Gas Phase Research Articles

An environmentally friendly deep eutectic solvent for CO2 capture

A leading cause of global warming is the increase of carbon dioxide (CO2) emissions due to anthropogenic activities which prompts an urgent need for substantial reduction. Recently, CO2 absorption in deep eutectic solvents (DESs) has attracted scientific attention, because of their adaptability compared to traditional ionic liquids and aqueous amine solutions. This study employs the heating method to synthesize DESs using tetrapropylammonium bromide (TPAB) and formic acid (Fa) with molar ratios of TPAB-Fa (1:1) and TPAB-Fa (1:2). Absorption experiments by static method quantified CO2 solubility in the DESs under varied pressures and temperatures. TPAB-Fa (1:2) at 25.0 °C was the most efficient with the CO2 solubility of 0.218. Thermodynamic modeling was performed by employing the nonrandom two liquids activity coefficient model and the Peng–Robinson equation of state for the liquid and gas phases, respectively. The Henry’s law constant was determined from experimental data. CO2 physical absorption was confirmed via nuclear magnetic resonance (NMR) and Fourier-transform infrared (FT-IR) analyses. TPAB-Fa (1:2), as the superior DES, exhibited regeneration efficiency of 99% after five absorption/desorption cycles.

Kinetic analysis of solid fuel combustion in chemical looping for clean energy conversion

Chemical looping combustion (CLC) offers an advanced, eco-friendly method for converting solid fuels into energy with inherent CO2 capture, presenting a cost-efficient solution. The kinetics of solid fuel CLC, crucial for reactor design, are not well-understood, limiting its application and optimisation. Conducting a comprehensive kinetic analysis of solid fuel CLC is crucial, as it examines the combustion of both volatiles and fixed carbon, thereby addressing existing knowledge gaps and advancing clean conversion of solid fuels. In this study, a comprehensive kinetic analysis method for the first time has been applied to investigate the kinetics of CLC of low-volatile semi-anthracite coal with CuO at temperatures of 700–950 °C under varied oxygen excess ratios (0.5, 1.0, and 2.0). The results show that the combustion of coal in CLC can be divided into three distinct stages. The combustion of coal with CuO initiates with the combustion of volatiles interacting with solid CuO at 450–580 °C, where the combustion efficiency varies between 3–6 wt%. This is followed by a complex simultaneous mechanism involving gas-phase volatiles and solid-phase CuO, as well as gas-phase oxygen and solid-phase fixed carbon under non-isothermal conditions. The combustion efficiency is ranged 19–71 wt% at the temperature ranges from 580 °C to the isothermal temperatures of 750–950 °C. The activation energy for the combustion of volatiles was determined as Ea = 119 kJ/mol, whereas the initial combustion of fixed carbon in the non-isothermal stage ranged between Ea = 39–53 kJ/mol. The rate of combustion is initially limited by the oxygen diffusion rate from CuO, but with additional oxygen carriers and increased temperature, the reaction becomes constrained by first-order kinetics. Upon reaching the isothermal stage, the final combustion phase between fixed carbon and gas phase oxygen occurs, and the combustion efficiency increases to 77–96 wt% at 750–950 °C. The activation energy for fixed carbon combustion under the isotherm stage was approximately Ea = 234 kJ/mol, with a reaction rate constant (k0) of 7.84 × 109 min−1. This pioneering study not only clarifies the multi-stage kinetics of solid fuel CLC, bridging significant gaps in current knowledge but also sets the foundation for the enhanced design and efficiency of CLC systems for cleaner energy production.

Effects of Fuel Bed Slope and Wind Direction on Flame Spread Characteristics Over a Bed of Pinus Silvestris Needles

