Prediction of the structures and heats of formation of MO2, MO3, and M2O5 for M = V, Nb, Ta, Pa

Structures for the mono-, di-, and tri-bridge isomers of M₂O₅ as well as those for the MO₂ and MO₃ fragments for M = V, Nb, Ta, and Pa were optimized at the density functional theory (DFT) level. Single point CCSD(T) calculations extrapolated to the complete basis set (CBS) limit at the DFT geometries were used to predict the energetics. The lowest energy dimer isomer was the di-bridge for M = V and Nb and the tri-bridge for M = Ta and Pa. The di-bridge isomers were predicted to be composed of MO₂⁺ and MO₃^- fragments, whereas the mono- and tri-bridge are two MO₂⁺ fragments linked by an O^2-. The heats of formation of M₂O₅ dimers, as well as MO₂ and MO₃ neutral and ionic species were predicted using the Feller-Peterson-Dixon (FPD) approach. The heats of formation of the MF₅ species were calculated to provide additional benchmarks. Dimerization energies to form the M₂O₅ dimers are predicted to become more negative going down group 5 and range from -29 to -45 kcal mol^-1. The ionization energies (IEs) for VO₂ and TaO₂ are essentially the same at 8.75 eV whereas the IEs for NbO₂ and PaO₂ are 8.10 and 6.25 eV, respectively. The predicted adiabatic electron affinities (AEAs) range from 3.75 eV to 4.45 eV for the MO₃ species and vertical detachment energies from 4.21 to 4.59 eV for MO₃^-. The calculated MO bond dissociation energies increase from 143 kcal mol^-1 for M = V to ∼170 kcal mol^-1 for M = Nb and Ta to ∼200 kcal mol^-1 for M = Pa. The M-O bond dissociation energies are all similar ranging from 97 to 107 kcal mol^-1. Natural bond analysis provided insights into the types of chemical bonds in terms of their ionic character. Pa₂O₅ is predicted to behave like an actinyl species dominated by the interactions of approximately linear PaO₂⁺ groups.

Converting CO2 to formic acid by tuning quantum states in metal chalcogenide clusters

The catalytic conversion of CO₂ into valuable chemicals is an effective strategy for reducing its adverse impact on the environment. In this work, the formation of formic acid via CO₂ hydrogenation on bare and ligated Ti₆Se₈ clusters is investigated with gradient-corrected density functional theory. It is shown that attaching suitable ligands (i.e., PMe₃, CO) to a metal-chalcogenide cluster transforms it into an effective donor/acceptor enabling it to serve as an efficient catalyst. Furthermore, by controlling the ratio of the attached donor/acceptor ligands, it is possible to predictably alter the barrier heights of the CO₂ hydrogenation reaction and, thereby, the rate of CO₂ conversion. Our calculation further reveals that by using this strategy, the barrier heights of CO₂ hydrogenation can be reduced to ~0.12 eV or possibly even lower, providing unique opportunities to control the reaction rates by using different combinations of donor/acceptor ligands.

The Minderoo-Monaco Commission on Plastics and Human Health

Background

Plastics have conveyed great benefits to humanity and made possible some of the most significant advances of modern civilization in fields as diverse as medicine, electronics, aerospace, construction, food packaging, and sports. It is now clear, however, that plastics are also responsible for significant harms to human health, the economy, and the earth's environment. These harms occur at every stage of the plastic life cycle, from extraction of the coal, oil, and gas that are its main feedstocks through to ultimate disposal into the environment. The extent of these harms not been systematically assessed, their magnitude not fully quantified, and their economic costs not comprehensively counted.

Goals

The goals of this Minderoo-Monaco Commission on Plastics and Human Health are to comprehensively examine plastics' impacts across their life cycle on: (1) human health and well-being; (2) the global environment, especially the ocean; (3) the economy; and (4) vulnerable populations-the poor, minorities, and the world's children. On the basis of this examination, the Commission offers science-based recommendations designed to support development of a Global Plastics Treaty, protect human health, and save lives.

Report Structure

This Commission report contains seven Sections. Following an Introduction, Section 2 presents a narrative review of the processes involved in plastic production, use, and disposal and notes the hazards to human health and the environment associated with each of these stages. Section 3 describes plastics' impacts on the ocean and notes the potential for plastic in the ocean to enter the marine food web and result in human exposure. Section 4 details plastics' impacts on human health. Section 5 presents a first-order estimate of plastics' health-related economic costs. Section 6 examines the intersection between plastic, social inequity, and environmental injustice. Section 7 presents the Commission's findings and recommendations.

Plastics

Plastics are complex, highly heterogeneous, synthetic chemical materials. Over 98% of plastics are produced from fossil carbon- coal, oil and gas. Plastics are comprised of a carbon-based polymer backbone and thousands of additional chemicals that are incorporated into polymers to convey specific properties such as color, flexibility, stability, water repellence, flame retardation, and ultraviolet resistance. Many of these added chemicals are highly toxic. They include carcinogens, neurotoxicants and endocrine disruptors such as phthalates, bisphenols, per- and poly-fluoroalkyl substances (PFAS), brominated flame retardants, and organophosphate flame retardants. They are integral components of plastic and are responsible for many of plastics' harms to human health and the environment.Global plastic production has increased almost exponentially since World War II, and in this time more than 8,300 megatons (Mt) of plastic have been manufactured. Annual production volume has grown from under 2 Mt in 1950 to 460 Mt in 2019, a 230-fold increase, and is on track to triple by 2060. More than half of all plastic ever made has been produced since 2002. Single-use plastics account for 35-40% of current plastic production and represent the most rapidly growing segment of plastic manufacture.Explosive recent growth in plastics production reflects a deliberate pivot by the integrated multinational fossil-carbon corporations that produce coal, oil and gas and that also manufacture plastics. These corporations are reducing their production of fossil fuels and increasing plastics manufacture. The two principal factors responsible for this pivot are decreasing global demand for carbon-based fuels due to increases in 'green' energy, and massive expansion of oil and gas production due to fracking.Plastic manufacture is energy-intensive and contributes significantly to climate change. At present, plastic production is responsible for an estimated 3.7% of global greenhouse gas emissions, more than the contribution of Brazil. This fraction is projected to increase to 4.5% by 2060 if current trends continue unchecked.

Plastic Life Cycle

The plastic life cycle has three phases: production, use, and disposal. In production, carbon feedstocks-coal, gas, and oil-are transformed through energy-intensive, catalytic processes into a vast array of products. Plastic use occurs in every aspect of modern life and results in widespread human exposure to the chemicals contained in plastic. Single-use plastics constitute the largest portion of current use, followed by synthetic fibers and construction.Plastic disposal is highly inefficient, with recovery and recycling rates below 10% globally. The result is that an estimated 22 Mt of plastic waste enters the environment each year, much of it single-use plastic and are added to the more than 6 gigatons of plastic waste that have accumulated since 1950. Strategies for disposal of plastic waste include controlled and uncontrolled landfilling, open burning, thermal conversion, and export. Vast quantities of plastic waste are exported each year from high-income to low-income countries, where it accumulates in landfills, pollutes air and water, degrades vital ecosystems, befouls beaches and estuaries, and harms human health-environmental injustice on a global scale. Plastic-laden e-waste is particularly problematic.

Environmental Findings

Plastics and plastic-associated chemicals are responsible for widespread pollution. They contaminate aquatic (marine and freshwater), terrestrial, and atmospheric environments globally. The ocean is the ultimate destination for much plastic, and plastics are found throughout the ocean, including coastal regions, the sea surface, the deep sea, and polar sea ice. Many plastics appear to resist breakdown in the ocean and could persist in the global environment for decades. Macro- and micro-plastic particles have been identified in hundreds of marine species in all major taxa, including species consumed by humans. Trophic transfer of microplastic particles and the chemicals within them has been demonstrated. Although microplastic particles themselves (>10 µm) appear not to undergo biomagnification, hydrophobic plastic-associated chemicals bioaccumulate in marine animals and biomagnify in marine food webs. The amounts and fates of smaller microplastic and nanoplastic particles (MNPs <10 µm) in aquatic environments are poorly understood, but the potential for harm is worrying given their mobility in biological systems. Adverse environmental impacts of plastic pollution occur at multiple levels from molecular and biochemical to population and ecosystem. MNP contamination of seafood results in direct, though not well quantified, human exposure to plastics and plastic-associated chemicals. Marine plastic pollution endangers the ocean ecosystems upon which all humanity depends for food, oxygen, livelihood, and well-being.

