Search Results (86)

Methanol is a promising low-carbon fuel that can effectively reduce environmental pollution from ships compared to traditional fuels. The timing of methanol injection is a major factor affecting the performance of internal combustion engines, and either too late or too early injection can severely impact the combustion efficiency of an engine. This paper focused on a 4135Aca marine diesel engine produced by the Shanghai Diesel Engine Factory in China. Using CONVERGE/3.0 software for numerical simulation, the study analyzed the impact of methanol injection timing on the combustion and emission characteristics of marine diesel engines. It was found that the determination of methanol injection timing should comprehensively consider the effects of the combustion start point, mixture quality, flame front propagation speed, and evaporation heat absorption. Appropriate methanol injection timing can improve the combustion duration, cylinder pressure, and heat release rate, enhancing the power performance of marine diesel engines. This study shows that methanol injection at −30 °CA can effectively control the in-cylinder combustion process, improve combustion efficiency, and significantly reduce the emissions of pollutants such as soot (by 60.5%), HC (by 3.6%), CO (by 95.3%), etc. However, it can lead to an increase in NOx (by 3.7%) generation under high-temperature conditions. This research can provide a certain reference for the engineering application of methanol direct injection engines for ships. Full article

Diagnosing ozone (O₃) formation sensitivity using tropospheric observations of O₃ and its precursors is important for formulating O₃ pollution control strategies. Photochemical reactions producing O₃ occur at the earth’s surface and in the elevated layers, indicating the importance of diagnosing O₃ formation sensitivity at different layers. Synchronous measurements of tropospheric O₃ and its precursors nitrogen dioxide (NO₂) and formaldehyde (HCHO) were performed in urban Hefei to diagnose O₃ formation sensitivity at different atmospheric layers using multi-axis differential optical absorption spectroscopy observations. The retrieved surface NO₂ and O₃ were validated with in situ measurements (correlation coefficients (R) = 0.81 and 0.80), and the retrieved NO₂ and HCHO vertical column densities (VCDs) were consistent with TROPOMI results (R = 0.81 and 0.77). The regime transitions of O₃ formation sensitivity at different layers were derived using HCHO/NO₂ ratios and O₃ profiles, with contributions of VOC-limited, VOC-NO_x-limited, and NO_x-limited regimes of 74.19%, 7.33%, and 18.48%, respectively. In addition, the surface O₃ formation sensitivity between HCHO/NO₂ ratios and O₃ (or increased O₃, ΔO₃) had similar regime transitions of 2.21–2.46 and 2.39–2.71, respectively. Moreover, the O₃ formation sensitivity of the lower planetary boundary layer on polluted and non-polluted days was analyzed. On non-polluted days, the contributions of the VOC-limited regime were predominant in the lower planetary boundary layer, whereas those of the NO_x-limited regime were predominant in the elevated layers during polluted days. These results will help us understand the evolution of O₃ formation sensitivity and formulate O₃ mitigation strategies in the Yangtze River Delta region. Full article

The greenhouse effect and global warming, driven by the accumulation of pollutants, such as sulfur oxides (SOx), nitrogen oxides (NOx), and CO₂, are primarily caused by the combustion of fossil fuels and volcanic eruptions. These phenomena represent an international crisis that negatively impacts human health and the environment. Several studies have reported novel carbon capture, utilization, and storage (CCUS) technologies, promising solutions. Notable methods include chemical absorption using solvents, and the development of functionalized porous materials, such as MCM-41, impregnated with amines like polyethyleneimine. These technologies have demonstrated high capture capacity and thermal stability; however, they face challenges related to recyclability and high operating costs. In parallel, biodegradable polymers and hydrogels present sustainable alternatives with a lower environmental impact, although their industrial scalability remains limited. This review comprehensively analyzes CO₂ capture methods, focusing on silica-based porous supports, polymers, hydrogels, and emerging techniques, like CCUS and MOFs, while including traditional methods and a bibliometric analysis to update the field’s scientific dynamics. With increasing investigations focused on developing new CCUS technologies, this study highlights a growing interest in eco-friendly alternatives. A bibliometric analysis of 903 articles published between 2010 and 2024 provides an overview of current research on environmentally friendly carbon capture technologies. Countries such as the United States, the United Kingdom, and India are leading research efforts in this field, emphasizing the importance of scientific collaboration. Despite these advancements, implementing these technologies in industrial sectors with high greenhouse gas emissions remains scarce. This underscores the need for public policies and financing to promote their development and application in these sectors. Future research should prioritize materials with high capture capacity, efficient transformation, and valorization of CO₂ while promoting circular economy approaches and decarbonizing challenging sectors, such as energy and transportation. Integrating environmentally friendly materials, energy optimization, and sustainable strategies is essential to position these technologies as key tools in the fight against climate change. Full article

