Search Results (253)

Thermocatalytic sensors are used as universal explosion meters for measurement of the Lower Explosive Limit (LEL) of hydrocarbon gases mixtures. Historically, thermo-catalytic sensors, with their bulky “pellistor” design, have been poorly suited for mass production using group microelectronic processing. Another significant challenge for developers of new sensor designs is to minimize power dissipation while enhancing the service life and resistance of catalytic elements to poisoning from silicon–organic and sulfur-containing gases. To meet the specified requirements, we developed a low-power thermocatalytic sensor utilizing ceramic technology, capable of holding the temperature of technology operations up to 900 °C. Full article

Reaction conditions (RCs) are a crucial part of reaction definition, and their accurate prediction is an important component of chemical synthesis planning. The existence of multiple combinations of RCs capable of achieving the desired result complicates the task of condition recommendation. Herein, we propose a conditional variational autoencoder (CVAE) generative model to predict suitable RCs. The CVAE model has been customized to generate diverse sets of valid conditions, ensuring high flexibility and accuracy, while circumventing the necessity for enumeration or combinatorial search of potential RCs. The efficacy of the CVAE approaches was evaluated using hydrogenation reactions and other H₂-mediated reactions, predicting the set of catalysts, additives (acid, base, and catalytic poison), ranges of temperature, and pressure. The CVAE models predicted conditions with different “heads”, each corresponding to specific condition components, and their respective losses. CVAE models were tested on two datasets: a small one containing 31K reactions with 2232 potential conditions’ combinations and a big one having 196K reactions with ~7 × 10⁴² potential conditions’ combinations to evaluate the model’s ability to predict varying complexity and diversity conditions. To optimize the accuracy of the models, we experimented with three latent distribution variants—Gaussian (g-CVAE), Riemannian Normalizing Flow (rnf-CVAE), and Hyperspherical Uniform (h-CVAE). In our experiments, the h-CVAE model demonstrated robust overall performance, making it the optimal choice for scenarios requiring high accuracy across multiple top-k predictions. Benchmarking analyses demonstrated the high performance of the CVAE models compared to state-of-the-art reaction condition prediction approaches. Full article

The nano-technological approach and supramolecular chemistry principles relation to the encapsulation of enzymes pave the way for creating next-generation nano-system-functionalized nano-compartments. The most promising approach for prophylaxis and the treatment of organophosphate (OP) poisoning is the use of stable, bioavailable nano-compartments containing OP-scavenging enzymes. Such enzymes, like butyrylcholinesterase (BChE), wild type and mutants, could also be used for the detoxification of other poisonous esters. There are two types of IRD-labeled human BChE-containing nano-scavengers: PEGylated liposomes and polyethyleneglycol–polypropylenesulfide polymersomes, which were developed with diameter close to 100 nm. BChE-polymersomes have higher encapsulation efficiency (95%) and slower release rate of enzymes (more than 7 days) compared to BChE-liposomes. The catalytic properties of encapsulated enzymes were analyzed for nano-compartment formulations, lipophilicity, the structure of block copolymers, and for different ester substrate polarity: positively charged butyrylthiocholine iodide, neutral phenyl acetate, and negatively charged aspirin. The highest k_cat (more than three times) compared to non-encapsulated BChE was for polymersomes based on diblock PEG-PPS polymersomes towards the neutral phenyl acetate substrate. Full article

Microbial fuel cells are a new alternative for sustainable energy generation and wastewater treatment technology. To scale up this technology, cost-effective electrodes are required. The electrochemical reduction of oxygen at the cathode is a key reaction for power generation. Noble metals, especially Pt, are extensively used as cathode catalysts in MFC; however, its application is limited to its high cost and catalyst poisoning. Ferroelectric materials are reported as a good candidate due to their spontaneous polarization. The main objective of this study is to prepare and characterize the cost-effective ferroelectric materials LiTa_0.6 Nb_0.4 O₃ and Li_0.95 Ta_0.57 Nb_0.38 Mg_0.15 O₃ in order to test their catalytic activity in air-cathode MFC. Powders were prepared following the solid-state synthesis and characterized using Scanning Electron Microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. To evaluate the electrochemical performance of the catalysts, electrochemical studies such as EIS, CV, LSV, and CA were conducted. In MFC, the performance of our material has been investigated using COD determination and polarization measurement. The obtained results demonstrate the potential of Li_0.95 Ta_0.57 Nb_0.38 Mg_0.15 O₃ as a low-cost and effective catalyst material in MFCs, showing a high COD removal up to 75%, and power-density output of 764 mW/m². Full article

