Articles de revues : « Magnetic heterogeneous catalyst »

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Hülsey, Max J., Chia Wei Lim et Ning Yan. « Promoting heterogeneous catalysis beyond catalyst design ». Chemical Science 11, n^o 6 (2020) : 1456–68. http://dx.doi.org/10.1039/c9sc05947d.

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Kang, Na, Yindi Fan, Dan Li, Xiaoli Jia et Sanhu Zhao. « Preparation of Magnetic Nano-Catalyst Containing Schiff Base Unit and Its Application in the Chemical Fixation of CO2 into Cyclic Carbonates ». Magnetochemistry 10, n^o 5 (26 avril 2024) : 33. http://dx.doi.org/10.3390/magnetochemistry10050033.

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The development of a catalyst for the conversion of CO2 and epoxides to the corresponding cyclic carbonates is still a very attractive topic. Magnetic nano-catalysts are widely used in various organic reactions due to their magnetic separation and recycling properties. Here, a magnetic nano-catalyst containing a Schiff base unit was designed, synthesized and used as a heterogeneous catalyst to catalyze CO2 and epoxides to form cyclic carbonates without solvents and co-catalysts. The catalyst was characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric (TG), VSM, SEM, TEM and BET. The results show that the magnetic nano-catalyst containing the Schiff base unit has a high activity in the solvent-free cycloaddition reaction of CO2 with epoxide under mild conditions, and is easily separated from the reaction mixture driven by external magnetic force. The recovered catalyst maintains a high performance after five cycles.

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Wang, Baohua, Bingquan Wang, Sudheesh K. Shukla et Rui Wang. « Enabling Catalysts for Biodiesel Production via Transesterification ». Catalysts 13, n^o 4 (13 avril 2023) : 740. http://dx.doi.org/10.3390/catal13040740.

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With the rapid development of industry and the increasing demand for transportation, traditional sources of energy have been excessively consumed. Biodiesel as an alternative energy source has become a research focus. The most common method for biodiesel production is transesterification, in which lipid and low carbon alcohol are commonly used as raw materials, in the presence of a catalyst. In the process of transesterification, the performance of the catalyst is the key factor of the biodiesel yield. This paper reviews the recent research progress on homogeneous and heterogeneous catalysts in biodiesel production. The advantages and disadvantages of current homogeneous acid catalysts and homogeneous base catalysts are discussed, and heteropolyacid heterogeneous catalysts and biomass-derived base catalysts are described. The applications of the homogeneous and heterogeneous catalyst derivatives ionic liquids/deep eutectic solvents and nanocatalysts/magnetic catalysts in biodiesel production are reviewed. The mechanism and economic cost of current homogeneous acid catalysts and homogeneous base catalysts are also analyzed. The unique advantages of each type of catalyst are compared to better understand the microscopic details behind biodiesel. Finally, some challenges of current biodiesel catalysts are summarized, and future research directions are presented. This review will provide general and in-depth knowledge on the achievements, directions, and research priorities in developing novel homogeneous/heterogeneous catalysts for the green and cost-effective production of biodiesel.

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Gutiérrez-Ortega, Norma, Esthela Ramos-Ramírez, Alma Serafín-Muñoz, Adrián Zamorategui-Molina et Jesús Monjaraz-Vallejo. « Use of Co/Fe-Mixed Oxides as Heterogeneous Catalysts in Obtaining Biodiesel ». Catalysts 9, n^o 5 (29 avril 2019) : 403. http://dx.doi.org/10.3390/catal9050403.

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Catalyst-type mixed metal oxides with different compositions and Co/Fe ratios were obtained from layered double hydroxides to be used as heterogeneous catalysts in the production of biodiesel. The effect of the Co/Fe ratio on the precursors of the catalysts was analyzed, considering their thermal, textural and structural properties. The physicochemical properties of the catalysts were determined by thermogravimetric analysis (differential scanning calorimetry and thermogravimetric), X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy and N2-physisorption. The conversion to biodiesel using the different catalysts obtained was determined by diffuse reflectance infrared Fourier-transform spectroscopy and 1H-Nuclear magnetic resonance spectroscopy, allowing us to correlate the effect of the catalyst composition with the catalytic capacity. The conditions for obtaining biodiesel were optimized by selecting the catalyst and varying the percentage of catalyst, the methanol/oil ratio and the reaction time. The catalysts reached yields of conversion to biodiesel of up to 96% in 20 min of reaction using only 2% catalyst. The catalyst that showed the best catalytic activity contains a mixture of predominant crystalline and amorphous phases of CoFe2O4 and NaxCoO2. The results suggest that cobalt is a determinant in the activity of the catalyst when forming active sites in the crystalline network of mixed oxides for the transesterification of triglycerides, with high conversion capacity and selectivity to biodiesel.

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Kovtunov, Kirill V., Oleg G. Salnikov, Ivan V. Skovpin, Nikita V. Chukanov, Dudari B. Burueva et Igor V. Koptyug. « Catalytic hydrogenation with parahydrogen : a bridge from homogeneous to heterogeneous catalysis ». Pure and Applied Chemistry 92, n^o 7 (28 juillet 2020) : 1029–46. http://dx.doi.org/10.1515/pac-2020-0203.

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AbstractOne of the essential themes in modern catalysis is that of bridging the gap between its homogeneous and heterogeneous counterparts to combine their individual advantages and overcome shortcomings. One more incentive can now be added to the list, namely the ability of transition metal complexes to provide strong nuclear magnetic resonance (NMR) signal enhancement upon their use in homogeneous hydrogenations of unsaturated compounds with parahydrogen in solution. The addition of both H atoms of a parahydrogen molecule to the same substrate, a prerequisite for such effects, is implemented naturally with metal complexes that operate via the formation of a dihydride intermediate, but not with most heterogeneous catalysts. Despite that, it has been demonstrated in recent years that various types of heterogeneous catalysts are able to perform the required pairwise H2 addition at least to some extent. This has opened a major gateway for developing highly sensitive and informative tools for mechanistic studies of heterogeneous hydrogenations and other processes involving H2. Besides, production of catalyst-free fluids with NMR signals enhanced by 3-4 orders of magnitude is essential for modern applications of magnetic resonance imaging (MRI), including biomedical research and practice. The ongoing efforts to design heterogeneous catalysts which can implement the homogeneous (pairwise) hydrogenation mechanism are reported.

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Panda, Niranjan, Ashis Kumar Jena et Sasmita Mohapatra. « Heterogeneous magnetic catalyst for S-arylation reactions ». Applied Catalysis A : General 433-434 (août 2012) : 258–64. http://dx.doi.org/10.1016/j.apcata.2012.05.026.

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Taufik, Ardiansyah, Shofianina Djalaluidin et Rosari Saleh. « Photocatalytic and Sonophotocatalytic Activity of Magnetic Heterogeneous Fe₃O₄/TiO₂/CuO Catalyst ». Materials Science Forum 864 (août 2016) : 128–33. http://dx.doi.org/10.4028/www.scientific.net/msf.864.128.

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Magnetic heterogeneous Fe3O4/TiO2/CuO catalyst were synthesized using sol-gel method. The molar ratio of Fe3O4/TiO2/CuO were varied from 1:1:0.1 until 1:1:5. The all synthesized catalyst were characterized using X-ray Diffraction (XRD), Energy Dispersive X-ray (EDX), Field Emission Scanning Electron Microscope (FE-SEM), and Vibrating Sample Magnetometer (VSM). The result show that the magnetic heterogeneous Fe3O4/TiO2/CuO catalyst exhibit ferromagnetic behavior under room temperature. The catalytic performance were evaluated on the degradation of methylene blue under UV light and combination of ultrasound and UV-light Irradiation. The combination of ultrasound and UV-light irradiation exhibit batter catalytic performance than ultrasound irradiation only. The Magnetic heterogeneous Fe3O4/TiO2/CuO with molar ratio 1:1:0.1 shows highest catalytic performance. The reusability of catalyst were also observed.

