Kinetic modeling and reactor simulation for ethanol steam reforming

Ethanol steam reforming (ESR) attracted raising attention in the recent past as a way to produce hydrogen and syngas from renewable sources. The process is sufficiently mature, as for catalysts development, so that the attention can be conveniently turned to process development and modelling. Although the main reactions are quite satisfactorily reproduced in most literature reports, there is a fundamental lack of kinetic models and relative kinetic parameters accounting for important intermediate products, such as acetaldehyde, ethylene and coke. Comprehensive modelling of these compounds is a must for proper reactor design for ESR, to account for the possible accumulation of undesired species in the process. Therefore, in the present work we propose a complete kinetic model to account for the production of main products and possible intermediates. The model has been built by non linear regression of original experimental data collected over a catalyst prepared in our lab, under specifically designed reaction conditions to account for byproducts formation. The model has been also validated by regression of literature data to adapt it to experimental conditions that do not lead to byproducts accumulation. A Nickel-based catalyst for ESR supported on Zirconia has been synthetised by flame-pyrolysis; the comparison between different alkali promoters has shown that Potassium is the more effective in inhibiting ethanol dehydration to ethylene and the formation of filamentous coke. Activity tests of the material in a pilot PFR reactor fed with an Ethanol/Water mixture above 500 °C have shown that: 1) the process generates acetaldehyde and then methane and CO, 2) higher water ratios enhance H2 yield and inhibit coking, 3) higher temperature lower coking and promote methane reforming, 4) higher contact times are needed to fully convert intermediates and 5) the WGS reaction brings CO2 and residual CO to a steady state depending only on temperature and water feed. Two large datasets have been fitted to a fair accuracy with a Langmuir-Hinshelwood kinetic model accounting for acetaldehyde, ethylene and coke formation; the parallel interpolation of methane and coke data has confirmed the importance of methane reforming via CO and the Bouduard reactions. Different reactor modeling strategies have shown the robustness of the model to predict ethanol conversion and hydrogen yield. References 1. Surrname, M. Angew. Chem., Int. Ed. Engl. 1989, 28, 322-325. (10 pt) 2. Surrname, R. J. Bioorg. Med. Chem. 2002, 10, 3379-3383.