Reaction Scheme Research Articles

Liquid phase oxidation of cyclopentanone over metal-free carbon catalysts

Oxidation of cyclopentanone (CPO) was studied over metal-free carbon catalysts in solvent-free conditions. Norit SX plus (900 m2 g−1) and Vulcan XC72 (240 m2 g−1) were used as pristine materials. Catalysts were prepared by activation in nitrogen and by treatment with urea, calcined in nitrogen at 500 °C and 950 °C. SEM, EDX, XPS, X-ray powder diffraction, nitrogen adsorption–desorption isotherms, acid–base titration, FTIR and Raman techniques were used for characterization. Catalytic tests carried out at 0.45 MPa and 80–110 °C enabled to find the best results: 30% selectivity to glutaric acid (GA) and 3% to succinic acid at 25% conversion of CPO, over Vulcan type catalysts. A low activity, selectivity and strong deactivation of Norit type catalysts can be ascribed to a higher specific surface in a disordered arrangement providing a high concentration of unselective catalytic sites. A higher extent of side reactions can yield in higher molar mass products, which stick on the surface and block catalytic sites. Optimum amount of accessible planar domains, represented by graphene and/or graphitic plates with some disorders present in Vulcan type catalysts classified them superior to Norit catalysts. A redox reaction scheme of oxidation of CPO to GA is also proposed.Graphical abstract

СУЧАСНІ ТЕНДЕНЦІЇ РОЗВИТКУ СИСТЕМ КОМПЕНСАЦІЇ РЕАКТИВНОЇ ПОТУЖНОСТІ

This paper surveys current trends and developments in reactive power compensation systems, elucidating their significance in enhancing system capacity and flexibility. By analyzing the capacity factor enhancement enabled by reactive power compensation, the study underscores its role in optimizing electricity delivery, thus conserving energy resources and facilitating the integration of renewable energy sources. It explores the key models and concepts driving advancements in reactive power compensation within power grids. As modern electrical systems grow in complexity, ongoing research into improving compensation methods becomes imperative to ensure the reliability and efficiency of industrial power grids. Future endeavors will involve developing a model utilizing real-world enterprise data to investigate the effects of technological variations in filter parameters on the performance of complex reactive power compensation schemes, encompassing both filters and capacitor banks. Keywords: reactive power, compensation systems, filter-compensating circuit, industrial power grid, electric power. Context. The paper considers the current trends used in the field of reactive power compensation, and the main directions of development of modern methods of reactive power compensation. Objective. The purpose of the work is to overview of current trends in the development of reactive power compensation systems, as well as an overview of possible ways of their effective application in various industrial networks. Methods. The paper presents a key aspect of reactive power compensation is its ability to increase system capacity and flexibility. By improving the capacity factor, utilities can deliver electricity more efficiently, reducing the need for excess capacity and thus conserving energy resources. In addition, this process plays an important role in supporting the integration of renewable energy sources such as wind and solar power, which often introduce volatility into electricity generation schemes. Results. The paper presents the main models and concepts in the field of reactive power compensation in power grids. Conclusions. Given the growing complexity of modern electrical systems, it is important to continue research into improving methods and means of reactive power compensation to ensure the reliability and efficiency of industrial power grids. In further research, it is planned to develop a model using a real enterprise as an example and investigate the impact of technological deviations of filter parameters on the steady-state and transient performance of complex reactive power compensation schemes, including not only filters but also capacitor banks.

