Formation Of Reaction Products Research Articles

New Method for Obtaining Carboxylic Derivatives of Oxazolo[5,4-b]pyridine Based on 3-Aminopyridine-2(1H)-ones

Current methods for synthesis of oxazolo[5,4-b]- and oxazolo[4,5-b]pyridines have several limitations, such as severe reaction conditions, lengthy reaction times, low yields and concurrent formation of side reaction products. This article presents the results of study focused on a one-step method for the synthesis of new derivatives of oxazolo[5,4-b]pyridine incorporating an aliphatic carboxylic group as a linker. During the investigation of acylation reactions of 3-aminopyridine-2(1H)-ones with cyclic anhydrides of dicarboxylic acids (succinic, maleic and glutaric), it was found that the monoamides formed at the initial stage undergo intramolecular cyclization yielding derivatives of oxazolo[5,4-b]pyridine. Subsequently, the reaction conditions were studied and optimized to achieve the target compounds with high yield and purity. The potential anti-inflammatory activity of the obtained derivatives of oxazolo[5,4-b]pyridine was evaluated by molecular docking method using AutoDock Vina software. Compounds 11-14b exhibited higher binding affinity with the selected target protein Prostaglandin synthase-2 (1CX2) compared to the reference anti-inflammatory drug diclofenac. Thus, taking into account the results of in silico analyses, the newly synthesized oxazolo[5,4-b]pyridine derivatives based on 3-aminopyridine-2(1H)-ones are promising candidates for further investigation of their potential anti-inflammatory activity through in vivo methods.

Enhanced wettability of gallium-based liquid metal alloys on copper films by promoting intermetallic reactions

Gallium-based liquid metal alloys (LMs) have promising prospects as circuit components for flexible electronics, while, their high surface tension is now challenging for wetting of LMs on polymer surfaces and further patterning. In this study, we prepared functional Cu thin films on PDMS to enhance wettability of EGaIn liquid metal, using metal reaction-enhanced wetting. By adjusting the deposition pressure for Cu film deposition and introducing silicon-bound PDMS, both surface characteristics and microstructures of the Cu films change greatly. The corresponding contact angle of EGaIn can be tuned from 19° to 79.5°. The folded texture of the Cu film surface reduces the actual contact area, leading to an increase in the contact angle. The higher I(111)/I(200) ratio in the Cu films improves the surface wettability, probably due to the fact that the (111)-phase orientation promotes the formation of CuGa2 reaction products. This tunable wettability of LMs is expected to improve the performance of flexible electronic devices.

Microscale Chaotic Mixing as a Driver for Chemical Reactions in Porous Media.

Mixing-induced reactions play a key role in a large range of biogeochemical and contaminant transport processes in the subsurface. Fluid flow through porous media was recently shown to exhibit chaotic mixing dynamics at the pore scale, enhancing microscale concentration gradients and controlling mixing rates. While this phenomenon is likely ubiquitous in environmental systems, it is not known how it affects chemical reactions. Here, we use refractive index matching and laser-induced fluorescence imaging of a bimolecular redox reaction to investigate the consequence of pore scale chaotic mixing on the reaction rates. The overestimation of measured reaction rates by the classical macrodispersion model highlights the persistence of incomplete mixing on the pore scale. We show that the reaction product formation is controlled by microscale chaotic mixing, which induces an exponential increase of the mixing interface and of the reaction rates. We derive a reactive transport model that captures experimental results and predicts that chaotic mixing has a first order control on reaction rates across a large range of time scales and Péclet and Damköhler numbers. These findings provide a new framework for understanding, assessing, and predicting mixing-induced reactions and their role on the fate and mobility of environmental compounds in natural porous media.

