Reaction Chemistry & Engineering最新文献

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.

To address the low utilization rate of refractory ferromanganese ores, this study proposes an innovative technology, namely the pre-enrichment-hydrogen-based mineral phase transformation–magnetic separation, to realize the separation and enrichment of manganese and iron from the ores. The suitable process parameters were determined as follows: a pre-enrichment magnetic field strength of 6500 Oe, a processing capacity of 80 kg h⁻¹, a CO dosage of 7.5 m³ h⁻¹, a H₂ dosage of 3.8 m³ h⁻¹, a N₂ dosage of 13.8 m³ h⁻¹, a roasting temperature of 500 °C, a total gas volume of 25.1 m³ h⁻¹, an excess coefficient of the reductant of 1.4, and a magnetic field strength of 1520 Oe. Through the stabilization test, iron concentrate with a TFe grade over 67% and iron recovery over 87% and manganese concentrate with manganese grade over 48% and manganese recovery rate over 77% can be obtained. Product analysis reveals that pre-enrichment technology achieved the removal of silicon containing gangue minerals, and the iron-containing minerals (mainly hematite) and manganese-containing minerals (pyrolusite, braunite, psilomelane, and manganite) are selectively converted to magnetite and manganosite, respectively, through mineral phase transformation. The magnetite and manganosite are then cleanly and efficiently separated and enriched in the magnetic concentrate and tailings, respectively, by weak magnetic separation.

We synthesize a novel hydrogel with exceptional stretchability, capable of extending up to 260 times its original length. Its synthesis is guided by systematic optimization of key components: ammonium persulfate (APS), methylenebisacrylamide, dimethylacrylamide, and polyethylene oxide (PEO). We hypothesize that this extreme stretchability arises from a unique architecture—termed span networks—in which the primary dimethylacrylamide-based polymer network is cross-linked by methylenebisacrylamide and connected by linear PEO chains capable of undergoing random chain scission. Given the intractability of exhaustively analyzing all possible reaction pathways, we employ an AI-based reaction prediction system to investigate the underlying chemistry. This approach reveals a novel network formation mechanism involving PEO chains that link polymer networks through scission–prone interactions. These predicted mechanisms, including chain scission events between PEO and carboxyl groups, are experimentally validated using Fourier-transform infrared (FTIR) spectroscopy.

The present study investigates the sinergetic role of pH and metal ions promoters (Cu²⁺ and Ni²⁺) in the tailoring of polydopamine (PDA) functionalization of carbon nanotubes (CNTs) with the ultimate goal of integration and control of copper matrix composites. We hereby demonstrate that mildly alkaline conditions combined with the presence of redox-active metal ions significantly enhance the yield of PDA coating on CNTs surface, by promoting dopamine polymerization via metal-assisted autoxidation and chelation mechanisms. The use of a catecholamine (PDA) coating and incorporation of metal promoters like copper and nickel enabled stability of the spraying solution. The effects of the CNTs surface modifications on the polymerization yield and electrical properties were evaluated. Although PDA reduces the functionalized CNTs conductivity due to its insulating nature, its role as a versatile interfacial layer is amplified in the presence of metal ions, which facilitate denser and more homogeneous polymer deposition. These findings reveal how surface modification enhances copper–carbon interfaces in CNT-based metal matrix composites, improving composite design and performance for lightweight applications requiring high current resistance, such as lightning strike protection in aircraft.

Continuous production of chemicals under flow conditions is one of the most modern synthesis methods in the industry. The industry takes full advantage by using primarily stainless steel reactors. These industrial reactors are very expensive, and the more cost-effective alternatives, such as coiled tubes, often lack sufficient mixing capacities and are not suitable for laboratory work due to their large volume. Herein we present 3D-printed stainless steel (316L) flow reactors, which could be printed using a standard desktop FDM printer, making this technology easily accessible for every research facility. Thermal conductivity is one of the major advantages in choosing stainless steel as the reactor material. Therefore, we developed an application that allows the reactor to be heated or cooled directly, making the device very compact and easy to handle. The reactor can be heated directly up to 200 °C with a heating element, and the cooling can be accomplished using a Peltier element reaching temperatures under −20 °C. To investigate the functionality of the microreactors, we performed a Diels–Alder reaction with methyl vinyl ketone and a cannabinoid derivative at high temperatures and a subsequent reduction of the carbonyl group with DIBAL-H at low temperatures. In addition to its high thermal conductivity, stainless steel also features favorable chemical and mechanical resistance, highlighting the need for a convenient and simple way to manufacture such reactors. With this technology, we aim to provide a solution that enhances usability and amplifies the impact of flow chemistry in research.

We have developed a facile flow system to encapsulate photosensitizers (rose bengal) in the silica matrix via photocrosslinking to form redox-responsive silica nanocomposites pf-ReSiNPs with a throughput > one order of magnitude than that of batch synthesis. The organodisulfide synthesis via pf-ReSiNPs effectively addresses the issues of photobleaching, purification, and environmental impact, typically seen using photosensitizers as catalysts in reactions.

