and alkanoic acids, except for n-alkanedioic acids. Differences were found in some yield amounts between the methods; the yields of cinnamyl phenols (at 358 °C and 590 °C) and n-C14–C18 alkanoic acids (at 358 °C) obtained by the TMAH method significantly exceeding those obtained by the CuO method. Additionally, cutin acid yields obtained by the TMAH method were substantially lower than those obtained from the CuO method. We recommend using lower temperatures for the TMAH reaction to optimize this analytical method for different compound classes.

Insoluble macromolecular organic matter in the Winchcombe meteorite

AbstractThe Winchcombe meteorite fell on February 28, 2021 in Gloucestershire, United Kingdom. As the most accurately recorded carbonaceous chondrite fall, the Winchcombe meteorite represents an opportunity to link a tangible sample of known chemical constitution to a specific region of the solar system whose chemistry can only be otherwise predicted or observed remotely. Winchcombe is a CM carbonaceous chondrite, a group known for their rich and varied abiotic organic chemistry. The rapid collection of Winchcombe provides an opportunity to study a relatively terrestrial contaminant‐limited meteoritic organic assemblage. The majority of the organic matter in CM chondrites is macromolecular in nature and we have performed nondestructive and destructive analyses of Winchcombe by Raman spectroscopy, online pyrolysis–gas chromatography–mass spectrometry (pyrolysis–GC–MS), and stepped combustion. The Winchcombe pyrolysis products were consistent with a CM chondrite, namely aromatic and polycyclic aromatic hydrocarbons, sulfur‐containing units including thiophenes, oxygen‐containing units such as phenols and furans, and nitrogen‐containing units such as pyridine; many substituted/alkylated forms of these units were also present. The presence of phenols in the online pyrolysis products indicated only limited influence from aqueous alteration, which can deplete the phenol precursors in the macromolecule when aqueous alteration is extensive. Raman spectroscopy and stepped combustion also generated responses consistent with a CM chondrite. The pyrolysis–GC–MS data are likely to reflect the more labile and thermally sensitive portions of the macromolecular materials while the Raman and stepped combustion data will also reflect the more refractory and nonpyrolyzable component; hence, we accessed the complete macromolecular fraction of the recently fallen Winchcombe meteorite and revealed a chemical constitution that is similar to other meteorites of the CM group.

Online hyphenation of size-exclusion chromatography and pyrolysis-gas chromatography for polymer characterization

An understanding of the composition and molecular heterogeneities of complex industrial polymers forms the basis of gaining control of the physical properties of materials. In the current work we report on the development of an online method to hyphenate liquid polymer chromatography with pyrolysis-GC (Py-GC). The designed workflow included a 10-port valve for fractionation of the first-dimension effluent. Collected fractions were transferred to the Py-GC by means of a second LC pump, a 6-port valve was used to control injection in the Py-GC, allowing the second pump to operate continuously. The optimized large volume injection (LVI) method was capable of analyzing 117 µL of the LC effluent in a 6 min GC separation with a total cycle time of 8.45 min. This resulted in a total run time of 2.1 h while obtaining 15 Py-GC runs over the molar mass separation.The method was demonstrated on various real-life samples including a complex industrial copolymer with a bimodal molar mass distribution. The developed method was used to monitor the relative concentration of 5 different monomers over the molar mass distribution. Furthermore, the molar mass-dependent distribution of a low abundant comonomer (styrene, <1% of total composition) was demonstrated, highlighting the low detection limits and increased resolving power of this approach over e.g. online NMR or IR spectroscopy. The developed method provides a flexible and widely applicable approach to LC-Py-GC hyphenation without having to resort to costly and specialized instrumentation.

