Search Results (1,323)

Incorporating comonomers in propylene polymerization plays a critical role in tuning the physical and chemical properties of the resulting polymers. In this study, the impact of three developed comonomers on propylene polymerization over the triethylaluminum-treated TiCl₃ catalyst was investigated in detail by DFT. The results indicate that these comonomers remain highly stable under actual catalytic conditions, with their ions or functional groups showing a low propensity for detachment, which would otherwise poison the catalyst or disrupt the polymerization process. However, the three comonomers on the surface with a strong adsorption capacity may compete with propylene for adsorption, which will affect the polymerization. Among them, Vinyltrimethoxysilane, which exhibits the strongest adsorption ability, tends to form bonds with the ethyl on the catalyst surface, leading to catalyst poisoning and inhibiting the reaction. In contrast, 5-hexenyl methyldichlorosilane demonstrates relatively higher activity due to its balanced properties. The order of reactivity in the polymerization reaction: 5-hexenyl methyldichlorosilane > 5-hexenyldichlorophosphonane > vinyltrimethoxysilane. This work provides fundamental mechanistic insights into how functional comonomers interact with catalytic active sites through adsorption, competitive reactions, and insertion processes. Additional free energy analysis at 333 K confirms that these mechanistic trends remain unchanged under realistic reaction conditions. Rather than directly simulating industrial catalysts, the present study focuses on a model TiCl₃ system to elucidate intrinsic structure-reactivity relationships. These findings contribute to a deeper understanding of comonomer effects in olefin polymerization at the molecular level. Full article

The in situ-generated thiocarbonyl S-methanides derived from cycloaliphatic thioketones undergo (3+2) cycloaddition onto the C=C bond of levoglucosenone yielding anticipated, polycyclic tetrahydrothiophene derivatives in a regio- and stereoselective manner. The cycloaddition process occurred stereoselectively via the less hindered exo-face approach; exo-diastereoisomers were formed in all studied reactions. Some of the obtained crystalline (3+2) cycloadducts were studied by the monocrystal X-ray diffraction analysis, which unambiguously confirmed the postulated structure. Stable (3+2) cycloadducts were isolated in good yields (50–80%). Full article

Silicone rubber is an important external insulating material for composite bushings, composite insulators, and other power equipment. During long-term service, it is inevitably exposed to coupled environmental and electrical stresses, such as elevated temperature, moisture ingress, strong electric fields, and partial discharge, which may lead to hydrophobicity loss, surface chalking, crack propagation, and particle shedding. To reveal the microscopic degradation mechanism of silicone rubber under complex operating conditions, a molecular model of methyl vinyl silicone rubber was constructed using Materials Studio. A stable silicone rubber molecular structure was obtained through crosslinking, geometry optimization, and ensemble relaxation. Subsequently, a reactive molecular dynamics simulation system under coupled temperature–humidity–electric field conditions was established using LAMMPS and the ReaxFF reactive force field. Different temperature gradients, electric field intensities, and aging–recovery stages were designed to investigate the degradation behavior of silicone rubber. The evolution of the maximum carbon content, maximum silicon content, carbon-containing decomposition products, and typical small-molecule products, including H₂, H₂O, CH₄, C₂H₂, C₂H₄, and C₂H₆, was statistically analyzed. In addition, atomic trajectory tracking was performed to clarify the processes of methyl group detachment, Si-O bond cleavage, water molecule participation, and molecular chain reconstruction. The results show that high temperature mainly promotes methyl group detachment from side chains and fracture of the siloxane main chain, while a strong electric field accelerates the decomposition process and induces the transformation of long siloxane chains into shorter chains. Water molecules can react with broken siloxane chains to form hydroxyl-containing structures, making the structural degradation partially irreversible. The degradation process of silicone rubber under coupled temperature–humidity–electric field stress can be summarized as side-chain detachment, main-chain scission, water-assisted reactions, free-radical recombination, and local molecular aggregation. This study provides a molecular-level theoretical basis for aging mechanism analysis, condition assessment, and lifetime prediction of composite external insulating materials. Full article

