Reaction Chemistry & Engineering最新文献

Scaling-up of continuous-flow photocatalytic reactions is of great importance for widespread implementation in the industry. Despite several successful demonstrations for the homogeneous photochemistry, much less progress has been made on the heterogeneous photochemistry. Herein, we report the scale-up of slurry Taylor flow photosynthesis of azo-compounds (azoxybenzene and azobenzene) from nitrobenzene. Sizing-up strategy was applied to boost the throughput of the reactor, in combination with a high-power LED light source to provide effective irradiation. The effects of various operating parameters were investigated to achieve the best synergy of multi-phase flow, interphase transfer and photon transfer process. The scaled-up slurry Taylor flow process was finally validated on a 50 gram scale for azo-compounds, which was 22 times higher than the recently reported value. Furthermore, a correlation was proposed to predict the overall photocatalytic productivity during the scale-up. This work demonstrates a cost-effective and efficient scale-up methodology for the heterogeneous photosynthesis of azo-compounds.

We present an ultrasonic microreactor for synthesising poly(lactic-co-glycolic) acid (PLGA) nanoparticles through the emulsion-solvent evaporation technique. Monodispersed PLGA nanoparticles (polydispersity index (PDI) < 0.3) in the size range of 20–300 nm are desired for biomedical applications. An ultrasonic microreactor with rough microchannels is utilised for the synthesis of PLGA nanoparticles. Through a comprehensive parametric investigation, we identify the optimal ultrasonic power, PLGA concentration, and aqueous-to-organic phase flow rate ratio, to minimise the size of the PLGA nanoparticles. By varying the operational parameters and the concentration of PLGA, the mean hydrodynamic diameter of the monodispersed PLGA nanoparticles (PDI of 0.1–0.2) can be varied within the range of 115–150 nm. Furthermore, the successful encapsulation of a hydrophobic dye, Nile Red, is demonstrated, where a dye loading (DL) of up to 0.34% is achieved, which is in agreement with the previously reported loading of Nile Red. The in vitro release study performed for the Nile Red-loaded PLGA nanoparticles (NR-PLGA) reveals a triphasic release profile of Nile Red. In summary, this work highlights the potential of the ultrasonic microreactor as a versatile platform for the synthesis of PLGA nanoparticles suitable for biomedical applications.

The development of efficient and selective catalysts for the oxidative dehydrogenation (ODH) of n-butane to produce butenes and butadiene with high performance has been the subject of intense research in recent years. Herein, we report a novel approach for predicting the performance of mixed metal oxides supported on Al₂O₃ for ODH using artificial intelligence (AI). Specifically, artificial neural networks (ANNs), support vector regression with nu parameter (NuSVR), extreme gradient boosting regressor (XGBR), and gradient boosting regression (GBR) machine learning algorithms were trained with a dataset of consistent experimental data to build the chemometric models using reaction temperatures, feed ratios of O₂ : C₄, and catalyst composition as input features to predict the yield of ODH products as a measure of catalyst performance. The results show that the AI-based models can proficiently predict the performance of mixed metal oxide catalysts for ODH of n-butane, with a prediction accuracy of 82%, 89%, 92%, and 94% using ANN, NuSVR, XGBR, and GBR models, respectively. Feature importance analyses also revealed that the amount of Ni loading in the catalyst(s) has the greatest influence on the yield of butenes and butadiene. These findings demonstrate that accurate predictions of catalyst performance can be made even with simple and easily accessible features, thus paving the way for the development and discovery of more efficient catalysts.

