Reaction Chemistry & Engineering最新文献

In this paper, we use the concept of the HPLC 3D calibration surface for evaluating reaction performance in micromole scale self-optimizing flow systems. This approach enables comparing the analyte and internal standard relative levels for a wide range of internal standard concentrations. This approach considers fluctuations in response factors and potential nonlinearities in the Beer–Lambert law, which arise from performing HPLC analyses at different concentration ranges. The concept is validated by constructing a calibration surface for a formal [3 + 3] cycloaddition. The robustness of the 3D calibration surface is assessed in an autonomous flow self-optimization in a non-steady-state regime, where a standard 2D calibration curve produces inconsistent results due to variable concentration HPLC injections.

Hydroxyapatite, a mineral from the apatite group, is widely distributed in living organisms and largely studied because of its many properties, including the adsorption of many different substances. In this work, two functionalized nanohydroxyapatites were synthesized starting from their precursors (calcium hydroxide and phosphoric acid) in the presence of Fe(II)/(III) ions and bio-based substances (BBS) isolated from green compost. The products were characterized with different techniques (nitrogen adsorption/desorption, ATR-FTIR, XRD, TGA and ζ-potential measurements) and compared to nanohydroxyapatite obtained without further functionalization. The ability of these materials to remove different water pollutants by adsorption was tested using two organic dyes (crystal violet and methyl orange) and four inorganic ions, Al(III), Cr(III), Ni(II) and As(V), characterized by different ionic charges, dimensions and nature. Moreover, for the same purpose, the antibacterial properties of iron- and iron/BBS-added materials were also tested. The result showed the effective adsorption capability of the materials, in particular with respect to crystal violet, Al(III) and Cr(III), and an enhancement of adsorption capacity with respect to all the adsorbates after functionalization. Finally, the tests towards Staphylococcus aureus and Escherichia coli showed high antimicrobial activity for the bare nanohydroxyapatite samples, whereas the doping with iron and BBS or the high-temperature treatment remarkably impacted this capacity depending on the bacterial strain to eliminate.

The α-hydroxymethylation reactions hold a significant position within the pharmaceutical industry due to their intriguing nature. Despite numerous reported methods, they often entail prolonged reaction times and moderate yields. Moreover, the prevalent use of aqueous formaldehyde restricts the applicability of this chemistry to water-compatible substrates. Gaseous formaldehyde remains largely avoided due to its toxicity, hazards, and requirement for substantial excess. Within this context, paraformaldehyde emerges as a promising alternative for the C1 building block, offering safety and ease of handling. Continuous flow methodology is employed to facilitate the in situ depolymerization of paraformaldehyde under optimized conditions, enabling direct utilization of the released formaldehyde gas. This research explores the use of a paraformaldehyde slurry in continuous flow for α-hydroxymethylation reactions, with methyl vinyl ketone serving as a proof-of-concept substrate. A solid-compatible continuous flow reactor was self-constructed and the hydroxymethylation of methyl vinyl ketone could successfully be optimised, resulting in a STY of 2040 kg h⁻¹ m⁻³.

Ketonization of methyl palmitate to palmitone, a bio-lube precursor, was investigated over noble metal (Pt, Ru, and Pd) incorporated TiO₂ catalysts in the presence of water under an atmospheric H₂/N₂ flow. Methyl palmitate underwent hydrolysis to palmitic acid that ketonized to palmitone over Lewis Ti³⁺ sites. The water co-feeding also suppressed hydrodeoxygenation of methyl palmitate and palmitone cracking leading to high palmitone selectivity. The incorporated metals facilitated H₂ dissociation/spillover on TiO₂ which generated more Lewis Ti³⁺ sites for higher ketonization activity. At 400 °C, 0.5Pd/TiO₂ provided ∼90% conversion with >85% palmitone selectivity and >25 h stability, due to its efficient H₂ dissociation/spillover to continually recover Lewis Ti³⁺ sites. Meanwhile 0.5Pt/TiO₂ promoted excessive hydrodeoxygenation, leading to the deactivation from CO poisoning at the metallic Pt sites. The findings of this study offer a sustainable approach for the selective production of bio-lube precursors from renewable fatty acid methyl esters.