In order to demonstrate the feasibility of the tunable diode laser absorption spectroscopy (TDLAS) technology for monitoring NO_x emissions from inland vessels, an equipment is designed to monitor emissions for inland vessels. The equipment was installed at the Jianbi locks, where experimental measurements were conducted on vessels passing through the locks, with a total of 330 vessels being measured. The detection rate for vessels was 50.3%, with a detection rate of 72.4% for fully loaded vessels and 24.7% for unloaded vessels. In addition, the exhaust emission patterns of inland vessels, the NO_x emission patterns and detection rate of fully loaded and unloaded vessels, and the key parameter of the NO_x emission factor of inland vessels were comprehensively analyzed. The experimental results show that CO₂ and NO_x in the exhaust gas of inland vessels have high signal intensity and good synchronization and can be applied to the regulatory monitoring of NO_x emissions from inland vessels. Furthermore, the ratios of NO/CO₂ and NO₂/CO₂ from fully loaded and unloaded vessels were significantly different. indicating that the NO₂ indicator must be included in the remote monitoring indicators for inland vessel exhaust gases. Otherwise, the remote monitoring results for NO_x may be significantly underestimated. Full article

Strontium titanate (STO) and its variants have emerged as leading materials in photocatalysis, particularly for degrading nitrogen oxides (NOx), due to their non-toxic nature, structural adaptability, and exceptional thermal stability. Although the one-pot sol-gel method leads to high-quality photocatalysts, areas remain for improvement. This study examines the impact of ethanol as a cosolvent in STO synthesis, focusing on optimizing the water-to-ethanol volume ratio. The findings reveal that a 1:3 ratio significantly enhances macropore formation and photocatalytic efficiency, achieving 42% NOx degradation under LED within three hours. Furthermore, incorporating 8.0 wt.% Ag into STO substantially improves visible light absorption and enables complete NOx elimination, thanks to enhanced charge separation and localized surface plasmon resonance. Even at high temperatures (1100 °C), the Ag-STO photocatalyst maintains partial activity, despite exceeding silver’s melting point. These results highlight the potential of STO-based materials for industrial applications, positioning them as a promising solution for effective NOx mitigation. Full article

Sensitivity to ambient air temperatures, consuming a large amount of fuel, and wasting a significant amount of heat dumped into the ambient atmosphere are three major challenges facing gas turbine power plants. This study was conducted to simultaneously solve all three aforementioned GT problems using solar energy and introducing a new configuration that consists of solar preheating and inlet-air-cooling systems. In this study, air was preheated at a combustion chamber inlet using parabolic trough collectors. Then, inlet air to the compressor was cooled by these collectors by operating an absorption cooling cycle. At the design point conditions, this novel proposed integration resulted in a 6.87% relative increase in generated power and a 10.53% relative decrement in fuel consumption, achieving a 19.45% relative increment in the plant’s thermal efficiency. This was accompanied by a reduction of 0.026 kg/s, 4.2 kg/s, and 0.278 kg/s in CO₂, CO, and NOx emissions, respectively. Finally, spider diagrams were employed to assess the impact of the operating parameters on the overall system’s performance and its associated environmental implications. Full article

Increasing concerns about air quality due to fossil fuel combustion, especially nitrogen oxides (NO_x) from marine and diesel engines, necessitate advanced monitoring systems due to the significant health and environmental impacts of nitrogen dioxide (NO₂). In this study, a gas detection system based on the principle of the non-dispersive infrared (NDIR) technique is proposed. Firstly, the pyroelectric detector was developed by employing an ultra-thin LiTaO₃ (LT) layer as the sensitive element, integrated with nanoscale carbon material prepared by wafer-level graphics technology as the infrared absorption layer. Then, the sensor was hermetically sealed using inert gas through energy storage welding technology, exhibiting a high detectivity (D*) value of 4.19 × 10⁸ cm·√Hz/W. Subsequently, a NO₂ gas sensor was engineered based on the NDIR principle employing a Micro Electro Mechanical System (MEMS) infrared (IR) emitter, featuring a light path chamber length of 1.5 m, along with integrated signal processing and software calibration algorithms. This gas sensor was capable of detecting NO₂ concentrations within the range of 0–500 ppm. Initial tests indicated that the gas sensor exhibited a full-scale relative error of less than 0.46%, a limit of 2.8 ppm, a linearity of −1.09%, a repeatability of 0.47% at a concentration of 500 ppm, and a stability of 2% at a concentration of 500 ppm. The developed gas sensor demonstrated significant potential for application in areas such as industrial monitoring and analytical instrumentation. Full article