Human Health Findings

Coal miners, oil workers and gas field workers who extract fossil carbon feedstocks for plastic production suffer increased mortality from traumatic injury, coal workers' pneumoconiosis, silicosis, cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer. Plastic production workers are at increased risk of leukemia, lymphoma, hepatic angiosarcoma, brain cancer, breast cancer, mesothelioma, neurotoxic injury, and decreased fertility. Workers producing plastic textiles die of bladder cancer, lung cancer, mesothelioma, and interstitial lung disease at increased rates. Plastic recycling workers have increased rates of cardiovascular disease, toxic metal poisoning, neuropathy, and lung cancer. Residents of "fenceline" communities adjacent to plastic production and waste disposal sites experience increased risks of premature birth, low birth weight, asthma, childhood leukemia, cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer.During use and also in disposal, plastics release toxic chemicals including additives and residual monomers into the environment and into people. National biomonitoring surveys in the USA document population-wide exposures to these chemicals. Plastic additives disrupt endocrine function and increase risk for premature births, neurodevelopmental disorders, male reproductive birth defects, infertility, obesity, cardiovascular disease, renal disease, and cancers. Chemical-laden MNPs formed through the environmental degradation of plastic waste can enter living organisms, including humans. Emerging, albeit still incomplete evidence indicates that MNPs may cause toxicity due to their physical and toxicological effects as well as by acting as vectors that transport toxic chemicals and bacterial pathogens into tissues and cells.Infants in the womb and young children are two populations at particularly high risk of plastic-related health effects. Because of the exquisite sensitivity of early development to hazardous chemicals and children's unique patterns of exposure, plastic-associated exposures are linked to increased risks of prematurity, stillbirth, low birth weight, birth defects of the reproductive organs, neurodevelopmental impairment, impaired lung growth, and childhood cancer. Early-life exposures to plastic-associated chemicals also increase the risk of multiple non-communicable diseases later in life.

Economic Findings

Plastic's harms to human health result in significant economic costs. We estimate that in 2015 the health-related costs of plastic production exceeded $250 billion (2015 Int$) globally, and that in the USA alone the health costs of disease and disability caused by the plastic-associated chemicals PBDE, BPA and DEHP exceeded $920 billion (2015 Int$). Plastic production results in greenhouse gas (GHG) emissions equivalent to 1.96 gigatons of carbon dioxide (CO2e) annually. Using the US Environmental Protection Agency's (EPA) social cost of carbon metric, we estimate the annual costs of these GHG emissions to be $341 billion (2015 Int$).These costs, large as they are, almost certainly underestimate the full economic losses resulting from plastics' negative impacts on human health and the global environment. All of plastics' economic costs-and also its social costs-are externalized by the petrochemical and plastic manufacturing industry and are borne by citizens, taxpayers, and governments in countries around the world without compensation.

Social Justice Findings

The adverse effects of plastics and plastic pollution on human health, the economy and the environment are not evenly distributed. They disproportionately affect poor, disempowered, and marginalized populations such as workers, racial and ethnic minorities, "fenceline" communities, Indigenous groups, women, and children, all of whom had little to do with creating the current plastics crisis and lack the political influence or the resources to address it. Plastics' harmful impacts across its life cycle are most keenly felt in the Global South, in small island states, and in disenfranchised areas in the Global North. Social and environmental justice (SEJ) principles require reversal of these inequitable burdens to ensure that no group bears a disproportionate share of plastics' negative impacts and that those who benefit economically from plastic bear their fair share of its currently externalized costs.

Conclusions

It is now clear that current patterns of plastic production, use, and disposal are not sustainable and are responsible for significant harms to human health, the environment, and the economy as well as for deep societal injustices.The main driver of these worsening harms is an almost exponential and still accelerating increase in global plastic production. Plastics' harms are further magnified by low rates of recovery and recycling and by the long persistence of plastic waste in the environment.The thousands of chemicals in plastics-monomers, additives, processing agents, and non-intentionally added substances-include amongst their number known human carcinogens, endocrine disruptors, neurotoxicants, and persistent organic pollutants. These chemicals are responsible for many of plastics' known harms to human and planetary health. The chemicals leach out of plastics, enter the environment, cause pollution, and result in human exposure and disease. All efforts to reduce plastics' hazards must address the hazards of plastic-associated chemicals.

Recommendations

To protect human and planetary health, especially the health of vulnerable and at-risk populations, and put the world on track to end plastic pollution by 2040, this Commission supports urgent adoption by the world's nations of a strong and comprehensive Global Plastics Treaty in accord with the mandate set forth in the March 2022 resolution of the United Nations Environment Assembly (UNEA).International measures such as a Global Plastics Treaty are needed to curb plastic production and pollution, because the harms to human health and the environment caused by plastics, plastic-associated chemicals and plastic waste transcend national boundaries, are planetary in their scale, and have disproportionate impacts on the health and well-being of people in the world's poorest nations. Effective implementation of the Global Plastics Treaty will require that international action be coordinated and complemented by interventions at the national, regional, and local levels.This Commission urges that a cap on global plastic production with targets, timetables, and national contributions be a central provision of the Global Plastics Treaty. We recommend inclusion of the following additional provisions:The Treaty needs to extend beyond microplastics and marine litter to include all of the many thousands of chemicals incorporated into plastics.The Treaty needs to include a provision banning or severely restricting manufacture and use of unnecessary, avoidable, and problematic plastic items, especially single-use items such as manufactured plastic microbeads.The Treaty needs to include requirements on extended producer responsibility (EPR) that make fossil carbon producers, plastic producers, and the manufacturers of plastic products legally and financially responsible for the safety and end-of-life management of all the materials they produce and sell.The Treaty needs to mandate reductions in the chemical complexity of plastic products; health-protective standards for plastics and plastic additives; a requirement for use of sustainable non-toxic materials; full disclosure of all components; and traceability of components. International cooperation will be essential to implementing and enforcing these standards.The Treaty needs to include SEJ remedies at each stage of the plastic life cycle designed to fill gaps in community knowledge and advance both distributional and procedural equity.This Commission encourages inclusion in the Global Plastic Treaty of a provision calling for exploration of listing at least some plastic polymers as persistent organic pollutants (POPs) under the Stockholm Convention.This Commission encourages a strong interface between the Global Plastics Treaty and the Basel and London Conventions to enhance management of hazardous plastic waste and slow current massive exports of plastic waste into the world's least-developed countries.This Commission recommends the creation of a Permanent Science Policy Advisory Body to guide the Treaty's implementation. The main priorities of this Body would be to guide Member States and other stakeholders in evaluating which solutions are most effective in reducing plastic consumption, enhancing plastic waste recovery and recycling, and curbing the generation of plastic waste. This Body could also assess trade-offs among these solutions and evaluate safer alternatives to current plastics. It could monitor the transnational export of plastic waste. It could coordinate robust oceanic-, land-, and air-based MNP monitoring programs.This Commission recommends urgent investment by national governments in research into solutions to the global plastic crisis. This research will need to determine which solutions are most effective and cost-effective in the context of particular countries and assess the risks and benefits of proposed solutions. Oceanographic and environmental research is needed to better measure concentrations and impacts of plastics <10 µm and understand their distribution and fate in the global environment. Biomedical research is needed to elucidate the human health impacts of plastics, especially MNPs.

Summary

This Commission finds that plastics are both a boon to humanity and a stealth threat to human and planetary health. Plastics convey enormous benefits, but current linear patterns of plastic production, use, and disposal that pay little attention to sustainable design or safe materials and a near absence of recovery, reuse, and recycling are responsible for grave harms to health, widespread environmental damage, great economic costs, and deep societal injustices. These harms are rapidly worsening.While there remain gaps in knowledge about plastics' harms and uncertainties about their full magnitude, the evidence available today demonstrates unequivocally that these impacts are great and that they will increase in severity in the absence of urgent and effective intervention at global scale. Manufacture and use of essential plastics may continue. However, reckless increases in plastic production, and especially increases in the manufacture of an ever-increasing array of unnecessary single-use plastic products, need to be curbed.Global intervention against the plastic crisis is needed now because the costs of failure to act will be immense.