Encapsulation of probiotic Lacticaseibacillus casei with whey protein isolate/soybean hull polysaccharide enhances cell viability in harsh conditions

Whey protein isolate (WPI)-soybean hull polysaccharide (SHP) Maillard reaction conjugates were used to encapsulate Lacticaseibacillus casei and determine the effect of encapsulation on bacterial viability during freeze drying, simulated pasteurization simulated gastrointestinal digestion and storage. The WPI-SHP conjugates were characterized by degree of conjugation, size-exclusion chromatography, infrared and fluorescence spectroscopy and other analyses. The degree of conjugation, the formation of Maillard reaction products and the content of high molecular weight conjugates increased with reaction time. The emulsification capacity and glass transition temperature (Tg) of the WPI-SHP conjugates peaked after 4 days of reaction, at a Tg of 140.51 ± 2.76 °C, an emulsification activity index of 9.12 m2/g and emulsion stability index of 87.01%. WPI-SHP4d had the best protection effect of probiotics under freeze drying, simulated pasteurization and gastrointestinal digestion. These findings provide valuable insights into the selection of encapsulating agents to improve probiotic viability in functional foods.

Mechanisms of flavonoid inhibition of Maillard reaction product formation in relation to whole grains processing

Whole grains (WG) are beneficial to health but have reduced sensory quality, partly attributable to inhibition of Maillard reaction products (MRP) by WG phenolics. The study investigated how major flavonoid classes in cereals affect Maillard reaction pathways. Flavonoids were reacted with xylose-lysine aqueous system at 160 °C/12 min. Additionally, breads were made with catechin, and wheat and sorghum bran fortification. Low Mw MRP were profiled using UPLC-MS/MS, while melanoidins were characterized using fluorescence spectroscopy and HPSEC-MALS. The flavonoids significantly (p < 0.05) reduced both melanoidin content (by 33–86%) and Mw (3.5–15 kDa vs 20 kDa control), leading to lighter bread crust. Flavonoids inhibited MRP via direct condensation with early-stage amines and carbonyls into stable adducts, and reduction of late-stage polymerization reactions, increasing accumulation of cyclic N-containing intermediates. Inhibitory trend was flavones>flavanones>flavanols. C-Ring π-bond dramatically enhance flavonoid MRP inhibition; thus flavone-rich cereal grains are likely to strongly impact MRP-dependent sensory attributes of WG products.

Influence of chemistry and surface roughness of various thermal barrier coatings on the wettability of molten sand

High temperature wettability experiments were carried out to investigate how chemistry and surface roughness affect wetting characteristics of molten sand several promising thermal/environmental barrier coatings. Contact angle experiments were performed on varying as-sprayed and polished yttria-stabilized zirconia (YSZ), rare-earth oxide-YSZ (REO-YSZ), and rare-earth silicate coatings subjected to molten synthetic sand at 1260 °C. The results showed that the spreading rate of molten sand was higher on silicate-based environmental barrier coatings (~60°/min) than on Zr-based thermal barrier coatings (~25°/min). Increased surface roughness had opposite effects on the wettability depending on the reactivity of the coatings. Wettability decreased on coatings such as YSZ (which did not react with sand) but increased for REO-YSZ coatings (which formed reaction products with sand). It was found that while the REO-YSZ coatings were able to promote formation of the apatite that performed as a sealing layer to reduce further infiltration, molten sand wetting increased. YSZ was found to have greater wetting resistance in the roughened state while the REO-YSZ coatings had greater wetting resistance in the polished state. Surface energy, microstructure, and molten sand penetration also play a key role in the wetting kinetics and are discussed. This work reveals the dependency of chemistry and surface roughness on influencing the “sandphobicity” (analogous to hydrophobicity) of a material and provides insights for optimizing these variables to realize more “sandphobic” coatings.

Insight into reaction performance and product formation in a novel coal pyrolyzer of pilot-scale test

The pyrolysis behavior of coal in a pilot-scale moving bed with internals is modeled through computational fluid dynamics (CFD) simulations. The temperature field, reaction field, volatile flow paths inside the reactor, and effects of the internal design and operating parameters on the tar yield are systematically investigated. The simulation results show that the central gas channel allows the majority of generated volatiles to laterally pass through the low-temperature bed layer. This not only enhanced the primary volatile generation reaction but also significantly reduced the secondary cracking of tar. However, the placement of the heat transfer plates had a dual effect. While the plates significantly enhanced heat transfer, thereby promoting primary reactions, they could cause the volatiles to bend towards the high-temperature zone near the plates, resulting in the partial loss of tar. The tar yield may decrease with an increase in the number or area of heat transfer plates. Furthermore, investigations into the operational parameters revealed that increasing the furnace temperature appropriately and reducing the mass flux of coal were favorable for the heat transfer and yield increase in tar.