Synthesis and characterization of amino-functionalized guar gum based polyurea: Preparation of iodine complexes, structural investigation and release studies

Biobased materials are expanding dramatically in various industrial applications due to their unique intrinsic properties. In this study, various chemical functionalization procedures were used to synthesize guar gum, a naturally occurring polysaccharide-based polyurea, and its iodine complexes. Firstly, guar gum was subjected to tosylation reaction using p-toluene sulphonyl chloride to introduce tosyl moieties in the polymer chain with the degree of substitution (DS) ranging between 0.16 and 1.54. Sample having the highest degree of tosyl moiety was further reacted with tris(2-aminoethyl) amine to produce 6-deoxy-6-tris(2-aminoethyl) amine derivative via nucleophilic substitution reaction to impart amino functional groups. The degree of substitution in 6-deoxy-6-tris(2-aminoethyl) amine derivative was found to be 0.59. 6-deoxy-6-tris(2-aminoethyl) amine derivative was reacted with different diisocyanates (Toluene-2,4-diisocyanate (TDI), 1,6-diisocyanatohexane (HMDI)) to produce guar gum based polyurea. Iodine complexes of the resulting polyurea were prepared by reacting with different iodinating agents. Different chemical reactions, formation of polyurea and its iodine complexes were thoroughly analyzed by different analytical techniques such as FT-IR, NMR, elemental analysis, XRD, UV–Vis spectroscopy, and a reaction scheme has been proposed. Morphological and rheological characteristics were analyzed by SEM and viscosity measurement. Thermal analysis was carried out by TGA and DSC studies. Finally, by examining the complex's UV–Vis spectra, the iodine release characteristics from polyurea‑iodine complexes were investigated.

A comparative analysis of square-wave voltammetry and multi-frequency electrochemical Faradaic spectroscopy for kinetic characterisation

A rigorous comparison between square-wave voltammetry (SWV) and the recently proposed multi-frequency electrochemical Faradaic spectroscopy (MEFS) is presented for both a quasireversible electrode reaction of a dissolved redox couple at a planar macroscopic electrode and a catalytic regenerative electrode mechanism (EC′ reaction scheme) by means of numerical simulations. MEFS offers fast kinetic characterisation with a minimal set of experiments, as the system is interrogated with a range of SW frequencies in a single experiment. By changing the mid-potential Em, a critical parameter of MEFS, a broad range of standard rate constants for the heterogeneous interfacial electron transfer is accessible, ranging between 0.006 and 0.12 cm s−1. In the case of the EC′ mechanism, features of the current components in both SWV and MEFS reflect the involvement of the follow-up regenerative chemical reaction (i.e. C′ catalytic step). However, for the kinetic characterisation of the EC′ mechanism, the comparative analysis suggests that SWV should be the main operating technique.

Synthesis of N-Glyoxylyl Peptides Enabled by a Lossen Rearrangement-Induced Intramolecular Redox Reaction of N-Terminal Glycyl Hydroxamic Acid.

An oxidant-free approach to the synthesis of N-glyoxylyl peptides has been developed that utilizes the Lossen rearrangement of the N-terminal glycyl hydroxamic acid residue. The synthesis proceeds via an intramolecular redox mechanism to yield the glyoxylyl peptides, which are then subjected to various peptide cyclization procedures. The reaction scheme is suitable for oxidation-sensitive moieties including amino acids.

Investigating the Mukaiyama-type epoxidation reaction of alkenes with Cr(III) salophen catalysts: A confrontation between experiments and DFT calculations

This study aimed at the complete elucidation of the mechanism of the Mukaiyama-type alkene epoxidation reaction using the [(salophen)CrIIICl] precatalyst, by combining spectroscopic (UV–visible and EPR) studies, catalytic reactivity and quantum chemical modeling. These studies performed in parallel allowed us to propose a detailed reaction scheme, in which two consecutive active species incorporating both {salophen(CrV = O)} moieties were formed in situ, resulting in two distinct catalytic regimes.

Lightweight Crypto-Ransomware Detection in Android Based on Reactive Honeyfile Monitoring.

Given the high relevance and impact of ransomware in companies, organizations, and individuals around the world, coupled with the widespread adoption of mobile and IoT-related devices for both personal and professional use, the development of effective and efficient ransomware mitigation schemes is a necessity nowadays. Although a number of proposals are available in the literature in this line, most of them rely on machine-learning schemes that usually involve high computational cost and resource consumption. Since current personal devices are small and limited in capacities and resources, the mentioned schemes are generally not feasible and usable in practical environments. Based on a honeyfile detection solution previously introduced by the authors for Linux and Window OSs, this paper presents a ransomware detection tool for Android platforms where the use of trap files is combined with a reactive monitoring scheme, with three main characteristics: (i) the trap files are properly deployed around the target file system, (ii) the FileObserver service is used to early alert events that access the traps following certain suspicious sequences, and (iii) the experimental results show high performance of the solution in terms of detection accuracy and efficiency.