Key characterization efforts to support the graffiti ink removal and care of Mark Rothko’s painting ‘Black on Maroon’ 1958

Analytical characterization efforts carried out in support of the conservation treatment of Mark Rothko's painting 'Black on Maroon' 1958 (Tate T01170), involving the removal of graffiti (tag) ink, are summarized. The proprietary ink product, of unfamiliar and unknown composition, was investigated using a suite of analytical techniques (IR spectroscopy, GC–MS, ICP-MS, pyrolysis GC–MS, thin layer chromatography, SEC, MALDI-TOF–MS, and UHPLC-MS) to identify key colorants and other components. The ink solubility properties proved vital to informing the solvent selection process for the ink removal procedure, which helped enable the re-display of the painting at Tate Modern in 2014. The possible impact of ink residues remaining within the cotton duck canvas support of the conserved painting was also explored using mockup canvas mechanical strength data, measured before and after ‘soiling’ at two ink levels to assess whether the ink residues had any immediate and possible longer-term effects on canvas properties. These findings, elucidated using a range of complementary analytical techniques, provide information on this hitherto-unknown graffiti product, contribute to a growing body of knowledge in this area, and offer analytical approaches which may be useful for the characterization of similar unknown materials, whether used to damage, augment, or create works of art.

Thermal degradation kinetics and pyrolysis GC–MS study of curcumin

The objective of this work was to study kinetics of thermal degradation of curcumin in ambient–1023 K range and identify degradation products by GC–MS. No weight loss was observed up to ∼470 K and two major weight losses occurred beyond this. Sixteen degradation products were identified by GC–MS. Pharmacological properties, including LD50, LC50, gastrointestinal absorption, blood-brain barrier permeation and effect on cytochromes, of the products were calculated using standard software. The LD50 values indicated that the degradation products are more toxic than curcumin. All the decomposition products, except 2-methyl-6-(4-methylphenyl)-hept-2-en-4-one, have the potential to cross the blood–brain barrier that can affect brain functions. Twelve of the compounds showed the potential to inhibit the metabolism of xenobiotics and all the compounds appeared to be non-inhibitors of CYP2C9 and CYP3A4 in contrast to curcumin. Thus, this study suggests that the food materials containing curcumin when heated beyond 470 K will produce toxic substances.

Engineering Lignin-Derived Carbon–Silicon Nanocomposite Electrodes: Insight into the Copyrolysis Mechanism and Process–Structure–Property–Performance Relationships

As a renewable source, available in a large quantity, it is rewarding to find applications for lignin with high added value. We report the use of lignin in synthesizing a three-dimensional, interconnected carbon/silicon nanoparticle (C/Si NP) composite material as a low-cost replacement to conventional anode materials synthesized using expensive and toxic solvents and binders such as polyvinylidene in today’s lithium-ion battery (LIB) manufacturing process. To understand how lignin pyrolysis chemistry and processing conditions affect the structure, mechanical property, and electrochemical performance of the synthesized electrode materials, the thermochemical conversion process was, for the first time, quantitatively investigated using analytical pyrolysis–gas chromatography–mass spectrometry (GC–MS) along with a suite of other analytical tools. Results suggest that the surface bonding interaction of the C/Si NPs was evolved from pristine Si to −Si–O–C–, to −O═Si═O–, with the increase of pyrolysis temperature. The −Si–O–C– bond plays a key role in enhancing the cohesive strength and thus improving the electrochemical performance of the Si composite electrode. The pyrolysis–GC–MS can serve as a useful tool to predict the optimal pyrolysis temperature or tailor the properties of the synthesized composite electrodes by controlling the pyrolysis conditions. This study elucidates the processing–structure–property–performance relationships among lignin pyrolysis chemistry, carbon material structure and properties, and the electrochemical performance of the resulting electrode materials. Such knowledge serves as a basis for designing lignin-derived composite materials for electrochemical energy storage applications.

