Dry reforming of methane (DRM) is considered to be one of the most promising key technologies in the context of a successful carbon dioxide management, since CO2 and CH4 can effectively be utilised to obtain a syngas with a low H2/CO ratio. CO-rich syngas mixtures are an important feedstock for various petrochemical products, such as formic acid, acetic acid, polycarbonates, phosgene, dimethyl ether and oxo products. However, the high endothermicity of the DRM process and the strong deactivation tendency of the DRM catalysts under industrially relevant reaction conditions, mainly driven by sintering and coking, make the industrial large-scale realisation of the DRM process challenging. To overcome these issues, research focussed on catalyst design strategies to prevent coking and sintering, either by targeting the design of the environment of active metal species or by the modification of specific properties of the support material.

A two-site mean field extended microkinetic model was developed based on DFT data to investigate the methane oxidation reaction over PdO(1 0 1) for environmental applications at atmospheric to moderate pressures, fuel-lean and low-temperature model exhaust gas conditions. The mechanism includes various carbonaceous pathways for methane oxidation together with lattice oxygen vacancy formation via Marsvan-Krevelen steps. The mechanism was compared with catalytic light-off curves (573-823 K) on a Pd/Al2O3 coated on monolith for CH4/O-2/H2O/N-2 mixtures with 1000 ppm CH4, 10 vol% O-2 at varying H2O feed concentration (0-12 vol%) and pressure (1-4 bar). The mechanism was demonstrated to quantitatively reproduce experimental light-off curves for dry and wet feeds and capture the water inhibition phenomena, when catalyst deactivation and/or particle size dependent kinetic effects are taken into account. A degree of rate control analysis reveals dissociative CH4 adsorption via hydrogen abstraction over Pd-cus-O-cus site-pairs as the major rate controlling step during light-off. Supplementary in situ DRIFTS investigations analyzed for dry and wet reactive gas-mixtures containing different types of C-1-fuels, namely methane, methanol and formic acid were conducted to identify surface species during catalytic methane oxidation and hydroxide formation. (C) 2018 Elsevier Inc. All rights reserved.

This paper presents the concepts of an open software tool (CaRMeN) that can be used to rapidly analyse and derive models, in particular chemical kinetics. The software automates the workflow of comparing model vs. experiment, which must currently be done manually and is thus a time-consuming and error-prone task. The capabilities of the software are illustrated through a case study. Experimental data for the conversion of methane over rhodium catalysts in a wide range of conditions and experimental setups are numerically simulated using five different mechanisms from the literature. The applicability of the mechanisms as well as differences between flow and diffusion models are evaluated. The results show that no single mechanism reliably predicts the chemical conversions of all of the experiments. Although the software was initially developed for chemical kinetics applications, it can also be extended to run any simulation code, and can therefore be applied in other scenarios.

The oxidation state of the active metal is an important factor for catalyst stability under dry and steam reforming conditions. This work explores the correlation of the oxidation state of the active metal with the coking behavior of alumina‐supported cobalt and nickel catalysts from a thermodynamic point of view. To this end, the thermodynamics of the oxidation of Co/γ‐Al2O3 and Ni/γ‐Al2O3 were investigated by using calculations at both standard and technical reforming conditions. It is shown that oxidation of nickel by water or CO2 cannot occur spontaneously under reforming conditions regardless of participation of the alumina support material because of the positive Gibbs reaction energies. Cobalt, in contrast, is more easily oxidized and may form CoAl2O4 through interaction with the support. This phase may react with surface carbon to regenerate the catalyst after carbon formation through thermal cracking of methane. A Mars–van Krevelen type reaction scheme is proposed to explain the higher coking resistance of cobalt compared to nickel.

A kinetic modeling study on methane oxidation over reduced Pd for various fuel-rich conditions around the stoichiometric point of the partial oxidation at high temperatures (900–1100 K) is presented. A thermodynamically consistent detailed surface reaction mechanism is developed within the mean field approximation. The proposed kinetic model consists of 54 elementary-step based reactions including seven gas-phase species and 15 surface intermediates. Three different methane activation paths are implemented, comprising pyrolytic C–H bond dissociation steps, oxygen-assisted and dual-oxygen-assisted CH4 activation. In situ experimental measurements in a quasi-autothermally operated flow reactor, using the capillary sampling technique, are performed for model evaluation. The provided experimental data includes spatially resolved temperature and concentration profiles within a single catalytic channel of a Pd/Al2O3-coated monolith. Supplementary numerical simulations based on literature data for fuel-lean and fuel-rich conditions at high temperatures extend the model’s capability to predict a wide range of different experimental conditions.

