Chain Propagation Research Articles

Organo‐Photocatalytic Anti‐Markovnikov Hydroamidation of Alkenes with Sulfonyl Azides: A Combined Experimental and Computational Study

AbstractThe construction of C(sp3)−N bonds via direct N‐centered radical addition with olefins under benign conditions is a desirable but challenging strategy. Herein, we describe an organo‐photocatalytic approach to achieve anti‐Markovnikov alkene hydroamidation with sulfonyl azides in a highly efficient manner under transition‐metal‐free and mild conditions. A broad range of substrates, including both activated and unactivated alkenes, are suitable for this protocol, providing a convenient and practical method to construct sulfonylamide derivatives. A synergistic experimental and computational mechanistic study suggests that the additive, Hantzsch ester (HE), might undergo a triplet‐triplet energy transfer manner to achieve photosensitization by the organo‐photocatalyst under visible light irradiation. Next, the resulted triplet excited state 3HE* could lead to a homolytic cleavage of C4−H bond, which triggers a straightforward H‐atom transfer (HAT) style in converting sulfonyl azide to the corresponding key amidyl radical. Subsequently, the addition of the amidyl radical to alkene followed by HAT from p‐toluenethiol could proceed to afford the desired anti‐Markovnikov hydroamidation product. It is worth noting that mechanistic pathway bifurcation could be possible for this reaction. A feasible radical chain propagation mechanistic pathway is also proposed to rationalize the high efficiency of this reaction.

Initiation and Carbene Induced Radical Chain Reactions in CH2F2 Pyrolysis.

High temperature dissociations of organic molecules typically involve a competition between radical and molecular processes. In this work, we use a modeling, experiment, theory (MET) framework to characterize the high temperature thermal dissociation of CH2F2, a flammable hydrofluorocarbon (HFC) that finds widespread use as a refrigerant. Initiation in CH2F2 proceeds via a molecular elimination channel; CH2F2→CHF+HF. Here we show that the subsequent self-reactions of the singlet carbene, CHF, are fast multichannel processes and a facile source of radicals that initiate rapid chain propagation reactions. These have a marked influence on the decomposition kinetics of CH2F2. The inclusion of these reactions brings the simulations into better agreement with the present and literature experiments. Additionally, flame simulations indicate that inclusion of the CHF+CHF multichannel reaction leads to a noticeable enhancement in predictions of laminar flame speeds, a key parameter that is used to determine the flammability of a refrigerant.

Solvent solute interaction (IEFPCM model), Michael addition-based anticancer drug synthesis, FTIR, NMR, and UV–visible investigations of spirooxindole-pyranoindole (2AIPC) − in vitro and in silico anti-cancer activity

Herein, click chemistry was chosen to synthesize 2AIPC using Knoevenegel and Michael addition reactions. In this synthesis, Lewis base was attracted by the generation of sp3 hybridized carbanion at active methylene group in the reactants for propagation reaction proceeding towards conducting the Michael addition product. The synthesized 2AIPC was characterized by NMR(13C and 1H), UV, FTR and FT-IR analytical tools; it was also evaluated utilizing density functional theory. According to DFT analyses, the comparative study of the functional groups of 2AIPC molecule was successfully described using Raman and FT-IR spectra with simulated spectra. NLO behaviour and charge exchange utilizing the hyperpolarizability and FMO band gap characteristics were also investigated. Through computational studies using MEP, FUKUI, RDG, and NBO, intermolecular interaction and the reactive area of the synthesized molecule were demonstrated.Moreover, the anticancer activity under the in-vitro analysis was tested, and the molecule showed 61.04 % GI against the K-562 leukemia cells at 10-5 M. Molecular docking also evaluated cytotoxicity by in silico study against leukemia-related proteins (60QN, 6OQC, 1EMR, and 606F). The docked complexes showed binding affinities of −7.82, −7.1, −6.9, and −6.71 kcal/mol. A nucleophile elimination process at 2AIPC’s main amino group may also increase the molecule’s potential to be a more effective lead medication.

