The development of simple and scalable synthesis methods that yield new materials or unique morphologies [1, 2] opens up new possibilities for customizing surface and bulk properties for energy storage and conversion applications. Layered perovskite tantalates are a particularly attractive group of oxide materials, exhibiting interesting optical, piezoelectric, and/or photocatalytic properties. Herein, a rapid molten salt synthesis route was used to synthesize RbLaTa₂O₇ layered perovskite with improved structural and electronic properties. Different samples were prepared by using a stoichiometric ratio of Rb: La: Ta = 1:1:2, a 10-fold molar excess of molten RbCl at 1200 °C, and various reaction times (e.g., 4 h and 7 h). The effects of the flux-to-tantalate precursor ratio, the purity of the solids, and the synthesis duration on the particle growth of RbLaTa₂O₇ were examined and compared with the reference sample prepared through solid state reaction (SSR). XRD patterns revealed that the solid synthesized with molten RbCl in a short reaction time (4 h) primarily formed RbLaTa₂O₇, with only small amounts of LaTaO₄ impurities and unreacted RbCl. Increasing the reaction time to 7 h resulted in a pure RbLaTa₂O₇ phase with a tetragonal structure. The solid obtained by molten RbCl during 4 h led to well-defined platelet and rod morphologies, while a longer reaction time (7h) led to larger platelets with smooth surfaces. The molten salt approach led to products with larger specific surface areas and smaller band gaps than the reference. The CO₂-TPD profiles of molten salt-based perovskites exhibited a prominent peak in the 550 – 650 °C range, attributed to the presence of strongly basic sites. This study emphasizes the benefits of the molten salt-assisted method, which not only shortens the synthesis duration but also yields high-purity layered materials with well-controlled structural and electronic properties.

Among sustainable alternative solutions, catalysis represents a keystone in chemical processes, offering numerous benefits, including energy and time management, resource management and environmental sustainability. Heterogeneous and homogeneous catalyses are widely used as sustainable alternatives for various processes in diverse fields of the chemical industry ¹. Among these processes, catalytic chlorination represents a convenient way to synthesize allylic and vinylic chloride derivatives ². These derivatives are highly valuable organic compounds that serve as building blocks in the synthesis of more complex atomic arrangements ³. The present work focuses on the valorization of industrial iron-based waste material via catalytic chlorination. First, a characterization study of the waste material was carried out using different advanced techniques. Thereafter, the catalytic activity was investigated, for the first time, using magnetically recoverable iron-based waste material as an efficient heterogeneous catalyst in a selective catalytic allylic chlorination reaction. The optimization of the catalytic reaction was carried out with carvone in the presence of sodium dichloroisocyanurate (NaDCC) as an eco-friendly, highly stable and freely available chlorine (FAC) agent. The optimized conditions were used to study other functionalized terpenic olefins to obtain high value-added allylic chlorides in good to excellent yields.

References:

[1] C. Vogt and B. M. Weckhuysen, Nature Reviews Chemistry, 6, 89–111, 2022.

[2] S. A. Labyad, A. A. Mekkaoui, M. Laayati, H. Orfi, L. El Firdoussi, S. El Houssame, RSC Adv., 13, 30548–30561, 2023.

[3] A. A. Mekkaoui, M. Laayati, H. Orfi, L. El Firdoussi, and S. El Houssame, Journal of Chemistry, 2020, 1–8, 2020.

The hydrosilylation of ketones is an essential reaction in organic synthesis, with significant applications in the pharmaceutical and specialty chemical industries. This study explores the use of copper oxide (CuO) nanoparticles, synthesized via thermal decomposition in the absence of ligands, as catalysts for this reaction. ¹ CuO nanoparticles were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), and scanning electron microscopy (SEM), confirming their high purity and well-defined structural and morphological properties. ² Their catalytic activity was evaluated using dimethylphenylsilane as the hydrosilylation agent on various ketone substrates. The reaction products were analyzed by nuclear magnetic resonance (NMR) spectroscopy, including ¹H, ¹³C, and ²⁹Si NMR, to ensure precise structural identification. These results highlight the potential of CuO nanoparticles as efficient, durable, and cost-effective catalysts for hydrosilylation. Ongoing studies aim to optimize reaction conditions and evaluate the recyclability of the catalyst, underscoring its relevance for industrial applications and green chemistry practices.³