Selenate reduction mediated by underpotentially deposited Cu on the low index faces of Au in aqueous perchloric acid

Underpotential deposited Cu on the low index faces of single crystal Au electrodes has been found to promote the reduction of selenate, SeO42−(aq),in 0.1 M HClO4 solutions, a behavior analogous to that reported earlier in our laboratory for polycrystalline Au (Strobl et al. J. Electrochem. Soc.2016,163 (13), H1066). Sequential potential step-linear scan voltammetry data collected for Au(111) film electrodes in solutions containing Cu2+(aq) in the μM range afforded evidence that the onset for the electrocatalytic activity occurs for Cu(UPD) coverages, θCu ≈ 0.18, the same value at which complementary microgravimetric data displayed a clear increase in mass. On this basis, a reaction mechanism has been proposed involving the initial reversible formation of an adsorbed adduct, we denote as Cu|SeO42−(ads), followed by a first order irreversible reduction to yield a yet to be identified species, which we denote as Cu|Se(ads), as the rate determining step. Support for this reaction scheme was obtained from numerical solutions of the coupled differential equations that govern the time evolution of Cu|SeO4−(ads) and Cu|Se(ads), yielding best agreement with the experimental data for values of the equilibrium constant for adduct formation and the adduct reduction rate constant of 2.5 × 106 cm3 mol−1, and 9.1 × 10−3 s−1, respectively. This unique electrocatalytic effect has been attributed to a shift in the potential of zero charge of the bare Au substrates induced by Cu(UPD), which promotes the adsorption of HSeO4−(aq) at potentials more negative than those found for the bare substrates, allowing access to overpotentials high enough for its activation and further reduction to ensue.

Thermochemistry of Gas-Phase Thermal Oxidation of C2 to C8 Perfluorinated Sulfonic Acids with Extrapolation to C16.

New ideal-gas thermochemistry Cp°(T), H°(T), S°(T), and G°(T) are predicted for 53 species involved in the thermal destruction of perfluorinated sulfonic acids (PFSAs) ranging from C2 to C8 in perfluorinated alkyl chain length. Species were selected by considering both the pyrolytic and oxidative pathways of PFSA destruction. After the sulfur-containing moieties are removed, subsequent reactions largely involve species from a prior set of thermochemistry for the thermal destruction of perfluorinated carboxylic acids (Ram et al., J. Phys. Chem. A, 2024, 128, 7, 1313-1326). Enthalpies of formation at 0 K are computed using a new isogyric reaction scheme. Rigid-rotor harmonic-oscillator partition functions were calculated over a 200-2500 K temperature range using rovibrational properties at G4 (≤C3S1 species) and M06-2X-D3(0)/def2-QZVPP (≥C4S1 species), employing the 1D hindered rotor approximation to correct for torsional modes. Seven-coefficient NASA polynomial fits are reported in standardized formats. Bond dissociation energies and important reaction equilibria are examined to provide insights into the reactivity of potentially persistent species. Extrapolated NASA polynomials are also systematically predicted for 126 species larger than C8/C8S1 in size, allowing reasonably accurate estimates of thermochemistry without the need for expensive electronic structure calculations.