D-Talose, classified as a rare and expensive sugar molecule, is gaining attraction due to its antimicrobial and anti-inflammatory properties. Its production is widely investigated by adopting biological enzymes, which is costly. However, alternative chemical methodologies have reported its formation as a side product and in minor amounts. We report for the first time its significant synthesis using D-galactose (which comprises whey and hemicellulose) by employing a finely tuned molybdenum oxide (MoO₃) solid acid catalyst. The nitric acid treatment of MoO₃ modulated the valency ratio in Mo species (Mo^5+/6+), resulting in an improved Lewis acidity with up to 199 μmol g⁻¹ acidic sites and porosity of up to 48% relative to the pristine MoO₃, attributed to the generated oxygen vacancies. Combined together these have assisted in an augmented D-talose synthesis with as high as 25% yield, 70% selectivity and 98% carbon balance in a water medium under modest reaction conditions (120 °C and 30 min). As proposed, Mo's interaction with D-galactose to form a Mo–sugar complex has influenced the C1–C2 carbon shift to yield D-talose. Furthermore, the typical isotopic labelling NMR characterization has confirmed the Bílik mechanism of C2-galactose epimerization. Overall, the heterogeneous catalytic setup represents a sustainable and feasible method for producing rare sugar for food additive and pharma applications.

Dehydrogenation of cycloalkanes derived from plastic waste presents an attractive approach for hydrogen production and plastic waste valorization. In this study, we developed Pt/Al₂O₃ nanosheet catalysts with tailored support properties by adjusting the calcination temperature. Comprehensive characterization of the catalysts revealed that the support properties, including crystal phase, surface area, acid sites, hydroxyl groups, and defect sites, were modulated by increasing the heat treatment temperature. Consequently, these variations led to differences in Pt particle size, dispersion, and the chemical environment of active sites on the resulting Pt/Al₂O₃ catalysts. The catalytic dehydrogenation of methylcyclohexane exhibited a volcano-like trend in terms of catalytic activities, while the stability of the catalyst showed a concave relationship with increasing calcination temperature. The Pt/Al₂O₃-700 nanosheet catalyst, prepared using a support calcined at 700 °C, exhibited exceptional catalytic activity and stability. It achieved a remarkable hydrogen production rate of 3402 mmol g_Pt⁻¹ min⁻¹ at 350 °C, surpassing most Pt-based catalysts reported in the literature. In addition, this catalyst is also effective for the dehydrogenation of plastic waste derived 1,4-dimethylcyclohexane and 1,3-dimethylcyclohexane. The catalytic activity is strongly influenced by factors such as surface area, Pt particle size, the fraction of surface Pt⁰ species, and the electronic density of surface Pt species. On the other hand, the stability of this catalyst is closely associated with acid sites and hydroxyl groups present on the Al₂O₃ support. The superior performance observed in the Pt/Al₂O₃-700 catalyst can be attributed to its optimal combination of factors including a high surface area, an appropriate particle size of 1.4 nm, a desirable amount of metallic Pt species on the surface, and a moderate electron density of surface Pt species that provide a balance between accessible active sites and toluene desorption. Furthermore, its excellent stability can be attributed to an optimal ratio between acid sites and hydroxyl groups that effectively inhibit coke formation and sintering of Pt nanoparticles. This study emphasizes the importance of regulating a rational support with optimal properties to enhance the catalytic efficiency for cycloalkane dehydrogenation.

In both batch and continuous-flow reactor technology, reproducibility can be challenging for photochemical processes due to setup variability. One major contributor to this issue is the lack of standardized reactor solutions, particularly in academic laboratories where cost is often a prohibitive factor to purchase commercially-available reactor technology. However, advancements in 3D printing technologies and the availability of high-intensity light sources present an opportunity to develop cost-effective laboratory equipment. In this work, we present a diverse set of open-source reactor designs aimed at democratizing photochemistry while reducing the barrier of expensive technology. We introduce three new reactor designs: the UFO reactor for batch reactions, the Uflow reactor for seamless transition to flow processes, and the Fidget reactor for scale-up. After detailing the design principles and rationale behind these configurations, we characterize and evaluate their performance through simulations and experiments. These designs offer a standardized and affordable point of entry for researchers interested in exploring batch and flow photochemistry.

