Chain Growth Research Articles

Transient Kinetic Investigation of Chain Growth and the Accumulation of Surface Carbon During CO Hydrogenation on Cobalt Catalysts

AbstractCO hydrogenation is a promising approach for the storage of renewable energy in the form of hydrocarbons via the Fischer–Tropsch synthesis (FTS). Since transient operation of FTS reactors might be necessary and even be beneficial, transient kinetics for a rational catalyst and reactor design are essential. In order to advance the development of such transient kinetics, the periodic transient kinetics (PTK) method was applied to the CO hydrogenation on a Co/TiO2 catalyst under FT‐like conditions. It was revealed that there are two carbon species of different reactivity, Cα and Cβ, present on the catalyst surface during the reaction. Cα forms fast, within a few seconds, and is highly reactive. Whereas Cβ forms slowly, is accumulating on the surface over a longer time, and imposes an inhibiting effect. The results indicate an important role of the Cβ species to chain growth and the formation of C2+ products. Finally, the transient experimental results were evaluated based on a material balance and the amounts of Cα and Cβ present on the catalyst surface during the reaction were determined.

Soot particle morphology and polycyclic aromatic hydrocarbons formation molecular dynamics during diffusion combustion of three pentanol biofuels

Soot particles constitute a major pollutant in engine diffusion combustion, posing a serious threat to human health and the atmospheric environment. The employment of carbon-neutral biofuel, pentanol, in engines contributes to reducing soot emissions; however, its effectiveness is contingent upon the position of the OH functional group. This work investigated the soot morphology and microstructural parameters evolution of three pentanol isomers, and explored the influence mechanism of OH functional group positional isomerism on the entire process of PAHs formation at the atomic level. The results showed that the peak of primary particle size and soot volume fraction in pentanol flames showed a trend of 2-pentanol>3-pentanol>1-pentanol, and the initial formation time of soot in 1-pentanol flame is the latest, and the particle aggregate size is the smallest. The entire process of pentanol isomers soot formation can be divided into four stages: fuel pyrolysis forming initial ring, PAHs growing into initial soot, soot chain growth and structural evolution, soot morphology transformation and maturation. Among the three isomers, 2-pentanol has the fastest initial ring formation rate, the highest peak C-number in the largest molecule, and ultimately forms a more mature fullerene-like structure. 1-pentanol has the slowest initial ring formation rate, the lowest peak C-number in the largest molecule, ultimately forms a lower maturity layered structure. In terms of reaction pathways, H-atom abstraction and dehydroxylation reactions jointly dominate the initial decomposition pathway in 1-pentanol combustion, while in 2-pentanol, dehydroxylation becomes the main initial decomposition pathway due to the high stability of H atoms on β‑carbon. The dehydroxylation reaction tends to generate olefins, promoting the generation of C1-C4 hydrocarbon. The oxygen atom bonded on the α‑carbon site exhibits a stronger carbon fixation ability, and C1-C4 hydrocarbons are more inclined to participate in oxidation to form CO rather than promote the soot production.

Research on Supply Chain Finance Financing Mode in China under Digitalization

Digital empowerment may help businesses manage their supply networks more effectively, improve the efficiency and quality of supply chain financing, broaden equity financing channels, and encourage sustainable and healthy growth. Against this backdrop, new requirements have been raised for supply chain finance, making the transformation to digital empowerment in supply chain finance imperative. The effective application of supply chain finance financing methods aids enterprises in achieving innovative development and improving their core competitiveness. Based on this, the article studies the supply chain finance financing mode under the digital economy, starting from traditional supply chain financing modes in China. It examines supply chain finance's innovation and growth in the context of digitalization, thoroughly examines the current state of supply chain finance's integration with digital technology, and suggests methods of optimization for digital empowerment within the framework of Chinese supply chain finance financing.