Highly efficient metal-free borocarbonitride catalysts for electrochemical reduction of N2 to NH3

The electrocatalytic nitrogen reduction reaction (NRR) for ammonia (NH₃) under ambient conditions is emerging as a potentially sustainable alternative to the traditional, energy-intensive Haber-Bosch process for ammonia production. Currently, metal-based electrocatalysts constitute the majority of reported NRR catalysts. However, they often suffer from the shortcomings of competitive reactions of nitrogen adsorption/activation and hydrogen generation. Therefore, there is an urgent need to develop more environmentally friendly, low energy consumption, and non-polluting high-performance metal-free electrocatalysts. In this study, borocarbonitride (BCN) materials derived from boron imidazolate framework (BIF-20) were used to boost efficient electrochemical nitrogen conversion to ammonia under ambient conditions. The BCN catalyst demonstrated excellent performance in 0.1 M KOH, with an ammonia yield of 21.62 μg h^-1 mg_cat^-1 and a Faradaic efficiency of 9.88% at -0.3 V (Reversible Hydrogen Electrode, RHE). This performance is superior to most metal-free catalysts and even some metal catalysts for NRR. The ¹⁵N₂/¹⁴N₂ isotope labeling experiments and density functional theory (DFT) calculations showed that N₂ can be adsorbed and converted to NH₃ on the surface of BCN, and that the energy barrier can be significantly reduced by structural design for BCN. This work highlights the important role played by the presence of Lewis acid-base pairs in metal-free catalysts for enhancing electrochemical NRR performance.

Graphene in Polymeric Nanocomposite Membranes—Current State and Progress

One important application of polymer/graphene nanocomposites is in membrane technology. In this context, promising polymer/graphene nanocomposites have been developed and applied in the production of high-performance membranes. This review basically highlights the designs, properties, and use of polymer/graphene nanocomposite membranes in the field of gas separation and purification. Various polymer matrices (polysulfone, poly(dimethylsiloxane), poly(methyl methacrylate), polyimide, etc.), have been reinforced with graphene to develop nanocomposite membranes. Various facile strategies, such as solution casting, phase separation, infiltration, self-assembly, etc., have been employed in the design of gas separation polymer/graphene nanocomposite membranes. The inclusion of graphene in polymeric membranes affects their morphology, physical properties, gas permeability, selectivity, and separation processes. Furthermore, the final membrane properties are affected by the nanofiller content, modification, dispersion, and processing conditions. Moreover, the development of polymer/graphene nanofibrous membranes has introduced novelty in the field of gas separation membranes. These high-performance membranes have the potential to overcome challenges arising from gas separation conditions. Hence, this overview provides up-to-date coverage of advances in polymer/graphene nanocomposite membranes, especially for gas separation applications. The separation processes of polymer/graphene nanocomposite membranes (in parting gases) are dependent upon variations in the structural design and processing techniques used. Current challenges and future opportunities related to polymer/graphene nanocomposite membranes are also discussed.

Research on engineered electrocatalysts for efficient water splitting: a comprehensive review

Water electrolysis plays an interesting role toward hydrogen generation for overcoming global environmental crisis and solving the energy storage problem. However, there is still a deficiency of efficient electrocatalysts to overcome sluggish kinetics for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Great efforts have been employed to produce potential catalysts with low overpotential, rapid kinetics, and excellent stability for HER and OER. At present, hydrogen economy is driven by electrocatalysts with excellent characteristics; thus, systematic design strategy has become the driving force to exploit earth-abundant transition metal-based electrocatalysts toward H₂ economy. In this review, the recent progress on newer materials including metals, alloys, and transition metal oxides (manganese oxides, cobalt oxides, nickel oxides, PBA-derived metal oxides, and metal complexes) as photocatalysts/electrocatalysts has been overviewed together with some methodologies for efficient water splitting. Metal-organic framework (MOF)-based electrocatalysts have been highly exploited owing to their interesting functionalities. The photovoltaic-electrocatalytic (PV-EC) process focused on harvesting high solar-to-hydrogen efficiency (STH) among various solar energy conversion as well as storage systems. Electrocatalysts/photocatalysts with high efficiency have become an urgent need for overall water splitting. Also, cutting-edge achievements in the fabrication of electrocatalysts along with theoretical consideration have been discussed.

The Combined Impact of Ni-Based Catalysts and a Binary Carbonate Salts Mixture on the CO2 Gasification Performance of Olive Kernel Biomass Fuel

In the present work, the individual or synergistic effect of Ni-based catalysts (Ni/CeO2, Ni/Al2O3) and an eutectic carbonate salt mixture (MS) on the CO2 gasification performance of olive kernels was investigated. It was found that the Ni/CeO2 catalyst presented a relatively superior instant gasification reaction rate (Rco) compared to Ni/Al2O3, in line with the significant redox capability of CeO2. On the other hand, the use of the binary eutectic carbonate salt mixture (MS) lowered the onset and maximum CO2 gasification temperatures, resulting in a notably higher carbon conversion efficiency (81%) compared to the individual Ni-based catalysts and non-catalytic gasification tests (60%). Interestingly, a synergetic catalyst-carbonate salt mixture effect was revealed in the low and intermediate CO2 gasification temperature regimes, boosting the instant gasification reaction rate (Rco). In fact, in the temperature range of 300 to 550 °C, the maximum Rco value for both MS-Ni/Al2O3 and MS-Ni/CeO2 systems were four times higher (4 × 10−3 min−1 at 460 °C) compared to the individual counterparts. The present results demonstrated for the first time the combined effect of two different Ni-based catalysts and an eutectic carbonate salt mixture towards enhancing the CO production rate during CO2 gasification of olive kernel biomass fuel, especially in the devolatilization and tar cracking/reforming zones. On the basis of a systematic characterization study and lab-scale gasification experiments, the beneficial role of catalysts and molten carbonate salts on the gasification process was revealed, which can be ascribed to the catalytic activity as well as the improved mass and heat transport properties offered by the molten carbonate salts.

The Key to Solving Plastic Packaging Wastes: Design for Recycling and Recycling Technology

Confronted with serious environmental problems caused by the growing mountains of plastic packaging waste, the prevention and control of plastic waste has become a major concern for most countries. In addition to the recycling of plastic wastes, design for recycling can effectively prevent plastic packaging from turning into solid waste at the source. The reasons are that the design for recycling can extend the life cycle of plastic packaging and increase the recycling values of plastic waste; moreover, recycling technologies are helpful for improving the properties of recycled plastics and expanding the application market for recycled materials. This review systematically discussed the present theory, practice, strategies, and methods of design for recycling plastic packaging and extracted valuable advanced design ideas and successful cases. Furthermore, the development status of automatic sorting methods, mechanical recycling of individual and mixed plastic waste, as well as chemical recycling of thermoplastic and thermosetting plastic waste, were comprehensively summarized. The combination of the front-end design for recycling and the back-end recycling technologies can accelerate the transformation of the plastic packaging industry from an unsustainable model to an economic cycle model and then achieve the unity of economic, ecological, and social benefits.

Interactions in Ammonia and Hydrogen Oxidation Examined in a Flow Reactor and a Shock Tube

Ammonia (NH₃) is a promising fuel, because it is carbon-free and easier to store and transport than hydrogen (H₂). However, an ignition enhancer such as H₂ might be needed for technical applications, because of the rather poor ignition properties of NH₃. The combustion of pure NH₃ and H₂ has been explored widely. However, for mixtures of both gases, mostly only global parameters such as ignition delay times or flame speeds were reported. Studies with extensive experimental species profiles are scarce. Therefore, we experimentally investigated the interactions in the oxidation of different NH₃/H₂ mixtures in the temperature range of 750-1173 K at 0.97 bar in a plug-flow reactor (PFR), as well as in the temperature range of 1615-2358 K with an average pressure of 3.16 bar in a shock tube. In the PFR, temperature-dependent mole fraction profiles of the main species were obtained via electron ionization molecular-beam mass spectrometry (EI-MBMS). Additionally, for the first time, tunable diode laser absorption spectroscopy (TDLAS) with a scanned-wavelength method was adapted to the PFR for the quantification of nitric oxide (NO). In the shock tube, time-resolved NO profiles were also measured by TDLAS using a fixed-wavelength approach. The experimental results both in PFR and shock tube reveal the reactivity enhancement by H₂ on ammonia oxidation. The extensive sets of results were compared with predictions by four NH₃-related reaction mechanisms. None of the mechanisms can well predict all experimental results, but the Stagni et al. [React. Chem. Eng. 2020, 5, 696-711] and Zhu et al. [Combust. Flame 2022, 246, 115389] mechanisms perform best for the PFR and shock tube conditions, respectively. Exploratory kinetic analysis was conducted to identify the effect of H₂ addition on ammonia oxidation and NO formation, as well as sensitive reactions in different temperature regimes. The results presented in this study can provide valuable information for further model development and highlight relevant properties of H₂-assisted NH₃ combustion.