ABSTRACT Important factors influencing the flame characteristics over a bed of dry pine needles from Siberian Boreal forests (Pinus silvestris) in lab-scale is provided. Factors such as slope of the fuel bed, wind velocity, and direction of spread (concurrent flow or opposed flow), which play significant roles in determining the flame spread rate, have been investigated. Systematic lab-scale experiments have been carried out in a wind tunnel with varying air velocities and on an inclined fuel bed in still air. Numerical simulations have been carried out using a three-dimensional physics-based flame spread model available in Fire Dynamics Simulator, and the results are validated against a wide range of measured flame characteristics. The validated numerical model is then used to simulate concurrent flow and opposed flow flame spread over a sloping fuel bed in the presence of wind. Gas phase temperature on and above the bed surface and total and radiative heat flux measurements for concurrent flow and opposed flow flame spread under the influence of wind as well as for upslope flame spread in still air are presented. A stationary flame propagation mode is observed for a flat fuel surface. Predicted temperature, flow, and species concentration fields have been reported for selected cases to understand the flow and flame dynamics in gas phase and within the fuel beds. These data serve as a validation of the numerical model used for simulating the experimental cases. Further, it can be used to validate popular fire models such as Fire Foam and Fire-Star 3D.

Investigation on Enhancement of AP/HTPB/Al Composite Solid Propellant Combustion Characteristics via DC Electric Field

ABSTRACT To investigate the influence mechanisms of DC electric fields on the combustion of solid propellants, a numerical model for the combustion characteristics of AP/HTPB/Al composite solid propellant under the DC electric field is established. Effects of the applied electric field on combustion flame structure, combustion surface temperature distribution, and mixing fraction distribution are analyzed. The results indicate that the applied electric field enhances the mixing effect of the propellant gas phase decomposition products, thereby altering the flame structure and bringing it closer to the combustion surface. The application of the electric field leads to an increase in the combustion surface temperature by 20–70 K. The effect of the negative electric field on the combustion surface temperature and burning rate is more significant compared to that of the positive electric field. The results provide valuable theoretical guidance in the field of solid engine combustion control.

Analysis of effective area and mass transfer in a structure packing column using machine learning and response surface methodology

The study examined mass transfer coefficients in a structured CO2 absorption column using machine learning (ML) and response surface methodology (RSM). Three correlations for the fractional effective area (af), gas phase mass transfer coefficient (kG), and liquid phase mass transfer coefficient (kL) were derived with coefficient of determination (R2) values of 0.9717, 0.9907 and 0.9323, respectively. To develop these correlations, four characteristics of structured packings, including packing surface area (ap), packing corrugation angle (θ), packing channel base (B), and packing crimp height (h), were used. ML used five models, represented as random forest (RF), radial basis function neural network (RBF), multilayer perceptron (MLP), XGB Regressor, and Extra Trees Regressor (ETR), with the best models being radial basis function neural network (RBF) for af (R2 = 0.9813, MSE = 0.00088), RBF for kG (R2 = 0.9933, MSE = 0.00056), and multilayer perceptron (MLP) for kL (R2 = 0.9871, MSE = 0.00089). The channel base had the most impact on af and kL, while crimp height affected kG the most. Although the RSM method produced adequate equations for each output variable with good predictability, the ML method provides superior modeling capabilities.

A versatile pH-sensitive hydrogel based on a high-performance dye: Monitoring the freshness of milk and chicken meat

There is a growing interest in soft-matter sensors at the research and application level. Colorimetric hydrogel-based sensors can work as smart tools for the fast, simple, and low-cost monitoring of food freshness and spoilage. Herein we developed a hydrogel pH indicator working from pH 2–12 with a specific colorimetric pattern. A fast-responsive, easily formed and mouldable hydrogel was obtained by adding a minimal amount of a single pH-sensitive dye to an agar matrix. Optical, mechanical, and morphologic characteristic of the hydrogel were examined in detail. An easy-to-use smartphone app ensures color tone capture and correlation of color changes to pH levels. Practical applications of the versatile gel sensor were tested in solution and in the gaseous phase. The sensor was employed to assess the freshness of milk samples and to monitor the volatile basic nitrogen compounds resulting from packaged chicken spoilage.