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Ngoie, Wighens I., Pamela J. Welz, Daniel Ikhu-Omoregbe et Oluwaseun O. Oyekola. « Heterogeneous Nanomagnetic Catalyst from Cupriferous Mineral Processing Gangue for the Production of Biodiesel ». Catalysts 9, n^o 12 (10 décembre 2019) : 1047. http://dx.doi.org/10.3390/catal9121047.

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The commercialisation of biodiesel as an alternative energy source is challenged by high production costs. The cost of feedstock, catalyst and separation of the dissolved catalyst (homogeneous catalyst) from the product are the major contributors to the total manufacturing cost of biodiesel. This study investigated the potential of a heterogeneous catalyst produced from mineral processing waste for biodiesel production. Tailings from the concentration of cupriferous minerals served as the starting material for synthesis of the catalyst. The nanomagnetic catalysts were prepared using co-precipitation (CMCO) and sol-gel (CMSG) methods, combined with zero-valent iron nanoparticles (ZVINPs) to form a hydride catalyst (CMSG/ZVINPs). Catalyst properties were assessed using SEM, TEM, BET and EDX. The catalyst activity was enhanced by a large number of basic sites that were afforded by the presence of calcite and magnesite. Good surface areas and particle sizes of 58.9 m2/g and 15.4 nm, and 52.6 m2/g and 16.9 nm were observed for the catalysts that were prepared using the CMSG and CMCO methods, respectively. 173 emu/g mass magnetisation was obtained for CMSG/ZVINPs, which was sufficient for the catalyst to be regenerated and reused for biodiesel production by exploiting the magnetic properties. The maximum yield obtained with this catalyst was 88% and an average of 27% decrease in biodiesel yield was observed after four reaction cycles. The physicochemical properties of the biodiesel produced complied with the ASTM standard specification. The results showed that mineral processing tailings are a viable starting material for catalyst preparation in biodiesel production.

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de Abreu, Wiury C., Marco A. S. Garcia, Sabrina Nicolodi, Carla V. R. de Moura et Edmilson M. de Moura. « Magnesium surface enrichment of CoFe2O4 magnetic nanoparticles immobilized with gold : reusable catalysts for green oxidation of benzyl alcohol ». RSC Advances 8, n^o 7 (2018) : 3903–9. http://dx.doi.org/10.1039/c7ra13590d.

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Gold nanoparticles have shown excellent activity for selective oxidation of alcohols; such catalytic systems are highly dependent on the initial activation of the substrates, which must occur on the catalyst surface in heterogeneous catalysts.

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Afshari, Mozhgan, Sónia A. C. Carabineiro et Maryam Gorjizadeh. « Sulfonated Silica Coated CoFe2O4 Magnetic Nanoparticles for the Synthesis of 3,4-Dihydropyrimidin-2(1H)-One and Octahydroquinazoline Derivatives ». Catalysts 13, n^o 6 (9 juin 2023) : 989. http://dx.doi.org/10.3390/catal13060989.

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Sulfonated-silica-coated cobalt ferrite (CoFe2O4) magnetic nanoparticles (MNPs-SiCoFe-SO3H) are efficient heterogeneous catalysts for the synthesis of 3,4-dihydropyrimidin-2(1H)-one and octahydroquinazoline derivatives in the absence of solvent. The effects of solvent, temperature, and catalyst amount on the reaction are investigated. The easy separation, reusability of the catalyst, simplicity of the procedure, mild reaction conditions, and good yields (68–95%) within short reaction times (15–70 min) are the advantages of this method. The catalyst can be reused up to eight times with not much loss of activity. Scanning electron microscopy images, X-ray diffraction spectra, and elemental analysis of the recycled catalyst show that the catalyst is stable after the reaction.

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Nezhad, Shefa Mirani, Seied Ali Pourmousavi, Ehsan Nazarzadeh Zare, Golnaz Heidari et Pooyan Makvandi. « Magnetic Sulfonated Melamine-Formaldehyde Resin as an Efficient Catalyst for the Synthesis of Antioxidant and Antimicrobial Pyrazolone Derivatives ». Catalysts 12, n^o 6 (7 juin 2022) : 626. http://dx.doi.org/10.3390/catal12060626.

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Sulfonated polymer-based materials, among heterogeneous catalysts, are frequently utilized in chemical transformations due to their outstanding chemical and physical durability. In this regard, a magnetic sulfonated melamine–formaldehyde resin (MSMF) catalyst was successfully prepared from a mixture of sulfonated melamine–formaldehyde and Fe3O4 nanoparticles in two steps. MSMF was used as a heterogeneous catalyst for the one-pot, three-component condensation of benzyl pyrazolyl naphthoquinones in water as a green solvent and 4-[(indol-3-yl)-arylmethyl]-1-phenyl-3-methyl-5-pyrazolones. The antimicrobial and antioxidant activities of catalyst, benzyl pyrazolyl naphthoquinones, and 4-[(indol-3-yl)-arylmethyl]-1-phenyl-3-methyl-5-pyrazolones were evaluated using agar disk-diffusion and DPPH assays, respectively. The antioxidant activity of the catalyst and 4-[(indol-3-yl)-arylmethyl]-1-phenyl-3-methyl-5-pyrazolones was found to be 75% and 90%, respectively. Furthermore, catalyst, benzyl pyrazolyl naphthoquinones, and 4-[(indol-3-yl)-arylmethyl]-1-phenyl-3-methyl-5-pyrazolones exhibited antimicrobial activity against Staphylococcus aureus and Escherichia coli. In conclusion, MSMF is a superior catalyst for green chemical processes, owing to its high catalytic activity, stability, and reusability.

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Yang, Weisen, Li Wei, Feiyan Yi et Mingzhong Cai. « Heterogeneous Gold(III)-Catalysed Double Hydroamination of 2-Alkynylanilines with Terminal Alkynes Leading to N-Vinylindoles ». Journal of Chemical Research 42, n^o 11 (novembre 2018) : 558–63. http://dx.doi.org/10.3184/174751918x15403975136742.

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Heterogeneous double hydroamination of 2-alkynylanilines with terminal alkynes was achieved by using a magnetic nanoparticles-supported gold(III)-2,2′-bipyridine complex and silver trifluoromethanesulfonate as catalysts to afford the corresponding N-vinylindoles in moderate to good yields under mild and solvent-free conditions. The heterogeneous gold catalyst can easily be separated from the reaction mixture by simply applying an external magnet and can be recycled up to seven times without significant loss of activity.

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Hanif, Maryam, Ijaz Ahmad Bhatti, Muhammad Asif Hanif, Umer Rashid, Bryan R. Moser, Asma Hanif et Fahad A. Alharthi. « Nano-Magnetic CaO/Fe2O3/Feldspar Catalysts for the Production of Biodiesel from Waste Oils ». Catalysts 13, n^o 6 (13 juin 2023) : 998. http://dx.doi.org/10.3390/catal13060998.