Valorization of Delonix regia Pods for Bioethanol Production

Delonix regia (common name: Flame tree) pods, an inexpensive lignocellulosic waste matrix, were successfully used to produce value-added bioethanol. Initially, the potentiality of D. regia pods as a lignocellulosic biomass was assessed by Fourier-transform infrared spectroscopy (FTIR), which revealed the presence of several functional groups belonging to cellulose, hemicellulose, and lignin, implying that D. regia pods could serve as an excellent lignocellulosic biomass. Response Surface Methodology (RSM) and Central Composite Design (CCD) were used to optimize pretreatment conditions of incubation time (10–70 min), H2SO4 concentration (0.5–3%), amount of substrate (0.02–0.22 g), and temperature (45–100 °C). Then, RSM-suggested 30 trials of pretreatment conditions experimented in the laboratory, and a trial using 0.16 g substrate, 3% H2SO4, 70 min incubation at 90 °C, yielded the highest amount of glucose (0.296 mg·mL−1), and xylose (0.477 mg·mL−1). Subsequently, the same trial conditions were chosen in the downstream process, and pretreated D. regia pods were subjected to enzymatic hydrolysis with 5 mL of indigenously produced cellulase enzyme (74 filter per unit [FPU]) at 50 °C for 72 h to augment the yield of fermentable sugars, yielding up to 55.57 mg·mL−1 of glucose. Finally, the released sugars were fermented to ethanol by Saccharomyces cerevisiae, yielding a maximum of 7.771% ethanol after 72 h of incubation at 30 °C. Conclusively, this study entails the successful valorization of D. regia pods for bioethanol production.

Use of additives to improve collective biogas plant performances: A comprehensive review

Nowadays, anaerobic digestion (AD) is being increasingly encouraged to increase the production of biogas and thus of biomethane. Due to the high diversity among feedstocks used, the variability of operating parameters and the size of collective biogas plants, different incidents and limitations may occur (e.g., inhibitions, foaming, complex rheology). To improve performance and overcome these limitations, several additives can be used. This literature review aims to summarize the effects of the addition of various additives in co-digestion continuous or semi-continuous reactors to fit as much as possible with collective biogas plant challenges. The addition of (i) microbial strains or consortia, (ii) enzymes and (iii) inorganic additives (trace elements, carbon-based materials) in digester is analyzed and discussed. Several challenges associated with the use of additives for AD process at collective biogas plant scale requiring further research work are highlighted: elucidation of mechanisms, dosage and combination of additives, environmental assessment, economic feasibility, etc.

Studies on the Kinetics of the CH + H2 Reaction and Implications for the Reverse Reaction, 3CH2 + H

The reaction of CH radicals with H₂ has been studied by the use of laser flash photolysis, probing CH decays under pseudo-first-order conditions using laser-induced fluorescence (LIF) over the temperature range 298-748 K at pressures of ∼5-100 Torr. Careful data analysis was required to separate the CH LIF signal at ∼428 nm from broad background fluorescence, and this interference increased with temperature. We believe that this interference may have been the source of anomalous pressure behavior reported previously in the literature (Brownsword, R. A.; J. Chem. Phys. 1997, 106, 7662-7677). The rate coefficient k₁ shows complex behavior: at low pressures, the main route for the CH₃* formed from the insertion of CH into H₂ is the formation of ³CH₂ + H, and as the pressure is increased, CH₃* is increasingly stabilized to CH₃. The kinetic data on CH + H₂ have been combined with experimental shock tube data on methyl decomposition and literature thermochemistry within a master equation program to precisely determine the rate coefficient of the reverse reaction, ³CH₂ + H → CH + H₂. The resulting parametrization is k_CH2+H(T) = (1.69 ± 0.11) × 10^-10 × (T/298 K)^{(0.05±0.010)} cm³ molecule^-1 s^-1, where the errors are 1σ.

Boosting the performance and durability of heterogeneous electrodes for solid oxide electrochemical cells utilizing a data-driven powder-to-power framework

Solid oxide electrochemical cells (SOCs) hold potential as a critical component in the future landscape of renewable energy storage and conversion systems. However, the commercialization of SOCs still requires further breakthroughs in new material development and engineering designs to achieve high performance and durability. In this study, a data-driven powder-to-power framework has been presented, fully digitizing the morphology evolution of heterogeneous electrodes from fabrication to long-term operation. This framework enables accurate performance prediction over the full life cycle. The intrinsic correlation between microstructural parameters and electrode durability is elucidated through parameter analysis. Rational control of the ion-conducting phase volume fraction can effectively suppress Ni coarsening and mitigate the excessive ohmic loss caused by Ni migration. The initial and degraded electrode performances are attributed to the interplay of multiple parameters. A practical optimization strategy to enhance the initial performance and durability of the electrode is proposed through the construction of the surrogate model and the application of the optimization algorithm. The optimal electrode parameters are determined to accommodate various maximum operation time requirements. By implementing the data-driven powder-to-power framework, it is possible to reduce the degradation rate of Ni-based electrodes from 2.132% to 0.703% kh^-1 with a required maximum operation time of over 50,000 h.

Proton-donating and chemistry-dependent buffering capability of amino acids for the hydrogen evolution reaction

The hydrogen evolution reaction (HER) has been widely demonstrated to have a strong dependence on pH and on the source of protons, where a clear kinetic advantage arises in acidic conditions over near-neutral and alkaline conditions due to the switch in reactant from H₃O⁺ to H₂O. Playing on the acid/base chemistry of aqueous systems can avoid the kinetic frailties. For example, buffer systems can be used to maintain proton concentration at intermediate pH, driving H₃O⁺ reduction over H₂O. In light of this, we examine the influence of amino acids on HER kinetics at platinum surfaces using rotating disk electrodes. We demonstrate that aspartic acid (Asp) and glutamic acid (Glu) can act not only as proton donors, but also have sufficient buffering action to sustain H₃O⁺ reduction even at large current density. Comparing with histidine (His) and serine (Ser), we reveal that the buffering capacity of amino acids occurs due to the proximity of their isoelectric point (pI) and their buffering pK_a. This study further exemplifies HER's dependence on pH and pK_a and that amino acids can be used to probe this relationship.

Deposit formation from evaporating urea-water droplets on substrates of different wettability

HYPOTHESIS

During the evaporation of urea water solution (UWS), the wall temperature and surface properties influence the dynamics of deposit formation by affecting the internal mass transport. These effects are expected to be reflected in the resulting deposit morphology and allow different deposit regimes to be distinguished.

EXPERIMENTS

The temperature of metallic substrates is varied for three different surface treatments to analyze the wetting, evaporation behavior and the crystallization process of single UWS droplets in situ using a high-speed camera. The deposit morphology is captured by confocal microscopy and analyzed via the power spectral density method (PSD). PSD is used to extract the height of different surface features for each deposit, providing valuable information about the local crystallization history.

FINDINGS

A significant influence of the surface properties on the crystallization process as well as on the morphology of the final deposit is found. The influence of wettability is described by the resulting internal mass transport, which determine the urea distribution. PSD analysis quantified distinct trends in the scaling tendencies of the deposit aggregates under different wall conditions. The local crystal growth history extracted by PSD agrees well with proposed crystallization mechanisms, which is further supported by high-speed and SEM imaging.

Self-supporting NiMo-Fe-P nanowire arrays as bifunctional catalysts for efficient overall water splitting

Developing efficient bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts is beneficial for simplifying the design of electrolytic cells and reducing the cost of device manufacturing. Herein, a metal phosphide nanoarray (NiMo-Fe-P) electrocatalyst was designed by in situ ion exchange and low-temperature phosphating to promote overall water splitting in 1 M KOH. NiMo-Fe-P demonstrates superb HER and OER activities as reflected by the low overpotentials of 73.1 mV and 215.2 mV, respectively, at a current density of 10 mA cm^-2. The addition of Fe changes the electronic structure of Ni, which is conducive to the chemisorption of oxygen-containing intermediates and reduces the energy barrier for water decomposition. Besides, the metal phosphide not only acts as the active site of the HER, but also improves the conductivity of the catalyst. Furthermore, nanowire arrays and the small particles generated on their surfaces provide a high electrochemical active surface area (ECSA), which was beneficial for the exposure of active sites. Attributed to these advantages, the cell voltage of the water electrolyzer constructed with NiMo-Fe-P as both the cathode and anode is only 1.526 V at 10 mA cm^-2, and it maintains excellent stability for 100 h with near negligible changes in potential.

