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Porous Polymer for Heterogeneous Catalysis
Published in Inamuddin, Mohd Imran Ahamed, Rajender Boddula, Porous Polymer Science and Applications, 2022
Vivek Mishra, Simran Aggarwal, Shubham Pandey
4-nitrophenol (4NP) is broadly used in the agricultural industry but is harmful and its detoxification should be done. But due to its high chemical stability, it is not easy to remove it by traditional water treatment techniques. Therefore, it is reduced to 4-aminophenol (4AP) which is widely used in the plastic and pharmaceutical industry. Earlier this reduction was carried out by using precious metals like Au, Pt, Pd, Ru, etc., which are very costly and difficult to recycle. To achieve a cost-effective methodology for the reduction of 4NP to 4AP use of Cu metal is suggested.
Catalytic Application of Magnetic Nanocomposites
Published in Sam Zhang, Dongliang Zhao, Advances in Magnetic Materials, 2017
Poly(N,N′-methylenebis(acrylamide)-co-poly(2-dimethylaminoethylmethacry late)- functionalized, magnetic nanoparticle-supported Au-NPs, named Au-NPs/Fe3O4@SiO2@PHEMA-co-PDMAEMA, were reported with a small and narrow-distributed Au-NPs (∼3.7 nm) [106]. The catalyst catalyzed reduction reaction of 4-nitrophenol to 4-aminophenol quantitatively within 15 min at room temperature. The catalyst was reused six times with sustained activity [106]. However, metal nanoparticle leaching may cause a decrease in catalyst performance due to the loss of active centers. Meanwhile, the leaching metals may also contaminate the products. To maintain the high activity, Yao et al. reported a catalyst comprising of mesoporous SiO2-coated, magnetic nanoparticle-supported Pd-NPs (Pd-NPs/FexOy)@SiO2 [107]. The coating layer of mesoporous SiO2 was slightly larger than the magnetic core, and thus the layer was movable to enhance the interaction between Pd active centers and substrates. The catalyst is highly active in reduction of 4-nitrophenol to 4- aminophenol with NaBH4 and recyclable at least 10 times with sustained activity (100% conversion). The hybrid was found highly stable even at ultrasonic treatment [107]. Interestingly, pristine Fe3O4 magnetic nanoparticles produced in situ by reducing an iron complex such as Fe(acac)3, FeAc2, FeCl3 ⋅ 6H2O, and FeCl2 ⋅ 4H2O with hydrazine in excess also showed high activity in the hydrogenation of nitroaromaticles under microwave irradiation [108,109]. With the catalysts, various functionalized aniline products were obtained in 95%–99% yields from corresponding nitroarenes using hydrazine hydrate as the reductant within 2–8 min [108,109]. The in situ- prepared, Fe3O4 nanoparticle-based catalysts were also recyclable with sustained activity. However, both commercially available Fe3O4 and Fe0 powders were not active in this type of reaction [108,109]. Fe25Co75 nanoparticles were prepared and deposited onto the surface of grapheme oxide; the supported MNPs exhibited high activity for the reduction of 4-nitrophenol with NaBH4 in a TOF value of 2.9 × 1016 s−1 [110,111]. Other active and magnetic recyclable catalysts, including Fe3O4-NPs/GOs [112] and Ni-NPs/GOs [113], were also reported using NaBH4 as the reducing agent. It was found that the activity of these magnetic nanoparticles-based catalysts could be significantly improved by near-infrared irradiation [114]. Ma and others prepared Pt-NPs (∼5 nm) catalyst supported on a carbon-coated MNPs, Pt-NPs/Fe3O4@C [115]. The catalyst was highly effective for substituted nitrobenzene, R-C6H4-NO2 (R = H, 4-Cl, 4-Br, 4-Me, 2-NH2, 3-NH2, 4-NH2, 2-OH, 4-OH, 4-CHO, 4-CH2OH, 4-COMe, and 2-NO2), to the corresponding anilines in 95%–99% yields with H2 as the reductant at room temperature [115].
Green synthesis, characterization and catalytic activity evaluation of palladium nanoparticles facilitated by Punica granatum peel extract
Published in Inorganic and Nano-Metal Chemistry, 2021
Şule Şahin Ün, Aişe Ünlü, İlker Ün, Salim Ok
Upon obtaining PdNPs with well-defined size and shape, the catalytic activity of PdNPs is tested in reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The motivation factor in testing the catalytic capacity of PdNPs on 4-nitrophenol (4-NP) is that 4-nitrophenol (4-NP) has several health threats because of being carcinogenic and genotoxic to human beings and wildlife. 4-aminophenol (4-AP) is an important industrial intermediate for producing analgesic and antipyretic drugs, and it might be produced by the reduction of 4-NP.[47] Therefore, finding and advancing an efficient, durable, and environmentally friendly approach, for example by PdNPs derived by a green synthetic route, to generate 4-AP has importance in the catalytic research.
Microwave-assisted fabrication of g-C3N4 nanosheets sustained Bi2S3 heterojunction composites for the catalytic reduction of 4-nitrophenol
Published in Environmental Technology, 2021
Dasari Ayodhya, Guttena Veerabhadram
The nitroaromatic compounds are common and important intractable organic environmental pollutant which extensively used in many industries to deal with the manufacture of pharmaceuticals, pigments, dyes, pesticides, plastics, and industrial solvents [1]. These compounds are considered as toxic/hazardous pollutants in the environment because of their toxicity and carcinogenic to humans, animals, and plants [2]. Among the nitroaromatic compounds, 4-nitrophenol (4-NP) is the most toxic effluent and serious endangers to human health, which can cause damage to the eyes, kidneys, and human blood [3]. It has been listed as a priority pollutant by the United State Environmental Protection Agency (USEPA) due to the toxicity, high stability in the environment without degradation, and it resists biodegradation [4]. Thus, 4-NP and its derivatives have been a cause of serious environmental problems. Recently, many methods are developed to solve the environmental pollution issues by the removal of 4-NP using photodegradation, adsorption, and microbial degradation. However, these methods are hardly applied in practical applications, owing to the longer operation time, lower production efficiency, and higher operation cost [5]. Therefore, it is a hot subject to develop advanced methods including catalytic reduction, iron-acid reduction, and electrolytic reduction to avoid the shortages [6]. Among them, the catalytic reduction is the most efficient method for its high conversion efficiency and mild operating conditions [5,7]. Currently, the catalytic conversion of 4-NP into 4-aminophenol (4-AP) has attracted attention due to the widespread use of 4-AP is an intermediate in the production of dyes, pigments, agrochemicals, photographic developers, and pharmaceuticals [8]. The 4-AP is less toxic than the 4-NP and it can be degraded by microorganisms. Therefore, it is regarded as a promising conversion route to convert 4-NP into 4-AP through catalytic reduction method. Now a lot of efforts have been done devote to the development of the catalysts including noble metals, metal oxides, and semiconductors for efficient reduction of 4-NP under mild conditions. However, these noble metals are expensive and rare, which makes the future of the noble metal-containing catalysts become doubtful. Hence, it recently became a research hotspot to develop metal-free catalysts such as g-C3N4 and these catalysts exhibit high catalytic activity for the reduction of 4-NP [9].