The oxidative dehydrogenation of n-butane and butenes has been studied in a two-zone fluidized bed reactor using Mo-V-MgO and Bi-Mo-MgO catalysts. All catalysts have been prepared by incipient wetness impregnation. The operating conditions temperature, flow velocity, hydrocarbon inlet height and oxygen/hydrocarbon molar ratio were varied to maximize 1,3-butadiene yield. At suitable conditions, the two-zone fluidized bed reactor can be operated at steady state performing chemical conversion and catalyst regeneration in a single vessel. Axial concentration profiles in the fluidized bed prove that the regeneration zone at the bottom of the fluidized bed was used to burn coke depositions as well as to fill up lattice oxygen of the catalyst. The efficient usage of the oxygen leads to high 1,3-butadiene selectivity.

Chemie Ingenieur TechnikVolume 86, Issue 9 p. 1539-1539 PosterFree Access Untersuchung der Dehydrierung und der oxidativen Dehydrierung von n-Butan an Platin und V-basierten Katalysatoren in einem Zwei-Zonen-Wirbelschichtreaktor Prof. Dr. O. Deutschmann, Corresponding Author Prof. Dr. O. Deutschmann olaf.deutschmann@kit.edu Karlsruher Institut für Technologie (KIT), Institut für Technische Chemie und Polymerchemie (ITCP), Engesserstraße 18, D-76131 Karlsruhe, Germany Karlsruher Institut für Technologie (KIT), Institut für Katalyseforschung und -technologie (IKFT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, GermanyKarlsruher Institut für Technologie (KIT), Institut für Technische Chemie und Polymerchemie (ITCP), Engesserstraße 18, D-76131 Karlsruhe, Germany===Search for more papers by this authorJ. Rischard, J. Rischard Karlsruher Institut für Technologie (KIT), Institut für Technische Chemie und Polymerchemie (ITCP), Engesserstraße 18, D-76131 Karlsruhe, GermanySearch for more papers by this authorDr. C. Diehm, Dr. C. Diehm Karlsruher Institut für Technologie (KIT), Institut für Katalyseforschung und -technologie (IKFT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, GermanySearch for more papers by this authorDr. L. Maier, Dr. L. Maier Karlsruher Institut für Technologie (KIT), Institut für Katalyseforschung und -technologie (IKFT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, GermanySearch for more papers by this author Prof. Dr. O. Deutschmann, Corresponding Author Prof. Dr. O. Deutschmann olaf.deutschmann@kit.edu Karlsruher Institut für Technologie (KIT), Institut für Technische Chemie und Polymerchemie (ITCP), Engesserstraße 18, D-76131 Karlsruhe, Germany Karlsruher Institut für Technologie (KIT), Institut für Katalyseforschung und -technologie (IKFT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, GermanyKarlsruher Institut für Technologie (KIT), Institut für Technische Chemie und Polymerchemie (ITCP), Engesserstraße 18, D-76131 Karlsruhe, Germany===Search for more papers by this authorJ. Rischard, J. Rischard Karlsruher Institut für Technologie (KIT), Institut für Technische Chemie und Polymerchemie (ITCP), Engesserstraße 18, D-76131 Karlsruhe, GermanySearch for more papers by this authorDr. C. Diehm, Dr. C. Diehm Karlsruher Institut für Technologie (KIT), Institut für Katalyseforschung und -technologie (IKFT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, GermanySearch for more papers by this authorDr. L. Maier, Dr. L. Maier Karlsruher Institut für Technologie (KIT), Institut für Katalyseforschung und -technologie (IKFT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, GermanySearch for more papers by this author First published: 28 August 2014 https://doi.org/10.1002/cite.201450578AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. REFERENCES 1 M. P. Lobera et al., Ind. Eng. Chem. Res. 2009, 48 (14), 6573– 6578. 2 J. Soler et al., Ind. Eng. Chem. Res. 1999, 38 (1), 90– 97. Volume86, Issue9Special Issue: ProcessNet-Jahrestagung 2014 und 31. DECHEMA-Jahrestagung der BiotechnologenSeptember, 2014Pages 1539-1539 ReferencesRelatedInformation

A detailed multi-step reaction mechanism is developed for modeling steam reforming of methane over nickel-based catalysts. The mechanism also includes partial and total oxidation reactions, water–gas shift reactions, formation of carbon monolayers, and methanation reactions. A method is presented for ensuring thermodynamic consistency in the development of surface reaction mechanisms. The applicability of the mechanism is tested by simulating experimental investigations of SR of methane on a Ni-coated monolithic cordierite catalyst as well as experimental studies from literature. The reactive flow in the channels of the experimentally used monolithic structures is modeled by a two-dimensional flow field analysis of a single monolith channel coupled with the reaction mechanism developed. The gas composition and surface coverage with adsorbed species are calculated as function of the position in the channel. The model developed is able to properly describe steam reforming of methane over the nickel catalysts for wide ranges of temperature and steam/methane ratio.