Nanostructured Conducting Polymers and Their Applications in Energy Storage Devices

Due to the energy requirements for various human activities, and the need for a substantial change in the energy matrix, it is important to research and design new materials that allow the availability of appropriate technologies. In this sense, together with proposals that advocate a reduction in the conversion, storage, and feeding of clean energies, such as fuel cells and electrochemical capacitors energy consumption, there is an approach that is based on the development of better applications for and batteries. An alternative to commonly used inorganic materials is conducting polymers (CP). Strategies based on the formation of composite materials and nanostructures allow outstanding performances in electrochemical energy storage devices such as those mentioned. Particularly, the nanostructuring of CP stands out because, in the last two decades, there has been an important evolution in the design of various types of nanostructures, with a strong focus on their synergistic combination with other types of materials. This bibliographic compilation reviews state of the art in this area, with a special focus on how nanostructured CP would contribute to the search for new materials for the development of energy storage devices, based mainly on the morphology they present and on their versatility to be combined with other materials, which allows notable improvements in aspects such as reduction in ionic diffusion trajectories and electronic transport, optimization of spaces for ion penetration, a greater number of electrochemically active sites and better stability in charge/discharge cycles.

Electrothermal Water-Gas Shift Reaction at Room Temperature with a Silicomolybdate-Based Palladium Single-Atom Catalyst

The water-gas shift (WGS) reaction is often conducted at elevated temperature and requires energy-intensive separation of hydrogen (H₂ ) from methane (CH₄ ), carbon dioxide (CO₂ ), and residual carbon monoxide (CO). Designing processes to decouple CO oxidation and H₂ production provides an alternative strategy to obtain high-purity H₂ streams. We report an electrothermal WGS process combining thermal oxidation of CO on a silicomolybdic acid (SMA)-supported Pd single-atom catalyst (Pd₁ /CsSMA) and electrocatalytic H₂ evolution. The two half-reactions are coupled through phosphomolybdic acid (PMA) as a redox mediator at a moderate anodic potential of 0.6 V (versus Ag/AgCl). Under optimized conditions, our catalyst exhibited a TOF of 1.2 s^-1 with turnover numbers above 40 000 mol CO 2 ${{_{{\rm CO}{_{2}}}}}$  mol_Pd ^-1 achieving stable H₂ production with a purity consistently exceeding 99.99 %.

Tools for Optimization of Biomass-to-Energy Conversion Processes

Biomasses are renewable sources used in energy conversion processes to obtain diverse products through different technologies. The production chain, which involves delivery, logistics, pre-treatment, storage and conversion as general components, can be costly and uncertain due to inherent variability. Optimization methods are widely applied for modeling the biomass supply chain (BSC) for energy processes. In this qualitative review, the main aspects and global trends of using geographic information systems (GISs), linear programming (LP) and neural networks to optimize the BSC are presented. Modeling objectives and factors considered in studies published in the last 25 years are reviewed, enabling a broad overview of the BSC to support decisions at strategic, tactical and operational levels. Combined techniques have been used for different purposes: GISs for spatial analyses of biomass; neural networks for higher heating value (HHV) correlations; and linear programming and its variations for achieving objectives in general, such as costs and emissions reduction. This study reinforces the progress evidenced in the literature and envisions the increasing inclusion of socio-environmental criteria as a challenge in future modeling efforts.

Limits of identification using VUV spectroscopy applied to C8H18 isomers isolated by GC×GC

The vacuum ultraviolet detector for gas chromatography can be used to identify structural differences between isomers with similar chromatographic elution times, which adds detail to characterization, valuable for prescreening of sustainable aviation fuel candidates. Although this capability has been introduced elsewhere, vacuum ultraviolet spectroscopy for saturated hydrocarbons has been examined minimally, as the similarities between their spectra are much less significant than their aromatic counterparts. The fidelity with which structural differences can be identified has been unclear. In this work, all possible structural isomers of C₈H₁₈ are measured and determined to have unambiguously unique vacuum ultraviolet spectra. Using a statistically based residual comparison approach, the concentration limits at which the spectral differences are interpretable are tested in both a controlled study and a real fuel application. The concentration limit at which the spectral differences between C₈H₁₈ isomers are unambiguous is below 0.40% by mass and less than 0.20% with human discretion in our experimental configuration.

Emissions of Toxic Substances from Biomass Burning: A Review of Methods and Technical Influencing Factors

In the perspective of energy sustainability, biomass is the widely used renewable domestic energy with low cost and easy availability. Increasing studies have reported the health impacts of toxic substances from biomass burning emissions. To make proper use of biomass as residential solid energy, the evaluation of its health risks and environmental impacts is of necessity. Empirical studies on the characteristics of toxic emissions from biomass burning would provide scientific data and drive the development of advanced technologies. This review focuses on the emission of four toxic substances, including heavy metals, polycyclic aromatic hydrocarbons (PAHs), elemental carbon (EC), and volatile organic compounds (VOCs) emitted from biomass burning, which have received increasing attention in recent studies worldwide. We focus on the developments in empirical studies, methods of measurements, and technical factors. The influences of key technical factors on biomass burning emissions are combustion technology and the type of biomass. The methods of sampling and testing are summarized and associated with various corresponding parameters, as there are no standard sampling methods for the biomass burning sector. Integration of the findings from previous studies indicated that modern combustion technologies result in a 2–4 times reduction, compared with traditional stoves. Types of biomass burning are dominant contributors to certain toxic substances, which may help with the invention or implementation of targeted control technologies. The implications of previous studies would provide scientific evidence to push the improvements of control technologies and establish appropriate strategies to improve the prevention of health hazards.

Microalgal Feedstock for Biofuel Production: Recent Advances, Challenges, and Future Perspective

Globally, nations are trying to address environmental issues such as global warming and climate change, along with the burden of declining fossil fuel reserves. Furthermore, countries aim to reach zero carbon emissions within the existing and rising global energy crisis. Therefore, bio-based alternative sustainable feedstocks are being explored for producing bioenergy. One such renewable energy resource is microalgae; these are photosynthetic microorganisms that grow on non-arable land, in extreme climatic conditions, and have the ability to thrive even in sea and wastewater. Microalgae have high photosynthetic efficiencies and biomass productivity compared to other terrestrial plants. Whole microalgae biomass or their extracted metabolites can be converted to various biofuels such as bioethanol, biodiesel, biocrude oil, pyrolytic bio-oil, biomethane, biohydrogen, and bio jet fuel. However, several challenges still exist before faster and broader commercial application of microalgae as a sustainable bioenergy feedstock for biofuel production. Selection of appropriate microalgal strains, development of biomass pre-concentrating techniques, and utilization of wet microalgal biomass for biofuel production, coupled with an integrated biorefinery approach for producing value-added products, could improve the environmental sustainability and economic viability of microalgal biofuel. This article will review the current status of research on microalgal biofuels and their future perspective.

Application of Pyrolysis for the Evaluation of Organic Compounds in Medical Plastic Waste Generated in the City of Cartagena-Colombia Applying TG-GC/MS

In this study, the thermal degradation and pyrolysis of hospital plastic waste consisting of polyethylene (PE), polystyrene (PS), and polypropylene (PP) were investigated using TG-GC/MS. The identified molecules with the functional groups of alkanes, alkenes, alkynes, alcohols, aromatics, phenols, CO and CO2 were found in the gas stream from pyrolysis and oxidation, and are chemical structures with derivatives of aromatic rings. They are mainly related to the degradation of PS hospital waste, and the alkanes and alkenes groups originate mainly from PP and PE-based medical waste. The pyrolysis of this hospital waste did not show the presence of derivatives of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, which is an advantage over classical incineration methodologies. CO, CO2, phenol, acetic acid and benzoic acid concentrations were higher in the gases from the oxidative degradation than in those generated in the pyrolysis with helium. In this article, we propose different pathways of reaction mechanisms that allow us to explain the presence of molecules with other functional groups, such as alkanes, alkenes, carboxylic acids, alcohols, aromatics and permanent gases.