Spectroscopic, solvent interactions, topological analysis, docking evaluation with biological studies on 1,3,3-trimethyl-2-oxybicyclo[2.2.2] octane by anti-cancer proteins

In the current study the title molecules have been shown the anticancer properties of few cancers cell line and biological activity. Electron transition, solute solvent, experimental and computational exploring on the natural bio-molecular structure 1,3,3-tri methyl-2-oxybicyclo[2.2.2] octane stimulated by B3LYP/6–311++G (d,p) set. The 1TOBO molecular structure has identified from GC–MS study by extract of Zingiber Officianale Roscoe. The optimized parameters are correlated with XRD data and NBO expressed the delocalization of charge due to intermolecular interactions and their stronger stabilization E(2) = 4.01 Kcal/mol. The experimental spectral data recorded in the range 400–4000 cm−1 of 1TOBO and strong correlated with computational spectral have been estimated. The UV–vis spectra of corresponding gas phase and solvent-liquid estimated by TD-SCT process well agreement with reported spectra. 1H and 13C NMR spectrum have been capturing the chemical shifts of 1TOBO interpreted by Gauge Independent Atomic Orbital (GIAO) approach with carbinol solvent. The HOMO-LUMO values, Mulliken charges and MEP surface were used to predict the regioselectivity reaction in the region of electrophilic and nucleophilic attack. The topological analysis of LOL and ELF surfaces have been estimated and RDG-NCI map exhibits the van der Walls, steric effect and strong hydrogen bond interaction within the molecules. The Electron-hole distribution analysis revealed the electron transition of three excited states. Furthermore, the quantitative analysis of drug likeness and ADMET were studied. The molecular docking determines the lowest binding impact on the 1TOBO against cancer proteins 7QTZ, 1OXR have been estimated by Auto dock software.

DFT-based computational analysis of 2,4-dimethyl-6-tert-butylphenol (DTBP) as an antioxidant in aviation fuels

Antioxidants are indispensable additives for ensuring the long-term stability, performance, and reliability of aviation fuels. They prevent the formation of gum and other insoluble deposits in the fuel which clog fuel systems, leading to engine problems. This is achieved by inhibiting free radical chain reactions involved in the oxidation of hydrocarbons in the fuel. The compound 2,4-Dimethyl-6-tert-butyl phenol (DTBP) is one of the widely used antioxidants in aviation fuels. In this report, the radical scavenging done by DTBP is analysed computationally by density functional theory (DFT) with the model chemistry X/6-31+G(d,p), where X represents certain Minnesota functionals such as MN15, M05-2X, M06-2X, M08-HX, and M11. Among the well-known modes of radical scavenging, namely HAT, SETPT, and SPLET, the HAT mode is preferred in the gaseous phase, while SPLET operates in non-polar solvents, as computations indicate. Fukui indices, global reactivity descriptors, electronic spectra, and natural bond orbitals (NBOs) are also generated to explain the results. Understanding the mechanism of radical scavenging is important in designing powerful and efficient antioxidants for aviation fuels such as jet fuel, aviation gasoline, Jet B, and bio-kerosene.

Experimental study and mathematical modeling of the pectinases production by Aspergillus flavipes FP-500 in an airlift bioreactor

Mathematical models are indispensable for designing, optimizing, and controlling large-scale bioprocesses. In the present work, the production of pectinases was studied experimentally using an internal loop airlift bioreactor, pectin as a substrate, and Aspergillus flavipes FP-500 as a biocatalyst. The N-tanks-in-series (NTIS) model was implemented to predict the behavior of fungal growth, pectin and dissolved oxygen consumption, pectinases production, and the oxygen mass transfer rate from gas phase to liquid culture medium. A double Monod-Logistic kinetic model was used to describe the biomass growth rate as a function of biomass, pectin, and dissolved oxygen concentrations. In contrast, a Luedeking-Piret kinetic model was used to describe the production rate of endo and exo pectinases. A hydrodynamic model was utilized to estimate gas hold-ups, volumetric mass transfer coefficients, and air inflow velocities. Good agreement was observed between the experimental data and the theoretical results, demonstrating the predictive capacity of the NTIS model to describe pectinase production, the oxygen consumption rate, and the oxygen evolution in the gas phase. The model highlighted its robust capability to capture the critical parameters of aerobic fermentation processes. Therefore, it could be used as a tool for the scalability of the airlift bioreactors.