Non-parameter clustering algorithm based on chain propagation and natural neighbor

Clustering analysis is a powerful tool for discovering potential knowledge in datasets. However, numerous existing clustering algorithms suffer from heavy reliance on parameter settings and cannot cluster complex manifold data very well. Moreover, although non-parameter clustering algorithms aim to lower the usage threshold, their actual performance in clustering is often unsatisfactory. Addressing how to achieve similar clustering effects for numerous data points with only a few core data points during clustering is a valuable consideration. To alleviate these challenges, a non-parameter clustering algorithm is proposed and named Non-parameter Clustering Algorithm based on Chain Propagation and Natural Neighbor (NPCCPN) in this paper, by jointly using chain propagation and natural neighbor. Specifically, NPCCPN identifies core points through chain propagation and clusters them using the saturated neighborhood graph. This makes the core data extraction and clustering process efficient and non-parameter. Finally, the performance of the method is validated on 15 complex synthetic datasets and 10 real datasets from public UCI database. The experimental results show that the effectiveness and superiority of the proposed algorithm. Purity scores first. ACC scores second without parameters, but the score first algorithm needs to set the parameters.

Use of pyridine derivatives as inhibitor/retarding agent for photoinduced cationic polymerization of epoxides

In this study, the cationic photopolymerization of epoxy controlled by pyridine derivative was investigated. Two pyridines were selected in order to explore the impact of the associated pKa and the amine steric hindrance on the polymerization. The inhibition, the polymerization rate, the heat flow and the conversion during dark polymerization were found to be affected depending of the pyridine derivative structure. Two mechanisms seem to be involved. 1) During the initiation step, the proton is trapped by pyridine derivative, a fact which delays the polymerization reaction, because of less growing chains and lower exothermicity. 2) During the propagation reaction, an interaction between the oxonium ion and the pyridine derivative takes place, which results in a decrease of the rate of polymerization. These two mechanisms depend on the concentration, but also on the associated pKa and on the steric hindrance of the amine, which allows a tailorable control over the cationic polymerization kinetics.

Influence of component parameters on propagation characteristics of foaming polyurethane grout in rock fractures

Polyurethane grouting is an important technical solution used for seepage prevention and mechanical reinforcement of fractured rock. Various components of polyurethane grout significantly affect the grout properties and propagation behavior. The present study focuses on the crucial role of component parameters in controlling the propagation process and designing grouting parameters for foaming polyurethane grout. A coupled modeling approach combining chemical reactions and flow field analysis is developed to investigate the polyurethane foaming process. The proposed modeling approach is validated by comparing simulation results with experimental data from the literature. The influence of key component parameters: isocyanate index, initial water concentration and physical blowing agent, on the propagation characteristics (including propagation distance, maximum pressure, final density, reaction time and maximum temperature) of foaming polyurethane grout in rock fractures are further analyzed. The results reveal two distinct types of effects caused by the components, i.e., a monotonic relationship and a parabolic trend. Critical values are identified for the impact of isocyanate index on maximum propagation distance, final density and characteristic time, as well as for the influence of physical blowing agent on maximum propagation distance, final density and maximum pressure. Other parameters demonstrated a monotonic relationship. Additionally, a quantitative assessment is conducted to evaluate the impact of multiple components on propagation characteristics. The finding indicates that the initial water concentration has a significant effect on all properties, while isocyanate index exerts a more pronounced impact on reaction time and maximum temperature. The effect of the physical blowing agent is relatively minor compared to other factors. This study is helpful for material selection and proportioning of polyurethane grout in practical engineering applications.

Inhibition mechanism of CHF3 on hydrogen–oxygen combustion: Insights from reactive force field molecular dynamics simulations

To mitigate the risks linked to hydrogen and oxygen (H2–O2) combustion through CHF3 additives, Reactive Force Field Molecular Dynamics (ReaxFF MD) simulations are performed in this study. The primary objective is to investigate the inhibition mechanism of CHF3 on H2–O2 combustion from 2000 K to 2800 K. The simulation results demonstrate that the reaction pathways of hydrogen combustion are changed under the extended second explosion limit, and the main radicals involved in elementary reactions transform from H, OH, and O to H, OH, and HO2. CHF3 predominantly engages in reactions with H radicals to impede the continuation of chain reactions by forming stable HF molecules. OH radicals react with modest amounts of secondary fluorides such as CHF2OH, CH2F, and so on, while HO2 radicals are combined with even fewer intermediates like CHF2O and CHFOH to prevent chain propagations. Moreover, comprehensive and novel reaction pathways are proposed for the inhibition of H2–O2 combustion by CHF3. The parameters of the reaction kinetics indicate that the ignition delay is advanced and the activation energy for the combustion process is increased under the influence of CHF3. This study is expected to provide practical guidance on the inhibition of H2–O2 combustion by CHF3.

