Search Results (1,024)

Dual-fuel, diesel–LPG (LPG being Liquified Petroleum Gas, e.g., propane) compression-ignition engines reduce CO₂ and particulate emissions compared to diesel-only operation but are prone to knock at high load due to charge homogeneity and increased ignition delay. AdBlue port injection (API) was evaluated as a combustion stabilisation strategy for a diesel–LPG engine and compared with water port injection (WPI). Experiments were performed on a 2.0 L diesel–LPG engine operated at 2000 RPM, BMEP ≈ 9 bar, λ ≈ 1.27 and LPG substitution of 72%. Knock intensity was quantified using knock-induced signal energy (KISE) derived from the oscillatory component of the in-cylinder pressure over a knock-sensitive crank angle window. Characterisation of combustion was done through HRR analyses, MFB analyses and FFT-based frequency characterisation. Baseline operation exhibited severe knock with a peak HRR ≈ 200 J/°CA and mean KISE of 307.2 bar². WPI at a water mass ratio WMR of 130% reduced the peak HRR by 56% and mean KISE by 88%, but decreased the peak pressure, BMEP and BTE. API at an AdBlue mass ratio AMR of 130% reduced the peak HRR by 37% and KISE by 82.6% while maintaining BMEP and BTE within baseline variability. Both strategies attenuated the dominant ~19.8 kHz (1,2) mode. NOx emissions decreased with WPI but increased at a high AMR. Full article

The paper presents computational fluid dynamics (CFD) simulations of a propane-fueled and under-ventilated fire in a reduced-scale corridor-like enclosure. The fire source is positioned at the closed end of the corridor. Due to the restricted inflow of oxygen, the flame lifts off from the gaseous burner and travels—along with unburned fuel—all the way to the open doorway at the opposite end of the corridor. Oxygen calorimetry shows that a quasi-steady state plateau is established, during which the heat release rate (HRR) within the enclosure is equal to the theoretical value ${\dot{Q}}_{in}=1500 A_o\sqrt{H_o}$ where $A_o\sqrt{H_o}$ is the ventilation factor. Then, external flaming occurs. CFD simulations with the Fire Dynamics Simulator (FDS) captured well the overall flame dynamics. More specifically, the HRR plateau is well predicted, provided that the actual autoignition temperature of propane, AIT = 450 °C, is prescribed instead of the default AIT = −273 °C. However, the occurrence time of external flaming remains significantly underestimated and is better predicted by setting AIT = 600 °C. This aspect of the modelling, linked to extinction and (re-)ignition, remains to be further investigated in the future. Full article

This paper presents a comparative analysis of direct expansion solar-assisted heat pumps (DX-SAHP) with and without photovoltaic cells (PVT-DX-SAHP). Two sets of experiments were conducted to validate the mathematical model: one with PVT-DX-SAHP and another with DX-SAHP. The mathematical model used in this study is based on physical equations using energy, mass, and entropy balance. The heat exchangers were modeled using the moving boundaries technique. The compressor and photovoltaic cells were modeled using a black box model with equations for the efficiencies of these components. The low-global-warming-potential (GWP) refrigerant R290 (propane) was used in this study. Two independent sets of experimental data were used to validate the model, with a mean absolute deviation of 4.8%. The results indicated that PVT-DX-SAHP had a higher season performance factor (SPF) and a lower total equivalent warming impact (TEWI) compared to DX-SAHP, with an average SPF increase of 81% and a TEWI reduction of 30%. The findings also showed that PVT-DX-SAHP had a 24% higher longer payback period than DX-SAHP. Full article

A functional Huangjiu-based liqueur (called by Lujiu in China), a type of Chinese rice wine, was developed by incorporating Chinese gall leaven, as a medicinal–edible homologous ingredient, into the fermentation process to enhance its bioactivity. The physicochemical properties and enzymatic activities were investigated and found that supplementation with 2% (v/v) Chinese gall leaven optimized fermentation efficiency and substrate utilization. The co-fermentation significantly elevated the concentrations of bioactive compounds and improved antioxidant capacity, particularly free radical scavenging activity. Compared to traditional Chinese rice wine, the supplemented variant exhibited markedly higher levels of malic acid and phenolic acids. GC-MS analysis identified 85 and 84 volatile flavor compounds in the two supplemented variants, respectively, exceeding the 70 compounds detected in traditional Huangjiu. GC-IMS further revealed significant enrichment of key alcohols (e.g., 3-methyl-1-butanol, 2-methyl-1-propanol) and aldehydes (e.g., propanal, acetaldehyde) in the supplemented group. Microbial community analysis indicated distinct shifts, with increased relative abundances of Pediococcus, Lactiplantibacillus, Aspergillus, and Saccharomyces in the Chinese gall leaven-supplemented fermentation. These results suggest that the native microflora and enzymatic systems of Chinese gall leaven could enhance microbial metabolism and fermentation efficiency, thus contributing to the unique characteristics of rice wine and providing a novel strategy for functional Huangjiu-based liqueur production. Full article