Simultaneous catalytic elimination of nitrogen oxides (NO_x) and volatile organic compounds (VOCs) represents a promising technology for addressing the synergistic pollution of fine particulate matters of <2.5 μm diameter (PM_2.5) and O₃. Nevertheless, it has been maintaining significant challenges in practical implementation, particularly the inherent mismatch in temperature windows between NO_x reduction and VOCs oxidation pathways, coupled with catalyst poisoning and deactivation phenomena. These limitations have hindered the industrial application of bifunctional catalysts for the removal of concurrent pollutant. This review systematically explored the fundamental mechanisms and functional roles of active sites in controlling synchronous catalytic processes. The mechanism of catalyst deactivation caused by multiple toxic substances has been comprehensively analyzed, including sulfur dioxide (SO₂), water vapor (H₂O), chlorine-containing species (Cl*), reaction by-products, and heavy metal contaminants. Furthermore, we critically evaluated the strategies of doping regulation, nanostructure engineering and morphology optimization to enhance the performance and toxicity resistance of catalysts. Meanwhile, emerging regeneration techniques and reactor design optimizations are discussed as potential solutions to improve the durability of catalysts. Based on the above critical aspects, this review aims to provide insights and guidelines for developing robust catalytic systems capable of controlling multi-pollutants in practical applications, and to offer theoretical guidance and technical solutions to bridge the gap between laboratory research and industrial environmental governance applications. Full article

Catalytic upgrading of bioethanol via a C–C coupling reaction is a sustainable method of producing 1-butanol, a high-performance biofuel. This reaction was studied using a flow-through microreactor system with Pd/MgO-Al₂O₃ and bimetallic Pd-Cu/MgO-Al₂O₃ mixed oxide-based catalysts in a H₂ carrier gas at a pressure of 21 bar and temperatures ranging from 200 to 350 °C. The effect of the metal promoter(s) on the hydrogen transfer reaction steps in the overall reaction was investigated. The palladium promoter significantly improved the activity and butanol selectivity across the entire temperature range. However, the yield of liquid products decreased significantly at temperatures higher than 250 °C, primarily because the decarbonylation side reaction of the acetaldehyde intermediate accelerated. The promoting effect of Pd was most beneficial below 250 °C because the decarbonylation reaction was inhibited by the reversible poisoning effect of CO on multiple Pd sites responsible for decarbonylation. Diluting the Pd phase with Cu increased liquid yields due to gradually decreasing decarbonylation activity. However, the dehydrogenation–hydrogenation activity decreased as well, as did the promoting effect on the corresponding reaction steps in the coupling reaction. Additionally, the product distribution changed dramatically, decreasing 1-butanol selectivity, because metallic Cu can catalyze the formation of ethyl acetate and ketone products. Full article

This study introduces the preparation and tailoring of the catalytic properties of a novel biomass-based composite to produce a sustainable biolubricant, trimethylolpropane fatty acid triester (TFATE), via the transesterification of fatty acid methyl esters (FAMEs). This novel catalyst was prepared from avocado seed and chicken eggshell residues using a Taguchi experimental design to determine the best synthesis conditions. The variables tested in the catalyst preparation included CaO impregnation time and temperature, mass ratio of CaO/char, and activation temperature. The transesterification conditions to obtain TFATE were analyzed using the best eggshell-/char-based catalyst, and the reaction kinetics were measured at 120 and 150 °C. The results showed an endothermic reactive system with calculated kinetic rate constants of 7.45 × 10⁻³–10.31 × 10⁻³ L/mmol·min, and an activation energy of 15 kJ/mol. This new catalyst achieved 90% TFATE formation under optimized reaction conditions. Reuse tests indicated that catalyst deactivation occurred due to active-site poisoning, despite very low calcium leaching. Catalyst characterization confirmed the relevance of the crystalline structure and CaO loading on the avocado char surface to obtain the best catalytic properties, while ¹H nuclear magnetic resonance analysis proved TFATE formation. This low-cost catalyst can be an alternative for enhancing sustainable biolubricant production with the aim of replacing petrochemical-based counterparts. Full article