Studies on Borosiloxane Oligomers from Mixtures of Vinyltriethoxysilane and Phenyltrialkoxysilanes

Polycondensation of boric acid (BA) with mixtures of phenyltriethoxysilane (PTEOS) and vinyltriethoxysilane (VTEOS) and with mixtures of phenyltrimethoxysilane (PTMOS) and vinyltriethoxysilane (VTEOS) in diglyme at 83–87 °C using HCl as catalyst resulted in vinyl-functionalized borosiloxane oligomers. Effect of variation of PTEOS:VTEOS and PTMOS:VTEOS ratio (keeping BA:alkoxysilanes ratio constant) and the effect of variation of BA:alkoxysilane (BA:PTEOS:VTEOS and BA:PTMOS:VTEOS) ratio on the solubility, thermal stability and ceramic residue were studied. The oligomers obtained were characterized by FTIR, GPC, pyrolysis GC and TGA. For PTEOS + VTEOS system all the oligomers were soluble in the reaction medium, but after removal of alcohol (byproduct) and diglyme (solvent), the oligomers obtained in the solid form were insoluble in common organic solvents. Unlike the PTEOS-based system, for PTMOS-based system the oligomers synthesized from monomer feed ratios (BA:PTMOS:VTEOS) 1:1:1 and 1:1.67:0.33 even after the removal of ethanol and diglyme are soluble in tetrahydrofuran, dioxane and diglyme. These two soluble oligomers show bimodal molecular weight distribution with $$\overline{{\text{M}}}_{{_{{\text{W}}} }}$$ of 3,650 and $${\overline{\text{M}}}_{{\text{n}}}$$ of 1860 for 1:1:1 mol ratio, and $$\overline{{\text{M}}}_{{_{{\text{W}}} }}$$ of 2,540 and $${\overline{\text{M}}}_{{\text{n}}}$$ of 1700 for 1:1.67:0.33 mol ratio. 29Si-NMR spectra of the soluble oligomers show peaks at − 69 and − 78 ppm which are attributed to T2 and T3 structures respectively. Thermogravimetric analysis of vinyl-functionalized borosiloxane oligomers from PTEOS and PTMOS indicates that the ceramic residue of the oligomers in argon atmosphere at 900 °C varies from 68 to 89% depending on the monomer feed ratio of BA to organoalkoxysilane ratio and phenyltrialkoxysilane to VTEOS ratio. With the increase in concentration of VTEOS in the monomer feed the thermal stability as well as the ceramic residue of the oligomers increase and a reverse trend is observed for variation of BA concentration. Pyrolysis of the oligomers produce C2, C3 hydrocarbons and benzene as the main pyrolysis products. Ceramic conversion of a typical oligomer was carried out at 900 °C, 1500 °C and 1650 °C in argon atmosphere. The ceramics obtained at 900 °C and 1500 °C are amorphous SiBOC which transform to β-SiC at 1650 °C.

Synthesis and characterization of chitosan pyridyl imine palladium (CPIP) complex as green catalyst for organic transformations

In this work, the modification of chitosan using 2-acetyl pyridine has been used to prepare an intermediate, chitosan pyridyl imine (CPI), in first step and then in second step it is further reacted with Pd(OAc)2 to develop chitosan pyridyl imine palladium (CPIP) complex catalyst in a very simplistic way. The formed CPIP has been extensively characterized with respect to raw chitosan utilizing methods including FT-IR, pyrolysis GC–MS, XRD, XPS, FE-SEM, EDS, TGA-DTG and DSC. TG-DSC study suggested that the catalyst is thermally stable up to 300 °C. This catalyst shows an excellent activity in the reduction of toxic pollutant nitrobenzene to less toxic aniline. CPIP complex has also been found to give magnificent results in Suzuki–Miyaura and Heck cross-coupling reactions, and therefore, using this green catalyst, the toxic phosphine ligand can be excluded from cross-coupling reactions. This study furnishes an economic and eco-friendly catalyst for organic transformation in sustainable chemistry.

