Particle Deposition Pattern on an Automotive Diesel Filter Using an Eulerian Probability Density Function Method

A full 3D numerical simulation of the two-phase flow made up of (bio)diesel and particles, has been carried out to reproduce the deposition pattern of particles in a BOSCH automotive filter. From a probability density function (PDF), a simple Eulerian-Eulerian two-phase model is proposed for diesel and particles. The proposed formulation allows for a detailed description of the relationship between the velocity and size of the particles. A Brinkman-Darcy approximation has been considered for the flow through the filtering paper and is proved to be sufficient for the typical filter working conditions. The new tool is able to reproduce the deposition pattern shown by the used filters.

High Calorific Values Boron Powder: Ignition and Combustion Mechanism, Surface Modification Strategies and Properties

Boron powder is a kind of metal fuel with high gravimetric and volumetric calorific values, which has been widely used in military fields such as solid propellants, high-energy explosives, and pyrotechnics. However, the easily formed liquid oxide layer can adhere to the surface of boron powder and react with the hydroxyl (-OH) group of hydroxyl-terminated polybutadiene (HTPB) binder to form a gel layer that is detrimental to propellant processing and restricts the complete oxidation of boron powder. Therefore, to improve the combustion efficiency of boron powder, the ignition and combustion mechanisms of boron powder have been studied, and surface coating modification strategies have been developed by researchers worldwide, aiming to optimize the surface properties, improve the reaction activity, and promote the energy release of boron powder. In this review, recent studies on the ignition and combustion mechanisms of boron powder are discussed. Moreover, the reported boron powder coating materials are classified according to the chemical structure and reaction mechanism. Additionally, the mechanisms and characteristics of different coating materials are summarized, and the mechanism diagrams of fluoride and metal oxide are provided. Furthermore, promising directions for modification methods and the potential application prospects of boron powder are also proposed.

Microbial production of high octane and high sensitivity olefinic ester biofuels

BACKGROUND

Advanced spark ignition engines require high performance fuels with improved resistance to autoignition. Biologically derived olefinic alcohols have arisen as promising blendstock candidates due to favorable octane numbers and synergistic blending characteristics. However, production and downstream separation of these alcohols are limited by their intrinsic toxicity and high aqueous solubility, respectively. Bioproduction of carboxylate esters of alcohols can improve partitioning and reduce toxicity, but in practice has been limited to saturated esters with characteristically low octane sensitivity. If olefinic esters retain the synergistic blending characteristics of their alcohol counterparts, they could improve the bioblendstock combustion performance while also retaining the production advantages of the ester moiety.

RESULTS

Optimization of Escherichia coli isoprenoid pathways has led to high titers of isoprenol and prenol, which are not only excellent standalone biofuel and blend candidates, but also novel targets for esterification. Here, a selection of olefinic esters enhanced blendstock performance according to their degree of unsaturation and branching. E. coli strains harboring optimized mevalonate pathways, thioester pathways, and heterologous alcohol acyltransferases (ATF1, ATF2, and SAAT) were engineered for the bioproduction of four novel olefinic esters. Although prenyl and isoprenyl lactate titers were limited to 1.48 ± 0.41 mg/L and 5.57 ± 1.36 mg/L, strains engineered for prenyl and isoprenyl acetate attained titers of 176.3 ± 16.0 mg/L and 3.08 ± 0.27 g/L, respectively. Furthermore, prenyl acetate (20% bRON = 125.8) and isoprenyl acetate (20% bRON = 108.4) exhibited blend properties comparable to ethanol and significantly better than any saturated ester. By further scaling cultures to a 2-L bioreactor under fed-batch conditions, 15.0 ± 0.9 g/L isoprenyl acetate was achieved on minimal medium. Metabolic engineering of acetate pathway flux further improved titer to attain an unprecedented 28.0 ± 1.0 g/L isoprenyl acetate, accounting for 75.7% theoretical yield from glucose.

CONCLUSION

Our study demonstrated novel bioproduction of four isoprenoid oxygenates for fuel blending. Our optimized E. coli production strain generated an unprecedented titer of isoprenyl acetate and when paired with its favorable blend properties, may enable rapid scale-up of olefinic alcohol esters for use as a fuel blend additive or as a precursor for longer-chain biofuels and biochemicals.

