Search Results (108)

Temporal variability in emissions from oil and gas supply chains depends on the spatial scale at which emissions are aggregated. This work demonstrates a framework for simulating temporally and spatially resolved emission inventories that can be broadly applied in oil and gas production regions. Emissions of methane, ethane, volatile organic compounds (VOCs), and nitrogen oxides (NOxs) from oil and gas facilities in the Marcellus production region were estimated at a one-hour time resolution for the calendar year 2023 and were aggregated at the grid cell (4 km by 4 km), county, and basin level. Maximum to average emission rate ratios decreased as the scale of spatial aggregation increased and differed by pollutant. At the grid cell level, ratios of maximum to average emission rates exceeded 100 in some grid cells for VOCs. In contrast, basin level maximum to average ratios for NOx emission rates were less than 1.1. The sources driving temporal variability in hydrocarbon emissions were well completions and liquid unloadings, while the sources driving temporal variability in NOx emissions were preproduction activities such as drilling and hydraulic fracturing. Temporally and spatially resolved inventories can inform pollutant- and region-specific measurement campaigns and mitigation strategies. Reconciliation between inventories and observations must consider event frequency, duration, and persistence, along with the spatial scale and timing of measurements. Full article

The study employed a green, template-free ball milling method to construct a series of Ni-Al mixed oxide catalysts modulated by different nickel precursors (nitrate, acetate, carbonate, sulfate, and chlorate). Through multiscale characterization techniques (XRD, TEM, XPS, H₂-TPR, etc.) and catalytic performance evaluations, we systematically elucidated the regulatory mechanism of precursor types on the structure-performance relationship. The NiAlO_x-CO₃²⁻ catalyst derived from nickel carbonate exhibited a unique structure, an optimal Ni/Al ratio, and well-tuned active oxygen species, thereby demonstrating exceptional catalytic performance in the oxidative dehydrogenation of ethane (ODHE) at 475 °C with 53.2% ethane conversion, 72.6% ethylene selectivity, and maintained stability over 40 h of continuous operation. Beyond developing high-performance ODHE catalysts, this work establishes a “precursor chemistry–material structure–catalytic performance” relationship model, offering new insights for the rational design of efficient catalysts for light alkane conversion. Full article

Accurate methane emission estimates are essential for climate policy, yet current field methods often struggle with spatial constraints and source complexity. Ground-based mobile approaches frequently miss key plume features, introducing bias and uncertainty in emission rate estimates. This study addresses these limitations by using small unmanned aerial systems equipped with precision gas sensors to measure methane alongside co-released tracers. We tested whether arc-shaped flight paths and alternative ratio estimation methods could improve the accuracy of tracer-based emission quantification under real-world constraints. Controlled releases using ethane and nitrous oxide tracers showed that (1) arc flights provided stronger plume capture and higher correlation between methane and tracer concentrations than traditional flight paths; (2) the cumulative sum method yielded the lowest relative error (as low as 3.3%) under ideal mixing conditions; and (3) the arc flight pattern yielded the lowest relative error and uncertainty across all experimental configurations, demonstrating its robustness for quantifying methane emissions from downwind plume measurements. These findings demonstrate a practical and scalable approach to reducing uncertainty in methane quantification. The method is well-suited for challenging environments and lays the groundwork for future applications at the facility scale. Full article

The oxidative coupling of methane (OCM) is a promising process for converting methane directly into more valuable ethane and ethylene. In this work, high time resolution online mass spectrometry was employed to track the OCM reaction over a commercial La₂O₃ catalyst, focusing on the effects of methane to oxygen ratio, gas hourly space velocity (GHSV), and the presence of H₂O and CO in the feed gas on methane conversion and C₂ yield. The results demonstrated that an optimized GHSV (44,640 to 93,000 mL·g⁻¹·h⁻¹) and methane to oxygen ratio (CH₄/O₂ = 3) would achieve the highest methane conversion and C₂ yield at 740 °C. Furthermore, at a GHSV of 44,640 mL·g⁻¹·h⁻¹, the introduction of 1% H₂O into the reaction mixture resulted in a twofold increase in C₂ yield at 650 °C, while the addition of 1% CO led to a threefold increase in C₂ yield at 550 °C. A model in which only the front-end catalyst is active was also developed to show excellent agreement with the experimental data. The relationship between catalytic performance and the effective catalyst position in the catalyst bed provides important insights into optimizing reactor design and operating conditions to maximize C₂ yield and selectivity in the OCM reaction. Full article

