Flash Pyrolysis Research Articles

From cassava peel (Manihot esculenta) to hydrocarbon-rich bio-oil: Catalytic flash pyrolysis as a new valorization route

The valorization of agroindustrial residues for second-generation biofuels has garnered attention due to the increasing demand for low-carbon fuels aligned with transportation sector decarbonization efforts. In this context, cassava processing residues, particularly cassava peel, remain largely unexplored but offer a cheap, abundant, and renewable feedstock that can be converted into hydrocarbon-rich biofuel. Thus, the originality of this study lies in investigating the selective conversion of cassava peel into renewable aromatic hydrocarbons through flash pyrolysis catalyzed by an environmentally friendly MFI-type zeolite synthesized from rice husk ash and diatomite residue. A micro-pyrolyzer interfaced with chromatographic separation and mass spectrometry detection was used to compare the composition of condensable volatile products from catalytic pyrolysis over HZSM-5 with those from catalyst-free pyrolysis. Cassava peel, characterized by high volatile matter content (84.3 %), low ash content (3.19 %), and reasonable energy content (15 MJ kg −1), yielded a high content of valuable platform chemicals, such as carboxylic acids and furans, when subjected to catalyst-free pyrolysis. The catalytic upgrading pyrolysis vapors over the environmentally friendly HZSM-5 catalyst yielded approximately 56.0 % industrially relevant aromatic hydrocarbons and 39.9 % light organic acids. Other strengths of using HZSM-5 in upgrading pyrolysis vapors were its low selectivity for naphthalenes, precursors for coke formation, and the production of hydrocarbons in the gasoline range. Thus, HZSM-5 was an efficient catalyst for promoting deoxygenation and improving hydrocarbon content, with high selectivity for valuable aromatic hydrocarbons. In conclusion, cassava peel showed favorable prospects for conversion into hydrocarbon-rich bio-oil, serving as a valuable precursor for low-carbon biofuels.

Lunar in-situ ironmaking through laser-assisted flash vacuum pyrolysis of iron oxide

The in-situ metallurgy of lunar regolith minerals for extracting metals and oxygen is a promising approach for the future construction of lunar bases. In this study, a novel laser-assisted flash vacuum pyrolysis (LFVP) method was proposed and developed for the production of metallic iron and oxygen from lunar regolith using iron oxide as raw material. First, the theoretical feasibility of vacuum pyrolysis of FeO was conducted through thermodynamic calculations. Subsequently, an experiment on laser heating of iron oxides was performed, with a reduction rate of FeO of approximately 15.5 % (±0.6 %). Scanning electron microscopy and transmission electron microscopy images revealed that the micronano-level metallic iron exhibited spherical particles, strip-like and irregularly shaped aggregates. The spatial distribution unevenness of the formed metallic Fe, differences in the condensation conditions of gaseous products, and the surface tension effects of liquid metallic iron were mainly attributed to the disparities in the morphology of metallic iron. Meanwhile, the process mechanism of vacuum pyrolysis of FeO was also analyzed. Therefore, LFVP of FeO for producing metallic iron represents a novel ironmaking technology, offering a promising solution for extracting metals and oxygen in situ from lunar minerals for future lunar base construction.

Volatile-char interactions during biomass pyrolysis: Effects of functionalized graphitized carbon nanotubes on volatile distribution of cellulose and its model compounds

