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Mishra P.,Indian Institute of Technology Guwahati | Mekala S.,Indian Institute of Technology Guwahati | Dreisbach F.,Universitatsstr 142 | Mandal B.,Indian Institute of Technology Guwahati | Gumma S.,Indian Institute of Technology Guwahati
Separation and Purification Technology | Year: 2012

In this work, we report the gas adsorption properties of a zinc based metal organic framework, (Zn 2(bdc) 2(dabco)(H 2O) 0.5(DMF) 4), more commonly known as ZnDABCO. Equilibrium adsorption isotherms for four industrially relevant gases (CO 2, CO, CH 4 and N 2) were measured up to 26 bar at three different temperatures (294, 314 and 350 K) using a standard gravimetric method. The isotherms were modeled using modified virial equation. Ideal Adsorbed Solution Theory (IAST) was used to predict selectivity of binary mixtures. The results indicate that absence of open metal centers in the ZnDABCO framework, results in lower capacities and adsorption enthalpies when compared to MOFs like CuBTC and MIL-101. The small values of adsorption enthalpy and Henry constant should make it easier to regenerate the adsorbent. IAST predicts an increase in the selectivity of CO 2 over the other three gases, with increasing pressure and CO 2 mole-fraction; this phenomenon is attributed to the increase in lateral interactions between the adsorbed CO 2 molecules. IAST predictions also indicate that this framework shows selectivity for CH 4 over CO. © 2011 Elsevier B.V. All rights reserved.


Harte R.,University of Wuppertal | Hoffer R.,Ruhr University Bochum | Kratzig W.B.,Kratzig and Partner Ingenieurgesellschaft MbH | Mark P.,Ruhr University Bochum | Niemann H.-J.,Universitatsstr 142
Engineering Structures | Year: 2013

Solar updraft power technology will generate highly sustainable electricity in world-wide deserts in future. It will overcome certain deficits of present renewable energy technologies. In several countries, such power plants are in pre-design stage, forming an important contribution of structural engineering to future energy supply. The present manuscript starts with the working principles of solar updraft power plants, followed by explaining climatic and wind-technologic design assumptions. Then the central solar updraft chimney - the power tower - is treated in more detail: a thin ring-stiffened RC shell of extreme height, forming the utmost structural challenge of such plants. This part is followed by technical requirements for the collector constructions, by far the largest glass-covered areas ever built, and of the wind-loading on the glazing. Then, further design aspects are extracted by the durability requirements for at least 100. years of operation in extreme desert climates. The paper closes with some cost estimates for the generated electricity. © 2013 Elsevier Ltd.


Niemann H.-J.,Ruhr University Bochum | Diburg S.,Universitatsstr 142
Computers and Structures | Year: 2013

The "Comité Européen de Normalisation" developed unified technical standards for application within the EU. The Eurocode EN 1990 is the basic document regarding the requirements for structural reliability. The code is based on the partial factor method. The Gumbel Type I probability distribution is applied to predict extreme values of climatic actions. The authors extend this approach to the generalised Gumbel distribution allowing including an upper limit of the climatic variable. For estimating the distribution parameters, a statistical methodology called ProGumbel has been developed. The implications for statistical analyses of wind speeds and determination of design wind speeds are discussed. © 2013 Elsevier Ltd.


Rincon R.A.,Ruhr University Bochum | Battistel A.,Ruhr University Bochum | Ventosa E.,Ruhr University Bochum | Chen X.,Ruhr University Bochum | And 3 more authors.
ChemSusChem | Year: 2015

Cavity microelectrodes were used as a binder-free platform to evaluate oxygen evolution reaction (OER) electrocatalysts with respect to gas bubble formation and departure. Electrochemical noise measurements were performed by using RuO2 as a benchmark catalyst and the perovskite La0.58Sr0.4Fe0.8Co0.2O3 as a non-noble metal OER catalyst with lower intrinsic conductivity. Changes in the current during the OER originate from variations in electrolyte resistance during the formation of the gas phase and partial coverage of the active area. Fluctuations observed in current and conductance transients were used to establish the contribution from the ohmic overpotential and to determine the characteristic frequency of oxygen evolution. The proposed quantitative determination of gas bubble growth and departure opens up the route for a rational interface design by considering gas bubble growth and departure as a main contributing factor to the overall electrocatalytic activity at high current densities. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.


Moellmer J.,Institute fur Nichtklassische Chemie E.V. | Moeller A.,Institute fur Nichtklassische Chemie E.V. | Dreisbach F.,Universitatsstr 142 | Glaeser R.,Institute fur Nichtklassische Chemie E.V. | And 2 more authors.
Microporous and Mesoporous Materials | Year: 2011

High pressure adsorption phenomena are discussed for different gases on HKUST-1 (Cu3(BTC)2, commercially available product BasoliteTM C300). Sorption isotherms for hydrogen, nitrogen, methane and carbon dioxide on HKUST-1 were measured in the temperature range of 273-343 K and at pressures up to 50 MPa. The calculated surface excess adsorption capacities for all four adsorptive are one of the highest reported in the literature for HKUST-1 samples. All surface excess data were further calculated from the experimental data by using the helium buoyancy correction. A detailed description was given. Also a procedure to calculate the absolute amount adsorbed from the surface excess amount by using two different models is shown. Using one model, the density and the volume of the adsorbed phase can be calculated. The density of the adsorbed phase ρads corresponds to the liquid density of the adsorptive at its boiling point ρ liq,BP. In case of hydrogen no excess maximum was found up to 50 MPa, so that one model could not be applied. Finally, the isosteric heat of adsorption for each gas was calculated by using the Clausius-Clapeyron equation. © 2010 Elsevier Inc. All rights reserved.

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