LaOCl-mediated ethane chlorination into 1,2-dichloroethane offers a promising pathway for low-temperature, large-scale ethane upgrading. However, under Cl₂-rich conditions, LaOCl undergoes detrimental chlorination into lanthanum chloride (LaCl₃), accompanied by extensive surface hydroxylation. Such severe structural evolution limits the practical application of La-based catalysts under industrially relevant conditions. In this study, an alumina-stabilized La catalyst was prepared via a coprecipitation method. We demonstrated that strong La-O-Al interactions effectively resist structural degradation of La species under reaction conditions, enabling the modified catalyst to maintain exceptional stability under high Cl₂ concentrations. At a C₂H₆/Cl₂ ratio of 4:9, the optimized catalyst achieves an ethane conversion of 61%, with 1,2-dichloroethane selectivity sustained above 74% for 12 h without noticeable deactivation. In contrast, the bulk LaOCl counterpart suffers from rapid over-chlorination, shifting product dominance to trichloroethane within 10 h. Advanced spectroscopy characterization reveals that selectivity loss in LaOCl originates from phase collapse into LaCl₃, whereas Al₂O₃ stabilization preserves the metastable LaOCl_x phase in a highly dispersed state, ensuring selective C–Cl bond formation. These results highlight the critical role of stabilizing metastable oxychloride phases through robust metal oxide interactions, establishing a design framework for rare-earth catalysts in high-concentration chlorine environments. Full article

Chemical–structural characteristics of three differently synthesized research-benchmark Mn-Na-W-O_x/SiO₂ catalysts for the Oxidative Coupling of Methane (OCM) were systematically studied in this research. XRD, EDX, ICP-OES, and SEM/FIB-SEM techniques, as well as Carrier Gas Hot Extraction (CGHE) and high-temperature XRD analyses, were performed to explain the functional features of the studied catalysts, in particular, the features affecting the quantity and quality of the interactions of oxygen and methane with the catalyst surface and with other molecular and radical species. These enable tracking the potential for the oxygen activation and dynamic transformation of the solid-state chemistry on the surface and sub-surface of these Mn-Na-W-O_x/SiO₂ catalysts. These catalysts were synthesized, respectively, via the sol–gel synthesis method (Cat₁) and the incipient wetness impregnation of the non-structured silica support (Cat₂) and structured SBA-15 silica support (Cat₃), under different sets of temperatures and gas compositions. The catalysts with the homogenous distribution of active components, namely Cat₁ and Cat₃, showed similar trends in terms of their dynamic interaction with oxygen species. They also showed higher levels of crystallinity of the active materials and higher catalytic selectivity towards ethane and ethylene. An explanation is given as to how the structural characteristics of the catalysts on the nanometer–micrometer scale contribute to these. The gained knowledge will be crucial in the selection and treatment of the support and developing a proper synthesis approach for the ultimate goal of designing a selective OCM catalyst. Full article

The role of SO₂ in the catalytic oxidation of light hydrocarbons remains controversial, especially in terms of its effects on catalyst performance and reaction pathways. In this study, the Pt/CeZrTiO₂ catalyst was synthesized to explore the influence of SO₂ during the catalytic combustion of ethane. The results revealed two distinct roles of SO₂: (1) SO₂ interacts with the catalyst, forming new active structures that facilitate C-H bond cleavage, alter the ethane oxidation pathway, and enhance low-temperature C₂H₆ conversion. (2) SO₂ participates in the reaction process, replenishing active sites and maintaining a balance between two ethane oxidation pathways, leading to improved high-temperature C₂H₆ conversion and enhanced catalytic combustion efficiency. This study provides new insights into the role of SO₂ in modulating catalyst properties and reaction pathways for efficient light hydrocarbon combustion. Full article

Catalytic reactor engineering bridges the active-site scale and the industrial-reactor scale, with kinetics as the primary bottleneck in scale-up. The main challenge in kinetics is conceptualizing the active site and formulating the reaction mechanism, leading to multiple approaches without clear guidance on their reliability for industrial-reactor design. This work assesses different approaches to active-site conceptualization and reaction-mechanism formulation for selective oxidation over a complex multi-metal catalyst. It integrates atomistic-scale insights from periodic Density Functional Theory (DFT) calculations into kinetic-model development. This approach contrasts with the macroscopic classical method, which treats the catalyst as a black box, as well as with alternative atomistic methods that conceptualize the active site as a single metal atom on different catalytic-surface regions. As a case study, this work examines ethane oxidative dehydrogenation to ethylene over the multi-metal oxide catalyst MoVTeNbO, which has a complex structure. This analysis provides insights into the ability of DFT to accurately describe reactions on such materials. Additionally, it compares DFT predictions to experimental data obtained from a non-idealized MoVTeNbO catalyst synthesized and assessed under kinetic control at the laboratory scale. The findings indicate that while the black-box active-site conceptualization best describes observed trends, its reaction mechanism and parameters lack reliability compared to DFT calculations. Furthermore, atomistic active-site conceptualizations lead to different parameter sets depending on how the active site and reaction mechanism are defined. Unlike previous studies, our approach determines activation-energy profiles within the range predicted by DFT. The resulting kinetic model describes experimental trends while maintaining phenomenological and statistical reliability. The corrections required for primary parameters remain below 20 kJ mol${}^{-1}$, consistent with the inherent uncertainties in DFT calculations. In summary, this work demonstrates the feasibility of integrating atomistic insights into kinetic modeling, offering different perspectives on active-site conceptualization and reaction-mechanism formulation, paving the way for future studies on rational catalyst and industrial-reactor design. Full article