The selective conversion of syngas (CO + H₂) to higher alcohols (C₂₊OH) via Fischer–Tropsch synthesis (FTS) is a strategically important but challenging process, requiring catalysts that can simultaneously sustain C–C chain growth and preserve C–O bonds in reactive intermediates. Over the past decade (2015–2025), perovskite-type complex oxides with the formula ABO₃ have emerged as powerful precatalysts for this application, with LaCoO₃ attracting particular attention due to its structural flexibility, controllable reducibility, and the unique catalytic role of the La₂O₃ phase formed upon reduction. This review systematically covers recent advances in synthesis strategies for LaCoO₃ and substituted perovskites, including sol–gel, co-precipitation, mechanochemical, and template-assisted (KIT-6, SBA-15) methods; effects of A-site (Sr) and B-site (Cu, Ga, Ni, Mn) substitution on reducibility, active phase dispersion, and product selectivity; alkali promotion and its interaction with the perovskite-derived active phase; mechanistic understanding of the alcohol-forming pathway, including the Co⁰/Co³⁺ bifunctional site concept, CO insertion mechanism, and the role of La₂O₃ in suppressing the Boudouard reaction; and catalyst stability and deactivation pathways under FTS conditions. Original data from LaCoO₃ catalysts prepared by co-precipitation with ethylene glycol (LCO-1: S_KOH = 90%, Y_KOH = 57 mg·g⁻¹·h⁻¹) and via citrate/KIT-6 template synthesis (LCO/KIT-6: Y_KOH = 80 mg·g⁻¹·h⁻¹, S_BET = 220 m²/g) at 240 °C and 2 MPa serve as the primary experimental reference throughout. Key challenges, including the surface area–selectivity trade-off, long-term stability under industrial conditions, and opportunities in CO₂ hydrogenation, are critically discussed. Full article

To address gas channeling, low sweep efficiency, and water sensitivity in CO₂ flooding of shale reservoirs, amidine-functionalized graphene quantum dots (FN-GQDs) were synthesized via amidation of citric acid-derived GQDs. FTIR and UV-Vis confirmed successful grafting. Conductometric titration showed an optimal reaction time of 24 h with a grafting ratio of 58%, in good agreement with the 60% saturation predicted by molecular dynamics simulation. Upon CO₂ introduction, protonation of amidine groups induced a nonlinear viscosity increase from 0.298 to 2.0 mPa·s at 0.02 wt% via electrostatic attraction and hydrogen bonding, forming a dynamic crosslinking network. FN-GQDs maintained low oil-water interfacial tension of 0.12–0.25 mN/m at 80–120 °C and rapidly reversed rock wettability from strongly oil-wet to water-wet, reducing the contact angle from 141.7° to 38.9° within 80 min. The positively charged surface inhibited clay swelling, achieving 92% at 0.20 wt%. Core flooding and NMR T₂ spectra revealed that alternating CO₂ and FN-GQDs injection at a 2:1 gas–water ratio achieved a final oil recovery of 52.5%, significantly higher than pure CO₂ flooding. Through synergistic effects of interfacial tension reduction, wettability alteration, viscosity enhancement, and anti-swelling, FN-GQDs improve microscopic displacement efficiency and macroscopic sweep volume, showing great potential for CO₂-enhanced oil recovery in shale reservoirs. Full article

High-zinc blast furnace dust is a zinc-bearing solid waste generated during ironmaking. Efficient de-zincing and iron enrichment are required for its resource utilization. This study investigated the high-temperature reduction behavior and kinetic transition mechanism of cold-bonded briquettes made from high-zinc blast furnace dust with a small addition of iron ore powder, with particular emphasis on the effects of reduction temperature (1000–1200 °C) and holding time (10–60 min). The results show that reduction at 1200 °C for 60 min can effectively remove zinc and enrich iron. The de-zincing rate reached 92%, and the TFe grade increased to 50 wt.%, achieving the goal of efficiently removing zinc while improving the TFe grade of the reacted briquettes. During the middle and later stages of reduction (1100–1200 °C, 30–60 min), the content of newly formed metallic iron increased, which restored the briquette strength to 524 N after reduction. In addition, the reduction kinetics of the system evolved from interfacial chemical reaction control in the initial stage to three-dimensional internal diffusion control in the middle and later stages. These results provide a theoretical basis and technical reference for the resource utilization of high-zinc blast furnace dust. Full article