Bridging sodium storage behavior and microstructure in broad-leaf lignin hard carbon for sodium-ion batteries

Hard carbon (HC) has emerged as the most promising anode material for the sodium ion battery because high theoretical capacity and cost-effective properties. However, unsatisfactory specific capacity and initial Coulombic efficiency (ICE) significantly impede its further advancement. Moreover, the correlation between the microstructure and electrochemical performance has been not thoroughly elaborated. Here, a straightforward approach to regulate the closed nanopore and defect structure in the hard carbon matrix by adjusting the pyrolysis temperatures. Higher pyrolysis temperature will promote the growth of a long carbon chain and further fold and shrink generating more closed nanopores, which was beneficial to improve the Na+ plateau capacity. The long-range ordered turbostratic graphite domain structure should be avoided, as it can lead to a reduction in reversible capacity. Through detailed analysis of the hard carbon microstructure evolution and electrochemical performance, the relationship of which has been established. Simultaneously, the optimized hard carbon pyrolyzed at 1500 °C displays a remarkable reversible specific capacity of 338 mAh g-1 at 0.1 C with a high ICE of 87%. Based on the detailed analysis, a microstructure-dependent mechanism ‘adsorption-intercalation-filling’ was proposed for a comprehensive understanding of the sodium ion storage behavior. More significantly, fabricated 18650 cylindrical batteries demonstrate a high reversible capacity of 1175 mAh at 0.1 C with outstanding cycle stability (82.9% after 225 cycles at 0.5 C), outperforming commercial hard carbon counterparts. Our work provides deep insight into the rational design of the hard carbon structure and provides the possibility of building practical SIBs with high performance.

Structural Challenges and a Role Innew Health Policy Management in Future India

Objectives: This paper aims to investigate the evolution of supply chain management (SCM) in the globalization era, which is typified by the focus on global supplier relationship systems and the growth of supply chains across national borders and continents. Methods: The introduction of the mathematical models, which include a broad range of linear, integer, and non-linear programming models, is the first section of this paper. Location modeling and transportation planning are two common applications for heuristic models. Although mathematical and heuristic models are best suited for analytical problem solving, complex real-world issues frequently call for basic assumptions. In simulation models, the intricacies of the problem and the relationships between different variables are represented by equations, and then an attempt is made to discuss a comparative analysis of the results. Results: Once put into place, the system always has a lifespan that is determined by the previously mentioned factors and problems. It would be more accurate to say that all developed systems should be reviewed on a regular basis and any necessary adjustments made to maintain their functionality and effectiveness. Conclusion: According to this paper, the fiercely competitive food production market is largely driven by time-based competition, and a producer's or farmer's ability to offer a customer a flexible and responsive supply determines its competitive edge. These businesses understand that providing creative products and outstanding customer service is essential to retaining clients and opening up new revenue streams.

Formation Mechanism of Polypyrrole-Coated Hollow Glass Microspheres (PPy@HGMs) Composite Powder.

Coating conductive nanoparticles onto the surface of hollow glass microspheres (HGMs) is essential for broadening their applications. However, the low density and high specific surface area of HGM powders, along with the thin walls of the cavity shells and poor surface adhesion, pose challenges for the uniform attachment of functional particles. In this study, we developed a novel integrated process that combines flotation, hydroxylation, and amination pretreatment for HGMs with in situ surface polymerization to achieve a uniform coating of polypyrrole (PPy) on the surface of HGMs. We explored the corresponding growth process and coating mechanism. Our findings indicate that the amount of coating, particle size, and uniformity of PPy on the surface of HGMs are significantly influenced by the pretreatment and the in situ polymerization time, as well as the microspheres/pyrrole feedstock ratio. The in situ polymerization on the surface of HGMs resulted in a uniform encapsulation of spherical PPy, with the average particle size of PPy-coated HGMs (PPy@HGMs) increasing by 14.60% compared to the original HGMs. The elemental nitrogen in the PPy@HGMs primarily exists in the form of C-N and N-H bonds. This study demonstrates that the surface functional groups of HGMs engage in chemical bonding and interactions with PPy molecules. Mechanistic analysis reveals that the hydroxyl and amino groups enriched on the surface of the pretreated HGMs serve as activation centers, facilitating the uniform enrichment of pyrrole monomers and promoting chain growth polymerization of the conjugated chain through nucleophilic and electrophilic interactions with the subamino groups in the pyrrole ring. Additionally, the reaction between the Lewis acid properties of PPy and the Lewis-type electron-donating amino groups in KH550 fosters strong bonding and the formation of a robust interface.

Activation and Deactivation of Chirality Transfer in the Superbundles of Sequence-defined Stereoisomers.