Catalytic effect of N-phenylaminopropyl polyheadral oligomeric silsesquioxane in the synthesis of hybrid nanocomposites based on polycyanurate

Organic-inorganic nanocomposites based on heat-resistant crosslinked polycyanurate (PCN) and N-phenylaminopropyl polyhedral oligomeric silsesquioxane (NPAP-POSS), containing eight reactive secondary amino groups, were synthesized using the in situ reactive formation method. Fourier transmission infrared (FTIR) spectroscopy and dynamic differential scanning calorimetry (DSC) methods were used to study the effect of NPAP-POSS on the kinetics of bisphenol E dicyanate ester (DCBE) polycyclotrimerization during the formation of PCN in PCN/NPAP-POSS nanocomposites. The content of the nanofiller was varied from 0.05 to 1.00 wt.%. Based on the results of FTIR spectral studies, the main kinetic peculiarities of PCN formation were found and their changes under the action of NPAP-POSS nanofiller were determined. A significant catalytic effect of NPAP-POSS on the polycyclotrimerization of DCBE was found, which is confirmed by a decrease in the time of the onset of auto-acceleration, an acceleration of the conversion of cyanate groups of DCBE and the formation of triazine cycles of PCN, an increase in the values of the maximum reaction rate, a decrease in the duration of the reaction, etc. The dynamic DSC method also confirmed the catalytic effect of NPAP-POSS on the formation of PCN in the nanocomposites and established the main kinetic characteristics depending on the content of the nanofiller: a significant decrease in the temperature of the exothermic maximum, an increase in the reaction enthalpy, non-monotonic changes in the induction period and reaction rate, etc. From the analysis of the experimental data, it was concluded that the detected changes in the kinetics of the in situ reaction formation of PCN/NPAP-POSS nanocomposites and the recorded catalytic effect of the nanofiller are due to the fact that two chemical processes occur during the synthesis of the nanocomposites: chemical interaction of –O–C≡N groups of DCBE with secondary –NH groups of NPAP-POSS, which led to further embedding of nanoparticles into the resulting polymer matrix and the direct polycyclotrimerization of DCBE with formation of hybrid polycyanurate network. Schemes of the sequential reactions explaining the catalytic effect of the nanofiller in the synthesis of hybrid PCN/NPAP-POSS nanocomposites are proposed. It was concluded that under the selected conditions of the synthesis, the greatest catalytic effect of the nanofiller is manifested at its content of 0.10 wt.%, since for this sample the maximum shift of the reaction exothermic peak towards lower temperatures, the maximum reaction rate, and the minimum induction period and reaction start temperature were recorded. The results of the research make it possible to optimize the synthesis of heat-resistant materials promising for use in special-purpose structures.

Unraveling Enyne Bonding via Dehydrogenation–Hydrogenation Processes in On‐Surface Synthesis with Terminal Alkynes

AbstractOn‐surface reactions of terminal alkynes in ultrahigh vacuum have attracted widespread attention due to their high technological promise. However, employing different precursors and substrate materials often intricate reaction schemes appear far from being well‐understood. Thus, recent investigations of alkyne coupling on noble metal surfaces suggest non‐dehydrogenative scenarios, contradicting earlier reports. Herein, the study employs noncontact atomic force microscopy (nc‐AFM) with high spatial resolution to conclusively characterize exemplary alkyne coupling products. Contrary to initial interpretations proposing dehydrogenative homocoupling on Ag(111), bond‐resolved AFM imaging reveals the expression of enyne motifs. Based on complementary, extensive density functional theory calculations, the pertaining reaction mechanisms are explored. It is proposed that enyne formation initiates with a direct carbon–carbon coupling between two alkyne groups, followed by surface‐assisted dehydrogenation‐hydrogenation processes. Thereby consecutive steps of atomic hydrogen cleavage, surface migration and recombination to a different carbon atom enable bridging via carbon–carbon double bonding. The new results shed light on subtle, but crucial surface‐mediated hydrogen transfer processes involved in the chemical bond formation, which are suggested to be of general relevance in on‐surface synthesis.