Enhancement of galactose uptake for bioethanol production from Eucheuma denticulatum hydrolysate using galactose-adapted yeasts

Eucheuma denticulatum is a red macroalgae with a high carbohydrate content. The fermentable sugars from E. denticulatum were obtained through sequential thermal acid hydrolysis, enzymatic saccharification, and detoxification. Thermal acid hydrolysis of E. denticulatum was optimized under the condition of 10% (w/v) slurry content and 300 mM HNO₃ at 121 ℃ for 90 min. The maximum monosaccharide concentration after thermal acid hydrolysis was 31.0 g/L with an efficiency (E_TAH) of 44.7%. By further enzymatic hydrolysis of pretreated biomass solution under 20 U/mL Cellic CTec2 at 50 ℃ and 160 rpm for 72 h, the maximum monosaccharide concentration reached 79.9 g/L with an efficiency of 66.2% (E_S). To remove 5-hydroxymethylfurfural (5-HMF), a fermentation inhibitor, absorption using 2% activated carbon was performed for 2 min. Ethanol fermentation was performed using wild-type and high galactose-adapted strains of Saccharomyces cerevisiae, Kluyveromyces marxianus, and Candida lusitaniae. As a result, galactose-adapted strains showed higher ethanol production than wild-type strains. Especially, the fermentation result by adaptively evolved S. cerevisiae produced the highest ethanol of 37.6 g/L and with Y_EtOH of 0.48 g/g. Moreover, the transcript level of MIG1 in the galactose-adapted strain was slightly lower than that in the wild-type strain. The application of adaptive evolution of microorganisms was efficient for bioethanol production.

Effect of Lipid Type on the Acidogenic Performance of Food Waste

Due to its high lipid content and intricate constitution, food waste poses a considerable challenge for biotreatment. This research aims to investigate the potential influence of diverse lipid species on anaerobic fermentation, induced by the varying dietary patterns observed in distinct regions. The investigation involved incorporating 5% (w/w) of beef tallow, mutton fat, soybean oil, peanut oil, and rapeseed oil, separately, into simulated food waste, and subjected it to batch mode acidogenic fermentation. The inclusion of unsaturated fatty acids resulted in a redirection of the metabolic pathway from the lactic acid type to the ethanol, acetic acid, and butyric acid types. The succession of the acidogenic metabolic pathway was highly correlated with the lipid types; beef tallow, mutton fat, soybean oil, and peanut oil delayed the metabolic process by 1, 2, 3, and 8 d, respectively, whereas rapeseed oil accelerated it by 2 d. The lipids contained within the food waste did not facilitate the buildup of soluble substances, resulting in a decrease of 14.0~59.7%. Notwithstanding, valeric acid was exclusively generated during the beef tallow and peanut oil treatments, whereas the production of lactic acid in peanut oil showed a 35.9% increase in comparison to the control.

Strategy for efficiently utilizing Escherichia coli cells producing isobutanol by combining isobutanol and indigo production systems

Isobutanol is a potential biofuel, and its microbial production systems have demonstrated promising results. In a microbial system, the isobutanol produced is secreted into the media; however, the cells remaining after fermentation cannot be used efficiently during the isobutanol recovery process and are discarded as waste. To address this, we aimed to investigate the strategy of utilizing these remaining cells by combining the isobutanol production system with the indigo production system, wherein the product accumulates intracellularly. Accordingly, we constructed E. coli systems with genes, such as acetolactate synthase gene (alsS), ketol-acid reductoisomerase gene (ilvC), dihydroxyl-acid dehydratase (ilvD), and alpha-ketoisovalerate decarboxylase gene (kivD), for isobutanol production and genes, such as tryptophanase gene (tnaA) and flavin-containing monooxygenase gene (FMO), for indigo production. This system produced isobutanol and indigo simultaneously while accumulating indigo within cells. The production of isobutanol and indigo exhibited a strong linear correlation up to 72 h of production time; however, the pattern of isobutanol and indigo production varied. To our knowledge, this study is the first to simultaneously produce isobutanol and indigo and can potentially enhance the economy of biochemical production.