Composition and lability of riverine dissolved organic matter: Insights from thermal slicing ramped pyrolysis GC–MS, amino acid, and stable isotope analyses

Dissolved organic matter (DOM) is one of the key carbon substrates transported by rivers from land to sea, yet only a small fraction of it has been characterized at the molecular level. Here we characterize high molecular weight DOM (HMW-DOM, >1 kDa) isolated by ultrafiltration from nine North American rivers using thermal slicing ramped pyrolysis gas chromatography mass spectrometry (TSRP-GC–MS), carbon and nitrogen stable isotopes, elemental composition and total hydrolyzable amino acids (THAA). Samples from the more anthropogenically altered watersheds carried more enriched δ15N-HMW-DOM signatures than observed in samples from the more pristine watersheds. The TSRP-GC–MS results, coupled with THAA data, constrained DOM degradation process. Specifically, the diversity of pyrolyzates of HMW-DOM samples correlated well with the degradation index derived from the THAA data, with more degraded samples being more thermally stable and less molecularly diverse. The relationship between degradation index and pyrolyzate diversity observed in the HMW-DOM samples from across such a broad spatial scale suggests that degradative processes reduce riverine DOM complexity through the loss of more reactive moieties. Overall, TSRP-GC–MS, in combination with specific compound or isotope analyses, illuminates processes controlling DOM composition in different North American river systems with varying degrees of bio-lability and anthropogenic influence.

Off-line analytical pyrolysis GC–MS to study the accumulation of polystyrene microparticles in exposed mussels

An analytical procedure based on off-line analytical pyrolysis was utilized to study the bioaccumulation of polystyrene microspheres with different size (3 μm and 45 μm) by gills and digestive glands of Mytilus galloprovincialis exposed for 4 days at different concentrations of the polymer (3 μm: 0.015–1.5 μg L−1; 45 μm: 5−500 μg L−1). The mussel tissues were treated with 10 % KOH at 90 °C with good digestion efficiency (97 ± 1 %) and extracted with toluene. After evaporation the residue was pyrolysed at 500 °C with a resistively heated platinum filament. Pyrolysis products were trapped onto a charcoal cartridge, eluted with toluene and analysed by GC–MS under selected ion monitoring. Polystyrene concentrations were determined by the internal standard method from the peak areas of styrene. The procedure provided information on the effect of particle size, exposure level and tissue type on the bioaccumulation of polystyrene particles in terms of mass concentrations. Accumulation was observed in digestive glands, not in gills. The accumulation of larger particles in digestive glands increased with increasing concentrations of polystyrene in water and peaked at 14 ± 4 μg g−1. The reduction of lysosome membrane stability was observed for both particles size at a water concentration of 10,000 particles per litre, that corresponded to a lower mass concentration for the smaller particles. This study confirmed the capability of analytical pyrolysis to provide microplastic concentrations in terms of mass concentration in complex matrices.

An investigation on thermal performance of wollastonite and bentonite reinforced intumescent fire-retardant coating for steel structures

This research investigates the synthesis of new formulations of intumescent coating with improved thermal performance for steel structures. The coating formulations were based on the expandable graphite reinforced with wollastonite and bentonite. Ten samples of five formulations were synthesized by varying grinding time duration between 1 and 2 min. To analyse the substrate temperature of coated steel, fire test was performed according to ASTM-E119. The char morphology was observed by Field Emission Scanning Electron (FESEM) and Transmission Electron Microscopy (TEM). FTIR and X-ray Diffraction (XRD) test is conducted to analyse the composition of the residual char. The residual char mass was perceived by Thermogravimetric analysis (TGA) of the coating. X-ray Photo Electron Spectroscopy (XPS) was utilized for binding energy and elemental composition of the char. One-hour fire protection test showed 166 °C, the lowest substrate temperature of IFRC5-2 and 40.46% residual mass was obtained by TGA analysis. XRD analysis showed that residual char has aluminum borate and borophosphate and confirmed by functional group analysis using and FTIR. FESEM and TEM illustrated that char relates to hexagonal particles of wollastonite. XPS analysis of IFRC5-2 showed the carbon and oxygen contents were 41.40% and 51.20%. Pyrolysis-Gas Chromatography–Mass Spectrometry (Pyrolysis GC–MS) results showed IFRC-5 produced less concentration of the gaseous products compared to IFRC-C. The formulations developed by grinding solid ingredients for 2 min showed improved thermal performance compared with the formulation produced by grinding solid ingredients for 1 min. Longer grinding time and higher amount of filler improved the thermal properties of the intumescent coating.

