Reaction Chemistry & Engineering最新文献

This study presents a straightforward and efficient approach for sensitizing titanium dioxide (TiO₂) through surface complexation. Epichlorohydrin (ECH), as an industrially significant and cost-effective covalent linker, was successfully grafted onto the surface of n-TiO₂-P25. The modified nano-particles were then allowed to react efficiently with ethylene diamine to obtain an immobilized ligand. Subsequently, the prepared nano-particles were treated with solutions of Cu²⁺, Co²⁺, and Ni²⁺ salts to obtain complex-modified photocatalysts. Furthermore, the sensitized nano-particles were applied as effective photocatalysts for the oxidation reaction of benzyl alcohol to benzaldehyde under visible light irradiation, which resulted in short reaction times, high selectivity, and good product yields.

Carbon-supported catalysts have been widely investigated and applied in the catalytic reforming reaction and water–gas shift reaction (WGS) for hydrogen production due to their remarkable stability and superior catalytic activity. However, the effect of hydrophilic–hydrophobic properties of carbon-supported catalysts on catalytic performance remains unclear. Among the Pt-based Mn and K co-modified carbon-supported catalysts developed in this study, the catalyst modified with KMnO₄ exhibited the best performance in methanol steam reforming. The KMnO₄ treatment introduced abundant oxygen-containing functional groups and oxygen vacancies on the carbon support, significantly enhancing its hydrophilicity and water adsorption capacity. This facilitated the activation and dissociation of water molecules, which is the rate-determining step in the WGS reaction. The synergistic effect of improved hydrophilicity and increased oxygen vacancies promoted the overall reaction process, thereby enhancing the catalytic performance. Kinetic analysis of the WGS reaction was conducted between 150 °C and 250 °C, using a power-law model to fit experimental data and calculate apparent activation energies. The PtMnK/AC-Ox catalyst exhibited a significantly lower apparent activation energy of 33.1 kJ mol⁻¹, compared to 54.6 kJ mol⁻¹ for the PtMnK/AC catalyst. This lower activation energy highlights the superior performance of the catalyst for the WGS reaction, particularly in promoting efficient CO conversion.

Metal oxides play a critical role in controlling coke formation, balancing reaction pathways, and enhancing the performance and durability of SAPO-34 catalysts in the methanol-to-olefin (MTO) process. This study focuses on indium oxide (In₂O₃) doping as a novel approach to address coke formation and extend catalyst lifespan. A comprehensive experimental and theoretical methodology was adopted, including detailed catalyst characterization, catalytic performance testing, and molecular dynamics (MD) simulations. Structural analyses confirmed that the CHA framework of SAPO-34 is preserved after doping, with modifications such as reduced crystallite size and increased mesoporosity, which enhance active site accessibility. Physicochemical characterization revealed that nitrogen adsorption showed increased mesopore volume while NH₃-TPD analysis indicated a balanced acid site redistribution in In-doped SAPO-34 (SP-I), collectively enhancing intermediate species stability and catalytic activity. MD simulations provided a mechanistic understanding of the In₂O₃ impact, revealing its ability to suppress coke precursor (CHO-θ) formation, facilitate carbon removal via CO₂ activation and the reverse Boudouard reaction, and enhance reaction reversibility. Catalytic performance testing validated these findings, with SP-I achieving prolonged activity, higher selectivity for light olefins (up to 80.3%), and greater resistance to deactivation compared to pristine SAPO-34. These findings underscore the efficacy of In₂O₃ as a dopant for improving SAPO-34 catalysts and offer insights into the development of sustainable and efficient catalysts for industrial MTO applications.

Since its discovery by Otto Roelen, hydroformylation has attracted extensive attention due to its ability to extend the carbon chain of olefins. Aldehydes, which are converted by the hydroformylation of olefins and syngas (CO/H₂), are not only high-value products, but also intermediates to produce fine chemicals, such as alcohols, esters and amines. The currently used homogeneous catalysts bring about the loss of precious metals and the discharge of phosphorus-containing waste. Therefore, heterogeneous catalysts are developed to simplify the separation process and enhance catalyst recovery. However, the reaction kinetics of heterogeneous hydroformylation, especially the hydroformylation of long-chain olefins, remains unclear. Unlike homogeneous hydroformylation, terminal olefins can be isomerized to internal olefins on heterogeneous catalysts, and can be further converted to different branched aldehydes. Thus, the reaction kinetics of heterogeneous hydroformylation is more complex. In this work, we established a kinetic model for the heterogeneous hydroformylation of long-chain terminal olefins on Rh-based phosphides, using 1-hexene as the model reactant. This kinetic model agrees well with the density functional theory (DFT) results, and can be used to predict the regioselectivity under different reaction conditions. This study reveals the kinetic mechanism of heterogeneous hydroformylation of long-chain terminal olefins, which paves the way for the rational design of heterogeneous catalysts and the theoretical optimization of reaction conditions.