This work investigates Ferro-Rock concrete as a carbon-negative alternative to ordinary Portland cement (OPC), which accounts for 5–9% of global CO₂ emissions, and evaluates its viability as a sustainable construction material. Ferro-Rock is an iron-based binder comprising recycled iron powder, fly ash, metakaolin, limestone powder, and oxalic acid. This is enhanced by a carbonation reaction in which iron particles react with CO₂ and water to form iron (II) carbonate (FeCO₃), the main binding phase, thereby locking in atmospheric CO₂. The experimental program was divided into two groups. Group 1 studied 100% Ferro-Rock binders with different types of aggregate, specimen sizes, and CO₂ curing periods (0–6 days) with a new locally manufactured stainless steel curing chamber that provided a controlled CO₂ environment of 99.9% and 1.2–1.5 bar gauge pressure. Group 2 investigated Ferro-Rock as a partial cement replacement at 0%, 5%, 10%, 15% and 20% levels of substitution with 5% increments. The 7 and 28 days of compressive, flexural and indirect tensile strengths were determined. The results showed the Ferro-Rock with 100% iron ductile waste aggregates (Mix F4) achieved a 28-day compressive strength of 5.5 MPa, 37.5% higher than the standard Ferro-Rock reference mix. The optimum replacement range of Group 2 was 5–10% with an increase in compressive strength by 5–10%, flexural strength by 11%, and indirect tensile strength by 16% over the OPC control. When replacement exceeded 25%, the bonding was weakened, and all strength measures decreased significantly, reaching a 46% reduction in compressive strength at 50% substitution. Scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDS) microstructural analysis verified the gradual formation of the iron carbonate crystalline phase and provided mechanistic insights into the observed strength trends. Fully cured Ferro-Rock specimens sequestered as much as 11% CO₂ by weight, with a verifiably carbon-negative profile that no OPC-based system can match. Full article

Magnetic covalent organic frameworks (MCOFs) offer efficient adsorption via designable pore channels and active sites, along with rapid magnetic separation due to their intrinsic superparamagnetism. However, physical mixing or non-covalent assembly often leads to weak binding, causing the leaching or detachment of magnetic components during use, and compromises the well-defined crystallinity of the COF. In this study, we employed an in situ synthesis strategy at room temperature based on amidation and Schiff base reactions to fabricate a magnetic TAPT-DHTA-COF with good crystallinity and superparamagnetism. This material was used as a magnetic solid-phase extraction (MSPE) adsorbent to establish an MSPE-GC-MS/MS method for the determination of amide herbicides (AHs). The TAPT-DHTA-COF is rich in hydroxyl groups, which form strong hydrogen bonds with the polar AH molecules. In a green tea matrix, six AHs showed good linearity within the concentration range of 1–500 ng g⁻¹, with correlation coefficients ranging from 0.9910 to 0.9982. The limits of detection were between 0.25 and 0.73 ng g⁻¹, spiked recoveries ranged from 80.1% to 94.8%, and relative standard deviations were below 6.2%. This work offers an improved synthesis strategy for novel magnetic COFs and insights into their application in adsorbing polar pesticides. Full article

Nitrogen-containing molecules are fundamental components of astrobiology and play a key role in planetary environments. These species are particularly important because they may serve as key precursors to prebiotic molecules and contribute to chemical complexity. Reactions involving the highly reactive species methylidyne (CH) play a key role in complex organic formation in astrochemical environments, yet their interactions with nitriles such as acetonitrile (CH₃CN) remain relatively unexplored. In this work, we investigate the reaction network of CH + CH₃CN using high-level quantum-chemical calculations with RRKM and microcanonical transition-state theories to characterize the relative energies of reactants, intermediates, transition states, and products to identify the most favorable reaction pathways. Our results reveal that the most energetically favorable reaction channels proceed via barrierless CH addition to the triple CN bond and three-membered ring opening or CH insertion into a C-H bond, followed by a hydrogen elimination to form acrylonitrile (C₂H₃CN). This route highlights an efficient pathway toward a molecule of astrobiological interest. Acrylonitrile is particularly significant due to its stability and dual functional groups, which enable molecular growth complexity, both in planetary atmospheres and on surfaces, under astrochemical conditions. In addition to acrylonitrile, we identified a few other competing channels leading to an isonitrile species, which emphasizes a previously unexplored aspect of isomerization chemistry in the atmospheric planetary science. These isonitrile products, while less abundant, provide insight to the diversity of nitrogen-containing molecules that may form in environments such as Titan’s atmosphere or the interstellar medium. In these environments, acrylonitrile may serve as a reactive precursor that facilitates cyclization and molecular growth, which enables the formation of nitrogen-containing polycyclic aromatic molecules and N-heterocycles. This, in turn, contributes to the emergence of larger, more complex organic species relevant to prebiotic chemistry and potential origin of life in our solar system. Full article

