Application of carbonized ion exchange resin beads as catalyst support for gas phase hydrogenation processes
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Carbonized ion exchange resin beads were prepared as catalyst for gas phase hydrogenation processes. Amberlite IR 120 polystyrene based sulfonated ion exchange beads were carbonized at 900 °C. The process of carbonization was monitored by FTIR combined thermogravimetric analysis. During the carbonization formed sulfur dioxide, carbon dioxide and organic compounds. The carbon pearls were used as catalyst support for Pd nanoparticles. The catalyst was characterized by scanning electron microscopy and X-ray diffractometry. The diameters of the palladium nanoparticles on the catalyst surface were between 15 and 50 nm, but bigger aggregates were also detected. The catalyst was tested during the gas phased heterogeneous catalytic hydrogenation of 1-butene. The hydrogenation process was followed by FTIR measurements, 93% conversion was reached after 10 min.
KeywordsResin beads Carbonization Gas phased hydrogenation
Carbon based catalysts have an important role in industrial catalytic processes due to the high specific surface area [1, 2], and excellent heat conductivity  of the various carbon allotropes which makes them exceptional catalyst supports. Activated carbon , norit , or carbon nanotubes  usually decorated with catalytically active metal particles like Pd, Rh, or Pt and applied in many different reactions such as hydrocarbon oxidation , fuel production from biomass  or hydrogenation reactions. Among these, hydrogenation has far the most significant applications [9, 10, 11], particularly in case of carbon nanotube supported systems [12, 13, 14]. By applying carbon supported catalysts, the hydrogenation of nitrobenzene was successfully carried out to produce aniline [15, 16, 17]. Another important application is the gas phase hydrogenation of olefins [18, 19].
For these applications, carbon-based support materials should be created. Many different methods have already been developed for carbon material production like CVD method, ultrasonic synthesis, or electric arc technique [20, 21, 22] but one of the best methods is carbonization [23, 24, 25]. For example, activated carbon can be made by carbonizing different natural sources like bamboo chips, cherry stones, fox nut shell, sugarcane , coconut husk  and rice-straw . The carbonization of ion exchange resins is another valid method to prepare carbon nanomaterials  and the resulted nanoporous carbon materials have a wide range of applications . Singare and his colleges successfully created carbon layers from acidic cation exchange resin with thermal degradation to prepare an electrically conductive coating . Zhao et al. made porous carbon support by carbonizing phenol resin and by decorating it with Pt particles the system was stable and well usable for methanol oxidation in fuel cells . Other carbon nanostructure based catalysts were also tested successfully in oxidative reactions of different aromatic compounds [33, 34, 35, 36].Carbonized resin supports are promising materials in catalytic applications, and they have been employed in liquid phase reactions successfully . However, despite their special structure, to the best of our knowledge, resin based supports have not applied in gas phase processes. For this reason, the potential catalytic application of ion exchange resin beads has been investigated and they have been carbonized and applied as catalyst support in a gas phase hydrogenation process.
Materials and methods
Amberlite IR120 cation exchange resin (H+ form, Sigma Aldrich) was used in the measurements. Palladium(II) nitrate dihydrate (Pd(NO3)2·2H2O, Merck) was applied to prepare the catalyst. Nitrogen (99.995, Messer) and hydrogen (99.9990, Messer) were used for carbonization and catalyst activation.
The process of carbonization of the Amberlite resin was followed by Fourier transform infrared spectroscopy supported with thermogravimetric analysis (FTIR–TGA). The gas cell of Bruker Vertex 70 spectrometer was combined with NETZSCH TG 209 Tarsus thermo-microbalance. The gases formed during the heat-decomposition were detected by FTIR (from 4000 to 400 cm−1 at 4 cm−1 optical resolution) depending on the heating temperature. The thermogravimetric analysis was carried out in a range of 35–900 °C, while the heating rate was 10 °C/min in synthetic air atmosphere, and the flow velocity was 20 ml/min.
The functional groups on the surface of the oxidized carbon nanotubes were determined by Bruker Vertex 70 FTIR spectroscope. All samples were investigated in potassium bromide pellets (5 mg N-BCNT in 250 mg KBr).
The different phases formed by the palladium particles on the surface of the carbon beads identified by X-ray diffraction analysis (XRD) with Rigaku Miniflex instrument (Cu Kα source).
The surface and particle morphology of the catalytic palladium particles have been characterized by scanning electron microscopy (SEM, Hitachi S 4800), while the samples were fixed with carbon tape rubber.
The sulfur, carbon, and hydrogen content of the Amberlite IR120 and the carbonized resin have been measured by Vario Macro CHNS element analyzer and the carrier gas was helium (99.9990%).
During the catalyst preparation, palladium nanoparticles were deposited onto the surface of the carbonized resin pearls. The carbon beads (12 g) were impregnated by 15 ml 2 wt% palladium solution (1 g Pd(NO3)2·2H2O in 50 ml water) which was added to 100 ml distilled water. The water was evaporated and the carbon beads impregnated with Pd were dried at 120 °C overnight. The impregnated beads were heat-treated in nitrogen flow at 400 °C for 20 min. Then, to form catalytically active Pd nanoparticles on the surface of the beads, the system was hydrogenated at 400 °C for 30 min.
The system was calibrated for five different 1-butene concentrations to ensure a linear quantitative response.
First step of the catalyst preparation: decomposition of the ion exchange resin measured by FTIR–TGA
Results of the elemental analysis of the Amberlite IR120 resin and its carbonized counterpart
Amberlite IR 120
FTIR analysis of the non-carbonized and the carbonized ion exchange resin
Second step of the catalyst preparation: deposition of Pd nanoparticles on the surface of the carbonized resin have been proved by XRD results
Surface characterization of the Pd catalyst based on SEM–EDS results
Catalytic test of the Pd/carbonized resin catalyst
Carbon beads were synthesized from polystyrene based ion exchange resin pearls. The carbonization process was followed by FTIR–TGA measurements. On the surface of the carbon beads several hydroxyl groups were detected, which were applicable for the anchoring of catalytically active metal ions. The presence of hydroxyl groups on the surface of the beads makes them easily wettable in the aqueous phase of catalytic metal precursors. The activation step (reduction in H2) of the palladium precursor impregnated carbon beads was efficient based on the XRD results, and it was similar to the conventional catalyst activation. On the surface of the catalyst, palladium nanoparticles were identified in homogeneous dispersibility with small particle size (the average diameter was 39 nm). The prepared Pd/carbonized resin catalyst was successfully tested in 1-butene hydrogenation. High catalytic activity was achieved (93% conversion). By the carbonization of ion exchange resin beads, excellent catalyst support materials could be produced, which are easily applicable in gas phased hydrogenation of olefins.
Open access funding provided by University of Miskolc (ME). This research was supported by the European Union and the Hungarian State, co-financed by the European Regional Development Fund in the framework of the GINOP-2.3.4-15-2016-00004 project, aimed to promote the cooperation between the higher education and the industry.
Compliance with ethical standards
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
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