Search Results (1,045)

This study reports the synthesis and catalytic evaluation of a series of imidazolium-based polymeric ionic liquids (PILs) for the cycloaddition of CO₂ to epichlorohydrin (ECH). The synthesized catalysts include homopolymers, poly(3-hydroxyethyl-1-vinylimidazole chloride) (p[HVIm][Cl]) and poly(3-carboxymethyl-1-vinylimidazole chloride) (p[CMVIm][Cl]), and their block copolymers with polystyrene, synthesized for the first time, pS-b-p[HVIm][Cl] and pS-b-p[CMVIm][Cl]. Structural characterization by NMR, IR spectroscopy, and gel permeation chromatography confirmed the successful synthesis. The block copolymers exhibited a low polydispersity index (PDI 1.1–1.2), which is indicative of homogeneous chain lengths and the propensity to form ordered nanostructures, whereas the homopolymers showed higher PDI (2.4–2.9). Catalytic testing at 90 °C and 1 MPa CO₂ for 4 h revealed a clear activity trend: p[CMVIm][Cl] < p[HVIm][Cl] < pS-b-p[CMVIm][Cl] < pS-b-p[HVIm][Cl], with conversions exceeding 75% for all catalysts and a maximum of 82.69% for pS-b-p[HVIm][Cl]. These results demonstrate that the catalytic performance of PILs is governed by a synergistic interplay between the local chemical functionality of the ionic moiety and the overall polymer architecture. Based on these results, the synthesized polymeric ionic liquids, particularly pS-b-p[HVIm][Cl], demonstrate strong potential for creating multifunctional materials. Their ability to self-assemble into ordered nanostructures with distinct hydrophobic and hydrophilic domains provides a foundational architecture for combined gas separation and catalysis. The observed “micellar catalytic effect”, which enhances local reagent concentration near active sites, could be leveraged in a membrane reactor to simultaneously capture and convert CO₂ directly within the membrane. This integrated “separation–reaction” approach represents a promising strategy for advancing circular carbon economy technologies. Full article

The catalytic dehydration of fructose to 5-ethoxymethylfurfural (EMF) in ethanol provides a promising approach for low-carbon chemical production. However, current catalytic systems generally suffer from a trade-off between reaction efficiency and product selectivity. Herein, we show that incorporating solvent moieties to sulfonated polymer enables the highly efficient conversion of fructose to furan compounds in ethanol via restraining product degradation. The co-polymerization of N-vinyl-2-pyrrolidinone, with divinylbenzene (DVB) and sodium p-styrene sulfonate (SPSS) gave 1.5VP/0.64SPSS/0.37DVB that has slightly lower acid contents and inferior pore structure than the co-polymer of DVB and SPSS. The 1.5VP/0.64SPSS/0.37DVB catalyst exhibited maximal EMF yield of 81.9% with a total furan yield of 92.7%, Which is remarkably higher than previous reports. Moreover, the 1.5VP/0.64SPSS/0.37DVB catalyst gave a high HMF yield in pure tetrahydrofuran. The superior performance was attributed to the improved stability of the product. Our findings will instruct the design of active and selective catalysts to facilitate the production of biomass-derived products. Full article

The aza-Michael reaction is a fundamental transformation for carbon–nitrogen bond formation, providing efficient access to β-amino carbonyl compounds, nitriles, and related nitrogen-containing building blocks of broad importance in medicinal chemistry and organic synthesis. Over the past two decades, ionic liquids (ILs) have attracted considerable attention as alternative reaction media, promoters, and catalysts for aza-Michael reactions, owing to their distinctive physicochemical properties and tunable structures. This review presents a comprehensive and critical overview of ionic-liquid-mediated aza-Michael reactions, emphasizing the evolution of IL design from early imidazolium-based systems to modern task-specific, supported, and bio-derived ionic liquids. Conventional room-temperature ionic liquids are discussed as non-innocent solvents capable of stabilizing charged intermediates and enhancing electrophilicity, thereby enabling catalyst-free or metal-assisted aza-Michael additions. Subsequent sections focus on task-specific ionic liquids incorporating Brønsted acidic, basic, hydrogen-bond-donating, or bifunctional motifs, highlighting how rational structural design translates into improved activity, selectivity, and substrate scope. Particular attention is devoted to guanidine-, DABCO-, and DBU-based ionic liquids, where mechanistic studies reveal cooperative activation modes rather than simple acid–base catalysis. Recent advances in supported and polymeric ionic liquids are also reviewed, demonstrating effective strategies to combine IL-like reactivity with enhanced recyclability and operational simplicity. Overall, this review clarifies the diverse roles of ionic liquids in aza-Michael chemistry and outlines current challenges and future perspectives toward more sustainable and efficient C–N bond-forming methodologies. Full article