A modeling and simulation concept is presented for a better understanding of the interaction of heterogeneous and homogeneous conversion with mass and heat transfer in compact, autothermal reformers of logistic fuels for the production of hydrogen-rich synthesis gas. The model couples elementary-step based reaction mechanisms with a two-dimensional parabolic description of the flow field in a representative number of monolith channels and of heat transport in the entire solid structure of the reactor including catalyst, heat shields, insulation, and reactor wall. The concept is applied to analyze conversion, selectivity, and temperature profiles in partial oxidation of iso-octane, a gasoline surrogate, over a rhodium/alumina monolithic catalyst. The counter-intuitive flow rate effect on hydrogen yield is explained by the ratio of chemical heat release to physical heat loss. Coking tendency is related to the C/O ratio, the flow rate, and the occurrence of homogeneous fuel conversion. C/O ratios close to unity and reasonably high flow rates are found to maximize hydrogen yield at minimum production of coke precursors.

Hydrogen production by catalytic partial oxidation of iso-octane is experimentally and numerically studied over a rhodium/alumina coated honeycomb monolith at millisecond contact times by varying both fuel-to-oxygen ratio and flow rates and at varying flow rates. At fuel rich conditions, the formation of by-products potentially serving as coke precursors is observed. The quantity of by-products strongly depends on the flow rate. Both fuel conversion and hydrogen yield increase with increasing flow rate, i.e., decreasing residence time. This extraordinary behavior of autothermally operated short-contact time reactors can be understood by the interaction of mass and heat transport and chemical reactions. Therefore, an elementary-step-like heterogeneous reaction mechanism is implemented into a two-dimensional flow field description of a single monolith channel, coupled with a heat balance of the entire monolithic structure.

Catalytic partial oxidation of iso-octane over a rhodium/alumina coated honeycomb monolith is experimentally and numerically studied at short-contact times for varying fuel-to-oxygen ratios. A new experimental set-up with well-defined inlet and boundary conditions is presented. The conversion on the catalyst and in the gas-phase is modeled by detailed reaction mechanisms including 857 gas-phase and 17 adsorbed species. Elementary-step based heterogeneous and homogeneous reaction mechanisms are implemented into two-dimensional flow field description of a single monolith channel. Experiment and simulation provide new insights into the complex reaction network leading to varying product distribution as function of fuel-to-oxygen ratio. At fuel rich conditions, the formation of by-products that can serve as coke precursors is observed and interpreted.

We discuss the modeling, simulation, and, for the first time, optimization of the reactive flow in a channel of a catalytic monolith with detailed chemistry. We use boundary layer approximation to model the process and obtain a high dimensional PDE. We discuss numerical methods based on the efficient solution of high dimensional stiff DAEs arising from spatial semi-discretization and SQP method for the optimal control problem parameterized by the direct approach. We have investigated the application of conversion of ethane to ethylene which involves a complex reaction scheme for gas phase and surface chemistry. Our optimization results show that the maximum yield, an improvement of a factor of two, is achieved for temperatures around 1300 K.

This paper reports experimental and modeling investigations of thermal methane reforming chemistry within porous Ni-YSZ anode materials. Because the reforming chemistry is difficult to observe directly in an operating fuel cell, a specially designed experiment is developed. In the experiment a 0.75 mm-thick anode is sandwiched between two small co-flowing gas channels. One channel represents the fuel channel of a solid-oxide fuel cell (SOFC). The composition in the other channel carries the species that would be produced in an operating fuel cell by the electrochemical charge-transfer reactions in the thin three-phase regions near the interface between the anode and the dense electrolyte membrane (i.e., H2O and CO2). Because the anode structure is porous (and there is no dense electrolyte or cathode applied), there is convective and diffusive species flux between the two flow channels. The entire assembly is maintained at approximately 800 degrees C in a furnace. The results of heterogeneous reforming kinetics are determined by using mass spectrometry to measure the species composition at the outlet of both channels. Experimental results are interpreted using a computational model that incorporates channel gas flow, porous-media transport, and elementary heterogeneous chemical kinetics. The overall objective is to develop quantitative models of non-electrochemical heterogeneous reforming chemistry within a Ni-YSZ anode. (c) 2005 Elsevier B.V. All rights reserved.