The use of metal-free porous carbon catalysts can be considered one of the best alternatives for implementing a more sustainable fine chemical synthesis, as a challenge necessary to protect both our planet and society. It is recognized that the selection of the appropriate functional carbon catalyst, operating under the optimal reaction conditions, undoubtedly improves both the conversion and selectivity of a great variety of distinctive organic transformations, often through cascade reactions or even multicomponent synthesis. Increasing our knowledge of synthetic methodologies for metal-free carbon-based materials (including many of them on a large scale or even at an industrial scale), available characterization techniques, and computational methods represents an excellent opportunity to make these types of materials promising catalysts for a more sustainable future. In this context, this review is addressed to revisit the benefits and limitations of using each type of metal-free porous carbon catalyst in fine chemical synthesis, particularly in multi-bond forming processes for the synthesis of relevant heterocyclic systems. Full article

Spent lithium-ion battery electrolytes contain fluorine-, sulfur-, and phosphorus-bearing toxins, necessitating deep detoxification and directional conversion into C₁–C₆ light hydrocarbons. To elucidate the specific catalytic roles and sequential activation of cathode metals (Li, Ni, Co, Mn), this work systematically deconvolutes their mono- and multi-metallic migration mechanisms over a CaO-ZSM-5* catalyst during vacuum catalytic pyrolysis (530 °C, 100 Pa). Results reveal that Li⁺ and Ni²⁺ dominate C–O bond cleavage in carbonates and CaO-ZSM-5*-assisted decarboxylation and oxygen fixation, significantly increasing the relative hydrocarbon content. Conversely, Co^2/3+ and Mn⁴⁺ release reactive oxygen species, causing deep oxidation of hydrocarbons into CO₂ and antagonizing the targeted conversion. In multi-metallic systems, forming composite metal oxides (M_xN_yO_z) increases the energy barrier for releasing active catalytic ions, hindering carbonate cleavage and leaving unreacted carbonate feedstocks. For detoxification, F and P are effectively immobilized as CaF₂ and Ca₂P₂O₇. The relative content of detected gas-phase nitriles is minimized to <2% due to the strong antagonistic effect of Ni²⁺ on Li⁺-promoted hexanedinitrile cleavage, while sulfur species derived from 1,3-propane sultone are converted to SO₂ and ultimately mineralized as calcium and metal-sulfur salts. Mechanistically, product distributions and crystallographic properties suggest a hypothesized sequential activation model—Li⁺ → Ni²⁺ → Mn⁴⁺—governing reactivity, whereas Co^2/3+ does not participate in the synergistic detoxification and selective upgrading process. This migration–reaction coupling framework provides critical insights for cathode-assisted in situ catalytic pyrolysis and closed-loop electrolyte recycling. Full article

Simultaneously achieving high densification, excellent mechanical properties, and high thermal conductivity remains challenging for aluminum nitride–silicon carbide (AlN-SiC) composites. In this study, fine-grained AlN-SiC composite ceramics were fabricated via in situ reaction hot pressing with the addition of small amounts of silicon (Si) and carbon (C). At an optimal sintering temperature of 1800 °C, the primary phase composition consisted of AlN, SiC and residual graphite, with an average AlN grain size of 0.94 μm. The Si additive melted and wetted the AlN matrix via capillary action, thereby providing sufficient kinetic driving force for densification. Meanwhile, the C additive not only removed oxygen impurities and purified grain boundaries but also reacted in situ with liquid Si to form SiC. The uniformly dispersed SiC particles inhibited the abnormal growth of AlN grains via the grain boundary pinning effect. Consequently, the relative density, flexural strength, and Vickers hardness of the obtained AlN-SiC ceramics reached 99.08%, 365 MPa and 22.58 GPa, respectively. At room temperature, the composite exhibited a thermal conductivity of 66 W/(m·K) and a thermal diffusivity of 32.6 mm²/s. This superior thermal performance is attributed to the purified grain boundaries, uniform SiC distribution, high densification, and tightly bonded SiC/AlN interfaces, which result in weak phonon interfacial scattering. Full article