Impact of physicochemical properties on stabilities of aqueous solutions of potassium 1-fluorobenzoyltrifluoroborate salt

Physicochemical properties of aqueous solutions of potassium 4-fluorobenzoyl-trifluoroborate salt have been studied to know the effect of concentrations and time on its stabilities because these properties are essential to predict and control chemical reactions and, to develop new substances with innovative applications. Here, pH, refractive index, density, conductivity and molar refractivity have been evaluated during 92 days and, the Ka and pKa for all solutions have been calculated. Salt concentrations and time show effects on the densities, pH and conductivities of the solutions while the refractive indexes and molar refractivity remain practically constant during the time studied. The infrared, Raman and UV–vis spectra of acid in gas phase and aqueous solution have been predicted by using hybrid B3LYP/6-311++G** calculations. Intra-molecular halogen OH…F interactions predicted for the acid in both media probably explain the decreasing observed in the conductivity values. Full vibrational assignments of acid and its scaled force constants in both media are reported. The decreasing observed in the f(νBF3) force constants of the three species in both media suggest that the trifluoroborate group plays an important role in the properties of salt. The predicted UV spectrum of acid in aqueous solution compared with the experimental of salt suggest that the anion, acid and salt species are present in aqueous solution, as evidenced by the physicochemical properties. Hence, the presence of three species in solution justify the variations observed in the pH, density, conductivity, force constants and positions of IR and Raman bands related to OH and BF3 groups.

A van der Waals Model of Solvation Thermodynamics.

Exploiting the van der Waals model of liquids, it is possible to derive analytical formulas for the thermodynamic functions governing solvation, the transfer of a solute molecule from a fixed position in the ideal gas phase to a fixed position in the liquid phase. The solvation Gibbs free energy change consists of two contributions: (a) the high number density of all liquids and the repulsive interactions due to the basic fact that each molecule has its own body leading to the need to spend free energy to produce an appropriate cavity to contain the solute molecule; (b) the ubiquitous intermolecular attractive interactions lead to a gain in free energy for switching-on attractions between the solute molecule and neighboring liquid molecules. Also the solvation entropy change consists of two contributions: (a) there is an entropy loss in all liquids because the cavity presence limits the space accessible to liquid molecules during their continuous translations; (b) there is an entropy gain in all liquids, at room temperature, due to the liquid structural reorganization as a response to the perturbation represented by solute addition. The latter entropy contribution is balanced by a corresponding enthalpy term. The scenario that emerged from the van der Waals model is in qualitative agreement with experimental results.

Experimental and thermodynamic modelling of hydrate dissociation conditions for CO[formula omitted] + propane mixtures

The possibility of hydrate formation poses a central issue for Carbon Capture and Storage (CCS) and Enhanced Oil Recovery with Water-Alternating-Gas (EOR/WAG) injection projects. In most of the cases, however, the available fluid for this purpose consists of a CO2-rich stream containing contaminants such as hydrocarbons and permanent gases. As a result, there is a growing interest in evaluating the effect of small impurities concentrations on the phase behaviour of such streams. This work investigates the impact of propane as a promoter in carbon dioxide hydrate formation, covering a concentration range in the feed gas phase between 10 and 69% on mole basis. The study also considers the Lw-LCO2-H region, taking into account liquid and supercritical transportation commonly encountered in CCS projects. Additionally, a procedure to estimate uncertainties in the graphical determination of the dissociation temperature and pressure is discussed. The thermodynamic modelling approach includes three different modifications of cubic equations of state (CEoS): asymmetric mixing rule, advanced Huron-Vidal mixing rule, and cubic-plus-association approach. An alternative procedure based on setting different sets of CO2 Kihara’s parameters when shifting between structures was also used. While satisfactory average temperature deviations were obtained for those equations of state, maximum deviation between calculated and experimental temperatures spanned from 0.5 to 2.5 K, depending on the thermodynamic model.