Hemisynthesis and cytotoxic evaluation of manoyl oxide analogs from sclareol: effect of two tertiary hydroxyls & Heck coupling on cytotoxicity

Sclareol, a bioactive diterpene alcohol isolated from Salvia sclarea, was subjected to structural modification and cytotoxic evaluation. Boron-Heck-coupled analogs of manoyl oxide were prepared from sclareol in a two-step reaction scheme. In the first step manoyl oxide was prepared from sclareol using cerium (IV) ammonium nitrate. Further the structural modification of manoyl oxide via Palladium (II) catalysed Boron-Heck coupling reaction produced a new series of compounds. All the synthesised compounds were screened for in vitro cytotoxic evaluation against four cancer cell lines HCT-116, MCF-7, MDA-MB231and MDA-MB468. The results showed that manoyl oxide is less active than sclareol. Sclareol shows an IC50 of 2.0 µM compared to manoyl oxide with an IC50 of 50 µM against the MCF-7 cell line. From the results it was inferred that the presence of two tertiary hydroxyls in sclareol are necessary for its cytotoxic activity and Heck coupled analogs are more active than sclareol and manoyl oxide.

Properties of APTES-Modified CNC Films.

Sulfated cellulose nanocrystals' (CNCs') facile aqueous dispersibility enables producing films, fibers, and other materials using only water as a solvent but prevents using sulfated CNCs in applications that require water immersion. We report that modifying CNCs with 3-aminopropyl-triethoxysilane (APTES) via a simple, single-pot reaction scheme dramatically improves the hydrolytic stability of CNC films. The effects of APTES modification on CNCs' properties were studied using attenuated total reflectance Fourier transform infrared spectroscopy, atomic force and optical microscopy, thermogravimetric analysis, dynamic light scattering, and ultimate analysis. Substituting a mere 12.6% of the CNCs' available hydroxyl groups with APTES dramatically increased the hydrolytic stability of shear cast films while only having minor impacts on their mechanical properties. In addition, quartz crystal microbalance with dissipation monitoring (QCMD) and multiparametric surface plasmon resonance (MP-SPR) studies showed that the CNC-APTES films also had a greater irreversible binding with carbofuran, a pesticide and emerging contaminant. These results highlight that APTES modification is a promising method for increasing the utility of sulfated CNCs in sensors, adsorbents, and other applications requiring water immersion.

Phase equilibria and solidification behavior of Mg–Al–Gd casting alloys

The Mg–Al–Gd ternary system was re-assessed by the CALPHAD (CALculation of PHAse Diagrams) method and a set of self-consistent thermodynamic parameters of the system were obtained. The long-period stacking ordered (LPSO) phases, 14H and 18R, were described by thermodynamic model of Mgx(TM,Mg)6(RE,Mg)8 (TM=Transition Metal, RE=Rare Earth). Representative isothermal sections, vertical sections, liquidus projections and the related invariant reactions were calculated and compared with the experimental data, showing the reliability of the obtained thermodynamic parameters. Reaction scheme for the whole ternary system was also presented. The Scheil solidification paths and the phase fractions of several Mg–Al–Gd alloys were calculated and analyzed. The phase formation during solidification and the phase content of γ and LPSO phases are clearly described with the increase of Gd content, which is crucial to the microhardness, ultimate tensile strength and yield strength of Mg–Al–Gd casting alloys.

Experimental and numerical investigations of the laminar burning velocities of premixed fuel-rich methane oxy-fuel and oxygen-enhanced flames