Unveiling the synergistic effect of in-situ generated calcium carbonate by CO2 mixing on the reaction of calcined clay

This study investigates the effect of in-situ generated calcium carbonate by CO2 mixing on the reaction of calcined clay and demonstrates that the in-situ generated calcium carbonate remarkably accelerates the reaction of calcined clay. The mechanism is revealed through the application of multiple techniques and thermodynamical modeling. The in-situ generated calcium carbonates are generally nano/micro-particles and provide the seeding effect for promoting the formation of reaction product. More importantly, it is found that in-situ generated calcium carbonates are highly reactive and could react with metakaolin from calcined clay to form carboaluminate, while prohibits the formation of stratlingite. Therefore, this study unveils the synergistic effect of in-situ generated calcium carbonate in promoting the reaction of calcined clay, indicating that CO2 mixing is a promising technique in promoting the performance of calcined clay based cementitious materials.

A Gently Processed Skim Milk-Derived Whey Protein Concentrate for Infant Formula: Effects on Gut Development and Immunity in Preterm Pigs.

Processing of whey protein concentrate (WPC) for infant formulas may induce protein modifications with severe consequences for preterm newborn development. The study investigates how conventional WPC and a gently processed skim milk-derived WPC (SPC) affect gut and immune development after birth. Newborn, preterm pigs used as a model of preterm infants were fed formula containing WPC, SPC, extra heat-treated SPC (HT-SPC), or stored HT-SPC (HTS-SPC) for 5 days. SPC contained no protein aggregates and more native lactoferrin, and despite higher Maillard reaction product (MRP) formation, the clinical response and most gut and immune parameters are similar to WPC pigs. SPC feeding negatively impacts intestinal MRP accumulation, mucosa, and bacterial diversity. In contrast, circulating T-cells are decreased and oxidative stress- and inflammation-related genes are upregulated in WPC pigs. Protein aggregation and MRP formation increase in HTS-SPC, leading to reduced antibacterial activity, lactase/maltase ratio, circulating neutrophils, and cytotoxic T-cells besides increased gut MRP accumulation and expression of TNFAIP3. The gently processed SPC has more native protein, but higher MRP levels than WPC, resulting in similar tolerability but subclinical adverse gut effects in preterm pigs. Additional heat treatment and storage further induce MRP formation, gut inflammation, and intestinal mucosal damage.

Hydration kinetics of cation exchanged clinoptilolite zeolite based cementitious materials

This paper provides information on the global reaction path and hydration kinetics of a natural clinoptilolite-Ca zeolite blended portland cementitious system. The replacement of up to 20% as-received clinoptilolite-Ca zeolite with portland cement substantially minimized the tricalcium aluminate (C3A) peak heat of hydration as observed using isothermal calorimetry. Inductively coupled plasma-optical emission spectrometry results showed that the zeolite-blended samples had a higher initial chemical dissolution of calcium and aluminate; but subsequently, the consumption of both was higher compared to the neat cement control sample, likely due to the formation of new hydration reaction products, indicating an interaction between cement and clinoptilolite-Ca zeolite. Clinoptilolite-Ca zeolite transformed into clinoptilolite-Na zeolite using NaOH and NaCl solutions showed a distinct aluminate (C3A) peak heat flow, indicating a different reaction path compared to clinoptilolite-Ca zeolite. Micro-chemical analysis using energy dispersive spectroscopy suggests a different hydration reaction mechanism for both calcium and sodium-based zeolite, along with the possibility of reduction in the formation of C–S–H, ettringite, and monosulfate due to the formation of new hydration products. The clinoptilolite-Ca zeolite consumed significantly higher aluminate contents leading to the formation of amorphous calcium-aluminum-silicate-hydrate (C-A-S-H) gels, which consequently reduced the aluminate-related reaction (C3A) heat flow in the system. In contrast, the clinoptilolite-Na zeolite released sodium ions through cation exchange to produce sodium aluminosilicate hydrate (N-A-S-H) in the blended system, which did not interfere with the C3A peak heat flow during the hydration process.