Paracetamol (PAR) was selected as an emerging micropollutant model to evaluate the effectiveness of the photo-Fenton process using natural Bandjéli ore (BO) as a heterogeneous source of iron. An aliquot of 1 mL of the activated product was introduced into 200 mL of an aqueous solution of paracetamol at a defined concentration. The tests were conducted in a double-jacketed glass photoreactor (0.2 L), continuously stirred and equipped with two UVA PL-L lamps (36 W, λ = 365 nm), with the temperature maintained at 20 °C and the pH around 2.4. The photo-Fenton process was applied with different initial paracetamol concentrations (10–50 mg/L), different ${\mathrm{H}}_2{\mathrm{O}}_2/\mathrm{P}\mathrm{A}\mathrm{R}$ initial molar ratios (10:1 and 5:1), and different ferric ion concentrations (2.84–4.73 mg/L). Under these conditions, complete disappearance of the parent compound (paracetamol) was achieved in less than 3 h for iron contents below 5 mg/L, in compliance with the discharge standards applicable in France and Togo. Inhibition tests with propan-2-ol highlighted the predominant role of hydroxyl radicals and the secondary involvement of superoxide radicals in the subsequent stages. Taken together, these results demonstrate that Bandjéli iron ore is an effective, sustainable, and economically advantageous alternative to commercial iron salts for implementing the photo-Fenton process in the decontamination of water polluted by organic micropollutants. Full article

This study reports on the performance of alumina-supported copper-based catalysts in the oxidative dehydrogenation of propane, with copper dispersed on two distinct commercial aluminium oxide supports made of micro- and nanosized alumina, respectively. The activity and selectivity of the two catalysts was investigated at temperatures between 250 and 550 °C. At a propane-to-O₂ ratio of 1:1, Cu/nanoAl₂O₃ achieves propylene selectivity of 35–48% at low temperatures (250–300 °C), while Cu/Al₂O₃ only exhibits activity starting at 350 °C with about 40% propylene selectivity. Altering the propylene-to-oxygen ratio to 3:1 enhances selectivity towards propylene in both catalysts, up to about 64% on Cu/Al₂O₃ at temperatures of 250–350 °C. The switch to the mild oxidant CO₂ boosts propylene selectivity to 100%. In case of Cu/nanoAl₂O₃, the rate of propylene formation doubles that of the obtained with O₂ used as oxidant. While with CO₂ the Cu/nanoAl₂O₃ catalyst retains 100% propylene selectivity up to 500 °C, on the less active Cu/Al₂O₃ cracking sets off already at 400 °C. The different size of copper particles in the two catalysts is seen as a primary factor determining the observed differences in the performance of the studied catalysts. Full article

This review examines 14 volatile organic compounds (VOCs) across nine Taiwanese Photochemical Assessment Monitoring Station sites over nearly two decades from 2006 to 2024, categorised as aromatic compounds, alkanes, and alkenes. Aromatic compounds and alkenes declined significantly (47.2–82.2%), reflecting regulatory success, while alkanes showed variable trends, including a 2023 Tainan spike (ethane: 9.12 ppbC, propane: 9.10 ppbC). Urban sites (Wanhua and Tucheng) exhibited high VOC levels from traffic, industrial sites (Xiaogang, Qiaotou) showed petrochemical influences, and rural sites (Chaozhou, Puzi, Taixi) were more alkane-dominated. Winter peaks and rush-hour diurnal patterns were meteorologically driven, with isoprene peaking in summer due to biogenic emissions. Cluster analysis of raw and standardised data separated urban–industrial from rural sites and early (2006–2010) from later (2018–2024) years, revealing compositional shifts. Benzene posed cancer risks (range 2.2 × 10⁻⁶–7.8 × 10⁻⁶) across sites and periods; as an illustrative example, prior to 2010 the risk at industrial Xiaogang was 6.2 × 10⁻⁶, but since 2020 has halved to 3.2 × 10⁻⁶. Taken together, these long-term observations demonstrate how declining anthropogenic VOC emissions can coexist with compositional shifts and an increasing relative influence of biogenic compounds, while also highlighting the ongoing challenge of ozone. This shows the value of monitoring networks as tools for understanding evolving atmospheric chemical regimes, rather than solely for reporting trends. Full article

