A facial, scalable, and green synthesis of superparamagnetic palladium–carbon catalyst and its use in disproportionation of gum rosin
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We reported here the preparation, characterization, and catalytic ability of a Fe3O4–supported palladium–carbon (Fe3O4–Pd–C) as an efficient catalyst in disproportionation of gum rosin. The magnetic nanocatalyst was prepared by a simple method and was characterized by FTIR, XRD, TEM, N2 adsorption–desorption, VSM, and atomic absorption analysis. The prepared catalyst displayed excellent activity in disproportionation of gum rosin. The magnetic Fe3O4–Pd–C catalyst was successfully recycled three times with keeping its catalytic performance. The simplicity of the nanocatalyst production method and simple separation and recyclability, on the other hand, make possible the industrial production and application of the catalyst.
KeywordsMagnetic palladium–carbon Palladium–carbon Magnetic active carbon Disproportionated rosin (DPR) Gum rosin Activated carbon
An attractive alternative to filtration or centrifugation is magnetic separation [5, 6, 7, 8]. Magnetic separation method due to simplicity, high efficiency, and low cost has been widely used. In this regard, many researches are concentrating on modified active carbon [9, 10, 11, 12]. For example, recently, Schuth et al. have reported in situ preparation of magnetic-activated carbon by formation of Fe3O4 nanoparticles in the pores of carbon . More recently, preparation of activated maize cob coated with magnetic nanoparticles have been reported by Morad et al. for methylene blue (MB) adsorption . Kakavandi et al. used magnetic-activated carbon for removal of aniline . Mohan et al. used magnetic-activated carbon for tri-nitrophenol removal from aqueous solution . However, in the most of these reports, magnetic active carbon is used as an absorbent, and research on modified carbon using magnetic nanoparticles as a support for application in catalytic reaction has not been reported before.
In our recently efforts, we have found that the activated carbon-supported palladium nanoparticles are an efficient nanocatalyst for the disproportionation of rosin . Here in, the catalytic activity of magnetic palladium–carbon for disproportionation of rosin is reported.
All reagents and chemicals were purchased from the Daejung, Merck and Aldrich companies, and gum rosin was obtained as a gift from Padideh Shimi Jam Co.
Preparation of the activated carbon-supported palladium nanoparticles (Pd–NP–AC)
Twenty grams of activated carbon was dispersed in 50 ml distilled water at 80 °C. One gram of palladium metal was dissolved in aqua regia (4 ml) and added to the reaction mixture. After 2 h, the resulting black solid was filtered and washed by the use of distilled hot water for three times. The sample was dispersed in 60 ml distilled water, and using 2 M sodium hydroxide solution the pH was increased to 9. Next, 60 ml formaldehyde solution (37%) was added to the reaction. After 2 h at 80 °C, the resulting solid was filtered and washed using hot water and dried at 105 °C.
Preparation Fe3O4–palladium–active carbon (Fe3O4–Pd–C)
FeCl3·6H2O (8.7 mmol) and FeCl2·4H2O (4.3 mmol) were dissolved in distilled water at N2 atmosphere. Subsequently, at 90 °C, 15 ml ammonia (25%) and 1 g of palladium–active carbon were added to the reaction mixture. After 30 min, the formed Fe3O4–Pd–C was collected with a magnet, washed three times with distilled hot water and dried at 105 °C. Fe3O4 nanoparticles were individually prepared according to the above procedure without adding palladium–carbon.
General procedure for gum rosin disproportionation by Fe3O4–Pd–C
In a three-neck flask fitted with a stirrer, condenser, and thermometer, 100 g of gum rosin was heated under N2 atmosphere. Once temperature of reaction was reached to 280 °C, and a sample was withdrawn. Subsequently, Fe3O4–Pd–C was added to reaction flask and more samples were withdrawn every 1 h. A gas chromatography analysis was performed for a quantitative analysis of the samples .
Recyclability of Fe3O4–Pd–C catalyst
To recycle the Fe3O4–Pd–C catalyst, the catalyst was collected by a magnet, washed with iso-propanol, and dried at 80 °C.
Result and discussion
The crystal size of the Fe3O4 nanoparticles was calculated using Scherrer’s equation . The determined particle size for Fe3O4 nanoparticles in the Fe3O4 and Fe3O4–Pd–C came out to be 28 nm and 7.5 nm, respectively. This reveals that during the synthesis of the Fe3O4 nanoparticles, Pd–C prevents aggregation of these nanoparticles and because of that Fe3O4 nanoparticles loaded on activated carbon had the smallest sizes.
Here in, the catalytic activity of Fe3O4–Pd–C in the synthesis of DPR from gum rosin was studied, and the reaction was checked by gas chromatography (GC) analysis . A control experiment showed that Fe3O4 and Fe3O4–active carbon could not catalyze this disproportionation reaction, and the presence of palladium is essential. When the reaction was carried out with Fe3O4–Pd–C (0.1% w/w), dehydroabietic acid was obtained in 65% yield after 6 h. If the reaction temperature is decreased from 280 to 220 °C, dehydroabietic acid will obtain in 19.6% yield. After evaluation of the catalytic activity of Fe3O4–Pd–C, optimization shows that the best result was obtained by using of 0.25% w/w of Fe3O4–Pd–C with an optimal reaction temperature of 280 °C. In this condition, dehydroabietic acid was obtained in 74% yield after 1 h.
Reusability test of catal
DAA % First run
DAA % Second run
DAA % Third run
In conclusion, the catalytic disproportionation of gum rosin over a magnetic palladium–carbon (Fe3O4–Pd–C) was investigated. The catalyst obtained via the pathway described in this manuscript is essentially superparamagnetic, has high porosities and high surface areas, and displayed suitable activity in disproportionation of gum rosin. The Fe3O4–Pd–C catalyst was stable and reusable for at least three reaction runs. Such findings are important because the simplicity of the nanocatalyst production method and simple separation and recyclability on the other hand make possible the industrial production and application of the catalyst.
We are thanks the INSF (Iran National Science Foundation), Tarbiat Modares University and Padideh Shimi Jam Co. for supporting of this work.
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