Effect of milled pegmatite quarry wastes powders on structure, microstructure and mechanical properties of pegmatite-based geopolymers

In this investigation, mechanical activation (MA) of pegmatite quarry wastes was perform via an eccentric vibratory mill to improve the geopolymeric reactivity. The MA at miscellaneous times (0 to 90 min) resulted in different activation degrees of samples with improved the fineness of particle size and specific surface area from 2.974 to 5.311 m2.g− 1. Geopolymer binders were synthesized by partly replacing the pegmatite quarry waste with 12.5 wt% of metakaolin. The activating solution used was a mixture of 10 M NaOH and Na2SiO3 solution with a volume ratio of 1:1. Reaction kinetics, compressive strength, water absorption, chemical (FT-IR, XRD, 27Al and 29Si MAS NMR), and microstructural (SEM/EDS and TEM) analyses were done to characterize the obtained geopolymer binders. The microstructural characterization reveals that undissolved/unreacted particles decreased while the non-bridge particles increased with pegmatite milled. Under SEM/EDS and TEM, fineness of pegmatite particles is highlighted by the formation of more reaction product. As a result, the compressive strength of geopolymer binders improved from 22.3 to 51.6 MPa for 0 to 60 min of milling. From these results, there is feasibility of valorising feldspathic (pegmatite) quarry wastes as alternative aluminosilicate precursors to develop environmentally-friendly geopolymer binders. The resulting binders with high-strength and low water absorption (≤ 8.6%) associated to minimization of CO2-emissions can be used as potential candidate in structural applications.

Ceria-Catalyzed Hydrolytic Cleavage of Sulfonamides.

Nanoceria is a promising nanomaterial for the catalytic hydrolysis of a wide variety of substances. In this study, it was experimentally demonstrated for the first time that CeO2 nanostructures show extraordinary reactivity toward sulfonamide drugs (sulfadimethoxine, sulfamerazine, and sulfapyridine) in aqueous solution without any illumination, activation, or pH adjustment. Hydrolytic cleavage of various bonds, including S-N, C-N, and C-S, was proposed as the main reaction mechanism and was indicated by the formation of various reaction products, namely, sulfanilic acid, sulfanilamide, and aniline, which were identified by HPLC-DAD, LC-MS/MS, and NMR spectroscopy. The kinetics and efficiency of the ceria-catalyzed hydrolytic cleavage were dependent on the structure of the sulfonamide molecule and physicochemical properties of Nanoceria prepared by three different precipitation methods. However, in general, all three ceria samples were able to cleave SA drugs tested, proving the robust and unique surface reactivity toward these compounds inherent to cerium dioxide. The demonstrated reactivity of CeO2 to molecules containing sulfonamide or even sulfonyl (and similar) functional groups may be significant for both heterogeneous catalysis and environmentally important degradation reactions.

Use of Glutathione, Pure or as a Specific Inactivated Yeast, as an Alternative to Sulphur Dioxide for Protecting White Grape Must from Browning.