Discrete oligomers can be used to precisely evaluate the structure-property relationship and enable unique chiroptical activities, however, the role of stereochemical sequences on chirality transfer is still unclear. Herein, we report the successful synthesis of a series of sequence-defined chiral azobenzene (Azo) oligomers via iterative stepwise chain growth strategy. Sequence-defined stereoisomers with one single chiral (L or D) stereocenter at the α-position, ω-position and middle- (m-) position have completely different self-assembly dynamics. ω-positional stereocenter can effectively command all Azo building blocks to adopt a tilted π-π stacking along the helical superbundles, exhibiting the activation of chirality transfer. However, discrete oligomers with the stereocenter at other positions can only self-assemble into non-helical nanowires, accompanied by the deactivation of chirality transfer.Cooperative supramolecular interactions, including the π-π interaction between Azo units, the intermolecular hydrogen bonding and steric hindrance, are intrinsic driving forces for these differentiations.

Activation and Deactivation of Chirality Transfer in the Superbundles of Sequence‐defined Stereoisomers

AbstractDiscrete oligomers can be used to precisely evaluate the structure–property relationship and enable unique chiroptical activities, however, the role of stereochemical sequences on chirality transfer is still unclear. Herein, we report the successful synthesis of a series of sequence‐defined chiral azobenzene (Azo) oligomers via iterative stepwise chain growth strategy. Sequence‐defined stereoisomers with one single chiral (L or D) stereocenter at the α‐position, ω‐position and middle‐ (m−) position have completely different self‐assembly dynamics. ω‐positional stereocenter can effectively command all Azo building blocks to adopt a tilted π–π stacking along the helical superbundles, exhibiting the activation of chirality transfer. However, discrete oligomers with the stereocenter at other positions can only self‐assemble into non‐helical nanowires, accompanied by the deactivation of chirality transfer.Cooperative supramolecular interactions, including the π–π interaction between Azo units, the intermolecular hydrogen bonding and steric hindrance, are intrinsic driving forces for these differentiations.

DIGITAL TRANSFORMATION IN SUPPLY CHAINS: BENEFITS, CHALLENGES AND TECHNOLOGICAL INNOVATIONS

Digitalization is revolutionizing supply chains, resulting in significant gains in efficiency and competitiveness. This study investigates the role of digital technologies, such as the Internet of Things (IoT), artificial intelligence (AI), big data, and blockchain, in transforming supply chain management. The research presents a review of the current literature and analyzes case studies of companies that have adopted these innovations. The results show that the integration of these technologies allows for better visibility into processes, facilitating informed and agile decision-making. The automation of routine tasks and demand prediction through AI algorithms contribute to cost reduction and waste minimization. In addition, the use of digital platforms improves collaboration between the various actors in the chain, optimizing the flow of information. However, the study also highlights the challenges associated with digitalization, such as resistance to change, the need for significant investments, and the shortage of technical skills. The analysis concludes that, despite the barriers, the benefits of digitalization outweigh the challenges, making it essential for the sustainability and growth of supply chains.

Exploration on structure-activity relationship over substituted Co-doped spinel AlFe2O4 for enhanced CO2 hydrogenation into C2-C4 hydrocarbons

As the main greenhouse gas, CO2 has caused some serious environmental problems. Hence the abatement of CO2 allows of no delay. Among all strategies for CO2 reduction, CO2 hydrogenation reveals the great potential for industrial application, and becomes the efficient path to achieve target of “Carbon Neutral”. In this work, the Co-doped AlFe2O4 catalysts were firstly reported for CO2 hydrogenation test, and the enhancement of Co doping on activity was explored systematically via a series of conventional characterization methods. The Fischer-Tropsch synthesis-based CO2 hydrogenation was conducted over Co-doped AlFe2O4, thus the dissociation of CO2 and the carbon chain growth were both important. The observation of CoFe2O4 in the composites indicated the strong electronic interaction between Co and Fe species. This could strengthen the electrons transfer to generate more metallic Co and Fe species during H2 reduction, and then increased the Fe3C percentage during CO2 hydrogenation process. Moreover, the generated Co0 species could provide the additional adsorption sites for reactant gas. Therefore, the strategy of Co doping could strengthen the CO2 hydrogenation performance, reflected in the increase of CO2 conversion, the selectivity and space time yield of C2-C4 products. However, the formed “too stable” structure in the condition of the excessive Co doping prohibited the electrons transfer and the generation of Fe3C active species, thus existing an optimum Co doping amount.

