RESUMEN
This study reports a versatile process for the fabrication of a microporous heterogeneous palladium nanocatalyst on a novel spherical, biodegradable, and chemically/physically resistant catalyst support consisting of chitosan (CS) and cigarette waste-derived activated carbon (CAC). The physicochemical properties of the microporous Pd-CS-CAC nanocatalyst developed were successfully determined by FTIR, XRD, FE-SEM, TEM, BET, and EDS techniques. TEM studies showed that the average particle size of the synthesized Pd NPs was about 30 nm. The catalytic prowess of microporous Pd-CS-CAC was evaluated in the reduction/decolorization of various nitroarenes (2-nitroaniline (2-NA), 4-nitroaniline (4-NA), 4-nitrophenol (4-NP), and 4-nitro-o-phenylenediamine (4-NPD)) and organic dyes (methyl red (MR), methyl orange (MO), methylene blue (MB), congo red (CR), and rhodamine B (RhB)) in an aqueous medium in the presence of NaBH4 as the reducing agent at room temperature. The catalytic activities were studied by UV-Vis absorption spectroscopy of the supernatant at regular time intervals. The short reaction times, mild reaction conditions, high efficiency (100% conversion), easy separation, and excellent chemical stability of the catalyst due to its heterogeneity and reusability are the advantages of this method. The results of the tests showed that reduction/decolorization reactions were successfully carried out within 10-140 s due to the good catalytic ability of Pd-CS-CAC. Moreover, Pd-CS-CAC was reused for 5 consecutive times with no loss of the initial shape, size, and morphology, confirming that it was a sustainable and robust nanocatalyst.
Asunto(s)
Quitosano , Paladio , Paladio/química , Quitosano/química , Colorantes/química , Rojo Congo/química , Extractos Vegetales/química , CatálisisRESUMEN
Hibiscus Rosasinensis L. extract mediated biosynthesis of Pd nanoparticles (NPs) and their deposition on the magnetic calcium lignosulfonate (MCaLig), as a simple and eco-friendly process for the preparation of Pd NPs@Fe3O4-lignin, is reported. The Pd NPs@Fe3O4-lignin was characterized by TEM, XRD, EDS, FE-SEM, FT-IR, VSM, and UV-Vis. The magnetic NPs were employed as exceptional catalysts in the catalytic reduction of Cr(VI) and Suzuki-Miyaura reaction between PhB(OH)2 and substituted aryl halides in EtOH:H2O as well as under ligand free conditions in the presence of K2CO3 with satisfactory product yields. Regeneration of the Pd NPs@Fe3O4-lignin was carried out by a magnet after the preparation of biphenyls. Catalytic efficiency retention was achieved after seven cycles.
Asunto(s)
Cromo/química , Compuestos Férricos/química , Hibiscus/química , Lignina/química , Nanopartículas/química , Paladio/química , Extractos Vegetales/química , Compuestos de Bifenilo/química , Catálisis , Tecnología Química Verde/métodos , Lignina/análogos & derivados , Magnetismo/métodos , Hojas de la Planta/química , Espectroscopía Infrarroja por Transformada de Fourier/métodosRESUMEN
One of the most important problems in catalytic systems is metal leaching due to weak interactions between the supporting material and the metal ions. It adversely affects the reusability and catalytic performance of catalysts. In this study, a novel support material, which is a composed Schiff base functionalized pectin bio-polymer with good coordination performance against palladium ions, was designed and characterized to overcome the afore-mentioned problems. Then the catalytic activity of the designed pectin supported palladium catalyst (Pct-Pd) was evaluated in Suzuki-Miyaura coupling reactions. Pct-Pd catalyst provided excellent conversion yields in the reactions within 8â¯min. Additionally, Pct-Pd catalyst displayed superior reproducibility by giving 91% of conversion yield after 12 successive runs. Leaching test revealed that leaching of palladium ions from prepared support was negligible even after 12 runs. This study shows that the designed Pct-Pd catalyst can be transferred from academic laboratory to industrial applications due to its excellent reusability and catalytic activity.