Salens are a class of important ligands and have been widely applied in asymmetric catalytic organic reactions. Enlarged salen-like ligands containing flexible chains were synthesized from L-phenylalanine, ethane/propanediamines, and salicylaldehydes, and successfully utilized in the scandium-catalyzed enantioselective Michael addition of indoles and enones (2-cinnamoylpyridine 1-oxides). The catalytic system demonstrates excellent reactivity and stereoselective control over electron-rich indole substrates with up to 99% yield and 99% enantiomeric excess. The enlarged Salen ligands with flexible and rigid combined linkers fit their coordination with large rare earth elements. Their coordination abilities were tuned by the electronic effect of substituents on their salicylaldehyde moiety, facilitating the construction of excellent chiral environments in the scandium(III)-catalyzed asymmetric Michael addition of indoles to 2-cinnamoylpyridine 1-oxides. Full article

Rare earth phosphate (XPO₄) is an extremely important rare earth compound. It can exhibit excellent activity and stability in catalytic applications by modifying its inherent properties. Porous single-crystalline (PSC) PrPO₄ and SmPO₄ with a large surface area consist of ordered lattices and disordered interconnected pores, resulting in activity similar to nanocrystals and stability resembling bulk crystals. Herein, we present a study in which centimeter-scale PSC PrPO₄ and SmPO₄ monoliths were developed and oxygen defects in the crystal lattice were stabilized using single-crystal nature to synergistically improve catalytic activity in the oxidative dehydrogenation of ethane (ODE). The surface structure of the oxygen vacancies with unsaturated coordination is favorable for the adsorption and activation of ethane. The PSC PrPO₄ and SmPO₄ monoliths showed favorable performance with ~51% conversion of C₂H₆ and ~19% yield of C₂H₄ at 600 °C, while also exhibiting superior long-term stability during the catalytic process over a period of 115 h. In the presented work, we investigate a practical method for development and application in single-crystalline porous rare earth phosphate materials. Full article

The fusion of catalytic and electronic properties, coupled with empirical data, provides enriched perspectives into catalyst evaluation and design, thus propelling advancement and innovation in the domain of heterogeneous catalytic reactions, including the oxidative coupling of methane (OCM) reaction. Comparative assessment of various machine learning methodologies on OCM reaction datasets reveals that the Random Forest regression (RFR) model excels in C₂H₄ and C₂H₆ combined yield (C₂y) predictive accuracy, boasting an average R² value of 0.98. The hierarchy of modeling performance stands as follows: RFR > XGBR > SVR > DNN. The MSE and MAE metrics of the RFR models were observed to be lower compared to alternative models, ranging from 0.12 to 9.03 for MSE and 0.21 to 2.02 for MAE. Model accuracy follows the order of C₂H₆y > C₂H₄y > C₂y > CO₂y > CH₄_conv (methane conversion). When examining the influence of model features, C₂y increases proportionally with an augmentation in dataset attributes, including the quantity of alkali/alkali-earth metal moles in the catalyst (13.69%), the atomic number (6.24%) of the catalyst promoter, and the Fermi energy of the metal, with a less pronounced impact compared to the case of temperature (33.70%). This suggests a highly nonlinear correlation between combined ethylene and ethane yield and temperature. Other factors, such as the bandgap of the active metal oxide and the support, as well as the Fermi energy of the catalyst support, were observed to have a relatively modest effect on the predictive models for combined ethylene and ethane yield and methane conversion. Full article

