ACS Engineering Au最新文献

Ni/MgAl₂O₄ catalysts with and without K promotion were tested in steam reforming of phenol (SRP), ethanol (SRE), and butanol (SRB), to evaluate the effect of K on catalytic activity and methane formation. The catalysts were prepared by a wet impregnation method and were characterized using nitrogen adsorption, in situ XRD, H₂-TPR, TEM, XPS, and XANES techniques. Catalytic evaluations were performed at temperatures ranging from 250 to 650 °C. DFT calculations were employed to study the hydrogenation of CH_x species on Ni modified by K. The addition of K to the Ni catalysts weakened the NiO-support interaction, causing NiO agglomeration and an increase in Ni particle size. The effect of K on CH₄ formation was strongly influenced by the structure of the reformed molecule, leading to the formation of different CH_x species during the reaction. The introduction of K into the Ni catalyst suppressed formation of CH₄ by hydrogenation of CH, with this effect diminishing for CH₂ and being absent for CH₃ species. DFT calculations of the interaction between CH_x species absorbed in an Ni₄ cluster (CH_x-Ni₄) and K, particularly KOH, indicated that species such as HOKH_xC–Ni₄ were stabilized, with decreased energies of −291.5, −242.4, and −27.7 kJ/mol for CH, CH₂, and CH₃, respectively. The increased heat of adsorption for CH and CH₂ species reduced their hydrogenation activity toward methane.

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.