Temperature regulation of gas-phase ethylene polymerization fluidized bed reactors (FBRs) is challenging due to strong nonlinearities, highly exothermic reaction kinetics, and frequent process disturbances. Conventional Proportional–Integral–Derivative (PID) control often exhibits limited robustness under such conditions, while advanced strategies such as Nonlinear Model Predictive Control (NMPC) may suffer from sensitivity to model mismatch and disturbances. In this study, an Adaptive Integral Sliding Mode Control (AISMC) strategy is proposed for temperature control of nonlinear gas-phase FBRs. The controller integrates adaptive gain adjustment with an integral sliding surface to improve disturbance rejection and steady-state accuracy while mitigating chattering. The performance of the proposed approach is evaluated through closed-loop simulations over an 18 h dynamic operating scenario involving multiple setpoint changes, catalyst activity variations, and feed flow disturbances. Simulation results demonstrate that AISMC achieves the best overall tracking performance, with a mean absolute error (MAE) of 0.092 K and the lowest maximum temperature deviation among the evaluated controllers. Compared to PID (MAE = 0.794 K) and conventional sliding mode control (MAE = 0.179 K), AISMC provides substantial improvements in transient and steady-state behaviors. In contrast, NMPC exhibits degraded tracking performance (MAE = 0.809 K) under the considered disturbance conditions. All controllers demonstrate sub-millisecond execution times; however, AISMC attains superior accuracy without excessive computational cost. These results indicate that AISMC offers an effective balance between robustness, accuracy, and real-time feasibility for industrial gas-phase polymerization reactors. Full article

The plasma-catalytic conversion of CO₂ is a promising route toward sustainable fuel and chemical production under mild operating conditions. However, many aspects still need to be better understood to improve performance and better understand the catalyst-plasma synergies. Among them, one aspect concerns understanding whether photons emitted by plasma discharges could induce changes in the catalyst, thereby promoting interaction between plasma species and the catalyst. This question was addressed by investigating the CO₂ splitting reaction in a planar dielectric barrier discharge (pDBD) reactor using titania-based catalysts that simultaneously act as discharge electrodes. Four systems were examined feeding pure CO₂ at different flow rates and applied voltage: bare titanium gauze, anodically formed TiO₂ nanotubes (TiNT), TiNT decorated with Ag–Au nanoparticles (TiNTAgAu), and TiNT supporting Ag–Au nanoparticles coated with polyaniline (TiNTAgAu/PANI). The TiNTAgAu exhibited the highest CO₂ conversion (35% at 10 mL min⁻¹ and 5.45 kV) and the most intense optical emission, even in the absence of external light irradiation, suggesting that the improvement is primarily attributed to plasma–nanoparticle interactions and self-induced localized surface plasmon resonance (si-LSPR) rather than conventional photocatalytic pathways. SEM analyses indicated severe plasma-induced degradation of TiNT and TiNTAgAu surfaces, leading to performance decay over time. In contrast, the TiNTAgAu/PANI catalyst retained structural integrity, with the polymeric coating mitigating plasma etching while maintaining competitive efficiency. There is thus a complex behavior with catalytic performance governed by nanostructure stability, plasmonic enhancement, and the interfacial protection. The results demonstrate how integrating plasmonic nanoparticles and conductive polymers can enable the rational design of durable and efficient plasma-photocatalysts for CO₂ valorization and other plasma-assisted catalytic processes. Full article