A series of Pd/MgO catalysts based on nanocrystalline MgO were prepared via different sol–gel approaches. In the first two cases, palladium was introduced during the gel preparation, followed by drying it in supercritical or ambient conditions. In the third case, aerogel-prepared MgO was impregnated with an ethanol solution of Pd(NO₃)₂. The prepared catalysts differ in particle size and oxidation state of palladium. The catalytic performance and thermal stability of the samples were examined in a model reaction of CO oxidation at prompt thermal aging conditions. The as-prepared and aged materials were characterized by low-temperature nitrogen adsorption, UV-vis spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and ethane hydrogenolysis testing reaction. The highest initial activity (T₅₀ = 103 °C) was demonstrated by the impregnated sample, containing Pd⁰ particles of 3 nm in size. The lowest T₅₀ value (215 °C) after aging at 1000 °C was demonstrated by the impregnated Pd/MgO-WI sample. The high-temperature behavior of the catalysts was found to be affected by the initial oxidation state and dispersion of Pd. Two deactivation mechanisms, such as the agglomeration of Pd particles and migration of small Pd species into the bulk of the MgO support with the formation of Pd-MgO solid solutions, were discussed. Full article

Performance analysis of the adsorptive separation of ethylene downstream of an oxidative coupling of methane (OCM) process, being an alternative process for converting methane content of natural gas or other methane-rich sources to ethylene, was studied in this research for a production capacity of 1 Mt/yr. This was motivated by observing promising adsorption characteristics and efficiency in the selective adsorption of ethylene using 13X zeolite-based sorbent. The energy and economic performance of alternative scenarios for retrofitting the adsorption unit into an integrated OCM process were analyzed. Simulations of the integrated OCM process scenarios include OCM unit, CO₂-hydrogenation, ethane dehydrogenation and methane reforming sections. The use of efficient ethylene adsorption separation enabled the improvement of the economic and energy efficiency of the integrated OCM process under specific operating conditions. For instance, the invested amount of energy and the associated energy cost per ton of ethylene in the cryogenic ethylene-purification section of the integrated process using adsorption unit are, respectively, 75% and 89% lower than the reference integrated OCM process. Under the conditions considered in this analysis, the return on investment for the final proposed integrated OCM process structure using adsorption separation was found to be less than 9 years, and the potential for further improvement was also discussed. Full article

The synthesis, antioxidant capacity, and anti-inflammatory activity of four novel N-benzyl-2-[4-(aryl)-1H-1,2,3-triazol-1-yl]ethan-1-imine oxides 10a–d are reported herein. The nitrones 10a–d were tested for their antioxidant properties and their ability to inhibit soybean lipoxygenase (LOX). Four diverse antioxidant tests were used for in vitro antioxidant assays, namely, interaction with the stable free radical DPPH (1,1-diphenyl-2-picrylhydrazyl radical) as well as with the water-soluble azo compound AAPH (2,2′-azobis(2-amidinopropane) dihydrochloride), competition with DMSO for hydroxyl radicals, and the scavenging of cationic radical ABTS^•+ (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) radical cation). Nitrones 10b, 10c, and 10d, having the 4-fluorophenyl, 2,4-difluorophenyl, and 4-fluoro-3-methylphenyl motif, respectively, exhibited high interaction with DPPH (64.5–81% after 20 min; 79–96% after 60 min), whereas nitrone 10a with unfunctionalized phenyl group showed the lowest inhibitory potency (57% after 20 min, 78% after 60 min). Nitrones 10a and 10d, decorated with phenyl and 4-fluoro-3-methylphenyl motif, respectively, appeared the most potent inhibitors of lipid peroxidation. The results obtained from radical cation ABTS^•+ were not significant, since all tested compounds 10a–d showed negligible activity (8–46%), much lower than Trolox (91%). Nitrone 10c, bearing the 2,4-difluorophenyl motif, was found to be the most potent LOX inhibitor (IC₅₀ = 10 μM). Full article

Emission inventories (EIs) are vital for air quality modeling. Specific research goals often require modifying EIs from diverse data sources, demanding significant code development. In this study, we utilized and further developed the High Elective Resolution Modeling Emission System version three for Global and Regional domains (HERMESv3_gr). This user-friendly processing system was adapted for generating EIs compatible with the Chemistry Transport Model Tracel Model 5 Massive Parallel (TM5-MP). The results indicate that HERMESv3_gr is capable of generating EIs with negligible biases (${10}^{-7}$ relative differences) for TM5-MP, showcasing its effectiveness. We applied HERMESv3_gr to integrate the EI Regional Emission inventory in Asia (REAS) into the global EI Community Emission Data System (CEDS). Comparison of model results using CEDS alone and the integrated EI against measurement data for various pollutants globally revealed small improvements for carbon monoxide (1%) ethane (1–2%), and nitrogen oxide (2%) and larger for propane (5–7%). Ozone in the northern hemisphere improved by about 2% while in the southern hemisphere improvements of 5% could be observed. Our findings highlight the importance of carefully considering the effects of EI integration for accurate air quality modeling. Full article