References

• Singh J, Kaur G, Rawat M. A Brief Review on Synthesis and Characterization of Copper Oxide Nanoparticles and its Applications. J Bioelectron Nanotechnol 2016 ;1(1) : 9.
• Darezereshki / JMM 47 (1) B (2011) 73 – 78, DOI :10.2298/JMMB1101073D
• Kantam, M. L., Laha, S., Yadav, J., Likhar, P. R., Sreedhar, B., & Choudary, B. M. (2007). Asymmetric Hydrosilylation of Prochiral Ketones Catalyzed by Nanocrystalline Copper (II) Oxide. Advanced Synthesis & Catalysis, 349(10), 1797–1802.

The thermocatalytic CO₂ hydrogenation reaction is a high-energy-consuming process, and for this reason, it is important to develop new hybrid catalytic approaches, such as photo-thermocatalysis, in order to increase the efficency of this process and overcome its main disadvantages. The aim of this research is to synthesize a set of new Layer Double Hydroxide-derived composite materials to be used as photo-thermocatalysts to perform in the CO₂ methanation reaction. LDHs are in fact an excellent candidate for the photo-thermocatalytic conversion of CO₂. This is due to their great adsorption properties, their surface basicity and the presence of optical band-gaps that can be modulated due to the possibility of interposing different metal ions within the LDH structure or on its surface. In this study, ternary LDHs were synthesized by co-precipitation and hydrothermal treatment, inserting different metal species such as Ni or Co as catalytic active species, Mg, Zn, or Zr as photocatalytic active species, and Al or Ce for the structural role. The LDHs were then modified with SiC or different phyllosilicates such as Halloysite, Bentonite, Sepiolite, and Montmorillonite to obtain new materials able to absorb a larger portion of the solar emission spectrum and to increase the conversion of solar radiation into thermal energy, favouring the methanation reaction through a photo-assisted thermocatalytic mechanism. Catalytic tests showed that SiC significantly increased the photo-thermocatalytic activity of LDHs, enhancing yield and selectivity in methane at lower temperatures compared to thermocatalytic tests, while the samples modified with phyllosilicate are currently under investigation. Future objectives of this work include exploring different compositions for the synthesis of LDH–phyllosilicates and the synthesis of LDH–MXene composites to take advantage of the LSPR effect of MXenes so as to improve the photo-driven thermocatalytic activity of the materials.

Introduction

The transition to a greener and more renewable productive model has been raised as a main challenge for science during recent decades. Reducingdependence on petrol fuels and finding new sources for industrial chemical precursors requires brand-new approaches with a lower or, ideally, no carbon footprint. In this context, photocatalysis has emerged as a greatly encouraging solution. Among the most promising heterogeneous photocatalysts, we can find reticular organic materials such as Covalent Organic Frameworks (COFs) and related amorphous materials, such as Covalent Triazine Frameworks (CTFs) or Conjugated Microporous Polymers (CMPs).

Results

A variety of conjugated microporous polymers (CMPs) and covalent triazine frameworks (CTFs) have been recently synthesized in our laboratory. A particular family of such materials is that containing quinoline fragments acting as photocatalytic moieties. Predetermined series of CMPs and CTFs with similar structural and photophysical properties show divergent photocatalytic activities for environmentally relevant reactions such as hydrogen evolution and the oxidation of furfural derivatives. Different catalytic behaviors arise from differences in their electronic structures, which were analyzed from both experimental and theoretical studies.

Conclusions

The esults obtained suggest that nitrogen doping and electron-donating groups play a critical role in tuning the photocatalytic properties of organic materials, offering a powerful strategy for designing building blocks in heterogeneous organic photocatalysts. This underscores the versatility and broad applicability of nitrogen-enriched materials for various photocatalytic processes, from oxidation reactions to hydrogen generation.

