Reaction Chemistry & Engineering最新文献

The preparation of efficient and eco-friendly catalysts for the cycloaddition of CO₂ and epoxides has been extensively researched for a long time with the aim of achieving green chemistry and net zero emissions. Herein, we report commercial and synthesized boron-doped ZnO nanocatalysts for the formation of target cyclic carbonates by enhancing the efficiency of cyclization reactions of CO₂ and various epoxides through a strong synergistic effect between the metal active site and Lewis acidic boron molecules. FT-IR spectroscopy, UV-vis spectroscopy, TGA-DTA, ICP-OES, XRD, SEM, and EDX-mapping techniques were utilized for structural characterization of ZnO and ZnO-B_(1–3) nanocatalysts. The optimized ZnO and ZnO-B_(1–3) nanocatalysts efficiently carried out the coupling reaction of CO₂ and epoxides to form organic cyclic carbonates under ambient pressure, without the need for solvent, and as an alternative to the toxic and expensive phosgene gas. Among these prepared catalysts, the ZnO-B₁/PPNCl binary catalytic system was found to be the most active catalyst for the effective transformation of CO₂ into value-added cyclic carbonates, yielding 99% with ≥99% selectivity under ambient pressure at 100 °C for 24 h using epichlorohydrin (ECH). According to the catalytic results obtained, the electronic properties and defect dynamics of the ZnO structure and the synergistic effect due to the Lewis acidic properties of boron compounds significantly improved the catalytic performance during the conversion of CO₂ to cyclic carbonates. Moreover, the ZnO-B₁/PPNCl binary catalytic system demonstrated exceptional recyclability, exhibiting no decline in catalytic activity over five consecutive reaction cycles. The kinetic studies show the rate constant of the catalytic CO₂ cycloaddition reaction, and the kinetics of this coupling reaction were estimated to be pseudo-first-order, and the rate constant was 0.0875 h⁻¹ at 100 °C under similar reaction conditions.

The textile industry is one of the most polluting sectors worldwide, generating large amounts of post-consumer and industrial waste with limited recycling options and significant greenhouse gas emissions. This study assesses the environmental viability of energy recovery from textile waste through fluidized bed combustion and oxycombustion, followed by post-combustion catalytic treatment, thermal plasma application, and carbon capture. A gate-to-gate life cycle assessment (LCA) was performed using process simulation data for textile waste with a composition of 50% cotton and 50% polyester, integrating selective catalytic reduction for NO_x abatement, CaO-based treatment for CO₂ capture, and also incorporating real thermal plasma data for the destruction of dioxins and furans. Environmental impacts were quantified using the ReCiPe 2016 Midpoint (H) method. Results show that combustion with carbon capture and thermal plasma application achieved a global warming potential (GWP) of 3.6 kg CO₂ eq. per kg textile. In comparison, oxycombustion with carbon capture and thermal plasma application achieved 4.3 kg CO₂ eq. per kg textile, representing reductions of 27–57% compared to textile waste disposal in landfills, incineration, or mechanical/chemical recycling. CO₂ capture and thermal plasma were the primary contributors to environmental burdens, whereas steam generation provided significant offsetting credits. Oxycombustion increased NO_x and particulate emissions but reduced eutrophication and aquatic ecotoxicity. Overall, combustion and oxycombustion with post-combustion catalytic treatment, thermal plasma application, and carbon capture offer a promising route for the energetic valorization of non-recyclable textile waste, combining greenhouse gas reduction, energy recovery, and lower environmental impacts, supporting circular economy strategies.