Nitrogen oxides (NO_x) are major atmospheric pollutants, and their escalating emissions, driven by rapid economic development and urbanization, pose a severe threat to both the ecological environment and human health. Conventional denitrification technologies are often hampered by high costs, significant energy consumption, and stringent operational conditions, making them increasingly inadequate in the face of tightening environmental regulations. In this context, photocatalytic technology, particularly systems based on graphitic carbon nitride (g-C₃N₄), has garnered significant research interest for NO_x removal due to its visible-light responsiveness, high stability, and environmental benignity. To advance the performance of g-C₃N₄, numerous modification strategies have been explored, including morphology control, elemental doping, defect engineering, and heterostructure construction. These approaches effectively broaden the light absorption range, enhance the separation efficiency of photogenerated electron-hole pairs, and improve the adsorption and conversion capacities for NO_x. Notably, constructing heterojunctions between g-C₃N₄ and other materials (e.g., metal oxides, noble metals, metal–organic frameworks (MOFs)) has proven highly effective in boosting catalytic activity and stability. Furthermore, the underlying photocatalytic mechanisms, encompassing the generation and migration pathways of charge carriers, the redox reaction pathways of NO_x, and the influence of external factors like light intensity and reaction temperature, have been extensively investigated. From an application perspective, g-C₃N₄-based photocatalysis demonstrates considerable potential in flue gas denitrification, vehicle exhaust purification, and air purification. Despite these advancements, several challenges remain, such as limited solar energy utilization, rapid charge carrier recombination, and insufficient long-term stability, which hinder large-scale implementation. Future research should focus on further optimizing the material structure, developing greener synthesis routes, enhancing catalyst stability and poison resistance, and advancing cost-effective engineering applications to facilitate the practical deployment of g-C₃N₄-based photocatalytic technology in air pollution control. Full article

Propane is a typical volatile organic compound (VOC) in coal chemical processing and petroleum refining. However, coexisting SO₂ significantly impairs its catalytic oxidative removal, potentially causing catalyst poisoning and deactivation. This study systematically elucidated the inhibitory effects of SO₂ on the catalytic oxidation of propane over the Ru@CoMn₂O₄ catalyst system. Under continuous exposure to 30 ppm SO₂, propane conversion plummeted by 30% within two hours. Mechanistic studies revealed that SO₂ selectively bound to high-valent Mn sites rather than preferentially interacting with Co sites, leading to the formation of MnSO₄ particles. These particles were directly corroborated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. After four hours of exposure to SO₂, roughly 11.8 mole percent of manganese in the catalyst was converted into MnSO₄. These deposits physically blocked active sites, reduced specific surface area, and disrupted redox cycling. As a result, their combined effects diminished performance progressively, ultimately leading to complete deactivation. Furthermore, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirmed that SO₂ suppressed C=C bond oxidation in propane intermediates, thereby directly limiting conversion efficiency. Combining qualitative and quantitative methods, we characterized SO₂-induced poisoning during propane oxidation. This work provides guidelines and strategies for designing anti-sulfur catalysts at the elemental scale for the catalytic combustion of low-carbon alkanes. Full article