Volatile-char interactions are prevalent in biomass pyrolysis processes. To gain deeper insights into their impact on biomass pyrolysis volatile distribution, interactions between volatile compounds and char during flash pyrolysis of glucose, cellobiose, and cellulose were investigated using a pyrolysis–gas chromatography/mass spectrometry detection technique, by modifying both the chain lengths of the raw materials and the functional groups of graphitized multi-walled carbon nanotubes (CNTs). The results reveal that volatile-char interactions markedly influence the distribution of the final pyrolysis products derived from glucose-based compounds. In the presence of any type of CNTs, dehydrated saccharides in the primary products, particularly levoglucosan (LG), exhibit the highest sensitivity to the interactions. Consequently, primary products such as LG and 5-hydroxymethylfurfural (HMF) undergo secondary pyrolysis, yielding compounds such as levoglucosenone (LGO) and 5-methyl-2-furancarboxaldehyde (FCM). Additionally, CNTs without functional groups are advantageous for the production of expensive LGO (The relative abundance reached 9.65%), whereas the relative abundance of FCM increases significantly with hydroxyl-, carboxyl-, and amino-modified carbon nanotubes. Particularly, the relative abundance of FCM is highest in the presence of amino-modified carbon nanotubes, regardless of whether the feedstock is glucose, cellobiose, or cellulose, with values of 25.14%, 23.32%, and 4.23%, respectively. Furthermore, consistent changes in product distribution trends among different glucose-based compounds under identical CNT conditions suggest that glycosidic bonds have minimal impact on volatile-char interactions.

Imidazo[2,1-b][1,3,4]thiadiazoles: Microwave-assisted synthesis, gas phase thermolysis and integrative mechanistic approach

The present study, deals with the synthesis of 2-substituted-6-phenyl-imidazo[2,1-b][1,3,4]thiadiazoles from 2-amino-5-substituted-1,3,4-thiadiazoles and 2-bromo-1-phenylethanone, which was carried out applying a microwave-assisted aqueous procedure. Furthermore, the gas-phase thermal behaviour of these imidazothiadiazoles in flash vacuum pyrolysis reactions has been studied. It has been shown that thermolysis conditions induce thiadiazole fragmentation to give indole-carbonitriles and other nitriles. The quantum chemical calculations support a stepwise mechanism for the fragmentation of imidazothiadiazoles to afford products.

Efficient CO2 capture using a novel Zn-doped activated carbon developed from agricultural liquid biomass: Adsorption study, mechanism and transition state

A Zn-doped carbon was prepared and used as an effective CO2 adsorbent. This carbonaceous material was developed from olive mill wastewater (OMWW) by an innovative process using thermal shock flash pyrolysis followed by zinc chloride impregnation at ambient temperature. The developed Zn-doped carbon is highly porous (1406.56 m2.g−1), thermally stable and rich in active sites. The Temkin isotherm and the pseudo-second order kinetic model best describe the adsorption of CO2 on the developed material, and the storage capacity is of 370.41 mg g−1 (293 K). Thermodynamic parameters showed favorable, exothermic, and orderly adsorption. Two new isotherms, based on the number of layers formed at the surface, developed by advanced statistical modelling, were adapted and used to understand the mechanism in depth. The analysis of the results showed that CO2 adsorption occurs through the appearance of double layers on the adsorbent surface. Adapted models showed: only one molecule was adsorbed per surface active site, a very low degree of aggregation of CO2 molecules before adsorption and the molecules were adsorbed in a parallel orientation. The activation parameters showed a rapid and physical adsorption with a drop in entropy at the transition state. The mechanisms involved were governed by thermodynamic control with the possibility of easy desorption at high temperature. Zn-doped carbon is an ecological approach to reduce CO2 emissions on the globe.

Flash Vacuum Pyrolysis: Principles, Instrumentation, and Applications

Flash Vacuum Pyrolysis: Principles, Instrumentation, and Applications

Effect of ethanolysis on the structure evolution, pyrolysis kinetics, and volatile products of waste poplar sawdust

Ethanolysis had been the promising approach for the deoxygenation of waste poplar sawdust (WPS), and its effect of structure variation and pyrolysis behaviors on the WPS was investigated in present research. The decreasing of C–O chemical bonds and the increasing of C content was typical phenomenon during the ethanolysis of WPS. The pyrolysis behaviors of sample were performed by thermogravimetric analyzer at three different heating rates. The pyrolysis kinetics and thermodynamics of WPS, residue230 (R230), and residue260 (R260) were well determined on the basic of three model-free iso-conversional methods. Average activation energy derived from the Kissinger-Akahira-Sunose (KAS) method of R260 displayed the high value (445.06 kJ/mol), followed by 224.88 kJ/mol for R230, then 200.68 kJ/mol for WPS. Thermodynamics data suggested that R260 required more total energy consumption for the breakage of chemical bonds. Additionally, pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) results showed that the highest relative content of volatile products compound derived from the flash pyrolysis of R230 and R260 was 47.12 % (d-Allose) and 38.69 % (Phenols), respectively, and RC value of arenes significantly increased to 15.82 % after ethanolysis. The findings would significantly contribute to the valuable utilization of waste biomass and its residues.