The synthesis of enantiomerically pure chiral β-nitroalcohols is a crucial objective in asymmetric catalysis. In order to efficiently obtain such chiral products, we developed a series of thermoresponsive, oxazoline–copper catalysts (Cu^II-PN_xFe_yO_z) via sequential reversible addition–fragmentation chain transfer (RAFT) polymerization. These catalysts can self-assemble in water into single-chain nanoparticles (SCNPs) with biomimetic behavior, in which intramolecular hydrophobic and metal-coordination interactions generate a confined hydrophobic cavity. Comprehensive characterization by FT-IR, TEM, DLS, CD, CA, and ICP analysis confirmed the nanostructure and composition. When applied to the aqueous-phase asymmetric Henry reaction between nitromethane and 4-nitrobenzaldehyde, the optimal catalyst (2.0 mol%) achieved a quantitative yield (96%) with excellent enantioselectivity (up to 99%) within 12 h. Furthermore, the thermosensitive poly(N-isopropylacrylamide, NIPAAm) block enabled facile catalyst recovery through temperature-induced precipitation above its lower critical solution temperature (LCST). This work presents an efficient and recyclable biomimetic catalytic system, offering a novel strategy for designing sustainable chiral catalysts for green organic synthesis. Full article

The industrial preparation via solid-state polymerization (SSP) of high-viscosity copolyamides 6/66 (PA6/66) addresses the challenges, including prolonged reaction times, high energy consumption, and uneven viscosity distribution. In this study, sodium hypophosphite was introduced into the PA6/66 copolymerization system as a solid-state polymerization catalyst. The effects of this catalyst on the solid-state viscosity-increasing rate and relative viscosity were systematically investigated, and the extraction process was optimized to solve the loss of catalyst and controllable extractable content. The results showed that the relative viscosity of PA6/66 increased linearly with the SSP time, and the apparent viscosity increase rate could be stably maintained at 0.14 h⁻¹ at 160 °C due to the catalytic action. Based on the phosphorus (P) content in the chips, the viscosity increase rate is not further large when the P content is 25 ppm at 150 °C and 30 ppm at 160 °C, which can be added as a “control concentration” as a catalyst. The extraction kinetics showed that the catalyst concentration of the chip could be kept higher than the control concentration, and the extractable content can satisfy the requirements for processing. The catalyst of sodium hypophosphite was utilized on the 4500 tons/year PA6/66 continuous polymerization test line, and the high-viscosity PA6/66 chips with uniform viscosity were stably prepared. This study provides a reliable theoretical basis and process route for the large-scale continuous preparation of high-quality and high-viscosity PA6/66 resin. Full article

Infectious pathogens pose serious threats to public health, necessitating the development of more antimicrobials. In this study, oligohydroxybutyrates were obtained through the catalyzed polymerization of β-butyrolactone using N, N-dimethyl-4-aminopyridine (DMAP) and aluminum isopropoxide [Al(OiPr)₃] and applied as sustainable antimicrobial agents. The poly3-hydroxybutyrate (PHB) oligomers exhibited broad-spectrum antibacterial activities against both Gram-negative (E. coli) and Gram-positive (S. aureus) model bacteria. Additionally, PHB oligomers displayed robust (inhibiting rate: >95%) and rapid (action time: <20 min) antiviral activity against three notorious single-stranded RNA viruses, that is, influenza A virus (H1N1 and H3N2) and coronavirus (SARS-CoV-2). In particular, a comprehensive set of advanced experimental characterizations, including FT-IR, ¹H- and ¹³C-NMR, and H-ESI-MS/MS, was applied to analyze their chemical structures. The results confirmed the loss of terminal hydroxyl groups in the PHB intermediate and end products associated with theoretical calculations. These findings will also help provide deep insight into the major chain growth mechanism during the synthesis of PHB. The structural variations, which were treated as unwanted side reactions, were identified as a pivotal factor by deactivating the terminal hydroxy during chain growth. Their effective sterilization properties and degradability endowed the as-prepared PHB oligomers with a promising biomedical potential, including for use as disinfectants, sanitizers, and antiseptics. Full article

Poly(L-lactide-co-ε-caprolactones) (PLCL) are promising biodegradable polymers with tunable properties for various biomedical applications. Along with the composition, the microstructure of PLCL chain is an important factor affecting its properties, crystallinity, and degradation profile. In this study, to find effective ways for tailoring the microstructure of PLCL chain, kinetic patterns of L-lactide/ε-caprolactone (75:25) ring-opening copolymerization in the presence of two different catalysts were evaluated. The kinetic studies, accompanied by the assessment of the evolution of PLCL microstructure over the reaction course, provided the optimal regimes for synthesis of PLCL with a fixed composition (LA:CL = 75:25) and different chain microstructure. This was achieved by employing two types of catalysts (tin(II) 2-ethylhexanoate and zirconium(IV) acetylacetonate) and delayed co-monomer addition approach. The control of average LA block length (l_LA) was achieved in a wide range from 4 to 14 monomeric units. Differential scanning calorimetry and wide-angle X-ray scattering revealed a pronounced effect of l_LA on glass transition temperature, melting temperature, and crystallinity. Full article