This study presents the design and fabrication of a laboratory-scale bubble column fermenter specifically developed for fermentation studies employing immobilized enzymes. Constructed from stainless steel for durability and sterility, the fermenter incorporates advanced features to ensure precision and reliability. An air supply system, powered by a compressor, ensures consistent aeration, while precise temperature control is achieved through a jacketed reactor connected to a circulating water bath. These features are critical for maintaining optimal conditions for enzymatic reactions. To optimize the fermenter’s functionality, rate and design equations for bubble column fermenters were employed in calculating the operational parameters. The bioreactor boasts a working volume of 65 mL, a height of 80 mm, and an internal diameter of 10 mm, tailored for small-scale experimental setups. A custom-designed sparger with five evenly spaced 0.5 mm holes and a 0.2 mm spacing ensures uniform bubble formation. The generated bubble sizes, ranging from 0.5 mm to 3.93 mm, exhibited a controlled rise velocity of 0.1 cm/s, facilitating effective gas–liquid interactions critical for fermentation efficiency. Designed for a maximum operating temperature of 38°C, the system incorporates a compressor with a power rating of 0.152 kW, ensuring robust performance. Performance testing validated the fermenter’s utility, achieving a maximum ethanol production efficiency of 50.58%. This result underscores the system’s reliability for enzyme-mediated biochemical processes. The fabricated bubble column fermenter demonstrates significant potential as a versatile and efficient tool for both research and industrial applications in bioprocess engineering. By combining precision engineering with practical functionality, this study provides a valuable platform for advancing enzyme-based fermentation technologies, offering insights into scalable designs for broader biochemical and biotechnological applications.

Usually, in the presence of base active sites, the Claisen–Schmidt condensation reaction between benzaldehyde and cyclohexanone leads to the formation of a di-condensed compound, e.g. 2,6-dibenzylidene cyclohexanone^[1]. The optimization of layered double hydroxide-type (LDH) catalysts by means of the partial substitution of Mg with Cu(II) cations leads to a shift in the selectivity towards the mono-condensed product (e.g. 2-benzylidene cyclohexanone). Six Mg_0.375Cu_0.375Al_0.125 LDH materials were prepared from metal chlorides, nitrates and sulfate as precursors by applying two methods, co-precipitation and the mechano-chemical method, while using either the usual inorganic alkalis or a non-traditionally organic one for pH adjustment. The influence of the memory effect on the physico-structural properties of the considered materials was also investigated by hydrating them with bi-distilled water of the mixed oxides that were obtained by means of the calcination of the parent LDH at 460 °C for 18 h under an air atmosphere. The characterization of solids with different techniques (e.g. XRD, DRIFT, ATR, DR-UV-Vis, BET and basicity determination using irreversible adsorption organic molecules with different pK_a values) revealed that the pure layered structure was contaminated with different amounts of copper hydroxide depending on the metal salt precursors. The memory effect did not lead to a total reintegration of the Cu(II) in the octahedral positions of the layered structure, since part of it remained as stable CuO, obtained in the calcination step. The basicity and the catalytic activities for Claisen–Schmidt condensation showed similar variation trends, e.g., reconstructed LDH > parent LDH > mixed oxides. The copper's presence in the LDH structure decreased the basicity, leading to a higher selectivity to the mono-condensed product than the one that was obtained with unmodified MgAl-LDH. The copper-containing catalysts also promoted the transformation of benzaldehyde into benzoic acid as a side reaction.

[1] B. Cojocaru, B.C. Jurca, R. Zavoianu, R. Bîrjega, V.I. Parvulescu, O.D. Pavel, Catalysis Communications 170 (2022) 106485

Due to its acidity and high ionization energy and the strength of the C-H bond (439 kJmol^-1), there are challenges with the chemical utilization of CH₄. The low volumetric energy density of methane makes its transportation and storage difficult; this results in the flaring of methane. Instead of flaring, methane can be converted to a valuable product such as methanol, which is not only useful for transportation but can also be used as a valuable feedstock for other chemical syntheses.