Nitrile Imine Cyclizations and Rearrangements: N-Phenyl-C-styrylnitrile Imine and N-Phenyl-C-phenylethynylnitrile Imine.

The formation and rearrangements of nitrile imines are of ongoing synthetic and theoretical interest. In this paper, we report a computational investigation at the M06/6-311 + G(d,p) level of the formation and rearrangement of propargylic N-phenyl-C-styrylnitrile imine 3 from 2-phenyl-5-styryltetrazole 1 by flash vacuum pyrolysis (FVP). Nitrile imine 3 cyclizes to 3aH-3-styrylindazole 4, which is also generated by H-shifts in the FVP of 3-styrylindazole 8. Tautomerization of 4 and N2-elimination afford cyclohexadienylidene 14, which by cyclization followed by H-shifts yields the primary pyrolysis product, 3-phenylindene 5. An alternate path via 7aH-3-styrylindazole, phenyl(styryl)diazomethane, and phenyl(styryl)carbene is potentially possible. The analogous pyrolysis of 2-phenyl-5-phenylethynyltetrazole 1' afforded cyclopenta[fg]fluorene and cyclopenta[def]phenanthrene via N-phenyl-C-phenylethynylnitrile imine 3' and 3aH-3-phenylethynylindazole 4'. In both cases, 3 and 3', rearrangement to diazocyclohexadienes and cyclohexadienylidenes (e.g., 14) is energetically preferred over alternate aryldiazomethane and arylcarbene intermediates.

Catalytic flash pyrolysis for recovery of gasoline-range hydrocarbons from electric cable residue using a low-cost natural catalyst: An analytical Py–GC/MS study

This investigation’s novelty and objective reside in exploring catalytic flash pyrolysis of cross-linked polyethylene (XLPE) plastic residue in the presence of kaolin, with the perspective of achieving sustainable production of gasoline-range hydrocarbons. Through proximate analysis, thermogravimetric analysis, and heating value determination, this study also assessed the energy-related characteristics of cross-linked polyethylene plastic residue, revealing its potential as an energy source (44.58 MJ kg−1) and suitable raw material for pyrolysis due to its low ash content and high volatile matter content. To understand the performance as a low-cost catalyst in the flash pyrolysis of cross-linked polyethylene plastic residue, natural kaolin was subjected to characterization through thermogravimetric analysis, X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray fluorescence (XRF). Cross-linked polyethylene plastic residue was subjected to thermal and catalytic pyrolysis in an analytical microreactor coupled to gas chromatography-mass spectrometry (Py–GC/MS system), operating at 500 °C, to characterize the distribution and composition of volatile reaction products. The application of kaolin as a catalyst resulted in a decline of the relative concentration of hydrocarbons in the diesel range (C8-C24) from approximately 87 % to 28 %, and a reduction in lubricating oils (C14-C50) from about 70 % to 13 %, while concomitantly increasing the relative concentration of lighter hydrocarbons in the gasoline range (C8-C12) from around 28 % to 87 %. Therefore, catalytic flash pyrolysis offers the potential for converting this plastic waste into a new and abundant chemical source of gasoline-range hydrocarbons. This process can be deemed viable and sustainable for managing and valorizing cross-linked polyethylene plastic residue.

Flash Pyrolysis of Waste Tires in an Entrained Flow Reactor-An Experimental Study.