A sustainable circular pathway was developed for poly(ethylene terephthalate) (PET) nanocomposites through a catalyst-driven polymerization and depolymerization process. In this study, calcium dodecylbenzene sulfonate with n-butyl alcohol modified ZnAl layered double hydroxides (LDHs) were utilized as bifunctional catalysts to synthesize highly exfoliated PET/LDH nanocomposites via in situ polycondensation of bis(2-hydroxyethyl) terephthalate (BHET). The organic modification of LDHs expanded interlayer spacing, improved interfacial compatibility, and promoted uniform dispersion, leading to enhanced mechanical, thermal, and barrier properties. In the second stage, the pristine LDH catalyst efficiently depolymerized the prepared PET/LDH nanocomposites back into BHET through glycolysis, completing a closed-loop BHET-to-BHET cycle. This integrated strategy demonstrates the reversible catalytic functionality of LDHs in both polymerization and depolymerization, reducing metal contamination and energy demand. The proposed approach represents a sustainable route for designing recyclable high-performance PET nanocomposites aligned with the principles of green chemistry and circular material systems. Full article

Plastic streams dominated by polyethylene (PE) including PE HD/MD (High Density/Medium Density) and PE LD/LLD (Low Density/Linear Low Density), polypropylene (PP), and polyvinyl chloride (PVC) across Europe demand a design framework that links synthesis with end of life reactivity, supporting circular economic goals and European Union waste management targets. This work integrates polymerization derived chain architecture and depolymerization mechanisms to guide selective valorization of commercial plastic wastes in the European context. Catalytic topologies such as Bronsted or Lewis acidity, framework aluminum siting, micro and mesoporosity, initiators, and strategies for process termination are evaluated under relevant variables including temperature, heating rate, vapor residence time, and pressure as encountered in industrial practice throughout Europe. The analysis demonstrates that polymer chain architecture constrains reaction pathways and attainable product profiles, while additives, catalyst residues, and contaminants in real waste streams can shift radical populations and observed selectivity under otherwise similar operating windows. For example, strong Bronsted acidity and shape selective micropores favor the formation of C₂ to C₄ olefins and Benzene, Toluene, and Xylene (BTX) aromatics, while weaker acidity and hierarchical porosity help preserve chain length, resulting in paraffinic oils and waxes. Increasing mesopore content shortens contact times and limits undesired secondary cracking. The use of suitable initiators lowers the energy threshold and broadens processing options, whereas diffusion management and surface passivation help reduce catalyst deactivation. In the case of PVC, continuous hydrogen chloride removal and the use of basic or redox co catalysts or ionic liquids reduce the dehydrochlorination temperature and improve fraction purity. Staged dechlorination followed by subsequent residue cracking is essential to obtain high quality output and prevent the release of harmful by products within European Union approved processes. Framing process design as a sequence that connects chain architecture, degradation chemistry, and operating windows supports mechanistically informed selection of catalysts, severity, and residence time, while recognizing that reported selectivity varies strongly with reactor configuration and feed heterogeneity and that focused comparative studies are required to validate quantitative structure to selectivity links. In European post consumer sorting chains, PS and PC are frequently handled as separate fractions or appear in residues with distinct processing routes, therefore they are not included in the polymer set analyzed here. Polystyrene and polycarbonate are outside the scope of this review because they are commonly handled as separate fractions and are typically optimized toward different product slates than the gas, oil, and wax focused pathways emphasized here. Full article