Analysis of the Scale of Global Human Needs and Opportunities for Sustainable Catalytic Technologies

We analyzed the enormous scale of global human needs, their carbon footprint, and how they are connected to energy availability. We established that most challenges related to resource security and sustainability can be solved by providing distributed, affordable, and clean energy. Catalyzed chemical transformations powered by renewable electricity are emerging successor technologies that have the potential to replace fossil fuels without sacrificing the wellbeing of humans. We highlighted the technical, economic, and societal advantages and drawbacks of short- to medium-term decarbonization solutions to gauge their practicability, economic feasibility, and likelihood for widespread acceptance on a global scale. We detailed catalysis solutions that enhance sustainability, along with strategies for catalyst and process development, frontiers, challenges, and limitations, and emphasized the need for planetary stewardship. Electrocatalytic processes enable the production of solar fuels and commodity chemicals that address universal issues of the water, energy and food security nexus, clothing, the building sector, heating and cooling, transportation, information and communication technology, chemicals, consumer goods and services, and healthcare, toward providing global resource security and sustainability and enhancing environmental and social justice.

A Recent Review of Primary Hydrogen Carriers, Hydrogen Production Methods, and Applications

Hydrogen is a promising energy carrier, especially for transportation, owing to its unique physical and chemical properties. Moreover, the combustion of hydrogen gas generates only pure water; thus, its wide utilization can positively affect human society to achieve global net zero CO2 emissions by 2050. This review summarizes the characteristics of the primary hydrogen carriers, such as water, methane, methanol, ammonia, and formic acid, and their corresponding hydrogen production methods. Additionally, state-of-the-art studies and hydrogen energy applications in recent years are also included in this review. In addition, in the conclusion section, we summarize the advantages and disadvantages of hydrogen carriers and hydrogen production techniques and suggest the challenging tasks for future research.

Experimental and Computational Evaluation of 1,2,4-Triazolium-Based Ionic Liquids for Carbon Dioxide Capture

Utilization of ionic liquids (ILs) for carbon dioxide (CO2) capture is continuously growing, and further understanding of the factors that influence its solubility (notably for new ILs) is crucial. Herein, CO2 absorption of two 1,2,4-triazolium-based ILs was compared with imidazolium-based Ils of different anions, namely bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, and glycinate. The CO2 absorption capacity was determined using an isochoric saturation method and compared with predicted solubility employing COnductor-like Screening Model for Real Solvents (COSMO-RS). To gain an understanding of the effects of cations and anions of the ILs on the CO2 solubility, the molecular orbitals energy levels were calculated using TURBOMOLE. Triazolium-based ILs exhibit higher absorption capacity when compared to imidazolium-based ILs for the same anions. The results also showed that the anions’ energy levels are more determinant towards solubility than the cations’ energy levels, which can be explained by the higher tendency of CO2 to accept electrons than to donate them.

Modeling and Performance Analysis of Municipal Solid Waste Treatment in Plasma Torch Reactor

Thermal plasma has emerged as a technology with tremendous promise for municipal wastes that should be disposed of sustainably. A numerical simulation of a symmetric turbulent plasma jet from a thermal air plasma torch was developed using COMSOL Multiphysics®5.4 engineering simulation software. The velocities, temperature, arc root motion, and joule heating of the plasma jet were examined under the impact of the gas mass flow rate and current. Moreover, the electrical power required for the municipal solid waste (MSW) processing was estimated. The enthalpy and the effectiveness of the plasma torch were analyzed and discussed. Subsequently an investigation was conducted into the gasification characteristics of MSW using air and steam gases. The torch’s power and efficiency could be enhanced with a higher mass flow rate and temperature. Three operating modes were identified from the current–arc flow combination. Among the plasma gas considered, the air gas plasma torch guarantees an acceptable thermal efficiency and a low anode erosion rate. Plasma gasification produces cleaner syngas with higher efficiency (84%) than the conventional process due to the elevated temperature used during the process that breaks down all the char, dioxins, and tars.

On the Importance of Model Selection for CFD Analysis of High Temperature Gas-Solid Reactive Flow; Case Study: Post Combustion Chamber of HIsarna Off-Gas System

In this paper a CFD analysis of HIsarna off-gas system for post combustion of CO-H2-carbon particle mixture is presented to evaluate the effect of different sub-models and parameters on the accuracy of predictions and simulation time. The effects of different mesh type, mesh grid size, radiation models, turbulent models, kinetic mechanism, turbulence chemistry interaction models, including and excluding gas-solid reactions, number of reactive solid particles are investigated in detail. Based on the accuracy of the predictions and agreement with counterpart measured values, the best combination is selected and conclusions are derived. It was found that radiation and turbulence chemistry interaction model have a major effect on the temperature and composition profile prediction along the studied off-gas system, compared to the variations in other models. The effect of these two models becomes even more evident when the temperature and fuel content of the flue gas are high.

Biodiesel Production through the Transesterification of Waste Cooking Oil over Typical Heterogeneous Base or Acid Catalysts

For the production of biodiesel from waste cooking oil with an acid value of 1.86 mg KOH/g, five heterogeneous catalysts—Ba(OH)2, CaO, MgO, ZnO, and AlCl3—were employed. To optimize the reaction parameters of each catalyst, the influence of crucial process variables, such as catalyst loading, methanol-to-oil ratio, and reaction duration, was investigated. In addition, the effect of acetone as a cosolvent toward the progress of biodiesel production and the reusability of the heterogeneous catalysts were also examined, and the data were statistically evaluated with a 95% confidence level. Ba(OH)2 performed exceptionally well, with a 92 wt.% biodiesel yield, followed by CaO with an 84 wt.% yield. However, none of the results for MgO, ZnO, or AlCl3 were adequate. In addition, regardless of the type of catalyst utilized, adding 20 vol.% acetone to the biodiesel manufacturing process led to an increase in output. Furthermore, every heterogeneous catalyst was reusable, but only Ba(OH)2 and CaO produced a significant yield until the third cycle. The other catalysts did not produce yields of any significance.

A Review on Tetrabromobisphenol A: Human Biomonitoring, Toxicity, Detection and Treatment in the Environment

Tetrabromobisphenol A (TBBPA) is a known endocrine disruptor employed in a range of consumer products and has been predominantly found in different environments through industrial processes and in human samples. In this review, we aimed to summarize published scientific evidence on human biomonitoring, toxic effects and mode of action of TBBPA in humans. Interestingly, an overview of various pretreatment methods, emerging detection methods, and treatment methods was elucidated. Studies on exposure routes in humans, a combination of detection methods, adsorbent-based treatments and degradation of TBBPA are in the preliminary phase and have several limitations. Therefore, in-depth studies on these subjects should be considered to enhance the accurate body load of non-invasive matrix, external exposure levels, optimal design of combined detection techniques, and degrading technology of TBBPA. Overall, this review will improve the scientific comprehension of TBBPA in humans as well as the environment, and the breakthrough for treating waste products containing TBBPA.

Soot Formation in Methane Pyrolysis Reactor: Modeling Soot Growth and Particle Characterization

Methane pyrolysis is a very attractive and climate-friendly process for hydrogen production and the sequestration of carbon as solid material. The formation of soot particles in methane pyrolysis reactors needs to be understood for technology scale-up calling for appropriate soot growth models. A monodisperse model is coupled with a plug flow reactor model and elementary-step reaction mechanisms to numerically simulate processes in methane pyrolysis reactors, namely, the chemical conversion of methane to hydrogen, formation of C-C coupling products and polycyclic aromatic hydrocarbons, and growth of soot particles. The soot growth model accounts for the effective structure of the aggregates by calculating the coagulation frequency from the free-molecular regime to the continuum regime. It predicts the soot mass, particle number, area, and volume concentration, along with the particle size distribution. For comparison, experiments on methane pyrolysis are carried out at different temperatures and collected soot samples are characterized using Raman spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS).

Experimental and Updated Kinetic Modeling Study of Neopentane Low Temperature Oxidation

Neopentane is an ideal fuel model to study low-temperature oxidation chemistry. The significant discrepancies between experimental data and simulations using the existing neopentane models indicate that an updated study of neopentane oxidation is needed. In this work, neopentane oxidation experiments are carried out using two jet-stirred reactors (JSRs) at 1 atm, at a residence time of 3 s, and at three different equivalence ratios of 0.5, 0.9, and 1.62. Two different analytical methods (synchrotron vacuum ultraviolet photoionization mass spectrometry and gas chromatography) were used to investigate the species distributions. Numerous oxidation intermediates were detected and quantified, including acetone, 3,3-dimethyloxetane, methacrolein, isobutene, 2-methylpropanal, isobutyric acid, and peroxides, which are valuable for validating the kinetic model describing neopentane oxidation. In the model development, the pressure dependencies of the rate constants for the reaction classes Q̇OOH + O₂ and Q̇OOH decompositions are considered. This addition improves the prediction of the low-temperature oxidation reactivity of neopentane. Another focus of model development is to improve the prediction of carboxylic acids formed during the low-temperature oxidation of neopentane. The detection and identification of isobutyric acid indicates the existence of the Korcek mechanism during neopentane oxidation. Regarding the formation of acetic acid, the reaction channels are considered to be initiated from the reactions of ȮH radical addition to acetaldehyde/acetone. This updated kinetic model is validated extensively against the experimental data in this work and various experimental data available in the literature, including ignition delay times (IDTs) from both shock tubes (STs) and rapid compression machines (RCMs) and JSR speciation data at high temperatures.