In the last few years, increasing interest from researchers and companies has been shown in the development of photocatalytic coatings for air purification and self-cleaning applications. In order to maintain the photocatalyst’s concentration as low as possible, highly active materials and/or combinations of them are required. In this work, novel photocatalytic formulations containing g-C₃N₄/TiO₂ composites were prepared and deposited in the form of coatings on a-block substrates. The obtained photocatalytic surfaces were tested for NOx and acetaldehyde removal from model air. It was found that the addition of only 0.5 wt% g-C₃N₄ towards TiO₂ content results in over 50% increase in the photocatalytic activity under visible light irradiation in comparison to pure TiO₂ coating, while the activity under UV light was not affected. The result was related to the creation of a g-C₃N₄/TiO₂ heterojunction that improves the light absorption and the separation of photogenerated electron-hole pairs, as well as to the inhibition of TiO₂ particles’ agglomeration due to the presence of g-C₃N₄ sheets. Full article

Climate neutrality for the year 2050 is the goal assumed at the level of the EU_27+UK. As Romania is no exception, it has assumed the gradual mitigation of pollution generated by the energy sector, and by 2030, according to ‘Fit for 55’, the share of energy from renewable sources must reach 42.5% from total energy consumption. For the rest of the energy produced from traditional sources, natural gas and/or coal, modern technologies will be used to retain the gaseous noxes. Even if they are not greenhouse gases, NO and SO₂, generated from fossil fuel combustion, cause negative effects on the environment and biodiversity. The adsorption capacity of different materials, three nanomaterials developed in-house and three commercial adsorbents, both for NO and SO₂, was tackled through gas chromatography, elemental analysis, and Fourier-transform infrared spectroscopy. Fe-BTC has proven to be an excellent material for separation efficiency and adsorption capacity under studied conditions, and is shown to be versatile both in the case of NO (80.00 cm³/g) and SO₂ (63.07 cm³/g). All the developed nanomaterials generated superior results in comparison to the commercial adsorbents. The increase in pressure enhanced the performance of the absorption process, while temperature showed an opposite influence, by blocking the active centers on the surface. Full article

Light-duty vehicle emission regulations worldwide set limits for the following gaseous pollutants: carbon monoxide (CO), nitric oxides (NO_X), hydrocarbons (HCs), and/or non-methane hydrocarbons (NMHCs). Carbon dioxide (CO₂) is indirectly limited by fleet CO₂ or fuel consumption targets. Measurements are carried out at the dilution tunnel with “standard” laboratory-grade instruments following well-defined principles of operation: non-dispersive infrared (NDIR) analyzers for CO and CO₂, flame ionization detectors (FIDs) for hydrocarbons, and chemiluminescence analyzers (CLAs) or non-dispersive ultraviolet detectors (NDUVs) for NO_X. In the United States in 2012 and in China in 2020, with Stage 6, nitrous oxide (N₂O) was also included. Brazil is phasing in NH₃ in its regulation. Alternative instruments that can measure some or all these pollutants include Fourier transform infrared (FTIR)- and laser absorption spectroscopy (LAS)-based instruments. In the second category, quantum cascade laser (QCL) spectroscopy in the mid-infrared area or laser diode spectroscopy (LDS) in the near-infrared area, such as tunable diode laser absorption spectroscopy (TDLAS), are included. According to current regulations and technical specifications, NH₃ is the only component that has to be measured at the tailpipe to avoid ammonia losses due to its hydrophilic properties and adsorption on the transfer lines. There are not many studies that have evaluated such instruments, in particular those for “non-regulated” worldwide pollutants. For this reason, we compared laboratory-grade “standard” analyzers with FTIR- and TDLAS-based instruments measuring NH₃. One diesel and two gasoline vehicles at different ambient temperatures and with different test cycles produced emissions in a wide range. In general, the agreement among the instruments was very good (in most cases, within ±10%), confirming their suitability for the measurement of pollutants. Full article