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Production of biodiesel from edible vegetable oils using homogenous catalysts negatively impacts food availability and cost while generating significant amounts of caustic wastewater during purification. Thus, there is an urgent need to utilize low-cost, non-food feedstocks for the production of biodiesel using sustainable heterogeneous catalysis. The objective of this study was to synthesize a novel supported nano-magnetic catalyst (CaO/Fe2O3/feldspar) for the production of biodiesel (fatty acid methyl esters) from waste and low-cost plant seed oils, including Sinapis arvensis (wild mustard), Carthamus oxyacantha (wild safflower) and Pongamia pinnata (karanja). The structure, morphology, surface area, porosity, crystallinity, and magnetization of the nano-magnetic catalyst was confirmed using XRD, FESEM/EDX, BET, and VSM. The maximum biodiesel yield (93.6–99.9%) was achieved at 1.0 or 1.5 wt.% catalyst with methanol-to-oil molar ratios of 5:1 or 10:1 at 40 °C for 2 h. The CaO/Fe2O3/feldspar catalyst retained high activity for four consecutive cycles for conversion of karanja, wild mustard, and wild safflower oils. The effective separation of the catalyst from biodiesel was achieved using an external magnet. Various different physico-chemical parameters, such as pour point, density, cloud point, iodine value, acid value, and cetane number, were also determined for the optimized fuels and found to be within the ranges specified in ASTM D6751 and EN 14214, where applicable.

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Hu, Yu, Nan Yao, Jin Tan et Yang Liu. « An Efficient and Reusable Multifunctional Composite Magnetic Nanocatalyst for Knoevenagel Condensation ». Synlett 30, n^o 06 (6 mars 2019) : 699–702. http://dx.doi.org/10.1055/s-0037-1612076.

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A range of multifunctional magnetic metal–organic framework nanomaterials consisting of various mass ratios of the metal–organic framework MIL-53(Fe) and magnetic SiO2@NiFe2O4 nanoparticles were designed, prepared, characterized, and evaluated as heterogeneous catalysts for the Knoevenagel condensation. The as-fabricated nanomaterials, especially the nanocatalyst MIL-53(Fe)@SiO2@NiFe2O4(1.0), showed good catalytic performance in the Knoevenagel condensation at room temperature as a result of synergistic interaction between the Lewis acid iron sites of MIL-53(Fe) and the active sites of the magnetic SiO2@NiFe2O4 nanoparticles. In addition, the heterogeneous catalyst was readily recovered and a recycling test showed that it could be reused for five times without significant loss of its catalytic activity, making it economical and environmentally friendly.

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Yang, Chun Wei, Dong Wang et Qian Tang. « Magnetic Nd₂Fe₁₄B Actived Carbon : Fabrication and Heterogeneous Fenton Oxidation of Congo Red ». Applied Mechanics and Materials 675-677 (octobre 2014) : 426–29. http://dx.doi.org/10.4028/www.scientific.net/amm.675-677.426.

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Magnetic Nd2Fe14B activated carbon, a new kind of heterogeneous Fenton catalyst has been synthesis to treat the dyestuff wastewater. The obtained catalysts were characterized by X-raydiffraction (XRD) and vibrating sample magnetometer (VSM), and the catalytic activity in heterogeneous Fenton oxidation of Congo red was evaluated. Experiments show that the Nd2Fe14B activated carbon has hard magnetic properties. The saturated magnetization, remanence and coercive force were 15.93emu/g, 6.0emu/g, and 1313Oe, respectively. The results also indicated that Nd2Fe14B activated carbon has good performance on azo dye Congo red oxidation with heterogeneous Fenton process. Under the optimum conditions ([NdFeB-AC-FC]0=20g/L, [H2O2]0= 8mmol/L and pH=7.0), Congo red degradation rate could reach 83.4%. The pH had few effects on heterogeneous Fenton process degraded Congo red. The kinetics studied shown that Congo red degraded followed the pseudo-first-order reaction by heterogeneous Fenton process.

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Scharnagl, Florian Korbinian, Maximilian Franz Hertrich, Francesco Ferretti, Carsten Kreyenschulte, Henrik Lund, Ralf Jackstell et Matthias Beller. « Hydrogenation of terminal and internal olefins using a biowaste-derived heterogeneous cobalt catalyst ». Science Advances 4, n^o 9 (septembre 2018) : eaau1248. http://dx.doi.org/10.1126/sciadv.aau1248.

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Hydrogenation of olefins is achieved using biowaste-derived cobalt chitosan catalysts. Characterization of the optimal Co@Chitosan-700 by STEM (scanning transmission electron microscopy), EELS (electron energy loss spectroscopy), PXRD (powder x-ray diffraction), and elemental analysis revealed the formation of a distinctive magnetic composite material with high metallic Co content. The general performance of this catalyst is demonstrated in the hydrogenation of 50 olefins including terminal, internal, and functionalized derivatives, as well as renewables. Using this nonnoble metal composite, hydrogenation of terminal C==C double bonds occurs under very mild and benign conditions (water or methanol, 40° to 60°C). The utility of Co@Chitosan-700 is showcased for efficient hydrogenation of the industrially relevant examples diisobutene, fatty acids, and their triglycerides. Because of the magnetic behavior of this material and water as solvent, product separation and recycling of the catalyst are straightforward.

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Dhariwal, Jyoti, Ravina Yadav, Sheetal Yadav, Anshu Kumar Sinha, Chandra Mohan Srivastava, Gyandshwar Kumar Rao, Manish Srivastava et al. « Magnetic Spinel Ferrite : An Efficient, Reusable Nano Catalyst for HMFsynthesis ». Current Catalysis 10, n^o 3 (décembre 2021) : 206–13. http://dx.doi.org/10.2174/2211544710666211119094247.

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Aim: In the present work, the preparation and catalytic activity of spinel ferrite (MFe2O4; M = Fe, Mn, Co, Cu, Ni) nanoparticles to synthesize 5-hydroxymethylfurfural (HMF) have been discussed. Background: Ferrites possess unique physicochemical properties, including excellent magnetic characteristics, high specific surface area, active surface sites, high chemical stability, tunable shape and size, and easy functionalization. These properties make them essential heterogeneous catalysts in many organic reactions. Objective: This study aims to synthesize a series of transition metal ferrite nanoparticles and use them in the dehydration of carbohydrates for 5-hydroxymethylfurfural (HMF) synthesis. Method: The ferrite nanoparticles were prepared via the co-precipitation method, and PXRD confirmed their phase stability. The surface area and the crystallite size of the nanoparticles were calculated using BET and PXRD, respectively. Result: The easily prepared heterogeneous nanocatalyst showed a significant catalytic performance, and among all spinel ferrites, CuFe2O4 revealed maximum catalytic ability. Conclusion: Being a heterogeneous catalyst and magnetic in nature, ferrite nanoparticles were easily recovered by using an external magnet and reused up to several runs without substantial loss in catalytic activity. Others: HMF was synthesized from fructose in a good yield of 71%.

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Testa, Maria Luisa, et Valeria La Parola. « Sulfonic Acid-Functionalized Inorganic Materials as Efficient Catalysts in Various Applications : A Minireview ». Catalysts 11, n^o 10 (23 septembre 2021) : 1143. http://dx.doi.org/10.3390/catal11101143.

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Acid catalysis is widely used in the chemical industry, and nowadays many efforts are being focused on replacing the more common homogeneous catalysts with heterogeneous ones in order to make greener the industrial processes. In this perspective, sulfonic solid acid materials represent a valid alternative to the homogenous mineral acid in several acid catalyzed reactions. In this minireview, an overview of the recent advances on the preparation, stability and application of these materials is reported. Special attention is addressed to the sustainability of the considered processes, starting from the catalyst’s preparation, the use of green solvents and reducing the possible reaction steps. Ways to tackle the main drawback represented by easy leaching of acid groups are described. For an easy catalyst recovery, the use of a magnetic core in a catalyst particle, with the related synthetic approaches, is also illustrated. Finally, a section is dedicated to the principal characterization techniques to identify the structural properties of the catalysts.