On the shape of the simulated infrared spectral density of strongly hydrogen-bonded systems: Mapping and identification of Hadži ABC structure in phosphonic acid dimers in gas phase

Herein, we explore the origin of three-peaked structure, referred to as the Hadži ABC structure, illustrated within the absorption bands in infrared (IR) spectra of strongly H-bonded systems. The exploration is particularly elucidated for two phosphinic acid dimers (R2POOH) in gas phase, namely bis-(iodomethyl)-phosphinic acid dimer (i.e., R = CH2I) at 465 K and dibutyl-phosphinic acid dimer (i.e., R = C4H9O) at 425 K. A direct theoretical illustration of this spectral signature, related predominantly to very strongly hydrogen bonded complexes, is proposed. The spectral density, υSO−H,is determined by the aid of an approach describing the high-frequency O − H stretching modes by harmonic potentials. The intermolecular potential modes (O…O) are assumed to be of anharmonic nature. The approach is founded on the strong anharmonic coupling approximation, which prescribes a linear dependency of the O − H frequency on the O…O stretching coordinate as rationalized by the fundamental model of Maréchal and Witkowski. Both direct relaxation of the O − H vibrational mode and its homolog, indirect one, affecting the O…O stretching mode are taken into consideration. The model also considers Davydov coupling, which describes the mutual interaction that takes place in the centrosymmetric dimer between the two existent hydrogen bonds as well as Fermi resonances, which occur between the bending modes arising in- and out-of-plane of the dimer and the fundamental O − H stretching mode. Interestingly, we illustrate how the (A, B, and C) triplet detected in the IR absorption band of phosphonic acids can be generated and discuss how the ABC structure can be numerically simulated. The approach provides a direct explanation of the emergence of this unusual feature and mainly reveals that the A peak is due to the Davydov coupling mechanism, whereas the BC diad is found to be generated by Fermi resonances. This was elucidated in a distinctly different approach, rationalized by Sheppard and Claydon, affirming that the provenance of the BC diad is exclusively due to Fermi resonances mechanism. Altogether, our results highlight the congregated effects of both Fermi resonance mechanism and Davydov coupling for the formation of the ABC structure. The model paves the way for a deeper understanding of the ABC structure, characteristic of very toxic strongly hydrogen-bonded dimers. This is of capital importance as it allows one to develop a solid understanding of nerve agents, such as phosphonic acids, from theory alone, so as to avoid difficult and dangerous experiments since they are extremely toxic.

Complexes of Hydrogen Peroxide, the Simplest Chiral Molecule, with L- and D-Serine Enantiomers and Their Clusters: MP2 and DFT Calculations.

The interaction between natural amino acids and hydrogen peroxide is of paramount importance due to the widespread use of hydrogen peroxide in biological and environmentally significant processes. Given that both amino acids and hydrogen peroxide occur in nature in two enantiomeric forms, it is crucial to investigate the formation of complexes between them, considering the role of molecular chirality. In this work, we report a theoretical study on the hydrogen peroxide enantiomers and their interactions with L- and S-serine and their clusters. We aimed to evaluate the non-covalent interactions between each hydrogen peroxide enantiomer and the L- and D-enantiomers of the non-essential amino acid serine and their clusters. First, the potential energy surfaces (PES) of transitions between enantiomers of the simplest chiral molecule, hydrogen peroxide, in the gas phase and in aqueous solution were studied using the Møller-Plesset theory method MP2/aug-cc-pVDZ. The activation energies of such transitions were calculated. The interactions of both hydrogen peroxide enantiomers (P and M) with L- and D-serine enantiomers were analyzed by density functional theory (DFT) with ωb97xd/6-311+G**, B3Lyp/6-311+G**, B3P86/6-311+G**, and M06/6-311+G** functionals. We found that both enantiomers of hydrogen peroxide bind more strongly to L-serine and its clusters than to D-serine, especially highlighting that the L form is the predominant natural form of this and other chiral amino acids. The optimized geometric parameters, interaction energies, and HOMO-LUMO energies for various complexes were estimated. Furthermore, circular dichroism (CD) spectra, which are optical chirality characteristics, were simulated for all the complexes under study.