Pyrolysis activation energy of cellulosic fibres investigated by a method derived from the first order global model

The pyrolysis kinetics of cellulosic fibres, a natural cotton yarn (NCY) and a mercerized cotton yarn (MCY), has been explored with a modified first order global analysis method (FOG), via a series of non-isothermal experiments, using thermogravimetric analysis (TGA). The modified FOG analysis routine was developed to overcome discrepancy in heating rate and the difference between exact results and approximations in integrals. The intrinsic pyrolysis activation energy, with temperature range tending to zero, was found to be independent of heating rate and approximation used, giving average values of 153 ± 2 kJ/mol for NCY and 192 ± 7 kJ/mol for MCY. This proves the applicability of the reported analysis routine under the conducted TGA measurements. The reasons for different values were hypothesized to be the difference in chemical composition and crystalline structure. The findings provide a new approach in the investigation on pyrolysis kinetics of biomass and factors impacting their pyrolytic behaviour.

The Curious Case of 1-Ethylpyridinium Triflate: Ionic Liquid Exhibiting the Mpemba Effect

Here, we report the results of qualitative and quantitative investigations of the first-order phase transition in the ionic liquid 1-ethylpyridinium triflate exhibiting a high variability of temperature ranges, within which the freezing and melting occur. By two methods, the direct fast quenching/annealing and the slow temperature-controlled differential scanning calorimeter, it is revealed that despite the almost constant absolute enthalpies of phase transition, the freezing occurs faster with the larger temperature contrast (cooling rate) between the initially hotter sample and the colder surrounding. This feature is a clear exhibition of the Mpemba effect. The regularity in the change of the melting point is analyzed as well.

Exploring Simultaneous Upgrading and Purification of Biomass−Gasified Gases Using Plasma Catalysis

Tar and substantial CH4 and CO2 are contained in gasified fuels, which pose an obstacle to direct chemical synthesis, and this is a predominant challenge for biomass gasification technology. Herein, a packed−bed dielectric barrier discharge (DBD) reactor was built for simultaneous CH4 dry reforming and tar removal with a La−Ni/γ−Al2O3 catalyst. The interaction between CH4 dry reforming and tar removal in plasma catalysis was investigated. The results indicated that plasma catalysis can achieve high−efficiency simultaneous tar removal and CH4 dry reforming, as indicated by the reactants’ conversion (14% increase for CCH4 and CCO2 at 450 °C in the presence of tar and a 37% increase for the tar removal rate at 360 °C when CH4 and CO2 were introduced), and the mechanism for mutual promotion of CH4 dry reforming and tar removal was elucidated through catalyst characterization results. In addition, a possible reaction mechanism for tar removal via plasma catalysis was proposed. These findings provide valuable insights for simultaneous upgrading and purification of gases generated by biomass gasification.

Degradation of lignin in different lignocellulosic biomass by steam explosion combined with microbial consortium treatment

The difficulty of degrading lignin is the main factor limiting the high-value conversion process of lignocellulosic biomass. The biodegradation of lignin has attracted much attention because of its strong environmental friendliness, but it still faces some dilemmas such as slow degradation rate and poor adaptability. The microbial consortia with high lignin degradation efficiency and strong environmental adaptability were obtained in our previous research. To further increase the lignin degradation efficiency, this paper proposes a composite treatment technology of steam explosion combined with microbial consortium degradation to treat three kinds of biomass. We measured the lignin degradation efficiency, selectivity value (SV) and enzymatic saccharification efficiency. The structural changes of the biomass materials and microbial consortium structure were also investigated. The experimental results showed that after 1.6 MPa steam explosion treatment, the lignin degradation efficiency of the eucalyptus root reached 35.35% on the 7th days by microbial consortium. At the same time, the lignin degradation efficiency of the bagasse and corn straw treated by steam explosion followed by microbial biotreatment was 37.61-44.24%, respectively, after only 7 days of biotreatment. The microbial consortium also showed strong selectivity degradation to lignin. The composite treatment technology can significantly improve the enzymatic saccharification efficiency. Saccharomycetales, Ralstonia and Pseudomonadaceae were the dominant microorganisms in the biomass degradation systems. It was proved that the combined treatment technology of steam explosion and microbial consortium degradation could overcome the drawbacks of traditional microbial pretreatment technology, and can facilitate the subsequent high-value conversion of lignocellulose.