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Zhang, Sufeng, Yongshe Xu, Dongyan Zhao, Wenqiang Chen, Hao Li et Chen Hou. « Preparation of Magnetic CuFe2O4@Ag@ZIF-8 Nanocomposites with Highly Catalytic Activity Based on Cellulose Nanocrystals ». Molecules 25, n^o 1 (28 décembre 2019) : 124. http://dx.doi.org/10.3390/molecules25010124.

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A facile approach was successfully developed for synthesis of cellulose nanocrystals (CNC)-supported magnetic CuFe2O4@Ag@ZIF-8 nanospheres which consist of a paramagnetic CuFe2O4@Ag core and porous ZIF-8 shell. The CuFe2O4 nanoparticles (NPs) were first prepared in the presence of CNC and dispersant. Ag NPs were then deposited on the CuFe2O4/CNC composites via an in situ reduction directed by dopamine polymerization (PDA). The CuFe2O4/CNC@Ag@ZIF-8 nanocomposite was characterized by TEM, FTIR, XRD, N2 adsorption-desorption isotherms, VSM, and XPS. Catalytic studies showed that the CuFe2O4/CNC@Ag@ZIF-8 catalyst had much higher catalytic activity than CuFe2O4@Ag catalyst with the rate constant of 0.64 min−1. Because of the integration of ZIF-8 with CuFe2O4/CNC@Ag that combines the advantaged of each component, the nanocomposites were demonstrated to have an enhanced catalytic activity in heterogeneous catalysis. Therefore, these results demonstrate a new method for the fabrication of CNC-supported magnetic core-shell catalysts, which display great potential for application in biocatalysis and environmental chemistry.

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Yue, Chuan-Jun, Qiu-Neng Xu, Li-Ping Gu et Jin-Fang Wang. « Ionic [Ru] complex with recyclability by electro-adsorption for efficient catalytic transfer hydrogenation of aryl ketones ». Polish Journal of Chemical Technology 19, n^o 4 (1 décembre 2017) : 75–79. http://dx.doi.org/10.1515/pjct-2017-0070.

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Abstract The efficient reuse of homogeneous catalyst is important. Cation complex of [Ru(η6-p-cymene)(PPh3)(CH3CN) Cl]PF6 with different ligands was synthesized and characterized by infrared spectroscopy (IR), 1H-, 13C- and 31P-nuclear magnetic resonance spectroscopy (1H-, 13C- and 31P-NMR), element analysis (EA), and high resolution mass spectrometry (HR-MS). The complex was used as a catalyst for the hydrogen transfer reduction of carbonyl for the first time, presenting an excellent catalytic performance of 89%–98% conversion of acetophenone and its derivatives. The catalyst may be efficiently reused by the electro-adsorption of 10 times to one catalyst recovery. The cation [Ru] complex presented advantages of both homogeneous and heterogeneous catalysts.

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Hasan, Shehadi, Al-Bab et Elgamouz. « Magnetic Chitosan-Supported Silver Nanoparticles : A Heterogeneous Catalyst for the Reduction of 4-Nitrophenol ». Catalysts 9, n^o 10 (10 octobre 2019) : 839. http://dx.doi.org/10.3390/catal9100839.

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Developing heterogeneous catalyst using chitosan (CS) and magnetic Fe3O4 as support has been remarkably attractive due to their availability, low cost and non-toxicity. In this work, a heterogeneous catalyst (denoted as Fe3O4@CS@MS@Ag) was fabricated by the deposition of silver nanoparticles on magnetic chitosan via an easy and facile modification of its surface with methyl salicylate (MS). The catalyst was characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). To the best of our knowledge, for the first time, CS decorated Fe3O4 (Fe3O4@CS) has shown the catalytic activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in presence of NaBH4. Surface modified magnetic chitosan (Fe3O4@CS@MS) also acts as active catalyst towards the reduction of 4-NP. However, catalytic efficiency has increased fourfold when silver-nanoparticles-deposited magnetic chitosan (Fe3O4@CS@MS@Ag) used as our target catalyst. The catalyst was separated with external magnet after each cycle of catalytic reaction and reused effectively five times with almost 90% efficiency.

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Musin, A. I., Yu G. Borisova, G. Z. Raskil’dina, R. R. Daminev, A. R. Davletshin et S. S. Zlotskii. « Heterogeneous catalytic reduction of substituted 5-acyl-1,3-dioxanes ». Fine Chemical Technologies 17, n^o 3 (31 juillet 2022) : 201–9. http://dx.doi.org/10.32362/2410-6593-2022-17-3-201-209.

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Objectives. To study the hydrogenation of substituted 5-acyl-1,3-dioxanes in the presence of metal-containing catalysts (Pt/Re, Pd/C, Ni/kieselguhr, and Ni/Mo).Methods. In order to determine the qualitative and quantitative composition of the reaction masses, the following analysis methods were used: gas-liquid chromatography (using the Kristall 2000 hardware complex); mass-spectroscopy (using Chromatec-Kristall 5000M device with NIST 2012); nuclear magnetic resonance (NMR) spectrometry (using Bruker AM-500 device with operating frequencies of 500 and 125 MHz).Results. Hydrogenation of substituted 5-acyl-1,3-dioxanes obtained by condensation of carbonyl compounds with paraformaldehyde and sulfuric acid was used to synthesize heterocyclic alcohols in the presence of metal-containing catalysts with a conversion of the initial ketones of 60–90% and a formation selectivity of target products of 70–90%. Substances were analyzed and confirmed by gas-liquid chromatography, mass spectrometry and NMR spectroscopy.Conclusions. The best catalyst for the reduction of substituted 5-acyl-1,3-dioxanes is Pd/C. By using this catalyst, it is possible to achieve a high selectivity for the formation of the corresponding heterocyclic alcohols at a conversion rate of the initial ketones of 60–90%.

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Daniele Silvéria Brandão e Silva, Raynara Kelly da Silva dos Santos, Maria Eduarda Silva Carneiro, Sérgio Thode Filho, Fabíola da Silveira Maranhão et Fernando Gomes de Souza Junior. « The Importance of Viscosity Analysis in Biodiesel ». Brazilian Journal of Experimental Design, Data Analysis and Inferential Statistics 1, n^o 1 (29 décembre 2023) : 33–36. http://dx.doi.org/10.55747/bjedis.v1i2.62228.

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One of the primary motivations for studying biofuels is to meet global energy needs. Biodiesel, as a promising renewable energy source, has the potential to reduce dependence on fossil fuels if implemented effectively. It is derived from chemical reactions (transesterification) in vegetable oils or animal fats, facilitated by a catalyst that accelerates the reaction. Currently, industrial processes employed by biodiesel plants predominantly utilize homogeneous catalysts. However, heterogeneous catalysts are emerging as promising alternatives in biodiesel production, distinguished by their environmentally friendly nature and the ability to regenerate and be reused. This study aims to investigate the viscosity of biodiesel through the methylic route, employing geopolymers with added magnetic nanoparticles as a heterogeneous catalyst. Kinematic viscosity measurements of biofuels were conducted to assess their impact on combustion efficiency and engine performance. The results obtained indicate that the values fall within the parameters established by the National Petroleum Agency (ANP).

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Parvulescu, Vasile I., et Simona M. Coman. « Core-Magnetic Composites Catalysts for the Valorization and Up-grading of the Renewable Feedstocks : A Minireview ». Current Catalysis 8, n^o 1 (21 juin 2019) : 2–19. http://dx.doi.org/10.2174/2211544708666181227152000.

