ACS Engineering Au最新文献

The model-based scale-up of a homogeneously catalyzed Sonogashira coupling reaction is performed in a 3D printed metal continuous-flow reactor. The reaction is monitored with inline Raman spectroscopy with a low calibration effort, applying a multivariate curve resolution approach. Manufacturing conditions result in a space time yield of 412 kg m^–3 h^–1 and a productivity rate of 0.078 kg h^–1.

Polyurethane foams (PUF) are essential materials known for their exceptional chemical and mechanical properties, making them ubiquitous in a wide range of applications. Conventionally, PUF are produced through polyaddition reactions between polyols and polyisocyanates at room temperature, where water plays a critical role in this process by hydrolyzing the isocyanates, leading to the release of carbon dioxide (CO₂) as a blowing agent. In recent years, isocyanates have raised significant concerns in industries and consumers due to their high toxicity. Therefore, driving the need to explore alternative synthesis routes for PUF that do not involve the use of isocyanates. Nonisocyanate polyurethane foams (NIPUF) derived from the aminolysis of cyclic carbonates have emerged as the most promising solution to replace the conventional method of producing PUF. Despite this, the challenging aspect lies in identifying a suitable foaming strategy for NIPUF that can satisfy both sustainability and performance requirements. In view of this, the first part of this review focuses on the background, chemistry, and challenges of PUF. In the second part, the chemistry of NIPUF and the various foaming strategies used to prepare them are discussed and analyzed. Finally, the outlook and future research focus areas for NIPUF are outlined.

This work investigates the kinetics of the enantioselective transesterification of ethyl butyrate and (R)-2-pentanol in a solventless medium biocatalyzed by Novozym435, an immobilized Candida antarctica Lipase B. A reaction-diffusion reversible Ping-Pong bi-bi model was developed to represent the reaction rate with the additional estimation of the internal mass transfer using an orthogonal collocations method. A total of 18 experiments (774 data points) were realized in the SpinChem Vessel V2 batch reactor at a constant stirring speed of 400 rpm, varying temperatures (30–60 °C), component initial molar fraction (0.2–0.8), catalyst ratio (1–4% wt), and size fraction (200–1000 μm). Kinetics data were fitted using the model with a mean average percentage error of 3.45%, the 10 optimized kinetic parameters being coherent with the expected behavior of the Ping-Pong Michaelis–Menten mechanisms. Values for the effectiveness factor η for intraparticle mass transfer diffusion vary between 0.37 and 1, confirming the necessity to include mass transfer into kinetic modeling in our case.

In this study, the synthesis and application of rare earth tungstates Ce₄W₉O₃₃ (CeW), Sm₂(WO₄)₃ (SmW), and Gd₂(WO₄)₃ (GdW) for the electrochemical detection of 4-nitrotoluene were investigated. The nanoparticles were synthesized using a deep eutectic solvent (DES)-assisted solvothermal method, a technique known for its precision and reproducibility. It resulted in materials with high thermal stability, excellent catalytic activity, and enhanced electronic properties. The synthesized CeW, SmW, and GdW were employed to modify screen-printed carbon electrodes (SPCEs), a widely used and well-established method in the field, which were then characterized using various techniques. Electrochemical performance was evaluated through cyclic voltammetry, differential pulse voltammetry, and amperometric (i-t) responses, all of which are standard methods in electrochemical analysis. The modified electrodes exhibited superior electrochemical behavior compared to bare SPCEs, with CeW/SPCE showing the highest reduction peak current for 4-nitrotoluene detection. The linear range for detection was found to be for DPV= 0.01–576 μM and for i-t = 0.001–306 μM, with a limit of detection of DPV = 0.034 μM and i-t = 0.012 μM. The sensors demonstrated excellent selectivity, reproducibility, and stability, with minimal interference from other substances commonly found in environmental samples. Real-world applicability was confirmed by testing the modified electrodes in the river and tap water samples spiked with 4-nitrotoluene. The CeW/SPCE sensor showed rapid and sensitive response in both matrices, highlighting its potential for environmental monitoring. The robust performance of CeW, SmW, and GdW-modified electrodes underscores their suitability for practical applications in detecting nitrophenols, contributing to effective environmental monitoring and pollution control. This research has the potential to inspire further advancements in the field of electrochemical detection and environmental monitoring.

Understanding the spreading dynamics of compound droplets is crucial for emerging applications like micromixers, microreactors, and mechano-responsive artificial cells. Integrating magnetic fields expands the potential of these technologies in soft robotics and medical imaging. Despite extensive research on individual droplets, the magnetowetting processes of compound droplets on hydrophobic surfaces remain underexplored. To address this gap, we use a finite element framework to conduct numerical simulations, focusing on the spreading behavior of compound droplets on hydrophobic surfaces under magnetic fields. Our approach is validated against experimental and theoretical paradigms from existing single-droplet studies. Additionally, we verify our model for the temporal evolution of compound droplet wetting in the absence of magnetic fields against existing numerical results. This research systematically explores wetting behaviors and shell fluid disintegration by manipulating key parameters, including magnetic field intensity and inner-to-outer droplet size ratios. These findings have significant implications for enhancing magnetically controlled soft fluidic systems, particularly in digital microfluidics and drug development.

We report effects of SO₂ and SO₃ exposure on ammonium nitrate (AN) and N₂O formation in Cu-CHA used for NH₃–SCR. First-principles calculations and several characterizations (ICP, BET, XRD, UV–vis–DRS) were applied to characterize the Cu-CHA material and speciation of sulfur species. The first-principles calculations demonstrate that the SO₂ exposure results in both (bi)sulfite and (bi)sulfate whereas the SO₃ exposure yields only (bi)sulfate. Furthermore, SOx adsorption on framework-bound dicopper species is shown to be favored with respect to adsorption onto framework-bound monocopper species. Temperature-programmed reduction with H₂ shows two clear reduction states and larger sulfur uptake for the SO₃-exposed Cu-CHA compared to the SO₂-exposed counterpart. Temperature-programmed desorption of formed ammonium nitrate (AN) highlights a significant decrease in nitrate storage due to sulfur species interacting with copper sites in the form of ammonium/copper (bi)bisulfite/sulfate. Especially, highly stable sulfur species from SO₃ exposure influence the NO₂–SCR chemistry by decreasing the N₂O selectivity during NH₃–SCR whereas an increased N₂O selectivity was observed for the SO₂-exposed Cu-CHA sample. This study provides fundamental insights into how SO₂ and SO₃ affect the N₂O formation during ammonium nitrate decomposition in NH₃–SCR applications, which is a very important topic for practical applications.