The development of environmentally benign methods for synthesizing carbon nanomaterials from biomass is gaining momentum due to growing concerns about sustainability and industrial pollution. In this study, Pinus roxburghii biomass was utilized as a renewable precursor for the hydrothermal synthesis of functionalized carbon nanotubes (f-CNTs). Natural deep eutectic solvents (NADESs), formulated using various hydrogen bond donors (HBDs) and choline chloride (ChCl) as a hydrogen bond acceptor (HBA), were explored as green, structure-directing, and functionalizing agents. Among the tested combinations, [ChCl/oxalic acid] (1 : 1 molar ratio) proved most effective in directing the formation of well-defined tubular nanostructures under optimized conditions (120 °C, 5 h). The synthesized f-CNTs were subsequently applied for the adsorption of reactive orange 16 (RO16), a persistent azo dye commonly found in industrial effluents from textile-dense regions. Adsorption performance was evaluated through studying the adsorption isotherms and kinetic models, revealing that the process followed chemisorption. The thermodynamic analysis of the process was also conducted, depicting the endothermic (ΔH = 6783.47 J mol⁻¹) and spontaneous nature of the process. The synthesized f-CNTs offered a maximum adsorption capacity of 111.11 mg g⁻¹. Thus, this study illustrates the green route for the synthesis of CNTs using NADESs while meeting the sustainable development goals and also curbing the water pollution caused by reactive dyes.

Hydrogenated bisphenol A is a high-performance, long-term color-stable, safe and environmentally friendly monomer material for epoxy resins. This research demonstrates the in-depth investigation of the reaction mechanism for the hydrogenation of bisphenol A over a highly dispersed ultra-small ruthenium nanoparticle catalyst in a continuous fixed-bed hydrogenation reactor. Findings reveal that the acidic support promotes the adsorption of aromatic functional groups, ultimately enhancing the hydrogenation activity in coordination with the highly dispersed ultra-small ruthenium nanoparticle catalyst. Interestingly, the acidity regulation of the catalyst support by MgO modification not only favors the formation of highly dispersed ultra-small Ru nanoparticles but also inhibits the side reactions of C–OH and C–C cleavage, finally leading to an improved selectivity for the target product. Furthermore, an ingeniously controllable three-stage hydrogenation reaction is designed, which provides valuable insights into the reaction mechanism.

In this paper, we present the development of a kinetic model for multi-step transformations, comprising of a Paal–Knorr pyrrole reaction followed by a nucleophilic aromatic substitution within a continuous-flow process, utilizing data obtained from sequential dynamic flow experiments. The reaction networks were fitted to achieve successful parameter estimation (7 parameters in total) with a R² of 0.974 for the desired Paal–Knorr product and a R² of 0.998 for the nucleophilic aromatic substitution product. Model validation based on dynamic flow experiments was extended beyond the previously explored experimental space. In silico simulation involving a threefold higher concentration of the nucleophile than previously studied resulted in approximately 7% model predicted difference to the experimental results.

Isocyanides are of relevance to several scientific fields; however, over the last 150 years only a limited number of synthetic strategies have been reported for preparing them. In a newly developed flow approach, a neglected method for preparing isocyanides, the Hofmann carbylamine reaction, has been revisited and revitalised. The approach developed afforded the preparation of a diverse library of isocyanides in good conversions while only requiring a 15 min residence time at 70 °C. In addition, the method is operationally easy to apply, and it affords several advantages over the more commonly employed strategy of preparing isocyanides which involves the conversion of amines to formamides followed by dehydration to an isocyanide.

Molecular-level reactions predominantly dictate all macro-level properties in the materials world. Understanding nano-level molecular reactions opens up the door to grasping how bottom-up building blocks lead to novel molecules and thus materials. Here, free radicals from the thermal decomposition of peroxide molecules were pursued to explore different plausible reactions with polyethylene oxide as a macromolecular polymer model. Many chemical compounds with different functional groups, such as acetals or hemiacetals, alkoxy ethers, geminal diols, aldehydes, ketenes and orthoesters, were detected. An important observation was chain scission due to tertiary radical formation that created oligomers with carboxylic end groups, a plausible sign of the deterioration of the final product's mechanical properties. Additionally, theoretical prediction enhanced our understanding of intermediate outcomes and revealed hydrogels with the potential to degrade in dilute acids due to vulnerable acetal, hemiacetal or orthoester functional groups, with profound effects on the macroscopic-level properties.