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Background: Core-magnetic composites offer unique possibilities to accommodate adequate amounts of acid-base and redox functional sites and hence to catalyze the biomass conversion reactions in a one-pot way. Moreover, due to the dual functionality, the core-magnetic composites provide a bridge between homogeneous and heterogeneous catalysis. Hence, this minireview aims to offer a comprehensive account of remarkable recent applications of core-magnetic composites in the catalytic processes for biomass valorization. Methods: A critical evaluation of synthetic methodologies utilized for the production of the magnetic nanoparticles, characterization techniques and catalytic applications is provided. Results: The benefits of their utilization are exemplified by most representative examples of one-pot transformation of cellulose and upgrading processes. Other recent examples constitute the lignin fragmentation on magnetic iron oxide-based catalysts and the renewable crude glycerol up-grading using core-shell magnetic iron oxide bio-based materials. Conclusion: The review provides important information on the distinctive properties of the functionalized core-magnetic composites. Moreover, this review offers useful information affording a largescale production development, in terms of catalyst and reaction conditions, tailoring selectivity, and the potential to regenerate the catalysts.

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Hazmi, Balkis, Umer Rashid, Yun Hin Taufiq-Yap, Mohd Lokman Ibrahim et Imededdine Arbi Nehdi. « Supermagnetic Nano-Bifunctional Catalyst from Rice Husk : Synthesis, Characterization and Application for Conversion of Used Cooking Oil to Biodiesel ». Catalysts 10, n^o 2 (13 février 2020) : 225. http://dx.doi.org/10.3390/catal10020225.

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The present work investigated the biodiesel production from used cooking oil catalyzed by nano-bifunctional supermagnetic heterogeneous catalysts (RHC/K2O/Fe) derived from rice husk doped with K2O and Fe synthesized by the wet impregnation method. The synthesized catalysts (RHC/K2O/Fe) were characterized for crystallinity by X-ray diffraction spectroscopy (XRD), total acidity and basicity using CO2/NH3-TPD, textural properties through Brunauer-Emmett-Teller (BET), thermal stability via thermogravimetric analyzer (TGA), functional group determination by Fourier-transform infrared spectroscopy (FTIR), surface morphology through field emission scanning electron microscopy (FESEM), and magnetic properties by vibrating sample magnetometer (VSM). The VSM result demonstrated that the super-paramagnetic catalyst (RHC/K2O-20%/Fe-5%) could be simply separated and regained after the reaction using an external magnetic field. The operating conditions such as catalyst loading, methanol/oil molar ratio, temperature, and reaction duration were studied. The screened RHC/K2O-20%/Fe-5% catalyst was selected for further optimization and the optimum reaction parameters found were 4 wt % of catalyst, a molar ratio of methanol/oil of 12:1, 4 h reaction duration, and 75 °C reaction temperature with a maximal yield of 98.6%. The reusability study and reactivation results revealed that the nano-bifunctional magnetic catalyst (RHC/K2O-20%/Fe-5%) could be preserved by high catalytic activity even after being reused five times.

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Albalawi, Marzough A., Amira K. Hajri, Bassem Jamoussi et Omnia A. Albalawi. « A Novel Recyclable Magnetic Nano-Catalyst for Fenton-Photodegradation of Methyl Orange and Imidazole Derivatives Catalytic Synthesis ». Polymers 16, n^o 1 (1 janvier 2024) : 140. http://dx.doi.org/10.3390/polym16010140.

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A magnetite chlorodeoxycellulose/ferroferric oxide (CDC@Fe3O4) heterogeneous photocatalyst was synthesised via treated and modified cotton in two steps. The designed nanocomposites were characterised by FTIR, TGA, XRD, SEM, and VSM analyses. The Fenton-photocatalytic decomposition efficiency of the synthesised magnetic catalyst was evaluated under visible sunlight using Methyl Orange (MO) as a model organic pollutant. The impacts of several degradation parameters, including the light source, catalyst load, irradiation temperature, oxidant dose, and pH of the dye aqueous solution and its corresponding concentration on the Fenton photodegradation performance, were methodically investigated. The (CDC@Fe3O4) heterogeneous catalyst showed a remarkable MO removal rate of 97.9% at 10 min under visible-light irradiation. (CDC@Fe3O4) nanomaterials were also used in a heterogeneous catalytic optimised protocol for a multicomponent reaction procedure to obtain nine tetra-substituted imidazole derivatives. The green protocol afforded imidazole derivatives in 30 min with good yields (91–97%) at room temperature and under ultrasound irradiation. Generally, a synthesised recyclable heterogeneous nano-catalyst is a good example and is suitable for wastewater treatment and organic synthesis.

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Kung, Mayfair C., Mark V. Riofski, Michael N. Missaghi et Harold H. Kung. « Organosilicon platforms : bridging homogeneous, heterogeneous, and bioinspired catalysis ». Chem. Commun. 50, n^o 25 (2014) : 3262–76. http://dx.doi.org/10.1039/c3cc48766k.

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Organosilicon compounds form versatile structures such as cubic metallasiloxanes, cage-like silsesquioxanes, macromolecular nanocages, and flexible dendrimers and linear metallasiloxanes, and are useful as catalysts, ligands for metal complexes, and catalyst supports.

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Pourjavadi, Ali, Anahita Motamedi, Seyed Hassan Hosseini et Mojtaba Nazari. « Magnetic starch nanocomposite as a green heterogeneous support for immobilization of large amounts of copper ions : heterogeneous catalyst for click synthesis of 1,2,3-triazoles ». RSC Advances 6, n^o 23 (2016) : 19128–35. http://dx.doi.org/10.1039/c5ra25519h.

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A new magnetic heterogeneous copper catalyst was prepared by immobilization of copper ions onto a cross-linked polymeric nanocomposite composed of starch grafted polyacrylamide and functionalized Fe₃O₄ magnetic nanoparticles.

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Pang, Xiaoyan, Xin Ge, Jianye Ji, Weijie Liang, Xunjun Chen et Jianfang Ge. « Facile Route for Bio-Phenol Siloxane Synthesis via Heterogeneous Catalytic Method and its Autonomic Antibacterial Property ». Polymers 10, n^o 10 (16 octobre 2018) : 1151. http://dx.doi.org/10.3390/polym10101151.

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Eugenol, used as bio-phenol, was designed to replace the hydrogen atom of hydrogenterminated siloxane by hydrosilylation reaction under the presence of alumina-supported platinum catalyst (Pt-Al2O3), silica-supported platinum catalyst (Pt-SiO2) and carbon nanotube-supported platinum catalyst (Pt-CNT), respectively. The catalytic activities of these three platinum catalysts were measured by nuclear magnetic resonance hydrogen spectrometer (1H NMR). The properties of bio-phenol siloxane were characterized by Fourier transform infrared spectrometer (FT–IR), UV-visible spectrophotometer (UV) and thermogravimeter (TGA), and its antibacterial property against Escherichia coli was also studied. The results showed that the catalytic activity of the catalyst Pt-CNT was preferable. When the catalyst concentration was 100 ppm, the reaction temperature was 80 °C and reaction time was 6 h, the reactant conversion rate reached 97%. After modification with bio-phenol, the thermal stability of the obtained bio-phenol siloxane was improved. For bio-phenol siloxane, when the ratio of weight loss reached 98%, the pyrolysis temperature was raised to 663 °C which was 60 °C higher than hydrogenterminated siloxane. Meanwhile, its autonomic antibacterial property against Escherichia coli was improved significantly.

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Flores, Ariadna, Karina Nesprias, Paula Vitale, Julia Tasca, Araceli Lavat, Nora Eyler et Adriana Cañizo. « Heterogeneous Photocatalytic Discoloration/Degradation of Rhodamine B with H2O2 and Spinel Copper Ferrite Magnetic Nanoparticles ». Australian Journal of Chemistry 67, n^o 4 (2014) : 609. http://dx.doi.org/10.1071/ch13435.

