Facu;ty of Engineering

The effects of catalyst synthesis method (i.e. precipitation (PT), coprecipitation (CP) and impregnation (IM)), Ni loading and reduction temperature on the characteristics and performance of Ni/Al 2 O 3 catalysts were evaluated for the reforming of crude ethanol for H 2 production. The results showed that in the calcined PT catalysts, no NiAl 2 O 4 species were observed whereas this was a major species in CP and IM catalysts. As a result, PT catalysts were more reducible than CP and IM catalysts. PT catalysts exhibited slightly lower crystallite sizes of NiO species than the corresponding CP catalysts. On the other hand, IM catalysts had extremely large crystallite sizes except IM10 (IM catalyst with 10% Ni loading) which had the smallest crystallite size. A combination of small crystallite size and high reducibility for PT catalysts resulted in higher crude ethanol conversions for the PT catalysts. In contrast, the IM catalysts with larger crystallite sizes and lower reducibility yielded the lowest crude ethanol conversions. Catalysts with 15% Ni loading gave the best crude ethanol conversions for each method of synthesis with PT15 giving the best overall crude ethanol conversion of 85 mol% again because of its smaller crystallite size and higher reducibility. In terms of H 2 yield, CP15 was the optimum catalyst because of its higher H 2 selectivity as compared to PT15 and IM15 catalysts. Coking was observed at the onset of the reaction but stabilized after 180 min TOS. #

A rigorous numerical model was developed to simulate the production of hydrogen from the reforming of crude ethanol in a packed bed tubular reactor (PBTR). The model was based on the coupling of mass and energy balance equations as well as a new kinetic model developed for the process. The simulation results for crude ethanol conversion were found to be in accordance with the experimental data obtained at various operating conditions. This confirms the validity of the numerical model. A further validation of the model was obtained by using the model to simulate a well-documented reaction process. In addition, the predicted variations of the concentration and temperature profiles for our process in the radial direction indicate that the assumption of plug flow and isothermal behavior is justified within certain kinetics operating conditions. However, even within these operating conditions, our results have proven that the axial dispersion terms in both the mass and the energy balance equations cannot be neglected. ᭧

Artificial neural network (ANN) approach was used to design an optimum Ni/Al 2 O 3 catalyst for the production of hydrogen by the catalytic reforming of crude ethanol based on determining the inter-relationships between catalyst-preparation methods, nickel loading, catalyst characteristics and catalyst performance. ANN could predict hydrogen production performance of various Ni/Al 2 O 3 catalysts of various elemental compositions and methods of preparation in the production of hydrogen by the catalytic reforming of crude ethanol in terms of crude-ethanol conversion, hydrogen selectivity and hydrogen yield. Specifically on catalyst design, ANN was used to determine the optimum catalyst conditions for obtaining maximum hydrogen production performance of a Ni/Al 2 O 3 catalyst for the production of hydrogen by the catalytic reforming of crude ethanol. The optimal hydrogen yield was 4.4 mol %, and the associated crude-ethanol conversion and H 2 selectivity for the optimal hydrogen yield were 79.6 and 91.4 mol%, respectively. The optimal catalyst was the one prepared by the coprecipitation method with the optimal nickel loading of 12.4 wt% and an optimal aluminum composition of 42.5 wt%.