Improving access to functionalized N-aryl amides efficiently remains a key challenge in organic synthesis, particularly when starting from nitroaromatic compounds. Direct amidation of nitroarenes has emerged as an attractive alternative to multistep synthetic sequences; however, existing methods often require long reaction times, transition metals, and harsh and inert conditions, and exhibit limited functional group tolerance. Herein, we describe a fast, metal-free, and scalable flow protocol for the synthesis of functionalized N-aryl amides directly from nitroarenes. This protocol integrates an electrochemical reduction of nitroarene with a CO₂-mediated amidation of carboxylic acids, enabling the synthesis of twenty amides in yields of up to 89% while containing valuable yet reducible functional groups, in a semi-telescoped fashion.

The development of sustainable photooxygenation processes is a key challenge in green chemical engineering, particularly for the efficient transformation of bio-based molecules under mild and environmentally friendly conditions. However, the implementation of efficient photosensitizers remains limited, with recyclability and process compatibility often being the major bottlenecks. This study addresses the engineering challenge of implementing advanced polymer colloids functionalized with rose bengal (RB) as robust heterogeneous photosensitizers that deliver both high photoreactivity and operational stability. We present an original continuous-flow approach using an LED-driven spiral-shaped millireactor and core–shell RB-functionalized colloids that are synthesized directly in a green solvent used for the selective photooxygenation of α-terpinene to ascaridole. Photoactive colloids were used under visible light irradiation and transported by the Taylor (slurry) flows using air as a sustainable reactant. The reactor configuration enabled fine control over irradiation conditions, residence time, and gas–liquid mass transfer, which were essential for consistent and efficient photoreactivity. Strikingly, the colloids retained their photooxygenation efficiency across different particle sizes and compositions, an unusual feature that underscores their robustness and sets them apart from most reported heterogeneous systems. Equally remarkable, their reactivity matched that of soluble RB, demonstrating that embedding the dye in a colloidal microenvironment does not compromise photochemical efficiency. As a result, all the tested colloidal systems showed very good performance and could be reused over multiple reaction cycles. To support process development and scale-up, a model was established to predict reaction rates as a function of operating parameters, providing valuable insights into the interplay between bubbly flow dynamics, light absorption, and photochemical kinetics. This work demonstrates a promising route for the implementation of recyclable heterogeneous photosensitizers in scalable continuous-flow photooxidation processes according to the principles of green chemical engineering.

Methanol is an attractive chemical hydrogen carrier that can provide hydrogen on demand by catalytic steam reforming – an endothermic reaction which requires efficient heat supply to the catalyst. The catalytic static mixer (CSM) technology offers an efficient way to provide sufficient heat and reactant supply to the catalytic center by high thermal conductivity and short diffusion pathways. In this study, an In₂O₃/ZrO₂ catalyst was deposited on highly conductive 3D printed stainless steel scaffolds, reaching uniform and durable coatings. These CSMs were investigated for the methanol steam reforming reaction in a single tube reactor at 330 °C and 350 °C. Their performance was compared to a conventional fixed bed configuration with In₂O₃/ZrO₂ pellet catalysts. The highest overall conversion for the methanol steam reforming, yielding 93%, was achieved using the CSM system at 330 °C, a low feed flow rate of 0.4 mL min⁻¹ and a water : MeOH ratio of 1 : 1. The highest CO₂ selectivity of 98% was achieved using the CSM system at 330 °C, a high feed flow rate of 2.0 mL min⁻¹ and a water : MeOH ratio of 1 : 2. For most experiments, the CSM results were slightly improved from the corresponding pellet results. Although this effect is believed to be small at the relatively small pipe diameter used herein, it is an indication of the expected superior heat transfer and fluid flow performance of the CSM system over pellets inside of a catalytic reactor.