While traditional equations of state can determine thermophysical properties, they are computationally demanding, as most formulations are implicit and require iterative solutions. Dynamic simulation of complex energy systems involves various components defined by mathematical equations. Incorporating equations of state for refrigerant properties adds complexity, slowing down the computation. Moreover, studies have demonstrated that calculations of refrigerant thermophysical properties have the most significant impact on computational speed. Therefore, this work develops fast, accurate, and explicit thermodynamic formulations for thermophysical properties of propane, a widely used natural refrigerant for the new generation of heat pumps. The developed set of formulations yielded a mean absolute relative deviation of less than 1% for most of the formulations across the saturated lines and the different phase regions. The results show that using the explicit formulations for dynamic simulation of an air-source heat pump cycle achieves up to a 117× speedup compared to CoolProp, with a maximum relative error around 1% for the COP. This level of accuracy is suitable for applications such as vapor-compression cycle simulations, where accuracy is sacrificed in favor of computational speed. In addition, they offer greater flexibility for modelling and optimizing complex energy systems. Full article

A novel chemosensor has been developed for the accurate and sensitive detection of Hg²⁺ ions in industrial wastewater. This sensor uses a stick-like nanocellulose architecture synthesized via a green method. The unique morphology and surface area of nanocellulose make it an ideal mesoporous substrate for immobilizing the chromophore 1-(benzothiophenyl)-3-(benzooxazolyl)-2-((4-bromophenyl)diazenyl)propane-1,3-dione (azo-dione ligand, ADOL). Comprehensive characterization of the fabricated chemosensor and its nanocellulose base was carried out using FTIR, SEM, TEM, BET surface area, and XRD to evaluate their structural and morphological properties. Spectrophotometric parameters, including pH, response time, selectivity, and sensitivity, were extensively optimized to ensure optimal sensing performance, enabling detection of Hg²⁺ at very low concentrations. Method validation was performed in accordance with ICH (International Council for Harmonisation) guidelines, confirming the reliability of the sensor in terms of limit of detection (LOD), limit of quantification (LOQ), linearity, and precision. The spectrophotometric method achieved a highly sensitive LOD of 9.07 µg L⁻¹. Moreover, the ADOL chemosensor demonstrated excellent reusability, maintaining performance over five cycles following regeneration with 0.1 M thiourea, underscoring its sustainability. Finally, the sensor exhibited outstanding performance in detecting Hg²⁺ across various industrial wastewater samples, highlighting its practical applicability, exceptional selectivity, and high sensitivity for real-world environmental monitoring. Full article

Based on continuous field observations conducted at the Shangdianzi Regional Atmospheric Background Station from 21 October to 20 November 2024 and from 1 December 2024, to 2 January 2025, this study systematically analyzed the concentration levels, seasonal variations, diurnal patterns, and ozone formation potential (OFP) of 24 carbonyl compounds (OVOCs) in the atmosphere during autumn and winter. Source apportionment was further investigated using characteristic ratios, correlation analysis, and multiple linear regression. The results indicate that the average concentration of Σ24OVOCs during the observation period was 2.70 ± 1.55 ppb. Formaldehyde, acetone, and acetaldehyde were the dominant species, accounting for 94.5% of the total concentration in this background area. A significant seasonal difference in carbonyl concentrations was observed, with the average concentration in autumn (3.68 ± 1.66 ppb) being approximately 2.1 times higher than that in winter (1.78 ± 0.58 ppb). The diurnal variation in most carbonyls exhibited a pattern of nighttime accumulation and daytime depletion, which was consistent with the trend of NO₂. The OFP results show that the average OFP of Σ24OVOCs was 30 ± 16 μg/m³, with formaldehyde contributing 86.9%, identifying it as a key precursor for ozone formation in the background region. Source analysis revealed that carbonyl compounds in autumn were influenced by combined natural, vehicular, and industrial sources, with significant secondary formation (27–36%) observed for C2 (acetaldehyde) and C3 (mainly acetone and propanal) species. In winter, anthropogenic contributions to carbonyls increased, with C2 and C3 species primarily originating from combustion sources, vehicle emissions, and industrial releases. This study provides the first insights into the pollution characteristics and source profiles of carbonyl compounds during autumn and winter at the Shangdianzi background site, offering a scientific basis for understanding regional atmospheric oxidative capacity and formulating integrated air pollution control strategies. Full article