Boreal tree species affect soil organic matter composition and saprotrophic mineralization rates

AimsTo investigate how different tree species affect the composition of SOM and its mineralization in boreal forest ecosystems.MethodsWe used pyrolysis GC–MS for molecular-level characterization of the SOM formed under five common boreal tree species at a replicated field experiment ~50years after plantation. We incubated soil samples at 4, 9, 14 and 19 °C and measured inherent CO2 production and substrate-induced respiration. We then evaluated if the saprotrophic microbial activity and its temperature sensitivity was controlled by the SOM composition.ResultsThe molecular composition of the SOM emerged as key factor influencing SOM properties in plots with different tree species. Most of the variance in the SOM content was explained by the organo-chemical composition of the SOM. More importantly, the fraction of the microbial community able to utilize the native SOM was largely controlled by the SOM organo-chemical composition. Temperature sensitivity of CO2 production (Q10) was not explained by SOM composition. However, the microbial access to different SOM pools varied with temperature.ConclusionsThese results bridge the gap between the paradigms of short-term litter and long-term SOM decomposition showing that, on an intermediate timescale (~50 years), boreal tree species affect SOM molecular composition and saprotrophic mineralization rates.

Comparison of pyrolyzed lignin before and after milled wood lignin purification of Norway spruce with increasing steam explosion

Increasing energy and chemical needs have to be covered by renewable resources, such as biomass, in the near future. Steam explosion is a green pretreatment for utilizing biomass, but it produces a by-product, pseudo-lignin. By comparing milled wood lignin purified and unpurified samples after steam explosion with pyrolysis–GC–MS, the components of pseudo-lignin should be evident. 2D NMR HSQC was also conducted on the purified samples, in addition to compositional analysis after steam explosion. After steam explosion, there is about 6 wt% of pseudo-lignin, and the pyrolysis shows an increase in diol benzenes and furan components in the unpurified samples, which is associated with pseudo-lignin.

Novel instrumentation for tracking molecular products in fast pyrolysis of carbohydrates with sub-second temporal resolution

Despite recent advances, little has been experimentally established regarding the detailed chemical processes that occur during biomass pyrolysis reactions. We developed a new technique that allows for the monitoring of each molecular product from fast pyrolysis with ∼0.2 s temporal resolution. This was achieved by directly coupling a micropyrolyzer with a time-of-flight mass spectrometer via a soft ionization. Molecular products studied were produced in thin-film pyrolysis of a series of glucose-based carbohydrates. Unprecedented details of the pyrolysis reaction process were revealed, including the timescale of molecular product formation and the existence of metastable intermediates. Small carbohydrates are completely pyrolyzed within one second and as short as one-half second for glucose pyrolysis. Individual time profiles could be extracted and examined for each molecular product. Additionally, the effect of sample dimensions on the pyrolysis of cellulose and α-cyclodextrin, as both thin films and particles, was studied. A surprising time delay of one second is observed for the thin-film pyrolysis of cellulose and α-cyclodextrin, which is attributed to the transition to the molten phase. When a large amount of cellulose or α-cyclodextrin is pyrolyzed, random fluctuations of temporal profiles are observed and explained as coming from aerosol ejections. This is well correlated with the high abundance of non-volatile products such as cellobiosan that cannot be detected in typical GC–MS or pyrolysis GC–MS analysis.