In the context of Oxy-fuel combustion, there is a strong industrial interest in highly fuel-rich flames, characterized by an equivalence ratio (Φ) exceeding 2.5, for the production of H2-CO-rich synthesis gas. The validation of existing chemical reaction mechanisms for this specific regime pose a significant challenge due to the scarcity of experimental data for this particular range of equivalence ratio.The scope of this study was therefore the determination of the laminar burning velocity sL of ultra-rich CH4-O2 flames under varying conditions, such as high equivalence ratios and preheating temperatures using the heat flux burner method. The laminar burning velocity was determined for equivalence ratio within the range of 2.3 < Φ < 3.6 and preheating temperature ranging from 300 K to 455 K. Additionally, the impact of the of reducing the oxygen content in the oxidizer on sL was investigated by argon addition in molar percentages ranging from 40 % to 100 %.The results of our study reveal laminar burning velocities ranging from 5 cm/s to 45 cm/s for pure oxy-fuel CH4 flames. Preheating is shown to increase sL and this effect can be represented by a power law correlation sL = sL,0(T/T0)α with α = 1.53. Furthermore, the dilution of the oxidizer with argon leads to a significant decrease in sL of approximately 50 % compared to pure oxy-fuel flames. It is worth noting that detailed reaction mechanisms in combination with molecular transport data are typically not validated within the selected equivalence ratio range.To assess the performance of such reaction schemes in predicting laminar burning velocity under the specified selected conditions, we evaluated 13 different reaction mechanisms sourced from the literature. We compared the laminar burning velocities obtained through calculations of laminar premixed 1D flames and, additionally compared these with experimental data. A sensitivity analysis of the laminar burning velocity were carried out for selected mechanisms. Among the mechanisms, the CalTech2.3 mechanism exhibited the most consistent and accurate performance, particularly at high equivalence ratios.

Study on combustion mechanism of methanol/nitromethane based on reactive molecular dynamics simulation

Oxygenated fuels and nitro fuels are effective strategies for addressing incomplete combustion by increasing the oxygen-fuel ratio. A computational approach based on reactive molecular dynamics simulations reveals oxidation mechanisms of temperature-induced effects on a mixed fuel of methanol and nitromethane. The method enables the demonstration of the initial reaction scheme of a binary fuel mixture, even for complicated interplay and coupling reactions. The results showed that the first reaction step of nitromethane was homolysis in poor-oxygen conditions, mainly via CH3NO2 → CH3 + NO2 (Net flux = 183, ratio = 92.89%). Methanol undergoes dehydrogenation reaction with the assistance of active radicals (OH, HO2, CH3, NO, and NO2), and the participation rates of these active groups are 60%, 17.14%, 8.57%, 7.62%, and 6.67%, respectively. The decomposition of nitromethane provided NO2 and CH3 radicals and significantly increased the amount of OH and NO via a reaction of NO2 + H → HNO2 → OH + NO. By fragment analysis, the main C1 intermediates are formed by pyrolysis of methanol/nitromethane such as formaldehyde, hydroxymethyl radical, and formyl radical. The CH3OH and CH2O are relatively stable, and the dehydrogenation is mainly highly active groups such as OH and NO. In contrast, the dehydrogenation of CH2OH and CHO free radicals is completed by self-cleavage or with the help of O2, NO2, etc. Our findings shed light on the oxidation behaviors of methanol/nitromethane mixed fuel in combustion.

Causes and mechanism of thermal runaway in lithium-ion batteries, contradictions in the generally accepted mechanism

In this paper, experimental results are analyzed that contradict the generally accepted scheme of thermal runaway reactions. Also, it was experimentally proved that three main exothermic reactions determine the thermal runaway process of lithium-ion batteries. The first main exothermic reaction of the thermal runaway is the reaction releasing the electrochemical energy accumulated in the lithium-ion batteries during their charging. The second main exothermic reaction of the thermal runaway is the reaction of lithiation of surface layers of a cathode active material; this reaction is performed by the lithium atoms coming from both the anode and the inner layers of the cathode active material. The third main exothermic reaction of the thermal runaway is the reaction of the cathode metal-oxides decomposition and the electrolyte oxidation by the released oxygen. Besides, it is shown here that the open circuit voltage drop in batteries during the thermal runaway is mainly due to the lithiation of the cathode active material and – to a much lesser extent – to short circuits occurrence of the electrodes. The established mechanism of thermal runaway of lithium-ion batteries makes it possible to quantitatively describe all currently known experimental results.

