Ruthenium Supported on Ionically Cross-linked Chitosan-Carrageenan Hybrid MnFe2O4 Catalysts for 4-Nitrophenol Reduction

Palladium Nanoparticles on Chitosan-Coated Superparamagnetic Manganese Ferrite: A Biocompatible Heterogeneous Catalyst for Nitroarene Reduction and Allyl Carbamate Deprotection

Although metallic nanocatalysts such as palladium nanoparticles (Pd NPs) are known to possess higher catalytic activity due to their large surface-to-volume ratio, however, in nanosize greatly reducing their activity due to aggregation. To overcome this challenge, superparamagnetic chitosan-coated manganese ferrite was successfully prepared and used as a support for the immobilization of palladium nanoparticles to overcome the above-mentioned challenge. The Pd-Chit@MnFe₂O₄ catalyst exhibited high catalytic activity in 4-nitrophenol and 4-nitroaniline reductions, with respective turnover frequencies of 357.1 min^-1 and 571.4 min^-1, respectively. The catalyst can also be recovered easily by magnetic separation after each reaction. Additionally, the Pd-Chit@MnFe₂O₄ catalyst performed well in the reductive deprotection of allyl carbamate. Coating the catalyst with chitosan reduced the Pd leaching and its cytotoxicity. Therefore, the catalytic activity of Pd-Chit@MnFe₂O₄ was proven to be unrestricted in biology conditions.

Progress and prospective of heterogeneous catalysts for H2O2 production via anthraquinone process

This paper reviews the improvement in the field of catalytic hydrogenation of 2-ethylanthraquinone to 2-ethylanthrahydroquinone for the successful production of hydrogen peroxide. Hydrogen peroxide is being used in almost all industrial areas, particularly in the chemical industry and in environmental protection, as the most promising oxidant for cleaner and environmentally safer processes. A variety of hydrogenation catalysts have been introduced for hydrogenation of 2-ethylanthraquinone in the production of hydrogen peroxide via anthraquinone (AQ) process. The aim of the present study is to describe the catalysts used in the hydrogenation of 2-ethylanthraquinone and the reaction mechanism involved with different catalytic systems. The hydrogenation of 2-ethylanthraquinone using metals, alloy, bimetallic composite, and supported metal catalyst with the structural modifications has been incorporated for the production of hydrogen peroxide. The comprehensive comparison reveals that the supported metal catalysts required lesser catalyst amount, produced lower AQ decay, and provided higher catalyst activity and selectivity. Furthermore, the replacement of conventional catalysts by metal and metal alloy-supported catalyst rises as a hydrogenation trend, enhancing by several times the catalytic performance.

Facile synthesis of green and efficient magnetic nanocomposites of carrageenan/copper for the reduction of nitrophenol derivatives

A green and facile method for preparation of Kappa-Carrageenan or Iota-Carrageenan grafted N,N'-methylenebisacrylamide/Fe₃O₄/Cu nanoparticles (κC-g-MBA/MNPs/Cu and ιC-g-MBA/MNPs/Cu) catalysts was developed to place copper on a magnetic carrageenan surface. The structure and morphology of the prepared catalysts were identified using FT-IR, XRD, BET, VSM, TGA, EDX, mapping, FE-SEM, TEM, and ICP-OES analyses. The catalytic activity of the catalysts was investigated to reduce 4-nitrophenol, 2-nitrophenol, 3-nitroaniline, and 4-nitroaniline compounds using the UV-Vis spectrum. To reduce 4-nitrophenol using κC-g-MBA/MNPs/Cu and ιC-g-MBA/MNPs/Cu, the rate constants (K_app) obtained were 0.37 and 0.25 min^-1, and the activity factors (k') were 134 and 193 s^-1 g^-1, respectively. The catalysts had a good performance in reducing the nitrophenol compounds and due to the magnetic properties of the catalysts, they could easily be separated and used multiple times.

Hyaluronic acid coated spinel ferrite for combination of chemo and photodynamic therapy: Green synthesis, characterization, and in vitro and in vivo biocompatibility study

In this project, different photosensitizers were prepared using different ratios of nickel, manganese, and iron. Then, multiple analysis were performed to evaluate their efficiency, and the most suitable one was used to be coated by hyaluronic acid to improve the nano-platform's biocompatibility and target ability. Moreover, another chemical targeting agent (riboflavin) was used to further improve the target ability of the prepared nano-platform. Different spectroscopies and thermal analysis were used to determine the physical and chemical characteristics of the prepared nano-platform. Also, in order to determine the biocompatibility of the nano-platform, in vitro and in vivo tests such as blood hemolysis, blood aggregation and lethal dose were performed. Then, an anti-cancer agent (curcumin) was loaded on the selected nano-platform to makes us able utilizing the synergistic effect of chemotherapy and photodynamic therapy simultaneously. Finally, the cell cytotoxicity results showed that the prepared nano-platform had a great anti-cancer potential which can make it a great candidate as a dual photo and chemo therapy agent for treatment of breast cancers.