Influence of activation/deactivation process on surface-initiated atom transfer radical polymerization: An in silico investigation

We propose a simulation approach to explore surface-initiated atom transfer radical polymerization (SI-ATRP), in which how the chain growth is affected by activation/deactivation process could be considered explicitly. Our findings indicate that these activation and deactivation mechanisms provide all polymer chains with equal growth opportunities. This process leads to a significant increase of grafting density while concurrently reducing the dispersity of the grafted chains. The ratio of activated and dormant chains is theoretically proved to eventually reach equilibrated within the activation/deactivation process. The shorter lifetime of activation/deactivation cycle leads to an even equal opportunity and a faster “stop-continue” pace for the growth of all chains. Our study is helpful for better understanding the role of activation/deactivation process in SI-ATRP from a microscopic perspective.

The advancement of EVA polymerization kinetics and development of high-performance EVOH polymerization process

Ethylene-vinyl alcohol copolymer (EVOH) is a material with excellent barrier properties, produced via the radical copolymerization of ethylene and vinyl acetate in solution, followed by alcoholysis in methanol with NaOH as a catalyst. It is widely used in packaging and medical materials. However, balancing the barrier properties and processability remains challenging. Currently, multi-scale research methods using density functional theory (DFT) to explore polymerization mechanisms and obtain kinetic data, combined with process simulation methods to develop high-performance EVOH polymerization process, are gaining attention. Therefore, this study employs DFT and transition state theory (TST) methods to study the kinetics of chain growth and chain transfer reactions of radicals at first, yielding the average chain growth and chain transfer rate constants for copolymerization reactions. Then, based on these rate constants, process simulations were used to model the ethylene–vinyl acetate solution copolymerization reactor, developing polymerization process for EVOH with high barrier properties as well as EVOH with both high barrier properties and good processability. These findings provide suggestions and guidance for EVOH production and application.

Exploring synthesis techniques for an imidazole-based one-component epoxy latent curing agent: Chemical capping and mechano-chemical capsuling

The increasing demand for one-component epoxy is driven by its eco-friendliness, convenience, and cost-effectiveness, underscoring the importance of developing latent curing agents that trigger reactions under specific conditions. This study introduces an imidazole-based latent curing agent (ICM-SU) characterized by superior storage stability and low-temperature curing capabilities, achieved through dual protections of chemical capping and mechano-chemical capsuling. The process commences with the synthesis of isophorone diisocyanate capped 2-methylimidazole (ICM), wherein the reactivity of 2-methylimidazole (2MI) is controlled via the inductive effect of isophorone diisocyanate, achieved through chemical capping. Subsequently, ICM-SU is produced by uniformly coating it with silica nanoparticles and a urea shell through mechano-fusion system’s dry processing for mechano-chemical capsuling, effectively isolating it from contact with epoxy. The curing mechanism and chemical structure of ICM-SU are identified in four stages: de-capping, de-shelling, formation of epoxy-imidazole adducts, and chain growth. Notably, the melting point of the urea shell (122 °C) closely matches the curing onset temperature, suggesting that the exposure of epoxy to restored 2MI initiates the curing process. As a result, ICM-SU demonstrates significantly enhances storage stability at 20 °C for over 42 days, a stark improvement over 2MI, which solidifies within 8 h. Moreover, specimens cured with ICM-SU exhibits a 32 % increase in tensile strength and a 25 % improvement in Young’s modulus compared to those cured with 2MI, attributed to the reinforcing filler effect of silica nanoparticles.

Crystallization-driven formation of cluster assemblies on surface for super-hydrophobic poly (L-lactic acid)/ZnO composite membrane.