One of the problems that most seriously affects oenology today is enzymatic browning, especially when grapes are infected by grey rot. We studied the capacity of glutathione (GSH) and a specific inactivated dry yeast rich in glutathione (IDY-GSH) to protect white grape must from browning compared to that of sulphur dioxide (SO2). The results indicate that SO2 drastically reduces the oxygen consumption rate (by around 72%), protects hydroxycinnamic acids from oxidation and prevents grape must against browning even in the presence of laccase. Specifically, the presence of SO2 reduced the colour's blue-yellow component (b*) by around 91% in control conditions and around 76% in the presence of laccase. GSH, pure or in the form of IDY-GSH, also reduces the oxygen consumption rate (by 23% and 36%, respectively) but to a lesser extent than SO2. GSH also favours the formation of grape reaction product (GRP) from hydroxycinnamic acids and effectively protects grape must against browning in healthy grape conditions. Specifically, the presence of GSH reduced b* by around 81% in control conditions. Nevertheless, in the presence of laccase, it was not effective enough, reducing b* by around 39% in the case of pure GSH and 24% in the case of IDY-GSH. Therefore, both forms of GSH can be considered as interesting alternative tools to SO2 for preventing browning in white grape must, but only when the grapes are healthy.

A new aspect of metabolic disorders in obesity: carbonyl stress

The literature review examines the problem of obesity in modern society. It has been shown that obesity aggravates concomitant diseases, increases the probability of developing metabolic disorders and related pathologies, increases the risk of complications and mortality. The secretory function of adipose tissue, its participation in the regulation of biological processes is considered in detail. The concept of carbonyl stress and its components is revealed, the role of carbonyl compounds in the body is described, the metabolic pathways leading to the formation of carbonyl reaction products are shown, the participation of free radicals in these metabolic pathways is noted. The mechanisms of pathogenesis associated with the development of carbonyl stress in obesity are discussed; the greatest contribution to the development of car bonyl pathology in obesity is made by two types of processes: lipid peroxidation reactions resulting in the formation of carbonyl products of lipoperoxidation and the processes activated by hyperglycemia (glycolysis, polyol and hexоzamine pathways) leading to the formation of glyoxal, methylglyoxal, and active carbonyl forms of glucose. The question of the contribution of advanced glycation end products (AGEs) and advanced oxidation protein products (AOРР) to the development of carbonyl pathology in obesity remains controversial. It is assumed that AGEs and AOРР levels depend on the severity of obesity and the development of metabolic syndrome.

Atmospheric Degradation of Ecologically Important Biogenic Volatiles: Investigating the Ozonolysis of (E)-β-Ocimene, Isomers of α and β-Farnesene, α-Terpinene and 6-Methyl-5-Hepten-2-One, and Their Gas-Phase Products.

Biogenic volatile organic compounds (bVOCs), synthesised by plants, are important mediators of ecological interactions that can also undergo a series of reactions in the atmosphere. Ground-level ozone is a secondary pollutant generated through sunlight-driven reactions between nitrogen oxides (NOx) and VOCs. Its levels have increased since the industrial revolution and reactions involving ozone drive many chemical processes in the troposphere. While ozone precursors often originate in urban areas, winds may carry these hundreds of kilometres, causing ozone formation to also occur in less populated rural regions. Under elevated ozone conditions, ozonolysis of bVOCs can result in quantitative and qualitative changes in the gas phase, reducing the concentrations of certain bVOCs and resulting in the formation of other compounds. Such changes can result in disruption of bVOC-mediated behavioural or ecological interactions. Through a series of gas-phase experiments using Gas Chromatography Mass Spectrometry (GC-MS) and Proton Transfer Reaction Mass Spectrometry (PTR-MS), we investigated the products and their yields from the ozonolysis of a range of ubiquitous bVOCs, which were selected because of their importance in mediating ecological interactions such as pollinator and natural enemy attraction and plant-to-plant communication, namely: (E)-β-ocimene, isomers of α and β-farnesene, α-terpinene and 6-methyl-5-hepten-2-one. New products from the ozonolysis of these compounds were identified, and the formation of these compounds is consistent with terpene-ozone oxidation mechanisms. We present the degradation mechanism of our model bVOCs and identify their reaction products. We discuss the potential ecological implications of the degradation of each bVOC and of the formation of reaction products.