Development of High-Efficiency, Magnetically Separable Palladium-Decorated Manganese-Ferrite Catalyst for Nitrobenzene Hydrogenation

Aniline (AN) is one of the most important compounds in the chemical industry and is prepared by the catalytic hydrogenation of nitrobenzene (NB). The development of novel, multifunctional catalysts which are easily recoverable from the reaction mixture is, therefore, of paramount importance. Compared to conventional filtration, magnetic separation is favored because it is cheaper and more facile. For satisfying these requirements, we developed manganese ferrite (MnFe₂O₄)–supported, magnetically separable palladium catalysts with high catalytic activity in the hydrogenation of nitrobenzene to aniline. In addition to high NB conversion and AN yield, remarkable aniline selectivity (above 96 n/n%) was achieved. Surprisingly, the magnetic support alone also shows moderate catalytic activity even without noble metals, and thus, up to 94 n/n% nitrobenzene conversion, along with 47 n/n% aniline yield, are attainable. After adding palladium nanoparticles to the support, the combined catalytic activity of the two nanomaterials yielded a fast, efficient, and highly selective catalyst. During the test of the Pd/MnFe₂O₄ catalyst in NB hydrogenation, no by-products were detected, and consequently, above 96 n/n% aniline yield and 96 n/n% selectivity were achieved. The activity of the Pd/MnFe₂O₄ catalyst was not particularly sensitive to the hydrogenation temperature, and reuse tests indicate its applicability in at least four cycles without regeneration. The remarkable catalytic activity and other favorable properties can make our catalyst potentially applicable to both NB hydrogenation and other similar or slightly different reactions.

Performance of Pd catalyst supported on trimetallic nanohybrid Zr–Al–La in hydrogenation of ethylanthraquinone

In light of the recent COVID-19 pandemic, the demand for hydrogen peroxide has increased significantly due to its widespread use in disinfectant formulations. The present study aims to develop an efficient nanohybrid material as catalyst support for the successful hydrogenation of ethylanthraquinone for the production of hydrogen peroxide. Co-precipitation and wet impregnation methods were used to prepare nanohybrid Zr–Al–La supported Pd catalyst (Pd/Zr–Al–La). The high surface area (146.56 m2/g) of Zr–Al–La makes it suitable to use as support and causes to lower the mass transfer resistance and dispersion of active metal. XRF, BET, FTIR, and TGA were used to characterize the developed catalyst. The catalytic activity of the developed catalyst was studied using a high-pressure autoclave reactor to obtain a notable yield of H2O2 as 93.8% at 75 °C, 0.3 MPa, and 0.5 g of catalyst dose, a significant enhancement over the traditional Pd catalyst with Al2O3 support (63%) with the loss of active quinone compound. The mass transfer limitation of the reaction is high using only a Pd catalyst. The calculated mass transfer resistance of the reaction over Pd/Zr–Al–La catalyst was found to be moderate with a diffusion coefficient of the reactant (H2) as 0.0133 × 10−6 m2/s at 75 °C. It was also verified and confirmed with the Thiele modulus (calculated as 0.0314), no mass transfer resistance. The effectiveness factor (η s ) was found to be 1.0, indicating the negligible mass transfer resistance in the hydrogenation reaction using Pd/Zr–Al–La catalyst.

Preparation, Antibacterial Activity, and Catalytic Application of Magnetic Graphene Oxide-Fucoidan in the Synthesis of 1,4-Dihydropyridines and Polyhydroquinolines

Polymer-coated magnetic nanoparticles are emerging as a useful tool for a variety of applications, including catalysis. In the present study, fucoidan-coated magnetic graphene oxide was synthesized using a natural sulfated polysaccharide. The prepared BaFe12 O19 @GO@Fu (Fu=fucoidan, GO=graphene oxide) was characterized using Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) analysis, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), Raman spectroscopy, and X-ray diffraction (XRD). The catalytic proficiency of BaFe12 O19 @GO@Fu was investigated in the synthesis of 1,4-dihydropyridine and polyhydroquinoline derivatives. Excellent turnover numbers (TON) and turnover frequencies (TOF) (6330 and 25320 h-1 ) testify to the high efficiency of the catalyst. Moreover, the antimicrobial activity of BaFe12 O19 @GO@Fu was evaluated against Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus) through the Agar well diffusion method, indicating that BaFe12 O19 @GO@Fu has antibacterial activity against S. aureus.