This study analyzed the differences in ozone (O₃) sensitivity in four different urban areas in China from February 2019 to January 2020 based on data on various near-surface pollutants from passive multi-axis differential optical absorption spectroscopy (MAX-DOAS) sites and nearby China National Environmental Monitoring Center (CNEMC) sites. Across the four cities, the nitrogen dioxide (NO₂) and formaldehyde (HCHO) concentrations varied seasonally. Xianghe consistently displayed the lowest NO₂ levels, suggesting reduced emissions compared to other cities. Guangzhou, a city with a robust economy and a high level of vehicle ownership, exhibited higher concentrations in spring. Summer brought elevated HCHO levels in Guangzhou, Xianghe, and Shenyang due to intensified photochemical processes. Autumn and winter showed higher HCHO concentrations in Guangzhou and Xianghe compared to Lanzhou and Shenyang. Overall, Guangzhou recorded the highest annual averages, due to its developed economy, while Xianghe’s lower NO₂ levels were offset by the elevated HCHO due to higher O₃ values. The analysis delved into primary and secondary HCHO sources across seasons and used carbon monoxide (CO) and O₃ data. Xianghe showcased the dominance of secondary sources in summer and autumn, while Lanzhou was characterized by primary dominance throughout the year. Shenyang mirrored Xianghe’s evolution due to industrial emissions. In Guangzhou, due to the high levels of vehicular traffic and sunlight conditions, secondary sources predominantly influenced HCHO concentrations. These findings highlight the interplay between primary and secondary emissions in diverse urban settings. This study explored O₃ sensitivity variations across seasons. Xianghe exhibited a balanced distribution among volatile organic compound (VOC)-limited conditions, nitrogen oxide (NO_x)-limited conditions, and transitional influences. Lanzhou was mainly affected by VOC-limited conditions in winter and NO_x-limited conditions in other seasons. Shenyang’s sensitivity varied with the seasons and was primarily influenced by transitions between VOCs and NO_x in autumn and NO_x-limited conditions otherwise. Guangzhou experienced varied influences. During periods of high O₃ pollution, all regions were affected by NO_x-limited conditions, indicating the necessity of NO_x monitoring in these areas, especially during summer in all regions and during autumn in Xianghe and Guangzhou. Full article

Multifunctional road marking coatings with the functions of high-temperature stability, degradation of exhaust gas, and self-cleaning are of great significance for the safe operation and environmental protection of tunnels. This article uses active acrylic resin and an organosilicon hydrophobic agent as the base material, selects expanded vermiculite and glass microspheres as insulation fillers, and uses ammonium polyphosphate, pentaerythritol, melamine, and aluminum hydroxide as high-thermal-stability systems to prepare a two-component road marking coating base material. Then, nano SiO₂ and modified nano TiO₂ are added as modifiers to prepare a multifunctional road marking coating for tunnels. The physical and chemical properties of multifunctional road marking coatings are evaluating based on laboratory tests including thermogravimetry and derivative thermogravimetry, differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy, exhaust degradation, and contact angle tests. The results indicate that the developed multifunctional road marking coating effectively reduces the thermal conductivity of the carbon layer through physical changes in the flame retardant system and the heat resistance formed by the high breaking bond energy of nano SiO₂ during the combustion process. It forms a ceramic-like structure of titanium pyrophosphate with nano TiO₂ that is beneficial for improving flame retardancy without generating harmful volatile gases and has good flame retardant properties. N–V co-doping reduces the bandgap of TiO₂, broadens the absorption range of visible light by nano TiO₂, improves the catalytic efficiency of visible light, and achieves the degradation efficiency of the four harmful components NO_x, HC, CO, and CO₂ in automotive exhaust by 23.4%, 8.3%, 2.5%, and 2.9%, respectively. The solid–liquid phase separation in the multifunctional road marking coating in the tunnel causes the formation and accumulation of nano SiO₂ and TiO₂ particles on the coating surface, resulting in a microstructure similar to the “micro–nano micro-convex” on the lotus leaf surface and making a water droplet contact angle of 134.2° on the coating surface. Full article