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The discoloration/degradation of the artificial dye Rhodamine B (RhB) was investigated using advanced oxidation technologies. Aqueous solutions of RhB containing spinel copper ferrites (CuFe2O4) as a heterogeneous catalyst were exposed to UV irradiation/hydrogen peroxide. Under these experimental conditions the discoloration/degradation of RhB is strongly promoted by copper ferrites, reaching 95 % discoloration of the dye in 10 min and 97 % degradation in 200 min. The influence of the catalyst amount, H2O2 concentration, light source, and UV light intensity were studied. Optimum concentrations of H2O2 and catalyst dosage were found for the RhB degradation reaction. The catalyst had high magnetic sensitivity under an external magnetic field, which allowed its magnetic separation from water avoiding secondary pollution processes, and its recycling. A markedly synergetic effect of spinel copper ferrite and UV light irradiation was observed for the RhB discoloration/degradation with H2O2 as a green oxidant.

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Baráth, Eszter. « Selective Reduction of Carbonyl Compounds via (Asymmetric) Transfer Hydrogenation on Heterogeneous Catalysts ». Synthesis 52, n^o 04 (2 janvier 2020) : 504–20. http://dx.doi.org/10.1055/s-0039-1691542.

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Based on the ever-increasing demand for optically pure compounds, the development of efficient methods to produce such products is very important. Homogeneous asymmetric catalysis occupies a prominent position in the ranking of chemical transformations, with transition metals coordinated to chiral ligands being applied extensively for this purpose. However, heterogeneous catalysts have the ability to further extend the field of asymmetric transformations, because of their beneficial properties such as high stability, ease of separation and regeneration, and the possibility to apply them in continuous processes. The main challenge is to find potential synthetic routes that can provide a chemically and thermally stable heterogeneous catalyst having the necessary chiral information, whilst keeping the catalytic activity and enantioselectivity equally high (or even higher) than the corresponding homogeneous counterpart. Within this short review, the most relevant immobilization modes and preparative strategies depending on the support material used are summarized. From the reaction scope viewpoint, metal catalysts supported on the various solid materials studied in (asymmetric) transfer hydrogenation of carbonyl compounds are selected and represent the main focus of the second part of this overview.1 Introduction2 Synthesis of Chiral Heterogeneous Catalysts2.1 Immobilization of Homogeneous Asymmetric Catalysts2.1.1 Immobilization on Inorganic Supports2.1.2 Immobilization on Organic Polymers as Supports2.1.3 Immobilization on Dendrimer-Type Materials as Supports2.1.4 Self-Supported Chiral Catalysts: Coordination Polymers2.1.5 Immobilization Using Non-Conventional Media2.2 Chirally Modified Metal Surfaces for Heterogeneous Asymmetric Catalysis3 Examples of Transfer Hydrogenation on Heterogeneous Catalysts3.1 Silicon-Immobilized Catalysts3.2 Carbon-Material-Immobilized Catalysts3.3 Polymer-Immobilized Catalysts3.4 Magnetic-Nanoparticle-Immobilized Catalysts4 Conclusions

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Bączek, Natalia, Krzysztof Strzelec et Karolina Wąsikowska. « Magnetic recykling of complex catalysts immobilized on thiol-functionalized polymer supports ». Polish Journal of Chemical Technology 15, n^o 3 (1 septembre 2013) : 65–68. http://dx.doi.org/10.2478/pjct-2013-0046.

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Abstract In this work, the application of the thiol-functionalized epoxy resin encapsulated on magnetic core as supports for palladium catalysts is reported. The study focuses on obtaining of heterogeneous catalysts which can be separated by magnetic field. Palladium complex catalyst [PdCl2(PhCN)2] has been heterogenized by anchoring to these supports via ligand exchange reaction. The characterization of polymeric supports and heterogenized palladium catalysts has involved research methods like time-of-flight secondary ion mass spectrometry (TOF-SIMS), scanning electron microscopy (SEM) and nitrogen BET surface area measurements. The activity and stability during long-term use of the investigated catalytic systems were tested in a Heck and hydrogenation reaction. The influence of the type of thiols used as epoxy hardeners and the morphology of the supports on the catalytic properties of epoxy-supported palladium catalysts was discussed.

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Ciccotti, L., L. A. S. do Vale, T. L. R. Hewer et R. S. Freire. « Fe3O4@TiO2preparation and catalytic activity in heterogeneous photocatalytic and ozonation processes ». Catalysis Science & ; Technology 5, n^o 2 (2015) : 1143–52. http://dx.doi.org/10.1039/c4cy01242a.

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Li, Zishun, Xuekun Tang, Kun Liu, Jing Huang, Yueyang Xu, Qian Peng et Minlin Ao. « Synthesis of a MnO2/Fe3O4/diatomite nanocomposite as an efficient heterogeneous Fenton-like catalyst for methylene blue degradation ». Beilstein Journal of Nanotechnology 9 (6 juillet 2018) : 1940–50. http://dx.doi.org/10.3762/bjnano.9.185.

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Heterogeneous Fenton-like catalysts with the activation of peroxymonosulfate (PMS), which offer the advantages of fast reaction rate, wide functional pH range and cost efficiency, have attracted great interest in wastewater treatment. In this study, a novel magnetic MnO2/Fe3O4/diatomite nanocomposite is synthesized and then used as heterogeneous Fenton-like catalyst to degrade the organic pollutant methylene blue (MB) with the activation of PMS. The characterization results show that the Fe3O4 nanoparticles and nanoflower-like MnO2 are evenly distributed layer-by-layer on the surface of diatomite, which can be readily magnetically separated from the solution. The as-prepared catalyst, compared with other Fenton-like catalysts, shows a superb MB degradation rate of nearly 100% in 45 min in the pH range of 4 to 8 and temperature range of 25 to 55 °C. Moreover, the nanocomposite shows a good mineralization rate of about 60% in 60 min and great recyclability with a recycle efficiency of 86.78% after five runs for MB. The probable mechanism of this catalytic system is also proposed as a synergistic effect between MnO2 and Fe3O4.

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Mardina, Primata, Hesti Wijayanti, Rinna Juwita, Meilana Dharma Putra, Iryanti Fatyasari Nata, Rowina Lestari, Muhammad Faqih Al-Amin, Regi Abizar Suciagi, Oktefani Kusuma Rawei et Liza Lestari. « Corncob-Derived Sulfonated Magnetic Solid Catalyst Synthesis as Heterogeneous Catalyst in The Esterification of Waste Cooking Oil and Bibliometric Analysis ». Indonesian Journal of Science and Technology 9, n^o 1 (9 novembre 2023) : 109–24. http://dx.doi.org/10.17509/ijost.v9i1.64219.

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A corncob-derived magnetic solid acid catalyst was synthesized through the sulfonation method and an impregnation process, respectively. In the sulfonation process, the concentrated H2SO4 was utilized as an activation agent to obtain acidic properties. The solution of ferric sulphate-ferrous sulphate was utilized for impregnation to generate the magnetic behaviour of the material. The prepared magnetic acid solid catalyst had a high saturation magnetisation value of 16.48 emu/g and a total acidity of 1.43 mmol/g. The performance of the catalyst was evaluated in the esterification reaction of waste cooking oil. The best result presented 86.12% FFA conversion under reaction conditions of 5% catalyst loading and a 1:15 oil-to-methanol molar ratio at 60oC for 4 h. The catalyst was separated magnetically from the reaction solution and exhibited a good reusability with 61% remaining active after 5 consecutive cycles of reaction. This study resulted in a promising method to obtain magnetic-sulfonated carbon-based catalyst from corncob residue, and it is economical potentially and environmentally friendly for the esterification of low-quality feedstock for biodiesel production.