Proton exchange membranes (PEMs) are essential for fuel cells, yet conventional materials like Nafion suffer from humidity dependence and limited thermal stability. This study introduces sulfonated phenylene-bridged periodic mesoporous organosilicas (PMOs) as promising inorganic–organic hybrid PEMs, synthesized via surfactant-templating with varying alkyl chain lengths for different mesopore sizes. Post-synthetic functionalization involves nitration of phenylene moieties, reduction to amines, and ring-opening of propane or butane sultones to graft sulfonic acid groups via flexible spacers, achieving homogeneous distribution along pore walls. Post-functionalization is confirmed by powder X-ray diffraction (PXRD), revealing preserved 2D hexagonal p6mm ordering and phenylene stacking. N₂ physisorption shows type IV isotherms with reduced pore volumes and pore sizes. ¹H NMR is used to quantify functionalization degrees. Impedance spectroscopy on pressed pellets demonstrates proton conductivities up to 2 × 10⁻³ S cm⁻¹ at 30 °C and 90% RH, depending on the functionalization degree, confirming sulfonic acid-mediated conduction. Full article

As a source of non-protein nitrogen, ammonium chloride (NH₄Cl) is widely utilized in ruminant diets to reduce feed costs. However, the impact of its supplementation level on the flavor of sheep meat remains unclear, despite the known influence of fat on meat flavor. This study aimed to investigate the effects of dietary NH₄Cl supplementation levels on the lipidome and flavor compounds of subcutaneous adipose tissue in Tibetan sheep, providing a scientific basis for dietary optimization in Tibetan sheep farming. Eighty 2-month-old early-weaned Tibetan lambs were selected and randomly allocated into four groups, fed diets supplemented with 0% (N0 group), 1.49% (N1 group), 2.24% (N2 group), and 3.01% (N3 group) NH₄Cl for an experimental period of 105 days. The study conducted histomorphological observations, lipidomics analysis, and determination of flavor compounds. The results showed that NH₄Cl supplementation significantly reduced (p < 0.05) the contents of various unsaturated fatty acids and n-3 polyunsaturated fatty acids (n-3 PUFA) in the subcutaneous adipose tissue of Tibetan sheep. Specifically, the total saturated fatty acid (total SFA) content in the N3 group was significantly higher than that in the other groups, while the total monounsaturated fatty acid (total MUFA) content was significantly lower than that in the N1 and N2 groups (p < 0.05). The absolute contents of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and the sum of triglycerides (TGs) and diglycerides (DGs) in the N3 group were significantly higher (p < 0.05) than those in the other groups. Regarding flavor compounds, the contents of ketone aroma compounds, such as 2-propanone and 2-butanone monomer, were significantly higher (p < 0.05) in the N0 group than in the other groups. The ammonia content in the N1 and N3 groups was significantly higher (p < 0.05) than that in the N0 and N2 groups, while the allyl sulfide content in the N2 group was significantly higher (p < 0.05) than that in the other groups. Correlation analysis revealed that the majority of TG and DG differential lipids were significantly positively correlated with allyl sulfide, and most differential lipids belonging to the PC, PE, and hexosylceramide (Hex1Cer) classes were significantly positively correlated with ammonia (|r| ≥ 0.80, p < 0.01). Conversely, PC (16:0_18:3) exhibited significant negative correlations with multiple beneficial aroma compounds (|r| ≥ 0.80, p < 0.01). The study indicates that dietary NH₄Cl supplementation levels exceeding 2.24% are associated with alterations in lipid metabolism and reduced synthesis of unsaturated fatty acids and beneficial flavor compounds, such as 2-propanone and 2-butanone, in subcutaneous adipose tissue. This is also associated with the abnormal accumulation of phospholipids and ceramides, which correlate strongly with elevated ammonia concentrations in adipose tissue and the generation of oxidation products such as propanal, potentially compromising meat flavor quality. Full article