Gamma noise to non-invasively monitor nuclear research reactors

Autonomous nuclear reactor monitoring is a key aspect of the International Atomic Energy Agency’s strategy to ensure nonproliferation treaty compliance. From the rise of small modular reactor technology, decentralized nuclear reactor fleets may strain the capacities of such monitoring and requires new approaches. We demonstrate the superior capabilities of a gamma detection system to monitor the criticality of a zero power nuclear reactor from beyond typical vessel boundaries, offering a powerful alternative to neutron-based systems by providing direct information on fission chain propagation. Using the case example of the research reactor CROCUS, we demonstrate how two bismuth germanate scintillators placed outside the reactor vessel can precisely observe reactor criticality using so called noise methods and provide core status information in seconds. Our results indicate a wide range of applications due to the newly gained geometric flexibility that could find use in fields beyond nuclear safety.

Temperature Dependence of the Number of Defect-Structures in Poly(vinylidene fluoride).

Poly(vinylidene fluoride) (PVDF) is predominantly characterized by alternating CH2 and CF2 units in a polymer backbone, originating from the head-to-tail addition of monomers or regular propagation. Due, to a small extent, to inverse monomer addition, so-called defect structures occur which influence the macroscopic properties of PVDF significantly. The amount of defect structures in the material is determined by the polymerization conditions. Here, the temperature dependence of the fraction of defect structures in PVDF obtained from polymerizations between 45 and 90 °C is reported. We utilized 19F-NMR spectroscopy to determine the fraction of defect structures as a function of temperature. To derive kinetic data, the polymerization of VDF is considered a quasi-copolymerization described by the Terminal Model involving four different propagation reactions. Based on the experimentally determined temperature-dependent fractions of defect structures, the known overall propagation rate coefficient, and taking into account the self-healing behavior of the macroradical, the Arrhenius parameters of the individual propagation rate coefficients were determined using the Monte Carlo methods.

Assessing the Chemical-Free Oxidation of Trace Organic Chemicals by VUV/UV as an Alternative to Conventional UV/H2O2.

Low-pressure mercury lamps with high-purity quartz can emit both vacuum-UV (VUV, 185 nm) and UV (254 nm) and are commercially available and promising for eliminating recalcitrant organic pollutants. The feasibility of VUV/UV as a chemical-free oxidation process was verified and quantitatively assessed by the concept of H2O2 equivalence (EQH2O2), at which UV/H2O2 showed the same performance as VUV/UV for the degradation of trace organic contaminants (TOrCs). Although VUV showed superior H2O activation and oxidation performance, its performance highly varied as a function of light path length (Lp) in water, while that of UV/H2O2 proportionally decreased with decreasing H2O2 dose regardless of Lp. On increasing Lp from 1.0 to 3.0 cm, the EQH2O2 of VUV/UV decreased from 0.81 to 0.22 mM H2O2. Chloride and nitrate hardly influenced UV/H2O2, but they dramatically inhibited VUV/UV. The competitive absorbance of VUV by chloride and nitrate was verified as the main reason. The inhibitory effect was partially compensated by •OH formation from the propagation reactions of chloride or nitrate VUV photolysis, which was verified by kinetic modeling in Kintecus. In water with an Lp of 2.0 cm, the EQH2O2 of VUV/UV decreased from 0.43 to 0.17 mM (60.8% decrease) on increasing the chloride concentration from 0 to 15 mM and to 0.20 mM (53.5% decrease) at 4 mM nitrate. The results of this study provide a comprehensive understanding of VUV/UV oxidation in comparison to UV/H2O2, which underscores the suitability and efficiency of chemical-free oxidation with VUV/UV.

Wave propagation in finite discrete chains unravelled by virtual measurement of dispersion properties

AbstractTravelling waves in circuit chains are studied to measure continuous dispersion. A lock‐in frequency meter (LIF) is suitable for precisely determining k for each set of waves in finite alternate LC chains, where LIF has been proven to be more accurate than the fast Fourier transform. In addition to the –k measurement, the wave impedance spectrum of the travelling wave can be measured simultaneously, for investigating the dispersion and splitting of pulse propagation. The measured dispersion is validated to be consistent with the derived theoretical equations. The result provides an independent way to precisely obtain dynamical system properties for chains composed of non‐ideal components, such as resistors for researching non‐Hermitian behaviour under dissipation. Systematical mapping of relative deviation dependence of wave dispersion measurement with LIF on different chain length and component variation is studied, indicating boundaries of 1%, 0.1%, and 0.01% precision for guidance of experiments.