Cascade reactions are an important synthetic strategy for efficient and rapid access to molecular complexity in chemical synthesis. In this study, the vapor-phase cascade heterocyclization was further developed, starting with the coupling of biomass-derived lactic acid with aniline to yield high-value quinoline derivatives. Mesoporous Hβ zeolite was employed as an eco-friendly heterogeneous catalyst, which was prepared via zeolitic dissolution–recrystallization treatment to generate abundant mesopore volume. The assessment of the catalyst activity and stability confirmed that the presence of mesopores within the zeolite significantly improved the life of the catalyst. This enhancement was primarily attributed to the facilitated diffusion of the bulky quinoline products through the pore channels of the mesoporous Hβ zeolite, which mitigates the formation of the coke deposits. Notably, the deactivation of the catalyst was reversible, and its catalytic activity could be almost entirely restored through simple calcination in air to eliminate the coking. Furthermore, this work elucidated the plausible mechanisms relating to the generation of diverse quinoline derivatives and byproducts from the reaction between lactic acid and aniline, which contribute to a better understanding of the complex reaction pathways involved in this cascade synthetic approach.

Olefin–paraffin separation is a critical yet energy-intensive process in the chemical industry, accounting for over 250 trillion BTU per year of global energy consumption. This work explores the use of a redox-active nickel maleonitriledithiolate complex for olefin–paraffin separations. Key performance factors, namely the electrochemical oxidation of the complex and olefin capture utilization fraction, were systematically quantified. Electrochemical studies revealed near-complete oxidation of Ni(II) to Ni(IV) species, suggesting that the electrochemical oxidation step is not a limiting factor in olefin capture. The utilization fraction was found to be strongly dependent on the complexation equilibrium behavior between olefin-bound and unbound states of the complex. Time-resolved kinetic measurements unveiled a sluggish complexation rate, requiring over 36 hours to approach equilibrium. These insights highlight the importance of driving the complexation equilibrium and improving the kinetics to enhance the performance of Ni-based electrochemical swing absorbers for energy-efficient olefin–paraffin separations. The findings lay the groundwork for future optimization strategies and industrial implementation of this sustainable separation technology.

The thermal behaviour of waste tractor tyre tread was investigated using 5-, 10-, 15- and 20 mm cubes and video recording of the process – an experimental approach for which no precedent could be found in the literature. Pyrolysis and gasification under CO₂ flow in the range of 400 °C to 1000 °C were studied using a pre-heated tube furnace under near-isothermal reaction conditions. The video-graphic timeline and thermal history observations were used to correlate the results with first-order heat-transfer calculations and TGA-derived kinetics published previously. For pyrolysis, heat-transfer becomes the rate limiting step in the region 800–900 °C and above. Experimental evidence shows that the full pyrolysis time may be estimated from the algebraic sum of the local kinetic component and a heat-transfer component. The pressure build-up due to the release of gaseous products results in shattering of the solid into sub-millimetre char fragments. The kinetics of the reverse-Boudouard reaction can be described by a standard gas–solid shrinking particle model; however the character of the charred remains complicates this. Mass transfer limits are predicted only to become significant above 1200 °C, for a well-characterised char surface.

In this work, a simple reactor model for evaluating the intrinsic rate constant of a photocyclization reaction is presented. The photoreaction was performed in a standardized capillary microreactor that ensures isothermal and uniform irradiation conditions. The effects of residence time and incident light intensity on the reaction performance were studied, and a reaction kinetic model was established based on a plug flow assumption. The reaction order with respect to the F-tagged amide precursor was found to be 2 in the photochemical transformation, and apparent rate constants under various light intensities were obtained. Comprehensive mass transport diagnostics were performed by using dimensionless numbers based on the established effective reaction kinetics. The intrinsic rate constant of the photoreaction was extracted from the experimental data using a simplified reactor model, in which a parameter representing the photon absorption fraction of the photocatalyst was introduced. Moreover, the proposed reactor model gives a general overview for improving the space–time yield of photochemical processes in microreactors.

The current global energy scenario calls for the urgent replacement of fossil fuels for alternative, environmentally affordable, abundant and cheap energy sources. Among the different options available, MOlecular Solar Thermal (MOST) systems have emerged in the last few years as a promising alternative. While this technology has already shown great potential under lab conditions, some difficulties remain to be dealt with when it comes to its application in real devices. In this minireview, we briefly summarize the basic concepts of MOST systems and we focus on the critical problems yet to be solved to turn this technology into a real alternative for energy generation and storage.