Unveiling 5-fluorouracil anti-cancer drug encapsulation within pristine and silver-doped boron, aluminum, and gallium nitride nanotubes: A DFT investigation for advancing nanomedicine

Nanomaterials represent a promising frontier in drug delivery systems for combating cancer, offering precise targeting of tumour cells. This study delves into the encapsulation capabilities of 5-fluorouracil (5-FU) on pristine armchair (6,6) single-wall boron-, aluminium-, and gallium-nitride nanotubes (BNNT, AlNNT, GaNNT), both in their natural state and doped with silver (Ag) atoms under gas phase and water solution conditions. Employing density functional theory calculations at the M06-2X level, we scrutinise the geometric stabilities, encapsulation efficiencies, and electronic interactions between 5-FU molecules and NNTs. Our results reveal that a shorter distance between the drug and nanotube cavity enhances encapsulation ability and solubility while facilitating larger charge transfers, especially within Ag-doped NNTs. The Ag doping significantly augments the reactivity of NNTs towards 5-FU molecules, with thermodynamic analyses indicating exothermic and spontaneous interactions with Ag-doped NNTs. The decapsulation of 5-FU from Ag-BNNT, Ag-AlNNT, and Ag-GaNNT necessitates recovery time 6.42E+00, 3.21E+05, and 2.19E−04 s, with corresponding adsorption energies of −38.70, −49.52, and −28.42 kcal/mol, respectively. Electronic analyses demonstrate notable changes in states’ energy gap and density post-5-FU encapsulation in Ag-doped NNTs, suggesting enhanced sensitivity. Moreover, our investigation delves into topological features, molecular stability, bond strength, and intermolecular interactions using various analytical techniques, including MEPs, ELF maps, NBO, QTAIM, Hirshfeld surface, and RDG analyses. These comprehensive findings underscore the potential of Ag-doped NNTs as promising components for drug delivery systems and biosensors in nanomedicine applications, particularly in sensing and catalytic functions for 5-FU molecule encapsulation and detection.

Visual study of hydrate particles agglomeration and rolling characteristic in gas-oil-water phase using a flow loop

Natural gas hydrate blockage always leads to safety problems in oil and gas transportation pipelines. It is important to look for the characteristic of hydrate blockage process. The hydrate blockage was visually investigated under gas-oil-water multi-phase flow conditions in a flow loop in this study. The change of pressure drop with water conversion rate variations were detected. The hydrate particle movements were also observed in the visual pipes at different liquid loadings and water cuts. It was found that the hydrate particles may agglomerate and deposit with an obvious rolling process in low water cut conditions. The oil phase will accelerate particles agglomeration in the contact interface of oil, gas and water, and form a large number of flocculent hydrates. A theoretical hydrate particle rolling model was conducted to analysis the experiment results, and the hydrate particle velocity increases first and then decreases with the increase of particle diameter due to the comprehensive influence of van der Waals force and drag force. The results also confirmed the maximum of the pressure drop increased when the liquid loading increased. However, the hydrate formation and blockage speed also slow down due to small component of the gas phase in high liquid loading. In addition, comparing with 20 % and 80 % water cut, 50 % water cut has the fastest hydrate formation speed in different experimental conditions. Furthermore, the maximum water conversion rate increased with have a higher water cut. More hydrate will form in the condition, which will lead to the decrease of flow velocity in the pipeline.

A Thorium(IV) metallacyclopropyne complex

Actinide metallacyclic chemistry has been of interest due to its involvement in various chemical processes. However, fundamental understanding on the key species, actinide metallacyclic complexes, is limited to metallacyclopropenes whereas little is known about the actinide metallacyclopropynes presumably due to their unusual high reactivity. Herein, we report the preparation of a thorium metallacyclopropyne complex (η2-C ≡ C)ThCl3– in the gas phase by using electrospray ionization mass spectrometry, and it is generated via a single-ligand strategy through sequential losses of CO2 and HCl from the monopropynoate precursor (HC ≡ CCO2)ThCl4– upon collision-induced dissociation. Alternatively, the dual-ligand strategy involving consecutive losses of two CO2 and one C2H2 from the dipropynoate precursor (HC ≡ CCO2)2ThCl3– works as well. According to the reactivity experiments and theoretical calculations, (η2-C ≡ C)ThCl3– possesses a dianionic ligand C22– coordinated to the Th(IV) center in a side-on fashion. Further bonding analysis demonstrates the presence of a triple bond between the two C atoms, and the Th 5 f orbitals are significantly involved in the Th-(C ≡ C) bonding. A Th metallacyclopropyne structure is thus established for (η2-C ≡ C)ThCl3–.