Enhanced Mechanistic Understanding Through the Detection of Radical Intermediates in Organic Reactions.

Two applications of a radical trap based on a homolytic substitution reaction (SH2') are presented for the trapping of short-lived radical intermediates in organic reactions. The first example is a photochemical cyanomethylation catalyzed by a Ru complex. Two intermediate radicals in the radical chain propagation have been trapped and detected using mass spectrometry (MS), along with the starting materials, products and catalyst degradation fragments. Although qualitative, these results helped to elucidate the reaction mechanism. In the second example, the trapping method was applied to study the radical initiation catalyzed by a triethylboronoxygen mixture. In this case, the concentration of trapped radicals was sufficiently high to enable their detection by nuclear magnetic resonance (NMR). Quantitative measurements made it possible to characterize the radical flux in the system under different reaction conditions (including variations of solvent, temperature and concentration) where modelling was complicated by chain reactions and heterogeneous mass transfer.

Achieving Long‐Life Ni‐Rich Cathodes with Improved Mechanical‐Chemical Properties Via Concentration Gradient Structure

AbstractThe irreversible deterioration of electrochemical performance in Ni‐rich cathode materials, attributed to crack propagation and undesired side reactions, poses a critical barrier to the further development of high‐energy power batteries for electrical vehicles (EVs). Herein, a concentration gradient strategy is proposed for synthesizing a Ni‐rich cathode with enhanced mechanical and electrochemical stability to address the issues related to the irreversible structural deterioration. Notably, the concentration gradient structure contributes to superior mechanical strength in secondary particles due to the radially orientated primary particles resulted from Mn composition grading, which effectively alleviate the internal strain caused by structural changes and fatigue destruction during successive cycling. Moreover, the Mn‐rich surface minimizes the parasitic side reactions at the electrode–electrolyte interface. Benefitting from the above, the concentration gradient sample can deliver ≈180.1 mA h g−1 at 1 C and retain 96.2% of its initial discharge capacity after 100 cycles. This work demonstrates that the concentration gradient structure can simultaneously improve the mechanical and chemical stabilities of Ni‐rich cathode and offers a feasible way for designing stable lithium‐ion batteries with high energy density.

Recent Advances in Controlled Production of Long-Chain Branched Polyolefins.

Polyolefins, composed of carbon and hydrogen atoms, dominate global polymer production. This stems from the wide range of physical and mechanical properties that various polyolefins can cover. Their versatile properties are largely tuned by chain microstructure, including molar mass distribution, comonomer content, and long-chain branching (LCB). Specifically, LCB imparts unique characteristics, notably enhances processability crucial for downstream applications. Tailoring LCB structural features has encouraged academic and industrial efforts, chronicle in this review from a chemistry standpoint. While encompassing post-reaction modification based traditional methods like peroxide grafting, ionizing beam irradiation, and coupling reactions, the main focus is given to catalyst-centric strategies and innovative polymerization schemes. The advent of single-site catalysts-metallocenes and late transition metals catalysts-amplifies interest in tailored chemical methods, but the progress in LCB formation flourishes via tandem catalytic systems and bimetallic catalysts under controlled reaction conditions. Specifically, the breakthrough in coordinative chain transfer polymerization unveils a novel avenue for controlled LCB synthesis by sequential chain propagation, transfer, liberation, and enchainment. This short review highlights recent approaches for the production of LCB polyolefins that can provide a roadmap crucial for researchers in academia and industry, steering their efforts toward further advancements in the production of tailored polyolefin.

Nickel-Catalyzed Ethylene Copolymerization with Vinylalkoxysilanes: A Computational Study.