The reliance on carbon-based fuels remains a major contributor to greenhouse gas emissions, emphasizing the need for sustainable alternatives such as hydrogen. Sodium borohydride (NaBH₄), with a hydrogen content of 10.6 wt%, is a promising chemical hydrogen storage material capable of releasing four moles of H₂ per mole through hydrolysis; however, effective catalysts are essential for practical implementation. In this study, silver nanoparticles supported on glucose-derived carbon microspheres (AgSC) were synthesized and evaluated for catalytic NaBH₄ hydrolysis. Structural characterization (XRD, TEM, SEM, EDS) confirmed the uniform dispersion of metallic silver nanoparticles on the carbon support with no detectable Ag₂O phase. AgSC exhibited superior catalytic activity compared to unsupported Ag or bare carbon, achieving the highest hydrogen generation under neutral pH, elevated temperatures, and 835 µmol NaBH₄. The catalyst displayed an activation energy of 54 kJ mol⁻¹, turnover numbers (TONs) of 1.4 × 10⁵–1.9 × 10⁵, and turnover frequencies (TOFs) of 7.1 × 10⁴–9.3 × 10⁴ h⁻¹, demonstrating efficient utilization of active sites. pH-dependent studies revealed optimal hydrogen yield under neutral conditions, while acidic and basic media reduced performance due to surface poisoning and BH₄⁻ stabilization, respectively. Reusability tests showed only ~5% activity loss after five cycles. These findings establish AgSC as a stable, efficient, and recyclable catalyst for on-demand hydrogen generation, supporting sustainable clean fuel technologies. Full article

The ethanol oxidation reaction (EOR) is a key process for direct ethanol fuel cells (DEFCs), offering a high-energy-density and carbon-neutral pathway for sustainable energy conversion. However, the practical implementation of DEFCs is significantly hindered by the EOR due to its sluggish kinetics, complex multi-electron transfer pathways, and severe catalyst poisoning by carbonaceous intermediates. This review provides a comprehensive and mechanistically grounded overview of recent advances in EOR electrocatalysts, with a particular emphasis on the structure–activity relationships of noble metals (Pt, Pd, Rh, Au) and non-noble metals. The effects of catalyst composition, surface structure, and electronic configuration on C–C bond cleavage efficiency, product selectivity (C1 vs. C2), and CO tolerance are critically evaluated. Special attention is given to the mechanistic distinctions among different metal systems, highlighting how these factors influence reaction pathways and catalytic behavior. Key performance-enhancing strategies—including alloying, nanostructuring, surface defect engineering, and support interactions—are systematically discussed, with mechanistic insights supported by in situ characterization and theoretical modeling. Finally, this review identifies major challenges and emerging opportunities, outlining rational design principles for next-generation EOR catalysts that integrate high activity, durability, and scalability for real-world DEFC applications. Full article

Heme enzymes that bind and reduce O₂ are susceptible to poisoning by NO. The high reactivity and affinity of NO for ferrous heme produces stable ferrous-NO complexes, which in theory should preclude O₂ binding and turnover. However, NO inhibition is often competitive with respect to O₂ and rapidly reversible, thus providing cellular and organismal survival advantages. This kinetic paradox has prompted a search for mechanisms for reversal and hence resistance. Here, I critically review proposed resistance mechanisms for NO dioxygenase (NOD) and cytochrome c oxidase (CcO), which substantiate reduction or oxidation of the tightly bound NO but nevertheless fail to provide kinetically viable solutions. A ferrous heme intermediate is clearly not available during rapid steady-state turnover. Reversible inhibition can be attributed to NO competing with O₂ in transient low-affinity interactions with either the ferric heme in NOD or the ferric heme-cupric center in CcO. Toward resolution, I review the underlying principles and evidence for kinetic control of ferric heme reduction via an O₂-triggered ferric heme spin crossover and an electronically-forced motion of the heme and structurally-linked protein side chains that elicit electron transfer and activate O₂ in the flavohemoglobin-type NOD. For CcO, kinetics, structures, and density functional theory point to the existence of an analogous O₂ and reduced oxygen intermediate-controlled electron-transfer gate with a linked proton pump function. A catalytic cycle and mechanism for CcO is finally at hand that links each of the four O₂-reducing electrons to each of the four pumped protons in time and space. A novel proton-conducting tunnel and channel, electron path, and pump mechanism, most notably first hypothesized by Mårten Wikström in 1977 and pursued since, are laid out for further scrutiny. In both models, low-energy spin-orbit couplings or ‘spintronic’ interactions with O₂ and NO or copper trigger the electronic motions within heme that activate electron transfer to O₂, and the exergonic reactions of transient reactive oxygen intermediates ultimately drive all enzyme, electron, and proton motions. Full article