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Kothandapani, Jagatheeswaran, et Subramaniapillai S. Ganesan. « Concise Review on the Applications of Magnetically Separable Brønsted Acidic Catalysts ». Current Organic Chemistry 23, n^o 3 (9 mai 2019) : 313–34. http://dx.doi.org/10.2174/1385272823666190312152209.

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Magnetically separable Brønsted acidic catalysts combine the advantages of high efficiency of homogeneous Brønsted acidic catalyst with the ease of magnetic separation from the reaction medium. In addition to their ease of separation, the magnetically separable Brønsted acidic catalysts also possess high stability towards air and moisture, facile functionalization and tunable hydrophobic properties. This review portrays the applications of sulfonic acid anchored γ -Fe2O3 or Fe3O4 nanoparticles, magnetic core encapsulated acid functionalized silica or mesoporous nanoparticles, functionalized ionic liquid coated acidic magnetically separable nanoparticles and miscellaneous magnetically separable Brønsted acidic nanoparticles in diverse organic transformations. In addition, the merits of magnetically separable Brønsted acid nanocatalyst are also summarized and compared with the traditional homogeneous/heterogeneous Brønsted acidic catalysts.

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Zhou, Jun, Yue Zhang, Song Li et Jing Chen. « Ni/NiO Nanocomposites with Rich Oxygen Vacancies as High-Performance Catalysts for Nitrophenol Hydrogenation ». Catalysts 9, n^o 11 (11 novembre 2019) : 944. http://dx.doi.org/10.3390/catal9110944.

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Heterogeneous catalysis often involves charge transfer between adsorbed molecules and the surface of catalyst, and thus their activity depends on the surface charge density. The efficiency of charge transfer could be optimized by adjusting the concentration of oxygen vacancies (Ov). In this work, hexagonal Ni(OH)2 nanoparticles were initially synthesized by a hydrothermal process using aluminum powder as the sacrificial agent, and were then converted into 2D Ni/NiO nanocomposites through in situ reduction in hydrogen flow. The oxygen vacancy concentration in the NiO nanosheet could be well-controlled by adjusting the reduction temperature. This resulted in strikingly high activities for hydrogenation of nitrophenol. The Ni/NiO nanocomposite could easily be recovered by a magnetic field for reuse. The present finding is beneficial for producing better hydrogenation catalysts and paves the way for the design of highly efficient catalysts.

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Li, Xinyu, Xinfeng Zhu, Junfeng Wu, Hongbin Gao, Weichun Yang et Xiaoxian Hu. « Enhanced Heterogeneous Peroxymonosulfate Activation by MOF-Derived Magnetic Carbonaceous Nanocomposite for Phenol Degradation ». Materials 16, n^o 9 (24 avril 2023) : 3325. http://dx.doi.org/10.3390/ma16093325.

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Degradation efficiency and catalyst stability are crucial issues in the control of organic compounds in wastewater by advanced oxidation processes (AOPs). However, it is difficult for catalysts used in AOPs to have both high catalytic activity and high stability. Combined with the excellent activity of cobalt/copper oxides and the good stability of carbon, highly dispersed cobalt-oxide and copper-oxide nanoparticles embedded in carbon-matrix composites (Co-Cu@C) were prepared for the catalytic activation of peroxymonosulfate (PMS). The catalysts exhibited a stable structure and excellent performance for complete phenol degradation (20 mg L−1) within 5 min in the Cu-Co@C-5/PMS system, as well as low metal-ion-leaching rates and great reusability. Moreover, a quenching test and an EPR analysis revealed that ·OH, O2·−, and 1O2 were generated in the Co-Cu@C/PMS system for phenol degradation. The possible mechanism for the radical and non-radical pathways in the activation of the PMS by the Co-Cu@C was proposed. The present study provides a new strategy with which to construct heterostructures for environmentally friendly and efficient PMS-activation catalysts.

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Kraupner, Alexander, Markus Antonietti, Regina Palkovits, Klaus Schlicht et Cristina Giordano. « Mesoporous Fe3C sponges as magnetic supports and as heterogeneous catalyst ». Journal of Materials Chemistry 20, n^o 29 (2010) : 6019. http://dx.doi.org/10.1039/c0jm00774a.

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Jenie, S. N. Aisyiyah, Anis Kristiani, Sudiyarmanto, Deni S. Khaerudini et Kaoru Takeishi. « Sulfonated magnetic nanobiochar as heterogeneous acid catalyst for esterification reaction ». Journal of Environmental Chemical Engineering 8, n^o 4 (août 2020) : 103912. http://dx.doi.org/10.1016/j.jece.2020.103912.

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Manteghi, Faranak, Fatemeh Zakeri, Owen James Guy et Zari Tehrani. « MIL-101(Cr), an Efficient Heterogeneous Catalyst for One Pot Synthesis of 2,4,5-tri Substituted Imidazoles under Solvent Free Conditions ». Nanomaterials 11, n^o 4 (26 mars 2021) : 845. http://dx.doi.org/10.3390/nano11040845.

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A chromium-containing metal-organic framework (MOF), MIL-101 (Chromium(III) benzene-1,4-dicarboxylate), was used to catalyze the one pot, three component synthesis of some 2,4,5-trisubstituted imidazoles under solvent-free conditions. The advantages of using this heterogeneous catalyst include short reaction time, high yields, easy and quick isolation of catalyst and products, low amount of catalyst needed, and that the addition of solvent, salt, and additives are not needed. This catalyst is highly efficient and can be recovered at least 5 times with a slight loss of efficiency. The structure of the metal-organic frameworks (MOF) was confirmed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (HNMR) were performed to confirm some of the synthesized products. Experimental data indicated that the optimum amount of catalyst was 5 mg for benzil (1 mmol), 4-chlorobenzaldehyde (1 mmol), and ammonium acetate (2.5 mmol), and the synthetic route to the various imidazoles is performed in 10 min by 95% yield, an acceptable result rivalling those of other catalysts.

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Tao, Yongkang, Lihua Li, Lixiong Ren, Yu Liang et Xin Wang. « Effect of calcination temperature on the catalytic performance of CoFe2O4/Nitrogen doped sludge based activated carbon in activation of peroxymonosulfate for degradation of coking wastewater ». MATEC Web of Conferences 238 (2018) : 03009. http://dx.doi.org/10.1051/matecconf/201823803009.

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A novel supported heterogeneous magnetic catalyst CoFe2O4/N-doped sludge based activated carbon (CoFe2O4/N-SAC) was prepared by polymer network gel method for the first time. The physicochemical properties of the materials were characterized by means of XRD, SEM, TEM, VSM and XPS techniques. The prepared catalyst is applied to the heterogeneous activation of peroxymonosulfate for degradation of coking wastewater, and the effect of calcination temperature on the catalytic activity was investigated. The result reveals that the catalyst shows the highest catalytic activities under the calcination temperature is 800 °C with the TOC removal rate of coking wastewater is 84.31%.

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Naikwade, Altafhusen, Megha Jagadale, Dolly Kale et Gajanan Rashinkar. « Magnetic Nanoparticle Supported Ionic Liquid Phase Catalyst for Oxidation of Alcohols ». Australian Journal of Chemistry 73, n^o 11 (2020) : 1088. http://dx.doi.org/10.1071/ch19627.