Since the discovery of α-diimine catalysts in 1995, an extensive series of Brookhart-type complexes have shown their excellence in catalyzing ethylene polymerizations with remarkable activity and a high molecular weight. However, although this class of palladium complexes has proven proficiency in catalyzing ethylene copolymerization with various polar monomers, the α-diimine nickel catalysts have generally exhibited a much worse performance in these copolymerizations compared to their palladium counterparts. Recently, Brookhart et al. reported a notable exception, demonstrating that α-diimine nickel catalysts could catalyze the ethylene copolymerization with some vinylalkoxysilanes effectively, producing functionalized polyethylene incorporating trialkoxysilane (-Si(OR)3) groups. This breakthrough is significant since Pd-catalyzed copolymerizations are commercially less usable due to the high cost of palladium. Thus, the utilization of Ni, given its abundance in raw materials and cost-effectiveness, is a landmark in ethylene/polar vinyl monomer copolymerization. Inspired by these findings, we used density functional theory (DFT) calculations to investigate the mechanistic study of ethylene copolymerization with vinyltrimethoxysilane (VTMoS) catalyzed by Brookhart-type nickel catalysts, aiming to elucidate the molecular-level understanding of this unique reaction. Initially, the nickel complexes and cationic active species were optimized through DFT calculations. Subsequently, we explored the mechanisms including the chain initiation, chain propagation, and chain termination of ethylene homopolymerization and copolymerization catalyzed by Brookhart-type complexes. Finally, we conducted an energetic analysis of both the in-chain and chain-end of silane enchainment. It was found that chain initiation is the dominant step in the ethylene homopolymerization catalyzed by the α-diimine Ni complex. The 1,2- and 2,1-insertion of vinylalkoxysilane exhibit similar barriers, explaining the fact that both five-membered and four-membered chelates were identified experimentally. After the VTMoS insertion, the barriers of ethylene reinsertion become higher, indicating that this step is the rate-determining step, which could be attributed to the steric hindrance between the incoming ethylene and the bulky silane substrate. We have also reported the energetic analysis of the distribution of polar substrates. The dominant pathway of chain-end -Si(OR)3 incorporation is suggested as chain-walking → ring-opening → ethylene insertion, and the preference of chain-end -Si(OR)3 incorporation is primarily attributed to the steric repulsion between the pre-inserted silane group and the incoming ethylene molecule, reducing the likelihood of in-chain incorporation.

The properties of sustainable aviation fuel II: Laminar flame speed

This work reports on the study of flame characteristics and laminar flame speeds (LFS) of sustainable aviation fuel (SAF) and conventional fuels (Jet-A1 and JP-5) premixed with air at elevated pressures. The experimental facilities included the constant volume combustion chamber (CVCC) and used a shadowgraph system to quantify the LFS. The effects of equivalence ratio and ambient pressure on the flame speeds were examined by varying the initial pressure 1, 2, and 3 bar (in addition to 0.1 and 0.5 bar for flame morphology) and the equivalence ratio from 0.8 to 1.8 at 423 K of temperature. The results indicated that JP-5 had the highest LFS value (90.1 cm/s) compared to the other two fuels. Jet-A1 and SAF have the same LFS result, which is less than a 15% difference, excluding the high equivalence ratio and initial pressure. The higher the initial pressure, the lower the LFS for all conditions. The equivalence ratio of 1.2 resulted in the highest LFSs. In addition, in order to understand the laminar flame speed of SAF and its combustion chemical kinetics. Therefore, the sensitivity analysis of SAF was performed. Results indicated that the chain branching reaction (O2 + HOH + O) positively enhanced flame speed as equivalence ratios (φ) increased, while chain propagation reactions, notably O2 + HHO2 (+M), had a negative effect on flame speed, particularly diminishing their influence at higher φ due to limited oxygen availability.

Leveraging the Activated Monomer Mechanism to Create Grafted Polymer Networks in Epoxide–Acrylate Hybrid Photopolymerizations

Hybrid epoxide–acrylate photopolymerization enables the temporal structuring of polymer networks for advanced material properties. The ability to design polymer network architectures and to tune mechanical properties can be realized through the control of the cationic active center propagation reaction (active chain end mechanism) relative to the cationic chain transfer reaction (activated monomer mechanism). Grafted polymer networks (GPNs) can be developed through the covalent bonding of epoxide chains to acrylate chains through hydroxyl substituents, making hydroxyl-containing acrylates a promising class of chain transfer agents. This work demonstrates the formation of these GPNs and explores the physical properties obtained through the control of hydroxyl content and hybrid formulation composition. The GPNs exhibit a lower glass transition temperature than the neat epoxide network and result in a more homogeneous network. Further investigations of hydroxyl-containing acrylates as chain transfer agents will generate a wider range of physical property options for photopolymerized hybrid coatings, sealants, and adhesives.