In this study, a flash pyrolysis process is developed using an entrained flow reactor for recycling of waste tires. The flash pyrolysis system is tested for process stability and reproducibility of the products under similar operating conditions when operated continuously. The study is performed with two different feedstock materials, i.e., passenger car (PCT) and truck tire (TT) granulates, to understand the influence of feedstock on the yield and properties of the pyrolysis products. The different pyrolytic products i.e., pyrolytic carbon black (pCB), oil, and pyro-gas, are analyzed, and their key properties are discussed. The potential applications for the obtained pyrolytic products are discussed. Finally, a mass and energy balance analysis has been performed for the developed pyrolysis process. The study provides insight into the governing mechanisms of the flash pyrolysis process for waste tires, which is useful to optimize the process depending on the desired applications for the pyrolysis products, and also to scale up the pyrolysis process.

Flash vacuum pyrolysis of steroid propargyl ethers

Owing to its unique rearrangement and cyclization processes via flash vacuum pyrolysis (FVP), the acetylenic moiety has attracted considerable attention by organic chemists as a key building block in the construction of innovative organic architects. Herein, a series of seven steroid propargyl ether precursors have been successfully synthesized and pyrolyzed. Analysis and characterization of the FVP products revealed that the propargyl ethers of phenolic steroids undergo Claisen-rearrangement to give 2-indanone and benzo cyclobutene derivatives, while propargyl ethers of non-aromatic steroids resulted in the corresponding α, β-unsaturated ketones.

Thermal decomposition and isomerization of 1-Butyl and 1-Pentyl radical by flash pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry.

Thermal decomposition and isomerization of 1-butyl and 1-pentyl radical were studied in the temperature range of 500-1480 K on a short time scale of 20-100 µs using flash pyrolysis vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry. 1-Bromobutane and 1-bromopentane were used as precursors for the 1-butyl and 1-pentyl radical, respectively. The reactive intermediates in the thermal dissociation reactions were directly observed. The 1-butyl radical decomposed to ethene and ethyl radical with ethyl radical rapidly losing an H atom to form a second ethene molecule. Loss of H atom from butyl radical was also a significant decomposition channel. Isomerization of 1-butyl via 1,3-H migration was observed as a minor channel at 1380 K and above with a branching ratio of less than 3% at 1430 K. The 1-pentyl radical was observed to decompose mainly by isomerization to 2-pentyl radical followed by β-scission to produce propene and ethyl radicals at temperatures approximately 900 K and below. Above 900 K, β-scission of 1-pentyl to produce ethene and 1-propyl radical became increasingly important. Isomerization to 3-pentyl was verified to be a minor channel.

Catalytic hydropyrolysis of cashew de-oiled shell using Py-GC/MS

The present study delves into the impact of different metal oxides (Al2O3, Nb2O5, CaO, CeO2, and ZrO2) and temperatures (350, 450, and 550℃) on the flash pyrolysis of cashew de-oiled shell. Upon analysis using Pyrolysis Gas Chromatography and Mass Spectrometry (Py-GC/MS), the resulting functionalities, including carbonyls, furans, phenolics, hydrocarbons, sugars, and N-containing compounds, have been identified. Additionally, the potential of flash hydro-pyrolysis to upgrade pyrolysis vapors into fuel-grade hydrocarbons has also been studied. The study investigates the effect of hydrogen pressure variations (1, 5, and 10 bar) and the catalytic activity of metal oxides on hydropyrolysis. Characterization of the metal oxides through BET, XRD, SEM, and TPD reveals distinct properties. Notably, incorporating Al2O3 significantly enhances the production of aliphatic hydrocarbons, reaching 78.4 area% at 10 bar of hydrogen. This research advances our understanding of flash pyrolysis and provides insights into sustainable fuel production through targeted catalytic processes.