Sepsis can trigger acute respiratory distress syndrome (ARDS), which can lead to a series of physiological changes, modifying the effectiveness of therapy and culminating in death. For all experiments, male Wistar rats (200–250 g) were split into the following groups: control and sepsis-induced by endotoxin lipopolysaccharide (LPS); the control group received only intraperitoneal saline or saline + CEF while the treated groups received ceftriaxone (CEF) (100 mg/kg) IP; previously or not with sepsis induction by LPS (1 mg/kg) IP. We evaluated respiratory mechanics, and alveolar bronchial lavage was collected for nitrite and vascular endothelial growth factor (VEGF) quantification and cell evaluation. For pharmacokinetic evaluation, two groups received ceftriaxone, one already exposed to LPS. Respiratory mechanics shows a decrease in total airway resistance, dissipation of viscous energy, and elastance of lung tissues in all sepsis-induced groups compared to the control group. VEGF and NOx values were higher in sepsis animals compared to the control group, and ceftriaxone was able to reduce both parameters. The pharmacokinetic parameters for ceftriaxone, such as bioavailability, absorption, and terminal half-life, were smaller in the sepsis-induced group than in the control group since clearance was higher in septic animals. Despite the pharmacokinetic changes, ceftriaxone showed a reduction in resistance in the airways. In addition, CEF lowers nitrite levels in the lungs and acts on their adverse effects, reflecting pharmacological therapy of the disease. Full article

Replacing alkaline for alkaline-earth metal hydroxide in the synthesis gel during the synthesis of siliceous SSZ-13 zeolite (Si/Al~10) yields SSZ-13 with novel, advantageous properties. Its NH₄-form ion-exchanges higher amount of isolated divalent M(II) ions than the conventional one: this is the consequence of an increased number of Al pairs in the structure induced by the +2 charge of Sr(II) cations in the synthesis gel that force two charge-compensating AlO₄⁻ motives to reside closer together. We characterize the +2 state of Co(II) ions in these materials with infra-red spectroscopy and X-ray absorption spectroscopy measurements and show their utility for NOx pollutant adsorption from ambient air: the ones derived from SSZ-13 with higher Al pair content contain more isolated cobalt(II) and, thus, perform better as ambient-air NOx adsorbers. Notably, Co(II)/SSZ-13 with an increased number of Al pairs is significantly more hydrothermally stable than its NaOH-derived analogue. Loading Pd(II) into Co-SSZ-13(Sr) produces an active NOx adsorber (PNA) material that can be used for NOx adsorption from simulated diesel engine exhaust. The critical issue for these applications is hydrothermal stability of Pd-zeolites. Pd/SSZ-13 synthesized in the presence of Sr(OH)₂ does not lose its PNA capacity after extremely harsh aging at 850 and 900 °C (10 h in 10% H₂O/air flow) and loses only ~55% capacity after hydrothermal aging at 930 °C. This can be extended to other divalent metals for catalytic applications, such as copper: we show that Cu/SSZ-13 catalyst can survive hydrothermal aging at 920 °C without losing its catalytic properties, metal dispersion and crystalline structure. Thus, we provide a new, simple, and scalable strategy for making remarkably (hydro)thermally stable metal-zeolite materials/catalysts with a number of useful applications. Full article

Globally, there is a growing concern about air pollution due to rapid industrialization and urbanization. Therefore, in this study, an experimental study was conducted to evaluate the performance of reducing nitrogen oxides, a precursor to fine dust, in mortars coated with a titanium dioxide (TiO₂) photocatalyst, which has the effect of decomposing pollutants. In particular, in this study, zeolite and activated red clay were used as cement substitutes to improve the fine dust reduction performance of the TiO₂ photocatalyst. A total of 14 different mixtures were designed, considering the substitution rates of zeolite and activated red clay (30%, 40%, and 50%) and the cement–fine aggregate ratio (1:2 and 1:3) as experimental variables. A TiO₂ photocatalyst was employed in this study to evaluate the NO_x reduction performance. As zeolite and activated red clay were added, the compressive strength and flexural strength of the mortars decreased by 15% to 60%, while the absorption rate increased by 5% to 16%. The NO_x reduction efficiency of up to 67.4% was confirmed in the H50-3 specimen with the TiO₂ catalyst. The NO_x reduction performance of mortars with the TiO₂ photocatalyst sprayed on their surface improved as the substitution ratio of zeolite and activated red clay increased. Additionally, it was confirmed that the NO_x reduction effect of specimens using activated red clay was superior to those using zeolite. Therefore, through this study, it was confirmed that the NO_x reduction performance of the TiO₂ photocatalyst can be improved when zeolite and activated red clay are used as cement substitutes. Full article