Magnesium phosphate cement (MPC) shows great potential for complex underground environments due to its rapid-hardening and early-strength properties. However, its large-scale application is hindered by several drawbacks, including high hydration heat, rapid setting, and insufficient long-term durability. To address these limitations, this study developed a novel MPC grouting material modified with steel slag (SS) and redispersible latex powder (LP). We systematically investigated the workability, mechanical properties, durability, and microstructural evolution of this modified system. Results indicate that incorporating SS and LP decreases both the fluidity and setting time of the grout. An optimal SS dosage accelerates reaction kinetics and raises the peak hydration temperature. Conversely, the LP-induced polymer film suppresses the overall temperature rise, delaying the first exothermic peak and advancing the second. The incorporation of 5% steel slag increased the 28-day compressive strength of the MPC to 54.86 MPa. Building on this, the combined addition of 0.15% latex powder further elevated the strength to 58.82 MPa. Microstructural and pore analyses confirmed that the steel slag enhanced interfacial bonding through physical filling and the formation of calcium phosphate crystals. Meanwhile, the latex powder formed a continuous polymer film, which tightly wrapped and bridged the hydration products and unreacted particles. This synergistic mechanism effectively sealed the capillary pores and reduced the proportion of harmful pores by 15.99% compared to the control group. Consequently, the densified MPC matrix laid a solid microstructural foundation for the material’s excellent durability. It offers reliable, high-performance material for seepage control and strata reinforcement in complex environments. Full article

This study used UV-Vis absorption spectroscopy to investigate the interactions of flavonoids—baicalein (with ortho-dihydroxyl on the A-ring) and apigenin (with 4′-monohydroxyl on the B-ring)—with metal ions (Co²⁺, Ce⁴⁺) and membrane–mimetic systems (CTAB/SDS micelles, liposomes, vesicles). It revealed how flavonoid spectral properties related to molecular structure and microenvironment. Key findings were as follows: pH affected absorption spectra by altering phenolic hydroxyl protonation. Metal chelation depended on hydroxyl position: baicalein’s A-ring ortho-dihydroxyl formed a stable charge-transfer complex with Cu²⁺. In acidic medium, apigenin reduced Ce(IV) more effectively than baicalein, which contradicted the classic antioxidant role of ortho-dihydroxyl groups. This showed that reaction microenvironments could change hydroxyl reactivity and electron transfer paths. Membrane–mimetic systems (liposomes/vesicles) raised apparent pKa, enhanced solubility and stability. The study first quantified distinct ΔpKa values for different flavonoids (e.g., quercetin vs. baicalein), which were linked to intramolecular H-bonding and membrane preference. Quercetin’s B-ring ortho-dihydroxyl enabled the formation of hydrophobic interfacial anions in nanocarriers under alkaline pH, ensuring high stability. Kaempferol showed sustained leakage. These findings provided a basis for structure-guided flavonoid carrier design, bioavailability, and antioxidant delivery. By integrating reaction microenvironment, membrane interface effects, and carrier stability, this work clarified flavonoid bioactivity mechanisms and supported targeted delivery strategies. Full article

In this work, welan gum (WG) was investigated as a green corrosion inhibitor for metals in acidic petroleum drilling fluids. The side chain of WG was subsequently modified by grafting with 3-chloropropionic acid (WG-CAR), further improving the corrosion inhibition performance. At the same concentration, WG exhibited a better corrosion inhibition efficiency than the commercial β-cyclodextrin. Moreover, the graft-modified WG-CAR achieved 60.35% at a concentration as low as 100 ppm, whereas WG and β-cyclodextrin only reached 28.25% and 25.42%, respectively. These improvements are attributed to their electron-donating hydroxyl and carboxyl functional groups, through which the lone pair electrons in oxygen atoms can fill the unoccupied d-orbitals of iron atoms, forming coordination bonds. This promotes Langmuir chemisorption, thereby forming a protective layer on the steel surface that inhibits anodic and cathodic corrosion reactions. In addition, calculations show that the WG-CAR molecule possesses a larger dipole moment and enhanced electron-donating capacity, resulting in stronger coordination interactions for the protective layer. Even at a high temperature of 323 K, WG-CAR (200 ppm) maintains an inhibition performance of 36.80%, higher than that of WG (10.66%). This work broadens the application of WG and brings new perspectives for the development and design of corrosion inhibitors. Full article