THE ASSESSMENT OF ANALYTICAL DOUBLE-SHOT PYROLYSIS WITH GAS CHROMATOGRAPH-MASS SPECTROMETRY APPLICATION OPPORTUNITY FOR THE HUMIC MATTER INVESTIGATION IN SITU

Double-shot pyrolysis with gas chromatography and mass detection (Double-shot GC MS) was conducted for a sample of typical chernozem and humic acids separated from it. The humic acids preparations were pyrolyzed at 500, 600 and 700°C. The data were compared with the lignin pyrograms witch were obtained under similar conditions. It was shown that 500°C is the optimum temperature for pyrolysis of humic acids obtained from Chernozems. Toluene in pyrolysis products may be considered as a marker of excessively high temperature occurring during the experiment. The results of a Doubleshot pyrolysis for the soil itself and the humic acids which were extracted from it were compared. Eight products of the soil pyrolysis coincided with substances determined in humic acids (with a total of 41). In the case of thermal desorption of the soil, there were only three such substances, and they also were detected during subsequent pyrolysis of the soil sample. The data obtained speak about the predominantly macromolecular composition of humic substances. The conducted works demonstrate the posibility and perspective for using the Doubleshot pyrolysis GC MS for in situ investigation of soil organic matter, humus matter in general and humic acids in particular.

Characterisation of the products of low temperature pyrolysis of Victorian brown coal in a semi-continuous/flow through system

Two Victorian brown coal samples, a run-of-mine Loy Yang coal (LY) and a Loy Yang light lithotype (LL), were subjected to pyrolysis at 420–460 °C and 330–460 °C, respectively, under a continuous nitrogen flow. The process produced condensed products in two phases, oil and aqueous, as well as solid residue and gaseous products. An increase in the condensed product yields with increasing temperature was observed for both coals, with LL achieving higher yield than LY at a given temperature (e.g. 26.3 wt% vs 19.5 wt% at 460 °C). The condensed products were characterized by 1H and 13C NMR as well as GC–MS. Abundant triterpenoid polycyclics and aliphatic hydrocarbons were found in the oils from both coals produced at lower temperatures, whilst the yield of aromatics significantly increased with increasing pyrolysis temperature. Analyses of the solid residues by FTIR, solid state 13C NMR and flash pyrolysis GC–MS (Py-GC–MS) also revealed an increasing aromaticity of the residues at higher temperatures. Py-GC–MS analysis identified compound groups released by flash pyrolysis at 650 °C and the results were found to correspond to those of GC–MS for the oil.

Corn stover lignin is modified differently by acetic acid compared to sulfuric acid

In this study, two acid catalysts, acetic acid (HAc) and sulfuric acid (H2SO4), were compared in thermal pretreatments of corn stover, in particular to assess the less understood fate of lignin. HAc-insoluble lignin, analyzed by pyrolysis GC–MS, showed decreasing levels (%) of Cα-oxidized (from 3.7 ± 0.2 to 1.8 ± 0.1), propenyl (from 2.5 ± 0.1 to 1.0 ± 0.1), vinyl-G (from 34.5 ± 1.8 to 28.4 ± 0.9), vinyl-S (from 4.2 ± 0.2 to 3.7 ± 0.1) and methylated (from 4.9 ± 0.04 to 2.8 ± 0.1) lignin units at increasing HAc amounts. Concurrently, unsubstituted and vinyl-H units increased (from 7.5 ± 0.5 to 11.3 ± 0.2 and from 40.5 ± 1.9 to 49.9 ± 0.9, respectively). Similar trends were seen for residual lignin in H2SO4 catalyzed pretreatments, although the composition differed from that of residual HAc-lignin. In particular, H2SO4-lignin showed slightly lower values (%) for unsubstituted (9.9 ± 0.2) and vinyl-H (45.7 ± 4.1) units, while Cα-oxidized (3.4 ± 0.4), propenyl (1.9 ± 0.1), vinyl-G (28.5 ± 0.9), vinyl-S (4.4 ± 0.6) and methylated (4.6 ± 0.2) lignin units remained higher compared to HAc-catalysis at similar pH values. Xylan yields and corresponding enzymatic conversions of the solids were similar regardless the type of acid. Our findings show that HAc in pretreatments decreased lignin complexity, possibly due to cleavage reactions, although subsequent recondensation reactions increased solid lignin yields, more than H2SO4, while removal of xylan and enzymatic conversion of solids were equal.

