Search Results (791)

Over the past few decades, electrosynthesis has advanced significantly, enabling numerous valuable transformations for synthetic chemists. Olefins are inexpensive, readily available industrial feedstocks extensively used in organic synthesis. Therefore, achieving high-value transformation of olefins is of great value. However, the use of stoichiometric oxidants and the generation of stoichiometric waste hinder its broader application. Utilizing electrochemistry to achieve high-value transformations of olefins represents a green, environmentally friendly, and sustainable strategy, since it eliminates the need for external oxidants. This review discusses recent advances in the high-value conversion of alkenes induced by electrochemistry. The article introduces two modes of electrochemical olefin transformation, discussing both synthetic applications and mechanistic studies. It highlights their advantages and suggests future directions to tackle the existing challenges in this synthetic domain. Full article

The hydroformylation of alkenylbenzenes remains insufficiently defined, despite the relevance of these substrates as biomass-derived aromatic feedstocks within sustainable chemical transformations. In this work, we present an experimental (catalytic and kinetic) study of their conversion into aldehydes under rhodium-phosphine catalysis, using complexes bearing mono-, bi- and tridentate phosphine ligands, [Rh(H)(CO)₂(PPh₃)₂], [Rh(H)(CO)(triphos)] and [Rh(H)(CO)₂(dppe)], under mild reaction conditions (80 °C and 2–30 bar of syngas for eugenol; 80 °C and 20–50 bar of syngas for estragole and trans-anethole). The catalytic activity order of the complexes was Rh (PPh₃) > Rh(triphos) > Rh(dppe), while the substrate reactivity followed the trend eugenol > estragole >> trans-anethole. Reaction rates were measured across a wide CO and H₂ pressure range, revealing redistribution between the active monocarbonyl species and an off-cycle (acyl)dicarbonyl complex that becomes dominant at elevated p(CO). The kinetic behavior observed for eugenol hydroformylation with Rh(PPh₃) was consistent with the established hydroformylation sequence involving alkene coordination, hydride migration to substrate and the CO-dependent re-coordination steps that determine catalyst speciation; the subsequent transfer of the alkyl group to the carbonyl ligand and hydrogenolysis complete the catalytic cycle; the H₂ addition or the hydride transfer to the alkene was identified as the rate-determining step, depending on whether low or high p(H₂) values were employed. To obtain statistically reliable kinetic parameters- often challenging in hydroformylation because of parameter covariance and restricted identifiability- we complemented conventional nonlinear regression with Bayesian inference based on the Markov Chain Monte Carlo approach. The resulting posterior distributions were well centered, exhibited realistic variance and provided parameter sets that are sufficiently robust to support mechanistic interpretation and subsequent kinetic modeling. Full article

The photocycloaddition (PCA) of chalcones represents an important reaction pathway for accessing substituted cyclobutanes, which is a molecular framework with utility in synthetic chemistry, materials science, and medicine. In the past, our group has demonstrated the utility of the large cavity of γ-CD as a container for encapsulating two photo reactants for directing the PCA of several classes of aryl alkenes with high stereo- and regioselectivity: the cavitand-mediated photodimerization (CMP) approach. The CMP of chalcones reported in this work further demonstrates the effectiveness of this approach as high yields of dimers were observed in the photoreactions, while they were non-reactive in the solid state and yielded only the isomerization product in homogeneous media. The γ-CD CMP of chalcones yielded predominantly dimerized products in very good to high yields (>70%), composed of a mixture of three dimers in different proportions with syn HH as the major product. Computational analysis of the ground state complex structures revealed a strong correlation between the stability of the complex and predominance of the stereoisomer in the mixture. Further insights were deduced from temperature-dependence studies, which showed a shift in dimer selectivity tending towards a single stereoisomer. Full article

Volatile organic compound (VOC) emissions from industrial parks are a crucial source of urban air pollution. This study assessed VOC emissions and their impact on secondary pollution from three key industries—packaging and printing, pharmaceutical manufacturing, and furniture manufacturing—in a typical industrial park in the Guanzhong region of China. The results revealed considerable variation in organized outlet VOC concentrations between the different industries, with the highest level observed in furniture manufacturing (3449.9 ± 437.6 µg/m³) and the lowest level discovered for pharmaceutical manufacturing (410.9 ± 205.5 μg/m³). The VOCs were mainly aromatics (40.7%) and alkanes (21.8%), with pentane, isopentane, xylene, and ethylbenzene the most abundant species. Although organized emissions (1151.6 t/y) constituted the primary source of emissions, fugitive emissions (358.1 t/y) remained a major contributor and primarily contributed aromatics and alkanes. Critically, reactivity-based assessment demonstrated that alkenes and aromatics were the principal contributors to the ozone formation potential (>80%). With regard to the secondary organic aerosol formation potential, aromatics were overwhelmingly dominant, accounting for approximately 87% of the total potential, with xylene and ethylbenzene in furniture manufacturing alone contributing 72.9%. The findings highlight the importance of prioritizing controls on highly reactive alkenes and aromatics. Fugitive emission management during storage, mixing, and curing stages should be enhanced and solvents should be substituted to effectively control VOC emissions in industrial parks. Full article