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A new magnetic nanoparticle supported ionic liquid phase (SILP) catalyst containing perruthenate anions was prepared by a multistep procedure. The various analytical techniques such as FT-IR spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, thermogravimetric analysis, energy dispersive X-ray analysis, and vibrating sample magnetometer analysis ascertained the successful formation of catalyst. The performance of a magnetically retrievable SILP catalyst was evaluated in the selective oxidation of alcohols. The split test and leaching studies of the SILP catalyst confirmed its heterogeneous nature. In addition, the reusability potential of SILP catalyst was also investigated which revealed its robust activity up to six consecutive cycles.

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Rezgui, Soumaya, Aida M. Díez, Lotfi Monser, Nafaa Adhoum, Marta Pazos et M. Ángeles Sanromán. « Magnetic TiO2/Fe3O4-Chitosan Beads : A Highly Efficient and Reusable Catalyst for Photo-Electro-Fenton Process ». Catalysts 12, n^o 11 (13 novembre 2022) : 1425. http://dx.doi.org/10.3390/catal12111425.

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Heterogeneous photo-electro-Fenton process is an attractive technology for the removal of recalcitrant pollutants. To better exploit the presence of an irradiation source, a bifunctional catalyst with TiO2 nanoparticles embedded into an iron–chitosan matrix was developed. The catalytic activity of the catalyst was improved by the optimization of the loaded TiO2 content. The prepared composite catalysts based on TiO2, Fe3O4 and chitosan were called TiO2/Fe3O4-CS beads. The best catalyst with an optimal ratio TiO2/Fe = 2 exhibited a high efficiency in the degradation and mineralization of chlordimeform (CDM) insecticide. Under the optimum conditions (concentration of catalyst equal to 1 g L−1 and applied current intensity equal to 70 mA), a real effluent doped with 30 mg L−1 of CDM was efficiently treated, leading to 80.8 ± 1.9% TOC reduction after 6 h of treatment, with total removal of CDM after only 1 h.The generated carboxylic acids and minerals were identified and quantified. Furthermore, the stability and reusability of the developed catalyst was examined, and an insignificant reduction in catalytic activity was noticed for four consecutive cycles of the photo-electro-Fenton process. Analyses using SEM, XRD and VSM showed a good stability of the physicochemical properties of the catalyst after use.

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Huang, Xuanlin, Wei Du, Rong Chen et Fengxi Chen. « Adsorption-enhanced catalytic wet peroxide oxidation of aromatic compounds on ionothermally synthesised copper-doped magnetite magnetic nanoparticles ». Environmental Chemistry 17, n^o 6 (2020) : 426. http://dx.doi.org/10.1071/en19245.

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Environmental contextAromatic compounds are major organic pollutants that are hard to clean up by either adsorption or biological treatment processes. We synthesised Cu-doped Fe3O4 magnetic nanoparticles and showed that they efficiently degrade various aromatic compounds with H2O2 under mild conditions. This active and stabile heterogeneous Fenton-like catalyst has the potential for various environmental applications. AbstractMagnetite magnetic nanoparticles (Fe3O4 MNPs) have great potential in environmental remediation owing to the intrinsic peroxidase-like activity, which is unfortunately not strong enough to activate H2O2 for practical applications. Herein, Cu-doped Fe3O4 MNPs (Fe2.88Cu0.12O4) were ionothermally synthesised and demonstrated as a highly efficient and stable heterogeneous Fenton-like catalyst for the catalytic wet peroxide oxidation of aromatic compounds with H2O2 at pH ~7 and 25°C. Theoretical calculations found that the interaction between aromatic compounds (e.g. orange G) and Cu2+ through a terminal end-on binding mode with moderate strength was favourable to enhance their adsorption on Fe2.88Cu0.12O4. In addition, copper dopants increased the decomposition rate of H2O2 at 25°C about four-fold (0.584h−1 on Fe2.88Cu0.12O4 versus 0.153h−1 on Fe3O4), which is attributed to efficient redox cycling of iron and copper ions for synergistic activation of H2O2. Copper-enhanced adsorption of aromatic compounds, together with synergistic activation of H2O2 by surface iron and copper active sites, explained the higher catalytic activity of Fe2.88Cu0.12O4. This study provided new insight for improving the catalytic performance of magnetite-based heterogeneous catalysts for various environmental and biomedical applications.

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Moghaddam, Firouz Matloubi, et Seyed Ebrahim Ayati. « Copper immobilized onto a triazole functionalized magnetic nanoparticle : a robust magnetically recoverable catalyst for “click” reactions ». RSC Advances 5, n^o 5 (2015) : 3894–902. http://dx.doi.org/10.1039/c4ra13330g.

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Liu, Wang, Gao, Wang, Cheng, Wang et Zhang. « Low Temperature Chemoselective Hydrogenation of Aldehydes over a Magnetic Pd Catalyst ». Applied Sciences 9, n^o 9 (29 avril 2019) : 1792. http://dx.doi.org/10.3390/app9091792.

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Chemoselective hydrogenation of aldehydes with heterogeneous catalysts under mild conditions is of great importance but remains a major challenge. Herein, an efficient strategy was developed for low temperature chemoselective hydrogenation of aldehydes with broad substrate scope over a magnetic material supported palladium catalyst (γ-Fe2O3@HAP-Pd). Aldehydes bearing various reducible functional groups readily underwent hydrogenation to give the corresponding primary alcohols with moderate to excellent yield at room temperature in aqueous solutions. The Hammett equation revealed that the hydrogenation of aromatic aldehydes proceeded via an anionic intermediate. Additionally, when the temperature increased to 70 °C, toluene was obtained by the deoxygenation of benzaldehyde in excellent yield. Furthermore, the γ-Fe2O3@HAP-Pd could be recycled up to six times without loss of activity and metal leaching.

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Pourjavadi, Ali, Niloofar Safaie, Seyed Hassan Hosseini et Craig Bennett. « Highly dispersible and magnetically recyclable poly(1-vinyl imidazole) brush coated magnetic nanoparticles : an effective support for the immobilization of palladium nanoparticles ». New Journal of Chemistry 40, n^o 2 (2016) : 1729–36. http://dx.doi.org/10.1039/c5nj02576a.

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Gogoi, Aniruddha, Madhukar Navgire, Kanak Chandra Sarma et Parikshit Gogoi. « Novel highly stable β-cyclodextrin fullerene mixed valent Fe-metal framework for quick Fenton degradation of alizarin ». RSC Advances 7, n^o 64 (2017) : 40371–82. http://dx.doi.org/10.1039/c7ra06447k.

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Bai, Dong, et Peng Yan. « Magnetic Nanoscaled Fe₃O₄ as an Efficient and Reusable Heterogeneous Catalyst for Degradation of Methyl Orange in Microwave-Enhanced Fenton-Like System ». Applied Mechanics and Materials 448-453 (octobre 2013) : 830–33. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.830.

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In this study, the Fe3O4magnetic nanoparticles (MNPs) were synthesized as heterogeneous catalysts to effectively degrade methyl orange. The coulping method of microwave irradiation and Fenton-like reaction was used for degradation of methyl orange waste water. The effects of Fe3O4dosage, initial H2O2concentration, catalyst cycles, reaction temperature and so on were assessed systematically. The experimental results showed that the microwave-assisted Fenton-like process using H2O2/Fe3O4was the most effective treatment process compared with other traditional methods. According to degradation of methyl orange, it has been found that the oxidation by Fenton-likes reagent is dependent on Fe3O4dosage, H2O2dosage, reaction temperature. The results indicate that under the optimal conditions, the removal rate of methyl orange could reach nearly 100%. Moreover, six cyclic tests for methyl orange degradation showed that the magnetic catalyst was very stable, recoverable, highly active, and easy to separate using an external magnet. Hence, the coulping method of microwave irradiation and Fenton-like reaction with magnetic nanomaterials of Fe3O4as the catalyst has potential use in organic pollutant removal.

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