The synthesis, characterization and catalytic performance assessment of Pt–Ag and Pt–Ag–Sn bimetallic and trimetallic catalysts supported on KOH-treated γ-Al₂O₃ for the direct propane dehydrogenation reaction have been carried out. The bimetallic catalysts contained 0.3 wt% Pt and 0.5 wt% K, with x = 0.1, 0.3, 0.5, 0.7, 0.9, and 1.1, corresponding to the amount of Ag (0.3Pt–xAg/0.5K–Al₂O₃). The trimetallic catalysts contained 0.3 wt% Pt, 0.7 wt% Sn and 0.5 wt% K, with the same x values for Ag (0.3Pt–xAg–0.7Sn/0.5K–Al₂O₃). The catalytic tests were run on real samples (1.8 mm spheres). The 0.3Pt–0.9Ag–0.7Sn/0.5K–Al₂O₃ composition resulted in the highest yield of propylene (31.4%), highest propylene selectivity (79.3%) and minimum deactivation after 200 min on stream at a gas hourly space velocity of 10 000 cm³ g per catalyst per h at a reaction temperature of 580 °C, comparable to the performance of a DeH-16 commercial catalyst under the same operating conditions. Based on X-ray diffraction, H₂-temperature-programmed reduction, X-ray photoelectron spectroscopy, NH₃-temperature-programmed desorption, electron microscopy, Raman spectroscopy and temperature-programmed oxidation analysis, the performance of the optimum sample was attributed to the synergetic electronic and geometrical effects induced by the formation of Pt–Ag and Pt–Sn alloys and partial coverage of support acidic sites by Ag and Sn clusters.

The kinetics of CO₂ hydrogenation to methanol over a self-developed Cu/ZnO/ZrO₂ (CZZ) catalyst was studied in a wide range of process conditions. Experiments were performed at industrially relevant pressures (30–60 bar) and temperatures (190–250 °C), as well as H₂ to CO₂ ratios between 1 and 6, addressing the use of hydrogen from renewable energy sources and the use of CO₂ as a C1 raw material in Power-to-X technologies. The CZZ catalyst has shown improved performance and higher stability in CO₂ hydrogenation to methanol in comparison to other Cu/ZnO-based catalysts. A mathematical description of the kinetics is crucial to enable model-based design for the industrial implementation of this catalyst. Therefore, a lumped 6-parameter kinetic model was developed to fit the experimental data, resulting in one of the predictive models with the broadest validity range (experimental database of 500 points) for the CZZ system. This new kinetic model is compared to state-of-the-art literature models with more parameters, and our model performs equally well or even better in terms of sensitivity to process parameters and extrapolability.

In light of the prohibitive expense associated with commercially available ZSM-5 catalysts, this investigation aimed to develop a cost-effective alternative exhibiting similar or superior catalytic activity compared to existing benchmarks. Unlike traditional synthesis optimization techniques, which typically employ isolated modification strategies, this study presents an innovative multiple-approach methodology, combining boron incorporation and application of a suspension form ball-milled silicalite-1 seed with adjusting the crystallization parameters, for the production of high-silica H-[B]-ZSM-5 (Si/Al = 200), the factors that have frequently been overlooked in the majority of studies. Through systematic variation of crystallization time and temperature, an integrated synthesis protocol was established, yielding enhanced catalytic performance beyond conventional optimization techniques. Building on extensive prior investigations, H-[B]-ZSM-5 catalysts were synthesized using ball-milled silicalite-1 seeds under various crystallization time and temperature (CtT) conditions (150–170 °C, 18–42 hours). The properties of the samples were characterized through XRD, FE-SEM, BET, NH₃-TPD, and FT-IR analyses. The catalytic performance in the MTP reaction was evaluated in a fixed-bed reactor under severe operating conditions (WHSV = 8 h⁻¹, MeOH/H₂O = 90/10). The optimal CtT conditions (170 °C, 18 h) at a semi-industrial scale (2.5 L) resulted in a H-[B]-ZSM-5 catalyst with high crystallinity, appropriate acidity, and superior catalytic activity (377 g_propylene g_cat⁻¹), accompanied by a reduction in preparation time and energy consumption (18 h vs. 48 h for the conventional catalyst with 10 °C less required temperature). Demonstrating a 47% enhancement in catalytic performance compared to the commercial benchmark (255 g_propylene g_cat⁻¹) under identical reaction conditions, this study establishes a scalable and cost-effective strategy for fabricating high-performance H-[B]-ZSM-5 tailored for industrial MTP applications.

The measurement of pK_a values for water insoluble compounds has long posed a challenge to pharmaceutical development. Previous work has focused on solubilizing such compounds by admixture of water miscible organic solvents followed by potentiometric titrations. Herein, a method to determine aqueous pK_a values in water : dimethylsulfoxide (DMSO) mixtures is presented using automated NMR titrations. The aqueous pK_a was calculated by the Yasuda–Shedlovsky extrapolation. This method offers several advantages notably that sparingly water-soluble compounds can be measured and the location of each pK_a value in the molecular structure can be determined. The method was benchmarked against several well-known pK_a values as well as demonstrated on some heterocyclic building blocks and an FDA approved drug.