Aluminosilicate zeolites are indispensable in many branches of the chemical industry. Conventionally, they are synthesised by the hydrothermal method from pure sources of SiO₂ and Al₂O₃, whose production is relatively expensive and associated with waste generation. Recently, there has been a growing interest in kaolin as a low-cost alternative natural raw material for zeolite synthesis. In this case, the synthesis route includes kaolin pretreatment steps. For the development of feasible technology, it is necessary to have insight into new and basic synthesis steps and prove that the kaolin-based process is really green and low-cost. These aspects are often silent in research papers, which makes one doubt the idea. We have conducted an extensive literature review to fill these gaps. Collected data has been systematised and put in an easy-to-compare form. Synthesis routes from the literature have been divided into separate steps (grinding and screening, purification, metakaolinisation, alkali fusion, dealumination, hydrothermal process) to elucidate their conditions, theoretical basis and mechanisms, research progress, effect on the overall process, and compliance with economic and environmental requirements. It has turned out that alkali fusion is impracticable, and dealumination is not industrially applicable economically and environmentally (additional SiO₂ is a feasible alternative). The other steps are essential. As a result, we have found that the synthesis of only low-silica zeolites can be considered green and low-cost. So, involved researchers should focus on this direction. Also, the review provides in-depth details about hydrothermal synthesis and may become information support for any researchers studying zeolite synthesis.

With the advent of nanotechnology, the rational engineering of core–shell nanostructure-based catalysts has received significant attention owing to their potential for exhibiting unique properties such as durability, structural flexibility, and porous shell adaptability. In this study, we designed a magnetic core–shell based heterogeneous nanocatalyst [Pd(0)@His-SiO₂/CoFe₂O₄] comprising a histidine functionalized silica supported cobalt ferrite core encapsulated with a Pd(0) nanoparticle shell. Cobalt ferrite was synthesized using a hydrothermal process and modified with silica to obtain homogeneous dispersion and a dense structure as well as to prevent self-agglomeration in the core. Further, the core moiety was functionalized using a non-toxic amine linker, i.e. histidine, which acts as a robust anchor for holding the Pd(0) shell. The catalytic activity of Pd(0)@His-SiO₂/CoFe₂O₄ was evaluated for the oxidative deprotection of oximes and Heck coupling, and excellent results were obtained with high recyclability of the catalyst. Comparative study showed that the Pd(0) nanoparticle shell is the active species and the cobalt ferrite core plays a promotional role. XPS showed the existence of synergism between the core and the shell, suggesting that the electron density was drifted from the cobalt ferrite core towards the Pd(0) shell, which could be the reason for its enhanced catalytic performance. VSM demonstrated high saturation magnetization in both fresh and reused catalysts, which facilitates the separation of the catalyst from the reaction mixture. Thus the proposed approach based on the core–shell nanostructure provides a useful platform for the fabrication of an active metal such as Pd(0) with easy accessibility, excellent activity and convenient recovery.

The field of reaction engineering is in a constant state of evolution, adapting to new technologies and the changing demands of process development on accelerated timelines. Recent advancements in laboratory automation, data-rich experimentation, and machine learning have revolutionized chemical synthesis research, bringing significant enhancements to reaction engineering. To showcase these advantages, this study introduces a machine-assisted process development workflow that uses data-rich experimentation to optimize reaction conditions for drug substance manufacturing. The workflow adopts a scientist-in-the-loop approach, ensuring valuable contributions and informed decision-making throughout the entire procedure. Two case studies are presented: a copper-catalyzed methoxylation of an aryl bromide and the global bromination of primary alcohols in gamma-cyclodextrin. In addition to identifying the optimal reaction conditions, the workflow emphasizes the importance of process knowledge. Data-driven reaction models are constructed for both case studies, showcasing how early-stage reaction data can inform late-stage process characterization and control strategies. The speed and efficiency offered by the machine-assisted approach enabled complete reaction optimization and reaction modeling in one week, approximately. This reaction data, along with other process knowledge obtained throughout development, highlight the future prospects for reaction engineering in drug substance development. As the field continues to embrace innovative technologies and methodologies, there is vast potential for further advancements in reaction engineering practices, leading to more streamlined and efficient process development and accelerating the discovery and optimization of chemical manufacturing processes.