Clausthal-Zellerfeld, Germany
Clausthal-Zellerfeld, Germany

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Atanasov V.,Institute of Chemical Process Engineering | Oleynikov A.,Institute of Chemical Process Engineering | Xia J.,Institute of Chemical Process Engineering | Lyonnard S.,CNRS Structure and Properties of Molecular Architectures Laboratory | And 2 more authors.
Journal of Power Sources | Year: 2017

In this paper we introduce polyelectrolyte membranes based on phosphonated poly(pentafluorostyrene) (PPFS) and their performances in a fuel cell. The polyelectrolytes were obtained via partial phosphonation of PPFS varying the phosphonation degree from 17 to 66%. These membranes showed a high resistance to temperature (Tdecomp. = 355–381 °C) and radical attack (96–288 h in Fenton's test). A blend membrane consisting of 82 wt% fully phosphonated PPFS and 18 wt% poly(benzimidazole) is compared to the 66% phosphonated membrane having similar ion-conductivity (σ = 57 mS cm−1 at 120 °C, 90% RH). In the fuel cell the blend showed the best performance reaching 0.40 W cm−2 against 0.34 W cm−2 for the 42 wt% phosphonated membrane and 0.35 W cm−2 for Nafion 212. Furthermore, the blend maintained its operation at potentiostatic regime (0.5 V) for 620 h without declining in its performance. The highest power density of 0.78 W cm−2 was reached for the blend with a thickness of 15 μm using humidified oxygen (RH > 90%) at the cathode side. The switch from humidified to dry gasses during operation reduced the current density down to 0.6 A cm−2, but the cell maintained under operation for 66 h. © 2017 Elsevier B.V.


Kelling R.,Institute of Chemical Process Engineering | Bickel J.,Institute of Chemical Process Engineering | Nieken U.,Institute of Chemical Process Engineering
Computers and Chemical Engineering | Year: 2014

Convection dominated processes in chemical engineering are frequently accompanied by steep propagating fronts. Numerical simulation of corresponding models with uniform fixed grids requires an excessive amount of grid points along the expected range of the front movement. In this contribution the implementation of an efficient adaptive grid method is presented and applied to two relevant spatially one-dimensional cases, the chlorination stage of the Deacon process and oxygen storage processes in a three-way catalyst. The algorithm exhibits a high accuracy with a much lower number of grid points and a therefore reduced computational effort as opposed to a fixed grid simulation. The present work demonstrates that the algorithm allows for a robust, simple, and fast implementation of the adaptive grid method in common simulation tools and, together with adequate supplementary material, aims to make the method readily accessible to the interested reader. © 2014 Elsevier Ltd.


Kelling R.,Institute of Chemical Process Engineering | Kolios G.,BASF | Tellaeche C.,BASF | Wegerle U.,BASF | And 2 more authors.
Chemical Engineering Science | Year: 2012

Hydrocarbon processes are frequently accompanied by catalyst deactivation through coke deposition on the catalyst surface. A control strategy is proposed for catalyst regeneration in a novel dehydrogenation process designed to be operated in a cyclic production-regeneration mode. The task of the controller is to ensure complete regeneration while maintaining strict limits regarding regeneration time and maximum temperature. The major challenge arises from the uncertainty in the total amount and the spatial distribution of coke loading. The problem is tackled by a model-based approach. This includes a modular analysis of the open-loop behavior and a consistent controller configuration. © 2011 Elsevier Ltd.


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.


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.


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.


Darwish M.S.A.,Institute of Chemical Process Engineering | MacHunsky S.,Institute of Mechanical Process Engineering and Mineral Processing | Peuker U.,Institute of Mechanical Process Engineering and Mineral Processing | Kunz U.,Institute of Chemical Process Engineering | Turek T.,Institute of Chemical Process Engineering
Journal of Polymer Research | Year: 2011

Magnetic composite particles with a magnetic core consisting of superparamagnetic iron oxide and a cover layer of hydrophobic polyvinylbenzylchloride are described. The magnetite was prepared by precipitation starting with mixed iron II and iron III salts and coating of the solid with oleic acid. The coating is conducted via the liquid-liquid phase transfer. Thereby oleic acid adsorbed on the magnetite surface. In a second step the oleic acid treated magnetite was coated with polyvinylbenzylchloride in a miniemulsion polymerization to get a protective layer. The obtained magnetite core-shell nano-composites with chlorine functionality were characterized by different methods: particle size measurement, acid treatment, iron content, morphology and elemental profiles across the composite particles diameter. The test result reveals the binding of the iron oxide inside the composites which can be also recognize in TEM pictures. © 2010 Springer Science+Business Media B.V.


Hirschler M.,Institute of Chemical Process Engineering | Sackel W.,Institute of Chemical Process Engineering | Nieken U.,Institute of Chemical Process Engineering
International Journal of Heat and Mass Transfer | Year: 2016

In this work we present one possible approach to discretize the Maxwell–Stefan equation for coupled multi-component mass transport in Smoothed Particle Hydrodynamics (SPH). By the knowledge of the authors this is the first time that Maxwell–Stefan diffusion is investigated in the context of SPH. We validate the proposed model using the Stefan problem to demonstrate convergence and compare it to experimental and numerical references. Good agreement was found. An application to a phase separating ternary mixture demonstrates its applicability. © 2016 Elsevier Ltd


Pinnow S.,Institute of Chemical Process Engineering | Chavan N.,Institute of Chemical Process Engineering | Turek T.,Institute of Chemical Process Engineering
Journal of Applied Electrochemistry | Year: 2011

A mathematical model for a porous, silver-based electrode for the oxygen reduction in alkaline solutions, based on the thin film flooded agglomerate theory, was developed. These electrodes are employed in the energy-efficient chlor-alkali electrolysis with oxygen depolarized cathodes. The model parameters were determined from overpotentials at different oxygen concentrations obtained in half-cell measurements. For the description of the reaction kinetics, it was necessary to introduce two Tafel equations, which might be explained by a change of the adsorption isotherm of the intermediate species during oxygen reduction. The model allows for a successful description of the overpotentials in the region of industrially relevant current densities. The analysis of the oxygen concentration distribution in the liquid electrolyte reveals that massive diffusion limitations occur although the calculated size of the agglomerates is only in the range of a few micrometers. © 2011 Springer Science+Business Media B.V.


Kelling R.,Institute of Chemical Process Engineering | Eigenberger G.,Institute of Chemical Process Engineering | Nieken U.,Institute of Chemical Process Engineering
Catalysis Today | Year: 2016

Dry reforming (DRM) is a very promising route for producing carbon rich syngas from key future feed stocks of chemical industry: CO2 and methane. Partial combustion of methane with pure oxygen, preferably produced via water electrolysis, can be used to compensate for the required heat of reaction in autothermal operation of DRM. Therefore, a novel reactor concept is presented. The multitubular reactor consists of an inert section to perform efficient heat integration and a catalytically coated reaction section where temperatures far above 1000°C are realized by means of ceramic materials, a suitable catalyst, and simultaneous combustion. A prototype laboratory scale reactor, equilibrium models, and a detailed kinetic model are used to measure the reactor performance in laboratory and in industrial scale. A stable operation is predicted in large scale reactors since constantly high reaction temperatures around 1000°C can prevent harmful coke formation. Besides, the high temperatures enable CO2 conversions above 60% along the catalyst zone in a reactor which is characterized by a very simple and scalable design. © 2016 Elsevier B.V.

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