Propylene (C₃H₆) is a vital building block in the chemical industry as it serves as a key raw material for producing plastics, synthetic fibers and numerous daily-use chemicals. However, the current production routes of C₃H₆ are energy-intensive and face sustainability challenges, prompting the scientific community to explore alternative technologies for its production. The oxidative dehydrogenation of propane (ODHP) using CO₂ as a soft oxidant offers a safe and sustainable pathway for C₃H₆ production, where CO₂ can act as a hydrogen scavenger, coke suppressor and site re-activator. Gallium- and chromium-based catalysts are among the most studied systems for CO₂-assisted ODHP, yet they operate by distinct mechanisms: Ga catalysts follow pathways where both acidic and basic sites are involved, while Cr catalysts rely on redox cycles involving variations in the oxidation state of chromium. In addition to performance and reaction mechanism, Ga- and Cr-based catalysts differ markedly in terms of sustainability, with Cr systems facing environmental and regulatory challenges associated with Cr⁶⁺ species toxicity, while Ga systems, although less toxic, are constrained by gallium scarcity and cost. This review compares Ga- and Cr-based catalysts side by side, emphasizing how support effects, addition of promoters and mechanistic insights fine tune their performance. The aim is to highlight the advantages, the limitations as well as the sustainability implications of these materials and finally to outline future directions for designing more efficient and environmentally friendly catalysts for propylene production. Full article

Efficiently separating propene and propane is paramount for the chemical industry but notoriously difficult due to their minimal size and volatility differences. Here, an efficient strategy to overcome this separation challenge was demonstrated through the design of bimetallic zeolitic imidazolate framework (ZIF)-based mixed-matrix membranes (MMMs). Thin-film composite (TFC) membranes were fabricated by integrating monometallic ZIF-8, ZIF-67, and a synergistic bimetallic ZIF-8-67 into a uniquely formulated ionic liquid–cellulose acetate (IL–CA) polymer matrix. Structural and morphological analyses confirmed the high crystallinity of the ZIF fillers and their seamless integration within the polymer. The resultant ZIF-8-67/IL-CA membrane exhibited notable separation performance, surpassing its monometallic counterparts by a threefold increase in both C₃H₆ permeance and C₃H₆/C₃H₈ ideal selectivity relative to the base membrane. Under industrially relevant mixed-gas testing, the membrane achieved a competitive separation factor of eight for propene over propane. These findings reveal that the strategic integration of bimetallic nodes in ZIFs can unlock synergistic properties unattainable with single-metal frameworks. This work presents a robust and scalable platform for developing next-generation membranes that defy conventional performance trade-offs, paving the way for efficient membrane-based olefin/paraffin separations. Full article

This study presents a detailed numerical analysis of impinging propane flames within confined enclosures using the Fire Dynamics Simulator (FDS, v6.5.3). Two archetypal configurations were examined: (i) free buoyant plumes in unconfined environments, and (ii) ceiling-impinging flames under both open and confined conditions. The investigation encompassed a range of heat release rates (0.5–18.6 kW) and five degrees of ventilation confinement. The simulation results confirm that FDS reliably reproduces flame height evolution under free plume conditions, exhibiting strong consistency with Heskestad’s empirical correlation and available experimental benchmarks. Under ceiling impingement, confinement markedly influences the thermal field, the distribution of major gas species (O₂, CO₂, C₃H₈), and the accumulation of unburnt gas. Distinct from previous works primarily centered on unconfined plume dynamics, the present study systematically characterizes the onset of auto-ignition through combined lower flammability limit (LFL) and auto-ignition temperature (AIT) criteria for confined propane combustion. The highest auto-ignition risk was identified in partially confined configurations (Conf. 2 and Conf. 3) at an HRR of 18.6 kW, where unburnt propane concentrations locally exceeded the LFL (≈0.2%) and ceiling temperatures surpassed the AIT of propane (455 °C). The findings elucidate critical trade-offs between ventilation and safety. They also contribute to a validated FDS-based methodology for evaluating fire-induced flow structures, combustion behavior, and ignition hazards in confined spaces. Full article