Water consumption and biodiversity: Responses to global emergency events

Given that it was a once-in-a-century emergency event, the confinement measures related to the coronavirus disease 2019 (COVID-19) pandemic caused diverse disruptions and changes in life and work patterns. These changes significantly affected water consumption both during and after the pandemic, with direct and indirect consequences on biodiversity. However, there has been a lack of holistic evaluation of these responses. Here, we propose a novel framework to study the impacts of this unique global emergency event by embedding an environmentally extended supply-constrained global multi-regional input-output model (MRIO) into the drivers-pressure-state-impact-response (DPSIR) framework. This framework allowed us to develop scenarios related to COVID-19 confinement measures to quantify country-sector-specific changes in freshwater consumption and the associated changes in biodiversity for the period of 2020–2025. The results suggest progressively diminishing impacts due to the implementation of COVID-19 vaccines and the socio-economic system’s self-adjustment to the new normal. In 2020, the confinement measures were estimated to decrease global water consumption by about 5.7% on average across all scenarios when compared with the baseline level with no confinement measures. Further, such a decrease is estimated to lead to a reduction of around 5% in the related pressure on biodiversity. Given the interdependencies and interactions across global supply chains, even those countries and sectors that were not directly affected by the COVID-19 shocks experienced significant impacts: Our results indicate that the supply chain propagations contributed to 79% of the total estimated decrease in water consumption and 84% of the reduction in biodiversity loss on average. Our study demonstrates that the MRIO-enhanced DSPIR framework can help quantify resource pressures and the resultant environmental impacts across supply chains when facing a global emergency event. Further, we recommend the development of more locally based water conservation measures—to mitigate the effects of trade disruptions—and the explicit inclusion of water resources in post-pandemic recovery schemes. In addition, innovations that help conserve natural resources are essential for maintaining environmental gains in the post-pandemic world.

Enhancing the Efficiency of Enterprise Shutdowns for Environmental Protection: An Agent-Based Modeling Approach with High Spatial–Temporal Resolution Data

Top-down environmental policies aim to mitigate environmental risks but inevitably lead to economic losses due to the market entry or exit of enterprises. This study developed a universal dynamic agent-based supply chain model to achieve tradeoffs between environmental risk reduction and economic sustainability. The model was used to conduct high-resolution daily simulations of the dynamic shifts in enterprise operations and their cascading effects on supply chain networks. It includes production, consumption, and transportation agents, attributing economic features to supply chain components and capturing their interactions. It also accounts for adaptive responses to daily external shocks and replicates realistic firm behaviors. By coupling high spatial–temporal resolution firm-level data from 18 916 chemical enterprises, this study investigates the economic and environmental impacts of an environmental policy resulting in the closure of 1800 chemical enterprises over three years. The results revealed a significant economic loss of 25.8 billion USD, ranging from 23.8 billion to 31.8 billion USD. Notably, over 80% of this loss was attributed to supply chain propagation. Counterfactual analyses indicated that implementing a staggered shutdown strategy prevented 18.8% of supply chain losses, highlighting the importance of a gradual policy implementation to prevent abrupt supply chain disruptions. Furthermore, the study highlights the effectiveness of a multi-objective policy design in reducing economic losses (about 29%) and environmental risks (about 40%), substantially enhancing the efficiency of the environmental policy. The high-resolution simulations provide valuable insights for policy designers to formulate strategies with staggered implementation and multiple objectives to mitigate supply chain losses and environmental risks and ensure a sustainable future.

The Spatiotemporal Evolution Mechanism of Urban Rail Transit Fault Propagation in Networked Operation Modes

The cascading propagation and evolution of metro operation failures can significantly impact the safety of metro operation. To overcome this challenge, this study pre-processes a massive amount of metro operation log data through noise reduction. Moreover, a professional terminology dictionary is constructed along with a custom stop-word dictionary to segment the preprocessed data. Subsequently, the AFP-tree algorithm is employed to mine the segmented log data and identify key hazards. A weighted urban rail transit network is established, considering the effective path time cost, and the shortest travel OD path. To simulate the dynamic evolution of the failure chain propagation, a model based on disaster propagation theory is constructed. Taking the Shanghai Metro line as a case, multiple simulation scenarios are established with 25 key hazards as triggering points, and the number of cascade failure stations affected under different scenarios is outputted. The results indicate that the fault stations caused by the large passenger flow are the largest. Meanwhile, the number of stations affected by the door clamp is the smallest. The scale of fault stations reaches a maximum value in 16–20 min. Through case analysis, a positive correlation is found when the self-recovery factor is between 14 and 18, and the number of fault stations shows a significant increasing trend. The research results can provide decision-making support and theoretical guidance for rail transit operation safety management enterprises.