Synergistic effects of mechanochemical activation and selective O-alkylation on the chemical structure and gaseous products evolution during coal flash pyrolysis

Mechanochemical activation offers significant advantages in enhancing the pore structure and active sites of materials, while selective O-alkylation boosts both the homogeneous and heterogeneous reactivity of coal. In this work, mechanochemical activation and selective O-alkylation are synergistically applied to modify pulverized coal. The evolution of the chemical structure was thoroughly characterized using ultimate analysis, Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR). Pyrolysis gas chromatography-mass spectrometry (PY-GC-MS) was utilized to investigate the release of crucial gaseous products during the pyrolysis. Additionally, this study focuses on the synergistic effects of mechanochemistry and selective O-alkylation on the chemical structure and pyrolysis characteristics. The results reveal that alkylation boosts the formation of C-O bonds and aliphatic carbon while reducing the presence of aromatic carbon. Moreover, by disrupting intermolecular forces, alkylation induces the fragmentation of expansive aromatic layers into smaller aromatic fragments, thereby generating additional structural defects. Furthermore, the electron transfer process facilitates the conversion of aromatic carbon into aliphatic forms through ring-opening reactions. On the other hand, incorporating alkyl functional groups and initiating ring-opening reactions of aromatic carbons lead to a rise in aliphatic hydrocarbons during the pyrolysis of alkylated coal. However, intensified mechanochemical action hinders the production of aliphatic hydrocarbons. Additionally, during alkylation, the creation of esters and ethers with elevated thermal stability delays the release of oxygen-containing gas products. The findings propose a new pretreatment method for coal utilization, promoting the development of new low-NOx combustion technology.

Catalytic upgrading of polyethylene plastic waste using GMOF catalyst: Morphology, pyrolysis, and product analysis

Since 2000, global plastic waste production and consumption have doubled, escalating from 250 to 500 million tonnes. Merely 9 % of plastic waste undergoes global recycling, leaving the majority either in landfills or poorly managed. This research introduces a new catalyst, GMOF, created by growing Metal-Organic Framework (MOFs) rods on the flaked, carpet-like structure of Graphene Oxide (GO) nanosheets. The aim is to enhance the quality of pyrolysis products derived from high-density polyethylene (HDPE) and low-density polyethylene (LDPE) waste using this GMOF catalyst. HDPE and LDPE, sourced from post-consumer plastic packaging, underwent specific treatment involving cleaning, drying, and shredding. Morphological and property evaluations of GO nanosheets before and after MOF decoration employed techniques including Field-Emission Scanning Electron Microscopy (FE-SEM), Energy-Dispersive X-ray Spectroscopy (EDS), and Fourier Transform Infrared Spectroscopy (FTIR). Flash pyrolysis at 500 °C for 1 min using a sample-to-catalyst ratio of 4:1 in a Quartz Wool Matrix (QWM) reactor was conducted via a Thermogravimetric Analyzer (TGA) and Frontier LAB pyrolizers. Thermal stability and characteristics of feedstocks and catalysts were assessed using TGA. Gas Chromatography-Mass Spectrometry (GC–MS) analyzed and quantified pyrolysis product compounds, while a Micro GC Fusion system determined non-condensable pyrolyzate permanent gas distribution. Results showcased that the GMOF catalyst's unique morphology efficiently captured smaller radicals on its surface, providing increased surface area for effective radical–radical interactions during pyrolysis. In HDPE pyrolysis, the GMOF catalyst notably decreased selectivity of C21-C40 and C40 + wax fractions to 49.07 % and 7.73 %, respectively, while boosting C1-C20 olefin production by 2.54 %. Conversely, LDPE pyrolysis with the GMOF catalyst notably amplified the CO2 peak intensity by 3.17 %, signifying a gasification phase. Primary gases produced were C3 aliphatic hydrocarbons, propane, and propylene, yielding 79.46 % collectively.

Colored cotton crop wastes valorization through pyrolysis: a study of energetic characterization and analytical Py-GC/MS

The present work aimed to study different parts of colored cotton waste through energetic characterization and analytical flash pyrolysis. Stalks and bolls of BRS cotton cultivars from Sementes do Brasil (Green, Ruby, Topaz and Jade) were studied, using white cotton (BRS 286) as a comparison. The energetic potential of biomass was evaluated by bulk density, High Heating Value (HHV), proximate and ultimate analysis, compositional and thermogravimetric analysis (TGA). Pyrolysis was performed in a micro-pyrolyzer and the products were identified by gas chromatography and mass spectroscopy (Py-GC/MS). The results indicated a significant energetic potential, suggesting that can be used as an alternative energy source for thermochemical processes. The results of conventional pyrolysis indicated the presence of oxygenated compounds of different organic groups: aldehydes, ketones, phenols, furans and ethers, characteristic of the decomposition of lignocellulosic materials. Light organic acids in the C1-C4 range stood out the most, followed by phenols that appeared in a considerable proportion. Finally, it is concluded that the energy potential and pyrolysis products of the different parts (stalks and bolls) of colored cotton waste can be used to generate bioenergy and various chemical compounds of plant origin from green chemistry.

