Kinetic modeling and reactor simulation for ethanol steam reforming

An extended kinetic model has been proposed for the ethanol steam reforming reaction that includes kinetic steps for the formation of important byproducts such as ethylene, acetaldehyde, and coke. The model has been applied to the regression of new kinetic data obtained with the use of a 9 wt % K2O/10 wt % Ni/ZrO2 catalyst prepared by flame pyrolysis. The kinetic tests were performed by varying the temperature, space velocity, and the water/ethanol ratio according to a central composite experimental design. The model was validated against literature data collected over a different catalytic system and without the presence of the selected byproducts to check its versatility and robustness. The model gave very straightforward predictions of catalyst performance for the literature data: in this case the lump sum of all the square residues (calculated vs. tabulated mol fractions) is 2.88×10−2 over a dataset of 408 points. For our own kinetic data, the model interpreted the conversion of ethanol and the evolution of the main byproducts, which include ethylene and acetaldehyde, correctly. The evolution of coke was interpreted less satisfactorily because of a missing step for coke gasification. Rate-limiting steps have been identified together with very rapid reaction steps, which can be considered to be substantially equilibrated.