Multiwavelength Speciation in Pyrolysis of n-Pentane and Experimental Determination of the Rate Coefficient of nC5H12 = nC3H7 + C2H5 in a Shock Tube

We report the application of a multiwavelength speciation strategy to the study of n-pentane (nC₅H₁₂) pyrolysis behind reflected shock waves in a shock tube. Experiments were conducted with 2% nC₅H₁₂/0.8%CO₂/Ar (by mole) between 1150 and 1520 K in the pressure range of 1-2 atm. Utilization of laser absorption spectroscopy at eight wavelengths allowed time-resolved measurements of n-pentane, ethylene, methane, heavy alkenes, and temperature. The measured time histories were compared against the predictions of four recently developed chemical kinetic models for heavy hydrocarbons. It was found that none of the models reconciled the measured species time histories simultaneously. Sensitivity analysis was conducted to identify key reactions influencing the evolution of ethylene and other major pyrolysis products. The analysis revealed that the unimolecular decomposition of n-pentane into n-propyl and ethyl radicals has a dominating influence over the evolution of ethylene in the temperature range of 1150-1450 K. The rate coefficient of this reaction was then adjusted to match the measured ethylene time histories for each experiment. The rate coefficients thus determined, were fit against temperature using an Arrhenius expression given by k₁(T) = 3.5 × 10¹⁴ exp(-67.2 kcal/RT) s^-1. The average overall 2σ uncertainty of the measured rate coefficient was found to be ±35%, resulting primarily from uncertainties in the rate coefficients of secondary reactions. The measured rate coefficient, when used with the models, leads to a significant improvement in the prediction of species time histories. Further improvements in the model are possible if the rate coefficients of relevant reactions pertaining to small hydrocarbon chemistry are determined with an improved accuracy, and less uncertainty. To the best knowledge of the authors, this is the first experimental determination of the rate coefficient of C₅H₁₂ → nC₃H₇ + C₂H_5.

A Combined Experimental and Modeling Study on Isopropyl Nitrate Pyrolysis

Alkyl nitrates thermally decompose by homolytic cleavage of the weak nitrate bond at very low temperatures (e.g., around 500 K at reaction times of a few seconds). This provides the opportunity to study the subsequent chemistry of the initially formed radical (or its subsequent pyrolysis products, if unstable) and nitrogen dioxide at such mild conditions. In this work this idea is applied to isopropyl nitrate (iPN) pyrolysis, which is studied in a tubular reactor at atmospheric pressure, temperatures ranging from 373 to 773 K, and residence times of around 2 s. At the experimental conditions, iPN decomposition starts at 473 K with O-N bond fission producing isopropoxy radical (i-C₃H₇O) and NO₂. i-C₃H₇O is rapidly converted to acetaldehyde (CH₃CHO), which is the most abundant product detected, and methyl radicals. Other major products detected are formaldehyde (CH₂O), methanol (CH₃OH), nitromethane (CH₃NO₂), NO, methane, formamide (CHONH₂), and methyl nitrite (CH₃ONO). Four literature nitrogen chemistry models─three of those augmented with iPN specific reactions─have been tested for their ability to predict the iPN decomposition and product profiles. The mechanism by the Curran group performs best, but it still underpredicts the observed high formaldehyde and methanol yields. A rate analysis indicates that the branching ratio of the reaction between methyl radicals and nitrogen dioxide is of significant importance. Based on recent theoretical and experimental data, new rate expressions for the two reactions CH₃ + NO₂ → CH₃O + NO and CH₃ + NO₂ + He → CH₃ONO₂ + He are calculated and incorporated in the kinetic models. It is shown that this change clearly improves the predictions, although additional work is needed to achieve good agreement between calculated and measured species profiles.

Hydrolysis of regenerated cellulose from ionic liquids and deep eutectic solvent over sulfonated carbon catalysts

The efficient hydrolysis of cellulose into its monomer unit such as glucose or valuable cello-oligosaccharides is the critical step for the cost-effective production of biofuels and biochemicals. However, the current cellulose hydrolysis process involves high energy-demanding pretreatment (e.g., ball-milling) and long reaction times (>24 h). Herein, we investigated the feasibility of the dissolution/regeneration (DR) of cellulose in ionic liquids (ILs) and deep eutectic solvent (DES) as an alternative to ball-milling pretreatment for the effective hydrolysis of cellulose. Because chlorine-based solvents were reported to be the most active for cellulose pretreatment, [EMIM]Cl and [DMIM]DMP were selected as the IL molecules, and choline chloride-lactic acid and choline chloride-imidazole were selected as the DES molecules. The level of the crystallinity reduction of the regenerated cellulose were analyzed using XRD and SEM measurements. The hydrolysis kinetics of the regenerated cellulose from ILs and DES were examined at 150 °C using sulfonated carbon catalysts and compared with those of the ball-milled cellulose. Overall, the cellulose pretreatment using the ILs and the DES had superior kinetics for cellulose hydrolysis to the conventional ball milling treatment, suggesting a possibility to replace the current high energy-demanding ball-milling process with the energy-saving DR process. In addition, the utilization of supercritical carbon dioxide-induced carbonic acid as an in situ acid catalyst for the enhanced hydrolysis of cellulose was presented for the first time.

Recycling of Plastics from E-Waste via Photodegradation in a Low-Pressure Reactor: The Case of Decabromodiphenyl Ether Dispersed in Poly(acrylonitrile-butadiene-styrene) and Poly(carbonate)

Recycling of plastic waste from electrical and electronic equipment (EEE), containing brominated flame retardants (BFR) remains difficult due to the increasingly stringent regulations on their handling and recovery. This report deals with photodegradation in a low-pressure reactor applying UV-visible light on Decabromodiphenyl ether (DBDE or BDE-209) randomly dispersed in commercially available Poly(acrylonitrile-butadiene-styrene) (ABS) and Poly(carbonate) (PC). The aim of this study is to investigate the possibility of decomposing a BFR in plastic waste from EEE while maintaining the specifications of the polymeric materials in order to allow for their recycling. The photodegradation of the extracted BFR was monitored using infrared spectroscopy and gas chromatography coupled with mass spectroscopy. DBDE underwent rapid photodegradation during the first minutes of exposure to UV-visible light and reached degradation yields superior to 90% after 15 min of irradiation. The evaluation of polymer properties (ABS and PC) after irradiation revealed superficial crosslinking effects, which were slightly accelerated in the presence of DBDE. However, the use of a low-pressure reactor avoids large photooxidation and allowed to maintain the thermal and structural properties of the virgin polymers.

The Materials Science behind Sustainable Metals and Alloys

Production of metals stands for 40% of all industrial greenhouse gas emissions, 10% of the global energy consumption, 3.2 billion tonnes of minerals mined, and several billion tonnes of by-products every year. Therefore, metals must become more sustainable. A circular economy model does not work, because market demand exceeds the available scrap currently by about two-thirds. Even under optimal conditions, at least one-third of the metals will also in the future come from primary production, creating huge emissions. Although the influence of metals on global warming has been discussed with respect to mitigation strategies and socio-economic factors, the fundamental materials science to make the metallurgical sector more sustainable has been less addressed. This may be attributed to the fact that the field of sustainable metals describes a global challenge, but not yet a homogeneous research field. However, the sheer magnitude of this challenge and its huge environmental effects, caused by more than 2 billion tonnes of metals produced every year, make its sustainability an essential research topic not only from a technological point of view but also from a basic materials research perspective. Therefore, this paper aims to identify and discuss the most pressing scientific bottleneck questions and key mechanisms, considering metal synthesis from primary (minerals), secondary (scrap), and tertiary (re-mined) sources as well as the energy-intensive downstream processing. Focus is placed on materials science aspects, particularly on those that help reduce CO₂ emissions, and less on process engineering or economy. The paper does not describe the devastating influence of metal-related greenhouse gas emissions on climate, but scientific approaches how to solve this problem, through research that can render metallurgy fossil-free. The content is considering only direct measures to metallurgical sustainability (production) and not indirect measures that materials leverage through their properties (strength, weight, longevity, functionality).