Structure, Property, and Performance of Catalyst Layers in Proton Exchange Membrane Fuel Cells

Catalyst layer (CL) is the core component of proton exchange membrane (PEM) fuel cells, which determines the performance, durability, and cost. However, difficulties remain for a thorough understanding of the CLs' inhomogeneous structure, and its impact on the physicochemical and electrochemical properties, operating performance, and durability. The inhomogeneous structure of the CLs is formed during the manufacturing process, which is sensitive to the associated materials, composition, fabrication methods, procedures, and conditions. The state-of-the-art visualization and characterization techniques are crucial to examine the CL structure. The structure-dependent physicochemical and electrochemical properties are then thoroughly scrutinized in terms of fundamental concepts, theories, and recent progress in advanced experimental techniques. The relation between the CL structure and the associated effective properties is also examined based on experimental and theoretical findings. Recent studies indicated that the CL inhomogeneous structure also strongly affects the performance and degradation of the whole fuel cell, and thus, the interconnection between the fuel cell performance, failure modes, and CL structure is comprehensively reviewed. An analytical model is established to understand the effect of the CL structure on the effective properties, performance, and durability of the PEM fuel cells. Finally, the challenges and prospects of the CL structure-associated studies are highlighted for the development of high-performing PEM fuel cells.

Graphical abstract

Availability of Biomass and Potential of Nanotechnologies for Bioenergy Production in Jordan

Jordan’s energy situation is in a critical state of dependency, with the country relying heavily on imports to satisfy its ever-increasing energy requirements. Renewable energy is a more competitive and consistent source of energy that can supply a large proportion of a country’s energy demand. It is environmentally friendly and minimizes atmospheric pollutant emissions. Thus, bioenergy has the potential to be a crucial alternative energy source in Jordan. Biomass is the principal source of bioenergy; it accounts for approximately 13% of the primary energy demand and is anticipated to supply half of the total primary energy demand by 2050. Nanotechnology has emerged as an important scientific research area with numerous applications, including biofuels. This review summarizes the application of nanoparticles to improve the properties and processes of biofuels. It presents the availability and viability of nanotechnology-supported bioenergy production in Jordan. Jordan generates up to 5.8 million tons of biomass each year and has access to abundant nonedible plant resources (such as Jojoba, Handal, and Jatropha). The theoretical energy potential of waste and residue available in Jordan was also assessed; it was discovered that the 1.28 million tons of dry crop residues (vegetables, fruits, and farming crops) could generate 6.8 PJ of energy per year and that biogas could be generated at a rate of 817 MCM/year

A near real-time web-system for predicting fire spread across the Cerrado biome

Wildfires are aggravating due to climate change. Public policies need territorial intelligence to prevent and promptly fight fires, especially in vast regions like Brazil. To this end, we have developed a fire-spread prediction system for the Brazilian Cerrado, the biome most affected by wildfires in South America. The system automatically uploads hot pixels and satellite data to calculate maps of fuels loads, vegetation moisture, and probability of burning for simulating fire spread thrice a day for the entire Cerrado at 25 ha and for nine conservation units at 0.04 ha spatial resolution. In both versions, the model attains 65-89% of spatial match. Model results together with ancillary data, e.g., historical burned areas and annual CO₂ emissions from fires, are available on an interactive web-platform that serves as a tool for fire prevention and fight, particularly in the selected conservation units where the platform is being used for daily operations.