Poly(lactic acid) (PLA) has emerged as a leading bio-based polymer due to its renewability, processability, and biodegradability, yet its broader adoption remains constrained by limitations in thermal stability, mechanical performance, and end-of-life control. This review provides a comparative and application-oriented overview of recent advances in PLA from synthesis and catalyst landscapes to structure–property–biodegradation relationships and practical applications. Representative polymerization routes and catalyst systems are critically compared in terms of achievable molecular weight, stereochemical control, scalability, and sustainability. Key structure–property modification strategies—including stereocomplex formation, blending, and copolymerization—are quantitatively evaluated with respect to thermal and mechanical properties, highlighting inherent trade-offs. Importantly, environment-specific biodegradation behaviors are assessed using representative quantitative metrics under industrial composting, soil, marine, and enzymatic conditions, underscoring the strong dependence of degradation on both material design and testing environment. Finally, application-driven requirements for food packaging, fibers, and agricultural materials are discussed alongside regulatory considerations, processing constraints, and qualitative cost positioning relative to conventional polymers. By integrating recent representative studies into comparative tables and synthesis-driven discussions, this review offers design guidelines for tailoring PLA-based materials toward targeted performance and sustainable deployment. Full article

This work reports on the synthesis and ring-opening metathesis polymerization (ROMP) of two novel homologous sulfonyl-containing norbornene dicarboximide monomers, specifically, N-4-(trifluoromethylsulfonyl)phenyl-norbornene-5,6-dicarboximide (1a) and N-4-(trifluoromethylsulfonyl)phenyl-7-oxanorbornene-5,6-dicarboximide (1b) using the Grubbs 2nd generation catalyst (I). The polymers are thoroughly characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), thermomechanical analysis (TMA), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and X-ray diffraction (XRD), among other techniques. A comparative study of gas transport in membranes based on these ROMP-prepared polymers is performed and the gases studied are hydrogen, oxygen, nitrogen, carbon dioxide, methane, ethylene and propylene. It is found that the presence of sulfonyl pendant groups in the polymer backbone increases the gas permselectivity in slight detriment of the gas permeability compared to a polynorbornene dicarboximide lacking sulfonyl groups. The membrane of the sulfonyl-containing polymer with an oxygen heteroatom in the cyclopentane ring, 2b, is also found to have one of the largest permselectivity coefficients reported to date for the separation of H₂/C₃H₆ in glassy polynorbornene dicarboximides. Full article

Poly(ethylene terephthalate) (PET) is a widely used polymer that accumulates in the environment due to its low degradability, requiring efficient recycling strategies. In this study, CaO filler derived from calcium carbide slag (CS) waste was used for the first time as a catalyst for PET depolymerization. PET/CaO composites were prepared via hot extrusion of PET with the finely dispersed CaO filler. The resulting composite demonstrated consistently higher PET conversion (≥95%) and the yields of dimethyl and dibutyl terephthalates (80 and 84%, respectively). Kinetic studies of glycolysis demonstrated that embedding 1 wt% of CaO in the PET matrix doubled the bis(2-hydroxyethyl) terephthalate (BHET) formation rate relative to an externally added CaO catalyst, which resulted in BHET yields of 84.7% and 41.1% after 40 min. SEM and EDX investigations demonstrated good adhesion between the polymer matrix and the filler. The recovered BHET was successfully re-polymerized to produce recycled PET (r-PET). The maximum rate of weight loss of r-PET samples (at T_max = 438.7–444.7 °C) was comparable to the original materials (at T_max = 455.3–457.7 °C). In fact, the direct incorporation of CaO catalyst derived from waste into the polymer matrix during additive manufacturing enabled the implementation of an efficient and scalable closed-loop recycling strategy. Full article

The synthesis of phthalaldehyde-based polymers has exclusively been carried out in dichloromethane, which causes environmental problems due to its halogen content and ozone-depleting attributes. In this study, an alternative solvent for the polymerization of o-phthalaldehyde-based polyaldehydes is disclosed. Ethyl acetate, a solvent that is widely used in consumer products, dissolves a sufficient amount of reactants and polymer product at the reaction conditions, −86 °C, to provide a comparable yield to synthesis in dichloromethane. A significant learning from this study is that the reaction solvent does not have to fully dissolve all the reactants and products to produce stable polymer, compared to dichloromethane, which fully dissolves reactants and products. The polymer product precipitated from the ethyl acetate solution as the polymer formed. Although the reactants and products were not fully soluble in ethyl acetate, they retained sufficient mobility to allow the catalyst to initiate polymer chains and achieve molecular weights as high as 83.4 kg/mol. The synthesis of cyclic copolymers from o-phthalaldehyde and aliphatic aldehydes is also possible in ethyl acetate if the catalyst is added at a temperature below the ceiling temperature of the monomers and above the point where they crystallize from solution. Full article