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Clausthal-Zellerfeld, Germany

Darwish M.S.A.,Egyptian Petroleum Research Institute | Kunz U.,Institute of Chemical Process Engineering | Peuker U.,Institute of Mechanical Process Engineering
Advanced Materials Research | Year: 2013

Different types of functionalized polymer magnetic core with diameters of 10-20 nm were prepared by condensation polymerization. Bi-layered polymer magnetic core nanoparticles were prepared by coating of magnetic core hydrophobic polymer shell composites of magnetic polyvinylbenzyl chloride with another layer. The second layer consists of 3-amino-1-propanol, butyl-l, 4-diamine or hexamethylenediamine The morphology and size of the magnetic polymer nanoparticles were characterized by TEM. The structure was characterized by IR, TGA and chemical stability against concentrated hydrochloric acid. The magnetic nanocomposites with hydrophilic behavior were easily separated by magnetic field and gives enhancing for using as nanocarrier in bioapplications. © (2013) Trans Tech Publications, Switzerland. Source


Darwish M.S.A.,Egyptian Petroleum Research Institute | Kunz U.,Institute of Chemical Process Engineering | Peuker U.,Institute of Mechanical Process Engineering and Mineral Processing
Journal of Applied Polymer Science | Year: 2013

Platinum (Pt) nanoparticles show high activity as catalysts in various chemical reactions. The control of the morphology of Pt nanostructures can provide an opportunity to improve their catalytic properties. The preparation of Pt-loaded iron-oxide polyvinylbenzyl chloride nanocomposites was done in several stages: first by the formation of the core consisting of magnetite nanoparticles and second by the polymerization of vinylbenzyl chloride in the presence of the magnetic core particles. The third step is the amination of the chlorine group with ammonia, which leads to an ion exchange resin. Then, the Pt precursor (H2PtCl6) is attached by ion exchange. Finally, the Pt ions are reduced to Pt metal with NaBH4. The obtained material can be dispersed easily and be used as a catalyst which can be separated after the reaction by magnetic fields. Characterization of the resulting metallic nanocomposites is evaluated by atomic absorption spectroscopy, thermal gravimetric analysis, transmission electron microscopy, infrared spectroscopy, and gas chromatography. The activity of Pt at magnetic core/shell nanocomposites was measured for the reduction reaction of cinnamaldehyde to cinnamyl alcohol. © 2012 Wiley Periodicals, Inc. Source


Wess R.,Institute of Chemical Process Engineering | Nores-Pondal F.,CONICET | Laborde M.,CONICET | Giunta P.,CONICET
Chemical Engineering Science | Year: 2015

The effect of CO2 removal with CaO in the production and purification of fuel cell-grade H2 by glycerol steam reforming is studied from a thermodynamic point of view. Results obtained with the non-stoichiometric method show that CaO enables some improvements to the conventional steam reforming since four simultaneous processes take place at the same stage: H2 production, CO2 separation, CO elimination and heat supply: by separating the CO2 from the gaseous mixture, CaO also shifts the equilibrium towards the production of H2 compared to conventional reforming, and the operating temperature is lowered with respect to conventional steam reforming. The removal of CO2 not only enables higher H2 purity (close to 100% on dry basis) but reduces the amounts of CO as well. For temperatures below ca. 750K, a level lower than 20ppm (on dry basis) can be reached, thus avoiding the need of a purification stage. Since the reaction of CaO with CO2 is exothermic, the heat is supplied within the reactor. Finally, it was found that the system behavior was strongly dependent on the presence of Ca(OH)2.This four-in-one process can be a way of enhancing the efficiency of the overall system of production-purification of H2. © 2015 Elsevier Ltd. Source


Voelskow K.,Institute of Chemical Process Engineering | Nickelsen L.,Institute of Chemical Process Engineering | Becker M.J.,Universitatsstr 150 | Xia W.,Universitatsstr 150 | And 4 more authors.
Chemical Engineering Journal | Year: 2013

A setup for optically monitoring the agglomerate growth of multiwalled carbon nanotubes (MWCNTs) by catalytic chemical vapor deposition on single Co-Mn-Al-Mg oxide catalyst particles with ethene as carbon precursor has been developed. Ethene concentrations and temperatures were varied between 5. -75. Vol.% and 550-770. °C, respectively. It could be shown that the agglomerate growth is rapid and the final diameter is reached after a few ten seconds to about 3. min depending on the reaction conditions. The average enlargement factor of the agglomerates over all experiments was found to be 6.5. ±. 1.2 compared to the original diameter of the catalyst particle. The growth rate is enhanced by both, reaction temperature and ethene concentration. Hence it is concluded that the agglomerate growth rate is associated with the reaction rate of MWCNT synthesis. Short time experiments and analysis of the resulting agglomerates have confirmed an earlier proposed growth mechanism. © 2013 Elsevier B.V. Source


Voelskow K.,Institute of Chemical Process Engineering | Becker M.J.,Ruhr University Bochum | Xia W.,Ruhr University Bochum | Muhler M.,Ruhr University Bochum | Turek T.,Institute of Chemical Process Engineering
Chemical Engineering Journal | Year: 2014

CNT growth experiments on a cobalt-based catalyst were conducted in a tubular fixed bed reactor at different temperatures and ethene concentrations. The measured kinetic data were analyzed with an isothermal, dynamic reactor model taking into account pore and film diffusion as well as the size of CNT agglomerates as a function of time. Based on previously published results it was found that the CNT agglomerates are enlarged by an average factor of 6.5 compared to the original diameter of the catalyst particle. Under these conditions, the development of the agglomerate diameter with time can be described with a single parameter which is independent of the reaction conditions. The rate of the CNT growth was determined to be first order in the ethene concentration with an activation energy of 107. kJ/mol. The catalyst deactivation by cumulative encapsulation of active sites was found to be second order with respect to the consumed amount of ethene with a rate constant independent of the temperature. Nevertheless, deactivation takes place faster at higher temperatures and/or ethene concentrations, since the deactivation process is directly coupled to the rate of CNT synthesis. © 2014 Elsevier B.V. Source

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