A retrospective analysis of atmospheric volatile organic compounds in urban Beijing during spring 2017–2019 and 2025 reveals a profound transition in pollution characteristics following long-term control policies. Integrating field observations with positive matrix factorization (PMF), results reveal a fundamental atmospheric transition toward mobile source predominance and reduced chemical reactivity. Total volatile organic compound concentrations declined by 31.0% (to 23.7 μg/m³), driven by a massive 90.7% reduction in aromatics. Conversely, gasoline vehicle exhaust surged to constitute 66.9% of total volatile organic compound mass. This shift altered the chemical reactivity pattern: alkenes replaced aromatics as the primary drivers of ozone formation potential (46.4%), yet residual aromatics continued to dominate secondary organic aerosol formation potential (83.3%). Crucially, a coordinated total volatile organic compounds:NOx reduction ratio of 0.48:1 compared to 2017 successfully lowered spring O₃ levels by 8.4%. These findings substantiate the efficacy of past synergistic controls but emphasize that future deep abatement must prioritize targeting high-reactivity alkenes from mobile sources and residual solvent-based aromatics. Full article

The purity of titanium sponge is crucial for determining the performance of final titanium alloys, underscoring the importance of impurity control in its precursor, TiCl₄. Among these impurities, VOCl₃ is particularly challenging to remove due to its similar boiling point and complete miscibility with TiCl₄. Although organic reagents are widely employed for vanadium removal, their complex compositions complicate the identification of key active components. This study systematically compares the vanadium removal efficiency of six organic compounds bearing different functional groups. Results demonstrate that 1-dodecene exhibits superior performance, achieving a VOCl₃ removal efficiency of 93.35%. Mechanistic studies reveal that 1-dodecene initially undergoes cyclization to form cyclododecane, followed by aromatization and subsequent carbonization through stacking, dehydrogenation, and coking, ultimately yielding partially graphitized amorphous carbon. In this process, VOCl₃ interacts not only with the incompletely carbonized organic precursor but also directly with the alkenes. These findings elucidate the reaction pathway and central role of linear α-alkenes in vanadium removal, providing a theoretical foundation for developing efficient and stable vanadium removal agents. Full article

This study evaluates the pyrolysis of recycled linear low-density and low-density polyethylene (rLLDPE/rLDPE) blends for producing wax suitable as a precursor for corrosion-resistant coatings. Experiments were performed in a horizontal quartz tubular reactor under argon, and we investigated different pyrolysis temperature (400, 450, 500 °C), residence time (45, 60, 75 min), and heating rate (3, 5, 10 °C min⁻¹). Factorial design and response surface methodology (RSM) were applied to quantify factors and optimize wax yield. Analysis of Variance (ANOVA) indicated statistically significant models (p < 0.05), with heating rate having the highest standardized effect. The highest measured yield was 82% at 400 °C, 75 min, and 3 °C min⁻¹; the DOE optimizer predicted an 84% yield at 400 °C, 45 min, and 3 °C min⁻¹. Product quality was assessed by GC-MS analysis, which showed that the waxes were predominantly composed of 1-alkenes and n-alkanes (C9–C32), consistent with the literature and closely matching compositions of commercial waxes. Overall, slow heating at low temperature with short residence time maximized wax yield without compromising quality, confirming that pyrolysis of recycled PE is a viable route to produce high-yield, specification-consistent waxes suitable for protective coating applications. Full article

Ground-level ozone (O₃) pollution remains persistently high in China, despite the implementation of stringent emission controls targeting primary pollutants. However, understanding of the drivers and formation mechanisms of this secondary pollutant remains limited. Herein, comprehensive field observations of O₃ and its precursors were conducted in a medium-sized city in eastern China. The average O₃ concentration was 93.60 ± 61.98 μg·m⁻³, with severe pollution accounting for 47.05% (high-temperature, low-humidity conditions). The peak O₃ concentration during pollution episodes (207.13 ± 34.93 μg·m⁻³) exceeded that of non-pollution periods (108.77 ± 43.99 μg·m⁻³) by more than twofold. A generalized additive model (GAM) was employed to identify the key drivers of O₃ pollution, revealing relative humidity (RH) (F = 36.95) and volatile organic compounds (VOCs) (F = 8.03) as dominant drivers. Further interaction analysis using the GAM showed synergistic effects between RH and nitric oxide (NOx) as well as the temperature (T) and NOx on O₃ evolution. O₃ formation sensitivity analysis demonstrated that O₃ production was primarily within a VOC-limited regime (VOCs/NOx < 5.5). Alkenes were found to be the most prominent component, contributing 41.20–45.38% to the in situ O₃ formation potential (OFP), especially for ethylene and acetaldehyde (>10 μg·m⁻³). The toluene/benzene ratio indicated that Taizhou’s ambient VOCs were dominated by vehicle exhaust emissions, with minor contributions from solvents, oils, and gases, and LPG volatilization, making vehicle exhaust control the core of VOC reduction. The air mass transport from the Yellow Sea also significantly affected the local O₃. This study quantifies the effects of multiple factors of summertime O₃ pollution and provides scientific support for targeted O₃ control strategies in a medium-sized city in eastern China. Full article