The ro-vibrational ν2 mode spectrum of methane investigated by ultrabroadband coherent Raman spectroscopy

We present the first experimental application of coherent Raman spectroscopy (CRS) on the ro-vibrational ν₂ mode spectrum of methane (CH₄). Ultrabroadband femtosecond/picosecond (fs/ps) CRS is performed in the molecular fingerprint region from 1100 to 2000 cm^-1, employing fs laser-induced filamentation as the supercontinuum generation mechanism to provide the ultrabroadband excitation pulses. We introduce a time-domain model of the CH₄ ν₂ CRS spectrum, including all five ro-vibrational branches allowed by the selection rules Δv = 1, ΔJ = 0, ±1, ±2; the model includes collisional linewidths, computed according to a modified exponential gap scaling law and validated experimentally. The use of ultrabroadband CRS for in situ monitoring of the CH₄ chemistry is demonstrated in a laboratory CH₄/air diffusion flame: CRS measurements in the fingerprint region, performed across the laminar flame front, allow the simultaneous detection of molecular oxygen (O₂), carbon dioxide (CO₂), and molecular hydrogen (H₂), along with CH₄. Fundamental physicochemical processes, such as H₂ production via CH₄ pyrolysis, are observed through the Raman spectra of these chemical species. In addition, we demonstrate ro-vibrational CH₄ v₂ CRS thermometry, and we validate it against CO₂ CRS measurements. The present technique offers an interesting diagnostics approach to in situ measurement of CH₄-rich environments, e.g., in plasma reactors for CH₄ pyrolysis and H₂ production.

Respiratory Health Effects of In Vivo Sub-Chronic Diesel and Biodiesel Exhaust Exposure

Biodiesel, which can be made from a variety of natural oils, is currently promoted as a sustainable, healthier replacement for commercial mineral diesel despite little experimental data supporting this. The aim of our research was to investigate the health impacts of exposure to exhaust generated by the combustion of diesel and two different biodiesels. Male BALB/c mice (n = 24 per group) were exposed for 2 h/day for 8 days to diluted exhaust from a diesel engine running on ultra-low sulfur diesel (ULSD) or Tallow or Canola biodiesel, with room air exposures used as control. A variety of respiratory-related end-point measurements were assessed, including lung function, responsiveness to methacholine, airway inflammation and cytokine response, and airway morphometry. Exposure to Tallow biodiesel exhaust resulted in the most significant health impacts compared to Air controls, including increased airway hyperresponsiveness and airway inflammation. In contrast, exposure to Canola biodiesel exhaust resulted in fewer negative health effects. Exposure to ULSD resulted in health impacts between those of the two biodiesels. The health effects of biodiesel exhaust exposure vary depending on the feedstock used to make the fuel.

Subcritical Water Pretreatment for Anaerobic Digestion Enhancement: A Review

This work reviews hydrothermal subcritical water pretreatment to enhance biogas production through anaerobic digestion. The complexity of the lignocellulosic structure has been the main limitation contributing to unsatisfactory biogas production throughout the anaerobic digestion. The high resistance of the structure to biological hydrolysis has increased the interest in applying pretreatment prior to anaerobic digestion to facilitate hydrolysis. Hydrothermal subcritical water technology, an environmentally friendly pretreatment that uses water as the main medium, is gaining prominence in biogas enhancement. However, the subcritical water pretreatment influence on structural properties, biogas production, and the production of anaerobic process inhibitors signifies a knowledge gap and needs an evaluation. This review presents the need for pretreatment reaction and properties in the subcritical water region, biogas production from subcritical water pre-treated waste, production of inhibitors, and its challenges are discussed. This pretreatment could be a promising option and further enhance biogas production throughout the anaerobic digestion process.

Design of New Dispersants Using Machine Learning and Visual Analytics

Artificial intelligence (AI) is an emerging technology that is revolutionizing the discovery of new materials. One key application of AI is virtual screening of chemical libraries, which enables the accelerated discovery of materials with desired properties. In this study, we developed computational models to predict the dispersancy efficiency of oil and lubricant additives, a critical property in their design that can be estimated through a quantity named blotter spot. We propose a comprehensive approach that combines machine learning techniques with visual analytics strategies in an interactive tool that supports domain experts' decision-making. We evaluated the proposed models quantitatively and illustrated their benefits through a case study. Specifically, we analyzed a series of virtual polyisobutylene succinimide (PIBSI) molecules derived from a known reference substrate. Our best-performing probabilistic model was Bayesian Additive Regression Trees (BART), which achieved a mean absolute error of 5.50±0.34 and a root mean square error of 7.56±0.47, as estimated through 5-fold cross-validation. To facilitate future research, we have made the dataset, including the potential dispersants used for modeling, publicly available. Our approach can help accelerate the discovery of new oil and lubricant additives, and our interactive tool can aid domain experts in making informed decisions based on blotter spot and other key properties.

2D Covalent Organic Framework for Water Harvesting with Fast Kinetics and Low Regeneration Temperature

Atmospheric water harvesting represents a promising technique to address water stress. Advanced adsorbents have been rationally designed to achieve high water uptake, yet their water sorption kinetics and regeneration temperature greatly limit water production efficiency. Herein, we demonstrated that 2D covalent organic frameworks (COFs), featuring hydrophobic skeleton, proper hydrophilic site density, and 1D open channels significantly lowered the water diffusion and desorption energy barrier. DHTA-Pa COF showed a high water uptake of 0.48 g/g at 30 % R.H. with a remarkable adsorption rate of 0.72 L/Kg/h (298 K) and a desorption rate of 2.58 L/Kg/h (333 K). Moreover, more than 90 % adsorbed water could be released within 20 min at 313 K. This kinetic performance surpassed the reported porous materials and boosted the efficiency for multiple water extraction cycles. It may shed light on the material design strategy to achieve high daily water production with low-energy input.

Advanced zeolite and ordered mesoporous silica-based catalysts for the conversion of CO2 to chemicals and fuels

For many years, capturing, storing or sequestering CO₂ from concentrated emission sources or from air has been a powerful technique for reducing atmospheric CO₂. Moreover, the use of CO₂ as a C1 building block to mitigate CO₂ emissions and, at the same time, produce sustainable chemicals or fuels is a challenging and promising alternative to meet global demand for chemicals and energy. Hence, the chemical incorporation and conversion of CO₂ into valuable chemicals has received much attention in the last decade, since CO₂ is an abundant, inexpensive, nontoxic, nonflammable, and renewable one-carbon building block. Nevertheless, CO₂ is the most oxidized form of carbon, thermodynamically the most stable form and kinetically inert. Consequently, the chemical conversion of CO₂ requires highly reactive, rich-energy substrates, highly stable products to be formed or harder reaction conditions. The use of catalysts constitutes an important tool in the development of sustainable chemistry, since catalysts increase the rate of the reaction without modifying the overall standard Gibbs energy in the reaction. Therefore, special attention has been paid to catalysis, and in particular to heterogeneous catalysis because of its environmentally friendly and recyclable nature attributed to simple separation and recovery, as well as its applicability to continuous reactor operations. Focusing on heterogeneous catalysts, we decided to center on zeolite and ordered mesoporous materials due to their high thermal and chemical stability and versatility, which make them good candidates for the design and development of catalysts for CO₂ conversion. In the present review, we analyze the state of the art in the last 25 years and the potential opportunities for using zeolite and OMS (ordered mesoporous silica) based materials to convert CO₂ into valuable chemicals essential for our daily lives and fuels, and to pave the way towards reducing carbon footprint. In this review, we have compiled, to the best of our knowledge, the different reactions involving catalysts based on zeolites and OMS to convert CO₂ into cyclic and dialkyl carbonates, acyclic carbamates, 2-oxazolidones, carboxylic acids, methanol, dimethylether, methane, higher alcohols (C₂₊OH), C₂₊ (gasoline, olefins and aromatics), syngas (RWGS, dry reforming of methane and alcohols), olefins (oxidative dehydrogenation of alkanes) and simple fuels by photoreduction. The use of advanced zeolite and OMS-based materials, and the development of new processes and technologies should provide a new impulse to boost the conversion of CO₂ into chemicals and fuels.