The poly(L-lactic acid) (PLLA)/ZnO composite membrane with cluster assemblies microstructure was constructed by a combination of non-solvent induced phase separation (NIPS) and the Breath-Figure method. In this novel method, the controllable diffusion rate between solvent and non-solvent was introduced to the system by adjusting the non-solvent solubility parameters. The humidity was adjusted to control non-solvent solubility parameters in the Breath-Figure method, which avoids the instantaneous phase separation induced by direct coagulation of water droplets. Hydrophobic modified ZnO nanoparticles were used as heterogeneous nucleation points to induce PLLA crystallization and formation of micro-nano structures. Controlling molecular chain growth with crystal nuclei as templates and constructing cluster assemblies microscopic morphology at 99 % humidity, and the size of the cluster decreases gradually from 10 μm to 3 μm as the nanoparticles content increased up to 5 wt%. The surface water contact angle could reach 153.8° with cluster morphology. In addition, the porous structure formed by the polymer-lean phase could increase the porosity to 93.1 % and exhibit an excellent oil absorption capacity up to 12.64 g/g. It is foreseeable that porous PLLA/ZnO composite membranes have potential applications as biodegradable oil-water separation materials.

Effects of Crystallinity and Branched Chain on Thermal Degradation of Polyethylene: A SCC-DFTB Molecular Dynamics Study.

As a widely used plastic, the aging and degradation of polyethylene (PE) are inevitable problems, whether the goal is to prolong the life of PE products or address the issue of white pollution. Molecular simulation is a vital scientific tool in elucidating the mechanisms and processes of chemical reactions. To obtain the distribution and evolution process of PE's thermal oxidation products, this work employs the self-consistent charge-density functional tight binding (SCC-DFTB) method to perform molecular simulations of the thermal oxidation of PE with different crystallinity and branched structures. We discovered that crystallinity does not affect the thermal oxidation mechanism of PE, but higher crystallinity makes PE more susceptible to cross-linking and carbon chain growth, reducing the degree of PE carbon chain breakage. The branched structure of PE results in differences in free volumes between the carbon chains, with larger pores leading to a concentrated distribution of O2 and chemical defects subsequently formed. The breakdown of PE is slowed down when chemical defects are localized in low-density regions of the carbon chain. The specifics and mechanism of PE's thermal oxidation are clearly revealed in this paper, which is essential for understanding the process in depth and for the development of anti-aging PE products.

Optimized spacing of active sites in Ni-Mo catalysts enhances ethanol production in syngas conversion

The direct conversion of syngas to ethanol is highly attractive but remains challenging due to low CO conversion and poor EtOH/ROH. We investigated the conversion of syngas over a KNiMo2C catalyst modified with carbon dots (CDs) derived from Ligustrum lucidum leaves. On the Ni0.54Mo-A catalyst, a CO conversion of 43.4 % was achieved, with oxygenates selectivity and EtOH/ROH，reaching 48.2 % and 63.7 %, the space-time yield of ethanol was 132.5 mg/gcat/h. Comprehensive characterization revealed that CDs regulate the distance between Ni-Mo active sites, preventing excessive proximity and maintaining an optimal separation. This adjustment significantly enhances EtOH/ROH by modulating the probability of carbon chain growth. A potential new reaction pathway for directly converting syngas to ethanol is proposed, The C-C coupling of CHx* with *COOH or *CO2 is identified as a key step in carbon chain growth. This work provides a new catalytic pathway for the syngas to ethanol industry.

Electrochemical reduction of nitrate to ammonia using Fe-based catalyst: Insights into N2, CO2, and CO environments

Electrochemical (EC) reduction of nitrate/nitrite for ammonia production is a key area of research in the realm of nitrogen pollutant treatment and recycling efforts. In this study, we utilized a commercial Fe(Mn) alloy to investigate EC reductions of nitrate/nitrite ions under N2, CO, and CO2-saturated conditions, shedding light on the influences of different feeding gases. Under N2 conditions, the ammonia production Faradaic efficiency (FE) reached 60 %; however, it significantly decreased under CO2 conditions. The presence of CO as a feeding gas proved detrimental, resulting in no ammonia production. Surprisingly, the Fe(Mn) alloy demonstrated superior EC Fischer-Tropsch (F-T) synthesis chemistry under CO conditions, generating CH4 and long-chain hydrocarbons (CnH2n+2 and CnH2n, where n=2–7). This contrasts with existing literature, where such alloys typically perform better under CO2 conditions. Notably, alkanes were found to be more predominant than their corresponding alkenes. The Anderson-Schulz-Flory equation plots exhibited significant linearity, resembling the traditional Fischer-Tropsch chain growth mechanism. This original discovery introduces new possibilities for employing commercial-grade Fe alloy in the direct EC F-T synthesis using CO, facilitating the production of long-chain hydrocarbons. Moreover, it paves the way for nitrate/nitrite ion treatments in analogous processes within diverse gas environments.