Resolving fluorescence spectra of Maillard reaction products formed on bovine serum albumin using parallel factor analysis

Formation of Maillard reaction products (MRPs) is increasingly studied by the use of fluorescence spectroscopy, and most often, by measuring single excitation/emission pairs or use of unresolved spectra. However, due to the matrix complexity and potential co-formation of fluorescent oxidation products on tryptophan and tyrosine residues, this practice will often introduce errors in both identification and quantification. The present study investigates the combination of fluorescence excitation emission matrix (EEM) spectroscopy and parallel factor analysis (PARAFAC) to resolve the EEMs into its underlying fluorescent signals, allowing for better identification and quantification of MRPs. EEMs were recorded on a sample system of bovine serum albumin incubated at 40 °C for up to one week with either glucose, methylglyoxal or glyoxal added. Ten unique PARAFAC components were resolved, and assignment was attempted based on similarity with fluorescence of pure standards of MRPs and oxidation products and reported data from literature. Of the ten fluorescent PARAFAC components, tyrosine and buried and exposed tryptophan were resolved and identified, as well as the formation of specific MRPs (argpyrimidine and Nα-acetyl-Nδ-(5-methyl-4-imidazolon-2-yl)ornithine) and tryptophan oxidation products (kynurenine and dioxindolylalanine). The formation of the PARAFAC resolved protein modifications were qualitatively validated by liquid chromatography-mass spectrometry.

THE ANALYSIS OF THE SELECTED BIOACTIVE PARAMETERS OF BLACK GARLIC PREPARED IN THE SHORT FERMENTATION MODE

Background. Garlic (Allium sativum L.) is characterized by many health-promoting properties due to the presence of sulfur compounds, including allillin, S-allyllocysteine and the high content of polyphenolic compounds. In order to eliminate specific organoleptic characteristics – unfavorable from some consumers’ point of view, garlic can be subjected to a special, low-temperature heat treatment, referred to as aging. This process results in the hydrolysis of poly- and oligosaccharides (fructans) with the participation of intracellular enzymes (fermentation) and the formation of Maillard reaction products (condensation of sugars with amines). As a result, the color, consistency, taste and smell of the final product change and the so-called black garlic is obtained. The aim of the study was to compare the antioxidant properties and the level of total polyphenols, saccharide profile, the content of selected B vitamins and released amino acids of two varieties of raw and black garlic. The experiments were carried out with the use of a commercial short-term fermentation unit from TIROSS. The process was carried out at 70 °C for 192 hours. The amo unt of released amino acids was determined by the ninhydrin method, the content of polyphenols was found using the Folin-Ciocâlteu reagent,antioxidant properties were specified using DPPH free radical and the content of vitamin B and saccharide profile by HPLC. Results and conclusions. The results obtained indicate not only an increase in antioxidant activity, the sum of polyphenols and riboflavin, but also a decrease in the level of free amino acids and thiamine in the garlic obtained after the aging process. The project is in line with a global trend related to the nutrition model oriented towards a vegan diet and the search for new, health-promoting ingredients or recipes based on raw materials with already pre-confirmed attributes as ingredients of functional food.

Reoxidation Phenomena of Liquid Steel in Secondary Refining and Continuous Casting Processes: A Review

This review article reports the critical issue of reoxidation in clean steel production during secondary refining and continuous casting processes. Reoxidation presents substantial challenges to process stability and final product quality. Various sources of reoxidation, including exposure to oxidizing gases, reducible oxides in slag and refractories, and the presence of ferroalloys are explored. Fundamental reactions and their consequences, such as changes in steel composition, inclusion composition/morphology, and the formation of reaction products at the interface between liquid steel and refractory materials, are reviewed. High oxygen partial pressure on the refractory side is identified as a significant factor, particularly in tundish and continuous casting processes. To address reoxidation effectively, the review discusses modeling approaches like computational fluid dynamics and thermodynamic/kinetic modeling. In the industrial context, reoxidation in the tundish is mainly attributed to open‐eye formation in the tundish flux and reducible oxides like SiO2 in an insulating cover powder, for example, rice hust ash. Maintaining precise tundish flux control is crucial for steel cleanliness. In conclusion, this review highlights the multifaceted nature of reoxidation challenges in clean steel production. A comprehensive understanding of reoxidation mechanisms and the implementation of effective strategies are essential for achieving cleaner steel production.