Preparation of Reduced-Graphene-Oxide-Supported CoPt and Ag Nanoparticles for the Catalytic Reduction of 4-Nitrophenol

Composite nanostructure materials are widely used in catalysis. They exhibit several characteristics, such as the unique structural advantage and the synergism among their components, which significantly enhances their catalytic performance. In this work, CoPt nanoparticles and reduced-graphene-oxide-based nanocomposite catalysts (rGO/CoPt, rGO/CoPt/Ag) were prepared by using a facile co-reduction strategy. The crystalline structure, morphology, composition, and optical characteristics of the CoPt nanoparticles, rGO/CoPt nanocomposite, and rGO/CoPt/Ag nanocomposite catalysts were investigated by a set of techniques. The ID/IG value of the rGO/CoPt/Ag nanocomposite is 1.158, higher than that of rGO/CoPt (1.042). The kinetic apparent rate constant, k, of the rGO/CoPt/Ag nanocomposite against 4-nitrophenol (4-NP) reduction is 5.306 min−1, which is higher than that of CoPt (0.495 min−1) and rGO/CoPt (1.283 min−1). The normalized rate constant, knor, of the rGO/CoPt/Ag nanocomposite is 56.76 min−1mg−1, which is higher than some other catalytic materials. The rGO/CoPt/Ag nanocomposite shows a significantly enhanced catalytic performance when compared to CoPt nanoparticles and the rGO/CoPt nanocomposite, which may confirm that the novel rGO/CoPt/Ag nanocomposite is a promising catalyst for the application of catalytic fields.

Chitosan as capping agent in a robust one-pot procedure for a magnetic catalyst synthesis

Here, we report a one-pot solvothermal method for the development of magnetically recoverable catalysts with Ru or Ag nanoparticles (NPs) capped by chitosan (CS), a derivative of natural chitin. The formation of iron oxide NPs was carried out in situ in the presence of CS and iron acetylacetonate in boiling triethyleneglycol (TEG) due to CS solubilization in warm TEG. Coordination with Ru or Ag species and the NP formation take place in the same reaction solution, eliminating intermediate steps. In optimal conditions the method developed allows stabilization of 2.2 nm monodisperse Ru NPs (containing both Ru⁰ and Ru⁴⁺ species) that are evenly distributed through the catalyst, while for Ag NPs, this stabilizing medium is inferior, leading to exceptionally large Ag nanocrystals. Catalytic testing of CS-Ru magnetically recoverable catalysts in the reduction of 4-nitrophenol to 4-aminophenol with excess NaBH₄ revealed that the catalyst with 2.2 nm Ru NPs exhibits the highest catalytic activity compared to samples with larger Ru NPs (2.9-3.2 nm). Moreover, this catalyst displayed extraordinary shelf-life in the aqueous solution (up to ten months) and excellent reusability in ten consecutive reactions with easy magnetic separation at each step which were assigned to its conformational rigidity at a constant pH. These characteristics as well as favorable environmental factors of the catalyst fabrication, make it promising for nitroarene reduction.

Facile fabrication of Co@C nanoparticles with different carbon-shell thicknesses: high-performance microwave absorber and efficient catalyst for the reduction of 4-nitrophenol

Co@C nanoparticles with different carbon-shell thicknesses can be used as a multifunctional material for a high-performance microwave absorber and as an efficient catalyst for the reduction of 4-nitrophenol.

Magnetic chitosan nanocomposite: As a novel catalyst for the synthesis of new derivatives of N-sulfonylamidine and N-sulfonylimidate

This study reports the synthesis and characterization of a highly active catalyst based on chelated copper iodide on magnetic chitosan-salicylaldehyde Schiff base. This catalyst was successfully used for the three-component reaction of N-propargylphthalimide, tosylazide, and NH or OH containing nucleophiles to access new classes of N-sulfonylamidine or N-sulfonylimidate derivatives. The products, which were constructed via an in situ generated sulfonyl keteneimine intermediate, were obtained in good to excellent yields. Short reaction times, easy separation and reusability without significant loss of catalyst activity were found to be the notable features of this synthetic protocol.

Preparation of Modified Chitosan Microsphere-Supported Copper Catalysts for the Borylation of α,β-Unsaturated Compounds

Chitosan microspheres modified by 2-pyridinecarboxaldehyde were prepared and used in the construction of a heterogeneous catalyst loaded with nano-Cu prepared by a reduction reaction. The chemical structure of the catalyst was investigated by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS). Under mild conditions, such as no ligand at room temperature, the catalyst was successfully applied to catalyze the borylation of α,β-unsaturated receptors in a water-methanol medium, yielding 17%-100% of the corresponding -hydroxy product. Even after repeated use five times, the catalyst still exhibited excellent catalytic activity.