Ionization by XFEL radiation produces distinct structure in liquid water

In the warm dense matter (WDM) regime, where condensed, gas, and plasma phases coexist, matter frequently exhibits unusual properties that cannot be described by contemporary theory. Experiments reporting phenomena in WDM are therefore of interest to advance our physical understanding of this regime, which is found in dwarf stars, giant planets, and fusion ignition experiments. Using 7.1 keV X-ray free electron laser radiation (nominally 5×105 J/cm2), we produced and probed transient WDM in liquid water. Wide-angle X-ray scattering (WAXS) from the probe reveals a new ~9 Å structure that forms within 75 fs. By 100 fs, the WAXS peak corresponding to this new structure is of comparable magnitude to the ambient water peak, which is attenuated. Simulations suggest that the experiment probes a superposition of two regimes. In the first, fluences expected at the focus severely ionize the water, which becomes effectively transparent to the probe. In the second, out-of-focus pump radiation produces O1+ and O2+ ions, which rearrange due to Coulombic repulsion over 10 s of fs. Our simulations account for a decrease in ambient water signal and an increase in low-angle X-ray scattering but not the experimentally observed 9 Å feature, presenting a new challenge for theory.

Exploration of TKX-50-M (M=Pb, Bi and Cu) as insensitive high-energy combustion catalysts of HMX-CMDB propellant

In order to deal with the long-standing contradiction between safety and performance for propellent combustion catalyst, the TKX-50-M (M=Pb, Bi and Cu) were designed, synthesized and characterized. The density, thermal decomposition, mechanical sensitivity and energy performance of the prepared TKX-50-M were studied systemically. By taking NTO-Pb as the benchmark, the TKX-50-M exhibited much better energetic and safety properties. Besides, the combination of TKX-50-Pb, TKX-50-Cu and carbon black is conductive to the combustion of HMX-CMDB propellant. The burning rate of HMX-CMDB propellant increases from 16.80 to 21.28 mm s−1 at 20 MPa, and the pressure index reduces from 0.87 to 0.39 in the pressure range of 10–20 MPa. The catalytic mechanism of TKX-50-M were explored according to the results of combustion wave structure, flame image and characteristics of burning out surface. The catalytic effect of TKX-50-Pb is mainly reflected in the gas phase region, and the introduction of TKX-50-Cu and carbon black shows a significant synergistic catalytic effect. The results of this study not only help to explore insensitive high-energy combustion catalyst, but also helps to improve the combustion, energy and safety performance of CMDB propellants.

Experimental Investigation of Sulfur and Nitrogen Oxide Emissions and Corrosion Propensity During the Combustion of Coals and Biomass Fuels

ABSTRACT The increasing use of biomass in Indonesian coal-fired power plants, mainly through co-firing, presents challenges due to different fuel characteristics, which can affect gas emissions, ash deposition, and combustion efficiency. This study assesses flue gas emissions (SO2 and NOx) and corrosion tendencies of various biomass types and coal. The study begins with characteristic testing and ash analysis of coal and biomass samples, including proximate, ultimate, and calorific value analyses, to determine their suitability as fuels. Preliminary calculations predict flue gas emissions and ash deposit formation, followed by laboratory-scale combustion experiments using a DTF to assess flue gas and ash deposit characteristics. The results show that sulfur in biomass is converted to the gas phase up to 99%, while in coal, it is converted up to 95% at high temperatures. NOx levels are primarily affected by the nitrogen contents of the fuels; for instance, Coal-B at 0.88 wt% produces less NOx than solid recovered fuel (SRF) and refused derived fuel (RDF) with 1.73 wt% and 1.51 wt%, respectively, yet still generates higher emissions than the other three biomass types. In general, wood chips (WC), rise husk (RH), and palm kernel shell (PKS) emit 30–80% less flue gas compared to coal. However, ash deposition results indicate that PKS, SRF, and RDF exhibit corrosion tendencies due to the dominance of albite (NaAlSi3O8) in the mineral phase. Additionally, the high chlorine content in SRF (0.544 wt%) and RDF (0.224 wt%) leads to the formation of sticky ash deposits, which potentially impact heat transfer surfaces. These findings contribute to identifying suitable biomass types for both co-firing or dedicated combustion in coal-fired power plants.