Asunto(s)
Microondas , Paladio/química , Pectinas/química , Bases de Schiff/químicaRESUMEN
Bio-based catalyst support materials with high thermal and structural stability are desired for catalysts systems requiring harsh conditions. In this study, a thermally stable palladium catalyst (up to 440°C) was designed from sporopollenin, which occurs naturally in the outer exine layer of pollens and is widely acknowledged as chemically very stable and inert biological material. Catalyst design procedure included (1) extraction of sporopollenin microcapsules from Betula pendula pollens (â¼25µm), (2) amino-functionalisation of the microcapsules, (3) Schiff base modification and (4) preparation of Pd(II) catalyst. The catalytic activity of the sporopollenin microcapsule supported palladium catalyst was tested in catalysis of biaryls by following a fast, simple and green microwave-assisted method. We recorded outstanding turnover number (TON: 40,000) and frequency (TOF: 400,000) for the catalyst in Suzuki coupling reactions. The catalyst proved to be reusable at least in eight cycles. The catalyst can be suggested for different catalyst systems due to its thermal and structural durability, reusability, inertness to air and its eco-friendly nature.
Asunto(s)
Anisoles/química , Biopolímeros/química , Ácidos Borónicos/química , Carotenoides/química , Paladio/química , Bases de Schiff/química , Betula/química , Biopolímeros/aislamiento & purificación , Cápsulas/química , Carotenoides/aislamiento & purificación , Catálisis , Técnicas de Química Sintética , Equipo Reutilizado , Microondas , Polen/químicaRESUMEN
Differences in the physichochemical properties of the chitin structure of the exoskeleton of seven species from four genera were investigated in this study. The same method was used to isolate the chitin structure of the seven species. The physicochemical properties of the isolated chitins were revealed by ESEM, FTIR, TGA and XRD analyses. The FTIR, TGA and XRD results from the chitin samples were similar. The surface morphologies of the chitins were investigated by ESEM and interesting results were noted. While the surface morphologies of the chitins isolated from two species within the same genus were quite different, the surface morphologies of chitins isolated from species belonging to different genera showed similarity. It was determined that the dry weight chitin contents of the grasshopper species varied between 5.3% and 8.9%. The results of molecular analysis showed that the chitins from seven Orthoptera species (between 5.2 and 6.8 kDa) have low molecular weights. Considering that these invasive and harmful species are killed with insecticides and go to waste in large amounts, this study suggests that they should be collected and evaluated as an alternative chitin source.
Asunto(s)
Quitina/química , Ortópteros/química , Animales , Quitina/aislamiento & purificación , Quitina/ultraestructura , Conformación Molecular , Peso Molecular , Extractos Vegetales/química , Extractos Vegetales/aislamiento & purificación , Espectroscopía Infrarroja por Transformada de Fourier , Termogravimetría , Difracción de Rayos XRESUMEN
Biosorbents have been widely used in heavy metal removal. New resources should be exploited to develop more efficient biosorbents. This study reports the preparation of three novel chitosan microcapsules from pollens of three common, wind-pollinated plants (Acer negundo, Cupressus sempervirens and Populus nigra). The microcapsules were characterized (Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and elemental analysis) and used in removal of heavy metal ions: Cd(II), Cr(III), Cu(II), Ni(II) and Zn(II). Their sorption capacities were compared to those of cross-linked chitosan beads without pollen grains. C. sempervirens-chitosan microcapsules exhibited better performance (Cd(II): 65.98; Cu(II): 67.10 and Zn(II): 49.55 mg g(-1)) than the other microcapsules and the cross-linked beads. A. negundo-chitosan microcapsules were more efficient in Cr(III) (70.40 mg g(-1)) removal. P. nigra-chitosan microcapsules were found to be less efficient. Chitosan-pollen microcapsules (except P. nigra-chitosan microcapsules) can be used in heavy metal removal.