Oxidative Conversion of Chars Generated from the Fixed-Bed Pyrolysis of Wood Torrefied at Different Temperatures and Holding Times

Fixed-bed pyrolysis of torrefied spruce wood, for a heating temperature of 800 K, results in char yields between about 27–57 wt% (versus 23 wt% for untreated wood), depending on both pre-treatment temperatures (533–583 K) and holding times (8–25 min). In this study char oxidation behavior and kinetics are investigated by means of thermogravimetric analysis. The differential thermogravimetric curves always showed a low-temperature zone of slow rates (oxidative devolatilization), followed by a high-rate zone with a well-defined peak (oxidation). As the torrefaction severity increases, the temperature range of the oxidative devolatilization enlarges. Moreover, the oxidation rates become slower (both burning and burnout temperatures tend to increase). As already found for untreated wood chars, the two stages are well described by a linear and a power-law rate reaction, respectively. Volatiles released from the devolatilizations are approximately around 20 wt%, but torrefaction causes lower activation energies (66–92 kJ/mol versus 117 kJ/mol). The oxidation activation energies also decreas (170–168 kJ/mol versus 193 kJ/mol), accompanied by small variations in the reaction order.

Experimental Studies on the Thermal Properties and Decomposition Course of a Novel Class of Heterocyclic Anticancer Drug Candidates

The experimental studies on the thermal properties and decomposition course of a novel class of potential anticancer drugs (1–5) containing in their heterobicyclic structures the asymmetrical triazine template were performed with the use of differential scanning calorimetry (DSC) and simultaneous thermogravimetry/differential scanning calorimetry (TG/DTG/DSC) coupled online with Fourier transform infrared spectroscopy (FTIR) and quadrupole mass spectrometry (QMS) in inert and oxidizing conditions. All the compounds were thermally characterized in detail for the first time in this article. The DSC studies proved that the melting points of the tested compounds depended on the position and type of the substituent at the phenyl moiety, whereas they did not depend on the furnace atmosphere. All the tested polynitrogenated heterocycles proved to be molecules with high thermal stability in both atmospheres, and most of them (1, 3–5) were more stable in oxidizing conditions, which indicated the formation of a more thermally stable form of the compounds when interacting with oxygen. The simultaneous TG/FTIR/QMS analyses confirmed that their pyrolysis process occurred in one main stage resulting in the emission of volatiles such as NH3, HNCO, HCN, CO, CO2, H2O, NO2, aromatic amine derivatives, alkenes (for compounds 1–5), and HCl (for the compound 5). On the other hand, the oxidative decomposition process was more complicated and proceeded in two main stages leading to the emission of NH3, CO2, CO, HCN, HNCO, H2O, some aromatics (for compounds 1–5), HCl (for compounds 3–5) as well as the additional volatiles such as N2, NO2, NH2OH, and (CN)2. The type of the formed volatiles indicated that the decomposition process of the studied heterocycles under the influence of heating was initiated by the radical mechanism. Their decomposition was related to the symmetric cleavage of C–N and C–C bonds (inert conditions) and additional reaction of the volatiles and residues with oxygen (oxidizing conditions).

Experimental Study of Model Refuse-Derived Fuel Pellets Swelling during Heating and Combustion

Composites of sawdust and crushed polyethylene were obtained by pressing at 5–10 atm. The resulting pellets with a size of about 10–20 mm were then burned in airflow in a muffle furnace at a temperature of 800 °C. The combustion process was recorded, and obtained video data were analyzed. The data obtained made it possible to estimate the change in particle size at different stages of combustion. An increase in linear dimensions during conversion was achieved of up to 2 times. Particle swelling led to a decrease in mechanical strength and destruction of particles before complete burnout.

Probing High-Temperature Amine Chemistry: Is the Reaction NH3 + NH2 ⇄ N2H3 + H2 Important?

The reaction NH₃ + NH₂ ⇄ N₂H₃ + H₂ (R1) has been identified as a key step to explain experimental results for pyrolysis and oxidation of ammonia. However, no direct experimental or theoretical evidence for the reaction has been reported. In the present work, the reaction was studied by ab initio theory and by reinterpretation of experimental data. We could not locate a transition state for R1 occurring as a direct process, but alternative mechanisms yielded an upper bound to k₁ of 1.5 × 10¹³ exp(-58.9 kcal mol^-1/RT) cm³ mol^-1 s^-1 over 1000-2500 K, several orders of magnitude lower than values applied in modeling. Consistent with the theoretical work, re-evaluation of NH₃ pyrolysis data supported a very low value of k₁. However, this finding opens up a novel unresolved issue. Current kinetic models cannot capture the NH₃ oxidation behavior in a number of laminar flow reactor and jet-stirred reactor experiments without adopting an improbably high value for k₁. Important oxidation steps might be underestimated or missing from mechanisms.