Photochemical transformations under solvent-free conditions provide a gateway to sustainable and green chemistry. In this work, we established a continuous-flow photochemical system with the capability to automatically switch between different capillary microreactors and synthesized quadricyclane from norbornadiene under solvent-free conditions at near-unity conversion and yield in short residence times and low photosensitizer loading. Various parameters, such as photocatalyst loading, capillary size, geometry and configuration, were investigated to optimize the quadricyclane yield and selectivity. We developed an updated kinetic model for this solvent-free reaction system and validated its zero-order kinetics by varying light intensity, initial NBD concentration and photosensitizers. This kinetic model was also validated under double-sided irradiation conditions that involved the presence of a reflecting mirror. Computational fluid dynamics (CFD) simulations were performed to characterize light intensity distribution, and the shape and size of the capillary microreactor were integrated into the reaction rate equation as an auxiliary variable of light intensity to define the effective specific surface area. Moreover, the scope of linear correlations between the effective surface area and apparent rate constants was extended for chip-based glass microreactors. Finally, based on the reaction rate equation, we designed and tested a reactor with high production capacity that can achieve a daily output of 3 kg of quadricyclane.

Many separation techniques, such as chromatography, adsorption, and filtration, are dynamic by nature, with the profiles of chemical species varying over time. This time-dependent behavior makes dynamic flow separation inherently batchwise. Recently, automation has enabled the transformation of these batchwise processes into continuous operations. Automation devices, including separators, detectors/transmitters, control systems, and control devices, can be implemented for either open-loop or closed-loop control. In this minireview, we provide an overview of recent technologies for automated dynamic flow separation systems. Major automated separation techniques, such as liquid–liquid extraction, counter-current chromatography, flash chromatography, and dead-end filtration, are highlighted to illustrate how automation facilitates their transition to continuous operation. Additional examples of integrated reaction–separation systems and self-optimizing platforms for identifying optimal separation conditions are presented as part of the outlook for automated setups. Challenges related to accurate in-line detection, complex sample matrices, and varying physical properties are also addressed.

The sustainable production of carbamates from biomass-derived molecules provides a viable alternative to petrochemical-based production routes. In this work, we reported an efficient catalytic strategy for synthesizing bio-based furfurylmethyl carbamate (FMC) through methoxycarbonylation of furfurylamine with dimethyl carbonate (DMC) under mild conditions. A novel Pb–Ni composite oxide catalyst with high activity and stability was developed, which significantly outperformed conventional monometallic oxide catalysts. Comprehensive characterization revealed that the synergistic interaction between Pb and Ni species constructed composite oxide nanoparticles (about 11.4 nm), with Pb species highly dispersed on the NiO matrix. Consequently, highly defective structure, abundant acid–base dual sites, and a high specific surface area were concurrently formed, which were identified as critical factors for activating both nucleophilic and electrophilic reactants. Significantly, appreciable quantities of furfuryl isocyanate (FIC) were detected, demonstrating the feasibility of a one-pot cascade synthesis of bio-based isocyanates from amines and DMC.

Magnetic core–shell nanostructures (for example, magnetic nanoparticles with a silica shell) are suitable substrates for catalyst stabilization. In this study, silica nanoparticles were obtained from rice husk. Then titanium dioxide was embedded in Fe₃O₄@RHA and the Fe₃O₄@RHA@TiO₂ nanocatalyst was synthesized and identified using VSM, EDX, XRD, FE-SEM, and FT-IR techniques. This nanocatalyst had spherical particles with an average particle size of about 27 nm and good magnetic properties of about 23 emu g⁻¹. In this research, the optimization of the reaction parameters in the preparation of pyran derivatives was done through the multicomponent condensation of aromatic aldehyde, propanedinitrile (malononitrile), and dimedone by using the statistical technique of response surface methodology. Accordingly, the highest efficiency for the synthesis of pyran derivatives was obtained using 0.011 g of the Fe₃O₄@RHA@TiO₂ nanocatalyst at the temperature range of 118–119 degrees in 53 minutes under solvent-free conditions. Titanium dioxide (TiO₂) provides sufficient acidic sites to facilitate the synthesis of pyran derivatives. Due to its low cost, high chemical stability, and non-toxicity, it serves as an excellent component for the fabrication of the Fe₃O₄@RHA@TiO₂ nanocatalyst, making it highly efficient for organic synthesis. This method offers several advantages, including environmental friendliness, simplicity, green chemistry approach, cost-effectiveness, high yield, short reaction time, excellent recyclability, good physical and chemical stability, low catalyst loading requirement, and easy catalyst separation. These features make it a promising strategy for the preparation of pyran derivatives.

Copper foam in its unmodified form was found to be an effective catalyst for the azide–alkyne cycloaddition reaction (CuAAC). The conditions for carrying out the process were selected, the possibility of reusing the catalyst was demonstrated, and a comparative microscopic study of the surface of foamed copper before and after recycles was carried out. A simple synthetic approach has been developed for obtaining PDMS with terminal acetylene groups via the siloxane ring opening mechanism, including the synthesis of a wide range of organosilicon molecules and polymers using the new CuAAC catalyst. The highest catalytic activity of this form of copper is shown in comparison with other published types of catalysts based on pure copper.

Correction for ‘Optimization of low-temperature pyrolysis of dioxins in fly ash from municipal solid waste incineration: adding catalysts and inhibitors’ by Zhuoyu Wen et al., React. Chem. Eng., 2025, 10, 1337–1349, https://doi.org/10.1039/d4re00592a.