The emissions from biomass combustion systems have recently been the subject of increased attention. In addition to elevated concentrations of particulate matter and hydrocarbons (HCs) in the flue gas, significant levels of NO_x emissions occur depending on the used fuel, such as biogenic residues. In response to legal requirements, owners of medium-sized plants (≈100 kW) are now also forced to minimize these emissions by means of selective catalytic reduction systems (SCR). The implementation of a selective sensor is essential for the efficient dosing of the reducing agent, which is converted to ammonia (NH₃) in the flue gas. Preliminary laboratory investigations on a capacitive NH₃ sensor based on a zeolite functional film have demonstrated a high sensitivity to ammonia with minimal cross-influences from H₂O and NO_x. Further investigations concern the application of this sensor in the real flue gas of an ordinary wood-burning stove and of combustion plants for biogenic residues with an ammonia dosage. The findings demonstrate a high degree of agreement between the NH₃ concentration measured by the sensor and an FTIR spectrometer. Furthermore, the investigation of the long-term stability of the sensor and the poisoning effects of SO₂ and HCl are of particular relevance to the laboratory measurements in this study, which show promising results. Full article

The sulfur content in crude oil varies between 1000 and 30,000 ppm (parts per million), meaning that its removal from fuels requires significant technical and economic effort. Growing concern about pollution, accompanied by stricter environmental regulations, have led to the development of strategies to mitigate the negative effects of sulfur-containing compounds in petroleum, which can cause malfunctions in manufacturing plants and refineries, such as causing catalyst poisoning in catalytic reforming equipment and sulfur dioxide emissions that have been generated through the use of fuels in vehicles, vessels, furnaces, etc. Sulfur is one of the main pollutants found in diesel and gasoline. The hydrodesulfurization method removes sulfur and nitrogen-containing compounds from diesel and gasoline, ensuring compliance with current environmental regulations established for the import and export of fuels. In addition, hydrodesulfurization contributes to reducing sulfur dioxide and nitrogen dioxide emissions into the environment and prevents corrosion, which increases safety for both manufacturing plants and end consumers. This situation is analyzed in this paper, considering Mexican legislation about fuels and their usage. Sulfur is an important pollutant contained in diesel and gasoline fuels; it exhibits lubricant properties, helping to reduce the maintenance intervals of the machines and increase engine life. Therefore, its removal from fuel blends is a topic of great scientific interest as researchers look for different lubricant alternatives, which are relevant to motor vehicle engines. Full article

Pt/TiO₂ and Pt-Eu₂O₃/TiO₂ catalysts were prepared via the impregnation method for catalytic oxidation of CO. The Pt-2Eu₂O₃/TiO₂ catalyst exhibited better CO oxidation activity as well as greater SO₂ resistance than the Pt/TiO₂ catalyst. For the inlet gas consisting of 0.8% CO, 5% O₂, and balanced N₂, the lowest complete conversion temperatures (T₁₀₀) of CO were 120 °C and 140 °C for the Pt-2Eu₂O₃/TiO₂ and Pt/TiO₂ catalysts, respectively. During the 72 h SO₂-resistance test at 200 °C under an inlet gas composition of 0.8% CO, 5% O₂, 15% H₂O, 50 ppm SO₂, and balanced N₂, the CO conversion on the Pt-2Eu₂O₃/TiO₂ catalyst remained >99%, while that on the Pt/TiO₂ catalyst gradually decreased to 77.8%. Pre-loading 2 wt% Eu₂O₃ on TiO₂ enhanced the dispersion of Pt, increased the proportion of Pt⁰, and facilitated the adsorption and dissociation of H₂O, all of which promoted CO oxidation. SO₂ preferentially occupied the Eu₂O₃ sites by forming stable sulfates on the Pt-2Eu₂O₃/TiO₂ catalyst, which protected the Pt active sites from poisoning. The OH* species produced from the dissociation of H₂O played a significant role in promoting CO oxidation through the formation of COOH* as the key reaction intermediate. The developed Pt-2Eu₂O₃/TiO₂ catalyst has great application potential in terms of the removal of CO from industrial flue gases. Full article