Mass transfer analyses of reactive boundary schemes for lattice Boltzmann method with staircase approximation

Lattice Boltzmann (LB) methods with reactive boundary conditions are widely used in pore-scale simulations of dissolution and ablation processes. The staircase approximation of curved boundary is often employed because of its simplicity in handling solid structure changes. In this work, the mass transfer of two typical LB reactive boundary schemes are analyzed for the staircase boundary. The Type I boundary scheme is based on relations of local distribution functions and a wet-node boundary mesh. The Type II boundary scheme adopts the half-way bounce-back scheme. Boundary concentrations are determined by finite difference, and a link-wise boundary mesh is used. The analyses demonstrate that for straight boundaries, both the boundary schemes have accurate mass transfer rates, which means the mass transfer calculated by exchanges of distribution functions is the same as that calculated by reaction rates. For curved boundaries with staircase approximation, including interfacial normal directions in the Type I boundary scheme can provide accurate mass transfer for inclined straight boundaries. However, if the staircase boundary geometry is used directly without normal directions, the reaction rate will be overestimated. One-dimensional and two-dimensional reaction-diffusion processes with dissolution are simulated to validate the analyses. Both the boundary schemes work well for one-dimensional simulations. For two-dimensional simulations, the Type II boundary scheme significantly overestimates the reaction rate, and stronger artificial anisotropic effects are observed. The Type I boundary scheme with normal directions has better performance, but error still exists.

From Pulp to Aromatic Products-Reaction Pathways of Lignin Depolymerization.

This study investigated the depolymerization of lignin into aromatic monomer compounds under hydrothermal conditions. A reaction scheme highlighting secondary alkylation reactions as well as the molecular weight shift was developed based on the experimental data. Lignin is produced in large quantities in paper production and dissolved in what is known as black liquor (BL). To avoid lignin recovery as an additional process step, BL is used directly as feedstock in the hydrothermal liquefaction (HTL) in this work. We performed various batch experiments in micro autoclaves with BL and model substances at different reaction temperatures (TR = 250-400 °C) and a holdingtime of tR = 20 min, as well as continuous experiments (TR = 325-375 °C, tR = 20 min). We were able to show that different derivatives of catechols are the main products among the monomers in our process. With the help of the model substance experiments, we were able to work out three main reactions: demethoxylation, demethylation, and alkylation. This behavior could be observed in the case of BL from hardwood as well as from softwood. 31P nuclear magnetic resonance (NMR) spectroscopy analysis has shown that these reactions take place on aromatic monomers as well as on larger aromatic oligomer structures. At higher temperatures, a large fraction of the carbon ends up in the solid product, while the yields of the monomers decrease sharply. 13C NMR spectroscopy of the solid material shows that the monomers are probably incorporated into the solid phase by repolymerization. We were also able to see this effect using size exclusion chromatography analysis based on the relative molecular weight. From all of the analytical results of the products, a reaction scheme was developed that describes the reaction pathways of the lignin during HTL. Based on this, a reaction kinetic model can be developed in the next step.

Co-pyrolysis model for polylactic acid (PLA)/wood composite and its application in predicting combustion behaviors

Polylactic acid (PLA)/wood composite has gained great popularity in applications due to its renewable and biodegradable features, whereas quantitative modelling from microscale co-pyrolysis to bench-scale combustion was barely reported. To challenge this issue, poplar wood, PLA and three PLA/wood composites with mass ratios of 1:3, 1:1, and 3:1 were adopted to conduct thermogravimetric analysis (TGA) and cone calorimeter tests. A numerical model was utilized to examine the interaction between wood and PLA during co-pyrolysis. Kinetics and temperature-dependent thermodynamics of each component were determined by inversely modelling some specific experimental results, while the remaining data were used for model validation. Effective heats of combustion of gas products were estimated by fitting the recorded heat release rates (HRR) in combustion tests. The results showed that PLA/wood composites considerably reduced the peak temperature of co-pyrolysis by 21.7–23.7 K compared to neat PLA. Pyrolysis of wood and PLA could be described by a four-component reaction scheme and a single-step reaction, respectively, whereas two additional reactions were needed to quantify the interaction between PLA and wood. Three methods were used to predict the measured HRRs, and all calculated curves fitted the experimental results well. PLA/wood composites decelerated the thickness regression rate and prolonged the combustion time. Meanwhile, measured CO and CO2 production rates were thoroughly analyzed.