Flash vacuum pyrolysis of steroid esters

We report here our synthetic approach to acetylenic esters of six different steroids. The use of flash vacuum pyrolysis (FVP) is a very appealing tool for the acetylenic moiety to efficiently cyclize and rearrange which allows access to medicinally and pharmaceutically valuable products. Each substrate was subjected to FVP. The products were analyzed, identified and characterized. Acetylenic esters of aromatic steroids resulted in 2H-cyclohepta[b]furan-2-one, and 2H-chromen-2-one derivatives, while aliphatic esters afforded unsaturated polycyclic hydrocarbons via elimination of propiolic acid.

Valorization of Wood Residues from Vegetation Suppression during Wind Energy Plant Implementation and Its Potential for Renewable Phenolic Compounds through Flash Pyrolysis: A Case Study in Northeast Brazil’s Semi-Arid Region

In the past few years, wind power has become a viable alternative in Brazil to diversify the energy mix and mitigate pollutant emissions from fossil fuels. Significant wind energy generation potential is inherent in the Brazilian Northeast state of Rio Grande do Norte, due to prevailing strong winds along the coastline and elevated regions. However, clean and renewable wind energy may lead to potential biodiversity impacts, including the removal of native vegetation during plant construction and operation. This case study explores the flash pyrolysis-based valorization of three commonly suppressed species, namely Cenostigma pyramidale (CP), Commiphora leptophloeos (CL), and Aspidosperma pyrifolium (AP), in a wind farm situated within the Mato Grande region of Rio Grande do Norte State. The study centers on determining their bioenergy-related properties and assessing their potential for producing phenolic-rich bio-oil. The investigation of three wood residues as potential sources of high-value chemicals, specifically phenolic compounds, was conducted using a micro-furnace type temperature programmable pyrolyzer combined with gas chromatography/mass spectrometry (Py–GC/MS setup). The range of higher heating values observed for three wood residues was 17.5–18.4 MJ kg−1, with the highest value attributed to AP wood residue. The bulk density ranged from 126.5 to 268.7 kg m−3, while ash content, volatile matter content, fixed carbon content, and lignin content were within the respective ranges of 0.8–2.9 wt.%, 78.5–89.6 wt.%, 2.6–9.5 wt.%, and 19.1–30.6 wt.%. Although the energy-related properties signifying the potential value of three wood residues as energy resources are evident, their applicability in the bioenergy sector can be expanded via pelleting or briquetting. Yields of phenolic compounds exceeding 40% from the volatile pyrolysis products of CL and AP wood residues at 500 °C make them favorable for phenolic-rich bio-oil production. The findings of this study endorse the utilization of wood residues resulting from vegetation suppression during the installation of wind energy plants as potential feedstocks for producing bioenergy and sustainable phenolic compounds. This presents a solution for addressing a regional environmental concern following the principles of green chemistry.

Pyrolysis of macroalgae: Insight into product yields and biochar morphology and stability