In this study, we developed a gas phase reaction that involves passing CH₄, O₂ and H₂O over a superhydrophobic modified NiO-Ce/Al₂O₃ catalyst to selectively produce methanol. The catalyst was prepared by means of co-impregnation of nickel and cerium metal salts on Al₂O₃, followed by calcination at 450^oC and superhydrophobic modification with perfluoro alkyl. Different reaction conditions such as hydrophobic modification, steam flow rate, time on stream and methane-to-oxygen ratio were explored to determine the optimum conditions for higher productivity. The modified catalyst has a methanol productivity of 298 µmol.g^-1_Ni.h^-1, while the hydrophilic unmodified NiO-Ce/Al₂O₃ has a lower productivity of 35 µmol.g^-1_Ni.h^-1 after a 10 hr run in a tubular fixed-bed reactor. Increasing the reaction temperature and lowering the gas flow rate while increasing the CH₄:O₂ ratio enhanced the productivity of CH₃OH.

NiO-Ce/Al₂O₃ shows good activity towards direct methane-to-methanol conversion. It is evident that hydrophobic modification improves the activity and stability of this catalyst.

The aim of this research is to synthesize and thoroughly characterize a ceramic material with the chemical formula FeSb₂O₆. The iron antimony oxide, FeSb₂O₆, crystallizes in a trirutile-type structure, classified under the tetragonal space group P42/mnm. Its crystal structure is composed of octahedral units, where FeO₆ and SbO₆ octahedra share edges in an alternating sequence of FeO₆–SbO₆–SbO₆ along the [001] axis. Additionally, vertex-sharing octahedra are observed within the (001) planes, contributing to its distinct structural features.

FeSb₂O₆ is recognized as an n-type semiconductor. Recently, this compound has attracted significant interest due to its potential applications in photocatalysis, as well as in gas sensors, for detecting nitrogen oxides (NOₓ) and hydrogen sulfide (H₂S). Furthermore, it shows promise as a dielectric material for microwave devices and is considered a viable alternative to commercial materials in lithium-ion batteries (LIBs) due to its advanced lithium storage properties and high specific capacity.

In this study, the sample was synthesized using the traditional ceramic method. Stoichiometric amounts of FeO and Sb₂O₃ were mixed and calcined at 950 °C for 24 hours in an electric furnace under an air atmosphere. The synthesized material was characterized using various techniques, including powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR).

This study investigates the catalytic oxidation of phenol using an iron-supported purified natural illite clay catalyst, focusing on optimizing operational parameters and elucidating the degradation mechanism to achieve high efficiency and minimize environmental impact. The effects of pH (2–10), initial phenol concentration (20–100 mg/L), temperature (30–90°C), iron content (3–7%), catalyst dosage (0.5–1.5 g/L), and H₂O₂ concentration (4.75–12 mM) were systematically studied. Optimal conditions were determined at pH 3, a phenol concentration of 50 mg/L, 50°C, 5% iron content, a catalyst dosage of 1 g/L, and 8.7 mM H₂O₂, enhancing hydroxyl radical formation and reaction kinetics. Under these conditions, the catalyst achieved a 99% degradation rate for phenols and an 83% reduction in chemical oxygen demand (COD), with minimal iron leaching. The identification of intermediate by-products using HPLC enabled the construction of a detailed stepwise degradation mechanism, shedding light on the oxidative pathways and confirming the effectiveness of the process. The purified illite catalyst demonstrated excellent stability and reusability over multiple cycles, maintaining performance with minimal activity loss. Comprehensive material characterization (XRD, TGA, BET, SEM, FTIR, and laser granulometry) confirmed the structural and morphological integrity of the catalyst and provided insights into its active sites. This study underscores the potential of iron-impregnated purified natural clays as sustainable, cost-effective catalysts for treating phenolic pollutants in wastewater.