Flavor improving effects of cysteine in xylose–glycine–fish waste protein hydrolysates (FPHs) Maillard reaction system

A promising way to utilize fish by-products is to develop hydrolysis of fish proteins with enzymes. The obtained fish protein hydrolysates (FPHs) are rich in peptides and amino acids, but bitterness and aroma defects impede further utilization of FPHs. The present study adopted Maillard reaction to improve FPHs’ flavor and illustrated the role of cysteine in this system. We investigated the impact of cysteine (0, 0.25%, 0.5%, 0.75%, and 1%) on the browning intensity, free amino acids (FAAs), molecular weight distribution, structure of MRPs, volatile compounds changes and organoleptic characteristics of xylose–glycine–FPHs Maillard reaction systems. Results showed that the addition of cysteine lowered the browning degree of Maillard reaction products (MRPs) by inhibiting the cross-linking of small peptides and reducing the production of melanin. GC–MS and GC–IMS analysis indicated that cysteine inhibited the formation of furans and nitrogen-containing compounds and facilitated the formation of sulfur-containing compounds contributing to the meaty flavor. Sensory analysis revealed that 0.25–0.75% range of cysteine increased the meaty, caramel, umami, mouthfulness and salty notes, and caused a decrease in bitter taste of the MRPs as confirmed by GC–MS. A highly significant correlation between the organoleptic characteristics and physicochemical indicators of MRPs was found by Mantel test. These results elucidated the influence of cysteine on the formation of Maillard reaction products and will help improve the flavor profile of meat flavorings.Graphical

Unlocking the potential of pequi (Caryocar brasiliense) residues for bioenergy and renewable chemicals: Multicomponent kinetic modeling, thermodynamic parameter estimation, and characterization of volatile products through TGA and Py-GC/MS experiments

The first study in the literature on the pyrolysis of pequi (Caryocar brasiliense) residues, focusing on the kinetic triplet, thermodynamic parameters, and characterization of volatile products utilizing TGA and Py−GC/MS techniques, is presented in this paper. Slow pyrolysis experiments were conducted on a thermogravimetric scale in a controlled atmosphere of pure nitrogen, with five distinct heating rates (5, 10, 20, 30 and 40 ºC min−1). The pyrolysis progress profiles were fitted using the Asym2Sig function to deconvolute the devolatilization rates of individual biomass pseudo-components, including extractives, hemicellulose, cellulose, and lignin. The average activation energies for pequi peel pyrolysis, as determined by the isoconversional methods of Friedman, Flynn−Wall−Ozawa, Kissinger−Akahira−Sunose and Starink, were higher (114.30 −319.13 kJ mol−1) than those estimated for pequi seeds (88.05 −168.39 kJ mol−1). The pre-exponential factors, obtained through the kinetic compensation effect method, exhibited a range of values between 3.6 × 1011 and 2.4 × 1030 min−1 for pequi peel and between 1.2 × 107 and 9.4 × 108 min−1 for pequi seeds. Utilizing the master-plots method revealed the involvement of F-type, A-type, and D-type reaction models in the pyrolysis of pequi residues. A slight difference between the Ea and ΔH values, less than 5 kJ mol−1, indicates the facile formation of reaction products during pyrolysis. The main organic volatile products obtained from the fast pyrolysis of pequi peel, as revealed by Py−GC/MS analysis, include furans, ketones, aldehydes, and ethers, constituting up to 52% of the total yield of the condensable fraction at 550 °C. Aliphatic hydrocarbons are the major organic volatile products derived from the fast pyrolysis of pequi seeds, accounting for approximately 74% of the total condensable fraction yield at 650 °C. This study provides new insights into the valorization of residues resulting from pequi fruit processing. As a result, a novel pathway for bioenergy and biobased chemical production via pyrolysis is established, aligning with the circular economy principle and capable of promoting energy matrix diversification.