Pyrolysis of biomass residues into biochar is seen as a feasible way to mitigate climate change by biological carbon storage (carbon dioxide removal, CDR) and to substitute fossil fuel with sustainable biofuel. This study applies a combination of flash and ramp heating pyrolysis, and organic petrography to investigate the hydrocarbon (biofuel) potential and biochar stability and morphotypes of eight brown, red, and green macroalgal species of different tissue complexity. The carbon stability of biochar derived from macroalgae has not previously been assessed using organic petrography (reflectance measurements) and evaluated in the context of the geological carbon cycle. The biochar, hydrocarbon, and CO + CO2 yields vary due to different chemical composition of the macroalgal species, but the product yield variations are not related to the brown, red, or green macroalgal groups. The total biofuel yield shows an inverse trend with biochar yield. A slower heating rate produces more biochar and higher CO + CO2 and lower biofuel yields than the combined flash pyrolysis and faster heating rate. The morphotype composition of the biochar was qualitatively examined by reflected light microscopy while carbon stability was assessed by random reflectance (Ro) measurements. The diverse morphotype compositions observed in biochar formed under similar pyrolysis conditions likely stem from variations in the original algal composition. While some biochar samples show morphologies resembling the original macroalgal structure, porous morphotypes predominantly characterize the biochar samples overall. Despite a maximum pyrolysis production temperature (PT) of 650 °C, the highest mean Ro value among all biochar samples is 2.91%, corresponding to a carbonization temperature (CT) of 526 °C. This observation is tentatively related to the less lignocellulosic structure of the macroalgae compared to terrigenous biomass. Four biochar samples have their entire Ro distribution range above the inertinite benchmark (IBRo2%) of Ro = 2% indicating high carbon stability. Conversely, the remaining four biochar samples exhibit Ro distributions extending below IBRo2%, indicating the presence of a carbon fraction with lower long-term stability in soil. The statistically significant inverse relationship observed between the mean Ro values and the peak hydrocarbon generation temperature (Tmax) can be attributed to the behavior of residual macromolecules within the biochar. When these macromolecules reach peak biofuel generation at a lower temperature, they undergo carbonization over a more extended time interval during pyrolysis. Consequently, this prolonged exposure to the pyrolysis process leads to higher degrees of carbonization, as reflected by higher Ro values. In conclusion, the findings from pyrolysis and organic petrography reveal: (1) Macroalgae demonstrate potential for biofuel production, although biofuel yields contingent upon both the species of macroalgal and the heating rate employed, and (2) This study documents for the first time that flash+ramp pyrolysis of macroalgae yields biochar suitable for long-term carbon storage. However, both the carbon stability inferred from Ro frequency distributions and biochar yields show variations across different macroalgal species and heating rate.

Rearrangement of Arylsulfamates and Sulfates to Para-Sulfonyl Anilines and Phenols.

The C(sp2)-aryl sulfonate functional group is found in bioactive molecules, but their synthesis can involve extreme temperatures (>190 °C or flash vacuum pyrolysis) and strongly acidic reaction conditions. Inspired by the 1917 Tyrer industrial process for a sulfa dye that involved an aniline N(sp2)-SO3 intermediate en route to a C(sp2)-SO3 rearranged product, we investigated tributylsulfoammonium betaine (TBSAB) as a milder N-sulfamation to C-sulfonate relay reagent. Initial investigations of a stepwise route involving TBSAB on selected anilines at room temperature enabled the isolation of N(sp2)-sulfamate. Subsequent thermal rearrangement demonstrated the intermediary of a sulfamate en route to the sulfonate; however, it was low-yielding. Investigation of the N-sulfamate to C--sulfonate mechanism through control experiments with variation at the heteroatom positions and kinetic isotope experiments (KIEH/D) confirmed the formation of a key N(sp2)-SO3 intermediate and further confirmed an intermolecular mechanism. Furthermore, compounds without an accessible nitrogen (or oxygen) lone pair did not undergo sulfamation- (or sulfation) -to-sulfonation under these conditions. A one-pot sulfamation and thermal sulfonation reaction was ultimately developed and explored on a range of aniline and heterocyclic scaffolds with high conversions, including N(sp2)-sulfamates (O(sp2)-sulfates) and C(sp2)-sulfonates, in up to 99 and 80% (and 88% for a phenolic example) isolated yield, respectively. Encouragingly, the ability to modulate the ortho-para selectivity of the products obtained was observed under thermal control. A sulfonated analog of the intravenous anesthetic propofol was isolated (88% yield), demonstrating a proof-of-concept modification of a licensed drug alongside a range of nitrogen- and sulfur-containing heterocyclic fragments used in drug discovery.