Surface‐Functionalization of Oleate‐Capped Nano‐Emitters for Stable Dispersion in 3D‐Printable Polymers

AbstractTwo‐photon polymerization 3D‐printing is a well‐known technique for fabricating passive micro/nanoscale structures, such as microlenses and inversely designed polarization splitters. The integration of light emitting nanoparticle (NP) dopants, such as quantum dots (QDs) and rare‐earth doped nanoparticles (RENPs), into a polymer resist would enable 3D printing of active polymer micro‐photonic devices, including sensors, lasers, and solid‐state displays. Many NPs contain oleic acid ligands to prevent degradation, but oleate‐capped NPs (oc‐NPs) tend to agglomerate in nonpolar media despite the hydrophobicity of the ligand. This results in an uneven nanoparticle distribution and increased optical extinction. In this work, a general approach is proposed for dispersing oc‐NPs in commercial 3D printable polymers. Controlled growth of small carbon chains around the oc‐NPs is achieved by functionalizing them with methyl‐methacrylate monomers. The proposed approach is validated on RENPs (≈65 nm) and CdSe/ZnS quantum dots (≈12 nm) using commercial polymer resists (IP‐Dip and IP‐Visio). Dispersions of functionalized NPs (f‐NPs) have improved the NP density by an order of magnitude and are shown to be stable for several weeks with minimal impact on printing quality. The approach is generalizable to other oc‐NPs, enabling synthesis of functional resins for high‐quality polymer‐based optical and electronic devices.

Growing polyion complex micelles: kinetics and mechanism of electrostatic template polymerization and assembly

HypothesisElectrostatic-templated polymerization (ETP) is a recently developed strategy for robust fabrication of stable polyion complex (PIC) micelles with regulated size and morphology, yet the kinetics and mechanism about this one pot process remain elusive. ExperimentsIn ETP method, ionic monomers are polymerized in the presence of an oppositely charged ionic-neutral diblock copolymer as template. We investigate the monomer conversion and electrostatic assembly as a function of time, under different polymerization conditions of ionic strength, pH, template/monomer molar ratio and the presence of a cross-linker. FindingsThe template copolymer accelerates the monomer conversion and formation of PIC micelles dependent on ionic strength and pH. The process follows the “Pick-up” mechanism, where monomers first convert into oligomers which complex with template to induce further chain growth and electrostatic assembly. Introducing cross-linker hardly impacts the reaction kinetics and “Pick-up” route, while it creates PIC micelles containing cross-linked ionic network assembly with the template. Further removing the template by concentrated salt provides purified ionic nanogels. The disclosed findings not only provide a better understanding of the polymerization-assembly process, but also optimize the controls of electrostatic-templated polymerization for the rational design and fabrication of diverse PIC micelles and polyelectrolyte particles.

Insight into the synthesis of alkali metal modified Co-doped ZnFe2O4 with faveolate spinel structure and their enhanced selectivity of olefins during CO2 hydrogenation

Emission reduction of CO2 allows of no delay, and CO2 hydrogenation strategy reveals the great potential to achieve target of “Carbon Neutral”. Trapped with the low selectivity of olefins in our previous work of Co-doped ZnFe2O4, the alkali metal (Na, K) modified Co-doped ZnFe2O4 were synthesized, and their enhanced selectivity of olefins were present. The promotion caused by alkali metal modification revealed that more generation of metallic Fe and the additional generation of Fe5C2 species could be ascribed for the enhanced selectivity of C2-C4 olefins and C5+ products. The introduced alkali metal via the strong electronic interaction increased the outer electrons density around Fe atoms, which could promote the adsorption of CO2 and prohibited the secondary hydrogenation reaction of the formed olefins. Therefore, the enhanced selectivity of C2-C4 olefins over the alkali metal (Na, K) modified Co-doped ZnFe2O4 was emerged, while the CO2 conversion was suppressed (caused by the less generation of Fe3O4). Compared with Na-modified samples, the introduced K could make more generation of Fe5C2 to promote the carbon chain growth, due to its stronger alkalinity, thus leading to the highest selectivity of C5+ products over K-modified samples while the highest selectivity of C2-C4 olefins over Na-modified samples.