The effect of palladium addition to a hybrid Co/SiO₂ + HZSM-5 + Al₂O₃ catalyst on the combined Fischer–Tropsch (FT) synthesis and hydrocarbon hydroconversion process was studied. Catalysts with a Pd content of 0.075–0.3 wt.% were characterized by a complex of physicochemical methods, including synchrotron radiation X-ray diffraction (SR-XRD), temperature-programmed reduction with hydrogen (H₂-TPR), temperature-programmed desorption of hydrogen with oxygen titration (H₂-TPD/O₂ titration), IR spectroscopy of adsorbed pyridine, and STEM-EDX analysis. It was found that the addition of palladium decreases the cobalt oxide reduction temperature due to interphase hydrogen transfer. Tests in hydrocarbon synthesis at 240–250 °C, a pressure of 2 MPa, and an H₂/CO ratio of 2 showed that the sample with 0.15% Pd exhibits the highest selectivity for C₅+ hydrocarbons (66.8% at 240 °C) and stability for 150 h. Analysis of the synthesis products revealed a fivefold decrease in the proportion of alkenes and an increase in isoalkanes with increasing Pd concentration. This effect enables the in situ hydroprocessing of primary FT products in a single reactor. The results demonstrate that the targeted introduction of palladium into the hybrid system is an effective strategy for regulating its functionality, allowing for the one-stage production of high-quality fuels with a controlled hydrocarbon composition from syngas. 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

A commercially available attapulgite sample (Red Attapulgite) was acid-pretreated to enhance its catalytic activity. It turned out to efficiently facilitate the dehydration of a range of substituted alcohols. The dehydration of the primary alcohol was conducted at 150–180 °C, which represents energy-saving conditions when taking into account the typical dehydration conditions of primary alcohols with temperatures of >300 °C. The alkene yields obtained in this study were found to be comparable to those when utilizing commercially available montmorillonite as catalysts, thereby underscoring the potential of the acid-pretreated attapulgite as a catalyst for a variety of reactions. In a parallel study, dehydration catalyzed by a range of Brønsted acids was investigated. However, only two of these acids were found to be suitable for the dehydration of primary alcohols. Nevertheless, these acids lacked both dehydration activity and recyclability. Therefore, a recyclability study was conducted in the presence of the acid-pretreated attapulgite sample. It is remarkable that no loss of activity was found over five cycles. We hypothesize that after acid-pretreatment, a synergistic effect of the Brønsted and Lewis acid sites is the cause for the high catalytic activity of the sample. Full article

Higher olefins are a class of alkenes widely used as intermediates in the production of essential consumer and industrial products. This radiolabel disposition and partial mass balance study investigated the distribution and excretion of four ¹⁴C-radiolabelled alpha higher olefins (i.e., 1-octene, 1-decene, 1-hexadecene, and 1-eicosene) in male Wistar rats following a single oral dose (100 mg/kg). Blood, liver, kidney, adipose tissue, urine, and faeces were collected and analysed for total ¹⁴C-derived radioactivity. Urinary elimination was rapid, with approximately 70% and 90% of total radioactivity recovered in urinary excreted within 24 and 48 h, respectively. Excretion patterns showed a clear chain-length-dependent trend: shorter-chain olefins (C8, C10) exhibited higher urinary excretion, indicating greater systemic absorption, while longer-chain olefins (C16, C20) were primarily eliminated via faeces, suggesting limited intestinal uptake. Tissue distribution was minimal in blood, liver, and kidney, but adipose tissue retention increased with chain length. Total recovery of administered radioactivity in the analysed matrices was low, ranging from 17% to 60%. Importantly, because exhaled ¹⁴CO₂ and volatile parent compounds were not captured, the missing fraction cannot be quantified and the balance cannot be considered closed. All in all, the current study describes the partial disposition of higher olefins and highlights the influence of molecular size and lipophilicity on the biological fat, though further studies are required to fully characterise their metabolic profile and total elimination kinetics. Full article

The conversion of alkanes/alkenes into useful intermediates is highly important in the chemical industry. In this study, the physicochemical properties and catalytically active forms of bismuth molybdates (BiMo) were investigated using the selective oxidation of propene to acrolein as a model reaction. The catalysts were prepared by two methods, coprecipitation and spray-drying, with emphasis on spray-drying. The catalysts were characterized using X-ray diffraction, N₂ adsorption/desorption isotherms, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The catalytic properties of the BiMo samples were studied in a conventional fixed-bed reactor operated under different reaction conditions. The one-dimensional (1D) pseudohomogeneous model was applied to describe the obtained experimental results. The experimental kinetic data were correlated with two complex kinetic models based on multiple reactions (parallel and serial reaction systems). The proposed models were verified by comparing computer simulation data with experimental laboratory results. This study aimed to extend the understanding of the relationship between catalyst composition/structure and catalyst activity/selectivity for different BiMo structures, and to propose kinetic models using two approaches based on parallel and series reactions, in line with efforts to improve the valorization of light olefins. Full article