Steam reforming of hydrocarbons is a well established chemical process which provides synthesis gas (H2 and CO). These synthesis products can hence be converted to numerous valuable basic chemicals. For the industrial application of steam reforming, a detailed understanding of the process is a prerequisite. Models that capture the detailed homogeneous and heterogeneous reaction kinetics and the comprehensive transport processes as well as their interaction have the potential to optimize the catalytic process without expensive experimental campaigns. In this paper, a detailed investigation has been done using a multi-step reaction mechanism for modeling steam reforming of methane over nickel-based catalyst using a one-dimensional (1D) model, LOGEcat [1]. The model is applicable to the simulation of all standard after-treatment catalytic processes of combustion exhaust gas along with other chemical processes involving heterogeneous catalysis, such as, the Sabatier process [27]. It is a 1D tool, thus is computationally cost effective and is based on a series of perfectly stirred reactors (PSR). The model is used to perform the simulations for various reactor conditions in terms of temperature, pressure, flow rates and steam-to-carbon (S/C) ratio. Several chemical reaction terms, such as, selectivity, yield, conversion, and mole fraction have been shown with respect to the varied parameters and the results are compared with 2D simulations and experimental reference data. We report a very good agreement of the various profiles produced with 1D model as compared to the reference data. Note that the main aim of this study is to check how far the 1D model can capture the basic chemistry for modeling steam reforming of methane over nickel-based catalysts. It is interesting to note that the cost effective reduced order model is capable to capture the physics and chemistry involved with a multi-step reaction mechanism showing the predictive capability of the model. This study forms the basis for further analysis towards the thermochemistry of the species to develop a kinetically consistent reaction mechanism.

A one-dimensional model, LOGEcat is used to develop a detailed surface reaction mechanism for modeling the steam reforming of methane over a nickel-based catalyst. The focus of the paper is to develop a kinetically consistent surface reaction mechanism. The two terms, kinetically and thermodynamically consistent mechanisms, will be used frequently in this article. Note that when the mechanism is thermodynamically consistent then the thermodynamic data or the thermochemistry of the species is not used and all the reactions in the mechanism are forward reactions (no backward reactions included) which need the Arrhenius parameters (pre-exponential factor, $$A_{r}$$ A r ; activation energy, $$E_{r}$$ E r ; temperature exponent, $$\beta _r$$ β r ) explicitly for each reaction. The kinetically consistent mechanisms need Arrhenius parameters only for the forward reactions and does not need these parameters for backward reactions making the backward reactions independent of the kinetics. The rate for the backward reactions is calculated with the help of thermochemistry of the intermediate species involved in the reaction mechanism. Since the thermochemistry of the intermediate species are not easily available, this makes such studies much more complex. The original multi-step reaction mechanism consists of 42 reactions which are thermodynamically consistent. In this study we have modified this reaction mechanism from literature and used only 21 (reversible) direct reactions. This aspect is important because by using only 21 reactions, we use the thermochemistry of the species to achieve thermodynamic equilibrium instead of providing the Arrhenius parameters for forward and backward reactions. We use the same $$A_{r}$$ A r , $$E_{r}$$ E r and $$\beta _r$$ β r values as used in the reference paper for the considered 21 reactions which are in equilibrium. However, the value of $$A_{r}$$ A r , $$E_{r}$$ E r and $$\beta _r$$ β r for the inverse/backward reactions are not given in the mechanism and the reverse rates are calculated by using the equilibrium and forward rate. Therefore, a sensitivity analysis on thermochemistry of the species is performed for a better agreement with the literature data. The method is presented for ensuring kinetic consistency and bringing thermochemistry of species in play while developing a surface reaction mechanism. The applicability of the mechanism is tested for two different simulation set-ups available in literature considering various reactor conditions in terms of parameters given as temperature and steam-to-carbon (S/C) ratio. Several chemical reaction terms, such as, selectivity, conversion and $$\mathrm {H_2}/{\text{CO}}$$ H 2 / CO ratio are shown for different parameters in comparison with the available reference data. The detailed mechanism developed in this study is able to accurately express the steam reforming of methane over the nickel catalyst for complete ranges of temperature for both the set-ups and within acceptable limit for S/C ratio considered for the analysis.

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3D Kinetic Monte Carlo (KMC) simulations have been carried out on the epitaxial growth of the silicon (100)2×1 surface as a function of surface temperature (570‐870 °C). The KMC model explicitly takes into account the anisotropy of the silicon (100)2×1 surface and the interaction of neighboring sites as a reaction event at a given surface site not only depends on the chemical nature of the site itself but also on steric factors and the local environment. Thus the model includes data about the local structure of the surface, the nature of the surface adatoms and their neighbors, the kinetic reaction parameters, and the incident precursor atoms. Reaction probabilities are calculated with the Arrhenius equation, kinetic parameters are taken from experimental and calculated data from the literature. First estimations are given for missing values. Silane is assumed to be the only gas‐phase reactant on the surface, coupling with the gas phase is carried out by silane partial pressure. For the first time a really complex algorithm comprehending 12 different surface sites and more than 100 reactions such as silane adsorption, SiHx decomposition and diffusion of adsorbed species is presented. The model provides a good fit to experimental observations and theoretical knowledge. Experimental data of growth rate and hydrogen coverage can be reproduced (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)