Effects of nano-sized boron nitride on thermal decomposition and water resistance behaviour of epoxy-based intumescent coating

In present research work, the effect of nano-sized boron nitride (BN) was studied on intumescent fire retardant coating (IFRC) for structural application. The coated steel substrates were subjected to furnace fire test at 800 °C for 2 h and fire protection test for 1 h. The coatings were characterized by Thermogravimetric analysis (TGA) while the char from fire test was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Furnace fire test showed that IFRC reinforced with 4 mass% of nano-sized BN expanded more than 54.84% compared to the BN-1 formulation. Fire protection test performed for 1 h showed minimum substrate temperature of 140 °C with 4 mass% of BN which proved that the IFRC can successfully protect steel substrates within its critical temperature. A maximum of 44.49% residual mass was also recorded for the same coating. XRD analysis revealed that the remaining char contained boron phosphate, boron nitride and phosphoric nitride which are stable at high temperature. The presence of these compounds was also confirmed by functional group analysis using FTIR. FESEM confirmed that micrograph of char contained hexagonal BN. XPS analysis showed a fraction decrease in carbon contents of char residues of intumescent coating formulations with the increase of BN quantity. Pyrolysis GC–MS confirmed that formulations BN-4 released less gaseous product concentration compared to BN-1. Water immersion test showed that there was no trend of mass gain percentage with increasing amount of nano-sized boron nitride incorporated into the coating. The mass gain remained between 1.74% to 2.82%. Overall concluded that the formulation with 4 mass% BN effectively promoted the amount of char acted as a passive protective layer to the substrate resulting in lower substrate temperature with higher coating residual mass.

Assessing the diversity of lipids formed via Fischer-Tropsch-type reactions

Lipid biomarkers are commonly used for tracking life through Earth’s history and are also gaining in importance in the search for extraterrestrial life. However, some lipids may also be formed in-situ via abiotic Fischer-Tropsch-type (FTT) reactions. These processes have been considered as a source of prebiotic organic matter. Here we report on a FTT synthesis experiment performed under hydrothermal conditions, focusing on more complex, previously undescribed FTT reaction products that may potentially mimic biological signals. The experiment was carried out in stainless steel reactors by heating aqueous solutions of oxalic acid mixed with montmorillonite to 175 °C for 3 days. Organic extracts of the products and extraction residues were analyzed by gas chromatography–mass spectrometry (GC–MS) and combustion-infrared detection, attenuated total reflectance Fourier transform infrared spectroscopy and pyrolysis GC–MS. FTT reactions led to a number of biomarker-like lipids such as linear and methyl-branched alkanes and alkanols as well as n-alkanoic acids. However, FTT reactions a priori produce unimodal chain length distributions and isomeric mixtures of methyl-branched compounds, as opposed to biolipids which typically show preferences of individual homologs and/or isomers. Experimental maturation of an immature kerogen demonstrated how these biological signatures may pass into unimodal distributions similar to FTT reaction products by thermal overprint. Therefore, discrimination of biologically derived compounds from FTT organics may become increasingly problematic with ongoing thermal maturation. Extraction residues of FTT reaction products contained organic material, possibly in form of an organic polymer. However, it remains to be tested whether these residual organics can evolve into kerogen-like material.