Unimolecular Reactions of 2,4-Dimethyloxetanyl Radicals

Alkyl-substituted oxetanes are cyclic ethers formed via unimolecular reactions of QOOH radicals produced via a six-membered transition state in the preceding isomerization step of organic peroxy radicals, ROO. Owing to radical isomer-specific formation pathways, cyclic ethers are unambiguous proxies for inferring QOOH reaction rates. Therefore, accounting for subsequent oxidation of cyclic ethers is important in order to accurately determine rates for QOOH → products. Cyclic ethers can react via unimolecular reaction (ring-opening) or via bimolecular reaction with O₂ to form cyclic ether-peroxy adducts. The computations herein provide reaction mechanisms and theoretical rate coefficients for the former type in order to determine competing pathways for the cyclic ether radicals. Rate coefficients of unimolecular reactions of 2,4-dimethyloxetanyl radicals were computed using master equation modeling from 0.01 to 100 atm and from 300 to 1000 K. Coupled-cluster methods were utilized for stationary-point energy calculations, and uncertainties in the computed rate coefficients were accounted for using variation in barrier heights and in well depths. The potential energy surfaces reveal accessible channels to several species via crossover reactions, such as 2-methyltetrahydrofuran-5-yl and pentanonyl isomers. For the range of temperature over which 2,4-dimethyloxetane forms during n-pentane oxidation, the following are the major channels: 2,4-dimethyloxetan-1-yl → acetaldehyde + allyl, 2,4-dimethyloxetan-2-yl → propene + acetyl, and 2,4-dimethyloxetan-3-yl → 3-butenal + methyl, or, 1-penten-3-yl-4-ol. Well-skipping reactions were significant in a number of channels and also exhibited a markedly different pressure dependence. The calculations show that rate coefficients for ring-opening are approximately an order of magnitude lower for the tertiary 2,4-dimethyloxetanyl radicals than for the primary and secondary 2,4-dimethyloxetanyl radicals. Unlike for reactions of the corresponding ROO radicals, however, unimolecular rate coefficients are independent of the stereochemistry. Moreover, rate coefficients of cyclic ether radical ring-opening are of the same order of magnitude as O₂ addition, underscoring the point that a competing network of reactions is necessary to include for accurate chemical kinetics modeling of species profiles for cyclic ethers.

Radical-Radical Reactions in Molecular Weight Growth: The Phenyl + Propargyl Reaction

The mechanism for hydrocarbon ring growth in sooting environments is still the subject of considerable debate. The reaction of phenyl radical (C₆H₅) with propargyl radical (H₂CCCH) provides an important prototype for radical-radical ring-growth pathways. We studied this reaction experimentally over the temperature range of 300-1000 K and pressure range of 4-10 Torr using time-resolved multiplexed photoionization mass spectrometry. We detect both the C₉H₈ and C₉H₇ + H product channels and report experimental isomer-resolved product branching fractions for the C₉H₈ product. We compare these experiments to theoretical kinetics predictions from a recently published study augmented by new calculations. These ab initio transition state theory-based master equation calculations employ high-quality potential energy surfaces, conventional transition state theory for the tight transition states, and direct CASPT2-based variable reaction coordinate transition state theory (VRC-TST) for the barrierless channels. At 300 K only the direct adducts from radical-radical addition are observed, with good agreement between experimental and theoretical branching fractions, supporting the VRC-TST calculations of the barrierless entrance channel. As the temperature is increased to 1000 K we observe two additional isomers, including indene, a two-ring polycyclic aromatic hydrocarbon, and a small amount of bimolecular products C₉H₇ + H. Our calculated branching fractions for the phenyl + propargyl reaction predict significantly less indene than observed experimentally. We present further calculations and experimental evidence that the most likely cause of this discrepancy is the contribution of H atom reactions, both H + indenyl (C₉H₇) recombination to indene and H-assisted isomerization that converts less stable C₉H₈ isomers into indene. Especially at low pressures typical of laboratory investigations, H-atom-assisted isomerization needs to be considered. Regardless, the experimental observation of indene demonstrates that the title reaction leads, either directly or indirectly, to the formation of the second ring in polycyclic aromatic hydrocarbons.

Polycyclic Aromatic Hydrocarbons as Anode Materials in Lithium-Ion Batteries: A DFT Study

The structure and energetics of the interactive behavior of Li⁺ and Li with polycyclic aromatic hydrocarbons (PAHs) have been studied at the wB97XD/6-311G(d,p) level of DFT. The electron distribution in the PAHs, analyzed using the topology of the molecular electrostatic potential (MESP), led to the categorization of their aromatic rings into five types, viz R_s, R_n, R_d, R_b, and R_e. Among the different rings, sextet-type R_s and naphthalene-type R_n rings showed the highest interaction with Li⁺. The change in MESP at the nucleus of Li⁺ (ΔV_Li⁺) due to the formation of the complex Li⁺...PAH is found to be proportional to the adsorption energy (E₁). In Li...PAH, the spin density on Li is close to zero, suggesting the formation of Li⁺...PAH^•- due to the electron transfer from Li to PAH. The adsorption energy (E₂) for Li...PAH does not correlate with the change in MESP at the nucleus of Li, whereas the dissociation energy (E₃) of Li⁺...PAH^•- to yield Li⁺ and PAH^•- correlates well with the MESP data, ΔV_Li. The study confirms that the change in MESP at the nucleus of Li⁺ due to complex formation gives a quantitative measure of the electronic effect of the cation-π binding. The cell potential (V_cell) is predicted for the lithium ion battery (LIB) using the Li⁺...PAH and Li...PAH adsorption energies. On the basis of the V_cell data, "carbon nanoflake"-type systems, viz coronene, circumbiphenyl, C₄₂H₁₆, and C₅₀H₁₈ are suggested as good anode materials for LIBs.

A Thermo-Catalytic Pyrolysis of Polystyrene Waste Review: A Systematic, Statistical, and Bibliometric Approach

Global polystyrene (PS) production has been influenced by the lightness and heat resistance this material offers in different applications, such as construction and packaging. However, population growth and the lack of PS recycling lead to a large waste generation, affecting the environment. Pyrolysis has been recognized as an effective recycling method, converting PS waste into valuable products in the chemical industry. The present work addresses a systematic, bibliometric, and statistical analysis of results carried out from 2015 to 2022, making an extensive critique of the most influential operation parameters in the thermo-catalytic pyrolysis of PS and its waste. The systematic study showed that the conversion of PS into a liquid with high aromatic content (84.75% of styrene) can be achieved by pyrolysis. Discussion of PS as fuel is described compared to commercial fuels. In addition, PS favors the production of liquid fuel when subjected to co-pyrolysis with biomass, improving its properties such as viscosity and energy content. A statistical analysis of the data compilation was also discussed, evaluating the influence of temperature, reactor design, and catalysts on product yield.

Frontal Polymerizations: From Chemical Perspectives to Macroscopic Properties and Applications

The synthesis and processing of most thermoplastics and thermoset polymeric materials rely on energy-inefficient and environmentally burdensome manufacturing methods. Frontal polymerization is an attractive, scalable alternative due to its exploitation of polymerization heat that is generally wasted and unutilized. The only external energy needed for frontal polymerization is an initial thermal (or photo) stimulus that locally ignites the reaction. The subsequent reaction exothermicity provides local heating; the transport of this thermal energy to neighboring monomers in either a liquid or gel-like state results in a self-perpetuating reaction zone that provides fully cured thermosets and thermoplastics. Propagation of this polymerization front continues through the unreacted monomer media until either all reactants are consumed or sufficient heat loss stalls further reaction. Several different polymerization mechanisms support frontal processes, including free-radical, cat- or anionic, amine-cure epoxides, and ring-opening metathesis polymerization. The choice of monomer, initiator/catalyst, and additives dictates how fast the polymer front traverses the reactant medium, as well as the maximum temperature achievable. Numerous applications of frontally generated materials exist, ranging from porous substrate reinforcement to fabrication of patterned composites. In this review, we examine in detail the physical and chemical phenomena that govern frontal polymerization, as well as outline the existing applications.